build: move package sources from src/pkg to src

Preparation was in CL 134570043.
This CL contains only the effect of 'hg mv src/pkg/* src'.
For more about the move, see golang.org/s/go14nopkg.

240 files changed, 54136 insertions, 0 deletions

diff --git a/src/net/cgo_android.go b/src/net/cgo_android.go
new file mode 100644
index 000000000..3819ce56a
--- /dev/null
+++ b/src/net/cgo_android.go
@@ -0,0 +1,14 @@
+// Copyright 2014 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build cgo,!netgo
+
+package net
+
+//#include <netdb.h>
+import "C"
+
+func cgoAddrInfoFlags() C.int {
+	return C.AI_CANONNAME
+}
diff --git a/src/net/cgo_bsd.go b/src/net/cgo_bsd.go
new file mode 100644
index 000000000..3090d3019
--- /dev/null
+++ b/src/net/cgo_bsd.go
@@ -0,0 +1,17 @@
+// Copyright 2011 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build !netgo
+// +build darwin dragonfly freebsd solaris
+
+package net
+
+/*
+#include <netdb.h>
+*/
+import "C"
+
+func cgoAddrInfoFlags() C.int {
+	return (C.AI_CANONNAME | C.AI_V4MAPPED | C.AI_ALL) & C.AI_MASK
+}
diff --git a/src/net/cgo_linux.go b/src/net/cgo_linux.go
new file mode 100644
index 000000000..4ef2d0cd1
--- /dev/null
+++ b/src/net/cgo_linux.go
@@ -0,0 +1,22 @@
+// Copyright 2011 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build !android,cgo,!netgo
+
+package net
+
+/*
+#include <netdb.h>
+*/
+import "C"
+
+func cgoAddrInfoFlags() C.int {
+	// NOTE(rsc): In theory there are approximately balanced
+	// arguments for and against including AI_ADDRCONFIG
+	// in the flags (it includes IPv4 results only on IPv4 systems,
+	// and similarly for IPv6), but in practice setting it causes
+	// getaddrinfo to return the wrong canonical name on Linux.
+	// So definitely leave it out.
+	return C.AI_CANONNAME | C.AI_V4MAPPED | C.AI_ALL
+}
diff --git a/src/net/cgo_netbsd.go b/src/net/cgo_netbsd.go
new file mode 100644
index 000000000..09c5ad2d9
--- /dev/null
+++ b/src/net/cgo_netbsd.go
@@ -0,0 +1,16 @@
+// Copyright 2011 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build cgo,!netgo
+
+package net
+
+/*
+#include <netdb.h>
+*/
+import "C"
+
+func cgoAddrInfoFlags() C.int {
+	return C.AI_CANONNAME
+}
diff --git a/src/net/cgo_openbsd.go b/src/net/cgo_openbsd.go
new file mode 100644
index 000000000..09c5ad2d9
--- /dev/null
+++ b/src/net/cgo_openbsd.go
@@ -0,0 +1,16 @@
+// Copyright 2011 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build cgo,!netgo
+
+package net
+
+/*
+#include <netdb.h>
+*/
+import "C"
+
+func cgoAddrInfoFlags() C.int {
+	return C.AI_CANONNAME
+}
diff --git a/src/net/cgo_stub.go b/src/net/cgo_stub.go
new file mode 100644
index 000000000..f533c1421
--- /dev/null
+++ b/src/net/cgo_stub.go
@@ -0,0 +1,25 @@
+// Copyright 2011 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build !cgo netgo
+
+// Stub cgo routines for systems that do not use cgo to do network lookups.
+
+package net
+
+func cgoLookupHost(name string) (addrs []string, err error, completed bool) {
+	return nil, nil, false
+}
+
+func cgoLookupPort(network, service string) (port int, err error, completed bool) {
+	return 0, nil, false
+}
+
+func cgoLookupIP(name string) (addrs []IP, err error, completed bool) {
+	return nil, nil, false
+}
+
+func cgoLookupCNAME(name string) (cname string, err error, completed bool) {
+	return "", nil, false
+}
diff --git a/src/net/cgo_unix.go b/src/net/cgo_unix.go
new file mode 100644
index 000000000..1f366ee5c
--- /dev/null
+++ b/src/net/cgo_unix.go
@@ -0,0 +1,164 @@
+// Copyright 2011 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build !netgo
+// +build darwin dragonfly freebsd linux netbsd openbsd
+
+package net
+
+/*
+#include <sys/types.h>
+#include <sys/socket.h>
+#include <netinet/in.h>
+#include <netdb.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <string.h>
+*/
+import "C"
+
+import (
+	"syscall"
+	"unsafe"
+)
+
+func cgoLookupHost(name string) (addrs []string, err error, completed bool) {
+	ip, err, completed := cgoLookupIP(name)
+	for _, p := range ip {
+		addrs = append(addrs, p.String())
+	}
+	return
+}
+
+func cgoLookupPort(net, service string) (port int, err error, completed bool) {
+	acquireThread()
+	defer releaseThread()
+
+	var res *C.struct_addrinfo
+	var hints C.struct_addrinfo
+
+	switch net {
+	case "":
+		// no hints
+	case "tcp", "tcp4", "tcp6":
+		hints.ai_socktype = C.SOCK_STREAM
+		hints.ai_protocol = C.IPPROTO_TCP
+	case "udp", "udp4", "udp6":
+		hints.ai_socktype = C.SOCK_DGRAM
+		hints.ai_protocol = C.IPPROTO_UDP
+	default:
+		return 0, UnknownNetworkError(net), true
+	}
+	if len(net) >= 4 {
+		switch net[3] {
+		case '4':
+			hints.ai_family = C.AF_INET
+		case '6':
+			hints.ai_family = C.AF_INET6
+		}
+	}
+
+	s := C.CString(service)
+	defer C.free(unsafe.Pointer(s))
+	if C.getaddrinfo(nil, s, &hints, &res) == 0 {
+		defer C.freeaddrinfo(res)
+		for r := res; r != nil; r = r.ai_next {
+			switch r.ai_family {
+			default:
+				continue
+			case C.AF_INET:
+				sa := (*syscall.RawSockaddrInet4)(unsafe.Pointer(r.ai_addr))
+				p := (*[2]byte)(unsafe.Pointer(&sa.Port))
+				return int(p[0])<<8 | int(p[1]), nil, true
+			case C.AF_INET6:
+				sa := (*syscall.RawSockaddrInet6)(unsafe.Pointer(r.ai_addr))
+				p := (*[2]byte)(unsafe.Pointer(&sa.Port))
+				return int(p[0])<<8 | int(p[1]), nil, true
+			}
+		}
+	}
+	return 0, &AddrError{"unknown port", net + "/" + service}, true
+}
+
+func cgoLookupIPCNAME(name string) (addrs []IP, cname string, err error, completed bool) {
+	acquireThread()
+	defer releaseThread()
+
+	var res *C.struct_addrinfo
+	var hints C.struct_addrinfo
+
+	hints.ai_flags = cgoAddrInfoFlags()
+	hints.ai_socktype = C.SOCK_STREAM
+
+	h := C.CString(name)
+	defer C.free(unsafe.Pointer(h))
+	gerrno, err := C.getaddrinfo(h, nil, &hints, &res)
+	if gerrno != 0 {
+		var str string
+		if gerrno == C.EAI_NONAME {
+			str = noSuchHost
+		} else if gerrno == C.EAI_SYSTEM {
+			if err == nil {
+				// err should not be nil, but sometimes getaddrinfo returns
+				// gerrno == C.EAI_SYSTEM with err == nil on Linux.
+				// The report claims that it happens when we have too many
+				// open files, so use syscall.EMFILE (too many open files in system).
+				// Most system calls would return ENFILE (too many open files),
+				// so at the least EMFILE should be easy to recognize if this
+				// comes up again. golang.org/issue/6232.
+				err = syscall.EMFILE
+			}
+			str = err.Error()
+		} else {
+			str = C.GoString(C.gai_strerror(gerrno))
+		}
+		return nil, "", &DNSError{Err: str, Name: name}, true
+	}
+	defer C.freeaddrinfo(res)
+	if res != nil {
+		cname = C.GoString(res.ai_canonname)
+		if cname == "" {
+			cname = name
+		}
+		if len(cname) > 0 && cname[len(cname)-1] != '.' {
+			cname += "."
+		}
+	}
+	for r := res; r != nil; r = r.ai_next {
+		// We only asked for SOCK_STREAM, but check anyhow.
+		if r.ai_socktype != C.SOCK_STREAM {
+			continue
+		}
+		switch r.ai_family {
+		default:
+			continue
+		case C.AF_INET:
+			sa := (*syscall.RawSockaddrInet4)(unsafe.Pointer(r.ai_addr))
+			addrs = append(addrs, copyIP(sa.Addr[:]))
+		case C.AF_INET6:
+			sa := (*syscall.RawSockaddrInet6)(unsafe.Pointer(r.ai_addr))
+			addrs = append(addrs, copyIP(sa.Addr[:]))
+		}
+	}
+	return addrs, cname, nil, true
+}
+
+func cgoLookupIP(name string) (addrs []IP, err error, completed bool) {
+	addrs, _, err, completed = cgoLookupIPCNAME(name)
+	return
+}
+
+func cgoLookupCNAME(name string) (cname string, err error, completed bool) {
+	_, cname, err, completed = cgoLookupIPCNAME(name)
+	return
+}
+
+func copyIP(x IP) IP {
+	if len(x) < 16 {
+		return x.To16()
+	}
+	y := make(IP, len(x))
+	copy(y, x)
+	return y
+}
diff --git a/src/net/cgo_unix_test.go b/src/net/cgo_unix_test.go
new file mode 100644
index 000000000..33566ce9c
--- /dev/null
+++ b/src/net/cgo_unix_test.go
@@ -0,0 +1,24 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build cgo,!netgo
+// +build darwin dragonfly freebsd linux netbsd openbsd
+
+package net
+
+import "testing"
+
+func TestCgoLookupIP(t *testing.T) {
+	host := "localhost"
+	_, err, ok := cgoLookupIP(host)
+	if !ok {
+		t.Errorf("cgoLookupIP must not be a placeholder")
+	}
+	if err != nil {
+		t.Errorf("cgoLookupIP failed: %v", err)
+	}
+	if _, err := goLookupIP(host); err != nil {
+		t.Errorf("goLookupIP failed: %v", err)
+	}
+}
diff --git a/src/net/conn_test.go b/src/net/conn_test.go
new file mode 100644
index 000000000..9c9d1a805
--- /dev/null
+++ b/src/net/conn_test.go
@@ -0,0 +1,124 @@
+// Copyright 2012 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// This file implements API tests across platforms and will never have a build
+// tag.
+
+package net
+
+import (
+	"os"
+	"runtime"
+	"testing"
+	"time"
+)
+
+var connTests = []struct {
+	net  string
+	addr string
+}{
+	{"tcp", "127.0.0.1:0"},
+	{"unix", testUnixAddr()},
+	{"unixpacket", testUnixAddr()},
+}
+
+// someTimeout is used just to test that net.Conn implementations
+// don't explode when their SetFooDeadline methods are called.
+// It isn't actually used for testing timeouts.
+const someTimeout = 10 * time.Second
+
+func TestConnAndListener(t *testing.T) {
+	for _, tt := range connTests {
+		switch tt.net {
+		case "unix":
+			switch runtime.GOOS {
+			case "nacl", "plan9", "windows":
+				continue
+			}
+		case "unixpacket":
+			switch runtime.GOOS {
+			case "android", "darwin", "nacl", "openbsd", "plan9", "windows":
+				continue
+			case "freebsd": // FreeBSD 8 doesn't support unixpacket
+				continue
+			}
+		}
+
+		ln, err := Listen(tt.net, tt.addr)
+		if err != nil {
+			t.Fatalf("Listen failed: %v", err)
+		}
+		defer func(ln Listener, net, addr string) {
+			ln.Close()
+			switch net {
+			case "unix", "unixpacket":
+				os.Remove(addr)
+			}
+		}(ln, tt.net, tt.addr)
+		if ln.Addr().Network() != tt.net {
+			t.Fatalf("got %v; expected %v", ln.Addr().Network(), tt.net)
+		}
+
+		done := make(chan int)
+		go transponder(t, ln, done)
+
+		c, err := Dial(tt.net, ln.Addr().String())
+		if err != nil {
+			t.Fatalf("Dial failed: %v", err)
+		}
+		defer c.Close()
+		if c.LocalAddr().Network() != tt.net || c.LocalAddr().Network() != tt.net {
+			t.Fatalf("got %v->%v; expected %v->%v", c.LocalAddr().Network(), c.RemoteAddr().Network(), tt.net, tt.net)
+		}
+		c.SetDeadline(time.Now().Add(someTimeout))
+		c.SetReadDeadline(time.Now().Add(someTimeout))
+		c.SetWriteDeadline(time.Now().Add(someTimeout))
+
+		if _, err := c.Write([]byte("CONN TEST")); err != nil {
+			t.Fatalf("Conn.Write failed: %v", err)
+		}
+		rb := make([]byte, 128)
+		if _, err := c.Read(rb); err != nil {
+			t.Fatalf("Conn.Read failed: %v", err)
+		}
+
+		<-done
+	}
+}
+
+func transponder(t *testing.T, ln Listener, done chan<- int) {
+	defer func() { done <- 1 }()
+
+	switch ln := ln.(type) {
+	case *TCPListener:
+		ln.SetDeadline(time.Now().Add(someTimeout))
+	case *UnixListener:
+		ln.SetDeadline(time.Now().Add(someTimeout))
+	}
+	c, err := ln.Accept()
+	if err != nil {
+		t.Errorf("Listener.Accept failed: %v", err)
+		return
+	}
+	defer c.Close()
+	network := ln.Addr().Network()
+	if c.LocalAddr().Network() != network || c.LocalAddr().Network() != network {
+		t.Errorf("got %v->%v; expected %v->%v", c.LocalAddr().Network(), c.RemoteAddr().Network(), network, network)
+		return
+	}
+	c.SetDeadline(time.Now().Add(someTimeout))
+	c.SetReadDeadline(time.Now().Add(someTimeout))
+	c.SetWriteDeadline(time.Now().Add(someTimeout))
+
+	b := make([]byte, 128)
+	n, err := c.Read(b)
+	if err != nil {
+		t.Errorf("Conn.Read failed: %v", err)
+		return
+	}
+	if _, err := c.Write(b[:n]); err != nil {
+		t.Errorf("Conn.Write failed: %v", err)
+		return
+	}
+}
diff --git a/src/net/dial.go b/src/net/dial.go
new file mode 100644
index 000000000..e6f0436cd
--- /dev/null
+++ b/src/net/dial.go
@@ -0,0 +1,302 @@
+// Copyright 2010 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package net
+
+import (
+	"errors"
+	"time"
+)
+
+// A Dialer contains options for connecting to an address.
+//
+// The zero value for each field is equivalent to dialing
+// without that option. Dialing with the zero value of Dialer
+// is therefore equivalent to just calling the Dial function.
+type Dialer struct {
+	// Timeout is the maximum amount of time a dial will wait for
+	// a connect to complete. If Deadline is also set, it may fail
+	// earlier.
+	//
+	// The default is no timeout.
+	//
+	// With or without a timeout, the operating system may impose
+	// its own earlier timeout. For instance, TCP timeouts are
+	// often around 3 minutes.
+	Timeout time.Duration
+
+	// Deadline is the absolute point in time after which dials
+	// will fail. If Timeout is set, it may fail earlier.
+	// Zero means no deadline, or dependent on the operating system
+	// as with the Timeout option.
+	Deadline time.Time
+
+	// LocalAddr is the local address to use when dialing an
+	// address. The address must be of a compatible type for the
+	// network being dialed.
+	// If nil, a local address is automatically chosen.
+	LocalAddr Addr
+
+	// DualStack allows a single dial to attempt to establish
+	// multiple IPv4 and IPv6 connections and to return the first
+	// established connection when the network is "tcp" and the
+	// destination is a host name that has multiple address family
+	// DNS records.
+	DualStack bool
+
+	// KeepAlive specifies the keep-alive period for an active
+	// network connection.
+	// If zero, keep-alives are not enabled. Network protocols
+	// that do not support keep-alives ignore this field.
+	KeepAlive time.Duration
+}
+
+// Return either now+Timeout or Deadline, whichever comes first.
+// Or zero, if neither is set.
+func (d *Dialer) deadline() time.Time {
+	if d.Timeout == 0 {
+		return d.Deadline
+	}
+	timeoutDeadline := time.Now().Add(d.Timeout)
+	if d.Deadline.IsZero() || timeoutDeadline.Before(d.Deadline) {
+		return timeoutDeadline
+	} else {
+		return d.Deadline
+	}
+}
+
+func parseNetwork(net string) (afnet string, proto int, err error) {
+	i := last(net, ':')
+	if i < 0 { // no colon
+		switch net {
+		case "tcp", "tcp4", "tcp6":
+		case "udp", "udp4", "udp6":
+		case "ip", "ip4", "ip6":
+		case "unix", "unixgram", "unixpacket":
+		default:
+			return "", 0, UnknownNetworkError(net)
+		}
+		return net, 0, nil
+	}
+	afnet = net[:i]
+	switch afnet {
+	case "ip", "ip4", "ip6":
+		protostr := net[i+1:]
+		proto, i, ok := dtoi(protostr, 0)
+		if !ok || i != len(protostr) {
+			proto, err = lookupProtocol(protostr)
+			if err != nil {
+				return "", 0, err
+			}
+		}
+		return afnet, proto, nil
+	}
+	return "", 0, UnknownNetworkError(net)
+}
+
+func resolveAddr(op, net, addr string, deadline time.Time) (netaddr, error) {
+	afnet, _, err := parseNetwork(net)
+	if err != nil {
+		return nil, err
+	}
+	if op == "dial" && addr == "" {
+		return nil, errMissingAddress
+	}
+	switch afnet {
+	case "unix", "unixgram", "unixpacket":
+		return ResolveUnixAddr(afnet, addr)
+	}
+	return resolveInternetAddr(afnet, addr, deadline)
+}
+
+// Dial connects to the address on the named network.
+//
+// Known networks are "tcp", "tcp4" (IPv4-only), "tcp6" (IPv6-only),
+// "udp", "udp4" (IPv4-only), "udp6" (IPv6-only), "ip", "ip4"
+// (IPv4-only), "ip6" (IPv6-only), "unix", "unixgram" and
+// "unixpacket".
+//
+// For TCP and UDP networks, addresses have the form host:port.
+// If host is a literal IPv6 address it must be enclosed
+// in square brackets as in "[::1]:80" or "[ipv6-host%zone]:80".
+// The functions JoinHostPort and SplitHostPort manipulate addresses
+// in this form.
+//
+// Examples:
+//	Dial("tcp", "12.34.56.78:80")
+//	Dial("tcp", "google.com:http")
+//	Dial("tcp", "[2001:db8::1]:http")
+//	Dial("tcp", "[fe80::1%lo0]:80")
+//
+// For IP networks, the network must be "ip", "ip4" or "ip6" followed
+// by a colon and a protocol number or name and the addr must be a
+// literal IP address.
+//
+// Examples:
+//	Dial("ip4:1", "127.0.0.1")
+//	Dial("ip6:ospf", "::1")
+//
+// For Unix networks, the address must be a file system path.
+func Dial(network, address string) (Conn, error) {
+	var d Dialer
+	return d.Dial(network, address)
+}
+
+// DialTimeout acts like Dial but takes a timeout.
+// The timeout includes name resolution, if required.
+func DialTimeout(network, address string, timeout time.Duration) (Conn, error) {
+	d := Dialer{Timeout: timeout}
+	return d.Dial(network, address)
+}
+
+// Dial connects to the address on the named network.
+//
+// See func Dial for a description of the network and address
+// parameters.
+func (d *Dialer) Dial(network, address string) (Conn, error) {
+	ra, err := resolveAddr("dial", network, address, d.deadline())
+	if err != nil {
+		return nil, &OpError{Op: "dial", Net: network, Addr: nil, Err: err}
+	}
+	dialer := func(deadline time.Time) (Conn, error) {
+		return dialSingle(network, address, d.LocalAddr, ra.toAddr(), deadline)
+	}
+	if ras, ok := ra.(addrList); ok && d.DualStack && network == "tcp" {
+		dialer = func(deadline time.Time) (Conn, error) {
+			return dialMulti(network, address, d.LocalAddr, ras, deadline)
+		}
+	}
+	c, err := dial(network, ra.toAddr(), dialer, d.deadline())
+	if d.KeepAlive > 0 && err == nil {
+		if tc, ok := c.(*TCPConn); ok {
+			tc.SetKeepAlive(true)
+			tc.SetKeepAlivePeriod(d.KeepAlive)
+			testHookSetKeepAlive()
+		}
+	}
+	return c, err
+}
+
+var testHookSetKeepAlive = func() {} // changed by dial_test.go
+
+// dialMulti attempts to establish connections to each destination of
+// the list of addresses. It will return the first established
+// connection and close the other connections. Otherwise it returns
+// error on the last attempt.
+func dialMulti(net, addr string, la Addr, ras addrList, deadline time.Time) (Conn, error) {
+	type racer struct {
+		Conn
+		error
+	}
+	// Sig controls the flow of dial results on lane. It passes a
+	// token to the next racer and also indicates the end of flow
+	// by using closed channel.
+	sig := make(chan bool, 1)
+	lane := make(chan racer, 1)
+	for _, ra := range ras {
+		go func(ra Addr) {
+			c, err := dialSingle(net, addr, la, ra, deadline)
+			if _, ok := <-sig; ok {
+				lane <- racer{c, err}
+			} else if err == nil {
+				// We have to return the resources
+				// that belong to the other
+				// connections here for avoiding
+				// unnecessary resource starvation.
+				c.Close()
+			}
+		}(ra.toAddr())
+	}
+	defer close(sig)
+	lastErr := errTimeout
+	nracers := len(ras)
+	for nracers > 0 {
+		sig <- true
+		racer := <-lane
+		if racer.error == nil {
+			return racer.Conn, nil
+		}
+		lastErr = racer.error
+		nracers--
+	}
+	return nil, lastErr
+}
+
+// dialSingle attempts to establish and returns a single connection to
+// the destination address.
+func dialSingle(net, addr string, la, ra Addr, deadline time.Time) (c Conn, err error) {
+	if la != nil && la.Network() != ra.Network() {
+		return nil, &OpError{Op: "dial", Net: net, Addr: ra, Err: errors.New("mismatched local address type " + la.Network())}
+	}
+	switch ra := ra.(type) {
+	case *TCPAddr:
+		la, _ := la.(*TCPAddr)
+		c, err = dialTCP(net, la, ra, deadline)
+	case *UDPAddr:
+		la, _ := la.(*UDPAddr)
+		c, err = dialUDP(net, la, ra, deadline)
+	case *IPAddr:
+		la, _ := la.(*IPAddr)
+		c, err = dialIP(net, la, ra, deadline)
+	case *UnixAddr:
+		la, _ := la.(*UnixAddr)
+		c, err = dialUnix(net, la, ra, deadline)
+	default:
+		return nil, &OpError{Op: "dial", Net: net, Addr: ra, Err: &AddrError{Err: "unexpected address type", Addr: addr}}
+	}
+	if err != nil {
+		return nil, err // c is non-nil interface containing nil pointer
+	}
+	return c, nil
+}
+
+// Listen announces on the local network address laddr.
+// The network net must be a stream-oriented network: "tcp", "tcp4",
+// "tcp6", "unix" or "unixpacket".
+// See Dial for the syntax of laddr.
+func Listen(net, laddr string) (Listener, error) {
+	la, err := resolveAddr("listen", net, laddr, noDeadline)
+	if err != nil {
+		return nil, &OpError{Op: "listen", Net: net, Addr: nil, Err: err}
+	}
+	var l Listener
+	switch la := la.toAddr().(type) {
+	case *TCPAddr:
+		l, err = ListenTCP(net, la)
+	case *UnixAddr:
+		l, err = ListenUnix(net, la)
+	default:
+		return nil, &OpError{Op: "listen", Net: net, Addr: la, Err: &AddrError{Err: "unexpected address type", Addr: laddr}}
+	}
+	if err != nil {
+		return nil, err // l is non-nil interface containing nil pointer
+	}
+	return l, nil
+}
+
+// ListenPacket announces on the local network address laddr.
+// The network net must be a packet-oriented network: "udp", "udp4",
+// "udp6", "ip", "ip4", "ip6" or "unixgram".
+// See Dial for the syntax of laddr.
+func ListenPacket(net, laddr string) (PacketConn, error) {
+	la, err := resolveAddr("listen", net, laddr, noDeadline)
+	if err != nil {
+		return nil, &OpError{Op: "listen", Net: net, Addr: nil, Err: err}
+	}
+	var l PacketConn
+	switch la := la.toAddr().(type) {
+	case *UDPAddr:
+		l, err = ListenUDP(net, la)
+	case *IPAddr:
+		l, err = ListenIP(net, la)
+	case *UnixAddr:
+		l, err = ListenUnixgram(net, la)
+	default:
+		return nil, &OpError{Op: "listen", Net: net, Addr: la, Err: &AddrError{Err: "unexpected address type", Addr: laddr}}
+	}
+	if err != nil {
+		return nil, err // l is non-nil interface containing nil pointer
+	}
+	return l, nil
+}
diff --git a/src/net/dial_gen.go b/src/net/dial_gen.go
new file mode 100644
index 000000000..ada623300
--- /dev/null
+++ b/src/net/dial_gen.go
@@ -0,0 +1,46 @@
+// Copyright 2012 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build windows plan9
+
+package net
+
+import (
+	"time"
+)
+
+var testingIssue5349 bool // used during tests
+
+// dialChannel is the simple pure-Go implementation of dial, still
+// used on operating systems where the deadline hasn't been pushed
+// down into the pollserver. (Plan 9 and some old versions of Windows)
+func dialChannel(net string, ra Addr, dialer func(time.Time) (Conn, error), deadline time.Time) (Conn, error) {
+	var timeout time.Duration
+	if !deadline.IsZero() {
+		timeout = deadline.Sub(time.Now())
+	}
+	if timeout <= 0 {
+		return dialer(noDeadline)
+	}
+	t := time.NewTimer(timeout)
+	defer t.Stop()
+	type racer struct {
+		Conn
+		error
+	}
+	ch := make(chan racer, 1)
+	go func() {
+		if testingIssue5349 {
+			time.Sleep(time.Millisecond)
+		}
+		c, err := dialer(noDeadline)
+		ch <- racer{c, err}
+	}()
+	select {
+	case <-t.C:
+		return nil, &OpError{Op: "dial", Net: net, Addr: ra, Err: errTimeout}
+	case racer := <-ch:
+		return racer.Conn, racer.error
+	}
+}
diff --git a/src/net/dial_gen_test.go b/src/net/dial_gen_test.go
new file mode 100644
index 000000000..c857acd06
--- /dev/null
+++ b/src/net/dial_gen_test.go
@@ -0,0 +1,11 @@
+// Copyright 2013 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build windows plan9
+
+package net
+
+func init() {
+	testingIssue5349 = true
+}
diff --git a/src/net/dial_test.go b/src/net/dial_test.go
new file mode 100644
index 000000000..c5c3236cc
--- /dev/null
+++ b/src/net/dial_test.go
@@ -0,0 +1,536 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package net
+
+import (
+	"bytes"
+	"flag"
+	"fmt"
+	"io"
+	"os"
+	"os/exec"
+	"reflect"
+	"regexp"
+	"runtime"
+	"strconv"
+	"sync"
+	"testing"
+	"time"
+)
+
+func newLocalListener(t *testing.T) Listener {
+	ln, err := Listen("tcp", "127.0.0.1:0")
+	if err != nil {
+		ln, err = Listen("tcp6", "[::1]:0")
+	}
+	if err != nil {
+		t.Fatal(err)
+	}
+	return ln
+}
+
+func TestDialTimeout(t *testing.T) {
+	origBacklog := listenerBacklog
+	defer func() {
+		listenerBacklog = origBacklog
+	}()
+	listenerBacklog = 1
+
+	ln := newLocalListener(t)
+	defer ln.Close()
+
+	errc := make(chan error)
+
+	numConns := listenerBacklog + 100
+
+	// TODO(bradfitz): It's hard to test this in a portable
+	// way. This is unfortunate, but works for now.
+	switch runtime.GOOS {
+	case "linux":
+		// The kernel will start accepting TCP connections before userspace
+		// gets a chance to not accept them, so fire off a bunch to fill up
+		// the kernel's backlog.  Then we test we get a failure after that.
+		for i := 0; i < numConns; i++ {
+			go func() {
+				_, err := DialTimeout("tcp", ln.Addr().String(), 200*time.Millisecond)
+				errc <- err
+			}()
+		}
+	case "darwin", "plan9", "windows":
+		// At least OS X 10.7 seems to accept any number of
+		// connections, ignoring listen's backlog, so resort
+		// to connecting to a hopefully-dead 127/8 address.
+		// Same for windows.
+		//
+		// Use an IANA reserved port (49151) instead of 80, because
+		// on our 386 builder, this Dial succeeds, connecting
+		// to an IIS web server somewhere.  The data center
+		// or VM or firewall must be stealing the TCP connection.
+		//
+		// IANA Service Name and Transport Protocol Port Number Registry
+		// <http://www.iana.org/assignments/service-names-port-numbers/service-names-port-numbers.xml>
+		go func() {
+			c, err := DialTimeout("tcp", "127.0.71.111:49151", 200*time.Millisecond)
+			if err == nil {
+				err = fmt.Errorf("unexpected: connected to %s!", c.RemoteAddr())
+				c.Close()
+			}
+			errc <- err
+		}()
+	default:
+		// TODO(bradfitz):
+		// OpenBSD may have a reject route to 127/8 except 127.0.0.1/32
+		// by default. FreeBSD likely works, but is untested.
+		// TODO(rsc):
+		// The timeout never happens on Windows.  Why?  Issue 3016.
+		t.Skipf("skipping test on %q; untested.", runtime.GOOS)
+	}
+
+	connected := 0
+	for {
+		select {
+		case <-time.After(15 * time.Second):
+			t.Fatal("too slow")
+		case err := <-errc:
+			if err == nil {
+				connected++
+				if connected == numConns {
+					t.Fatal("all connections connected; expected some to time out")
+				}
+			} else {
+				terr, ok := err.(timeout)
+				if !ok {
+					t.Fatalf("got error %q; want error with timeout interface", err)
+				}
+				if !terr.Timeout() {
+					t.Fatalf("got error %q; not a timeout", err)
+				}
+				// Pass. We saw a timeout error.
+				return
+			}
+		}
+	}
+}
+
+func TestSelfConnect(t *testing.T) {
+	if runtime.GOOS == "windows" {
+		// TODO(brainman): do not know why it hangs.
+		t.Skip("skipping known-broken test on windows")
+	}
+	// Test that Dial does not honor self-connects.
+	// See the comment in DialTCP.
+
+	// Find a port that would be used as a local address.
+	l, err := Listen("tcp", "127.0.0.1:0")
+	if err != nil {
+		t.Fatal(err)
+	}
+	c, err := Dial("tcp", l.Addr().String())
+	if err != nil {
+		t.Fatal(err)
+	}
+	addr := c.LocalAddr().String()
+	c.Close()
+	l.Close()
+
+	// Try to connect to that address repeatedly.
+	n := 100000
+	if testing.Short() {
+		n = 1000
+	}
+	switch runtime.GOOS {
+	case "darwin", "dragonfly", "freebsd", "netbsd", "openbsd", "plan9", "solaris", "windows":
+		// Non-Linux systems take a long time to figure
+		// out that there is nothing listening on localhost.
+		n = 100
+	}
+	for i := 0; i < n; i++ {
+		c, err := DialTimeout("tcp", addr, time.Millisecond)
+		if err == nil {
+			c.Close()
+			t.Errorf("#%d: Dial %q succeeded", i, addr)
+		}
+	}
+}
+
+var runErrorTest = flag.Bool("run_error_test", false, "let TestDialError check for dns errors")
+
+type DialErrorTest struct {
+	Net     string
+	Raddr   string
+	Pattern string
+}
+
+var dialErrorTests = []DialErrorTest{
+	{
+		"datakit", "mh/astro/r70",
+		"dial datakit mh/astro/r70: unknown network datakit",
+	},
+	{
+		"tcp", "127.0.0.1:☺",
+		"dial tcp 127.0.0.1:☺: unknown port tcp/☺",
+	},
+	{
+		"tcp", "no-such-name.google.com.:80",
+		"dial tcp no-such-name.google.com.:80: lookup no-such-name.google.com.( on .*)?: no (.*)",
+	},
+	{
+		"tcp", "no-such-name.no-such-top-level-domain.:80",
+		"dial tcp no-such-name.no-such-top-level-domain.:80: lookup no-such-name.no-such-top-level-domain.( on .*)?: no (.*)",
+	},
+	{
+		"tcp", "no-such-name:80",
+		`dial tcp no-such-name:80: lookup no-such-name\.(.*\.)?( on .*)?: no (.*)`,
+	},
+	{
+		"tcp", "mh/astro/r70:http",
+		"dial tcp mh/astro/r70:http: lookup mh/astro/r70: invalid domain name",
+	},
+	{
+		"unix", "/etc/file-not-found",
+		"dial unix /etc/file-not-found: no such file or directory",
+	},
+	{
+		"unix", "/etc/",
+		"dial unix /etc/: (permission denied|socket operation on non-socket|connection refused)",
+	},
+	{
+		"unixpacket", "/etc/file-not-found",
+		"dial unixpacket /etc/file-not-found: no such file or directory",
+	},
+	{
+		"unixpacket", "/etc/",
+		"dial unixpacket /etc/: (permission denied|socket operation on non-socket|connection refused)",
+	},
+}
+
+var duplicateErrorPattern = `dial (.*) dial (.*)`
+
+func TestDialError(t *testing.T) {
+	if !*runErrorTest {
+		t.Logf("test disabled; use -run_error_test to enable")
+		return
+	}
+	for i, tt := range dialErrorTests {
+		c, err := Dial(tt.Net, tt.Raddr)
+		if c != nil {
+			c.Close()
+		}
+		if err == nil {
+			t.Errorf("#%d: nil error, want match for %#q", i, tt.Pattern)
+			continue
+		}
+		s := err.Error()
+		match, _ := regexp.MatchString(tt.Pattern, s)
+		if !match {
+			t.Errorf("#%d: %q, want match for %#q", i, s, tt.Pattern)
+		}
+		match, _ = regexp.MatchString(duplicateErrorPattern, s)
+		if match {
+			t.Errorf("#%d: %q, duplicate error return from Dial", i, s)
+		}
+	}
+}
+
+var invalidDialAndListenArgTests = []struct {
+	net  string
+	addr string
+	err  error
+}{
+	{"foo", "bar", &OpError{Op: "dial", Net: "foo", Addr: nil, Err: UnknownNetworkError("foo")}},
+	{"baz", "", &OpError{Op: "listen", Net: "baz", Addr: nil, Err: UnknownNetworkError("baz")}},
+	{"tcp", "", &OpError{Op: "dial", Net: "tcp", Addr: nil, Err: errMissingAddress}},
+}
+
+func TestInvalidDialAndListenArgs(t *testing.T) {
+	for _, tt := range invalidDialAndListenArgTests {
+		var err error
+		switch tt.err.(*OpError).Op {
+		case "dial":
+			_, err = Dial(tt.net, tt.addr)
+		case "listen":
+			_, err = Listen(tt.net, tt.addr)
+		}
+		if !reflect.DeepEqual(tt.err, err) {
+			t.Fatalf("got %#v; expected %#v", err, tt.err)
+		}
+	}
+}
+
+func TestDialTimeoutFDLeak(t *testing.T) {
+	if runtime.GOOS != "linux" {
+		// TODO(bradfitz): test on other platforms
+		t.Skipf("skipping test on %q", runtime.GOOS)
+	}
+
+	ln := newLocalListener(t)
+	defer ln.Close()
+
+	type connErr struct {
+		conn Conn
+		err  error
+	}
+	dials := listenerBacklog + 100
+	// used to be listenerBacklog + 5, but was found to be unreliable, issue 4384.
+	maxGoodConnect := listenerBacklog + runtime.NumCPU()*10
+	resc := make(chan connErr)
+	for i := 0; i < dials; i++ {
+		go func() {
+			conn, err := DialTimeout("tcp", ln.Addr().String(), 500*time.Millisecond)
+			resc <- connErr{conn, err}
+		}()
+	}
+
+	var firstErr string
+	var ngood int
+	var toClose []io.Closer
+	for i := 0; i < dials; i++ {
+		ce := <-resc
+		if ce.err == nil {
+			ngood++
+			if ngood > maxGoodConnect {
+				t.Errorf("%d good connects; expected at most %d", ngood, maxGoodConnect)
+			}
+			toClose = append(toClose, ce.conn)
+			continue
+		}
+		err := ce.err
+		if firstErr == "" {
+			firstErr = err.Error()
+		} else if err.Error() != firstErr {
+			t.Fatalf("inconsistent error messages: first was %q, then later %q", firstErr, err)
+		}
+	}
+	for _, c := range toClose {
+		c.Close()
+	}
+	for i := 0; i < 100; i++ {
+		if got := numFD(); got < dials {
+			// Test passes.
+			return
+		}
+		time.Sleep(10 * time.Millisecond)
+	}
+	if got := numFD(); got >= dials {
+		t.Errorf("num fds after %d timeouts = %d; want <%d", dials, got, dials)
+	}
+}
+
+func numTCP() (ntcp, nopen, nclose int, err error) {
+	lsof, err := exec.Command("lsof", "-n", "-p", strconv.Itoa(os.Getpid())).Output()
+	if err != nil {
+		return 0, 0, 0, err
+	}
+	ntcp += bytes.Count(lsof, []byte("TCP"))
+	for _, state := range []string{"LISTEN", "SYN_SENT", "SYN_RECEIVED", "ESTABLISHED"} {
+		nopen += bytes.Count(lsof, []byte(state))
+	}
+	for _, state := range []string{"CLOSED", "CLOSE_WAIT", "LAST_ACK", "FIN_WAIT_1", "FIN_WAIT_2", "CLOSING", "TIME_WAIT"} {
+		nclose += bytes.Count(lsof, []byte(state))
+	}
+	return ntcp, nopen, nclose, nil
+}
+
+func TestDialMultiFDLeak(t *testing.T) {
+	if !supportsIPv4 || !supportsIPv6 {
+		t.Skip("neither ipv4 nor ipv6 is supported")
+	}
+
+	halfDeadServer := func(dss *dualStackServer, ln Listener) {
+		for {
+			if c, err := ln.Accept(); err != nil {
+				return
+			} else {
+				// It just keeps established
+				// connections like a half-dead server
+				// does.
+				dss.putConn(c)
+			}
+		}
+	}
+	dss, err := newDualStackServer([]streamListener{
+		{net: "tcp4", addr: "127.0.0.1"},
+		{net: "tcp6", addr: "[::1]"},
+	})
+	if err != nil {
+		t.Fatalf("newDualStackServer failed: %v", err)
+	}
+	defer dss.teardown()
+	if err := dss.buildup(halfDeadServer); err != nil {
+		t.Fatalf("dualStackServer.buildup failed: %v", err)
+	}
+
+	_, before, _, err := numTCP()
+	if err != nil {
+		t.Skipf("skipping test; error finding or running lsof: %v", err)
+	}
+
+	var wg sync.WaitGroup
+	portnum, _, _ := dtoi(dss.port, 0)
+	ras := addrList{
+		// Losers that will fail to connect, see RFC 6890.
+		&TCPAddr{IP: IPv4(198, 18, 0, 254), Port: portnum},
+		&TCPAddr{IP: ParseIP("2001:2::254"), Port: portnum},
+
+		// Winner candidates of this race.
+		&TCPAddr{IP: IPv4(127, 0, 0, 1), Port: portnum},
+		&TCPAddr{IP: IPv6loopback, Port: portnum},
+
+		// Losers that will have established connections.
+		&TCPAddr{IP: IPv4(127, 0, 0, 1), Port: portnum},
+		&TCPAddr{IP: IPv6loopback, Port: portnum},
+	}
+	const T1 = 10 * time.Millisecond
+	const T2 = 2 * T1
+	const N = 10
+	for i := 0; i < N; i++ {
+		wg.Add(1)
+		go func() {
+			defer wg.Done()
+			if c, err := dialMulti("tcp", "fast failover test", nil, ras, time.Now().Add(T1)); err == nil {
+				c.Close()
+			}
+		}()
+	}
+	wg.Wait()
+	time.Sleep(T2)
+
+	ntcp, after, nclose, err := numTCP()
+	if err != nil {
+		t.Skipf("skipping test; error finding or running lsof: %v", err)
+	}
+	t.Logf("tcp sessions: %v, open sessions: %v, closing sessions: %v", ntcp, after, nclose)
+
+	if after != before {
+		t.Fatalf("got %v open sessions; expected %v", after, before)
+	}
+}
+
+func numFD() int {
+	if runtime.GOOS == "linux" {
+		f, err := os.Open("/proc/self/fd")
+		if err != nil {
+			panic(err)
+		}
+		defer f.Close()
+		names, err := f.Readdirnames(0)
+		if err != nil {
+			panic(err)
+		}
+		return len(names)
+	}
+	// All tests using this should be skipped anyway, but:
+	panic("numFDs not implemented on " + runtime.GOOS)
+}
+
+func TestDialer(t *testing.T) {
+	ln, err := Listen("tcp4", "127.0.0.1:0")
+	if err != nil {
+		t.Fatalf("Listen failed: %v", err)
+	}
+	defer ln.Close()
+	ch := make(chan error, 1)
+	go func() {
+		c, err := ln.Accept()
+		if err != nil {
+			ch <- fmt.Errorf("Accept failed: %v", err)
+			return
+		}
+		defer c.Close()
+		ch <- nil
+	}()
+
+	laddr, err := ResolveTCPAddr("tcp4", "127.0.0.1:0")
+	if err != nil {
+		t.Fatalf("ResolveTCPAddr failed: %v", err)
+	}
+	d := &Dialer{LocalAddr: laddr}
+	c, err := d.Dial("tcp4", ln.Addr().String())
+	if err != nil {
+		t.Fatalf("Dial failed: %v", err)
+	}
+	defer c.Close()
+	c.Read(make([]byte, 1))
+	err = <-ch
+	if err != nil {
+		t.Error(err)
+	}
+}
+
+func TestDialDualStackLocalhost(t *testing.T) {
+	if ips, err := LookupIP("localhost"); err != nil {
+		t.Fatalf("LookupIP failed: %v", err)
+	} else if len(ips) < 2 || !supportsIPv4 || !supportsIPv6 {
+		t.Skip("localhost doesn't have a pair of different address family IP addresses")
+	}
+
+	touchAndByeServer := func(dss *dualStackServer, ln Listener) {
+		for {
+			if c, err := ln.Accept(); err != nil {
+				return
+			} else {
+				c.Close()
+			}
+		}
+	}
+	dss, err := newDualStackServer([]streamListener{
+		{net: "tcp4", addr: "127.0.0.1"},
+		{net: "tcp6", addr: "[::1]"},
+	})
+	if err != nil {
+		t.Fatalf("newDualStackServer failed: %v", err)
+	}
+	defer dss.teardown()
+	if err := dss.buildup(touchAndByeServer); err != nil {
+		t.Fatalf("dualStackServer.buildup failed: %v", err)
+	}
+
+	d := &Dialer{DualStack: true}
+	for range dss.lns {
+		if c, err := d.Dial("tcp", "localhost:"+dss.port); err != nil {
+			t.Errorf("Dial failed: %v", err)
+		} else {
+			if addr := c.LocalAddr().(*TCPAddr); addr.IP.To4() != nil {
+				dss.teardownNetwork("tcp4")
+			} else if addr.IP.To16() != nil && addr.IP.To4() == nil {
+				dss.teardownNetwork("tcp6")
+			}
+			c.Close()
+		}
+	}
+}
+
+func TestDialerKeepAlive(t *testing.T) {
+	ln := newLocalListener(t)
+	defer ln.Close()
+	defer func() {
+		testHookSetKeepAlive = func() {}
+	}()
+	go func() {
+		for {
+			c, err := ln.Accept()
+			if err != nil {
+				return
+			}
+			c.Close()
+		}
+	}()
+	for _, keepAlive := range []bool{false, true} {
+		got := false
+		testHookSetKeepAlive = func() { got = true }
+		var d Dialer
+		if keepAlive {
+			d.KeepAlive = 30 * time.Second
+		}
+		c, err := d.Dial("tcp", ln.Addr().String())
+		if err != nil {
+			t.Fatal(err)
+		}
+		c.Close()
+		if got != keepAlive {
+			t.Errorf("Dialer.KeepAlive = %v: SetKeepAlive called = %v, want %v", d.KeepAlive, got, !got)
+		}
+	}
+}
diff --git a/src/net/dialgoogle_test.go b/src/net/dialgoogle_test.go
new file mode 100644
index 000000000..df5895afa
--- /dev/null
+++ b/src/net/dialgoogle_test.go
@@ -0,0 +1,209 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package net
+
+import (
+	"flag"
+	"fmt"
+	"io"
+	"strings"
+	"syscall"
+	"testing"
+)
+
+// If an IPv6 tunnel is running, we can try dialing a real IPv6 address.
+var testIPv6 = flag.Bool("ipv6", false, "assume ipv6 tunnel is present")
+
+func TestResolveGoogle(t *testing.T) {
+	if testing.Short() || !*testExternal {
+		t.Skip("skipping test to avoid external network")
+	}
+
+	for _, network := range []string{"tcp", "tcp4", "tcp6"} {
+		addr, err := ResolveTCPAddr(network, "www.google.com:http")
+		if err != nil {
+			if (network == "tcp" || network == "tcp4") && !supportsIPv4 {
+				t.Logf("ipv4 is not supported: %v", err)
+			} else if network == "tcp6" && !supportsIPv6 {
+				t.Logf("ipv6 is not supported: %v", err)
+			} else {
+				t.Errorf("ResolveTCPAddr failed: %v", err)
+			}
+			continue
+		}
+		if (network == "tcp" || network == "tcp4") && addr.IP.To4() == nil {
+			t.Errorf("got %v; expected an IPv4 address on %v", addr, network)
+		} else if network == "tcp6" && (addr.IP.To16() == nil || addr.IP.To4() != nil) {
+			t.Errorf("got %v; expected an IPv6 address on %v", addr, network)
+		}
+	}
+}
+
+func TestDialGoogle(t *testing.T) {
+	if testing.Short() || !*testExternal {
+		t.Skip("skipping test to avoid external network")
+	}
+
+	d := &Dialer{DualStack: true}
+	for _, network := range []string{"tcp", "tcp4", "tcp6"} {
+		if network == "tcp" && !supportsIPv4 && !supportsIPv6 {
+			t.Logf("skipping test; both ipv4 and ipv6 are not supported")
+			continue
+		} else if network == "tcp4" && !supportsIPv4 {
+			t.Logf("skipping test; ipv4 is not supported")
+			continue
+		} else if network == "tcp6" && !supportsIPv6 {
+			t.Logf("skipping test; ipv6 is not supported")
+			continue
+		} else if network == "tcp6" && !*testIPv6 {
+			t.Logf("test disabled; use -ipv6 to enable")
+			continue
+		}
+		if c, err := d.Dial(network, "www.google.com:http"); err != nil {
+			t.Errorf("Dial failed: %v", err)
+		} else {
+			c.Close()
+		}
+	}
+}
+
+// fd is already connected to the destination, port 80.
+// Run an HTTP request to fetch the appropriate page.
+func fetchGoogle(t *testing.T, fd Conn, network, addr string) {
+	req := []byte("GET /robots.txt HTTP/1.0\r\nHost: www.google.com\r\n\r\n")
+	n, err := fd.Write(req)
+
+	buf := make([]byte, 1000)
+	n, err = io.ReadFull(fd, buf)
+
+	if n < 1000 {
+		t.Errorf("fetchGoogle: short HTTP read from %s %s - %v", network, addr, err)
+		return
+	}
+}
+
+func doDial(t *testing.T, network, addr string) {
+	fd, err := Dial(network, addr)
+	if err != nil {
+		t.Errorf("Dial(%q, %q, %q) = _, %v", network, "", addr, err)
+		return
+	}
+	fetchGoogle(t, fd, network, addr)
+	fd.Close()
+}
+
+var googleaddrsipv4 = []string{
+	"%d.%d.%d.%d:80",
+	"www.google.com:80",
+	"%d.%d.%d.%d:http",
+	"www.google.com:http",
+	"%03d.%03d.%03d.%03d:0080",
+	"[::ffff:%d.%d.%d.%d]:80",
+	"[::ffff:%02x%02x:%02x%02x]:80",
+	"[0:0:0:0:0000:ffff:%d.%d.%d.%d]:80",
+	"[0:0:0:0:000000:ffff:%d.%d.%d.%d]:80",
+	"[0:0:0:0::ffff:%d.%d.%d.%d]:80",
+}
+
+func TestDialGoogleIPv4(t *testing.T) {
+	if testing.Short() || !*testExternal {
+		t.Skip("skipping test to avoid external network")
+	}
+
+	// Insert an actual IPv4 address for google.com
+	// into the table.
+	addrs, err := LookupIP("www.google.com")
+	if err != nil {
+		t.Fatalf("lookup www.google.com: %v", err)
+	}
+	var ip IP
+	for _, addr := range addrs {
+		if x := addr.To4(); x != nil {
+			ip = x
+			break
+		}
+	}
+	if ip == nil {
+		t.Fatalf("no IPv4 addresses for www.google.com")
+	}
+
+	for i, s := range googleaddrsipv4 {
+		if strings.Contains(s, "%") {
+			googleaddrsipv4[i] = fmt.Sprintf(s, ip[0], ip[1], ip[2], ip[3])
+		}
+	}
+
+	for i := 0; i < len(googleaddrsipv4); i++ {
+		addr := googleaddrsipv4[i]
+		if addr == "" {
+			continue
+		}
+		t.Logf("-- %s --", addr)
+		doDial(t, "tcp", addr)
+		if addr[0] != '[' {
+			doDial(t, "tcp4", addr)
+			if supportsIPv6 {
+				// make sure syscall.SocketDisableIPv6 flag works.
+				syscall.SocketDisableIPv6 = true
+				doDial(t, "tcp", addr)
+				doDial(t, "tcp4", addr)
+				syscall.SocketDisableIPv6 = false
+			}
+		}
+	}
+}
+
+var googleaddrsipv6 = []string{
+	"[%02x%02x:%02x%02x:%02x%02x:%02x%02x:%02x%02x:%02x%02x:%02x%02x:%02x%02x]:80",
+	"ipv6.google.com:80",
+	"[%02x%02x:%02x%02x:%02x%02x:%02x%02x:%02x%02x:%02x%02x:%02x%02x:%02x%02x]:http",
+	"ipv6.google.com:http",
+}
+
+func TestDialGoogleIPv6(t *testing.T) {
+	if testing.Short() || !*testExternal {
+		t.Skip("skipping test to avoid external network")
+	}
+	// Only run tcp6 if the kernel will take it.
+	if !supportsIPv6 {
+		t.Skip("skipping test; ipv6 is not supported")
+	}
+	if !*testIPv6 {
+		t.Skip("test disabled; use -ipv6 to enable")
+	}
+
+	// Insert an actual IPv6 address for ipv6.google.com
+	// into the table.
+	addrs, err := LookupIP("ipv6.google.com")
+	if err != nil {
+		t.Fatalf("lookup ipv6.google.com: %v", err)
+	}
+	var ip IP
+	for _, addr := range addrs {
+		if x := addr.To16(); x != nil {
+			ip = x
+			break
+		}
+	}
+	if ip == nil {
+		t.Fatalf("no IPv6 addresses for ipv6.google.com")
+	}
+
+	for i, s := range googleaddrsipv6 {
+		if strings.Contains(s, "%") {
+			googleaddrsipv6[i] = fmt.Sprintf(s, ip[0], ip[1], ip[2], ip[3], ip[4], ip[5], ip[6], ip[7], ip[8], ip[9], ip[10], ip[11], ip[12], ip[13], ip[14], ip[15])
+		}
+	}
+
+	for i := 0; i < len(googleaddrsipv6); i++ {
+		addr := googleaddrsipv6[i]
+		if addr == "" {
+			continue
+		}
+		t.Logf("-- %s --", addr)
+		doDial(t, "tcp", addr)
+		doDial(t, "tcp6", addr)
+	}
+}
diff --git a/src/net/dnsclient.go b/src/net/dnsclient.go
new file mode 100644
index 000000000..e8014e4ff
--- /dev/null
+++ b/src/net/dnsclient.go
@@ -0,0 +1,249 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package net
+
+import (
+	"math/rand"
+	"sort"
+)
+
+// DNSError represents a DNS lookup error.
+type DNSError struct {
+	Err       string // description of the error
+	Name      string // name looked for
+	Server    string // server used
+	IsTimeout bool
+}
+
+func (e *DNSError) Error() string {
+	if e == nil {
+		return "<nil>"
+	}
+	s := "lookup " + e.Name
+	if e.Server != "" {
+		s += " on " + e.Server
+	}
+	s += ": " + e.Err
+	return s
+}
+
+func (e *DNSError) Timeout() bool   { return e.IsTimeout }
+func (e *DNSError) Temporary() bool { return e.IsTimeout }
+
+const noSuchHost = "no such host"
+
+// reverseaddr returns the in-addr.arpa. or ip6.arpa. hostname of the IP
+// address addr suitable for rDNS (PTR) record lookup or an error if it fails
+// to parse the IP address.
+func reverseaddr(addr string) (arpa string, err error) {
+	ip := ParseIP(addr)
+	if ip == nil {
+		return "", &DNSError{Err: "unrecognized address", Name: addr}
+	}
+	if ip.To4() != nil {
+		return itoa(int(ip[15])) + "." + itoa(int(ip[14])) + "." + itoa(int(ip[13])) + "." +
+			itoa(int(ip[12])) + ".in-addr.arpa.", nil
+	}
+	// Must be IPv6
+	buf := make([]byte, 0, len(ip)*4+len("ip6.arpa."))
+	// Add it, in reverse, to the buffer
+	for i := len(ip) - 1; i >= 0; i-- {
+		v := ip[i]
+		buf = append(buf, hexDigit[v&0xF])
+		buf = append(buf, '.')
+		buf = append(buf, hexDigit[v>>4])
+		buf = append(buf, '.')
+	}
+	// Append "ip6.arpa." and return (buf already has the final .)
+	buf = append(buf, "ip6.arpa."...)
+	return string(buf), nil
+}
+
+// Find answer for name in dns message.
+// On return, if err == nil, addrs != nil.
+func answer(name, server string, dns *dnsMsg, qtype uint16) (cname string, addrs []dnsRR, err error) {
+	addrs = make([]dnsRR, 0, len(dns.answer))
+
+	if dns.rcode == dnsRcodeNameError && dns.recursion_available {
+		return "", nil, &DNSError{Err: noSuchHost, Name: name}
+	}
+	if dns.rcode != dnsRcodeSuccess {
+		// None of the error codes make sense
+		// for the query we sent.  If we didn't get
+		// a name error and we didn't get success,
+		// the server is behaving incorrectly.
+		return "", nil, &DNSError{Err: "server misbehaving", Name: name, Server: server}
+	}
+
+	// Look for the name.
+	// Presotto says it's okay to assume that servers listed in
+	// /etc/resolv.conf are recursive resolvers.
+	// We asked for recursion, so it should have included
+	// all the answers we need in this one packet.
+Cname:
+	for cnameloop := 0; cnameloop < 10; cnameloop++ {
+		addrs = addrs[0:0]
+		for _, rr := range dns.answer {
+			if _, justHeader := rr.(*dnsRR_Header); justHeader {
+				// Corrupt record: we only have a
+				// header. That header might say it's
+				// of type qtype, but we don't
+				// actually have it. Skip.
+				continue
+			}
+			h := rr.Header()
+			if h.Class == dnsClassINET && h.Name == name {
+				switch h.Rrtype {
+				case qtype:
+					addrs = append(addrs, rr)
+				case dnsTypeCNAME:
+					// redirect to cname
+					name = rr.(*dnsRR_CNAME).Cname
+					continue Cname
+				}
+			}
+		}
+		if len(addrs) == 0 {
+			return "", nil, &DNSError{Err: noSuchHost, Name: name, Server: server}
+		}
+		return name, addrs, nil
+	}
+
+	return "", nil, &DNSError{Err: "too many redirects", Name: name, Server: server}
+}
+
+func isDomainName(s string) bool {
+	// See RFC 1035, RFC 3696.
+	if len(s) == 0 {
+		return false
+	}
+	if len(s) > 255 {
+		return false
+	}
+
+	last := byte('.')
+	ok := false // Ok once we've seen a letter.
+	partlen := 0
+	for i := 0; i < len(s); i++ {
+		c := s[i]
+		switch {
+		default:
+			return false
+		case 'a' <= c && c <= 'z' || 'A' <= c && c <= 'Z' || c == '_':
+			ok = true
+			partlen++
+		case '0' <= c && c <= '9':
+			// fine
+			partlen++
+		case c == '-':
+			// Byte before dash cannot be dot.
+			if last == '.' {
+				return false
+			}
+			partlen++
+		case c == '.':
+			// Byte before dot cannot be dot, dash.
+			if last == '.' || last == '-' {
+				return false
+			}
+			if partlen > 63 || partlen == 0 {
+				return false
+			}
+			partlen = 0
+		}
+		last = c
+	}
+	if last == '-' || partlen > 63 {
+		return false
+	}
+
+	return ok
+}
+
+// An SRV represents a single DNS SRV record.
+type SRV struct {
+	Target   string
+	Port     uint16
+	Priority uint16
+	Weight   uint16
+}
+
+// byPriorityWeight sorts SRV records by ascending priority and weight.
+type byPriorityWeight []*SRV
+
+func (s byPriorityWeight) Len() int { return len(s) }
+
+func (s byPriorityWeight) Swap(i, j int) { s[i], s[j] = s[j], s[i] }
+
+func (s byPriorityWeight) Less(i, j int) bool {
+	return s[i].Priority < s[j].Priority ||
+		(s[i].Priority == s[j].Priority && s[i].Weight < s[j].Weight)
+}
+
+// shuffleByWeight shuffles SRV records by weight using the algorithm
+// described in RFC 2782.
+func (addrs byPriorityWeight) shuffleByWeight() {
+	sum := 0
+	for _, addr := range addrs {
+		sum += int(addr.Weight)
+	}
+	for sum > 0 && len(addrs) > 1 {
+		s := 0
+		n := rand.Intn(sum)
+		for i := range addrs {
+			s += int(addrs[i].Weight)
+			if s > n {
+				if i > 0 {
+					addrs[0], addrs[i] = addrs[i], addrs[0]
+				}
+				break
+			}
+		}
+		sum -= int(addrs[0].Weight)
+		addrs = addrs[1:]
+	}
+}
+
+// sort reorders SRV records as specified in RFC 2782.
+func (addrs byPriorityWeight) sort() {
+	sort.Sort(addrs)
+	i := 0
+	for j := 1; j < len(addrs); j++ {
+		if addrs[i].Priority != addrs[j].Priority {
+			addrs[i:j].shuffleByWeight()
+			i = j
+		}
+	}
+	addrs[i:].shuffleByWeight()
+}
+
+// An MX represents a single DNS MX record.
+type MX struct {
+	Host string
+	Pref uint16
+}
+
+// byPref implements sort.Interface to sort MX records by preference
+type byPref []*MX
+
+func (s byPref) Len() int { return len(s) }
+
+func (s byPref) Less(i, j int) bool { return s[i].Pref < s[j].Pref }
+
+func (s byPref) Swap(i, j int) { s[i], s[j] = s[j], s[i] }
+
+// sort reorders MX records as specified in RFC 5321.
+func (s byPref) sort() {
+	for i := range s {
+		j := rand.Intn(i + 1)
+		s[i], s[j] = s[j], s[i]
+	}
+	sort.Sort(s)
+}
+
+// An NS represents a single DNS NS record.
+type NS struct {
+	Host string
+}
diff --git a/src/net/dnsclient_test.go b/src/net/dnsclient_test.go
new file mode 100644
index 000000000..435eb3550
--- /dev/null
+++ b/src/net/dnsclient_test.go
@@ -0,0 +1,69 @@
+// Copyright 2014 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package net
+
+import (
+	"math/rand"
+	"testing"
+)
+
+func checkDistribution(t *testing.T, data []*SRV, margin float64) {
+	sum := 0
+	for _, srv := range data {
+		sum += int(srv.Weight)
+	}
+
+	results := make(map[string]int)
+
+	count := 1000
+	for j := 0; j < count; j++ {
+		d := make([]*SRV, len(data))
+		copy(d, data)
+		byPriorityWeight(d).shuffleByWeight()
+		key := d[0].Target
+		results[key] = results[key] + 1
+	}
+
+	actual := results[data[0].Target]
+	expected := float64(count) * float64(data[0].Weight) / float64(sum)
+	diff := float64(actual) - expected
+	t.Logf("actual: %v diff: %v e: %v m: %v", actual, diff, expected, margin)
+	if diff < 0 {
+		diff = -diff
+	}
+	if diff > (expected * margin) {
+		t.Errorf("missed target weight: expected %v, %v", expected, actual)
+	}
+}
+
+func testUniformity(t *testing.T, size int, margin float64) {
+	rand.Seed(1)
+	data := make([]*SRV, size)
+	for i := 0; i < size; i++ {
+		data[i] = &SRV{Target: string('a' + i), Weight: 1}
+	}
+	checkDistribution(t, data, margin)
+}
+
+func TestUniformity(t *testing.T) {
+	testUniformity(t, 2, 0.05)
+	testUniformity(t, 3, 0.10)
+	testUniformity(t, 10, 0.20)
+	testWeighting(t, 0.05)
+}
+
+func testWeighting(t *testing.T, margin float64) {
+	rand.Seed(1)
+	data := []*SRV{
+		{Target: "a", Weight: 60},
+		{Target: "b", Weight: 30},
+		{Target: "c", Weight: 10},
+	}
+	checkDistribution(t, data, margin)
+}
+
+func TestWeighting(t *testing.T) {
+	testWeighting(t, 0.05)
+}
diff --git a/src/net/dnsclient_unix.go b/src/net/dnsclient_unix.go
new file mode 100644
index 000000000..abe7da05c
--- /dev/null
+++ b/src/net/dnsclient_unix.go
@@ -0,0 +1,423 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build darwin dragonfly freebsd linux nacl netbsd openbsd solaris
+
+// DNS client: see RFC 1035.
+// Has to be linked into package net for Dial.
+
+// TODO(rsc):
+//	Could potentially handle many outstanding lookups faster.
+//	Could have a small cache.
+//	Random UDP source port (net.Dial should do that for us).
+//	Random request IDs.
+
+package net
+
+import (
+	"errors"
+	"io"
+	"math/rand"
+	"os"
+	"sync"
+	"time"
+)
+
+// A dnsConn represents a DNS transport endpoint.
+type dnsConn interface {
+	Conn
+
+	// readDNSResponse reads a DNS response message from the DNS
+	// transport endpoint and returns the received DNS response
+	// message.
+	readDNSResponse() (*dnsMsg, error)
+
+	// writeDNSQuery writes a DNS query message to the DNS
+	// connection endpoint.
+	writeDNSQuery(*dnsMsg) error
+}
+
+func (c *UDPConn) readDNSResponse() (*dnsMsg, error) {
+	b := make([]byte, 512) // see RFC 1035
+	n, err := c.Read(b)
+	if err != nil {
+		return nil, err
+	}
+	msg := &dnsMsg{}
+	if !msg.Unpack(b[:n]) {
+		return nil, errors.New("cannot unmarshal DNS message")
+	}
+	return msg, nil
+}
+
+func (c *UDPConn) writeDNSQuery(msg *dnsMsg) error {
+	b, ok := msg.Pack()
+	if !ok {
+		return errors.New("cannot marshal DNS message")
+	}
+	if _, err := c.Write(b); err != nil {
+		return err
+	}
+	return nil
+}
+
+func (c *TCPConn) readDNSResponse() (*dnsMsg, error) {
+	b := make([]byte, 1280) // 1280 is a reasonable initial size for IP over Ethernet, see RFC 4035
+	if _, err := io.ReadFull(c, b[:2]); err != nil {
+		return nil, err
+	}
+	l := int(b[0])<<8 | int(b[1])
+	if l > len(b) {
+		b = make([]byte, l)
+	}
+	n, err := io.ReadFull(c, b[:l])
+	if err != nil {
+		return nil, err
+	}
+	msg := &dnsMsg{}
+	if !msg.Unpack(b[:n]) {
+		return nil, errors.New("cannot unmarshal DNS message")
+	}
+	return msg, nil
+}
+
+func (c *TCPConn) writeDNSQuery(msg *dnsMsg) error {
+	b, ok := msg.Pack()
+	if !ok {
+		return errors.New("cannot marshal DNS message")
+	}
+	l := uint16(len(b))
+	b = append([]byte{byte(l >> 8), byte(l)}, b...)
+	if _, err := c.Write(b); err != nil {
+		return err
+	}
+	return nil
+}
+
+func (d *Dialer) dialDNS(network, server string) (dnsConn, error) {
+	switch network {
+	case "tcp", "tcp4", "tcp6", "udp", "udp4", "udp6":
+	default:
+		return nil, UnknownNetworkError(network)
+	}
+	// Calling Dial here is scary -- we have to be sure not to
+	// dial a name that will require a DNS lookup, or Dial will
+	// call back here to translate it. The DNS config parser has
+	// already checked that all the cfg.servers[i] are IP
+	// addresses, which Dial will use without a DNS lookup.
+	c, err := d.Dial(network, server)
+	if err != nil {
+		return nil, err
+	}
+	switch network {
+	case "tcp", "tcp4", "tcp6":
+		return c.(*TCPConn), nil
+	case "udp", "udp4", "udp6":
+		return c.(*UDPConn), nil
+	}
+	panic("unreachable")
+}
+
+// exchange sends a query on the connection and hopes for a response.
+func exchange(server, name string, qtype uint16, timeout time.Duration) (*dnsMsg, error) {
+	d := Dialer{Timeout: timeout}
+	out := dnsMsg{
+		dnsMsgHdr: dnsMsgHdr{
+			recursion_desired: true,
+		},
+		question: []dnsQuestion{
+			{name, qtype, dnsClassINET},
+		},
+	}
+	for _, network := range []string{"udp", "tcp"} {
+		c, err := d.dialDNS(network, server)
+		if err != nil {
+			return nil, err
+		}
+		defer c.Close()
+		if timeout > 0 {
+			c.SetDeadline(time.Now().Add(timeout))
+		}
+		out.id = uint16(rand.Int()) ^ uint16(time.Now().UnixNano())
+		if err := c.writeDNSQuery(&out); err != nil {
+			return nil, err
+		}
+		in, err := c.readDNSResponse()
+		if err != nil {
+			return nil, err
+		}
+		if in.id != out.id {
+			return nil, errors.New("DNS message ID mismatch")
+		}
+		if in.truncated { // see RFC 5966
+			continue
+		}
+		return in, nil
+	}
+	return nil, errors.New("no answer from DNS server")
+}
+
+// Do a lookup for a single name, which must be rooted
+// (otherwise answer will not find the answers).
+func tryOneName(cfg *dnsConfig, name string, qtype uint16) (string, []dnsRR, error) {
+	if len(cfg.servers) == 0 {
+		return "", nil, &DNSError{Err: "no DNS servers", Name: name}
+	}
+	if len(name) >= 256 {
+		return "", nil, &DNSError{Err: "DNS name too long", Name: name}
+	}
+	timeout := time.Duration(cfg.timeout) * time.Second
+	var lastErr error
+	for i := 0; i < cfg.attempts; i++ {
+		for _, server := range cfg.servers {
+			server = JoinHostPort(server, "53")
+			msg, err := exchange(server, name, qtype, timeout)
+			if err != nil {
+				lastErr = &DNSError{
+					Err:    err.Error(),
+					Name:   name,
+					Server: server,
+				}
+				if nerr, ok := err.(Error); ok && nerr.Timeout() {
+					lastErr.(*DNSError).IsTimeout = true
+				}
+				continue
+			}
+			cname, addrs, err := answer(name, server, msg, qtype)
+			if err == nil || err.(*DNSError).Err == noSuchHost {
+				return cname, addrs, err
+			}
+			lastErr = err
+		}
+	}
+	return "", nil, lastErr
+}
+
+func convertRR_A(records []dnsRR) []IP {
+	addrs := make([]IP, len(records))
+	for i, rr := range records {
+		a := rr.(*dnsRR_A).A
+		addrs[i] = IPv4(byte(a>>24), byte(a>>16), byte(a>>8), byte(a))
+	}
+	return addrs
+}
+
+func convertRR_AAAA(records []dnsRR) []IP {
+	addrs := make([]IP, len(records))
+	for i, rr := range records {
+		a := make(IP, IPv6len)
+		copy(a, rr.(*dnsRR_AAAA).AAAA[:])
+		addrs[i] = a
+	}
+	return addrs
+}
+
+var cfg struct {
+	ch        chan struct{}
+	mu        sync.RWMutex // protects dnsConfig and dnserr
+	dnsConfig *dnsConfig
+	dnserr    error
+}
+var onceLoadConfig sync.Once
+
+// Assume dns config file is /etc/resolv.conf here
+func loadDefaultConfig() {
+	loadConfig("/etc/resolv.conf", 5*time.Second, nil)
+}
+
+func loadConfig(resolvConfPath string, reloadTime time.Duration, quit <-chan chan struct{}) {
+	var mtime time.Time
+	cfg.ch = make(chan struct{}, 1)
+	if fi, err := os.Stat(resolvConfPath); err != nil {
+		cfg.dnserr = err
+	} else {
+		mtime = fi.ModTime()
+		cfg.dnsConfig, cfg.dnserr = dnsReadConfig(resolvConfPath)
+	}
+	go func() {
+		for {
+			time.Sleep(reloadTime)
+			select {
+			case qresp := <-quit:
+				qresp <- struct{}{}
+				return
+			case <-cfg.ch:
+			}
+
+			// In case of error, we keep the previous config
+			fi, err := os.Stat(resolvConfPath)
+			if err != nil {
+				continue
+			}
+			// If the resolv.conf mtime didn't change, do not reload
+			m := fi.ModTime()
+			if m.Equal(mtime) {
+				continue
+			}
+			mtime = m
+			// In case of error, we keep the previous config
+			ncfg, err := dnsReadConfig(resolvConfPath)
+			if err != nil || len(ncfg.servers) == 0 {
+				continue
+			}
+			cfg.mu.Lock()
+			cfg.dnsConfig = ncfg
+			cfg.dnserr = nil
+			cfg.mu.Unlock()
+		}
+	}()
+}
+
+func lookup(name string, qtype uint16) (cname string, addrs []dnsRR, err error) {
+	if !isDomainName(name) {
+		return name, nil, &DNSError{Err: "invalid domain name", Name: name}
+	}
+	onceLoadConfig.Do(loadDefaultConfig)
+
+	select {
+	case cfg.ch <- struct{}{}:
+	default:
+	}
+
+	cfg.mu.RLock()
+	defer cfg.mu.RUnlock()
+
+	if cfg.dnserr != nil || cfg.dnsConfig == nil {
+		err = cfg.dnserr
+		return
+	}
+	// If name is rooted (trailing dot) or has enough dots,
+	// try it by itself first.
+	rooted := len(name) > 0 && name[len(name)-1] == '.'
+	if rooted || count(name, '.') >= cfg.dnsConfig.ndots {
+		rname := name
+		if !rooted {
+			rname += "."
+		}
+		// Can try as ordinary name.
+		cname, addrs, err = tryOneName(cfg.dnsConfig, rname, qtype)
+		if rooted || err == nil {
+			return
+		}
+	}
+
+	// Otherwise, try suffixes.
+	for i := 0; i < len(cfg.dnsConfig.search); i++ {
+		rname := name + "." + cfg.dnsConfig.search[i]
+		if rname[len(rname)-1] != '.' {
+			rname += "."
+		}
+		cname, addrs, err = tryOneName(cfg.dnsConfig, rname, qtype)
+		if err == nil {
+			return
+		}
+	}
+
+	// Last ditch effort: try unsuffixed only if we haven't already,
+	// that is, name is not rooted and has less than ndots dots.
+	if count(name, '.') < cfg.dnsConfig.ndots {
+		cname, addrs, err = tryOneName(cfg.dnsConfig, name+".", qtype)
+		if err == nil {
+			return
+		}
+	}
+
+	if e, ok := err.(*DNSError); ok {
+		// Show original name passed to lookup, not suffixed one.
+		// In general we might have tried many suffixes; showing
+		// just one is misleading. See also golang.org/issue/6324.
+		e.Name = name
+	}
+	return
+}
+
+// goLookupHost is the native Go implementation of LookupHost.
+// Used only if cgoLookupHost refuses to handle the request
+// (that is, only if cgoLookupHost is the stub in cgo_stub.go).
+// Normally we let cgo use the C library resolver instead of
+// depending on our lookup code, so that Go and C get the same
+// answers.
+func goLookupHost(name string) (addrs []string, err error) {
+	// Use entries from /etc/hosts if they match.
+	addrs = lookupStaticHost(name)
+	if len(addrs) > 0 {
+		return
+	}
+	ips, err := goLookupIP(name)
+	if err != nil {
+		return
+	}
+	addrs = make([]string, 0, len(ips))
+	for _, ip := range ips {
+		addrs = append(addrs, ip.String())
+	}
+	return
+}
+
+// goLookupIP is the native Go implementation of LookupIP.
+// Used only if cgoLookupIP refuses to handle the request
+// (that is, only if cgoLookupIP is the stub in cgo_stub.go).
+// Normally we let cgo use the C library resolver instead of
+// depending on our lookup code, so that Go and C get the same
+// answers.
+func goLookupIP(name string) (addrs []IP, err error) {
+	// Use entries from /etc/hosts if possible.
+	haddrs := lookupStaticHost(name)
+	if len(haddrs) > 0 {
+		for _, haddr := range haddrs {
+			if ip := ParseIP(haddr); ip != nil {
+				addrs = append(addrs, ip)
+			}
+		}
+		if len(addrs) > 0 {
+			return
+		}
+	}
+	type racer struct {
+		qtype uint16
+		rrs   []dnsRR
+		error
+	}
+	lane := make(chan racer, 1)
+	qtypes := [...]uint16{dnsTypeA, dnsTypeAAAA}
+	for _, qtype := range qtypes {
+		go func(qtype uint16) {
+			_, rrs, err := lookup(name, qtype)
+			lane <- racer{qtype, rrs, err}
+		}(qtype)
+	}
+	var lastErr error
+	for range qtypes {
+		racer := <-lane
+		if racer.error != nil {
+			lastErr = racer.error
+			continue
+		}
+		switch racer.qtype {
+		case dnsTypeA:
+			addrs = append(addrs, convertRR_A(racer.rrs)...)
+		case dnsTypeAAAA:
+			addrs = append(addrs, convertRR_AAAA(racer.rrs)...)
+		}
+	}
+	if len(addrs) == 0 && lastErr != nil {
+		return nil, lastErr
+	}
+	return addrs, nil
+}
+
+// goLookupCNAME is the native Go implementation of LookupCNAME.
+// Used only if cgoLookupCNAME refuses to handle the request
+// (that is, only if cgoLookupCNAME is the stub in cgo_stub.go).
+// Normally we let cgo use the C library resolver instead of
+// depending on our lookup code, so that Go and C get the same
+// answers.
+func goLookupCNAME(name string) (cname string, err error) {
+	_, rr, err := lookup(name, dnsTypeCNAME)
+	if err != nil {
+		return
+	}
+	cname = rr[0].(*dnsRR_CNAME).Cname
+	return
+}
diff --git a/src/net/dnsclient_unix_test.go b/src/net/dnsclient_unix_test.go
new file mode 100644
index 000000000..1167c26b3
--- /dev/null
+++ b/src/net/dnsclient_unix_test.go
@@ -0,0 +1,246 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build darwin dragonfly freebsd linux netbsd openbsd solaris
+
+package net
+
+import (
+	"io"
+	"io/ioutil"
+	"os"
+	"path"
+	"reflect"
+	"testing"
+	"time"
+)
+
+var dnsTransportFallbackTests = []struct {
+	server  string
+	name    string
+	qtype   uint16
+	timeout int
+	rcode   int
+}{
+	// Querying "com." with qtype=255 usually makes an answer
+	// which requires more than 512 bytes.
+	{"8.8.8.8:53", "com.", dnsTypeALL, 2, dnsRcodeSuccess},
+	{"8.8.4.4:53", "com.", dnsTypeALL, 4, dnsRcodeSuccess},
+}
+
+func TestDNSTransportFallback(t *testing.T) {
+	if testing.Short() || !*testExternal {
+		t.Skip("skipping test to avoid external network")
+	}
+
+	for _, tt := range dnsTransportFallbackTests {
+		timeout := time.Duration(tt.timeout) * time.Second
+		msg, err := exchange(tt.server, tt.name, tt.qtype, timeout)
+		if err != nil {
+			t.Error(err)
+			continue
+		}
+		switch msg.rcode {
+		case tt.rcode, dnsRcodeServerFailure:
+		default:
+			t.Errorf("got %v from %v; want %v", msg.rcode, tt.server, tt.rcode)
+			continue
+		}
+	}
+}
+
+// See RFC 6761 for further information about the reserved, pseudo
+// domain names.
+var specialDomainNameTests = []struct {
+	name  string
+	qtype uint16
+	rcode int
+}{
+	// Name resoltion APIs and libraries should not recongnize the
+	// followings as special.
+	{"1.0.168.192.in-addr.arpa.", dnsTypePTR, dnsRcodeNameError},
+	{"test.", dnsTypeALL, dnsRcodeNameError},
+	{"example.com.", dnsTypeALL, dnsRcodeSuccess},
+
+	// Name resoltion APIs and libraries should recongnize the
+	// followings as special and should not send any queries.
+	// Though, we test those names here for verifying nagative
+	// answers at DNS query-response interaction level.
+	{"localhost.", dnsTypeALL, dnsRcodeNameError},
+	{"invalid.", dnsTypeALL, dnsRcodeNameError},
+}
+
+func TestSpecialDomainName(t *testing.T) {
+	if testing.Short() || !*testExternal {
+		t.Skip("skipping test to avoid external network")
+	}
+
+	server := "8.8.8.8:53"
+	for _, tt := range specialDomainNameTests {
+		msg, err := exchange(server, tt.name, tt.qtype, 0)
+		if err != nil {
+			t.Error(err)
+			continue
+		}
+		switch msg.rcode {
+		case tt.rcode, dnsRcodeServerFailure:
+		default:
+			t.Errorf("got %v from %v; want %v", msg.rcode, server, tt.rcode)
+			continue
+		}
+	}
+}
+
+type resolvConfTest struct {
+	*testing.T
+	dir     string
+	path    string
+	started bool
+	quitc   chan chan struct{}
+}
+
+func newResolvConfTest(t *testing.T) *resolvConfTest {
+	dir, err := ioutil.TempDir("", "resolvConfTest")
+	if err != nil {
+		t.Fatalf("could not create temp dir: %v", err)
+	}
+
+	// Disable the default loadConfig
+	onceLoadConfig.Do(func() {})
+
+	r := &resolvConfTest{
+		T:     t,
+		dir:   dir,
+		path:  path.Join(dir, "resolv.conf"),
+		quitc: make(chan chan struct{}),
+	}
+
+	return r
+}
+
+func (r *resolvConfTest) Start() {
+	loadConfig(r.path, 100*time.Millisecond, r.quitc)
+	r.started = true
+}
+
+func (r *resolvConfTest) SetConf(s string) {
+	// Make sure the file mtime will be different once we're done here,
+	// even on systems with coarse (1s) mtime resolution.
+	time.Sleep(time.Second)
+
+	f, err := os.OpenFile(r.path, os.O_CREATE|os.O_TRUNC|os.O_WRONLY, 0600)
+	if err != nil {
+		r.Fatalf("failed to create temp file %s: %v", r.path, err)
+	}
+	if _, err := io.WriteString(f, s); err != nil {
+		f.Close()
+		r.Fatalf("failed to write temp file: %v", err)
+	}
+	f.Close()
+
+	if r.started {
+		cfg.ch <- struct{}{} // fill buffer
+		cfg.ch <- struct{}{} // wait for reload to begin
+		cfg.ch <- struct{}{} // wait for reload to complete
+	}
+}
+
+func (r *resolvConfTest) WantServers(want []string) {
+	cfg.mu.RLock()
+	defer cfg.mu.RUnlock()
+	if got := cfg.dnsConfig.servers; !reflect.DeepEqual(got, want) {
+		r.Fatalf("Unexpected dns server loaded, got %v want %v", got, want)
+	}
+}
+
+func (r *resolvConfTest) Close() {
+	resp := make(chan struct{})
+	r.quitc <- resp
+	<-resp
+	if err := os.RemoveAll(r.dir); err != nil {
+		r.Logf("failed to remove temp dir %s: %v", r.dir, err)
+	}
+}
+
+func TestReloadResolvConfFail(t *testing.T) {
+	if testing.Short() || !*testExternal {
+		t.Skip("skipping test to avoid external network")
+	}
+
+	r := newResolvConfTest(t)
+	defer r.Close()
+
+	// resolv.conf.tmp does not exist yet
+	r.Start()
+	if _, err := goLookupIP("golang.org"); err == nil {
+		t.Fatal("goLookupIP(missing) succeeded")
+	}
+
+	r.SetConf("nameserver 8.8.8.8")
+	if _, err := goLookupIP("golang.org"); err != nil {
+		t.Fatalf("goLookupIP(missing; good) failed: %v", err)
+	}
+
+	// Using a bad resolv.conf while we had a good
+	// one before should not update the config
+	r.SetConf("")
+	if _, err := goLookupIP("golang.org"); err != nil {
+		t.Fatalf("goLookupIP(missing; good; bad) failed: %v", err)
+	}
+}
+
+func TestReloadResolvConfChange(t *testing.T) {
+	if testing.Short() || !*testExternal {
+		t.Skip("skipping test to avoid external network")
+	}
+
+	r := newResolvConfTest(t)
+	defer r.Close()
+
+	r.SetConf("nameserver 8.8.8.8")
+	r.Start()
+
+	if _, err := goLookupIP("golang.org"); err != nil {
+		t.Fatalf("goLookupIP(good) failed: %v", err)
+	}
+	r.WantServers([]string{"8.8.8.8"})
+
+	// Using a bad resolv.conf when we had a good one
+	// before should not update the config
+	r.SetConf("")
+	if _, err := goLookupIP("golang.org"); err != nil {
+		t.Fatalf("goLookupIP(good; bad) failed: %v", err)
+	}
+
+	// A new good config should get picked up
+	r.SetConf("nameserver 8.8.4.4")
+	r.WantServers([]string{"8.8.4.4"})
+}
+
+func BenchmarkGoLookupIP(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		goLookupIP("www.example.com")
+	}
+}
+
+func BenchmarkGoLookupIPNoSuchHost(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		goLookupIP("some.nonexistent")
+	}
+}
+
+func BenchmarkGoLookupIPWithBrokenNameServer(b *testing.B) {
+	onceLoadConfig.Do(loadDefaultConfig)
+	if cfg.dnserr != nil || cfg.dnsConfig == nil {
+		b.Fatalf("loadConfig failed: %v", cfg.dnserr)
+	}
+	// This looks ugly but it's safe as long as benchmarks are run
+	// sequentially in package testing.
+	orig := cfg.dnsConfig
+	cfg.dnsConfig.servers = append([]string{"203.0.113.254"}, cfg.dnsConfig.servers...) // use TEST-NET-3 block, see RFC 5737
+	for i := 0; i < b.N; i++ {
+		goLookupIP("www.example.com")
+	}
+	cfg.dnsConfig = orig
+}
diff --git a/src/net/dnsconfig_unix.go b/src/net/dnsconfig_unix.go
new file mode 100644
index 000000000..ebb6e673f
--- /dev/null
+++ b/src/net/dnsconfig_unix.go
@@ -0,0 +1,96 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build darwin dragonfly freebsd linux nacl netbsd openbsd solaris
+
+// Read system DNS config from /etc/resolv.conf
+
+package net
+
+type dnsConfig struct {
+	servers  []string // servers to use
+	search   []string // suffixes to append to local name
+	ndots    int      // number of dots in name to trigger absolute lookup
+	timeout  int      // seconds before giving up on packet
+	attempts int      // lost packets before giving up on server
+	rotate   bool     // round robin among servers
+}
+
+// See resolv.conf(5) on a Linux machine.
+// TODO(rsc): Supposed to call uname() and chop the beginning
+// of the host name to get the default search domain.
+func dnsReadConfig(filename string) (*dnsConfig, error) {
+	file, err := open(filename)
+	if err != nil {
+		return nil, &DNSConfigError{err}
+	}
+	defer file.close()
+	conf := &dnsConfig{
+		ndots:    1,
+		timeout:  5,
+		attempts: 2,
+	}
+	for line, ok := file.readLine(); ok; line, ok = file.readLine() {
+		f := getFields(line)
+		if len(f) < 1 {
+			continue
+		}
+		switch f[0] {
+		case "nameserver": // add one name server
+			if len(f) > 1 && len(conf.servers) < 3 { // small, but the standard limit
+				// One more check: make sure server name is
+				// just an IP address.  Otherwise we need DNS
+				// to look it up.
+				if parseIPv4(f[1]) != nil {
+					conf.servers = append(conf.servers, f[1])
+				} else if ip, _ := parseIPv6(f[1], true); ip != nil {
+					conf.servers = append(conf.servers, f[1])
+				}
+			}
+
+		case "domain": // set search path to just this domain
+			if len(f) > 1 {
+				conf.search = []string{f[1]}
+			}
+
+		case "search": // set search path to given servers
+			conf.search = make([]string, len(f)-1)
+			for i := 0; i < len(conf.search); i++ {
+				conf.search[i] = f[i+1]
+			}
+
+		case "options": // magic options
+			for i := 1; i < len(f); i++ {
+				s := f[i]
+				switch {
+				case hasPrefix(s, "ndots:"):
+					n, _, _ := dtoi(s, 6)
+					if n < 1 {
+						n = 1
+					}
+					conf.ndots = n
+				case hasPrefix(s, "timeout:"):
+					n, _, _ := dtoi(s, 8)
+					if n < 1 {
+						n = 1
+					}
+					conf.timeout = n
+				case hasPrefix(s, "attempts:"):
+					n, _, _ := dtoi(s, 9)
+					if n < 1 {
+						n = 1
+					}
+					conf.attempts = n
+				case s == "rotate":
+					conf.rotate = true
+				}
+			}
+		}
+	}
+	return conf, nil
+}
+
+func hasPrefix(s, prefix string) bool {
+	return len(s) >= len(prefix) && s[:len(prefix)] == prefix
+}
diff --git a/src/net/dnsconfig_unix_test.go b/src/net/dnsconfig_unix_test.go
new file mode 100644
index 000000000..94fb0c32e
--- /dev/null
+++ b/src/net/dnsconfig_unix_test.go
@@ -0,0 +1,69 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build darwin dragonfly freebsd linux netbsd openbsd solaris
+
+package net
+
+import (
+	"reflect"
+	"testing"
+)
+
+var dnsReadConfigTests = []struct {
+	name string
+	conf dnsConfig
+}{
+	{
+		name: "testdata/resolv.conf",
+		conf: dnsConfig{
+			servers:  []string{"8.8.8.8", "2001:4860:4860::8888", "fe80::1%lo0"},
+			search:   []string{"localdomain"},
+			ndots:    5,
+			timeout:  10,
+			attempts: 3,
+			rotate:   true,
+		},
+	},
+	{
+		name: "testdata/domain-resolv.conf",
+		conf: dnsConfig{
+			servers:  []string{"8.8.8.8"},
+			search:   []string{"localdomain"},
+			ndots:    1,
+			timeout:  5,
+			attempts: 2,
+		},
+	},
+	{
+		name: "testdata/search-resolv.conf",
+		conf: dnsConfig{
+			servers:  []string{"8.8.8.8"},
+			search:   []string{"test", "invalid"},
+			ndots:    1,
+			timeout:  5,
+			attempts: 2,
+		},
+	},
+	{
+		name: "testdata/empty-resolv.conf",
+		conf: dnsConfig{
+			ndots:    1,
+			timeout:  5,
+			attempts: 2,
+		},
+	},
+}
+
+func TestDNSReadConfig(t *testing.T) {
+	for _, tt := range dnsReadConfigTests {
+		conf, err := dnsReadConfig(tt.name)
+		if err != nil {
+			t.Fatal(err)
+		}
+		if !reflect.DeepEqual(conf, &tt.conf) {
+			t.Errorf("got %v; want %v", conf, &tt.conf)
+		}
+	}
+}
diff --git a/src/net/dnsmsg.go b/src/net/dnsmsg.go
new file mode 100644
index 000000000..161afb2a5
--- /dev/null
+++ b/src/net/dnsmsg.go
@@ -0,0 +1,887 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// DNS packet assembly.  See RFC 1035.
+//
+// This is intended to support name resolution during Dial.
+// It doesn't have to be blazing fast.
+//
+// Each message structure has a Walk method that is used by
+// a generic pack/unpack routine. Thus, if in the future we need
+// to define new message structs, no new pack/unpack/printing code
+// needs to be written.
+//
+// The first half of this file defines the DNS message formats.
+// The second half implements the conversion to and from wire format.
+// A few of the structure elements have string tags to aid the
+// generic pack/unpack routines.
+//
+// TODO(rsc):  There are enough names defined in this file that they're all
+// prefixed with dns.  Perhaps put this in its own package later.
+
+package net
+
+// Packet formats
+
+// Wire constants.
+const (
+	// valid dnsRR_Header.Rrtype and dnsQuestion.qtype
+	dnsTypeA     = 1
+	dnsTypeNS    = 2
+	dnsTypeMD    = 3
+	dnsTypeMF    = 4
+	dnsTypeCNAME = 5
+	dnsTypeSOA   = 6
+	dnsTypeMB    = 7
+	dnsTypeMG    = 8
+	dnsTypeMR    = 9
+	dnsTypeNULL  = 10
+	dnsTypeWKS   = 11
+	dnsTypePTR   = 12
+	dnsTypeHINFO = 13
+	dnsTypeMINFO = 14
+	dnsTypeMX    = 15
+	dnsTypeTXT   = 16
+	dnsTypeAAAA  = 28
+	dnsTypeSRV   = 33
+
+	// valid dnsQuestion.qtype only
+	dnsTypeAXFR  = 252
+	dnsTypeMAILB = 253
+	dnsTypeMAILA = 254
+	dnsTypeALL   = 255
+
+	// valid dnsQuestion.qclass
+	dnsClassINET   = 1
+	dnsClassCSNET  = 2
+	dnsClassCHAOS  = 3
+	dnsClassHESIOD = 4
+	dnsClassANY    = 255
+
+	// dnsMsg.rcode
+	dnsRcodeSuccess        = 0
+	dnsRcodeFormatError    = 1
+	dnsRcodeServerFailure  = 2
+	dnsRcodeNameError      = 3
+	dnsRcodeNotImplemented = 4
+	dnsRcodeRefused        = 5
+)
+
+// A dnsStruct describes how to iterate over its fields to emulate
+// reflective marshalling.
+type dnsStruct interface {
+	// Walk iterates over fields of a structure and calls f
+	// with a reference to that field, the name of the field
+	// and a tag ("", "domain", "ipv4", "ipv6") specifying
+	// particular encodings. Possible concrete types
+	// for v are *uint16, *uint32, *string, or []byte, and
+	// *int, *bool in the case of dnsMsgHdr.
+	// Whenever f returns false, Walk must stop and return
+	// false, and otherwise return true.
+	Walk(f func(v interface{}, name, tag string) (ok bool)) (ok bool)
+}
+
+// The wire format for the DNS packet header.
+type dnsHeader struct {
+	Id                                 uint16
+	Bits                               uint16
+	Qdcount, Ancount, Nscount, Arcount uint16
+}
+
+func (h *dnsHeader) Walk(f func(v interface{}, name, tag string) bool) bool {
+	return f(&h.Id, "Id", "") &&
+		f(&h.Bits, "Bits", "") &&
+		f(&h.Qdcount, "Qdcount", "") &&
+		f(&h.Ancount, "Ancount", "") &&
+		f(&h.Nscount, "Nscount", "") &&
+		f(&h.Arcount, "Arcount", "")
+}
+
+const (
+	// dnsHeader.Bits
+	_QR = 1 << 15 // query/response (response=1)
+	_AA = 1 << 10 // authoritative
+	_TC = 1 << 9  // truncated
+	_RD = 1 << 8  // recursion desired
+	_RA = 1 << 7  // recursion available
+)
+
+// DNS queries.
+type dnsQuestion struct {
+	Name   string `net:"domain-name"` // `net:"domain-name"` specifies encoding; see packers below
+	Qtype  uint16
+	Qclass uint16
+}
+
+func (q *dnsQuestion) Walk(f func(v interface{}, name, tag string) bool) bool {
+	return f(&q.Name, "Name", "domain") &&
+		f(&q.Qtype, "Qtype", "") &&
+		f(&q.Qclass, "Qclass", "")
+}
+
+// DNS responses (resource records).
+// There are many types of messages,
+// but they all share the same header.
+type dnsRR_Header struct {
+	Name     string `net:"domain-name"`
+	Rrtype   uint16
+	Class    uint16
+	Ttl      uint32
+	Rdlength uint16 // length of data after header
+}
+
+func (h *dnsRR_Header) Header() *dnsRR_Header {
+	return h
+}
+
+func (h *dnsRR_Header) Walk(f func(v interface{}, name, tag string) bool) bool {
+	return f(&h.Name, "Name", "domain") &&
+		f(&h.Rrtype, "Rrtype", "") &&
+		f(&h.Class, "Class", "") &&
+		f(&h.Ttl, "Ttl", "") &&
+		f(&h.Rdlength, "Rdlength", "")
+}
+
+type dnsRR interface {
+	dnsStruct
+	Header() *dnsRR_Header
+}
+
+// Specific DNS RR formats for each query type.
+
+type dnsRR_CNAME struct {
+	Hdr   dnsRR_Header
+	Cname string `net:"domain-name"`
+}
+
+func (rr *dnsRR_CNAME) Header() *dnsRR_Header {
+	return &rr.Hdr
+}
+
+func (rr *dnsRR_CNAME) Walk(f func(v interface{}, name, tag string) bool) bool {
+	return rr.Hdr.Walk(f) && f(&rr.Cname, "Cname", "domain")
+}
+
+type dnsRR_HINFO struct {
+	Hdr dnsRR_Header
+	Cpu string
+	Os  string
+}
+
+func (rr *dnsRR_HINFO) Header() *dnsRR_Header {
+	return &rr.Hdr
+}
+
+func (rr *dnsRR_HINFO) Walk(f func(v interface{}, name, tag string) bool) bool {
+	return rr.Hdr.Walk(f) && f(&rr.Cpu, "Cpu", "") && f(&rr.Os, "Os", "")
+}
+
+type dnsRR_MB struct {
+	Hdr dnsRR_Header
+	Mb  string `net:"domain-name"`
+}
+
+func (rr *dnsRR_MB) Header() *dnsRR_Header {
+	return &rr.Hdr
+}
+
+func (rr *dnsRR_MB) Walk(f func(v interface{}, name, tag string) bool) bool {
+	return rr.Hdr.Walk(f) && f(&rr.Mb, "Mb", "domain")
+}
+
+type dnsRR_MG struct {
+	Hdr dnsRR_Header
+	Mg  string `net:"domain-name"`
+}
+
+func (rr *dnsRR_MG) Header() *dnsRR_Header {
+	return &rr.Hdr
+}
+
+func (rr *dnsRR_MG) Walk(f func(v interface{}, name, tag string) bool) bool {
+	return rr.Hdr.Walk(f) && f(&rr.Mg, "Mg", "domain")
+}
+
+type dnsRR_MINFO struct {
+	Hdr   dnsRR_Header
+	Rmail string `net:"domain-name"`
+	Email string `net:"domain-name"`
+}
+
+func (rr *dnsRR_MINFO) Header() *dnsRR_Header {
+	return &rr.Hdr
+}
+
+func (rr *dnsRR_MINFO) Walk(f func(v interface{}, name, tag string) bool) bool {
+	return rr.Hdr.Walk(f) && f(&rr.Rmail, "Rmail", "domain") && f(&rr.Email, "Email", "domain")
+}
+
+type dnsRR_MR struct {
+	Hdr dnsRR_Header
+	Mr  string `net:"domain-name"`
+}
+
+func (rr *dnsRR_MR) Header() *dnsRR_Header {
+	return &rr.Hdr
+}
+
+func (rr *dnsRR_MR) Walk(f func(v interface{}, name, tag string) bool) bool {
+	return rr.Hdr.Walk(f) && f(&rr.Mr, "Mr", "domain")
+}
+
+type dnsRR_MX struct {
+	Hdr  dnsRR_Header
+	Pref uint16
+	Mx   string `net:"domain-name"`
+}
+
+func (rr *dnsRR_MX) Header() *dnsRR_Header {
+	return &rr.Hdr
+}
+
+func (rr *dnsRR_MX) Walk(f func(v interface{}, name, tag string) bool) bool {
+	return rr.Hdr.Walk(f) && f(&rr.Pref, "Pref", "") && f(&rr.Mx, "Mx", "domain")
+}
+
+type dnsRR_NS struct {
+	Hdr dnsRR_Header
+	Ns  string `net:"domain-name"`
+}
+
+func (rr *dnsRR_NS) Header() *dnsRR_Header {
+	return &rr.Hdr
+}
+
+func (rr *dnsRR_NS) Walk(f func(v interface{}, name, tag string) bool) bool {
+	return rr.Hdr.Walk(f) && f(&rr.Ns, "Ns", "domain")
+}
+
+type dnsRR_PTR struct {
+	Hdr dnsRR_Header
+	Ptr string `net:"domain-name"`
+}
+
+func (rr *dnsRR_PTR) Header() *dnsRR_Header {
+	return &rr.Hdr
+}
+
+func (rr *dnsRR_PTR) Walk(f func(v interface{}, name, tag string) bool) bool {
+	return rr.Hdr.Walk(f) && f(&rr.Ptr, "Ptr", "domain")
+}
+
+type dnsRR_SOA struct {
+	Hdr     dnsRR_Header
+	Ns      string `net:"domain-name"`
+	Mbox    string `net:"domain-name"`
+	Serial  uint32
+	Refresh uint32
+	Retry   uint32
+	Expire  uint32
+	Minttl  uint32
+}
+
+func (rr *dnsRR_SOA) Header() *dnsRR_Header {
+	return &rr.Hdr
+}
+
+func (rr *dnsRR_SOA) Walk(f func(v interface{}, name, tag string) bool) bool {
+	return rr.Hdr.Walk(f) &&
+		f(&rr.Ns, "Ns", "domain") &&
+		f(&rr.Mbox, "Mbox", "domain") &&
+		f(&rr.Serial, "Serial", "") &&
+		f(&rr.Refresh, "Refresh", "") &&
+		f(&rr.Retry, "Retry", "") &&
+		f(&rr.Expire, "Expire", "") &&
+		f(&rr.Minttl, "Minttl", "")
+}
+
+type dnsRR_TXT struct {
+	Hdr dnsRR_Header
+	Txt string // not domain name
+}
+
+func (rr *dnsRR_TXT) Header() *dnsRR_Header {
+	return &rr.Hdr
+}
+
+func (rr *dnsRR_TXT) Walk(f func(v interface{}, name, tag string) bool) bool {
+	return rr.Hdr.Walk(f) && f(&rr.Txt, "Txt", "")
+}
+
+type dnsRR_SRV struct {
+	Hdr      dnsRR_Header
+	Priority uint16
+	Weight   uint16
+	Port     uint16
+	Target   string `net:"domain-name"`
+}
+
+func (rr *dnsRR_SRV) Header() *dnsRR_Header {
+	return &rr.Hdr
+}
+
+func (rr *dnsRR_SRV) Walk(f func(v interface{}, name, tag string) bool) bool {
+	return rr.Hdr.Walk(f) &&
+		f(&rr.Priority, "Priority", "") &&
+		f(&rr.Weight, "Weight", "") &&
+		f(&rr.Port, "Port", "") &&
+		f(&rr.Target, "Target", "domain")
+}
+
+type dnsRR_A struct {
+	Hdr dnsRR_Header
+	A   uint32 `net:"ipv4"`
+}
+
+func (rr *dnsRR_A) Header() *dnsRR_Header {
+	return &rr.Hdr
+}
+
+func (rr *dnsRR_A) Walk(f func(v interface{}, name, tag string) bool) bool {
+	return rr.Hdr.Walk(f) && f(&rr.A, "A", "ipv4")
+}
+
+type dnsRR_AAAA struct {
+	Hdr  dnsRR_Header
+	AAAA [16]byte `net:"ipv6"`
+}
+
+func (rr *dnsRR_AAAA) Header() *dnsRR_Header {
+	return &rr.Hdr
+}
+
+func (rr *dnsRR_AAAA) Walk(f func(v interface{}, name, tag string) bool) bool {
+	return rr.Hdr.Walk(f) && f(rr.AAAA[:], "AAAA", "ipv6")
+}
+
+// Packing and unpacking.
+//
+// All the packers and unpackers take a (msg []byte, off int)
+// and return (off1 int, ok bool).  If they return ok==false, they
+// also return off1==len(msg), so that the next unpacker will
+// also fail.  This lets us avoid checks of ok until the end of a
+// packing sequence.
+
+// Map of constructors for each RR wire type.
+var rr_mk = map[int]func() dnsRR{
+	dnsTypeCNAME: func() dnsRR { return new(dnsRR_CNAME) },
+	dnsTypeHINFO: func() dnsRR { return new(dnsRR_HINFO) },
+	dnsTypeMB:    func() dnsRR { return new(dnsRR_MB) },
+	dnsTypeMG:    func() dnsRR { return new(dnsRR_MG) },
+	dnsTypeMINFO: func() dnsRR { return new(dnsRR_MINFO) },
+	dnsTypeMR:    func() dnsRR { return new(dnsRR_MR) },
+	dnsTypeMX:    func() dnsRR { return new(dnsRR_MX) },
+	dnsTypeNS:    func() dnsRR { return new(dnsRR_NS) },
+	dnsTypePTR:   func() dnsRR { return new(dnsRR_PTR) },
+	dnsTypeSOA:   func() dnsRR { return new(dnsRR_SOA) },
+	dnsTypeTXT:   func() dnsRR { return new(dnsRR_TXT) },
+	dnsTypeSRV:   func() dnsRR { return new(dnsRR_SRV) },
+	dnsTypeA:     func() dnsRR { return new(dnsRR_A) },
+	dnsTypeAAAA:  func() dnsRR { return new(dnsRR_AAAA) },
+}
+
+// Pack a domain name s into msg[off:].
+// Domain names are a sequence of counted strings
+// split at the dots.  They end with a zero-length string.
+func packDomainName(s string, msg []byte, off int) (off1 int, ok bool) {
+	// Add trailing dot to canonicalize name.
+	if n := len(s); n == 0 || s[n-1] != '.' {
+		s += "."
+	}
+
+	// Each dot ends a segment of the name.
+	// We trade each dot byte for a length byte.
+	// There is also a trailing zero.
+	// Check that we have all the space we need.
+	tot := len(s) + 1
+	if off+tot > len(msg) {
+		return len(msg), false
+	}
+
+	// Emit sequence of counted strings, chopping at dots.
+	begin := 0
+	for i := 0; i < len(s); i++ {
+		if s[i] == '.' {
+			if i-begin >= 1<<6 { // top two bits of length must be clear
+				return len(msg), false
+			}
+			msg[off] = byte(i - begin)
+			off++
+			for j := begin; j < i; j++ {
+				msg[off] = s[j]
+				off++
+			}
+			begin = i + 1
+		}
+	}
+	msg[off] = 0
+	off++
+	return off, true
+}
+
+// Unpack a domain name.
+// In addition to the simple sequences of counted strings above,
+// domain names are allowed to refer to strings elsewhere in the
+// packet, to avoid repeating common suffixes when returning
+// many entries in a single domain.  The pointers are marked
+// by a length byte with the top two bits set.  Ignoring those
+// two bits, that byte and the next give a 14 bit offset from msg[0]
+// where we should pick up the trail.
+// Note that if we jump elsewhere in the packet,
+// we return off1 == the offset after the first pointer we found,
+// which is where the next record will start.
+// In theory, the pointers are only allowed to jump backward.
+// We let them jump anywhere and stop jumping after a while.
+func unpackDomainName(msg []byte, off int) (s string, off1 int, ok bool) {
+	s = ""
+	ptr := 0 // number of pointers followed
+Loop:
+	for {
+		if off >= len(msg) {
+			return "", len(msg), false
+		}
+		c := int(msg[off])
+		off++
+		switch c & 0xC0 {
+		case 0x00:
+			if c == 0x00 {
+				// end of name
+				break Loop
+			}
+			// literal string
+			if off+c > len(msg) {
+				return "", len(msg), false
+			}
+			s += string(msg[off:off+c]) + "."
+			off += c
+		case 0xC0:
+			// pointer to somewhere else in msg.
+			// remember location after first ptr,
+			// since that's how many bytes we consumed.
+			// also, don't follow too many pointers --
+			// maybe there's a loop.
+			if off >= len(msg) {
+				return "", len(msg), false
+			}
+			c1 := msg[off]
+			off++
+			if ptr == 0 {
+				off1 = off
+			}
+			if ptr++; ptr > 10 {
+				return "", len(msg), false
+			}
+			off = (c^0xC0)<<8 | int(c1)
+		default:
+			// 0x80 and 0x40 are reserved
+			return "", len(msg), false
+		}
+	}
+	if ptr == 0 {
+		off1 = off
+	}
+	return s, off1, true
+}
+
+// packStruct packs a structure into msg at specified offset off, and
+// returns off1 such that msg[off:off1] is the encoded data.
+func packStruct(any dnsStruct, msg []byte, off int) (off1 int, ok bool) {
+	ok = any.Walk(func(field interface{}, name, tag string) bool {
+		switch fv := field.(type) {
+		default:
+			println("net: dns: unknown packing type")
+			return false
+		case *uint16:
+			i := *fv
+			if off+2 > len(msg) {
+				return false
+			}
+			msg[off] = byte(i >> 8)
+			msg[off+1] = byte(i)
+			off += 2
+		case *uint32:
+			i := *fv
+			msg[off] = byte(i >> 24)
+			msg[off+1] = byte(i >> 16)
+			msg[off+2] = byte(i >> 8)
+			msg[off+3] = byte(i)
+			off += 4
+		case []byte:
+			n := len(fv)
+			if off+n > len(msg) {
+				return false
+			}
+			copy(msg[off:off+n], fv)
+			off += n
+		case *string:
+			s := *fv
+			switch tag {
+			default:
+				println("net: dns: unknown string tag", tag)
+				return false
+			case "domain":
+				off, ok = packDomainName(s, msg, off)
+				if !ok {
+					return false
+				}
+			case "":
+				// Counted string: 1 byte length.
+				if len(s) > 255 || off+1+len(s) > len(msg) {
+					return false
+				}
+				msg[off] = byte(len(s))
+				off++
+				off += copy(msg[off:], s)
+			}
+		}
+		return true
+	})
+	if !ok {
+		return len(msg), false
+	}
+	return off, true
+}
+
+// unpackStruct decodes msg[off:] into the given structure, and
+// returns off1 such that msg[off:off1] is the encoded data.
+func unpackStruct(any dnsStruct, msg []byte, off int) (off1 int, ok bool) {
+	ok = any.Walk(func(field interface{}, name, tag string) bool {
+		switch fv := field.(type) {
+		default:
+			println("net: dns: unknown packing type")
+			return false
+		case *uint16:
+			if off+2 > len(msg) {
+				return false
+			}
+			*fv = uint16(msg[off])<<8 | uint16(msg[off+1])
+			off += 2
+		case *uint32:
+			if off+4 > len(msg) {
+				return false
+			}
+			*fv = uint32(msg[off])<<24 | uint32(msg[off+1])<<16 |
+				uint32(msg[off+2])<<8 | uint32(msg[off+3])
+			off += 4
+		case []byte:
+			n := len(fv)
+			if off+n > len(msg) {
+				return false
+			}
+			copy(fv, msg[off:off+n])
+			off += n
+		case *string:
+			var s string
+			switch tag {
+			default:
+				println("net: dns: unknown string tag", tag)
+				return false
+			case "domain":
+				s, off, ok = unpackDomainName(msg, off)
+				if !ok {
+					return false
+				}
+			case "":
+				if off >= len(msg) || off+1+int(msg[off]) > len(msg) {
+					return false
+				}
+				n := int(msg[off])
+				off++
+				b := make([]byte, n)
+				for i := 0; i < n; i++ {
+					b[i] = msg[off+i]
+				}
+				off += n
+				s = string(b)
+			}
+			*fv = s
+		}
+		return true
+	})
+	if !ok {
+		return len(msg), false
+	}
+	return off, true
+}
+
+// Generic struct printer. Prints fields with tag "ipv4" or "ipv6"
+// as IP addresses.
+func printStruct(any dnsStruct) string {
+	s := "{"
+	i := 0
+	any.Walk(func(val interface{}, name, tag string) bool {
+		i++
+		if i > 1 {
+			s += ", "
+		}
+		s += name + "="
+		switch tag {
+		case "ipv4":
+			i := *val.(*uint32)
+			s += IPv4(byte(i>>24), byte(i>>16), byte(i>>8), byte(i)).String()
+		case "ipv6":
+			i := val.([]byte)
+			s += IP(i).String()
+		default:
+			var i int64
+			switch v := val.(type) {
+			default:
+				// can't really happen.
+				s += "<unknown type>"
+				return true
+			case *string:
+				s += *v
+				return true
+			case []byte:
+				s += string(v)
+				return true
+			case *bool:
+				if *v {
+					s += "true"
+				} else {
+					s += "false"
+				}
+				return true
+			case *int:
+				i = int64(*v)
+			case *uint:
+				i = int64(*v)
+			case *uint8:
+				i = int64(*v)
+			case *uint16:
+				i = int64(*v)
+			case *uint32:
+				i = int64(*v)
+			case *uint64:
+				i = int64(*v)
+			case *uintptr:
+				i = int64(*v)
+			}
+			s += itoa(int(i))
+		}
+		return true
+	})
+	s += "}"
+	return s
+}
+
+// Resource record packer.
+func packRR(rr dnsRR, msg []byte, off int) (off2 int, ok bool) {
+	var off1 int
+	// pack twice, once to find end of header
+	// and again to find end of packet.
+	// a bit inefficient but this doesn't need to be fast.
+	// off1 is end of header
+	// off2 is end of rr
+	off1, ok = packStruct(rr.Header(), msg, off)
+	off2, ok = packStruct(rr, msg, off)
+	if !ok {
+		return len(msg), false
+	}
+	// pack a third time; redo header with correct data length
+	rr.Header().Rdlength = uint16(off2 - off1)
+	packStruct(rr.Header(), msg, off)
+	return off2, true
+}
+
+// Resource record unpacker.
+func unpackRR(msg []byte, off int) (rr dnsRR, off1 int, ok bool) {
+	// unpack just the header, to find the rr type and length
+	var h dnsRR_Header
+	off0 := off
+	if off, ok = unpackStruct(&h, msg, off); !ok {
+		return nil, len(msg), false
+	}
+	end := off + int(h.Rdlength)
+
+	// make an rr of that type and re-unpack.
+	// again inefficient but doesn't need to be fast.
+	mk, known := rr_mk[int(h.Rrtype)]
+	if !known {
+		return &h, end, true
+	}
+	rr = mk()
+	off, ok = unpackStruct(rr, msg, off0)
+	if off != end {
+		return &h, end, true
+	}
+	return rr, off, ok
+}
+
+// Usable representation of a DNS packet.
+
+// A manually-unpacked version of (id, bits).
+// This is in its own struct for easy printing.
+type dnsMsgHdr struct {
+	id                  uint16
+	response            bool
+	opcode              int
+	authoritative       bool
+	truncated           bool
+	recursion_desired   bool
+	recursion_available bool
+	rcode               int
+}
+
+func (h *dnsMsgHdr) Walk(f func(v interface{}, name, tag string) bool) bool {
+	return f(&h.id, "id", "") &&
+		f(&h.response, "response", "") &&
+		f(&h.opcode, "opcode", "") &&
+		f(&h.authoritative, "authoritative", "") &&
+		f(&h.truncated, "truncated", "") &&
+		f(&h.recursion_desired, "recursion_desired", "") &&
+		f(&h.recursion_available, "recursion_available", "") &&
+		f(&h.rcode, "rcode", "")
+}
+
+type dnsMsg struct {
+	dnsMsgHdr
+	question []dnsQuestion
+	answer   []dnsRR
+	ns       []dnsRR
+	extra    []dnsRR
+}
+
+func (dns *dnsMsg) Pack() (msg []byte, ok bool) {
+	var dh dnsHeader
+
+	// Convert convenient dnsMsg into wire-like dnsHeader.
+	dh.Id = dns.id
+	dh.Bits = uint16(dns.opcode)<<11 | uint16(dns.rcode)
+	if dns.recursion_available {
+		dh.Bits |= _RA
+	}
+	if dns.recursion_desired {
+		dh.Bits |= _RD
+	}
+	if dns.truncated {
+		dh.Bits |= _TC
+	}
+	if dns.authoritative {
+		dh.Bits |= _AA
+	}
+	if dns.response {
+		dh.Bits |= _QR
+	}
+
+	// Prepare variable sized arrays.
+	question := dns.question
+	answer := dns.answer
+	ns := dns.ns
+	extra := dns.extra
+
+	dh.Qdcount = uint16(len(question))
+	dh.Ancount = uint16(len(answer))
+	dh.Nscount = uint16(len(ns))
+	dh.Arcount = uint16(len(extra))
+
+	// Could work harder to calculate message size,
+	// but this is far more than we need and not
+	// big enough to hurt the allocator.
+	msg = make([]byte, 2000)
+
+	// Pack it in: header and then the pieces.
+	off := 0
+	off, ok = packStruct(&dh, msg, off)
+	for i := 0; i < len(question); i++ {
+		off, ok = packStruct(&question[i], msg, off)
+	}
+	for i := 0; i < len(answer); i++ {
+		off, ok = packRR(answer[i], msg, off)
+	}
+	for i := 0; i < len(ns); i++ {
+		off, ok = packRR(ns[i], msg, off)
+	}
+	for i := 0; i < len(extra); i++ {
+		off, ok = packRR(extra[i], msg, off)
+	}
+	if !ok {
+		return nil, false
+	}
+	return msg[0:off], true
+}
+
+func (dns *dnsMsg) Unpack(msg []byte) bool {
+	// Header.
+	var dh dnsHeader
+	off := 0
+	var ok bool
+	if off, ok = unpackStruct(&dh, msg, off); !ok {
+		return false
+	}
+	dns.id = dh.Id
+	dns.response = (dh.Bits & _QR) != 0
+	dns.opcode = int(dh.Bits>>11) & 0xF
+	dns.authoritative = (dh.Bits & _AA) != 0
+	dns.truncated = (dh.Bits & _TC) != 0
+	dns.recursion_desired = (dh.Bits & _RD) != 0
+	dns.recursion_available = (dh.Bits & _RA) != 0
+	dns.rcode = int(dh.Bits & 0xF)
+
+	// Arrays.
+	dns.question = make([]dnsQuestion, dh.Qdcount)
+	dns.answer = make([]dnsRR, 0, dh.Ancount)
+	dns.ns = make([]dnsRR, 0, dh.Nscount)
+	dns.extra = make([]dnsRR, 0, dh.Arcount)
+
+	var rec dnsRR
+
+	for i := 0; i < len(dns.question); i++ {
+		off, ok = unpackStruct(&dns.question[i], msg, off)
+	}
+	for i := 0; i < int(dh.Ancount); i++ {
+		rec, off, ok = unpackRR(msg, off)
+		if !ok {
+			return false
+		}
+		dns.answer = append(dns.answer, rec)
+	}
+	for i := 0; i < int(dh.Nscount); i++ {
+		rec, off, ok = unpackRR(msg, off)
+		if !ok {
+			return false
+		}
+		dns.ns = append(dns.ns, rec)
+	}
+	for i := 0; i < int(dh.Arcount); i++ {
+		rec, off, ok = unpackRR(msg, off)
+		if !ok {
+			return false
+		}
+		dns.extra = append(dns.extra, rec)
+	}
+	//	if off != len(msg) {
+	//		println("extra bytes in dns packet", off, "<", len(msg));
+	//	}
+	return true
+}
+
+func (dns *dnsMsg) String() string {
+	s := "DNS: " + printStruct(&dns.dnsMsgHdr) + "\n"
+	if len(dns.question) > 0 {
+		s += "-- Questions\n"
+		for i := 0; i < len(dns.question); i++ {
+			s += printStruct(&dns.question[i]) + "\n"
+		}
+	}
+	if len(dns.answer) > 0 {
+		s += "-- Answers\n"
+		for i := 0; i < len(dns.answer); i++ {
+			s += printStruct(dns.answer[i]) + "\n"
+		}
+	}
+	if len(dns.ns) > 0 {
+		s += "-- Name servers\n"
+		for i := 0; i < len(dns.ns); i++ {
+			s += printStruct(dns.ns[i]) + "\n"
+		}
+	}
+	if len(dns.extra) > 0 {
+		s += "-- Extra\n"
+		for i := 0; i < len(dns.extra); i++ {
+			s += printStruct(dns.extra[i]) + "\n"
+		}
+	}
+	return s
+}
diff --git a/src/net/dnsmsg_test.go b/src/net/dnsmsg_test.go
new file mode 100644
index 000000000..c39dbdb04
--- /dev/null
+++ b/src/net/dnsmsg_test.go
@@ -0,0 +1,113 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package net
+
+import (
+	"encoding/hex"
+	"reflect"
+	"testing"
+)
+
+func TestDNSParseSRVReply(t *testing.T) {
+	data, err := hex.DecodeString(dnsSRVReply)
+	if err != nil {
+		t.Fatal(err)
+	}
+	msg := new(dnsMsg)
+	ok := msg.Unpack(data)
+	if !ok {
+		t.Fatalf("unpacking packet failed")
+	}
+	msg.String() // exercise this code path
+	if g, e := len(msg.answer), 5; g != e {
+		t.Errorf("len(msg.answer) = %d; want %d", g, e)
+	}
+	for idx, rr := range msg.answer {
+		if g, e := rr.Header().Rrtype, uint16(dnsTypeSRV); g != e {
+			t.Errorf("rr[%d].Header().Rrtype = %d; want %d", idx, g, e)
+		}
+		if _, ok := rr.(*dnsRR_SRV); !ok {
+			t.Errorf("answer[%d] = %T; want *dnsRR_SRV", idx, rr)
+		}
+	}
+	_, addrs, err := answer("_xmpp-server._tcp.google.com.", "foo:53", msg, uint16(dnsTypeSRV))
+	if err != nil {
+		t.Fatalf("answer: %v", err)
+	}
+	if g, e := len(addrs), 5; g != e {
+		t.Errorf("len(addrs) = %d; want %d", g, e)
+		t.Logf("addrs = %#v", addrs)
+	}
+	// repack and unpack.
+	data2, ok := msg.Pack()
+	msg2 := new(dnsMsg)
+	msg2.Unpack(data2)
+	switch {
+	case !ok:
+		t.Errorf("failed to repack message")
+	case !reflect.DeepEqual(msg, msg2):
+		t.Errorf("repacked message differs from original")
+	}
+}
+
+func TestDNSParseCorruptSRVReply(t *testing.T) {
+	data, err := hex.DecodeString(dnsSRVCorruptReply)
+	if err != nil {
+		t.Fatal(err)
+	}
+	msg := new(dnsMsg)
+	ok := msg.Unpack(data)
+	if !ok {
+		t.Fatalf("unpacking packet failed")
+	}
+	msg.String() // exercise this code path
+	if g, e := len(msg.answer), 5; g != e {
+		t.Errorf("len(msg.answer) = %d; want %d", g, e)
+	}
+	for idx, rr := range msg.answer {
+		if g, e := rr.Header().Rrtype, uint16(dnsTypeSRV); g != e {
+			t.Errorf("rr[%d].Header().Rrtype = %d; want %d", idx, g, e)
+		}
+		if idx == 4 {
+			if _, ok := rr.(*dnsRR_Header); !ok {
+				t.Errorf("answer[%d] = %T; want *dnsRR_Header", idx, rr)
+			}
+		} else {
+			if _, ok := rr.(*dnsRR_SRV); !ok {
+				t.Errorf("answer[%d] = %T; want *dnsRR_SRV", idx, rr)
+			}
+		}
+	}
+	_, addrs, err := answer("_xmpp-server._tcp.google.com.", "foo:53", msg, uint16(dnsTypeSRV))
+	if err != nil {
+		t.Fatalf("answer: %v", err)
+	}
+	if g, e := len(addrs), 4; g != e {
+		t.Errorf("len(addrs) = %d; want %d", g, e)
+		t.Logf("addrs = %#v", addrs)
+	}
+}
+
+// Valid DNS SRV reply
+const dnsSRVReply = "0901818000010005000000000c5f786d70702d736572766572045f74637006676f6f67" +
+	"6c6503636f6d0000210001c00c002100010000012c00210014000014950c786d70702d" +
+	"73657276657234016c06676f6f676c6503636f6d00c00c002100010000012c00210014" +
+	"000014950c786d70702d73657276657232016c06676f6f676c6503636f6d00c00c0021" +
+	"00010000012c00210014000014950c786d70702d73657276657233016c06676f6f676c" +
+	"6503636f6d00c00c002100010000012c00200005000014950b786d70702d7365727665" +
+	"72016c06676f6f676c6503636f6d00c00c002100010000012c00210014000014950c78" +
+	"6d70702d73657276657231016c06676f6f676c6503636f6d00"
+
+// Corrupt DNS SRV reply, with its final RR having a bogus length
+// (perhaps it was truncated, or it's malicious) The mutation is the
+// capital "FF" below, instead of the proper "21".
+const dnsSRVCorruptReply = "0901818000010005000000000c5f786d70702d736572766572045f74637006676f6f67" +
+	"6c6503636f6d0000210001c00c002100010000012c00210014000014950c786d70702d" +
+	"73657276657234016c06676f6f676c6503636f6d00c00c002100010000012c00210014" +
+	"000014950c786d70702d73657276657232016c06676f6f676c6503636f6d00c00c0021" +
+	"00010000012c00210014000014950c786d70702d73657276657233016c06676f6f676c" +
+	"6503636f6d00c00c002100010000012c00200005000014950b786d70702d7365727665" +
+	"72016c06676f6f676c6503636f6d00c00c002100010000012c00FF0014000014950c78" +
+	"6d70702d73657276657231016c06676f6f676c6503636f6d00"
diff --git a/src/net/dnsname_test.go b/src/net/dnsname_test.go
new file mode 100644
index 000000000..57dd25fe4
--- /dev/null
+++ b/src/net/dnsname_test.go
@@ -0,0 +1,83 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package net
+
+import (
+	"strings"
+	"testing"
+)
+
+type testCase struct {
+	name   string
+	result bool
+}
+
+var tests = []testCase{
+	// RFC2181, section 11.
+	{"_xmpp-server._tcp.google.com", true},
+	{"foo.com", true},
+	{"1foo.com", true},
+	{"26.0.0.73.com", true},
+	{"fo-o.com", true},
+	{"fo1o.com", true},
+	{"foo1.com", true},
+	{"a.b..com", false},
+	{"a.b-.com", false},
+	{"a.b.com-", false},
+	{"a.b..", false},
+	{"b.com.", true},
+}
+
+func getTestCases(ch chan<- testCase) {
+	defer close(ch)
+	var char59 = ""
+	var char63 = ""
+	var char64 = ""
+	for i := 0; i < 59; i++ {
+		char59 += "a"
+	}
+	char63 = char59 + "aaaa"
+	char64 = char63 + "a"
+
+	for _, tc := range tests {
+		ch <- tc
+	}
+
+	ch <- testCase{char63 + ".com", true}
+	ch <- testCase{char64 + ".com", false}
+	// 255 char name is fine:
+	ch <- testCase{char59 + "." + char63 + "." + char63 + "." +
+		char63 + ".com",
+		true}
+	// 256 char name is bad:
+	ch <- testCase{char59 + "a." + char63 + "." + char63 + "." +
+		char63 + ".com",
+		false}
+}
+
+func TestDNSNames(t *testing.T) {
+	ch := make(chan testCase)
+	go getTestCases(ch)
+	for tc := range ch {
+		if isDomainName(tc.name) != tc.result {
+			t.Errorf("isDomainName(%v) failed: Should be %v",
+				tc.name, tc.result)
+		}
+	}
+}
+
+func BenchmarkDNSNames(b *testing.B) {
+	benchmarks := append(tests, []testCase{
+		{strings.Repeat("a", 63), true},
+		{strings.Repeat("a", 64), false},
+	}...)
+	for n := 0; n < b.N; n++ {
+		for _, tc := range benchmarks {
+			if isDomainName(tc.name) != tc.result {
+				b.Errorf("isDomainName(%q) = %v; want %v", tc.name, !tc.result, tc.result)
+			}
+		}
+	}
+}
diff --git a/src/net/empty.c b/src/net/empty.c
new file mode 100644
index 000000000..a515c2fe2
--- /dev/null
+++ b/src/net/empty.c
@@ -0,0 +1,8 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// This file is required to prevent compiler errors
+// when the package built with CGO_ENABLED=0.
+// Otherwise the compiler says:
+// pkg/net/fd_poll_runtime.go:15: missing function body
diff --git a/src/net/example_test.go b/src/net/example_test.go
new file mode 100644
index 000000000..6f2f9074c
--- /dev/null
+++ b/src/net/example_test.go
@@ -0,0 +1,36 @@
+// Copyright 2012 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package net_test
+
+import (
+	"io"
+	"log"
+	"net"
+)
+
+func ExampleListener() {
+	// Listen on TCP port 2000 on all interfaces.
+	l, err := net.Listen("tcp", ":2000")
+	if err != nil {
+		log.Fatal(err)
+	}
+	defer l.Close()
+	for {
+		// Wait for a connection.
+		conn, err := l.Accept()
+		if err != nil {
+			log.Fatal(err)
+		}
+		// Handle the connection in a new goroutine.
+		// The loop then returns to accepting, so that
+		// multiple connections may be served concurrently.
+		go func(c net.Conn) {
+			// Echo all incoming data.
+			io.Copy(c, c)
+			// Shut down the connection.
+			c.Close()
+		}(conn)
+	}
+}
diff --git a/src/net/fd_mutex.go b/src/net/fd_mutex.go
new file mode 100644
index 000000000..6d5509d7f
--- /dev/null
+++ b/src/net/fd_mutex.go
@@ -0,0 +1,184 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package net
+
+import "sync/atomic"
+
+// fdMutex is a specialized synchronization primitive
+// that manages lifetime of an fd and serializes access
+// to Read and Write methods on netFD.
+type fdMutex struct {
+	state uint64
+	rsema uint32
+	wsema uint32
+}
+
+// fdMutex.state is organized as follows:
+// 1 bit - whether netFD is closed, if set all subsequent lock operations will fail.
+// 1 bit - lock for read operations.
+// 1 bit - lock for write operations.
+// 20 bits - total number of references (read+write+misc).
+// 20 bits - number of outstanding read waiters.
+// 20 bits - number of outstanding write waiters.
+const (
+	mutexClosed  = 1 << 0
+	mutexRLock   = 1 << 1
+	mutexWLock   = 1 << 2
+	mutexRef     = 1 << 3
+	mutexRefMask = (1<<20 - 1) << 3
+	mutexRWait   = 1 << 23
+	mutexRMask   = (1<<20 - 1) << 23
+	mutexWWait   = 1 << 43
+	mutexWMask   = (1<<20 - 1) << 43
+)
+
+// Read operations must do RWLock(true)/RWUnlock(true).
+// Write operations must do RWLock(false)/RWUnlock(false).
+// Misc operations must do Incref/Decref. Misc operations include functions like
+// setsockopt and setDeadline. They need to use Incref/Decref to ensure that
+// they operate on the correct fd in presence of a concurrent Close call
+// (otherwise fd can be closed under their feet).
+// Close operation must do IncrefAndClose/Decref.
+
+// RWLock/Incref return whether fd is open.
+// RWUnlock/Decref return whether fd is closed and there are no remaining references.
+
+func (mu *fdMutex) Incref() bool {
+	for {
+		old := atomic.LoadUint64(&mu.state)
+		if old&mutexClosed != 0 {
+			return false
+		}
+		new := old + mutexRef
+		if new&mutexRefMask == 0 {
+			panic("net: inconsistent fdMutex")
+		}
+		if atomic.CompareAndSwapUint64(&mu.state, old, new) {
+			return true
+		}
+	}
+}
+
+func (mu *fdMutex) IncrefAndClose() bool {
+	for {
+		old := atomic.LoadUint64(&mu.state)
+		if old&mutexClosed != 0 {
+			return false
+		}
+		// Mark as closed and acquire a reference.
+		new := (old | mutexClosed) + mutexRef
+		if new&mutexRefMask == 0 {
+			panic("net: inconsistent fdMutex")
+		}
+		// Remove all read and write waiters.
+		new &^= mutexRMask | mutexWMask
+		if atomic.CompareAndSwapUint64(&mu.state, old, new) {
+			// Wake all read and write waiters,
+			// they will observe closed flag after wakeup.
+			for old&mutexRMask != 0 {
+				old -= mutexRWait
+				runtime_Semrelease(&mu.rsema)
+			}
+			for old&mutexWMask != 0 {
+				old -= mutexWWait
+				runtime_Semrelease(&mu.wsema)
+			}
+			return true
+		}
+	}
+}
+
+func (mu *fdMutex) Decref() bool {
+	for {
+		old := atomic.LoadUint64(&mu.state)
+		if old&mutexRefMask == 0 {
+			panic("net: inconsistent fdMutex")
+		}
+		new := old - mutexRef
+		if atomic.CompareAndSwapUint64(&mu.state, old, new) {
+			return new&(mutexClosed|mutexRefMask) == mutexClosed
+		}
+	}
+}
+
+func (mu *fdMutex) RWLock(read bool) bool {
+	var mutexBit, mutexWait, mutexMask uint64
+	var mutexSema *uint32
+	if read {
+		mutexBit = mutexRLock
+		mutexWait = mutexRWait
+		mutexMask = mutexRMask
+		mutexSema = &mu.rsema
+	} else {
+		mutexBit = mutexWLock
+		mutexWait = mutexWWait
+		mutexMask = mutexWMask
+		mutexSema = &mu.wsema
+	}
+	for {
+		old := atomic.LoadUint64(&mu.state)
+		if old&mutexClosed != 0 {
+			return false
+		}
+		var new uint64
+		if old&mutexBit == 0 {
+			// Lock is free, acquire it.
+			new = (old | mutexBit) + mutexRef
+			if new&mutexRefMask == 0 {
+				panic("net: inconsistent fdMutex")
+			}
+		} else {
+			// Wait for lock.
+			new = old + mutexWait
+			if new&mutexMask == 0 {
+				panic("net: inconsistent fdMutex")
+			}
+		}
+		if atomic.CompareAndSwapUint64(&mu.state, old, new) {
+			if old&mutexBit == 0 {
+				return true
+			}
+			runtime_Semacquire(mutexSema)
+			// The signaller has subtracted mutexWait.
+		}
+	}
+}
+
+func (mu *fdMutex) RWUnlock(read bool) bool {
+	var mutexBit, mutexWait, mutexMask uint64
+	var mutexSema *uint32
+	if read {
+		mutexBit = mutexRLock
+		mutexWait = mutexRWait
+		mutexMask = mutexRMask
+		mutexSema = &mu.rsema
+	} else {
+		mutexBit = mutexWLock
+		mutexWait = mutexWWait
+		mutexMask = mutexWMask
+		mutexSema = &mu.wsema
+	}
+	for {
+		old := atomic.LoadUint64(&mu.state)
+		if old&mutexBit == 0 || old&mutexRefMask == 0 {
+			panic("net: inconsistent fdMutex")
+		}
+		// Drop lock, drop reference and wake read waiter if present.
+		new := (old &^ mutexBit) - mutexRef
+		if old&mutexMask != 0 {
+			new -= mutexWait
+		}
+		if atomic.CompareAndSwapUint64(&mu.state, old, new) {
+			if old&mutexMask != 0 {
+				runtime_Semrelease(mutexSema)
+			}
+			return new&(mutexClosed|mutexRefMask) == mutexClosed
+		}
+	}
+}
+
+// Implemented in runtime package.
+func runtime_Semacquire(sema *uint32)
+func runtime_Semrelease(sema *uint32)
diff --git a/src/net/fd_mutex_test.go b/src/net/fd_mutex_test.go
new file mode 100644
index 000000000..c34ec59b9
--- /dev/null
+++ b/src/net/fd_mutex_test.go
@@ -0,0 +1,195 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package net
+
+import (
+	"math/rand"
+	"runtime"
+	"testing"
+	"time"
+)
+
+func TestMutexLock(t *testing.T) {
+	var mu fdMutex
+
+	if !mu.Incref() {
+		t.Fatal("broken")
+	}
+	if mu.Decref() {
+		t.Fatal("broken")
+	}
+
+	if !mu.RWLock(true) {
+		t.Fatal("broken")
+	}
+	if mu.RWUnlock(true) {
+		t.Fatal("broken")
+	}
+
+	if !mu.RWLock(false) {
+		t.Fatal("broken")
+	}
+	if mu.RWUnlock(false) {
+		t.Fatal("broken")
+	}
+}
+
+func TestMutexClose(t *testing.T) {
+	var mu fdMutex
+	if !mu.IncrefAndClose() {
+		t.Fatal("broken")
+	}
+
+	if mu.Incref() {
+		t.Fatal("broken")
+	}
+	if mu.RWLock(true) {
+		t.Fatal("broken")
+	}
+	if mu.RWLock(false) {
+		t.Fatal("broken")
+	}
+	if mu.IncrefAndClose() {
+		t.Fatal("broken")
+	}
+}
+
+func TestMutexCloseUnblock(t *testing.T) {
+	c := make(chan bool)
+	var mu fdMutex
+	mu.RWLock(true)
+	for i := 0; i < 4; i++ {
+		go func() {
+			if mu.RWLock(true) {
+				t.Error("broken")
+				return
+			}
+			c <- true
+		}()
+	}
+	// Concurrent goroutines must not be able to read lock the mutex.
+	time.Sleep(time.Millisecond)
+	select {
+	case <-c:
+		t.Fatal("broken")
+	default:
+	}
+	mu.IncrefAndClose() // Must unblock the readers.
+	for i := 0; i < 4; i++ {
+		select {
+		case <-c:
+		case <-time.After(10 * time.Second):
+			t.Fatal("broken")
+		}
+	}
+	if mu.Decref() {
+		t.Fatal("broken")
+	}
+	if !mu.RWUnlock(true) {
+		t.Fatal("broken")
+	}
+}
+
+func TestMutexPanic(t *testing.T) {
+	ensurePanics := func(f func()) {
+		defer func() {
+			if recover() == nil {
+				t.Fatal("does not panic")
+			}
+		}()
+		f()
+	}
+
+	var mu fdMutex
+	ensurePanics(func() { mu.Decref() })
+	ensurePanics(func() { mu.RWUnlock(true) })
+	ensurePanics(func() { mu.RWUnlock(false) })
+
+	ensurePanics(func() { mu.Incref(); mu.Decref(); mu.Decref() })
+	ensurePanics(func() { mu.RWLock(true); mu.RWUnlock(true); mu.RWUnlock(true) })
+	ensurePanics(func() { mu.RWLock(false); mu.RWUnlock(false); mu.RWUnlock(false) })
+
+	// ensure that it's still not broken
+	mu.Incref()
+	mu.Decref()
+	mu.RWLock(true)
+	mu.RWUnlock(true)
+	mu.RWLock(false)
+	mu.RWUnlock(false)
+}
+
+func TestMutexStress(t *testing.T) {
+	P := 8
+	N := int(1e6)
+	if testing.Short() {
+		P = 4
+		N = 1e4
+	}
+	defer runtime.GOMAXPROCS(runtime.GOMAXPROCS(P))
+	done := make(chan bool)
+	var mu fdMutex
+	var readState [2]uint64
+	var writeState [2]uint64
+	for p := 0; p < P; p++ {
+		go func() {
+			r := rand.New(rand.NewSource(rand.Int63()))
+			for i := 0; i < N; i++ {
+				switch r.Intn(3) {
+				case 0:
+					if !mu.Incref() {
+						t.Error("broken")
+						return
+					}
+					if mu.Decref() {
+						t.Error("broken")
+						return
+					}
+				case 1:
+					if !mu.RWLock(true) {
+						t.Error("broken")
+						return
+					}
+					// Ensure that it provides mutual exclusion for readers.
+					if readState[0] != readState[1] {
+						t.Error("broken")
+						return
+					}
+					readState[0]++
+					readState[1]++
+					if mu.RWUnlock(true) {
+						t.Error("broken")
+						return
+					}
+				case 2:
+					if !mu.RWLock(false) {
+						t.Error("broken")
+						return
+					}
+					// Ensure that it provides mutual exclusion for writers.
+					if writeState[0] != writeState[1] {
+						t.Error("broken")
+						return
+					}
+					writeState[0]++
+					writeState[1]++
+					if mu.RWUnlock(false) {
+						t.Error("broken")
+						return
+					}
+				}
+			}
+			done <- true
+		}()
+	}
+	for p := 0; p < P; p++ {
+		<-done
+	}
+	if !mu.IncrefAndClose() {
+		t.Fatal("broken")
+	}
+	if !mu.Decref() {
+		t.Fatal("broken")
+	}
+}
diff --git a/src/net/fd_plan9.go b/src/net/fd_plan9.go
new file mode 100644
index 000000000..5fe8effc2
--- /dev/null
+++ b/src/net/fd_plan9.go
@@ -0,0 +1,232 @@
+// Copyright 2009 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package net
+
+import (
+	"io"
+	"os"
+	"syscall"
+	"time"
+)
+
+// Network file descritor.
+type netFD struct {
+	// locking/lifetime of sysfd + serialize access to Read and Write methods
+	fdmu fdMutex
+
+	// immutable until Close
+	proto        string
+	n            string
+	dir          string
+	ctl, data    *os.File
+	laddr, raddr Addr
+}
+
+var (
+	netdir string // default network
+)
+
+func sysInit() {
+	netdir = "/net"
+}
+
+func dial(net string, ra Addr, dialer func(time.Time) (Conn, error), deadline time.Time) (Conn, error) {
+	// On plan9, use the relatively inefficient
+	// goroutine-racing implementation.
+	return dialChannel(net, ra, dialer, deadline)
+}
+
+func newFD(proto, name string, ctl, data *os.File, laddr, raddr Addr) (*netFD, error) {
+	return &netFD{proto: proto, n: name, dir: netdir + "/" + proto + "/" + name, ctl: ctl, data: data, laddr: laddr, raddr: raddr}, nil
+}
+
+func (fd *netFD) init() error {
+	// stub for future fd.pd.Init(fd)
+	return nil
+}
+
+func (fd *netFD) name() string {
+	var ls, rs string
+	if fd.laddr != nil {
+		ls = fd.laddr.String()
+	}
+	if fd.raddr != nil {
+		rs = fd.raddr.String()
+	}
+	return fd.proto + ":" + ls + "->" + rs
+}
+
+func (fd *netFD) ok() bool { return fd != nil && fd.ctl != nil }
+
+func (fd *netFD) destroy() {
+	if !fd.ok() {
+		return
+	}
+	err := fd.ctl.Close()
+	if fd.data != nil {
+		if err1 := fd.data.Close(); err1 != nil && err == nil {
+			err = err1
+		}
+	}
+	fd.ctl = nil
+	fd.data = nil
+}
+
+// Add a reference to this fd.
+// Returns an error if the fd cannot be used.
+func (fd *netFD) incref() error {
+	if !fd.fdmu.Incref() {
+		return errClosing
+	}
+	return nil
+}
+
+// Remove a reference to this FD and close if we've been asked to do so
+// (and there are no references left).
+func (fd *netFD) decref() {
+	if fd.fdmu.Decref() {
+		fd.destroy()
+	}
+}
+
+// Add a reference to this fd and lock for reading.
+// Returns an error if the fd cannot be used.
+func (fd *netFD) readLock() error {
+	if !fd.fdmu.RWLock(true) {
+		return errClosing
+	}
+	return nil
+}
+
+// Unlock for reading and remove a reference to this FD.
+func (fd *netFD) readUnlock() {
+	if fd.fdmu.RWUnlock(true) {
+		fd.destroy()
+	}
+}
+
+// Add a reference to this fd and lock for writing.
+// Returns an error if the fd cannot be used.
+func (fd *netFD) writeLock() error {
+	if !fd.fdmu.RWLock(false) {
+		return errClosing
+	}
+	return nil
+}
+
+// Unlock for writing and remove a reference to this FD.
+func (fd *netFD) writeUnlock() {
+	if fd.fdmu.RWUnlock(false) {
+		fd.destroy()
+	}
+}
+
+func (fd *netFD) Read(b []byte) (n int, err error) {
+	if !fd.ok() || fd.data == nil {
+		return 0, syscall.EINVAL
+	}
+	if err := fd.readLock(); err != nil {
+		return 0, err
+	}
+	defer fd.readUnlock()
+	n, err = fd.data.Read(b)
+	if fd.proto == "udp" && err == io.EOF {
+		n = 0
+		err = nil
+	}
+	return
+}
+
+func (fd *netFD) Write(b []byte) (n int, err error) {
+	if !fd.ok() || fd.data == nil {
+		return 0, syscall.EINVAL
+	}
+	if err := fd.writeLock(); err != nil {
+		return 0, err
+	}
+	defer fd.writeUnlock()
+	return fd.data.Write(b)
+}
+
+func (fd *netFD) closeRead() error {
+	if !fd.ok() {
+		return syscall.EINVAL
+	}
+	return syscall.EPLAN9
+}
+
+func (fd *netFD) closeWrite() error {
+	if !fd.ok() {
+		return syscall.EINVAL
+	}
+	return syscall.EPLAN9
+}
+
+func (fd *netFD) Close() error {
+	if !fd.fdmu.IncrefAndClose() {
+		return errClosing
+	}
+	if !fd.ok() {
+		return syscall.EINVAL
+	}
+	err := fd.ctl.Close()
+	if fd.data != nil {
+		if err1 := fd.data.Close(); err1 != nil && err == nil {
+			err = err1
+		}
+	}
+	fd.ctl = nil
+	fd.data = nil
+	return err
+}
+
+// This method is only called via Conn.
+func (fd *netFD) dup() (*os.File, error) {
+	if !fd.ok() || fd.data == nil {
+		return nil, syscall.EINVAL
+	}
+	return fd.file(fd.data, fd.dir+"/data")
+}
+
+func (l *TCPListener) dup() (*os.File, error) {
+	if !l.fd.ok() {
+		return nil, syscall.EINVAL
+	}
+	return l.fd.file(l.fd.ctl, l.fd.dir+"/ctl")
+}
+
+func (fd *netFD) file(f *os.File, s string) (*os.File, error) {
+	syscall.ForkLock.RLock()
+	dfd, err := syscall.Dup(int(f.Fd()), -1)
+	syscall.ForkLock.RUnlock()
+	if err != nil {
+		return nil, &OpError{"dup", s, fd.laddr, err}
+	}
+	return os.NewFile(uintptr(dfd), s), nil
+}
+
+func (fd *netFD) setDeadline(t time.Time) error {
+	return syscall.EPLAN9
+}
+
+func (fd *netFD) setReadDeadline(t time.Time) error {
+	return syscall.EPLAN9
+}
+
+func (fd *netFD) setWriteDeadline(t time.Time) error {
+	return syscall.EPLAN9
+}
+
+func setReadBuffer(fd *netFD, bytes int) error {
+	return syscall.EPLAN9
+}
+
+func setWriteBuffer(fd *netFD, bytes int) error {
+	return syscall.EPLAN9
+}
+
+func skipRawSocketTests() (skip bool, skipmsg string, err error) {
+	return true, "skipping test on plan9", nil
+}
diff --git a/src/net/fd_poll_nacl.go b/src/net/fd_poll_nacl.go
new file mode 100644
index 000000000..a3701f876
--- /dev/null
+++ b/src/net/fd_poll_nacl.go
@@ -0,0 +1,94 @@
+// Copyright 2013 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package net
+
+import (
+	"syscall"
+	"time"
+)
+
+type pollDesc struct {
+	fd      *netFD
+	closing bool
+}
+
+func (pd *pollDesc) Init(fd *netFD) error { pd.fd = fd; return nil }
+
+func (pd *pollDesc) Close() {}
+
+func (pd *pollDesc) Lock() {}
+
+func (pd *pollDesc) Unlock() {}
+
+func (pd *pollDesc) Wakeup() {}
+
+func (pd *pollDesc) Evict() bool {
+	pd.closing = true
+	if pd.fd != nil {
+		syscall.StopIO(pd.fd.sysfd)
+	}
+	return false
+}
+
+func (pd *pollDesc) Prepare(mode int) error {
+	if pd.closing {
+		return errClosing
+	}
+	return nil
+}
+
+func (pd *pollDesc) PrepareRead() error { return pd.Prepare('r') }
+
+func (pd *pollDesc) PrepareWrite() error { return pd.Prepare('w') }
+
+func (pd *pollDesc) Wait(mode int) error {
+	if pd.closing {
+		return errClosing
+	}
+	return errTimeout
+}
+
+func (pd *pollDesc) WaitRead() error { return pd.Wait('r') }
+
+func (pd *pollDesc) WaitWrite() error { return pd.Wait('w') }
+
+func (pd *pollDesc) WaitCanceled(mode int) {}
+
+func (pd *pollDesc) WaitCanceledRead() {}
+
+func (pd *pollDesc) WaitCanceledWrite() {}
+
+func (fd *netFD) setDeadline(t time.Time) error {
+	return setDeadlineImpl(fd, t, 'r'+'w')
+}
+
+func (fd *netFD) setReadDeadline(t time.Time) error {
+	return setDeadlineImpl(fd, t, 'r')
+}
+
+func (fd *netFD) setWriteDeadline(t time.Time) error {
+	return setDeadlineImpl(fd, t, 'w')
+}
+
+func setDeadlineImpl(fd *netFD, t time.Time, mode int) error {
+	d := t.UnixNano()
+	if t.IsZero() {
+		d = 0
+	}
+	if err := fd.incref(); err != nil {
+		return err
+	}
+	switch mode {
+	case 'r':
+		syscall.SetReadDeadline(fd.sysfd, d)
+	case 'w':
+		syscall.SetWriteDeadline(fd.sysfd, d)
+	case 'r' + 'w':
+		syscall.SetReadDeadline(fd.sysfd, d)
+		syscall.SetWriteDeadline(fd.sysfd, d)
+	}
+	fd.decref()
+	return nil
+}
diff --git a/src/net/fd_poll_runtime.go b/src/net/fd_poll_runtime.go
new file mode 100644
index 000000000..2bddc836c
--- /dev/null
+++ b/src/net/fd_poll_runtime.go
@@ -0,0 +1,144 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build darwin dragonfly freebsd linux netbsd openbsd windows solaris
+
+package net
+
+import (
+	"sync"
+	"syscall"
+	"time"
+)
+
+// runtimeNano returns the current value of the runtime clock in nanoseconds.
+func runtimeNano() int64
+
+func runtime_pollServerInit()
+func runtime_pollOpen(fd uintptr) (uintptr, int)
+func runtime_pollClose(ctx uintptr)
+func runtime_pollWait(ctx uintptr, mode int) int
+func runtime_pollWaitCanceled(ctx uintptr, mode int) int
+func runtime_pollReset(ctx uintptr, mode int) int
+func runtime_pollSetDeadline(ctx uintptr, d int64, mode int)
+func runtime_pollUnblock(ctx uintptr)
+
+type pollDesc struct {
+	runtimeCtx uintptr
+}
+
+var serverInit sync.Once
+
+func (pd *pollDesc) Init(fd *netFD) error {
+	serverInit.Do(runtime_pollServerInit)
+	ctx, errno := runtime_pollOpen(uintptr(fd.sysfd))
+	if errno != 0 {
+		return syscall.Errno(errno)
+	}
+	pd.runtimeCtx = ctx
+	return nil
+}
+
+func (pd *pollDesc) Close() {
+	if pd.runtimeCtx == 0 {
+		return
+	}
+	runtime_pollClose(pd.runtimeCtx)
+	pd.runtimeCtx = 0
+}
+
+func (pd *pollDesc) Lock() {
+}
+
+func (pd *pollDesc) Unlock() {
+}
+
+func (pd *pollDesc) Wakeup() {
+}
+
+// Evict evicts fd from the pending list, unblocking any I/O running on fd.
+// Return value is whether the pollServer should be woken up.
+func (pd *pollDesc) Evict() bool {
+	if pd.runtimeCtx == 0 {
+		return false
+	}
+	runtime_pollUnblock(pd.runtimeCtx)
+	return false
+}
+
+func (pd *pollDesc) Prepare(mode int) error {
+	res := runtime_pollReset(pd.runtimeCtx, mode)
+	return convertErr(res)
+}
+
+func (pd *pollDesc) PrepareRead() error {
+	return pd.Prepare('r')
+}
+
+func (pd *pollDesc) PrepareWrite() error {
+	return pd.Prepare('w')
+}
+
+func (pd *pollDesc) Wait(mode int) error {
+	res := runtime_pollWait(pd.runtimeCtx, mode)
+	return convertErr(res)
+}
+
+func (pd *pollDesc) WaitRead() error {
+	return pd.Wait('r')
+}
+
+func (pd *pollDesc) WaitWrite() error {
+	return pd.Wait('w')
+}
+
+func (pd *pollDesc) WaitCanceled(mode int) {
+	runtime_pollWaitCanceled(pd.runtimeCtx, mode)
+}
+
+func (pd *pollDesc) WaitCanceledRead() {
+	pd.WaitCanceled('r')
+}
+
+func (pd *pollDesc) WaitCanceledWrite() {
+	pd.WaitCanceled('w')
+}
+
+func convertErr(res int) error {
+	switch res {
+	case 0:
+		return nil
+	case 1:
+		return errClosing
+	case 2:
+		return errTimeout
+	}
+	println("unreachable: ", res)
+	panic("unreachable")
+}
+
+func (fd *netFD) setDeadline(t time.Time) error {
+	return setDeadlineImpl(fd, t, 'r'+'w')
+}
+
+func (fd *netFD) setReadDeadline(t time.Time) error {
+	return setDeadlineImpl(fd, t, 'r')
+}
+
+func (fd *netFD) setWriteDeadline(t time.Time) error {
+	return setDeadlineImpl(fd, t, 'w')
+}
+
+func setDeadlineImpl(fd *netFD, t time.Time, mode int) error {
+	d := runtimeNano() + int64(t.Sub(time.Now()))
+	if t.IsZero() {
+		d = 0
+	}
+	if err := fd.incref(); err != nil {
+		return err
+	}
+	runtime_pollSetDeadline(fd.pd.runtimeCtx, d, mode)
+	fd.decref()
+	return nil
+}
diff --git a/src/net/fd_unix.go b/src/net/fd_unix.go
new file mode 100644
index 000000000..7fa43f6ab
--- /dev/null
+++ b/src/net/fd_unix.go
@@ -0,0 +1,518 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build darwin dragonfly freebsd linux nacl netbsd openbsd solaris
+
+package net
+
+import (
+	"io"
+	"os"
+	"runtime"
+	"sync/atomic"
+	"syscall"
+	"time"
+)
+
+// Network file descriptor.
+type netFD struct {
+	// locking/lifetime of sysfd + serialize access to Read and Write methods
+	fdmu fdMutex
+
+	// immutable until Close
+	sysfd       int
+	family      int
+	sotype      int
+	isConnected bool
+	net         string
+	laddr       Addr
+	raddr       Addr
+
+	// wait server
+	pd pollDesc
+}
+
+func sysInit() {
+}
+
+func dial(network string, ra Addr, dialer func(time.Time) (Conn, error), deadline time.Time) (Conn, error) {
+	return dialer(deadline)
+}
+
+func newFD(sysfd, family, sotype int, net string) (*netFD, error) {
+	return &netFD{sysfd: sysfd, family: family, sotype: sotype, net: net}, nil
+}
+
+func (fd *netFD) init() error {
+	if err := fd.pd.Init(fd); err != nil {
+		return err
+	}
+	return nil
+}
+
+func (fd *netFD) setAddr(laddr, raddr Addr) {
+	fd.laddr = laddr
+	fd.raddr = raddr
+	runtime.SetFinalizer(fd, (*netFD).Close)
+}
+
+func (fd *netFD) name() string {
+	var ls, rs string
+	if fd.laddr != nil {
+		ls = fd.laddr.String()
+	}
+	if fd.raddr != nil {
+		rs = fd.raddr.String()
+	}
+	return fd.net + ":" + ls + "->" + rs
+}
+
+func (fd *netFD) connect(la, ra syscall.Sockaddr, deadline time.Time) error {
+	// Do not need to call fd.writeLock here,
+	// because fd is not yet accessible to user,
+	// so no concurrent operations are possible.
+	switch err := syscall.Connect(fd.sysfd, ra); err {
+	case syscall.EINPROGRESS, syscall.EALREADY, syscall.EINTR:
+	case nil, syscall.EISCONN:
+		if !deadline.IsZero() && deadline.Before(time.Now()) {
+			return errTimeout
+		}
+		if err := fd.init(); err != nil {
+			return err
+		}
+		return nil
+	case syscall.EINVAL:
+		// On Solaris we can see EINVAL if the socket has
+		// already been accepted and closed by the server.
+		// Treat this as a successful connection--writes to
+		// the socket will see EOF.  For details and a test
+		// case in C see http://golang.org/issue/6828.
+		if runtime.GOOS == "solaris" {
+			return nil
+		}
+		fallthrough
+	default:
+		return err
+	}
+	if err := fd.init(); err != nil {
+		return err
+	}
+	if !deadline.IsZero() {
+		fd.setWriteDeadline(deadline)
+		defer fd.setWriteDeadline(noDeadline)
+	}
+	for {
+		// Performing multiple connect system calls on a
+		// non-blocking socket under Unix variants does not
+		// necessarily result in earlier errors being
+		// returned. Instead, once runtime-integrated network
+		// poller tells us that the socket is ready, get the
+		// SO_ERROR socket option to see if the connection
+		// succeeded or failed. See issue 7474 for further
+		// details.
+		if err := fd.pd.WaitWrite(); err != nil {
+			return err
+		}
+		nerr, err := syscall.GetsockoptInt(fd.sysfd, syscall.SOL_SOCKET, syscall.SO_ERROR)
+		if err != nil {
+			return err
+		}
+		switch err := syscall.Errno(nerr); err {
+		case syscall.EINPROGRESS, syscall.EALREADY, syscall.EINTR:
+		case syscall.Errno(0), syscall.EISCONN:
+			return nil
+		default:
+			return err
+		}
+	}
+}
+
+func (fd *netFD) destroy() {
+	// Poller may want to unregister fd in readiness notification mechanism,
+	// so this must be executed before closesocket.
+	fd.pd.Close()
+	closesocket(fd.sysfd)
+	fd.sysfd = -1
+	runtime.SetFinalizer(fd, nil)
+}
+
+// Add a reference to this fd.
+// Returns an error if the fd cannot be used.
+func (fd *netFD) incref() error {
+	if !fd.fdmu.Incref() {
+		return errClosing
+	}
+	return nil
+}
+
+// Remove a reference to this FD and close if we've been asked to do so
+// (and there are no references left).
+func (fd *netFD) decref() {
+	if fd.fdmu.Decref() {
+		fd.destroy()
+	}
+}
+
+// Add a reference to this fd and lock for reading.
+// Returns an error if the fd cannot be used.
+func (fd *netFD) readLock() error {
+	if !fd.fdmu.RWLock(true) {
+		return errClosing
+	}
+	return nil
+}
+
+// Unlock for reading and remove a reference to this FD.
+func (fd *netFD) readUnlock() {
+	if fd.fdmu.RWUnlock(true) {
+		fd.destroy()
+	}
+}
+
+// Add a reference to this fd and lock for writing.
+// Returns an error if the fd cannot be used.
+func (fd *netFD) writeLock() error {
+	if !fd.fdmu.RWLock(false) {
+		return errClosing
+	}
+	return nil
+}
+
+// Unlock for writing and remove a reference to this FD.
+func (fd *netFD) writeUnlock() {
+	if fd.fdmu.RWUnlock(false) {
+		fd.destroy()
+	}
+}
+
+func (fd *netFD) Close() error {
+	fd.pd.Lock() // needed for both fd.incref(true) and pollDesc.Evict
+	if !fd.fdmu.IncrefAndClose() {
+		fd.pd.Unlock()
+		return errClosing
+	}
+	// Unblock any I/O.  Once it all unblocks and returns,
+	// so that it cannot be referring to fd.sysfd anymore,
+	// the final decref will close fd.sysfd.  This should happen
+	// fairly quickly, since all the I/O is non-blocking, and any
+	// attempts to block in the pollDesc will return errClosing.
+	doWakeup := fd.pd.Evict()
+	fd.pd.Unlock()
+	fd.decref()
+	if doWakeup {
+		fd.pd.Wakeup()
+	}
+	return nil
+}
+
+func (fd *netFD) shutdown(how int) error {
+	if err := fd.incref(); err != nil {
+		return err
+	}
+	defer fd.decref()
+	err := syscall.Shutdown(fd.sysfd, how)
+	if err != nil {
+		return &OpError{"shutdown", fd.net, fd.laddr, err}
+	}
+	return nil
+}
+
+func (fd *netFD) closeRead() error {
+	return fd.shutdown(syscall.SHUT_RD)
+}
+
+func (fd *netFD) closeWrite() error {
+	return fd.shutdown(syscall.SHUT_WR)
+}
+
+func (fd *netFD) Read(p []byte) (n int, err error) {
+	if err := fd.readLock(); err != nil {
+		return 0, err
+	}
+	defer fd.readUnlock()
+	if err := fd.pd.PrepareRead(); err != nil {
+		return 0, &OpError{"read", fd.net, fd.raddr, err}
+	}
+	for {
+		n, err = syscall.Read(int(fd.sysfd), p)
+		if err != nil {
+			n = 0
+			if err == syscall.EAGAIN {
+				if err = fd.pd.WaitRead(); err == nil {
+					continue
+				}
+			}
+		}
+		err = chkReadErr(n, err, fd)
+		break
+	}
+	if err != nil && err != io.EOF {
+		err = &OpError{"read", fd.net, fd.raddr, err}
+	}
+	return
+}
+
+func (fd *netFD) readFrom(p []byte) (n int, sa syscall.Sockaddr, err error) {
+	if err := fd.readLock(); err != nil {
+		return 0, nil, err
+	}
+	defer fd.readUnlock()
+	if err := fd.pd.PrepareRead(); err != nil {
+		return 0, nil, &OpError{"read", fd.net, fd.laddr, err}
+	}
+	for {
+		n, sa, err = syscall.Recvfrom(fd.sysfd, p, 0)
+		if err != nil {
+			n = 0
+			if err == syscall.EAGAIN {
+				if err = fd.pd.WaitRead(); err == nil {
+					continue
+				}
+			}
+		}
+		err = chkReadErr(n, err, fd)
+		break
+	}
+	if err != nil && err != io.EOF {
+		err = &OpError{"read", fd.net, fd.laddr, err}
+	}
+	return
+}
+
+func (fd *netFD) readMsg(p []byte, oob []byte) (n, oobn, flags int, sa syscall.Sockaddr, err error) {
+	if err := fd.readLock(); err != nil {
+		return 0, 0, 0, nil, err
+	}
+	defer fd.readUnlock()
+	if err := fd.pd.PrepareRead(); err != nil {
+		return 0, 0, 0, nil, &OpError{"read", fd.net, fd.laddr, err}
+	}
+	for {
+		n, oobn, flags, sa, err = syscall.Recvmsg(fd.sysfd, p, oob, 0)
+		if err != nil {
+			// TODO(dfc) should n and oobn be set to 0
+			if err == syscall.EAGAIN {
+				if err = fd.pd.WaitRead(); err == nil {
+					continue
+				}
+			}
+		}
+		err = chkReadErr(n, err, fd)
+		break
+	}
+	if err != nil && err != io.EOF {
+		err = &OpError{"read", fd.net, fd.laddr, err}
+	}
+	return
+}
+
+func chkReadErr(n int, err error, fd *netFD) error {
+	if n == 0 && err == nil && fd.sotype != syscall.SOCK_DGRAM && fd.sotype != syscall.SOCK_RAW {
+		return io.EOF
+	}
+	return err
+}
+
+func (fd *netFD) Write(p []byte) (nn int, err error) {
+	if err := fd.writeLock(); err != nil {
+		return 0, err
+	}
+	defer fd.writeUnlock()
+	if err := fd.pd.PrepareWrite(); err != nil {
+		return 0, &OpError{"write", fd.net, fd.raddr, err}
+	}
+	for {
+		var n int
+		n, err = syscall.Write(int(fd.sysfd), p[nn:])
+		if n > 0 {
+			nn += n
+		}
+		if nn == len(p) {
+			break
+		}
+		if err == syscall.EAGAIN {
+			if err = fd.pd.WaitWrite(); err == nil {
+				continue
+			}
+		}
+		if err != nil {
+			n = 0
+			break
+		}
+		if n == 0 {
+			err = io.ErrUnexpectedEOF
+			break
+		}
+	}
+	if err != nil {
+		err = &OpError{"write", fd.net, fd.raddr, err}
+	}
+	return nn, err
+}
+
+func (fd *netFD) writeTo(p []byte, sa syscall.Sockaddr) (n int, err error) {
+	if err := fd.writeLock(); err != nil {
+		return 0, err
+	}
+	defer fd.writeUnlock()
+	if err := fd.pd.PrepareWrite(); err != nil {
+		return 0, &OpError{"write", fd.net, fd.raddr, err}
+	}
+	for {
+		err = syscall.Sendto(fd.sysfd, p, 0, sa)
+		if err == syscall.EAGAIN {
+			if err = fd.pd.WaitWrite(); err == nil {
+				continue
+			}
+		}
+		break
+	}
+	if err == nil {
+		n = len(p)
+	} else {
+		err = &OpError{"write", fd.net, fd.raddr, err}
+	}
+	return
+}
+
+func (fd *netFD) writeMsg(p []byte, oob []byte, sa syscall.Sockaddr) (n int, oobn int, err error) {
+	if err := fd.writeLock(); err != nil {
+		return 0, 0, err
+	}
+	defer fd.writeUnlock()
+	if err := fd.pd.PrepareWrite(); err != nil {
+		return 0, 0, &OpError{"write", fd.net, fd.raddr, err}
+	}
+	for {
+		n, err = syscall.SendmsgN(fd.sysfd, p, oob, sa, 0)
+		if err == syscall.EAGAIN {
+			if err = fd.pd.WaitWrite(); err == nil {
+				continue
+			}
+		}
+		break
+	}
+	if err == nil {
+		oobn = len(oob)
+	} else {
+		err = &OpError{"write", fd.net, fd.raddr, err}
+	}
+	return
+}
+
+func (fd *netFD) accept() (netfd *netFD, err error) {
+	if err := fd.readLock(); err != nil {
+		return nil, err
+	}
+	defer fd.readUnlock()
+
+	var s int
+	var rsa syscall.Sockaddr
+	if err = fd.pd.PrepareRead(); err != nil {
+		return nil, &OpError{"accept", fd.net, fd.laddr, err}
+	}
+	for {
+		s, rsa, err = accept(fd.sysfd)
+		if err != nil {
+			if err == syscall.EAGAIN {
+				if err = fd.pd.WaitRead(); err == nil {
+					continue
+				}
+			} else if err == syscall.ECONNABORTED {
+				// This means that a socket on the listen queue was closed
+				// before we Accept()ed it; it's a silly error, so try again.
+				continue
+			}
+			return nil, &OpError{"accept", fd.net, fd.laddr, err}
+		}
+		break
+	}
+
+	if netfd, err = newFD(s, fd.family, fd.sotype, fd.net); err != nil {
+		closesocket(s)
+		return nil, err
+	}
+	if err = netfd.init(); err != nil {
+		fd.Close()
+		return nil, err
+	}
+	lsa, _ := syscall.Getsockname(netfd.sysfd)
+	netfd.setAddr(netfd.addrFunc()(lsa), netfd.addrFunc()(rsa))
+	return netfd, nil
+}
+
+// tryDupCloexec indicates whether F_DUPFD_CLOEXEC should be used.
+// If the kernel doesn't support it, this is set to 0.
+var tryDupCloexec = int32(1)
+
+func dupCloseOnExec(fd int) (newfd int, err error) {
+	if atomic.LoadInt32(&tryDupCloexec) == 1 {
+		r0, _, e1 := syscall.Syscall(syscall.SYS_FCNTL, uintptr(fd), syscall.F_DUPFD_CLOEXEC, 0)
+		if runtime.GOOS == "darwin" && e1 == syscall.EBADF {
+			// On OS X 10.6 and below (but we only support
+			// >= 10.6), F_DUPFD_CLOEXEC is unsupported
+			// and fcntl there falls back (undocumented)
+			// to doing an ioctl instead, returning EBADF
+			// in this case because fd is not of the
+			// expected device fd type.  Treat it as
+			// EINVAL instead, so we fall back to the
+			// normal dup path.
+			// TODO: only do this on 10.6 if we can detect 10.6
+			// cheaply.
+			e1 = syscall.EINVAL
+		}
+		switch e1 {
+		case 0:
+			return int(r0), nil
+		case syscall.EINVAL:
+			// Old kernel. Fall back to the portable way
+			// from now on.
+			atomic.StoreInt32(&tryDupCloexec, 0)
+		default:
+			return -1, e1
+		}
+	}
+	return dupCloseOnExecOld(fd)
+}
+
+// dupCloseOnExecUnixOld is the traditional way to dup an fd and
+// set its O_CLOEXEC bit, using two system calls.
+func dupCloseOnExecOld(fd int) (newfd int, err error) {
+	syscall.ForkLock.RLock()
+	defer syscall.ForkLock.RUnlock()
+	newfd, err = syscall.Dup(fd)
+	if err != nil {
+		return -1, err
+	}
+	syscall.CloseOnExec(newfd)
+	return
+}
+
+func (fd *netFD) dup() (f *os.File, err error) {
+	ns, err := dupCloseOnExec(fd.sysfd)
+	if err != nil {
+		return nil, &OpError{"dup", fd.net, fd.laddr, err}
+	}
+
+	// We want blocking mode for the new fd, hence the double negative.
+	// This also puts the old fd into blocking mode, meaning that
+	// I/O will block the thread instead of letting us use the epoll server.
+	// Everything will still work, just with more threads.
+	if err = syscall.SetNonblock(ns, false); err != nil {
+		return nil, &OpError{"setnonblock", fd.net, fd.laddr, err}
+	}
+
+	return os.NewFile(uintptr(ns), fd.name()), nil
+}
+
+func closesocket(s int) error {
+	return syscall.Close(s)
+}
+
+func skipRawSocketTests() (skip bool, skipmsg string, err error) {
+	if os.Getuid() != 0 {
+		return true, "skipping test; must be root", nil
+	}
+	return false, "", nil
+}
diff --git a/src/net/fd_unix_test.go b/src/net/fd_unix_test.go
new file mode 100644
index 000000000..fe8e8ff6a
--- /dev/null
+++ b/src/net/fd_unix_test.go
@@ -0,0 +1,58 @@
+// Copyright 2012 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build darwin dragonfly freebsd linux netbsd openbsd solaris
+
+package net
+
+import (
+	"io"
+	"syscall"
+	"testing"
+)
+
+var chkReadErrTests = []struct {
+	n        int
+	err      error
+	fd       *netFD
+	expected error
+}{
+
+	{100, nil, &netFD{sotype: syscall.SOCK_STREAM}, nil},
+	{100, io.EOF, &netFD{sotype: syscall.SOCK_STREAM}, io.EOF},
+	{100, errClosing, &netFD{sotype: syscall.SOCK_STREAM}, errClosing},
+	{0, nil, &netFD{sotype: syscall.SOCK_STREAM}, io.EOF},
+	{0, io.EOF, &netFD{sotype: syscall.SOCK_STREAM}, io.EOF},
+	{0, errClosing, &netFD{sotype: syscall.SOCK_STREAM}, errClosing},
+
+	{100, nil, &netFD{sotype: syscall.SOCK_DGRAM}, nil},
+	{100, io.EOF, &netFD{sotype: syscall.SOCK_DGRAM}, io.EOF},
+	{100, errClosing, &netFD{sotype: syscall.SOCK_DGRAM}, errClosing},
+	{0, nil, &netFD{sotype: syscall.SOCK_DGRAM}, nil},
+	{0, io.EOF, &netFD{sotype: syscall.SOCK_DGRAM}, io.EOF},
+	{0, errClosing, &netFD{sotype: syscall.SOCK_DGRAM}, errClosing},
+
+	{100, nil, &netFD{sotype: syscall.SOCK_SEQPACKET}, nil},
+	{100, io.EOF, &netFD{sotype: syscall.SOCK_SEQPACKET}, io.EOF},
+	{100, errClosing, &netFD{sotype: syscall.SOCK_SEQPACKET}, errClosing},
+	{0, nil, &netFD{sotype: syscall.SOCK_SEQPACKET}, io.EOF},
+	{0, io.EOF, &netFD{sotype: syscall.SOCK_SEQPACKET}, io.EOF},
+	{0, errClosing, &netFD{sotype: syscall.SOCK_SEQPACKET}, errClosing},
+
+	{100, nil, &netFD{sotype: syscall.SOCK_RAW}, nil},
+	{100, io.EOF, &netFD{sotype: syscall.SOCK_RAW}, io.EOF},
+	{100, errClosing, &netFD{sotype: syscall.SOCK_RAW}, errClosing},
+	{0, nil, &netFD{sotype: syscall.SOCK_RAW}, nil},
+	{0, io.EOF, &netFD{sotype: syscall.SOCK_RAW}, io.EOF},
+	{0, errClosing, &netFD{sotype: syscall.SOCK_RAW}, errClosing},
+}
+
+func TestChkReadErr(t *testing.T) {
+	for _, tt := range chkReadErrTests {
+		actual := chkReadErr(tt.n, tt.err, tt.fd)
+		if actual != tt.expected {
+			t.Errorf("chkReadError(%v, %v, %v): expected %v, actual %v", tt.n, tt.err, tt.fd.sotype, tt.expected, actual)
+		}
+	}
+}
diff --git a/src/net/fd_windows.go b/src/net/fd_windows.go
new file mode 100644
index 000000000..6d69e0624
--- /dev/null
+++ b/src/net/fd_windows.go
@@ -0,0 +1,644 @@
+// Copyright 2010 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package net
+
+import (
+	"errors"
+	"io"
+	"os"
+	"runtime"
+	"sync"
+	"syscall"
+	"time"
+	"unsafe"
+)
+
+var (
+	initErr error
+	ioSync  uint64
+)
+
+// CancelIo Windows API cancels all outstanding IO for a particular
+// socket on current thread. To overcome that limitation, we run
+// special goroutine, locked to OS single thread, that both starts
+// and cancels IO. It means, there are 2 unavoidable thread switches
+// for every IO.
+// Some newer versions of Windows has new CancelIoEx API, that does
+// not have that limitation and can be used from any thread. This
+// package uses CancelIoEx API, if present, otherwise it fallback
+// to CancelIo.
+
+var (
+	canCancelIO                               bool // determines if CancelIoEx API is present
+	skipSyncNotif                             bool
+	hasLoadSetFileCompletionNotificationModes bool
+)
+
+func sysInit() {
+	var d syscall.WSAData
+	e := syscall.WSAStartup(uint32(0x202), &d)
+	if e != nil {
+		initErr = os.NewSyscallError("WSAStartup", e)
+	}
+	canCancelIO = syscall.LoadCancelIoEx() == nil
+	if syscall.LoadGetAddrInfo() == nil {
+		lookupPort = newLookupPort
+		lookupIP = newLookupIP
+	}
+
+	hasLoadSetFileCompletionNotificationModes = syscall.LoadSetFileCompletionNotificationModes() == nil
+	if hasLoadSetFileCompletionNotificationModes {
+		// It's not safe to use FILE_SKIP_COMPLETION_PORT_ON_SUCCESS if non IFS providers are installed:
+		// http://support.microsoft.com/kb/2568167
+		skipSyncNotif = true
+		protos := [2]int32{syscall.IPPROTO_TCP, 0}
+		var buf [32]syscall.WSAProtocolInfo
+		len := uint32(unsafe.Sizeof(buf))
+		n, err := syscall.WSAEnumProtocols(&protos[0], &buf[0], &len)
+		if err != nil {
+			skipSyncNotif = false
+		} else {
+			for i := int32(0); i < n; i++ {
+				if buf[i].ServiceFlags1&syscall.XP1_IFS_HANDLES == 0 {
+					skipSyncNotif = false
+					break
+				}
+			}
+		}
+	}
+}
+
+func closesocket(s syscall.Handle) error {
+	return syscall.Closesocket(s)
+}
+
+func canUseConnectEx(net string) bool {
+	switch net {
+	case "udp", "udp4", "udp6", "ip", "ip4", "ip6":
+		// ConnectEx windows API does not support connectionless sockets.
+		return false
+	}
+	return syscall.LoadConnectEx() == nil
+}
+
+func dial(net string, ra Addr, dialer func(time.Time) (Conn, error), deadline time.Time) (Conn, error) {
+	if !canUseConnectEx(net) {
+		// Use the relatively inefficient goroutine-racing
+		// implementation of DialTimeout.
+		return dialChannel(net, ra, dialer, deadline)
+	}
+	return dialer(deadline)
+}
+
+// operation contains superset of data necessary to perform all async IO.
+type operation struct {
+	// Used by IOCP interface, it must be first field
+	// of the struct, as our code rely on it.
+	o syscall.Overlapped
+
+	// fields used by runtime.netpoll
+	runtimeCtx uintptr
+	mode       int32
+	errno      int32
+	qty        uint32
+
+	// fields used only by net package
+	fd     *netFD
+	errc   chan error
+	buf    syscall.WSABuf
+	sa     syscall.Sockaddr
+	rsa    *syscall.RawSockaddrAny
+	rsan   int32
+	handle syscall.Handle
+	flags  uint32
+}
+
+func (o *operation) InitBuf(buf []byte) {
+	o.buf.Len = uint32(len(buf))
+	o.buf.Buf = nil
+	if len(buf) != 0 {
+		o.buf.Buf = &buf[0]
+	}
+}
+
+// ioSrv executes net IO requests.
+type ioSrv struct {
+	req chan ioSrvReq
+}
+
+type ioSrvReq struct {
+	o      *operation
+	submit func(o *operation) error // if nil, cancel the operation
+}
+
+// ProcessRemoteIO will execute submit IO requests on behalf
+// of other goroutines, all on a single os thread, so it can
+// cancel them later. Results of all operations will be sent
+// back to their requesters via channel supplied in request.
+// It is used only when the CancelIoEx API is unavailable.
+func (s *ioSrv) ProcessRemoteIO() {
+	runtime.LockOSThread()
+	defer runtime.UnlockOSThread()
+	for r := range s.req {
+		if r.submit != nil {
+			r.o.errc <- r.submit(r.o)
+		} else {
+			r.o.errc <- syscall.CancelIo(r.o.fd.sysfd)
+		}
+	}
+}
+
+// ExecIO executes a single IO operation o. It submits and cancels
+// IO in the current thread for systems where Windows CancelIoEx API
+// is available. Alternatively, it passes the request onto
+// runtime netpoll and waits for completion or cancels request.
+func (s *ioSrv) ExecIO(o *operation, name string, submit func(o *operation) error) (int, error) {
+	fd := o.fd
+	// Notify runtime netpoll about starting IO.
+	err := fd.pd.Prepare(int(o.mode))
+	if err != nil {
+		return 0, &OpError{name, fd.net, fd.laddr, err}
+	}
+	// Start IO.
+	if canCancelIO {
+		err = submit(o)
+	} else {
+		// Send request to a special dedicated thread,
+		// so it can stop the IO with CancelIO later.
+		s.req <- ioSrvReq{o, submit}
+		err = <-o.errc
+	}
+	switch err {
+	case nil:
+		// IO completed immediately
+		if o.fd.skipSyncNotif {
+			// No completion message will follow, so return immediately.
+			return int(o.qty), nil
+		}
+		// Need to get our completion message anyway.
+	case syscall.ERROR_IO_PENDING:
+		// IO started, and we have to wait for its completion.
+		err = nil
+	default:
+		return 0, &OpError{name, fd.net, fd.laddr, err}
+	}
+	// Wait for our request to complete.
+	err = fd.pd.Wait(int(o.mode))
+	if err == nil {
+		// All is good. Extract our IO results and return.
+		if o.errno != 0 {
+			err = syscall.Errno(o.errno)
+			return 0, &OpError{name, fd.net, fd.laddr, err}
+		}
+		return int(o.qty), nil
+	}
+	// IO is interrupted by "close" or "timeout"
+	netpollErr := err
+	switch netpollErr {
+	case errClosing, errTimeout:
+		// will deal with those.
+	default:
+		panic("net: unexpected runtime.netpoll error: " + netpollErr.Error())
+	}
+	// Cancel our request.
+	if canCancelIO {
+		err := syscall.CancelIoEx(fd.sysfd, &o.o)
+		// Assuming ERROR_NOT_FOUND is returned, if IO is completed.
+		if err != nil && err != syscall.ERROR_NOT_FOUND {
+			// TODO(brainman): maybe do something else, but panic.
+			panic(err)
+		}
+	} else {
+		s.req <- ioSrvReq{o, nil}
+		<-o.errc
+	}
+	// Wait for cancellation to complete.
+	fd.pd.WaitCanceled(int(o.mode))
+	if o.errno != 0 {
+		err = syscall.Errno(o.errno)
+		if err == syscall.ERROR_OPERATION_ABORTED { // IO Canceled
+			err = netpollErr
+		}
+		return 0, &OpError{name, fd.net, fd.laddr, err}
+	}
+	// We issued cancellation request. But, it seems, IO operation succeeded
+	// before cancellation request run. We need to treat IO operation as
+	// succeeded (the bytes are actually sent/recv from network).
+	return int(o.qty), nil
+}
+
+// Start helper goroutines.
+var rsrv, wsrv *ioSrv
+var onceStartServer sync.Once
+
+func startServer() {
+	rsrv = new(ioSrv)
+	wsrv = new(ioSrv)
+	if !canCancelIO {
+		// Only CancelIo API is available. Lets start two special goroutines
+		// locked to an OS thread, that both starts and cancels IO. One will
+		// process read requests, while other will do writes.
+		rsrv.req = make(chan ioSrvReq)
+		go rsrv.ProcessRemoteIO()
+		wsrv.req = make(chan ioSrvReq)
+		go wsrv.ProcessRemoteIO()
+	}
+}
+
+// Network file descriptor.
+type netFD struct {
+	// locking/lifetime of sysfd + serialize access to Read and Write methods
+	fdmu fdMutex
+
+	// immutable until Close
+	sysfd         syscall.Handle
+	family        int
+	sotype        int
+	isConnected   bool
+	skipSyncNotif bool
+	net           string
+	laddr         Addr
+	raddr         Addr
+
+	rop operation // read operation
+	wop operation // write operation
+
+	// wait server
+	pd pollDesc
+}
+
+func newFD(sysfd syscall.Handle, family, sotype int, net string) (*netFD, error) {
+	if initErr != nil {
+		return nil, initErr
+	}
+	onceStartServer.Do(startServer)
+	return &netFD{sysfd: sysfd, family: family, sotype: sotype, net: net}, nil
+}
+
+func (fd *netFD) init() error {
+	if err := fd.pd.Init(fd); err != nil {
+		return err
+	}
+	if hasLoadSetFileCompletionNotificationModes {
+		// We do not use events, so we can skip them always.
+		flags := uint8(syscall.FILE_SKIP_SET_EVENT_ON_HANDLE)
+		// It's not safe to skip completion notifications for UDP:
+		// http://blogs.technet.com/b/winserverperformance/archive/2008/06/26/designing-applications-for-high-performance-part-iii.aspx
+		if skipSyncNotif && fd.net == "tcp" {
+			flags |= syscall.FILE_SKIP_COMPLETION_PORT_ON_SUCCESS
+		}
+		err := syscall.SetFileCompletionNotificationModes(fd.sysfd, flags)
+		if err == nil && flags&syscall.FILE_SKIP_COMPLETION_PORT_ON_SUCCESS != 0 {
+			fd.skipSyncNotif = true
+		}
+	}
+	fd.rop.mode = 'r'
+	fd.wop.mode = 'w'
+	fd.rop.fd = fd
+	fd.wop.fd = fd
+	fd.rop.runtimeCtx = fd.pd.runtimeCtx
+	fd.wop.runtimeCtx = fd.pd.runtimeCtx
+	if !canCancelIO {
+		fd.rop.errc = make(chan error)
+		fd.wop.errc = make(chan error)
+	}
+	return nil
+}
+
+func (fd *netFD) setAddr(laddr, raddr Addr) {
+	fd.laddr = laddr
+	fd.raddr = raddr
+	runtime.SetFinalizer(fd, (*netFD).Close)
+}
+
+func (fd *netFD) connect(la, ra syscall.Sockaddr, deadline time.Time) error {
+	// Do not need to call fd.writeLock here,
+	// because fd is not yet accessible to user,
+	// so no concurrent operations are possible.
+	if err := fd.init(); err != nil {
+		return err
+	}
+	if !deadline.IsZero() {
+		fd.setWriteDeadline(deadline)
+		defer fd.setWriteDeadline(noDeadline)
+	}
+	if !canUseConnectEx(fd.net) {
+		return syscall.Connect(fd.sysfd, ra)
+	}
+	// ConnectEx windows API requires an unconnected, previously bound socket.
+	if la == nil {
+		switch ra.(type) {
+		case *syscall.SockaddrInet4:
+			la = &syscall.SockaddrInet4{}
+		case *syscall.SockaddrInet6:
+			la = &syscall.SockaddrInet6{}
+		default:
+			panic("unexpected type in connect")
+		}
+		if err := syscall.Bind(fd.sysfd, la); err != nil {
+			return err
+		}
+	}
+	// Call ConnectEx API.
+	o := &fd.wop
+	o.sa = ra
+	_, err := wsrv.ExecIO(o, "ConnectEx", func(o *operation) error {
+		return syscall.ConnectEx(o.fd.sysfd, o.sa, nil, 0, nil, &o.o)
+	})
+	if err != nil {
+		return err
+	}
+	// Refresh socket properties.
+	return syscall.Setsockopt(fd.sysfd, syscall.SOL_SOCKET, syscall.SO_UPDATE_CONNECT_CONTEXT, (*byte)(unsafe.Pointer(&fd.sysfd)), int32(unsafe.Sizeof(fd.sysfd)))
+}
+
+func (fd *netFD) destroy() {
+	if fd.sysfd == syscall.InvalidHandle {
+		return
+	}
+	// Poller may want to unregister fd in readiness notification mechanism,
+	// so this must be executed before closesocket.
+	fd.pd.Close()
+	closesocket(fd.sysfd)
+	fd.sysfd = syscall.InvalidHandle
+	// no need for a finalizer anymore
+	runtime.SetFinalizer(fd, nil)
+}
+
+// Add a reference to this fd.
+// Returns an error if the fd cannot be used.
+func (fd *netFD) incref() error {
+	if !fd.fdmu.Incref() {
+		return errClosing
+	}
+	return nil
+}
+
+// Remove a reference to this FD and close if we've been asked to do so
+// (and there are no references left).
+func (fd *netFD) decref() {
+	if fd.fdmu.Decref() {
+		fd.destroy()
+	}
+}
+
+// Add a reference to this fd and lock for reading.
+// Returns an error if the fd cannot be used.
+func (fd *netFD) readLock() error {
+	if !fd.fdmu.RWLock(true) {
+		return errClosing
+	}
+	return nil
+}
+
+// Unlock for reading and remove a reference to this FD.
+func (fd *netFD) readUnlock() {
+	if fd.fdmu.RWUnlock(true) {
+		fd.destroy()
+	}
+}
+
+// Add a reference to this fd and lock for writing.
+// Returns an error if the fd cannot be used.
+func (fd *netFD) writeLock() error {
+	if !fd.fdmu.RWLock(false) {
+		return errClosing
+	}
+	return nil
+}
+
+// Unlock for writing and remove a reference to this FD.
+func (fd *netFD) writeUnlock() {
+	if fd.fdmu.RWUnlock(false) {
+		fd.destroy()
+	}
+}
+
+func (fd *netFD) Close() error {
+	if !fd.fdmu.IncrefAndClose() {
+		return errClosing
+	}
+	// unblock pending reader and writer
+	fd.pd.Evict()
+	fd.decref()
+	return nil
+}
+
+func (fd *netFD) shutdown(how int) error {
+	if err := fd.incref(); err != nil {
+		return err
+	}
+	defer fd.decref()
+	err := syscall.Shutdown(fd.sysfd, how)
+	if err != nil {
+		return &OpError{"shutdown", fd.net, fd.laddr, err}
+	}
+	return nil
+}
+
+func (fd *netFD) closeRead() error {
+	return fd.shutdown(syscall.SHUT_RD)
+}
+
+func (fd *netFD) closeWrite() error {
+	return fd.shutdown(syscall.SHUT_WR)
+}
+
+func (fd *netFD) Read(buf []byte) (int, error) {
+	if err := fd.readLock(); err != nil {
+		return 0, err
+	}
+	defer fd.readUnlock()
+	o := &fd.rop
+	o.InitBuf(buf)
+	n, err := rsrv.ExecIO(o, "WSARecv", func(o *operation) error {
+		return syscall.WSARecv(o.fd.sysfd, &o.buf, 1, &o.qty, &o.flags, &o.o, nil)
+	})
+	if err == nil && n == 0 {
+		err = io.EOF
+	}
+	if raceenabled {
+		raceAcquire(unsafe.Pointer(&ioSync))
+	}
+	return n, err
+}
+
+func (fd *netFD) readFrom(buf []byte) (n int, sa syscall.Sockaddr, err error) {
+	if len(buf) == 0 {
+		return 0, nil, nil
+	}
+	if err := fd.readLock(); err != nil {
+		return 0, nil, err
+	}
+	defer fd.readUnlock()
+	o := &fd.rop
+	o.InitBuf(buf)
+	n, err = rsrv.ExecIO(o, "WSARecvFrom", func(o *operation) error {
+		if o.rsa == nil {
+			o.rsa = new(syscall.RawSockaddrAny)
+		}
+		o.rsan = int32(unsafe.Sizeof(*o.rsa))
+		return syscall.WSARecvFrom(o.fd.sysfd, &o.buf, 1, &o.qty, &o.flags, o.rsa, &o.rsan, &o.o, nil)
+	})
+	if err != nil {
+		return 0, nil, err
+	}
+	sa, _ = o.rsa.Sockaddr()
+	return
+}
+
+func (fd *netFD) Write(buf []byte) (int, error) {
+	if err := fd.writeLock(); err != nil {
+		return 0, err
+	}
+	defer fd.writeUnlock()
+	if raceenabled {
+		raceReleaseMerge(unsafe.Pointer(&ioSync))
+	}
+	o := &fd.wop
+	o.InitBuf(buf)
+	return wsrv.ExecIO(o, "WSASend", func(o *operation) error {
+		return syscall.WSASend(o.fd.sysfd, &o.buf, 1, &o.qty, 0, &o.o, nil)
+	})
+}
+
+func (fd *netFD) writeTo(buf []byte, sa syscall.Sockaddr) (int, error) {
+	if len(buf) == 0 {
+		return 0, nil
+	}
+	if err := fd.writeLock(); err != nil {
+		return 0, err
+	}
+	defer fd.writeUnlock()
+	o := &fd.wop
+	o.InitBuf(buf)
+	o.sa = sa
+	return wsrv.ExecIO(o, "WSASendto", func(o *operation) error {
+		return syscall.WSASendto(o.fd.sysfd, &o.buf, 1, &o.qty, 0, o.sa, &o.o, nil)
+	})
+}
+
+func (fd *netFD) acceptOne(rawsa []syscall.RawSockaddrAny, o *operation) (*netFD, error) {
+	// Get new socket.
+	s, err := sysSocket(fd.family, fd.sotype, 0)
+	if err != nil {
+		return nil, &OpError{"socket", fd.net, fd.laddr, err}
+	}
+
+	// Associate our new socket with IOCP.
+	netfd, err := newFD(s, fd.family, fd.sotype, fd.net)
+	if err != nil {
+		closesocket(s)
+		return nil, &OpError{"accept", fd.net, fd.laddr, err}
+	}
+	if err := netfd.init(); err != nil {
+		fd.Close()
+		return nil, err
+	}
+
+	// Submit accept request.
+	o.handle = s
+	o.rsan = int32(unsafe.Sizeof(rawsa[0]))
+	_, err = rsrv.ExecIO(o, "AcceptEx", func(o *operation) error {
+		return syscall.AcceptEx(o.fd.sysfd, o.handle, (*byte)(unsafe.Pointer(&rawsa[0])), 0, uint32(o.rsan), uint32(o.rsan), &o.qty, &o.o)
+	})
+	if err != nil {
+		netfd.Close()
+		return nil, err
+	}
+
+	// Inherit properties of the listening socket.
+	err = syscall.Setsockopt(s, syscall.SOL_SOCKET, syscall.SO_UPDATE_ACCEPT_CONTEXT, (*byte)(unsafe.Pointer(&fd.sysfd)), int32(unsafe.Sizeof(fd.sysfd)))
+	if err != nil {
+		netfd.Close()
+		return nil, &OpError{"Setsockopt", fd.net, fd.laddr, err}
+	}
+
+	return netfd, nil
+}
+
+func (fd *netFD) accept() (*netFD, error) {
+	if err := fd.readLock(); err != nil {
+		return nil, err
+	}
+	defer fd.readUnlock()
+
+	o := &fd.rop
+	var netfd *netFD
+	var err error
+	var rawsa [2]syscall.RawSockaddrAny
+	for {
+		netfd, err = fd.acceptOne(rawsa[:], o)
+		if err == nil {
+			break
+		}
+		// Sometimes we see WSAECONNRESET and ERROR_NETNAME_DELETED is
+		// returned here. These happen if connection reset is received
+		// before AcceptEx could complete. These errors relate to new
+		// connection, not to AcceptEx, so ignore broken connection and
+		// try AcceptEx again for more connections.
+		operr, ok := err.(*OpError)
+		if !ok {
+			return nil, err
+		}
+		errno, ok := operr.Err.(syscall.Errno)
+		if !ok {
+			return nil, err
+		}
+		switch errno {
+		case syscall.ERROR_NETNAME_DELETED, syscall.WSAECONNRESET:
+			// ignore these and try again
+		default:
+			return nil, err
+		}
+	}
+
+	// Get local and peer addr out of AcceptEx buffer.
+	var lrsa, rrsa *syscall.RawSockaddrAny
+	var llen, rlen int32
+	syscall.GetAcceptExSockaddrs((*byte)(unsafe.Pointer(&rawsa[0])),
+		0, uint32(o.rsan), uint32(o.rsan), &lrsa, &llen, &rrsa, &rlen)
+	lsa, _ := lrsa.Sockaddr()
+	rsa, _ := rrsa.Sockaddr()
+
+	netfd.setAddr(netfd.addrFunc()(lsa), netfd.addrFunc()(rsa))
+	return netfd, nil
+}
+
+func skipRawSocketTests() (skip bool, skipmsg string, err error) {
+	// From http://msdn.microsoft.com/en-us/library/windows/desktop/ms740548.aspx:
+	// Note: To use a socket of type SOCK_RAW requires administrative privileges.
+	// Users running Winsock applications that use raw sockets must be a member of
+	// the Administrators group on the local computer, otherwise raw socket calls
+	// will fail with an error code of WSAEACCES. On Windows Vista and later, access
+	// for raw sockets is enforced at socket creation. In earlier versions of Windows,
+	// access for raw sockets is enforced during other socket operations.
+	s, err := syscall.Socket(syscall.AF_INET, syscall.SOCK_RAW, 0)
+	if err == syscall.WSAEACCES {
+		return true, "skipping test; no access to raw socket allowed", nil
+	}
+	if err != nil {
+		return true, "", err
+	}
+	defer syscall.Closesocket(s)
+	return false, "", nil
+}
+
+// Unimplemented functions.
+
+func (fd *netFD) dup() (*os.File, error) {
+	// TODO: Implement this
+	return nil, os.NewSyscallError("dup", syscall.EWINDOWS)
+}
+
+var errNoSupport = errors.New("address family not supported")
+
+func (fd *netFD) readMsg(p []byte, oob []byte) (n, oobn, flags int, sa syscall.Sockaddr, err error) {
+	return 0, 0, 0, nil, errNoSupport
+}
+
+func (fd *netFD) writeMsg(p []byte, oob []byte, sa syscall.Sockaddr) (n int, oobn int, err error) {
+	return 0, 0, errNoSupport
+}
diff --git a/src/net/file_plan9.go b/src/net/file_plan9.go
new file mode 100644
index 000000000..068f0881d
--- /dev/null
+++ b/src/net/file_plan9.go
@@ -0,0 +1,157 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package net
+
+import (
+	"errors"
+	"io"
+	"os"
+	"syscall"
+)
+
+func (fd *netFD) status(ln int) (string, error) {
+	if !fd.ok() {
+		return "", syscall.EINVAL
+	}
+
+	status, err := os.Open(fd.dir + "/status")
+	if err != nil {
+		return "", err
+	}
+	defer status.Close()
+	buf := make([]byte, ln)
+	n, err := io.ReadFull(status, buf[:])
+	if err != nil {
+		return "", err
+	}
+	return string(buf[:n]), nil
+}
+
+func newFileFD(f *os.File) (net *netFD, err error) {
+	var ctl *os.File
+	close := func(fd int) {
+		if err != nil {
+			syscall.Close(fd)
+		}
+	}
+
+	path, err := syscall.Fd2path(int(f.Fd()))
+	if err != nil {
+		return nil, os.NewSyscallError("fd2path", err)
+	}
+	comp := splitAtBytes(path, "/")
+	n := len(comp)
+	if n < 3 || comp[0][0:3] != "net" {
+		return nil, syscall.EPLAN9
+	}
+
+	name := comp[2]
+	switch file := comp[n-1]; file {
+	case "ctl", "clone":
+		syscall.ForkLock.RLock()
+		fd, err := syscall.Dup(int(f.Fd()), -1)
+		syscall.ForkLock.RUnlock()
+		if err != nil {
+			return nil, os.NewSyscallError("dup", err)
+		}
+		defer close(fd)
+
+		dir := netdir + "/" + comp[n-2]
+		ctl = os.NewFile(uintptr(fd), dir+"/"+file)
+		ctl.Seek(0, 0)
+		var buf [16]byte
+		n, err := ctl.Read(buf[:])
+		if err != nil {
+			return nil, err
+		}
+		name = string(buf[:n])
+	default:
+		if len(comp) < 4 {
+			return nil, errors.New("could not find control file for connection")
+		}
+		dir := netdir + "/" + comp[1] + "/" + name
+		ctl, err = os.OpenFile(dir+"/ctl", os.O_RDWR, 0)
+		if err != nil {
+			return nil, err
+		}
+		defer close(int(ctl.Fd()))
+	}
+	dir := netdir + "/" + comp[1] + "/" + name
+	laddr, err := readPlan9Addr(comp[1], dir+"/local")
+	if err != nil {
+		return nil, err
+	}
+	return newFD(comp[1], name, ctl, nil, laddr, nil)
+}
+
+func newFileConn(f *os.File) (c Conn, err error) {
+	fd, err := newFileFD(f)
+	if err != nil {
+		return nil, err
+	}
+	if !fd.ok() {
+		return nil, syscall.EINVAL
+	}
+
+	fd.data, err = os.OpenFile(fd.dir+"/data", os.O_RDWR, 0)
+	if err != nil {
+		return nil, err
+	}
+
+	switch fd.laddr.(type) {
+	case *TCPAddr:
+		return newTCPConn(fd), nil
+	case *UDPAddr:
+		return newUDPConn(fd), nil
+	}
+	return nil, syscall.EPLAN9
+}
+
+func newFileListener(f *os.File) (l Listener, err error) {
+	fd, err := newFileFD(f)
+	if err != nil {
+		return nil, err
+	}
+	switch fd.laddr.(type) {
+	case *TCPAddr:
+	default:
+		return nil, syscall.EPLAN9
+	}
+
+	// check that file corresponds to a listener
+	s, err := fd.status(len("Listen"))
+	if err != nil {
+		return nil, err
+	}
+	if s != "Listen" {
+		return nil, errors.New("file does not represent a listener")
+	}
+
+	return &TCPListener{fd}, nil
+}
+
+// FileConn returns a copy of the network connection corresponding to
+// the open file f.  It is the caller's responsibility to close f when
+// finished.  Closing c does not affect f, and closing f does not
+// affect c.
+func FileConn(f *os.File) (c Conn, err error) {
+	return newFileConn(f)
+}
+
+// FileListener returns a copy of the network listener corresponding
+// to the open file f.  It is the caller's responsibility to close l
+// when finished.  Closing l does not affect f, and closing f does not
+// affect l.
+func FileListener(f *os.File) (l Listener, err error) {
+	return newFileListener(f)
+}
+
+// FilePacketConn returns a copy of the packet network connection
+// corresponding to the open file f.  It is the caller's
+// responsibility to close f when finished.  Closing c does not affect
+// f, and closing f does not affect c.
+func FilePacketConn(f *os.File) (c PacketConn, err error) {
+	return nil, syscall.EPLAN9
+}
diff --git a/src/net/file_test.go b/src/net/file_test.go
new file mode 100644
index 000000000..d81bca782
--- /dev/null
+++ b/src/net/file_test.go
@@ -0,0 +1,205 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package net
+
+import (
+	"os"
+	"reflect"
+	"runtime"
+	"testing"
+)
+
+type listenerFile interface {
+	Listener
+	File() (f *os.File, err error)
+}
+
+type packetConnFile interface {
+	PacketConn
+	File() (f *os.File, err error)
+}
+
+type connFile interface {
+	Conn
+	File() (f *os.File, err error)
+}
+
+func testFileListener(t *testing.T, net, laddr string) {
+	switch net {
+	case "tcp", "tcp4", "tcp6":
+		laddr += ":0" // any available port
+	}
+	l, err := Listen(net, laddr)
+	if err != nil {
+		t.Fatalf("Listen failed: %v", err)
+	}
+	defer l.Close()
+	lf := l.(listenerFile)
+	f, err := lf.File()
+	if err != nil {
+		t.Fatalf("File failed: %v", err)
+	}
+	c, err := FileListener(f)
+	if err != nil {
+		t.Fatalf("FileListener failed: %v", err)
+	}
+	if !reflect.DeepEqual(l.Addr(), c.Addr()) {
+		t.Fatalf("Addrs not equal: %#v != %#v", l.Addr(), c.Addr())
+	}
+	if err := c.Close(); err != nil {
+		t.Fatalf("Close failed: %v", err)
+	}
+	if err := f.Close(); err != nil {
+		t.Fatalf("Close failed: %v", err)
+	}
+}
+
+var fileListenerTests = []struct {
+	net   string
+	laddr string
+	ipv6  bool // test with underlying AF_INET6 socket
+	linux bool // test with abstract unix domain socket, a Linux-ism
+}{
+	{net: "tcp", laddr: ""},
+	{net: "tcp", laddr: "0.0.0.0"},
+	{net: "tcp", laddr: "[::ffff:0.0.0.0]"},
+	{net: "tcp", laddr: "[::]", ipv6: true},
+
+	{net: "tcp", laddr: "127.0.0.1"},
+	{net: "tcp", laddr: "[::ffff:127.0.0.1]"},
+	{net: "tcp", laddr: "[::1]", ipv6: true},
+
+	{net: "tcp4", laddr: ""},
+	{net: "tcp4", laddr: "0.0.0.0"},
+	{net: "tcp4", laddr: "[::ffff:0.0.0.0]"},
+
+	{net: "tcp4", laddr: "127.0.0.1"},
+	{net: "tcp4", laddr: "[::ffff:127.0.0.1]"},
+
+	{net: "tcp6", laddr: "", ipv6: true},
+	{net: "tcp6", laddr: "[::]", ipv6: true},
+
+	{net: "tcp6", laddr: "[::1]", ipv6: true},
+
+	{net: "unix", laddr: "@gotest/net", linux: true},
+	{net: "unixpacket", laddr: "@gotest/net", linux: true},
+}
+
+func TestFileListener(t *testing.T) {
+	switch runtime.GOOS {
+	case "windows":
+		t.Skipf("skipping test on %q", runtime.GOOS)
+	}
+
+	for _, tt := range fileListenerTests {
+		if skipServerTest(tt.net, "unix", tt.laddr, tt.ipv6, false, tt.linux) {
+			continue
+		}
+		if skipServerTest(tt.net, "unixpacket", tt.laddr, tt.ipv6, false, tt.linux) {
+			continue
+		}
+		testFileListener(t, tt.net, tt.laddr)
+	}
+}
+
+func testFilePacketConn(t *testing.T, pcf packetConnFile, listen bool) {
+	f, err := pcf.File()
+	if err != nil {
+		t.Fatalf("File failed: %v", err)
+	}
+	c, err := FilePacketConn(f)
+	if err != nil {
+		t.Fatalf("FilePacketConn failed: %v", err)
+	}
+	if !reflect.DeepEqual(pcf.LocalAddr(), c.LocalAddr()) {
+		t.Fatalf("LocalAddrs not equal: %#v != %#v", pcf.LocalAddr(), c.LocalAddr())
+	}
+	if listen {
+		if _, err := c.WriteTo([]byte{}, c.LocalAddr()); err != nil {
+			t.Fatalf("WriteTo failed: %v", err)
+		}
+	}
+	if err := c.Close(); err != nil {
+		t.Fatalf("Close failed: %v", err)
+	}
+	if err := f.Close(); err != nil {
+		t.Fatalf("Close failed: %v", err)
+	}
+}
+
+func testFilePacketConnListen(t *testing.T, net, laddr string) {
+	switch net {
+	case "udp", "udp4", "udp6":
+		laddr += ":0" // any available port
+	}
+	l, err := ListenPacket(net, laddr)
+	if err != nil {
+		t.Fatalf("ListenPacket failed: %v", err)
+	}
+	testFilePacketConn(t, l.(packetConnFile), true)
+	if err := l.Close(); err != nil {
+		t.Fatalf("Close failed: %v", err)
+	}
+}
+
+func testFilePacketConnDial(t *testing.T, net, raddr string) {
+	switch net {
+	case "udp", "udp4", "udp6":
+		raddr += ":12345"
+	}
+	c, err := Dial(net, raddr)
+	if err != nil {
+		t.Fatalf("Dial failed: %v", err)
+	}
+	testFilePacketConn(t, c.(packetConnFile), false)
+	if err := c.Close(); err != nil {
+		t.Fatalf("Close failed: %v", err)
+	}
+}
+
+var filePacketConnTests = []struct {
+	net   string
+	addr  string
+	ipv6  bool // test with underlying AF_INET6 socket
+	linux bool // test with abstract unix domain socket, a Linux-ism
+}{
+	{net: "udp", addr: "127.0.0.1"},
+	{net: "udp", addr: "[::ffff:127.0.0.1]"},
+	{net: "udp", addr: "[::1]", ipv6: true},
+
+	{net: "udp4", addr: "127.0.0.1"},
+	{net: "udp4", addr: "[::ffff:127.0.0.1]"},
+
+	{net: "udp6", addr: "[::1]", ipv6: true},
+
+	{net: "ip4:icmp", addr: "127.0.0.1"},
+
+	{net: "unixgram", addr: "@gotest3/net", linux: true},
+}
+
+func TestFilePacketConn(t *testing.T) {
+	switch runtime.GOOS {
+	case "nacl", "plan9", "windows":
+		t.Skipf("skipping test on %q", runtime.GOOS)
+	}
+
+	for _, tt := range filePacketConnTests {
+		if skipServerTest(tt.net, "unixgram", tt.addr, tt.ipv6, false, tt.linux) {
+			continue
+		}
+		if os.Getuid() != 0 && tt.net == "ip4:icmp" {
+			t.Log("skipping test; must be root")
+			continue
+		}
+		testFilePacketConnListen(t, tt.net, tt.addr)
+		switch tt.addr {
+		case "", "0.0.0.0", "[::ffff:0.0.0.0]", "[::]":
+		default:
+			if tt.net != "unixgram" {
+				testFilePacketConnDial(t, tt.net, tt.addr)
+			}
+		}
+	}
+}
diff --git a/src/net/file_unix.go b/src/net/file_unix.go
new file mode 100644
index 000000000..07b3ecf62
--- /dev/null
+++ b/src/net/file_unix.go
@@ -0,0 +1,139 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build darwin dragonfly freebsd linux nacl netbsd openbsd solaris
+
+package net
+
+import (
+	"os"
+	"syscall"
+)
+
+func newFileFD(f *os.File) (*netFD, error) {
+	fd, err := dupCloseOnExec(int(f.Fd()))
+	if err != nil {
+		return nil, os.NewSyscallError("dup", err)
+	}
+
+	if err = syscall.SetNonblock(fd, true); err != nil {
+		closesocket(fd)
+		return nil, err
+	}
+
+	sotype, err := syscall.GetsockoptInt(fd, syscall.SOL_SOCKET, syscall.SO_TYPE)
+	if err != nil {
+		closesocket(fd)
+		return nil, os.NewSyscallError("getsockopt", err)
+	}
+
+	family := syscall.AF_UNSPEC
+	toAddr := sockaddrToTCP
+	lsa, _ := syscall.Getsockname(fd)
+	switch lsa.(type) {
+	default:
+		closesocket(fd)
+		return nil, syscall.EINVAL
+	case *syscall.SockaddrInet4:
+		family = syscall.AF_INET
+		if sotype == syscall.SOCK_DGRAM {
+			toAddr = sockaddrToUDP
+		} else if sotype == syscall.SOCK_RAW {
+			toAddr = sockaddrToIP
+		}
+	case *syscall.SockaddrInet6:
+		family = syscall.AF_INET6
+		if sotype == syscall.SOCK_DGRAM {
+			toAddr = sockaddrToUDP
+		} else if sotype == syscall.SOCK_RAW {
+			toAddr = sockaddrToIP
+		}
+	case *syscall.SockaddrUnix:
+		family = syscall.AF_UNIX
+		toAddr = sockaddrToUnix
+		if sotype == syscall.SOCK_DGRAM {
+			toAddr = sockaddrToUnixgram
+		} else if sotype == syscall.SOCK_SEQPACKET {
+			toAddr = sockaddrToUnixpacket
+		}
+	}
+	laddr := toAddr(lsa)
+	rsa, _ := syscall.Getpeername(fd)
+	raddr := toAddr(rsa)
+
+	netfd, err := newFD(fd, family, sotype, laddr.Network())
+	if err != nil {
+		closesocket(fd)
+		return nil, err
+	}
+	if err := netfd.init(); err != nil {
+		netfd.Close()
+		return nil, err
+	}
+	netfd.setAddr(laddr, raddr)
+	return netfd, nil
+}
+
+// FileConn returns a copy of the network connection corresponding to
+// the open file f.  It is the caller's responsibility to close f when
+// finished.  Closing c does not affect f, and closing f does not
+// affect c.
+func FileConn(f *os.File) (c Conn, err error) {
+	fd, err := newFileFD(f)
+	if err != nil {
+		return nil, err
+	}
+	switch fd.laddr.(type) {
+	case *TCPAddr:
+		return newTCPConn(fd), nil
+	case *UDPAddr:
+		return newUDPConn(fd), nil
+	case *IPAddr:
+		return newIPConn(fd), nil
+	case *UnixAddr:
+		return newUnixConn(fd), nil
+	}
+	fd.Close()
+	return nil, syscall.EINVAL
+}
+
+// FileListener returns a copy of the network listener corresponding
+// to the open file f.  It is the caller's responsibility to close l
+// when finished.  Closing l does not affect f, and closing f does not
+// affect l.
+func FileListener(f *os.File) (l Listener, err error) {
+	fd, err := newFileFD(f)
+	if err != nil {
+		return nil, err
+	}
+	switch laddr := fd.laddr.(type) {
+	case *TCPAddr:
+		return &TCPListener{fd}, nil
+	case *UnixAddr:
+		return &UnixListener{fd, laddr.Name}, nil
+	}
+	fd.Close()
+	return nil, syscall.EINVAL
+}
+
+// FilePacketConn returns a copy of the packet network connection
+// corresponding to the open file f.  It is the caller's
+// responsibility to close f when finished.  Closing c does not affect
+// f, and closing f does not affect c.
+func FilePacketConn(f *os.File) (c PacketConn, err error) {
+	fd, err := newFileFD(f)
+	if err != nil {
+		return nil, err
+	}
+	switch fd.laddr.(type) {
+	case *UDPAddr:
+		return newUDPConn(fd), nil
+	case *IPAddr:
+		return newIPConn(fd), nil
+	case *UnixAddr:
+		return newUnixConn(fd), nil
+	}
+	fd.Close()
+	return nil, syscall.EINVAL
+}
diff --git a/src/net/file_windows.go b/src/net/file_windows.go
new file mode 100644
index 000000000..ca2b9b226
--- /dev/null
+++ b/src/net/file_windows.go
@@ -0,0 +1,37 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package net
+
+import (
+	"os"
+	"syscall"
+)
+
+// FileConn returns a copy of the network connection corresponding to
+// the open file f.  It is the caller's responsibility to close f when
+// finished.  Closing c does not affect f, and closing f does not
+// affect c.
+func FileConn(f *os.File) (c Conn, err error) {
+	// TODO: Implement this
+	return nil, os.NewSyscallError("FileConn", syscall.EWINDOWS)
+}
+
+// FileListener returns a copy of the network listener corresponding
+// to the open file f.  It is the caller's responsibility to close l
+// when finished.  Closing l does not affect f, and closing f does not
+// affect l.
+func FileListener(f *os.File) (l Listener, err error) {
+	// TODO: Implement this
+	return nil, os.NewSyscallError("FileListener", syscall.EWINDOWS)
+}
+
+// FilePacketConn returns a copy of the packet network connection
+// corresponding to the open file f.  It is the caller's
+// responsibility to close f when finished.  Closing c does not affect
+// f, and closing f does not affect c.
+func FilePacketConn(f *os.File) (c PacketConn, err error) {
+	// TODO: Implement this
+	return nil, os.NewSyscallError("FilePacketConn", syscall.EWINDOWS)
+}
diff --git a/src/net/hosts.go b/src/net/hosts.go
new file mode 100644
index 000000000..9400503e4
--- /dev/null
+++ b/src/net/hosts.go
@@ -0,0 +1,86 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Read static host/IP entries from /etc/hosts.
+
+package net
+
+import (
+	"sync"
+	"time"
+)
+
+const cacheMaxAge = 5 * time.Minute
+
+// hostsPath points to the file with static IP/address entries.
+var hostsPath = "/etc/hosts"
+
+// Simple cache.
+var hosts struct {
+	sync.Mutex
+	byName map[string][]string
+	byAddr map[string][]string
+	expire time.Time
+	path   string
+}
+
+func readHosts() {
+	now := time.Now()
+	hp := hostsPath
+	if len(hosts.byName) == 0 || now.After(hosts.expire) || hosts.path != hp {
+		hs := make(map[string][]string)
+		is := make(map[string][]string)
+		var file *file
+		if file, _ = open(hp); file == nil {
+			return
+		}
+		for line, ok := file.readLine(); ok; line, ok = file.readLine() {
+			if i := byteIndex(line, '#'); i >= 0 {
+				// Discard comments.
+				line = line[0:i]
+			}
+			f := getFields(line)
+			if len(f) < 2 || ParseIP(f[0]) == nil {
+				continue
+			}
+			for i := 1; i < len(f); i++ {
+				h := f[i]
+				hs[h] = append(hs[h], f[0])
+				is[f[0]] = append(is[f[0]], h)
+			}
+		}
+		// Update the data cache.
+		hosts.expire = now.Add(cacheMaxAge)
+		hosts.path = hp
+		hosts.byName = hs
+		hosts.byAddr = is
+		file.close()
+	}
+}
+
+// lookupStaticHost looks up the addresses for the given host from /etc/hosts.
+func lookupStaticHost(host string) []string {
+	hosts.Lock()
+	defer hosts.Unlock()
+	readHosts()
+	if len(hosts.byName) != 0 {
+		if ips, ok := hosts.byName[host]; ok {
+			return ips
+		}
+	}
+	return nil
+}
+
+// lookupStaticAddr looks up the hosts for the given address from /etc/hosts.
+func lookupStaticAddr(addr string) []string {
+	hosts.Lock()
+	defer hosts.Unlock()
+	readHosts()
+	if len(hosts.byAddr) != 0 {
+		if hosts, ok := hosts.byAddr[addr]; ok {
+			return hosts
+		}
+	}
+	return nil
+}
diff --git a/src/net/hosts_test.go b/src/net/hosts_test.go
new file mode 100644
index 000000000..2fe358e07
--- /dev/null
+++ b/src/net/hosts_test.go
@@ -0,0 +1,81 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package net
+
+import (
+	"sort"
+	"testing"
+)
+
+type hostTest struct {
+	host string
+	ips  []IP
+}
+
+var hosttests = []hostTest{
+	{"odin", []IP{
+		IPv4(127, 0, 0, 2),
+		IPv4(127, 0, 0, 3),
+		ParseIP("::2"),
+	}},
+	{"thor", []IP{
+		IPv4(127, 1, 1, 1),
+	}},
+	{"loki", []IP{}},
+	{"ullr", []IP{
+		IPv4(127, 1, 1, 2),
+	}},
+	{"ullrhost", []IP{
+		IPv4(127, 1, 1, 2),
+	}},
+}
+
+func TestLookupStaticHost(t *testing.T) {
+	p := hostsPath
+	hostsPath = "testdata/hosts"
+	for i := 0; i < len(hosttests); i++ {
+		tt := hosttests[i]
+		ips := lookupStaticHost(tt.host)
+		if len(ips) != len(tt.ips) {
+			t.Errorf("# of hosts = %v; want %v",
+				len(ips), len(tt.ips))
+			continue
+		}
+		for k, v := range ips {
+			if tt.ips[k].String() != v {
+				t.Errorf("lookupStaticHost(%q) = %v; want %v",
+					tt.host, v, tt.ips[k])
+			}
+		}
+	}
+	hostsPath = p
+}
+
+// https://code.google.com/p/go/issues/detail?id=6646
+func TestSingleLineHostsFile(t *testing.T) {
+	p := hostsPath
+	hostsPath = "testdata/hosts_singleline"
+
+	ips := lookupStaticHost("odin")
+	if len(ips) != 1 || ips[0] != "127.0.0.2" {
+		t.Errorf("lookupStaticHost = %v, want %v", ips, []string{"127.0.0.2"})
+	}
+
+	hostsPath = p
+}
+
+func TestLookupHost(t *testing.T) {
+	// Can't depend on this to return anything in particular,
+	// but if it does return something, make sure it doesn't
+	// duplicate addresses (a common bug due to the way
+	// getaddrinfo works).
+	addrs, _ := LookupHost("localhost")
+	sort.Strings(addrs)
+	for i := 0; i+1 < len(addrs); i++ {
+		if addrs[i] == addrs[i+1] {
+			t.Fatalf("LookupHost(\"localhost\") = %v, has duplicate addresses", addrs)
+		}
+	}
+}
diff --git a/src/net/http/cgi/child.go b/src/net/http/cgi/child.go
new file mode 100644
index 000000000..45fc2e57c
--- /dev/null
+++ b/src/net/http/cgi/child.go
@@ -0,0 +1,206 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// This file implements CGI from the perspective of a child
+// process.
+
+package cgi
+
+import (
+	"bufio"
+	"crypto/tls"
+	"errors"
+	"fmt"
+	"io"
+	"io/ioutil"
+	"net"
+	"net/http"
+	"net/url"
+	"os"
+	"strconv"
+	"strings"
+)
+
+// Request returns the HTTP request as represented in the current
+// environment. This assumes the current program is being run
+// by a web server in a CGI environment.
+// The returned Request's Body is populated, if applicable.
+func Request() (*http.Request, error) {
+	r, err := RequestFromMap(envMap(os.Environ()))
+	if err != nil {
+		return nil, err
+	}
+	if r.ContentLength > 0 {
+		r.Body = ioutil.NopCloser(io.LimitReader(os.Stdin, r.ContentLength))
+	}
+	return r, nil
+}
+
+func envMap(env []string) map[string]string {
+	m := make(map[string]string)
+	for _, kv := range env {
+		if idx := strings.Index(kv, "="); idx != -1 {
+			m[kv[:idx]] = kv[idx+1:]
+		}
+	}
+	return m
+}
+
+// RequestFromMap creates an http.Request from CGI variables.
+// The returned Request's Body field is not populated.
+func RequestFromMap(params map[string]string) (*http.Request, error) {
+	r := new(http.Request)
+	r.Method = params["REQUEST_METHOD"]
+	if r.Method == "" {
+		return nil, errors.New("cgi: no REQUEST_METHOD in environment")
+	}
+
+	r.Proto = params["SERVER_PROTOCOL"]
+	var ok bool
+	r.ProtoMajor, r.ProtoMinor, ok = http.ParseHTTPVersion(r.Proto)
+	if !ok {
+		return nil, errors.New("cgi: invalid SERVER_PROTOCOL version")
+	}
+
+	r.Close = true
+	r.Trailer = http.Header{}
+	r.Header = http.Header{}
+
+	r.Host = params["HTTP_HOST"]
+
+	if lenstr := params["CONTENT_LENGTH"]; lenstr != "" {
+		clen, err := strconv.ParseInt(lenstr, 10, 64)
+		if err != nil {
+			return nil, errors.New("cgi: bad CONTENT_LENGTH in environment: " + lenstr)
+		}
+		r.ContentLength = clen
+	}
+
+	if ct := params["CONTENT_TYPE"]; ct != "" {
+		r.Header.Set("Content-Type", ct)
+	}
+
+	// Copy "HTTP_FOO_BAR" variables to "Foo-Bar" Headers
+	for k, v := range params {
+		if !strings.HasPrefix(k, "HTTP_") || k == "HTTP_HOST" {
+			continue
+		}
+		r.Header.Add(strings.Replace(k[5:], "_", "-", -1), v)
+	}
+
+	// TODO: cookies.  parsing them isn't exported, though.
+
+	uriStr := params["REQUEST_URI"]
+	if uriStr == "" {
+		// Fallback to SCRIPT_NAME, PATH_INFO and QUERY_STRING.
+		uriStr = params["SCRIPT_NAME"] + params["PATH_INFO"]
+		s := params["QUERY_STRING"]
+		if s != "" {
+			uriStr += "?" + s
+		}
+	}
+
+	// There's apparently a de-facto standard for this.
+	// http://docstore.mik.ua/orelly/linux/cgi/ch03_02.htm#ch03-35636
+	if s := params["HTTPS"]; s == "on" || s == "ON" || s == "1" {
+		r.TLS = &tls.ConnectionState{HandshakeComplete: true}
+	}
+
+	if r.Host != "" {
+		// Hostname is provided, so we can reasonably construct a URL.
+		rawurl := r.Host + uriStr
+		if r.TLS == nil {
+			rawurl = "http://" + rawurl
+		} else {
+			rawurl = "https://" + rawurl
+		}
+		url, err := url.Parse(rawurl)
+		if err != nil {
+			return nil, errors.New("cgi: failed to parse host and REQUEST_URI into a URL: " + rawurl)
+		}
+		r.URL = url
+	}
+	// Fallback logic if we don't have a Host header or the URL
+	// failed to parse
+	if r.URL == nil {
+		url, err := url.Parse(uriStr)
+		if err != nil {
+			return nil, errors.New("cgi: failed to parse REQUEST_URI into a URL: " + uriStr)
+		}
+		r.URL = url
+	}
+
+	// Request.RemoteAddr has its port set by Go's standard http
+	// server, so we do here too. We don't have one, though, so we
+	// use a dummy one.
+	r.RemoteAddr = net.JoinHostPort(params["REMOTE_ADDR"], "0")
+
+	return r, nil
+}
+
+// Serve executes the provided Handler on the currently active CGI
+// request, if any. If there's no current CGI environment
+// an error is returned. The provided handler may be nil to use
+// http.DefaultServeMux.
+func Serve(handler http.Handler) error {
+	req, err := Request()
+	if err != nil {
+		return err
+	}
+	if handler == nil {
+		handler = http.DefaultServeMux
+	}
+	rw := &response{
+		req:    req,
+		header: make(http.Header),
+		bufw:   bufio.NewWriter(os.Stdout),
+	}
+	handler.ServeHTTP(rw, req)
+	rw.Write(nil) // make sure a response is sent
+	if err = rw.bufw.Flush(); err != nil {
+		return err
+	}
+	return nil
+}
+
+type response struct {
+	req        *http.Request
+	header     http.Header
+	bufw       *bufio.Writer
+	headerSent bool
+}
+
+func (r *response) Flush() {
+	r.bufw.Flush()
+}
+
+func (r *response) Header() http.Header {
+	return r.header
+}
+
+func (r *response) Write(p []byte) (n int, err error) {
+	if !r.headerSent {
+		r.WriteHeader(http.StatusOK)
+	}
+	return r.bufw.Write(p)
+}
+
+func (r *response) WriteHeader(code int) {
+	if r.headerSent {
+		// Note: explicitly using Stderr, as Stdout is our HTTP output.
+		fmt.Fprintf(os.Stderr, "CGI attempted to write header twice on request for %s", r.req.URL)
+		return
+	}
+	r.headerSent = true
+	fmt.Fprintf(r.bufw, "Status: %d %s\r\n", code, http.StatusText(code))
+
+	// Set a default Content-Type
+	if _, hasType := r.header["Content-Type"]; !hasType {
+		r.header.Add("Content-Type", "text/html; charset=utf-8")
+	}
+
+	r.header.Write(r.bufw)
+	r.bufw.WriteString("\r\n")
+	r.bufw.Flush()
+}
diff --git a/src/net/http/cgi/child_test.go b/src/net/http/cgi/child_test.go
new file mode 100644
index 000000000..075d8411b
--- /dev/null
+++ b/src/net/http/cgi/child_test.go
@@ -0,0 +1,131 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Tests for CGI (the child process perspective)
+
+package cgi
+
+import (
+	"testing"
+)
+
+func TestRequest(t *testing.T) {
+	env := map[string]string{
+		"SERVER_PROTOCOL": "HTTP/1.1",
+		"REQUEST_METHOD":  "GET",
+		"HTTP_HOST":       "example.com",
+		"HTTP_REFERER":    "elsewhere",
+		"HTTP_USER_AGENT": "goclient",
+		"HTTP_FOO_BAR":    "baz",
+		"REQUEST_URI":     "/path?a=b",
+		"CONTENT_LENGTH":  "123",
+		"CONTENT_TYPE":    "text/xml",
+		"REMOTE_ADDR":     "5.6.7.8",
+	}
+	req, err := RequestFromMap(env)
+	if err != nil {
+		t.Fatalf("RequestFromMap: %v", err)
+	}
+	if g, e := req.UserAgent(), "goclient"; e != g {
+		t.Errorf("expected UserAgent %q; got %q", e, g)
+	}
+	if g, e := req.Method, "GET"; e != g {
+		t.Errorf("expected Method %q; got %q", e, g)
+	}
+	if g, e := req.Header.Get("Content-Type"), "text/xml"; e != g {
+		t.Errorf("expected Content-Type %q; got %q", e, g)
+	}
+	if g, e := req.ContentLength, int64(123); e != g {
+		t.Errorf("expected ContentLength %d; got %d", e, g)
+	}
+	if g, e := req.Referer(), "elsewhere"; e != g {
+		t.Errorf("expected Referer %q; got %q", e, g)
+	}
+	if req.Header == nil {
+		t.Fatalf("unexpected nil Header")
+	}
+	if g, e := req.Header.Get("Foo-Bar"), "baz"; e != g {
+		t.Errorf("expected Foo-Bar %q; got %q", e, g)
+	}
+	if g, e := req.URL.String(), "http://example.com/path?a=b"; e != g {
+		t.Errorf("expected URL %q; got %q", e, g)
+	}
+	if g, e := req.FormValue("a"), "b"; e != g {
+		t.Errorf("expected FormValue(a) %q; got %q", e, g)
+	}
+	if req.Trailer == nil {
+		t.Errorf("unexpected nil Trailer")
+	}
+	if req.TLS != nil {
+		t.Errorf("expected nil TLS")
+	}
+	if e, g := "5.6.7.8:0", req.RemoteAddr; e != g {
+		t.Errorf("RemoteAddr: got %q; want %q", g, e)
+	}
+}
+
+func TestRequestWithTLS(t *testing.T) {
+	env := map[string]string{
+		"SERVER_PROTOCOL": "HTTP/1.1",
+		"REQUEST_METHOD":  "GET",
+		"HTTP_HOST":       "example.com",
+		"HTTP_REFERER":    "elsewhere",
+		"REQUEST_URI":     "/path?a=b",
+		"CONTENT_TYPE":    "text/xml",
+		"HTTPS":           "1",
+		"REMOTE_ADDR":     "5.6.7.8",
+	}
+	req, err := RequestFromMap(env)
+	if err != nil {
+		t.Fatalf("RequestFromMap: %v", err)
+	}
+	if g, e := req.URL.String(), "https://example.com/path?a=b"; e != g {
+		t.Errorf("expected URL %q; got %q", e, g)
+	}
+	if req.TLS == nil {
+		t.Errorf("expected non-nil TLS")
+	}
+}
+
+func TestRequestWithoutHost(t *testing.T) {
+	env := map[string]string{
+		"SERVER_PROTOCOL": "HTTP/1.1",
+		"HTTP_HOST":       "",
+		"REQUEST_METHOD":  "GET",
+		"REQUEST_URI":     "/path?a=b",
+		"CONTENT_LENGTH":  "123",
+	}
+	req, err := RequestFromMap(env)
+	if err != nil {
+		t.Fatalf("RequestFromMap: %v", err)
+	}
+	if req.URL == nil {
+		t.Fatalf("unexpected nil URL")
+	}
+	if g, e := req.URL.String(), "/path?a=b"; e != g {
+		t.Errorf("URL = %q; want %q", g, e)
+	}
+}
+
+func TestRequestWithoutRequestURI(t *testing.T) {
+	env := map[string]string{
+		"SERVER_PROTOCOL": "HTTP/1.1",
+		"HTTP_HOST":       "example.com",
+		"REQUEST_METHOD":  "GET",
+		"SCRIPT_NAME":     "/dir/scriptname",
+		"PATH_INFO":       "/p1/p2",
+		"QUERY_STRING":    "a=1&b=2",
+		"CONTENT_LENGTH":  "123",
+	}
+	req, err := RequestFromMap(env)
+	if err != nil {
+		t.Fatalf("RequestFromMap: %v", err)
+	}
+	if req.URL == nil {
+		t.Fatalf("unexpected nil URL")
+	}
+	if g, e := req.URL.String(), "http://example.com/dir/scriptname/p1/p2?a=1&b=2"; e != g {
+		t.Errorf("URL = %q; want %q", g, e)
+	}
+}
diff --git a/src/net/http/cgi/host.go b/src/net/http/cgi/host.go
new file mode 100644
index 000000000..ec95a972c
--- /dev/null
+++ b/src/net/http/cgi/host.go
@@ -0,0 +1,377 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// This file implements the host side of CGI (being the webserver
+// parent process).
+
+// Package cgi implements CGI (Common Gateway Interface) as specified
+// in RFC 3875.
+//
+// Note that using CGI means starting a new process to handle each
+// request, which is typically less efficient than using a
+// long-running server.  This package is intended primarily for
+// compatibility with existing systems.
+package cgi
+
+import (
+	"bufio"
+	"fmt"
+	"io"
+	"log"
+	"net/http"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"regexp"
+	"runtime"
+	"strconv"
+	"strings"
+)
+
+var trailingPort = regexp.MustCompile(`:([0-9]+)$`)
+
+var osDefaultInheritEnv = map[string][]string{
+	"darwin":  {"DYLD_LIBRARY_PATH"},
+	"freebsd": {"LD_LIBRARY_PATH"},
+	"hpux":    {"LD_LIBRARY_PATH", "SHLIB_PATH"},
+	"irix":    {"LD_LIBRARY_PATH", "LD_LIBRARYN32_PATH", "LD_LIBRARY64_PATH"},
+	"linux":   {"LD_LIBRARY_PATH"},
+	"openbsd": {"LD_LIBRARY_PATH"},
+	"solaris": {"LD_LIBRARY_PATH", "LD_LIBRARY_PATH_32", "LD_LIBRARY_PATH_64"},
+	"windows": {"SystemRoot", "COMSPEC", "PATHEXT", "WINDIR"},
+}
+
+// Handler runs an executable in a subprocess with a CGI environment.
+type Handler struct {
+	Path string // path to the CGI executable
+	Root string // root URI prefix of handler or empty for "/"
+
+	// Dir specifies the CGI executable's working directory.
+	// If Dir is empty, the base directory of Path is used.
+	// If Path has no base directory, the current working
+	// directory is used.
+	Dir string
+
+	Env        []string    // extra environment variables to set, if any, as "key=value"
+	InheritEnv []string    // environment variables to inherit from host, as "key"
+	Logger     *log.Logger // optional log for errors or nil to use log.Print
+	Args       []string    // optional arguments to pass to child process
+
+	// PathLocationHandler specifies the root http Handler that
+	// should handle internal redirects when the CGI process
+	// returns a Location header value starting with a "/", as
+	// specified in RFC 3875 § 6.3.2. This will likely be
+	// http.DefaultServeMux.
+	//
+	// If nil, a CGI response with a local URI path is instead sent
+	// back to the client and not redirected internally.
+	PathLocationHandler http.Handler
+}
+
+// removeLeadingDuplicates remove leading duplicate in environments.
+// It's possible to override environment like following.
+//    cgi.Handler{
+//      ...
+//      Env: []string{"SCRIPT_FILENAME=foo.php"},
+//    }
+func removeLeadingDuplicates(env []string) (ret []string) {
+	n := len(env)
+	for i := 0; i < n; i++ {
+		e := env[i]
+		s := strings.SplitN(e, "=", 2)[0]
+		found := false
+		for j := i + 1; j < n; j++ {
+			if s == strings.SplitN(env[j], "=", 2)[0] {
+				found = true
+				break
+			}
+		}
+		if !found {
+			ret = append(ret, e)
+		}
+	}
+	return
+}
+
+func (h *Handler) ServeHTTP(rw http.ResponseWriter, req *http.Request) {
+	root := h.Root
+	if root == "" {
+		root = "/"
+	}
+
+	if len(req.TransferEncoding) > 0 && req.TransferEncoding[0] == "chunked" {
+		rw.WriteHeader(http.StatusBadRequest)
+		rw.Write([]byte("Chunked request bodies are not supported by CGI."))
+		return
+	}
+
+	pathInfo := req.URL.Path
+	if root != "/" && strings.HasPrefix(pathInfo, root) {
+		pathInfo = pathInfo[len(root):]
+	}
+
+	port := "80"
+	if matches := trailingPort.FindStringSubmatch(req.Host); len(matches) != 0 {
+		port = matches[1]
+	}
+
+	env := []string{
+		"SERVER_SOFTWARE=go",
+		"SERVER_NAME=" + req.Host,
+		"SERVER_PROTOCOL=HTTP/1.1",
+		"HTTP_HOST=" + req.Host,
+		"GATEWAY_INTERFACE=CGI/1.1",
+		"REQUEST_METHOD=" + req.Method,
+		"QUERY_STRING=" + req.URL.RawQuery,
+		"REQUEST_URI=" + req.URL.RequestURI(),
+		"PATH_INFO=" + pathInfo,
+		"SCRIPT_NAME=" + root,
+		"SCRIPT_FILENAME=" + h.Path,
+		"REMOTE_ADDR=" + req.RemoteAddr,
+		"REMOTE_HOST=" + req.RemoteAddr,
+		"SERVER_PORT=" + port,
+	}
+
+	if req.TLS != nil {
+		env = append(env, "HTTPS=on")
+	}
+
+	for k, v := range req.Header {
+		k = strings.Map(upperCaseAndUnderscore, k)
+		joinStr := ", "
+		if k == "COOKIE" {
+			joinStr = "; "
+		}
+		env = append(env, "HTTP_"+k+"="+strings.Join(v, joinStr))
+	}
+
+	if req.ContentLength > 0 {
+		env = append(env, fmt.Sprintf("CONTENT_LENGTH=%d", req.ContentLength))
+	}
+	if ctype := req.Header.Get("Content-Type"); ctype != "" {
+		env = append(env, "CONTENT_TYPE="+ctype)
+	}
+
+	if h.Env != nil {
+		env = append(env, h.Env...)
+	}
+
+	envPath := os.Getenv("PATH")
+	if envPath == "" {
+		envPath = "/bin:/usr/bin:/usr/ucb:/usr/bsd:/usr/local/bin"
+	}
+	env = append(env, "PATH="+envPath)
+
+	for _, e := range h.InheritEnv {
+		if v := os.Getenv(e); v != "" {
+			env = append(env, e+"="+v)
+		}
+	}
+
+	for _, e := range osDefaultInheritEnv[runtime.GOOS] {
+		if v := os.Getenv(e); v != "" {
+			env = append(env, e+"="+v)
+		}
+	}
+
+	env = removeLeadingDuplicates(env)
+
+	var cwd, path string
+	if h.Dir != "" {
+		path = h.Path
+		cwd = h.Dir
+	} else {
+		cwd, path = filepath.Split(h.Path)
+	}
+	if cwd == "" {
+		cwd = "."
+	}
+
+	internalError := func(err error) {
+		rw.WriteHeader(http.StatusInternalServerError)
+		h.printf("CGI error: %v", err)
+	}
+
+	cmd := &exec.Cmd{
+		Path:   path,
+		Args:   append([]string{h.Path}, h.Args...),
+		Dir:    cwd,
+		Env:    env,
+		Stderr: os.Stderr, // for now
+	}
+	if req.ContentLength != 0 {
+		cmd.Stdin = req.Body
+	}
+	stdoutRead, err := cmd.StdoutPipe()
+	if err != nil {
+		internalError(err)
+		return
+	}
+
+	err = cmd.Start()
+	if err != nil {
+		internalError(err)
+		return
+	}
+	if hook := testHookStartProcess; hook != nil {
+		hook(cmd.Process)
+	}
+	defer cmd.Wait()
+	defer stdoutRead.Close()
+
+	linebody := bufio.NewReaderSize(stdoutRead, 1024)
+	headers := make(http.Header)
+	statusCode := 0
+	headerLines := 0
+	sawBlankLine := false
+	for {
+		line, isPrefix, err := linebody.ReadLine()
+		if isPrefix {
+			rw.WriteHeader(http.StatusInternalServerError)
+			h.printf("cgi: long header line from subprocess.")
+			return
+		}
+		if err == io.EOF {
+			break
+		}
+		if err != nil {
+			rw.WriteHeader(http.StatusInternalServerError)
+			h.printf("cgi: error reading headers: %v", err)
+			return
+		}
+		if len(line) == 0 {
+			sawBlankLine = true
+			break
+		}
+		headerLines++
+		parts := strings.SplitN(string(line), ":", 2)
+		if len(parts) < 2 {
+			h.printf("cgi: bogus header line: %s", string(line))
+			continue
+		}
+		header, val := parts[0], parts[1]
+		header = strings.TrimSpace(header)
+		val = strings.TrimSpace(val)
+		switch {
+		case header == "Status":
+			if len(val) < 3 {
+				h.printf("cgi: bogus status (short): %q", val)
+				return
+			}
+			code, err := strconv.Atoi(val[0:3])
+			if err != nil {
+				h.printf("cgi: bogus status: %q", val)
+				h.printf("cgi: line was %q", line)
+				return
+			}
+			statusCode = code
+		default:
+			headers.Add(header, val)
+		}
+	}
+	if headerLines == 0 || !sawBlankLine {
+		rw.WriteHeader(http.StatusInternalServerError)
+		h.printf("cgi: no headers")
+		return
+	}
+
+	if loc := headers.Get("Location"); loc != "" {
+		if strings.HasPrefix(loc, "/") && h.PathLocationHandler != nil {
+			h.handleInternalRedirect(rw, req, loc)
+			return
+		}
+		if statusCode == 0 {
+			statusCode = http.StatusFound
+		}
+	}
+
+	if statusCode == 0 && headers.Get("Content-Type") == "" {
+		rw.WriteHeader(http.StatusInternalServerError)
+		h.printf("cgi: missing required Content-Type in headers")
+		return
+	}
+
+	if statusCode == 0 {
+		statusCode = http.StatusOK
+	}
+
+	// Copy headers to rw's headers, after we've decided not to
+	// go into handleInternalRedirect, which won't want its rw
+	// headers to have been touched.
+	for k, vv := range headers {
+		for _, v := range vv {
+			rw.Header().Add(k, v)
+		}
+	}
+
+	rw.WriteHeader(statusCode)
+
+	_, err = io.Copy(rw, linebody)
+	if err != nil {
+		h.printf("cgi: copy error: %v", err)
+		// And kill the child CGI process so we don't hang on
+		// the deferred cmd.Wait above if the error was just
+		// the client (rw) going away. If it was a read error
+		// (because the child died itself), then the extra
+		// kill of an already-dead process is harmless (the PID
+		// won't be reused until the Wait above).
+		cmd.Process.Kill()
+	}
+}
+
+func (h *Handler) printf(format string, v ...interface{}) {
+	if h.Logger != nil {
+		h.Logger.Printf(format, v...)
+	} else {
+		log.Printf(format, v...)
+	}
+}
+
+func (h *Handler) handleInternalRedirect(rw http.ResponseWriter, req *http.Request, path string) {
+	url, err := req.URL.Parse(path)
+	if err != nil {
+		rw.WriteHeader(http.StatusInternalServerError)
+		h.printf("cgi: error resolving local URI path %q: %v", path, err)
+		return
+	}
+	// TODO: RFC 3875 isn't clear if only GET is supported, but it
+	// suggests so: "Note that any message-body attached to the
+	// request (such as for a POST request) may not be available
+	// to the resource that is the target of the redirect."  We
+	// should do some tests against Apache to see how it handles
+	// POST, HEAD, etc. Does the internal redirect get the same
+	// method or just GET? What about incoming headers?
+	// (e.g. Cookies) Which headers, if any, are copied into the
+	// second request?
+	newReq := &http.Request{
+		Method:     "GET",
+		URL:        url,
+		Proto:      "HTTP/1.1",
+		ProtoMajor: 1,
+		ProtoMinor: 1,
+		Header:     make(http.Header),
+		Host:       url.Host,
+		RemoteAddr: req.RemoteAddr,
+		TLS:        req.TLS,
+	}
+	h.PathLocationHandler.ServeHTTP(rw, newReq)
+}
+
+func upperCaseAndUnderscore(r rune) rune {
+	switch {
+	case r >= 'a' && r <= 'z':
+		return r - ('a' - 'A')
+	case r == '-':
+		return '_'
+	case r == '=':
+		// Maybe not part of the CGI 'spec' but would mess up
+		// the environment in any case, as Go represents the
+		// environment as a slice of "key=value" strings.
+		return '_'
+	}
+	// TODO: other transformations in spec or practice?
+	return r
+}
+
+var testHookStartProcess func(*os.Process) // nil except for some tests
diff --git a/src/net/http/cgi/host_test.go b/src/net/http/cgi/host_test.go
new file mode 100644
index 000000000..8c16e6897
--- /dev/null
+++ b/src/net/http/cgi/host_test.go
@@ -0,0 +1,461 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Tests for package cgi
+
+package cgi
+
+import (
+	"bufio"
+	"fmt"
+	"io"
+	"net"
+	"net/http"
+	"net/http/httptest"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"runtime"
+	"strconv"
+	"strings"
+	"testing"
+	"time"
+)
+
+func newRequest(httpreq string) *http.Request {
+	buf := bufio.NewReader(strings.NewReader(httpreq))
+	req, err := http.ReadRequest(buf)
+	if err != nil {
+		panic("cgi: bogus http request in test: " + httpreq)
+	}
+	req.RemoteAddr = "1.2.3.4"
+	return req
+}
+
+func runCgiTest(t *testing.T, h *Handler, httpreq string, expectedMap map[string]string) *httptest.ResponseRecorder {
+	rw := httptest.NewRecorder()
+	req := newRequest(httpreq)
+	h.ServeHTTP(rw, req)
+
+	// Make a map to hold the test map that the CGI returns.
+	m := make(map[string]string)
+	m["_body"] = rw.Body.String()
+	linesRead := 0
+readlines:
+	for {
+		line, err := rw.Body.ReadString('\n')
+		switch {
+		case err == io.EOF:
+			break readlines
+		case err != nil:
+			t.Fatalf("unexpected error reading from CGI: %v", err)
+		}
+		linesRead++
+		trimmedLine := strings.TrimRight(line, "\r\n")
+		split := strings.SplitN(trimmedLine, "=", 2)
+		if len(split) != 2 {
+			t.Fatalf("Unexpected %d parts from invalid line number %v: %q; existing map=%v",
+				len(split), linesRead, line, m)
+		}
+		m[split[0]] = split[1]
+	}
+
+	for key, expected := range expectedMap {
+		got := m[key]
+		if key == "cwd" {
+			// For Windows. golang.org/issue/4645.
+			fi1, _ := os.Stat(got)
+			fi2, _ := os.Stat(expected)
+			if os.SameFile(fi1, fi2) {
+				got = expected
+			}
+		}
+		if got != expected {
+			t.Errorf("for key %q got %q; expected %q", key, got, expected)
+		}
+	}
+	return rw
+}
+
+var cgiTested, cgiWorks bool
+
+func check(t *testing.T) {
+	if !cgiTested {
+		cgiTested = true
+		cgiWorks = exec.Command("./testdata/test.cgi").Run() == nil
+	}
+	if !cgiWorks {
+		// No Perl on Windows, needed by test.cgi
+		// TODO: make the child process be Go, not Perl.
+		t.Skip("Skipping test: test.cgi failed.")
+	}
+}
+
+func TestCGIBasicGet(t *testing.T) {
+	check(t)
+	h := &Handler{
+		Path: "testdata/test.cgi",
+		Root: "/test.cgi",
+	}
+	expectedMap := map[string]string{
+		"test":                  "Hello CGI",
+		"param-a":               "b",
+		"param-foo":             "bar",
+		"env-GATEWAY_INTERFACE": "CGI/1.1",
+		"env-HTTP_HOST":         "example.com",
+		"env-PATH_INFO":         "",
+		"env-QUERY_STRING":      "foo=bar&a=b",
+		"env-REMOTE_ADDR":       "1.2.3.4",
+		"env-REMOTE_HOST":       "1.2.3.4",
+		"env-REQUEST_METHOD":    "GET",
+		"env-REQUEST_URI":       "/test.cgi?foo=bar&a=b",
+		"env-SCRIPT_FILENAME":   "testdata/test.cgi",
+		"env-SCRIPT_NAME":       "/test.cgi",
+		"env-SERVER_NAME":       "example.com",
+		"env-SERVER_PORT":       "80",
+		"env-SERVER_SOFTWARE":   "go",
+	}
+	replay := runCgiTest(t, h, "GET /test.cgi?foo=bar&a=b HTTP/1.0\nHost: example.com\n\n", expectedMap)
+
+	if expected, got := "text/html", replay.Header().Get("Content-Type"); got != expected {
+		t.Errorf("got a Content-Type of %q; expected %q", got, expected)
+	}
+	if expected, got := "X-Test-Value", replay.Header().Get("X-Test-Header"); got != expected {
+		t.Errorf("got a X-Test-Header of %q; expected %q", got, expected)
+	}
+}
+
+func TestCGIBasicGetAbsPath(t *testing.T) {
+	check(t)
+	pwd, err := os.Getwd()
+	if err != nil {
+		t.Fatalf("getwd error: %v", err)
+	}
+	h := &Handler{
+		Path: pwd + "/testdata/test.cgi",
+		Root: "/test.cgi",
+	}
+	expectedMap := map[string]string{
+		"env-REQUEST_URI":     "/test.cgi?foo=bar&a=b",
+		"env-SCRIPT_FILENAME": pwd + "/testdata/test.cgi",
+		"env-SCRIPT_NAME":     "/test.cgi",
+	}
+	runCgiTest(t, h, "GET /test.cgi?foo=bar&a=b HTTP/1.0\nHost: example.com\n\n", expectedMap)
+}
+
+func TestPathInfo(t *testing.T) {
+	check(t)
+	h := &Handler{
+		Path: "testdata/test.cgi",
+		Root: "/test.cgi",
+	}
+	expectedMap := map[string]string{
+		"param-a":             "b",
+		"env-PATH_INFO":       "/extrapath",
+		"env-QUERY_STRING":    "a=b",
+		"env-REQUEST_URI":     "/test.cgi/extrapath?a=b",
+		"env-SCRIPT_FILENAME": "testdata/test.cgi",
+		"env-SCRIPT_NAME":     "/test.cgi",
+	}
+	runCgiTest(t, h, "GET /test.cgi/extrapath?a=b HTTP/1.0\nHost: example.com\n\n", expectedMap)
+}
+
+func TestPathInfoDirRoot(t *testing.T) {
+	check(t)
+	h := &Handler{
+		Path: "testdata/test.cgi",
+		Root: "/myscript/",
+	}
+	expectedMap := map[string]string{
+		"env-PATH_INFO":       "bar",
+		"env-QUERY_STRING":    "a=b",
+		"env-REQUEST_URI":     "/myscript/bar?a=b",
+		"env-SCRIPT_FILENAME": "testdata/test.cgi",
+		"env-SCRIPT_NAME":     "/myscript/",
+	}
+	runCgiTest(t, h, "GET /myscript/bar?a=b HTTP/1.0\nHost: example.com\n\n", expectedMap)
+}
+
+func TestDupHeaders(t *testing.T) {
+	check(t)
+	h := &Handler{
+		Path: "testdata/test.cgi",
+	}
+	expectedMap := map[string]string{
+		"env-REQUEST_URI":     "/myscript/bar?a=b",
+		"env-SCRIPT_FILENAME": "testdata/test.cgi",
+		"env-HTTP_COOKIE":     "nom=NOM; yum=YUM",
+		"env-HTTP_X_FOO":      "val1, val2",
+	}
+	runCgiTest(t, h, "GET /myscript/bar?a=b HTTP/1.0\n"+
+		"Cookie: nom=NOM\n"+
+		"Cookie: yum=YUM\n"+
+		"X-Foo: val1\n"+
+		"X-Foo: val2\n"+
+		"Host: example.com\n\n",
+		expectedMap)
+}
+
+func TestPathInfoNoRoot(t *testing.T) {
+	check(t)
+	h := &Handler{
+		Path: "testdata/test.cgi",
+		Root: "",
+	}
+	expectedMap := map[string]string{
+		"env-PATH_INFO":       "/bar",
+		"env-QUERY_STRING":    "a=b",
+		"env-REQUEST_URI":     "/bar?a=b",
+		"env-SCRIPT_FILENAME": "testdata/test.cgi",
+		"env-SCRIPT_NAME":     "/",
+	}
+	runCgiTest(t, h, "GET /bar?a=b HTTP/1.0\nHost: example.com\n\n", expectedMap)
+}
+
+func TestCGIBasicPost(t *testing.T) {
+	check(t)
+	postReq := `POST /test.cgi?a=b HTTP/1.0
+Host: example.com
+Content-Type: application/x-www-form-urlencoded
+Content-Length: 15
+
+postfoo=postbar`
+	h := &Handler{
+		Path: "testdata/test.cgi",
+		Root: "/test.cgi",
+	}
+	expectedMap := map[string]string{
+		"test":               "Hello CGI",
+		"param-postfoo":      "postbar",
+		"env-REQUEST_METHOD": "POST",
+		"env-CONTENT_LENGTH": "15",
+		"env-REQUEST_URI":    "/test.cgi?a=b",
+	}
+	runCgiTest(t, h, postReq, expectedMap)
+}
+
+func chunk(s string) string {
+	return fmt.Sprintf("%x\r\n%s\r\n", len(s), s)
+}
+
+// The CGI spec doesn't allow chunked requests.
+func TestCGIPostChunked(t *testing.T) {
+	check(t)
+	postReq := `POST /test.cgi?a=b HTTP/1.1
+Host: example.com
+Content-Type: application/x-www-form-urlencoded
+Transfer-Encoding: chunked
+
+` + chunk("postfoo") + chunk("=") + chunk("postbar") + chunk("")
+
+	h := &Handler{
+		Path: "testdata/test.cgi",
+		Root: "/test.cgi",
+	}
+	expectedMap := map[string]string{}
+	resp := runCgiTest(t, h, postReq, expectedMap)
+	if got, expected := resp.Code, http.StatusBadRequest; got != expected {
+		t.Fatalf("Expected %v response code from chunked request body; got %d",
+			expected, got)
+	}
+}
+
+func TestRedirect(t *testing.T) {
+	check(t)
+	h := &Handler{
+		Path: "testdata/test.cgi",
+		Root: "/test.cgi",
+	}
+	rec := runCgiTest(t, h, "GET /test.cgi?loc=http://foo.com/ HTTP/1.0\nHost: example.com\n\n", nil)
+	if e, g := 302, rec.Code; e != g {
+		t.Errorf("expected status code %d; got %d", e, g)
+	}
+	if e, g := "http://foo.com/", rec.Header().Get("Location"); e != g {
+		t.Errorf("expected Location header of %q; got %q", e, g)
+	}
+}
+
+func TestInternalRedirect(t *testing.T) {
+	check(t)
+	baseHandler := http.HandlerFunc(func(rw http.ResponseWriter, req *http.Request) {
+		fmt.Fprintf(rw, "basepath=%s\n", req.URL.Path)
+		fmt.Fprintf(rw, "remoteaddr=%s\n", req.RemoteAddr)
+	})
+	h := &Handler{
+		Path:                "testdata/test.cgi",
+		Root:                "/test.cgi",
+		PathLocationHandler: baseHandler,
+	}
+	expectedMap := map[string]string{
+		"basepath":   "/foo",
+		"remoteaddr": "1.2.3.4",
+	}
+	runCgiTest(t, h, "GET /test.cgi?loc=/foo HTTP/1.0\nHost: example.com\n\n", expectedMap)
+}
+
+// TestCopyError tests that we kill the process if there's an error copying
+// its output. (for example, from the client having gone away)
+func TestCopyError(t *testing.T) {
+	check(t)
+	if runtime.GOOS == "windows" {
+		t.Skipf("skipping test on %q", runtime.GOOS)
+	}
+	h := &Handler{
+		Path: "testdata/test.cgi",
+		Root: "/test.cgi",
+	}
+	ts := httptest.NewServer(h)
+	defer ts.Close()
+
+	conn, err := net.Dial("tcp", ts.Listener.Addr().String())
+	if err != nil {
+		t.Fatal(err)
+	}
+	req, _ := http.NewRequest("GET", "http://example.com/test.cgi?bigresponse=1", nil)
+	err = req.Write(conn)
+	if err != nil {
+		t.Fatalf("Write: %v", err)
+	}
+
+	res, err := http.ReadResponse(bufio.NewReader(conn), req)
+	if err != nil {
+		t.Fatalf("ReadResponse: %v", err)
+	}
+
+	pidstr := res.Header.Get("X-CGI-Pid")
+	if pidstr == "" {
+		t.Fatalf("expected an X-CGI-Pid header in response")
+	}
+	pid, err := strconv.Atoi(pidstr)
+	if err != nil {
+		t.Fatalf("invalid X-CGI-Pid value")
+	}
+
+	var buf [5000]byte
+	n, err := io.ReadFull(res.Body, buf[:])
+	if err != nil {
+		t.Fatalf("ReadFull: %d bytes, %v", n, err)
+	}
+
+	childRunning := func() bool {
+		return isProcessRunning(t, pid)
+	}
+
+	if !childRunning() {
+		t.Fatalf("pre-conn.Close, expected child to be running")
+	}
+	conn.Close()
+
+	tries := 0
+	for tries < 25 && childRunning() {
+		time.Sleep(50 * time.Millisecond * time.Duration(tries))
+		tries++
+	}
+	if childRunning() {
+		t.Fatalf("post-conn.Close, expected child to be gone")
+	}
+}
+
+func TestDirUnix(t *testing.T) {
+	check(t)
+	if runtime.GOOS == "windows" {
+		t.Skipf("skipping test on %q", runtime.GOOS)
+	}
+	cwd, _ := os.Getwd()
+	h := &Handler{
+		Path: "testdata/test.cgi",
+		Root: "/test.cgi",
+		Dir:  cwd,
+	}
+	expectedMap := map[string]string{
+		"cwd": cwd,
+	}
+	runCgiTest(t, h, "GET /test.cgi HTTP/1.0\nHost: example.com\n\n", expectedMap)
+
+	cwd, _ = os.Getwd()
+	cwd = filepath.Join(cwd, "testdata")
+	h = &Handler{
+		Path: "testdata/test.cgi",
+		Root: "/test.cgi",
+	}
+	expectedMap = map[string]string{
+		"cwd": cwd,
+	}
+	runCgiTest(t, h, "GET /test.cgi HTTP/1.0\nHost: example.com\n\n", expectedMap)
+}
+
+func TestDirWindows(t *testing.T) {
+	if runtime.GOOS != "windows" {
+		t.Skip("Skipping windows specific test.")
+	}
+
+	cgifile, _ := filepath.Abs("testdata/test.cgi")
+
+	var perl string
+	var err error
+	perl, err = exec.LookPath("perl")
+	if err != nil {
+		t.Skip("Skipping test: perl not found.")
+	}
+	perl, _ = filepath.Abs(perl)
+
+	cwd, _ := os.Getwd()
+	h := &Handler{
+		Path: perl,
+		Root: "/test.cgi",
+		Dir:  cwd,
+		Args: []string{cgifile},
+		Env:  []string{"SCRIPT_FILENAME=" + cgifile},
+	}
+	expectedMap := map[string]string{
+		"cwd": cwd,
+	}
+	runCgiTest(t, h, "GET /test.cgi HTTP/1.0\nHost: example.com\n\n", expectedMap)
+
+	// If not specify Dir on windows, working directory should be
+	// base directory of perl.
+	cwd, _ = filepath.Split(perl)
+	if cwd != "" && cwd[len(cwd)-1] == filepath.Separator {
+		cwd = cwd[:len(cwd)-1]
+	}
+	h = &Handler{
+		Path: perl,
+		Root: "/test.cgi",
+		Args: []string{cgifile},
+		Env:  []string{"SCRIPT_FILENAME=" + cgifile},
+	}
+	expectedMap = map[string]string{
+		"cwd": cwd,
+	}
+	runCgiTest(t, h, "GET /test.cgi HTTP/1.0\nHost: example.com\n\n", expectedMap)
+}
+
+func TestEnvOverride(t *testing.T) {
+	cgifile, _ := filepath.Abs("testdata/test.cgi")
+
+	var perl string
+	var err error
+	perl, err = exec.LookPath("perl")
+	if err != nil {
+		t.Skipf("Skipping test: perl not found.")
+	}
+	perl, _ = filepath.Abs(perl)
+
+	cwd, _ := os.Getwd()
+	h := &Handler{
+		Path: perl,
+		Root: "/test.cgi",
+		Dir:  cwd,
+		Args: []string{cgifile},
+		Env: []string{
+			"SCRIPT_FILENAME=" + cgifile,
+			"REQUEST_URI=/foo/bar"},
+	}
+	expectedMap := map[string]string{
+		"cwd": cwd,
+		"env-SCRIPT_FILENAME": cgifile,
+		"env-REQUEST_URI":     "/foo/bar",
+	}
+	runCgiTest(t, h, "GET /test.cgi HTTP/1.0\nHost: example.com\n\n", expectedMap)
+}
diff --git a/src/net/http/cgi/matryoshka_test.go b/src/net/http/cgi/matryoshka_test.go
new file mode 100644
index 000000000..18c4803e7
--- /dev/null
+++ b/src/net/http/cgi/matryoshka_test.go
@@ -0,0 +1,228 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Tests a Go CGI program running under a Go CGI host process.
+// Further, the two programs are the same binary, just checking
+// their environment to figure out what mode to run in.
+
+package cgi
+
+import (
+	"bytes"
+	"errors"
+	"fmt"
+	"io"
+	"net/http"
+	"net/http/httptest"
+	"os"
+	"runtime"
+	"testing"
+	"time"
+)
+
+// This test is a CGI host (testing host.go) that runs its own binary
+// as a child process testing the other half of CGI (child.go).
+func TestHostingOurselves(t *testing.T) {
+	if runtime.GOOS == "nacl" {
+		t.Skip("skipping on nacl")
+	}
+
+	h := &Handler{
+		Path: os.Args[0],
+		Root: "/test.go",
+		Args: []string{"-test.run=TestBeChildCGIProcess"},
+	}
+	expectedMap := map[string]string{
+		"test":                  "Hello CGI-in-CGI",
+		"param-a":               "b",
+		"param-foo":             "bar",
+		"env-GATEWAY_INTERFACE": "CGI/1.1",
+		"env-HTTP_HOST":         "example.com",
+		"env-PATH_INFO":         "",
+		"env-QUERY_STRING":      "foo=bar&a=b",
+		"env-REMOTE_ADDR":       "1.2.3.4",
+		"env-REMOTE_HOST":       "1.2.3.4",
+		"env-REQUEST_METHOD":    "GET",
+		"env-REQUEST_URI":       "/test.go?foo=bar&a=b",
+		"env-SCRIPT_FILENAME":   os.Args[0],
+		"env-SCRIPT_NAME":       "/test.go",
+		"env-SERVER_NAME":       "example.com",
+		"env-SERVER_PORT":       "80",
+		"env-SERVER_SOFTWARE":   "go",
+	}
+	replay := runCgiTest(t, h, "GET /test.go?foo=bar&a=b HTTP/1.0\nHost: example.com\n\n", expectedMap)
+
+	if expected, got := "text/html; charset=utf-8", replay.Header().Get("Content-Type"); got != expected {
+		t.Errorf("got a Content-Type of %q; expected %q", got, expected)
+	}
+	if expected, got := "X-Test-Value", replay.Header().Get("X-Test-Header"); got != expected {
+		t.Errorf("got a X-Test-Header of %q; expected %q", got, expected)
+	}
+}
+
+type customWriterRecorder struct {
+	w io.Writer
+	*httptest.ResponseRecorder
+}
+
+func (r *customWriterRecorder) Write(p []byte) (n int, err error) {
+	return r.w.Write(p)
+}
+
+type limitWriter struct {
+	w io.Writer
+	n int
+}
+
+func (w *limitWriter) Write(p []byte) (n int, err error) {
+	if len(p) > w.n {
+		p = p[:w.n]
+	}
+	if len(p) > 0 {
+		n, err = w.w.Write(p)
+		w.n -= n
+	}
+	if w.n == 0 {
+		err = errors.New("past write limit")
+	}
+	return
+}
+
+// If there's an error copying the child's output to the parent, test
+// that we kill the child.
+func TestKillChildAfterCopyError(t *testing.T) {
+	if runtime.GOOS == "nacl" {
+		t.Skip("skipping on nacl")
+	}
+
+	defer func() { testHookStartProcess = nil }()
+	proc := make(chan *os.Process, 1)
+	testHookStartProcess = func(p *os.Process) {
+		proc <- p
+	}
+
+	h := &Handler{
+		Path: os.Args[0],
+		Root: "/test.go",
+		Args: []string{"-test.run=TestBeChildCGIProcess"},
+	}
+	req, _ := http.NewRequest("GET", "http://example.com/test.cgi?write-forever=1", nil)
+	rec := httptest.NewRecorder()
+	var out bytes.Buffer
+	const writeLen = 50 << 10
+	rw := &customWriterRecorder{&limitWriter{&out, writeLen}, rec}
+
+	donec := make(chan bool, 1)
+	go func() {
+		h.ServeHTTP(rw, req)
+		donec <- true
+	}()
+
+	select {
+	case <-donec:
+		if out.Len() != writeLen || out.Bytes()[0] != 'a' {
+			t.Errorf("unexpected output: %q", out.Bytes())
+		}
+	case <-time.After(5 * time.Second):
+		t.Errorf("timeout. ServeHTTP hung and didn't kill the child process?")
+		select {
+		case p := <-proc:
+			p.Kill()
+			t.Logf("killed process")
+		default:
+			t.Logf("didn't kill process")
+		}
+	}
+}
+
+// Test that a child handler writing only headers works.
+// golang.org/issue/7196
+func TestChildOnlyHeaders(t *testing.T) {
+	if runtime.GOOS == "nacl" {
+		t.Skip("skipping on nacl")
+	}
+
+	h := &Handler{
+		Path: os.Args[0],
+		Root: "/test.go",
+		Args: []string{"-test.run=TestBeChildCGIProcess"},
+	}
+	expectedMap := map[string]string{
+		"_body": "",
+	}
+	replay := runCgiTest(t, h, "GET /test.go?no-body=1 HTTP/1.0\nHost: example.com\n\n", expectedMap)
+	if expected, got := "X-Test-Value", replay.Header().Get("X-Test-Header"); got != expected {
+		t.Errorf("got a X-Test-Header of %q; expected %q", got, expected)
+	}
+}
+
+// golang.org/issue/7198
+func Test500WithNoHeaders(t *testing.T)     { want500Test(t, "/immediate-disconnect") }
+func Test500WithNoContentType(t *testing.T) { want500Test(t, "/no-content-type") }
+func Test500WithEmptyHeaders(t *testing.T)  { want500Test(t, "/empty-headers") }
+
+func want500Test(t *testing.T, path string) {
+	h := &Handler{
+		Path: os.Args[0],
+		Root: "/test.go",
+		Args: []string{"-test.run=TestBeChildCGIProcess"},
+	}
+	expectedMap := map[string]string{
+		"_body": "",
+	}
+	replay := runCgiTest(t, h, "GET "+path+" HTTP/1.0\nHost: example.com\n\n", expectedMap)
+	if replay.Code != 500 {
+		t.Errorf("Got code %d; want 500", replay.Code)
+	}
+}
+
+type neverEnding byte
+
+func (b neverEnding) Read(p []byte) (n int, err error) {
+	for i := range p {
+		p[i] = byte(b)
+	}
+	return len(p), nil
+}
+
+// Note: not actually a test.
+func TestBeChildCGIProcess(t *testing.T) {
+	if os.Getenv("REQUEST_METHOD") == "" {
+		// Not in a CGI environment; skipping test.
+		return
+	}
+	switch os.Getenv("REQUEST_URI") {
+	case "/immediate-disconnect":
+		os.Exit(0)
+	case "/no-content-type":
+		fmt.Printf("Content-Length: 6\n\nHello\n")
+		os.Exit(0)
+	case "/empty-headers":
+		fmt.Printf("\nHello")
+		os.Exit(0)
+	}
+	Serve(http.HandlerFunc(func(rw http.ResponseWriter, req *http.Request) {
+		rw.Header().Set("X-Test-Header", "X-Test-Value")
+		req.ParseForm()
+		if req.FormValue("no-body") == "1" {
+			return
+		}
+		if req.FormValue("write-forever") == "1" {
+			io.Copy(rw, neverEnding('a'))
+			for {
+				time.Sleep(5 * time.Second) // hang forever, until killed
+			}
+		}
+		fmt.Fprintf(rw, "test=Hello CGI-in-CGI\n")
+		for k, vv := range req.Form {
+			for _, v := range vv {
+				fmt.Fprintf(rw, "param-%s=%s\n", k, v)
+			}
+		}
+		for _, kv := range os.Environ() {
+			fmt.Fprintf(rw, "env-%s\n", kv)
+		}
+	}))
+	os.Exit(0)
+}
diff --git a/src/net/http/cgi/plan9_test.go b/src/net/http/cgi/plan9_test.go
new file mode 100644
index 000000000..c8235831b
--- /dev/null
+++ b/src/net/http/cgi/plan9_test.go
@@ -0,0 +1,18 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build plan9
+
+package cgi
+
+import (
+	"os"
+	"strconv"
+	"testing"
+)
+
+func isProcessRunning(t *testing.T, pid int) bool {
+	_, err := os.Stat("/proc/" + strconv.Itoa(pid))
+	return err == nil
+}
diff --git a/src/net/http/cgi/posix_test.go b/src/net/http/cgi/posix_test.go
new file mode 100644
index 000000000..5ff9e7d5e
--- /dev/null
+++ b/src/net/http/cgi/posix_test.go
@@ -0,0 +1,21 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build !plan9
+
+package cgi
+
+import (
+	"os"
+	"syscall"
+	"testing"
+)
+
+func isProcessRunning(t *testing.T, pid int) bool {
+	p, err := os.FindProcess(pid)
+	if err != nil {
+		return false
+	}
+	return p.Signal(syscall.Signal(0)) == nil
+}
diff --git a/src/net/http/cgi/testdata/test.cgi b/src/net/http/cgi/testdata/test.cgi
new file mode 100755
index 000000000..3214df6f0
--- /dev/null
+++ b/src/net/http/cgi/testdata/test.cgi
@@ -0,0 +1,91 @@
+#!/usr/bin/perl
+# Copyright 2011 The Go Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style
+# license that can be found in the LICENSE file.
+#
+# Test script run as a child process under cgi_test.go
+
+use strict;
+use Cwd;
+
+binmode STDOUT;
+
+my $q = MiniCGI->new;
+my $params = $q->Vars;
+
+if ($params->{"loc"}) {
+    print "Location: $params->{loc}\r\n\r\n";
+    exit(0);
+}
+
+print "Content-Type: text/html\r\n";
+print "X-CGI-Pid: $$\r\n";
+print "X-Test-Header: X-Test-Value\r\n";
+print "\r\n";
+
+if ($params->{"bigresponse"}) {
+    # 17 MB, for OS X: golang.org/issue/4958
+    for (1..(17 * 1024)) {
+        print "A" x 1024, "\r\n";
+    }
+    exit 0;
+}
+
+print "test=Hello CGI\r\n";
+
+foreach my $k (sort keys %$params) {
+    print "param-$k=$params->{$k}\r\n";
+}
+
+foreach my $k (sort keys %ENV) {
+    my $clean_env = $ENV{$k};
+    $clean_env =~ s/[\n\r]//g;
+    print "env-$k=$clean_env\r\n";
+}
+
+# NOTE: msys perl returns /c/go/src/... not C:\go\....
+my $dir = getcwd();
+if ($^O eq 'MSWin32' || $^O eq 'msys') {
+    if ($dir =~ /^.:/) {
+        $dir =~ s!/!\\!g;
+    } else {
+        my $cmd = $ENV{'COMSPEC'} || 'c:\\windows\\system32\\cmd.exe';
+        $cmd =~ s!\\!/!g;
+        $dir = `$cmd /c cd`;
+        chomp $dir;
+    }
+}
+print "cwd=$dir\r\n";
+
+# A minimal version of CGI.pm, for people without the perl-modules
+# package installed.  (CGI.pm used to be part of the Perl core, but
+# some distros now bundle perl-base and perl-modules separately...)
+package MiniCGI;
+
+sub new {
+    my $class = shift;
+    return bless {}, $class;
+}
+
+sub Vars {
+    my $self = shift;
+    my $pairs;
+    if ($ENV{CONTENT_LENGTH}) {
+        $pairs = do { local $/; <STDIN> };
+    } else {
+        $pairs = $ENV{QUERY_STRING};
+    }
+    my $vars = {};
+    foreach my $kv (split(/&/, $pairs)) {
+        my ($k, $v) = split(/=/, $kv, 2);
+        $vars->{_urldecode($k)} = _urldecode($v);
+    }
+    return $vars;
+}
+
+sub _urldecode {
+    my $v = shift;
+    $v =~ tr/+/ /;
+    $v =~ s/%([a-fA-F0-9][a-fA-F0-9])/pack("C", hex($1))/eg;
+    return $v;
+}
diff --git a/src/net/http/client.go b/src/net/http/client.go
new file mode 100644
index 000000000..a5a3abe61
--- /dev/null
+++ b/src/net/http/client.go
@@ -0,0 +1,487 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// HTTP client. See RFC 2616.
+//
+// This is the high-level Client interface.
+// The low-level implementation is in transport.go.
+
+package http
+
+import (
+	"encoding/base64"
+	"errors"
+	"fmt"
+	"io"
+	"io/ioutil"
+	"log"
+	"net/url"
+	"strings"
+	"sync"
+	"time"
+)
+
+// A Client is an HTTP client. Its zero value (DefaultClient) is a
+// usable client that uses DefaultTransport.
+//
+// The Client's Transport typically has internal state (cached TCP
+// connections), so Clients should be reused instead of created as
+// needed. Clients are safe for concurrent use by multiple goroutines.
+//
+// A Client is higher-level than a RoundTripper (such as Transport)
+// and additionally handles HTTP details such as cookies and
+// redirects.
+type Client struct {
+	// Transport specifies the mechanism by which individual
+	// HTTP requests are made.
+	// If nil, DefaultTransport is used.
+	Transport RoundTripper
+
+	// CheckRedirect specifies the policy for handling redirects.
+	// If CheckRedirect is not nil, the client calls it before
+	// following an HTTP redirect. The arguments req and via are
+	// the upcoming request and the requests made already, oldest
+	// first. If CheckRedirect returns an error, the Client's Get
+	// method returns both the previous Response and
+	// CheckRedirect's error (wrapped in a url.Error) instead of
+	// issuing the Request req.
+	//
+	// If CheckRedirect is nil, the Client uses its default policy,
+	// which is to stop after 10 consecutive requests.
+	CheckRedirect func(req *Request, via []*Request) error
+
+	// Jar specifies the cookie jar.
+	// If Jar is nil, cookies are not sent in requests and ignored
+	// in responses.
+	Jar CookieJar
+
+	// Timeout specifies a time limit for requests made by this
+	// Client. The timeout includes connection time, any
+	// redirects, and reading the response body. The timer remains
+	// running after Get, Head, Post, or Do return and will
+	// interrupt reading of the Response.Body.
+	//
+	// A Timeout of zero means no timeout.
+	//
+	// The Client's Transport must support the CancelRequest
+	// method or Client will return errors when attempting to make
+	// a request with Get, Head, Post, or Do. Client's default
+	// Transport (DefaultTransport) supports CancelRequest.
+	Timeout time.Duration
+}
+
+// DefaultClient is the default Client and is used by Get, Head, and Post.
+var DefaultClient = &Client{}
+
+// RoundTripper is an interface representing the ability to execute a
+// single HTTP transaction, obtaining the Response for a given Request.
+//
+// A RoundTripper must be safe for concurrent use by multiple
+// goroutines.
+type RoundTripper interface {
+	// RoundTrip executes a single HTTP transaction, returning
+	// the Response for the request req.  RoundTrip should not
+	// attempt to interpret the response.  In particular,
+	// RoundTrip must return err == nil if it obtained a response,
+	// regardless of the response's HTTP status code.  A non-nil
+	// err should be reserved for failure to obtain a response.
+	// Similarly, RoundTrip should not attempt to handle
+	// higher-level protocol details such as redirects,
+	// authentication, or cookies.
+	//
+	// RoundTrip should not modify the request, except for
+	// consuming and closing the Body, including on errors. The
+	// request's URL and Header fields are guaranteed to be
+	// initialized.
+	RoundTrip(*Request) (*Response, error)
+}
+
+// Given a string of the form "host", "host:port", or "[ipv6::address]:port",
+// return true if the string includes a port.
+func hasPort(s string) bool { return strings.LastIndex(s, ":") > strings.LastIndex(s, "]") }
+
+// Used in Send to implement io.ReadCloser by bundling together the
+// bufio.Reader through which we read the response, and the underlying
+// network connection.
+type readClose struct {
+	io.Reader
+	io.Closer
+}
+
+func (c *Client) send(req *Request) (*Response, error) {
+	if c.Jar != nil {
+		for _, cookie := range c.Jar.Cookies(req.URL) {
+			req.AddCookie(cookie)
+		}
+	}
+	resp, err := send(req, c.transport())
+	if err != nil {
+		return nil, err
+	}
+	if c.Jar != nil {
+		if rc := resp.Cookies(); len(rc) > 0 {
+			c.Jar.SetCookies(req.URL, rc)
+		}
+	}
+	return resp, err
+}
+
+// Do sends an HTTP request and returns an HTTP response, following
+// policy (e.g. redirects, cookies, auth) as configured on the client.
+//
+// An error is returned if caused by client policy (such as
+// CheckRedirect), or if there was an HTTP protocol error.
+// A non-2xx response doesn't cause an error.
+//
+// When err is nil, resp always contains a non-nil resp.Body.
+//
+// Callers should close resp.Body when done reading from it. If
+// resp.Body is not closed, the Client's underlying RoundTripper
+// (typically Transport) may not be able to re-use a persistent TCP
+// connection to the server for a subsequent "keep-alive" request.
+//
+// The request Body, if non-nil, will be closed by the underlying
+// Transport, even on errors.
+//
+// Generally Get, Post, or PostForm will be used instead of Do.
+func (c *Client) Do(req *Request) (resp *Response, err error) {
+	if req.Method == "GET" || req.Method == "HEAD" {
+		return c.doFollowingRedirects(req, shouldRedirectGet)
+	}
+	if req.Method == "POST" || req.Method == "PUT" {
+		return c.doFollowingRedirects(req, shouldRedirectPost)
+	}
+	return c.send(req)
+}
+
+func (c *Client) transport() RoundTripper {
+	if c.Transport != nil {
+		return c.Transport
+	}
+	return DefaultTransport
+}
+
+// send issues an HTTP request.
+// Caller should close resp.Body when done reading from it.
+func send(req *Request, t RoundTripper) (resp *Response, err error) {
+	if t == nil {
+		req.closeBody()
+		return nil, errors.New("http: no Client.Transport or DefaultTransport")
+	}
+
+	if req.URL == nil {
+		req.closeBody()
+		return nil, errors.New("http: nil Request.URL")
+	}
+
+	if req.RequestURI != "" {
+		req.closeBody()
+		return nil, errors.New("http: Request.RequestURI can't be set in client requests.")
+	}
+
+	// Most the callers of send (Get, Post, et al) don't need
+	// Headers, leaving it uninitialized.  We guarantee to the
+	// Transport that this has been initialized, though.
+	if req.Header == nil {
+		req.Header = make(Header)
+	}
+
+	if u := req.URL.User; u != nil {
+		username := u.Username()
+		password, _ := u.Password()
+		req.Header.Set("Authorization", "Basic "+basicAuth(username, password))
+	}
+	resp, err = t.RoundTrip(req)
+	if err != nil {
+		if resp != nil {
+			log.Printf("RoundTripper returned a response & error; ignoring response")
+		}
+		return nil, err
+	}
+	return resp, nil
+}
+
+// See 2 (end of page 4) http://www.ietf.org/rfc/rfc2617.txt
+// "To receive authorization, the client sends the userid and password,
+// separated by a single colon (":") character, within a base64
+// encoded string in the credentials."
+// It is not meant to be urlencoded.
+func basicAuth(username, password string) string {
+	auth := username + ":" + password
+	return base64.StdEncoding.EncodeToString([]byte(auth))
+}
+
+// True if the specified HTTP status code is one for which the Get utility should
+// automatically redirect.
+func shouldRedirectGet(statusCode int) bool {
+	switch statusCode {
+	case StatusMovedPermanently, StatusFound, StatusSeeOther, StatusTemporaryRedirect:
+		return true
+	}
+	return false
+}
+
+// True if the specified HTTP status code is one for which the Post utility should
+// automatically redirect.
+func shouldRedirectPost(statusCode int) bool {
+	switch statusCode {
+	case StatusFound, StatusSeeOther:
+		return true
+	}
+	return false
+}
+
+// Get issues a GET to the specified URL.  If the response is one of the following
+// redirect codes, Get follows the redirect, up to a maximum of 10 redirects:
+//
+//    301 (Moved Permanently)
+//    302 (Found)
+//    303 (See Other)
+//    307 (Temporary Redirect)
+//
+// An error is returned if there were too many redirects or if there
+// was an HTTP protocol error. A non-2xx response doesn't cause an
+// error.
+//
+// When err is nil, resp always contains a non-nil resp.Body.
+// Caller should close resp.Body when done reading from it.
+//
+// Get is a wrapper around DefaultClient.Get.
+func Get(url string) (resp *Response, err error) {
+	return DefaultClient.Get(url)
+}
+
+// Get issues a GET to the specified URL.  If the response is one of the
+// following redirect codes, Get follows the redirect after calling the
+// Client's CheckRedirect function.
+//
+//    301 (Moved Permanently)
+//    302 (Found)
+//    303 (See Other)
+//    307 (Temporary Redirect)
+//
+// An error is returned if the Client's CheckRedirect function fails
+// or if there was an HTTP protocol error. A non-2xx response doesn't
+// cause an error.
+//
+// When err is nil, resp always contains a non-nil resp.Body.
+// Caller should close resp.Body when done reading from it.
+func (c *Client) Get(url string) (resp *Response, err error) {
+	req, err := NewRequest("GET", url, nil)
+	if err != nil {
+		return nil, err
+	}
+	return c.doFollowingRedirects(req, shouldRedirectGet)
+}
+
+func (c *Client) doFollowingRedirects(ireq *Request, shouldRedirect func(int) bool) (resp *Response, err error) {
+	var base *url.URL
+	redirectChecker := c.CheckRedirect
+	if redirectChecker == nil {
+		redirectChecker = defaultCheckRedirect
+	}
+	var via []*Request
+
+	if ireq.URL == nil {
+		ireq.closeBody()
+		return nil, errors.New("http: nil Request.URL")
+	}
+
+	var reqmu sync.Mutex // guards req
+	req := ireq
+
+	var timer *time.Timer
+	if c.Timeout > 0 {
+		type canceler interface {
+			CancelRequest(*Request)
+		}
+		tr, ok := c.transport().(canceler)
+		if !ok {
+			return nil, fmt.Errorf("net/http: Client Transport of type %T doesn't support CancelRequest; Timeout not supported", c.transport())
+		}
+		timer = time.AfterFunc(c.Timeout, func() {
+			reqmu.Lock()
+			defer reqmu.Unlock()
+			tr.CancelRequest(req)
+		})
+	}
+
+	urlStr := "" // next relative or absolute URL to fetch (after first request)
+	redirectFailed := false
+	for redirect := 0; ; redirect++ {
+		if redirect != 0 {
+			nreq := new(Request)
+			nreq.Method = ireq.Method
+			if ireq.Method == "POST" || ireq.Method == "PUT" {
+				nreq.Method = "GET"
+			}
+			nreq.Header = make(Header)
+			nreq.URL, err = base.Parse(urlStr)
+			if err != nil {
+				break
+			}
+			if len(via) > 0 {
+				// Add the Referer header.
+				lastReq := via[len(via)-1]
+				if lastReq.URL.Scheme != "https" {
+					nreq.Header.Set("Referer", lastReq.URL.String())
+				}
+
+				err = redirectChecker(nreq, via)
+				if err != nil {
+					redirectFailed = true
+					break
+				}
+			}
+			reqmu.Lock()
+			req = nreq
+			reqmu.Unlock()
+		}
+
+		urlStr = req.URL.String()
+		if resp, err = c.send(req); err != nil {
+			break
+		}
+
+		if shouldRedirect(resp.StatusCode) {
+			// Read the body if small so underlying TCP connection will be re-used.
+			// No need to check for errors: if it fails, Transport won't reuse it anyway.
+			const maxBodySlurpSize = 2 << 10
+			if resp.ContentLength == -1 || resp.ContentLength <= maxBodySlurpSize {
+				io.CopyN(ioutil.Discard, resp.Body, maxBodySlurpSize)
+			}
+			resp.Body.Close()
+			if urlStr = resp.Header.Get("Location"); urlStr == "" {
+				err = errors.New(fmt.Sprintf("%d response missing Location header", resp.StatusCode))
+				break
+			}
+			base = req.URL
+			via = append(via, req)
+			continue
+		}
+		if timer != nil {
+			resp.Body = &cancelTimerBody{timer, resp.Body}
+		}
+		return resp, nil
+	}
+
+	method := ireq.Method
+	urlErr := &url.Error{
+		Op:  method[0:1] + strings.ToLower(method[1:]),
+		URL: urlStr,
+		Err: err,
+	}
+
+	if redirectFailed {
+		// Special case for Go 1 compatibility: return both the response
+		// and an error if the CheckRedirect function failed.
+		// See http://golang.org/issue/3795
+		return resp, urlErr
+	}
+
+	if resp != nil {
+		resp.Body.Close()
+	}
+	return nil, urlErr
+}
+
+func defaultCheckRedirect(req *Request, via []*Request) error {
+	if len(via) >= 10 {
+		return errors.New("stopped after 10 redirects")
+	}
+	return nil
+}
+
+// Post issues a POST to the specified URL.
+//
+// Caller should close resp.Body when done reading from it.
+//
+// Post is a wrapper around DefaultClient.Post
+func Post(url string, bodyType string, body io.Reader) (resp *Response, err error) {
+	return DefaultClient.Post(url, bodyType, body)
+}
+
+// Post issues a POST to the specified URL.
+//
+// Caller should close resp.Body when done reading from it.
+//
+// If the provided body is also an io.Closer, it is closed after the
+// request.
+func (c *Client) Post(url string, bodyType string, body io.Reader) (resp *Response, err error) {
+	req, err := NewRequest("POST", url, body)
+	if err != nil {
+		return nil, err
+	}
+	req.Header.Set("Content-Type", bodyType)
+	return c.doFollowingRedirects(req, shouldRedirectPost)
+}
+
+// PostForm issues a POST to the specified URL, with data's keys and
+// values URL-encoded as the request body.
+//
+// When err is nil, resp always contains a non-nil resp.Body.
+// Caller should close resp.Body when done reading from it.
+//
+// PostForm is a wrapper around DefaultClient.PostForm
+func PostForm(url string, data url.Values) (resp *Response, err error) {
+	return DefaultClient.PostForm(url, data)
+}
+
+// PostForm issues a POST to the specified URL,
+// with data's keys and values urlencoded as the request body.
+//
+// When err is nil, resp always contains a non-nil resp.Body.
+// Caller should close resp.Body when done reading from it.
+func (c *Client) PostForm(url string, data url.Values) (resp *Response, err error) {
+	return c.Post(url, "application/x-www-form-urlencoded", strings.NewReader(data.Encode()))
+}
+
+// Head issues a HEAD to the specified URL.  If the response is one of the
+// following redirect codes, Head follows the redirect after calling the
+// Client's CheckRedirect function.
+//
+//    301 (Moved Permanently)
+//    302 (Found)
+//    303 (See Other)
+//    307 (Temporary Redirect)
+//
+// Head is a wrapper around DefaultClient.Head
+func Head(url string) (resp *Response, err error) {
+	return DefaultClient.Head(url)
+}
+
+// Head issues a HEAD to the specified URL.  If the response is one of the
+// following redirect codes, Head follows the redirect after calling the
+// Client's CheckRedirect function.
+//
+//    301 (Moved Permanently)
+//    302 (Found)
+//    303 (See Other)
+//    307 (Temporary Redirect)
+func (c *Client) Head(url string) (resp *Response, err error) {
+	req, err := NewRequest("HEAD", url, nil)
+	if err != nil {
+		return nil, err
+	}
+	return c.doFollowingRedirects(req, shouldRedirectGet)
+}
+
+type cancelTimerBody struct {
+	t  *time.Timer
+	rc io.ReadCloser
+}
+
+func (b *cancelTimerBody) Read(p []byte) (n int, err error) {
+	n, err = b.rc.Read(p)
+	if err == io.EOF {
+		b.t.Stop()
+	}
+	return
+}
+
+func (b *cancelTimerBody) Close() error {
+	err := b.rc.Close()
+	b.t.Stop()
+	return err
+}
diff --git a/src/net/http/client_test.go b/src/net/http/client_test.go
new file mode 100644
index 000000000..6392c1baf
--- /dev/null
+++ b/src/net/http/client_test.go
@@ -0,0 +1,1038 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Tests for client.go
+
+package http_test
+
+import (
+	"bytes"
+	"crypto/tls"
+	"crypto/x509"
+	"encoding/base64"
+	"errors"
+	"fmt"
+	"io"
+	"io/ioutil"
+	"log"
+	"net"
+	. "net/http"
+	"net/http/httptest"
+	"net/url"
+	"reflect"
+	"sort"
+	"strconv"
+	"strings"
+	"sync"
+	"testing"
+	"time"
+)
+
+var robotsTxtHandler = HandlerFunc(func(w ResponseWriter, r *Request) {
+	w.Header().Set("Last-Modified", "sometime")
+	fmt.Fprintf(w, "User-agent: go\nDisallow: /something/")
+})
+
+// pedanticReadAll works like ioutil.ReadAll but additionally
+// verifies that r obeys the documented io.Reader contract.
+func pedanticReadAll(r io.Reader) (b []byte, err error) {
+	var bufa [64]byte
+	buf := bufa[:]
+	for {
+		n, err := r.Read(buf)
+		if n == 0 && err == nil {
+			return nil, fmt.Errorf("Read: n=0 with err=nil")
+		}
+		b = append(b, buf[:n]...)
+		if err == io.EOF {
+			n, err := r.Read(buf)
+			if n != 0 || err != io.EOF {
+				return nil, fmt.Errorf("Read: n=%d err=%#v after EOF", n, err)
+			}
+			return b, nil
+		}
+		if err != nil {
+			return b, err
+		}
+	}
+}
+
+type chanWriter chan string
+
+func (w chanWriter) Write(p []byte) (n int, err error) {
+	w <- string(p)
+	return len(p), nil
+}
+
+func TestClient(t *testing.T) {
+	defer afterTest(t)
+	ts := httptest.NewServer(robotsTxtHandler)
+	defer ts.Close()
+
+	r, err := Get(ts.URL)
+	var b []byte
+	if err == nil {
+		b, err = pedanticReadAll(r.Body)
+		r.Body.Close()
+	}
+	if err != nil {
+		t.Error(err)
+	} else if s := string(b); !strings.HasPrefix(s, "User-agent:") {
+		t.Errorf("Incorrect page body (did not begin with User-agent): %q", s)
+	}
+}
+
+func TestClientHead(t *testing.T) {
+	defer afterTest(t)
+	ts := httptest.NewServer(robotsTxtHandler)
+	defer ts.Close()
+
+	r, err := Head(ts.URL)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if _, ok := r.Header["Last-Modified"]; !ok {
+		t.Error("Last-Modified header not found.")
+	}
+}
+
+type recordingTransport struct {
+	req *Request
+}
+
+func (t *recordingTransport) RoundTrip(req *Request) (resp *Response, err error) {
+	t.req = req
+	return nil, errors.New("dummy impl")
+}
+
+func TestGetRequestFormat(t *testing.T) {
+	defer afterTest(t)
+	tr := &recordingTransport{}
+	client := &Client{Transport: tr}
+	url := "http://dummy.faketld/"
+	client.Get(url) // Note: doesn't hit network
+	if tr.req.Method != "GET" {
+		t.Errorf("expected method %q; got %q", "GET", tr.req.Method)
+	}
+	if tr.req.URL.String() != url {
+		t.Errorf("expected URL %q; got %q", url, tr.req.URL.String())
+	}
+	if tr.req.Header == nil {
+		t.Errorf("expected non-nil request Header")
+	}
+}
+
+func TestPostRequestFormat(t *testing.T) {
+	defer afterTest(t)
+	tr := &recordingTransport{}
+	client := &Client{Transport: tr}
+
+	url := "http://dummy.faketld/"
+	json := `{"key":"value"}`
+	b := strings.NewReader(json)
+	client.Post(url, "application/json", b) // Note: doesn't hit network
+
+	if tr.req.Method != "POST" {
+		t.Errorf("got method %q, want %q", tr.req.Method, "POST")
+	}
+	if tr.req.URL.String() != url {
+		t.Errorf("got URL %q, want %q", tr.req.URL.String(), url)
+	}
+	if tr.req.Header == nil {
+		t.Fatalf("expected non-nil request Header")
+	}
+	if tr.req.Close {
+		t.Error("got Close true, want false")
+	}
+	if g, e := tr.req.ContentLength, int64(len(json)); g != e {
+		t.Errorf("got ContentLength %d, want %d", g, e)
+	}
+}
+
+func TestPostFormRequestFormat(t *testing.T) {
+	defer afterTest(t)
+	tr := &recordingTransport{}
+	client := &Client{Transport: tr}
+
+	urlStr := "http://dummy.faketld/"
+	form := make(url.Values)
+	form.Set("foo", "bar")
+	form.Add("foo", "bar2")
+	form.Set("bar", "baz")
+	client.PostForm(urlStr, form) // Note: doesn't hit network
+
+	if tr.req.Method != "POST" {
+		t.Errorf("got method %q, want %q", tr.req.Method, "POST")
+	}
+	if tr.req.URL.String() != urlStr {
+		t.Errorf("got URL %q, want %q", tr.req.URL.String(), urlStr)
+	}
+	if tr.req.Header == nil {
+		t.Fatalf("expected non-nil request Header")
+	}
+	if g, e := tr.req.Header.Get("Content-Type"), "application/x-www-form-urlencoded"; g != e {
+		t.Errorf("got Content-Type %q, want %q", g, e)
+	}
+	if tr.req.Close {
+		t.Error("got Close true, want false")
+	}
+	// Depending on map iteration, body can be either of these.
+	expectedBody := "foo=bar&foo=bar2&bar=baz"
+	expectedBody1 := "bar=baz&foo=bar&foo=bar2"
+	if g, e := tr.req.ContentLength, int64(len(expectedBody)); g != e {
+		t.Errorf("got ContentLength %d, want %d", g, e)
+	}
+	bodyb, err := ioutil.ReadAll(tr.req.Body)
+	if err != nil {
+		t.Fatalf("ReadAll on req.Body: %v", err)
+	}
+	if g := string(bodyb); g != expectedBody && g != expectedBody1 {
+		t.Errorf("got body %q, want %q or %q", g, expectedBody, expectedBody1)
+	}
+}
+
+func TestClientRedirects(t *testing.T) {
+	defer afterTest(t)
+	var ts *httptest.Server
+	ts = httptest.NewServer(HandlerFunc(func(w ResponseWriter, r *Request) {
+		n, _ := strconv.Atoi(r.FormValue("n"))
+		// Test Referer header. (7 is arbitrary position to test at)
+		if n == 7 {
+			if g, e := r.Referer(), ts.URL+"/?n=6"; e != g {
+				t.Errorf("on request ?n=7, expected referer of %q; got %q", e, g)
+			}
+		}
+		if n < 15 {
+			Redirect(w, r, fmt.Sprintf("/?n=%d", n+1), StatusFound)
+			return
+		}
+		fmt.Fprintf(w, "n=%d", n)
+	}))
+	defer ts.Close()
+
+	c := &Client{}
+	_, err := c.Get(ts.URL)
+	if e, g := "Get /?n=10: stopped after 10 redirects", fmt.Sprintf("%v", err); e != g {
+		t.Errorf("with default client Get, expected error %q, got %q", e, g)
+	}
+
+	// HEAD request should also have the ability to follow redirects.
+	_, err = c.Head(ts.URL)
+	if e, g := "Head /?n=10: stopped after 10 redirects", fmt.Sprintf("%v", err); e != g {
+		t.Errorf("with default client Head, expected error %q, got %q", e, g)
+	}
+
+	// Do should also follow redirects.
+	greq, _ := NewRequest("GET", ts.URL, nil)
+	_, err = c.Do(greq)
+	if e, g := "Get /?n=10: stopped after 10 redirects", fmt.Sprintf("%v", err); e != g {
+		t.Errorf("with default client Do, expected error %q, got %q", e, g)
+	}
+
+	var checkErr error
+	var lastVia []*Request
+	c = &Client{CheckRedirect: func(_ *Request, via []*Request) error {
+		lastVia = via
+		return checkErr
+	}}
+	res, err := c.Get(ts.URL)
+	if err != nil {
+		t.Fatalf("Get error: %v", err)
+	}
+	res.Body.Close()
+	finalUrl := res.Request.URL.String()
+	if e, g := "<nil>", fmt.Sprintf("%v", err); e != g {
+		t.Errorf("with custom client, expected error %q, got %q", e, g)
+	}
+	if !strings.HasSuffix(finalUrl, "/?n=15") {
+		t.Errorf("expected final url to end in /?n=15; got url %q", finalUrl)
+	}
+	if e, g := 15, len(lastVia); e != g {
+		t.Errorf("expected lastVia to have contained %d elements; got %d", e, g)
+	}
+
+	checkErr = errors.New("no redirects allowed")
+	res, err = c.Get(ts.URL)
+	if urlError, ok := err.(*url.Error); !ok || urlError.Err != checkErr {
+		t.Errorf("with redirects forbidden, expected a *url.Error with our 'no redirects allowed' error inside; got %#v (%q)", err, err)
+	}
+	if res == nil {
+		t.Fatalf("Expected a non-nil Response on CheckRedirect failure (http://golang.org/issue/3795)")
+	}
+	res.Body.Close()
+	if res.Header.Get("Location") == "" {
+		t.Errorf("no Location header in Response")
+	}
+}
+
+func TestPostRedirects(t *testing.T) {
+	defer afterTest(t)
+	var log struct {
+		sync.Mutex
+		bytes.Buffer
+	}
+	var ts *httptest.Server
+	ts = httptest.NewServer(HandlerFunc(func(w ResponseWriter, r *Request) {
+		log.Lock()
+		fmt.Fprintf(&log.Buffer, "%s %s ", r.Method, r.RequestURI)
+		log.Unlock()
+		if v := r.URL.Query().Get("code"); v != "" {
+			code, _ := strconv.Atoi(v)
+			if code/100 == 3 {
+				w.Header().Set("Location", ts.URL)
+			}
+			w.WriteHeader(code)
+		}
+	}))
+	defer ts.Close()
+	tests := []struct {
+		suffix string
+		want   int // response code
+	}{
+		{"/", 200},
+		{"/?code=301", 301},
+		{"/?code=302", 200},
+		{"/?code=303", 200},
+		{"/?code=404", 404},
+	}
+	for _, tt := range tests {
+		res, err := Post(ts.URL+tt.suffix, "text/plain", strings.NewReader("Some content"))
+		if err != nil {
+			t.Fatal(err)
+		}
+		if res.StatusCode != tt.want {
+			t.Errorf("POST %s: status code = %d; want %d", tt.suffix, res.StatusCode, tt.want)
+		}
+	}
+	log.Lock()
+	got := log.String()
+	log.Unlock()
+	want := "POST / POST /?code=301 POST /?code=302 GET / POST /?code=303 GET / POST /?code=404 "
+	if got != want {
+		t.Errorf("Log differs.\n Got: %q\nWant: %q", got, want)
+	}
+}
+
+var expectedCookies = []*Cookie{
+	{Name: "ChocolateChip", Value: "tasty"},
+	{Name: "First", Value: "Hit"},
+	{Name: "Second", Value: "Hit"},
+}
+
+var echoCookiesRedirectHandler = HandlerFunc(func(w ResponseWriter, r *Request) {
+	for _, cookie := range r.Cookies() {
+		SetCookie(w, cookie)
+	}
+	if r.URL.Path == "/" {
+		SetCookie(w, expectedCookies[1])
+		Redirect(w, r, "/second", StatusMovedPermanently)
+	} else {
+		SetCookie(w, expectedCookies[2])
+		w.Write([]byte("hello"))
+	}
+})
+
+func TestClientSendsCookieFromJar(t *testing.T) {
+	tr := &recordingTransport{}
+	client := &Client{Transport: tr}
+	client.Jar = &TestJar{perURL: make(map[string][]*Cookie)}
+	us := "http://dummy.faketld/"
+	u, _ := url.Parse(us)
+	client.Jar.SetCookies(u, expectedCookies)
+
+	client.Get(us) // Note: doesn't hit network
+	matchReturnedCookies(t, expectedCookies, tr.req.Cookies())
+
+	client.Head(us) // Note: doesn't hit network
+	matchReturnedCookies(t, expectedCookies, tr.req.Cookies())
+
+	client.Post(us, "text/plain", strings.NewReader("body")) // Note: doesn't hit network
+	matchReturnedCookies(t, expectedCookies, tr.req.Cookies())
+
+	client.PostForm(us, url.Values{}) // Note: doesn't hit network
+	matchReturnedCookies(t, expectedCookies, tr.req.Cookies())
+
+	req, _ := NewRequest("GET", us, nil)
+	client.Do(req) // Note: doesn't hit network
+	matchReturnedCookies(t, expectedCookies, tr.req.Cookies())
+
+	req, _ = NewRequest("POST", us, nil)
+	client.Do(req) // Note: doesn't hit network
+	matchReturnedCookies(t, expectedCookies, tr.req.Cookies())
+}
+
+// Just enough correctness for our redirect tests. Uses the URL.Host as the
+// scope of all cookies.
+type TestJar struct {
+	m      sync.Mutex
+	perURL map[string][]*Cookie
+}
+
+func (j *TestJar) SetCookies(u *url.URL, cookies []*Cookie) {
+	j.m.Lock()
+	defer j.m.Unlock()
+	if j.perURL == nil {
+		j.perURL = make(map[string][]*Cookie)
+	}
+	j.perURL[u.Host] = cookies
+}
+
+func (j *TestJar) Cookies(u *url.URL) []*Cookie {
+	j.m.Lock()
+	defer j.m.Unlock()
+	return j.perURL[u.Host]
+}
+
+func TestRedirectCookiesJar(t *testing.T) {
+	defer afterTest(t)
+	var ts *httptest.Server
+	ts = httptest.NewServer(echoCookiesRedirectHandler)
+	defer ts.Close()
+	c := &Client{
+		Jar: new(TestJar),
+	}
+	u, _ := url.Parse(ts.URL)
+	c.Jar.SetCookies(u, []*Cookie{expectedCookies[0]})
+	resp, err := c.Get(ts.URL)
+	if err != nil {
+		t.Fatalf("Get: %v", err)
+	}
+	resp.Body.Close()
+	matchReturnedCookies(t, expectedCookies, resp.Cookies())
+}
+
+func matchReturnedCookies(t *testing.T, expected, given []*Cookie) {
+	if len(given) != len(expected) {
+		t.Logf("Received cookies: %v", given)
+		t.Errorf("Expected %d cookies, got %d", len(expected), len(given))
+	}
+	for _, ec := range expected {
+		foundC := false
+		for _, c := range given {
+			if ec.Name == c.Name && ec.Value == c.Value {
+				foundC = true
+				break
+			}
+		}
+		if !foundC {
+			t.Errorf("Missing cookie %v", ec)
+		}
+	}
+}
+
+func TestJarCalls(t *testing.T) {
+	defer afterTest(t)
+	ts := httptest.NewServer(HandlerFunc(func(w ResponseWriter, r *Request) {
+		pathSuffix := r.RequestURI[1:]
+		if r.RequestURI == "/nosetcookie" {
+			return // dont set cookies for this path
+		}
+		SetCookie(w, &Cookie{Name: "name" + pathSuffix, Value: "val" + pathSuffix})
+		if r.RequestURI == "/" {
+			Redirect(w, r, "http://secondhost.fake/secondpath", 302)
+		}
+	}))
+	defer ts.Close()
+	jar := new(RecordingJar)
+	c := &Client{
+		Jar: jar,
+		Transport: &Transport{
+			Dial: func(_ string, _ string) (net.Conn, error) {
+				return net.Dial("tcp", ts.Listener.Addr().String())
+			},
+		},
+	}
+	_, err := c.Get("http://firsthost.fake/")
+	if err != nil {
+		t.Fatal(err)
+	}
+	_, err = c.Get("http://firsthost.fake/nosetcookie")
+	if err != nil {
+		t.Fatal(err)
+	}
+	got := jar.log.String()
+	want := `Cookies("http://firsthost.fake/")
+SetCookie("http://firsthost.fake/", [name=val])
+Cookies("http://secondhost.fake/secondpath")
+SetCookie("http://secondhost.fake/secondpath", [namesecondpath=valsecondpath])
+Cookies("http://firsthost.fake/nosetcookie")
+`
+	if got != want {
+		t.Errorf("Got Jar calls:\n%s\nWant:\n%s", got, want)
+	}
+}
+
+// RecordingJar keeps a log of calls made to it, without
+// tracking any cookies.
+type RecordingJar struct {
+	mu  sync.Mutex
+	log bytes.Buffer
+}
+
+func (j *RecordingJar) SetCookies(u *url.URL, cookies []*Cookie) {
+	j.logf("SetCookie(%q, %v)\n", u, cookies)
+}
+
+func (j *RecordingJar) Cookies(u *url.URL) []*Cookie {
+	j.logf("Cookies(%q)\n", u)
+	return nil
+}
+
+func (j *RecordingJar) logf(format string, args ...interface{}) {
+	j.mu.Lock()
+	defer j.mu.Unlock()
+	fmt.Fprintf(&j.log, format, args...)
+}
+
+func TestStreamingGet(t *testing.T) {
+	defer afterTest(t)
+	say := make(chan string)
+	ts := httptest.NewServer(HandlerFunc(func(w ResponseWriter, r *Request) {
+		w.(Flusher).Flush()
+		for str := range say {
+			w.Write([]byte(str))
+			w.(Flusher).Flush()
+		}
+	}))
+	defer ts.Close()
+
+	c := &Client{}
+	res, err := c.Get(ts.URL)
+	if err != nil {
+		t.Fatal(err)
+	}
+	var buf [10]byte
+	for _, str := range []string{"i", "am", "also", "known", "as", "comet"} {
+		say <- str
+		n, err := io.ReadFull(res.Body, buf[0:len(str)])
+		if err != nil {
+			t.Fatalf("ReadFull on %q: %v", str, err)
+		}
+		if n != len(str) {
+			t.Fatalf("Receiving %q, only read %d bytes", str, n)
+		}
+		got := string(buf[0:n])
+		if got != str {
+			t.Fatalf("Expected %q, got %q", str, got)
+		}
+	}
+	close(say)
+	_, err = io.ReadFull(res.Body, buf[0:1])
+	if err != io.EOF {
+		t.Fatalf("at end expected EOF, got %v", err)
+	}
+}
+
+type writeCountingConn struct {
+	net.Conn
+	count *int
+}
+
+func (c *writeCountingConn) Write(p []byte) (int, error) {
+	*c.count++
+	return c.Conn.Write(p)
+}
+
+// TestClientWrites verifies that client requests are buffered and we
+// don't send a TCP packet per line of the http request + body.
+func TestClientWrites(t *testing.T) {
+	defer afterTest(t)
+	ts := httptest.NewServer(HandlerFunc(func(w ResponseWriter, r *Request) {
+	}))
+	defer ts.Close()
+
+	writes := 0
+	dialer := func(netz string, addr string) (net.Conn, error) {
+		c, err := net.Dial(netz, addr)
+		if err == nil {
+			c = &writeCountingConn{c, &writes}
+		}
+		return c, err
+	}
+	c := &Client{Transport: &Transport{Dial: dialer}}
+
+	_, err := c.Get(ts.URL)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if writes != 1 {
+		t.Errorf("Get request did %d Write calls, want 1", writes)
+	}
+
+	writes = 0
+	_, err = c.PostForm(ts.URL, url.Values{"foo": {"bar"}})
+	if err != nil {
+		t.Fatal(err)
+	}
+	if writes != 1 {
+		t.Errorf("Post request did %d Write calls, want 1", writes)
+	}
+}
+
+func TestClientInsecureTransport(t *testing.T) {
+	defer afterTest(t)
+	ts := httptest.NewTLSServer(HandlerFunc(func(w ResponseWriter, r *Request) {
+		w.Write([]byte("Hello"))
+	}))
+	errc := make(chanWriter, 10) // but only expecting 1
+	ts.Config.ErrorLog = log.New(errc, "", 0)
+	defer ts.Close()
+
+	// TODO(bradfitz): add tests for skipping hostname checks too?
+	// would require a new cert for testing, and probably
+	// redundant with these tests.
+	for _, insecure := range []bool{true, false} {
+		tr := &Transport{
+			TLSClientConfig: &tls.Config{
+				InsecureSkipVerify: insecure,
+			},
+		}
+		defer tr.CloseIdleConnections()
+		c := &Client{Transport: tr}
+		res, err := c.Get(ts.URL)
+		if (err == nil) != insecure {
+			t.Errorf("insecure=%v: got unexpected err=%v", insecure, err)
+		}
+		if res != nil {
+			res.Body.Close()
+		}
+	}
+
+	select {
+	case v := <-errc:
+		if !strings.Contains(v, "TLS handshake error") {
+			t.Errorf("expected an error log message containing 'TLS handshake error'; got %q", v)
+		}
+	case <-time.After(5 * time.Second):
+		t.Errorf("timeout waiting for logged error")
+	}
+
+}
+
+func TestClientErrorWithRequestURI(t *testing.T) {
+	defer afterTest(t)
+	req, _ := NewRequest("GET", "http://localhost:1234/", nil)
+	req.RequestURI = "/this/field/is/illegal/and/should/error/"
+	_, err := DefaultClient.Do(req)
+	if err == nil {
+		t.Fatalf("expected an error")
+	}
+	if !strings.Contains(err.Error(), "RequestURI") {
+		t.Errorf("wanted error mentioning RequestURI; got error: %v", err)
+	}
+}
+
+func newTLSTransport(t *testing.T, ts *httptest.Server) *Transport {
+	certs := x509.NewCertPool()
+	for _, c := range ts.TLS.Certificates {
+		roots, err := x509.ParseCertificates(c.Certificate[len(c.Certificate)-1])
+		if err != nil {
+			t.Fatalf("error parsing server's root cert: %v", err)
+		}
+		for _, root := range roots {
+			certs.AddCert(root)
+		}
+	}
+	return &Transport{
+		TLSClientConfig: &tls.Config{RootCAs: certs},
+	}
+}
+
+func TestClientWithCorrectTLSServerName(t *testing.T) {
+	defer afterTest(t)
+	ts := httptest.NewTLSServer(HandlerFunc(func(w ResponseWriter, r *Request) {
+		if r.TLS.ServerName != "127.0.0.1" {
+			t.Errorf("expected client to set ServerName 127.0.0.1, got: %q", r.TLS.ServerName)
+		}
+	}))
+	defer ts.Close()
+
+	c := &Client{Transport: newTLSTransport(t, ts)}
+	if _, err := c.Get(ts.URL); err != nil {
+		t.Fatalf("expected successful TLS connection, got error: %v", err)
+	}
+}
+
+func TestClientWithIncorrectTLSServerName(t *testing.T) {
+	defer afterTest(t)
+	ts := httptest.NewTLSServer(HandlerFunc(func(w ResponseWriter, r *Request) {}))
+	defer ts.Close()
+	errc := make(chanWriter, 10) // but only expecting 1
+	ts.Config.ErrorLog = log.New(errc, "", 0)
+
+	trans := newTLSTransport(t, ts)
+	trans.TLSClientConfig.ServerName = "badserver"
+	c := &Client{Transport: trans}
+	_, err := c.Get(ts.URL)
+	if err == nil {
+		t.Fatalf("expected an error")
+	}
+	if !strings.Contains(err.Error(), "127.0.0.1") || !strings.Contains(err.Error(), "badserver") {
+		t.Errorf("wanted error mentioning 127.0.0.1 and badserver; got error: %v", err)
+	}
+	select {
+	case v := <-errc:
+		if !strings.Contains(v, "TLS handshake error") {
+			t.Errorf("expected an error log message containing 'TLS handshake error'; got %q", v)
+		}
+	case <-time.After(5 * time.Second):
+		t.Errorf("timeout waiting for logged error")
+	}
+}
+
+// Test for golang.org/issue/5829; the Transport should respect TLSClientConfig.ServerName
+// when not empty.
+//
+// tls.Config.ServerName (non-empty, set to "example.com") takes
+// precedence over "some-other-host.tld" which previously incorrectly
+// took precedence. We don't actually connect to (or even resolve)
+// "some-other-host.tld", though, because of the Transport.Dial hook.
+//
+// The httptest.Server has a cert with "example.com" as its name.
+func TestTransportUsesTLSConfigServerName(t *testing.T) {
+	defer afterTest(t)
+	ts := httptest.NewTLSServer(HandlerFunc(func(w ResponseWriter, r *Request) {
+		w.Write([]byte("Hello"))
+	}))
+	defer ts.Close()
+
+	tr := newTLSTransport(t, ts)
+	tr.TLSClientConfig.ServerName = "example.com" // one of httptest's Server cert names
+	tr.Dial = func(netw, addr string) (net.Conn, error) {
+		return net.Dial(netw, ts.Listener.Addr().String())
+	}
+	defer tr.CloseIdleConnections()
+	c := &Client{Transport: tr}
+	res, err := c.Get("https://some-other-host.tld/")
+	if err != nil {
+		t.Fatal(err)
+	}
+	res.Body.Close()
+}
+
+func TestResponseSetsTLSConnectionState(t *testing.T) {
+	defer afterTest(t)
+	ts := httptest.NewTLSServer(HandlerFunc(func(w ResponseWriter, r *Request) {
+		w.Write([]byte("Hello"))
+	}))
+	defer ts.Close()
+
+	tr := newTLSTransport(t, ts)
+	tr.TLSClientConfig.CipherSuites = []uint16{tls.TLS_RSA_WITH_3DES_EDE_CBC_SHA}
+	tr.Dial = func(netw, addr string) (net.Conn, error) {
+		return net.Dial(netw, ts.Listener.Addr().String())
+	}
+	defer tr.CloseIdleConnections()
+	c := &Client{Transport: tr}
+	res, err := c.Get("https://example.com/")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer res.Body.Close()
+	if res.TLS == nil {
+		t.Fatal("Response didn't set TLS Connection State.")
+	}
+	if got, want := res.TLS.CipherSuite, tls.TLS_RSA_WITH_3DES_EDE_CBC_SHA; got != want {
+		t.Errorf("TLS Cipher Suite = %d; want %d", got, want)
+	}
+}
+
+// Verify Response.ContentLength is populated. http://golang.org/issue/4126
+func TestClientHeadContentLength(t *testing.T) {
+	defer afterTest(t)
+	ts := httptest.NewServer(HandlerFunc(func(w ResponseWriter, r *Request) {
+		if v := r.FormValue("cl"); v != "" {
+			w.Header().Set("Content-Length", v)
+		}
+	}))
+	defer ts.Close()
+	tests := []struct {
+		suffix string
+		want   int64
+	}{
+		{"/?cl=1234", 1234},
+		{"/?cl=0", 0},
+		{"", -1},
+	}
+	for _, tt := range tests {
+		req, _ := NewRequest("HEAD", ts.URL+tt.suffix, nil)
+		res, err := DefaultClient.Do(req)
+		if err != nil {
+			t.Fatal(err)
+		}
+		if res.ContentLength != tt.want {
+			t.Errorf("Content-Length = %d; want %d", res.ContentLength, tt.want)
+		}
+		bs, err := ioutil.ReadAll(res.Body)
+		if err != nil {
+			t.Fatal(err)
+		}
+		if len(bs) != 0 {
+			t.Errorf("Unexpected content: %q", bs)
+		}
+	}
+}
+
+func TestEmptyPasswordAuth(t *testing.T) {
+	defer afterTest(t)
+	gopher := "gopher"
+	ts := httptest.NewServer(HandlerFunc(func(w ResponseWriter, r *Request) {
+		auth := r.Header.Get("Authorization")
+		if strings.HasPrefix(auth, "Basic ") {
+			encoded := auth[6:]
+			decoded, err := base64.StdEncoding.DecodeString(encoded)
+			if err != nil {
+				t.Fatal(err)
+			}
+			expected := gopher + ":"
+			s := string(decoded)
+			if expected != s {
+				t.Errorf("Invalid Authorization header. Got %q, wanted %q", s, expected)
+			}
+		} else {
+			t.Errorf("Invalid auth %q", auth)
+		}
+	}))
+	defer ts.Close()
+	c := &Client{}
+	req, err := NewRequest("GET", ts.URL, nil)
+	if err != nil {
+		t.Fatal(err)
+	}
+	req.URL.User = url.User(gopher)
+	resp, err := c.Do(req)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer resp.Body.Close()
+}
+
+func TestBasicAuth(t *testing.T) {
+	defer afterTest(t)
+	tr := &recordingTransport{}
+	client := &Client{Transport: tr}
+
+	url := "http://My%20User:My%20Pass@dummy.faketld/"
+	expected := "My User:My Pass"
+	client.Get(url)
+
+	if tr.req.Method != "GET" {
+		t.Errorf("got method %q, want %q", tr.req.Method, "GET")
+	}
+	if tr.req.URL.String() != url {
+		t.Errorf("got URL %q, want %q", tr.req.URL.String(), url)
+	}
+	if tr.req.Header == nil {
+		t.Fatalf("expected non-nil request Header")
+	}
+	auth := tr.req.Header.Get("Authorization")
+	if strings.HasPrefix(auth, "Basic ") {
+		encoded := auth[6:]
+		decoded, err := base64.StdEncoding.DecodeString(encoded)
+		if err != nil {
+			t.Fatal(err)
+		}
+		s := string(decoded)
+		if expected != s {
+			t.Errorf("Invalid Authorization header. Got %q, wanted %q", s, expected)
+		}
+	} else {
+		t.Errorf("Invalid auth %q", auth)
+	}
+}
+
+func TestClientTimeout(t *testing.T) {
+	if testing.Short() {
+		t.Skip("skipping in short mode")
+	}
+	defer afterTest(t)
+	sawRoot := make(chan bool, 1)
+	sawSlow := make(chan bool, 1)
+	ts := httptest.NewServer(HandlerFunc(func(w ResponseWriter, r *Request) {
+		if r.URL.Path == "/" {
+			sawRoot <- true
+			Redirect(w, r, "/slow", StatusFound)
+			return
+		}
+		if r.URL.Path == "/slow" {
+			w.Write([]byte("Hello"))
+			w.(Flusher).Flush()
+			sawSlow <- true
+			time.Sleep(2 * time.Second)
+			return
+		}
+	}))
+	defer ts.Close()
+	const timeout = 500 * time.Millisecond
+	c := &Client{
+		Timeout: timeout,
+	}
+
+	res, err := c.Get(ts.URL)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	select {
+	case <-sawRoot:
+		// good.
+	default:
+		t.Fatal("handler never got / request")
+	}
+
+	select {
+	case <-sawSlow:
+		// good.
+	default:
+		t.Fatal("handler never got /slow request")
+	}
+
+	errc := make(chan error, 1)
+	go func() {
+		_, err := ioutil.ReadAll(res.Body)
+		errc <- err
+		res.Body.Close()
+	}()
+
+	const failTime = timeout * 2
+	select {
+	case err := <-errc:
+		if err == nil {
+			t.Error("expected error from ReadAll")
+		}
+		// Expected error.
+	case <-time.After(failTime):
+		t.Errorf("timeout after %v waiting for timeout of %v", failTime, timeout)
+	}
+}
+
+func TestClientRedirectEatsBody(t *testing.T) {
+	defer afterTest(t)
+	saw := make(chan string, 2)
+	ts := httptest.NewServer(HandlerFunc(func(w ResponseWriter, r *Request) {
+		saw <- r.RemoteAddr
+		if r.URL.Path == "/" {
+			Redirect(w, r, "/foo", StatusFound) // which includes a body
+		}
+	}))
+	defer ts.Close()
+
+	res, err := Get(ts.URL)
+	if err != nil {
+		t.Fatal(err)
+	}
+	_, err = ioutil.ReadAll(res.Body)
+	if err != nil {
+		t.Fatal(err)
+	}
+	res.Body.Close()
+
+	var first string
+	select {
+	case first = <-saw:
+	default:
+		t.Fatal("server didn't see a request")
+	}
+
+	var second string
+	select {
+	case second = <-saw:
+	default:
+		t.Fatal("server didn't see a second request")
+	}
+
+	if first != second {
+		t.Fatal("server saw different client ports before & after the redirect")
+	}
+}
+
+// eofReaderFunc is an io.Reader that runs itself, and then returns io.EOF.
+type eofReaderFunc func()
+
+func (f eofReaderFunc) Read(p []byte) (n int, err error) {
+	f()
+	return 0, io.EOF
+}
+
+func TestClientTrailers(t *testing.T) {
+	defer afterTest(t)
+	ts := httptest.NewServer(HandlerFunc(func(w ResponseWriter, r *Request) {
+		w.Header().Set("Connection", "close")
+		w.Header().Set("Trailer", "Server-Trailer-A, Server-Trailer-B")
+		w.Header().Add("Trailer", "Server-Trailer-C")
+
+		var decl []string
+		for k := range r.Trailer {
+			decl = append(decl, k)
+		}
+		sort.Strings(decl)
+
+		slurp, err := ioutil.ReadAll(r.Body)
+		if err != nil {
+			t.Errorf("Server reading request body: %v", err)
+		}
+		if string(slurp) != "foo" {
+			t.Errorf("Server read request body %q; want foo", slurp)
+		}
+		if r.Trailer == nil {
+			io.WriteString(w, "nil Trailer")
+		} else {
+			fmt.Fprintf(w, "decl: %v, vals: %s, %s",
+				decl,
+				r.Trailer.Get("Client-Trailer-A"),
+				r.Trailer.Get("Client-Trailer-B"))
+		}
+
+		// TODO: golang.org/issue/7759: there's no way yet for
+		// the server to set trailers without hijacking, so do
+		// that for now, just to test the client.  Later, in
+		// Go 1.4, it should be implicit that any mutations
+		// to w.Header() after the initial write are the
+		// trailers to be sent, if and only if they were
+		// previously declared with w.Header().Set("Trailer",
+		// ..keys..)
+		w.(Flusher).Flush()
+		conn, buf, _ := w.(Hijacker).Hijack()
+		t := Header{}
+		t.Set("Server-Trailer-A", "valuea")
+		t.Set("Server-Trailer-C", "valuec") // skipping B
+		buf.WriteString("0\r\n")            // eof
+		t.Write(buf)
+		buf.WriteString("\r\n") // end of trailers
+		buf.Flush()
+		conn.Close()
+	}))
+	defer ts.Close()
+
+	var req *Request
+	req, _ = NewRequest("POST", ts.URL, io.MultiReader(
+		eofReaderFunc(func() {
+			req.Trailer["Client-Trailer-A"] = []string{"valuea"}
+		}),
+		strings.NewReader("foo"),
+		eofReaderFunc(func() {
+			req.Trailer["Client-Trailer-B"] = []string{"valueb"}
+		}),
+	))
+	req.Trailer = Header{
+		"Client-Trailer-A": nil, //  to be set later
+		"Client-Trailer-B": nil, //  to be set later
+	}
+	req.ContentLength = -1
+	res, err := DefaultClient.Do(req)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if err := wantBody(res, err, "decl: [Client-Trailer-A Client-Trailer-B], vals: valuea, valueb"); err != nil {
+		t.Error(err)
+	}
+	want := Header{
+		"Server-Trailer-A": []string{"valuea"},
+		"Server-Trailer-B": nil,
+		"Server-Trailer-C": []string{"valuec"},
+	}
+	if !reflect.DeepEqual(res.Trailer, want) {
+		t.Errorf("Response trailers = %#v; want %#v", res.Trailer, want)
+	}
+}
diff --git a/src/net/http/cookie.go b/src/net/http/cookie.go
new file mode 100644
index 000000000..dc60ba87f
--- /dev/null
+++ b/src/net/http/cookie.go
@@ -0,0 +1,363 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package http
+
+import (
+	"bytes"
+	"fmt"
+	"log"
+	"net"
+	"strconv"
+	"strings"
+	"time"
+)
+
+// This implementation is done according to RFC 6265:
+//
+//    http://tools.ietf.org/html/rfc6265
+
+// A Cookie represents an HTTP cookie as sent in the Set-Cookie header of an
+// HTTP response or the Cookie header of an HTTP request.
+type Cookie struct {
+	Name       string
+	Value      string
+	Path       string
+	Domain     string
+	Expires    time.Time
+	RawExpires string
+
+	// MaxAge=0 means no 'Max-Age' attribute specified.
+	// MaxAge<0 means delete cookie now, equivalently 'Max-Age: 0'
+	// MaxAge>0 means Max-Age attribute present and given in seconds
+	MaxAge   int
+	Secure   bool
+	HttpOnly bool
+	Raw      string
+	Unparsed []string // Raw text of unparsed attribute-value pairs
+}
+
+// readSetCookies parses all "Set-Cookie" values from
+// the header h and returns the successfully parsed Cookies.
+func readSetCookies(h Header) []*Cookie {
+	cookies := []*Cookie{}
+	for _, line := range h["Set-Cookie"] {
+		parts := strings.Split(strings.TrimSpace(line), ";")
+		if len(parts) == 1 && parts[0] == "" {
+			continue
+		}
+		parts[0] = strings.TrimSpace(parts[0])
+		j := strings.Index(parts[0], "=")
+		if j < 0 {
+			continue
+		}
+		name, value := parts[0][:j], parts[0][j+1:]
+		if !isCookieNameValid(name) {
+			continue
+		}
+		value, success := parseCookieValue(value)
+		if !success {
+			continue
+		}
+		c := &Cookie{
+			Name:  name,
+			Value: value,
+			Raw:   line,
+		}
+		for i := 1; i < len(parts); i++ {
+			parts[i] = strings.TrimSpace(parts[i])
+			if len(parts[i]) == 0 {
+				continue
+			}
+
+			attr, val := parts[i], ""
+			if j := strings.Index(attr, "="); j >= 0 {
+				attr, val = attr[:j], attr[j+1:]
+			}
+			lowerAttr := strings.ToLower(attr)
+			val, success = parseCookieValue(val)
+			if !success {
+				c.Unparsed = append(c.Unparsed, parts[i])
+				continue
+			}
+			switch lowerAttr {
+			case "secure":
+				c.Secure = true
+				continue
+			case "httponly":
+				c.HttpOnly = true
+				continue
+			case "domain":
+				c.Domain = val
+				continue
+			case "max-age":
+				secs, err := strconv.Atoi(val)
+				if err != nil || secs != 0 && val[0] == '0' {
+					break
+				}
+				if secs <= 0 {
+					c.MaxAge = -1
+				} else {
+					c.MaxAge = secs
+				}
+				continue
+			case "expires":
+				c.RawExpires = val
+				exptime, err := time.Parse(time.RFC1123, val)
+				if err != nil {
+					exptime, err = time.Parse("Mon, 02-Jan-2006 15:04:05 MST", val)
+					if err != nil {
+						c.Expires = time.Time{}
+						break
+					}
+				}
+				c.Expires = exptime.UTC()
+				continue
+			case "path":
+				c.Path = val
+				continue
+			}
+			c.Unparsed = append(c.Unparsed, parts[i])
+		}
+		cookies = append(cookies, c)
+	}
+	return cookies
+}
+
+// SetCookie adds a Set-Cookie header to the provided ResponseWriter's headers.
+func SetCookie(w ResponseWriter, cookie *Cookie) {
+	w.Header().Add("Set-Cookie", cookie.String())
+}
+
+// String returns the serialization of the cookie for use in a Cookie
+// header (if only Name and Value are set) or a Set-Cookie response
+// header (if other fields are set).
+func (c *Cookie) String() string {
+	var b bytes.Buffer
+	fmt.Fprintf(&b, "%s=%s", sanitizeCookieName(c.Name), sanitizeCookieValue(c.Value))
+	if len(c.Path) > 0 {
+		fmt.Fprintf(&b, "; Path=%s", sanitizeCookiePath(c.Path))
+	}
+	if len(c.Domain) > 0 {
+		if validCookieDomain(c.Domain) {
+			// A c.Domain containing illegal characters is not
+			// sanitized but simply dropped which turns the cookie
+			// into a host-only cookie. A leading dot is okay
+			// but won't be sent.
+			d := c.Domain
+			if d[0] == '.' {
+				d = d[1:]
+			}
+			fmt.Fprintf(&b, "; Domain=%s", d)
+		} else {
+			log.Printf("net/http: invalid Cookie.Domain %q; dropping domain attribute",
+				c.Domain)
+		}
+	}
+	if c.Expires.Unix() > 0 {
+		fmt.Fprintf(&b, "; Expires=%s", c.Expires.UTC().Format(time.RFC1123))
+	}
+	if c.MaxAge > 0 {
+		fmt.Fprintf(&b, "; Max-Age=%d", c.MaxAge)
+	} else if c.MaxAge < 0 {
+		fmt.Fprintf(&b, "; Max-Age=0")
+	}
+	if c.HttpOnly {
+		fmt.Fprintf(&b, "; HttpOnly")
+	}
+	if c.Secure {
+		fmt.Fprintf(&b, "; Secure")
+	}
+	return b.String()
+}
+
+// readCookies parses all "Cookie" values from the header h and
+// returns the successfully parsed Cookies.
+//
+// if filter isn't empty, only cookies of that name are returned
+func readCookies(h Header, filter string) []*Cookie {
+	cookies := []*Cookie{}
+	lines, ok := h["Cookie"]
+	if !ok {
+		return cookies
+	}
+
+	for _, line := range lines {
+		parts := strings.Split(strings.TrimSpace(line), ";")
+		if len(parts) == 1 && parts[0] == "" {
+			continue
+		}
+		// Per-line attributes
+		parsedPairs := 0
+		for i := 0; i < len(parts); i++ {
+			parts[i] = strings.TrimSpace(parts[i])
+			if len(parts[i]) == 0 {
+				continue
+			}
+			name, val := parts[i], ""
+			if j := strings.Index(name, "="); j >= 0 {
+				name, val = name[:j], name[j+1:]
+			}
+			if !isCookieNameValid(name) {
+				continue
+			}
+			if filter != "" && filter != name {
+				continue
+			}
+			val, success := parseCookieValue(val)
+			if !success {
+				continue
+			}
+			cookies = append(cookies, &Cookie{Name: name, Value: val})
+			parsedPairs++
+		}
+	}
+	return cookies
+}
+
+// validCookieDomain returns wheter v is a valid cookie domain-value.
+func validCookieDomain(v string) bool {
+	if isCookieDomainName(v) {
+		return true
+	}
+	if net.ParseIP(v) != nil && !strings.Contains(v, ":") {
+		return true
+	}
+	return false
+}
+
+// isCookieDomainName returns whether s is a valid domain name or a valid
+// domain name with a leading dot '.'.  It is almost a direct copy of
+// package net's isDomainName.
+func isCookieDomainName(s string) bool {
+	if len(s) == 0 {
+		return false
+	}
+	if len(s) > 255 {
+		return false
+	}
+
+	if s[0] == '.' {
+		// A cookie a domain attribute may start with a leading dot.
+		s = s[1:]
+	}
+	last := byte('.')
+	ok := false // Ok once we've seen a letter.
+	partlen := 0
+	for i := 0; i < len(s); i++ {
+		c := s[i]
+		switch {
+		default:
+			return false
+		case 'a' <= c && c <= 'z' || 'A' <= c && c <= 'Z':
+			// No '_' allowed here (in contrast to package net).
+			ok = true
+			partlen++
+		case '0' <= c && c <= '9':
+			// fine
+			partlen++
+		case c == '-':
+			// Byte before dash cannot be dot.
+			if last == '.' {
+				return false
+			}
+			partlen++
+		case c == '.':
+			// Byte before dot cannot be dot, dash.
+			if last == '.' || last == '-' {
+				return false
+			}
+			if partlen > 63 || partlen == 0 {
+				return false
+			}
+			partlen = 0
+		}
+		last = c
+	}
+	if last == '-' || partlen > 63 {
+		return false
+	}
+
+	return ok
+}
+
+var cookieNameSanitizer = strings.NewReplacer("\n", "-", "\r", "-")
+
+func sanitizeCookieName(n string) string {
+	return cookieNameSanitizer.Replace(n)
+}
+
+// http://tools.ietf.org/html/rfc6265#section-4.1.1
+// cookie-value      = *cookie-octet / ( DQUOTE *cookie-octet DQUOTE )
+// cookie-octet      = %x21 / %x23-2B / %x2D-3A / %x3C-5B / %x5D-7E
+//           ; US-ASCII characters excluding CTLs,
+//           ; whitespace DQUOTE, comma, semicolon,
+//           ; and backslash
+// We loosen this as spaces and commas are common in cookie values
+// but we produce a quoted cookie-value in when value starts or ends
+// with a comma or space.
+// See http://golang.org/issue/7243 for the discussion.
+func sanitizeCookieValue(v string) string {
+	v = sanitizeOrWarn("Cookie.Value", validCookieValueByte, v)
+	if len(v) == 0 {
+		return v
+	}
+	if v[0] == ' ' || v[0] == ',' || v[len(v)-1] == ' ' || v[len(v)-1] == ',' {
+		return `"` + v + `"`
+	}
+	return v
+}
+
+func validCookieValueByte(b byte) bool {
+	return 0x20 <= b && b < 0x7f && b != '"' && b != ';' && b != '\\'
+}
+
+// path-av           = "Path=" path-value
+// path-value        = <any CHAR except CTLs or ";">
+func sanitizeCookiePath(v string) string {
+	return sanitizeOrWarn("Cookie.Path", validCookiePathByte, v)
+}
+
+func validCookiePathByte(b byte) bool {
+	return 0x20 <= b && b < 0x7f && b != ';'
+}
+
+func sanitizeOrWarn(fieldName string, valid func(byte) bool, v string) string {
+	ok := true
+	for i := 0; i < len(v); i++ {
+		if valid(v[i]) {
+			continue
+		}
+		log.Printf("net/http: invalid byte %q in %s; dropping invalid bytes", v[i], fieldName)
+		ok = false
+		break
+	}
+	if ok {
+		return v
+	}
+	buf := make([]byte, 0, len(v))
+	for i := 0; i < len(v); i++ {
+		if b := v[i]; valid(b) {
+			buf = append(buf, b)
+		}
+	}
+	return string(buf)
+}
+
+func parseCookieValue(raw string) (string, bool) {
+	// Strip the quotes, if present.
+	if len(raw) > 1 && raw[0] == '"' && raw[len(raw)-1] == '"' {
+		raw = raw[1 : len(raw)-1]
+	}
+	for i := 0; i < len(raw); i++ {
+		if !validCookieValueByte(raw[i]) {
+			return "", false
+		}
+	}
+	return raw, true
+}
+
+func isCookieNameValid(raw string) bool {
+	return strings.IndexFunc(raw, isNotToken) < 0
+}
diff --git a/src/net/http/cookie_test.go b/src/net/http/cookie_test.go
new file mode 100644
index 000000000..f78f37299
--- /dev/null
+++ b/src/net/http/cookie_test.go
@@ -0,0 +1,380 @@
+// Copyright 2010 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package http
+
+import (
+	"bytes"
+	"encoding/json"
+	"fmt"
+	"log"
+	"os"
+	"reflect"
+	"strings"
+	"testing"
+	"time"
+)
+
+var writeSetCookiesTests = []struct {
+	Cookie *Cookie
+	Raw    string
+}{
+	{
+		&Cookie{Name: "cookie-1", Value: "v$1"},
+		"cookie-1=v$1",
+	},
+	{
+		&Cookie{Name: "cookie-2", Value: "two", MaxAge: 3600},
+		"cookie-2=two; Max-Age=3600",
+	},
+	{
+		&Cookie{Name: "cookie-3", Value: "three", Domain: ".example.com"},
+		"cookie-3=three; Domain=example.com",
+	},
+	{
+		&Cookie{Name: "cookie-4", Value: "four", Path: "/restricted/"},
+		"cookie-4=four; Path=/restricted/",
+	},
+	{
+		&Cookie{Name: "cookie-5", Value: "five", Domain: "wrong;bad.abc"},
+		"cookie-5=five",
+	},
+	{
+		&Cookie{Name: "cookie-6", Value: "six", Domain: "bad-.abc"},
+		"cookie-6=six",
+	},
+	{
+		&Cookie{Name: "cookie-7", Value: "seven", Domain: "127.0.0.1"},
+		"cookie-7=seven; Domain=127.0.0.1",
+	},
+	{
+		&Cookie{Name: "cookie-8", Value: "eight", Domain: "::1"},
+		"cookie-8=eight",
+	},
+	// The "special" cookies have values containing commas or spaces which
+	// are disallowed by RFC 6265 but are common in the wild.
+	{
+		&Cookie{Name: "special-1", Value: "a z"},
+		`special-1=a z`,
+	},
+	{
+		&Cookie{Name: "special-2", Value: " z"},
+		`special-2=" z"`,
+	},
+	{
+		&Cookie{Name: "special-3", Value: "a "},
+		`special-3="a "`,
+	},
+	{
+		&Cookie{Name: "special-4", Value: " "},
+		`special-4=" "`,
+	},
+	{
+		&Cookie{Name: "special-5", Value: "a,z"},
+		`special-5=a,z`,
+	},
+	{
+		&Cookie{Name: "special-6", Value: ",z"},
+		`special-6=",z"`,
+	},
+	{
+		&Cookie{Name: "special-7", Value: "a,"},
+		`special-7="a,"`,
+	},
+	{
+		&Cookie{Name: "special-8", Value: ","},
+		`special-8=","`,
+	},
+	{
+		&Cookie{Name: "empty-value", Value: ""},
+		`empty-value=`,
+	},
+}
+
+func TestWriteSetCookies(t *testing.T) {
+	defer log.SetOutput(os.Stderr)
+	var logbuf bytes.Buffer
+	log.SetOutput(&logbuf)
+
+	for i, tt := range writeSetCookiesTests {
+		if g, e := tt.Cookie.String(), tt.Raw; g != e {
+			t.Errorf("Test %d, expecting:\n%s\nGot:\n%s\n", i, e, g)
+			continue
+		}
+	}
+
+	if got, sub := logbuf.String(), "dropping domain attribute"; !strings.Contains(got, sub) {
+		t.Errorf("Expected substring %q in log output. Got:\n%s", sub, got)
+	}
+}
+
+type headerOnlyResponseWriter Header
+
+func (ho headerOnlyResponseWriter) Header() Header {
+	return Header(ho)
+}
+
+func (ho headerOnlyResponseWriter) Write([]byte) (int, error) {
+	panic("NOIMPL")
+}
+
+func (ho headerOnlyResponseWriter) WriteHeader(int) {
+	panic("NOIMPL")
+}
+
+func TestSetCookie(t *testing.T) {
+	m := make(Header)
+	SetCookie(headerOnlyResponseWriter(m), &Cookie{Name: "cookie-1", Value: "one", Path: "/restricted/"})
+	SetCookie(headerOnlyResponseWriter(m), &Cookie{Name: "cookie-2", Value: "two", MaxAge: 3600})
+	if l := len(m["Set-Cookie"]); l != 2 {
+		t.Fatalf("expected %d cookies, got %d", 2, l)
+	}
+	if g, e := m["Set-Cookie"][0], "cookie-1=one; Path=/restricted/"; g != e {
+		t.Errorf("cookie #1: want %q, got %q", e, g)
+	}
+	if g, e := m["Set-Cookie"][1], "cookie-2=two; Max-Age=3600"; g != e {
+		t.Errorf("cookie #2: want %q, got %q", e, g)
+	}
+}
+
+var addCookieTests = []struct {
+	Cookies []*Cookie
+	Raw     string
+}{
+	{
+		[]*Cookie{},
+		"",
+	},
+	{
+		[]*Cookie{{Name: "cookie-1", Value: "v$1"}},
+		"cookie-1=v$1",
+	},
+	{
+		[]*Cookie{
+			{Name: "cookie-1", Value: "v$1"},
+			{Name: "cookie-2", Value: "v$2"},
+			{Name: "cookie-3", Value: "v$3"},
+		},
+		"cookie-1=v$1; cookie-2=v$2; cookie-3=v$3",
+	},
+}
+
+func TestAddCookie(t *testing.T) {
+	for i, tt := range addCookieTests {
+		req, _ := NewRequest("GET", "http://example.com/", nil)
+		for _, c := range tt.Cookies {
+			req.AddCookie(c)
+		}
+		if g := req.Header.Get("Cookie"); g != tt.Raw {
+			t.Errorf("Test %d:\nwant: %s\n got: %s\n", i, tt.Raw, g)
+			continue
+		}
+	}
+}
+
+var readSetCookiesTests = []struct {
+	Header  Header
+	Cookies []*Cookie
+}{
+	{
+		Header{"Set-Cookie": {"Cookie-1=v$1"}},
+		[]*Cookie{{Name: "Cookie-1", Value: "v$1", Raw: "Cookie-1=v$1"}},
+	},
+	{
+		Header{"Set-Cookie": {"NID=99=YsDT5i3E-CXax-; expires=Wed, 23-Nov-2011 01:05:03 GMT; path=/; domain=.google.ch; HttpOnly"}},
+		[]*Cookie{{
+			Name:       "NID",
+			Value:      "99=YsDT5i3E-CXax-",
+			Path:       "/",
+			Domain:     ".google.ch",
+			HttpOnly:   true,
+			Expires:    time.Date(2011, 11, 23, 1, 5, 3, 0, time.UTC),
+			RawExpires: "Wed, 23-Nov-2011 01:05:03 GMT",
+			Raw:        "NID=99=YsDT5i3E-CXax-; expires=Wed, 23-Nov-2011 01:05:03 GMT; path=/; domain=.google.ch; HttpOnly",
+		}},
+	},
+	{
+		Header{"Set-Cookie": {".ASPXAUTH=7E3AA; expires=Wed, 07-Mar-2012 14:25:06 GMT; path=/; HttpOnly"}},
+		[]*Cookie{{
+			Name:       ".ASPXAUTH",
+			Value:      "7E3AA",
+			Path:       "/",
+			Expires:    time.Date(2012, 3, 7, 14, 25, 6, 0, time.UTC),
+			RawExpires: "Wed, 07-Mar-2012 14:25:06 GMT",
+			HttpOnly:   true,
+			Raw:        ".ASPXAUTH=7E3AA; expires=Wed, 07-Mar-2012 14:25:06 GMT; path=/; HttpOnly",
+		}},
+	},
+	{
+		Header{"Set-Cookie": {"ASP.NET_SessionId=foo; path=/; HttpOnly"}},
+		[]*Cookie{{
+			Name:     "ASP.NET_SessionId",
+			Value:    "foo",
+			Path:     "/",
+			HttpOnly: true,
+			Raw:      "ASP.NET_SessionId=foo; path=/; HttpOnly",
+		}},
+	},
+	// Make sure we can properly read back the Set-Cookie headers we create
+	// for values containing spaces or commas:
+	{
+		Header{"Set-Cookie": {`special-1=a z`}},
+		[]*Cookie{{Name: "special-1", Value: "a z", Raw: `special-1=a z`}},
+	},
+	{
+		Header{"Set-Cookie": {`special-2=" z"`}},
+		[]*Cookie{{Name: "special-2", Value: " z", Raw: `special-2=" z"`}},
+	},
+	{
+		Header{"Set-Cookie": {`special-3="a "`}},
+		[]*Cookie{{Name: "special-3", Value: "a ", Raw: `special-3="a "`}},
+	},
+	{
+		Header{"Set-Cookie": {`special-4=" "`}},
+		[]*Cookie{{Name: "special-4", Value: " ", Raw: `special-4=" "`}},
+	},
+	{
+		Header{"Set-Cookie": {`special-5=a,z`}},
+		[]*Cookie{{Name: "special-5", Value: "a,z", Raw: `special-5=a,z`}},
+	},
+	{
+		Header{"Set-Cookie": {`special-6=",z"`}},
+		[]*Cookie{{Name: "special-6", Value: ",z", Raw: `special-6=",z"`}},
+	},
+	{
+		Header{"Set-Cookie": {`special-7=a,`}},
+		[]*Cookie{{Name: "special-7", Value: "a,", Raw: `special-7=a,`}},
+	},
+	{
+		Header{"Set-Cookie": {`special-8=","`}},
+		[]*Cookie{{Name: "special-8", Value: ",", Raw: `special-8=","`}},
+	},
+
+	// TODO(bradfitz): users have reported seeing this in the
+	// wild, but do browsers handle it? RFC 6265 just says "don't
+	// do that" (section 3) and then never mentions header folding
+	// again.
+	// Header{"Set-Cookie": {"ASP.NET_SessionId=foo; path=/; HttpOnly, .ASPXAUTH=7E3AA; expires=Wed, 07-Mar-2012 14:25:06 GMT; path=/; HttpOnly"}},
+}
+
+func toJSON(v interface{}) string {
+	b, err := json.Marshal(v)
+	if err != nil {
+		return fmt.Sprintf("%#v", v)
+	}
+	return string(b)
+}
+
+func TestReadSetCookies(t *testing.T) {
+	for i, tt := range readSetCookiesTests {
+		for n := 0; n < 2; n++ { // to verify readSetCookies doesn't mutate its input
+			c := readSetCookies(tt.Header)
+			if !reflect.DeepEqual(c, tt.Cookies) {
+				t.Errorf("#%d readSetCookies: have\n%s\nwant\n%s\n", i, toJSON(c), toJSON(tt.Cookies))
+				continue
+			}
+		}
+	}
+}
+
+var readCookiesTests = []struct {
+	Header  Header
+	Filter  string
+	Cookies []*Cookie
+}{
+	{
+		Header{"Cookie": {"Cookie-1=v$1", "c2=v2"}},
+		"",
+		[]*Cookie{
+			{Name: "Cookie-1", Value: "v$1"},
+			{Name: "c2", Value: "v2"},
+		},
+	},
+	{
+		Header{"Cookie": {"Cookie-1=v$1", "c2=v2"}},
+		"c2",
+		[]*Cookie{
+			{Name: "c2", Value: "v2"},
+		},
+	},
+	{
+		Header{"Cookie": {"Cookie-1=v$1; c2=v2"}},
+		"",
+		[]*Cookie{
+			{Name: "Cookie-1", Value: "v$1"},
+			{Name: "c2", Value: "v2"},
+		},
+	},
+	{
+		Header{"Cookie": {"Cookie-1=v$1; c2=v2"}},
+		"c2",
+		[]*Cookie{
+			{Name: "c2", Value: "v2"},
+		},
+	},
+}
+
+func TestReadCookies(t *testing.T) {
+	for i, tt := range readCookiesTests {
+		for n := 0; n < 2; n++ { // to verify readCookies doesn't mutate its input
+			c := readCookies(tt.Header, tt.Filter)
+			if !reflect.DeepEqual(c, tt.Cookies) {
+				t.Errorf("#%d readCookies:\nhave: %s\nwant: %s\n", i, toJSON(c), toJSON(tt.Cookies))
+				continue
+			}
+		}
+	}
+}
+
+func TestCookieSanitizeValue(t *testing.T) {
+	defer log.SetOutput(os.Stderr)
+	var logbuf bytes.Buffer
+	log.SetOutput(&logbuf)
+
+	tests := []struct {
+		in, want string
+	}{
+		{"foo", "foo"},
+		{"foo;bar", "foobar"},
+		{"foo\\bar", "foobar"},
+		{"foo\"bar", "foobar"},
+		{"\x00\x7e\x7f\x80", "\x7e"},
+		{`"withquotes"`, "withquotes"},
+		{"a z", "a z"},
+		{" z", `" z"`},
+		{"a ", `"a "`},
+	}
+	for _, tt := range tests {
+		if got := sanitizeCookieValue(tt.in); got != tt.want {
+			t.Errorf("sanitizeCookieValue(%q) = %q; want %q", tt.in, got, tt.want)
+		}
+	}
+
+	if got, sub := logbuf.String(), "dropping invalid bytes"; !strings.Contains(got, sub) {
+		t.Errorf("Expected substring %q in log output. Got:\n%s", sub, got)
+	}
+}
+
+func TestCookieSanitizePath(t *testing.T) {
+	defer log.SetOutput(os.Stderr)
+	var logbuf bytes.Buffer
+	log.SetOutput(&logbuf)
+
+	tests := []struct {
+		in, want string
+	}{
+		{"/path", "/path"},
+		{"/path with space/", "/path with space/"},
+		{"/just;no;semicolon\x00orstuff/", "/justnosemicolonorstuff/"},
+	}
+	for _, tt := range tests {
+		if got := sanitizeCookiePath(tt.in); got != tt.want {
+			t.Errorf("sanitizeCookiePath(%q) = %q; want %q", tt.in, got, tt.want)
+		}
+	}
+
+	if got, sub := logbuf.String(), "dropping invalid bytes"; !strings.Contains(got, sub) {
+		t.Errorf("Expected substring %q in log output. Got:\n%s", sub, got)
+	}
+}
diff --git a/src/net/http/cookiejar/jar.go b/src/net/http/cookiejar/jar.go
new file mode 100644
index 000000000..389ab58e4
--- /dev/null
+++ b/src/net/http/cookiejar/jar.go
@@ -0,0 +1,497 @@
+// Copyright 2012 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package cookiejar implements an in-memory RFC 6265-compliant http.CookieJar.
+package cookiejar
+
+import (
+	"errors"
+	"fmt"
+	"net"
+	"net/http"
+	"net/url"
+	"sort"
+	"strings"
+	"sync"
+	"time"
+)
+
+// PublicSuffixList provides the public suffix of a domain. For example:
+//      - the public suffix of "example.com" is "com",
+//      - the public suffix of "foo1.foo2.foo3.co.uk" is "co.uk", and
+//      - the public suffix of "bar.pvt.k12.ma.us" is "pvt.k12.ma.us".
+//
+// Implementations of PublicSuffixList must be safe for concurrent use by
+// multiple goroutines.
+//
+// An implementation that always returns "" is valid and may be useful for
+// testing but it is not secure: it means that the HTTP server for foo.com can
+// set a cookie for bar.com.
+//
+// A public suffix list implementation is in the package
+// code.google.com/p/go.net/publicsuffix.
+type PublicSuffixList interface {
+	// PublicSuffix returns the public suffix of domain.
+	//
+	// TODO: specify which of the caller and callee is responsible for IP
+	// addresses, for leading and trailing dots, for case sensitivity, and
+	// for IDN/Punycode.
+	PublicSuffix(domain string) string
+
+	// String returns a description of the source of this public suffix
+	// list. The description will typically contain something like a time
+	// stamp or version number.
+	String() string
+}
+
+// Options are the options for creating a new Jar.
+type Options struct {
+	// PublicSuffixList is the public suffix list that determines whether
+	// an HTTP server can set a cookie for a domain.
+	//
+	// A nil value is valid and may be useful for testing but it is not
+	// secure: it means that the HTTP server for foo.co.uk can set a cookie
+	// for bar.co.uk.
+	PublicSuffixList PublicSuffixList
+}
+
+// Jar implements the http.CookieJar interface from the net/http package.
+type Jar struct {
+	psList PublicSuffixList
+
+	// mu locks the remaining fields.
+	mu sync.Mutex
+
+	// entries is a set of entries, keyed by their eTLD+1 and subkeyed by
+	// their name/domain/path.
+	entries map[string]map[string]entry
+
+	// nextSeqNum is the next sequence number assigned to a new cookie
+	// created SetCookies.
+	nextSeqNum uint64
+}
+
+// New returns a new cookie jar. A nil *Options is equivalent to a zero
+// Options.
+func New(o *Options) (*Jar, error) {
+	jar := &Jar{
+		entries: make(map[string]map[string]entry),
+	}
+	if o != nil {
+		jar.psList = o.PublicSuffixList
+	}
+	return jar, nil
+}
+
+// entry is the internal representation of a cookie.
+//
+// This struct type is not used outside of this package per se, but the exported
+// fields are those of RFC 6265.
+type entry struct {
+	Name       string
+	Value      string
+	Domain     string
+	Path       string
+	Secure     bool
+	HttpOnly   bool
+	Persistent bool
+	HostOnly   bool
+	Expires    time.Time
+	Creation   time.Time
+	LastAccess time.Time
+
+	// seqNum is a sequence number so that Cookies returns cookies in a
+	// deterministic order, even for cookies that have equal Path length and
+	// equal Creation time. This simplifies testing.
+	seqNum uint64
+}
+
+// Id returns the domain;path;name triple of e as an id.
+func (e *entry) id() string {
+	return fmt.Sprintf("%s;%s;%s", e.Domain, e.Path, e.Name)
+}
+
+// shouldSend determines whether e's cookie qualifies to be included in a
+// request to host/path. It is the caller's responsibility to check if the
+// cookie is expired.
+func (e *entry) shouldSend(https bool, host, path string) bool {
+	return e.domainMatch(host) && e.pathMatch(path) && (https || !e.Secure)
+}
+
+// domainMatch implements "domain-match" of RFC 6265 section 5.1.3.
+func (e *entry) domainMatch(host string) bool {
+	if e.Domain == host {
+		return true
+	}
+	return !e.HostOnly && hasDotSuffix(host, e.Domain)
+}
+
+// pathMatch implements "path-match" according to RFC 6265 section 5.1.4.
+func (e *entry) pathMatch(requestPath string) bool {
+	if requestPath == e.Path {
+		return true
+	}
+	if strings.HasPrefix(requestPath, e.Path) {
+		if e.Path[len(e.Path)-1] == '/' {
+			return true // The "/any/" matches "/any/path" case.
+		} else if requestPath[len(e.Path)] == '/' {
+			return true // The "/any" matches "/any/path" case.
+		}
+	}
+	return false
+}
+
+// hasDotSuffix reports whether s ends in "."+suffix.
+func hasDotSuffix(s, suffix string) bool {
+	return len(s) > len(suffix) && s[len(s)-len(suffix)-1] == '.' && s[len(s)-len(suffix):] == suffix
+}
+
+// byPathLength is a []entry sort.Interface that sorts according to RFC 6265
+// section 5.4 point 2: by longest path and then by earliest creation time.
+type byPathLength []entry
+
+func (s byPathLength) Len() int { return len(s) }
+
+func (s byPathLength) Less(i, j int) bool {
+	if len(s[i].Path) != len(s[j].Path) {
+		return len(s[i].Path) > len(s[j].Path)
+	}
+	if !s[i].Creation.Equal(s[j].Creation) {
+		return s[i].Creation.Before(s[j].Creation)
+	}
+	return s[i].seqNum < s[j].seqNum
+}
+
+func (s byPathLength) Swap(i, j int) { s[i], s[j] = s[j], s[i] }
+
+// Cookies implements the Cookies method of the http.CookieJar interface.
+//
+// It returns an empty slice if the URL's scheme is not HTTP or HTTPS.
+func (j *Jar) Cookies(u *url.URL) (cookies []*http.Cookie) {
+	return j.cookies(u, time.Now())
+}
+
+// cookies is like Cookies but takes the current time as a parameter.
+func (j *Jar) cookies(u *url.URL, now time.Time) (cookies []*http.Cookie) {
+	if u.Scheme != "http" && u.Scheme != "https" {
+		return cookies
+	}
+	host, err := canonicalHost(u.Host)
+	if err != nil {
+		return cookies
+	}
+	key := jarKey(host, j.psList)
+
+	j.mu.Lock()
+	defer j.mu.Unlock()
+
+	submap := j.entries[key]
+	if submap == nil {
+		return cookies
+	}
+
+	https := u.Scheme == "https"
+	path := u.Path
+	if path == "" {
+		path = "/"
+	}
+
+	modified := false
+	var selected []entry
+	for id, e := range submap {
+		if e.Persistent && !e.Expires.After(now) {
+			delete(submap, id)
+			modified = true
+			continue
+		}
+		if !e.shouldSend(https, host, path) {
+			continue
+		}
+		e.LastAccess = now
+		submap[id] = e
+		selected = append(selected, e)
+		modified = true
+	}
+	if modified {
+		if len(submap) == 0 {
+			delete(j.entries, key)
+		} else {
+			j.entries[key] = submap
+		}
+	}
+
+	sort.Sort(byPathLength(selected))
+	for _, e := range selected {
+		cookies = append(cookies, &http.Cookie{Name: e.Name, Value: e.Value})
+	}
+
+	return cookies
+}
+
+// SetCookies implements the SetCookies method of the http.CookieJar interface.
+//
+// It does nothing if the URL's scheme is not HTTP or HTTPS.
+func (j *Jar) SetCookies(u *url.URL, cookies []*http.Cookie) {
+	j.setCookies(u, cookies, time.Now())
+}
+
+// setCookies is like SetCookies but takes the current time as parameter.
+func (j *Jar) setCookies(u *url.URL, cookies []*http.Cookie, now time.Time) {
+	if len(cookies) == 0 {
+		return
+	}
+	if u.Scheme != "http" && u.Scheme != "https" {
+		return
+	}
+	host, err := canonicalHost(u.Host)
+	if err != nil {
+		return
+	}
+	key := jarKey(host, j.psList)
+	defPath := defaultPath(u.Path)
+
+	j.mu.Lock()
+	defer j.mu.Unlock()
+
+	submap := j.entries[key]
+
+	modified := false
+	for _, cookie := range cookies {
+		e, remove, err := j.newEntry(cookie, now, defPath, host)
+		if err != nil {
+			continue
+		}
+		id := e.id()
+		if remove {
+			if submap != nil {
+				if _, ok := submap[id]; ok {
+					delete(submap, id)
+					modified = true
+				}
+			}
+			continue
+		}
+		if submap == nil {
+			submap = make(map[string]entry)
+		}
+
+		if old, ok := submap[id]; ok {
+			e.Creation = old.Creation
+			e.seqNum = old.seqNum
+		} else {
+			e.Creation = now
+			e.seqNum = j.nextSeqNum
+			j.nextSeqNum++
+		}
+		e.LastAccess = now
+		submap[id] = e
+		modified = true
+	}
+
+	if modified {
+		if len(submap) == 0 {
+			delete(j.entries, key)
+		} else {
+			j.entries[key] = submap
+		}
+	}
+}
+
+// canonicalHost strips port from host if present and returns the canonicalized
+// host name.
+func canonicalHost(host string) (string, error) {
+	var err error
+	host = strings.ToLower(host)
+	if hasPort(host) {
+		host, _, err = net.SplitHostPort(host)
+		if err != nil {
+			return "", err
+		}
+	}
+	if strings.HasSuffix(host, ".") {
+		// Strip trailing dot from fully qualified domain names.
+		host = host[:len(host)-1]
+	}
+	return toASCII(host)
+}
+
+// hasPort reports whether host contains a port number. host may be a host
+// name, an IPv4 or an IPv6 address.
+func hasPort(host string) bool {
+	colons := strings.Count(host, ":")
+	if colons == 0 {
+		return false
+	}
+	if colons == 1 {
+		return true
+	}
+	return host[0] == '[' && strings.Contains(host, "]:")
+}
+
+// jarKey returns the key to use for a jar.
+func jarKey(host string, psl PublicSuffixList) string {
+	if isIP(host) {
+		return host
+	}
+
+	var i int
+	if psl == nil {
+		i = strings.LastIndex(host, ".")
+		if i == -1 {
+			return host
+		}
+	} else {
+		suffix := psl.PublicSuffix(host)
+		if suffix == host {
+			return host
+		}
+		i = len(host) - len(suffix)
+		if i <= 0 || host[i-1] != '.' {
+			// The provided public suffix list psl is broken.
+			// Storing cookies under host is a safe stopgap.
+			return host
+		}
+	}
+	prevDot := strings.LastIndex(host[:i-1], ".")
+	return host[prevDot+1:]
+}
+
+// isIP reports whether host is an IP address.
+func isIP(host string) bool {
+	return net.ParseIP(host) != nil
+}
+
+// defaultPath returns the directory part of an URL's path according to
+// RFC 6265 section 5.1.4.
+func defaultPath(path string) string {
+	if len(path) == 0 || path[0] != '/' {
+		return "/" // Path is empty or malformed.
+	}
+
+	i := strings.LastIndex(path, "/") // Path starts with "/", so i != -1.
+	if i == 0 {
+		return "/" // Path has the form "/abc".
+	}
+	return path[:i] // Path is either of form "/abc/xyz" or "/abc/xyz/".
+}
+
+// newEntry creates an entry from a http.Cookie c. now is the current time and
+// is compared to c.Expires to determine deletion of c. defPath and host are the
+// default-path and the canonical host name of the URL c was received from.
+//
+// remove records whether the jar should delete this cookie, as it has already
+// expired with respect to now. In this case, e may be incomplete, but it will
+// be valid to call e.id (which depends on e's Name, Domain and Path).
+//
+// A malformed c.Domain will result in an error.
+func (j *Jar) newEntry(c *http.Cookie, now time.Time, defPath, host string) (e entry, remove bool, err error) {
+	e.Name = c.Name
+
+	if c.Path == "" || c.Path[0] != '/' {
+		e.Path = defPath
+	} else {
+		e.Path = c.Path
+	}
+
+	e.Domain, e.HostOnly, err = j.domainAndType(host, c.Domain)
+	if err != nil {
+		return e, false, err
+	}
+
+	// MaxAge takes precedence over Expires.
+	if c.MaxAge < 0 {
+		return e, true, nil
+	} else if c.MaxAge > 0 {
+		e.Expires = now.Add(time.Duration(c.MaxAge) * time.Second)
+		e.Persistent = true
+	} else {
+		if c.Expires.IsZero() {
+			e.Expires = endOfTime
+			e.Persistent = false
+		} else {
+			if !c.Expires.After(now) {
+				return e, true, nil
+			}
+			e.Expires = c.Expires
+			e.Persistent = true
+		}
+	}
+
+	e.Value = c.Value
+	e.Secure = c.Secure
+	e.HttpOnly = c.HttpOnly
+
+	return e, false, nil
+}
+
+var (
+	errIllegalDomain   = errors.New("cookiejar: illegal cookie domain attribute")
+	errMalformedDomain = errors.New("cookiejar: malformed cookie domain attribute")
+	errNoHostname      = errors.New("cookiejar: no host name available (IP only)")
+)
+
+// endOfTime is the time when session (non-persistent) cookies expire.
+// This instant is representable in most date/time formats (not just
+// Go's time.Time) and should be far enough in the future.
+var endOfTime = time.Date(9999, 12, 31, 23, 59, 59, 0, time.UTC)
+
+// domainAndType determines the cookie's domain and hostOnly attribute.
+func (j *Jar) domainAndType(host, domain string) (string, bool, error) {
+	if domain == "" {
+		// No domain attribute in the SetCookie header indicates a
+		// host cookie.
+		return host, true, nil
+	}
+
+	if isIP(host) {
+		// According to RFC 6265 domain-matching includes not being
+		// an IP address.
+		// TODO: This might be relaxed as in common browsers.
+		return "", false, errNoHostname
+	}
+
+	// From here on: If the cookie is valid, it is a domain cookie (with
+	// the one exception of a public suffix below).
+	// See RFC 6265 section 5.2.3.
+	if domain[0] == '.' {
+		domain = domain[1:]
+	}
+
+	if len(domain) == 0 || domain[0] == '.' {
+		// Received either "Domain=." or "Domain=..some.thing",
+		// both are illegal.
+		return "", false, errMalformedDomain
+	}
+	domain = strings.ToLower(domain)
+
+	if domain[len(domain)-1] == '.' {
+		// We received stuff like "Domain=www.example.com.".
+		// Browsers do handle such stuff (actually differently) but
+		// RFC 6265 seems to be clear here (e.g. section 4.1.2.3) in
+		// requiring a reject.  4.1.2.3 is not normative, but
+		// "Domain Matching" (5.1.3) and "Canonicalized Host Names"
+		// (5.1.2) are.
+		return "", false, errMalformedDomain
+	}
+
+	// See RFC 6265 section 5.3 #5.
+	if j.psList != nil {
+		if ps := j.psList.PublicSuffix(domain); ps != "" && !hasDotSuffix(domain, ps) {
+			if host == domain {
+				// This is the one exception in which a cookie
+				// with a domain attribute is a host cookie.
+				return host, true, nil
+			}
+			return "", false, errIllegalDomain
+		}
+	}
+
+	// The domain must domain-match host: www.mycompany.com cannot
+	// set cookies for .ourcompetitors.com.
+	if host != domain && !hasDotSuffix(host, domain) {
+		return "", false, errIllegalDomain
+	}
+
+	return domain, false, nil
+}
diff --git a/src/net/http/cookiejar/jar_test.go b/src/net/http/cookiejar/jar_test.go
new file mode 100644
index 000000000..3aa601586
--- /dev/null
+++ b/src/net/http/cookiejar/jar_test.go
@@ -0,0 +1,1267 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package cookiejar
+
+import (
+	"fmt"
+	"net/http"
+	"net/url"
+	"sort"
+	"strings"
+	"testing"
+	"time"
+)
+
+// tNow is the synthetic current time used as now during testing.
+var tNow = time.Date(2013, 1, 1, 12, 0, 0, 0, time.UTC)
+
+// testPSL implements PublicSuffixList with just two rules: "co.uk"
+// and the default rule "*".
+type testPSL struct{}
+
+func (testPSL) String() string {
+	return "testPSL"
+}
+func (testPSL) PublicSuffix(d string) string {
+	if d == "co.uk" || strings.HasSuffix(d, ".co.uk") {
+		return "co.uk"
+	}
+	return d[strings.LastIndex(d, ".")+1:]
+}
+
+// newTestJar creates an empty Jar with testPSL as the public suffix list.
+func newTestJar() *Jar {
+	jar, err := New(&Options{PublicSuffixList: testPSL{}})
+	if err != nil {
+		panic(err)
+	}
+	return jar
+}
+
+var hasDotSuffixTests = [...]struct {
+	s, suffix string
+}{
+	{"", ""},
+	{"", "."},
+	{"", "x"},
+	{".", ""},
+	{".", "."},
+	{".", ".."},
+	{".", "x"},
+	{".", "x."},
+	{".", ".x"},
+	{".", ".x."},
+	{"x", ""},
+	{"x", "."},
+	{"x", ".."},
+	{"x", "x"},
+	{"x", "x."},
+	{"x", ".x"},
+	{"x", ".x."},
+	{".x", ""},
+	{".x", "."},
+	{".x", ".."},
+	{".x", "x"},
+	{".x", "x."},
+	{".x", ".x"},
+	{".x", ".x."},
+	{"x.", ""},
+	{"x.", "."},
+	{"x.", ".."},
+	{"x.", "x"},
+	{"x.", "x."},
+	{"x.", ".x"},
+	{"x.", ".x."},
+	{"com", ""},
+	{"com", "m"},
+	{"com", "om"},
+	{"com", "com"},
+	{"com", ".com"},
+	{"com", "x.com"},
+	{"com", "xcom"},
+	{"com", "xorg"},
+	{"com", "org"},
+	{"com", "rg"},
+	{"foo.com", ""},
+	{"foo.com", "m"},
+	{"foo.com", "om"},
+	{"foo.com", "com"},
+	{"foo.com", ".com"},
+	{"foo.com", "o.com"},
+	{"foo.com", "oo.com"},
+	{"foo.com", "foo.com"},
+	{"foo.com", ".foo.com"},
+	{"foo.com", "x.foo.com"},
+	{"foo.com", "xfoo.com"},
+	{"foo.com", "xfoo.org"},
+	{"foo.com", "foo.org"},
+	{"foo.com", "oo.org"},
+	{"foo.com", "o.org"},
+	{"foo.com", ".org"},
+	{"foo.com", "org"},
+	{"foo.com", "rg"},
+}
+
+func TestHasDotSuffix(t *testing.T) {
+	for _, tc := range hasDotSuffixTests {
+		got := hasDotSuffix(tc.s, tc.suffix)
+		want := strings.HasSuffix(tc.s, "."+tc.suffix)
+		if got != want {
+			t.Errorf("s=%q, suffix=%q: got %v, want %v", tc.s, tc.suffix, got, want)
+		}
+	}
+}
+
+var canonicalHostTests = map[string]string{
+	"www.example.com":         "www.example.com",
+	"WWW.EXAMPLE.COM":         "www.example.com",
+	"wWw.eXAmple.CoM":         "www.example.com",
+	"www.example.com:80":      "www.example.com",
+	"192.168.0.10":            "192.168.0.10",
+	"192.168.0.5:8080":        "192.168.0.5",
+	"2001:4860:0:2001::68":    "2001:4860:0:2001::68",
+	"[2001:4860:0:::68]:8080": "2001:4860:0:::68",
+	"www.bücher.de":           "www.xn--bcher-kva.de",
+	"www.example.com.":        "www.example.com",
+	"[bad.unmatched.bracket:": "error",
+}
+
+func TestCanonicalHost(t *testing.T) {
+	for h, want := range canonicalHostTests {
+		got, err := canonicalHost(h)
+		if want == "error" {
+			if err == nil {
+				t.Errorf("%q: got nil error, want non-nil", h)
+			}
+			continue
+		}
+		if err != nil {
+			t.Errorf("%q: %v", h, err)
+			continue
+		}
+		if got != want {
+			t.Errorf("%q: got %q, want %q", h, got, want)
+			continue
+		}
+	}
+}
+
+var hasPortTests = map[string]bool{
+	"www.example.com":      false,
+	"www.example.com:80":   true,
+	"127.0.0.1":            false,
+	"127.0.0.1:8080":       true,
+	"2001:4860:0:2001::68": false,
+	"[2001::0:::68]:80":    true,
+}
+
+func TestHasPort(t *testing.T) {
+	for host, want := range hasPortTests {
+		if got := hasPort(host); got != want {
+			t.Errorf("%q: got %t, want %t", host, got, want)
+		}
+	}
+}
+
+var jarKeyTests = map[string]string{
+	"foo.www.example.com": "example.com",
+	"www.example.com":     "example.com",
+	"example.com":         "example.com",
+	"com":                 "com",
+	"foo.www.bbc.co.uk":   "bbc.co.uk",
+	"www.bbc.co.uk":       "bbc.co.uk",
+	"bbc.co.uk":           "bbc.co.uk",
+	"co.uk":               "co.uk",
+	"uk":                  "uk",
+	"192.168.0.5":         "192.168.0.5",
+}
+
+func TestJarKey(t *testing.T) {
+	for host, want := range jarKeyTests {
+		if got := jarKey(host, testPSL{}); got != want {
+			t.Errorf("%q: got %q, want %q", host, got, want)
+		}
+	}
+}
+
+var jarKeyNilPSLTests = map[string]string{
+	"foo.www.example.com": "example.com",
+	"www.example.com":     "example.com",
+	"example.com":         "example.com",
+	"com":                 "com",
+	"foo.www.bbc.co.uk":   "co.uk",
+	"www.bbc.co.uk":       "co.uk",
+	"bbc.co.uk":           "co.uk",
+	"co.uk":               "co.uk",
+	"uk":                  "uk",
+	"192.168.0.5":         "192.168.0.5",
+}
+
+func TestJarKeyNilPSL(t *testing.T) {
+	for host, want := range jarKeyNilPSLTests {
+		if got := jarKey(host, nil); got != want {
+			t.Errorf("%q: got %q, want %q", host, got, want)
+		}
+	}
+}
+
+var isIPTests = map[string]bool{
+	"127.0.0.1":            true,
+	"1.2.3.4":              true,
+	"2001:4860:0:2001::68": true,
+	"example.com":          false,
+	"1.1.1.300":            false,
+	"www.foo.bar.net":      false,
+	"123.foo.bar.net":      false,
+}
+
+func TestIsIP(t *testing.T) {
+	for host, want := range isIPTests {
+		if got := isIP(host); got != want {
+			t.Errorf("%q: got %t, want %t", host, got, want)
+		}
+	}
+}
+
+var defaultPathTests = map[string]string{
+	"/":           "/",
+	"/abc":        "/",
+	"/abc/":       "/abc",
+	"/abc/xyz":    "/abc",
+	"/abc/xyz/":   "/abc/xyz",
+	"/a/b/c.html": "/a/b",
+	"":            "/",
+	"strange":     "/",
+	"//":          "/",
+	"/a//b":       "/a/",
+	"/a/./b":      "/a/.",
+	"/a/../b":     "/a/..",
+}
+
+func TestDefaultPath(t *testing.T) {
+	for path, want := range defaultPathTests {
+		if got := defaultPath(path); got != want {
+			t.Errorf("%q: got %q, want %q", path, got, want)
+		}
+	}
+}
+
+var domainAndTypeTests = [...]struct {
+	host         string // host Set-Cookie header was received from
+	domain       string // domain attribute in Set-Cookie header
+	wantDomain   string // expected domain of cookie
+	wantHostOnly bool   // expected host-cookie flag
+	wantErr      error  // expected error
+}{
+	{"www.example.com", "", "www.example.com", true, nil},
+	{"127.0.0.1", "", "127.0.0.1", true, nil},
+	{"2001:4860:0:2001::68", "", "2001:4860:0:2001::68", true, nil},
+	{"www.example.com", "example.com", "example.com", false, nil},
+	{"www.example.com", ".example.com", "example.com", false, nil},
+	{"www.example.com", "www.example.com", "www.example.com", false, nil},
+	{"www.example.com", ".www.example.com", "www.example.com", false, nil},
+	{"foo.sso.example.com", "sso.example.com", "sso.example.com", false, nil},
+	{"bar.co.uk", "bar.co.uk", "bar.co.uk", false, nil},
+	{"foo.bar.co.uk", ".bar.co.uk", "bar.co.uk", false, nil},
+	{"127.0.0.1", "127.0.0.1", "", false, errNoHostname},
+	{"2001:4860:0:2001::68", "2001:4860:0:2001::68", "2001:4860:0:2001::68", false, errNoHostname},
+	{"www.example.com", ".", "", false, errMalformedDomain},
+	{"www.example.com", "..", "", false, errMalformedDomain},
+	{"www.example.com", "other.com", "", false, errIllegalDomain},
+	{"www.example.com", "com", "", false, errIllegalDomain},
+	{"www.example.com", ".com", "", false, errIllegalDomain},
+	{"foo.bar.co.uk", ".co.uk", "", false, errIllegalDomain},
+	{"127.www.0.0.1", "127.0.0.1", "", false, errIllegalDomain},
+	{"com", "", "com", true, nil},
+	{"com", "com", "com", true, nil},
+	{"com", ".com", "com", true, nil},
+	{"co.uk", "", "co.uk", true, nil},
+	{"co.uk", "co.uk", "co.uk", true, nil},
+	{"co.uk", ".co.uk", "co.uk", true, nil},
+}
+
+func TestDomainAndType(t *testing.T) {
+	jar := newTestJar()
+	for _, tc := range domainAndTypeTests {
+		domain, hostOnly, err := jar.domainAndType(tc.host, tc.domain)
+		if err != tc.wantErr {
+			t.Errorf("%q/%q: got %q error, want %q",
+				tc.host, tc.domain, err, tc.wantErr)
+			continue
+		}
+		if err != nil {
+			continue
+		}
+		if domain != tc.wantDomain || hostOnly != tc.wantHostOnly {
+			t.Errorf("%q/%q: got %q/%t want %q/%t",
+				tc.host, tc.domain, domain, hostOnly,
+				tc.wantDomain, tc.wantHostOnly)
+		}
+	}
+}
+
+// expiresIn creates an expires attribute delta seconds from tNow.
+func expiresIn(delta int) string {
+	t := tNow.Add(time.Duration(delta) * time.Second)
+	return "expires=" + t.Format(time.RFC1123)
+}
+
+// mustParseURL parses s to an URL and panics on error.
+func mustParseURL(s string) *url.URL {
+	u, err := url.Parse(s)
+	if err != nil || u.Scheme == "" || u.Host == "" {
+		panic(fmt.Sprintf("Unable to parse URL %s.", s))
+	}
+	return u
+}
+
+// jarTest encapsulates the following actions on a jar:
+//   1. Perform SetCookies with fromURL and the cookies from setCookies.
+//      (Done at time tNow + 0 ms.)
+//   2. Check that the entries in the jar matches content.
+//      (Done at time tNow + 1001 ms.)
+//   3. For each query in tests: Check that Cookies with toURL yields the
+//      cookies in want.
+//      (Query n done at tNow + (n+2)*1001 ms.)
+type jarTest struct {
+	description string   // The description of what this test is supposed to test
+	fromURL     string   // The full URL of the request from which Set-Cookie headers where received
+	setCookies  []string // All the cookies received from fromURL
+	content     string   // The whole (non-expired) content of the jar
+	queries     []query  // Queries to test the Jar.Cookies method
+}
+
+// query contains one test of the cookies returned from Jar.Cookies.
+type query struct {
+	toURL string // the URL in the Cookies call
+	want  string // the expected list of cookies (order matters)
+}
+
+// run runs the jarTest.
+func (test jarTest) run(t *testing.T, jar *Jar) {
+	now := tNow
+
+	// Populate jar with cookies.
+	setCookies := make([]*http.Cookie, len(test.setCookies))
+	for i, cs := range test.setCookies {
+		cookies := (&http.Response{Header: http.Header{"Set-Cookie": {cs}}}).Cookies()
+		if len(cookies) != 1 {
+			panic(fmt.Sprintf("Wrong cookie line %q: %#v", cs, cookies))
+		}
+		setCookies[i] = cookies[0]
+	}
+	jar.setCookies(mustParseURL(test.fromURL), setCookies, now)
+	now = now.Add(1001 * time.Millisecond)
+
+	// Serialize non-expired entries in the form "name1=val1 name2=val2".
+	var cs []string
+	for _, submap := range jar.entries {
+		for _, cookie := range submap {
+			if !cookie.Expires.After(now) {
+				continue
+			}
+			cs = append(cs, cookie.Name+"="+cookie.Value)
+		}
+	}
+	sort.Strings(cs)
+	got := strings.Join(cs, " ")
+
+	// Make sure jar content matches our expectations.
+	if got != test.content {
+		t.Errorf("Test %q Content\ngot  %q\nwant %q",
+			test.description, got, test.content)
+	}
+
+	// Test different calls to Cookies.
+	for i, query := range test.queries {
+		now = now.Add(1001 * time.Millisecond)
+		var s []string
+		for _, c := range jar.cookies(mustParseURL(query.toURL), now) {
+			s = append(s, c.Name+"="+c.Value)
+		}
+		if got := strings.Join(s, " "); got != query.want {
+			t.Errorf("Test %q #%d\ngot  %q\nwant %q", test.description, i, got, query.want)
+		}
+	}
+}
+
+// basicsTests contains fundamental tests. Each jarTest has to be performed on
+// a fresh, empty Jar.
+var basicsTests = [...]jarTest{
+	{
+		"Retrieval of a plain host cookie.",
+		"http://www.host.test/",
+		[]string{"A=a"},
+		"A=a",
+		[]query{
+			{"http://www.host.test", "A=a"},
+			{"http://www.host.test/", "A=a"},
+			{"http://www.host.test/some/path", "A=a"},
+			{"https://www.host.test", "A=a"},
+			{"https://www.host.test/", "A=a"},
+			{"https://www.host.test/some/path", "A=a"},
+			{"ftp://www.host.test", ""},
+			{"ftp://www.host.test/", ""},
+			{"ftp://www.host.test/some/path", ""},
+			{"http://www.other.org", ""},
+			{"http://sibling.host.test", ""},
+			{"http://deep.www.host.test", ""},
+		},
+	},
+	{
+		"Secure cookies are not returned to http.",
+		"http://www.host.test/",
+		[]string{"A=a; secure"},
+		"A=a",
+		[]query{
+			{"http://www.host.test", ""},
+			{"http://www.host.test/", ""},
+			{"http://www.host.test/some/path", ""},
+			{"https://www.host.test", "A=a"},
+			{"https://www.host.test/", "A=a"},
+			{"https://www.host.test/some/path", "A=a"},
+		},
+	},
+	{
+		"Explicit path.",
+		"http://www.host.test/",
+		[]string{"A=a; path=/some/path"},
+		"A=a",
+		[]query{
+			{"http://www.host.test", ""},
+			{"http://www.host.test/", ""},
+			{"http://www.host.test/some", ""},
+			{"http://www.host.test/some/", ""},
+			{"http://www.host.test/some/path", "A=a"},
+			{"http://www.host.test/some/paths", ""},
+			{"http://www.host.test/some/path/foo", "A=a"},
+			{"http://www.host.test/some/path/foo/", "A=a"},
+		},
+	},
+	{
+		"Implicit path #1: path is a directory.",
+		"http://www.host.test/some/path/",
+		[]string{"A=a"},
+		"A=a",
+		[]query{
+			{"http://www.host.test", ""},
+			{"http://www.host.test/", ""},
+			{"http://www.host.test/some", ""},
+			{"http://www.host.test/some/", ""},
+			{"http://www.host.test/some/path", "A=a"},
+			{"http://www.host.test/some/paths", ""},
+			{"http://www.host.test/some/path/foo", "A=a"},
+			{"http://www.host.test/some/path/foo/", "A=a"},
+		},
+	},
+	{
+		"Implicit path #2: path is not a directory.",
+		"http://www.host.test/some/path/index.html",
+		[]string{"A=a"},
+		"A=a",
+		[]query{
+			{"http://www.host.test", ""},
+			{"http://www.host.test/", ""},
+			{"http://www.host.test/some", ""},
+			{"http://www.host.test/some/", ""},
+			{"http://www.host.test/some/path", "A=a"},
+			{"http://www.host.test/some/paths", ""},
+			{"http://www.host.test/some/path/foo", "A=a"},
+			{"http://www.host.test/some/path/foo/", "A=a"},
+		},
+	},
+	{
+		"Implicit path #3: no path in URL at all.",
+		"http://www.host.test",
+		[]string{"A=a"},
+		"A=a",
+		[]query{
+			{"http://www.host.test", "A=a"},
+			{"http://www.host.test/", "A=a"},
+			{"http://www.host.test/some/path", "A=a"},
+		},
+	},
+	{
+		"Cookies are sorted by path length.",
+		"http://www.host.test/",
+		[]string{
+			"A=a; path=/foo/bar",
+			"B=b; path=/foo/bar/baz/qux",
+			"C=c; path=/foo/bar/baz",
+			"D=d; path=/foo"},
+		"A=a B=b C=c D=d",
+		[]query{
+			{"http://www.host.test/foo/bar/baz/qux", "B=b C=c A=a D=d"},
+			{"http://www.host.test/foo/bar/baz/", "C=c A=a D=d"},
+			{"http://www.host.test/foo/bar", "A=a D=d"},
+		},
+	},
+	{
+		"Creation time determines sorting on same length paths.",
+		"http://www.host.test/",
+		[]string{
+			"A=a; path=/foo/bar",
+			"X=x; path=/foo/bar",
+			"Y=y; path=/foo/bar/baz/qux",
+			"B=b; path=/foo/bar/baz/qux",
+			"C=c; path=/foo/bar/baz",
+			"W=w; path=/foo/bar/baz",
+			"Z=z; path=/foo",
+			"D=d; path=/foo"},
+		"A=a B=b C=c D=d W=w X=x Y=y Z=z",
+		[]query{
+			{"http://www.host.test/foo/bar/baz/qux", "Y=y B=b C=c W=w A=a X=x Z=z D=d"},
+			{"http://www.host.test/foo/bar/baz/", "C=c W=w A=a X=x Z=z D=d"},
+			{"http://www.host.test/foo/bar", "A=a X=x Z=z D=d"},
+		},
+	},
+	{
+		"Sorting of same-name cookies.",
+		"http://www.host.test/",
+		[]string{
+			"A=1; path=/",
+			"A=2; path=/path",
+			"A=3; path=/quux",
+			"A=4; path=/path/foo",
+			"A=5; domain=.host.test; path=/path",
+			"A=6; domain=.host.test; path=/quux",
+			"A=7; domain=.host.test; path=/path/foo",
+		},
+		"A=1 A=2 A=3 A=4 A=5 A=6 A=7",
+		[]query{
+			{"http://www.host.test/path", "A=2 A=5 A=1"},
+			{"http://www.host.test/path/foo", "A=4 A=7 A=2 A=5 A=1"},
+		},
+	},
+	{
+		"Disallow domain cookie on public suffix.",
+		"http://www.bbc.co.uk",
+		[]string{
+			"a=1",
+			"b=2; domain=co.uk",
+		},
+		"a=1",
+		[]query{{"http://www.bbc.co.uk", "a=1"}},
+	},
+	{
+		"Host cookie on IP.",
+		"http://192.168.0.10",
+		[]string{"a=1"},
+		"a=1",
+		[]query{{"http://192.168.0.10", "a=1"}},
+	},
+	{
+		"Port is ignored #1.",
+		"http://www.host.test/",
+		[]string{"a=1"},
+		"a=1",
+		[]query{
+			{"http://www.host.test", "a=1"},
+			{"http://www.host.test:8080/", "a=1"},
+		},
+	},
+	{
+		"Port is ignored #2.",
+		"http://www.host.test:8080/",
+		[]string{"a=1"},
+		"a=1",
+		[]query{
+			{"http://www.host.test", "a=1"},
+			{"http://www.host.test:8080/", "a=1"},
+			{"http://www.host.test:1234/", "a=1"},
+		},
+	},
+}
+
+func TestBasics(t *testing.T) {
+	for _, test := range basicsTests {
+		jar := newTestJar()
+		test.run(t, jar)
+	}
+}
+
+// updateAndDeleteTests contains jarTests which must be performed on the same
+// Jar.
+var updateAndDeleteTests = [...]jarTest{
+	{
+		"Set initial cookies.",
+		"http://www.host.test",
+		[]string{
+			"a=1",
+			"b=2; secure",
+			"c=3; httponly",
+			"d=4; secure; httponly"},
+		"a=1 b=2 c=3 d=4",
+		[]query{
+			{"http://www.host.test", "a=1 c=3"},
+			{"https://www.host.test", "a=1 b=2 c=3 d=4"},
+		},
+	},
+	{
+		"Update value via http.",
+		"http://www.host.test",
+		[]string{
+			"a=w",
+			"b=x; secure",
+			"c=y; httponly",
+			"d=z; secure; httponly"},
+		"a=w b=x c=y d=z",
+		[]query{
+			{"http://www.host.test", "a=w c=y"},
+			{"https://www.host.test", "a=w b=x c=y d=z"},
+		},
+	},
+	{
+		"Clear Secure flag from a http.",
+		"http://www.host.test/",
+		[]string{
+			"b=xx",
+			"d=zz; httponly"},
+		"a=w b=xx c=y d=zz",
+		[]query{{"http://www.host.test", "a=w b=xx c=y d=zz"}},
+	},
+	{
+		"Delete all.",
+		"http://www.host.test/",
+		[]string{
+			"a=1; max-Age=-1",                    // delete via MaxAge
+			"b=2; " + expiresIn(-10),             // delete via Expires
+			"c=2; max-age=-1; " + expiresIn(-10), // delete via both
+			"d=4; max-age=-1; " + expiresIn(10)}, // MaxAge takes precedence
+		"",
+		[]query{{"http://www.host.test", ""}},
+	},
+	{
+		"Refill #1.",
+		"http://www.host.test",
+		[]string{
+			"A=1",
+			"A=2; path=/foo",
+			"A=3; domain=.host.test",
+			"A=4; path=/foo; domain=.host.test"},
+		"A=1 A=2 A=3 A=4",
+		[]query{{"http://www.host.test/foo", "A=2 A=4 A=1 A=3"}},
+	},
+	{
+		"Refill #2.",
+		"http://www.google.com",
+		[]string{
+			"A=6",
+			"A=7; path=/foo",
+			"A=8; domain=.google.com",
+			"A=9; path=/foo; domain=.google.com"},
+		"A=1 A=2 A=3 A=4 A=6 A=7 A=8 A=9",
+		[]query{
+			{"http://www.host.test/foo", "A=2 A=4 A=1 A=3"},
+			{"http://www.google.com/foo", "A=7 A=9 A=6 A=8"},
+		},
+	},
+	{
+		"Delete A7.",
+		"http://www.google.com",
+		[]string{"A=; path=/foo; max-age=-1"},
+		"A=1 A=2 A=3 A=4 A=6 A=8 A=9",
+		[]query{
+			{"http://www.host.test/foo", "A=2 A=4 A=1 A=3"},
+			{"http://www.google.com/foo", "A=9 A=6 A=8"},
+		},
+	},
+	{
+		"Delete A4.",
+		"http://www.host.test",
+		[]string{"A=; path=/foo; domain=host.test; max-age=-1"},
+		"A=1 A=2 A=3 A=6 A=8 A=9",
+		[]query{
+			{"http://www.host.test/foo", "A=2 A=1 A=3"},
+			{"http://www.google.com/foo", "A=9 A=6 A=8"},
+		},
+	},
+	{
+		"Delete A6.",
+		"http://www.google.com",
+		[]string{"A=; max-age=-1"},
+		"A=1 A=2 A=3 A=8 A=9",
+		[]query{
+			{"http://www.host.test/foo", "A=2 A=1 A=3"},
+			{"http://www.google.com/foo", "A=9 A=8"},
+		},
+	},
+	{
+		"Delete A3.",
+		"http://www.host.test",
+		[]string{"A=; domain=host.test; max-age=-1"},
+		"A=1 A=2 A=8 A=9",
+		[]query{
+			{"http://www.host.test/foo", "A=2 A=1"},
+			{"http://www.google.com/foo", "A=9 A=8"},
+		},
+	},
+	{
+		"No cross-domain delete.",
+		"http://www.host.test",
+		[]string{
+			"A=; domain=google.com; max-age=-1",
+			"A=; path=/foo; domain=google.com; max-age=-1"},
+		"A=1 A=2 A=8 A=9",
+		[]query{
+			{"http://www.host.test/foo", "A=2 A=1"},
+			{"http://www.google.com/foo", "A=9 A=8"},
+		},
+	},
+	{
+		"Delete A8 and A9.",
+		"http://www.google.com",
+		[]string{
+			"A=; domain=google.com; max-age=-1",
+			"A=; path=/foo; domain=google.com; max-age=-1"},
+		"A=1 A=2",
+		[]query{
+			{"http://www.host.test/foo", "A=2 A=1"},
+			{"http://www.google.com/foo", ""},
+		},
+	},
+}
+
+func TestUpdateAndDelete(t *testing.T) {
+	jar := newTestJar()
+	for _, test := range updateAndDeleteTests {
+		test.run(t, jar)
+	}
+}
+
+func TestExpiration(t *testing.T) {
+	jar := newTestJar()
+	jarTest{
+		"Expiration.",
+		"http://www.host.test",
+		[]string{
+			"a=1",
+			"b=2; max-age=3",
+			"c=3; " + expiresIn(3),
+			"d=4; max-age=5",
+			"e=5; " + expiresIn(5),
+			"f=6; max-age=100",
+		},
+		"a=1 b=2 c=3 d=4 e=5 f=6", // executed at t0 + 1001 ms
+		[]query{
+			{"http://www.host.test", "a=1 b=2 c=3 d=4 e=5 f=6"}, // t0 + 2002 ms
+			{"http://www.host.test", "a=1 d=4 e=5 f=6"},         // t0 + 3003 ms
+			{"http://www.host.test", "a=1 d=4 e=5 f=6"},         // t0 + 4004 ms
+			{"http://www.host.test", "a=1 f=6"},                 // t0 + 5005 ms
+			{"http://www.host.test", "a=1 f=6"},                 // t0 + 6006 ms
+		},
+	}.run(t, jar)
+}
+
+//
+// Tests derived from Chromium's cookie_store_unittest.h.
+//
+
+// See http://src.chromium.org/viewvc/chrome/trunk/src/net/cookies/cookie_store_unittest.h?revision=159685&content-type=text/plain
+// Some of the original tests are in a bad condition (e.g.
+// DomainWithTrailingDotTest) or are not RFC 6265 conforming (e.g.
+// TestNonDottedAndTLD #1 and #6) and have not been ported.
+
+// chromiumBasicsTests contains fundamental tests. Each jarTest has to be
+// performed on a fresh, empty Jar.
+var chromiumBasicsTests = [...]jarTest{
+	{
+		"DomainWithTrailingDotTest.",
+		"http://www.google.com/",
+		[]string{
+			"a=1; domain=.www.google.com.",
+			"b=2; domain=.www.google.com.."},
+		"",
+		[]query{
+			{"http://www.google.com", ""},
+		},
+	},
+	{
+		"ValidSubdomainTest #1.",
+		"http://a.b.c.d.com",
+		[]string{
+			"a=1; domain=.a.b.c.d.com",
+			"b=2; domain=.b.c.d.com",
+			"c=3; domain=.c.d.com",
+			"d=4; domain=.d.com"},
+		"a=1 b=2 c=3 d=4",
+		[]query{
+			{"http://a.b.c.d.com", "a=1 b=2 c=3 d=4"},
+			{"http://b.c.d.com", "b=2 c=3 d=4"},
+			{"http://c.d.com", "c=3 d=4"},
+			{"http://d.com", "d=4"},
+		},
+	},
+	{
+		"ValidSubdomainTest #2.",
+		"http://a.b.c.d.com",
+		[]string{
+			"a=1; domain=.a.b.c.d.com",
+			"b=2; domain=.b.c.d.com",
+			"c=3; domain=.c.d.com",
+			"d=4; domain=.d.com",
+			"X=bcd; domain=.b.c.d.com",
+			"X=cd; domain=.c.d.com"},
+		"X=bcd X=cd a=1 b=2 c=3 d=4",
+		[]query{
+			{"http://b.c.d.com", "b=2 c=3 d=4 X=bcd X=cd"},
+			{"http://c.d.com", "c=3 d=4 X=cd"},
+		},
+	},
+	{
+		"InvalidDomainTest #1.",
+		"http://foo.bar.com",
+		[]string{
+			"a=1; domain=.yo.foo.bar.com",
+			"b=2; domain=.foo.com",
+			"c=3; domain=.bar.foo.com",
+			"d=4; domain=.foo.bar.com.net",
+			"e=5; domain=ar.com",
+			"f=6; domain=.",
+			"g=7; domain=/",
+			"h=8; domain=http://foo.bar.com",
+			"i=9; domain=..foo.bar.com",
+			"j=10; domain=..bar.com",
+			"k=11; domain=.foo.bar.com?blah",
+			"l=12; domain=.foo.bar.com/blah",
+			"m=12; domain=.foo.bar.com:80",
+			"n=14; domain=.foo.bar.com:",
+			"o=15; domain=.foo.bar.com#sup",
+		},
+		"", // Jar is empty.
+		[]query{{"http://foo.bar.com", ""}},
+	},
+	{
+		"InvalidDomainTest #2.",
+		"http://foo.com.com",
+		[]string{"a=1; domain=.foo.com.com.com"},
+		"",
+		[]query{{"http://foo.bar.com", ""}},
+	},
+	{
+		"DomainWithoutLeadingDotTest #1.",
+		"http://manage.hosted.filefront.com",
+		[]string{"a=1; domain=filefront.com"},
+		"a=1",
+		[]query{{"http://www.filefront.com", "a=1"}},
+	},
+	{
+		"DomainWithoutLeadingDotTest #2.",
+		"http://www.google.com",
+		[]string{"a=1; domain=www.google.com"},
+		"a=1",
+		[]query{
+			{"http://www.google.com", "a=1"},
+			{"http://sub.www.google.com", "a=1"},
+			{"http://something-else.com", ""},
+		},
+	},
+	{
+		"CaseInsensitiveDomainTest.",
+		"http://www.google.com",
+		[]string{
+			"a=1; domain=.GOOGLE.COM",
+			"b=2; domain=.www.gOOgLE.coM"},
+		"a=1 b=2",
+		[]query{{"http://www.google.com", "a=1 b=2"}},
+	},
+	{
+		"TestIpAddress #1.",
+		"http://1.2.3.4/foo",
+		[]string{"a=1; path=/"},
+		"a=1",
+		[]query{{"http://1.2.3.4/foo", "a=1"}},
+	},
+	{
+		"TestIpAddress #2.",
+		"http://1.2.3.4/foo",
+		[]string{
+			"a=1; domain=.1.2.3.4",
+			"b=2; domain=.3.4"},
+		"",
+		[]query{{"http://1.2.3.4/foo", ""}},
+	},
+	{
+		"TestIpAddress #3.",
+		"http://1.2.3.4/foo",
+		[]string{"a=1; domain=1.2.3.4"},
+		"",
+		[]query{{"http://1.2.3.4/foo", ""}},
+	},
+	{
+		"TestNonDottedAndTLD #2.",
+		"http://com./index.html",
+		[]string{"a=1"},
+		"a=1",
+		[]query{
+			{"http://com./index.html", "a=1"},
+			{"http://no-cookies.com./index.html", ""},
+		},
+	},
+	{
+		"TestNonDottedAndTLD #3.",
+		"http://a.b",
+		[]string{
+			"a=1; domain=.b",
+			"b=2; domain=b"},
+		"",
+		[]query{{"http://bar.foo", ""}},
+	},
+	{
+		"TestNonDottedAndTLD #4.",
+		"http://google.com",
+		[]string{
+			"a=1; domain=.com",
+			"b=2; domain=com"},
+		"",
+		[]query{{"http://google.com", ""}},
+	},
+	{
+		"TestNonDottedAndTLD #5.",
+		"http://google.co.uk",
+		[]string{
+			"a=1; domain=.co.uk",
+			"b=2; domain=.uk"},
+		"",
+		[]query{
+			{"http://google.co.uk", ""},
+			{"http://else.co.com", ""},
+			{"http://else.uk", ""},
+		},
+	},
+	{
+		"TestHostEndsWithDot.",
+		"http://www.google.com",
+		[]string{
+			"a=1",
+			"b=2; domain=.www.google.com."},
+		"a=1",
+		[]query{{"http://www.google.com", "a=1"}},
+	},
+	{
+		"PathTest",
+		"http://www.google.izzle",
+		[]string{"a=1; path=/wee"},
+		"a=1",
+		[]query{
+			{"http://www.google.izzle/wee", "a=1"},
+			{"http://www.google.izzle/wee/", "a=1"},
+			{"http://www.google.izzle/wee/war", "a=1"},
+			{"http://www.google.izzle/wee/war/more/more", "a=1"},
+			{"http://www.google.izzle/weehee", ""},
+			{"http://www.google.izzle/", ""},
+		},
+	},
+}
+
+func TestChromiumBasics(t *testing.T) {
+	for _, test := range chromiumBasicsTests {
+		jar := newTestJar()
+		test.run(t, jar)
+	}
+}
+
+// chromiumDomainTests contains jarTests which must be executed all on the
+// same Jar.
+var chromiumDomainTests = [...]jarTest{
+	{
+		"Fill #1.",
+		"http://www.google.izzle",
+		[]string{"A=B"},
+		"A=B",
+		[]query{{"http://www.google.izzle", "A=B"}},
+	},
+	{
+		"Fill #2.",
+		"http://www.google.izzle",
+		[]string{"C=D; domain=.google.izzle"},
+		"A=B C=D",
+		[]query{{"http://www.google.izzle", "A=B C=D"}},
+	},
+	{
+		"Verify A is a host cookie and not accessible from subdomain.",
+		"http://unused.nil",
+		[]string{},
+		"A=B C=D",
+		[]query{{"http://foo.www.google.izzle", "C=D"}},
+	},
+	{
+		"Verify domain cookies are found on proper domain.",
+		"http://www.google.izzle",
+		[]string{"E=F; domain=.www.google.izzle"},
+		"A=B C=D E=F",
+		[]query{{"http://www.google.izzle", "A=B C=D E=F"}},
+	},
+	{
+		"Leading dots in domain attributes are optional.",
+		"http://www.google.izzle",
+		[]string{"G=H; domain=www.google.izzle"},
+		"A=B C=D E=F G=H",
+		[]query{{"http://www.google.izzle", "A=B C=D E=F G=H"}},
+	},
+	{
+		"Verify domain enforcement works #1.",
+		"http://www.google.izzle",
+		[]string{"K=L; domain=.bar.www.google.izzle"},
+		"A=B C=D E=F G=H",
+		[]query{{"http://bar.www.google.izzle", "C=D E=F G=H"}},
+	},
+	{
+		"Verify domain enforcement works #2.",
+		"http://unused.nil",
+		[]string{},
+		"A=B C=D E=F G=H",
+		[]query{{"http://www.google.izzle", "A=B C=D E=F G=H"}},
+	},
+}
+
+func TestChromiumDomain(t *testing.T) {
+	jar := newTestJar()
+	for _, test := range chromiumDomainTests {
+		test.run(t, jar)
+	}
+
+}
+
+// chromiumDeletionTests must be performed all on the same Jar.
+var chromiumDeletionTests = [...]jarTest{
+	{
+		"Create session cookie a1.",
+		"http://www.google.com",
+		[]string{"a=1"},
+		"a=1",
+		[]query{{"http://www.google.com", "a=1"}},
+	},
+	{
+		"Delete sc a1 via MaxAge.",
+		"http://www.google.com",
+		[]string{"a=1; max-age=-1"},
+		"",
+		[]query{{"http://www.google.com", ""}},
+	},
+	{
+		"Create session cookie b2.",
+		"http://www.google.com",
+		[]string{"b=2"},
+		"b=2",
+		[]query{{"http://www.google.com", "b=2"}},
+	},
+	{
+		"Delete sc b2 via Expires.",
+		"http://www.google.com",
+		[]string{"b=2; " + expiresIn(-10)},
+		"",
+		[]query{{"http://www.google.com", ""}},
+	},
+	{
+		"Create persistent cookie c3.",
+		"http://www.google.com",
+		[]string{"c=3; max-age=3600"},
+		"c=3",
+		[]query{{"http://www.google.com", "c=3"}},
+	},
+	{
+		"Delete pc c3 via MaxAge.",
+		"http://www.google.com",
+		[]string{"c=3; max-age=-1"},
+		"",
+		[]query{{"http://www.google.com", ""}},
+	},
+	{
+		"Create persistent cookie d4.",
+		"http://www.google.com",
+		[]string{"d=4; max-age=3600"},
+		"d=4",
+		[]query{{"http://www.google.com", "d=4"}},
+	},
+	{
+		"Delete pc d4 via Expires.",
+		"http://www.google.com",
+		[]string{"d=4; " + expiresIn(-10)},
+		"",
+		[]query{{"http://www.google.com", ""}},
+	},
+}
+
+func TestChromiumDeletion(t *testing.T) {
+	jar := newTestJar()
+	for _, test := range chromiumDeletionTests {
+		test.run(t, jar)
+	}
+}
+
+// domainHandlingTests tests and documents the rules for domain handling.
+// Each test must be performed on an empty new Jar.
+var domainHandlingTests = [...]jarTest{
+	{
+		"Host cookie",
+		"http://www.host.test",
+		[]string{"a=1"},
+		"a=1",
+		[]query{
+			{"http://www.host.test", "a=1"},
+			{"http://host.test", ""},
+			{"http://bar.host.test", ""},
+			{"http://foo.www.host.test", ""},
+			{"http://other.test", ""},
+			{"http://test", ""},
+		},
+	},
+	{
+		"Domain cookie #1",
+		"http://www.host.test",
+		[]string{"a=1; domain=host.test"},
+		"a=1",
+		[]query{
+			{"http://www.host.test", "a=1"},
+			{"http://host.test", "a=1"},
+			{"http://bar.host.test", "a=1"},
+			{"http://foo.www.host.test", "a=1"},
+			{"http://other.test", ""},
+			{"http://test", ""},
+		},
+	},
+	{
+		"Domain cookie #2",
+		"http://www.host.test",
+		[]string{"a=1; domain=.host.test"},
+		"a=1",
+		[]query{
+			{"http://www.host.test", "a=1"},
+			{"http://host.test", "a=1"},
+			{"http://bar.host.test", "a=1"},
+			{"http://foo.www.host.test", "a=1"},
+			{"http://other.test", ""},
+			{"http://test", ""},
+		},
+	},
+	{
+		"Host cookie on IDNA domain #1",
+		"http://www.bücher.test",
+		[]string{"a=1"},
+		"a=1",
+		[]query{
+			{"http://www.bücher.test", "a=1"},
+			{"http://www.xn--bcher-kva.test", "a=1"},
+			{"http://bücher.test", ""},
+			{"http://xn--bcher-kva.test", ""},
+			{"http://bar.bücher.test", ""},
+			{"http://bar.xn--bcher-kva.test", ""},
+			{"http://foo.www.bücher.test", ""},
+			{"http://foo.www.xn--bcher-kva.test", ""},
+			{"http://other.test", ""},
+			{"http://test", ""},
+		},
+	},
+	{
+		"Host cookie on IDNA domain #2",
+		"http://www.xn--bcher-kva.test",
+		[]string{"a=1"},
+		"a=1",
+		[]query{
+			{"http://www.bücher.test", "a=1"},
+			{"http://www.xn--bcher-kva.test", "a=1"},
+			{"http://bücher.test", ""},
+			{"http://xn--bcher-kva.test", ""},
+			{"http://bar.bücher.test", ""},
+			{"http://bar.xn--bcher-kva.test", ""},
+			{"http://foo.www.bücher.test", ""},
+			{"http://foo.www.xn--bcher-kva.test", ""},
+			{"http://other.test", ""},
+			{"http://test", ""},
+		},
+	},
+	{
+		"Domain cookie on IDNA domain #1",
+		"http://www.bücher.test",
+		[]string{"a=1; domain=xn--bcher-kva.test"},
+		"a=1",
+		[]query{
+			{"http://www.bücher.test", "a=1"},
+			{"http://www.xn--bcher-kva.test", "a=1"},
+			{"http://bücher.test", "a=1"},
+			{"http://xn--bcher-kva.test", "a=1"},
+			{"http://bar.bücher.test", "a=1"},
+			{"http://bar.xn--bcher-kva.test", "a=1"},
+			{"http://foo.www.bücher.test", "a=1"},
+			{"http://foo.www.xn--bcher-kva.test", "a=1"},
+			{"http://other.test", ""},
+			{"http://test", ""},
+		},
+	},
+	{
+		"Domain cookie on IDNA domain #2",
+		"http://www.xn--bcher-kva.test",
+		[]string{"a=1; domain=xn--bcher-kva.test"},
+		"a=1",
+		[]query{
+			{"http://www.bücher.test", "a=1"},
+			{"http://www.xn--bcher-kva.test", "a=1"},
+			{"http://bücher.test", "a=1"},
+			{"http://xn--bcher-kva.test", "a=1"},
+			{"http://bar.bücher.test", "a=1"},
+			{"http://bar.xn--bcher-kva.test", "a=1"},
+			{"http://foo.www.bücher.test", "a=1"},
+			{"http://foo.www.xn--bcher-kva.test", "a=1"},
+			{"http://other.test", ""},
+			{"http://test", ""},
+		},
+	},
+	{
+		"Host cookie on TLD.",
+		"http://com",
+		[]string{"a=1"},
+		"a=1",
+		[]query{
+			{"http://com", "a=1"},
+			{"http://any.com", ""},
+			{"http://any.test", ""},
+		},
+	},
+	{
+		"Domain cookie on TLD becomes a host cookie.",
+		"http://com",
+		[]string{"a=1; domain=com"},
+		"a=1",
+		[]query{
+			{"http://com", "a=1"},
+			{"http://any.com", ""},
+			{"http://any.test", ""},
+		},
+	},
+	{
+		"Host cookie on public suffix.",
+		"http://co.uk",
+		[]string{"a=1"},
+		"a=1",
+		[]query{
+			{"http://co.uk", "a=1"},
+			{"http://uk", ""},
+			{"http://some.co.uk", ""},
+			{"http://foo.some.co.uk", ""},
+			{"http://any.uk", ""},
+		},
+	},
+	{
+		"Domain cookie on public suffix is ignored.",
+		"http://some.co.uk",
+		[]string{"a=1; domain=co.uk"},
+		"",
+		[]query{
+			{"http://co.uk", ""},
+			{"http://uk", ""},
+			{"http://some.co.uk", ""},
+			{"http://foo.some.co.uk", ""},
+			{"http://any.uk", ""},
+		},
+	},
+}
+
+func TestDomainHandling(t *testing.T) {
+	for _, test := range domainHandlingTests {
+		jar := newTestJar()
+		test.run(t, jar)
+	}
+}
diff --git a/src/net/http/cookiejar/punycode.go b/src/net/http/cookiejar/punycode.go
new file mode 100644
index 000000000..ea7ceb5ef
--- /dev/null
+++ b/src/net/http/cookiejar/punycode.go
@@ -0,0 +1,159 @@
+// Copyright 2012 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package cookiejar
+
+// This file implements the Punycode algorithm from RFC 3492.
+
+import (
+	"fmt"
+	"strings"
+	"unicode/utf8"
+)
+
+// These parameter values are specified in section 5.
+//
+// All computation is done with int32s, so that overflow behavior is identical
+// regardless of whether int is 32-bit or 64-bit.
+const (
+	base        int32 = 36
+	damp        int32 = 700
+	initialBias int32 = 72
+	initialN    int32 = 128
+	skew        int32 = 38
+	tmax        int32 = 26
+	tmin        int32 = 1
+)
+
+// encode encodes a string as specified in section 6.3 and prepends prefix to
+// the result.
+//
+// The "while h < length(input)" line in the specification becomes "for
+// remaining != 0" in the Go code, because len(s) in Go is in bytes, not runes.
+func encode(prefix, s string) (string, error) {
+	output := make([]byte, len(prefix), len(prefix)+1+2*len(s))
+	copy(output, prefix)
+	delta, n, bias := int32(0), initialN, initialBias
+	b, remaining := int32(0), int32(0)
+	for _, r := range s {
+		if r < 0x80 {
+			b++
+			output = append(output, byte(r))
+		} else {
+			remaining++
+		}
+	}
+	h := b
+	if b > 0 {
+		output = append(output, '-')
+	}
+	for remaining != 0 {
+		m := int32(0x7fffffff)
+		for _, r := range s {
+			if m > r && r >= n {
+				m = r
+			}
+		}
+		delta += (m - n) * (h + 1)
+		if delta < 0 {
+			return "", fmt.Errorf("cookiejar: invalid label %q", s)
+		}
+		n = m
+		for _, r := range s {
+			if r < n {
+				delta++
+				if delta < 0 {
+					return "", fmt.Errorf("cookiejar: invalid label %q", s)
+				}
+				continue
+			}
+			if r > n {
+				continue
+			}
+			q := delta
+			for k := base; ; k += base {
+				t := k - bias
+				if t < tmin {
+					t = tmin
+				} else if t > tmax {
+					t = tmax
+				}
+				if q < t {
+					break
+				}
+				output = append(output, encodeDigit(t+(q-t)%(base-t)))
+				q = (q - t) / (base - t)
+			}
+			output = append(output, encodeDigit(q))
+			bias = adapt(delta, h+1, h == b)
+			delta = 0
+			h++
+			remaining--
+		}
+		delta++
+		n++
+	}
+	return string(output), nil
+}
+
+func encodeDigit(digit int32) byte {
+	switch {
+	case 0 <= digit && digit < 26:
+		return byte(digit + 'a')
+	case 26 <= digit && digit < 36:
+		return byte(digit + ('0' - 26))
+	}
+	panic("cookiejar: internal error in punycode encoding")
+}
+
+// adapt is the bias adaptation function specified in section 6.1.
+func adapt(delta, numPoints int32, firstTime bool) int32 {
+	if firstTime {
+		delta /= damp
+	} else {
+		delta /= 2
+	}
+	delta += delta / numPoints
+	k := int32(0)
+	for delta > ((base-tmin)*tmax)/2 {
+		delta /= base - tmin
+		k += base
+	}
+	return k + (base-tmin+1)*delta/(delta+skew)
+}
+
+// Strictly speaking, the remaining code below deals with IDNA (RFC 5890 and
+// friends) and not Punycode (RFC 3492) per se.
+
+// acePrefix is the ASCII Compatible Encoding prefix.
+const acePrefix = "xn--"
+
+// toASCII converts a domain or domain label to its ASCII form. For example,
+// toASCII("bücher.example.com") is "xn--bcher-kva.example.com", and
+// toASCII("golang") is "golang".
+func toASCII(s string) (string, error) {
+	if ascii(s) {
+		return s, nil
+	}
+	labels := strings.Split(s, ".")
+	for i, label := range labels {
+		if !ascii(label) {
+			a, err := encode(acePrefix, label)
+			if err != nil {
+				return "", err
+			}
+			labels[i] = a
+		}
+	}
+	return strings.Join(labels, "."), nil
+}
+
+func ascii(s string) bool {
+	for i := 0; i < len(s); i++ {
+		if s[i] >= utf8.RuneSelf {
+			return false
+		}
+	}
+	return true
+}
diff --git a/src/net/http/cookiejar/punycode_test.go b/src/net/http/cookiejar/punycode_test.go
new file mode 100644
index 000000000..0301de14e
--- /dev/null
+++ b/src/net/http/cookiejar/punycode_test.go
@@ -0,0 +1,161 @@
+// Copyright 2012 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package cookiejar
+
+import (
+	"testing"
+)
+
+var punycodeTestCases = [...]struct {
+	s, encoded string
+}{
+	{"", ""},
+	{"-", "--"},
+	{"-a", "-a-"},
+	{"-a-", "-a--"},
+	{"a", "a-"},
+	{"a-", "a--"},
+	{"a-b", "a-b-"},
+	{"books", "books-"},
+	{"bücher", "bcher-kva"},
+	{"Hello世界", "Hello-ck1hg65u"},
+	{"ü", "tda"},
+	{"üý", "tdac"},
+
+	// The test cases below come from RFC 3492 section 7.1 with Errata 3026.
+	{
+		// (A) Arabic (Egyptian).
+		"\u0644\u064A\u0647\u0645\u0627\u0628\u062A\u0643\u0644" +
+			"\u0645\u0648\u0634\u0639\u0631\u0628\u064A\u061F",
+		"egbpdaj6bu4bxfgehfvwxn",
+	},
+	{
+		// (B) Chinese (simplified).
+		"\u4ED6\u4EEC\u4E3A\u4EC0\u4E48\u4E0D\u8BF4\u4E2D\u6587",
+		"ihqwcrb4cv8a8dqg056pqjye",
+	},
+	{
+		// (C) Chinese (traditional).
+		"\u4ED6\u5011\u7232\u4EC0\u9EBD\u4E0D\u8AAA\u4E2D\u6587",
+		"ihqwctvzc91f659drss3x8bo0yb",
+	},
+	{
+		// (D) Czech.
+		"\u0050\u0072\u006F\u010D\u0070\u0072\u006F\u0073\u0074" +
+			"\u011B\u006E\u0065\u006D\u006C\u0075\u0076\u00ED\u010D" +
+			"\u0065\u0073\u006B\u0079",
+		"Proprostnemluvesky-uyb24dma41a",
+	},
+	{
+		// (E) Hebrew.
+		"\u05DC\u05DE\u05D4\u05D4\u05DD\u05E4\u05E9\u05D5\u05D8" +
+			"\u05DC\u05D0\u05DE\u05D3\u05D1\u05E8\u05D9\u05DD\u05E2" +
+			"\u05D1\u05E8\u05D9\u05EA",
+		"4dbcagdahymbxekheh6e0a7fei0b",
+	},
+	{
+		// (F) Hindi (Devanagari).
+		"\u092F\u0939\u0932\u094B\u0917\u0939\u093F\u0928\u094D" +
+			"\u0926\u0940\u0915\u094D\u092F\u094B\u0902\u0928\u0939" +
+			"\u0940\u0902\u092C\u094B\u0932\u0938\u0915\u0924\u0947" +
+			"\u0939\u0948\u0902",
+		"i1baa7eci9glrd9b2ae1bj0hfcgg6iyaf8o0a1dig0cd",
+	},
+	{
+		// (G) Japanese (kanji and hiragana).
+		"\u306A\u305C\u307F\u3093\u306A\u65E5\u672C\u8A9E\u3092" +
+			"\u8A71\u3057\u3066\u304F\u308C\u306A\u3044\u306E\u304B",
+		"n8jok5ay5dzabd5bym9f0cm5685rrjetr6pdxa",
+	},
+	{
+		// (H) Korean (Hangul syllables).
+		"\uC138\uACC4\uC758\uBAA8\uB4E0\uC0AC\uB78C\uB4E4\uC774" +
+			"\uD55C\uAD6D\uC5B4\uB97C\uC774\uD574\uD55C\uB2E4\uBA74" +
+			"\uC5BC\uB9C8\uB098\uC88B\uC744\uAE4C",
+		"989aomsvi5e83db1d2a355cv1e0vak1dwrv93d5xbh15a0dt30a5j" +
+			"psd879ccm6fea98c",
+	},
+	{
+		// (I) Russian (Cyrillic).
+		"\u043F\u043E\u0447\u0435\u043C\u0443\u0436\u0435\u043E" +
+			"\u043D\u0438\u043D\u0435\u0433\u043E\u0432\u043E\u0440" +
+			"\u044F\u0442\u043F\u043E\u0440\u0443\u0441\u0441\u043A" +
+			"\u0438",
+		"b1abfaaepdrnnbgefbadotcwatmq2g4l",
+	},
+	{
+		// (J) Spanish.
+		"\u0050\u006F\u0072\u0071\u0075\u00E9\u006E\u006F\u0070" +
+			"\u0075\u0065\u0064\u0065\u006E\u0073\u0069\u006D\u0070" +
+			"\u006C\u0065\u006D\u0065\u006E\u0074\u0065\u0068\u0061" +
+			"\u0062\u006C\u0061\u0072\u0065\u006E\u0045\u0073\u0070" +
+			"\u0061\u00F1\u006F\u006C",
+		"PorqunopuedensimplementehablarenEspaol-fmd56a",
+	},
+	{
+		// (K) Vietnamese.
+		"\u0054\u1EA1\u0069\u0073\u0061\u006F\u0068\u1ECD\u006B" +
+			"\u0068\u00F4\u006E\u0067\u0074\u0068\u1EC3\u0063\u0068" +
+			"\u1EC9\u006E\u00F3\u0069\u0074\u0069\u1EBF\u006E\u0067" +
+			"\u0056\u0069\u1EC7\u0074",
+		"TisaohkhngthchnitingVit-kjcr8268qyxafd2f1b9g",
+	},
+	{
+		// (L) 3<nen>B<gumi><kinpachi><sensei>.
+		"\u0033\u5E74\u0042\u7D44\u91D1\u516B\u5148\u751F",
+		"3B-ww4c5e180e575a65lsy2b",
+	},
+	{
+		// (M) <amuro><namie>-with-SUPER-MONKEYS.
+		"\u5B89\u5BA4\u5948\u7F8E\u6075\u002D\u0077\u0069\u0074" +
+			"\u0068\u002D\u0053\u0055\u0050\u0045\u0052\u002D\u004D" +
+			"\u004F\u004E\u004B\u0045\u0059\u0053",
+		"-with-SUPER-MONKEYS-pc58ag80a8qai00g7n9n",
+	},
+	{
+		// (N) Hello-Another-Way-<sorezore><no><basho>.
+		"\u0048\u0065\u006C\u006C\u006F\u002D\u0041\u006E\u006F" +
+			"\u0074\u0068\u0065\u0072\u002D\u0057\u0061\u0079\u002D" +
+			"\u305D\u308C\u305E\u308C\u306E\u5834\u6240",
+		"Hello-Another-Way--fc4qua05auwb3674vfr0b",
+	},
+	{
+		// (O) <hitotsu><yane><no><shita>2.
+		"\u3072\u3068\u3064\u5C4B\u6839\u306E\u4E0B\u0032",
+		"2-u9tlzr9756bt3uc0v",
+	},
+	{
+		// (P) Maji<de>Koi<suru>5<byou><mae>
+		"\u004D\u0061\u006A\u0069\u3067\u004B\u006F\u0069\u3059" +
+			"\u308B\u0035\u79D2\u524D",
+		"MajiKoi5-783gue6qz075azm5e",
+	},
+	{
+		// (Q) <pafii>de<runba>
+		"\u30D1\u30D5\u30A3\u30FC\u0064\u0065\u30EB\u30F3\u30D0",
+		"de-jg4avhby1noc0d",
+	},
+	{
+		// (R) <sono><supiido><de>
+		"\u305D\u306E\u30B9\u30D4\u30FC\u30C9\u3067",
+		"d9juau41awczczp",
+	},
+	{
+		// (S) -> $1.00 <-
+		"\u002D\u003E\u0020\u0024\u0031\u002E\u0030\u0030\u0020" +
+			"\u003C\u002D",
+		"-> $1.00 <--",
+	},
+}
+
+func TestPunycode(t *testing.T) {
+	for _, tc := range punycodeTestCases {
+		if got, err := encode("", tc.s); err != nil {
+			t.Errorf(`encode("", %q): %v`, tc.s, err)
+		} else if got != tc.encoded {
+			t.Errorf(`encode("", %q): got %q, want %q`, tc.s, got, tc.encoded)
+		}
+	}
+}
diff --git a/src/net/http/doc.go b/src/net/http/doc.go
new file mode 100644
index 000000000..b1216e8da
--- /dev/null
+++ b/src/net/http/doc.go
@@ -0,0 +1,80 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+/*
+Package http provides HTTP client and server implementations.
+
+Get, Head, Post, and PostForm make HTTP (or HTTPS) requests:
+
+	resp, err := http.Get("http://example.com/")
+	...
+	resp, err := http.Post("http://example.com/upload", "image/jpeg", &buf)
+	...
+	resp, err := http.PostForm("http://example.com/form",
+		url.Values{"key": {"Value"}, "id": {"123"}})
+
+The client must close the response body when finished with it:
+
+	resp, err := http.Get("http://example.com/")
+	if err != nil {
+		// handle error
+	}
+	defer resp.Body.Close()
+	body, err := ioutil.ReadAll(resp.Body)
+	// ...
+
+For control over HTTP client headers, redirect policy, and other
+settings, create a Client:
+
+	client := &http.Client{
+		CheckRedirect: redirectPolicyFunc,
+	}
+
+	resp, err := client.Get("http://example.com")
+	// ...
+
+	req, err := http.NewRequest("GET", "http://example.com", nil)
+	// ...
+	req.Header.Add("If-None-Match", `W/"wyzzy"`)
+	resp, err := client.Do(req)
+	// ...
+
+For control over proxies, TLS configuration, keep-alives,
+compression, and other settings, create a Transport:
+
+	tr := &http.Transport{
+		TLSClientConfig:    &tls.Config{RootCAs: pool},
+		DisableCompression: true,
+	}
+	client := &http.Client{Transport: tr}
+	resp, err := client.Get("https://example.com")
+
+Clients and Transports are safe for concurrent use by multiple
+goroutines and for efficiency should only be created once and re-used.
+
+ListenAndServe starts an HTTP server with a given address and handler.
+The handler is usually nil, which means to use DefaultServeMux.
+Handle and HandleFunc add handlers to DefaultServeMux:
+
+	http.Handle("/foo", fooHandler)
+
+	http.HandleFunc("/bar", func(w http.ResponseWriter, r *http.Request) {
+		fmt.Fprintf(w, "Hello, %q", html.EscapeString(r.URL.Path))
+	})
+
+	log.Fatal(http.ListenAndServe(":8080", nil))
+
+More control over the server's behavior is available by creating a
+custom Server:
+
+	s := &http.Server{
+		Addr:           ":8080",
+		Handler:        myHandler,
+		ReadTimeout:    10 * time.Second,
+		WriteTimeout:   10 * time.Second,
+		MaxHeaderBytes: 1 << 20,
+	}
+	log.Fatal(s.ListenAndServe())
+*/
+package http
diff --git a/src/net/http/example_test.go b/src/net/http/example_test.go
new file mode 100644
index 000000000..88b97d9e3
--- /dev/null
+++ b/src/net/http/example_test.go
@@ -0,0 +1,88 @@
+// Copyright 2012 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package http_test
+
+import (
+	"fmt"
+	"io/ioutil"
+	"log"
+	"net/http"
+)
+
+func ExampleHijacker() {
+	http.HandleFunc("/hijack", func(w http.ResponseWriter, r *http.Request) {
+		hj, ok := w.(http.Hijacker)
+		if !ok {
+			http.Error(w, "webserver doesn't support hijacking", http.StatusInternalServerError)
+			return
+		}
+		conn, bufrw, err := hj.Hijack()
+		if err != nil {
+			http.Error(w, err.Error(), http.StatusInternalServerError)
+			return
+		}
+		// Don't forget to close the connection:
+		defer conn.Close()
+		bufrw.WriteString("Now we're speaking raw TCP. Say hi: ")
+		bufrw.Flush()
+		s, err := bufrw.ReadString('\n')
+		if err != nil {
+			log.Printf("error reading string: %v", err)
+			return
+		}
+		fmt.Fprintf(bufrw, "You said: %q\nBye.\n", s)
+		bufrw.Flush()
+	})
+}
+
+func ExampleGet() {
+	res, err := http.Get("http://www.google.com/robots.txt")
+	if err != nil {
+		log.Fatal(err)
+	}
+	robots, err := ioutil.ReadAll(res.Body)
+	res.Body.Close()
+	if err != nil {
+		log.Fatal(err)
+	}
+	fmt.Printf("%s", robots)
+}
+
+func ExampleFileServer() {
+	// Simple static webserver:
+	log.Fatal(http.ListenAndServe(":8080", http.FileServer(http.Dir("/usr/share/doc"))))
+}
+
+func ExampleFileServer_stripPrefix() {
+	// To serve a directory on disk (/tmp) under an alternate URL
+	// path (/tmpfiles/), use StripPrefix to modify the request
+	// URL's path before the FileServer sees it:
+	http.Handle("/tmpfiles/", http.StripPrefix("/tmpfiles/", http.FileServer(http.Dir("/tmp"))))
+}
+
+func ExampleStripPrefix() {
+	// To serve a directory on disk (/tmp) under an alternate URL
+	// path (/tmpfiles/), use StripPrefix to modify the request
+	// URL's path before the FileServer sees it:
+	http.Handle("/tmpfiles/", http.StripPrefix("/tmpfiles/", http.FileServer(http.Dir("/tmp"))))
+}
+
+type apiHandler struct{}
+
+func (apiHandler) ServeHTTP(http.ResponseWriter, *http.Request) {}
+
+func ExampleServeMux_Handle() {
+	mux := http.NewServeMux()
+	mux.Handle("/api/", apiHandler{})
+	mux.HandleFunc("/", func(w http.ResponseWriter, req *http.Request) {
+		// The "/" pattern matches everything, so we need to check
+		// that we're at the root here.
+		if req.URL.Path != "/" {
+			http.NotFound(w, req)
+			return
+		}
+		fmt.Fprintf(w, "Welcome to the home page!")
+	})
+}
diff --git a/src/net/http/export_test.go b/src/net/http/export_test.go
new file mode 100644
index 000000000..2c8735355
--- /dev/null
+++ b/src/net/http/export_test.go
@@ -0,0 +1,78 @@
+// Copyright 2011 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Bridge package to expose http internals to tests in the http_test
+// package.
+
+package http
+
+import (
+	"net"
+	"time"
+)
+
+func NewLoggingConn(baseName string, c net.Conn) net.Conn {
+	return newLoggingConn(baseName, c)
+}
+
+var ExportAppendTime = appendTime
+
+func (t *Transport) NumPendingRequestsForTesting() int {
+	t.reqMu.Lock()
+	defer t.reqMu.Unlock()
+	return len(t.reqCanceler)
+}
+
+func (t *Transport) IdleConnKeysForTesting() (keys []string) {
+	keys = make([]string, 0)
+	t.idleMu.Lock()
+	defer t.idleMu.Unlock()
+	if t.idleConn == nil {
+		return
+	}
+	for key := range t.idleConn {
+		keys = append(keys, key.String())
+	}
+	return
+}
+
+func (t *Transport) IdleConnCountForTesting(cacheKey string) int {
+	t.idleMu.Lock()
+	defer t.idleMu.Unlock()
+	if t.idleConn == nil {
+		return 0
+	}
+	for k, conns := range t.idleConn {
+		if k.String() == cacheKey {
+			return len(conns)
+		}
+	}
+	return 0
+}
+
+func (t *Transport) IdleConnChMapSizeForTesting() int {
+	t.idleMu.Lock()
+	defer t.idleMu.Unlock()
+	return len(t.idleConnCh)
+}
+
+func NewTestTimeoutHandler(handler Handler, ch <-chan time.Time) Handler {
+	f := func() <-chan time.Time {
+		return ch
+	}
+	return &timeoutHandler{handler, f, ""}
+}
+
+func ResetCachedEnvironment() {
+	httpProxyEnv.reset()
+	noProxyEnv.reset()
+}
+
+var DefaultUserAgent = defaultUserAgent
+
+// SetPendingDialHooks sets the hooks that run before and after handling
+// pending dials.
+func SetPendingDialHooks(before, after func()) {
+	prePendingDial, postPendingDial = before, after
+}
diff --git a/src/net/http/fcgi/child.go b/src/net/http/fcgi/child.go
new file mode 100644
index 000000000..a3beaa33a
--- /dev/null
+++ b/src/net/http/fcgi/child.go
@@ -0,0 +1,305 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package fcgi
+
+// This file implements FastCGI from the perspective of a child process.
+
+import (
+	"errors"
+	"fmt"
+	"io"
+	"io/ioutil"
+	"net"
+	"net/http"
+	"net/http/cgi"
+	"os"
+	"strings"
+	"sync"
+	"time"
+)
+
+// request holds the state for an in-progress request. As soon as it's complete,
+// it's converted to an http.Request.
+type request struct {
+	pw        *io.PipeWriter
+	reqId     uint16
+	params    map[string]string
+	buf       [1024]byte
+	rawParams []byte
+	keepConn  bool
+}
+
+func newRequest(reqId uint16, flags uint8) *request {
+	r := &request{
+		reqId:    reqId,
+		params:   map[string]string{},
+		keepConn: flags&flagKeepConn != 0,
+	}
+	r.rawParams = r.buf[:0]
+	return r
+}
+
+// parseParams reads an encoded []byte into Params.
+func (r *request) parseParams() {
+	text := r.rawParams
+	r.rawParams = nil
+	for len(text) > 0 {
+		keyLen, n := readSize(text)
+		if n == 0 {
+			return
+		}
+		text = text[n:]
+		valLen, n := readSize(text)
+		if n == 0 {
+			return
+		}
+		text = text[n:]
+		key := readString(text, keyLen)
+		text = text[keyLen:]
+		val := readString(text, valLen)
+		text = text[valLen:]
+		r.params[key] = val
+	}
+}
+
+// response implements http.ResponseWriter.
+type response struct {
+	req         *request
+	header      http.Header
+	w           *bufWriter
+	wroteHeader bool
+}
+
+func newResponse(c *child, req *request) *response {
+	return &response{
+		req:    req,
+		header: http.Header{},
+		w:      newWriter(c.conn, typeStdout, req.reqId),
+	}
+}
+
+func (r *response) Header() http.Header {
+	return r.header
+}
+
+func (r *response) Write(data []byte) (int, error) {
+	if !r.wroteHeader {
+		r.WriteHeader(http.StatusOK)
+	}
+	return r.w.Write(data)
+}
+
+func (r *response) WriteHeader(code int) {
+	if r.wroteHeader {
+		return
+	}
+	r.wroteHeader = true
+	if code == http.StatusNotModified {
+		// Must not have body.
+		r.header.Del("Content-Type")
+		r.header.Del("Content-Length")
+		r.header.Del("Transfer-Encoding")
+	} else if r.header.Get("Content-Type") == "" {
+		r.header.Set("Content-Type", "text/html; charset=utf-8")
+	}
+
+	if r.header.Get("Date") == "" {
+		r.header.Set("Date", time.Now().UTC().Format(http.TimeFormat))
+	}
+
+	fmt.Fprintf(r.w, "Status: %d %s\r\n", code, http.StatusText(code))
+	r.header.Write(r.w)
+	r.w.WriteString("\r\n")
+}
+
+func (r *response) Flush() {
+	if !r.wroteHeader {
+		r.WriteHeader(http.StatusOK)
+	}
+	r.w.Flush()
+}
+
+func (r *response) Close() error {
+	r.Flush()
+	return r.w.Close()
+}
+
+type child struct {
+	conn    *conn
+	handler http.Handler
+
+	mu       sync.Mutex          // protects requests:
+	requests map[uint16]*request // keyed by request ID
+}
+
+func newChild(rwc io.ReadWriteCloser, handler http.Handler) *child {
+	return &child{
+		conn:     newConn(rwc),
+		handler:  handler,
+		requests: make(map[uint16]*request),
+	}
+}
+
+func (c *child) serve() {
+	defer c.conn.Close()
+	var rec record
+	for {
+		if err := rec.read(c.conn.rwc); err != nil {
+			return
+		}
+		if err := c.handleRecord(&rec); err != nil {
+			return
+		}
+	}
+}
+
+var errCloseConn = errors.New("fcgi: connection should be closed")
+
+var emptyBody = ioutil.NopCloser(strings.NewReader(""))
+
+func (c *child) handleRecord(rec *record) error {
+	c.mu.Lock()
+	req, ok := c.requests[rec.h.Id]
+	c.mu.Unlock()
+	if !ok && rec.h.Type != typeBeginRequest && rec.h.Type != typeGetValues {
+		// The spec says to ignore unknown request IDs.
+		return nil
+	}
+
+	switch rec.h.Type {
+	case typeBeginRequest:
+		if req != nil {
+			// The server is trying to begin a request with the same ID
+			// as an in-progress request. This is an error.
+			return errors.New("fcgi: received ID that is already in-flight")
+		}
+
+		var br beginRequest
+		if err := br.read(rec.content()); err != nil {
+			return err
+		}
+		if br.role != roleResponder {
+			c.conn.writeEndRequest(rec.h.Id, 0, statusUnknownRole)
+			return nil
+		}
+		req = newRequest(rec.h.Id, br.flags)
+		c.mu.Lock()
+		c.requests[rec.h.Id] = req
+		c.mu.Unlock()
+		return nil
+	case typeParams:
+		// NOTE(eds): Technically a key-value pair can straddle the boundary
+		// between two packets. We buffer until we've received all parameters.
+		if len(rec.content()) > 0 {
+			req.rawParams = append(req.rawParams, rec.content()...)
+			return nil
+		}
+		req.parseParams()
+		return nil
+	case typeStdin:
+		content := rec.content()
+		if req.pw == nil {
+			var body io.ReadCloser
+			if len(content) > 0 {
+				// body could be an io.LimitReader, but it shouldn't matter
+				// as long as both sides are behaving.
+				body, req.pw = io.Pipe()
+			} else {
+				body = emptyBody
+			}
+			go c.serveRequest(req, body)
+		}
+		if len(content) > 0 {
+			// TODO(eds): This blocks until the handler reads from the pipe.
+			// If the handler takes a long time, it might be a problem.
+			req.pw.Write(content)
+		} else if req.pw != nil {
+			req.pw.Close()
+		}
+		return nil
+	case typeGetValues:
+		values := map[string]string{"FCGI_MPXS_CONNS": "1"}
+		c.conn.writePairs(typeGetValuesResult, 0, values)
+		return nil
+	case typeData:
+		// If the filter role is implemented, read the data stream here.
+		return nil
+	case typeAbortRequest:
+		println("abort")
+		c.mu.Lock()
+		delete(c.requests, rec.h.Id)
+		c.mu.Unlock()
+		c.conn.writeEndRequest(rec.h.Id, 0, statusRequestComplete)
+		if !req.keepConn {
+			// connection will close upon return
+			return errCloseConn
+		}
+		return nil
+	default:
+		b := make([]byte, 8)
+		b[0] = byte(rec.h.Type)
+		c.conn.writeRecord(typeUnknownType, 0, b)
+		return nil
+	}
+}
+
+func (c *child) serveRequest(req *request, body io.ReadCloser) {
+	r := newResponse(c, req)
+	httpReq, err := cgi.RequestFromMap(req.params)
+	if err != nil {
+		// there was an error reading the request
+		r.WriteHeader(http.StatusInternalServerError)
+		c.conn.writeRecord(typeStderr, req.reqId, []byte(err.Error()))
+	} else {
+		httpReq.Body = body
+		c.handler.ServeHTTP(r, httpReq)
+	}
+	r.Close()
+	c.mu.Lock()
+	delete(c.requests, req.reqId)
+	c.mu.Unlock()
+	c.conn.writeEndRequest(req.reqId, 0, statusRequestComplete)
+
+	// Consume the entire body, so the host isn't still writing to
+	// us when we close the socket below in the !keepConn case,
+	// otherwise we'd send a RST. (golang.org/issue/4183)
+	// TODO(bradfitz): also bound this copy in time. Or send
+	// some sort of abort request to the host, so the host
+	// can properly cut off the client sending all the data.
+	// For now just bound it a little and
+	io.CopyN(ioutil.Discard, body, 100<<20)
+	body.Close()
+
+	if !req.keepConn {
+		c.conn.Close()
+	}
+}
+
+// Serve accepts incoming FastCGI connections on the listener l, creating a new
+// goroutine for each. The goroutine reads requests and then calls handler
+// to reply to them.
+// If l is nil, Serve accepts connections from os.Stdin.
+// If handler is nil, http.DefaultServeMux is used.
+func Serve(l net.Listener, handler http.Handler) error {
+	if l == nil {
+		var err error
+		l, err = net.FileListener(os.Stdin)
+		if err != nil {
+			return err
+		}
+		defer l.Close()
+	}
+	if handler == nil {
+		handler = http.DefaultServeMux
+	}
+	for {
+		rw, err := l.Accept()
+		if err != nil {
+			return err
+		}
+		c := newChild(rw, handler)
+		go c.serve()
+	}
+}
diff --git a/src/net/http/fcgi/fcgi.go b/src/net/http/fcgi/fcgi.go
new file mode 100644
index 000000000..06bba0488
--- /dev/null
+++ b/src/net/http/fcgi/fcgi.go
@@ -0,0 +1,274 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package fcgi implements the FastCGI protocol.
+// Currently only the responder role is supported.
+// The protocol is defined at http://www.fastcgi.com/drupal/node/6?q=node/22
+package fcgi
+
+// This file defines the raw protocol and some utilities used by the child and
+// the host.
+
+import (
+	"bufio"
+	"bytes"
+	"encoding/binary"
+	"errors"
+	"io"
+	"sync"
+)
+
+// recType is a record type, as defined by
+// http://www.fastcgi.com/devkit/doc/fcgi-spec.html#S8
+type recType uint8
+
+const (
+	typeBeginRequest    recType = 1
+	typeAbortRequest    recType = 2
+	typeEndRequest      recType = 3
+	typeParams          recType = 4
+	typeStdin           recType = 5
+	typeStdout          recType = 6
+	typeStderr          recType = 7
+	typeData            recType = 8
+	typeGetValues       recType = 9
+	typeGetValuesResult recType = 10
+	typeUnknownType     recType = 11
+)
+
+// keep the connection between web-server and responder open after request
+const flagKeepConn = 1
+
+const (
+	maxWrite = 65535 // maximum record body
+	maxPad   = 255
+)
+
+const (
+	roleResponder = iota + 1 // only Responders are implemented.
+	roleAuthorizer
+	roleFilter
+)
+
+const (
+	statusRequestComplete = iota
+	statusCantMultiplex
+	statusOverloaded
+	statusUnknownRole
+)
+
+const headerLen = 8
+
+type header struct {
+	Version       uint8
+	Type          recType
+	Id            uint16
+	ContentLength uint16
+	PaddingLength uint8
+	Reserved      uint8
+}
+
+type beginRequest struct {
+	role     uint16
+	flags    uint8
+	reserved [5]uint8
+}
+
+func (br *beginRequest) read(content []byte) error {
+	if len(content) != 8 {
+		return errors.New("fcgi: invalid begin request record")
+	}
+	br.role = binary.BigEndian.Uint16(content)
+	br.flags = content[2]
+	return nil
+}
+
+// for padding so we don't have to allocate all the time
+// not synchronized because we don't care what the contents are
+var pad [maxPad]byte
+
+func (h *header) init(recType recType, reqId uint16, contentLength int) {
+	h.Version = 1
+	h.Type = recType
+	h.Id = reqId
+	h.ContentLength = uint16(contentLength)
+	h.PaddingLength = uint8(-contentLength & 7)
+}
+
+// conn sends records over rwc
+type conn struct {
+	mutex sync.Mutex
+	rwc   io.ReadWriteCloser
+
+	// to avoid allocations
+	buf bytes.Buffer
+	h   header
+}
+
+func newConn(rwc io.ReadWriteCloser) *conn {
+	return &conn{rwc: rwc}
+}
+
+func (c *conn) Close() error {
+	c.mutex.Lock()
+	defer c.mutex.Unlock()
+	return c.rwc.Close()
+}
+
+type record struct {
+	h   header
+	buf [maxWrite + maxPad]byte
+}
+
+func (rec *record) read(r io.Reader) (err error) {
+	if err = binary.Read(r, binary.BigEndian, &rec.h); err != nil {
+		return err
+	}
+	if rec.h.Version != 1 {
+		return errors.New("fcgi: invalid header version")
+	}
+	n := int(rec.h.ContentLength) + int(rec.h.PaddingLength)
+	if _, err = io.ReadFull(r, rec.buf[:n]); err != nil {
+		return err
+	}
+	return nil
+}
+
+func (r *record) content() []byte {
+	return r.buf[:r.h.ContentLength]
+}
+
+// writeRecord writes and sends a single record.
+func (c *conn) writeRecord(recType recType, reqId uint16, b []byte) error {
+	c.mutex.Lock()
+	defer c.mutex.Unlock()
+	c.buf.Reset()
+	c.h.init(recType, reqId, len(b))
+	if err := binary.Write(&c.buf, binary.BigEndian, c.h); err != nil {
+		return err
+	}
+	if _, err := c.buf.Write(b); err != nil {
+		return err
+	}
+	if _, err := c.buf.Write(pad[:c.h.PaddingLength]); err != nil {
+		return err
+	}
+	_, err := c.rwc.Write(c.buf.Bytes())
+	return err
+}
+
+func (c *conn) writeBeginRequest(reqId uint16, role uint16, flags uint8) error {
+	b := [8]byte{byte(role >> 8), byte(role), flags}
+	return c.writeRecord(typeBeginRequest, reqId, b[:])
+}
+
+func (c *conn) writeEndRequest(reqId uint16, appStatus int, protocolStatus uint8) error {
+	b := make([]byte, 8)
+	binary.BigEndian.PutUint32(b, uint32(appStatus))
+	b[4] = protocolStatus
+	return c.writeRecord(typeEndRequest, reqId, b)
+}
+
+func (c *conn) writePairs(recType recType, reqId uint16, pairs map[string]string) error {
+	w := newWriter(c, recType, reqId)
+	b := make([]byte, 8)
+	for k, v := range pairs {
+		n := encodeSize(b, uint32(len(k)))
+		n += encodeSize(b[n:], uint32(len(v)))
+		if _, err := w.Write(b[:n]); err != nil {
+			return err
+		}
+		if _, err := w.WriteString(k); err != nil {
+			return err
+		}
+		if _, err := w.WriteString(v); err != nil {
+			return err
+		}
+	}
+	w.Close()
+	return nil
+}
+
+func readSize(s []byte) (uint32, int) {
+	if len(s) == 0 {
+		return 0, 0
+	}
+	size, n := uint32(s[0]), 1
+	if size&(1<<7) != 0 {
+		if len(s) < 4 {
+			return 0, 0
+		}
+		n = 4
+		size = binary.BigEndian.Uint32(s)
+		size &^= 1 << 31
+	}
+	return size, n
+}
+
+func readString(s []byte, size uint32) string {
+	if size > uint32(len(s)) {
+		return ""
+	}
+	return string(s[:size])
+}
+
+func encodeSize(b []byte, size uint32) int {
+	if size > 127 {
+		size |= 1 << 31
+		binary.BigEndian.PutUint32(b, size)
+		return 4
+	}
+	b[0] = byte(size)
+	return 1
+}
+
+// bufWriter encapsulates bufio.Writer but also closes the underlying stream when
+// Closed.
+type bufWriter struct {
+	closer io.Closer
+	*bufio.Writer
+}
+
+func (w *bufWriter) Close() error {
+	if err := w.Writer.Flush(); err != nil {
+		w.closer.Close()
+		return err
+	}
+	return w.closer.Close()
+}
+
+func newWriter(c *conn, recType recType, reqId uint16) *bufWriter {
+	s := &streamWriter{c: c, recType: recType, reqId: reqId}
+	w := bufio.NewWriterSize(s, maxWrite)
+	return &bufWriter{s, w}
+}
+
+// streamWriter abstracts out the separation of a stream into discrete records.
+// It only writes maxWrite bytes at a time.
+type streamWriter struct {
+	c       *conn
+	recType recType
+	reqId   uint16
+}
+
+func (w *streamWriter) Write(p []byte) (int, error) {
+	nn := 0
+	for len(p) > 0 {
+		n := len(p)
+		if n > maxWrite {
+			n = maxWrite
+		}
+		if err := w.c.writeRecord(w.recType, w.reqId, p[:n]); err != nil {
+			return nn, err
+		}
+		nn += n
+		p = p[n:]
+	}
+	return nn, nil
+}
+
+func (w *streamWriter) Close() error {
+	// send empty record to close the stream
+	return w.c.writeRecord(w.recType, w.reqId, nil)
+}
diff --git a/src/net/http/fcgi/fcgi_test.go b/src/net/http/fcgi/fcgi_test.go
new file mode 100644
index 000000000..6c7e1a9ce
--- /dev/null
+++ b/src/net/http/fcgi/fcgi_test.go
@@ -0,0 +1,150 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package fcgi
+
+import (
+	"bytes"
+	"errors"
+	"io"
+	"testing"
+)
+
+var sizeTests = []struct {
+	size  uint32
+	bytes []byte
+}{
+	{0, []byte{0x00}},
+	{127, []byte{0x7F}},
+	{128, []byte{0x80, 0x00, 0x00, 0x80}},
+	{1000, []byte{0x80, 0x00, 0x03, 0xE8}},
+	{33554431, []byte{0x81, 0xFF, 0xFF, 0xFF}},
+}
+
+func TestSize(t *testing.T) {
+	b := make([]byte, 4)
+	for i, test := range sizeTests {
+		n := encodeSize(b, test.size)
+		if !bytes.Equal(b[:n], test.bytes) {
+			t.Errorf("%d expected %x, encoded %x", i, test.bytes, b)
+		}
+		size, n := readSize(test.bytes)
+		if size != test.size {
+			t.Errorf("%d expected %d, read %d", i, test.size, size)
+		}
+		if len(test.bytes) != n {
+			t.Errorf("%d did not consume all the bytes", i)
+		}
+	}
+}
+
+var streamTests = []struct {
+	desc    string
+	recType recType
+	reqId   uint16
+	content []byte
+	raw     []byte
+}{
+	{"single record", typeStdout, 1, nil,
+		[]byte{1, byte(typeStdout), 0, 1, 0, 0, 0, 0},
+	},
+	// this data will have to be split into two records
+	{"two records", typeStdin, 300, make([]byte, 66000),
+		bytes.Join([][]byte{
+			// header for the first record
+			{1, byte(typeStdin), 0x01, 0x2C, 0xFF, 0xFF, 1, 0},
+			make([]byte, 65536),
+			// header for the second
+			{1, byte(typeStdin), 0x01, 0x2C, 0x01, 0xD1, 7, 0},
+			make([]byte, 472),
+			// header for the empty record
+			{1, byte(typeStdin), 0x01, 0x2C, 0, 0, 0, 0},
+		},
+			nil),
+	},
+}
+
+type nilCloser struct {
+	io.ReadWriter
+}
+
+func (c *nilCloser) Close() error { return nil }
+
+func TestStreams(t *testing.T) {
+	var rec record
+outer:
+	for _, test := range streamTests {
+		buf := bytes.NewBuffer(test.raw)
+		var content []byte
+		for buf.Len() > 0 {
+			if err := rec.read(buf); err != nil {
+				t.Errorf("%s: error reading record: %v", test.desc, err)
+				continue outer
+			}
+			content = append(content, rec.content()...)
+		}
+		if rec.h.Type != test.recType {
+			t.Errorf("%s: got type %d expected %d", test.desc, rec.h.Type, test.recType)
+			continue
+		}
+		if rec.h.Id != test.reqId {
+			t.Errorf("%s: got request ID %d expected %d", test.desc, rec.h.Id, test.reqId)
+			continue
+		}
+		if !bytes.Equal(content, test.content) {
+			t.Errorf("%s: read wrong content", test.desc)
+			continue
+		}
+		buf.Reset()
+		c := newConn(&nilCloser{buf})
+		w := newWriter(c, test.recType, test.reqId)
+		if _, err := w.Write(test.content); err != nil {
+			t.Errorf("%s: error writing record: %v", test.desc, err)
+			continue
+		}
+		if err := w.Close(); err != nil {
+			t.Errorf("%s: error closing stream: %v", test.desc, err)
+			continue
+		}
+		if !bytes.Equal(buf.Bytes(), test.raw) {
+			t.Errorf("%s: wrote wrong content", test.desc)
+		}
+	}
+}
+
+type writeOnlyConn struct {
+	buf []byte
+}
+
+func (c *writeOnlyConn) Write(p []byte) (int, error) {
+	c.buf = append(c.buf, p...)
+	return len(p), nil
+}
+
+func (c *writeOnlyConn) Read(p []byte) (int, error) {
+	return 0, errors.New("conn is write-only")
+}
+
+func (c *writeOnlyConn) Close() error {
+	return nil
+}
+
+func TestGetValues(t *testing.T) {
+	var rec record
+	rec.h.Type = typeGetValues
+
+	wc := new(writeOnlyConn)
+	c := newChild(wc, nil)
+	err := c.handleRecord(&rec)
+	if err != nil {
+		t.Fatalf("handleRecord: %v", err)
+	}
+
+	const want = "\x01\n\x00\x00\x00\x12\x06\x00" +
+		"\x0f\x01FCGI_MPXS_CONNS1" +
+		"\x00\x00\x00\x00\x00\x00\x01\n\x00\x00\x00\x00\x00\x00"
+	if got := string(wc.buf); got != want {
+		t.Errorf(" got: %q\nwant: %q\n", got, want)
+	}
+}
diff --git a/src/net/http/filetransport.go b/src/net/http/filetransport.go
new file mode 100644
index 000000000..821787e0c
--- /dev/null
+++ b/src/net/http/filetransport.go
@@ -0,0 +1,123 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package http
+
+import (
+	"fmt"
+	"io"
+)
+
+// fileTransport implements RoundTripper for the 'file' protocol.
+type fileTransport struct {
+	fh fileHandler
+}
+
+// NewFileTransport returns a new RoundTripper, serving the provided
+// FileSystem. The returned RoundTripper ignores the URL host in its
+// incoming requests, as well as most other properties of the
+// request.
+//
+// The typical use case for NewFileTransport is to register the "file"
+// protocol with a Transport, as in:
+//
+//   t := &http.Transport{}
+//   t.RegisterProtocol("file", http.NewFileTransport(http.Dir("/")))
+//   c := &http.Client{Transport: t}
+//   res, err := c.Get("file:///etc/passwd")
+//   ...
+func NewFileTransport(fs FileSystem) RoundTripper {
+	return fileTransport{fileHandler{fs}}
+}
+
+func (t fileTransport) RoundTrip(req *Request) (resp *Response, err error) {
+	// We start ServeHTTP in a goroutine, which may take a long
+	// time if the file is large.  The newPopulateResponseWriter
+	// call returns a channel which either ServeHTTP or finish()
+	// sends our *Response on, once the *Response itself has been
+	// populated (even if the body itself is still being
+	// written to the res.Body, a pipe)
+	rw, resc := newPopulateResponseWriter()
+	go func() {
+		t.fh.ServeHTTP(rw, req)
+		rw.finish()
+	}()
+	return <-resc, nil
+}
+
+func newPopulateResponseWriter() (*populateResponse, <-chan *Response) {
+	pr, pw := io.Pipe()
+	rw := &populateResponse{
+		ch: make(chan *Response),
+		pw: pw,
+		res: &Response{
+			Proto:      "HTTP/1.0",
+			ProtoMajor: 1,
+			Header:     make(Header),
+			Close:      true,
+			Body:       pr,
+		},
+	}
+	return rw, rw.ch
+}
+
+// populateResponse is a ResponseWriter that populates the *Response
+// in res, and writes its body to a pipe connected to the response
+// body. Once writes begin or finish() is called, the response is sent
+// on ch.
+type populateResponse struct {
+	res          *Response
+	ch           chan *Response
+	wroteHeader  bool
+	hasContent   bool
+	sentResponse bool
+	pw           *io.PipeWriter
+}
+
+func (pr *populateResponse) finish() {
+	if !pr.wroteHeader {
+		pr.WriteHeader(500)
+	}
+	if !pr.sentResponse {
+		pr.sendResponse()
+	}
+	pr.pw.Close()
+}
+
+func (pr *populateResponse) sendResponse() {
+	if pr.sentResponse {
+		return
+	}
+	pr.sentResponse = true
+
+	if pr.hasContent {
+		pr.res.ContentLength = -1
+	}
+	pr.ch <- pr.res
+}
+
+func (pr *populateResponse) Header() Header {
+	return pr.res.Header
+}
+
+func (pr *populateResponse) WriteHeader(code int) {
+	if pr.wroteHeader {
+		return
+	}
+	pr.wroteHeader = true
+
+	pr.res.StatusCode = code
+	pr.res.Status = fmt.Sprintf("%d %s", code, StatusText(code))
+}
+
+func (pr *populateResponse) Write(p []byte) (n int, err error) {
+	if !pr.wroteHeader {
+		pr.WriteHeader(StatusOK)
+	}
+	pr.hasContent = true
+	if !pr.sentResponse {
+		pr.sendResponse()
+	}
+	return pr.pw.Write(p)
+}
diff --git a/src/net/http/filetransport_test.go b/src/net/http/filetransport_test.go
new file mode 100644
index 000000000..6f1a537e2
--- /dev/null
+++ b/src/net/http/filetransport_test.go
@@ -0,0 +1,65 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package http
+
+import (
+	"io/ioutil"
+	"os"
+	"path/filepath"
+	"testing"
+)
+
+func checker(t *testing.T) func(string, error) {
+	return func(call string, err error) {
+		if err == nil {
+			return
+		}
+		t.Fatalf("%s: %v", call, err)
+	}
+}
+
+func TestFileTransport(t *testing.T) {
+	check := checker(t)
+
+	dname, err := ioutil.TempDir("", "")
+	check("TempDir", err)
+	fname := filepath.Join(dname, "foo.txt")
+	err = ioutil.WriteFile(fname, []byte("Bar"), 0644)
+	check("WriteFile", err)
+	defer os.Remove(dname)
+	defer os.Remove(fname)
+
+	tr := &Transport{}
+	tr.RegisterProtocol("file", NewFileTransport(Dir(dname)))
+	c := &Client{Transport: tr}
+
+	fooURLs := []string{"file:///foo.txt", "file://../foo.txt"}
+	for _, urlstr := range fooURLs {
+		res, err := c.Get(urlstr)
+		check("Get "+urlstr, err)
+		if res.StatusCode != 200 {
+			t.Errorf("for %s, StatusCode = %d, want 200", urlstr, res.StatusCode)
+		}
+		if res.ContentLength != -1 {
+			t.Errorf("for %s, ContentLength = %d, want -1", urlstr, res.ContentLength)
+		}
+		if res.Body == nil {
+			t.Fatalf("for %s, nil Body", urlstr)
+		}
+		slurp, err := ioutil.ReadAll(res.Body)
+		check("ReadAll "+urlstr, err)
+		if string(slurp) != "Bar" {
+			t.Errorf("for %s, got content %q, want %q", urlstr, string(slurp), "Bar")
+		}
+	}
+
+	const badURL = "file://../no-exist.txt"
+	res, err := c.Get(badURL)
+	check("Get "+badURL, err)
+	if res.StatusCode != 404 {
+		t.Errorf("for %s, StatusCode = %d, want 404", badURL, res.StatusCode)
+	}
+	res.Body.Close()
+}
diff --git a/src/net/http/fs.go b/src/net/http/fs.go
new file mode 100644
index 000000000..bae902cd2
--- /dev/null
+++ b/src/net/http/fs.go
@@ -0,0 +1,552 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// HTTP file system request handler
+
+package http
+
+import (
+	"errors"
+	"fmt"
+	"io"
+	"mime"
+	"mime/multipart"
+	"net/textproto"
+	"net/url"
+	"os"
+	"path"
+	"path/filepath"
+	"strconv"
+	"strings"
+	"time"
+)
+
+// A Dir implements http.FileSystem using the native file
+// system restricted to a specific directory tree.
+//
+// An empty Dir is treated as ".".
+type Dir string
+
+func (d Dir) Open(name string) (File, error) {
+	if filepath.Separator != '/' && strings.IndexRune(name, filepath.Separator) >= 0 ||
+		strings.Contains(name, "\x00") {
+		return nil, errors.New("http: invalid character in file path")
+	}
+	dir := string(d)
+	if dir == "" {
+		dir = "."
+	}
+	f, err := os.Open(filepath.Join(dir, filepath.FromSlash(path.Clean("/"+name))))
+	if err != nil {
+		return nil, err
+	}
+	return f, nil
+}
+
+// A FileSystem implements access to a collection of named files.
+// The elements in a file path are separated by slash ('/', U+002F)
+// characters, regardless of host operating system convention.
+type FileSystem interface {
+	Open(name string) (File, error)
+}
+
+// A File is returned by a FileSystem's Open method and can be
+// served by the FileServer implementation.
+//
+// The methods should behave the same as those on an *os.File.
+type File interface {
+	io.Closer
+	io.Reader
+	Readdir(count int) ([]os.FileInfo, error)
+	Seek(offset int64, whence int) (int64, error)
+	Stat() (os.FileInfo, error)
+}
+
+func dirList(w ResponseWriter, f File) {
+	w.Header().Set("Content-Type", "text/html; charset=utf-8")
+	fmt.Fprintf(w, "<pre>\n")
+	for {
+		dirs, err := f.Readdir(100)
+		if err != nil || len(dirs) == 0 {
+			break
+		}
+		for _, d := range dirs {
+			name := d.Name()
+			if d.IsDir() {
+				name += "/"
+			}
+			// name may contain '?' or '#', which must be escaped to remain
+			// part of the URL path, and not indicate the start of a query
+			// string or fragment.
+			url := url.URL{Path: name}
+			fmt.Fprintf(w, "<a href=\"%s\">%s</a>\n", url.String(), htmlReplacer.Replace(name))
+		}
+	}
+	fmt.Fprintf(w, "</pre>\n")
+}
+
+// ServeContent replies to the request using the content in the
+// provided ReadSeeker.  The main benefit of ServeContent over io.Copy
+// is that it handles Range requests properly, sets the MIME type, and
+// handles If-Modified-Since requests.
+//
+// If the response's Content-Type header is not set, ServeContent
+// first tries to deduce the type from name's file extension and,
+// if that fails, falls back to reading the first block of the content
+// and passing it to DetectContentType.
+// The name is otherwise unused; in particular it can be empty and is
+// never sent in the response.
+//
+// If modtime is not the zero time, ServeContent includes it in a
+// Last-Modified header in the response.  If the request includes an
+// If-Modified-Since header, ServeContent uses modtime to decide
+// whether the content needs to be sent at all.
+//
+// The content's Seek method must work: ServeContent uses
+// a seek to the end of the content to determine its size.
+//
+// If the caller has set w's ETag header, ServeContent uses it to
+// handle requests using If-Range and If-None-Match.
+//
+// Note that *os.File implements the io.ReadSeeker interface.
+func ServeContent(w ResponseWriter, req *Request, name string, modtime time.Time, content io.ReadSeeker) {
+	sizeFunc := func() (int64, error) {
+		size, err := content.Seek(0, os.SEEK_END)
+		if err != nil {
+			return 0, errSeeker
+		}
+		_, err = content.Seek(0, os.SEEK_SET)
+		if err != nil {
+			return 0, errSeeker
+		}
+		return size, nil
+	}
+	serveContent(w, req, name, modtime, sizeFunc, content)
+}
+
+// errSeeker is returned by ServeContent's sizeFunc when the content
+// doesn't seek properly. The underlying Seeker's error text isn't
+// included in the sizeFunc reply so it's not sent over HTTP to end
+// users.
+var errSeeker = errors.New("seeker can't seek")
+
+// if name is empty, filename is unknown. (used for mime type, before sniffing)
+// if modtime.IsZero(), modtime is unknown.
+// content must be seeked to the beginning of the file.
+// The sizeFunc is called at most once. Its error, if any, is sent in the HTTP response.
+func serveContent(w ResponseWriter, r *Request, name string, modtime time.Time, sizeFunc func() (int64, error), content io.ReadSeeker) {
+	if checkLastModified(w, r, modtime) {
+		return
+	}
+	rangeReq, done := checkETag(w, r, modtime)
+	if done {
+		return
+	}
+
+	code := StatusOK
+
+	// If Content-Type isn't set, use the file's extension to find it, but
+	// if the Content-Type is unset explicitly, do not sniff the type.
+	ctypes, haveType := w.Header()["Content-Type"]
+	var ctype string
+	if !haveType {
+		ctype = mime.TypeByExtension(filepath.Ext(name))
+		if ctype == "" {
+			// read a chunk to decide between utf-8 text and binary
+			var buf [sniffLen]byte
+			n, _ := io.ReadFull(content, buf[:])
+			ctype = DetectContentType(buf[:n])
+			_, err := content.Seek(0, os.SEEK_SET) // rewind to output whole file
+			if err != nil {
+				Error(w, "seeker can't seek", StatusInternalServerError)
+				return
+			}
+		}
+		w.Header().Set("Content-Type", ctype)
+	} else if len(ctypes) > 0 {
+		ctype = ctypes[0]
+	}
+
+	size, err := sizeFunc()
+	if err != nil {
+		Error(w, err.Error(), StatusInternalServerError)
+		return
+	}
+
+	// handle Content-Range header.
+	sendSize := size
+	var sendContent io.Reader = content
+	if size >= 0 {
+		ranges, err := parseRange(rangeReq, size)
+		if err != nil {
+			Error(w, err.Error(), StatusRequestedRangeNotSatisfiable)
+			return
+		}
+		if sumRangesSize(ranges) > size {
+			// The total number of bytes in all the ranges
+			// is larger than the size of the file by
+			// itself, so this is probably an attack, or a
+			// dumb client.  Ignore the range request.
+			ranges = nil
+		}
+		switch {
+		case len(ranges) == 1:
+			// RFC 2616, Section 14.16:
+			// "When an HTTP message includes the content of a single
+			// range (for example, a response to a request for a
+			// single range, or to a request for a set of ranges
+			// that overlap without any holes), this content is
+			// transmitted with a Content-Range header, and a
+			// Content-Length header showing the number of bytes
+			// actually transferred.
+			// ...
+			// A response to a request for a single range MUST NOT
+			// be sent using the multipart/byteranges media type."
+			ra := ranges[0]
+			if _, err := content.Seek(ra.start, os.SEEK_SET); err != nil {
+				Error(w, err.Error(), StatusRequestedRangeNotSatisfiable)
+				return
+			}
+			sendSize = ra.length
+			code = StatusPartialContent
+			w.Header().Set("Content-Range", ra.contentRange(size))
+		case len(ranges) > 1:
+			sendSize = rangesMIMESize(ranges, ctype, size)
+			code = StatusPartialContent
+
+			pr, pw := io.Pipe()
+			mw := multipart.NewWriter(pw)
+			w.Header().Set("Content-Type", "multipart/byteranges; boundary="+mw.Boundary())
+			sendContent = pr
+			defer pr.Close() // cause writing goroutine to fail and exit if CopyN doesn't finish.
+			go func() {
+				for _, ra := range ranges {
+					part, err := mw.CreatePart(ra.mimeHeader(ctype, size))
+					if err != nil {
+						pw.CloseWithError(err)
+						return
+					}
+					if _, err := content.Seek(ra.start, os.SEEK_SET); err != nil {
+						pw.CloseWithError(err)
+						return
+					}
+					if _, err := io.CopyN(part, content, ra.length); err != nil {
+						pw.CloseWithError(err)
+						return
+					}
+				}
+				mw.Close()
+				pw.Close()
+			}()
+		}
+
+		w.Header().Set("Accept-Ranges", "bytes")
+		if w.Header().Get("Content-Encoding") == "" {
+			w.Header().Set("Content-Length", strconv.FormatInt(sendSize, 10))
+		}
+	}
+
+	w.WriteHeader(code)
+
+	if r.Method != "HEAD" {
+		io.CopyN(w, sendContent, sendSize)
+	}
+}
+
+// modtime is the modification time of the resource to be served, or IsZero().
+// return value is whether this request is now complete.
+func checkLastModified(w ResponseWriter, r *Request, modtime time.Time) bool {
+	if modtime.IsZero() {
+		return false
+	}
+
+	// The Date-Modified header truncates sub-second precision, so
+	// use mtime < t+1s instead of mtime <= t to check for unmodified.
+	if t, err := time.Parse(TimeFormat, r.Header.Get("If-Modified-Since")); err == nil && modtime.Before(t.Add(1*time.Second)) {
+		h := w.Header()
+		delete(h, "Content-Type")
+		delete(h, "Content-Length")
+		w.WriteHeader(StatusNotModified)
+		return true
+	}
+	w.Header().Set("Last-Modified", modtime.UTC().Format(TimeFormat))
+	return false
+}
+
+// checkETag implements If-None-Match and If-Range checks.
+//
+// The ETag or modtime must have been previously set in the
+// ResponseWriter's headers.  The modtime is only compared at second
+// granularity and may be the zero value to mean unknown.
+//
+// The return value is the effective request "Range" header to use and
+// whether this request is now considered done.
+func checkETag(w ResponseWriter, r *Request, modtime time.Time) (rangeReq string, done bool) {
+	etag := w.Header().get("Etag")
+	rangeReq = r.Header.get("Range")
+
+	// Invalidate the range request if the entity doesn't match the one
+	// the client was expecting.
+	// "If-Range: version" means "ignore the Range: header unless version matches the
+	// current file."
+	// We only support ETag versions.
+	// The caller must have set the ETag on the response already.
+	if ir := r.Header.get("If-Range"); ir != "" && ir != etag {
+		// The If-Range value is typically the ETag value, but it may also be
+		// the modtime date. See golang.org/issue/8367.
+		timeMatches := false
+		if !modtime.IsZero() {
+			if t, err := ParseTime(ir); err == nil && t.Unix() == modtime.Unix() {
+				timeMatches = true
+			}
+		}
+		if !timeMatches {
+			rangeReq = ""
+		}
+	}
+
+	if inm := r.Header.get("If-None-Match"); inm != "" {
+		// Must know ETag.
+		if etag == "" {
+			return rangeReq, false
+		}
+
+		// TODO(bradfitz): non-GET/HEAD requests require more work:
+		// sending a different status code on matches, and
+		// also can't use weak cache validators (those with a "W/
+		// prefix).  But most users of ServeContent will be using
+		// it on GET or HEAD, so only support those for now.
+		if r.Method != "GET" && r.Method != "HEAD" {
+			return rangeReq, false
+		}
+
+		// TODO(bradfitz): deal with comma-separated or multiple-valued
+		// list of If-None-match values.  For now just handle the common
+		// case of a single item.
+		if inm == etag || inm == "*" {
+			h := w.Header()
+			delete(h, "Content-Type")
+			delete(h, "Content-Length")
+			w.WriteHeader(StatusNotModified)
+			return "", true
+		}
+	}
+	return rangeReq, false
+}
+
+// name is '/'-separated, not filepath.Separator.
+func serveFile(w ResponseWriter, r *Request, fs FileSystem, name string, redirect bool) {
+	const indexPage = "/index.html"
+
+	// redirect .../index.html to .../
+	// can't use Redirect() because that would make the path absolute,
+	// which would be a problem running under StripPrefix
+	if strings.HasSuffix(r.URL.Path, indexPage) {
+		localRedirect(w, r, "./")
+		return
+	}
+
+	f, err := fs.Open(name)
+	if err != nil {
+		// TODO expose actual error?
+		NotFound(w, r)
+		return
+	}
+	defer f.Close()
+
+	d, err1 := f.Stat()
+	if err1 != nil {
+		// TODO expose actual error?
+		NotFound(w, r)
+		return
+	}
+
+	if redirect {
+		// redirect to canonical path: / at end of directory url
+		// r.URL.Path always begins with /
+		url := r.URL.Path
+		if d.IsDir() {
+			if url[len(url)-1] != '/' {
+				localRedirect(w, r, path.Base(url)+"/")
+				return
+			}
+		} else {
+			if url[len(url)-1] == '/' {
+				localRedirect(w, r, "../"+path.Base(url))
+				return
+			}
+		}
+	}
+
+	// use contents of index.html for directory, if present
+	if d.IsDir() {
+		index := name + indexPage
+		ff, err := fs.Open(index)
+		if err == nil {
+			defer ff.Close()
+			dd, err := ff.Stat()
+			if err == nil {
+				name = index
+				d = dd
+				f = ff
+			}
+		}
+	}
+
+	// Still a directory? (we didn't find an index.html file)
+	if d.IsDir() {
+		if checkLastModified(w, r, d.ModTime()) {
+			return
+		}
+		dirList(w, f)
+		return
+	}
+
+	// serveContent will check modification time
+	sizeFunc := func() (int64, error) { return d.Size(), nil }
+	serveContent(w, r, d.Name(), d.ModTime(), sizeFunc, f)
+}
+
+// localRedirect gives a Moved Permanently response.
+// It does not convert relative paths to absolute paths like Redirect does.
+func localRedirect(w ResponseWriter, r *Request, newPath string) {
+	if q := r.URL.RawQuery; q != "" {
+		newPath += "?" + q
+	}
+	w.Header().Set("Location", newPath)
+	w.WriteHeader(StatusMovedPermanently)
+}
+
+// ServeFile replies to the request with the contents of the named file or directory.
+func ServeFile(w ResponseWriter, r *Request, name string) {
+	dir, file := filepath.Split(name)
+	serveFile(w, r, Dir(dir), file, false)
+}
+
+type fileHandler struct {
+	root FileSystem
+}
+
+// FileServer returns a handler that serves HTTP requests
+// with the contents of the file system rooted at root.
+//
+// To use the operating system's file system implementation,
+// use http.Dir:
+//
+//     http.Handle("/", http.FileServer(http.Dir("/tmp")))
+func FileServer(root FileSystem) Handler {
+	return &fileHandler{root}
+}
+
+func (f *fileHandler) ServeHTTP(w ResponseWriter, r *Request) {
+	upath := r.URL.Path
+	if !strings.HasPrefix(upath, "/") {
+		upath = "/" + upath
+		r.URL.Path = upath
+	}
+	serveFile(w, r, f.root, path.Clean(upath), true)
+}
+
+// httpRange specifies the byte range to be sent to the client.
+type httpRange struct {
+	start, length int64
+}
+
+func (r httpRange) contentRange(size int64) string {
+	return fmt.Sprintf("bytes %d-%d/%d", r.start, r.start+r.length-1, size)
+}
+
+func (r httpRange) mimeHeader(contentType string, size int64) textproto.MIMEHeader {
+	return textproto.MIMEHeader{
+		"Content-Range": {r.contentRange(size)},
+		"Content-Type":  {contentType},
+	}
+}
+
+// parseRange parses a Range header string as per RFC 2616.
+func parseRange(s string, size int64) ([]httpRange, error) {
+	if s == "" {
+		return nil, nil // header not present
+	}
+	const b = "bytes="
+	if !strings.HasPrefix(s, b) {
+		return nil, errors.New("invalid range")
+	}
+	var ranges []httpRange
+	for _, ra := range strings.Split(s[len(b):], ",") {
+		ra = strings.TrimSpace(ra)
+		if ra == "" {
+			continue
+		}
+		i := strings.Index(ra, "-")
+		if i < 0 {
+			return nil, errors.New("invalid range")
+		}
+		start, end := strings.TrimSpace(ra[:i]), strings.TrimSpace(ra[i+1:])
+		var r httpRange
+		if start == "" {
+			// If no start is specified, end specifies the
+			// range start relative to the end of the file.
+			i, err := strconv.ParseInt(end, 10, 64)
+			if err != nil {
+				return nil, errors.New("invalid range")
+			}
+			if i > size {
+				i = size
+			}
+			r.start = size - i
+			r.length = size - r.start
+		} else {
+			i, err := strconv.ParseInt(start, 10, 64)
+			if err != nil || i > size || i < 0 {
+				return nil, errors.New("invalid range")
+			}
+			r.start = i
+			if end == "" {
+				// If no end is specified, range extends to end of the file.
+				r.length = size - r.start
+			} else {
+				i, err := strconv.ParseInt(end, 10, 64)
+				if err != nil || r.start > i {
+					return nil, errors.New("invalid range")
+				}
+				if i >= size {
+					i = size - 1
+				}
+				r.length = i - r.start + 1
+			}
+		}
+		ranges = append(ranges, r)
+	}
+	return ranges, nil
+}
+
+// countingWriter counts how many bytes have been written to it.
+type countingWriter int64
+
+func (w *countingWriter) Write(p []byte) (n int, err error) {
+	*w += countingWriter(len(p))
+	return len(p), nil
+}
+
+// rangesMIMESize returns the number of bytes it takes to encode the
+// provided ranges as a multipart response.
+func rangesMIMESize(ranges []httpRange, contentType string, contentSize int64) (encSize int64) {
+	var w countingWriter
+	mw := multipart.NewWriter(&w)
+	for _, ra := range ranges {
+		mw.CreatePart(ra.mimeHeader(contentType, contentSize))
+		encSize += ra.length
+	}
+	mw.Close()
+	encSize += int64(w)
+	return
+}
+
+func sumRangesSize(ranges []httpRange) (size int64) {
+	for _, ra := range ranges {
+		size += ra.length
+	}
+	return
+}
diff --git a/src/net/http/fs_test.go b/src/net/http/fs_test.go
new file mode 100644
index 000000000..a6f33cc42
--- /dev/null
+++ b/src/net/http/fs_test.go
@@ -0,0 +1,880 @@
+// Copyright 2010 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package http_test
+
+import (
+	"bytes"
+	"errors"
+	"fmt"
+	"io"
+	"io/ioutil"
+	"mime"
+	"mime/multipart"
+	"net"
+	. "net/http"
+	"net/http/httptest"
+	"net/url"
+	"os"
+	"os/exec"
+	"path"
+	"path/filepath"
+	"reflect"
+	"regexp"
+	"runtime"
+	"strconv"
+	"strings"
+	"testing"
+	"time"
+)
+
+const (
+	testFile    = "testdata/file"
+	testFileLen = 11
+)
+
+type wantRange struct {
+	start, end int64 // range [start,end)
+}
+
+var itoa = strconv.Itoa
+
+var ServeFileRangeTests = []struct {
+	r      string
+	code   int
+	ranges []wantRange
+}{
+	{r: "", code: StatusOK},
+	{r: "bytes=0-4", code: StatusPartialContent, ranges: []wantRange{{0, 5}}},
+	{r: "bytes=2-", code: StatusPartialContent, ranges: []wantRange{{2, testFileLen}}},
+	{r: "bytes=-5", code: StatusPartialContent, ranges: []wantRange{{testFileLen - 5, testFileLen}}},
+	{r: "bytes=3-7", code: StatusPartialContent, ranges: []wantRange{{3, 8}}},
+	{r: "bytes=20-", code: StatusRequestedRangeNotSatisfiable},
+	{r: "bytes=0-0,-2", code: StatusPartialContent, ranges: []wantRange{{0, 1}, {testFileLen - 2, testFileLen}}},
+	{r: "bytes=0-1,5-8", code: StatusPartialContent, ranges: []wantRange{{0, 2}, {5, 9}}},
+	{r: "bytes=0-1,5-", code: StatusPartialContent, ranges: []wantRange{{0, 2}, {5, testFileLen}}},
+	{r: "bytes=5-1000", code: StatusPartialContent, ranges: []wantRange{{5, testFileLen}}},
+	{r: "bytes=0-,1-,2-,3-,4-", code: StatusOK}, // ignore wasteful range request
+	{r: "bytes=0-" + itoa(testFileLen-2), code: StatusPartialContent, ranges: []wantRange{{0, testFileLen - 1}}},
+	{r: "bytes=0-" + itoa(testFileLen-1), code: StatusPartialContent, ranges: []wantRange{{0, testFileLen}}},
+	{r: "bytes=0-" + itoa(testFileLen), code: StatusPartialContent, ranges: []wantRange{{0, testFileLen}}},
+}
+
+func TestServeFile(t *testing.T) {
+	defer afterTest(t)
+	ts := httptest.NewServer(HandlerFunc(func(w ResponseWriter, r *Request) {
+		ServeFile(w, r, "testdata/file")
+	}))
+	defer ts.Close()
+
+	var err error
+
+	file, err := ioutil.ReadFile(testFile)
+	if err != nil {
+		t.Fatal("reading file:", err)
+	}
+
+	// set up the Request (re-used for all tests)
+	var req Request
+	req.Header = make(Header)
+	if req.URL, err = url.Parse(ts.URL); err != nil {
+		t.Fatal("ParseURL:", err)
+	}
+	req.Method = "GET"
+
+	// straight GET
+	_, body := getBody(t, "straight get", req)
+	if !bytes.Equal(body, file) {
+		t.Fatalf("body mismatch: got %q, want %q", body, file)
+	}
+
+	// Range tests
+Cases:
+	for _, rt := range ServeFileRangeTests {
+		if rt.r != "" {
+			req.Header.Set("Range", rt.r)
+		}
+		resp, body := getBody(t, fmt.Sprintf("range test %q", rt.r), req)
+		if resp.StatusCode != rt.code {
+			t.Errorf("range=%q: StatusCode=%d, want %d", rt.r, resp.StatusCode, rt.code)
+		}
+		if rt.code == StatusRequestedRangeNotSatisfiable {
+			continue
+		}
+		wantContentRange := ""
+		if len(rt.ranges) == 1 {
+			rng := rt.ranges[0]
+			wantContentRange = fmt.Sprintf("bytes %d-%d/%d", rng.start, rng.end-1, testFileLen)
+		}
+		cr := resp.Header.Get("Content-Range")
+		if cr != wantContentRange {
+			t.Errorf("range=%q: Content-Range = %q, want %q", rt.r, cr, wantContentRange)
+		}
+		ct := resp.Header.Get("Content-Type")
+		if len(rt.ranges) == 1 {
+			rng := rt.ranges[0]
+			wantBody := file[rng.start:rng.end]
+			if !bytes.Equal(body, wantBody) {
+				t.Errorf("range=%q: body = %q, want %q", rt.r, body, wantBody)
+			}
+			if strings.HasPrefix(ct, "multipart/byteranges") {
+				t.Errorf("range=%q content-type = %q; unexpected multipart/byteranges", rt.r, ct)
+			}
+		}
+		if len(rt.ranges) > 1 {
+			typ, params, err := mime.ParseMediaType(ct)
+			if err != nil {
+				t.Errorf("range=%q content-type = %q; %v", rt.r, ct, err)
+				continue
+			}
+			if typ != "multipart/byteranges" {
+				t.Errorf("range=%q content-type = %q; want multipart/byteranges", rt.r, typ)
+				continue
+			}
+			if params["boundary"] == "" {
+				t.Errorf("range=%q content-type = %q; lacks boundary", rt.r, ct)
+				continue
+			}
+			if g, w := resp.ContentLength, int64(len(body)); g != w {
+				t.Errorf("range=%q Content-Length = %d; want %d", rt.r, g, w)
+				continue
+			}
+			mr := multipart.NewReader(bytes.NewReader(body), params["boundary"])
+			for ri, rng := range rt.ranges {
+				part, err := mr.NextPart()
+				if err != nil {
+					t.Errorf("range=%q, reading part index %d: %v", rt.r, ri, err)
+					continue Cases
+				}
+				wantContentRange = fmt.Sprintf("bytes %d-%d/%d", rng.start, rng.end-1, testFileLen)
+				if g, w := part.Header.Get("Content-Range"), wantContentRange; g != w {
+					t.Errorf("range=%q: part Content-Range = %q; want %q", rt.r, g, w)
+				}
+				body, err := ioutil.ReadAll(part)
+				if err != nil {
+					t.Errorf("range=%q, reading part index %d body: %v", rt.r, ri, err)
+					continue Cases
+				}
+				wantBody := file[rng.start:rng.end]
+				if !bytes.Equal(body, wantBody) {
+					t.Errorf("range=%q: body = %q, want %q", rt.r, body, wantBody)
+				}
+			}
+			_, err = mr.NextPart()
+			if err != io.EOF {
+				t.Errorf("range=%q; expected final error io.EOF; got %v", rt.r, err)
+			}
+		}
+	}
+}
+
+var fsRedirectTestData = []struct {
+	original, redirect string
+}{
+	{"/test/index.html", "/test/"},
+	{"/test/testdata", "/test/testdata/"},
+	{"/test/testdata/file/", "/test/testdata/file"},
+}
+
+func TestFSRedirect(t *testing.T) {
+	defer afterTest(t)
+	ts := httptest.NewServer(StripPrefix("/test", FileServer(Dir("."))))
+	defer ts.Close()
+
+	for _, data := range fsRedirectTestData {
+		res, err := Get(ts.URL + data.original)
+		if err != nil {
+			t.Fatal(err)
+		}
+		res.Body.Close()
+		if g, e := res.Request.URL.Path, data.redirect; g != e {
+			t.Errorf("redirect from %s: got %s, want %s", data.original, g, e)
+		}
+	}
+}
+
+type testFileSystem struct {
+	open func(name string) (File, error)
+}
+
+func (fs *testFileSystem) Open(name string) (File, error) {
+	return fs.open(name)
+}
+
+func TestFileServerCleans(t *testing.T) {
+	defer afterTest(t)
+	ch := make(chan string, 1)
+	fs := FileServer(&testFileSystem{func(name string) (File, error) {
+		ch <- name
+		return nil, errors.New("file does not exist")
+	}})
+	tests := []struct {
+		reqPath, openArg string
+	}{
+		{"/foo.txt", "/foo.txt"},
+		{"//foo.txt", "/foo.txt"},
+		{"/../foo.txt", "/foo.txt"},
+	}
+	req, _ := NewRequest("GET", "http://example.com", nil)
+	for n, test := range tests {
+		rec := httptest.NewRecorder()
+		req.URL.Path = test.reqPath
+		fs.ServeHTTP(rec, req)
+		if got := <-ch; got != test.openArg {
+			t.Errorf("test %d: got %q, want %q", n, got, test.openArg)
+		}
+	}
+}
+
+func TestFileServerEscapesNames(t *testing.T) {
+	defer afterTest(t)
+	const dirListPrefix = "<pre>\n"
+	const dirListSuffix = "\n</pre>\n"
+	tests := []struct {
+		name, escaped string
+	}{
+		{`simple_name`, `<a href="simple_name">simple_name</a>`},
+		{`"'<>&`, `<a href="%22%27%3C%3E&">&#34;&#39;&lt;&gt;&amp;</a>`},
+		{`?foo=bar#baz`, `<a href="%3Ffoo=bar%23baz">?foo=bar#baz</a>`},
+		{`<combo>?foo`, `<a href="%3Ccombo%3E%3Ffoo">&lt;combo&gt;?foo</a>`},
+	}
+
+	// We put each test file in its own directory in the fakeFS so we can look at it in isolation.
+	fs := make(fakeFS)
+	for i, test := range tests {
+		testFile := &fakeFileInfo{basename: test.name}
+		fs[fmt.Sprintf("/%d", i)] = &fakeFileInfo{
+			dir:     true,
+			modtime: time.Unix(1000000000, 0).UTC(),
+			ents:    []*fakeFileInfo{testFile},
+		}
+		fs[fmt.Sprintf("/%d/%s", i, test.name)] = testFile
+	}
+
+	ts := httptest.NewServer(FileServer(&fs))
+	defer ts.Close()
+	for i, test := range tests {
+		url := fmt.Sprintf("%s/%d", ts.URL, i)
+		res, err := Get(url)
+		if err != nil {
+			t.Fatalf("test %q: Get: %v", test.name, err)
+		}
+		b, err := ioutil.ReadAll(res.Body)
+		if err != nil {
+			t.Fatalf("test %q: read Body: %v", test.name, err)
+		}
+		s := string(b)
+		if !strings.HasPrefix(s, dirListPrefix) || !strings.HasSuffix(s, dirListSuffix) {
+			t.Errorf("test %q: listing dir, full output is %q, want prefix %q and suffix %q", test.name, s, dirListPrefix, dirListSuffix)
+		}
+		if trimmed := strings.TrimSuffix(strings.TrimPrefix(s, dirListPrefix), dirListSuffix); trimmed != test.escaped {
+			t.Errorf("test %q: listing dir, filename escaped to %q, want %q", test.name, trimmed, test.escaped)
+		}
+		res.Body.Close()
+	}
+}
+
+func mustRemoveAll(dir string) {
+	err := os.RemoveAll(dir)
+	if err != nil {
+		panic(err)
+	}
+}
+
+func TestFileServerImplicitLeadingSlash(t *testing.T) {
+	defer afterTest(t)
+	tempDir, err := ioutil.TempDir("", "")
+	if err != nil {
+		t.Fatalf("TempDir: %v", err)
+	}
+	defer mustRemoveAll(tempDir)
+	if err := ioutil.WriteFile(filepath.Join(tempDir, "foo.txt"), []byte("Hello world"), 0644); err != nil {
+		t.Fatalf("WriteFile: %v", err)
+	}
+	ts := httptest.NewServer(StripPrefix("/bar/", FileServer(Dir(tempDir))))
+	defer ts.Close()
+	get := func(suffix string) string {
+		res, err := Get(ts.URL + suffix)
+		if err != nil {
+			t.Fatalf("Get %s: %v", suffix, err)
+		}
+		b, err := ioutil.ReadAll(res.Body)
+		if err != nil {
+			t.Fatalf("ReadAll %s: %v", suffix, err)
+		}
+		res.Body.Close()
+		return string(b)
+	}
+	if s := get("/bar/"); !strings.Contains(s, ">foo.txt<") {
+		t.Logf("expected a directory listing with foo.txt, got %q", s)
+	}
+	if s := get("/bar/foo.txt"); s != "Hello world" {
+		t.Logf("expected %q, got %q", "Hello world", s)
+	}
+}
+
+func TestDirJoin(t *testing.T) {
+	if runtime.GOOS == "windows" {
+		t.Skip("skipping test on windows")
+	}
+	wfi, err := os.Stat("/etc/hosts")
+	if err != nil {
+		t.Skip("skipping test; no /etc/hosts file")
+	}
+	test := func(d Dir, name string) {
+		f, err := d.Open(name)
+		if err != nil {
+			t.Fatalf("open of %s: %v", name, err)
+		}
+		defer f.Close()
+		gfi, err := f.Stat()
+		if err != nil {
+			t.Fatalf("stat of %s: %v", name, err)
+		}
+		if !os.SameFile(gfi, wfi) {
+			t.Errorf("%s got different file", name)
+		}
+	}
+	test(Dir("/etc/"), "/hosts")
+	test(Dir("/etc/"), "hosts")
+	test(Dir("/etc/"), "../../../../hosts")
+	test(Dir("/etc"), "/hosts")
+	test(Dir("/etc"), "hosts")
+	test(Dir("/etc"), "../../../../hosts")
+
+	// Not really directories, but since we use this trick in
+	// ServeFile, test it:
+	test(Dir("/etc/hosts"), "")
+	test(Dir("/etc/hosts"), "/")
+	test(Dir("/etc/hosts"), "../")
+}
+
+func TestEmptyDirOpenCWD(t *testing.T) {
+	test := func(d Dir) {
+		name := "fs_test.go"
+		f, err := d.Open(name)
+		if err != nil {
+			t.Fatalf("open of %s: %v", name, err)
+		}
+		defer f.Close()
+	}
+	test(Dir(""))
+	test(Dir("."))
+	test(Dir("./"))
+}
+
+func TestServeFileContentType(t *testing.T) {
+	defer afterTest(t)
+	const ctype = "icecream/chocolate"
+	ts := httptest.NewServer(HandlerFunc(func(w ResponseWriter, r *Request) {
+		switch r.FormValue("override") {
+		case "1":
+			w.Header().Set("Content-Type", ctype)
+		case "2":
+			// Explicitly inhibit sniffing.
+			w.Header()["Content-Type"] = []string{}
+		}
+		ServeFile(w, r, "testdata/file")
+	}))
+	defer ts.Close()
+	get := func(override string, want []string) {
+		resp, err := Get(ts.URL + "?override=" + override)
+		if err != nil {
+			t.Fatal(err)
+		}
+		if h := resp.Header["Content-Type"]; !reflect.DeepEqual(h, want) {
+			t.Errorf("Content-Type mismatch: got %v, want %v", h, want)
+		}
+		resp.Body.Close()
+	}
+	get("0", []string{"text/plain; charset=utf-8"})
+	get("1", []string{ctype})
+	get("2", nil)
+}
+
+func TestServeFileMimeType(t *testing.T) {
+	defer afterTest(t)
+	ts := httptest.NewServer(HandlerFunc(func(w ResponseWriter, r *Request) {
+		ServeFile(w, r, "testdata/style.css")
+	}))
+	defer ts.Close()
+	resp, err := Get(ts.URL)
+	if err != nil {
+		t.Fatal(err)
+	}
+	resp.Body.Close()
+	want := "text/css; charset=utf-8"
+	if h := resp.Header.Get("Content-Type"); h != want {
+		t.Errorf("Content-Type mismatch: got %q, want %q", h, want)
+	}
+}
+
+func TestServeFileFromCWD(t *testing.T) {
+	defer afterTest(t)
+	ts := httptest.NewServer(HandlerFunc(func(w ResponseWriter, r *Request) {
+		ServeFile(w, r, "fs_test.go")
+	}))
+	defer ts.Close()
+	r, err := Get(ts.URL)
+	if err != nil {
+		t.Fatal(err)
+	}
+	r.Body.Close()
+	if r.StatusCode != 200 {
+		t.Fatalf("expected 200 OK, got %s", r.Status)
+	}
+}
+
+func TestServeFileWithContentEncoding(t *testing.T) {
+	defer afterTest(t)
+	ts := httptest.NewServer(HandlerFunc(func(w ResponseWriter, r *Request) {
+		w.Header().Set("Content-Encoding", "foo")
+		ServeFile(w, r, "testdata/file")
+	}))
+	defer ts.Close()
+	resp, err := Get(ts.URL)
+	if err != nil {
+		t.Fatal(err)
+	}
+	resp.Body.Close()
+	if g, e := resp.ContentLength, int64(-1); g != e {
+		t.Errorf("Content-Length mismatch: got %d, want %d", g, e)
+	}
+}
+
+func TestServeIndexHtml(t *testing.T) {
+	defer afterTest(t)
+	const want = "index.html says hello\n"
+	ts := httptest.NewServer(FileServer(Dir(".")))
+	defer ts.Close()
+
+	for _, path := range []string{"/testdata/", "/testdata/index.html"} {
+		res, err := Get(ts.URL + path)
+		if err != nil {
+			t.Fatal(err)
+		}
+		b, err := ioutil.ReadAll(res.Body)
+		if err != nil {
+			t.Fatal("reading Body:", err)
+		}
+		if s := string(b); s != want {
+			t.Errorf("for path %q got %q, want %q", path, s, want)
+		}
+		res.Body.Close()
+	}
+}
+
+func TestFileServerZeroByte(t *testing.T) {
+	defer afterTest(t)
+	ts := httptest.NewServer(FileServer(Dir(".")))
+	defer ts.Close()
+
+	res, err := Get(ts.URL + "/..\x00")
+	if err != nil {
+		t.Fatal(err)
+	}
+	b, err := ioutil.ReadAll(res.Body)
+	if err != nil {
+		t.Fatal("reading Body:", err)
+	}
+	if res.StatusCode == 200 {
+		t.Errorf("got status 200; want an error. Body is:\n%s", string(b))
+	}
+}
+
+type fakeFileInfo struct {
+	dir      bool
+	basename string
+	modtime  time.Time
+	ents     []*fakeFileInfo
+	contents string
+}
+
+func (f *fakeFileInfo) Name() string       { return f.basename }
+func (f *fakeFileInfo) Sys() interface{}   { return nil }
+func (f *fakeFileInfo) ModTime() time.Time { return f.modtime }
+func (f *fakeFileInfo) IsDir() bool        { return f.dir }
+func (f *fakeFileInfo) Size() int64        { return int64(len(f.contents)) }
+func (f *fakeFileInfo) Mode() os.FileMode {
+	if f.dir {
+		return 0755 | os.ModeDir
+	}
+	return 0644
+}
+
+type fakeFile struct {
+	io.ReadSeeker
+	fi     *fakeFileInfo
+	path   string // as opened
+	entpos int
+}
+
+func (f *fakeFile) Close() error               { return nil }
+func (f *fakeFile) Stat() (os.FileInfo, error) { return f.fi, nil }
+func (f *fakeFile) Readdir(count int) ([]os.FileInfo, error) {
+	if !f.fi.dir {
+		return nil, os.ErrInvalid
+	}
+	var fis []os.FileInfo
+
+	limit := f.entpos + count
+	if count <= 0 || limit > len(f.fi.ents) {
+		limit = len(f.fi.ents)
+	}
+	for ; f.entpos < limit; f.entpos++ {
+		fis = append(fis, f.fi.ents[f.entpos])
+	}
+
+	if len(fis) == 0 && count > 0 {
+		return fis, io.EOF
+	} else {
+		return fis, nil
+	}
+}
+
+type fakeFS map[string]*fakeFileInfo
+
+func (fs fakeFS) Open(name string) (File, error) {
+	name = path.Clean(name)
+	f, ok := fs[name]
+	if !ok {
+		return nil, os.ErrNotExist
+	}
+	return &fakeFile{ReadSeeker: strings.NewReader(f.contents), fi: f, path: name}, nil
+}
+
+func TestDirectoryIfNotModified(t *testing.T) {
+	defer afterTest(t)
+	const indexContents = "I am a fake index.html file"
+	fileMod := time.Unix(1000000000, 0).UTC()
+	fileModStr := fileMod.Format(TimeFormat)
+	dirMod := time.Unix(123, 0).UTC()
+	indexFile := &fakeFileInfo{
+		basename: "index.html",
+		modtime:  fileMod,
+		contents: indexContents,
+	}
+	fs := fakeFS{
+		"/": &fakeFileInfo{
+			dir:     true,
+			modtime: dirMod,
+			ents:    []*fakeFileInfo{indexFile},
+		},
+		"/index.html": indexFile,
+	}
+
+	ts := httptest.NewServer(FileServer(fs))
+	defer ts.Close()
+
+	res, err := Get(ts.URL)
+	if err != nil {
+		t.Fatal(err)
+	}
+	b, err := ioutil.ReadAll(res.Body)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if string(b) != indexContents {
+		t.Fatalf("Got body %q; want %q", b, indexContents)
+	}
+	res.Body.Close()
+
+	lastMod := res.Header.Get("Last-Modified")
+	if lastMod != fileModStr {
+		t.Fatalf("initial Last-Modified = %q; want %q", lastMod, fileModStr)
+	}
+
+	req, _ := NewRequest("GET", ts.URL, nil)
+	req.Header.Set("If-Modified-Since", lastMod)
+
+	res, err = DefaultClient.Do(req)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if res.StatusCode != 304 {
+		t.Fatalf("Code after If-Modified-Since request = %v; want 304", res.StatusCode)
+	}
+	res.Body.Close()
+
+	// Advance the index.html file's modtime, but not the directory's.
+	indexFile.modtime = indexFile.modtime.Add(1 * time.Hour)
+
+	res, err = DefaultClient.Do(req)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if res.StatusCode != 200 {
+		t.Fatalf("Code after second If-Modified-Since request = %v; want 200; res is %#v", res.StatusCode, res)
+	}
+	res.Body.Close()
+}
+
+func mustStat(t *testing.T, fileName string) os.FileInfo {
+	fi, err := os.Stat(fileName)
+	if err != nil {
+		t.Fatal(err)
+	}
+	return fi
+}
+
+func TestServeContent(t *testing.T) {
+	defer afterTest(t)
+	type serveParam struct {
+		name        string
+		modtime     time.Time
+		content     io.ReadSeeker
+		contentType string
+		etag        string
+	}
+	servec := make(chan serveParam, 1)
+	ts := httptest.NewServer(HandlerFunc(func(w ResponseWriter, r *Request) {
+		p := <-servec
+		if p.etag != "" {
+			w.Header().Set("ETag", p.etag)
+		}
+		if p.contentType != "" {
+			w.Header().Set("Content-Type", p.contentType)
+		}
+		ServeContent(w, r, p.name, p.modtime, p.content)
+	}))
+	defer ts.Close()
+
+	type testCase struct {
+		// One of file or content must be set:
+		file    string
+		content io.ReadSeeker
+
+		modtime          time.Time
+		serveETag        string // optional
+		serveContentType string // optional
+		reqHeader        map[string]string
+		wantLastMod      string
+		wantContentType  string
+		wantStatus       int
+	}
+	htmlModTime := mustStat(t, "testdata/index.html").ModTime()
+	tests := map[string]testCase{
+		"no_last_modified": {
+			file:            "testdata/style.css",
+			wantContentType: "text/css; charset=utf-8",
+			wantStatus:      200,
+		},
+		"with_last_modified": {
+			file:            "testdata/index.html",
+			wantContentType: "text/html; charset=utf-8",
+			modtime:         htmlModTime,
+			wantLastMod:     htmlModTime.UTC().Format(TimeFormat),
+			wantStatus:      200,
+		},
+		"not_modified_modtime": {
+			file:    "testdata/style.css",
+			modtime: htmlModTime,
+			reqHeader: map[string]string{
+				"If-Modified-Since": htmlModTime.UTC().Format(TimeFormat),
+			},
+			wantStatus: 304,
+		},
+		"not_modified_modtime_with_contenttype": {
+			file:             "testdata/style.css",
+			serveContentType: "text/css", // explicit content type
+			modtime:          htmlModTime,
+			reqHeader: map[string]string{
+				"If-Modified-Since": htmlModTime.UTC().Format(TimeFormat),
+			},
+			wantStatus: 304,
+		},
+		"not_modified_etag": {
+			file:      "testdata/style.css",
+			serveETag: `"foo"`,
+			reqHeader: map[string]string{
+				"If-None-Match": `"foo"`,
+			},
+			wantStatus: 304,
+		},
+		"not_modified_etag_no_seek": {
+			content:   panicOnSeek{nil}, // should never be called
+			serveETag: `"foo"`,
+			reqHeader: map[string]string{
+				"If-None-Match": `"foo"`,
+			},
+			wantStatus: 304,
+		},
+		"range_good": {
+			file:      "testdata/style.css",
+			serveETag: `"A"`,
+			reqHeader: map[string]string{
+				"Range": "bytes=0-4",
+			},
+			wantStatus:      StatusPartialContent,
+			wantContentType: "text/css; charset=utf-8",
+		},
+		// An If-Range resource for entity "A", but entity "B" is now current.
+		// The Range request should be ignored.
+		"range_no_match": {
+			file:      "testdata/style.css",
+			serveETag: `"A"`,
+			reqHeader: map[string]string{
+				"Range":    "bytes=0-4",
+				"If-Range": `"B"`,
+			},
+			wantStatus:      200,
+			wantContentType: "text/css; charset=utf-8",
+		},
+		"range_with_modtime": {
+			file:    "testdata/style.css",
+			modtime: time.Date(2014, 6, 25, 17, 12, 18, 0 /* nanos */, time.UTC),
+			reqHeader: map[string]string{
+				"Range":    "bytes=0-4",
+				"If-Range": "Wed, 25 Jun 2014 17:12:18 GMT",
+			},
+			wantStatus:      StatusPartialContent,
+			wantContentType: "text/css; charset=utf-8",
+			wantLastMod:     "Wed, 25 Jun 2014 17:12:18 GMT",
+		},
+		"range_with_modtime_nanos": {
+			file:    "testdata/style.css",
+			modtime: time.Date(2014, 6, 25, 17, 12, 18, 123 /* nanos */, time.UTC),
+			reqHeader: map[string]string{
+				"Range":    "bytes=0-4",
+				"If-Range": "Wed, 25 Jun 2014 17:12:18 GMT",
+			},
+			wantStatus:      StatusPartialContent,
+			wantContentType: "text/css; charset=utf-8",
+			wantLastMod:     "Wed, 25 Jun 2014 17:12:18 GMT",
+		},
+	}
+	for testName, tt := range tests {
+		var content io.ReadSeeker
+		if tt.file != "" {
+			f, err := os.Open(tt.file)
+			if err != nil {
+				t.Fatalf("test %q: %v", testName, err)
+			}
+			defer f.Close()
+			content = f
+		} else {
+			content = tt.content
+		}
+
+		servec <- serveParam{
+			name:        filepath.Base(tt.file),
+			content:     content,
+			modtime:     tt.modtime,
+			etag:        tt.serveETag,
+			contentType: tt.serveContentType,
+		}
+		req, err := NewRequest("GET", ts.URL, nil)
+		if err != nil {
+			t.Fatal(err)
+		}
+		for k, v := range tt.reqHeader {
+			req.Header.Set(k, v)
+		}
+		res, err := DefaultClient.Do(req)
+		if err != nil {
+			t.Fatal(err)
+		}
+		io.Copy(ioutil.Discard, res.Body)
+		res.Body.Close()
+		if res.StatusCode != tt.wantStatus {
+			t.Errorf("test %q: status = %d; want %d", testName, res.StatusCode, tt.wantStatus)
+		}
+		if g, e := res.Header.Get("Content-Type"), tt.wantContentType; g != e {
+			t.Errorf("test %q: content-type = %q, want %q", testName, g, e)
+		}
+		if g, e := res.Header.Get("Last-Modified"), tt.wantLastMod; g != e {
+			t.Errorf("test %q: last-modified = %q, want %q", testName, g, e)
+		}
+	}
+}
+
+// verifies that sendfile is being used on Linux
+func TestLinuxSendfile(t *testing.T) {
+	defer afterTest(t)
+	if runtime.GOOS != "linux" {
+		t.Skip("skipping; linux-only test")
+	}
+	if _, err := exec.LookPath("strace"); err != nil {
+		t.Skip("skipping; strace not found in path")
+	}
+
+	ln, err := net.Listen("tcp", "127.0.0.1:0")
+	if err != nil {
+		t.Fatal(err)
+	}
+	lnf, err := ln.(*net.TCPListener).File()
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer ln.Close()
+
+	var buf bytes.Buffer
+	child := exec.Command("strace", "-f", "-q", "-e", "trace=sendfile,sendfile64", os.Args[0], "-test.run=TestLinuxSendfileChild")
+	child.ExtraFiles = append(child.ExtraFiles, lnf)
+	child.Env = append([]string{"GO_WANT_HELPER_PROCESS=1"}, os.Environ()...)
+	child.Stdout = &buf
+	child.Stderr = &buf
+	if err := child.Start(); err != nil {
+		t.Skipf("skipping; failed to start straced child: %v", err)
+	}
+
+	res, err := Get(fmt.Sprintf("http://%s/", ln.Addr()))
+	if err != nil {
+		t.Fatalf("http client error: %v", err)
+	}
+	_, err = io.Copy(ioutil.Discard, res.Body)
+	if err != nil {
+		t.Fatalf("client body read error: %v", err)
+	}
+	res.Body.Close()
+
+	// Force child to exit cleanly.
+	Get(fmt.Sprintf("http://%s/quit", ln.Addr()))
+	child.Wait()
+
+	rx := regexp.MustCompile(`sendfile(64)?\(\d+,\s*\d+,\s*NULL,\s*\d+\)\s*=\s*\d+\s*\n`)
+	rxResume := regexp.MustCompile(`<\.\.\. sendfile(64)? resumed> \)\s*=\s*\d+\s*\n`)
+	out := buf.String()
+	if !rx.MatchString(out) && !rxResume.MatchString(out) {
+		t.Errorf("no sendfile system call found in:\n%s", out)
+	}
+}
+
+func getBody(t *testing.T, testName string, req Request) (*Response, []byte) {
+	r, err := DefaultClient.Do(&req)
+	if err != nil {
+		t.Fatalf("%s: for URL %q, send error: %v", testName, req.URL.String(), err)
+	}
+	b, err := ioutil.ReadAll(r.Body)
+	if err != nil {
+		t.Fatalf("%s: for URL %q, reading body: %v", testName, req.URL.String(), err)
+	}
+	return r, b
+}
+
+// TestLinuxSendfileChild isn't a real test. It's used as a helper process
+// for TestLinuxSendfile.
+func TestLinuxSendfileChild(*testing.T) {
+	if os.Getenv("GO_WANT_HELPER_PROCESS") != "1" {
+		return
+	}
+	defer os.Exit(0)
+	fd3 := os.NewFile(3, "ephemeral-port-listener")
+	ln, err := net.FileListener(fd3)
+	if err != nil {
+		panic(err)
+	}
+	mux := NewServeMux()
+	mux.Handle("/", FileServer(Dir("testdata")))
+	mux.HandleFunc("/quit", func(ResponseWriter, *Request) {
+		os.Exit(0)
+	})
+	s := &Server{Handler: mux}
+	err = s.Serve(ln)
+	if err != nil {
+		panic(err)
+	}
+}
+
+type panicOnSeek struct{ io.ReadSeeker }
diff --git a/src/net/http/header.go b/src/net/http/header.go
new file mode 100644
index 000000000..153b94370
--- /dev/null
+++ b/src/net/http/header.go
@@ -0,0 +1,211 @@
+// Copyright 2010 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package http
+
+import (
+	"io"
+	"net/textproto"
+	"sort"
+	"strings"
+	"sync"
+	"time"
+)
+
+var raceEnabled = false // set by race.go
+
+// A Header represents the key-value pairs in an HTTP header.
+type Header map[string][]string
+
+// Add adds the key, value pair to the header.
+// It appends to any existing values associated with key.
+func (h Header) Add(key, value string) {
+	textproto.MIMEHeader(h).Add(key, value)
+}
+
+// Set sets the header entries associated with key to
+// the single element value.  It replaces any existing
+// values associated with key.
+func (h Header) Set(key, value string) {
+	textproto.MIMEHeader(h).Set(key, value)
+}
+
+// Get gets the first value associated with the given key.
+// If there are no values associated with the key, Get returns "".
+// To access multiple values of a key, access the map directly
+// with CanonicalHeaderKey.
+func (h Header) Get(key string) string {
+	return textproto.MIMEHeader(h).Get(key)
+}
+
+// get is like Get, but key must already be in CanonicalHeaderKey form.
+func (h Header) get(key string) string {
+	if v := h[key]; len(v) > 0 {
+		return v[0]
+	}
+	return ""
+}
+
+// Del deletes the values associated with key.
+func (h Header) Del(key string) {
+	textproto.MIMEHeader(h).Del(key)
+}
+
+// Write writes a header in wire format.
+func (h Header) Write(w io.Writer) error {
+	return h.WriteSubset(w, nil)
+}
+
+func (h Header) clone() Header {
+	h2 := make(Header, len(h))
+	for k, vv := range h {
+		vv2 := make([]string, len(vv))
+		copy(vv2, vv)
+		h2[k] = vv2
+	}
+	return h2
+}
+
+var timeFormats = []string{
+	TimeFormat,
+	time.RFC850,
+	time.ANSIC,
+}
+
+// ParseTime parses a time header (such as the Date: header),
+// trying each of the three formats allowed by HTTP/1.1:
+// TimeFormat, time.RFC850, and time.ANSIC.
+func ParseTime(text string) (t time.Time, err error) {
+	for _, layout := range timeFormats {
+		t, err = time.Parse(layout, text)
+		if err == nil {
+			return
+		}
+	}
+	return
+}
+
+var headerNewlineToSpace = strings.NewReplacer("\n", " ", "\r", " ")
+
+type writeStringer interface {
+	WriteString(string) (int, error)
+}
+
+// stringWriter implements WriteString on a Writer.
+type stringWriter struct {
+	w io.Writer
+}
+
+func (w stringWriter) WriteString(s string) (n int, err error) {
+	return w.w.Write([]byte(s))
+}
+
+type keyValues struct {
+	key    string
+	values []string
+}
+
+// A headerSorter implements sort.Interface by sorting a []keyValues
+// by key. It's used as a pointer, so it can fit in a sort.Interface
+// interface value without allocation.
+type headerSorter struct {
+	kvs []keyValues
+}
+
+func (s *headerSorter) Len() int           { return len(s.kvs) }
+func (s *headerSorter) Swap(i, j int)      { s.kvs[i], s.kvs[j] = s.kvs[j], s.kvs[i] }
+func (s *headerSorter) Less(i, j int) bool { return s.kvs[i].key < s.kvs[j].key }
+
+var headerSorterPool = sync.Pool{
+	New: func() interface{} { return new(headerSorter) },
+}
+
+// sortedKeyValues returns h's keys sorted in the returned kvs
+// slice. The headerSorter used to sort is also returned, for possible
+// return to headerSorterCache.
+func (h Header) sortedKeyValues(exclude map[string]bool) (kvs []keyValues, hs *headerSorter) {
+	hs = headerSorterPool.Get().(*headerSorter)
+	if cap(hs.kvs) < len(h) {
+		hs.kvs = make([]keyValues, 0, len(h))
+	}
+	kvs = hs.kvs[:0]
+	for k, vv := range h {
+		if !exclude[k] {
+			kvs = append(kvs, keyValues{k, vv})
+		}
+	}
+	hs.kvs = kvs
+	sort.Sort(hs)
+	return kvs, hs
+}
+
+// WriteSubset writes a header in wire format.
+// If exclude is not nil, keys where exclude[key] == true are not written.
+func (h Header) WriteSubset(w io.Writer, exclude map[string]bool) error {
+	ws, ok := w.(writeStringer)
+	if !ok {
+		ws = stringWriter{w}
+	}
+	kvs, sorter := h.sortedKeyValues(exclude)
+	for _, kv := range kvs {
+		for _, v := range kv.values {
+			v = headerNewlineToSpace.Replace(v)
+			v = textproto.TrimString(v)
+			for _, s := range []string{kv.key, ": ", v, "\r\n"} {
+				if _, err := ws.WriteString(s); err != nil {
+					return err
+				}
+			}
+		}
+	}
+	headerSorterPool.Put(sorter)
+	return nil
+}
+
+// CanonicalHeaderKey returns the canonical format of the
+// header key s.  The canonicalization converts the first
+// letter and any letter following a hyphen to upper case;
+// the rest are converted to lowercase.  For example, the
+// canonical key for "accept-encoding" is "Accept-Encoding".
+func CanonicalHeaderKey(s string) string { return textproto.CanonicalMIMEHeaderKey(s) }
+
+// hasToken reports whether token appears with v, ASCII
+// case-insensitive, with space or comma boundaries.
+// token must be all lowercase.
+// v may contain mixed cased.
+func hasToken(v, token string) bool {
+	if len(token) > len(v) || token == "" {
+		return false
+	}
+	if v == token {
+		return true
+	}
+	for sp := 0; sp <= len(v)-len(token); sp++ {
+		// Check that first character is good.
+		// The token is ASCII, so checking only a single byte
+		// is sufficient.  We skip this potential starting
+		// position if both the first byte and its potential
+		// ASCII uppercase equivalent (b|0x20) don't match.
+		// False positives ('^' => '~') are caught by EqualFold.
+		if b := v[sp]; b != token[0] && b|0x20 != token[0] {
+			continue
+		}
+		// Check that start pos is on a valid token boundary.
+		if sp > 0 && !isTokenBoundary(v[sp-1]) {
+			continue
+		}
+		// Check that end pos is on a valid token boundary.
+		if endPos := sp + len(token); endPos != len(v) && !isTokenBoundary(v[endPos]) {
+			continue
+		}
+		if strings.EqualFold(v[sp:sp+len(token)], token) {
+			return true
+		}
+	}
+	return false
+}
+
+func isTokenBoundary(b byte) bool {
+	return b == ' ' || b == ',' || b == '\t'
+}
diff --git a/src/net/http/header_test.go b/src/net/http/header_test.go
new file mode 100644
index 000000000..9dcd591fa
--- /dev/null
+++ b/src/net/http/header_test.go
@@ -0,0 +1,212 @@
+// Copyright 2011 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package http
+
+import (
+	"bytes"
+	"runtime"
+	"testing"
+	"time"
+)
+
+var headerWriteTests = []struct {
+	h        Header
+	exclude  map[string]bool
+	expected string
+}{
+	{Header{}, nil, ""},
+	{
+		Header{
+			"Content-Type":   {"text/html; charset=UTF-8"},
+			"Content-Length": {"0"},
+		},
+		nil,
+		"Content-Length: 0\r\nContent-Type: text/html; charset=UTF-8\r\n",
+	},
+	{
+		Header{
+			"Content-Length": {"0", "1", "2"},
+		},
+		nil,
+		"Content-Length: 0\r\nContent-Length: 1\r\nContent-Length: 2\r\n",
+	},
+	{
+		Header{
+			"Expires":          {"-1"},
+			"Content-Length":   {"0"},
+			"Content-Encoding": {"gzip"},
+		},
+		map[string]bool{"Content-Length": true},
+		"Content-Encoding: gzip\r\nExpires: -1\r\n",
+	},
+	{
+		Header{
+			"Expires":          {"-1"},
+			"Content-Length":   {"0", "1", "2"},
+			"Content-Encoding": {"gzip"},
+		},
+		map[string]bool{"Content-Length": true},
+		"Content-Encoding: gzip\r\nExpires: -1\r\n",
+	},
+	{
+		Header{
+			"Expires":          {"-1"},
+			"Content-Length":   {"0"},
+			"Content-Encoding": {"gzip"},
+		},
+		map[string]bool{"Content-Length": true, "Expires": true, "Content-Encoding": true},
+		"",
+	},
+	{
+		Header{
+			"Nil":          nil,
+			"Empty":        {},
+			"Blank":        {""},
+			"Double-Blank": {"", ""},
+		},
+		nil,
+		"Blank: \r\nDouble-Blank: \r\nDouble-Blank: \r\n",
+	},
+	// Tests header sorting when over the insertion sort threshold side:
+	{
+		Header{
+			"k1": {"1a", "1b"},
+			"k2": {"2a", "2b"},
+			"k3": {"3a", "3b"},
+			"k4": {"4a", "4b"},
+			"k5": {"5a", "5b"},
+			"k6": {"6a", "6b"},
+			"k7": {"7a", "7b"},
+			"k8": {"8a", "8b"},
+			"k9": {"9a", "9b"},
+		},
+		map[string]bool{"k5": true},
+		"k1: 1a\r\nk1: 1b\r\nk2: 2a\r\nk2: 2b\r\nk3: 3a\r\nk3: 3b\r\n" +
+			"k4: 4a\r\nk4: 4b\r\nk6: 6a\r\nk6: 6b\r\n" +
+			"k7: 7a\r\nk7: 7b\r\nk8: 8a\r\nk8: 8b\r\nk9: 9a\r\nk9: 9b\r\n",
+	},
+}
+
+func TestHeaderWrite(t *testing.T) {
+	var buf bytes.Buffer
+	for i, test := range headerWriteTests {
+		test.h.WriteSubset(&buf, test.exclude)
+		if buf.String() != test.expected {
+			t.Errorf("#%d:\n got: %q\nwant: %q", i, buf.String(), test.expected)
+		}
+		buf.Reset()
+	}
+}
+
+var parseTimeTests = []struct {
+	h   Header
+	err bool
+}{
+	{Header{"Date": {""}}, true},
+	{Header{"Date": {"invalid"}}, true},
+	{Header{"Date": {"1994-11-06T08:49:37Z00:00"}}, true},
+	{Header{"Date": {"Sun, 06 Nov 1994 08:49:37 GMT"}}, false},
+	{Header{"Date": {"Sunday, 06-Nov-94 08:49:37 GMT"}}, false},
+	{Header{"Date": {"Sun Nov  6 08:49:37 1994"}}, false},
+}
+
+func TestParseTime(t *testing.T) {
+	expect := time.Date(1994, 11, 6, 8, 49, 37, 0, time.UTC)
+	for i, test := range parseTimeTests {
+		d, err := ParseTime(test.h.Get("Date"))
+		if err != nil {
+			if !test.err {
+				t.Errorf("#%d:\n got err: %v", i, err)
+			}
+			continue
+		}
+		if test.err {
+			t.Errorf("#%d:\n  should err", i)
+			continue
+		}
+		if !expect.Equal(d) {
+			t.Errorf("#%d:\n got: %v\nwant: %v", i, d, expect)
+		}
+	}
+}
+
+type hasTokenTest struct {
+	header string
+	token  string
+	want   bool
+}
+
+var hasTokenTests = []hasTokenTest{
+	{"", "", false},
+	{"", "foo", false},
+	{"foo", "foo", true},
+	{"foo ", "foo", true},
+	{" foo", "foo", true},
+	{" foo ", "foo", true},
+	{"foo,bar", "foo", true},
+	{"bar,foo", "foo", true},
+	{"bar, foo", "foo", true},
+	{"bar,foo, baz", "foo", true},
+	{"bar, foo,baz", "foo", true},
+	{"bar,foo, baz", "foo", true},
+	{"bar, foo, baz", "foo", true},
+	{"FOO", "foo", true},
+	{"FOO ", "foo", true},
+	{" FOO", "foo", true},
+	{" FOO ", "foo", true},
+	{"FOO,BAR", "foo", true},
+	{"BAR,FOO", "foo", true},
+	{"BAR, FOO", "foo", true},
+	{"BAR,FOO, baz", "foo", true},
+	{"BAR, FOO,BAZ", "foo", true},
+	{"BAR,FOO, BAZ", "foo", true},
+	{"BAR, FOO, BAZ", "foo", true},
+	{"foobar", "foo", false},
+	{"barfoo ", "foo", false},
+}
+
+func TestHasToken(t *testing.T) {
+	for _, tt := range hasTokenTests {
+		if hasToken(tt.header, tt.token) != tt.want {
+			t.Errorf("hasToken(%q, %q) = %v; want %v", tt.header, tt.token, !tt.want, tt.want)
+		}
+	}
+}
+
+var testHeader = Header{
+	"Content-Length": {"123"},
+	"Content-Type":   {"text/plain"},
+	"Date":           {"some date at some time Z"},
+	"Server":         {DefaultUserAgent},
+}
+
+var buf bytes.Buffer
+
+func BenchmarkHeaderWriteSubset(b *testing.B) {
+	b.ReportAllocs()
+	for i := 0; i < b.N; i++ {
+		buf.Reset()
+		testHeader.WriteSubset(&buf, nil)
+	}
+}
+
+func TestHeaderWriteSubsetAllocs(t *testing.T) {
+	if testing.Short() {
+		t.Skip("skipping alloc test in short mode")
+	}
+	if raceEnabled {
+		t.Skip("skipping test under race detector")
+	}
+	if runtime.GOMAXPROCS(0) > 1 {
+		t.Skip("skipping; GOMAXPROCS>1")
+	}
+	n := testing.AllocsPerRun(100, func() {
+		buf.Reset()
+		testHeader.WriteSubset(&buf, nil)
+	})
+	if n > 0 {
+		t.Errorf("allocs = %g; want 0", n)
+	}
+}
diff --git a/src/net/http/httptest/example_test.go b/src/net/http/httptest/example_test.go
new file mode 100644
index 000000000..42a0ec953
--- /dev/null
+++ b/src/net/http/httptest/example_test.go
@@ -0,0 +1,50 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package httptest_test
+
+import (
+	"fmt"
+	"io/ioutil"
+	"log"
+	"net/http"
+	"net/http/httptest"
+)
+
+func ExampleResponseRecorder() {
+	handler := func(w http.ResponseWriter, r *http.Request) {
+		http.Error(w, "something failed", http.StatusInternalServerError)
+	}
+
+	req, err := http.NewRequest("GET", "http://example.com/foo", nil)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	w := httptest.NewRecorder()
+	handler(w, req)
+
+	fmt.Printf("%d - %s", w.Code, w.Body.String())
+	// Output: 500 - something failed
+}
+
+func ExampleServer() {
+	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		fmt.Fprintln(w, "Hello, client")
+	}))
+	defer ts.Close()
+
+	res, err := http.Get(ts.URL)
+	if err != nil {
+		log.Fatal(err)
+	}
+	greeting, err := ioutil.ReadAll(res.Body)
+	res.Body.Close()
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	fmt.Printf("%s", greeting)
+	// Output: Hello, client
+}
diff --git a/src/net/http/httptest/recorder.go b/src/net/http/httptest/recorder.go
new file mode 100644
index 000000000..5451f5423
--- /dev/null
+++ b/src/net/http/httptest/recorder.go
@@ -0,0 +1,72 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package httptest provides utilities for HTTP testing.
+package httptest
+
+import (
+	"bytes"
+	"net/http"
+)
+
+// ResponseRecorder is an implementation of http.ResponseWriter that
+// records its mutations for later inspection in tests.
+type ResponseRecorder struct {
+	Code      int           // the HTTP response code from WriteHeader
+	HeaderMap http.Header   // the HTTP response headers
+	Body      *bytes.Buffer // if non-nil, the bytes.Buffer to append written data to
+	Flushed   bool
+
+	wroteHeader bool
+}
+
+// NewRecorder returns an initialized ResponseRecorder.
+func NewRecorder() *ResponseRecorder {
+	return &ResponseRecorder{
+		HeaderMap: make(http.Header),
+		Body:      new(bytes.Buffer),
+		Code:      200,
+	}
+}
+
+// DefaultRemoteAddr is the default remote address to return in RemoteAddr if
+// an explicit DefaultRemoteAddr isn't set on ResponseRecorder.
+const DefaultRemoteAddr = "1.2.3.4"
+
+// Header returns the response headers.
+func (rw *ResponseRecorder) Header() http.Header {
+	m := rw.HeaderMap
+	if m == nil {
+		m = make(http.Header)
+		rw.HeaderMap = m
+	}
+	return m
+}
+
+// Write always succeeds and writes to rw.Body, if not nil.
+func (rw *ResponseRecorder) Write(buf []byte) (int, error) {
+	if !rw.wroteHeader {
+		rw.WriteHeader(200)
+	}
+	if rw.Body != nil {
+		rw.Body.Write(buf)
+	}
+	return len(buf), nil
+}
+
+// WriteHeader sets rw.Code.
+func (rw *ResponseRecorder) WriteHeader(code int) {
+	if !rw.wroteHeader {
+		rw.Code = code
+	}
+	rw.wroteHeader = true
+}
+
+// Flush sets rw.Flushed to true.
+func (rw *ResponseRecorder) Flush() {
+	if !rw.wroteHeader {
+		rw.WriteHeader(200)
+	}
+	rw.Flushed = true
+}
diff --git a/src/net/http/httptest/recorder_test.go b/src/net/http/httptest/recorder_test.go
new file mode 100644
index 000000000..2b563260c
--- /dev/null
+++ b/src/net/http/httptest/recorder_test.go
@@ -0,0 +1,90 @@
+// Copyright 2012 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package httptest
+
+import (
+	"fmt"
+	"net/http"
+	"testing"
+)
+
+func TestRecorder(t *testing.T) {
+	type checkFunc func(*ResponseRecorder) error
+	check := func(fns ...checkFunc) []checkFunc { return fns }
+
+	hasStatus := func(wantCode int) checkFunc {
+		return func(rec *ResponseRecorder) error {
+			if rec.Code != wantCode {
+				return fmt.Errorf("Status = %d; want %d", rec.Code, wantCode)
+			}
+			return nil
+		}
+	}
+	hasContents := func(want string) checkFunc {
+		return func(rec *ResponseRecorder) error {
+			if rec.Body.String() != want {
+				return fmt.Errorf("wrote = %q; want %q", rec.Body.String(), want)
+			}
+			return nil
+		}
+	}
+	hasFlush := func(want bool) checkFunc {
+		return func(rec *ResponseRecorder) error {
+			if rec.Flushed != want {
+				return fmt.Errorf("Flushed = %v; want %v", rec.Flushed, want)
+			}
+			return nil
+		}
+	}
+
+	tests := []struct {
+		name   string
+		h      func(w http.ResponseWriter, r *http.Request)
+		checks []checkFunc
+	}{
+		{
+			"200 default",
+			func(w http.ResponseWriter, r *http.Request) {},
+			check(hasStatus(200), hasContents("")),
+		},
+		{
+			"first code only",
+			func(w http.ResponseWriter, r *http.Request) {
+				w.WriteHeader(201)
+				w.WriteHeader(202)
+				w.Write([]byte("hi"))
+			},
+			check(hasStatus(201), hasContents("hi")),
+		},
+		{
+			"write sends 200",
+			func(w http.ResponseWriter, r *http.Request) {
+				w.Write([]byte("hi first"))
+				w.WriteHeader(201)
+				w.WriteHeader(202)
+			},
+			check(hasStatus(200), hasContents("hi first"), hasFlush(false)),
+		},
+		{
+			"flush",
+			func(w http.ResponseWriter, r *http.Request) {
+				w.(http.Flusher).Flush() // also sends a 200
+				w.WriteHeader(201)
+			},
+			check(hasStatus(200), hasFlush(true)),
+		},
+	}
+	r, _ := http.NewRequest("GET", "http://foo.com/", nil)
+	for _, tt := range tests {
+		h := http.HandlerFunc(tt.h)
+		rec := NewRecorder()
+		h.ServeHTTP(rec, r)
+		for _, check := range tt.checks {
+			if err := check(rec); err != nil {
+				t.Errorf("%s: %v", tt.name, err)
+			}
+		}
+	}
+}
diff --git a/src/net/http/httptest/server.go b/src/net/http/httptest/server.go
new file mode 100644
index 000000000..789e7bf41
--- /dev/null
+++ b/src/net/http/httptest/server.go
@@ -0,0 +1,228 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Implementation of Server
+
+package httptest
+
+import (
+	"crypto/tls"
+	"flag"
+	"fmt"
+	"net"
+	"net/http"
+	"os"
+	"sync"
+)
+
+// A Server is an HTTP server listening on a system-chosen port on the
+// local loopback interface, for use in end-to-end HTTP tests.
+type Server struct {
+	URL      string // base URL of form http://ipaddr:port with no trailing slash
+	Listener net.Listener
+
+	// TLS is the optional TLS configuration, populated with a new config
+	// after TLS is started. If set on an unstarted server before StartTLS
+	// is called, existing fields are copied into the new config.
+	TLS *tls.Config
+
+	// Config may be changed after calling NewUnstartedServer and
+	// before Start or StartTLS.
+	Config *http.Server
+
+	// wg counts the number of outstanding HTTP requests on this server.
+	// Close blocks until all requests are finished.
+	wg sync.WaitGroup
+}
+
+// historyListener keeps track of all connections that it's ever
+// accepted.
+type historyListener struct {
+	net.Listener
+	sync.Mutex // protects history
+	history    []net.Conn
+}
+
+func (hs *historyListener) Accept() (c net.Conn, err error) {
+	c, err = hs.Listener.Accept()
+	if err == nil {
+		hs.Lock()
+		hs.history = append(hs.history, c)
+		hs.Unlock()
+	}
+	return
+}
+
+func newLocalListener() net.Listener {
+	if *serve != "" {
+		l, err := net.Listen("tcp", *serve)
+		if err != nil {
+			panic(fmt.Sprintf("httptest: failed to listen on %v: %v", *serve, err))
+		}
+		return l
+	}
+	l, err := net.Listen("tcp", "127.0.0.1:0")
+	if err != nil {
+		if l, err = net.Listen("tcp6", "[::1]:0"); err != nil {
+			panic(fmt.Sprintf("httptest: failed to listen on a port: %v", err))
+		}
+	}
+	return l
+}
+
+// When debugging a particular http server-based test,
+// this flag lets you run
+//	go test -run=BrokenTest -httptest.serve=127.0.0.1:8000
+// to start the broken server so you can interact with it manually.
+var serve = flag.String("httptest.serve", "", "if non-empty, httptest.NewServer serves on this address and blocks")
+
+// NewServer starts and returns a new Server.
+// The caller should call Close when finished, to shut it down.
+func NewServer(handler http.Handler) *Server {
+	ts := NewUnstartedServer(handler)
+	ts.Start()
+	return ts
+}
+
+// NewUnstartedServer returns a new Server but doesn't start it.
+//
+// After changing its configuration, the caller should call Start or
+// StartTLS.
+//
+// The caller should call Close when finished, to shut it down.
+func NewUnstartedServer(handler http.Handler) *Server {
+	return &Server{
+		Listener: newLocalListener(),
+		Config:   &http.Server{Handler: handler},
+	}
+}
+
+// Start starts a server from NewUnstartedServer.
+func (s *Server) Start() {
+	if s.URL != "" {
+		panic("Server already started")
+	}
+	s.Listener = &historyListener{Listener: s.Listener}
+	s.URL = "http://" + s.Listener.Addr().String()
+	s.wrapHandler()
+	go s.Config.Serve(s.Listener)
+	if *serve != "" {
+		fmt.Fprintln(os.Stderr, "httptest: serving on", s.URL)
+		select {}
+	}
+}
+
+// StartTLS starts TLS on a server from NewUnstartedServer.
+func (s *Server) StartTLS() {
+	if s.URL != "" {
+		panic("Server already started")
+	}
+	cert, err := tls.X509KeyPair(localhostCert, localhostKey)
+	if err != nil {
+		panic(fmt.Sprintf("httptest: NewTLSServer: %v", err))
+	}
+
+	existingConfig := s.TLS
+	s.TLS = new(tls.Config)
+	if existingConfig != nil {
+		*s.TLS = *existingConfig
+	}
+	if s.TLS.NextProtos == nil {
+		s.TLS.NextProtos = []string{"http/1.1"}
+	}
+	if len(s.TLS.Certificates) == 0 {
+		s.TLS.Certificates = []tls.Certificate{cert}
+	}
+	tlsListener := tls.NewListener(s.Listener, s.TLS)
+
+	s.Listener = &historyListener{Listener: tlsListener}
+	s.URL = "https://" + s.Listener.Addr().String()
+	s.wrapHandler()
+	go s.Config.Serve(s.Listener)
+}
+
+func (s *Server) wrapHandler() {
+	h := s.Config.Handler
+	if h == nil {
+		h = http.DefaultServeMux
+	}
+	s.Config.Handler = &waitGroupHandler{
+		s: s,
+		h: h,
+	}
+}
+
+// NewTLSServer starts and returns a new Server using TLS.
+// The caller should call Close when finished, to shut it down.
+func NewTLSServer(handler http.Handler) *Server {
+	ts := NewUnstartedServer(handler)
+	ts.StartTLS()
+	return ts
+}
+
+// Close shuts down the server and blocks until all outstanding
+// requests on this server have completed.
+func (s *Server) Close() {
+	s.Listener.Close()
+	s.wg.Wait()
+	s.CloseClientConnections()
+	if t, ok := http.DefaultTransport.(*http.Transport); ok {
+		t.CloseIdleConnections()
+	}
+}
+
+// CloseClientConnections closes any currently open HTTP connections
+// to the test Server.
+func (s *Server) CloseClientConnections() {
+	hl, ok := s.Listener.(*historyListener)
+	if !ok {
+		return
+	}
+	hl.Lock()
+	for _, conn := range hl.history {
+		conn.Close()
+	}
+	hl.Unlock()
+}
+
+// waitGroupHandler wraps a handler, incrementing and decrementing a
+// sync.WaitGroup on each request, to enable Server.Close to block
+// until outstanding requests are finished.
+type waitGroupHandler struct {
+	s *Server
+	h http.Handler // non-nil
+}
+
+func (h *waitGroupHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
+	h.s.wg.Add(1)
+	defer h.s.wg.Done() // a defer, in case ServeHTTP below panics
+	h.h.ServeHTTP(w, r)
+}
+
+// localhostCert is a PEM-encoded TLS cert with SAN IPs
+// "127.0.0.1" and "[::1]", expiring at the last second of 2049 (the end
+// of ASN.1 time).
+// generated from src/crypto/tls:
+// go run generate_cert.go  --rsa-bits 512 --host 127.0.0.1,::1,example.com --ca --start-date "Jan 1 00:00:00 1970" --duration=1000000h
+var localhostCert = []byte(`-----BEGIN CERTIFICATE-----
+MIIBdzCCASOgAwIBAgIBADALBgkqhkiG9w0BAQUwEjEQMA4GA1UEChMHQWNtZSBD
+bzAeFw03MDAxMDEwMDAwMDBaFw00OTEyMzEyMzU5NTlaMBIxEDAOBgNVBAoTB0Fj
+bWUgQ28wWjALBgkqhkiG9w0BAQEDSwAwSAJBAN55NcYKZeInyTuhcCwFMhDHCmwa
+IUSdtXdcbItRB/yfXGBhiex00IaLXQnSU+QZPRZWYqeTEbFSgihqi1PUDy8CAwEA
+AaNoMGYwDgYDVR0PAQH/BAQDAgCkMBMGA1UdJQQMMAoGCCsGAQUFBwMBMA8GA1Ud
+EwEB/wQFMAMBAf8wLgYDVR0RBCcwJYILZXhhbXBsZS5jb22HBH8AAAGHEAAAAAAA
+AAAAAAAAAAAAAAEwCwYJKoZIhvcNAQEFA0EAAoQn/ytgqpiLcZu9XKbCJsJcvkgk
+Se6AbGXgSlq+ZCEVo0qIwSgeBqmsJxUu7NCSOwVJLYNEBO2DtIxoYVk+MA==
+-----END CERTIFICATE-----`)
+
+// localhostKey is the private key for localhostCert.
+var localhostKey = []byte(`-----BEGIN RSA PRIVATE KEY-----
+MIIBPAIBAAJBAN55NcYKZeInyTuhcCwFMhDHCmwaIUSdtXdcbItRB/yfXGBhiex0
+0IaLXQnSU+QZPRZWYqeTEbFSgihqi1PUDy8CAwEAAQJBAQdUx66rfh8sYsgfdcvV
+NoafYpnEcB5s4m/vSVe6SU7dCK6eYec9f9wpT353ljhDUHq3EbmE4foNzJngh35d
+AekCIQDhRQG5Li0Wj8TM4obOnnXUXf1jRv0UkzE9AHWLG5q3AwIhAPzSjpYUDjVW
+MCUXgckTpKCuGwbJk7424Nb8bLzf3kllAiA5mUBgjfr/WtFSJdWcPQ4Zt9KTMNKD
+EUO0ukpTwEIl6wIhAMbGqZK3zAAFdq8DD2jPx+UJXnh0rnOkZBzDtJ6/iN69AiEA
+1Aq8MJgTaYsDQWyU/hDq5YkDJc9e9DSCvUIzqxQWMQE=
+-----END RSA PRIVATE KEY-----`)
diff --git a/src/net/http/httptest/server_test.go b/src/net/http/httptest/server_test.go
new file mode 100644
index 000000000..500a9f0b8
--- /dev/null
+++ b/src/net/http/httptest/server_test.go
@@ -0,0 +1,29 @@
+// Copyright 2012 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package httptest
+
+import (
+	"io/ioutil"
+	"net/http"
+	"testing"
+)
+
+func TestServer(t *testing.T) {
+	ts := NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.Write([]byte("hello"))
+	}))
+	defer ts.Close()
+	res, err := http.Get(ts.URL)
+	if err != nil {
+		t.Fatal(err)
+	}
+	got, err := ioutil.ReadAll(res.Body)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if string(got) != "hello" {
+		t.Errorf("got %q, want hello", string(got))
+	}
+}
diff --git a/src/net/http/httputil/dump.go b/src/net/http/httputil/dump.go
new file mode 100644
index 000000000..2a7a413d0
--- /dev/null
+++ b/src/net/http/httputil/dump.go
@@ -0,0 +1,276 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package httputil
+
+import (
+	"bufio"
+	"bytes"
+	"errors"
+	"fmt"
+	"io"
+	"io/ioutil"
+	"net"
+	"net/http"
+	"net/url"
+	"strings"
+	"time"
+)
+
+// One of the copies, say from b to r2, could be avoided by using a more
+// elaborate trick where the other copy is made during Request/Response.Write.
+// This would complicate things too much, given that these functions are for
+// debugging only.
+func drainBody(b io.ReadCloser) (r1, r2 io.ReadCloser, err error) {
+	var buf bytes.Buffer
+	if _, err = buf.ReadFrom(b); err != nil {
+		return nil, nil, err
+	}
+	if err = b.Close(); err != nil {
+		return nil, nil, err
+	}
+	return ioutil.NopCloser(&buf), ioutil.NopCloser(bytes.NewReader(buf.Bytes())), nil
+}
+
+// dumpConn is a net.Conn which writes to Writer and reads from Reader
+type dumpConn struct {
+	io.Writer
+	io.Reader
+}
+
+func (c *dumpConn) Close() error                       { return nil }
+func (c *dumpConn) LocalAddr() net.Addr                { return nil }
+func (c *dumpConn) RemoteAddr() net.Addr               { return nil }
+func (c *dumpConn) SetDeadline(t time.Time) error      { return nil }
+func (c *dumpConn) SetReadDeadline(t time.Time) error  { return nil }
+func (c *dumpConn) SetWriteDeadline(t time.Time) error { return nil }
+
+type neverEnding byte
+
+func (b neverEnding) Read(p []byte) (n int, err error) {
+	for i := range p {
+		p[i] = byte(b)
+	}
+	return len(p), nil
+}
+
+// DumpRequestOut is like DumpRequest but includes
+// headers that the standard http.Transport adds,
+// such as User-Agent.
+func DumpRequestOut(req *http.Request, body bool) ([]byte, error) {
+	save := req.Body
+	dummyBody := false
+	if !body || req.Body == nil {
+		req.Body = nil
+		if req.ContentLength != 0 {
+			req.Body = ioutil.NopCloser(io.LimitReader(neverEnding('x'), req.ContentLength))
+			dummyBody = true
+		}
+	} else {
+		var err error
+		save, req.Body, err = drainBody(req.Body)
+		if err != nil {
+			return nil, err
+		}
+	}
+
+	// Since we're using the actual Transport code to write the request,
+	// switch to http so the Transport doesn't try to do an SSL
+	// negotiation with our dumpConn and its bytes.Buffer & pipe.
+	// The wire format for https and http are the same, anyway.
+	reqSend := req
+	if req.URL.Scheme == "https" {
+		reqSend = new(http.Request)
+		*reqSend = *req
+		reqSend.URL = new(url.URL)
+		*reqSend.URL = *req.URL
+		reqSend.URL.Scheme = "http"
+	}
+
+	// Use the actual Transport code to record what we would send
+	// on the wire, but not using TCP.  Use a Transport with a
+	// custom dialer that returns a fake net.Conn that waits
+	// for the full input (and recording it), and then responds
+	// with a dummy response.
+	var buf bytes.Buffer // records the output
+	pr, pw := io.Pipe()
+	dr := &delegateReader{c: make(chan io.Reader)}
+	// Wait for the request before replying with a dummy response:
+	go func() {
+		http.ReadRequest(bufio.NewReader(pr))
+		dr.c <- strings.NewReader("HTTP/1.1 204 No Content\r\n\r\n")
+	}()
+
+	t := &http.Transport{
+		Dial: func(net, addr string) (net.Conn, error) {
+			return &dumpConn{io.MultiWriter(&buf, pw), dr}, nil
+		},
+	}
+	defer t.CloseIdleConnections()
+
+	_, err := t.RoundTrip(reqSend)
+
+	req.Body = save
+	if err != nil {
+		return nil, err
+	}
+	dump := buf.Bytes()
+
+	// If we used a dummy body above, remove it now.
+	// TODO: if the req.ContentLength is large, we allocate memory
+	// unnecessarily just to slice it off here.  But this is just
+	// a debug function, so this is acceptable for now. We could
+	// discard the body earlier if this matters.
+	if dummyBody {
+		if i := bytes.Index(dump, []byte("\r\n\r\n")); i >= 0 {
+			dump = dump[:i+4]
+		}
+	}
+	return dump, nil
+}
+
+// delegateReader is a reader that delegates to another reader,
+// once it arrives on a channel.
+type delegateReader struct {
+	c chan io.Reader
+	r io.Reader // nil until received from c
+}
+
+func (r *delegateReader) Read(p []byte) (int, error) {
+	if r.r == nil {
+		r.r = <-r.c
+	}
+	return r.r.Read(p)
+}
+
+// Return value if nonempty, def otherwise.
+func valueOrDefault(value, def string) string {
+	if value != "" {
+		return value
+	}
+	return def
+}
+
+var reqWriteExcludeHeaderDump = map[string]bool{
+	"Host":              true, // not in Header map anyway
+	"Content-Length":    true,
+	"Transfer-Encoding": true,
+	"Trailer":           true,
+}
+
+// dumpAsReceived writes req to w in the form as it was received, or
+// at least as accurately as possible from the information retained in
+// the request.
+func dumpAsReceived(req *http.Request, w io.Writer) error {
+	return nil
+}
+
+// DumpRequest returns the as-received wire representation of req,
+// optionally including the request body, for debugging.
+// DumpRequest is semantically a no-op, but in order to
+// dump the body, it reads the body data into memory and
+// changes req.Body to refer to the in-memory copy.
+// The documentation for http.Request.Write details which fields
+// of req are used.
+func DumpRequest(req *http.Request, body bool) (dump []byte, err error) {
+	save := req.Body
+	if !body || req.Body == nil {
+		req.Body = nil
+	} else {
+		save, req.Body, err = drainBody(req.Body)
+		if err != nil {
+			return
+		}
+	}
+
+	var b bytes.Buffer
+
+	fmt.Fprintf(&b, "%s %s HTTP/%d.%d\r\n", valueOrDefault(req.Method, "GET"),
+		req.URL.RequestURI(), req.ProtoMajor, req.ProtoMinor)
+
+	host := req.Host
+	if host == "" && req.URL != nil {
+		host = req.URL.Host
+	}
+	if host != "" {
+		fmt.Fprintf(&b, "Host: %s\r\n", host)
+	}
+
+	chunked := len(req.TransferEncoding) > 0 && req.TransferEncoding[0] == "chunked"
+	if len(req.TransferEncoding) > 0 {
+		fmt.Fprintf(&b, "Transfer-Encoding: %s\r\n", strings.Join(req.TransferEncoding, ","))
+	}
+	if req.Close {
+		fmt.Fprintf(&b, "Connection: close\r\n")
+	}
+
+	err = req.Header.WriteSubset(&b, reqWriteExcludeHeaderDump)
+	if err != nil {
+		return
+	}
+
+	io.WriteString(&b, "\r\n")
+
+	if req.Body != nil {
+		var dest io.Writer = &b
+		if chunked {
+			dest = NewChunkedWriter(dest)
+		}
+		_, err = io.Copy(dest, req.Body)
+		if chunked {
+			dest.(io.Closer).Close()
+			io.WriteString(&b, "\r\n")
+		}
+	}
+
+	req.Body = save
+	if err != nil {
+		return
+	}
+	dump = b.Bytes()
+	return
+}
+
+// errNoBody is a sentinel error value used by failureToReadBody so we can detect
+// that the lack of body was intentional.
+var errNoBody = errors.New("sentinel error value")
+
+// failureToReadBody is a io.ReadCloser that just returns errNoBody on
+// Read.  It's swapped in when we don't actually want to consume the
+// body, but need a non-nil one, and want to distinguish the error
+// from reading the dummy body.
+type failureToReadBody struct{}
+
+func (failureToReadBody) Read([]byte) (int, error) { return 0, errNoBody }
+func (failureToReadBody) Close() error             { return nil }
+
+var emptyBody = ioutil.NopCloser(strings.NewReader(""))
+
+// DumpResponse is like DumpRequest but dumps a response.
+func DumpResponse(resp *http.Response, body bool) (dump []byte, err error) {
+	var b bytes.Buffer
+	save := resp.Body
+	savecl := resp.ContentLength
+
+	if !body {
+		resp.Body = failureToReadBody{}
+	} else if resp.Body == nil {
+		resp.Body = emptyBody
+	} else {
+		save, resp.Body, err = drainBody(resp.Body)
+		if err != nil {
+			return
+		}
+	}
+	err = resp.Write(&b)
+	if err == errNoBody {
+		err = nil
+	}
+	resp.Body = save
+	resp.ContentLength = savecl
+	if err != nil {
+		return nil, err
+	}
+	return b.Bytes(), nil
+}
diff --git a/src/net/http/httputil/dump_test.go b/src/net/http/httputil/dump_test.go
new file mode 100644
index 000000000..e1ffb3935
--- /dev/null
+++ b/src/net/http/httputil/dump_test.go
@@ -0,0 +1,263 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package httputil
+
+import (
+	"bytes"
+	"fmt"
+	"io"
+	"io/ioutil"
+	"net/http"
+	"net/url"
+	"runtime"
+	"strings"
+	"testing"
+)
+
+type dumpTest struct {
+	Req  http.Request
+	Body interface{} // optional []byte or func() io.ReadCloser to populate Req.Body
+
+	WantDump    string
+	WantDumpOut string
+	NoBody      bool // if true, set DumpRequest{,Out} body to false
+}
+
+var dumpTests = []dumpTest{
+
+	// HTTP/1.1 => chunked coding; body; empty trailer
+	{
+		Req: http.Request{
+			Method: "GET",
+			URL: &url.URL{
+				Scheme: "http",
+				Host:   "www.google.com",
+				Path:   "/search",
+			},
+			ProtoMajor:       1,
+			ProtoMinor:       1,
+			TransferEncoding: []string{"chunked"},
+		},
+
+		Body: []byte("abcdef"),
+
+		WantDump: "GET /search HTTP/1.1\r\n" +
+			"Host: www.google.com\r\n" +
+			"Transfer-Encoding: chunked\r\n\r\n" +
+			chunk("abcdef") + chunk(""),
+	},
+
+	// Verify that DumpRequest preserves the HTTP version number, doesn't add a Host,
+	// and doesn't add a User-Agent.
+	{
+		Req: http.Request{
+			Method:     "GET",
+			URL:        mustParseURL("/foo"),
+			ProtoMajor: 1,
+			ProtoMinor: 0,
+			Header: http.Header{
+				"X-Foo": []string{"X-Bar"},
+			},
+		},
+
+		WantDump: "GET /foo HTTP/1.0\r\n" +
+			"X-Foo: X-Bar\r\n\r\n",
+	},
+
+	{
+		Req: *mustNewRequest("GET", "http://example.com/foo", nil),
+
+		WantDumpOut: "GET /foo HTTP/1.1\r\n" +
+			"Host: example.com\r\n" +
+			"User-Agent: Go 1.1 package http\r\n" +
+			"Accept-Encoding: gzip\r\n\r\n",
+	},
+
+	// Test that an https URL doesn't try to do an SSL negotiation
+	// with a bytes.Buffer and hang with all goroutines not
+	// runnable.
+	{
+		Req: *mustNewRequest("GET", "https://example.com/foo", nil),
+
+		WantDumpOut: "GET /foo HTTP/1.1\r\n" +
+			"Host: example.com\r\n" +
+			"User-Agent: Go 1.1 package http\r\n" +
+			"Accept-Encoding: gzip\r\n\r\n",
+	},
+
+	// Request with Body, but Dump requested without it.
+	{
+		Req: http.Request{
+			Method: "POST",
+			URL: &url.URL{
+				Scheme: "http",
+				Host:   "post.tld",
+				Path:   "/",
+			},
+			ContentLength: 6,
+			ProtoMajor:    1,
+			ProtoMinor:    1,
+		},
+
+		Body: []byte("abcdef"),
+
+		WantDumpOut: "POST / HTTP/1.1\r\n" +
+			"Host: post.tld\r\n" +
+			"User-Agent: Go 1.1 package http\r\n" +
+			"Content-Length: 6\r\n" +
+			"Accept-Encoding: gzip\r\n\r\n",
+
+		NoBody: true,
+	},
+}
+
+func TestDumpRequest(t *testing.T) {
+	numg0 := runtime.NumGoroutine()
+	for i, tt := range dumpTests {
+		setBody := func() {
+			if tt.Body == nil {
+				return
+			}
+			switch b := tt.Body.(type) {
+			case []byte:
+				tt.Req.Body = ioutil.NopCloser(bytes.NewReader(b))
+			case func() io.ReadCloser:
+				tt.Req.Body = b()
+			}
+		}
+		setBody()
+		if tt.Req.Header == nil {
+			tt.Req.Header = make(http.Header)
+		}
+
+		if tt.WantDump != "" {
+			setBody()
+			dump, err := DumpRequest(&tt.Req, !tt.NoBody)
+			if err != nil {
+				t.Errorf("DumpRequest #%d: %s", i, err)
+				continue
+			}
+			if string(dump) != tt.WantDump {
+				t.Errorf("DumpRequest %d, expecting:\n%s\nGot:\n%s\n", i, tt.WantDump, string(dump))
+				continue
+			}
+		}
+
+		if tt.WantDumpOut != "" {
+			setBody()
+			dump, err := DumpRequestOut(&tt.Req, !tt.NoBody)
+			if err != nil {
+				t.Errorf("DumpRequestOut #%d: %s", i, err)
+				continue
+			}
+			if string(dump) != tt.WantDumpOut {
+				t.Errorf("DumpRequestOut %d, expecting:\n%s\nGot:\n%s\n", i, tt.WantDumpOut, string(dump))
+				continue
+			}
+		}
+	}
+	if dg := runtime.NumGoroutine() - numg0; dg > 4 {
+		t.Errorf("Unexpectedly large number of new goroutines: %d new", dg)
+	}
+}
+
+func chunk(s string) string {
+	return fmt.Sprintf("%x\r\n%s\r\n", len(s), s)
+}
+
+func mustParseURL(s string) *url.URL {
+	u, err := url.Parse(s)
+	if err != nil {
+		panic(fmt.Sprintf("Error parsing URL %q: %v", s, err))
+	}
+	return u
+}
+
+func mustNewRequest(method, url string, body io.Reader) *http.Request {
+	req, err := http.NewRequest(method, url, body)
+	if err != nil {
+		panic(fmt.Sprintf("NewRequest(%q, %q, %p) err = %v", method, url, body, err))
+	}
+	return req
+}
+
+var dumpResTests = []struct {
+	res  *http.Response
+	body bool
+	want string
+}{
+	{
+		res: &http.Response{
+			Status:        "200 OK",
+			StatusCode:    200,
+			Proto:         "HTTP/1.1",
+			ProtoMajor:    1,
+			ProtoMinor:    1,
+			ContentLength: 50,
+			Header: http.Header{
+				"Foo": []string{"Bar"},
+			},
+			Body: ioutil.NopCloser(strings.NewReader("foo")), // shouldn't be used
+		},
+		body: false, // to verify we see 50, not empty or 3.
+		want: `HTTP/1.1 200 OK
+Content-Length: 50
+Foo: Bar`,
+	},
+
+	{
+		res: &http.Response{
+			Status:        "200 OK",
+			StatusCode:    200,
+			Proto:         "HTTP/1.1",
+			ProtoMajor:    1,
+			ProtoMinor:    1,
+			ContentLength: 3,
+			Body:          ioutil.NopCloser(strings.NewReader("foo")),
+		},
+		body: true,
+		want: `HTTP/1.1 200 OK
+Content-Length: 3
+
+foo`,
+	},
+
+	{
+		res: &http.Response{
+			Status:           "200 OK",
+			StatusCode:       200,
+			Proto:            "HTTP/1.1",
+			ProtoMajor:       1,
+			ProtoMinor:       1,
+			ContentLength:    -1,
+			Body:             ioutil.NopCloser(strings.NewReader("foo")),
+			TransferEncoding: []string{"chunked"},
+		},
+		body: true,
+		want: `HTTP/1.1 200 OK
+Transfer-Encoding: chunked
+
+3
+foo
+0`,
+	},
+}
+
+func TestDumpResponse(t *testing.T) {
+	for i, tt := range dumpResTests {
+		gotb, err := DumpResponse(tt.res, tt.body)
+		if err != nil {
+			t.Errorf("%d. DumpResponse = %v", i, err)
+			continue
+		}
+		got := string(gotb)
+		got = strings.TrimSpace(got)
+		got = strings.Replace(got, "\r", "", -1)
+
+		if got != tt.want {
+			t.Errorf("%d.\nDumpResponse got:\n%s\n\nWant:\n%s\n", i, got, tt.want)
+		}
+	}
+}
diff --git a/src/net/http/httputil/httputil.go b/src/net/http/httputil/httputil.go
new file mode 100644
index 000000000..2e523e9e2
--- /dev/null
+++ b/src/net/http/httputil/httputil.go
@@ -0,0 +1,39 @@
+// Copyright 2014 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package httputil provides HTTP utility functions, complementing the
+// more common ones in the net/http package.
+package httputil
+
+import (
+	"io"
+	"net/http/internal"
+)
+
+// NewChunkedReader returns a new chunkedReader that translates the data read from r
+// out of HTTP "chunked" format before returning it.
+// The chunkedReader returns io.EOF when the final 0-length chunk is read.
+//
+// NewChunkedReader is not needed by normal applications. The http package
+// automatically decodes chunking when reading response bodies.
+func NewChunkedReader(r io.Reader) io.Reader {
+	return internal.NewChunkedReader(r)
+}
+
+// NewChunkedWriter returns a new chunkedWriter that translates writes into HTTP
+// "chunked" format before writing them to w. Closing the returned chunkedWriter
+// sends the final 0-length chunk that marks the end of the stream.
+//
+// NewChunkedWriter is not needed by normal applications. The http
+// package adds chunking automatically if handlers don't set a
+// Content-Length header. Using NewChunkedWriter inside a handler
+// would result in double chunking or chunking with a Content-Length
+// length, both of which are wrong.
+func NewChunkedWriter(w io.Writer) io.WriteCloser {
+	return internal.NewChunkedWriter(w)
+}
+
+// ErrLineTooLong is returned when reading malformed chunked data
+// with lines that are too long.
+var ErrLineTooLong = internal.ErrLineTooLong
diff --git a/src/net/http/httputil/persist.go b/src/net/http/httputil/persist.go
new file mode 100644
index 000000000..987bcc96b
--- /dev/null
+++ b/src/net/http/httputil/persist.go
@@ -0,0 +1,429 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package httputil
+
+import (
+	"bufio"
+	"errors"
+	"io"
+	"net"
+	"net/http"
+	"net/textproto"
+	"sync"
+)
+
+var (
+	ErrPersistEOF = &http.ProtocolError{ErrorString: "persistent connection closed"}
+	ErrClosed     = &http.ProtocolError{ErrorString: "connection closed by user"}
+	ErrPipeline   = &http.ProtocolError{ErrorString: "pipeline error"}
+)
+
+// This is an API usage error - the local side is closed.
+// ErrPersistEOF (above) reports that the remote side is closed.
+var errClosed = errors.New("i/o operation on closed connection")
+
+// A ServerConn reads requests and sends responses over an underlying
+// connection, until the HTTP keepalive logic commands an end. ServerConn
+// also allows hijacking the underlying connection by calling Hijack
+// to regain control over the connection. ServerConn supports pipe-lining,
+// i.e. requests can be read out of sync (but in the same order) while the
+// respective responses are sent.
+//
+// ServerConn is low-level and old. Applications should instead use Server
+// in the net/http package.
+type ServerConn struct {
+	lk              sync.Mutex // read-write protects the following fields
+	c               net.Conn
+	r               *bufio.Reader
+	re, we          error // read/write errors
+	lastbody        io.ReadCloser
+	nread, nwritten int
+	pipereq         map[*http.Request]uint
+
+	pipe textproto.Pipeline
+}
+
+// NewServerConn returns a new ServerConn reading and writing c. If r is not
+// nil, it is the buffer to use when reading c.
+//
+// ServerConn is low-level and old. Applications should instead use Server
+// in the net/http package.
+func NewServerConn(c net.Conn, r *bufio.Reader) *ServerConn {
+	if r == nil {
+		r = bufio.NewReader(c)
+	}
+	return &ServerConn{c: c, r: r, pipereq: make(map[*http.Request]uint)}
+}
+
+// Hijack detaches the ServerConn and returns the underlying connection as well
+// as the read-side bufio which may have some left over data. Hijack may be
+// called before Read has signaled the end of the keep-alive logic. The user
+// should not call Hijack while Read or Write is in progress.
+func (sc *ServerConn) Hijack() (c net.Conn, r *bufio.Reader) {
+	sc.lk.Lock()
+	defer sc.lk.Unlock()
+	c = sc.c
+	r = sc.r
+	sc.c = nil
+	sc.r = nil
+	return
+}
+
+// Close calls Hijack and then also closes the underlying connection
+func (sc *ServerConn) Close() error {
+	c, _ := sc.Hijack()
+	if c != nil {
+		return c.Close()
+	}
+	return nil
+}
+
+// Read returns the next request on the wire. An ErrPersistEOF is returned if
+// it is gracefully determined that there are no more requests (e.g. after the
+// first request on an HTTP/1.0 connection, or after a Connection:close on a
+// HTTP/1.1 connection).
+func (sc *ServerConn) Read() (req *http.Request, err error) {
+
+	// Ensure ordered execution of Reads and Writes
+	id := sc.pipe.Next()
+	sc.pipe.StartRequest(id)
+	defer func() {
+		sc.pipe.EndRequest(id)
+		if req == nil {
+			sc.pipe.StartResponse(id)
+			sc.pipe.EndResponse(id)
+		} else {
+			// Remember the pipeline id of this request
+			sc.lk.Lock()
+			sc.pipereq[req] = id
+			sc.lk.Unlock()
+		}
+	}()
+
+	sc.lk.Lock()
+	if sc.we != nil { // no point receiving if write-side broken or closed
+		defer sc.lk.Unlock()
+		return nil, sc.we
+	}
+	if sc.re != nil {
+		defer sc.lk.Unlock()
+		return nil, sc.re
+	}
+	if sc.r == nil { // connection closed by user in the meantime
+		defer sc.lk.Unlock()
+		return nil, errClosed
+	}
+	r := sc.r
+	lastbody := sc.lastbody
+	sc.lastbody = nil
+	sc.lk.Unlock()
+
+	// Make sure body is fully consumed, even if user does not call body.Close
+	if lastbody != nil {
+		// body.Close is assumed to be idempotent and multiple calls to
+		// it should return the error that its first invocation
+		// returned.
+		err = lastbody.Close()
+		if err != nil {
+			sc.lk.Lock()
+			defer sc.lk.Unlock()
+			sc.re = err
+			return nil, err
+		}
+	}
+
+	req, err = http.ReadRequest(r)
+	sc.lk.Lock()
+	defer sc.lk.Unlock()
+	if err != nil {
+		if err == io.ErrUnexpectedEOF {
+			// A close from the opposing client is treated as a
+			// graceful close, even if there was some unparse-able
+			// data before the close.
+			sc.re = ErrPersistEOF
+			return nil, sc.re
+		} else {
+			sc.re = err
+			return req, err
+		}
+	}
+	sc.lastbody = req.Body
+	sc.nread++
+	if req.Close {
+		sc.re = ErrPersistEOF
+		return req, sc.re
+	}
+	return req, err
+}
+
+// Pending returns the number of unanswered requests
+// that have been received on the connection.
+func (sc *ServerConn) Pending() int {
+	sc.lk.Lock()
+	defer sc.lk.Unlock()
+	return sc.nread - sc.nwritten
+}
+
+// Write writes resp in response to req. To close the connection gracefully, set the
+// Response.Close field to true. Write should be considered operational until
+// it returns an error, regardless of any errors returned on the Read side.
+func (sc *ServerConn) Write(req *http.Request, resp *http.Response) error {
+
+	// Retrieve the pipeline ID of this request/response pair
+	sc.lk.Lock()
+	id, ok := sc.pipereq[req]
+	delete(sc.pipereq, req)
+	if !ok {
+		sc.lk.Unlock()
+		return ErrPipeline
+	}
+	sc.lk.Unlock()
+
+	// Ensure pipeline order
+	sc.pipe.StartResponse(id)
+	defer sc.pipe.EndResponse(id)
+
+	sc.lk.Lock()
+	if sc.we != nil {
+		defer sc.lk.Unlock()
+		return sc.we
+	}
+	if sc.c == nil { // connection closed by user in the meantime
+		defer sc.lk.Unlock()
+		return ErrClosed
+	}
+	c := sc.c
+	if sc.nread <= sc.nwritten {
+		defer sc.lk.Unlock()
+		return errors.New("persist server pipe count")
+	}
+	if resp.Close {
+		// After signaling a keep-alive close, any pipelined unread
+		// requests will be lost. It is up to the user to drain them
+		// before signaling.
+		sc.re = ErrPersistEOF
+	}
+	sc.lk.Unlock()
+
+	err := resp.Write(c)
+	sc.lk.Lock()
+	defer sc.lk.Unlock()
+	if err != nil {
+		sc.we = err
+		return err
+	}
+	sc.nwritten++
+
+	return nil
+}
+
+// A ClientConn sends request and receives headers over an underlying
+// connection, while respecting the HTTP keepalive logic. ClientConn
+// supports hijacking the connection calling Hijack to
+// regain control of the underlying net.Conn and deal with it as desired.
+//
+// ClientConn is low-level and old. Applications should instead use
+// Client or Transport in the net/http package.
+type ClientConn struct {
+	lk              sync.Mutex // read-write protects the following fields
+	c               net.Conn
+	r               *bufio.Reader
+	re, we          error // read/write errors
+	lastbody        io.ReadCloser
+	nread, nwritten int
+	pipereq         map[*http.Request]uint
+
+	pipe     textproto.Pipeline
+	writeReq func(*http.Request, io.Writer) error
+}
+
+// NewClientConn returns a new ClientConn reading and writing c.  If r is not
+// nil, it is the buffer to use when reading c.
+//
+// ClientConn is low-level and old. Applications should use Client or
+// Transport in the net/http package.
+func NewClientConn(c net.Conn, r *bufio.Reader) *ClientConn {
+	if r == nil {
+		r = bufio.NewReader(c)
+	}
+	return &ClientConn{
+		c:        c,
+		r:        r,
+		pipereq:  make(map[*http.Request]uint),
+		writeReq: (*http.Request).Write,
+	}
+}
+
+// NewProxyClientConn works like NewClientConn but writes Requests
+// using Request's WriteProxy method.
+//
+// New code should not use NewProxyClientConn. See Client or
+// Transport in the net/http package instead.
+func NewProxyClientConn(c net.Conn, r *bufio.Reader) *ClientConn {
+	cc := NewClientConn(c, r)
+	cc.writeReq = (*http.Request).WriteProxy
+	return cc
+}
+
+// Hijack detaches the ClientConn and returns the underlying connection as well
+// as the read-side bufio which may have some left over data. Hijack may be
+// called before the user or Read have signaled the end of the keep-alive
+// logic. The user should not call Hijack while Read or Write is in progress.
+func (cc *ClientConn) Hijack() (c net.Conn, r *bufio.Reader) {
+	cc.lk.Lock()
+	defer cc.lk.Unlock()
+	c = cc.c
+	r = cc.r
+	cc.c = nil
+	cc.r = nil
+	return
+}
+
+// Close calls Hijack and then also closes the underlying connection
+func (cc *ClientConn) Close() error {
+	c, _ := cc.Hijack()
+	if c != nil {
+		return c.Close()
+	}
+	return nil
+}
+
+// Write writes a request. An ErrPersistEOF error is returned if the connection
+// has been closed in an HTTP keepalive sense. If req.Close equals true, the
+// keepalive connection is logically closed after this request and the opposing
+// server is informed. An ErrUnexpectedEOF indicates the remote closed the
+// underlying TCP connection, which is usually considered as graceful close.
+func (cc *ClientConn) Write(req *http.Request) (err error) {
+
+	// Ensure ordered execution of Writes
+	id := cc.pipe.Next()
+	cc.pipe.StartRequest(id)
+	defer func() {
+		cc.pipe.EndRequest(id)
+		if err != nil {
+			cc.pipe.StartResponse(id)
+			cc.pipe.EndResponse(id)
+		} else {
+			// Remember the pipeline id of this request
+			cc.lk.Lock()
+			cc.pipereq[req] = id
+			cc.lk.Unlock()
+		}
+	}()
+
+	cc.lk.Lock()
+	if cc.re != nil { // no point sending if read-side closed or broken
+		defer cc.lk.Unlock()
+		return cc.re
+	}
+	if cc.we != nil {
+		defer cc.lk.Unlock()
+		return cc.we
+	}
+	if cc.c == nil { // connection closed by user in the meantime
+		defer cc.lk.Unlock()
+		return errClosed
+	}
+	c := cc.c
+	if req.Close {
+		// We write the EOF to the write-side error, because there
+		// still might be some pipelined reads
+		cc.we = ErrPersistEOF
+	}
+	cc.lk.Unlock()
+
+	err = cc.writeReq(req, c)
+	cc.lk.Lock()
+	defer cc.lk.Unlock()
+	if err != nil {
+		cc.we = err
+		return err
+	}
+	cc.nwritten++
+
+	return nil
+}
+
+// Pending returns the number of unanswered requests
+// that have been sent on the connection.
+func (cc *ClientConn) Pending() int {
+	cc.lk.Lock()
+	defer cc.lk.Unlock()
+	return cc.nwritten - cc.nread
+}
+
+// Read reads the next response from the wire. A valid response might be
+// returned together with an ErrPersistEOF, which means that the remote
+// requested that this be the last request serviced. Read can be called
+// concurrently with Write, but not with another Read.
+func (cc *ClientConn) Read(req *http.Request) (resp *http.Response, err error) {
+	// Retrieve the pipeline ID of this request/response pair
+	cc.lk.Lock()
+	id, ok := cc.pipereq[req]
+	delete(cc.pipereq, req)
+	if !ok {
+		cc.lk.Unlock()
+		return nil, ErrPipeline
+	}
+	cc.lk.Unlock()
+
+	// Ensure pipeline order
+	cc.pipe.StartResponse(id)
+	defer cc.pipe.EndResponse(id)
+
+	cc.lk.Lock()
+	if cc.re != nil {
+		defer cc.lk.Unlock()
+		return nil, cc.re
+	}
+	if cc.r == nil { // connection closed by user in the meantime
+		defer cc.lk.Unlock()
+		return nil, errClosed
+	}
+	r := cc.r
+	lastbody := cc.lastbody
+	cc.lastbody = nil
+	cc.lk.Unlock()
+
+	// Make sure body is fully consumed, even if user does not call body.Close
+	if lastbody != nil {
+		// body.Close is assumed to be idempotent and multiple calls to
+		// it should return the error that its first invocation
+		// returned.
+		err = lastbody.Close()
+		if err != nil {
+			cc.lk.Lock()
+			defer cc.lk.Unlock()
+			cc.re = err
+			return nil, err
+		}
+	}
+
+	resp, err = http.ReadResponse(r, req)
+	cc.lk.Lock()
+	defer cc.lk.Unlock()
+	if err != nil {
+		cc.re = err
+		return resp, err
+	}
+	cc.lastbody = resp.Body
+
+	cc.nread++
+
+	if resp.Close {
+		cc.re = ErrPersistEOF // don't send any more requests
+		return resp, cc.re
+	}
+	return resp, err
+}
+
+// Do is convenience method that writes a request and reads a response.
+func (cc *ClientConn) Do(req *http.Request) (resp *http.Response, err error) {
+	err = cc.Write(req)
+	if err != nil {
+		return
+	}
+	return cc.Read(req)
+}
diff --git a/src/net/http/httputil/reverseproxy.go b/src/net/http/httputil/reverseproxy.go
new file mode 100644
index 000000000..ab4637018
--- /dev/null
+++ b/src/net/http/httputil/reverseproxy.go
@@ -0,0 +1,225 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// HTTP reverse proxy handler
+
+package httputil
+
+import (
+	"io"
+	"log"
+	"net"
+	"net/http"
+	"net/url"
+	"strings"
+	"sync"
+	"time"
+)
+
+// onExitFlushLoop is a callback set by tests to detect the state of the
+// flushLoop() goroutine.
+var onExitFlushLoop func()
+
+// ReverseProxy is an HTTP Handler that takes an incoming request and
+// sends it to another server, proxying the response back to the
+// client.
+type ReverseProxy struct {
+	// Director must be a function which modifies
+	// the request into a new request to be sent
+	// using Transport. Its response is then copied
+	// back to the original client unmodified.
+	Director func(*http.Request)
+
+	// The transport used to perform proxy requests.
+	// If nil, http.DefaultTransport is used.
+	Transport http.RoundTripper
+
+	// FlushInterval specifies the flush interval
+	// to flush to the client while copying the
+	// response body.
+	// If zero, no periodic flushing is done.
+	FlushInterval time.Duration
+
+	// ErrorLog specifies an optional logger for errors
+	// that occur when attempting to proxy the request.
+	// If nil, logging goes to os.Stderr via the log package's
+	// standard logger.
+	ErrorLog *log.Logger
+}
+
+func singleJoiningSlash(a, b string) string {
+	aslash := strings.HasSuffix(a, "/")
+	bslash := strings.HasPrefix(b, "/")
+	switch {
+	case aslash && bslash:
+		return a + b[1:]
+	case !aslash && !bslash:
+		return a + "/" + b
+	}
+	return a + b
+}
+
+// NewSingleHostReverseProxy returns a new ReverseProxy that rewrites
+// URLs to the scheme, host, and base path provided in target. If the
+// target's path is "/base" and the incoming request was for "/dir",
+// the target request will be for /base/dir.
+func NewSingleHostReverseProxy(target *url.URL) *ReverseProxy {
+	targetQuery := target.RawQuery
+	director := func(req *http.Request) {
+		req.URL.Scheme = target.Scheme
+		req.URL.Host = target.Host
+		req.URL.Path = singleJoiningSlash(target.Path, req.URL.Path)
+		if targetQuery == "" || req.URL.RawQuery == "" {
+			req.URL.RawQuery = targetQuery + req.URL.RawQuery
+		} else {
+			req.URL.RawQuery = targetQuery + "&" + req.URL.RawQuery
+		}
+	}
+	return &ReverseProxy{Director: director}
+}
+
+func copyHeader(dst, src http.Header) {
+	for k, vv := range src {
+		for _, v := range vv {
+			dst.Add(k, v)
+		}
+	}
+}
+
+// Hop-by-hop headers. These are removed when sent to the backend.
+// http://www.w3.org/Protocols/rfc2616/rfc2616-sec13.html
+var hopHeaders = []string{
+	"Connection",
+	"Keep-Alive",
+	"Proxy-Authenticate",
+	"Proxy-Authorization",
+	"Te", // canonicalized version of "TE"
+	"Trailers",
+	"Transfer-Encoding",
+	"Upgrade",
+}
+
+func (p *ReverseProxy) ServeHTTP(rw http.ResponseWriter, req *http.Request) {
+	transport := p.Transport
+	if transport == nil {
+		transport = http.DefaultTransport
+	}
+
+	outreq := new(http.Request)
+	*outreq = *req // includes shallow copies of maps, but okay
+
+	p.Director(outreq)
+	outreq.Proto = "HTTP/1.1"
+	outreq.ProtoMajor = 1
+	outreq.ProtoMinor = 1
+	outreq.Close = false
+
+	// Remove hop-by-hop headers to the backend.  Especially
+	// important is "Connection" because we want a persistent
+	// connection, regardless of what the client sent to us.  This
+	// is modifying the same underlying map from req (shallow
+	// copied above) so we only copy it if necessary.
+	copiedHeaders := false
+	for _, h := range hopHeaders {
+		if outreq.Header.Get(h) != "" {
+			if !copiedHeaders {
+				outreq.Header = make(http.Header)
+				copyHeader(outreq.Header, req.Header)
+				copiedHeaders = true
+			}
+			outreq.Header.Del(h)
+		}
+	}
+
+	if clientIP, _, err := net.SplitHostPort(req.RemoteAddr); err == nil {
+		// If we aren't the first proxy retain prior
+		// X-Forwarded-For information as a comma+space
+		// separated list and fold multiple headers into one.
+		if prior, ok := outreq.Header["X-Forwarded-For"]; ok {
+			clientIP = strings.Join(prior, ", ") + ", " + clientIP
+		}
+		outreq.Header.Set("X-Forwarded-For", clientIP)
+	}
+
+	res, err := transport.RoundTrip(outreq)
+	if err != nil {
+		p.logf("http: proxy error: %v", err)
+		rw.WriteHeader(http.StatusInternalServerError)
+		return
+	}
+	defer res.Body.Close()
+
+	for _, h := range hopHeaders {
+		res.Header.Del(h)
+	}
+
+	copyHeader(rw.Header(), res.Header)
+
+	rw.WriteHeader(res.StatusCode)
+	p.copyResponse(rw, res.Body)
+}
+
+func (p *ReverseProxy) copyResponse(dst io.Writer, src io.Reader) {
+	if p.FlushInterval != 0 {
+		if wf, ok := dst.(writeFlusher); ok {
+			mlw := &maxLatencyWriter{
+				dst:     wf,
+				latency: p.FlushInterval,
+				done:    make(chan bool),
+			}
+			go mlw.flushLoop()
+			defer mlw.stop()
+			dst = mlw
+		}
+	}
+
+	io.Copy(dst, src)
+}
+
+func (p *ReverseProxy) logf(format string, args ...interface{}) {
+	if p.ErrorLog != nil {
+		p.ErrorLog.Printf(format, args...)
+	} else {
+		log.Printf(format, args...)
+	}
+}
+
+type writeFlusher interface {
+	io.Writer
+	http.Flusher
+}
+
+type maxLatencyWriter struct {
+	dst     writeFlusher
+	latency time.Duration
+
+	lk   sync.Mutex // protects Write + Flush
+	done chan bool
+}
+
+func (m *maxLatencyWriter) Write(p []byte) (int, error) {
+	m.lk.Lock()
+	defer m.lk.Unlock()
+	return m.dst.Write(p)
+}
+
+func (m *maxLatencyWriter) flushLoop() {
+	t := time.NewTicker(m.latency)
+	defer t.Stop()
+	for {
+		select {
+		case <-m.done:
+			if onExitFlushLoop != nil {
+				onExitFlushLoop()
+			}
+			return
+		case <-t.C:
+			m.lk.Lock()
+			m.dst.Flush()
+			m.lk.Unlock()
+		}
+	}
+}
+
+func (m *maxLatencyWriter) stop() { m.done <- true }
diff --git a/src/net/http/httputil/reverseproxy_test.go b/src/net/http/httputil/reverseproxy_test.go
new file mode 100644
index 000000000..e9539b44b
--- /dev/null
+++ b/src/net/http/httputil/reverseproxy_test.go
@@ -0,0 +1,213 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Reverse proxy tests.
+
+package httputil
+
+import (
+	"io/ioutil"
+	"net/http"
+	"net/http/httptest"
+	"net/url"
+	"strings"
+	"testing"
+	"time"
+)
+
+const fakeHopHeader = "X-Fake-Hop-Header-For-Test"
+
+func init() {
+	hopHeaders = append(hopHeaders, fakeHopHeader)
+}
+
+func TestReverseProxy(t *testing.T) {
+	const backendResponse = "I am the backend"
+	const backendStatus = 404
+	backend := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if len(r.TransferEncoding) > 0 {
+			t.Errorf("backend got unexpected TransferEncoding: %v", r.TransferEncoding)
+		}
+		if r.Header.Get("X-Forwarded-For") == "" {
+			t.Errorf("didn't get X-Forwarded-For header")
+		}
+		if c := r.Header.Get("Connection"); c != "" {
+			t.Errorf("handler got Connection header value %q", c)
+		}
+		if c := r.Header.Get("Upgrade"); c != "" {
+			t.Errorf("handler got Upgrade header value %q", c)
+		}
+		if g, e := r.Host, "some-name"; g != e {
+			t.Errorf("backend got Host header %q, want %q", g, e)
+		}
+		w.Header().Set("X-Foo", "bar")
+		w.Header().Set("Upgrade", "foo")
+		w.Header().Set(fakeHopHeader, "foo")
+		w.Header().Add("X-Multi-Value", "foo")
+		w.Header().Add("X-Multi-Value", "bar")
+		http.SetCookie(w, &http.Cookie{Name: "flavor", Value: "chocolateChip"})
+		w.WriteHeader(backendStatus)
+		w.Write([]byte(backendResponse))
+	}))
+	defer backend.Close()
+	backendURL, err := url.Parse(backend.URL)
+	if err != nil {
+		t.Fatal(err)
+	}
+	proxyHandler := NewSingleHostReverseProxy(backendURL)
+	frontend := httptest.NewServer(proxyHandler)
+	defer frontend.Close()
+
+	getReq, _ := http.NewRequest("GET", frontend.URL, nil)
+	getReq.Host = "some-name"
+	getReq.Header.Set("Connection", "close")
+	getReq.Header.Set("Upgrade", "foo")
+	getReq.Close = true
+	res, err := http.DefaultClient.Do(getReq)
+	if err != nil {
+		t.Fatalf("Get: %v", err)
+	}
+	if g, e := res.StatusCode, backendStatus; g != e {
+		t.Errorf("got res.StatusCode %d; expected %d", g, e)
+	}
+	if g, e := res.Header.Get("X-Foo"), "bar"; g != e {
+		t.Errorf("got X-Foo %q; expected %q", g, e)
+	}
+	if c := res.Header.Get(fakeHopHeader); c != "" {
+		t.Errorf("got %s header value %q", fakeHopHeader, c)
+	}
+	if g, e := len(res.Header["X-Multi-Value"]), 2; g != e {
+		t.Errorf("got %d X-Multi-Value header values; expected %d", g, e)
+	}
+	if g, e := len(res.Header["Set-Cookie"]), 1; g != e {
+		t.Fatalf("got %d SetCookies, want %d", g, e)
+	}
+	if cookie := res.Cookies()[0]; cookie.Name != "flavor" {
+		t.Errorf("unexpected cookie %q", cookie.Name)
+	}
+	bodyBytes, _ := ioutil.ReadAll(res.Body)
+	if g, e := string(bodyBytes), backendResponse; g != e {
+		t.Errorf("got body %q; expected %q", g, e)
+	}
+}
+
+func TestXForwardedFor(t *testing.T) {
+	const prevForwardedFor = "client ip"
+	const backendResponse = "I am the backend"
+	const backendStatus = 404
+	backend := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if r.Header.Get("X-Forwarded-For") == "" {
+			t.Errorf("didn't get X-Forwarded-For header")
+		}
+		if !strings.Contains(r.Header.Get("X-Forwarded-For"), prevForwardedFor) {
+			t.Errorf("X-Forwarded-For didn't contain prior data")
+		}
+		w.WriteHeader(backendStatus)
+		w.Write([]byte(backendResponse))
+	}))
+	defer backend.Close()
+	backendURL, err := url.Parse(backend.URL)
+	if err != nil {
+		t.Fatal(err)
+	}
+	proxyHandler := NewSingleHostReverseProxy(backendURL)
+	frontend := httptest.NewServer(proxyHandler)
+	defer frontend.Close()
+
+	getReq, _ := http.NewRequest("GET", frontend.URL, nil)
+	getReq.Host = "some-name"
+	getReq.Header.Set("Connection", "close")
+	getReq.Header.Set("X-Forwarded-For", prevForwardedFor)
+	getReq.Close = true
+	res, err := http.DefaultClient.Do(getReq)
+	if err != nil {
+		t.Fatalf("Get: %v", err)
+	}
+	if g, e := res.StatusCode, backendStatus; g != e {
+		t.Errorf("got res.StatusCode %d; expected %d", g, e)
+	}
+	bodyBytes, _ := ioutil.ReadAll(res.Body)
+	if g, e := string(bodyBytes), backendResponse; g != e {
+		t.Errorf("got body %q; expected %q", g, e)
+	}
+}
+
+var proxyQueryTests = []struct {
+	baseSuffix string // suffix to add to backend URL
+	reqSuffix  string // suffix to add to frontend's request URL
+	want       string // what backend should see for final request URL (without ?)
+}{
+	{"", "", ""},
+	{"?sta=tic", "?us=er", "sta=tic&us=er"},
+	{"", "?us=er", "us=er"},
+	{"?sta=tic", "", "sta=tic"},
+}
+
+func TestReverseProxyQuery(t *testing.T) {
+	backend := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.Header().Set("X-Got-Query", r.URL.RawQuery)
+		w.Write([]byte("hi"))
+	}))
+	defer backend.Close()
+
+	for i, tt := range proxyQueryTests {
+		backendURL, err := url.Parse(backend.URL + tt.baseSuffix)
+		if err != nil {
+			t.Fatal(err)
+		}
+		frontend := httptest.NewServer(NewSingleHostReverseProxy(backendURL))
+		req, _ := http.NewRequest("GET", frontend.URL+tt.reqSuffix, nil)
+		req.Close = true
+		res, err := http.DefaultClient.Do(req)
+		if err != nil {
+			t.Fatalf("%d. Get: %v", i, err)
+		}
+		if g, e := res.Header.Get("X-Got-Query"), tt.want; g != e {
+			t.Errorf("%d. got query %q; expected %q", i, g, e)
+		}
+		res.Body.Close()
+		frontend.Close()
+	}
+}
+
+func TestReverseProxyFlushInterval(t *testing.T) {
+	const expected = "hi"
+	backend := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.Write([]byte(expected))
+	}))
+	defer backend.Close()
+
+	backendURL, err := url.Parse(backend.URL)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	proxyHandler := NewSingleHostReverseProxy(backendURL)
+	proxyHandler.FlushInterval = time.Microsecond
+
+	done := make(chan bool)
+	onExitFlushLoop = func() { done <- true }
+	defer func() { onExitFlushLoop = nil }()
+
+	frontend := httptest.NewServer(proxyHandler)
+	defer frontend.Close()
+
+	req, _ := http.NewRequest("GET", frontend.URL, nil)
+	req.Close = true
+	res, err := http.DefaultClient.Do(req)
+	if err != nil {
+		t.Fatalf("Get: %v", err)
+	}
+	defer res.Body.Close()
+	if bodyBytes, _ := ioutil.ReadAll(res.Body); string(bodyBytes) != expected {
+		t.Errorf("got body %q; expected %q", bodyBytes, expected)
+	}
+
+	select {
+	case <-done:
+		// OK
+	case <-time.After(5 * time.Second):
+		t.Error("maxLatencyWriter flushLoop() never exited")
+	}
+}
diff --git a/src/net/http/internal/chunked.go b/src/net/http/internal/chunked.go
new file mode 100644
index 000000000..9294deb3e
--- /dev/null
+++ b/src/net/http/internal/chunked.go
@@ -0,0 +1,202 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// The wire protocol for HTTP's "chunked" Transfer-Encoding.
+
+// Package internal contains HTTP internals shared by net/http and
+// net/http/httputil.
+package internal
+
+import (
+	"bufio"
+	"bytes"
+	"errors"
+	"fmt"
+	"io"
+)
+
+const maxLineLength = 4096 // assumed <= bufio.defaultBufSize
+
+var ErrLineTooLong = errors.New("header line too long")
+
+// NewChunkedReader returns a new chunkedReader that translates the data read from r
+// out of HTTP "chunked" format before returning it.
+// The chunkedReader returns io.EOF when the final 0-length chunk is read.
+//
+// NewChunkedReader is not needed by normal applications. The http package
+// automatically decodes chunking when reading response bodies.
+func NewChunkedReader(r io.Reader) io.Reader {
+	br, ok := r.(*bufio.Reader)
+	if !ok {
+		br = bufio.NewReader(r)
+	}
+	return &chunkedReader{r: br}
+}
+
+type chunkedReader struct {
+	r   *bufio.Reader
+	n   uint64 // unread bytes in chunk
+	err error
+	buf [2]byte
+}
+
+func (cr *chunkedReader) beginChunk() {
+	// chunk-size CRLF
+	var line []byte
+	line, cr.err = readLine(cr.r)
+	if cr.err != nil {
+		return
+	}
+	cr.n, cr.err = parseHexUint(line)
+	if cr.err != nil {
+		return
+	}
+	if cr.n == 0 {
+		cr.err = io.EOF
+	}
+}
+
+func (cr *chunkedReader) chunkHeaderAvailable() bool {
+	n := cr.r.Buffered()
+	if n > 0 {
+		peek, _ := cr.r.Peek(n)
+		return bytes.IndexByte(peek, '\n') >= 0
+	}
+	return false
+}
+
+func (cr *chunkedReader) Read(b []uint8) (n int, err error) {
+	for cr.err == nil {
+		if cr.n == 0 {
+			if n > 0 && !cr.chunkHeaderAvailable() {
+				// We've read enough. Don't potentially block
+				// reading a new chunk header.
+				break
+			}
+			cr.beginChunk()
+			continue
+		}
+		if len(b) == 0 {
+			break
+		}
+		rbuf := b
+		if uint64(len(rbuf)) > cr.n {
+			rbuf = rbuf[:cr.n]
+		}
+		var n0 int
+		n0, cr.err = cr.r.Read(rbuf)
+		n += n0
+		b = b[n0:]
+		cr.n -= uint64(n0)
+		// If we're at the end of a chunk, read the next two
+		// bytes to verify they are "\r\n".
+		if cr.n == 0 && cr.err == nil {
+			if _, cr.err = io.ReadFull(cr.r, cr.buf[:2]); cr.err == nil {
+				if cr.buf[0] != '\r' || cr.buf[1] != '\n' {
+					cr.err = errors.New("malformed chunked encoding")
+				}
+			}
+		}
+	}
+	return n, cr.err
+}
+
+// Read a line of bytes (up to \n) from b.
+// Give up if the line exceeds maxLineLength.
+// The returned bytes are a pointer into storage in
+// the bufio, so they are only valid until the next bufio read.
+func readLine(b *bufio.Reader) (p []byte, err error) {
+	if p, err = b.ReadSlice('\n'); err != nil {
+		// We always know when EOF is coming.
+		// If the caller asked for a line, there should be a line.
+		if err == io.EOF {
+			err = io.ErrUnexpectedEOF
+		} else if err == bufio.ErrBufferFull {
+			err = ErrLineTooLong
+		}
+		return nil, err
+	}
+	if len(p) >= maxLineLength {
+		return nil, ErrLineTooLong
+	}
+	return trimTrailingWhitespace(p), nil
+}
+
+func trimTrailingWhitespace(b []byte) []byte {
+	for len(b) > 0 && isASCIISpace(b[len(b)-1]) {
+		b = b[:len(b)-1]
+	}
+	return b
+}
+
+func isASCIISpace(b byte) bool {
+	return b == ' ' || b == '\t' || b == '\n' || b == '\r'
+}
+
+// NewChunkedWriter returns a new chunkedWriter that translates writes into HTTP
+// "chunked" format before writing them to w. Closing the returned chunkedWriter
+// sends the final 0-length chunk that marks the end of the stream.
+//
+// NewChunkedWriter is not needed by normal applications. The http
+// package adds chunking automatically if handlers don't set a
+// Content-Length header. Using newChunkedWriter inside a handler
+// would result in double chunking or chunking with a Content-Length
+// length, both of which are wrong.
+func NewChunkedWriter(w io.Writer) io.WriteCloser {
+	return &chunkedWriter{w}
+}
+
+// Writing to chunkedWriter translates to writing in HTTP chunked Transfer
+// Encoding wire format to the underlying Wire chunkedWriter.
+type chunkedWriter struct {
+	Wire io.Writer
+}
+
+// Write the contents of data as one chunk to Wire.
+// NOTE: Note that the corresponding chunk-writing procedure in Conn.Write has
+// a bug since it does not check for success of io.WriteString
+func (cw *chunkedWriter) Write(data []byte) (n int, err error) {
+
+	// Don't send 0-length data. It looks like EOF for chunked encoding.
+	if len(data) == 0 {
+		return 0, nil
+	}
+
+	if _, err = fmt.Fprintf(cw.Wire, "%x\r\n", len(data)); err != nil {
+		return 0, err
+	}
+	if n, err = cw.Wire.Write(data); err != nil {
+		return
+	}
+	if n != len(data) {
+		err = io.ErrShortWrite
+		return
+	}
+	_, err = io.WriteString(cw.Wire, "\r\n")
+
+	return
+}
+
+func (cw *chunkedWriter) Close() error {
+	_, err := io.WriteString(cw.Wire, "0\r\n")
+	return err
+}
+
+func parseHexUint(v []byte) (n uint64, err error) {
+	for _, b := range v {
+		n <<= 4
+		switch {
+		case '0' <= b && b <= '9':
+			b = b - '0'
+		case 'a' <= b && b <= 'f':
+			b = b - 'a' + 10
+		case 'A' <= b && b <= 'F':
+			b = b - 'A' + 10
+		default:
+			return 0, errors.New("invalid byte in chunk length")
+		}
+		n |= uint64(b)
+	}
+	return
+}
diff --git a/src/net/http/internal/chunked_test.go b/src/net/http/internal/chunked_test.go
new file mode 100644
index 000000000..ebc626ea9
--- /dev/null
+++ b/src/net/http/internal/chunked_test.go
@@ -0,0 +1,156 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package internal
+
+import (
+	"bufio"
+	"bytes"
+	"fmt"
+	"io"
+	"io/ioutil"
+	"strings"
+	"testing"
+)
+
+func TestChunk(t *testing.T) {
+	var b bytes.Buffer
+
+	w := NewChunkedWriter(&b)
+	const chunk1 = "hello, "
+	const chunk2 = "world! 0123456789abcdef"
+	w.Write([]byte(chunk1))
+	w.Write([]byte(chunk2))
+	w.Close()
+
+	if g, e := b.String(), "7\r\nhello, \r\n17\r\nworld! 0123456789abcdef\r\n0\r\n"; g != e {
+		t.Fatalf("chunk writer wrote %q; want %q", g, e)
+	}
+
+	r := NewChunkedReader(&b)
+	data, err := ioutil.ReadAll(r)
+	if err != nil {
+		t.Logf(`data: "%s"`, data)
+		t.Fatalf("ReadAll from reader: %v", err)
+	}
+	if g, e := string(data), chunk1+chunk2; g != e {
+		t.Errorf("chunk reader read %q; want %q", g, e)
+	}
+}
+
+func TestChunkReadMultiple(t *testing.T) {
+	// Bunch of small chunks, all read together.
+	{
+		var b bytes.Buffer
+		w := NewChunkedWriter(&b)
+		w.Write([]byte("foo"))
+		w.Write([]byte("bar"))
+		w.Close()
+
+		r := NewChunkedReader(&b)
+		buf := make([]byte, 10)
+		n, err := r.Read(buf)
+		if n != 6 || err != io.EOF {
+			t.Errorf("Read = %d, %v; want 6, EOF", n, err)
+		}
+		buf = buf[:n]
+		if string(buf) != "foobar" {
+			t.Errorf("Read = %q; want %q", buf, "foobar")
+		}
+	}
+
+	// One big chunk followed by a little chunk, but the small bufio.Reader size
+	// should prevent the second chunk header from being read.
+	{
+		var b bytes.Buffer
+		w := NewChunkedWriter(&b)
+		// fillBufChunk is 11 bytes + 3 bytes header + 2 bytes footer = 16 bytes,
+		// the same as the bufio ReaderSize below (the minimum), so even
+		// though we're going to try to Read with a buffer larger enough to also
+		// receive "foo", the second chunk header won't be read yet.
+		const fillBufChunk = "0123456789a"
+		const shortChunk = "foo"
+		w.Write([]byte(fillBufChunk))
+		w.Write([]byte(shortChunk))
+		w.Close()
+
+		r := NewChunkedReader(bufio.NewReaderSize(&b, 16))
+		buf := make([]byte, len(fillBufChunk)+len(shortChunk))
+		n, err := r.Read(buf)
+		if n != len(fillBufChunk) || err != nil {
+			t.Errorf("Read = %d, %v; want %d, nil", n, err, len(fillBufChunk))
+		}
+		buf = buf[:n]
+		if string(buf) != fillBufChunk {
+			t.Errorf("Read = %q; want %q", buf, fillBufChunk)
+		}
+
+		n, err = r.Read(buf)
+		if n != len(shortChunk) || err != io.EOF {
+			t.Errorf("Read = %d, %v; want %d, EOF", n, err, len(shortChunk))
+		}
+	}
+
+	// And test that we see an EOF chunk, even though our buffer is already full:
+	{
+		r := NewChunkedReader(bufio.NewReader(strings.NewReader("3\r\nfoo\r\n0\r\n")))
+		buf := make([]byte, 3)
+		n, err := r.Read(buf)
+		if n != 3 || err != io.EOF {
+			t.Errorf("Read = %d, %v; want 3, EOF", n, err)
+		}
+		if string(buf) != "foo" {
+			t.Errorf("buf = %q; want foo", buf)
+		}
+	}
+}
+
+func TestChunkReaderAllocs(t *testing.T) {
+	if testing.Short() {
+		t.Skip("skipping in short mode")
+	}
+	var buf bytes.Buffer
+	w := NewChunkedWriter(&buf)
+	a, b, c := []byte("aaaaaa"), []byte("bbbbbbbbbbbb"), []byte("cccccccccccccccccccccccc")
+	w.Write(a)
+	w.Write(b)
+	w.Write(c)
+	w.Close()
+
+	readBuf := make([]byte, len(a)+len(b)+len(c)+1)
+	byter := bytes.NewReader(buf.Bytes())
+	bufr := bufio.NewReader(byter)
+	mallocs := testing.AllocsPerRun(100, func() {
+		byter.Seek(0, 0)
+		bufr.Reset(byter)
+		r := NewChunkedReader(bufr)
+		n, err := io.ReadFull(r, readBuf)
+		if n != len(readBuf)-1 {
+			t.Fatalf("read %d bytes; want %d", n, len(readBuf)-1)
+		}
+		if err != io.ErrUnexpectedEOF {
+			t.Fatalf("read error = %v; want ErrUnexpectedEOF", err)
+		}
+	})
+	if mallocs > 1.5 {
+		t.Errorf("mallocs = %v; want 1", mallocs)
+	}
+}
+
+func TestParseHexUint(t *testing.T) {
+	for i := uint64(0); i <= 1234; i++ {
+		line := []byte(fmt.Sprintf("%x", i))
+		got, err := parseHexUint(line)
+		if err != nil {
+			t.Fatalf("on %d: %v", i, err)
+		}
+		if got != i {
+			t.Errorf("for input %q = %d; want %d", line, got, i)
+		}
+	}
+	_, err := parseHexUint([]byte("bogus"))
+	if err == nil {
+		t.Error("expected error on bogus input")
+	}
+}
diff --git a/src/net/http/jar.go b/src/net/http/jar.go
new file mode 100644
index 000000000..5c3de0dad
--- /dev/null
+++ b/src/net/http/jar.go
@@ -0,0 +1,27 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package http
+
+import (
+	"net/url"
+)
+
+// A CookieJar manages storage and use of cookies in HTTP requests.
+//
+// Implementations of CookieJar must be safe for concurrent use by multiple
+// goroutines.
+//
+// The net/http/cookiejar package provides a CookieJar implementation.
+type CookieJar interface {
+	// SetCookies handles the receipt of the cookies in a reply for the
+	// given URL.  It may or may not choose to save the cookies, depending
+	// on the jar's policy and implementation.
+	SetCookies(u *url.URL, cookies []*Cookie)
+
+	// Cookies returns the cookies to send in a request for the given URL.
+	// It is up to the implementation to honor the standard cookie use
+	// restrictions such as in RFC 6265.
+	Cookies(u *url.URL) []*Cookie
+}
diff --git a/src/net/http/lex.go b/src/net/http/lex.go
new file mode 100644
index 000000000..cb33318f4
--- /dev/null
+++ b/src/net/http/lex.go
@@ -0,0 +1,96 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package http
+
+// This file deals with lexical matters of HTTP
+
+var isTokenTable = [127]bool{
+	'!':  true,
+	'#':  true,
+	'$':  true,
+	'%':  true,
+	'&':  true,
+	'\'': true,
+	'*':  true,
+	'+':  true,
+	'-':  true,
+	'.':  true,
+	'0':  true,
+	'1':  true,
+	'2':  true,
+	'3':  true,
+	'4':  true,
+	'5':  true,
+	'6':  true,
+	'7':  true,
+	'8':  true,
+	'9':  true,
+	'A':  true,
+	'B':  true,
+	'C':  true,
+	'D':  true,
+	'E':  true,
+	'F':  true,
+	'G':  true,
+	'H':  true,
+	'I':  true,
+	'J':  true,
+	'K':  true,
+	'L':  true,
+	'M':  true,
+	'N':  true,
+	'O':  true,
+	'P':  true,
+	'Q':  true,
+	'R':  true,
+	'S':  true,
+	'T':  true,
+	'U':  true,
+	'W':  true,
+	'V':  true,
+	'X':  true,
+	'Y':  true,
+	'Z':  true,
+	'^':  true,
+	'_':  true,
+	'`':  true,
+	'a':  true,
+	'b':  true,
+	'c':  true,
+	'd':  true,
+	'e':  true,
+	'f':  true,
+	'g':  true,
+	'h':  true,
+	'i':  true,
+	'j':  true,
+	'k':  true,
+	'l':  true,
+	'm':  true,
+	'n':  true,
+	'o':  true,
+	'p':  true,
+	'q':  true,
+	'r':  true,
+	's':  true,
+	't':  true,
+	'u':  true,
+	'v':  true,
+	'w':  true,
+	'x':  true,
+	'y':  true,
+	'z':  true,
+	'|':  true,
+	'~':  true,
+}
+
+func isToken(r rune) bool {
+	i := int(r)
+	return i < len(isTokenTable) && isTokenTable[i]
+}
+
+func isNotToken(r rune) bool {
+	return !isToken(r)
+}
diff --git a/src/net/http/lex_test.go b/src/net/http/lex_test.go
new file mode 100644
index 000000000..6d9d294f7
--- /dev/null
+++ b/src/net/http/lex_test.go
@@ -0,0 +1,31 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package http
+
+import (
+	"testing"
+)
+
+func isChar(c rune) bool { return c <= 127 }
+
+func isCtl(c rune) bool { return c <= 31 || c == 127 }
+
+func isSeparator(c rune) bool {
+	switch c {
+	case '(', ')', '<', '>', '@', ',', ';', ':', '\\', '"', '/', '[', ']', '?', '=', '{', '}', ' ', '\t':
+		return true
+	}
+	return false
+}
+
+func TestIsToken(t *testing.T) {
+	for i := 0; i <= 130; i++ {
+		r := rune(i)
+		expected := isChar(r) && !isCtl(r) && !isSeparator(r)
+		if isToken(r) != expected {
+			t.Errorf("isToken(0x%x) = %v", r, !expected)
+		}
+	}
+}
diff --git a/src/net/http/npn_test.go b/src/net/http/npn_test.go
new file mode 100644
index 000000000..98b8930d0
--- /dev/null
+++ b/src/net/http/npn_test.go
@@ -0,0 +1,118 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package http_test
+
+import (
+	"bufio"
+	"crypto/tls"
+	"fmt"
+	"io"
+	"io/ioutil"
+	. "net/http"
+	"net/http/httptest"
+	"strings"
+	"testing"
+)
+
+func TestNextProtoUpgrade(t *testing.T) {
+	ts := httptest.NewUnstartedServer(HandlerFunc(func(w ResponseWriter, r *Request) {
+		fmt.Fprintf(w, "path=%s,proto=", r.URL.Path)
+		if r.TLS != nil {
+			w.Write([]byte(r.TLS.NegotiatedProtocol))
+		}
+		if r.RemoteAddr == "" {
+			t.Error("request with no RemoteAddr")
+		}
+		if r.Body == nil {
+			t.Errorf("request with nil Body")
+		}
+	}))
+	ts.TLS = &tls.Config{
+		NextProtos: []string{"unhandled-proto", "tls-0.9"},
+	}
+	ts.Config.TLSNextProto = map[string]func(*Server, *tls.Conn, Handler){
+		"tls-0.9": handleTLSProtocol09,
+	}
+	ts.StartTLS()
+	defer ts.Close()
+
+	tr := newTLSTransport(t, ts)
+	defer tr.CloseIdleConnections()
+	c := &Client{Transport: tr}
+
+	// Normal request, without NPN.
+	{
+		res, err := c.Get(ts.URL)
+		if err != nil {
+			t.Fatal(err)
+		}
+		body, err := ioutil.ReadAll(res.Body)
+		if err != nil {
+			t.Fatal(err)
+		}
+		if want := "path=/,proto="; string(body) != want {
+			t.Errorf("plain request = %q; want %q", body, want)
+		}
+	}
+
+	// Request to an advertised but unhandled NPN protocol.
+	// Server will hang up.
+	{
+		tr.CloseIdleConnections()
+		tr.TLSClientConfig.NextProtos = []string{"unhandled-proto"}
+		_, err := c.Get(ts.URL)
+		if err == nil {
+			t.Errorf("expected error on unhandled-proto request")
+		}
+	}
+
+	// Request using the "tls-0.9" protocol, which we register here.
+	// It is HTTP/0.9 over TLS.
+	{
+		tlsConfig := newTLSTransport(t, ts).TLSClientConfig
+		tlsConfig.NextProtos = []string{"tls-0.9"}
+		conn, err := tls.Dial("tcp", ts.Listener.Addr().String(), tlsConfig)
+		if err != nil {
+			t.Fatal(err)
+		}
+		conn.Write([]byte("GET /foo\n"))
+		body, err := ioutil.ReadAll(conn)
+		if err != nil {
+			t.Fatal(err)
+		}
+		if want := "path=/foo,proto=tls-0.9"; string(body) != want {
+			t.Errorf("plain request = %q; want %q", body, want)
+		}
+	}
+}
+
+// handleTLSProtocol09 implements the HTTP/0.9 protocol over TLS, for the
+// TestNextProtoUpgrade test.
+func handleTLSProtocol09(srv *Server, conn *tls.Conn, h Handler) {
+	br := bufio.NewReader(conn)
+	line, err := br.ReadString('\n')
+	if err != nil {
+		return
+	}
+	line = strings.TrimSpace(line)
+	path := strings.TrimPrefix(line, "GET ")
+	if path == line {
+		return
+	}
+	req, _ := NewRequest("GET", path, nil)
+	req.Proto = "HTTP/0.9"
+	req.ProtoMajor = 0
+	req.ProtoMinor = 9
+	rw := &http09Writer{conn, make(Header)}
+	h.ServeHTTP(rw, req)
+}
+
+type http09Writer struct {
+	io.Writer
+	h Header
+}
+
+func (w http09Writer) Header() Header  { return w.h }
+func (w http09Writer) WriteHeader(int) {} // no headers
diff --git a/src/net/http/pprof/pprof.go b/src/net/http/pprof/pprof.go
new file mode 100644
index 000000000..0c7548e3e
--- /dev/null
+++ b/src/net/http/pprof/pprof.go
@@ -0,0 +1,205 @@
+// Copyright 2010 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package pprof serves via its HTTP server runtime profiling data
+// in the format expected by the pprof visualization tool.
+// For more information about pprof, see
+// http://code.google.com/p/google-perftools/.
+//
+// The package is typically only imported for the side effect of
+// registering its HTTP handlers.
+// The handled paths all begin with /debug/pprof/.
+//
+// To use pprof, link this package into your program:
+//	import _ "net/http/pprof"
+//
+// If your application is not already running an http server, you
+// need to start one.  Add "net/http" and "log" to your imports and
+// the following code to your main function:
+//
+// 	go func() {
+// 		log.Println(http.ListenAndServe("localhost:6060", nil))
+// 	}()
+//
+// Then use the pprof tool to look at the heap profile:
+//
+//	go tool pprof http://localhost:6060/debug/pprof/heap
+//
+// Or to look at a 30-second CPU profile:
+//
+//	go tool pprof http://localhost:6060/debug/pprof/profile
+//
+// Or to look at the goroutine blocking profile:
+//
+//	go tool pprof http://localhost:6060/debug/pprof/block
+//
+// To view all available profiles, open http://localhost:6060/debug/pprof/
+// in your browser.
+//
+// For a study of the facility in action, visit
+//
+//	http://blog.golang.org/2011/06/profiling-go-programs.html
+//
+package pprof
+
+import (
+	"bufio"
+	"bytes"
+	"fmt"
+	"html/template"
+	"io"
+	"log"
+	"net/http"
+	"os"
+	"runtime"
+	"runtime/pprof"
+	"strconv"
+	"strings"
+	"time"
+)
+
+func init() {
+	http.Handle("/debug/pprof/", http.HandlerFunc(Index))
+	http.Handle("/debug/pprof/cmdline", http.HandlerFunc(Cmdline))
+	http.Handle("/debug/pprof/profile", http.HandlerFunc(Profile))
+	http.Handle("/debug/pprof/symbol", http.HandlerFunc(Symbol))
+}
+
+// Cmdline responds with the running program's
+// command line, with arguments separated by NUL bytes.
+// The package initialization registers it as /debug/pprof/cmdline.
+func Cmdline(w http.ResponseWriter, r *http.Request) {
+	w.Header().Set("Content-Type", "text/plain; charset=utf-8")
+	fmt.Fprintf(w, strings.Join(os.Args, "\x00"))
+}
+
+// Profile responds with the pprof-formatted cpu profile.
+// The package initialization registers it as /debug/pprof/profile.
+func Profile(w http.ResponseWriter, r *http.Request) {
+	sec, _ := strconv.ParseInt(r.FormValue("seconds"), 10, 64)
+	if sec == 0 {
+		sec = 30
+	}
+
+	// Set Content Type assuming StartCPUProfile will work,
+	// because if it does it starts writing.
+	w.Header().Set("Content-Type", "application/octet-stream")
+	if err := pprof.StartCPUProfile(w); err != nil {
+		// StartCPUProfile failed, so no writes yet.
+		// Can change header back to text content
+		// and send error code.
+		w.Header().Set("Content-Type", "text/plain; charset=utf-8")
+		w.WriteHeader(http.StatusInternalServerError)
+		fmt.Fprintf(w, "Could not enable CPU profiling: %s\n", err)
+		return
+	}
+	time.Sleep(time.Duration(sec) * time.Second)
+	pprof.StopCPUProfile()
+}
+
+// Symbol looks up the program counters listed in the request,
+// responding with a table mapping program counters to function names.
+// The package initialization registers it as /debug/pprof/symbol.
+func Symbol(w http.ResponseWriter, r *http.Request) {
+	w.Header().Set("Content-Type", "text/plain; charset=utf-8")
+
+	// We have to read the whole POST body before
+	// writing any output.  Buffer the output here.
+	var buf bytes.Buffer
+
+	// We don't know how many symbols we have, but we
+	// do have symbol information.  Pprof only cares whether
+	// this number is 0 (no symbols available) or > 0.
+	fmt.Fprintf(&buf, "num_symbols: 1\n")
+
+	var b *bufio.Reader
+	if r.Method == "POST" {
+		b = bufio.NewReader(r.Body)
+	} else {
+		b = bufio.NewReader(strings.NewReader(r.URL.RawQuery))
+	}
+
+	for {
+		word, err := b.ReadSlice('+')
+		if err == nil {
+			word = word[0 : len(word)-1] // trim +
+		}
+		pc, _ := strconv.ParseUint(string(word), 0, 64)
+		if pc != 0 {
+			f := runtime.FuncForPC(uintptr(pc))
+			if f != nil {
+				fmt.Fprintf(&buf, "%#x %s\n", pc, f.Name())
+			}
+		}
+
+		// Wait until here to check for err; the last
+		// symbol will have an err because it doesn't end in +.
+		if err != nil {
+			if err != io.EOF {
+				fmt.Fprintf(&buf, "reading request: %v\n", err)
+			}
+			break
+		}
+	}
+
+	w.Write(buf.Bytes())
+}
+
+// Handler returns an HTTP handler that serves the named profile.
+func Handler(name string) http.Handler {
+	return handler(name)
+}
+
+type handler string
+
+func (name handler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
+	w.Header().Set("Content-Type", "text/plain; charset=utf-8")
+	debug, _ := strconv.Atoi(r.FormValue("debug"))
+	p := pprof.Lookup(string(name))
+	if p == nil {
+		w.WriteHeader(404)
+		fmt.Fprintf(w, "Unknown profile: %s\n", name)
+		return
+	}
+	p.WriteTo(w, debug)
+	return
+}
+
+// Index responds with the pprof-formatted profile named by the request.
+// For example, "/debug/pprof/heap" serves the "heap" profile.
+// Index responds to a request for "/debug/pprof/" with an HTML page
+// listing the available profiles.
+func Index(w http.ResponseWriter, r *http.Request) {
+	if strings.HasPrefix(r.URL.Path, "/debug/pprof/") {
+		name := strings.TrimPrefix(r.URL.Path, "/debug/pprof/")
+		if name != "" {
+			handler(name).ServeHTTP(w, r)
+			return
+		}
+	}
+
+	profiles := pprof.Profiles()
+	if err := indexTmpl.Execute(w, profiles); err != nil {
+		log.Print(err)
+	}
+}
+
+var indexTmpl = template.Must(template.New("index").Parse(`<html>
+<head>
+<title>/debug/pprof/</title>
+</head>
+/debug/pprof/<br>
+<br>
+<body>
+profiles:<br>
+<table>
+{{range .}}
+<tr><td align=right>{{.Count}}<td><a href="/debug/pprof/{{.Name}}?debug=1">{{.Name}}</a>
+{{end}}
+</table>
+<br>
+<a href="/debug/pprof/goroutine?debug=2">full goroutine stack dump</a><br>
+</body>
+</html>
+`))
diff --git a/src/net/http/proxy_test.go b/src/net/http/proxy_test.go
new file mode 100644
index 000000000..b6aed3792
--- /dev/null
+++ b/src/net/http/proxy_test.go
@@ -0,0 +1,81 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package http
+
+import (
+	"net/url"
+	"os"
+	"testing"
+)
+
+// TODO(mattn):
+//	test ProxyAuth
+
+var UseProxyTests = []struct {
+	host  string
+	match bool
+}{
+	// Never proxy localhost:
+	{"localhost:80", false},
+	{"127.0.0.1", false},
+	{"127.0.0.2", false},
+	{"[::1]", false},
+	{"[::2]", true}, // not a loopback address
+
+	{"barbaz.net", false},     // match as .barbaz.net
+	{"foobar.com", false},     // have a port but match
+	{"foofoobar.com", true},   // not match as a part of foobar.com
+	{"baz.com", true},         // not match as a part of barbaz.com
+	{"localhost.net", true},   // not match as suffix of address
+	{"local.localhost", true}, // not match as prefix as address
+	{"barbarbaz.net", true},   // not match because NO_PROXY have a '.'
+	{"www.foobar.com", false}, // match because NO_PROXY includes "foobar.com"
+}
+
+func TestUseProxy(t *testing.T) {
+	ResetProxyEnv()
+	os.Setenv("NO_PROXY", "foobar.com, .barbaz.net")
+	for _, test := range UseProxyTests {
+		if useProxy(test.host+":80") != test.match {
+			t.Errorf("useProxy(%v) = %v, want %v", test.host, !test.match, test.match)
+		}
+	}
+}
+
+var cacheKeysTests = []struct {
+	proxy  string
+	scheme string
+	addr   string
+	key    string
+}{
+	{"", "http", "foo.com", "|http|foo.com"},
+	{"", "https", "foo.com", "|https|foo.com"},
+	{"http://foo.com", "http", "foo.com", "http://foo.com|http|"},
+	{"http://foo.com", "https", "foo.com", "http://foo.com|https|foo.com"},
+}
+
+func TestCacheKeys(t *testing.T) {
+	for _, tt := range cacheKeysTests {
+		var proxy *url.URL
+		if tt.proxy != "" {
+			u, err := url.Parse(tt.proxy)
+			if err != nil {
+				t.Fatal(err)
+			}
+			proxy = u
+		}
+		cm := connectMethod{proxy, tt.scheme, tt.addr}
+		if got := cm.key().String(); got != tt.key {
+			t.Fatalf("{%q, %q, %q} cache key = %q; want %q", tt.proxy, tt.scheme, tt.addr, got, tt.key)
+		}
+	}
+}
+
+func ResetProxyEnv() {
+	for _, v := range []string{"HTTP_PROXY", "http_proxy", "NO_PROXY", "no_proxy"} {
+		os.Setenv(v, "")
+	}
+	ResetCachedEnvironment()
+}
diff --git a/src/net/http/race.go b/src/net/http/race.go
new file mode 100644
index 000000000..766503967
--- /dev/null
+++ b/src/net/http/race.go
@@ -0,0 +1,11 @@
+// Copyright 2014 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build race
+
+package http
+
+func init() {
+	raceEnabled = true
+}
diff --git a/src/net/http/range_test.go b/src/net/http/range_test.go
new file mode 100644
index 000000000..ef911af7b
--- /dev/null
+++ b/src/net/http/range_test.go
@@ -0,0 +1,79 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package http
+
+import (
+	"testing"
+)
+
+var ParseRangeTests = []struct {
+	s      string
+	length int64
+	r      []httpRange
+}{
+	{"", 0, nil},
+	{"", 1000, nil},
+	{"foo", 0, nil},
+	{"bytes=", 0, nil},
+	{"bytes=7", 10, nil},
+	{"bytes= 7 ", 10, nil},
+	{"bytes=1-", 0, nil},
+	{"bytes=5-4", 10, nil},
+	{"bytes=0-2,5-4", 10, nil},
+	{"bytes=2-5,4-3", 10, nil},
+	{"bytes=--5,4--3", 10, nil},
+	{"bytes=A-", 10, nil},
+	{"bytes=A- ", 10, nil},
+	{"bytes=A-Z", 10, nil},
+	{"bytes= -Z", 10, nil},
+	{"bytes=5-Z", 10, nil},
+	{"bytes=Ran-dom, garbage", 10, nil},
+	{"bytes=0x01-0x02", 10, nil},
+	{"bytes=         ", 10, nil},
+	{"bytes= , , ,   ", 10, nil},
+
+	{"bytes=0-9", 10, []httpRange{{0, 10}}},
+	{"bytes=0-", 10, []httpRange{{0, 10}}},
+	{"bytes=5-", 10, []httpRange{{5, 5}}},
+	{"bytes=0-20", 10, []httpRange{{0, 10}}},
+	{"bytes=15-,0-5", 10, nil},
+	{"bytes=1-2,5-", 10, []httpRange{{1, 2}, {5, 5}}},
+	{"bytes=-2 , 7-", 11, []httpRange{{9, 2}, {7, 4}}},
+	{"bytes=0-0 ,2-2, 7-", 11, []httpRange{{0, 1}, {2, 1}, {7, 4}}},
+	{"bytes=-5", 10, []httpRange{{5, 5}}},
+	{"bytes=-15", 10, []httpRange{{0, 10}}},
+	{"bytes=0-499", 10000, []httpRange{{0, 500}}},
+	{"bytes=500-999", 10000, []httpRange{{500, 500}}},
+	{"bytes=-500", 10000, []httpRange{{9500, 500}}},
+	{"bytes=9500-", 10000, []httpRange{{9500, 500}}},
+	{"bytes=0-0,-1", 10000, []httpRange{{0, 1}, {9999, 1}}},
+	{"bytes=500-600,601-999", 10000, []httpRange{{500, 101}, {601, 399}}},
+	{"bytes=500-700,601-999", 10000, []httpRange{{500, 201}, {601, 399}}},
+
+	// Match Apache laxity:
+	{"bytes=   1 -2   ,  4- 5, 7 - 8 , ,,", 11, []httpRange{{1, 2}, {4, 2}, {7, 2}}},
+}
+
+func TestParseRange(t *testing.T) {
+	for _, test := range ParseRangeTests {
+		r := test.r
+		ranges, err := parseRange(test.s, test.length)
+		if err != nil && r != nil {
+			t.Errorf("parseRange(%q) returned error %q", test.s, err)
+		}
+		if len(ranges) != len(r) {
+			t.Errorf("len(parseRange(%q)) = %d, want %d", test.s, len(ranges), len(r))
+			continue
+		}
+		for i := range r {
+			if ranges[i].start != r[i].start {
+				t.Errorf("parseRange(%q)[%d].start = %d, want %d", test.s, i, ranges[i].start, r[i].start)
+			}
+			if ranges[i].length != r[i].length {
+				t.Errorf("parseRange(%q)[%d].length = %d, want %d", test.s, i, ranges[i].length, r[i].length)
+			}
+		}
+	}
+}
diff --git a/src/net/http/readrequest_test.go b/src/net/http/readrequest_test.go
new file mode 100644
index 000000000..e930d99af
--- /dev/null
+++ b/src/net/http/readrequest_test.go
@@ -0,0 +1,358 @@
+// Copyright 2010 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package http
+
+import (
+	"bufio"
+	"bytes"
+	"fmt"
+	"io"
+	"net/url"
+	"reflect"
+	"strings"
+	"testing"
+)
+
+type reqTest struct {
+	Raw     string
+	Req     *Request
+	Body    string
+	Trailer Header
+	Error   string
+}
+
+var noError = ""
+var noBody = ""
+var noTrailer Header = nil
+
+var reqTests = []reqTest{
+	// Baseline test; All Request fields included for template use
+	{
+		"GET http://www.techcrunch.com/ HTTP/1.1\r\n" +
+			"Host: www.techcrunch.com\r\n" +
+			"User-Agent: Fake\r\n" +
+			"Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8\r\n" +
+			"Accept-Language: en-us,en;q=0.5\r\n" +
+			"Accept-Encoding: gzip,deflate\r\n" +
+			"Accept-Charset: ISO-8859-1,utf-8;q=0.7,*;q=0.7\r\n" +
+			"Keep-Alive: 300\r\n" +
+			"Content-Length: 7\r\n" +
+			"Proxy-Connection: keep-alive\r\n\r\n" +
+			"abcdef\n???",
+
+		&Request{
+			Method: "GET",
+			URL: &url.URL{
+				Scheme: "http",
+				Host:   "www.techcrunch.com",
+				Path:   "/",
+			},
+			Proto:      "HTTP/1.1",
+			ProtoMajor: 1,
+			ProtoMinor: 1,
+			Header: Header{
+				"Accept":           {"text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8"},
+				"Accept-Language":  {"en-us,en;q=0.5"},
+				"Accept-Encoding":  {"gzip,deflate"},
+				"Accept-Charset":   {"ISO-8859-1,utf-8;q=0.7,*;q=0.7"},
+				"Keep-Alive":       {"300"},
+				"Proxy-Connection": {"keep-alive"},
+				"Content-Length":   {"7"},
+				"User-Agent":       {"Fake"},
+			},
+			Close:         false,
+			ContentLength: 7,
+			Host:          "www.techcrunch.com",
+			RequestURI:    "http://www.techcrunch.com/",
+		},
+
+		"abcdef\n",
+
+		noTrailer,
+		noError,
+	},
+
+	// GET request with no body (the normal case)
+	{
+		"GET / HTTP/1.1\r\n" +
+			"Host: foo.com\r\n\r\n",
+
+		&Request{
+			Method: "GET",
+			URL: &url.URL{
+				Path: "/",
+			},
+			Proto:         "HTTP/1.1",
+			ProtoMajor:    1,
+			ProtoMinor:    1,
+			Header:        Header{},
+			Close:         false,
+			ContentLength: 0,
+			Host:          "foo.com",
+			RequestURI:    "/",
+		},
+
+		noBody,
+		noTrailer,
+		noError,
+	},
+
+	// Tests that we don't parse a path that looks like a
+	// scheme-relative URI as a scheme-relative URI.
+	{
+		"GET //user@host/is/actually/a/path/ HTTP/1.1\r\n" +
+			"Host: test\r\n\r\n",
+
+		&Request{
+			Method: "GET",
+			URL: &url.URL{
+				Path: "//user@host/is/actually/a/path/",
+			},
+			Proto:         "HTTP/1.1",
+			ProtoMajor:    1,
+			ProtoMinor:    1,
+			Header:        Header{},
+			Close:         false,
+			ContentLength: 0,
+			Host:          "test",
+			RequestURI:    "//user@host/is/actually/a/path/",
+		},
+
+		noBody,
+		noTrailer,
+		noError,
+	},
+
+	// Tests a bogus abs_path on the Request-Line (RFC 2616 section 5.1.2)
+	{
+		"GET ../../../../etc/passwd HTTP/1.1\r\n" +
+			"Host: test\r\n\r\n",
+		nil,
+		noBody,
+		noTrailer,
+		"parse ../../../../etc/passwd: invalid URI for request",
+	},
+
+	// Tests missing URL:
+	{
+		"GET  HTTP/1.1\r\n" +
+			"Host: test\r\n\r\n",
+		nil,
+		noBody,
+		noTrailer,
+		"parse : empty url",
+	},
+
+	// Tests chunked body with trailer:
+	{
+		"POST / HTTP/1.1\r\n" +
+			"Host: foo.com\r\n" +
+			"Transfer-Encoding: chunked\r\n\r\n" +
+			"3\r\nfoo\r\n" +
+			"3\r\nbar\r\n" +
+			"0\r\n" +
+			"Trailer-Key: Trailer-Value\r\n" +
+			"\r\n",
+		&Request{
+			Method: "POST",
+			URL: &url.URL{
+				Path: "/",
+			},
+			TransferEncoding: []string{"chunked"},
+			Proto:            "HTTP/1.1",
+			ProtoMajor:       1,
+			ProtoMinor:       1,
+			Header:           Header{},
+			ContentLength:    -1,
+			Host:             "foo.com",
+			RequestURI:       "/",
+		},
+
+		"foobar",
+		Header{
+			"Trailer-Key": {"Trailer-Value"},
+		},
+		noError,
+	},
+
+	// CONNECT request with domain name:
+	{
+		"CONNECT www.google.com:443 HTTP/1.1\r\n\r\n",
+
+		&Request{
+			Method: "CONNECT",
+			URL: &url.URL{
+				Host: "www.google.com:443",
+			},
+			Proto:         "HTTP/1.1",
+			ProtoMajor:    1,
+			ProtoMinor:    1,
+			Header:        Header{},
+			Close:         false,
+			ContentLength: 0,
+			Host:          "www.google.com:443",
+			RequestURI:    "www.google.com:443",
+		},
+
+		noBody,
+		noTrailer,
+		noError,
+	},
+
+	// CONNECT request with IP address:
+	{
+		"CONNECT 127.0.0.1:6060 HTTP/1.1\r\n\r\n",
+
+		&Request{
+			Method: "CONNECT",
+			URL: &url.URL{
+				Host: "127.0.0.1:6060",
+			},
+			Proto:         "HTTP/1.1",
+			ProtoMajor:    1,
+			ProtoMinor:    1,
+			Header:        Header{},
+			Close:         false,
+			ContentLength: 0,
+			Host:          "127.0.0.1:6060",
+			RequestURI:    "127.0.0.1:6060",
+		},
+
+		noBody,
+		noTrailer,
+		noError,
+	},
+
+	// CONNECT request for RPC:
+	{
+		"CONNECT /_goRPC_ HTTP/1.1\r\n\r\n",
+
+		&Request{
+			Method: "CONNECT",
+			URL: &url.URL{
+				Path: "/_goRPC_",
+			},
+			Proto:         "HTTP/1.1",
+			ProtoMajor:    1,
+			ProtoMinor:    1,
+			Header:        Header{},
+			Close:         false,
+			ContentLength: 0,
+			Host:          "",
+			RequestURI:    "/_goRPC_",
+		},
+
+		noBody,
+		noTrailer,
+		noError,
+	},
+
+	// SSDP Notify request. golang.org/issue/3692
+	{
+		"NOTIFY * HTTP/1.1\r\nServer: foo\r\n\r\n",
+		&Request{
+			Method: "NOTIFY",
+			URL: &url.URL{
+				Path: "*",
+			},
+			Proto:      "HTTP/1.1",
+			ProtoMajor: 1,
+			ProtoMinor: 1,
+			Header: Header{
+				"Server": []string{"foo"},
+			},
+			Close:         false,
+			ContentLength: 0,
+			RequestURI:    "*",
+		},
+
+		noBody,
+		noTrailer,
+		noError,
+	},
+
+	// OPTIONS request. Similar to golang.org/issue/3692
+	{
+		"OPTIONS * HTTP/1.1\r\nServer: foo\r\n\r\n",
+		&Request{
+			Method: "OPTIONS",
+			URL: &url.URL{
+				Path: "*",
+			},
+			Proto:      "HTTP/1.1",
+			ProtoMajor: 1,
+			ProtoMinor: 1,
+			Header: Header{
+				"Server": []string{"foo"},
+			},
+			Close:         false,
+			ContentLength: 0,
+			RequestURI:    "*",
+		},
+
+		noBody,
+		noTrailer,
+		noError,
+	},
+
+	// Connection: close. golang.org/issue/8261
+	{
+		"GET / HTTP/1.1\r\nHost: issue8261.com\r\nConnection: close\r\n\r\n",
+		&Request{
+			Method: "GET",
+			URL: &url.URL{
+				Path: "/",
+			},
+			Header: Header{
+				// This wasn't removed from Go 1.0 to
+				// Go 1.3, so locking it in that we
+				// keep this:
+				"Connection": []string{"close"},
+			},
+			Host:       "issue8261.com",
+			Proto:      "HTTP/1.1",
+			ProtoMajor: 1,
+			ProtoMinor: 1,
+			Close:      true,
+			RequestURI: "/",
+		},
+
+		noBody,
+		noTrailer,
+		noError,
+	},
+}
+
+func TestReadRequest(t *testing.T) {
+	for i := range reqTests {
+		tt := &reqTests[i]
+		req, err := ReadRequest(bufio.NewReader(strings.NewReader(tt.Raw)))
+		if err != nil {
+			if err.Error() != tt.Error {
+				t.Errorf("#%d: error %q, want error %q", i, err.Error(), tt.Error)
+			}
+			continue
+		}
+		rbody := req.Body
+		req.Body = nil
+		testName := fmt.Sprintf("Test %d (%q)", i, tt.Raw)
+		diff(t, testName, req, tt.Req)
+		var bout bytes.Buffer
+		if rbody != nil {
+			_, err := io.Copy(&bout, rbody)
+			if err != nil {
+				t.Fatalf("%s: copying body: %v", testName, err)
+			}
+			rbody.Close()
+		}
+		body := bout.String()
+		if body != tt.Body {
+			t.Errorf("%s: Body = %q want %q", testName, body, tt.Body)
+		}
+		if !reflect.DeepEqual(tt.Trailer, req.Trailer) {
+			t.Errorf("%s: Trailers differ.\n got: %v\nwant: %v", testName, req.Trailer, tt.Trailer)
+		}
+	}
+}
diff --git a/src/net/http/request.go b/src/net/http/request.go
new file mode 100644
index 000000000..263c26c9b
--- /dev/null
+++ b/src/net/http/request.go
@@ -0,0 +1,920 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// HTTP Request reading and parsing.
+
+package http
+
+import (
+	"bufio"
+	"bytes"
+	"crypto/tls"
+	"encoding/base64"
+	"errors"
+	"fmt"
+	"io"
+	"io/ioutil"
+	"mime"
+	"mime/multipart"
+	"net/textproto"
+	"net/url"
+	"strconv"
+	"strings"
+	"sync"
+)
+
+const (
+	maxValueLength   = 4096
+	maxHeaderLines   = 1024
+	chunkSize        = 4 << 10  // 4 KB chunks
+	defaultMaxMemory = 32 << 20 // 32 MB
+)
+
+// ErrMissingFile is returned by FormFile when the provided file field name
+// is either not present in the request or not a file field.
+var ErrMissingFile = errors.New("http: no such file")
+
+// HTTP request parsing errors.
+type ProtocolError struct {
+	ErrorString string
+}
+
+func (err *ProtocolError) Error() string { return err.ErrorString }
+
+var (
+	ErrHeaderTooLong        = &ProtocolError{"header too long"}
+	ErrShortBody            = &ProtocolError{"entity body too short"}
+	ErrNotSupported         = &ProtocolError{"feature not supported"}
+	ErrUnexpectedTrailer    = &ProtocolError{"trailer header without chunked transfer encoding"}
+	ErrMissingContentLength = &ProtocolError{"missing ContentLength in HEAD response"}
+	ErrNotMultipart         = &ProtocolError{"request Content-Type isn't multipart/form-data"}
+	ErrMissingBoundary      = &ProtocolError{"no multipart boundary param in Content-Type"}
+)
+
+type badStringError struct {
+	what string
+	str  string
+}
+
+func (e *badStringError) Error() string { return fmt.Sprintf("%s %q", e.what, e.str) }
+
+// Headers that Request.Write handles itself and should be skipped.
+var reqWriteExcludeHeader = map[string]bool{
+	"Host":              true, // not in Header map anyway
+	"User-Agent":        true,
+	"Content-Length":    true,
+	"Transfer-Encoding": true,
+	"Trailer":           true,
+}
+
+// A Request represents an HTTP request received by a server
+// or to be sent by a client.
+//
+// The field semantics differ slightly between client and server
+// usage. In addition to the notes on the fields below, see the
+// documentation for Request.Write and RoundTripper.
+type Request struct {
+	// Method specifies the HTTP method (GET, POST, PUT, etc.).
+	// For client requests an empty string means GET.
+	Method string
+
+	// URL specifies either the URI being requested (for server
+	// requests) or the URL to access (for client requests).
+	//
+	// For server requests the URL is parsed from the URI
+	// supplied on the Request-Line as stored in RequestURI.  For
+	// most requests, fields other than Path and RawQuery will be
+	// empty. (See RFC 2616, Section 5.1.2)
+	//
+	// For client requests, the URL's Host specifies the server to
+	// connect to, while the Request's Host field optionally
+	// specifies the Host header value to send in the HTTP
+	// request.
+	URL *url.URL
+
+	// The protocol version for incoming requests.
+	// Client requests always use HTTP/1.1.
+	Proto      string // "HTTP/1.0"
+	ProtoMajor int    // 1
+	ProtoMinor int    // 0
+
+	// A header maps request lines to their values.
+	// If the header says
+	//
+	//	accept-encoding: gzip, deflate
+	//	Accept-Language: en-us
+	//	Connection: keep-alive
+	//
+	// then
+	//
+	//	Header = map[string][]string{
+	//		"Accept-Encoding": {"gzip, deflate"},
+	//		"Accept-Language": {"en-us"},
+	//		"Connection": {"keep-alive"},
+	//	}
+	//
+	// HTTP defines that header names are case-insensitive.
+	// The request parser implements this by canonicalizing the
+	// name, making the first character and any characters
+	// following a hyphen uppercase and the rest lowercase.
+	//
+	// For client requests certain headers are automatically
+	// added and may override values in Header.
+	//
+	// See the documentation for the Request.Write method.
+	Header Header
+
+	// Body is the request's body.
+	//
+	// For client requests a nil body means the request has no
+	// body, such as a GET request. The HTTP Client's Transport
+	// is responsible for calling the Close method.
+	//
+	// For server requests the Request Body is always non-nil
+	// but will return EOF immediately when no body is present.
+	// The Server will close the request body. The ServeHTTP
+	// Handler does not need to.
+	Body io.ReadCloser
+
+	// ContentLength records the length of the associated content.
+	// The value -1 indicates that the length is unknown.
+	// Values >= 0 indicate that the given number of bytes may
+	// be read from Body.
+	// For client requests, a value of 0 means unknown if Body is not nil.
+	ContentLength int64
+
+	// TransferEncoding lists the transfer encodings from outermost to
+	// innermost. An empty list denotes the "identity" encoding.
+	// TransferEncoding can usually be ignored; chunked encoding is
+	// automatically added and removed as necessary when sending and
+	// receiving requests.
+	TransferEncoding []string
+
+	// Close indicates whether to close the connection after
+	// replying to this request (for servers) or after sending
+	// the request (for clients).
+	Close bool
+
+	// For server requests Host specifies the host on which the
+	// URL is sought. Per RFC 2616, this is either the value of
+	// the "Host" header or the host name given in the URL itself.
+	// It may be of the form "host:port".
+	//
+	// For client requests Host optionally overrides the Host
+	// header to send. If empty, the Request.Write method uses
+	// the value of URL.Host.
+	Host string
+
+	// Form contains the parsed form data, including both the URL
+	// field's query parameters and the POST or PUT form data.
+	// This field is only available after ParseForm is called.
+	// The HTTP client ignores Form and uses Body instead.
+	Form url.Values
+
+	// PostForm contains the parsed form data from POST or PUT
+	// body parameters.
+	// This field is only available after ParseForm is called.
+	// The HTTP client ignores PostForm and uses Body instead.
+	PostForm url.Values
+
+	// MultipartForm is the parsed multipart form, including file uploads.
+	// This field is only available after ParseMultipartForm is called.
+	// The HTTP client ignores MultipartForm and uses Body instead.
+	MultipartForm *multipart.Form
+
+	// Trailer specifies additional headers that are sent after the request
+	// body.
+	//
+	// For server requests the Trailer map initially contains only the
+	// trailer keys, with nil values. (The client declares which trailers it
+	// will later send.)  While the handler is reading from Body, it must
+	// not reference Trailer. After reading from Body returns EOF, Trailer
+	// can be read again and will contain non-nil values, if they were sent
+	// by the client.
+	//
+	// For client requests Trailer must be initialized to a map containing
+	// the trailer keys to later send. The values may be nil or their final
+	// values. The ContentLength must be 0 or -1, to send a chunked request.
+	// After the HTTP request is sent the map values can be updated while
+	// the request body is read. Once the body returns EOF, the caller must
+	// not mutate Trailer.
+	//
+	// Few HTTP clients, servers, or proxies support HTTP trailers.
+	Trailer Header
+
+	// RemoteAddr allows HTTP servers and other software to record
+	// the network address that sent the request, usually for
+	// logging. This field is not filled in by ReadRequest and
+	// has no defined format. The HTTP server in this package
+	// sets RemoteAddr to an "IP:port" address before invoking a
+	// handler.
+	// This field is ignored by the HTTP client.
+	RemoteAddr string
+
+	// RequestURI is the unmodified Request-URI of the
+	// Request-Line (RFC 2616, Section 5.1) as sent by the client
+	// to a server. Usually the URL field should be used instead.
+	// It is an error to set this field in an HTTP client request.
+	RequestURI string
+
+	// TLS allows HTTP servers and other software to record
+	// information about the TLS connection on which the request
+	// was received. This field is not filled in by ReadRequest.
+	// The HTTP server in this package sets the field for
+	// TLS-enabled connections before invoking a handler;
+	// otherwise it leaves the field nil.
+	// This field is ignored by the HTTP client.
+	TLS *tls.ConnectionState
+}
+
+// ProtoAtLeast reports whether the HTTP protocol used
+// in the request is at least major.minor.
+func (r *Request) ProtoAtLeast(major, minor int) bool {
+	return r.ProtoMajor > major ||
+		r.ProtoMajor == major && r.ProtoMinor >= minor
+}
+
+// UserAgent returns the client's User-Agent, if sent in the request.
+func (r *Request) UserAgent() string {
+	return r.Header.Get("User-Agent")
+}
+
+// Cookies parses and returns the HTTP cookies sent with the request.
+func (r *Request) Cookies() []*Cookie {
+	return readCookies(r.Header, "")
+}
+
+var ErrNoCookie = errors.New("http: named cookie not present")
+
+// Cookie returns the named cookie provided in the request or
+// ErrNoCookie if not found.
+func (r *Request) Cookie(name string) (*Cookie, error) {
+	for _, c := range readCookies(r.Header, name) {
+		return c, nil
+	}
+	return nil, ErrNoCookie
+}
+
+// AddCookie adds a cookie to the request.  Per RFC 6265 section 5.4,
+// AddCookie does not attach more than one Cookie header field.  That
+// means all cookies, if any, are written into the same line,
+// separated by semicolon.
+func (r *Request) AddCookie(c *Cookie) {
+	s := fmt.Sprintf("%s=%s", sanitizeCookieName(c.Name), sanitizeCookieValue(c.Value))
+	if c := r.Header.Get("Cookie"); c != "" {
+		r.Header.Set("Cookie", c+"; "+s)
+	} else {
+		r.Header.Set("Cookie", s)
+	}
+}
+
+// Referer returns the referring URL, if sent in the request.
+//
+// Referer is misspelled as in the request itself, a mistake from the
+// earliest days of HTTP.  This value can also be fetched from the
+// Header map as Header["Referer"]; the benefit of making it available
+// as a method is that the compiler can diagnose programs that use the
+// alternate (correct English) spelling req.Referrer() but cannot
+// diagnose programs that use Header["Referrer"].
+func (r *Request) Referer() string {
+	return r.Header.Get("Referer")
+}
+
+// multipartByReader is a sentinel value.
+// Its presence in Request.MultipartForm indicates that parsing of the request
+// body has been handed off to a MultipartReader instead of ParseMultipartFrom.
+var multipartByReader = &multipart.Form{
+	Value: make(map[string][]string),
+	File:  make(map[string][]*multipart.FileHeader),
+}
+
+// MultipartReader returns a MIME multipart reader if this is a
+// multipart/form-data POST request, else returns nil and an error.
+// Use this function instead of ParseMultipartForm to
+// process the request body as a stream.
+func (r *Request) MultipartReader() (*multipart.Reader, error) {
+	if r.MultipartForm == multipartByReader {
+		return nil, errors.New("http: MultipartReader called twice")
+	}
+	if r.MultipartForm != nil {
+		return nil, errors.New("http: multipart handled by ParseMultipartForm")
+	}
+	r.MultipartForm = multipartByReader
+	return r.multipartReader()
+}
+
+func (r *Request) multipartReader() (*multipart.Reader, error) {
+	v := r.Header.Get("Content-Type")
+	if v == "" {
+		return nil, ErrNotMultipart
+	}
+	d, params, err := mime.ParseMediaType(v)
+	if err != nil || d != "multipart/form-data" {
+		return nil, ErrNotMultipart
+	}
+	boundary, ok := params["boundary"]
+	if !ok {
+		return nil, ErrMissingBoundary
+	}
+	return multipart.NewReader(r.Body, boundary), nil
+}
+
+// Return value if nonempty, def otherwise.
+func valueOrDefault(value, def string) string {
+	if value != "" {
+		return value
+	}
+	return def
+}
+
+// NOTE: This is not intended to reflect the actual Go version being used.
+// It was changed from "Go http package" to "Go 1.1 package http" at the
+// time of the Go 1.1 release because the former User-Agent had ended up
+// on a blacklist for some intrusion detection systems.
+// See https://codereview.appspot.com/7532043.
+const defaultUserAgent = "Go 1.1 package http"
+
+// Write writes an HTTP/1.1 request -- header and body -- in wire format.
+// This method consults the following fields of the request:
+//	Host
+//	URL
+//	Method (defaults to "GET")
+//	Header
+//	ContentLength
+//	TransferEncoding
+//	Body
+//
+// If Body is present, Content-Length is <= 0 and TransferEncoding
+// hasn't been set to "identity", Write adds "Transfer-Encoding:
+// chunked" to the header. Body is closed after it is sent.
+func (r *Request) Write(w io.Writer) error {
+	return r.write(w, false, nil)
+}
+
+// WriteProxy is like Write but writes the request in the form
+// expected by an HTTP proxy.  In particular, WriteProxy writes the
+// initial Request-URI line of the request with an absolute URI, per
+// section 5.1.2 of RFC 2616, including the scheme and host.
+// In either case, WriteProxy also writes a Host header, using
+// either r.Host or r.URL.Host.
+func (r *Request) WriteProxy(w io.Writer) error {
+	return r.write(w, true, nil)
+}
+
+// extraHeaders may be nil
+func (req *Request) write(w io.Writer, usingProxy bool, extraHeaders Header) error {
+	host := req.Host
+	if host == "" {
+		if req.URL == nil {
+			return errors.New("http: Request.Write on Request with no Host or URL set")
+		}
+		host = req.URL.Host
+	}
+
+	ruri := req.URL.RequestURI()
+	if usingProxy && req.URL.Scheme != "" && req.URL.Opaque == "" {
+		ruri = req.URL.Scheme + "://" + host + ruri
+	} else if req.Method == "CONNECT" && req.URL.Path == "" {
+		// CONNECT requests normally give just the host and port, not a full URL.
+		ruri = host
+	}
+	// TODO(bradfitz): escape at least newlines in ruri?
+
+	// Wrap the writer in a bufio Writer if it's not already buffered.
+	// Don't always call NewWriter, as that forces a bytes.Buffer
+	// and other small bufio Writers to have a minimum 4k buffer
+	// size.
+	var bw *bufio.Writer
+	if _, ok := w.(io.ByteWriter); !ok {
+		bw = bufio.NewWriter(w)
+		w = bw
+	}
+
+	_, err := fmt.Fprintf(w, "%s %s HTTP/1.1\r\n", valueOrDefault(req.Method, "GET"), ruri)
+	if err != nil {
+		return err
+	}
+
+	// Header lines
+	_, err = fmt.Fprintf(w, "Host: %s\r\n", host)
+	if err != nil {
+		return err
+	}
+
+	// Use the defaultUserAgent unless the Header contains one, which
+	// may be blank to not send the header.
+	userAgent := defaultUserAgent
+	if req.Header != nil {
+		if ua := req.Header["User-Agent"]; len(ua) > 0 {
+			userAgent = ua[0]
+		}
+	}
+	if userAgent != "" {
+		_, err = fmt.Fprintf(w, "User-Agent: %s\r\n", userAgent)
+		if err != nil {
+			return err
+		}
+	}
+
+	// Process Body,ContentLength,Close,Trailer
+	tw, err := newTransferWriter(req)
+	if err != nil {
+		return err
+	}
+	err = tw.WriteHeader(w)
+	if err != nil {
+		return err
+	}
+
+	err = req.Header.WriteSubset(w, reqWriteExcludeHeader)
+	if err != nil {
+		return err
+	}
+
+	if extraHeaders != nil {
+		err = extraHeaders.Write(w)
+		if err != nil {
+			return err
+		}
+	}
+
+	_, err = io.WriteString(w, "\r\n")
+	if err != nil {
+		return err
+	}
+
+	// Write body and trailer
+	err = tw.WriteBody(w)
+	if err != nil {
+		return err
+	}
+
+	if bw != nil {
+		return bw.Flush()
+	}
+	return nil
+}
+
+// ParseHTTPVersion parses a HTTP version string.
+// "HTTP/1.0" returns (1, 0, true).
+func ParseHTTPVersion(vers string) (major, minor int, ok bool) {
+	const Big = 1000000 // arbitrary upper bound
+	switch vers {
+	case "HTTP/1.1":
+		return 1, 1, true
+	case "HTTP/1.0":
+		return 1, 0, true
+	}
+	if !strings.HasPrefix(vers, "HTTP/") {
+		return 0, 0, false
+	}
+	dot := strings.Index(vers, ".")
+	if dot < 0 {
+		return 0, 0, false
+	}
+	major, err := strconv.Atoi(vers[5:dot])
+	if err != nil || major < 0 || major > Big {
+		return 0, 0, false
+	}
+	minor, err = strconv.Atoi(vers[dot+1:])
+	if err != nil || minor < 0 || minor > Big {
+		return 0, 0, false
+	}
+	return major, minor, true
+}
+
+// NewRequest returns a new Request given a method, URL, and optional body.
+//
+// If the provided body is also an io.Closer, the returned
+// Request.Body is set to body and will be closed by the Client
+// methods Do, Post, and PostForm, and Transport.RoundTrip.
+func NewRequest(method, urlStr string, body io.Reader) (*Request, error) {
+	u, err := url.Parse(urlStr)
+	if err != nil {
+		return nil, err
+	}
+	rc, ok := body.(io.ReadCloser)
+	if !ok && body != nil {
+		rc = ioutil.NopCloser(body)
+	}
+	req := &Request{
+		Method:     method,
+		URL:        u,
+		Proto:      "HTTP/1.1",
+		ProtoMajor: 1,
+		ProtoMinor: 1,
+		Header:     make(Header),
+		Body:       rc,
+		Host:       u.Host,
+	}
+	if body != nil {
+		switch v := body.(type) {
+		case *bytes.Buffer:
+			req.ContentLength = int64(v.Len())
+		case *bytes.Reader:
+			req.ContentLength = int64(v.Len())
+		case *strings.Reader:
+			req.ContentLength = int64(v.Len())
+		}
+	}
+
+	return req, nil
+}
+
+// BasicAuth returns the username and password provided in the request's
+// Authorization header, if the request uses HTTP Basic Authentication.
+// See RFC 2617, Section 2.
+func (r *Request) BasicAuth() (username, password string, ok bool) {
+	auth := r.Header.Get("Authorization")
+	if auth == "" {
+		return
+	}
+	return parseBasicAuth(auth)
+}
+
+// parseBasicAuth parses an HTTP Basic Authentication string.
+// "Basic QWxhZGRpbjpvcGVuIHNlc2FtZQ==" returns ("Aladdin", "open sesame", true).
+func parseBasicAuth(auth string) (username, password string, ok bool) {
+	if !strings.HasPrefix(auth, "Basic ") {
+		return
+	}
+	c, err := base64.StdEncoding.DecodeString(strings.TrimPrefix(auth, "Basic "))
+	if err != nil {
+		return
+	}
+	cs := string(c)
+	s := strings.IndexByte(cs, ':')
+	if s < 0 {
+		return
+	}
+	return cs[:s], cs[s+1:], true
+}
+
+// SetBasicAuth sets the request's Authorization header to use HTTP
+// Basic Authentication with the provided username and password.
+//
+// With HTTP Basic Authentication the provided username and password
+// are not encrypted.
+func (r *Request) SetBasicAuth(username, password string) {
+	r.Header.Set("Authorization", "Basic "+basicAuth(username, password))
+}
+
+// parseRequestLine parses "GET /foo HTTP/1.1" into its three parts.
+func parseRequestLine(line string) (method, requestURI, proto string, ok bool) {
+	s1 := strings.Index(line, " ")
+	s2 := strings.Index(line[s1+1:], " ")
+	if s1 < 0 || s2 < 0 {
+		return
+	}
+	s2 += s1 + 1
+	return line[:s1], line[s1+1 : s2], line[s2+1:], true
+}
+
+var textprotoReaderPool sync.Pool
+
+func newTextprotoReader(br *bufio.Reader) *textproto.Reader {
+	if v := textprotoReaderPool.Get(); v != nil {
+		tr := v.(*textproto.Reader)
+		tr.R = br
+		return tr
+	}
+	return textproto.NewReader(br)
+}
+
+func putTextprotoReader(r *textproto.Reader) {
+	r.R = nil
+	textprotoReaderPool.Put(r)
+}
+
+// ReadRequest reads and parses a request from b.
+func ReadRequest(b *bufio.Reader) (req *Request, err error) {
+
+	tp := newTextprotoReader(b)
+	req = new(Request)
+
+	// First line: GET /index.html HTTP/1.0
+	var s string
+	if s, err = tp.ReadLine(); err != nil {
+		return nil, err
+	}
+	defer func() {
+		putTextprotoReader(tp)
+		if err == io.EOF {
+			err = io.ErrUnexpectedEOF
+		}
+	}()
+
+	var ok bool
+	req.Method, req.RequestURI, req.Proto, ok = parseRequestLine(s)
+	if !ok {
+		return nil, &badStringError{"malformed HTTP request", s}
+	}
+	rawurl := req.RequestURI
+	if req.ProtoMajor, req.ProtoMinor, ok = ParseHTTPVersion(req.Proto); !ok {
+		return nil, &badStringError{"malformed HTTP version", req.Proto}
+	}
+
+	// CONNECT requests are used two different ways, and neither uses a full URL:
+	// The standard use is to tunnel HTTPS through an HTTP proxy.
+	// It looks like "CONNECT www.google.com:443 HTTP/1.1", and the parameter is
+	// just the authority section of a URL. This information should go in req.URL.Host.
+	//
+	// The net/rpc package also uses CONNECT, but there the parameter is a path
+	// that starts with a slash. It can be parsed with the regular URL parser,
+	// and the path will end up in req.URL.Path, where it needs to be in order for
+	// RPC to work.
+	justAuthority := req.Method == "CONNECT" && !strings.HasPrefix(rawurl, "/")
+	if justAuthority {
+		rawurl = "http://" + rawurl
+	}
+
+	if req.URL, err = url.ParseRequestURI(rawurl); err != nil {
+		return nil, err
+	}
+
+	if justAuthority {
+		// Strip the bogus "http://" back off.
+		req.URL.Scheme = ""
+	}
+
+	// Subsequent lines: Key: value.
+	mimeHeader, err := tp.ReadMIMEHeader()
+	if err != nil {
+		return nil, err
+	}
+	req.Header = Header(mimeHeader)
+
+	// RFC2616: Must treat
+	//	GET /index.html HTTP/1.1
+	//	Host: www.google.com
+	// and
+	//	GET http://www.google.com/index.html HTTP/1.1
+	//	Host: doesntmatter
+	// the same.  In the second case, any Host line is ignored.
+	req.Host = req.URL.Host
+	if req.Host == "" {
+		req.Host = req.Header.get("Host")
+	}
+	delete(req.Header, "Host")
+
+	fixPragmaCacheControl(req.Header)
+
+	err = readTransfer(req, b)
+	if err != nil {
+		return nil, err
+	}
+
+	req.Close = shouldClose(req.ProtoMajor, req.ProtoMinor, req.Header, false)
+	return req, nil
+}
+
+// MaxBytesReader is similar to io.LimitReader but is intended for
+// limiting the size of incoming request bodies. In contrast to
+// io.LimitReader, MaxBytesReader's result is a ReadCloser, returns a
+// non-EOF error for a Read beyond the limit, and Closes the
+// underlying reader when its Close method is called.
+//
+// MaxBytesReader prevents clients from accidentally or maliciously
+// sending a large request and wasting server resources.
+func MaxBytesReader(w ResponseWriter, r io.ReadCloser, n int64) io.ReadCloser {
+	return &maxBytesReader{w: w, r: r, n: n}
+}
+
+type maxBytesReader struct {
+	w       ResponseWriter
+	r       io.ReadCloser // underlying reader
+	n       int64         // max bytes remaining
+	stopped bool
+}
+
+func (l *maxBytesReader) Read(p []byte) (n int, err error) {
+	if l.n <= 0 {
+		if !l.stopped {
+			l.stopped = true
+			if res, ok := l.w.(*response); ok {
+				res.requestTooLarge()
+			}
+		}
+		return 0, errors.New("http: request body too large")
+	}
+	if int64(len(p)) > l.n {
+		p = p[:l.n]
+	}
+	n, err = l.r.Read(p)
+	l.n -= int64(n)
+	return
+}
+
+func (l *maxBytesReader) Close() error {
+	return l.r.Close()
+}
+
+func copyValues(dst, src url.Values) {
+	for k, vs := range src {
+		for _, value := range vs {
+			dst.Add(k, value)
+		}
+	}
+}
+
+func parsePostForm(r *Request) (vs url.Values, err error) {
+	if r.Body == nil {
+		err = errors.New("missing form body")
+		return
+	}
+	ct := r.Header.Get("Content-Type")
+	// RFC 2616, section 7.2.1 - empty type
+	//   SHOULD be treated as application/octet-stream
+	if ct == "" {
+		ct = "application/octet-stream"
+	}
+	ct, _, err = mime.ParseMediaType(ct)
+	switch {
+	case ct == "application/x-www-form-urlencoded":
+		var reader io.Reader = r.Body
+		maxFormSize := int64(1<<63 - 1)
+		if _, ok := r.Body.(*maxBytesReader); !ok {
+			maxFormSize = int64(10 << 20) // 10 MB is a lot of text.
+			reader = io.LimitReader(r.Body, maxFormSize+1)
+		}
+		b, e := ioutil.ReadAll(reader)
+		if e != nil {
+			if err == nil {
+				err = e
+			}
+			break
+		}
+		if int64(len(b)) > maxFormSize {
+			err = errors.New("http: POST too large")
+			return
+		}
+		vs, e = url.ParseQuery(string(b))
+		if err == nil {
+			err = e
+		}
+	case ct == "multipart/form-data":
+		// handled by ParseMultipartForm (which is calling us, or should be)
+		// TODO(bradfitz): there are too many possible
+		// orders to call too many functions here.
+		// Clean this up and write more tests.
+		// request_test.go contains the start of this,
+		// in TestParseMultipartFormOrder and others.
+	}
+	return
+}
+
+// ParseForm parses the raw query from the URL and updates r.Form.
+//
+// For POST or PUT requests, it also parses the request body as a form and
+// put the results into both r.PostForm and r.Form.
+// POST and PUT body parameters take precedence over URL query string values
+// in r.Form.
+//
+// If the request Body's size has not already been limited by MaxBytesReader,
+// the size is capped at 10MB.
+//
+// ParseMultipartForm calls ParseForm automatically.
+// It is idempotent.
+func (r *Request) ParseForm() error {
+	var err error
+	if r.PostForm == nil {
+		if r.Method == "POST" || r.Method == "PUT" || r.Method == "PATCH" {
+			r.PostForm, err = parsePostForm(r)
+		}
+		if r.PostForm == nil {
+			r.PostForm = make(url.Values)
+		}
+	}
+	if r.Form == nil {
+		if len(r.PostForm) > 0 {
+			r.Form = make(url.Values)
+			copyValues(r.Form, r.PostForm)
+		}
+		var newValues url.Values
+		if r.URL != nil {
+			var e error
+			newValues, e = url.ParseQuery(r.URL.RawQuery)
+			if err == nil {
+				err = e
+			}
+		}
+		if newValues == nil {
+			newValues = make(url.Values)
+		}
+		if r.Form == nil {
+			r.Form = newValues
+		} else {
+			copyValues(r.Form, newValues)
+		}
+	}
+	return err
+}
+
+// ParseMultipartForm parses a request body as multipart/form-data.
+// The whole request body is parsed and up to a total of maxMemory bytes of
+// its file parts are stored in memory, with the remainder stored on
+// disk in temporary files.
+// ParseMultipartForm calls ParseForm if necessary.
+// After one call to ParseMultipartForm, subsequent calls have no effect.
+func (r *Request) ParseMultipartForm(maxMemory int64) error {
+	if r.MultipartForm == multipartByReader {
+		return errors.New("http: multipart handled by MultipartReader")
+	}
+	if r.Form == nil {
+		err := r.ParseForm()
+		if err != nil {
+			return err
+		}
+	}
+	if r.MultipartForm != nil {
+		return nil
+	}
+
+	mr, err := r.multipartReader()
+	if err != nil {
+		return err
+	}
+
+	f, err := mr.ReadForm(maxMemory)
+	if err != nil {
+		return err
+	}
+	for k, v := range f.Value {
+		r.Form[k] = append(r.Form[k], v...)
+	}
+	r.MultipartForm = f
+
+	return nil
+}
+
+// FormValue returns the first value for the named component of the query.
+// POST and PUT body parameters take precedence over URL query string values.
+// FormValue calls ParseMultipartForm and ParseForm if necessary and ignores
+// any errors returned by these functions.
+// To access multiple values of the same key use ParseForm.
+func (r *Request) FormValue(key string) string {
+	if r.Form == nil {
+		r.ParseMultipartForm(defaultMaxMemory)
+	}
+	if vs := r.Form[key]; len(vs) > 0 {
+		return vs[0]
+	}
+	return ""
+}
+
+// PostFormValue returns the first value for the named component of the POST
+// or PUT request body. URL query parameters are ignored.
+// PostFormValue calls ParseMultipartForm and ParseForm if necessary and ignores
+// any errors returned by these functions.
+func (r *Request) PostFormValue(key string) string {
+	if r.PostForm == nil {
+		r.ParseMultipartForm(defaultMaxMemory)
+	}
+	if vs := r.PostForm[key]; len(vs) > 0 {
+		return vs[0]
+	}
+	return ""
+}
+
+// FormFile returns the first file for the provided form key.
+// FormFile calls ParseMultipartForm and ParseForm if necessary.
+func (r *Request) FormFile(key string) (multipart.File, *multipart.FileHeader, error) {
+	if r.MultipartForm == multipartByReader {
+		return nil, nil, errors.New("http: multipart handled by MultipartReader")
+	}
+	if r.MultipartForm == nil {
+		err := r.ParseMultipartForm(defaultMaxMemory)
+		if err != nil {
+			return nil, nil, err
+		}
+	}
+	if r.MultipartForm != nil && r.MultipartForm.File != nil {
+		if fhs := r.MultipartForm.File[key]; len(fhs) > 0 {
+			f, err := fhs[0].Open()
+			return f, fhs[0], err
+		}
+	}
+	return nil, nil, ErrMissingFile
+}
+
+func (r *Request) expectsContinue() bool {
+	return hasToken(r.Header.get("Expect"), "100-continue")
+}
+
+func (r *Request) wantsHttp10KeepAlive() bool {
+	if r.ProtoMajor != 1 || r.ProtoMinor != 0 {
+		return false
+	}
+	return hasToken(r.Header.get("Connection"), "keep-alive")
+}
+
+func (r *Request) wantsClose() bool {
+	return hasToken(r.Header.get("Connection"), "close")
+}
+
+func (r *Request) closeBody() {
+	if r.Body != nil {
+		r.Body.Close()
+	}
+}
diff --git a/src/net/http/request_test.go b/src/net/http/request_test.go
new file mode 100644
index 000000000..759ea4e8b
--- /dev/null
+++ b/src/net/http/request_test.go
@@ -0,0 +1,680 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package http_test
+
+import (
+	"bufio"
+	"bytes"
+	"encoding/base64"
+	"fmt"
+	"io"
+	"io/ioutil"
+	"mime/multipart"
+	. "net/http"
+	"net/http/httptest"
+	"net/url"
+	"os"
+	"reflect"
+	"regexp"
+	"strings"
+	"testing"
+)
+
+func TestQuery(t *testing.T) {
+	req := &Request{Method: "GET"}
+	req.URL, _ = url.Parse("http://www.google.com/search?q=foo&q=bar")
+	if q := req.FormValue("q"); q != "foo" {
+		t.Errorf(`req.FormValue("q") = %q, want "foo"`, q)
+	}
+}
+
+func TestPostQuery(t *testing.T) {
+	req, _ := NewRequest("POST", "http://www.google.com/search?q=foo&q=bar&both=x&prio=1&empty=not",
+		strings.NewReader("z=post&both=y&prio=2&empty="))
+	req.Header.Set("Content-Type", "application/x-www-form-urlencoded; param=value")
+
+	if q := req.FormValue("q"); q != "foo" {
+		t.Errorf(`req.FormValue("q") = %q, want "foo"`, q)
+	}
+	if z := req.FormValue("z"); z != "post" {
+		t.Errorf(`req.FormValue("z") = %q, want "post"`, z)
+	}
+	if bq, found := req.PostForm["q"]; found {
+		t.Errorf(`req.PostForm["q"] = %q, want no entry in map`, bq)
+	}
+	if bz := req.PostFormValue("z"); bz != "post" {
+		t.Errorf(`req.PostFormValue("z") = %q, want "post"`, bz)
+	}
+	if qs := req.Form["q"]; !reflect.DeepEqual(qs, []string{"foo", "bar"}) {
+		t.Errorf(`req.Form["q"] = %q, want ["foo", "bar"]`, qs)
+	}
+	if both := req.Form["both"]; !reflect.DeepEqual(both, []string{"y", "x"}) {
+		t.Errorf(`req.Form["both"] = %q, want ["y", "x"]`, both)
+	}
+	if prio := req.FormValue("prio"); prio != "2" {
+		t.Errorf(`req.FormValue("prio") = %q, want "2" (from body)`, prio)
+	}
+	if empty := req.FormValue("empty"); empty != "" {
+		t.Errorf(`req.FormValue("empty") = %q, want "" (from body)`, empty)
+	}
+}
+
+func TestPatchQuery(t *testing.T) {
+	req, _ := NewRequest("PATCH", "http://www.google.com/search?q=foo&q=bar&both=x&prio=1&empty=not",
+		strings.NewReader("z=post&both=y&prio=2&empty="))
+	req.Header.Set("Content-Type", "application/x-www-form-urlencoded; param=value")
+
+	if q := req.FormValue("q"); q != "foo" {
+		t.Errorf(`req.FormValue("q") = %q, want "foo"`, q)
+	}
+	if z := req.FormValue("z"); z != "post" {
+		t.Errorf(`req.FormValue("z") = %q, want "post"`, z)
+	}
+	if bq, found := req.PostForm["q"]; found {
+		t.Errorf(`req.PostForm["q"] = %q, want no entry in map`, bq)
+	}
+	if bz := req.PostFormValue("z"); bz != "post" {
+		t.Errorf(`req.PostFormValue("z") = %q, want "post"`, bz)
+	}
+	if qs := req.Form["q"]; !reflect.DeepEqual(qs, []string{"foo", "bar"}) {
+		t.Errorf(`req.Form["q"] = %q, want ["foo", "bar"]`, qs)
+	}
+	if both := req.Form["both"]; !reflect.DeepEqual(both, []string{"y", "x"}) {
+		t.Errorf(`req.Form["both"] = %q, want ["y", "x"]`, both)
+	}
+	if prio := req.FormValue("prio"); prio != "2" {
+		t.Errorf(`req.FormValue("prio") = %q, want "2" (from body)`, prio)
+	}
+	if empty := req.FormValue("empty"); empty != "" {
+		t.Errorf(`req.FormValue("empty") = %q, want "" (from body)`, empty)
+	}
+}
+
+type stringMap map[string][]string
+type parseContentTypeTest struct {
+	shouldError bool
+	contentType stringMap
+}
+
+var parseContentTypeTests = []parseContentTypeTest{
+	{false, stringMap{"Content-Type": {"text/plain"}}},
+	// Empty content type is legal - shoult be treated as
+	// application/octet-stream (RFC 2616, section 7.2.1)
+	{false, stringMap{}},
+	{true, stringMap{"Content-Type": {"text/plain; boundary="}}},
+	{false, stringMap{"Content-Type": {"application/unknown"}}},
+}
+
+func TestParseFormUnknownContentType(t *testing.T) {
+	for i, test := range parseContentTypeTests {
+		req := &Request{
+			Method: "POST",
+			Header: Header(test.contentType),
+			Body:   ioutil.NopCloser(strings.NewReader("body")),
+		}
+		err := req.ParseForm()
+		switch {
+		case err == nil && test.shouldError:
+			t.Errorf("test %d should have returned error", i)
+		case err != nil && !test.shouldError:
+			t.Errorf("test %d should not have returned error, got %v", i, err)
+		}
+	}
+}
+
+func TestParseFormInitializeOnError(t *testing.T) {
+	nilBody, _ := NewRequest("POST", "http://www.google.com/search?q=foo", nil)
+	tests := []*Request{
+		nilBody,
+		{Method: "GET", URL: nil},
+	}
+	for i, req := range tests {
+		err := req.ParseForm()
+		if req.Form == nil {
+			t.Errorf("%d. Form not initialized, error %v", i, err)
+		}
+		if req.PostForm == nil {
+			t.Errorf("%d. PostForm not initialized, error %v", i, err)
+		}
+	}
+}
+
+func TestMultipartReader(t *testing.T) {
+	req := &Request{
+		Method: "POST",
+		Header: Header{"Content-Type": {`multipart/form-data; boundary="foo123"`}},
+		Body:   ioutil.NopCloser(new(bytes.Buffer)),
+	}
+	multipart, err := req.MultipartReader()
+	if multipart == nil {
+		t.Errorf("expected multipart; error: %v", err)
+	}
+
+	req.Header = Header{"Content-Type": {"text/plain"}}
+	multipart, err = req.MultipartReader()
+	if multipart != nil {
+		t.Error("unexpected multipart for text/plain")
+	}
+}
+
+func TestParseMultipartForm(t *testing.T) {
+	req := &Request{
+		Method: "POST",
+		Header: Header{"Content-Type": {`multipart/form-data; boundary="foo123"`}},
+		Body:   ioutil.NopCloser(new(bytes.Buffer)),
+	}
+	err := req.ParseMultipartForm(25)
+	if err == nil {
+		t.Error("expected multipart EOF, got nil")
+	}
+
+	req.Header = Header{"Content-Type": {"text/plain"}}
+	err = req.ParseMultipartForm(25)
+	if err != ErrNotMultipart {
+		t.Error("expected ErrNotMultipart for text/plain")
+	}
+}
+
+func TestRedirect(t *testing.T) {
+	ts := httptest.NewServer(HandlerFunc(func(w ResponseWriter, r *Request) {
+		switch r.URL.Path {
+		case "/":
+			w.Header().Set("Location", "/foo/")
+			w.WriteHeader(StatusSeeOther)
+		case "/foo/":
+			fmt.Fprintf(w, "foo")
+		default:
+			w.WriteHeader(StatusBadRequest)
+		}
+	}))
+	defer ts.Close()
+
+	var end = regexp.MustCompile("/foo/$")
+	r, err := Get(ts.URL)
+	if err != nil {
+		t.Fatal(err)
+	}
+	r.Body.Close()
+	url := r.Request.URL.String()
+	if r.StatusCode != 200 || !end.MatchString(url) {
+		t.Fatalf("Get got status %d at %q, want 200 matching /foo/$", r.StatusCode, url)
+	}
+}
+
+func TestSetBasicAuth(t *testing.T) {
+	r, _ := NewRequest("GET", "http://example.com/", nil)
+	r.SetBasicAuth("Aladdin", "open sesame")
+	if g, e := r.Header.Get("Authorization"), "Basic QWxhZGRpbjpvcGVuIHNlc2FtZQ=="; g != e {
+		t.Errorf("got header %q, want %q", g, e)
+	}
+}
+
+func TestMultipartRequest(t *testing.T) {
+	// Test that we can read the values and files of a
+	// multipart request with FormValue and FormFile,
+	// and that ParseMultipartForm can be called multiple times.
+	req := newTestMultipartRequest(t)
+	if err := req.ParseMultipartForm(25); err != nil {
+		t.Fatal("ParseMultipartForm first call:", err)
+	}
+	defer req.MultipartForm.RemoveAll()
+	validateTestMultipartContents(t, req, false)
+	if err := req.ParseMultipartForm(25); err != nil {
+		t.Fatal("ParseMultipartForm second call:", err)
+	}
+	validateTestMultipartContents(t, req, false)
+}
+
+func TestMultipartRequestAuto(t *testing.T) {
+	// Test that FormValue and FormFile automatically invoke
+	// ParseMultipartForm and return the right values.
+	req := newTestMultipartRequest(t)
+	defer func() {
+		if req.MultipartForm != nil {
+			req.MultipartForm.RemoveAll()
+		}
+	}()
+	validateTestMultipartContents(t, req, true)
+}
+
+func TestMissingFileMultipartRequest(t *testing.T) {
+	// Test that FormFile returns an error if
+	// the named file is missing.
+	req := newTestMultipartRequest(t)
+	testMissingFile(t, req)
+}
+
+// Test that FormValue invokes ParseMultipartForm.
+func TestFormValueCallsParseMultipartForm(t *testing.T) {
+	req, _ := NewRequest("POST", "http://www.google.com/", strings.NewReader("z=post"))
+	req.Header.Set("Content-Type", "application/x-www-form-urlencoded; param=value")
+	if req.Form != nil {
+		t.Fatal("Unexpected request Form, want nil")
+	}
+	req.FormValue("z")
+	if req.Form == nil {
+		t.Fatal("ParseMultipartForm not called by FormValue")
+	}
+}
+
+// Test that FormFile invokes ParseMultipartForm.
+func TestFormFileCallsParseMultipartForm(t *testing.T) {
+	req := newTestMultipartRequest(t)
+	if req.Form != nil {
+		t.Fatal("Unexpected request Form, want nil")
+	}
+	req.FormFile("")
+	if req.Form == nil {
+		t.Fatal("ParseMultipartForm not called by FormFile")
+	}
+}
+
+// Test that ParseMultipartForm errors if called
+// after MultipartReader on the same request.
+func TestParseMultipartFormOrder(t *testing.T) {
+	req := newTestMultipartRequest(t)
+	if _, err := req.MultipartReader(); err != nil {
+		t.Fatalf("MultipartReader: %v", err)
+	}
+	if err := req.ParseMultipartForm(1024); err == nil {
+		t.Fatal("expected an error from ParseMultipartForm after call to MultipartReader")
+	}
+}
+
+// Test that MultipartReader errors if called
+// after ParseMultipartForm on the same request.
+func TestMultipartReaderOrder(t *testing.T) {
+	req := newTestMultipartRequest(t)
+	if err := req.ParseMultipartForm(25); err != nil {
+		t.Fatalf("ParseMultipartForm: %v", err)
+	}
+	defer req.MultipartForm.RemoveAll()
+	if _, err := req.MultipartReader(); err == nil {
+		t.Fatal("expected an error from MultipartReader after call to ParseMultipartForm")
+	}
+}
+
+// Test that FormFile errors if called after
+// MultipartReader on the same request.
+func TestFormFileOrder(t *testing.T) {
+	req := newTestMultipartRequest(t)
+	if _, err := req.MultipartReader(); err != nil {
+		t.Fatalf("MultipartReader: %v", err)
+	}
+	if _, _, err := req.FormFile(""); err == nil {
+		t.Fatal("expected an error from FormFile after call to MultipartReader")
+	}
+}
+
+var readRequestErrorTests = []struct {
+	in  string
+	err error
+}{
+	{"GET / HTTP/1.1\r\nheader:foo\r\n\r\n", nil},
+	{"GET / HTTP/1.1\r\nheader:foo\r\n", io.ErrUnexpectedEOF},
+	{"", io.EOF},
+}
+
+func TestReadRequestErrors(t *testing.T) {
+	for i, tt := range readRequestErrorTests {
+		_, err := ReadRequest(bufio.NewReader(strings.NewReader(tt.in)))
+		if err != tt.err {
+			t.Errorf("%d. got error = %v; want %v", i, err, tt.err)
+		}
+	}
+}
+
+func TestNewRequestHost(t *testing.T) {
+	req, err := NewRequest("GET", "http://localhost:1234/", nil)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if req.Host != "localhost:1234" {
+		t.Errorf("Host = %q; want localhost:1234", req.Host)
+	}
+}
+
+func TestNewRequestContentLength(t *testing.T) {
+	readByte := func(r io.Reader) io.Reader {
+		var b [1]byte
+		r.Read(b[:])
+		return r
+	}
+	tests := []struct {
+		r    io.Reader
+		want int64
+	}{
+		{bytes.NewReader([]byte("123")), 3},
+		{bytes.NewBuffer([]byte("1234")), 4},
+		{strings.NewReader("12345"), 5},
+		// Not detected:
+		{struct{ io.Reader }{strings.NewReader("xyz")}, 0},
+		{io.NewSectionReader(strings.NewReader("x"), 0, 6), 0},
+		{readByte(io.NewSectionReader(strings.NewReader("xy"), 0, 6)), 0},
+	}
+	for _, tt := range tests {
+		req, err := NewRequest("POST", "http://localhost/", tt.r)
+		if err != nil {
+			t.Fatal(err)
+		}
+		if req.ContentLength != tt.want {
+			t.Errorf("ContentLength(%T) = %d; want %d", tt.r, req.ContentLength, tt.want)
+		}
+	}
+}
+
+var parseHTTPVersionTests = []struct {
+	vers         string
+	major, minor int
+	ok           bool
+}{
+	{"HTTP/0.9", 0, 9, true},
+	{"HTTP/1.0", 1, 0, true},
+	{"HTTP/1.1", 1, 1, true},
+	{"HTTP/3.14", 3, 14, true},
+
+	{"HTTP", 0, 0, false},
+	{"HTTP/one.one", 0, 0, false},
+	{"HTTP/1.1/", 0, 0, false},
+	{"HTTP/-1,0", 0, 0, false},
+	{"HTTP/0,-1", 0, 0, false},
+	{"HTTP/", 0, 0, false},
+	{"HTTP/1,1", 0, 0, false},
+}
+
+func TestParseHTTPVersion(t *testing.T) {
+	for _, tt := range parseHTTPVersionTests {
+		major, minor, ok := ParseHTTPVersion(tt.vers)
+		if ok != tt.ok || major != tt.major || minor != tt.minor {
+			type version struct {
+				major, minor int
+				ok           bool
+			}
+			t.Errorf("failed to parse %q, expected: %#v, got %#v", tt.vers, version{tt.major, tt.minor, tt.ok}, version{major, minor, ok})
+		}
+	}
+}
+
+type getBasicAuthTest struct {
+	username, password string
+	ok                 bool
+}
+
+type parseBasicAuthTest getBasicAuthTest
+
+type basicAuthCredentialsTest struct {
+	username, password string
+}
+
+var getBasicAuthTests = []struct {
+	username, password string
+	ok                 bool
+}{
+	{"Aladdin", "open sesame", true},
+	{"Aladdin", "open:sesame", true},
+	{"", "", true},
+}
+
+func TestGetBasicAuth(t *testing.T) {
+	for _, tt := range getBasicAuthTests {
+		r, _ := NewRequest("GET", "http://example.com/", nil)
+		r.SetBasicAuth(tt.username, tt.password)
+		username, password, ok := r.BasicAuth()
+		if ok != tt.ok || username != tt.username || password != tt.password {
+			t.Errorf("BasicAuth() = %#v, want %#v", getBasicAuthTest{username, password, ok},
+				getBasicAuthTest{tt.username, tt.password, tt.ok})
+		}
+	}
+	// Unauthenticated request.
+	r, _ := NewRequest("GET", "http://example.com/", nil)
+	username, password, ok := r.BasicAuth()
+	if ok {
+		t.Errorf("expected false from BasicAuth when the request is unauthenticated")
+	}
+	want := basicAuthCredentialsTest{"", ""}
+	if username != want.username || password != want.password {
+		t.Errorf("expected credentials: %#v when the request is unauthenticated, got %#v",
+			want, basicAuthCredentialsTest{username, password})
+	}
+}
+
+var parseBasicAuthTests = []struct {
+	header, username, password string
+	ok                         bool
+}{
+	{"Basic " + base64.StdEncoding.EncodeToString([]byte("Aladdin:open sesame")), "Aladdin", "open sesame", true},
+	{"Basic " + base64.StdEncoding.EncodeToString([]byte("Aladdin:open:sesame")), "Aladdin", "open:sesame", true},
+	{"Basic " + base64.StdEncoding.EncodeToString([]byte(":")), "", "", true},
+	{"Basic" + base64.StdEncoding.EncodeToString([]byte("Aladdin:open sesame")), "", "", false},
+	{base64.StdEncoding.EncodeToString([]byte("Aladdin:open sesame")), "", "", false},
+	{"Basic ", "", "", false},
+	{"Basic Aladdin:open sesame", "", "", false},
+	{`Digest username="Aladdin"`, "", "", false},
+}
+
+func TestParseBasicAuth(t *testing.T) {
+	for _, tt := range parseBasicAuthTests {
+		r, _ := NewRequest("GET", "http://example.com/", nil)
+		r.Header.Set("Authorization", tt.header)
+		username, password, ok := r.BasicAuth()
+		if ok != tt.ok || username != tt.username || password != tt.password {
+			t.Errorf("BasicAuth() = %#v, want %#v", getBasicAuthTest{username, password, ok},
+				getBasicAuthTest{tt.username, tt.password, tt.ok})
+		}
+	}
+}
+
+type logWrites struct {
+	t   *testing.T
+	dst *[]string
+}
+
+func (l logWrites) WriteByte(c byte) error {
+	l.t.Fatalf("unexpected WriteByte call")
+	return nil
+}
+
+func (l logWrites) Write(p []byte) (n int, err error) {
+	*l.dst = append(*l.dst, string(p))
+	return len(p), nil
+}
+
+func TestRequestWriteBufferedWriter(t *testing.T) {
+	got := []string{}
+	req, _ := NewRequest("GET", "http://foo.com/", nil)
+	req.Write(logWrites{t, &got})
+	want := []string{
+		"GET / HTTP/1.1\r\n",
+		"Host: foo.com\r\n",
+		"User-Agent: " + DefaultUserAgent + "\r\n",
+		"\r\n",
+	}
+	if !reflect.DeepEqual(got, want) {
+		t.Errorf("Writes = %q\n  Want = %q", got, want)
+	}
+}
+
+func testMissingFile(t *testing.T, req *Request) {
+	f, fh, err := req.FormFile("missing")
+	if f != nil {
+		t.Errorf("FormFile file = %v, want nil", f)
+	}
+	if fh != nil {
+		t.Errorf("FormFile file header = %q, want nil", fh)
+	}
+	if err != ErrMissingFile {
+		t.Errorf("FormFile err = %q, want ErrMissingFile", err)
+	}
+}
+
+func newTestMultipartRequest(t *testing.T) *Request {
+	b := strings.NewReader(strings.Replace(message, "\n", "\r\n", -1))
+	req, err := NewRequest("POST", "/", b)
+	if err != nil {
+		t.Fatal("NewRequest:", err)
+	}
+	ctype := fmt.Sprintf(`multipart/form-data; boundary="%s"`, boundary)
+	req.Header.Set("Content-type", ctype)
+	return req
+}
+
+func validateTestMultipartContents(t *testing.T, req *Request, allMem bool) {
+	if g, e := req.FormValue("texta"), textaValue; g != e {
+		t.Errorf("texta value = %q, want %q", g, e)
+	}
+	if g, e := req.FormValue("textb"), textbValue; g != e {
+		t.Errorf("textb value = %q, want %q", g, e)
+	}
+	if g := req.FormValue("missing"); g != "" {
+		t.Errorf("missing value = %q, want empty string", g)
+	}
+
+	assertMem := func(n string, fd multipart.File) {
+		if _, ok := fd.(*os.File); ok {
+			t.Error(n, " is *os.File, should not be")
+		}
+	}
+	fda := testMultipartFile(t, req, "filea", "filea.txt", fileaContents)
+	defer fda.Close()
+	assertMem("filea", fda)
+	fdb := testMultipartFile(t, req, "fileb", "fileb.txt", filebContents)
+	defer fdb.Close()
+	if allMem {
+		assertMem("fileb", fdb)
+	} else {
+		if _, ok := fdb.(*os.File); !ok {
+			t.Errorf("fileb has unexpected underlying type %T", fdb)
+		}
+	}
+
+	testMissingFile(t, req)
+}
+
+func testMultipartFile(t *testing.T, req *Request, key, expectFilename, expectContent string) multipart.File {
+	f, fh, err := req.FormFile(key)
+	if err != nil {
+		t.Fatalf("FormFile(%q): %q", key, err)
+	}
+	if fh.Filename != expectFilename {
+		t.Errorf("filename = %q, want %q", fh.Filename, expectFilename)
+	}
+	var b bytes.Buffer
+	_, err = io.Copy(&b, f)
+	if err != nil {
+		t.Fatal("copying contents:", err)
+	}
+	if g := b.String(); g != expectContent {
+		t.Errorf("contents = %q, want %q", g, expectContent)
+	}
+	return f
+}
+
+const (
+	fileaContents = "This is a test file."
+	filebContents = "Another test file."
+	textaValue    = "foo"
+	textbValue    = "bar"
+	boundary      = `MyBoundary`
+)
+
+const message = `
+--MyBoundary
+Content-Disposition: form-data; name="filea"; filename="filea.txt"
+Content-Type: text/plain
+
+` + fileaContents + `
+--MyBoundary
+Content-Disposition: form-data; name="fileb"; filename="fileb.txt"
+Content-Type: text/plain
+
+` + filebContents + `
+--MyBoundary
+Content-Disposition: form-data; name="texta"
+
+` + textaValue + `
+--MyBoundary
+Content-Disposition: form-data; name="textb"
+
+` + textbValue + `
+--MyBoundary--
+`
+
+func benchmarkReadRequest(b *testing.B, request string) {
+	request = request + "\n"                             // final \n
+	request = strings.Replace(request, "\n", "\r\n", -1) // expand \n to \r\n
+	b.SetBytes(int64(len(request)))
+	r := bufio.NewReader(&infiniteReader{buf: []byte(request)})
+	b.ReportAllocs()
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		_, err := ReadRequest(r)
+		if err != nil {
+			b.Fatalf("failed to read request: %v", err)
+		}
+	}
+}
+
+// infiniteReader satisfies Read requests as if the contents of buf
+// loop indefinitely.
+type infiniteReader struct {
+	buf    []byte
+	offset int
+}
+
+func (r *infiniteReader) Read(b []byte) (int, error) {
+	n := copy(b, r.buf[r.offset:])
+	r.offset = (r.offset + n) % len(r.buf)
+	return n, nil
+}
+
+func BenchmarkReadRequestChrome(b *testing.B) {
+	// https://github.com/felixge/node-http-perf/blob/master/fixtures/get.http
+	benchmarkReadRequest(b, `GET / HTTP/1.1
+Host: localhost:8080
+Connection: keep-alive
+Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
+User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_8_2) AppleWebKit/537.17 (KHTML, like Gecko) Chrome/24.0.1312.52 Safari/537.17
+Accept-Encoding: gzip,deflate,sdch
+Accept-Language: en-US,en;q=0.8
+Accept-Charset: ISO-8859-1,utf-8;q=0.7,*;q=0.3
+Cookie: __utma=1.1978842379.1323102373.1323102373.1323102373.1; EPi:NumberOfVisits=1,2012-02-28T13:42:18; CrmSession=5b707226b9563e1bc69084d07a107c98; plushContainerWidth=100%25; plushNoTopMenu=0; hudson_auto_refresh=false
+`)
+}
+
+func BenchmarkReadRequestCurl(b *testing.B) {
+	// curl http://localhost:8080/
+	benchmarkReadRequest(b, `GET / HTTP/1.1
+User-Agent: curl/7.27.0
+Host: localhost:8080
+Accept: */*
+`)
+}
+
+func BenchmarkReadRequestApachebench(b *testing.B) {
+	// ab -n 1 -c 1 http://localhost:8080/
+	benchmarkReadRequest(b, `GET / HTTP/1.0
+Host: localhost:8080
+User-Agent: ApacheBench/2.3
+Accept: */*
+`)
+}
+
+func BenchmarkReadRequestSiege(b *testing.B) {
+	// siege -r 1 -c 1 http://localhost:8080/
+	benchmarkReadRequest(b, `GET / HTTP/1.1
+Host: localhost:8080
+Accept: */*
+Accept-Encoding: gzip
+User-Agent: JoeDog/1.00 [en] (X11; I; Siege 2.70)
+Connection: keep-alive
+`)
+}
+
+func BenchmarkReadRequestWrk(b *testing.B) {
+	// wrk -t 1 -r 1 -c 1 http://localhost:8080/
+	benchmarkReadRequest(b, `GET / HTTP/1.1
+Host: localhost:8080
+`)
+}
diff --git a/src/net/http/requestwrite_test.go b/src/net/http/requestwrite_test.go
new file mode 100644
index 000000000..7a6bd5878
--- /dev/null
+++ b/src/net/http/requestwrite_test.go
@@ -0,0 +1,623 @@
+// Copyright 2010 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package http
+
+import (
+	"bytes"
+	"errors"
+	"fmt"
+	"io"
+	"io/ioutil"
+	"net/url"
+	"strings"
+	"testing"
+)
+
+type reqWriteTest struct {
+	Req  Request
+	Body interface{} // optional []byte or func() io.ReadCloser to populate Req.Body
+
+	// Any of these three may be empty to skip that test.
+	WantWrite string // Request.Write
+	WantProxy string // Request.WriteProxy
+
+	WantError error // wanted error from Request.Write
+}
+
+var reqWriteTests = []reqWriteTest{
+	// HTTP/1.1 => chunked coding; no body; no trailer
+	{
+		Req: Request{
+			Method: "GET",
+			URL: &url.URL{
+				Scheme: "http",
+				Host:   "www.techcrunch.com",
+				Path:   "/",
+			},
+			Proto:      "HTTP/1.1",
+			ProtoMajor: 1,
+			ProtoMinor: 1,
+			Header: Header{
+				"Accept":           {"text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8"},
+				"Accept-Charset":   {"ISO-8859-1,utf-8;q=0.7,*;q=0.7"},
+				"Accept-Encoding":  {"gzip,deflate"},
+				"Accept-Language":  {"en-us,en;q=0.5"},
+				"Keep-Alive":       {"300"},
+				"Proxy-Connection": {"keep-alive"},
+				"User-Agent":       {"Fake"},
+			},
+			Body:  nil,
+			Close: false,
+			Host:  "www.techcrunch.com",
+			Form:  map[string][]string{},
+		},
+
+		WantWrite: "GET / HTTP/1.1\r\n" +
+			"Host: www.techcrunch.com\r\n" +
+			"User-Agent: Fake\r\n" +
+			"Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8\r\n" +
+			"Accept-Charset: ISO-8859-1,utf-8;q=0.7,*;q=0.7\r\n" +
+			"Accept-Encoding: gzip,deflate\r\n" +
+			"Accept-Language: en-us,en;q=0.5\r\n" +
+			"Keep-Alive: 300\r\n" +
+			"Proxy-Connection: keep-alive\r\n\r\n",
+
+		WantProxy: "GET http://www.techcrunch.com/ HTTP/1.1\r\n" +
+			"Host: www.techcrunch.com\r\n" +
+			"User-Agent: Fake\r\n" +
+			"Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8\r\n" +
+			"Accept-Charset: ISO-8859-1,utf-8;q=0.7,*;q=0.7\r\n" +
+			"Accept-Encoding: gzip,deflate\r\n" +
+			"Accept-Language: en-us,en;q=0.5\r\n" +
+			"Keep-Alive: 300\r\n" +
+			"Proxy-Connection: keep-alive\r\n\r\n",
+	},
+	// HTTP/1.1 => chunked coding; body; empty trailer
+	{
+		Req: Request{
+			Method: "GET",
+			URL: &url.URL{
+				Scheme: "http",
+				Host:   "www.google.com",
+				Path:   "/search",
+			},
+			ProtoMajor:       1,
+			ProtoMinor:       1,
+			Header:           Header{},
+			TransferEncoding: []string{"chunked"},
+		},
+
+		Body: []byte("abcdef"),
+
+		WantWrite: "GET /search HTTP/1.1\r\n" +
+			"Host: www.google.com\r\n" +
+			"User-Agent: Go 1.1 package http\r\n" +
+			"Transfer-Encoding: chunked\r\n\r\n" +
+			chunk("abcdef") + chunk(""),
+
+		WantProxy: "GET http://www.google.com/search HTTP/1.1\r\n" +
+			"Host: www.google.com\r\n" +
+			"User-Agent: Go 1.1 package http\r\n" +
+			"Transfer-Encoding: chunked\r\n\r\n" +
+			chunk("abcdef") + chunk(""),
+	},
+	// HTTP/1.1 POST => chunked coding; body; empty trailer
+	{
+		Req: Request{
+			Method: "POST",
+			URL: &url.URL{
+				Scheme: "http",
+				Host:   "www.google.com",
+				Path:   "/search",
+			},
+			ProtoMajor:       1,
+			ProtoMinor:       1,
+			Header:           Header{},
+			Close:            true,
+			TransferEncoding: []string{"chunked"},
+		},
+
+		Body: []byte("abcdef"),
+
+		WantWrite: "POST /search HTTP/1.1\r\n" +
+			"Host: www.google.com\r\n" +
+			"User-Agent: Go 1.1 package http\r\n" +
+			"Connection: close\r\n" +
+			"Transfer-Encoding: chunked\r\n\r\n" +
+			chunk("abcdef") + chunk(""),
+
+		WantProxy: "POST http://www.google.com/search HTTP/1.1\r\n" +
+			"Host: www.google.com\r\n" +
+			"User-Agent: Go 1.1 package http\r\n" +
+			"Connection: close\r\n" +
+			"Transfer-Encoding: chunked\r\n\r\n" +
+			chunk("abcdef") + chunk(""),
+	},
+
+	// HTTP/1.1 POST with Content-Length, no chunking
+	{
+		Req: Request{
+			Method: "POST",
+			URL: &url.URL{
+				Scheme: "http",
+				Host:   "www.google.com",
+				Path:   "/search",
+			},
+			ProtoMajor:    1,
+			ProtoMinor:    1,
+			Header:        Header{},
+			Close:         true,
+			ContentLength: 6,
+		},
+
+		Body: []byte("abcdef"),
+
+		WantWrite: "POST /search HTTP/1.1\r\n" +
+			"Host: www.google.com\r\n" +
+			"User-Agent: Go 1.1 package http\r\n" +
+			"Connection: close\r\n" +
+			"Content-Length: 6\r\n" +
+			"\r\n" +
+			"abcdef",
+
+		WantProxy: "POST http://www.google.com/search HTTP/1.1\r\n" +
+			"Host: www.google.com\r\n" +
+			"User-Agent: Go 1.1 package http\r\n" +
+			"Connection: close\r\n" +
+			"Content-Length: 6\r\n" +
+			"\r\n" +
+			"abcdef",
+	},
+
+	// HTTP/1.1 POST with Content-Length in headers
+	{
+		Req: Request{
+			Method: "POST",
+			URL:    mustParseURL("http://example.com/"),
+			Host:   "example.com",
+			Header: Header{
+				"Content-Length": []string{"10"}, // ignored
+			},
+			ContentLength: 6,
+		},
+
+		Body: []byte("abcdef"),
+
+		WantWrite: "POST / HTTP/1.1\r\n" +
+			"Host: example.com\r\n" +
+			"User-Agent: Go 1.1 package http\r\n" +
+			"Content-Length: 6\r\n" +
+			"\r\n" +
+			"abcdef",
+
+		WantProxy: "POST http://example.com/ HTTP/1.1\r\n" +
+			"Host: example.com\r\n" +
+			"User-Agent: Go 1.1 package http\r\n" +
+			"Content-Length: 6\r\n" +
+			"\r\n" +
+			"abcdef",
+	},
+
+	// default to HTTP/1.1
+	{
+		Req: Request{
+			Method: "GET",
+			URL:    mustParseURL("/search"),
+			Host:   "www.google.com",
+		},
+
+		WantWrite: "GET /search HTTP/1.1\r\n" +
+			"Host: www.google.com\r\n" +
+			"User-Agent: Go 1.1 package http\r\n" +
+			"\r\n",
+	},
+
+	// Request with a 0 ContentLength and a 0 byte body.
+	{
+		Req: Request{
+			Method:        "POST",
+			URL:           mustParseURL("/"),
+			Host:          "example.com",
+			ProtoMajor:    1,
+			ProtoMinor:    1,
+			ContentLength: 0, // as if unset by user
+		},
+
+		Body: func() io.ReadCloser { return ioutil.NopCloser(io.LimitReader(strings.NewReader("xx"), 0)) },
+
+		// RFC 2616 Section 14.13 says Content-Length should be specified
+		// unless body is prohibited by the request method.
+		// Also, nginx expects it for POST and PUT.
+		WantWrite: "POST / HTTP/1.1\r\n" +
+			"Host: example.com\r\n" +
+			"User-Agent: Go 1.1 package http\r\n" +
+			"Content-Length: 0\r\n" +
+			"\r\n",
+
+		WantProxy: "POST / HTTP/1.1\r\n" +
+			"Host: example.com\r\n" +
+			"User-Agent: Go 1.1 package http\r\n" +
+			"Content-Length: 0\r\n" +
+			"\r\n",
+	},
+
+	// Request with a 0 ContentLength and a 1 byte body.
+	{
+		Req: Request{
+			Method:        "POST",
+			URL:           mustParseURL("/"),
+			Host:          "example.com",
+			ProtoMajor:    1,
+			ProtoMinor:    1,
+			ContentLength: 0, // as if unset by user
+		},
+
+		Body: func() io.ReadCloser { return ioutil.NopCloser(io.LimitReader(strings.NewReader("xx"), 1)) },
+
+		WantWrite: "POST / HTTP/1.1\r\n" +
+			"Host: example.com\r\n" +
+			"User-Agent: Go 1.1 package http\r\n" +
+			"Transfer-Encoding: chunked\r\n\r\n" +
+			chunk("x") + chunk(""),
+
+		WantProxy: "POST / HTTP/1.1\r\n" +
+			"Host: example.com\r\n" +
+			"User-Agent: Go 1.1 package http\r\n" +
+			"Transfer-Encoding: chunked\r\n\r\n" +
+			chunk("x") + chunk(""),
+	},
+
+	// Request with a ContentLength of 10 but a 5 byte body.
+	{
+		Req: Request{
+			Method:        "POST",
+			URL:           mustParseURL("/"),
+			Host:          "example.com",
+			ProtoMajor:    1,
+			ProtoMinor:    1,
+			ContentLength: 10, // but we're going to send only 5 bytes
+		},
+		Body:      []byte("12345"),
+		WantError: errors.New("http: ContentLength=10 with Body length 5"),
+	},
+
+	// Request with a ContentLength of 4 but an 8 byte body.
+	{
+		Req: Request{
+			Method:        "POST",
+			URL:           mustParseURL("/"),
+			Host:          "example.com",
+			ProtoMajor:    1,
+			ProtoMinor:    1,
+			ContentLength: 4, // but we're going to try to send 8 bytes
+		},
+		Body:      []byte("12345678"),
+		WantError: errors.New("http: ContentLength=4 with Body length 8"),
+	},
+
+	// Request with a 5 ContentLength and nil body.
+	{
+		Req: Request{
+			Method:        "POST",
+			URL:           mustParseURL("/"),
+			Host:          "example.com",
+			ProtoMajor:    1,
+			ProtoMinor:    1,
+			ContentLength: 5, // but we'll omit the body
+		},
+		WantError: errors.New("http: Request.ContentLength=5 with nil Body"),
+	},
+
+	// Request with a 0 ContentLength and a body with 1 byte content and an error.
+	{
+		Req: Request{
+			Method:        "POST",
+			URL:           mustParseURL("/"),
+			Host:          "example.com",
+			ProtoMajor:    1,
+			ProtoMinor:    1,
+			ContentLength: 0, // as if unset by user
+		},
+
+		Body: func() io.ReadCloser {
+			err := errors.New("Custom reader error")
+			errReader := &errorReader{err}
+			return ioutil.NopCloser(io.MultiReader(strings.NewReader("x"), errReader))
+		},
+
+		WantError: errors.New("Custom reader error"),
+	},
+
+	// Request with a 0 ContentLength and a body without content and an error.
+	{
+		Req: Request{
+			Method:        "POST",
+			URL:           mustParseURL("/"),
+			Host:          "example.com",
+			ProtoMajor:    1,
+			ProtoMinor:    1,
+			ContentLength: 0, // as if unset by user
+		},
+
+		Body: func() io.ReadCloser {
+			err := errors.New("Custom reader error")
+			errReader := &errorReader{err}
+			return ioutil.NopCloser(errReader)
+		},
+
+		WantError: errors.New("Custom reader error"),
+	},
+
+	// Verify that DumpRequest preserves the HTTP version number, doesn't add a Host,
+	// and doesn't add a User-Agent.
+	{
+		Req: Request{
+			Method:     "GET",
+			URL:        mustParseURL("/foo"),
+			ProtoMajor: 1,
+			ProtoMinor: 0,
+			Header: Header{
+				"X-Foo": []string{"X-Bar"},
+			},
+		},
+
+		WantWrite: "GET /foo HTTP/1.1\r\n" +
+			"Host: \r\n" +
+			"User-Agent: Go 1.1 package http\r\n" +
+			"X-Foo: X-Bar\r\n\r\n",
+	},
+
+	// If no Request.Host and no Request.URL.Host, we send
+	// an empty Host header, and don't use
+	// Request.Header["Host"]. This is just testing that
+	// we don't change Go 1.0 behavior.
+	{
+		Req: Request{
+			Method: "GET",
+			Host:   "",
+			URL: &url.URL{
+				Scheme: "http",
+				Host:   "",
+				Path:   "/search",
+			},
+			ProtoMajor: 1,
+			ProtoMinor: 1,
+			Header: Header{
+				"Host": []string{"bad.example.com"},
+			},
+		},
+
+		WantWrite: "GET /search HTTP/1.1\r\n" +
+			"Host: \r\n" +
+			"User-Agent: Go 1.1 package http\r\n\r\n",
+	},
+
+	// Opaque test #1 from golang.org/issue/4860
+	{
+		Req: Request{
+			Method: "GET",
+			URL: &url.URL{
+				Scheme: "http",
+				Host:   "www.google.com",
+				Opaque: "/%2F/%2F/",
+			},
+			ProtoMajor: 1,
+			ProtoMinor: 1,
+			Header:     Header{},
+		},
+
+		WantWrite: "GET /%2F/%2F/ HTTP/1.1\r\n" +
+			"Host: www.google.com\r\n" +
+			"User-Agent: Go 1.1 package http\r\n\r\n",
+	},
+
+	// Opaque test #2 from golang.org/issue/4860
+	{
+		Req: Request{
+			Method: "GET",
+			URL: &url.URL{
+				Scheme: "http",
+				Host:   "x.google.com",
+				Opaque: "//y.google.com/%2F/%2F/",
+			},
+			ProtoMajor: 1,
+			ProtoMinor: 1,
+			Header:     Header{},
+		},
+
+		WantWrite: "GET http://y.google.com/%2F/%2F/ HTTP/1.1\r\n" +
+			"Host: x.google.com\r\n" +
+			"User-Agent: Go 1.1 package http\r\n\r\n",
+	},
+
+	// Testing custom case in header keys. Issue 5022.
+	{
+		Req: Request{
+			Method: "GET",
+			URL: &url.URL{
+				Scheme: "http",
+				Host:   "www.google.com",
+				Path:   "/",
+			},
+			Proto:      "HTTP/1.1",
+			ProtoMajor: 1,
+			ProtoMinor: 1,
+			Header: Header{
+				"ALL-CAPS": {"x"},
+			},
+		},
+
+		WantWrite: "GET / HTTP/1.1\r\n" +
+			"Host: www.google.com\r\n" +
+			"User-Agent: Go 1.1 package http\r\n" +
+			"ALL-CAPS: x\r\n" +
+			"\r\n",
+	},
+}
+
+func TestRequestWrite(t *testing.T) {
+	for i := range reqWriteTests {
+		tt := &reqWriteTests[i]
+
+		setBody := func() {
+			if tt.Body == nil {
+				return
+			}
+			switch b := tt.Body.(type) {
+			case []byte:
+				tt.Req.Body = ioutil.NopCloser(bytes.NewReader(b))
+			case func() io.ReadCloser:
+				tt.Req.Body = b()
+			}
+		}
+		setBody()
+		if tt.Req.Header == nil {
+			tt.Req.Header = make(Header)
+		}
+
+		var braw bytes.Buffer
+		err := tt.Req.Write(&braw)
+		if g, e := fmt.Sprintf("%v", err), fmt.Sprintf("%v", tt.WantError); g != e {
+			t.Errorf("writing #%d, err = %q, want %q", i, g, e)
+			continue
+		}
+		if err != nil {
+			continue
+		}
+
+		if tt.WantWrite != "" {
+			sraw := braw.String()
+			if sraw != tt.WantWrite {
+				t.Errorf("Test %d, expecting:\n%s\nGot:\n%s\n", i, tt.WantWrite, sraw)
+				continue
+			}
+		}
+
+		if tt.WantProxy != "" {
+			setBody()
+			var praw bytes.Buffer
+			err = tt.Req.WriteProxy(&praw)
+			if err != nil {
+				t.Errorf("WriteProxy #%d: %s", i, err)
+				continue
+			}
+			sraw := praw.String()
+			if sraw != tt.WantProxy {
+				t.Errorf("Test Proxy %d, expecting:\n%s\nGot:\n%s\n", i, tt.WantProxy, sraw)
+				continue
+			}
+		}
+	}
+}
+
+type closeChecker struct {
+	io.Reader
+	closed bool
+}
+
+func (rc *closeChecker) Close() error {
+	rc.closed = true
+	return nil
+}
+
+// TestRequestWriteClosesBody tests that Request.Write does close its request.Body.
+// It also indirectly tests NewRequest and that it doesn't wrap an existing Closer
+// inside a NopCloser, and that it serializes it correctly.
+func TestRequestWriteClosesBody(t *testing.T) {
+	rc := &closeChecker{Reader: strings.NewReader("my body")}
+	req, _ := NewRequest("POST", "http://foo.com/", rc)
+	if req.ContentLength != 0 {
+		t.Errorf("got req.ContentLength %d, want 0", req.ContentLength)
+	}
+	buf := new(bytes.Buffer)
+	req.Write(buf)
+	if !rc.closed {
+		t.Error("body not closed after write")
+	}
+	expected := "POST / HTTP/1.1\r\n" +
+		"Host: foo.com\r\n" +
+		"User-Agent: Go 1.1 package http\r\n" +
+		"Transfer-Encoding: chunked\r\n\r\n" +
+		// TODO: currently we don't buffer before chunking, so we get a
+		// single "m" chunk before the other chunks, as this was the 1-byte
+		// read from our MultiReader where we stiched the Body back together
+		// after sniffing whether the Body was 0 bytes or not.
+		chunk("m") +
+		chunk("y body") +
+		chunk("")
+	if buf.String() != expected {
+		t.Errorf("write:\n got: %s\nwant: %s", buf.String(), expected)
+	}
+}
+
+func chunk(s string) string {
+	return fmt.Sprintf("%x\r\n%s\r\n", len(s), s)
+}
+
+func mustParseURL(s string) *url.URL {
+	u, err := url.Parse(s)
+	if err != nil {
+		panic(fmt.Sprintf("Error parsing URL %q: %v", s, err))
+	}
+	return u
+}
+
+type writerFunc func([]byte) (int, error)
+
+func (f writerFunc) Write(p []byte) (int, error) { return f(p) }
+
+// TestRequestWriteError tests the Write err != nil checks in (*Request).write.
+func TestRequestWriteError(t *testing.T) {
+	failAfter, writeCount := 0, 0
+	errFail := errors.New("fake write failure")
+
+	// w is the buffered io.Writer to write the request to.  It
+	// fails exactly once on its Nth Write call, as controlled by
+	// failAfter. It also tracks the number of calls in
+	// writeCount.
+	w := struct {
+		io.ByteWriter // to avoid being wrapped by a bufio.Writer
+		io.Writer
+	}{
+		nil,
+		writerFunc(func(p []byte) (n int, err error) {
+			writeCount++
+			if failAfter == 0 {
+				err = errFail
+			}
+			failAfter--
+			return len(p), err
+		}),
+	}
+
+	req, _ := NewRequest("GET", "http://example.com/", nil)
+	const writeCalls = 4 // number of Write calls in current implementation
+	sawGood := false
+	for n := 0; n <= writeCalls+2; n++ {
+		failAfter = n
+		writeCount = 0
+		err := req.Write(w)
+		var wantErr error
+		if n < writeCalls {
+			wantErr = errFail
+		}
+		if err != wantErr {
+			t.Errorf("for fail-after %d Writes, err = %v; want %v", n, err, wantErr)
+			continue
+		}
+		if err == nil {
+			sawGood = true
+			if writeCount != writeCalls {
+				t.Fatalf("writeCalls constant is outdated in test")
+			}
+		}
+		if writeCount > writeCalls || writeCount > n+1 {
+			t.Errorf("for fail-after %d, saw unexpectedly high (%d) write calls", n, writeCount)
+		}
+	}
+	if !sawGood {
+		t.Fatalf("writeCalls constant is outdated in test")
+	}
+}
diff --git a/src/net/http/response.go b/src/net/http/response.go
new file mode 100644
index 000000000..5d2c39080
--- /dev/null
+++ b/src/net/http/response.go
@@ -0,0 +1,291 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// HTTP Response reading and parsing.
+
+package http
+
+import (
+	"bufio"
+	"bytes"
+	"crypto/tls"
+	"errors"
+	"io"
+	"net/textproto"
+	"net/url"
+	"strconv"
+	"strings"
+)
+
+var respExcludeHeader = map[string]bool{
+	"Content-Length":    true,
+	"Transfer-Encoding": true,
+	"Trailer":           true,
+}
+
+// Response represents the response from an HTTP request.
+//
+type Response struct {
+	Status     string // e.g. "200 OK"
+	StatusCode int    // e.g. 200
+	Proto      string // e.g. "HTTP/1.0"
+	ProtoMajor int    // e.g. 1
+	ProtoMinor int    // e.g. 0
+
+	// Header maps header keys to values.  If the response had multiple
+	// headers with the same key, they may be concatenated, with comma
+	// delimiters.  (Section 4.2 of RFC 2616 requires that multiple headers
+	// be semantically equivalent to a comma-delimited sequence.) Values
+	// duplicated by other fields in this struct (e.g., ContentLength) are
+	// omitted from Header.
+	//
+	// Keys in the map are canonicalized (see CanonicalHeaderKey).
+	Header Header
+
+	// Body represents the response body.
+	//
+	// The http Client and Transport guarantee that Body is always
+	// non-nil, even on responses without a body or responses with
+	// a zero-length body. It is the caller's responsibility to
+	// close Body.
+	//
+	// The Body is automatically dechunked if the server replied
+	// with a "chunked" Transfer-Encoding.
+	Body io.ReadCloser
+
+	// ContentLength records the length of the associated content.  The
+	// value -1 indicates that the length is unknown.  Unless Request.Method
+	// is "HEAD", values >= 0 indicate that the given number of bytes may
+	// be read from Body.
+	ContentLength int64
+
+	// Contains transfer encodings from outer-most to inner-most. Value is
+	// nil, means that "identity" encoding is used.
+	TransferEncoding []string
+
+	// Close records whether the header directed that the connection be
+	// closed after reading Body.  The value is advice for clients: neither
+	// ReadResponse nor Response.Write ever closes a connection.
+	Close bool
+
+	// Trailer maps trailer keys to values, in the same
+	// format as the header.
+	Trailer Header
+
+	// The Request that was sent to obtain this Response.
+	// Request's Body is nil (having already been consumed).
+	// This is only populated for Client requests.
+	Request *Request
+
+	// TLS contains information about the TLS connection on which the
+	// response was received. It is nil for unencrypted responses.
+	// The pointer is shared between responses and should not be
+	// modified.
+	TLS *tls.ConnectionState
+}
+
+// Cookies parses and returns the cookies set in the Set-Cookie headers.
+func (r *Response) Cookies() []*Cookie {
+	return readSetCookies(r.Header)
+}
+
+var ErrNoLocation = errors.New("http: no Location header in response")
+
+// Location returns the URL of the response's "Location" header,
+// if present.  Relative redirects are resolved relative to
+// the Response's Request.  ErrNoLocation is returned if no
+// Location header is present.
+func (r *Response) Location() (*url.URL, error) {
+	lv := r.Header.Get("Location")
+	if lv == "" {
+		return nil, ErrNoLocation
+	}
+	if r.Request != nil && r.Request.URL != nil {
+		return r.Request.URL.Parse(lv)
+	}
+	return url.Parse(lv)
+}
+
+// ReadResponse reads and returns an HTTP response from r.
+// The req parameter optionally specifies the Request that corresponds
+// to this Response. If nil, a GET request is assumed.
+// Clients must call resp.Body.Close when finished reading resp.Body.
+// After that call, clients can inspect resp.Trailer to find key/value
+// pairs included in the response trailer.
+func ReadResponse(r *bufio.Reader, req *Request) (*Response, error) {
+	tp := textproto.NewReader(r)
+	resp := &Response{
+		Request: req,
+	}
+
+	// Parse the first line of the response.
+	line, err := tp.ReadLine()
+	if err != nil {
+		if err == io.EOF {
+			err = io.ErrUnexpectedEOF
+		}
+		return nil, err
+	}
+	f := strings.SplitN(line, " ", 3)
+	if len(f) < 2 {
+		return nil, &badStringError{"malformed HTTP response", line}
+	}
+	reasonPhrase := ""
+	if len(f) > 2 {
+		reasonPhrase = f[2]
+	}
+	resp.Status = f[1] + " " + reasonPhrase
+	resp.StatusCode, err = strconv.Atoi(f[1])
+	if err != nil {
+		return nil, &badStringError{"malformed HTTP status code", f[1]}
+	}
+
+	resp.Proto = f[0]
+	var ok bool
+	if resp.ProtoMajor, resp.ProtoMinor, ok = ParseHTTPVersion(resp.Proto); !ok {
+		return nil, &badStringError{"malformed HTTP version", resp.Proto}
+	}
+
+	// Parse the response headers.
+	mimeHeader, err := tp.ReadMIMEHeader()
+	if err != nil {
+		if err == io.EOF {
+			err = io.ErrUnexpectedEOF
+		}
+		return nil, err
+	}
+	resp.Header = Header(mimeHeader)
+
+	fixPragmaCacheControl(resp.Header)
+
+	err = readTransfer(resp, r)
+	if err != nil {
+		return nil, err
+	}
+
+	return resp, nil
+}
+
+// RFC2616: Should treat
+//	Pragma: no-cache
+// like
+//	Cache-Control: no-cache
+func fixPragmaCacheControl(header Header) {
+	if hp, ok := header["Pragma"]; ok && len(hp) > 0 && hp[0] == "no-cache" {
+		if _, presentcc := header["Cache-Control"]; !presentcc {
+			header["Cache-Control"] = []string{"no-cache"}
+		}
+	}
+}
+
+// ProtoAtLeast reports whether the HTTP protocol used
+// in the response is at least major.minor.
+func (r *Response) ProtoAtLeast(major, minor int) bool {
+	return r.ProtoMajor > major ||
+		r.ProtoMajor == major && r.ProtoMinor >= minor
+}
+
+// Writes the response (header, body and trailer) in wire format. This method
+// consults the following fields of the response:
+//
+//  StatusCode
+//  ProtoMajor
+//  ProtoMinor
+//  Request.Method
+//  TransferEncoding
+//  Trailer
+//  Body
+//  ContentLength
+//  Header, values for non-canonical keys will have unpredictable behavior
+//
+// Body is closed after it is sent.
+func (r *Response) Write(w io.Writer) error {
+	// Status line
+	text := r.Status
+	if text == "" {
+		var ok bool
+		text, ok = statusText[r.StatusCode]
+		if !ok {
+			text = "status code " + strconv.Itoa(r.StatusCode)
+		}
+	}
+	protoMajor, protoMinor := strconv.Itoa(r.ProtoMajor), strconv.Itoa(r.ProtoMinor)
+	statusCode := strconv.Itoa(r.StatusCode) + " "
+	text = strings.TrimPrefix(text, statusCode)
+	if _, err := io.WriteString(w, "HTTP/"+protoMajor+"."+protoMinor+" "+statusCode+text+"\r\n"); err != nil {
+		return err
+	}
+
+	// Clone it, so we can modify r1 as needed.
+	r1 := new(Response)
+	*r1 = *r
+	if r1.ContentLength == 0 && r1.Body != nil {
+		// Is it actually 0 length? Or just unknown?
+		var buf [1]byte
+		n, err := r1.Body.Read(buf[:])
+		if err != nil && err != io.EOF {
+			return err
+		}
+		if n == 0 {
+			// Reset it to a known zero reader, in case underlying one
+			// is unhappy being read repeatedly.
+			r1.Body = eofReader
+		} else {
+			r1.ContentLength = -1
+			r1.Body = struct {
+				io.Reader
+				io.Closer
+			}{
+				io.MultiReader(bytes.NewReader(buf[:1]), r.Body),
+				r.Body,
+			}
+		}
+	}
+	// If we're sending a non-chunked HTTP/1.1 response without a
+	// content-length, the only way to do that is the old HTTP/1.0
+	// way, by noting the EOF with a connection close, so we need
+	// to set Close.
+	if r1.ContentLength == -1 && !r1.Close && r1.ProtoAtLeast(1, 1) && !chunked(r1.TransferEncoding) {
+		r1.Close = true
+	}
+
+	// Process Body,ContentLength,Close,Trailer
+	tw, err := newTransferWriter(r1)
+	if err != nil {
+		return err
+	}
+	err = tw.WriteHeader(w)
+	if err != nil {
+		return err
+	}
+
+	// Rest of header
+	err = r.Header.WriteSubset(w, respExcludeHeader)
+	if err != nil {
+		return err
+	}
+
+	// contentLengthAlreadySent may have been already sent for
+	// POST/PUT requests, even if zero length. See Issue 8180.
+	contentLengthAlreadySent := tw.shouldSendContentLength()
+	if r1.ContentLength == 0 && !chunked(r1.TransferEncoding) && !contentLengthAlreadySent {
+		if _, err := io.WriteString(w, "Content-Length: 0\r\n"); err != nil {
+			return err
+		}
+	}
+
+	// End-of-header
+	if _, err := io.WriteString(w, "\r\n"); err != nil {
+		return err
+	}
+
+	// Write body and trailer
+	err = tw.WriteBody(w)
+	if err != nil {
+		return err
+	}
+
+	// Success
+	return nil
+}
diff --git a/src/net/http/response_test.go b/src/net/http/response_test.go
new file mode 100644
index 000000000..2dd0fad11
--- /dev/null
+++ b/src/net/http/response_test.go
@@ -0,0 +1,646 @@
+// Copyright 2010 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package http
+
+import (
+	"bufio"
+	"bytes"
+	"compress/gzip"
+	"crypto/rand"
+	"fmt"
+	"io"
+	"io/ioutil"
+	"net/http/internal"
+	"net/url"
+	"reflect"
+	"regexp"
+	"strings"
+	"testing"
+)
+
+type respTest struct {
+	Raw  string
+	Resp Response
+	Body string
+}
+
+func dummyReq(method string) *Request {
+	return &Request{Method: method}
+}
+
+func dummyReq11(method string) *Request {
+	return &Request{Method: method, Proto: "HTTP/1.1", ProtoMajor: 1, ProtoMinor: 1}
+}
+
+var respTests = []respTest{
+	// Unchunked response without Content-Length.
+	{
+		"HTTP/1.0 200 OK\r\n" +
+			"Connection: close\r\n" +
+			"\r\n" +
+			"Body here\n",
+
+		Response{
+			Status:     "200 OK",
+			StatusCode: 200,
+			Proto:      "HTTP/1.0",
+			ProtoMajor: 1,
+			ProtoMinor: 0,
+			Request:    dummyReq("GET"),
+			Header: Header{
+				"Connection": {"close"}, // TODO(rsc): Delete?
+			},
+			Close:         true,
+			ContentLength: -1,
+		},
+
+		"Body here\n",
+	},
+
+	// Unchunked HTTP/1.1 response without Content-Length or
+	// Connection headers.
+	{
+		"HTTP/1.1 200 OK\r\n" +
+			"\r\n" +
+			"Body here\n",
+
+		Response{
+			Status:        "200 OK",
+			StatusCode:    200,
+			Proto:         "HTTP/1.1",
+			ProtoMajor:    1,
+			ProtoMinor:    1,
+			Header:        Header{},
+			Request:       dummyReq("GET"),
+			Close:         true,
+			ContentLength: -1,
+		},
+
+		"Body here\n",
+	},
+
+	// Unchunked HTTP/1.1 204 response without Content-Length.
+	{
+		"HTTP/1.1 204 No Content\r\n" +
+			"\r\n" +
+			"Body should not be read!\n",
+
+		Response{
+			Status:        "204 No Content",
+			StatusCode:    204,
+			Proto:         "HTTP/1.1",
+			ProtoMajor:    1,
+			ProtoMinor:    1,
+			Header:        Header{},
+			Request:       dummyReq("GET"),
+			Close:         false,
+			ContentLength: 0,
+		},
+
+		"",
+	},
+
+	// Unchunked response with Content-Length.
+	{
+		"HTTP/1.0 200 OK\r\n" +
+			"Content-Length: 10\r\n" +
+			"Connection: close\r\n" +
+			"\r\n" +
+			"Body here\n",
+
+		Response{
+			Status:     "200 OK",
+			StatusCode: 200,
+			Proto:      "HTTP/1.0",
+			ProtoMajor: 1,
+			ProtoMinor: 0,
+			Request:    dummyReq("GET"),
+			Header: Header{
+				"Connection":     {"close"},
+				"Content-Length": {"10"},
+			},
+			Close:         true,
+			ContentLength: 10,
+		},
+
+		"Body here\n",
+	},
+
+	// Chunked response without Content-Length.
+	{
+		"HTTP/1.1 200 OK\r\n" +
+			"Transfer-Encoding: chunked\r\n" +
+			"\r\n" +
+			"0a\r\n" +
+			"Body here\n\r\n" +
+			"09\r\n" +
+			"continued\r\n" +
+			"0\r\n" +
+			"\r\n",
+
+		Response{
+			Status:           "200 OK",
+			StatusCode:       200,
+			Proto:            "HTTP/1.1",
+			ProtoMajor:       1,
+			ProtoMinor:       1,
+			Request:          dummyReq("GET"),
+			Header:           Header{},
+			Close:            false,
+			ContentLength:    -1,
+			TransferEncoding: []string{"chunked"},
+		},
+
+		"Body here\ncontinued",
+	},
+
+	// Chunked response with Content-Length.
+	{
+		"HTTP/1.1 200 OK\r\n" +
+			"Transfer-Encoding: chunked\r\n" +
+			"Content-Length: 10\r\n" +
+			"\r\n" +
+			"0a\r\n" +
+			"Body here\n\r\n" +
+			"0\r\n" +
+			"\r\n",
+
+		Response{
+			Status:           "200 OK",
+			StatusCode:       200,
+			Proto:            "HTTP/1.1",
+			ProtoMajor:       1,
+			ProtoMinor:       1,
+			Request:          dummyReq("GET"),
+			Header:           Header{},
+			Close:            false,
+			ContentLength:    -1,
+			TransferEncoding: []string{"chunked"},
+		},
+
+		"Body here\n",
+	},
+
+	// Chunked response in response to a HEAD request
+	{
+		"HTTP/1.1 200 OK\r\n" +
+			"Transfer-Encoding: chunked\r\n" +
+			"\r\n",
+
+		Response{
+			Status:           "200 OK",
+			StatusCode:       200,
+			Proto:            "HTTP/1.1",
+			ProtoMajor:       1,
+			ProtoMinor:       1,
+			Request:          dummyReq("HEAD"),
+			Header:           Header{},
+			TransferEncoding: []string{"chunked"},
+			Close:            false,
+			ContentLength:    -1,
+		},
+
+		"",
+	},
+
+	// Content-Length in response to a HEAD request
+	{
+		"HTTP/1.0 200 OK\r\n" +
+			"Content-Length: 256\r\n" +
+			"\r\n",
+
+		Response{
+			Status:           "200 OK",
+			StatusCode:       200,
+			Proto:            "HTTP/1.0",
+			ProtoMajor:       1,
+			ProtoMinor:       0,
+			Request:          dummyReq("HEAD"),
+			Header:           Header{"Content-Length": {"256"}},
+			TransferEncoding: nil,
+			Close:            true,
+			ContentLength:    256,
+		},
+
+		"",
+	},
+
+	// Content-Length in response to a HEAD request with HTTP/1.1
+	{
+		"HTTP/1.1 200 OK\r\n" +
+			"Content-Length: 256\r\n" +
+			"\r\n",
+
+		Response{
+			Status:           "200 OK",
+			StatusCode:       200,
+			Proto:            "HTTP/1.1",
+			ProtoMajor:       1,
+			ProtoMinor:       1,
+			Request:          dummyReq("HEAD"),
+			Header:           Header{"Content-Length": {"256"}},
+			TransferEncoding: nil,
+			Close:            false,
+			ContentLength:    256,
+		},
+
+		"",
+	},
+
+	// No Content-Length or Chunked in response to a HEAD request
+	{
+		"HTTP/1.0 200 OK\r\n" +
+			"\r\n",
+
+		Response{
+			Status:           "200 OK",
+			StatusCode:       200,
+			Proto:            "HTTP/1.0",
+			ProtoMajor:       1,
+			ProtoMinor:       0,
+			Request:          dummyReq("HEAD"),
+			Header:           Header{},
+			TransferEncoding: nil,
+			Close:            true,
+			ContentLength:    -1,
+		},
+
+		"",
+	},
+
+	// explicit Content-Length of 0.
+	{
+		"HTTP/1.1 200 OK\r\n" +
+			"Content-Length: 0\r\n" +
+			"\r\n",
+
+		Response{
+			Status:     "200 OK",
+			StatusCode: 200,
+			Proto:      "HTTP/1.1",
+			ProtoMajor: 1,
+			ProtoMinor: 1,
+			Request:    dummyReq("GET"),
+			Header: Header{
+				"Content-Length": {"0"},
+			},
+			Close:         false,
+			ContentLength: 0,
+		},
+
+		"",
+	},
+
+	// Status line without a Reason-Phrase, but trailing space.
+	// (permitted by RFC 2616)
+	{
+		"HTTP/1.0 303 \r\n\r\n",
+		Response{
+			Status:        "303 ",
+			StatusCode:    303,
+			Proto:         "HTTP/1.0",
+			ProtoMajor:    1,
+			ProtoMinor:    0,
+			Request:       dummyReq("GET"),
+			Header:        Header{},
+			Close:         true,
+			ContentLength: -1,
+		},
+
+		"",
+	},
+
+	// Status line without a Reason-Phrase, and no trailing space.
+	// (not permitted by RFC 2616, but we'll accept it anyway)
+	{
+		"HTTP/1.0 303\r\n\r\n",
+		Response{
+			Status:        "303 ",
+			StatusCode:    303,
+			Proto:         "HTTP/1.0",
+			ProtoMajor:    1,
+			ProtoMinor:    0,
+			Request:       dummyReq("GET"),
+			Header:        Header{},
+			Close:         true,
+			ContentLength: -1,
+		},
+
+		"",
+	},
+
+	// golang.org/issue/4767: don't special-case multipart/byteranges responses
+	{
+		`HTTP/1.1 206 Partial Content
+Connection: close
+Content-Type: multipart/byteranges; boundary=18a75608c8f47cef
+
+some body`,
+		Response{
+			Status:     "206 Partial Content",
+			StatusCode: 206,
+			Proto:      "HTTP/1.1",
+			ProtoMajor: 1,
+			ProtoMinor: 1,
+			Request:    dummyReq("GET"),
+			Header: Header{
+				"Content-Type": []string{"multipart/byteranges; boundary=18a75608c8f47cef"},
+			},
+			Close:         true,
+			ContentLength: -1,
+		},
+
+		"some body",
+	},
+
+	// Unchunked response without Content-Length, Request is nil
+	{
+		"HTTP/1.0 200 OK\r\n" +
+			"Connection: close\r\n" +
+			"\r\n" +
+			"Body here\n",
+
+		Response{
+			Status:     "200 OK",
+			StatusCode: 200,
+			Proto:      "HTTP/1.0",
+			ProtoMajor: 1,
+			ProtoMinor: 0,
+			Header: Header{
+				"Connection": {"close"}, // TODO(rsc): Delete?
+			},
+			Close:         true,
+			ContentLength: -1,
+		},
+
+		"Body here\n",
+	},
+}
+
+func TestReadResponse(t *testing.T) {
+	for i, tt := range respTests {
+		resp, err := ReadResponse(bufio.NewReader(strings.NewReader(tt.Raw)), tt.Resp.Request)
+		if err != nil {
+			t.Errorf("#%d: %v", i, err)
+			continue
+		}
+		rbody := resp.Body
+		resp.Body = nil
+		diff(t, fmt.Sprintf("#%d Response", i), resp, &tt.Resp)
+		var bout bytes.Buffer
+		if rbody != nil {
+			_, err = io.Copy(&bout, rbody)
+			if err != nil {
+				t.Errorf("#%d: %v", i, err)
+				continue
+			}
+			rbody.Close()
+		}
+		body := bout.String()
+		if body != tt.Body {
+			t.Errorf("#%d: Body = %q want %q", i, body, tt.Body)
+		}
+	}
+}
+
+func TestWriteResponse(t *testing.T) {
+	for i, tt := range respTests {
+		resp, err := ReadResponse(bufio.NewReader(strings.NewReader(tt.Raw)), tt.Resp.Request)
+		if err != nil {
+			t.Errorf("#%d: %v", i, err)
+			continue
+		}
+		err = resp.Write(ioutil.Discard)
+		if err != nil {
+			t.Errorf("#%d: %v", i, err)
+			continue
+		}
+	}
+}
+
+var readResponseCloseInMiddleTests = []struct {
+	chunked, compressed bool
+}{
+	{false, false},
+	{true, false},
+	{true, true},
+}
+
+// TestReadResponseCloseInMiddle tests that closing a body after
+// reading only part of its contents advances the read to the end of
+// the request, right up until the next request.
+func TestReadResponseCloseInMiddle(t *testing.T) {
+	for _, test := range readResponseCloseInMiddleTests {
+		fatalf := func(format string, args ...interface{}) {
+			args = append([]interface{}{test.chunked, test.compressed}, args...)
+			t.Fatalf("on test chunked=%v, compressed=%v: "+format, args...)
+		}
+		checkErr := func(err error, msg string) {
+			if err == nil {
+				return
+			}
+			fatalf(msg+": %v", err)
+		}
+		var buf bytes.Buffer
+		buf.WriteString("HTTP/1.1 200 OK\r\n")
+		if test.chunked {
+			buf.WriteString("Transfer-Encoding: chunked\r\n")
+		} else {
+			buf.WriteString("Content-Length: 1000000\r\n")
+		}
+		var wr io.Writer = &buf
+		if test.chunked {
+			wr = internal.NewChunkedWriter(wr)
+		}
+		if test.compressed {
+			buf.WriteString("Content-Encoding: gzip\r\n")
+			wr = gzip.NewWriter(wr)
+		}
+		buf.WriteString("\r\n")
+
+		chunk := bytes.Repeat([]byte{'x'}, 1000)
+		for i := 0; i < 1000; i++ {
+			if test.compressed {
+				// Otherwise this compresses too well.
+				_, err := io.ReadFull(rand.Reader, chunk)
+				checkErr(err, "rand.Reader ReadFull")
+			}
+			wr.Write(chunk)
+		}
+		if test.compressed {
+			err := wr.(*gzip.Writer).Close()
+			checkErr(err, "compressor close")
+		}
+		if test.chunked {
+			buf.WriteString("0\r\n\r\n")
+		}
+		buf.WriteString("Next Request Here")
+
+		bufr := bufio.NewReader(&buf)
+		resp, err := ReadResponse(bufr, dummyReq("GET"))
+		checkErr(err, "ReadResponse")
+		expectedLength := int64(-1)
+		if !test.chunked {
+			expectedLength = 1000000
+		}
+		if resp.ContentLength != expectedLength {
+			fatalf("expected response length %d, got %d", expectedLength, resp.ContentLength)
+		}
+		if resp.Body == nil {
+			fatalf("nil body")
+		}
+		if test.compressed {
+			gzReader, err := gzip.NewReader(resp.Body)
+			checkErr(err, "gzip.NewReader")
+			resp.Body = &readerAndCloser{gzReader, resp.Body}
+		}
+
+		rbuf := make([]byte, 2500)
+		n, err := io.ReadFull(resp.Body, rbuf)
+		checkErr(err, "2500 byte ReadFull")
+		if n != 2500 {
+			fatalf("ReadFull only read %d bytes", n)
+		}
+		if test.compressed == false && !bytes.Equal(bytes.Repeat([]byte{'x'}, 2500), rbuf) {
+			fatalf("ReadFull didn't read 2500 'x'; got %q", string(rbuf))
+		}
+		resp.Body.Close()
+
+		rest, err := ioutil.ReadAll(bufr)
+		checkErr(err, "ReadAll on remainder")
+		if e, g := "Next Request Here", string(rest); e != g {
+			g = regexp.MustCompile(`(xx+)`).ReplaceAllStringFunc(g, func(match string) string {
+				return fmt.Sprintf("x(repeated x%d)", len(match))
+			})
+			fatalf("remainder = %q, expected %q", g, e)
+		}
+	}
+}
+
+func diff(t *testing.T, prefix string, have, want interface{}) {
+	hv := reflect.ValueOf(have).Elem()
+	wv := reflect.ValueOf(want).Elem()
+	if hv.Type() != wv.Type() {
+		t.Errorf("%s: type mismatch %v want %v", prefix, hv.Type(), wv.Type())
+	}
+	for i := 0; i < hv.NumField(); i++ {
+		hf := hv.Field(i).Interface()
+		wf := wv.Field(i).Interface()
+		if !reflect.DeepEqual(hf, wf) {
+			t.Errorf("%s: %s = %v want %v", prefix, hv.Type().Field(i).Name, hf, wf)
+		}
+	}
+}
+
+type responseLocationTest struct {
+	location string // Response's Location header or ""
+	requrl   string // Response.Request.URL or ""
+	want     string
+	wantErr  error
+}
+
+var responseLocationTests = []responseLocationTest{
+	{"/foo", "http://bar.com/baz", "http://bar.com/foo", nil},
+	{"http://foo.com/", "http://bar.com/baz", "http://foo.com/", nil},
+	{"", "http://bar.com/baz", "", ErrNoLocation},
+}
+
+func TestLocationResponse(t *testing.T) {
+	for i, tt := range responseLocationTests {
+		res := new(Response)
+		res.Header = make(Header)
+		res.Header.Set("Location", tt.location)
+		if tt.requrl != "" {
+			res.Request = &Request{}
+			var err error
+			res.Request.URL, err = url.Parse(tt.requrl)
+			if err != nil {
+				t.Fatalf("bad test URL %q: %v", tt.requrl, err)
+			}
+		}
+
+		got, err := res.Location()
+		if tt.wantErr != nil {
+			if err == nil {
+				t.Errorf("%d. err=nil; want %q", i, tt.wantErr)
+				continue
+			}
+			if g, e := err.Error(), tt.wantErr.Error(); g != e {
+				t.Errorf("%d. err=%q; want %q", i, g, e)
+				continue
+			}
+			continue
+		}
+		if err != nil {
+			t.Errorf("%d. err=%q", i, err)
+			continue
+		}
+		if g, e := got.String(), tt.want; g != e {
+			t.Errorf("%d. Location=%q; want %q", i, g, e)
+		}
+	}
+}
+
+func TestResponseStatusStutter(t *testing.T) {
+	r := &Response{
+		Status:     "123 some status",
+		StatusCode: 123,
+		ProtoMajor: 1,
+		ProtoMinor: 3,
+	}
+	var buf bytes.Buffer
+	r.Write(&buf)
+	if strings.Contains(buf.String(), "123 123") {
+		t.Errorf("stutter in status: %s", buf.String())
+	}
+}
+
+func TestResponseContentLengthShortBody(t *testing.T) {
+	const shortBody = "Short body, not 123 bytes."
+	br := bufio.NewReader(strings.NewReader("HTTP/1.1 200 OK\r\n" +
+		"Content-Length: 123\r\n" +
+		"\r\n" +
+		shortBody))
+	res, err := ReadResponse(br, &Request{Method: "GET"})
+	if err != nil {
+		t.Fatal(err)
+	}
+	if res.ContentLength != 123 {
+		t.Fatalf("Content-Length = %d; want 123", res.ContentLength)
+	}
+	var buf bytes.Buffer
+	n, err := io.Copy(&buf, res.Body)
+	if n != int64(len(shortBody)) {
+		t.Errorf("Copied %d bytes; want %d, len(%q)", n, len(shortBody), shortBody)
+	}
+	if buf.String() != shortBody {
+		t.Errorf("Read body %q; want %q", buf.String(), shortBody)
+	}
+	if err != io.ErrUnexpectedEOF {
+		t.Errorf("io.Copy error = %#v; want io.ErrUnexpectedEOF", err)
+	}
+}
+
+func TestReadResponseUnexpectedEOF(t *testing.T) {
+	br := bufio.NewReader(strings.NewReader("HTTP/1.1 301 Moved Permanently\r\n" +
+		"Location: http://example.com"))
+	_, err := ReadResponse(br, nil)
+	if err != io.ErrUnexpectedEOF {
+		t.Errorf("ReadResponse = %v; want io.ErrUnexpectedEOF", err)
+	}
+}
+
+func TestNeedsSniff(t *testing.T) {
+	// needsSniff returns true with an empty response.
+	r := &response{}
+	if got, want := r.needsSniff(), true; got != want {
+		t.Errorf("needsSniff = %t; want %t", got, want)
+	}
+	// needsSniff returns false when Content-Type = nil.
+	r.handlerHeader = Header{"Content-Type": nil}
+	if got, want := r.needsSniff(), false; got != want {
+		t.Errorf("needsSniff empty Content-Type = %t; want %t", got, want)
+	}
+}
diff --git a/src/net/http/responsewrite_test.go b/src/net/http/responsewrite_test.go
new file mode 100644
index 000000000..585b13b85
--- /dev/null
+++ b/src/net/http/responsewrite_test.go
@@ -0,0 +1,226 @@
+// Copyright 2010 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package http
+
+import (
+	"bytes"
+	"io/ioutil"
+	"strings"
+	"testing"
+)
+
+type respWriteTest struct {
+	Resp Response
+	Raw  string
+}
+
+func TestResponseWrite(t *testing.T) {
+	respWriteTests := []respWriteTest{
+		// HTTP/1.0, identity coding; no trailer
+		{
+			Response{
+				StatusCode:    503,
+				ProtoMajor:    1,
+				ProtoMinor:    0,
+				Request:       dummyReq("GET"),
+				Header:        Header{},
+				Body:          ioutil.NopCloser(strings.NewReader("abcdef")),
+				ContentLength: 6,
+			},
+
+			"HTTP/1.0 503 Service Unavailable\r\n" +
+				"Content-Length: 6\r\n\r\n" +
+				"abcdef",
+		},
+		// Unchunked response without Content-Length.
+		{
+			Response{
+				StatusCode:    200,
+				ProtoMajor:    1,
+				ProtoMinor:    0,
+				Request:       dummyReq("GET"),
+				Header:        Header{},
+				Body:          ioutil.NopCloser(strings.NewReader("abcdef")),
+				ContentLength: -1,
+			},
+			"HTTP/1.0 200 OK\r\n" +
+				"\r\n" +
+				"abcdef",
+		},
+		// HTTP/1.1 response with unknown length and Connection: close
+		{
+			Response{
+				StatusCode:    200,
+				ProtoMajor:    1,
+				ProtoMinor:    1,
+				Request:       dummyReq("GET"),
+				Header:        Header{},
+				Body:          ioutil.NopCloser(strings.NewReader("abcdef")),
+				ContentLength: -1,
+				Close:         true,
+			},
+			"HTTP/1.1 200 OK\r\n" +
+				"Connection: close\r\n" +
+				"\r\n" +
+				"abcdef",
+		},
+		// HTTP/1.1 response with unknown length and not setting connection: close
+		{
+			Response{
+				StatusCode:    200,
+				ProtoMajor:    1,
+				ProtoMinor:    1,
+				Request:       dummyReq11("GET"),
+				Header:        Header{},
+				Body:          ioutil.NopCloser(strings.NewReader("abcdef")),
+				ContentLength: -1,
+				Close:         false,
+			},
+			"HTTP/1.1 200 OK\r\n" +
+				"Connection: close\r\n" +
+				"\r\n" +
+				"abcdef",
+		},
+		// HTTP/1.1 response with unknown length and not setting connection: close, but
+		// setting chunked.
+		{
+			Response{
+				StatusCode:       200,
+				ProtoMajor:       1,
+				ProtoMinor:       1,
+				Request:          dummyReq11("GET"),
+				Header:           Header{},
+				Body:             ioutil.NopCloser(strings.NewReader("abcdef")),
+				ContentLength:    -1,
+				TransferEncoding: []string{"chunked"},
+				Close:            false,
+			},
+			"HTTP/1.1 200 OK\r\n" +
+				"Transfer-Encoding: chunked\r\n\r\n" +
+				"6\r\nabcdef\r\n0\r\n\r\n",
+		},
+		// HTTP/1.1 response 0 content-length, and nil body
+		{
+			Response{
+				StatusCode:    200,
+				ProtoMajor:    1,
+				ProtoMinor:    1,
+				Request:       dummyReq11("GET"),
+				Header:        Header{},
+				Body:          nil,
+				ContentLength: 0,
+				Close:         false,
+			},
+			"HTTP/1.1 200 OK\r\n" +
+				"Content-Length: 0\r\n" +
+				"\r\n",
+		},
+		// HTTP/1.1 response 0 content-length, and non-nil empty body
+		{
+			Response{
+				StatusCode:    200,
+				ProtoMajor:    1,
+				ProtoMinor:    1,
+				Request:       dummyReq11("GET"),
+				Header:        Header{},
+				Body:          ioutil.NopCloser(strings.NewReader("")),
+				ContentLength: 0,
+				Close:         false,
+			},
+			"HTTP/1.1 200 OK\r\n" +
+				"Content-Length: 0\r\n" +
+				"\r\n",
+		},
+		// HTTP/1.1 response 0 content-length, and non-nil non-empty body
+		{
+			Response{
+				StatusCode:    200,
+				ProtoMajor:    1,
+				ProtoMinor:    1,
+				Request:       dummyReq11("GET"),
+				Header:        Header{},
+				Body:          ioutil.NopCloser(strings.NewReader("foo")),
+				ContentLength: 0,
+				Close:         false,
+			},
+			"HTTP/1.1 200 OK\r\n" +
+				"Connection: close\r\n" +
+				"\r\nfoo",
+		},
+		// HTTP/1.1, chunked coding; empty trailer; close
+		{
+			Response{
+				StatusCode:       200,
+				ProtoMajor:       1,
+				ProtoMinor:       1,
+				Request:          dummyReq("GET"),
+				Header:           Header{},
+				Body:             ioutil.NopCloser(strings.NewReader("abcdef")),
+				ContentLength:    6,
+				TransferEncoding: []string{"chunked"},
+				Close:            true,
+			},
+
+			"HTTP/1.1 200 OK\r\n" +
+				"Connection: close\r\n" +
+				"Transfer-Encoding: chunked\r\n\r\n" +
+				"6\r\nabcdef\r\n0\r\n\r\n",
+		},
+
+		// Header value with a newline character (Issue 914).
+		// Also tests removal of leading and trailing whitespace.
+		{
+			Response{
+				StatusCode: 204,
+				ProtoMajor: 1,
+				ProtoMinor: 1,
+				Request:    dummyReq("GET"),
+				Header: Header{
+					"Foo": []string{" Bar\nBaz "},
+				},
+				Body:             nil,
+				ContentLength:    0,
+				TransferEncoding: []string{"chunked"},
+				Close:            true,
+			},
+
+			"HTTP/1.1 204 No Content\r\n" +
+				"Connection: close\r\n" +
+				"Foo: Bar Baz\r\n" +
+				"\r\n",
+		},
+
+		// Want a single Content-Length header. Fixing issue 8180 where
+		// there were two.
+		{
+			Response{
+				StatusCode:       StatusOK,
+				ProtoMajor:       1,
+				ProtoMinor:       1,
+				Request:          &Request{Method: "POST"},
+				Header:           Header{},
+				ContentLength:    0,
+				TransferEncoding: nil,
+				Body:             nil,
+			},
+			"HTTP/1.1 200 OK\r\nContent-Length: 0\r\n\r\n",
+		},
+	}
+
+	for i := range respWriteTests {
+		tt := &respWriteTests[i]
+		var braw bytes.Buffer
+		err := tt.Resp.Write(&braw)
+		if err != nil {
+			t.Errorf("error writing #%d: %s", i, err)
+			continue
+		}
+		sraw := braw.String()
+		if sraw != tt.Raw {
+			t.Errorf("Test %d, expecting:\n%q\nGot:\n%q\n", i, tt.Raw, sraw)
+			continue
+		}
+	}
+}
diff --git a/src/net/http/serve_test.go b/src/net/http/serve_test.go
new file mode 100644
index 000000000..ee4f20499
--- /dev/null
+++ b/src/net/http/serve_test.go
@@ -0,0 +1,2944 @@
+// Copyright 2010 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// End-to-end serving tests
+
+package http_test
+
+import (
+	"bufio"
+	"bytes"
+	"crypto/tls"
+	"errors"
+	"fmt"
+	"io"
+	"io/ioutil"
+	"log"
+	"math/rand"
+	"net"
+	. "net/http"
+	"net/http/httptest"
+	"net/http/httputil"
+	"net/url"
+	"os"
+	"os/exec"
+	"reflect"
+	"runtime"
+	"strconv"
+	"strings"
+	"sync"
+	"sync/atomic"
+	"syscall"
+	"testing"
+	"time"
+)
+
+type dummyAddr string
+type oneConnListener struct {
+	conn net.Conn
+}
+
+func (l *oneConnListener) Accept() (c net.Conn, err error) {
+	c = l.conn
+	if c == nil {
+		err = io.EOF
+		return
+	}
+	err = nil
+	l.conn = nil
+	return
+}
+
+func (l *oneConnListener) Close() error {
+	return nil
+}
+
+func (l *oneConnListener) Addr() net.Addr {
+	return dummyAddr("test-address")
+}
+
+func (a dummyAddr) Network() string {
+	return string(a)
+}
+
+func (a dummyAddr) String() string {
+	return string(a)
+}
+
+type noopConn struct{}
+
+func (noopConn) LocalAddr() net.Addr                { return dummyAddr("local-addr") }
+func (noopConn) RemoteAddr() net.Addr               { return dummyAddr("remote-addr") }
+func (noopConn) SetDeadline(t time.Time) error      { return nil }
+func (noopConn) SetReadDeadline(t time.Time) error  { return nil }
+func (noopConn) SetWriteDeadline(t time.Time) error { return nil }
+
+type rwTestConn struct {
+	io.Reader
+	io.Writer
+	noopConn
+
+	closeFunc func() error // called if non-nil
+	closec    chan bool    // else, if non-nil, send value to it on close
+}
+
+func (c *rwTestConn) Close() error {
+	if c.closeFunc != nil {
+		return c.closeFunc()
+	}
+	select {
+	case c.closec <- true:
+	default:
+	}
+	return nil
+}
+
+type testConn struct {
+	readBuf  bytes.Buffer
+	writeBuf bytes.Buffer
+	closec   chan bool // if non-nil, send value to it on close
+	noopConn
+}
+
+func (c *testConn) Read(b []byte) (int, error) {
+	return c.readBuf.Read(b)
+}
+
+func (c *testConn) Write(b []byte) (int, error) {
+	return c.writeBuf.Write(b)
+}
+
+func (c *testConn) Close() error {
+	select {
+	case c.closec <- true:
+	default:
+	}
+	return nil
+}
+
+// reqBytes treats req as a request (with \n delimiters) and returns it with \r\n delimiters,
+// ending in \r\n\r\n
+func reqBytes(req string) []byte {
+	return []byte(strings.Replace(strings.TrimSpace(req), "\n", "\r\n", -1) + "\r\n\r\n")
+}
+
+type handlerTest struct {
+	handler Handler
+}
+
+func newHandlerTest(h Handler) handlerTest {
+	return handlerTest{h}
+}
+
+func (ht handlerTest) rawResponse(req string) string {
+	reqb := reqBytes(req)
+	var output bytes.Buffer
+	conn := &rwTestConn{
+		Reader: bytes.NewReader(reqb),
+		Writer: &output,
+		closec: make(chan bool, 1),
+	}
+	ln := &oneConnListener{conn: conn}
+	go Serve(ln, ht.handler)
+	<-conn.closec
+	return output.String()
+}
+
+func TestConsumingBodyOnNextConn(t *testing.T) {
+	conn := new(testConn)
+	for i := 0; i < 2; i++ {
+		conn.readBuf.Write([]byte(
+			"POST / HTTP/1.1\r\n" +
+				"Host: test\r\n" +
+				"Content-Length: 11\r\n" +
+				"\r\n" +
+				"foo=1&bar=1"))
+	}
+
+	reqNum := 0
+	ch := make(chan *Request)
+	servech := make(chan error)
+	listener := &oneConnListener{conn}
+	handler := func(res ResponseWriter, req *Request) {
+		reqNum++
+		ch <- req
+	}
+
+	go func() {
+		servech <- Serve(listener, HandlerFunc(handler))
+	}()
+
+	var req *Request
+	req = <-ch
+	if req == nil {
+		t.Fatal("Got nil first request.")
+	}
+	if req.Method != "POST" {
+		t.Errorf("For request #1's method, got %q; expected %q",
+			req.Method, "POST")
+	}
+
+	req = <-ch
+	if req == nil {
+		t.Fatal("Got nil first request.")
+	}
+	if req.Method != "POST" {
+		t.Errorf("For request #2's method, got %q; expected %q",
+			req.Method, "POST")
+	}
+
+	if serveerr := <-servech; serveerr != io.EOF {
+		t.Errorf("Serve returned %q; expected EOF", serveerr)
+	}
+}
+
+type stringHandler string
+
+func (s stringHandler) ServeHTTP(w ResponseWriter, r *Request) {
+	w.Header().Set("Result", string(s))
+}
+
+var handlers = []struct {
+	pattern string
+	msg     string
+}{
+	{"/", "Default"},
+	{"/someDir/", "someDir"},
+	{"someHost.com/someDir/", "someHost.com/someDir"},
+}
+
+var vtests = []struct {
+	url      string
+	expected string
+}{
+	{"http://localhost/someDir/apage", "someDir"},
+	{"http://localhost/otherDir/apage", "Default"},
+	{"http://someHost.com/someDir/apage", "someHost.com/someDir"},
+	{"http://otherHost.com/someDir/apage", "someDir"},
+	{"http://otherHost.com/aDir/apage", "Default"},
+	// redirections for trees
+	{"http://localhost/someDir", "/someDir/"},
+	{"http://someHost.com/someDir", "/someDir/"},
+}
+
+func TestHostHandlers(t *testing.T) {
+	defer afterTest(t)
+	mux := NewServeMux()
+	for _, h := range handlers {
+		mux.Handle(h.pattern, stringHandler(h.msg))
+	}
+	ts := httptest.NewServer(mux)
+	defer ts.Close()
+
+	conn, err := net.Dial("tcp", ts.Listener.Addr().String())
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer conn.Close()
+	cc := httputil.NewClientConn(conn, nil)
+	for _, vt := range vtests {
+		var r *Response
+		var req Request
+		if req.URL, err = url.Parse(vt.url); err != nil {
+			t.Errorf("cannot parse url: %v", err)
+			continue
+		}
+		if err := cc.Write(&req); err != nil {
+			t.Errorf("writing request: %v", err)
+			continue
+		}
+		r, err := cc.Read(&req)
+		if err != nil {
+			t.Errorf("reading response: %v", err)
+			continue
+		}
+		switch r.StatusCode {
+		case StatusOK:
+			s := r.Header.Get("Result")
+			if s != vt.expected {
+				t.Errorf("Get(%q) = %q, want %q", vt.url, s, vt.expected)
+			}
+		case StatusMovedPermanently:
+			s := r.Header.Get("Location")
+			if s != vt.expected {
+				t.Errorf("Get(%q) = %q, want %q", vt.url, s, vt.expected)
+			}
+		default:
+			t.Errorf("Get(%q) unhandled status code %d", vt.url, r.StatusCode)
+		}
+	}
+}
+
+var serveMuxRegister = []struct {
+	pattern string
+	h       Handler
+}{
+	{"/dir/", serve(200)},
+	{"/search", serve(201)},
+	{"codesearch.google.com/search", serve(202)},
+	{"codesearch.google.com/", serve(203)},
+	{"example.com/", HandlerFunc(checkQueryStringHandler)},
+}
+
+// serve returns a handler that sends a response with the given code.
+func serve(code int) HandlerFunc {
+	return func(w ResponseWriter, r *Request) {
+		w.WriteHeader(code)
+	}
+}
+
+// checkQueryStringHandler checks if r.URL.RawQuery has the same value
+// as the URL excluding the scheme and the query string and sends 200
+// response code if it is, 500 otherwise.
+func checkQueryStringHandler(w ResponseWriter, r *Request) {
+	u := *r.URL
+	u.Scheme = "http"
+	u.Host = r.Host
+	u.RawQuery = ""
+	if "http://"+r.URL.RawQuery == u.String() {
+		w.WriteHeader(200)
+	} else {
+		w.WriteHeader(500)
+	}
+}
+
+var serveMuxTests = []struct {
+	method  string
+	host    string
+	path    string
+	code    int
+	pattern string
+}{
+	{"GET", "google.com", "/", 404, ""},
+	{"GET", "google.com", "/dir", 301, "/dir/"},
+	{"GET", "google.com", "/dir/", 200, "/dir/"},
+	{"GET", "google.com", "/dir/file", 200, "/dir/"},
+	{"GET", "google.com", "/search", 201, "/search"},
+	{"GET", "google.com", "/search/", 404, ""},
+	{"GET", "google.com", "/search/foo", 404, ""},
+	{"GET", "codesearch.google.com", "/search", 202, "codesearch.google.com/search"},
+	{"GET", "codesearch.google.com", "/search/", 203, "codesearch.google.com/"},
+	{"GET", "codesearch.google.com", "/search/foo", 203, "codesearch.google.com/"},
+	{"GET", "codesearch.google.com", "/", 203, "codesearch.google.com/"},
+	{"GET", "images.google.com", "/search", 201, "/search"},
+	{"GET", "images.google.com", "/search/", 404, ""},
+	{"GET", "images.google.com", "/search/foo", 404, ""},
+	{"GET", "google.com", "/../search", 301, "/search"},
+	{"GET", "google.com", "/dir/..", 301, ""},
+	{"GET", "google.com", "/dir/..", 301, ""},
+	{"GET", "google.com", "/dir/./file", 301, "/dir/"},
+
+	// The /foo -> /foo/ redirect applies to CONNECT requests
+	// but the path canonicalization does not.
+	{"CONNECT", "google.com", "/dir", 301, "/dir/"},
+	{"CONNECT", "google.com", "/../search", 404, ""},
+	{"CONNECT", "google.com", "/dir/..", 200, "/dir/"},
+	{"CONNECT", "google.com", "/dir/..", 200, "/dir/"},
+	{"CONNECT", "google.com", "/dir/./file", 200, "/dir/"},
+}
+
+func TestServeMuxHandler(t *testing.T) {
+	mux := NewServeMux()
+	for _, e := range serveMuxRegister {
+		mux.Handle(e.pattern, e.h)
+	}
+
+	for _, tt := range serveMuxTests {
+		r := &Request{
+			Method: tt.method,
+			Host:   tt.host,
+			URL: &url.URL{
+				Path: tt.path,
+			},
+		}
+		h, pattern := mux.Handler(r)
+		rr := httptest.NewRecorder()
+		h.ServeHTTP(rr, r)
+		if pattern != tt.pattern || rr.Code != tt.code {
+			t.Errorf("%s %s %s = %d, %q, want %d, %q", tt.method, tt.host, tt.path, rr.Code, pattern, tt.code, tt.pattern)
+		}
+	}
+}
+
+var serveMuxTests2 = []struct {
+	method  string
+	host    string
+	url     string
+	code    int
+	redirOk bool
+}{
+	{"GET", "google.com", "/", 404, false},
+	{"GET", "example.com", "/test/?example.com/test/", 200, false},
+	{"GET", "example.com", "test/?example.com/test/", 200, true},
+}
+
+// TestServeMuxHandlerRedirects tests that automatic redirects generated by
+// mux.Handler() shouldn't clear the request's query string.
+func TestServeMuxHandlerRedirects(t *testing.T) {
+	mux := NewServeMux()
+	for _, e := range serveMuxRegister {
+		mux.Handle(e.pattern, e.h)
+	}
+
+	for _, tt := range serveMuxTests2 {
+		tries := 1
+		turl := tt.url
+		for tries > 0 {
+			u, e := url.Parse(turl)
+			if e != nil {
+				t.Fatal(e)
+			}
+			r := &Request{
+				Method: tt.method,
+				Host:   tt.host,
+				URL:    u,
+			}
+			h, _ := mux.Handler(r)
+			rr := httptest.NewRecorder()
+			h.ServeHTTP(rr, r)
+			if rr.Code != 301 {
+				if rr.Code != tt.code {
+					t.Errorf("%s %s %s = %d, want %d", tt.method, tt.host, tt.url, rr.Code, tt.code)
+				}
+				break
+			}
+			if !tt.redirOk {
+				t.Errorf("%s %s %s, unexpected redirect", tt.method, tt.host, tt.url)
+				break
+			}
+			turl = rr.HeaderMap.Get("Location")
+			tries--
+		}
+		if tries < 0 {
+			t.Errorf("%s %s %s, too many redirects", tt.method, tt.host, tt.url)
+		}
+	}
+}
+
+// Tests for http://code.google.com/p/go/issues/detail?id=900
+func TestMuxRedirectLeadingSlashes(t *testing.T) {
+	paths := []string{"//foo.txt", "///foo.txt", "/../../foo.txt"}
+	for _, path := range paths {
+		req, err := ReadRequest(bufio.NewReader(strings.NewReader("GET " + path + " HTTP/1.1\r\nHost: test\r\n\r\n")))
+		if err != nil {
+			t.Errorf("%s", err)
+		}
+		mux := NewServeMux()
+		resp := httptest.NewRecorder()
+
+		mux.ServeHTTP(resp, req)
+
+		if loc, expected := resp.Header().Get("Location"), "/foo.txt"; loc != expected {
+			t.Errorf("Expected Location header set to %q; got %q", expected, loc)
+			return
+		}
+
+		if code, expected := resp.Code, StatusMovedPermanently; code != expected {
+			t.Errorf("Expected response code of StatusMovedPermanently; got %d", code)
+			return
+		}
+	}
+}
+
+func TestServerTimeouts(t *testing.T) {
+	if runtime.GOOS == "plan9" {
+		t.Skip("skipping test; see http://golang.org/issue/7237")
+	}
+	defer afterTest(t)
+	reqNum := 0
+	ts := httptest.NewUnstartedServer(HandlerFunc(func(res ResponseWriter, req *Request) {
+		reqNum++
+		fmt.Fprintf(res, "req=%d", reqNum)
+	}))
+	ts.Config.ReadTimeout = 250 * time.Millisecond
+	ts.Config.WriteTimeout = 250 * time.Millisecond
+	ts.Start()
+	defer ts.Close()
+
+	// Hit the HTTP server successfully.
+	tr := &Transport{DisableKeepAlives: true} // they interfere with this test
+	defer tr.CloseIdleConnections()
+	c := &Client{Transport: tr}
+	r, err := c.Get(ts.URL)
+	if err != nil {
+		t.Fatalf("http Get #1: %v", err)
+	}
+	got, _ := ioutil.ReadAll(r.Body)
+	expected := "req=1"
+	if string(got) != expected {
+		t.Errorf("Unexpected response for request #1; got %q; expected %q",
+			string(got), expected)
+	}
+
+	// Slow client that should timeout.
+	t1 := time.Now()
+	conn, err := net.Dial("tcp", ts.Listener.Addr().String())
+	if err != nil {
+		t.Fatalf("Dial: %v", err)
+	}
+	buf := make([]byte, 1)
+	n, err := conn.Read(buf)
+	latency := time.Since(t1)
+	if n != 0 || err != io.EOF {
+		t.Errorf("Read = %v, %v, wanted %v, %v", n, err, 0, io.EOF)
+	}
+	if latency < 200*time.Millisecond /* fudge from 250 ms above */ {
+		t.Errorf("got EOF after %s, want >= %s", latency, 200*time.Millisecond)
+	}
+
+	// Hit the HTTP server successfully again, verifying that the
+	// previous slow connection didn't run our handler.  (that we
+	// get "req=2", not "req=3")
+	r, err = Get(ts.URL)
+	if err != nil {
+		t.Fatalf("http Get #2: %v", err)
+	}
+	got, _ = ioutil.ReadAll(r.Body)
+	expected = "req=2"
+	if string(got) != expected {
+		t.Errorf("Get #2 got %q, want %q", string(got), expected)
+	}
+
+	if !testing.Short() {
+		conn, err := net.Dial("tcp", ts.Listener.Addr().String())
+		if err != nil {
+			t.Fatalf("Dial: %v", err)
+		}
+		defer conn.Close()
+		go io.Copy(ioutil.Discard, conn)
+		for i := 0; i < 5; i++ {
+			_, err := conn.Write([]byte("GET / HTTP/1.1\r\nHost: foo\r\n\r\n"))
+			if err != nil {
+				t.Fatalf("on write %d: %v", i, err)
+			}
+			time.Sleep(ts.Config.ReadTimeout / 2)
+		}
+	}
+}
+
+// golang.org/issue/4741 -- setting only a write timeout that triggers
+// shouldn't cause a handler to block forever on reads (next HTTP
+// request) that will never happen.
+func TestOnlyWriteTimeout(t *testing.T) {
+	if runtime.GOOS == "plan9" {
+		t.Skip("skipping test; see http://golang.org/issue/7237")
+	}
+	defer afterTest(t)
+	var conn net.Conn
+	var afterTimeoutErrc = make(chan error, 1)
+	ts := httptest.NewUnstartedServer(HandlerFunc(func(w ResponseWriter, req *Request) {
+		buf := make([]byte, 512<<10)
+		_, err := w.Write(buf)
+		if err != nil {
+			t.Errorf("handler Write error: %v", err)
+			return
+		}
+		conn.SetWriteDeadline(time.Now().Add(-30 * time.Second))
+		_, err = w.Write(buf)
+		afterTimeoutErrc <- err
+	}))
+	ts.Listener = trackLastConnListener{ts.Listener, &conn}
+	ts.Start()
+	defer ts.Close()
+
+	tr := &Transport{DisableKeepAlives: false}
+	defer tr.CloseIdleConnections()
+	c := &Client{Transport: tr}
+
+	errc := make(chan error)
+	go func() {
+		res, err := c.Get(ts.URL)
+		if err != nil {
+			errc <- err
+			return
+		}
+		_, err = io.Copy(ioutil.Discard, res.Body)
+		errc <- err
+	}()
+	select {
+	case err := <-errc:
+		if err == nil {
+			t.Errorf("expected an error from Get request")
+		}
+	case <-time.After(5 * time.Second):
+		t.Fatal("timeout waiting for Get error")
+	}
+	if err := <-afterTimeoutErrc; err == nil {
+		t.Error("expected write error after timeout")
+	}
+}
+
+// trackLastConnListener tracks the last net.Conn that was accepted.
+type trackLastConnListener struct {
+	net.Listener
+	last *net.Conn // destination
+}
+
+func (l trackLastConnListener) Accept() (c net.Conn, err error) {
+	c, err = l.Listener.Accept()
+	*l.last = c
+	return
+}
+
+// TestIdentityResponse verifies that a handler can unset
+func TestIdentityResponse(t *testing.T) {
+	defer afterTest(t)
+	handler := HandlerFunc(func(rw ResponseWriter, req *Request) {
+		rw.Header().Set("Content-Length", "3")
+		rw.Header().Set("Transfer-Encoding", req.FormValue("te"))
+		switch {
+		case req.FormValue("overwrite") == "1":
+			_, err := rw.Write([]byte("foo TOO LONG"))
+			if err != ErrContentLength {
+				t.Errorf("expected ErrContentLength; got %v", err)
+			}
+		case req.FormValue("underwrite") == "1":
+			rw.Header().Set("Content-Length", "500")
+			rw.Write([]byte("too short"))
+		default:
+			rw.Write([]byte("foo"))
+		}
+	})
+
+	ts := httptest.NewServer(handler)
+	defer ts.Close()
+
+	// Note: this relies on the assumption (which is true) that
+	// Get sends HTTP/1.1 or greater requests.  Otherwise the
+	// server wouldn't have the choice to send back chunked
+	// responses.
+	for _, te := range []string{"", "identity"} {
+		url := ts.URL + "/?te=" + te
+		res, err := Get(url)
+		if err != nil {
+			t.Fatalf("error with Get of %s: %v", url, err)
+		}
+		if cl, expected := res.ContentLength, int64(3); cl != expected {
+			t.Errorf("for %s expected res.ContentLength of %d; got %d", url, expected, cl)
+		}
+		if cl, expected := res.Header.Get("Content-Length"), "3"; cl != expected {
+			t.Errorf("for %s expected Content-Length header of %q; got %q", url, expected, cl)
+		}
+		if tl, expected := len(res.TransferEncoding), 0; tl != expected {
+			t.Errorf("for %s expected len(res.TransferEncoding) of %d; got %d (%v)",
+				url, expected, tl, res.TransferEncoding)
+		}
+		res.Body.Close()
+	}
+
+	// Verify that ErrContentLength is returned
+	url := ts.URL + "/?overwrite=1"
+	res, err := Get(url)
+	if err != nil {
+		t.Fatalf("error with Get of %s: %v", url, err)
+	}
+	res.Body.Close()
+
+	// Verify that the connection is closed when the declared Content-Length
+	// is larger than what the handler wrote.
+	conn, err := net.Dial("tcp", ts.Listener.Addr().String())
+	if err != nil {
+		t.Fatalf("error dialing: %v", err)
+	}
+	_, err = conn.Write([]byte("GET /?underwrite=1 HTTP/1.1\r\nHost: foo\r\n\r\n"))
+	if err != nil {
+		t.Fatalf("error writing: %v", err)
+	}
+
+	// The ReadAll will hang for a failing test, so use a Timer to
+	// fail explicitly.
+	goTimeout(t, 2*time.Second, func() {
+		got, _ := ioutil.ReadAll(conn)
+		expectedSuffix := "\r\n\r\ntoo short"
+		if !strings.HasSuffix(string(got), expectedSuffix) {
+			t.Errorf("Expected output to end with %q; got response body %q",
+				expectedSuffix, string(got))
+		}
+	})
+}
+
+func testTCPConnectionCloses(t *testing.T, req string, h Handler) {
+	defer afterTest(t)
+	s := httptest.NewServer(h)
+	defer s.Close()
+
+	conn, err := net.Dial("tcp", s.Listener.Addr().String())
+	if err != nil {
+		t.Fatal("dial error:", err)
+	}
+	defer conn.Close()
+
+	_, err = fmt.Fprint(conn, req)
+	if err != nil {
+		t.Fatal("print error:", err)
+	}
+
+	r := bufio.NewReader(conn)
+	res, err := ReadResponse(r, &Request{Method: "GET"})
+	if err != nil {
+		t.Fatal("ReadResponse error:", err)
+	}
+
+	didReadAll := make(chan bool, 1)
+	go func() {
+		select {
+		case <-time.After(5 * time.Second):
+			t.Error("body not closed after 5s")
+			return
+		case <-didReadAll:
+		}
+	}()
+
+	_, err = ioutil.ReadAll(r)
+	if err != nil {
+		t.Fatal("read error:", err)
+	}
+	didReadAll <- true
+
+	if !res.Close {
+		t.Errorf("Response.Close = false; want true")
+	}
+}
+
+// TestServeHTTP10Close verifies that HTTP/1.0 requests won't be kept alive.
+func TestServeHTTP10Close(t *testing.T) {
+	testTCPConnectionCloses(t, "GET / HTTP/1.0\r\n\r\n", HandlerFunc(func(w ResponseWriter, r *Request) {
+		ServeFile(w, r, "testdata/file")
+	}))
+}
+
+// TestClientCanClose verifies that clients can also force a connection to close.
+func TestClientCanClose(t *testing.T) {
+	testTCPConnectionCloses(t, "GET / HTTP/1.1\r\nConnection: close\r\n\r\n", HandlerFunc(func(w ResponseWriter, r *Request) {
+		// Nothing.
+	}))
+}
+
+// TestHandlersCanSetConnectionClose verifies that handlers can force a connection to close,
+// even for HTTP/1.1 requests.
+func TestHandlersCanSetConnectionClose11(t *testing.T) {
+	testTCPConnectionCloses(t, "GET / HTTP/1.1\r\n\r\n", HandlerFunc(func(w ResponseWriter, r *Request) {
+		w.Header().Set("Connection", "close")
+	}))
+}
+
+func TestHandlersCanSetConnectionClose10(t *testing.T) {
+	testTCPConnectionCloses(t, "GET / HTTP/1.0\r\nConnection: keep-alive\r\n\r\n", HandlerFunc(func(w ResponseWriter, r *Request) {
+		w.Header().Set("Connection", "close")
+	}))
+}
+
+func TestSetsRemoteAddr(t *testing.T) {
+	defer afterTest(t)
+	ts := httptest.NewServer(HandlerFunc(func(w ResponseWriter, r *Request) {
+		fmt.Fprintf(w, "%s", r.RemoteAddr)
+	}))
+	defer ts.Close()
+
+	res, err := Get(ts.URL)
+	if err != nil {
+		t.Fatalf("Get error: %v", err)
+	}
+	body, err := ioutil.ReadAll(res.Body)
+	if err != nil {
+		t.Fatalf("ReadAll error: %v", err)
+	}
+	ip := string(body)
+	if !strings.HasPrefix(ip, "127.0.0.1:") && !strings.HasPrefix(ip, "[::1]:") {
+		t.Fatalf("Expected local addr; got %q", ip)
+	}
+}
+
+func TestChunkedResponseHeaders(t *testing.T) {
+	defer afterTest(t)
+	log.SetOutput(ioutil.Discard) // is noisy otherwise
+	defer log.SetOutput(os.Stderr)
+
+	ts := httptest.NewServer(HandlerFunc(func(w ResponseWriter, r *Request) {
+		w.Header().Set("Content-Length", "intentional gibberish") // we check that this is deleted
+		w.(Flusher).Flush()
+		fmt.Fprintf(w, "I am a chunked response.")
+	}))
+	defer ts.Close()
+
+	res, err := Get(ts.URL)
+	if err != nil {
+		t.Fatalf("Get error: %v", err)
+	}
+	defer res.Body.Close()
+	if g, e := res.ContentLength, int64(-1); g != e {
+		t.Errorf("expected ContentLength of %d; got %d", e, g)
+	}
+	if g, e := res.TransferEncoding, []string{"chunked"}; !reflect.DeepEqual(g, e) {
+		t.Errorf("expected TransferEncoding of %v; got %v", e, g)
+	}
+	if _, haveCL := res.Header["Content-Length"]; haveCL {
+		t.Errorf("Unexpected Content-Length")
+	}
+}
+
+// Test304Responses verifies that 304s don't declare that they're
+// chunking in their response headers and aren't allowed to produce
+// output.
+func Test304Responses(t *testing.T) {
+	defer afterTest(t)
+	ts := httptest.NewServer(HandlerFunc(func(w ResponseWriter, r *Request) {
+		w.WriteHeader(StatusNotModified)
+		_, err := w.Write([]byte("illegal body"))
+		if err != ErrBodyNotAllowed {
+			t.Errorf("on Write, expected ErrBodyNotAllowed, got %v", err)
+		}
+	}))
+	defer ts.Close()
+	res, err := Get(ts.URL)
+	if err != nil {
+		t.Error(err)
+	}
+	if len(res.TransferEncoding) > 0 {
+		t.Errorf("expected no TransferEncoding; got %v", res.TransferEncoding)
+	}
+	body, err := ioutil.ReadAll(res.Body)
+	if err != nil {
+		t.Error(err)
+	}
+	if len(body) > 0 {
+		t.Errorf("got unexpected body %q", string(body))
+	}
+}
+
+// TestHeadResponses verifies that all MIME type sniffing and Content-Length
+// counting of GET requests also happens on HEAD requests.
+func TestHeadResponses(t *testing.T) {
+	defer afterTest(t)
+	ts := httptest.NewServer(HandlerFunc(func(w ResponseWriter, r *Request) {
+		_, err := w.Write([]byte("<html>"))
+		if err != nil {
+			t.Errorf("ResponseWriter.Write: %v", err)
+		}
+
+		// Also exercise the ReaderFrom path
+		_, err = io.Copy(w, strings.NewReader("789a"))
+		if err != nil {
+			t.Errorf("Copy(ResponseWriter, ...): %v", err)
+		}
+	}))
+	defer ts.Close()
+	res, err := Head(ts.URL)
+	if err != nil {
+		t.Error(err)
+	}
+	if len(res.TransferEncoding) > 0 {
+		t.Errorf("expected no TransferEncoding; got %v", res.TransferEncoding)
+	}
+	if ct := res.Header.Get("Content-Type"); ct != "text/html; charset=utf-8" {
+		t.Errorf("Content-Type: %q; want text/html; charset=utf-8", ct)
+	}
+	if v := res.ContentLength; v != 10 {
+		t.Errorf("Content-Length: %d; want 10", v)
+	}
+	body, err := ioutil.ReadAll(res.Body)
+	if err != nil {
+		t.Error(err)
+	}
+	if len(body) > 0 {
+		t.Errorf("got unexpected body %q", string(body))
+	}
+}
+
+func TestTLSHandshakeTimeout(t *testing.T) {
+	if runtime.GOOS == "plan9" {
+		t.Skip("skipping test; see http://golang.org/issue/7237")
+	}
+	defer afterTest(t)
+	ts := httptest.NewUnstartedServer(HandlerFunc(func(w ResponseWriter, r *Request) {}))
+	errc := make(chanWriter, 10) // but only expecting 1
+	ts.Config.ReadTimeout = 250 * time.Millisecond
+	ts.Config.ErrorLog = log.New(errc, "", 0)
+	ts.StartTLS()
+	defer ts.Close()
+	conn, err := net.Dial("tcp", ts.Listener.Addr().String())
+	if err != nil {
+		t.Fatalf("Dial: %v", err)
+	}
+	defer conn.Close()
+	goTimeout(t, 10*time.Second, func() {
+		var buf [1]byte
+		n, err := conn.Read(buf[:])
+		if err == nil || n != 0 {
+			t.Errorf("Read = %d, %v; want an error and no bytes", n, err)
+		}
+	})
+	select {
+	case v := <-errc:
+		if !strings.Contains(v, "timeout") && !strings.Contains(v, "TLS handshake") {
+			t.Errorf("expected a TLS handshake timeout error; got %q", v)
+		}
+	case <-time.After(5 * time.Second):
+		t.Errorf("timeout waiting for logged error")
+	}
+}
+
+func TestTLSServer(t *testing.T) {
+	defer afterTest(t)
+	ts := httptest.NewTLSServer(HandlerFunc(func(w ResponseWriter, r *Request) {
+		if r.TLS != nil {
+			w.Header().Set("X-TLS-Set", "true")
+			if r.TLS.HandshakeComplete {
+				w.Header().Set("X-TLS-HandshakeComplete", "true")
+			}
+		}
+	}))
+	ts.Config.ErrorLog = log.New(ioutil.Discard, "", 0)
+	defer ts.Close()
+
+	// Connect an idle TCP connection to this server before we run
+	// our real tests.  This idle connection used to block forever
+	// in the TLS handshake, preventing future connections from
+	// being accepted. It may prevent future accidental blocking
+	// in newConn.
+	idleConn, err := net.Dial("tcp", ts.Listener.Addr().String())
+	if err != nil {
+		t.Fatalf("Dial: %v", err)
+	}
+	defer idleConn.Close()
+	goTimeout(t, 10*time.Second, func() {
+		if !strings.HasPrefix(ts.URL, "https://") {
+			t.Errorf("expected test TLS server to start with https://, got %q", ts.URL)
+			return
+		}
+		noVerifyTransport := &Transport{
+			TLSClientConfig: &tls.Config{
+				InsecureSkipVerify: true,
+			},
+		}
+		client := &Client{Transport: noVerifyTransport}
+		res, err := client.Get(ts.URL)
+		if err != nil {
+			t.Error(err)
+			return
+		}
+		if res == nil {
+			t.Errorf("got nil Response")
+			return
+		}
+		defer res.Body.Close()
+		if res.Header.Get("X-TLS-Set") != "true" {
+			t.Errorf("expected X-TLS-Set response header")
+			return
+		}
+		if res.Header.Get("X-TLS-HandshakeComplete") != "true" {
+			t.Errorf("expected X-TLS-HandshakeComplete header")
+		}
+	})
+}
+
+type serverExpectTest struct {
+	contentLength    int // of request body
+	chunked          bool
+	expectation      string // e.g. "100-continue"
+	readBody         bool   // whether handler should read the body (if false, sends StatusUnauthorized)
+	expectedResponse string // expected substring in first line of http response
+}
+
+func expectTest(contentLength int, expectation string, readBody bool, expectedResponse string) serverExpectTest {
+	return serverExpectTest{
+		contentLength:    contentLength,
+		expectation:      expectation,
+		readBody:         readBody,
+		expectedResponse: expectedResponse,
+	}
+}
+
+var serverExpectTests = []serverExpectTest{
+	// Normal 100-continues, case-insensitive.
+	expectTest(100, "100-continue", true, "100 Continue"),
+	expectTest(100, "100-cOntInUE", true, "100 Continue"),
+
+	// No 100-continue.
+	expectTest(100, "", true, "200 OK"),
+
+	// 100-continue but requesting client to deny us,
+	// so it never reads the body.
+	expectTest(100, "100-continue", false, "401 Unauthorized"),
+	// Likewise without 100-continue:
+	expectTest(100, "", false, "401 Unauthorized"),
+
+	// Non-standard expectations are failures
+	expectTest(0, "a-pony", false, "417 Expectation Failed"),
+
+	// Expect-100 requested but no body (is apparently okay: Issue 7625)
+	expectTest(0, "100-continue", true, "200 OK"),
+	// Expect-100 requested but handler doesn't read the body
+	expectTest(0, "100-continue", false, "401 Unauthorized"),
+	// Expect-100 continue with no body, but a chunked body.
+	{
+		expectation:      "100-continue",
+		readBody:         true,
+		chunked:          true,
+		expectedResponse: "100 Continue",
+	},
+}
+
+// Tests that the server responds to the "Expect" request header
+// correctly.
+func TestServerExpect(t *testing.T) {
+	defer afterTest(t)
+	ts := httptest.NewServer(HandlerFunc(func(w ResponseWriter, r *Request) {
+		// Note using r.FormValue("readbody") because for POST
+		// requests that would read from r.Body, which we only
+		// conditionally want to do.
+		if strings.Contains(r.URL.RawQuery, "readbody=true") {
+			ioutil.ReadAll(r.Body)
+			w.Write([]byte("Hi"))
+		} else {
+			w.WriteHeader(StatusUnauthorized)
+		}
+	}))
+	defer ts.Close()
+
+	runTest := func(test serverExpectTest) {
+		conn, err := net.Dial("tcp", ts.Listener.Addr().String())
+		if err != nil {
+			t.Fatalf("Dial: %v", err)
+		}
+		defer conn.Close()
+
+		// Only send the body immediately if we're acting like an HTTP client
+		// that doesn't send 100-continue expectations.
+		writeBody := test.contentLength != 0 && strings.ToLower(test.expectation) != "100-continue"
+
+		go func() {
+			contentLen := fmt.Sprintf("Content-Length: %d", test.contentLength)
+			if test.chunked {
+				contentLen = "Transfer-Encoding: chunked"
+			}
+			_, err := fmt.Fprintf(conn, "POST /?readbody=%v HTTP/1.1\r\n"+
+				"Connection: close\r\n"+
+				"%s\r\n"+
+				"Expect: %s\r\nHost: foo\r\n\r\n",
+				test.readBody, contentLen, test.expectation)
+			if err != nil {
+				t.Errorf("On test %#v, error writing request headers: %v", test, err)
+				return
+			}
+			if writeBody {
+				var targ io.WriteCloser = struct {
+					io.Writer
+					io.Closer
+				}{
+					conn,
+					ioutil.NopCloser(nil),
+				}
+				if test.chunked {
+					targ = httputil.NewChunkedWriter(conn)
+				}
+				body := strings.Repeat("A", test.contentLength)
+				_, err = fmt.Fprint(targ, body)
+				if err == nil {
+					err = targ.Close()
+				}
+				if err != nil {
+					if !test.readBody {
+						// Server likely already hung up on us.
+						// See larger comment below.
+						t.Logf("On test %#v, acceptable error writing request body: %v", test, err)
+						return
+					}
+					t.Errorf("On test %#v, error writing request body: %v", test, err)
+				}
+			}
+		}()
+		bufr := bufio.NewReader(conn)
+		line, err := bufr.ReadString('\n')
+		if err != nil {
+			if writeBody && !test.readBody {
+				// This is an acceptable failure due to a possible TCP race:
+				// We were still writing data and the server hung up on us. A TCP
+				// implementation may send a RST if our request body data was known
+				// to be lost, which may trigger our reads to fail.
+				// See RFC 1122 page 88.
+				t.Logf("On test %#v, acceptable error from ReadString: %v", test, err)
+				return
+			}
+			t.Fatalf("On test %#v, ReadString: %v", test, err)
+		}
+		if !strings.Contains(line, test.expectedResponse) {
+			t.Errorf("On test %#v, got first line = %q; want %q", test, line, test.expectedResponse)
+		}
+	}
+
+	for _, test := range serverExpectTests {
+		runTest(test)
+	}
+}
+
+// Under a ~256KB (maxPostHandlerReadBytes) threshold, the server
+// should consume client request bodies that a handler didn't read.
+func TestServerUnreadRequestBodyLittle(t *testing.T) {
+	conn := new(testConn)
+	body := strings.Repeat("x", 100<<10)
+	conn.readBuf.Write([]byte(fmt.Sprintf(
+		"POST / HTTP/1.1\r\n"+
+			"Host: test\r\n"+
+			"Content-Length: %d\r\n"+
+			"\r\n", len(body))))
+	conn.readBuf.Write([]byte(body))
+
+	done := make(chan bool)
+
+	ls := &oneConnListener{conn}
+	go Serve(ls, HandlerFunc(func(rw ResponseWriter, req *Request) {
+		defer close(done)
+		if conn.readBuf.Len() < len(body)/2 {
+			t.Errorf("on request, read buffer length is %d; expected about 100 KB", conn.readBuf.Len())
+		}
+		rw.WriteHeader(200)
+		rw.(Flusher).Flush()
+		if g, e := conn.readBuf.Len(), 0; g != e {
+			t.Errorf("after WriteHeader, read buffer length is %d; want %d", g, e)
+		}
+		if c := rw.Header().Get("Connection"); c != "" {
+			t.Errorf(`Connection header = %q; want ""`, c)
+		}
+	}))
+	<-done
+}
+
+// Over a ~256KB (maxPostHandlerReadBytes) threshold, the server
+// should ignore client request bodies that a handler didn't read
+// and close the connection.
+func TestServerUnreadRequestBodyLarge(t *testing.T) {
+	conn := new(testConn)
+	body := strings.Repeat("x", 1<<20)
+	conn.readBuf.Write([]byte(fmt.Sprintf(
+		"POST / HTTP/1.1\r\n"+
+			"Host: test\r\n"+
+			"Content-Length: %d\r\n"+
+			"\r\n", len(body))))
+	conn.readBuf.Write([]byte(body))
+	conn.closec = make(chan bool, 1)
+
+	ls := &oneConnListener{conn}
+	go Serve(ls, HandlerFunc(func(rw ResponseWriter, req *Request) {
+		if conn.readBuf.Len() < len(body)/2 {
+			t.Errorf("on request, read buffer length is %d; expected about 1MB", conn.readBuf.Len())
+		}
+		rw.WriteHeader(200)
+		rw.(Flusher).Flush()
+		if conn.readBuf.Len() < len(body)/2 {
+			t.Errorf("post-WriteHeader, read buffer length is %d; expected about 1MB", conn.readBuf.Len())
+		}
+	}))
+	<-conn.closec
+
+	if res := conn.writeBuf.String(); !strings.Contains(res, "Connection: close") {
+		t.Errorf("Expected a Connection: close header; got response: %s", res)
+	}
+}
+
+func TestTimeoutHandler(t *testing.T) {
+	defer afterTest(t)
+	sendHi := make(chan bool, 1)
+	writeErrors := make(chan error, 1)
+	sayHi := HandlerFunc(func(w ResponseWriter, r *Request) {
+		<-sendHi
+		_, werr := w.Write([]byte("hi"))
+		writeErrors <- werr
+	})
+	timeout := make(chan time.Time, 1) // write to this to force timeouts
+	ts := httptest.NewServer(NewTestTimeoutHandler(sayHi, timeout))
+	defer ts.Close()
+
+	// Succeed without timing out:
+	sendHi <- true
+	res, err := Get(ts.URL)
+	if err != nil {
+		t.Error(err)
+	}
+	if g, e := res.StatusCode, StatusOK; g != e {
+		t.Errorf("got res.StatusCode %d; expected %d", g, e)
+	}
+	body, _ := ioutil.ReadAll(res.Body)
+	if g, e := string(body), "hi"; g != e {
+		t.Errorf("got body %q; expected %q", g, e)
+	}
+	if g := <-writeErrors; g != nil {
+		t.Errorf("got unexpected Write error on first request: %v", g)
+	}
+
+	// Times out:
+	timeout <- time.Time{}
+	res, err = Get(ts.URL)
+	if err != nil {
+		t.Error(err)
+	}
+	if g, e := res.StatusCode, StatusServiceUnavailable; g != e {
+		t.Errorf("got res.StatusCode %d; expected %d", g, e)
+	}
+	body, _ = ioutil.ReadAll(res.Body)
+	if !strings.Contains(string(body), "<title>Timeout</title>") {
+		t.Errorf("expected timeout body; got %q", string(body))
+	}
+
+	// Now make the previously-timed out handler speak again,
+	// which verifies the panic is handled:
+	sendHi <- true
+	if g, e := <-writeErrors, ErrHandlerTimeout; g != e {
+		t.Errorf("expected Write error of %v; got %v", e, g)
+	}
+}
+
+// See issues 8209 and 8414.
+func TestTimeoutHandlerRace(t *testing.T) {
+	defer afterTest(t)
+
+	delayHi := HandlerFunc(func(w ResponseWriter, r *Request) {
+		ms, _ := strconv.Atoi(r.URL.Path[1:])
+		if ms == 0 {
+			ms = 1
+		}
+		for i := 0; i < ms; i++ {
+			w.Write([]byte("hi"))
+			time.Sleep(time.Millisecond)
+		}
+	})
+
+	ts := httptest.NewServer(TimeoutHandler(delayHi, 20*time.Millisecond, ""))
+	defer ts.Close()
+
+	var wg sync.WaitGroup
+	gate := make(chan bool, 10)
+	n := 50
+	if testing.Short() {
+		n = 10
+		gate = make(chan bool, 3)
+	}
+	for i := 0; i < n; i++ {
+		gate <- true
+		wg.Add(1)
+		go func() {
+			defer wg.Done()
+			defer func() { <-gate }()
+			res, err := Get(fmt.Sprintf("%s/%d", ts.URL, rand.Intn(50)))
+			if err == nil {
+				io.Copy(ioutil.Discard, res.Body)
+				res.Body.Close()
+			}
+		}()
+	}
+	wg.Wait()
+}
+
+// See issues 8209 and 8414.
+func TestTimeoutHandlerRaceHeader(t *testing.T) {
+	defer afterTest(t)
+
+	delay204 := HandlerFunc(func(w ResponseWriter, r *Request) {
+		w.WriteHeader(204)
+	})
+
+	ts := httptest.NewServer(TimeoutHandler(delay204, time.Nanosecond, ""))
+	defer ts.Close()
+
+	var wg sync.WaitGroup
+	gate := make(chan bool, 50)
+	n := 500
+	if testing.Short() {
+		n = 10
+	}
+	for i := 0; i < n; i++ {
+		gate <- true
+		wg.Add(1)
+		go func() {
+			defer wg.Done()
+			defer func() { <-gate }()
+			res, err := Get(ts.URL)
+			if err != nil {
+				t.Error(err)
+				return
+			}
+			defer res.Body.Close()
+			io.Copy(ioutil.Discard, res.Body)
+		}()
+	}
+	wg.Wait()
+}
+
+// Verifies we don't path.Clean() on the wrong parts in redirects.
+func TestRedirectMunging(t *testing.T) {
+	req, _ := NewRequest("GET", "http://example.com/", nil)
+
+	resp := httptest.NewRecorder()
+	Redirect(resp, req, "/foo?next=http://bar.com/", 302)
+	if g, e := resp.Header().Get("Location"), "/foo?next=http://bar.com/"; g != e {
+		t.Errorf("Location header was %q; want %q", g, e)
+	}
+
+	resp = httptest.NewRecorder()
+	Redirect(resp, req, "http://localhost:8080/_ah/login?continue=http://localhost:8080/", 302)
+	if g, e := resp.Header().Get("Location"), "http://localhost:8080/_ah/login?continue=http://localhost:8080/"; g != e {
+		t.Errorf("Location header was %q; want %q", g, e)
+	}
+}
+
+func TestRedirectBadPath(t *testing.T) {
+	// This used to crash. It's not valid input (bad path), but it
+	// shouldn't crash.
+	rr := httptest.NewRecorder()
+	req := &Request{
+		Method: "GET",
+		URL: &url.URL{
+			Scheme: "http",
+			Path:   "not-empty-but-no-leading-slash", // bogus
+		},
+	}
+	Redirect(rr, req, "", 304)
+	if rr.Code != 304 {
+		t.Errorf("Code = %d; want 304", rr.Code)
+	}
+}
+
+// TestZeroLengthPostAndResponse exercises an optimization done by the Transport:
+// when there is no body (either because the method doesn't permit a body, or an
+// explicit Content-Length of zero is present), then the transport can re-use the
+// connection immediately. But when it re-uses the connection, it typically closes
+// the previous request's body, which is not optimal for zero-lengthed bodies,
+// as the client would then see http.ErrBodyReadAfterClose and not 0, io.EOF.
+func TestZeroLengthPostAndResponse(t *testing.T) {
+	defer afterTest(t)
+	ts := httptest.NewServer(HandlerFunc(func(rw ResponseWriter, r *Request) {
+		all, err := ioutil.ReadAll(r.Body)
+		if err != nil {
+			t.Fatalf("handler ReadAll: %v", err)
+		}
+		if len(all) != 0 {
+			t.Errorf("handler got %d bytes; expected 0", len(all))
+		}
+		rw.Header().Set("Content-Length", "0")
+	}))
+	defer ts.Close()
+
+	req, err := NewRequest("POST", ts.URL, strings.NewReader(""))
+	if err != nil {
+		t.Fatal(err)
+	}
+	req.ContentLength = 0
+
+	var resp [5]*Response
+	for i := range resp {
+		resp[i], err = DefaultClient.Do(req)
+		if err != nil {
+			t.Fatalf("client post #%d: %v", i, err)
+		}
+	}
+
+	for i := range resp {
+		all, err := ioutil.ReadAll(resp[i].Body)
+		if err != nil {
+			t.Fatalf("req #%d: client ReadAll: %v", i, err)
+		}
+		if len(all) != 0 {
+			t.Errorf("req #%d: client got %d bytes; expected 0", i, len(all))
+		}
+	}
+}
+
+func TestHandlerPanicNil(t *testing.T) {
+	testHandlerPanic(t, false, nil)
+}
+
+func TestHandlerPanic(t *testing.T) {
+	testHandlerPanic(t, false, "intentional death for testing")
+}
+
+func TestHandlerPanicWithHijack(t *testing.T) {
+	testHandlerPanic(t, true, "intentional death for testing")
+}
+
+func testHandlerPanic(t *testing.T, withHijack bool, panicValue interface{}) {
+	defer afterTest(t)
+	// Unlike the other tests that set the log output to ioutil.Discard
+	// to quiet the output, this test uses a pipe.  The pipe serves three
+	// purposes:
+	//
+	//   1) The log.Print from the http server (generated by the caught
+	//      panic) will go to the pipe instead of stderr, making the
+	//      output quiet.
+	//
+	//   2) We read from the pipe to verify that the handler
+	//      actually caught the panic and logged something.
+	//
+	//   3) The blocking Read call prevents this TestHandlerPanic
+	//      function from exiting before the HTTP server handler
+	//      finishes crashing. If this text function exited too
+	//      early (and its defer log.SetOutput(os.Stderr) ran),
+	//      then the crash output could spill into the next test.
+	pr, pw := io.Pipe()
+	log.SetOutput(pw)
+	defer log.SetOutput(os.Stderr)
+	defer pw.Close()
+
+	ts := httptest.NewServer(HandlerFunc(func(w ResponseWriter, r *Request) {
+		if withHijack {
+			rwc, _, err := w.(Hijacker).Hijack()
+			if err != nil {
+				t.Logf("unexpected error: %v", err)
+			}
+			defer rwc.Close()
+		}
+		panic(panicValue)
+	}))
+	defer ts.Close()
+
+	// Do a blocking read on the log output pipe so its logging
+	// doesn't bleed into the next test.  But wait only 5 seconds
+	// for it.
+	done := make(chan bool, 1)
+	go func() {
+		buf := make([]byte, 4<<10)
+		_, err := pr.Read(buf)
+		pr.Close()
+		if err != nil && err != io.EOF {
+			t.Error(err)
+		}
+		done <- true
+	}()
+
+	_, err := Get(ts.URL)
+	if err == nil {
+		t.Logf("expected an error")
+	}
+
+	if panicValue == nil {
+		return
+	}
+
+	select {
+	case <-done:
+		return
+	case <-time.After(5 * time.Second):
+		t.Fatal("expected server handler to log an error")
+	}
+}
+
+func TestNoDate(t *testing.T) {
+	defer afterTest(t)
+	ts := httptest.NewServer(HandlerFunc(func(w ResponseWriter, r *Request) {
+		w.Header()["Date"] = nil
+	}))
+	defer ts.Close()
+	res, err := Get(ts.URL)
+	if err != nil {
+		t.Fatal(err)
+	}
+	_, present := res.Header["Date"]
+	if present {
+		t.Fatalf("Expected no Date header; got %v", res.Header["Date"])
+	}
+}
+
+func TestStripPrefix(t *testing.T) {
+	defer afterTest(t)
+	h := HandlerFunc(func(w ResponseWriter, r *Request) {
+		w.Header().Set("X-Path", r.URL.Path)
+	})
+	ts := httptest.NewServer(StripPrefix("/foo", h))
+	defer ts.Close()
+
+	res, err := Get(ts.URL + "/foo/bar")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if g, e := res.Header.Get("X-Path"), "/bar"; g != e {
+		t.Errorf("test 1: got %s, want %s", g, e)
+	}
+	res.Body.Close()
+
+	res, err = Get(ts.URL + "/bar")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if g, e := res.StatusCode, 404; g != e {
+		t.Errorf("test 2: got status %v, want %v", g, e)
+	}
+	res.Body.Close()
+}
+
+func TestRequestLimit(t *testing.T) {
+	defer afterTest(t)
+	ts := httptest.NewServer(HandlerFunc(func(w ResponseWriter, r *Request) {
+		t.Fatalf("didn't expect to get request in Handler")
+	}))
+	defer ts.Close()
+	req, _ := NewRequest("GET", ts.URL, nil)
+	var bytesPerHeader = len("header12345: val12345\r\n")
+	for i := 0; i < ((DefaultMaxHeaderBytes+4096)/bytesPerHeader)+1; i++ {
+		req.Header.Set(fmt.Sprintf("header%05d", i), fmt.Sprintf("val%05d", i))
+	}
+	res, err := DefaultClient.Do(req)
+	if err != nil {
+		// Some HTTP clients may fail on this undefined behavior (server replying and
+		// closing the connection while the request is still being written), but
+		// we do support it (at least currently), so we expect a response below.
+		t.Fatalf("Do: %v", err)
+	}
+	defer res.Body.Close()
+	if res.StatusCode != 413 {
+		t.Fatalf("expected 413 response status; got: %d %s", res.StatusCode, res.Status)
+	}
+}
+
+type neverEnding byte
+
+func (b neverEnding) Read(p []byte) (n int, err error) {
+	for i := range p {
+		p[i] = byte(b)
+	}
+	return len(p), nil
+}
+
+type countReader struct {
+	r io.Reader
+	n *int64
+}
+
+func (cr countReader) Read(p []byte) (n int, err error) {
+	n, err = cr.r.Read(p)
+	atomic.AddInt64(cr.n, int64(n))
+	return
+}
+
+func TestRequestBodyLimit(t *testing.T) {
+	defer afterTest(t)
+	const limit = 1 << 20
+	ts := httptest.NewServer(HandlerFunc(func(w ResponseWriter, r *Request) {
+		r.Body = MaxBytesReader(w, r.Body, limit)
+		n, err := io.Copy(ioutil.Discard, r.Body)
+		if err == nil {
+			t.Errorf("expected error from io.Copy")
+		}
+		if n != limit {
+			t.Errorf("io.Copy = %d, want %d", n, limit)
+		}
+	}))
+	defer ts.Close()
+
+	nWritten := new(int64)
+	req, _ := NewRequest("POST", ts.URL, io.LimitReader(countReader{neverEnding('a'), nWritten}, limit*200))
+
+	// Send the POST, but don't care it succeeds or not.  The
+	// remote side is going to reply and then close the TCP
+	// connection, and HTTP doesn't really define if that's
+	// allowed or not.  Some HTTP clients will get the response
+	// and some (like ours, currently) will complain that the
+	// request write failed, without reading the response.
+	//
+	// But that's okay, since what we're really testing is that
+	// the remote side hung up on us before we wrote too much.
+	_, _ = DefaultClient.Do(req)
+
+	if atomic.LoadInt64(nWritten) > limit*100 {
+		t.Errorf("handler restricted the request body to %d bytes, but client managed to write %d",
+			limit, nWritten)
+	}
+}
+
+// TestClientWriteShutdown tests that if the client shuts down the write
+// side of their TCP connection, the server doesn't send a 400 Bad Request.
+func TestClientWriteShutdown(t *testing.T) {
+	if runtime.GOOS == "plan9" {
+		t.Skip("skipping test; see http://golang.org/issue/7237")
+	}
+	defer afterTest(t)
+	ts := httptest.NewServer(HandlerFunc(func(w ResponseWriter, r *Request) {}))
+	defer ts.Close()
+	conn, err := net.Dial("tcp", ts.Listener.Addr().String())
+	if err != nil {
+		t.Fatalf("Dial: %v", err)
+	}
+	err = conn.(*net.TCPConn).CloseWrite()
+	if err != nil {
+		t.Fatalf("Dial: %v", err)
+	}
+	donec := make(chan bool)
+	go func() {
+		defer close(donec)
+		bs, err := ioutil.ReadAll(conn)
+		if err != nil {
+			t.Fatalf("ReadAll: %v", err)
+		}
+		got := string(bs)
+		if got != "" {
+			t.Errorf("read %q from server; want nothing", got)
+		}
+	}()
+	select {
+	case <-donec:
+	case <-time.After(10 * time.Second):
+		t.Fatalf("timeout")
+	}
+}
+
+// Tests that chunked server responses that write 1 byte at a time are
+// buffered before chunk headers are added, not after chunk headers.
+func TestServerBufferedChunking(t *testing.T) {
+	conn := new(testConn)
+	conn.readBuf.Write([]byte("GET / HTTP/1.1\r\n\r\n"))
+	conn.closec = make(chan bool, 1)
+	ls := &oneConnListener{conn}
+	go Serve(ls, HandlerFunc(func(rw ResponseWriter, req *Request) {
+		rw.(Flusher).Flush() // force the Header to be sent, in chunking mode, not counting the length
+		rw.Write([]byte{'x'})
+		rw.Write([]byte{'y'})
+		rw.Write([]byte{'z'})
+	}))
+	<-conn.closec
+	if !bytes.HasSuffix(conn.writeBuf.Bytes(), []byte("\r\n\r\n3\r\nxyz\r\n0\r\n\r\n")) {
+		t.Errorf("response didn't end with a single 3 byte 'xyz' chunk; got:\n%q",
+			conn.writeBuf.Bytes())
+	}
+}
+
+// Tests that the server flushes its response headers out when it's
+// ignoring the response body and waits a bit before forcefully
+// closing the TCP connection, causing the client to get a RST.
+// See http://golang.org/issue/3595
+func TestServerGracefulClose(t *testing.T) {
+	defer afterTest(t)
+	ts := httptest.NewServer(HandlerFunc(func(w ResponseWriter, r *Request) {
+		Error(w, "bye", StatusUnauthorized)
+	}))
+	defer ts.Close()
+
+	conn, err := net.Dial("tcp", ts.Listener.Addr().String())
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer conn.Close()
+	const bodySize = 5 << 20
+	req := []byte(fmt.Sprintf("POST / HTTP/1.1\r\nHost: foo.com\r\nContent-Length: %d\r\n\r\n", bodySize))
+	for i := 0; i < bodySize; i++ {
+		req = append(req, 'x')
+	}
+	writeErr := make(chan error)
+	go func() {
+		_, err := conn.Write(req)
+		writeErr <- err
+	}()
+	br := bufio.NewReader(conn)
+	lineNum := 0
+	for {
+		line, err := br.ReadString('\n')
+		if err == io.EOF {
+			break
+		}
+		if err != nil {
+			t.Fatalf("ReadLine: %v", err)
+		}
+		lineNum++
+		if lineNum == 1 && !strings.Contains(line, "401 Unauthorized") {
+			t.Errorf("Response line = %q; want a 401", line)
+		}
+	}
+	// Wait for write to finish. This is a broken pipe on both
+	// Darwin and Linux, but checking this isn't the point of
+	// the test.
+	<-writeErr
+}
+
+func TestCaseSensitiveMethod(t *testing.T) {
+	defer afterTest(t)
+	ts := httptest.NewServer(HandlerFunc(func(w ResponseWriter, r *Request) {
+		if r.Method != "get" {
+			t.Errorf(`Got method %q; want "get"`, r.Method)
+		}
+	}))
+	defer ts.Close()
+	req, _ := NewRequest("get", ts.URL, nil)
+	res, err := DefaultClient.Do(req)
+	if err != nil {
+		t.Error(err)
+		return
+	}
+	res.Body.Close()
+}
+
+// TestContentLengthZero tests that for both an HTTP/1.0 and HTTP/1.1
+// request (both keep-alive), when a Handler never writes any
+// response, the net/http package adds a "Content-Length: 0" response
+// header.
+func TestContentLengthZero(t *testing.T) {
+	ts := httptest.NewServer(HandlerFunc(func(rw ResponseWriter, req *Request) {}))
+	defer ts.Close()
+
+	for _, version := range []string{"HTTP/1.0", "HTTP/1.1"} {
+		conn, err := net.Dial("tcp", ts.Listener.Addr().String())
+		if err != nil {
+			t.Fatalf("error dialing: %v", err)
+		}
+		_, err = fmt.Fprintf(conn, "GET / %v\r\nConnection: keep-alive\r\nHost: foo\r\n\r\n", version)
+		if err != nil {
+			t.Fatalf("error writing: %v", err)
+		}
+		req, _ := NewRequest("GET", "/", nil)
+		res, err := ReadResponse(bufio.NewReader(conn), req)
+		if err != nil {
+			t.Fatalf("error reading response: %v", err)
+		}
+		if te := res.TransferEncoding; len(te) > 0 {
+			t.Errorf("For version %q, Transfer-Encoding = %q; want none", version, te)
+		}
+		if cl := res.ContentLength; cl != 0 {
+			t.Errorf("For version %q, Content-Length = %v; want 0", version, cl)
+		}
+		conn.Close()
+	}
+}
+
+func TestCloseNotifier(t *testing.T) {
+	defer afterTest(t)
+	gotReq := make(chan bool, 1)
+	sawClose := make(chan bool, 1)
+	ts := httptest.NewServer(HandlerFunc(func(rw ResponseWriter, req *Request) {
+		gotReq <- true
+		cc := rw.(CloseNotifier).CloseNotify()
+		<-cc
+		sawClose <- true
+	}))
+	conn, err := net.Dial("tcp", ts.Listener.Addr().String())
+	if err != nil {
+		t.Fatalf("error dialing: %v", err)
+	}
+	diec := make(chan bool)
+	go func() {
+		_, err = fmt.Fprintf(conn, "GET / HTTP/1.1\r\nConnection: keep-alive\r\nHost: foo\r\n\r\n")
+		if err != nil {
+			t.Fatal(err)
+		}
+		<-diec
+		conn.Close()
+	}()
+For:
+	for {
+		select {
+		case <-gotReq:
+			diec <- true
+		case <-sawClose:
+			break For
+		case <-time.After(5 * time.Second):
+			t.Fatal("timeout")
+		}
+	}
+	ts.Close()
+}
+
+func TestCloseNotifierChanLeak(t *testing.T) {
+	defer afterTest(t)
+	req := reqBytes("GET / HTTP/1.0\nHost: golang.org")
+	for i := 0; i < 20; i++ {
+		var output bytes.Buffer
+		conn := &rwTestConn{
+			Reader: bytes.NewReader(req),
+			Writer: &output,
+			closec: make(chan bool, 1),
+		}
+		ln := &oneConnListener{conn: conn}
+		handler := HandlerFunc(func(rw ResponseWriter, r *Request) {
+			// Ignore the return value and never read from
+			// it, testing that we don't leak goroutines
+			// on the sending side:
+			_ = rw.(CloseNotifier).CloseNotify()
+		})
+		go Serve(ln, handler)
+		<-conn.closec
+	}
+}
+
+func TestOptions(t *testing.T) {
+	uric := make(chan string, 2) // only expect 1, but leave space for 2
+	mux := NewServeMux()
+	mux.HandleFunc("/", func(w ResponseWriter, r *Request) {
+		uric <- r.RequestURI
+	})
+	ts := httptest.NewServer(mux)
+	defer ts.Close()
+
+	conn, err := net.Dial("tcp", ts.Listener.Addr().String())
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer conn.Close()
+
+	// An OPTIONS * request should succeed.
+	_, err = conn.Write([]byte("OPTIONS * HTTP/1.1\r\nHost: foo.com\r\n\r\n"))
+	if err != nil {
+		t.Fatal(err)
+	}
+	br := bufio.NewReader(conn)
+	res, err := ReadResponse(br, &Request{Method: "OPTIONS"})
+	if err != nil {
+		t.Fatal(err)
+	}
+	if res.StatusCode != 200 {
+		t.Errorf("Got non-200 response to OPTIONS *: %#v", res)
+	}
+
+	// A GET * request on a ServeMux should fail.
+	_, err = conn.Write([]byte("GET * HTTP/1.1\r\nHost: foo.com\r\n\r\n"))
+	if err != nil {
+		t.Fatal(err)
+	}
+	res, err = ReadResponse(br, &Request{Method: "GET"})
+	if err != nil {
+		t.Fatal(err)
+	}
+	if res.StatusCode != 400 {
+		t.Errorf("Got non-400 response to GET *: %#v", res)
+	}
+
+	res, err = Get(ts.URL + "/second")
+	if err != nil {
+		t.Fatal(err)
+	}
+	res.Body.Close()
+	if got := <-uric; got != "/second" {
+		t.Errorf("Handler saw request for %q; want /second", got)
+	}
+}
+
+// Tests regarding the ordering of Write, WriteHeader, Header, and
+// Flush calls.  In Go 1.0, rw.WriteHeader immediately flushed the
+// (*response).header to the wire. In Go 1.1, the actual wire flush is
+// delayed, so we could maybe tack on a Content-Length and better
+// Content-Type after we see more (or all) of the output. To preserve
+// compatibility with Go 1, we need to be careful to track which
+// headers were live at the time of WriteHeader, so we write the same
+// ones, even if the handler modifies them (~erroneously) after the
+// first Write.
+func TestHeaderToWire(t *testing.T) {
+	tests := []struct {
+		name    string
+		handler func(ResponseWriter, *Request)
+		check   func(output string) error
+	}{
+		{
+			name: "write without Header",
+			handler: func(rw ResponseWriter, r *Request) {
+				rw.Write([]byte("hello world"))
+			},
+			check: func(got string) error {
+				if !strings.Contains(got, "Content-Length:") {
+					return errors.New("no content-length")
+				}
+				if !strings.Contains(got, "Content-Type: text/plain") {
+					return errors.New("no content-length")
+				}
+				return nil
+			},
+		},
+		{
+			name: "Header mutation before write",
+			handler: func(rw ResponseWriter, r *Request) {
+				h := rw.Header()
+				h.Set("Content-Type", "some/type")
+				rw.Write([]byte("hello world"))
+				h.Set("Too-Late", "bogus")
+			},
+			check: func(got string) error {
+				if !strings.Contains(got, "Content-Length:") {
+					return errors.New("no content-length")
+				}
+				if !strings.Contains(got, "Content-Type: some/type") {
+					return errors.New("wrong content-type")
+				}
+				if strings.Contains(got, "Too-Late") {
+					return errors.New("don't want too-late header")
+				}
+				return nil
+			},
+		},
+		{
+			name: "write then useless Header mutation",
+			handler: func(rw ResponseWriter, r *Request) {
+				rw.Write([]byte("hello world"))
+				rw.Header().Set("Too-Late", "Write already wrote headers")
+			},
+			check: func(got string) error {
+				if strings.Contains(got, "Too-Late") {
+					return errors.New("header appeared from after WriteHeader")
+				}
+				return nil
+			},
+		},
+		{
+			name: "flush then write",
+			handler: func(rw ResponseWriter, r *Request) {
+				rw.(Flusher).Flush()
+				rw.Write([]byte("post-flush"))
+				rw.Header().Set("Too-Late", "Write already wrote headers")
+			},
+			check: func(got string) error {
+				if !strings.Contains(got, "Transfer-Encoding: chunked") {
+					return errors.New("not chunked")
+				}
+				if strings.Contains(got, "Too-Late") {
+					return errors.New("header appeared from after WriteHeader")
+				}
+				return nil
+			},
+		},
+		{
+			name: "header then flush",
+			handler: func(rw ResponseWriter, r *Request) {
+				rw.Header().Set("Content-Type", "some/type")
+				rw.(Flusher).Flush()
+				rw.Write([]byte("post-flush"))
+				rw.Header().Set("Too-Late", "Write already wrote headers")
+			},
+			check: func(got string) error {
+				if !strings.Contains(got, "Transfer-Encoding: chunked") {
+					return errors.New("not chunked")
+				}
+				if strings.Contains(got, "Too-Late") {
+					return errors.New("header appeared from after WriteHeader")
+				}
+				if !strings.Contains(got, "Content-Type: some/type") {
+					return errors.New("wrong content-length")
+				}
+				return nil
+			},
+		},
+		{
+			name: "sniff-on-first-write content-type",
+			handler: func(rw ResponseWriter, r *Request) {
+				rw.Write([]byte("<html><head></head><body>some html</body></html>"))
+				rw.Header().Set("Content-Type", "x/wrong")
+			},
+			check: func(got string) error {
+				if !strings.Contains(got, "Content-Type: text/html") {
+					return errors.New("wrong content-length; want html")
+				}
+				return nil
+			},
+		},
+		{
+			name: "explicit content-type wins",
+			handler: func(rw ResponseWriter, r *Request) {
+				rw.Header().Set("Content-Type", "some/type")
+				rw.Write([]byte("<html><head></head><body>some html</body></html>"))
+			},
+			check: func(got string) error {
+				if !strings.Contains(got, "Content-Type: some/type") {
+					return errors.New("wrong content-length; want html")
+				}
+				return nil
+			},
+		},
+		{
+			name: "empty handler",
+			handler: func(rw ResponseWriter, r *Request) {
+			},
+			check: func(got string) error {
+				if !strings.Contains(got, "Content-Type: text/plain") {
+					return errors.New("wrong content-length; want text/plain")
+				}
+				if !strings.Contains(got, "Content-Length: 0") {
+					return errors.New("want 0 content-length")
+				}
+				return nil
+			},
+		},
+		{
+			name: "only Header, no write",
+			handler: func(rw ResponseWriter, r *Request) {
+				rw.Header().Set("Some-Header", "some-value")
+			},
+			check: func(got string) error {
+				if !strings.Contains(got, "Some-Header") {
+					return errors.New("didn't get header")
+				}
+				return nil
+			},
+		},
+		{
+			name: "WriteHeader call",
+			handler: func(rw ResponseWriter, r *Request) {
+				rw.WriteHeader(404)
+				rw.Header().Set("Too-Late", "some-value")
+			},
+			check: func(got string) error {
+				if !strings.Contains(got, "404") {
+					return errors.New("wrong status")
+				}
+				if strings.Contains(got, "Some-Header") {
+					return errors.New("shouldn't have seen Too-Late")
+				}
+				return nil
+			},
+		},
+	}
+	for _, tc := range tests {
+		ht := newHandlerTest(HandlerFunc(tc.handler))
+		got := ht.rawResponse("GET / HTTP/1.1\nHost: golang.org")
+		if err := tc.check(got); err != nil {
+			t.Errorf("%s: %v\nGot response:\n%s", tc.name, err, got)
+		}
+	}
+}
+
+// goTimeout runs f, failing t if f takes more than ns to complete.
+func goTimeout(t *testing.T, d time.Duration, f func()) {
+	ch := make(chan bool, 2)
+	timer := time.AfterFunc(d, func() {
+		t.Errorf("Timeout expired after %v", d)
+		ch <- true
+	})
+	defer timer.Stop()
+	go func() {
+		defer func() { ch <- true }()
+		f()
+	}()
+	<-ch
+}
+
+type errorListener struct {
+	errs []error
+}
+
+func (l *errorListener) Accept() (c net.Conn, err error) {
+	if len(l.errs) == 0 {
+		return nil, io.EOF
+	}
+	err = l.errs[0]
+	l.errs = l.errs[1:]
+	return
+}
+
+func (l *errorListener) Close() error {
+	return nil
+}
+
+func (l *errorListener) Addr() net.Addr {
+	return dummyAddr("test-address")
+}
+
+func TestAcceptMaxFds(t *testing.T) {
+	log.SetOutput(ioutil.Discard) // is noisy otherwise
+	defer log.SetOutput(os.Stderr)
+
+	ln := &errorListener{[]error{
+		&net.OpError{
+			Op:  "accept",
+			Err: syscall.EMFILE,
+		}}}
+	err := Serve(ln, HandlerFunc(HandlerFunc(func(ResponseWriter, *Request) {})))
+	if err != io.EOF {
+		t.Errorf("got error %v, want EOF", err)
+	}
+}
+
+func TestWriteAfterHijack(t *testing.T) {
+	req := reqBytes("GET / HTTP/1.1\nHost: golang.org")
+	var buf bytes.Buffer
+	wrotec := make(chan bool, 1)
+	conn := &rwTestConn{
+		Reader: bytes.NewReader(req),
+		Writer: &buf,
+		closec: make(chan bool, 1),
+	}
+	handler := HandlerFunc(func(rw ResponseWriter, r *Request) {
+		conn, bufrw, err := rw.(Hijacker).Hijack()
+		if err != nil {
+			t.Error(err)
+			return
+		}
+		go func() {
+			bufrw.Write([]byte("[hijack-to-bufw]"))
+			bufrw.Flush()
+			conn.Write([]byte("[hijack-to-conn]"))
+			conn.Close()
+			wrotec <- true
+		}()
+	})
+	ln := &oneConnListener{conn: conn}
+	go Serve(ln, handler)
+	<-conn.closec
+	<-wrotec
+	if g, w := buf.String(), "[hijack-to-bufw][hijack-to-conn]"; g != w {
+		t.Errorf("wrote %q; want %q", g, w)
+	}
+}
+
+func TestDoubleHijack(t *testing.T) {
+	req := reqBytes("GET / HTTP/1.1\nHost: golang.org")
+	var buf bytes.Buffer
+	conn := &rwTestConn{
+		Reader: bytes.NewReader(req),
+		Writer: &buf,
+		closec: make(chan bool, 1),
+	}
+	handler := HandlerFunc(func(rw ResponseWriter, r *Request) {
+		conn, _, err := rw.(Hijacker).Hijack()
+		if err != nil {
+			t.Error(err)
+			return
+		}
+		_, _, err = rw.(Hijacker).Hijack()
+		if err == nil {
+			t.Errorf("got err = nil;  want err != nil")
+		}
+		conn.Close()
+	})
+	ln := &oneConnListener{conn: conn}
+	go Serve(ln, handler)
+	<-conn.closec
+}
+
+// http://code.google.com/p/go/issues/detail?id=5955
+// Note that this does not test the "request too large"
+// exit path from the http server. This is intentional;
+// not sending Connection: close is just a minor wire
+// optimization and is pointless if dealing with a
+// badly behaved client.
+func TestHTTP10ConnectionHeader(t *testing.T) {
+	defer afterTest(t)
+
+	mux := NewServeMux()
+	mux.Handle("/", HandlerFunc(func(resp ResponseWriter, req *Request) {}))
+	ts := httptest.NewServer(mux)
+	defer ts.Close()
+
+	// net/http uses HTTP/1.1 for requests, so write requests manually
+	tests := []struct {
+		req    string   // raw http request
+		expect []string // expected Connection header(s)
+	}{
+		{
+			req:    "GET / HTTP/1.0\r\n\r\n",
+			expect: nil,
+		},
+		{
+			req:    "OPTIONS * HTTP/1.0\r\n\r\n",
+			expect: nil,
+		},
+		{
+			req:    "GET / HTTP/1.0\r\nConnection: keep-alive\r\n\r\n",
+			expect: []string{"keep-alive"},
+		},
+	}
+
+	for _, tt := range tests {
+		conn, err := net.Dial("tcp", ts.Listener.Addr().String())
+		if err != nil {
+			t.Fatal("dial err:", err)
+		}
+
+		_, err = fmt.Fprint(conn, tt.req)
+		if err != nil {
+			t.Fatal("conn write err:", err)
+		}
+
+		resp, err := ReadResponse(bufio.NewReader(conn), &Request{Method: "GET"})
+		if err != nil {
+			t.Fatal("ReadResponse err:", err)
+		}
+		conn.Close()
+		resp.Body.Close()
+
+		got := resp.Header["Connection"]
+		if !reflect.DeepEqual(got, tt.expect) {
+			t.Errorf("wrong Connection headers for request %q. Got %q expect %q", tt.req, got, tt.expect)
+		}
+	}
+}
+
+// See golang.org/issue/5660
+func TestServerReaderFromOrder(t *testing.T) {
+	defer afterTest(t)
+	pr, pw := io.Pipe()
+	const size = 3 << 20
+	ts := httptest.NewServer(HandlerFunc(func(rw ResponseWriter, req *Request) {
+		rw.Header().Set("Content-Type", "text/plain") // prevent sniffing path
+		done := make(chan bool)
+		go func() {
+			io.Copy(rw, pr)
+			close(done)
+		}()
+		time.Sleep(25 * time.Millisecond) // give Copy a chance to break things
+		n, err := io.Copy(ioutil.Discard, req.Body)
+		if err != nil {
+			t.Errorf("handler Copy: %v", err)
+			return
+		}
+		if n != size {
+			t.Errorf("handler Copy = %d; want %d", n, size)
+		}
+		pw.Write([]byte("hi"))
+		pw.Close()
+		<-done
+	}))
+	defer ts.Close()
+
+	req, err := NewRequest("POST", ts.URL, io.LimitReader(neverEnding('a'), size))
+	if err != nil {
+		t.Fatal(err)
+	}
+	res, err := DefaultClient.Do(req)
+	if err != nil {
+		t.Fatal(err)
+	}
+	all, err := ioutil.ReadAll(res.Body)
+	if err != nil {
+		t.Fatal(err)
+	}
+	res.Body.Close()
+	if string(all) != "hi" {
+		t.Errorf("Body = %q; want hi", all)
+	}
+}
+
+// Issue 6157, Issue 6685
+func TestCodesPreventingContentTypeAndBody(t *testing.T) {
+	for _, code := range []int{StatusNotModified, StatusNoContent, StatusContinue} {
+		ht := newHandlerTest(HandlerFunc(func(w ResponseWriter, r *Request) {
+			if r.URL.Path == "/header" {
+				w.Header().Set("Content-Length", "123")
+			}
+			w.WriteHeader(code)
+			if r.URL.Path == "/more" {
+				w.Write([]byte("stuff"))
+			}
+		}))
+		for _, req := range []string{
+			"GET / HTTP/1.0",
+			"GET /header HTTP/1.0",
+			"GET /more HTTP/1.0",
+			"GET / HTTP/1.1",
+			"GET /header HTTP/1.1",
+			"GET /more HTTP/1.1",
+		} {
+			got := ht.rawResponse(req)
+			wantStatus := fmt.Sprintf("%d %s", code, StatusText(code))
+			if !strings.Contains(got, wantStatus) {
+				t.Errorf("Code %d: Wanted %q Modified for %q: %s", code, wantStatus, req, got)
+			} else if strings.Contains(got, "Content-Length") {
+				t.Errorf("Code %d: Got a Content-Length from %q: %s", code, req, got)
+			} else if strings.Contains(got, "stuff") {
+				t.Errorf("Code %d: Response contains a body from %q: %s", code, req, got)
+			}
+		}
+	}
+}
+
+func TestContentTypeOkayOn204(t *testing.T) {
+	ht := newHandlerTest(HandlerFunc(func(w ResponseWriter, r *Request) {
+		w.Header().Set("Content-Length", "123") // suppressed
+		w.Header().Set("Content-Type", "foo/bar")
+		w.WriteHeader(204)
+	}))
+	got := ht.rawResponse("GET / HTTP/1.1")
+	if !strings.Contains(got, "Content-Type: foo/bar") {
+		t.Errorf("Response = %q; want Content-Type: foo/bar", got)
+	}
+	if strings.Contains(got, "Content-Length: 123") {
+		t.Errorf("Response = %q; don't want a Content-Length", got)
+	}
+}
+
+// Issue 6995
+// A server Handler can receive a Request, and then turn around and
+// give a copy of that Request.Body out to the Transport (e.g. any
+// proxy).  So then two people own that Request.Body (both the server
+// and the http client), and both think they can close it on failure.
+// Therefore, all incoming server requests Bodies need to be thread-safe.
+func TestTransportAndServerSharedBodyRace(t *testing.T) {
+	defer afterTest(t)
+
+	const bodySize = 1 << 20
+
+	unblockBackend := make(chan bool)
+	backend := httptest.NewServer(HandlerFunc(func(rw ResponseWriter, req *Request) {
+		io.CopyN(rw, req.Body, bodySize/2)
+		<-unblockBackend
+	}))
+	defer backend.Close()
+
+	backendRespc := make(chan *Response, 1)
+	proxy := httptest.NewServer(HandlerFunc(func(rw ResponseWriter, req *Request) {
+		if req.RequestURI == "/foo" {
+			rw.Write([]byte("bar"))
+			return
+		}
+		req2, _ := NewRequest("POST", backend.URL, req.Body)
+		req2.ContentLength = bodySize
+
+		bresp, err := DefaultClient.Do(req2)
+		if err != nil {
+			t.Errorf("Proxy outbound request: %v", err)
+			return
+		}
+		_, err = io.CopyN(ioutil.Discard, bresp.Body, bodySize/4)
+		if err != nil {
+			t.Errorf("Proxy copy error: %v", err)
+			return
+		}
+		backendRespc <- bresp // to close later
+
+		// Try to cause a race: Both the DefaultTransport and the proxy handler's Server
+		// will try to read/close req.Body (aka req2.Body)
+		DefaultTransport.(*Transport).CancelRequest(req2)
+		rw.Write([]byte("OK"))
+	}))
+	defer proxy.Close()
+
+	req, _ := NewRequest("POST", proxy.URL, io.LimitReader(neverEnding('a'), bodySize))
+	res, err := DefaultClient.Do(req)
+	if err != nil {
+		t.Fatalf("Original request: %v", err)
+	}
+
+	// Cleanup, so we don't leak goroutines.
+	res.Body.Close()
+	close(unblockBackend)
+	(<-backendRespc).Body.Close()
+}
+
+// Test that a hanging Request.Body.Read from another goroutine can't
+// cause the Handler goroutine's Request.Body.Close to block.
+func TestRequestBodyCloseDoesntBlock(t *testing.T) {
+	t.Skipf("Skipping known issue; see golang.org/issue/7121")
+	if testing.Short() {
+		t.Skip("skipping in -short mode")
+	}
+	defer afterTest(t)
+
+	readErrCh := make(chan error, 1)
+	errCh := make(chan error, 2)
+
+	server := httptest.NewServer(HandlerFunc(func(rw ResponseWriter, req *Request) {
+		go func(body io.Reader) {
+			_, err := body.Read(make([]byte, 100))
+			readErrCh <- err
+		}(req.Body)
+		time.Sleep(500 * time.Millisecond)
+	}))
+	defer server.Close()
+
+	closeConn := make(chan bool)
+	defer close(closeConn)
+	go func() {
+		conn, err := net.Dial("tcp", server.Listener.Addr().String())
+		if err != nil {
+			errCh <- err
+			return
+		}
+		defer conn.Close()
+		_, err = conn.Write([]byte("POST / HTTP/1.1\r\nConnection: close\r\nHost: foo\r\nContent-Length: 100000\r\n\r\n"))
+		if err != nil {
+			errCh <- err
+			return
+		}
+		// And now just block, making the server block on our
+		// 100000 bytes of body that will never arrive.
+		<-closeConn
+	}()
+	select {
+	case err := <-readErrCh:
+		if err == nil {
+			t.Error("Read was nil. Expected error.")
+		}
+	case err := <-errCh:
+		t.Error(err)
+	case <-time.After(5 * time.Second):
+		t.Error("timeout")
+	}
+}
+
+func TestResponseWriterWriteStringAllocs(t *testing.T) {
+	ht := newHandlerTest(HandlerFunc(func(w ResponseWriter, r *Request) {
+		if r.URL.Path == "/s" {
+			io.WriteString(w, "Hello world")
+		} else {
+			w.Write([]byte("Hello world"))
+		}
+	}))
+	before := testing.AllocsPerRun(50, func() { ht.rawResponse("GET / HTTP/1.0") })
+	after := testing.AllocsPerRun(50, func() { ht.rawResponse("GET /s HTTP/1.0") })
+	if int(after) >= int(before) {
+		t.Errorf("WriteString allocs of %v >= Write allocs of %v", after, before)
+	}
+}
+
+func TestAppendTime(t *testing.T) {
+	var b [len(TimeFormat)]byte
+	t1 := time.Date(2013, 9, 21, 15, 41, 0, 0, time.FixedZone("CEST", 2*60*60))
+	res := ExportAppendTime(b[:0], t1)
+	t2, err := ParseTime(string(res))
+	if err != nil {
+		t.Fatalf("Error parsing time: %s", err)
+	}
+	if !t1.Equal(t2) {
+		t.Fatalf("Times differ; expected: %v, got %v (%s)", t1, t2, string(res))
+	}
+}
+
+func TestServerConnState(t *testing.T) {
+	defer afterTest(t)
+	handler := map[string]func(w ResponseWriter, r *Request){
+		"/": func(w ResponseWriter, r *Request) {
+			fmt.Fprintf(w, "Hello.")
+		},
+		"/close": func(w ResponseWriter, r *Request) {
+			w.Header().Set("Connection", "close")
+			fmt.Fprintf(w, "Hello.")
+		},
+		"/hijack": func(w ResponseWriter, r *Request) {
+			c, _, _ := w.(Hijacker).Hijack()
+			c.Write([]byte("HTTP/1.0 200 OK\r\nConnection: close\r\n\r\nHello."))
+			c.Close()
+		},
+		"/hijack-panic": func(w ResponseWriter, r *Request) {
+			c, _, _ := w.(Hijacker).Hijack()
+			c.Write([]byte("HTTP/1.0 200 OK\r\nConnection: close\r\n\r\nHello."))
+			c.Close()
+			panic("intentional panic")
+		},
+	}
+	ts := httptest.NewUnstartedServer(HandlerFunc(func(w ResponseWriter, r *Request) {
+		handler[r.URL.Path](w, r)
+	}))
+	defer ts.Close()
+
+	var mu sync.Mutex // guard stateLog and connID
+	var stateLog = map[int][]ConnState{}
+	var connID = map[net.Conn]int{}
+
+	ts.Config.ErrorLog = log.New(ioutil.Discard, "", 0)
+	ts.Config.ConnState = func(c net.Conn, state ConnState) {
+		if c == nil {
+			t.Errorf("nil conn seen in state %s", state)
+			return
+		}
+		mu.Lock()
+		defer mu.Unlock()
+		id, ok := connID[c]
+		if !ok {
+			id = len(connID) + 1
+			connID[c] = id
+		}
+		stateLog[id] = append(stateLog[id], state)
+	}
+	ts.Start()
+
+	mustGet(t, ts.URL+"/")
+	mustGet(t, ts.URL+"/close")
+
+	mustGet(t, ts.URL+"/")
+	mustGet(t, ts.URL+"/", "Connection", "close")
+
+	mustGet(t, ts.URL+"/hijack")
+	mustGet(t, ts.URL+"/hijack-panic")
+
+	// New->Closed
+	{
+		c, err := net.Dial("tcp", ts.Listener.Addr().String())
+		if err != nil {
+			t.Fatal(err)
+		}
+		c.Close()
+	}
+
+	// New->Active->Closed
+	{
+		c, err := net.Dial("tcp", ts.Listener.Addr().String())
+		if err != nil {
+			t.Fatal(err)
+		}
+		if _, err := io.WriteString(c, "BOGUS REQUEST\r\n\r\n"); err != nil {
+			t.Fatal(err)
+		}
+		c.Close()
+	}
+
+	// New->Idle->Closed
+	{
+		c, err := net.Dial("tcp", ts.Listener.Addr().String())
+		if err != nil {
+			t.Fatal(err)
+		}
+		if _, err := io.WriteString(c, "GET / HTTP/1.1\r\nHost: foo\r\n\r\n"); err != nil {
+			t.Fatal(err)
+		}
+		res, err := ReadResponse(bufio.NewReader(c), nil)
+		if err != nil {
+			t.Fatal(err)
+		}
+		if _, err := io.Copy(ioutil.Discard, res.Body); err != nil {
+			t.Fatal(err)
+		}
+		c.Close()
+	}
+
+	want := map[int][]ConnState{
+		1: {StateNew, StateActive, StateIdle, StateActive, StateClosed},
+		2: {StateNew, StateActive, StateIdle, StateActive, StateClosed},
+		3: {StateNew, StateActive, StateHijacked},
+		4: {StateNew, StateActive, StateHijacked},
+		5: {StateNew, StateClosed},
+		6: {StateNew, StateActive, StateClosed},
+		7: {StateNew, StateActive, StateIdle, StateClosed},
+	}
+	logString := func(m map[int][]ConnState) string {
+		var b bytes.Buffer
+		for id, l := range m {
+			fmt.Fprintf(&b, "Conn %d: ", id)
+			for _, s := range l {
+				fmt.Fprintf(&b, "%s ", s)
+			}
+			b.WriteString("\n")
+		}
+		return b.String()
+	}
+
+	for i := 0; i < 5; i++ {
+		time.Sleep(time.Duration(i) * 50 * time.Millisecond)
+		mu.Lock()
+		match := reflect.DeepEqual(stateLog, want)
+		mu.Unlock()
+		if match {
+			return
+		}
+	}
+
+	mu.Lock()
+	t.Errorf("Unexpected events.\nGot log: %s\n   Want: %s\n", logString(stateLog), logString(want))
+	mu.Unlock()
+}
+
+func mustGet(t *testing.T, url string, headers ...string) {
+	req, err := NewRequest("GET", url, nil)
+	if err != nil {
+		t.Fatal(err)
+	}
+	for len(headers) > 0 {
+		req.Header.Add(headers[0], headers[1])
+		headers = headers[2:]
+	}
+	res, err := DefaultClient.Do(req)
+	if err != nil {
+		t.Errorf("Error fetching %s: %v", url, err)
+		return
+	}
+	_, err = ioutil.ReadAll(res.Body)
+	defer res.Body.Close()
+	if err != nil {
+		t.Errorf("Error reading %s: %v", url, err)
+	}
+}
+
+func TestServerKeepAlivesEnabled(t *testing.T) {
+	defer afterTest(t)
+	ts := httptest.NewUnstartedServer(HandlerFunc(func(w ResponseWriter, r *Request) {}))
+	ts.Config.SetKeepAlivesEnabled(false)
+	ts.Start()
+	defer ts.Close()
+	res, err := Get(ts.URL)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer res.Body.Close()
+	if !res.Close {
+		t.Errorf("Body.Close == false; want true")
+	}
+}
+
+// golang.org/issue/7856
+func TestServerEmptyBodyRace(t *testing.T) {
+	defer afterTest(t)
+	var n int32
+	ts := httptest.NewServer(HandlerFunc(func(rw ResponseWriter, req *Request) {
+		atomic.AddInt32(&n, 1)
+	}))
+	defer ts.Close()
+	var wg sync.WaitGroup
+	const reqs = 20
+	for i := 0; i < reqs; i++ {
+		wg.Add(1)
+		go func() {
+			defer wg.Done()
+			res, err := Get(ts.URL)
+			if err != nil {
+				t.Error(err)
+				return
+			}
+			defer res.Body.Close()
+			_, err = io.Copy(ioutil.Discard, res.Body)
+			if err != nil {
+				t.Error(err)
+				return
+			}
+		}()
+	}
+	wg.Wait()
+	if got := atomic.LoadInt32(&n); got != reqs {
+		t.Errorf("handler ran %d times; want %d", got, reqs)
+	}
+}
+
+func TestServerConnStateNew(t *testing.T) {
+	sawNew := false // if the test is buggy, we'll race on this variable.
+	srv := &Server{
+		ConnState: func(c net.Conn, state ConnState) {
+			if state == StateNew {
+				sawNew = true // testing that this write isn't racy
+			}
+		},
+		Handler: HandlerFunc(func(w ResponseWriter, r *Request) {}), // irrelevant
+	}
+	srv.Serve(&oneConnListener{
+		conn: &rwTestConn{
+			Reader: strings.NewReader("GET / HTTP/1.1\r\nHost: foo\r\n\r\n"),
+			Writer: ioutil.Discard,
+		},
+	})
+	if !sawNew { // testing that this read isn't racy
+		t.Error("StateNew not seen")
+	}
+}
+
+func BenchmarkClientServer(b *testing.B) {
+	b.ReportAllocs()
+	b.StopTimer()
+	ts := httptest.NewServer(HandlerFunc(func(rw ResponseWriter, r *Request) {
+		fmt.Fprintf(rw, "Hello world.\n")
+	}))
+	defer ts.Close()
+	b.StartTimer()
+
+	for i := 0; i < b.N; i++ {
+		res, err := Get(ts.URL)
+		if err != nil {
+			b.Fatal("Get:", err)
+		}
+		all, err := ioutil.ReadAll(res.Body)
+		res.Body.Close()
+		if err != nil {
+			b.Fatal("ReadAll:", err)
+		}
+		body := string(all)
+		if body != "Hello world.\n" {
+			b.Fatal("Got body:", body)
+		}
+	}
+
+	b.StopTimer()
+}
+
+func BenchmarkClientServerParallel4(b *testing.B) {
+	benchmarkClientServerParallel(b, 4, false)
+}
+
+func BenchmarkClientServerParallel64(b *testing.B) {
+	benchmarkClientServerParallel(b, 64, false)
+}
+
+func BenchmarkClientServerParallelTLS4(b *testing.B) {
+	benchmarkClientServerParallel(b, 4, true)
+}
+
+func BenchmarkClientServerParallelTLS64(b *testing.B) {
+	benchmarkClientServerParallel(b, 64, true)
+}
+
+func benchmarkClientServerParallel(b *testing.B, parallelism int, useTLS bool) {
+	b.ReportAllocs()
+	ts := httptest.NewUnstartedServer(HandlerFunc(func(rw ResponseWriter, r *Request) {
+		fmt.Fprintf(rw, "Hello world.\n")
+	}))
+	if useTLS {
+		ts.StartTLS()
+	} else {
+		ts.Start()
+	}
+	defer ts.Close()
+	b.ResetTimer()
+	b.SetParallelism(parallelism)
+	b.RunParallel(func(pb *testing.PB) {
+		noVerifyTransport := &Transport{
+			TLSClientConfig: &tls.Config{
+				InsecureSkipVerify: true,
+			},
+		}
+		client := &Client{Transport: noVerifyTransport}
+		for pb.Next() {
+			res, err := client.Get(ts.URL)
+			if err != nil {
+				b.Logf("Get: %v", err)
+				continue
+			}
+			all, err := ioutil.ReadAll(res.Body)
+			res.Body.Close()
+			if err != nil {
+				b.Logf("ReadAll: %v", err)
+				continue
+			}
+			body := string(all)
+			if body != "Hello world.\n" {
+				panic("Got body: " + body)
+			}
+		}
+	})
+}
+
+// A benchmark for profiling the server without the HTTP client code.
+// The client code runs in a subprocess.
+//
+// For use like:
+//   $ go test -c
+//   $ ./http.test -test.run=XX -test.bench=BenchmarkServer -test.benchtime=15s -test.cpuprofile=http.prof
+//   $ go tool pprof http.test http.prof
+//   (pprof) web
+func BenchmarkServer(b *testing.B) {
+	b.ReportAllocs()
+	// Child process mode;
+	if url := os.Getenv("TEST_BENCH_SERVER_URL"); url != "" {
+		n, err := strconv.Atoi(os.Getenv("TEST_BENCH_CLIENT_N"))
+		if err != nil {
+			panic(err)
+		}
+		for i := 0; i < n; i++ {
+			res, err := Get(url)
+			if err != nil {
+				log.Panicf("Get: %v", err)
+			}
+			all, err := ioutil.ReadAll(res.Body)
+			res.Body.Close()
+			if err != nil {
+				log.Panicf("ReadAll: %v", err)
+			}
+			body := string(all)
+			if body != "Hello world.\n" {
+				log.Panicf("Got body: %q", body)
+			}
+		}
+		os.Exit(0)
+		return
+	}
+
+	var res = []byte("Hello world.\n")
+	b.StopTimer()
+	ts := httptest.NewServer(HandlerFunc(func(rw ResponseWriter, r *Request) {
+		rw.Header().Set("Content-Type", "text/html; charset=utf-8")
+		rw.Write(res)
+	}))
+	defer ts.Close()
+	b.StartTimer()
+
+	cmd := exec.Command(os.Args[0], "-test.run=XXXX", "-test.bench=BenchmarkServer")
+	cmd.Env = append([]string{
+		fmt.Sprintf("TEST_BENCH_CLIENT_N=%d", b.N),
+		fmt.Sprintf("TEST_BENCH_SERVER_URL=%s", ts.URL),
+	}, os.Environ()...)
+	out, err := cmd.CombinedOutput()
+	if err != nil {
+		b.Errorf("Test failure: %v, with output: %s", err, out)
+	}
+}
+
+func BenchmarkServerFakeConnNoKeepAlive(b *testing.B) {
+	b.ReportAllocs()
+	req := reqBytes(`GET / HTTP/1.0
+Host: golang.org
+Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
+User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_8_2) AppleWebKit/537.17 (KHTML, like Gecko) Chrome/24.0.1312.52 Safari/537.17
+Accept-Encoding: gzip,deflate,sdch
+Accept-Language: en-US,en;q=0.8
+Accept-Charset: ISO-8859-1,utf-8;q=0.7,*;q=0.3
+`)
+	res := []byte("Hello world!\n")
+
+	conn := &testConn{
+		// testConn.Close will not push into the channel
+		// if it's full.
+		closec: make(chan bool, 1),
+	}
+	handler := HandlerFunc(func(rw ResponseWriter, r *Request) {
+		rw.Header().Set("Content-Type", "text/html; charset=utf-8")
+		rw.Write(res)
+	})
+	ln := new(oneConnListener)
+	for i := 0; i < b.N; i++ {
+		conn.readBuf.Reset()
+		conn.writeBuf.Reset()
+		conn.readBuf.Write(req)
+		ln.conn = conn
+		Serve(ln, handler)
+		<-conn.closec
+	}
+}
+
+// repeatReader reads content count times, then EOFs.
+type repeatReader struct {
+	content []byte
+	count   int
+	off     int
+}
+
+func (r *repeatReader) Read(p []byte) (n int, err error) {
+	if r.count <= 0 {
+		return 0, io.EOF
+	}
+	n = copy(p, r.content[r.off:])
+	r.off += n
+	if r.off == len(r.content) {
+		r.count--
+		r.off = 0
+	}
+	return
+}
+
+func BenchmarkServerFakeConnWithKeepAlive(b *testing.B) {
+	b.ReportAllocs()
+
+	req := reqBytes(`GET / HTTP/1.1
+Host: golang.org
+Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
+User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_8_2) AppleWebKit/537.17 (KHTML, like Gecko) Chrome/24.0.1312.52 Safari/537.17
+Accept-Encoding: gzip,deflate,sdch
+Accept-Language: en-US,en;q=0.8
+Accept-Charset: ISO-8859-1,utf-8;q=0.7,*;q=0.3
+`)
+	res := []byte("Hello world!\n")
+
+	conn := &rwTestConn{
+		Reader: &repeatReader{content: req, count: b.N},
+		Writer: ioutil.Discard,
+		closec: make(chan bool, 1),
+	}
+	handled := 0
+	handler := HandlerFunc(func(rw ResponseWriter, r *Request) {
+		handled++
+		rw.Header().Set("Content-Type", "text/html; charset=utf-8")
+		rw.Write(res)
+	})
+	ln := &oneConnListener{conn: conn}
+	go Serve(ln, handler)
+	<-conn.closec
+	if b.N != handled {
+		b.Errorf("b.N=%d but handled %d", b.N, handled)
+	}
+}
+
+// same as above, but representing the most simple possible request
+// and handler. Notably: the handler does not call rw.Header().
+func BenchmarkServerFakeConnWithKeepAliveLite(b *testing.B) {
+	b.ReportAllocs()
+
+	req := reqBytes(`GET / HTTP/1.1
+Host: golang.org
+`)
+	res := []byte("Hello world!\n")
+
+	conn := &rwTestConn{
+		Reader: &repeatReader{content: req, count: b.N},
+		Writer: ioutil.Discard,
+		closec: make(chan bool, 1),
+	}
+	handled := 0
+	handler := HandlerFunc(func(rw ResponseWriter, r *Request) {
+		handled++
+		rw.Write(res)
+	})
+	ln := &oneConnListener{conn: conn}
+	go Serve(ln, handler)
+	<-conn.closec
+	if b.N != handled {
+		b.Errorf("b.N=%d but handled %d", b.N, handled)
+	}
+}
+
+const someResponse = "<html>some response</html>"
+
+// A Response that's just no bigger than 2KB, the buffer-before-chunking threshold.
+var response = bytes.Repeat([]byte(someResponse), 2<<10/len(someResponse))
+
+// Both Content-Type and Content-Length set. Should be no buffering.
+func BenchmarkServerHandlerTypeLen(b *testing.B) {
+	benchmarkHandler(b, HandlerFunc(func(w ResponseWriter, r *Request) {
+		w.Header().Set("Content-Type", "text/html")
+		w.Header().Set("Content-Length", strconv.Itoa(len(response)))
+		w.Write(response)
+	}))
+}
+
+// A Content-Type is set, but no length. No sniffing, but will count the Content-Length.
+func BenchmarkServerHandlerNoLen(b *testing.B) {
+	benchmarkHandler(b, HandlerFunc(func(w ResponseWriter, r *Request) {
+		w.Header().Set("Content-Type", "text/html")
+		w.Write(response)
+	}))
+}
+
+// A Content-Length is set, but the Content-Type will be sniffed.
+func BenchmarkServerHandlerNoType(b *testing.B) {
+	benchmarkHandler(b, HandlerFunc(func(w ResponseWriter, r *Request) {
+		w.Header().Set("Content-Length", strconv.Itoa(len(response)))
+		w.Write(response)
+	}))
+}
+
+// Neither a Content-Type or Content-Length, so sniffed and counted.
+func BenchmarkServerHandlerNoHeader(b *testing.B) {
+	benchmarkHandler(b, HandlerFunc(func(w ResponseWriter, r *Request) {
+		w.Write(response)
+	}))
+}
+
+func benchmarkHandler(b *testing.B, h Handler) {
+	b.ReportAllocs()
+	req := reqBytes(`GET / HTTP/1.1
+Host: golang.org
+`)
+	conn := &rwTestConn{
+		Reader: &repeatReader{content: req, count: b.N},
+		Writer: ioutil.Discard,
+		closec: make(chan bool, 1),
+	}
+	handled := 0
+	handler := HandlerFunc(func(rw ResponseWriter, r *Request) {
+		handled++
+		h.ServeHTTP(rw, r)
+	})
+	ln := &oneConnListener{conn: conn}
+	go Serve(ln, handler)
+	<-conn.closec
+	if b.N != handled {
+		b.Errorf("b.N=%d but handled %d", b.N, handled)
+	}
+}
+
+func BenchmarkServerHijack(b *testing.B) {
+	b.ReportAllocs()
+	req := reqBytes(`GET / HTTP/1.1
+Host: golang.org
+`)
+	h := HandlerFunc(func(w ResponseWriter, r *Request) {
+		conn, _, err := w.(Hijacker).Hijack()
+		if err != nil {
+			panic(err)
+		}
+		conn.Close()
+	})
+	conn := &rwTestConn{
+		Writer: ioutil.Discard,
+		closec: make(chan bool, 1),
+	}
+	ln := &oneConnListener{conn: conn}
+	for i := 0; i < b.N; i++ {
+		conn.Reader = bytes.NewReader(req)
+		ln.conn = conn
+		Serve(ln, h)
+		<-conn.closec
+	}
+}
diff --git a/src/net/http/server.go b/src/net/http/server.go
new file mode 100644
index 000000000..203037e9f
--- /dev/null
+++ b/src/net/http/server.go
@@ -0,0 +1,2051 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// HTTP server.  See RFC 2616.
+
+package http
+
+import (
+	"bufio"
+	"crypto/tls"
+	"errors"
+	"fmt"
+	"io"
+	"io/ioutil"
+	"log"
+	"net"
+	"net/url"
+	"os"
+	"path"
+	"runtime"
+	"strconv"
+	"strings"
+	"sync"
+	"sync/atomic"
+	"time"
+)
+
+// Errors introduced by the HTTP server.
+var (
+	ErrWriteAfterFlush = errors.New("Conn.Write called after Flush")
+	ErrBodyNotAllowed  = errors.New("http: request method or response status code does not allow body")
+	ErrHijacked        = errors.New("Conn has been hijacked")
+	ErrContentLength   = errors.New("Conn.Write wrote more than the declared Content-Length")
+)
+
+// Objects implementing the Handler interface can be
+// registered to serve a particular path or subtree
+// in the HTTP server.
+//
+// ServeHTTP should write reply headers and data to the ResponseWriter
+// and then return.  Returning signals that the request is finished
+// and that the HTTP server can move on to the next request on
+// the connection.
+type Handler interface {
+	ServeHTTP(ResponseWriter, *Request)
+}
+
+// A ResponseWriter interface is used by an HTTP handler to
+// construct an HTTP response.
+type ResponseWriter interface {
+	// Header returns the header map that will be sent by WriteHeader.
+	// Changing the header after a call to WriteHeader (or Write) has
+	// no effect.
+	Header() Header
+
+	// Write writes the data to the connection as part of an HTTP reply.
+	// If WriteHeader has not yet been called, Write calls WriteHeader(http.StatusOK)
+	// before writing the data.  If the Header does not contain a
+	// Content-Type line, Write adds a Content-Type set to the result of passing
+	// the initial 512 bytes of written data to DetectContentType.
+	Write([]byte) (int, error)
+
+	// WriteHeader sends an HTTP response header with status code.
+	// If WriteHeader is not called explicitly, the first call to Write
+	// will trigger an implicit WriteHeader(http.StatusOK).
+	// Thus explicit calls to WriteHeader are mainly used to
+	// send error codes.
+	WriteHeader(int)
+}
+
+// The Flusher interface is implemented by ResponseWriters that allow
+// an HTTP handler to flush buffered data to the client.
+//
+// Note that even for ResponseWriters that support Flush,
+// if the client is connected through an HTTP proxy,
+// the buffered data may not reach the client until the response
+// completes.
+type Flusher interface {
+	// Flush sends any buffered data to the client.
+	Flush()
+}
+
+// The Hijacker interface is implemented by ResponseWriters that allow
+// an HTTP handler to take over the connection.
+type Hijacker interface {
+	// Hijack lets the caller take over the connection.
+	// After a call to Hijack(), the HTTP server library
+	// will not do anything else with the connection.
+	// It becomes the caller's responsibility to manage
+	// and close the connection.
+	Hijack() (net.Conn, *bufio.ReadWriter, error)
+}
+
+// The CloseNotifier interface is implemented by ResponseWriters which
+// allow detecting when the underlying connection has gone away.
+//
+// This mechanism can be used to cancel long operations on the server
+// if the client has disconnected before the response is ready.
+type CloseNotifier interface {
+	// CloseNotify returns a channel that receives a single value
+	// when the client connection has gone away.
+	CloseNotify() <-chan bool
+}
+
+// A conn represents the server side of an HTTP connection.
+type conn struct {
+	remoteAddr string               // network address of remote side
+	server     *Server              // the Server on which the connection arrived
+	rwc        net.Conn             // i/o connection
+	sr         liveSwitchReader     // where the LimitReader reads from; usually the rwc
+	lr         *io.LimitedReader    // io.LimitReader(sr)
+	buf        *bufio.ReadWriter    // buffered(lr,rwc), reading from bufio->limitReader->sr->rwc
+	tlsState   *tls.ConnectionState // or nil when not using TLS
+
+	mu           sync.Mutex // guards the following
+	clientGone   bool       // if client has disconnected mid-request
+	closeNotifyc chan bool  // made lazily
+	hijackedv    bool       // connection has been hijacked by handler
+}
+
+func (c *conn) hijacked() bool {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+	return c.hijackedv
+}
+
+func (c *conn) hijack() (rwc net.Conn, buf *bufio.ReadWriter, err error) {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+	if c.hijackedv {
+		return nil, nil, ErrHijacked
+	}
+	if c.closeNotifyc != nil {
+		return nil, nil, errors.New("http: Hijack is incompatible with use of CloseNotifier")
+	}
+	c.hijackedv = true
+	rwc = c.rwc
+	buf = c.buf
+	c.rwc = nil
+	c.buf = nil
+	c.setState(rwc, StateHijacked)
+	return
+}
+
+func (c *conn) closeNotify() <-chan bool {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+	if c.closeNotifyc == nil {
+		c.closeNotifyc = make(chan bool, 1)
+		if c.hijackedv {
+			// to obey the function signature, even though
+			// it'll never receive a value.
+			return c.closeNotifyc
+		}
+		pr, pw := io.Pipe()
+
+		readSource := c.sr.r
+		c.sr.Lock()
+		c.sr.r = pr
+		c.sr.Unlock()
+		go func() {
+			_, err := io.Copy(pw, readSource)
+			if err == nil {
+				err = io.EOF
+			}
+			pw.CloseWithError(err)
+			c.noteClientGone()
+		}()
+	}
+	return c.closeNotifyc
+}
+
+func (c *conn) noteClientGone() {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+	if c.closeNotifyc != nil && !c.clientGone {
+		c.closeNotifyc <- true
+	}
+	c.clientGone = true
+}
+
+// A switchReader can have its Reader changed at runtime.
+// It's not safe for concurrent Reads and switches.
+type switchReader struct {
+	io.Reader
+}
+
+// A switchWriter can have its Writer changed at runtime.
+// It's not safe for concurrent Writes and switches.
+type switchWriter struct {
+	io.Writer
+}
+
+// A liveSwitchReader is a switchReader that's safe for concurrent
+// reads and switches, if its mutex is held.
+type liveSwitchReader struct {
+	sync.Mutex
+	r io.Reader
+}
+
+func (sr *liveSwitchReader) Read(p []byte) (n int, err error) {
+	sr.Lock()
+	r := sr.r
+	sr.Unlock()
+	return r.Read(p)
+}
+
+// This should be >= 512 bytes for DetectContentType,
+// but otherwise it's somewhat arbitrary.
+const bufferBeforeChunkingSize = 2048
+
+// chunkWriter writes to a response's conn buffer, and is the writer
+// wrapped by the response.bufw buffered writer.
+//
+// chunkWriter also is responsible for finalizing the Header, including
+// conditionally setting the Content-Type and setting a Content-Length
+// in cases where the handler's final output is smaller than the buffer
+// size. It also conditionally adds chunk headers, when in chunking mode.
+//
+// See the comment above (*response).Write for the entire write flow.
+type chunkWriter struct {
+	res *response
+
+	// header is either nil or a deep clone of res.handlerHeader
+	// at the time of res.WriteHeader, if res.WriteHeader is
+	// called and extra buffering is being done to calculate
+	// Content-Type and/or Content-Length.
+	header Header
+
+	// wroteHeader tells whether the header's been written to "the
+	// wire" (or rather: w.conn.buf). this is unlike
+	// (*response).wroteHeader, which tells only whether it was
+	// logically written.
+	wroteHeader bool
+
+	// set by the writeHeader method:
+	chunking bool // using chunked transfer encoding for reply body
+}
+
+var (
+	crlf       = []byte("\r\n")
+	colonSpace = []byte(": ")
+)
+
+func (cw *chunkWriter) Write(p []byte) (n int, err error) {
+	if !cw.wroteHeader {
+		cw.writeHeader(p)
+	}
+	if cw.res.req.Method == "HEAD" {
+		// Eat writes.
+		return len(p), nil
+	}
+	if cw.chunking {
+		_, err = fmt.Fprintf(cw.res.conn.buf, "%x\r\n", len(p))
+		if err != nil {
+			cw.res.conn.rwc.Close()
+			return
+		}
+	}
+	n, err = cw.res.conn.buf.Write(p)
+	if cw.chunking && err == nil {
+		_, err = cw.res.conn.buf.Write(crlf)
+	}
+	if err != nil {
+		cw.res.conn.rwc.Close()
+	}
+	return
+}
+
+func (cw *chunkWriter) flush() {
+	if !cw.wroteHeader {
+		cw.writeHeader(nil)
+	}
+	cw.res.conn.buf.Flush()
+}
+
+func (cw *chunkWriter) close() {
+	if !cw.wroteHeader {
+		cw.writeHeader(nil)
+	}
+	if cw.chunking {
+		// zero EOF chunk, trailer key/value pairs (currently
+		// unsupported in Go's server), followed by a blank
+		// line.
+		cw.res.conn.buf.WriteString("0\r\n\r\n")
+	}
+}
+
+// A response represents the server side of an HTTP response.
+type response struct {
+	conn          *conn
+	req           *Request // request for this response
+	wroteHeader   bool     // reply header has been (logically) written
+	wroteContinue bool     // 100 Continue response was written
+
+	w  *bufio.Writer // buffers output in chunks to chunkWriter
+	cw chunkWriter
+	sw *switchWriter // of the bufio.Writer, for return to putBufioWriter
+
+	// handlerHeader is the Header that Handlers get access to,
+	// which may be retained and mutated even after WriteHeader.
+	// handlerHeader is copied into cw.header at WriteHeader
+	// time, and privately mutated thereafter.
+	handlerHeader Header
+	calledHeader  bool // handler accessed handlerHeader via Header
+
+	written       int64 // number of bytes written in body
+	contentLength int64 // explicitly-declared Content-Length; or -1
+	status        int   // status code passed to WriteHeader
+
+	// close connection after this reply.  set on request and
+	// updated after response from handler if there's a
+	// "Connection: keep-alive" response header and a
+	// Content-Length.
+	closeAfterReply bool
+
+	// requestBodyLimitHit is set by requestTooLarge when
+	// maxBytesReader hits its max size. It is checked in
+	// WriteHeader, to make sure we don't consume the
+	// remaining request body to try to advance to the next HTTP
+	// request. Instead, when this is set, we stop reading
+	// subsequent requests on this connection and stop reading
+	// input from it.
+	requestBodyLimitHit bool
+
+	handlerDone bool // set true when the handler exits
+
+	// Buffers for Date and Content-Length
+	dateBuf [len(TimeFormat)]byte
+	clenBuf [10]byte
+}
+
+// requestTooLarge is called by maxBytesReader when too much input has
+// been read from the client.
+func (w *response) requestTooLarge() {
+	w.closeAfterReply = true
+	w.requestBodyLimitHit = true
+	if !w.wroteHeader {
+		w.Header().Set("Connection", "close")
+	}
+}
+
+// needsSniff reports whether a Content-Type still needs to be sniffed.
+func (w *response) needsSniff() bool {
+	_, haveType := w.handlerHeader["Content-Type"]
+	return !w.cw.wroteHeader && !haveType && w.written < sniffLen
+}
+
+// writerOnly hides an io.Writer value's optional ReadFrom method
+// from io.Copy.
+type writerOnly struct {
+	io.Writer
+}
+
+func srcIsRegularFile(src io.Reader) (isRegular bool, err error) {
+	switch v := src.(type) {
+	case *os.File:
+		fi, err := v.Stat()
+		if err != nil {
+			return false, err
+		}
+		return fi.Mode().IsRegular(), nil
+	case *io.LimitedReader:
+		return srcIsRegularFile(v.R)
+	default:
+		return
+	}
+}
+
+// ReadFrom is here to optimize copying from an *os.File regular file
+// to a *net.TCPConn with sendfile.
+func (w *response) ReadFrom(src io.Reader) (n int64, err error) {
+	// Our underlying w.conn.rwc is usually a *TCPConn (with its
+	// own ReadFrom method). If not, or if our src isn't a regular
+	// file, just fall back to the normal copy method.
+	rf, ok := w.conn.rwc.(io.ReaderFrom)
+	regFile, err := srcIsRegularFile(src)
+	if err != nil {
+		return 0, err
+	}
+	if !ok || !regFile {
+		return io.Copy(writerOnly{w}, src)
+	}
+
+	// sendfile path:
+
+	if !w.wroteHeader {
+		w.WriteHeader(StatusOK)
+	}
+
+	if w.needsSniff() {
+		n0, err := io.Copy(writerOnly{w}, io.LimitReader(src, sniffLen))
+		n += n0
+		if err != nil {
+			return n, err
+		}
+	}
+
+	w.w.Flush()  // get rid of any previous writes
+	w.cw.flush() // make sure Header is written; flush data to rwc
+
+	// Now that cw has been flushed, its chunking field is guaranteed initialized.
+	if !w.cw.chunking && w.bodyAllowed() {
+		n0, err := rf.ReadFrom(src)
+		n += n0
+		w.written += n0
+		return n, err
+	}
+
+	n0, err := io.Copy(writerOnly{w}, src)
+	n += n0
+	return n, err
+}
+
+// noLimit is an effective infinite upper bound for io.LimitedReader
+const noLimit int64 = (1 << 63) - 1
+
+// debugServerConnections controls whether all server connections are wrapped
+// with a verbose logging wrapper.
+const debugServerConnections = false
+
+// Create new connection from rwc.
+func (srv *Server) newConn(rwc net.Conn) (c *conn, err error) {
+	c = new(conn)
+	c.remoteAddr = rwc.RemoteAddr().String()
+	c.server = srv
+	c.rwc = rwc
+	if debugServerConnections {
+		c.rwc = newLoggingConn("server", c.rwc)
+	}
+	c.sr = liveSwitchReader{r: c.rwc}
+	c.lr = io.LimitReader(&c.sr, noLimit).(*io.LimitedReader)
+	br := newBufioReader(c.lr)
+	bw := newBufioWriterSize(c.rwc, 4<<10)
+	c.buf = bufio.NewReadWriter(br, bw)
+	return c, nil
+}
+
+var (
+	bufioReaderPool   sync.Pool
+	bufioWriter2kPool sync.Pool
+	bufioWriter4kPool sync.Pool
+)
+
+func bufioWriterPool(size int) *sync.Pool {
+	switch size {
+	case 2 << 10:
+		return &bufioWriter2kPool
+	case 4 << 10:
+		return &bufioWriter4kPool
+	}
+	return nil
+}
+
+func newBufioReader(r io.Reader) *bufio.Reader {
+	if v := bufioReaderPool.Get(); v != nil {
+		br := v.(*bufio.Reader)
+		br.Reset(r)
+		return br
+	}
+	return bufio.NewReader(r)
+}
+
+func putBufioReader(br *bufio.Reader) {
+	br.Reset(nil)
+	bufioReaderPool.Put(br)
+}
+
+func newBufioWriterSize(w io.Writer, size int) *bufio.Writer {
+	pool := bufioWriterPool(size)
+	if pool != nil {
+		if v := pool.Get(); v != nil {
+			bw := v.(*bufio.Writer)
+			bw.Reset(w)
+			return bw
+		}
+	}
+	return bufio.NewWriterSize(w, size)
+}
+
+func putBufioWriter(bw *bufio.Writer) {
+	bw.Reset(nil)
+	if pool := bufioWriterPool(bw.Available()); pool != nil {
+		pool.Put(bw)
+	}
+}
+
+// DefaultMaxHeaderBytes is the maximum permitted size of the headers
+// in an HTTP request.
+// This can be overridden by setting Server.MaxHeaderBytes.
+const DefaultMaxHeaderBytes = 1 << 20 // 1 MB
+
+func (srv *Server) maxHeaderBytes() int {
+	if srv.MaxHeaderBytes > 0 {
+		return srv.MaxHeaderBytes
+	}
+	return DefaultMaxHeaderBytes
+}
+
+func (srv *Server) initialLimitedReaderSize() int64 {
+	return int64(srv.maxHeaderBytes()) + 4096 // bufio slop
+}
+
+// wrapper around io.ReaderCloser which on first read, sends an
+// HTTP/1.1 100 Continue header
+type expectContinueReader struct {
+	resp       *response
+	readCloser io.ReadCloser
+	closed     bool
+}
+
+func (ecr *expectContinueReader) Read(p []byte) (n int, err error) {
+	if ecr.closed {
+		return 0, ErrBodyReadAfterClose
+	}
+	if !ecr.resp.wroteContinue && !ecr.resp.conn.hijacked() {
+		ecr.resp.wroteContinue = true
+		ecr.resp.conn.buf.WriteString("HTTP/1.1 100 Continue\r\n\r\n")
+		ecr.resp.conn.buf.Flush()
+	}
+	return ecr.readCloser.Read(p)
+}
+
+func (ecr *expectContinueReader) Close() error {
+	ecr.closed = true
+	return ecr.readCloser.Close()
+}
+
+// TimeFormat is the time format to use with
+// time.Parse and time.Time.Format when parsing
+// or generating times in HTTP headers.
+// It is like time.RFC1123 but hard codes GMT as the time zone.
+const TimeFormat = "Mon, 02 Jan 2006 15:04:05 GMT"
+
+// appendTime is a non-allocating version of []byte(t.UTC().Format(TimeFormat))
+func appendTime(b []byte, t time.Time) []byte {
+	const days = "SunMonTueWedThuFriSat"
+	const months = "JanFebMarAprMayJunJulAugSepOctNovDec"
+
+	t = t.UTC()
+	yy, mm, dd := t.Date()
+	hh, mn, ss := t.Clock()
+	day := days[3*t.Weekday():]
+	mon := months[3*(mm-1):]
+
+	return append(b,
+		day[0], day[1], day[2], ',', ' ',
+		byte('0'+dd/10), byte('0'+dd%10), ' ',
+		mon[0], mon[1], mon[2], ' ',
+		byte('0'+yy/1000), byte('0'+(yy/100)%10), byte('0'+(yy/10)%10), byte('0'+yy%10), ' ',
+		byte('0'+hh/10), byte('0'+hh%10), ':',
+		byte('0'+mn/10), byte('0'+mn%10), ':',
+		byte('0'+ss/10), byte('0'+ss%10), ' ',
+		'G', 'M', 'T')
+}
+
+var errTooLarge = errors.New("http: request too large")
+
+// Read next request from connection.
+func (c *conn) readRequest() (w *response, err error) {
+	if c.hijacked() {
+		return nil, ErrHijacked
+	}
+
+	if d := c.server.ReadTimeout; d != 0 {
+		c.rwc.SetReadDeadline(time.Now().Add(d))
+	}
+	if d := c.server.WriteTimeout; d != 0 {
+		defer func() {
+			c.rwc.SetWriteDeadline(time.Now().Add(d))
+		}()
+	}
+
+	c.lr.N = c.server.initialLimitedReaderSize()
+	var req *Request
+	if req, err = ReadRequest(c.buf.Reader); err != nil {
+		if c.lr.N == 0 {
+			return nil, errTooLarge
+		}
+		return nil, err
+	}
+	c.lr.N = noLimit
+
+	req.RemoteAddr = c.remoteAddr
+	req.TLS = c.tlsState
+
+	w = &response{
+		conn:          c,
+		req:           req,
+		handlerHeader: make(Header),
+		contentLength: -1,
+	}
+	w.cw.res = w
+	w.w = newBufioWriterSize(&w.cw, bufferBeforeChunkingSize)
+	return w, nil
+}
+
+func (w *response) Header() Header {
+	if w.cw.header == nil && w.wroteHeader && !w.cw.wroteHeader {
+		// Accessing the header between logically writing it
+		// and physically writing it means we need to allocate
+		// a clone to snapshot the logically written state.
+		w.cw.header = w.handlerHeader.clone()
+	}
+	w.calledHeader = true
+	return w.handlerHeader
+}
+
+// maxPostHandlerReadBytes is the max number of Request.Body bytes not
+// consumed by a handler that the server will read from the client
+// in order to keep a connection alive.  If there are more bytes than
+// this then the server to be paranoid instead sends a "Connection:
+// close" response.
+//
+// This number is approximately what a typical machine's TCP buffer
+// size is anyway.  (if we have the bytes on the machine, we might as
+// well read them)
+const maxPostHandlerReadBytes = 256 << 10
+
+func (w *response) WriteHeader(code int) {
+	if w.conn.hijacked() {
+		w.conn.server.logf("http: response.WriteHeader on hijacked connection")
+		return
+	}
+	if w.wroteHeader {
+		w.conn.server.logf("http: multiple response.WriteHeader calls")
+		return
+	}
+	w.wroteHeader = true
+	w.status = code
+
+	if w.calledHeader && w.cw.header == nil {
+		w.cw.header = w.handlerHeader.clone()
+	}
+
+	if cl := w.handlerHeader.get("Content-Length"); cl != "" {
+		v, err := strconv.ParseInt(cl, 10, 64)
+		if err == nil && v >= 0 {
+			w.contentLength = v
+		} else {
+			w.conn.server.logf("http: invalid Content-Length of %q", cl)
+			w.handlerHeader.Del("Content-Length")
+		}
+	}
+}
+
+// extraHeader is the set of headers sometimes added by chunkWriter.writeHeader.
+// This type is used to avoid extra allocations from cloning and/or populating
+// the response Header map and all its 1-element slices.
+type extraHeader struct {
+	contentType      string
+	connection       string
+	transferEncoding string
+	date             []byte // written if not nil
+	contentLength    []byte // written if not nil
+}
+
+// Sorted the same as extraHeader.Write's loop.
+var extraHeaderKeys = [][]byte{
+	[]byte("Content-Type"),
+	[]byte("Connection"),
+	[]byte("Transfer-Encoding"),
+}
+
+var (
+	headerContentLength = []byte("Content-Length: ")
+	headerDate          = []byte("Date: ")
+)
+
+// Write writes the headers described in h to w.
+//
+// This method has a value receiver, despite the somewhat large size
+// of h, because it prevents an allocation. The escape analysis isn't
+// smart enough to realize this function doesn't mutate h.
+func (h extraHeader) Write(w *bufio.Writer) {
+	if h.date != nil {
+		w.Write(headerDate)
+		w.Write(h.date)
+		w.Write(crlf)
+	}
+	if h.contentLength != nil {
+		w.Write(headerContentLength)
+		w.Write(h.contentLength)
+		w.Write(crlf)
+	}
+	for i, v := range []string{h.contentType, h.connection, h.transferEncoding} {
+		if v != "" {
+			w.Write(extraHeaderKeys[i])
+			w.Write(colonSpace)
+			w.WriteString(v)
+			w.Write(crlf)
+		}
+	}
+}
+
+// writeHeader finalizes the header sent to the client and writes it
+// to cw.res.conn.buf.
+//
+// p is not written by writeHeader, but is the first chunk of the body
+// that will be written.  It is sniffed for a Content-Type if none is
+// set explicitly.  It's also used to set the Content-Length, if the
+// total body size was small and the handler has already finished
+// running.
+func (cw *chunkWriter) writeHeader(p []byte) {
+	if cw.wroteHeader {
+		return
+	}
+	cw.wroteHeader = true
+
+	w := cw.res
+	keepAlivesEnabled := w.conn.server.doKeepAlives()
+	isHEAD := w.req.Method == "HEAD"
+
+	// header is written out to w.conn.buf below. Depending on the
+	// state of the handler, we either own the map or not. If we
+	// don't own it, the exclude map is created lazily for
+	// WriteSubset to remove headers. The setHeader struct holds
+	// headers we need to add.
+	header := cw.header
+	owned := header != nil
+	if !owned {
+		header = w.handlerHeader
+	}
+	var excludeHeader map[string]bool
+	delHeader := func(key string) {
+		if owned {
+			header.Del(key)
+			return
+		}
+		if _, ok := header[key]; !ok {
+			return
+		}
+		if excludeHeader == nil {
+			excludeHeader = make(map[string]bool)
+		}
+		excludeHeader[key] = true
+	}
+	var setHeader extraHeader
+
+	// If the handler is done but never sent a Content-Length
+	// response header and this is our first (and last) write, set
+	// it, even to zero. This helps HTTP/1.0 clients keep their
+	// "keep-alive" connections alive.
+	// Exceptions: 304/204/1xx responses never get Content-Length, and if
+	// it was a HEAD request, we don't know the difference between
+	// 0 actual bytes and 0 bytes because the handler noticed it
+	// was a HEAD request and chose not to write anything.  So for
+	// HEAD, the handler should either write the Content-Length or
+	// write non-zero bytes.  If it's actually 0 bytes and the
+	// handler never looked at the Request.Method, we just don't
+	// send a Content-Length header.
+	if w.handlerDone && bodyAllowedForStatus(w.status) && header.get("Content-Length") == "" && (!isHEAD || len(p) > 0) {
+		w.contentLength = int64(len(p))
+		setHeader.contentLength = strconv.AppendInt(cw.res.clenBuf[:0], int64(len(p)), 10)
+	}
+
+	// If this was an HTTP/1.0 request with keep-alive and we sent a
+	// Content-Length back, we can make this a keep-alive response ...
+	if w.req.wantsHttp10KeepAlive() && keepAlivesEnabled {
+		sentLength := header.get("Content-Length") != ""
+		if sentLength && header.get("Connection") == "keep-alive" {
+			w.closeAfterReply = false
+		}
+	}
+
+	// Check for a explicit (and valid) Content-Length header.
+	hasCL := w.contentLength != -1
+
+	if w.req.wantsHttp10KeepAlive() && (isHEAD || hasCL) {
+		_, connectionHeaderSet := header["Connection"]
+		if !connectionHeaderSet {
+			setHeader.connection = "keep-alive"
+		}
+	} else if !w.req.ProtoAtLeast(1, 1) || w.req.wantsClose() {
+		w.closeAfterReply = true
+	}
+
+	if header.get("Connection") == "close" || !keepAlivesEnabled {
+		w.closeAfterReply = true
+	}
+
+	// Per RFC 2616, we should consume the request body before
+	// replying, if the handler hasn't already done so.  But we
+	// don't want to do an unbounded amount of reading here for
+	// DoS reasons, so we only try up to a threshold.
+	if w.req.ContentLength != 0 && !w.closeAfterReply {
+		ecr, isExpecter := w.req.Body.(*expectContinueReader)
+		if !isExpecter || ecr.resp.wroteContinue {
+			n, _ := io.CopyN(ioutil.Discard, w.req.Body, maxPostHandlerReadBytes+1)
+			if n >= maxPostHandlerReadBytes {
+				w.requestTooLarge()
+				delHeader("Connection")
+				setHeader.connection = "close"
+			} else {
+				w.req.Body.Close()
+			}
+		}
+	}
+
+	code := w.status
+	if bodyAllowedForStatus(code) {
+		// If no content type, apply sniffing algorithm to body.
+		_, haveType := header["Content-Type"]
+		if !haveType {
+			setHeader.contentType = DetectContentType(p)
+		}
+	} else {
+		for _, k := range suppressedHeaders(code) {
+			delHeader(k)
+		}
+	}
+
+	if _, ok := header["Date"]; !ok {
+		setHeader.date = appendTime(cw.res.dateBuf[:0], time.Now())
+	}
+
+	te := header.get("Transfer-Encoding")
+	hasTE := te != ""
+	if hasCL && hasTE && te != "identity" {
+		// TODO: return an error if WriteHeader gets a return parameter
+		// For now just ignore the Content-Length.
+		w.conn.server.logf("http: WriteHeader called with both Transfer-Encoding of %q and a Content-Length of %d",
+			te, w.contentLength)
+		delHeader("Content-Length")
+		hasCL = false
+	}
+
+	if w.req.Method == "HEAD" || !bodyAllowedForStatus(code) {
+		// do nothing
+	} else if code == StatusNoContent {
+		delHeader("Transfer-Encoding")
+	} else if hasCL {
+		delHeader("Transfer-Encoding")
+	} else if w.req.ProtoAtLeast(1, 1) {
+		// HTTP/1.1 or greater: use chunked transfer encoding
+		// to avoid closing the connection at EOF.
+		// TODO: this blows away any custom or stacked Transfer-Encoding they
+		// might have set.  Deal with that as need arises once we have a valid
+		// use case.
+		cw.chunking = true
+		setHeader.transferEncoding = "chunked"
+	} else {
+		// HTTP version < 1.1: cannot do chunked transfer
+		// encoding and we don't know the Content-Length so
+		// signal EOF by closing connection.
+		w.closeAfterReply = true
+		delHeader("Transfer-Encoding") // in case already set
+	}
+
+	// Cannot use Content-Length with non-identity Transfer-Encoding.
+	if cw.chunking {
+		delHeader("Content-Length")
+	}
+	if !w.req.ProtoAtLeast(1, 0) {
+		return
+	}
+
+	if w.closeAfterReply && (!keepAlivesEnabled || !hasToken(cw.header.get("Connection"), "close")) {
+		delHeader("Connection")
+		if w.req.ProtoAtLeast(1, 1) {
+			setHeader.connection = "close"
+		}
+	}
+
+	w.conn.buf.WriteString(statusLine(w.req, code))
+	cw.header.WriteSubset(w.conn.buf, excludeHeader)
+	setHeader.Write(w.conn.buf.Writer)
+	w.conn.buf.Write(crlf)
+}
+
+// statusLines is a cache of Status-Line strings, keyed by code (for
+// HTTP/1.1) or negative code (for HTTP/1.0). This is faster than a
+// map keyed by struct of two fields. This map's max size is bounded
+// by 2*len(statusText), two protocol types for each known official
+// status code in the statusText map.
+var (
+	statusMu    sync.RWMutex
+	statusLines = make(map[int]string)
+)
+
+// statusLine returns a response Status-Line (RFC 2616 Section 6.1)
+// for the given request and response status code.
+func statusLine(req *Request, code int) string {
+	// Fast path:
+	key := code
+	proto11 := req.ProtoAtLeast(1, 1)
+	if !proto11 {
+		key = -key
+	}
+	statusMu.RLock()
+	line, ok := statusLines[key]
+	statusMu.RUnlock()
+	if ok {
+		return line
+	}
+
+	// Slow path:
+	proto := "HTTP/1.0"
+	if proto11 {
+		proto = "HTTP/1.1"
+	}
+	codestring := strconv.Itoa(code)
+	text, ok := statusText[code]
+	if !ok {
+		text = "status code " + codestring
+	}
+	line = proto + " " + codestring + " " + text + "\r\n"
+	if ok {
+		statusMu.Lock()
+		defer statusMu.Unlock()
+		statusLines[key] = line
+	}
+	return line
+}
+
+// bodyAllowed returns true if a Write is allowed for this response type.
+// It's illegal to call this before the header has been flushed.
+func (w *response) bodyAllowed() bool {
+	if !w.wroteHeader {
+		panic("")
+	}
+	return bodyAllowedForStatus(w.status)
+}
+
+// The Life Of A Write is like this:
+//
+// Handler starts. No header has been sent. The handler can either
+// write a header, or just start writing.  Writing before sending a header
+// sends an implicitly empty 200 OK header.
+//
+// If the handler didn't declare a Content-Length up front, we either
+// go into chunking mode or, if the handler finishes running before
+// the chunking buffer size, we compute a Content-Length and send that
+// in the header instead.
+//
+// Likewise, if the handler didn't set a Content-Type, we sniff that
+// from the initial chunk of output.
+//
+// The Writers are wired together like:
+//
+// 1. *response (the ResponseWriter) ->
+// 2. (*response).w, a *bufio.Writer of bufferBeforeChunkingSize bytes
+// 3. chunkWriter.Writer (whose writeHeader finalizes Content-Length/Type)
+//    and which writes the chunk headers, if needed.
+// 4. conn.buf, a bufio.Writer of default (4kB) bytes
+// 5. the rwc, the net.Conn.
+//
+// TODO(bradfitz): short-circuit some of the buffering when the
+// initial header contains both a Content-Type and Content-Length.
+// Also short-circuit in (1) when the header's been sent and not in
+// chunking mode, writing directly to (4) instead, if (2) has no
+// buffered data.  More generally, we could short-circuit from (1) to
+// (3) even in chunking mode if the write size from (1) is over some
+// threshold and nothing is in (2).  The answer might be mostly making
+// bufferBeforeChunkingSize smaller and having bufio's fast-paths deal
+// with this instead.
+func (w *response) Write(data []byte) (n int, err error) {
+	return w.write(len(data), data, "")
+}
+
+func (w *response) WriteString(data string) (n int, err error) {
+	return w.write(len(data), nil, data)
+}
+
+// either dataB or dataS is non-zero.
+func (w *response) write(lenData int, dataB []byte, dataS string) (n int, err error) {
+	if w.conn.hijacked() {
+		w.conn.server.logf("http: response.Write on hijacked connection")
+		return 0, ErrHijacked
+	}
+	if !w.wroteHeader {
+		w.WriteHeader(StatusOK)
+	}
+	if lenData == 0 {
+		return 0, nil
+	}
+	if !w.bodyAllowed() {
+		return 0, ErrBodyNotAllowed
+	}
+
+	w.written += int64(lenData) // ignoring errors, for errorKludge
+	if w.contentLength != -1 && w.written > w.contentLength {
+		return 0, ErrContentLength
+	}
+	if dataB != nil {
+		return w.w.Write(dataB)
+	} else {
+		return w.w.WriteString(dataS)
+	}
+}
+
+func (w *response) finishRequest() {
+	w.handlerDone = true
+
+	if !w.wroteHeader {
+		w.WriteHeader(StatusOK)
+	}
+
+	w.w.Flush()
+	putBufioWriter(w.w)
+	w.cw.close()
+	w.conn.buf.Flush()
+
+	// Close the body (regardless of w.closeAfterReply) so we can
+	// re-use its bufio.Reader later safely.
+	w.req.Body.Close()
+
+	if w.req.MultipartForm != nil {
+		w.req.MultipartForm.RemoveAll()
+	}
+
+	if w.req.Method != "HEAD" && w.contentLength != -1 && w.bodyAllowed() && w.contentLength != w.written {
+		// Did not write enough. Avoid getting out of sync.
+		w.closeAfterReply = true
+	}
+}
+
+func (w *response) Flush() {
+	if !w.wroteHeader {
+		w.WriteHeader(StatusOK)
+	}
+	w.w.Flush()
+	w.cw.flush()
+}
+
+func (c *conn) finalFlush() {
+	if c.buf != nil {
+		c.buf.Flush()
+
+		// Steal the bufio.Reader (~4KB worth of memory) and its associated
+		// reader for a future connection.
+		putBufioReader(c.buf.Reader)
+
+		// Steal the bufio.Writer (~4KB worth of memory) and its associated
+		// writer for a future connection.
+		putBufioWriter(c.buf.Writer)
+
+		c.buf = nil
+	}
+}
+
+// Close the connection.
+func (c *conn) close() {
+	c.finalFlush()
+	if c.rwc != nil {
+		c.rwc.Close()
+		c.rwc = nil
+	}
+}
+
+// rstAvoidanceDelay is the amount of time we sleep after closing the
+// write side of a TCP connection before closing the entire socket.
+// By sleeping, we increase the chances that the client sees our FIN
+// and processes its final data before they process the subsequent RST
+// from closing a connection with known unread data.
+// This RST seems to occur mostly on BSD systems. (And Windows?)
+// This timeout is somewhat arbitrary (~latency around the planet).
+const rstAvoidanceDelay = 500 * time.Millisecond
+
+// closeWrite flushes any outstanding data and sends a FIN packet (if
+// client is connected via TCP), signalling that we're done.  We then
+// pause for a bit, hoping the client processes it before `any
+// subsequent RST.
+//
+// See http://golang.org/issue/3595
+func (c *conn) closeWriteAndWait() {
+	c.finalFlush()
+	if tcp, ok := c.rwc.(*net.TCPConn); ok {
+		tcp.CloseWrite()
+	}
+	time.Sleep(rstAvoidanceDelay)
+}
+
+// validNPN reports whether the proto is not a blacklisted Next
+// Protocol Negotiation protocol.  Empty and built-in protocol types
+// are blacklisted and can't be overridden with alternate
+// implementations.
+func validNPN(proto string) bool {
+	switch proto {
+	case "", "http/1.1", "http/1.0":
+		return false
+	}
+	return true
+}
+
+func (c *conn) setState(nc net.Conn, state ConnState) {
+	if hook := c.server.ConnState; hook != nil {
+		hook(nc, state)
+	}
+}
+
+// Serve a new connection.
+func (c *conn) serve() {
+	origConn := c.rwc // copy it before it's set nil on Close or Hijack
+	defer func() {
+		if err := recover(); err != nil {
+			const size = 64 << 10
+			buf := make([]byte, size)
+			buf = buf[:runtime.Stack(buf, false)]
+			c.server.logf("http: panic serving %v: %v\n%s", c.remoteAddr, err, buf)
+		}
+		if !c.hijacked() {
+			c.close()
+			c.setState(origConn, StateClosed)
+		}
+	}()
+
+	if tlsConn, ok := c.rwc.(*tls.Conn); ok {
+		if d := c.server.ReadTimeout; d != 0 {
+			c.rwc.SetReadDeadline(time.Now().Add(d))
+		}
+		if d := c.server.WriteTimeout; d != 0 {
+			c.rwc.SetWriteDeadline(time.Now().Add(d))
+		}
+		if err := tlsConn.Handshake(); err != nil {
+			c.server.logf("http: TLS handshake error from %s: %v", c.rwc.RemoteAddr(), err)
+			return
+		}
+		c.tlsState = new(tls.ConnectionState)
+		*c.tlsState = tlsConn.ConnectionState()
+		if proto := c.tlsState.NegotiatedProtocol; validNPN(proto) {
+			if fn := c.server.TLSNextProto[proto]; fn != nil {
+				h := initNPNRequest{tlsConn, serverHandler{c.server}}
+				fn(c.server, tlsConn, h)
+			}
+			return
+		}
+	}
+
+	for {
+		w, err := c.readRequest()
+		if c.lr.N != c.server.initialLimitedReaderSize() {
+			// If we read any bytes off the wire, we're active.
+			c.setState(c.rwc, StateActive)
+		}
+		if err != nil {
+			if err == errTooLarge {
+				// Their HTTP client may or may not be
+				// able to read this if we're
+				// responding to them and hanging up
+				// while they're still writing their
+				// request.  Undefined behavior.
+				io.WriteString(c.rwc, "HTTP/1.1 413 Request Entity Too Large\r\n\r\n")
+				c.closeWriteAndWait()
+				break
+			} else if err == io.EOF {
+				break // Don't reply
+			} else if neterr, ok := err.(net.Error); ok && neterr.Timeout() {
+				break // Don't reply
+			}
+			io.WriteString(c.rwc, "HTTP/1.1 400 Bad Request\r\n\r\n")
+			break
+		}
+
+		// Expect 100 Continue support
+		req := w.req
+		if req.expectsContinue() {
+			if req.ProtoAtLeast(1, 1) && req.ContentLength != 0 {
+				// Wrap the Body reader with one that replies on the connection
+				req.Body = &expectContinueReader{readCloser: req.Body, resp: w}
+			}
+			req.Header.Del("Expect")
+		} else if req.Header.get("Expect") != "" {
+			w.sendExpectationFailed()
+			break
+		}
+
+		// HTTP cannot have multiple simultaneous active requests.[*]
+		// Until the server replies to this request, it can't read another,
+		// so we might as well run the handler in this goroutine.
+		// [*] Not strictly true: HTTP pipelining.  We could let them all process
+		// in parallel even if their responses need to be serialized.
+		serverHandler{c.server}.ServeHTTP(w, w.req)
+		if c.hijacked() {
+			return
+		}
+		w.finishRequest()
+		if w.closeAfterReply {
+			if w.requestBodyLimitHit {
+				c.closeWriteAndWait()
+			}
+			break
+		}
+		c.setState(c.rwc, StateIdle)
+	}
+}
+
+func (w *response) sendExpectationFailed() {
+	// TODO(bradfitz): let ServeHTTP handlers handle
+	// requests with non-standard expectation[s]? Seems
+	// theoretical at best, and doesn't fit into the
+	// current ServeHTTP model anyway.  We'd need to
+	// make the ResponseWriter an optional
+	// "ExpectReplier" interface or something.
+	//
+	// For now we'll just obey RFC 2616 14.20 which says
+	// "If a server receives a request containing an
+	// Expect field that includes an expectation-
+	// extension that it does not support, it MUST
+	// respond with a 417 (Expectation Failed) status."
+	w.Header().Set("Connection", "close")
+	w.WriteHeader(StatusExpectationFailed)
+	w.finishRequest()
+}
+
+// Hijack implements the Hijacker.Hijack method. Our response is both a ResponseWriter
+// and a Hijacker.
+func (w *response) Hijack() (rwc net.Conn, buf *bufio.ReadWriter, err error) {
+	if w.wroteHeader {
+		w.cw.flush()
+	}
+	// Release the bufioWriter that writes to the chunk writer, it is not
+	// used after a connection has been hijacked.
+	rwc, buf, err = w.conn.hijack()
+	if err == nil {
+		putBufioWriter(w.w)
+		w.w = nil
+	}
+	return rwc, buf, err
+}
+
+func (w *response) CloseNotify() <-chan bool {
+	return w.conn.closeNotify()
+}
+
+// The HandlerFunc type is an adapter to allow the use of
+// ordinary functions as HTTP handlers.  If f is a function
+// with the appropriate signature, HandlerFunc(f) is a
+// Handler object that calls f.
+type HandlerFunc func(ResponseWriter, *Request)
+
+// ServeHTTP calls f(w, r).
+func (f HandlerFunc) ServeHTTP(w ResponseWriter, r *Request) {
+	f(w, r)
+}
+
+// Helper handlers
+
+// Error replies to the request with the specified error message and HTTP code.
+// The error message should be plain text.
+func Error(w ResponseWriter, error string, code int) {
+	w.Header().Set("Content-Type", "text/plain; charset=utf-8")
+	w.WriteHeader(code)
+	fmt.Fprintln(w, error)
+}
+
+// NotFound replies to the request with an HTTP 404 not found error.
+func NotFound(w ResponseWriter, r *Request) { Error(w, "404 page not found", StatusNotFound) }
+
+// NotFoundHandler returns a simple request handler
+// that replies to each request with a ``404 page not found'' reply.
+func NotFoundHandler() Handler { return HandlerFunc(NotFound) }
+
+// StripPrefix returns a handler that serves HTTP requests
+// by removing the given prefix from the request URL's Path
+// and invoking the handler h. StripPrefix handles a
+// request for a path that doesn't begin with prefix by
+// replying with an HTTP 404 not found error.
+func StripPrefix(prefix string, h Handler) Handler {
+	if prefix == "" {
+		return h
+	}
+	return HandlerFunc(func(w ResponseWriter, r *Request) {
+		if p := strings.TrimPrefix(r.URL.Path, prefix); len(p) < len(r.URL.Path) {
+			r.URL.Path = p
+			h.ServeHTTP(w, r)
+		} else {
+			NotFound(w, r)
+		}
+	})
+}
+
+// Redirect replies to the request with a redirect to url,
+// which may be a path relative to the request path.
+func Redirect(w ResponseWriter, r *Request, urlStr string, code int) {
+	if u, err := url.Parse(urlStr); err == nil {
+		// If url was relative, make absolute by
+		// combining with request path.
+		// The browser would probably do this for us,
+		// but doing it ourselves is more reliable.
+
+		// NOTE(rsc): RFC 2616 says that the Location
+		// line must be an absolute URI, like
+		// "http://www.google.com/redirect/",
+		// not a path like "/redirect/".
+		// Unfortunately, we don't know what to
+		// put in the host name section to get the
+		// client to connect to us again, so we can't
+		// know the right absolute URI to send back.
+		// Because of this problem, no one pays attention
+		// to the RFC; they all send back just a new path.
+		// So do we.
+		oldpath := r.URL.Path
+		if oldpath == "" { // should not happen, but avoid a crash if it does
+			oldpath = "/"
+		}
+		if u.Scheme == "" {
+			// no leading http://server
+			if urlStr == "" || urlStr[0] != '/' {
+				// make relative path absolute
+				olddir, _ := path.Split(oldpath)
+				urlStr = olddir + urlStr
+			}
+
+			var query string
+			if i := strings.Index(urlStr, "?"); i != -1 {
+				urlStr, query = urlStr[:i], urlStr[i:]
+			}
+
+			// clean up but preserve trailing slash
+			trailing := strings.HasSuffix(urlStr, "/")
+			urlStr = path.Clean(urlStr)
+			if trailing && !strings.HasSuffix(urlStr, "/") {
+				urlStr += "/"
+			}
+			urlStr += query
+		}
+	}
+
+	w.Header().Set("Location", urlStr)
+	w.WriteHeader(code)
+
+	// RFC2616 recommends that a short note "SHOULD" be included in the
+	// response because older user agents may not understand 301/307.
+	// Shouldn't send the response for POST or HEAD; that leaves GET.
+	if r.Method == "GET" {
+		note := "<a href=\"" + htmlEscape(urlStr) + "\">" + statusText[code] + "</a>.\n"
+		fmt.Fprintln(w, note)
+	}
+}
+
+var htmlReplacer = strings.NewReplacer(
+	"&", "&amp;",
+	"<", "&lt;",
+	">", "&gt;",
+	// "&#34;" is shorter than "&quot;".
+	`"`, "&#34;",
+	// "&#39;" is shorter than "&apos;" and apos was not in HTML until HTML5.
+	"'", "&#39;",
+)
+
+func htmlEscape(s string) string {
+	return htmlReplacer.Replace(s)
+}
+
+// Redirect to a fixed URL
+type redirectHandler struct {
+	url  string
+	code int
+}
+
+func (rh *redirectHandler) ServeHTTP(w ResponseWriter, r *Request) {
+	Redirect(w, r, rh.url, rh.code)
+}
+
+// RedirectHandler returns a request handler that redirects
+// each request it receives to the given url using the given
+// status code.
+func RedirectHandler(url string, code int) Handler {
+	return &redirectHandler{url, code}
+}
+
+// ServeMux is an HTTP request multiplexer.
+// It matches the URL of each incoming request against a list of registered
+// patterns and calls the handler for the pattern that
+// most closely matches the URL.
+//
+// Patterns name fixed, rooted paths, like "/favicon.ico",
+// or rooted subtrees, like "/images/" (note the trailing slash).
+// Longer patterns take precedence over shorter ones, so that
+// if there are handlers registered for both "/images/"
+// and "/images/thumbnails/", the latter handler will be
+// called for paths beginning "/images/thumbnails/" and the
+// former will receive requests for any other paths in the
+// "/images/" subtree.
+//
+// Note that since a pattern ending in a slash names a rooted subtree,
+// the pattern "/" matches all paths not matched by other registered
+// patterns, not just the URL with Path == "/".
+//
+// Patterns may optionally begin with a host name, restricting matches to
+// URLs on that host only.  Host-specific patterns take precedence over
+// general patterns, so that a handler might register for the two patterns
+// "/codesearch" and "codesearch.google.com/" without also taking over
+// requests for "http://www.google.com/".
+//
+// ServeMux also takes care of sanitizing the URL request path,
+// redirecting any request containing . or .. elements to an
+// equivalent .- and ..-free URL.
+type ServeMux struct {
+	mu    sync.RWMutex
+	m     map[string]muxEntry
+	hosts bool // whether any patterns contain hostnames
+}
+
+type muxEntry struct {
+	explicit bool
+	h        Handler
+	pattern  string
+}
+
+// NewServeMux allocates and returns a new ServeMux.
+func NewServeMux() *ServeMux { return &ServeMux{m: make(map[string]muxEntry)} }
+
+// DefaultServeMux is the default ServeMux used by Serve.
+var DefaultServeMux = NewServeMux()
+
+// Does path match pattern?
+func pathMatch(pattern, path string) bool {
+	if len(pattern) == 0 {
+		// should not happen
+		return false
+	}
+	n := len(pattern)
+	if pattern[n-1] != '/' {
+		return pattern == path
+	}
+	return len(path) >= n && path[0:n] == pattern
+}
+
+// Return the canonical path for p, eliminating . and .. elements.
+func cleanPath(p string) string {
+	if p == "" {
+		return "/"
+	}
+	if p[0] != '/' {
+		p = "/" + p
+	}
+	np := path.Clean(p)
+	// path.Clean removes trailing slash except for root;
+	// put the trailing slash back if necessary.
+	if p[len(p)-1] == '/' && np != "/" {
+		np += "/"
+	}
+	return np
+}
+
+// Find a handler on a handler map given a path string
+// Most-specific (longest) pattern wins
+func (mux *ServeMux) match(path string) (h Handler, pattern string) {
+	var n = 0
+	for k, v := range mux.m {
+		if !pathMatch(k, path) {
+			continue
+		}
+		if h == nil || len(k) > n {
+			n = len(k)
+			h = v.h
+			pattern = v.pattern
+		}
+	}
+	return
+}
+
+// Handler returns the handler to use for the given request,
+// consulting r.Method, r.Host, and r.URL.Path. It always returns
+// a non-nil handler. If the path is not in its canonical form, the
+// handler will be an internally-generated handler that redirects
+// to the canonical path.
+//
+// Handler also returns the registered pattern that matches the
+// request or, in the case of internally-generated redirects,
+// the pattern that will match after following the redirect.
+//
+// If there is no registered handler that applies to the request,
+// Handler returns a ``page not found'' handler and an empty pattern.
+func (mux *ServeMux) Handler(r *Request) (h Handler, pattern string) {
+	if r.Method != "CONNECT" {
+		if p := cleanPath(r.URL.Path); p != r.URL.Path {
+			_, pattern = mux.handler(r.Host, p)
+			url := *r.URL
+			url.Path = p
+			return RedirectHandler(url.String(), StatusMovedPermanently), pattern
+		}
+	}
+
+	return mux.handler(r.Host, r.URL.Path)
+}
+
+// handler is the main implementation of Handler.
+// The path is known to be in canonical form, except for CONNECT methods.
+func (mux *ServeMux) handler(host, path string) (h Handler, pattern string) {
+	mux.mu.RLock()
+	defer mux.mu.RUnlock()
+
+	// Host-specific pattern takes precedence over generic ones
+	if mux.hosts {
+		h, pattern = mux.match(host + path)
+	}
+	if h == nil {
+		h, pattern = mux.match(path)
+	}
+	if h == nil {
+		h, pattern = NotFoundHandler(), ""
+	}
+	return
+}
+
+// ServeHTTP dispatches the request to the handler whose
+// pattern most closely matches the request URL.
+func (mux *ServeMux) ServeHTTP(w ResponseWriter, r *Request) {
+	if r.RequestURI == "*" {
+		if r.ProtoAtLeast(1, 1) {
+			w.Header().Set("Connection", "close")
+		}
+		w.WriteHeader(StatusBadRequest)
+		return
+	}
+	h, _ := mux.Handler(r)
+	h.ServeHTTP(w, r)
+}
+
+// Handle registers the handler for the given pattern.
+// If a handler already exists for pattern, Handle panics.
+func (mux *ServeMux) Handle(pattern string, handler Handler) {
+	mux.mu.Lock()
+	defer mux.mu.Unlock()
+
+	if pattern == "" {
+		panic("http: invalid pattern " + pattern)
+	}
+	if handler == nil {
+		panic("http: nil handler")
+	}
+	if mux.m[pattern].explicit {
+		panic("http: multiple registrations for " + pattern)
+	}
+
+	mux.m[pattern] = muxEntry{explicit: true, h: handler, pattern: pattern}
+
+	if pattern[0] != '/' {
+		mux.hosts = true
+	}
+
+	// Helpful behavior:
+	// If pattern is /tree/, insert an implicit permanent redirect for /tree.
+	// It can be overridden by an explicit registration.
+	n := len(pattern)
+	if n > 0 && pattern[n-1] == '/' && !mux.m[pattern[0:n-1]].explicit {
+		// If pattern contains a host name, strip it and use remaining
+		// path for redirect.
+		path := pattern
+		if pattern[0] != '/' {
+			// In pattern, at least the last character is a '/', so
+			// strings.Index can't be -1.
+			path = pattern[strings.Index(pattern, "/"):]
+		}
+		mux.m[pattern[0:n-1]] = muxEntry{h: RedirectHandler(path, StatusMovedPermanently), pattern: pattern}
+	}
+}
+
+// HandleFunc registers the handler function for the given pattern.
+func (mux *ServeMux) HandleFunc(pattern string, handler func(ResponseWriter, *Request)) {
+	mux.Handle(pattern, HandlerFunc(handler))
+}
+
+// Handle registers the handler for the given pattern
+// in the DefaultServeMux.
+// The documentation for ServeMux explains how patterns are matched.
+func Handle(pattern string, handler Handler) { DefaultServeMux.Handle(pattern, handler) }
+
+// HandleFunc registers the handler function for the given pattern
+// in the DefaultServeMux.
+// The documentation for ServeMux explains how patterns are matched.
+func HandleFunc(pattern string, handler func(ResponseWriter, *Request)) {
+	DefaultServeMux.HandleFunc(pattern, handler)
+}
+
+// Serve accepts incoming HTTP connections on the listener l,
+// creating a new service goroutine for each.  The service goroutines
+// read requests and then call handler to reply to them.
+// Handler is typically nil, in which case the DefaultServeMux is used.
+func Serve(l net.Listener, handler Handler) error {
+	srv := &Server{Handler: handler}
+	return srv.Serve(l)
+}
+
+// A Server defines parameters for running an HTTP server.
+// The zero value for Server is a valid configuration.
+type Server struct {
+	Addr           string        // TCP address to listen on, ":http" if empty
+	Handler        Handler       // handler to invoke, http.DefaultServeMux if nil
+	ReadTimeout    time.Duration // maximum duration before timing out read of the request
+	WriteTimeout   time.Duration // maximum duration before timing out write of the response
+	MaxHeaderBytes int           // maximum size of request headers, DefaultMaxHeaderBytes if 0
+	TLSConfig      *tls.Config   // optional TLS config, used by ListenAndServeTLS
+
+	// TLSNextProto optionally specifies a function to take over
+	// ownership of the provided TLS connection when an NPN
+	// protocol upgrade has occurred.  The map key is the protocol
+	// name negotiated. The Handler argument should be used to
+	// handle HTTP requests and will initialize the Request's TLS
+	// and RemoteAddr if not already set.  The connection is
+	// automatically closed when the function returns.
+	TLSNextProto map[string]func(*Server, *tls.Conn, Handler)
+
+	// ConnState specifies an optional callback function that is
+	// called when a client connection changes state. See the
+	// ConnState type and associated constants for details.
+	ConnState func(net.Conn, ConnState)
+
+	// ErrorLog specifies an optional logger for errors accepting
+	// connections and unexpected behavior from handlers.
+	// If nil, logging goes to os.Stderr via the log package's
+	// standard logger.
+	ErrorLog *log.Logger
+
+	disableKeepAlives int32 // accessed atomically.
+}
+
+// A ConnState represents the state of a client connection to a server.
+// It's used by the optional Server.ConnState hook.
+type ConnState int
+
+const (
+	// StateNew represents a new connection that is expected to
+	// send a request immediately. Connections begin at this
+	// state and then transition to either StateActive or
+	// StateClosed.
+	StateNew ConnState = iota
+
+	// StateActive represents a connection that has read 1 or more
+	// bytes of a request. The Server.ConnState hook for
+	// StateActive fires before the request has entered a handler
+	// and doesn't fire again until the request has been
+	// handled. After the request is handled, the state
+	// transitions to StateClosed, StateHijacked, or StateIdle.
+	StateActive
+
+	// StateIdle represents a connection that has finished
+	// handling a request and is in the keep-alive state, waiting
+	// for a new request. Connections transition from StateIdle
+	// to either StateActive or StateClosed.
+	StateIdle
+
+	// StateHijacked represents a hijacked connection.
+	// This is a terminal state. It does not transition to StateClosed.
+	StateHijacked
+
+	// StateClosed represents a closed connection.
+	// This is a terminal state. Hijacked connections do not
+	// transition to StateClosed.
+	StateClosed
+)
+
+var stateName = map[ConnState]string{
+	StateNew:      "new",
+	StateActive:   "active",
+	StateIdle:     "idle",
+	StateHijacked: "hijacked",
+	StateClosed:   "closed",
+}
+
+func (c ConnState) String() string {
+	return stateName[c]
+}
+
+// serverHandler delegates to either the server's Handler or
+// DefaultServeMux and also handles "OPTIONS *" requests.
+type serverHandler struct {
+	srv *Server
+}
+
+func (sh serverHandler) ServeHTTP(rw ResponseWriter, req *Request) {
+	handler := sh.srv.Handler
+	if handler == nil {
+		handler = DefaultServeMux
+	}
+	if req.RequestURI == "*" && req.Method == "OPTIONS" {
+		handler = globalOptionsHandler{}
+	}
+	handler.ServeHTTP(rw, req)
+}
+
+// ListenAndServe listens on the TCP network address srv.Addr and then
+// calls Serve to handle requests on incoming connections.  If
+// srv.Addr is blank, ":http" is used.
+func (srv *Server) ListenAndServe() error {
+	addr := srv.Addr
+	if addr == "" {
+		addr = ":http"
+	}
+	ln, err := net.Listen("tcp", addr)
+	if err != nil {
+		return err
+	}
+	return srv.Serve(tcpKeepAliveListener{ln.(*net.TCPListener)})
+}
+
+// Serve accepts incoming connections on the Listener l, creating a
+// new service goroutine for each.  The service goroutines read requests and
+// then call srv.Handler to reply to them.
+func (srv *Server) Serve(l net.Listener) error {
+	defer l.Close()
+	var tempDelay time.Duration // how long to sleep on accept failure
+	for {
+		rw, e := l.Accept()
+		if e != nil {
+			if ne, ok := e.(net.Error); ok && ne.Temporary() {
+				if tempDelay == 0 {
+					tempDelay = 5 * time.Millisecond
+				} else {
+					tempDelay *= 2
+				}
+				if max := 1 * time.Second; tempDelay > max {
+					tempDelay = max
+				}
+				srv.logf("http: Accept error: %v; retrying in %v", e, tempDelay)
+				time.Sleep(tempDelay)
+				continue
+			}
+			return e
+		}
+		tempDelay = 0
+		c, err := srv.newConn(rw)
+		if err != nil {
+			continue
+		}
+		c.setState(c.rwc, StateNew) // before Serve can return
+		go c.serve()
+	}
+}
+
+func (s *Server) doKeepAlives() bool {
+	return atomic.LoadInt32(&s.disableKeepAlives) == 0
+}
+
+// SetKeepAlivesEnabled controls whether HTTP keep-alives are enabled.
+// By default, keep-alives are always enabled. Only very
+// resource-constrained environments or servers in the process of
+// shutting down should disable them.
+func (s *Server) SetKeepAlivesEnabled(v bool) {
+	if v {
+		atomic.StoreInt32(&s.disableKeepAlives, 0)
+	} else {
+		atomic.StoreInt32(&s.disableKeepAlives, 1)
+	}
+}
+
+func (s *Server) logf(format string, args ...interface{}) {
+	if s.ErrorLog != nil {
+		s.ErrorLog.Printf(format, args...)
+	} else {
+		log.Printf(format, args...)
+	}
+}
+
+// ListenAndServe listens on the TCP network address addr
+// and then calls Serve with handler to handle requests
+// on incoming connections.  Handler is typically nil,
+// in which case the DefaultServeMux is used.
+//
+// A trivial example server is:
+//
+//	package main
+//
+//	import (
+//		"io"
+//		"net/http"
+//		"log"
+//	)
+//
+//	// hello world, the web server
+//	func HelloServer(w http.ResponseWriter, req *http.Request) {
+//		io.WriteString(w, "hello, world!\n")
+//	}
+//
+//	func main() {
+//		http.HandleFunc("/hello", HelloServer)
+//		err := http.ListenAndServe(":12345", nil)
+//		if err != nil {
+//			log.Fatal("ListenAndServe: ", err)
+//		}
+//	}
+func ListenAndServe(addr string, handler Handler) error {
+	server := &Server{Addr: addr, Handler: handler}
+	return server.ListenAndServe()
+}
+
+// ListenAndServeTLS acts identically to ListenAndServe, except that it
+// expects HTTPS connections. Additionally, files containing a certificate and
+// matching private key for the server must be provided. If the certificate
+// is signed by a certificate authority, the certFile should be the concatenation
+// of the server's certificate followed by the CA's certificate.
+//
+// A trivial example server is:
+//
+//	import (
+//		"log"
+//		"net/http"
+//	)
+//
+//	func handler(w http.ResponseWriter, req *http.Request) {
+//		w.Header().Set("Content-Type", "text/plain")
+//		w.Write([]byte("This is an example server.\n"))
+//	}
+//
+//	func main() {
+//		http.HandleFunc("/", handler)
+//		log.Printf("About to listen on 10443. Go to https://127.0.0.1:10443/")
+//		err := http.ListenAndServeTLS(":10443", "cert.pem", "key.pem", nil)
+//		if err != nil {
+//			log.Fatal(err)
+//		}
+//	}
+//
+// One can use generate_cert.go in crypto/tls to generate cert.pem and key.pem.
+func ListenAndServeTLS(addr string, certFile string, keyFile string, handler Handler) error {
+	server := &Server{Addr: addr, Handler: handler}
+	return server.ListenAndServeTLS(certFile, keyFile)
+}
+
+// ListenAndServeTLS listens on the TCP network address srv.Addr and
+// then calls Serve to handle requests on incoming TLS connections.
+//
+// Filenames containing a certificate and matching private key for
+// the server must be provided. If the certificate is signed by a
+// certificate authority, the certFile should be the concatenation
+// of the server's certificate followed by the CA's certificate.
+//
+// If srv.Addr is blank, ":https" is used.
+func (srv *Server) ListenAndServeTLS(certFile, keyFile string) error {
+	addr := srv.Addr
+	if addr == "" {
+		addr = ":https"
+	}
+	config := &tls.Config{}
+	if srv.TLSConfig != nil {
+		*config = *srv.TLSConfig
+	}
+	if config.NextProtos == nil {
+		config.NextProtos = []string{"http/1.1"}
+	}
+
+	var err error
+	config.Certificates = make([]tls.Certificate, 1)
+	config.Certificates[0], err = tls.LoadX509KeyPair(certFile, keyFile)
+	if err != nil {
+		return err
+	}
+
+	ln, err := net.Listen("tcp", addr)
+	if err != nil {
+		return err
+	}
+
+	tlsListener := tls.NewListener(tcpKeepAliveListener{ln.(*net.TCPListener)}, config)
+	return srv.Serve(tlsListener)
+}
+
+// TimeoutHandler returns a Handler that runs h with the given time limit.
+//
+// The new Handler calls h.ServeHTTP to handle each request, but if a
+// call runs for longer than its time limit, the handler responds with
+// a 503 Service Unavailable error and the given message in its body.
+// (If msg is empty, a suitable default message will be sent.)
+// After such a timeout, writes by h to its ResponseWriter will return
+// ErrHandlerTimeout.
+func TimeoutHandler(h Handler, dt time.Duration, msg string) Handler {
+	f := func() <-chan time.Time {
+		return time.After(dt)
+	}
+	return &timeoutHandler{h, f, msg}
+}
+
+// ErrHandlerTimeout is returned on ResponseWriter Write calls
+// in handlers which have timed out.
+var ErrHandlerTimeout = errors.New("http: Handler timeout")
+
+type timeoutHandler struct {
+	handler Handler
+	timeout func() <-chan time.Time // returns channel producing a timeout
+	body    string
+}
+
+func (h *timeoutHandler) errorBody() string {
+	if h.body != "" {
+		return h.body
+	}
+	return "<html><head><title>Timeout</title></head><body><h1>Timeout</h1></body></html>"
+}
+
+func (h *timeoutHandler) ServeHTTP(w ResponseWriter, r *Request) {
+	done := make(chan bool, 1)
+	tw := &timeoutWriter{w: w}
+	go func() {
+		h.handler.ServeHTTP(tw, r)
+		done <- true
+	}()
+	select {
+	case <-done:
+		return
+	case <-h.timeout():
+		tw.mu.Lock()
+		defer tw.mu.Unlock()
+		if !tw.wroteHeader {
+			tw.w.WriteHeader(StatusServiceUnavailable)
+			tw.w.Write([]byte(h.errorBody()))
+		}
+		tw.timedOut = true
+	}
+}
+
+type timeoutWriter struct {
+	w ResponseWriter
+
+	mu          sync.Mutex
+	timedOut    bool
+	wroteHeader bool
+}
+
+func (tw *timeoutWriter) Header() Header {
+	return tw.w.Header()
+}
+
+func (tw *timeoutWriter) Write(p []byte) (int, error) {
+	tw.mu.Lock()
+	defer tw.mu.Unlock()
+	tw.wroteHeader = true // implicitly at least
+	if tw.timedOut {
+		return 0, ErrHandlerTimeout
+	}
+	return tw.w.Write(p)
+}
+
+func (tw *timeoutWriter) WriteHeader(code int) {
+	tw.mu.Lock()
+	defer tw.mu.Unlock()
+	if tw.timedOut || tw.wroteHeader {
+		return
+	}
+	tw.wroteHeader = true
+	tw.w.WriteHeader(code)
+}
+
+// tcpKeepAliveListener sets TCP keep-alive timeouts on accepted
+// connections. It's used by ListenAndServe and ListenAndServeTLS so
+// dead TCP connections (e.g. closing laptop mid-download) eventually
+// go away.
+type tcpKeepAliveListener struct {
+	*net.TCPListener
+}
+
+func (ln tcpKeepAliveListener) Accept() (c net.Conn, err error) {
+	tc, err := ln.AcceptTCP()
+	if err != nil {
+		return
+	}
+	tc.SetKeepAlive(true)
+	tc.SetKeepAlivePeriod(3 * time.Minute)
+	return tc, nil
+}
+
+// globalOptionsHandler responds to "OPTIONS *" requests.
+type globalOptionsHandler struct{}
+
+func (globalOptionsHandler) ServeHTTP(w ResponseWriter, r *Request) {
+	w.Header().Set("Content-Length", "0")
+	if r.ContentLength != 0 {
+		// Read up to 4KB of OPTIONS body (as mentioned in the
+		// spec as being reserved for future use), but anything
+		// over that is considered a waste of server resources
+		// (or an attack) and we abort and close the connection,
+		// courtesy of MaxBytesReader's EOF behavior.
+		mb := MaxBytesReader(w, r.Body, 4<<10)
+		io.Copy(ioutil.Discard, mb)
+	}
+}
+
+type eofReaderWithWriteTo struct{}
+
+func (eofReaderWithWriteTo) WriteTo(io.Writer) (int64, error) { return 0, nil }
+func (eofReaderWithWriteTo) Read([]byte) (int, error)         { return 0, io.EOF }
+
+// eofReader is a non-nil io.ReadCloser that always returns EOF.
+// It has a WriteTo method so io.Copy won't need a buffer.
+var eofReader = &struct {
+	eofReaderWithWriteTo
+	io.Closer
+}{
+	eofReaderWithWriteTo{},
+	ioutil.NopCloser(nil),
+}
+
+// Verify that an io.Copy from an eofReader won't require a buffer.
+var _ io.WriterTo = eofReader
+
+// initNPNRequest is an HTTP handler that initializes certain
+// uninitialized fields in its *Request. Such partially-initialized
+// Requests come from NPN protocol handlers.
+type initNPNRequest struct {
+	c *tls.Conn
+	h serverHandler
+}
+
+func (h initNPNRequest) ServeHTTP(rw ResponseWriter, req *Request) {
+	if req.TLS == nil {
+		req.TLS = &tls.ConnectionState{}
+		*req.TLS = h.c.ConnectionState()
+	}
+	if req.Body == nil {
+		req.Body = eofReader
+	}
+	if req.RemoteAddr == "" {
+		req.RemoteAddr = h.c.RemoteAddr().String()
+	}
+	h.h.ServeHTTP(rw, req)
+}
+
+// loggingConn is used for debugging.
+type loggingConn struct {
+	name string
+	net.Conn
+}
+
+var (
+	uniqNameMu   sync.Mutex
+	uniqNameNext = make(map[string]int)
+)
+
+func newLoggingConn(baseName string, c net.Conn) net.Conn {
+	uniqNameMu.Lock()
+	defer uniqNameMu.Unlock()
+	uniqNameNext[baseName]++
+	return &loggingConn{
+		name: fmt.Sprintf("%s-%d", baseName, uniqNameNext[baseName]),
+		Conn: c,
+	}
+}
+
+func (c *loggingConn) Write(p []byte) (n int, err error) {
+	log.Printf("%s.Write(%d) = ....", c.name, len(p))
+	n, err = c.Conn.Write(p)
+	log.Printf("%s.Write(%d) = %d, %v", c.name, len(p), n, err)
+	return
+}
+
+func (c *loggingConn) Read(p []byte) (n int, err error) {
+	log.Printf("%s.Read(%d) = ....", c.name, len(p))
+	n, err = c.Conn.Read(p)
+	log.Printf("%s.Read(%d) = %d, %v", c.name, len(p), n, err)
+	return
+}
+
+func (c *loggingConn) Close() (err error) {
+	log.Printf("%s.Close() = ...", c.name)
+	err = c.Conn.Close()
+	log.Printf("%s.Close() = %v", c.name, err)
+	return
+}
diff --git a/src/net/http/sniff.go b/src/net/http/sniff.go
new file mode 100644
index 000000000..68f519b05
--- /dev/null
+++ b/src/net/http/sniff.go
@@ -0,0 +1,214 @@
+// Copyright 2011 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package http
+
+import (
+	"bytes"
+	"encoding/binary"
+)
+
+// The algorithm uses at most sniffLen bytes to make its decision.
+const sniffLen = 512
+
+// DetectContentType implements the algorithm described
+// at http://mimesniff.spec.whatwg.org/ to determine the
+// Content-Type of the given data.  It considers at most the
+// first 512 bytes of data.  DetectContentType always returns
+// a valid MIME type: if it cannot determine a more specific one, it
+// returns "application/octet-stream".
+func DetectContentType(data []byte) string {
+	if len(data) > sniffLen {
+		data = data[:sniffLen]
+	}
+
+	// Index of the first non-whitespace byte in data.
+	firstNonWS := 0
+	for ; firstNonWS < len(data) && isWS(data[firstNonWS]); firstNonWS++ {
+	}
+
+	for _, sig := range sniffSignatures {
+		if ct := sig.match(data, firstNonWS); ct != "" {
+			return ct
+		}
+	}
+
+	return "application/octet-stream" // fallback
+}
+
+func isWS(b byte) bool {
+	return bytes.IndexByte([]byte("\t\n\x0C\r "), b) != -1
+}
+
+type sniffSig interface {
+	// match returns the MIME type of the data, or "" if unknown.
+	match(data []byte, firstNonWS int) string
+}
+
+// Data matching the table in section 6.
+var sniffSignatures = []sniffSig{
+	htmlSig("<!DOCTYPE HTML"),
+	htmlSig("<HTML"),
+	htmlSig("<HEAD"),
+	htmlSig("<SCRIPT"),
+	htmlSig("<IFRAME"),
+	htmlSig("<H1"),
+	htmlSig("<DIV"),
+	htmlSig("<FONT"),
+	htmlSig("<TABLE"),
+	htmlSig("<A"),
+	htmlSig("<STYLE"),
+	htmlSig("<TITLE"),
+	htmlSig("<B"),
+	htmlSig("<BODY"),
+	htmlSig("<BR"),
+	htmlSig("<P"),
+	htmlSig("<!--"),
+
+	&maskedSig{mask: []byte("\xFF\xFF\xFF\xFF\xFF"), pat: []byte("<?xml"), skipWS: true, ct: "text/xml; charset=utf-8"},
+
+	&exactSig{[]byte("%PDF-"), "application/pdf"},
+	&exactSig{[]byte("%!PS-Adobe-"), "application/postscript"},
+
+	// UTF BOMs.
+	&maskedSig{mask: []byte("\xFF\xFF\x00\x00"), pat: []byte("\xFE\xFF\x00\x00"), ct: "text/plain; charset=utf-16be"},
+	&maskedSig{mask: []byte("\xFF\xFF\x00\x00"), pat: []byte("\xFF\xFE\x00\x00"), ct: "text/plain; charset=utf-16le"},
+	&maskedSig{mask: []byte("\xFF\xFF\xFF\x00"), pat: []byte("\xEF\xBB\xBF\x00"), ct: "text/plain; charset=utf-8"},
+
+	&exactSig{[]byte("GIF87a"), "image/gif"},
+	&exactSig{[]byte("GIF89a"), "image/gif"},
+	&exactSig{[]byte("\x89\x50\x4E\x47\x0D\x0A\x1A\x0A"), "image/png"},
+	&exactSig{[]byte("\xFF\xD8\xFF"), "image/jpeg"},
+	&exactSig{[]byte("BM"), "image/bmp"},
+	&maskedSig{
+		mask: []byte("\xFF\xFF\xFF\xFF\x00\x00\x00\x00\xFF\xFF\xFF\xFF\xFF\xFF"),
+		pat:  []byte("RIFF\x00\x00\x00\x00WEBPVP"),
+		ct:   "image/webp",
+	},
+	&exactSig{[]byte("\x00\x00\x01\x00"), "image/vnd.microsoft.icon"},
+	&exactSig{[]byte("\x4F\x67\x67\x53\x00"), "application/ogg"},
+	&maskedSig{
+		mask: []byte("\xFF\xFF\xFF\xFF\x00\x00\x00\x00\xFF\xFF\xFF\xFF"),
+		pat:  []byte("RIFF\x00\x00\x00\x00WAVE"),
+		ct:   "audio/wave",
+	},
+	&exactSig{[]byte("\x1A\x45\xDF\xA3"), "video/webm"},
+	&exactSig{[]byte("\x52\x61\x72\x20\x1A\x07\x00"), "application/x-rar-compressed"},
+	&exactSig{[]byte("\x50\x4B\x03\x04"), "application/zip"},
+	&exactSig{[]byte("\x1F\x8B\x08"), "application/x-gzip"},
+
+	// TODO(dsymonds): Re-enable this when the spec is sorted w.r.t. MP4.
+	//mp4Sig(0),
+
+	textSig(0), // should be last
+}
+
+type exactSig struct {
+	sig []byte
+	ct  string
+}
+
+func (e *exactSig) match(data []byte, firstNonWS int) string {
+	if bytes.HasPrefix(data, e.sig) {
+		return e.ct
+	}
+	return ""
+}
+
+type maskedSig struct {
+	mask, pat []byte
+	skipWS    bool
+	ct        string
+}
+
+func (m *maskedSig) match(data []byte, firstNonWS int) string {
+	if m.skipWS {
+		data = data[firstNonWS:]
+	}
+	if len(data) < len(m.mask) {
+		return ""
+	}
+	for i, mask := range m.mask {
+		db := data[i] & mask
+		if db != m.pat[i] {
+			return ""
+		}
+	}
+	return m.ct
+}
+
+type htmlSig []byte
+
+func (h htmlSig) match(data []byte, firstNonWS int) string {
+	data = data[firstNonWS:]
+	if len(data) < len(h)+1 {
+		return ""
+	}
+	for i, b := range h {
+		db := data[i]
+		if 'A' <= b && b <= 'Z' {
+			db &= 0xDF
+		}
+		if b != db {
+			return ""
+		}
+	}
+	// Next byte must be space or right angle bracket.
+	if db := data[len(h)]; db != ' ' && db != '>' {
+		return ""
+	}
+	return "text/html; charset=utf-8"
+}
+
+type mp4Sig int
+
+func (mp4Sig) match(data []byte, firstNonWS int) string {
+	// c.f. section 6.1.
+	if len(data) < 8 {
+		return ""
+	}
+	boxSize := int(binary.BigEndian.Uint32(data[:4]))
+	if boxSize%4 != 0 || len(data) < boxSize {
+		return ""
+	}
+	if !bytes.Equal(data[4:8], []byte("ftyp")) {
+		return ""
+	}
+	for st := 8; st < boxSize; st += 4 {
+		if st == 12 {
+			// minor version number
+			continue
+		}
+		seg := string(data[st : st+3])
+		switch seg {
+		case "mp4", "iso", "M4V", "M4P", "M4B":
+			return "video/mp4"
+			/* The remainder are not in the spec.
+			case "M4A":
+				return "audio/mp4"
+			case "3gp":
+				return "video/3gpp"
+			case "jp2":
+				return "image/jp2" // JPEG 2000
+			*/
+		}
+	}
+	return ""
+}
+
+type textSig int
+
+func (textSig) match(data []byte, firstNonWS int) string {
+	// c.f. section 5, step 4.
+	for _, b := range data[firstNonWS:] {
+		switch {
+		case 0x00 <= b && b <= 0x08,
+			b == 0x0B,
+			0x0E <= b && b <= 0x1A,
+			0x1C <= b && b <= 0x1F:
+			return ""
+		}
+	}
+	return "text/plain; charset=utf-8"
+}
diff --git a/src/net/http/sniff_test.go b/src/net/http/sniff_test.go
new file mode 100644
index 000000000..24ca27afc
--- /dev/null
+++ b/src/net/http/sniff_test.go
@@ -0,0 +1,171 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package http_test
+
+import (
+	"bytes"
+	"fmt"
+	"io"
+	"io/ioutil"
+	"log"
+	. "net/http"
+	"net/http/httptest"
+	"reflect"
+	"strconv"
+	"strings"
+	"testing"
+)
+
+var sniffTests = []struct {
+	desc        string
+	data        []byte
+	contentType string
+}{
+	// Some nonsense.
+	{"Empty", []byte{}, "text/plain; charset=utf-8"},
+	{"Binary", []byte{1, 2, 3}, "application/octet-stream"},
+
+	{"HTML document #1", []byte(`<HtMl><bOdY>blah blah blah</body></html>`), "text/html; charset=utf-8"},
+	{"HTML document #2", []byte(`<HTML></HTML>`), "text/html; charset=utf-8"},
+	{"HTML document #3 (leading whitespace)", []byte(`   <!DOCTYPE HTML>...`), "text/html; charset=utf-8"},
+	{"HTML document #4 (leading CRLF)", []byte("\r\n<html>..."), "text/html; charset=utf-8"},
+
+	{"Plain text", []byte(`This is not HTML. It has ☃ though.`), "text/plain; charset=utf-8"},
+
+	{"XML", []byte("\n<?xml!"), "text/xml; charset=utf-8"},
+
+	// Image types.
+	{"GIF 87a", []byte(`GIF87a`), "image/gif"},
+	{"GIF 89a", []byte(`GIF89a...`), "image/gif"},
+
+	// TODO(dsymonds): Re-enable this when the spec is sorted w.r.t. MP4.
+	//{"MP4 video", []byte("\x00\x00\x00\x18ftypmp42\x00\x00\x00\x00mp42isom<\x06t\xbfmdat"), "video/mp4"},
+	//{"MP4 audio", []byte("\x00\x00\x00\x20ftypM4A \x00\x00\x00\x00M4A mp42isom\x00\x00\x00\x00"), "audio/mp4"},
+}
+
+func TestDetectContentType(t *testing.T) {
+	for _, tt := range sniffTests {
+		ct := DetectContentType(tt.data)
+		if ct != tt.contentType {
+			t.Errorf("%v: DetectContentType = %q, want %q", tt.desc, ct, tt.contentType)
+		}
+	}
+}
+
+func TestServerContentType(t *testing.T) {
+	defer afterTest(t)
+	ts := httptest.NewServer(HandlerFunc(func(w ResponseWriter, r *Request) {
+		i, _ := strconv.Atoi(r.FormValue("i"))
+		tt := sniffTests[i]
+		n, err := w.Write(tt.data)
+		if n != len(tt.data) || err != nil {
+			log.Fatalf("%v: Write(%q) = %v, %v want %d, nil", tt.desc, tt.data, n, err, len(tt.data))
+		}
+	}))
+	defer ts.Close()
+
+	for i, tt := range sniffTests {
+		resp, err := Get(ts.URL + "/?i=" + strconv.Itoa(i))
+		if err != nil {
+			t.Errorf("%v: %v", tt.desc, err)
+			continue
+		}
+		if ct := resp.Header.Get("Content-Type"); ct != tt.contentType {
+			t.Errorf("%v: Content-Type = %q, want %q", tt.desc, ct, tt.contentType)
+		}
+		data, err := ioutil.ReadAll(resp.Body)
+		if err != nil {
+			t.Errorf("%v: reading body: %v", tt.desc, err)
+		} else if !bytes.Equal(data, tt.data) {
+			t.Errorf("%v: data is %q, want %q", tt.desc, data, tt.data)
+		}
+		resp.Body.Close()
+	}
+}
+
+// Issue 5953: shouldn't sniff if the handler set a Content-Type header,
+// even if it's the empty string.
+func TestServerIssue5953(t *testing.T) {
+	defer afterTest(t)
+	ts := httptest.NewServer(HandlerFunc(func(w ResponseWriter, r *Request) {
+		w.Header()["Content-Type"] = []string{""}
+		fmt.Fprintf(w, "<html><head></head><body>hi</body></html>")
+	}))
+	defer ts.Close()
+
+	resp, err := Get(ts.URL)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	got := resp.Header["Content-Type"]
+	want := []string{""}
+	if !reflect.DeepEqual(got, want) {
+		t.Errorf("Content-Type = %q; want %q", got, want)
+	}
+	resp.Body.Close()
+}
+
+func TestContentTypeWithCopy(t *testing.T) {
+	defer afterTest(t)
+
+	const (
+		input    = "\n<html>\n\t<head>\n"
+		expected = "text/html; charset=utf-8"
+	)
+
+	ts := httptest.NewServer(HandlerFunc(func(w ResponseWriter, r *Request) {
+		// Use io.Copy from a bytes.Buffer to trigger ReadFrom.
+		buf := bytes.NewBuffer([]byte(input))
+		n, err := io.Copy(w, buf)
+		if int(n) != len(input) || err != nil {
+			t.Errorf("io.Copy(w, %q) = %v, %v want %d, nil", input, n, err, len(input))
+		}
+	}))
+	defer ts.Close()
+
+	resp, err := Get(ts.URL)
+	if err != nil {
+		t.Fatalf("Get: %v", err)
+	}
+	if ct := resp.Header.Get("Content-Type"); ct != expected {
+		t.Errorf("Content-Type = %q, want %q", ct, expected)
+	}
+	data, err := ioutil.ReadAll(resp.Body)
+	if err != nil {
+		t.Errorf("reading body: %v", err)
+	} else if !bytes.Equal(data, []byte(input)) {
+		t.Errorf("data is %q, want %q", data, input)
+	}
+	resp.Body.Close()
+}
+
+func TestSniffWriteSize(t *testing.T) {
+	defer afterTest(t)
+	ts := httptest.NewServer(HandlerFunc(func(w ResponseWriter, r *Request) {
+		size, _ := strconv.Atoi(r.FormValue("size"))
+		written, err := io.WriteString(w, strings.Repeat("a", size))
+		if err != nil {
+			t.Errorf("write of %d bytes: %v", size, err)
+			return
+		}
+		if written != size {
+			t.Errorf("write of %d bytes wrote %d bytes", size, written)
+		}
+	}))
+	defer ts.Close()
+	for _, size := range []int{0, 1, 200, 600, 999, 1000, 1023, 1024, 512 << 10, 1 << 20} {
+		res, err := Get(fmt.Sprintf("%s/?size=%d", ts.URL, size))
+		if err != nil {
+			t.Fatalf("size %d: %v", size, err)
+		}
+		if _, err := io.Copy(ioutil.Discard, res.Body); err != nil {
+			t.Fatalf("size %d: io.Copy of body = %v", size, err)
+		}
+		if err := res.Body.Close(); err != nil {
+			t.Fatalf("size %d: body Close = %v", size, err)
+		}
+	}
+}
diff --git a/src/net/http/status.go b/src/net/http/status.go
new file mode 100644
index 000000000..d253bd5cb
--- /dev/null
+++ b/src/net/http/status.go
@@ -0,0 +1,120 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package http
+
+// HTTP status codes, defined in RFC 2616.
+const (
+	StatusContinue           = 100
+	StatusSwitchingProtocols = 101
+
+	StatusOK                   = 200
+	StatusCreated              = 201
+	StatusAccepted             = 202
+	StatusNonAuthoritativeInfo = 203
+	StatusNoContent            = 204
+	StatusResetContent         = 205
+	StatusPartialContent       = 206
+
+	StatusMultipleChoices   = 300
+	StatusMovedPermanently  = 301
+	StatusFound             = 302
+	StatusSeeOther          = 303
+	StatusNotModified       = 304
+	StatusUseProxy          = 305
+	StatusTemporaryRedirect = 307
+
+	StatusBadRequest                   = 400
+	StatusUnauthorized                 = 401
+	StatusPaymentRequired              = 402
+	StatusForbidden                    = 403
+	StatusNotFound                     = 404
+	StatusMethodNotAllowed             = 405
+	StatusNotAcceptable                = 406
+	StatusProxyAuthRequired            = 407
+	StatusRequestTimeout               = 408
+	StatusConflict                     = 409
+	StatusGone                         = 410
+	StatusLengthRequired               = 411
+	StatusPreconditionFailed           = 412
+	StatusRequestEntityTooLarge        = 413
+	StatusRequestURITooLong            = 414
+	StatusUnsupportedMediaType         = 415
+	StatusRequestedRangeNotSatisfiable = 416
+	StatusExpectationFailed            = 417
+	StatusTeapot                       = 418
+
+	StatusInternalServerError     = 500
+	StatusNotImplemented          = 501
+	StatusBadGateway              = 502
+	StatusServiceUnavailable      = 503
+	StatusGatewayTimeout          = 504
+	StatusHTTPVersionNotSupported = 505
+
+	// New HTTP status codes from RFC 6585. Not exported yet in Go 1.1.
+	// See discussion at https://codereview.appspot.com/7678043/
+	statusPreconditionRequired          = 428
+	statusTooManyRequests               = 429
+	statusRequestHeaderFieldsTooLarge   = 431
+	statusNetworkAuthenticationRequired = 511
+)
+
+var statusText = map[int]string{
+	StatusContinue:           "Continue",
+	StatusSwitchingProtocols: "Switching Protocols",
+
+	StatusOK:                   "OK",
+	StatusCreated:              "Created",
+	StatusAccepted:             "Accepted",
+	StatusNonAuthoritativeInfo: "Non-Authoritative Information",
+	StatusNoContent:            "No Content",
+	StatusResetContent:         "Reset Content",
+	StatusPartialContent:       "Partial Content",
+
+	StatusMultipleChoices:   "Multiple Choices",
+	StatusMovedPermanently:  "Moved Permanently",
+	StatusFound:             "Found",
+	StatusSeeOther:          "See Other",
+	StatusNotModified:       "Not Modified",
+	StatusUseProxy:          "Use Proxy",
+	StatusTemporaryRedirect: "Temporary Redirect",
+
+	StatusBadRequest:                   "Bad Request",
+	StatusUnauthorized:                 "Unauthorized",
+	StatusPaymentRequired:              "Payment Required",
+	StatusForbidden:                    "Forbidden",
+	StatusNotFound:                     "Not Found",
+	StatusMethodNotAllowed:             "Method Not Allowed",
+	StatusNotAcceptable:                "Not Acceptable",
+	StatusProxyAuthRequired:            "Proxy Authentication Required",
+	StatusRequestTimeout:               "Request Timeout",
+	StatusConflict:                     "Conflict",
+	StatusGone:                         "Gone",
+	StatusLengthRequired:               "Length Required",
+	StatusPreconditionFailed:           "Precondition Failed",
+	StatusRequestEntityTooLarge:        "Request Entity Too Large",
+	StatusRequestURITooLong:            "Request URI Too Long",
+	StatusUnsupportedMediaType:         "Unsupported Media Type",
+	StatusRequestedRangeNotSatisfiable: "Requested Range Not Satisfiable",
+	StatusExpectationFailed:            "Expectation Failed",
+	StatusTeapot:                       "I'm a teapot",
+
+	StatusInternalServerError:     "Internal Server Error",
+	StatusNotImplemented:          "Not Implemented",
+	StatusBadGateway:              "Bad Gateway",
+	StatusServiceUnavailable:      "Service Unavailable",
+	StatusGatewayTimeout:          "Gateway Timeout",
+	StatusHTTPVersionNotSupported: "HTTP Version Not Supported",
+
+	statusPreconditionRequired:          "Precondition Required",
+	statusTooManyRequests:               "Too Many Requests",
+	statusRequestHeaderFieldsTooLarge:   "Request Header Fields Too Large",
+	statusNetworkAuthenticationRequired: "Network Authentication Required",
+}
+
+// StatusText returns a text for the HTTP status code. It returns the empty
+// string if the code is unknown.
+func StatusText(code int) string {
+	return statusText[code]
+}
diff --git a/src/net/http/testdata/file b/src/net/http/testdata/file
new file mode 100644
index 000000000..11f11f9be
--- /dev/null
+++ b/src/net/http/testdata/file
@@ -0,0 +1 @@
+0123456789
diff --git a/src/net/http/testdata/index.html b/src/net/http/testdata/index.html
new file mode 100644
index 000000000..da8e1e93d
--- /dev/null
+++ b/src/net/http/testdata/index.html
@@ -0,0 +1 @@
+index.html says hello
diff --git a/src/net/http/testdata/style.css b/src/net/http/testdata/style.css
new file mode 100644
index 000000000..208d16d42
--- /dev/null
+++ b/src/net/http/testdata/style.css
@@ -0,0 +1 @@
+body {}
diff --git a/src/net/http/transfer.go b/src/net/http/transfer.go
new file mode 100644
index 000000000..520500330
--- /dev/null
+++ b/src/net/http/transfer.go
@@ -0,0 +1,737 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package http
+
+import (
+	"bufio"
+	"bytes"
+	"errors"
+	"fmt"
+	"io"
+	"io/ioutil"
+	"net/http/internal"
+	"net/textproto"
+	"sort"
+	"strconv"
+	"strings"
+	"sync"
+)
+
+// ErrLineTooLong is returned when reading request or response bodies
+// with malformed chunked encoding.
+var ErrLineTooLong = internal.ErrLineTooLong
+
+type errorReader struct {
+	err error
+}
+
+func (r *errorReader) Read(p []byte) (n int, err error) {
+	return 0, r.err
+}
+
+// transferWriter inspects the fields of a user-supplied Request or Response,
+// sanitizes them without changing the user object and provides methods for
+// writing the respective header, body and trailer in wire format.
+type transferWriter struct {
+	Method           string
+	Body             io.Reader
+	BodyCloser       io.Closer
+	ResponseToHEAD   bool
+	ContentLength    int64 // -1 means unknown, 0 means exactly none
+	Close            bool
+	TransferEncoding []string
+	Trailer          Header
+}
+
+func newTransferWriter(r interface{}) (t *transferWriter, err error) {
+	t = &transferWriter{}
+
+	// Extract relevant fields
+	atLeastHTTP11 := false
+	switch rr := r.(type) {
+	case *Request:
+		if rr.ContentLength != 0 && rr.Body == nil {
+			return nil, fmt.Errorf("http: Request.ContentLength=%d with nil Body", rr.ContentLength)
+		}
+		t.Method = rr.Method
+		t.Body = rr.Body
+		t.BodyCloser = rr.Body
+		t.ContentLength = rr.ContentLength
+		t.Close = rr.Close
+		t.TransferEncoding = rr.TransferEncoding
+		t.Trailer = rr.Trailer
+		atLeastHTTP11 = rr.ProtoAtLeast(1, 1)
+		if t.Body != nil && len(t.TransferEncoding) == 0 && atLeastHTTP11 {
+			if t.ContentLength == 0 {
+				// Test to see if it's actually zero or just unset.
+				var buf [1]byte
+				n, rerr := io.ReadFull(t.Body, buf[:])
+				if rerr != nil && rerr != io.EOF {
+					t.ContentLength = -1
+					t.Body = &errorReader{rerr}
+				} else if n == 1 {
+					// Oh, guess there is data in this Body Reader after all.
+					// The ContentLength field just wasn't set.
+					// Stich the Body back together again, re-attaching our
+					// consumed byte.
+					t.ContentLength = -1
+					t.Body = io.MultiReader(bytes.NewReader(buf[:]), t.Body)
+				} else {
+					// Body is actually empty.
+					t.Body = nil
+					t.BodyCloser = nil
+				}
+			}
+			if t.ContentLength < 0 {
+				t.TransferEncoding = []string{"chunked"}
+			}
+		}
+	case *Response:
+		if rr.Request != nil {
+			t.Method = rr.Request.Method
+		}
+		t.Body = rr.Body
+		t.BodyCloser = rr.Body
+		t.ContentLength = rr.ContentLength
+		t.Close = rr.Close
+		t.TransferEncoding = rr.TransferEncoding
+		t.Trailer = rr.Trailer
+		atLeastHTTP11 = rr.ProtoAtLeast(1, 1)
+		t.ResponseToHEAD = noBodyExpected(t.Method)
+	}
+
+	// Sanitize Body,ContentLength,TransferEncoding
+	if t.ResponseToHEAD {
+		t.Body = nil
+		if chunked(t.TransferEncoding) {
+			t.ContentLength = -1
+		}
+	} else {
+		if !atLeastHTTP11 || t.Body == nil {
+			t.TransferEncoding = nil
+		}
+		if chunked(t.TransferEncoding) {
+			t.ContentLength = -1
+		} else if t.Body == nil { // no chunking, no body
+			t.ContentLength = 0
+		}
+	}
+
+	// Sanitize Trailer
+	if !chunked(t.TransferEncoding) {
+		t.Trailer = nil
+	}
+
+	return t, nil
+}
+
+func noBodyExpected(requestMethod string) bool {
+	return requestMethod == "HEAD"
+}
+
+func (t *transferWriter) shouldSendContentLength() bool {
+	if chunked(t.TransferEncoding) {
+		return false
+	}
+	if t.ContentLength > 0 {
+		return true
+	}
+	// Many servers expect a Content-Length for these methods
+	if t.Method == "POST" || t.Method == "PUT" {
+		return true
+	}
+	if t.ContentLength == 0 && isIdentity(t.TransferEncoding) {
+		return true
+	}
+
+	return false
+}
+
+func (t *transferWriter) WriteHeader(w io.Writer) error {
+	if t.Close {
+		if _, err := io.WriteString(w, "Connection: close\r\n"); err != nil {
+			return err
+		}
+	}
+
+	// Write Content-Length and/or Transfer-Encoding whose values are a
+	// function of the sanitized field triple (Body, ContentLength,
+	// TransferEncoding)
+	if t.shouldSendContentLength() {
+		if _, err := io.WriteString(w, "Content-Length: "); err != nil {
+			return err
+		}
+		if _, err := io.WriteString(w, strconv.FormatInt(t.ContentLength, 10)+"\r\n"); err != nil {
+			return err
+		}
+	} else if chunked(t.TransferEncoding) {
+		if _, err := io.WriteString(w, "Transfer-Encoding: chunked\r\n"); err != nil {
+			return err
+		}
+	}
+
+	// Write Trailer header
+	if t.Trailer != nil {
+		keys := make([]string, 0, len(t.Trailer))
+		for k := range t.Trailer {
+			k = CanonicalHeaderKey(k)
+			switch k {
+			case "Transfer-Encoding", "Trailer", "Content-Length":
+				return &badStringError{"invalid Trailer key", k}
+			}
+			keys = append(keys, k)
+		}
+		if len(keys) > 0 {
+			sort.Strings(keys)
+			// TODO: could do better allocation-wise here, but trailers are rare,
+			// so being lazy for now.
+			if _, err := io.WriteString(w, "Trailer: "+strings.Join(keys, ",")+"\r\n"); err != nil {
+				return err
+			}
+		}
+	}
+
+	return nil
+}
+
+func (t *transferWriter) WriteBody(w io.Writer) error {
+	var err error
+	var ncopy int64
+
+	// Write body
+	if t.Body != nil {
+		if chunked(t.TransferEncoding) {
+			cw := internal.NewChunkedWriter(w)
+			_, err = io.Copy(cw, t.Body)
+			if err == nil {
+				err = cw.Close()
+			}
+		} else if t.ContentLength == -1 {
+			ncopy, err = io.Copy(w, t.Body)
+		} else {
+			ncopy, err = io.Copy(w, io.LimitReader(t.Body, t.ContentLength))
+			if err != nil {
+				return err
+			}
+			var nextra int64
+			nextra, err = io.Copy(ioutil.Discard, t.Body)
+			ncopy += nextra
+		}
+		if err != nil {
+			return err
+		}
+		if err = t.BodyCloser.Close(); err != nil {
+			return err
+		}
+	}
+
+	if !t.ResponseToHEAD && t.ContentLength != -1 && t.ContentLength != ncopy {
+		return fmt.Errorf("http: ContentLength=%d with Body length %d",
+			t.ContentLength, ncopy)
+	}
+
+	// TODO(petar): Place trailer writer code here.
+	if chunked(t.TransferEncoding) {
+		// Write Trailer header
+		if t.Trailer != nil {
+			if err := t.Trailer.Write(w); err != nil {
+				return err
+			}
+		}
+		// Last chunk, empty trailer
+		_, err = io.WriteString(w, "\r\n")
+	}
+	return err
+}
+
+type transferReader struct {
+	// Input
+	Header        Header
+	StatusCode    int
+	RequestMethod string
+	ProtoMajor    int
+	ProtoMinor    int
+	// Output
+	Body             io.ReadCloser
+	ContentLength    int64
+	TransferEncoding []string
+	Close            bool
+	Trailer          Header
+}
+
+// bodyAllowedForStatus reports whether a given response status code
+// permits a body.  See RFC2616, section 4.4.
+func bodyAllowedForStatus(status int) bool {
+	switch {
+	case status >= 100 && status <= 199:
+		return false
+	case status == 204:
+		return false
+	case status == 304:
+		return false
+	}
+	return true
+}
+
+var (
+	suppressedHeaders304    = []string{"Content-Type", "Content-Length", "Transfer-Encoding"}
+	suppressedHeadersNoBody = []string{"Content-Length", "Transfer-Encoding"}
+)
+
+func suppressedHeaders(status int) []string {
+	switch {
+	case status == 304:
+		// RFC 2616 section 10.3.5: "the response MUST NOT include other entity-headers"
+		return suppressedHeaders304
+	case !bodyAllowedForStatus(status):
+		return suppressedHeadersNoBody
+	}
+	return nil
+}
+
+// msg is *Request or *Response.
+func readTransfer(msg interface{}, r *bufio.Reader) (err error) {
+	t := &transferReader{RequestMethod: "GET"}
+
+	// Unify input
+	isResponse := false
+	switch rr := msg.(type) {
+	case *Response:
+		t.Header = rr.Header
+		t.StatusCode = rr.StatusCode
+		t.ProtoMajor = rr.ProtoMajor
+		t.ProtoMinor = rr.ProtoMinor
+		t.Close = shouldClose(t.ProtoMajor, t.ProtoMinor, t.Header, true)
+		isResponse = true
+		if rr.Request != nil {
+			t.RequestMethod = rr.Request.Method
+		}
+	case *Request:
+		t.Header = rr.Header
+		t.ProtoMajor = rr.ProtoMajor
+		t.ProtoMinor = rr.ProtoMinor
+		// Transfer semantics for Requests are exactly like those for
+		// Responses with status code 200, responding to a GET method
+		t.StatusCode = 200
+	default:
+		panic("unexpected type")
+	}
+
+	// Default to HTTP/1.1
+	if t.ProtoMajor == 0 && t.ProtoMinor == 0 {
+		t.ProtoMajor, t.ProtoMinor = 1, 1
+	}
+
+	// Transfer encoding, content length
+	t.TransferEncoding, err = fixTransferEncoding(t.RequestMethod, t.Header)
+	if err != nil {
+		return err
+	}
+
+	realLength, err := fixLength(isResponse, t.StatusCode, t.RequestMethod, t.Header, t.TransferEncoding)
+	if err != nil {
+		return err
+	}
+	if isResponse && t.RequestMethod == "HEAD" {
+		if n, err := parseContentLength(t.Header.get("Content-Length")); err != nil {
+			return err
+		} else {
+			t.ContentLength = n
+		}
+	} else {
+		t.ContentLength = realLength
+	}
+
+	// Trailer
+	t.Trailer, err = fixTrailer(t.Header, t.TransferEncoding)
+	if err != nil {
+		return err
+	}
+
+	// If there is no Content-Length or chunked Transfer-Encoding on a *Response
+	// and the status is not 1xx, 204 or 304, then the body is unbounded.
+	// See RFC2616, section 4.4.
+	switch msg.(type) {
+	case *Response:
+		if realLength == -1 &&
+			!chunked(t.TransferEncoding) &&
+			bodyAllowedForStatus(t.StatusCode) {
+			// Unbounded body.
+			t.Close = true
+		}
+	}
+
+	// Prepare body reader.  ContentLength < 0 means chunked encoding
+	// or close connection when finished, since multipart is not supported yet
+	switch {
+	case chunked(t.TransferEncoding):
+		if noBodyExpected(t.RequestMethod) {
+			t.Body = eofReader
+		} else {
+			t.Body = &body{src: internal.NewChunkedReader(r), hdr: msg, r: r, closing: t.Close}
+		}
+	case realLength == 0:
+		t.Body = eofReader
+	case realLength > 0:
+		t.Body = &body{src: io.LimitReader(r, realLength), closing: t.Close}
+	default:
+		// realLength < 0, i.e. "Content-Length" not mentioned in header
+		if t.Close {
+			// Close semantics (i.e. HTTP/1.0)
+			t.Body = &body{src: r, closing: t.Close}
+		} else {
+			// Persistent connection (i.e. HTTP/1.1)
+			t.Body = eofReader
+		}
+	}
+
+	// Unify output
+	switch rr := msg.(type) {
+	case *Request:
+		rr.Body = t.Body
+		rr.ContentLength = t.ContentLength
+		rr.TransferEncoding = t.TransferEncoding
+		rr.Close = t.Close
+		rr.Trailer = t.Trailer
+	case *Response:
+		rr.Body = t.Body
+		rr.ContentLength = t.ContentLength
+		rr.TransferEncoding = t.TransferEncoding
+		rr.Close = t.Close
+		rr.Trailer = t.Trailer
+	}
+
+	return nil
+}
+
+// Checks whether chunked is part of the encodings stack
+func chunked(te []string) bool { return len(te) > 0 && te[0] == "chunked" }
+
+// Checks whether the encoding is explicitly "identity".
+func isIdentity(te []string) bool { return len(te) == 1 && te[0] == "identity" }
+
+// Sanitize transfer encoding
+func fixTransferEncoding(requestMethod string, header Header) ([]string, error) {
+	raw, present := header["Transfer-Encoding"]
+	if !present {
+		return nil, nil
+	}
+
+	delete(header, "Transfer-Encoding")
+
+	encodings := strings.Split(raw[0], ",")
+	te := make([]string, 0, len(encodings))
+	// TODO: Even though we only support "identity" and "chunked"
+	// encodings, the loop below is designed with foresight. One
+	// invariant that must be maintained is that, if present,
+	// chunked encoding must always come first.
+	for _, encoding := range encodings {
+		encoding = strings.ToLower(strings.TrimSpace(encoding))
+		// "identity" encoding is not recorded
+		if encoding == "identity" {
+			break
+		}
+		if encoding != "chunked" {
+			return nil, &badStringError{"unsupported transfer encoding", encoding}
+		}
+		te = te[0 : len(te)+1]
+		te[len(te)-1] = encoding
+	}
+	if len(te) > 1 {
+		return nil, &badStringError{"too many transfer encodings", strings.Join(te, ",")}
+	}
+	if len(te) > 0 {
+		// Chunked encoding trumps Content-Length. See RFC 2616
+		// Section 4.4. Currently len(te) > 0 implies chunked
+		// encoding.
+		delete(header, "Content-Length")
+		return te, nil
+	}
+
+	return nil, nil
+}
+
+// Determine the expected body length, using RFC 2616 Section 4.4. This
+// function is not a method, because ultimately it should be shared by
+// ReadResponse and ReadRequest.
+func fixLength(isResponse bool, status int, requestMethod string, header Header, te []string) (int64, error) {
+
+	// Logic based on response type or status
+	if noBodyExpected(requestMethod) {
+		return 0, nil
+	}
+	if status/100 == 1 {
+		return 0, nil
+	}
+	switch status {
+	case 204, 304:
+		return 0, nil
+	}
+
+	// Logic based on Transfer-Encoding
+	if chunked(te) {
+		return -1, nil
+	}
+
+	// Logic based on Content-Length
+	cl := strings.TrimSpace(header.get("Content-Length"))
+	if cl != "" {
+		n, err := parseContentLength(cl)
+		if err != nil {
+			return -1, err
+		}
+		return n, nil
+	} else {
+		header.Del("Content-Length")
+	}
+
+	if !isResponse && requestMethod == "GET" {
+		// RFC 2616 doesn't explicitly permit nor forbid an
+		// entity-body on a GET request so we permit one if
+		// declared, but we default to 0 here (not -1 below)
+		// if there's no mention of a body.
+		return 0, nil
+	}
+
+	// Body-EOF logic based on other methods (like closing, or chunked coding)
+	return -1, nil
+}
+
+// Determine whether to hang up after sending a request and body, or
+// receiving a response and body
+// 'header' is the request headers
+func shouldClose(major, minor int, header Header, removeCloseHeader bool) bool {
+	if major < 1 {
+		return true
+	} else if major == 1 && minor == 0 {
+		if !strings.Contains(strings.ToLower(header.get("Connection")), "keep-alive") {
+			return true
+		}
+		return false
+	} else {
+		// TODO: Should split on commas, toss surrounding white space,
+		// and check each field.
+		if strings.ToLower(header.get("Connection")) == "close" {
+			if removeCloseHeader {
+				header.Del("Connection")
+			}
+			return true
+		}
+	}
+	return false
+}
+
+// Parse the trailer header
+func fixTrailer(header Header, te []string) (Header, error) {
+	raw := header.get("Trailer")
+	if raw == "" {
+		return nil, nil
+	}
+
+	header.Del("Trailer")
+	trailer := make(Header)
+	keys := strings.Split(raw, ",")
+	for _, key := range keys {
+		key = CanonicalHeaderKey(strings.TrimSpace(key))
+		switch key {
+		case "Transfer-Encoding", "Trailer", "Content-Length":
+			return nil, &badStringError{"bad trailer key", key}
+		}
+		trailer[key] = nil
+	}
+	if len(trailer) == 0 {
+		return nil, nil
+	}
+	if !chunked(te) {
+		// Trailer and no chunking
+		return nil, ErrUnexpectedTrailer
+	}
+	return trailer, nil
+}
+
+// body turns a Reader into a ReadCloser.
+// Close ensures that the body has been fully read
+// and then reads the trailer if necessary.
+type body struct {
+	src     io.Reader
+	hdr     interface{}   // non-nil (Response or Request) value means read trailer
+	r       *bufio.Reader // underlying wire-format reader for the trailer
+	closing bool          // is the connection to be closed after reading body?
+
+	mu     sync.Mutex // guards closed, and calls to Read and Close
+	closed bool
+}
+
+// ErrBodyReadAfterClose is returned when reading a Request or Response
+// Body after the body has been closed. This typically happens when the body is
+// read after an HTTP Handler calls WriteHeader or Write on its
+// ResponseWriter.
+var ErrBodyReadAfterClose = errors.New("http: invalid Read on closed Body")
+
+func (b *body) Read(p []byte) (n int, err error) {
+	b.mu.Lock()
+	defer b.mu.Unlock()
+	if b.closed {
+		return 0, ErrBodyReadAfterClose
+	}
+	return b.readLocked(p)
+}
+
+// Must hold b.mu.
+func (b *body) readLocked(p []byte) (n int, err error) {
+	n, err = b.src.Read(p)
+
+	if err == io.EOF {
+		// Chunked case. Read the trailer.
+		if b.hdr != nil {
+			if e := b.readTrailer(); e != nil {
+				err = e
+			}
+			b.hdr = nil
+		} else {
+			// If the server declared the Content-Length, our body is a LimitedReader
+			// and we need to check whether this EOF arrived early.
+			if lr, ok := b.src.(*io.LimitedReader); ok && lr.N > 0 {
+				err = io.ErrUnexpectedEOF
+			}
+		}
+	}
+
+	// If we can return an EOF here along with the read data, do
+	// so. This is optional per the io.Reader contract, but doing
+	// so helps the HTTP transport code recycle its connection
+	// earlier (since it will see this EOF itself), even if the
+	// client doesn't do future reads or Close.
+	if err == nil && n > 0 {
+		if lr, ok := b.src.(*io.LimitedReader); ok && lr.N == 0 {
+			err = io.EOF
+		}
+	}
+
+	return n, err
+}
+
+var (
+	singleCRLF = []byte("\r\n")
+	doubleCRLF = []byte("\r\n\r\n")
+)
+
+func seeUpcomingDoubleCRLF(r *bufio.Reader) bool {
+	for peekSize := 4; ; peekSize++ {
+		// This loop stops when Peek returns an error,
+		// which it does when r's buffer has been filled.
+		buf, err := r.Peek(peekSize)
+		if bytes.HasSuffix(buf, doubleCRLF) {
+			return true
+		}
+		if err != nil {
+			break
+		}
+	}
+	return false
+}
+
+var errTrailerEOF = errors.New("http: unexpected EOF reading trailer")
+
+func (b *body) readTrailer() error {
+	// The common case, since nobody uses trailers.
+	buf, err := b.r.Peek(2)
+	if bytes.Equal(buf, singleCRLF) {
+		b.r.ReadByte()
+		b.r.ReadByte()
+		return nil
+	}
+	if len(buf) < 2 {
+		return errTrailerEOF
+	}
+	if err != nil {
+		return err
+	}
+
+	// Make sure there's a header terminator coming up, to prevent
+	// a DoS with an unbounded size Trailer.  It's not easy to
+	// slip in a LimitReader here, as textproto.NewReader requires
+	// a concrete *bufio.Reader.  Also, we can't get all the way
+	// back up to our conn's LimitedReader that *might* be backing
+	// this bufio.Reader.  Instead, a hack: we iteratively Peek up
+	// to the bufio.Reader's max size, looking for a double CRLF.
+	// This limits the trailer to the underlying buffer size, typically 4kB.
+	if !seeUpcomingDoubleCRLF(b.r) {
+		return errors.New("http: suspiciously long trailer after chunked body")
+	}
+
+	hdr, err := textproto.NewReader(b.r).ReadMIMEHeader()
+	if err != nil {
+		if err == io.EOF {
+			return errTrailerEOF
+		}
+		return err
+	}
+	switch rr := b.hdr.(type) {
+	case *Request:
+		mergeSetHeader(&rr.Trailer, Header(hdr))
+	case *Response:
+		mergeSetHeader(&rr.Trailer, Header(hdr))
+	}
+	return nil
+}
+
+func mergeSetHeader(dst *Header, src Header) {
+	if *dst == nil {
+		*dst = src
+		return
+	}
+	for k, vv := range src {
+		(*dst)[k] = vv
+	}
+}
+
+func (b *body) Close() error {
+	b.mu.Lock()
+	defer b.mu.Unlock()
+	if b.closed {
+		return nil
+	}
+	var err error
+	switch {
+	case b.hdr == nil && b.closing:
+		// no trailer and closing the connection next.
+		// no point in reading to EOF.
+	default:
+		// Fully consume the body, which will also lead to us reading
+		// the trailer headers after the body, if present.
+		_, err = io.Copy(ioutil.Discard, bodyLocked{b})
+	}
+	b.closed = true
+	return err
+}
+
+// bodyLocked is a io.Reader reading from a *body when its mutex is
+// already held.
+type bodyLocked struct {
+	b *body
+}
+
+func (bl bodyLocked) Read(p []byte) (n int, err error) {
+	if bl.b.closed {
+		return 0, ErrBodyReadAfterClose
+	}
+	return bl.b.readLocked(p)
+}
+
+// parseContentLength trims whitespace from s and returns -1 if no value
+// is set, or the value if it's >= 0.
+func parseContentLength(cl string) (int64, error) {
+	cl = strings.TrimSpace(cl)
+	if cl == "" {
+		return -1, nil
+	}
+	n, err := strconv.ParseInt(cl, 10, 64)
+	if err != nil || n < 0 {
+		return 0, &badStringError{"bad Content-Length", cl}
+	}
+	return n, nil
+
+}
diff --git a/src/net/http/transfer_test.go b/src/net/http/transfer_test.go
new file mode 100644
index 000000000..48cd540b9
--- /dev/null
+++ b/src/net/http/transfer_test.go
@@ -0,0 +1,64 @@
+// Copyright 2012 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package http
+
+import (
+	"bufio"
+	"io"
+	"strings"
+	"testing"
+)
+
+func TestBodyReadBadTrailer(t *testing.T) {
+	b := &body{
+		src: strings.NewReader("foobar"),
+		hdr: true, // force reading the trailer
+		r:   bufio.NewReader(strings.NewReader("")),
+	}
+	buf := make([]byte, 7)
+	n, err := b.Read(buf[:3])
+	got := string(buf[:n])
+	if got != "foo" || err != nil {
+		t.Fatalf(`first Read = %d (%q), %v; want 3 ("foo")`, n, got, err)
+	}
+
+	n, err = b.Read(buf[:])
+	got = string(buf[:n])
+	if got != "bar" || err != nil {
+		t.Fatalf(`second Read = %d (%q), %v; want 3 ("bar")`, n, got, err)
+	}
+
+	n, err = b.Read(buf[:])
+	got = string(buf[:n])
+	if err == nil {
+		t.Errorf("final Read was successful (%q), expected error from trailer read", got)
+	}
+}
+
+func TestFinalChunkedBodyReadEOF(t *testing.T) {
+	res, err := ReadResponse(bufio.NewReader(strings.NewReader(
+		"HTTP/1.1 200 OK\r\n"+
+			"Transfer-Encoding: chunked\r\n"+
+			"\r\n"+
+			"0a\r\n"+
+			"Body here\n\r\n"+
+			"09\r\n"+
+			"continued\r\n"+
+			"0\r\n"+
+			"\r\n")), nil)
+	if err != nil {
+		t.Fatal(err)
+	}
+	want := "Body here\ncontinued"
+	buf := make([]byte, len(want))
+	n, err := res.Body.Read(buf)
+	if n != len(want) || err != io.EOF {
+		t.Logf("body = %#v", res.Body)
+		t.Errorf("Read = %v, %v; want %d, EOF", n, err, len(want))
+	}
+	if string(buf) != want {
+		t.Errorf("buf = %q; want %q", buf, want)
+	}
+}
diff --git a/src/net/http/transport.go b/src/net/http/transport.go
new file mode 100644
index 000000000..527ed8bdd
--- /dev/null
+++ b/src/net/http/transport.go
@@ -0,0 +1,1242 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// HTTP client implementation. See RFC 2616.
+//
+// This is the low-level Transport implementation of RoundTripper.
+// The high-level interface is in client.go.
+
+package http
+
+import (
+	"bufio"
+	"compress/gzip"
+	"crypto/tls"
+	"errors"
+	"fmt"
+	"io"
+	"log"
+	"net"
+	"net/url"
+	"os"
+	"strings"
+	"sync"
+	"time"
+)
+
+// DefaultTransport is the default implementation of Transport and is
+// used by DefaultClient. It establishes network connections as needed
+// and caches them for reuse by subsequent calls. It uses HTTP proxies
+// as directed by the $HTTP_PROXY and $NO_PROXY (or $http_proxy and
+// $no_proxy) environment variables.
+var DefaultTransport RoundTripper = &Transport{
+	Proxy: ProxyFromEnvironment,
+	Dial: (&net.Dialer{
+		Timeout:   30 * time.Second,
+		KeepAlive: 30 * time.Second,
+	}).Dial,
+	TLSHandshakeTimeout: 10 * time.Second,
+}
+
+// DefaultMaxIdleConnsPerHost is the default value of Transport's
+// MaxIdleConnsPerHost.
+const DefaultMaxIdleConnsPerHost = 2
+
+// Transport is an implementation of RoundTripper that supports HTTP,
+// HTTPS, and HTTP proxies (for either HTTP or HTTPS with CONNECT).
+// Transport can also cache connections for future re-use.
+type Transport struct {
+	idleMu      sync.Mutex
+	idleConn    map[connectMethodKey][]*persistConn
+	idleConnCh  map[connectMethodKey]chan *persistConn
+	reqMu       sync.Mutex
+	reqCanceler map[*Request]func()
+	altMu       sync.RWMutex
+	altProto    map[string]RoundTripper // nil or map of URI scheme => RoundTripper
+
+	// Proxy specifies a function to return a proxy for a given
+	// Request. If the function returns a non-nil error, the
+	// request is aborted with the provided error.
+	// If Proxy is nil or returns a nil *URL, no proxy is used.
+	Proxy func(*Request) (*url.URL, error)
+
+	// Dial specifies the dial function for creating unencrypted
+	// TCP connections.
+	// If Dial is nil, net.Dial is used.
+	Dial func(network, addr string) (net.Conn, error)
+
+	// DialTLS specifies an optional dial function for creating
+	// TLS connections for non-proxied HTTPS requests.
+	//
+	// If DialTLS is nil, Dial and TLSClientConfig are used.
+	//
+	// If DialTLS is set, the Dial hook is not used for HTTPS
+	// requests and the TLSClientConfig and TLSHandshakeTimeout
+	// are ignored. The returned net.Conn is assumed to already be
+	// past the TLS handshake.
+	DialTLS func(network, addr string) (net.Conn, error)
+
+	// TLSClientConfig specifies the TLS configuration to use with
+	// tls.Client. If nil, the default configuration is used.
+	TLSClientConfig *tls.Config
+
+	// TLSHandshakeTimeout specifies the maximum amount of time waiting to
+	// wait for a TLS handshake. Zero means no timeout.
+	TLSHandshakeTimeout time.Duration
+
+	// DisableKeepAlives, if true, prevents re-use of TCP connections
+	// between different HTTP requests.
+	DisableKeepAlives bool
+
+	// DisableCompression, if true, prevents the Transport from
+	// requesting compression with an "Accept-Encoding: gzip"
+	// request header when the Request contains no existing
+	// Accept-Encoding value. If the Transport requests gzip on
+	// its own and gets a gzipped response, it's transparently
+	// decoded in the Response.Body. However, if the user
+	// explicitly requested gzip it is not automatically
+	// uncompressed.
+	DisableCompression bool
+
+	// MaxIdleConnsPerHost, if non-zero, controls the maximum idle
+	// (keep-alive) to keep per-host.  If zero,
+	// DefaultMaxIdleConnsPerHost is used.
+	MaxIdleConnsPerHost int
+
+	// ResponseHeaderTimeout, if non-zero, specifies the amount of
+	// time to wait for a server's response headers after fully
+	// writing the request (including its body, if any). This
+	// time does not include the time to read the response body.
+	ResponseHeaderTimeout time.Duration
+
+	// TODO: tunable on global max cached connections
+	// TODO: tunable on timeout on cached connections
+}
+
+// ProxyFromEnvironment returns the URL of the proxy to use for a
+// given request, as indicated by the environment variables
+// $HTTP_PROXY and $NO_PROXY (or $http_proxy and $no_proxy).
+// An error is returned if the proxy environment is invalid.
+// A nil URL and nil error are returned if no proxy is defined in the
+// environment, or a proxy should not be used for the given request.
+//
+// As a special case, if req.URL.Host is "localhost" (with or without
+// a port number), then a nil URL and nil error will be returned.
+func ProxyFromEnvironment(req *Request) (*url.URL, error) {
+	proxy := httpProxyEnv.Get()
+	if proxy == "" {
+		return nil, nil
+	}
+	if !useProxy(canonicalAddr(req.URL)) {
+		return nil, nil
+	}
+	proxyURL, err := url.Parse(proxy)
+	if err != nil || !strings.HasPrefix(proxyURL.Scheme, "http") {
+		// proxy was bogus. Try prepending "http://" to it and
+		// see if that parses correctly. If not, we fall
+		// through and complain about the original one.
+		if proxyURL, err := url.Parse("http://" + proxy); err == nil {
+			return proxyURL, nil
+		}
+	}
+	if err != nil {
+		return nil, fmt.Errorf("invalid proxy address %q: %v", proxy, err)
+	}
+	return proxyURL, nil
+}
+
+// ProxyURL returns a proxy function (for use in a Transport)
+// that always returns the same URL.
+func ProxyURL(fixedURL *url.URL) func(*Request) (*url.URL, error) {
+	return func(*Request) (*url.URL, error) {
+		return fixedURL, nil
+	}
+}
+
+// transportRequest is a wrapper around a *Request that adds
+// optional extra headers to write.
+type transportRequest struct {
+	*Request        // original request, not to be mutated
+	extra    Header // extra headers to write, or nil
+}
+
+func (tr *transportRequest) extraHeaders() Header {
+	if tr.extra == nil {
+		tr.extra = make(Header)
+	}
+	return tr.extra
+}
+
+// RoundTrip implements the RoundTripper interface.
+//
+// For higher-level HTTP client support (such as handling of cookies
+// and redirects), see Get, Post, and the Client type.
+func (t *Transport) RoundTrip(req *Request) (resp *Response, err error) {
+	if req.URL == nil {
+		req.closeBody()
+		return nil, errors.New("http: nil Request.URL")
+	}
+	if req.Header == nil {
+		req.closeBody()
+		return nil, errors.New("http: nil Request.Header")
+	}
+	if req.URL.Scheme != "http" && req.URL.Scheme != "https" {
+		t.altMu.RLock()
+		var rt RoundTripper
+		if t.altProto != nil {
+			rt = t.altProto[req.URL.Scheme]
+		}
+		t.altMu.RUnlock()
+		if rt == nil {
+			req.closeBody()
+			return nil, &badStringError{"unsupported protocol scheme", req.URL.Scheme}
+		}
+		return rt.RoundTrip(req)
+	}
+	if req.URL.Host == "" {
+		req.closeBody()
+		return nil, errors.New("http: no Host in request URL")
+	}
+	treq := &transportRequest{Request: req}
+	cm, err := t.connectMethodForRequest(treq)
+	if err != nil {
+		req.closeBody()
+		return nil, err
+	}
+
+	// Get the cached or newly-created connection to either the
+	// host (for http or https), the http proxy, or the http proxy
+	// pre-CONNECTed to https server.  In any case, we'll be ready
+	// to send it requests.
+	pconn, err := t.getConn(req, cm)
+	if err != nil {
+		t.setReqCanceler(req, nil)
+		req.closeBody()
+		return nil, err
+	}
+
+	return pconn.roundTrip(treq)
+}
+
+// RegisterProtocol registers a new protocol with scheme.
+// The Transport will pass requests using the given scheme to rt.
+// It is rt's responsibility to simulate HTTP request semantics.
+//
+// RegisterProtocol can be used by other packages to provide
+// implementations of protocol schemes like "ftp" or "file".
+func (t *Transport) RegisterProtocol(scheme string, rt RoundTripper) {
+	if scheme == "http" || scheme == "https" {
+		panic("protocol " + scheme + " already registered")
+	}
+	t.altMu.Lock()
+	defer t.altMu.Unlock()
+	if t.altProto == nil {
+		t.altProto = make(map[string]RoundTripper)
+	}
+	if _, exists := t.altProto[scheme]; exists {
+		panic("protocol " + scheme + " already registered")
+	}
+	t.altProto[scheme] = rt
+}
+
+// CloseIdleConnections closes any connections which were previously
+// connected from previous requests but are now sitting idle in
+// a "keep-alive" state. It does not interrupt any connections currently
+// in use.
+func (t *Transport) CloseIdleConnections() {
+	t.idleMu.Lock()
+	m := t.idleConn
+	t.idleConn = nil
+	t.idleConnCh = nil
+	t.idleMu.Unlock()
+	for _, conns := range m {
+		for _, pconn := range conns {
+			pconn.close()
+		}
+	}
+}
+
+// CancelRequest cancels an in-flight request by closing its
+// connection.
+func (t *Transport) CancelRequest(req *Request) {
+	t.reqMu.Lock()
+	cancel := t.reqCanceler[req]
+	t.reqMu.Unlock()
+	if cancel != nil {
+		cancel()
+	}
+}
+
+//
+// Private implementation past this point.
+//
+
+var (
+	httpProxyEnv = &envOnce{
+		names: []string{"HTTP_PROXY", "http_proxy"},
+	}
+	noProxyEnv = &envOnce{
+		names: []string{"NO_PROXY", "no_proxy"},
+	}
+)
+
+// envOnce looks up an environment variable (optionally by multiple
+// names) once. It mitigates expensive lookups on some platforms
+// (e.g. Windows).
+type envOnce struct {
+	names []string
+	once  sync.Once
+	val   string
+}
+
+func (e *envOnce) Get() string {
+	e.once.Do(e.init)
+	return e.val
+}
+
+func (e *envOnce) init() {
+	for _, n := range e.names {
+		e.val = os.Getenv(n)
+		if e.val != "" {
+			return
+		}
+	}
+}
+
+// reset is used by tests
+func (e *envOnce) reset() {
+	e.once = sync.Once{}
+	e.val = ""
+}
+
+func (t *Transport) connectMethodForRequest(treq *transportRequest) (cm connectMethod, err error) {
+	cm.targetScheme = treq.URL.Scheme
+	cm.targetAddr = canonicalAddr(treq.URL)
+	if t.Proxy != nil {
+		cm.proxyURL, err = t.Proxy(treq.Request)
+	}
+	return cm, nil
+}
+
+// proxyAuth returns the Proxy-Authorization header to set
+// on requests, if applicable.
+func (cm *connectMethod) proxyAuth() string {
+	if cm.proxyURL == nil {
+		return ""
+	}
+	if u := cm.proxyURL.User; u != nil {
+		username := u.Username()
+		password, _ := u.Password()
+		return "Basic " + basicAuth(username, password)
+	}
+	return ""
+}
+
+// putIdleConn adds pconn to the list of idle persistent connections awaiting
+// a new request.
+// If pconn is no longer needed or not in a good state, putIdleConn
+// returns false.
+func (t *Transport) putIdleConn(pconn *persistConn) bool {
+	if t.DisableKeepAlives || t.MaxIdleConnsPerHost < 0 {
+		pconn.close()
+		return false
+	}
+	if pconn.isBroken() {
+		return false
+	}
+	key := pconn.cacheKey
+	max := t.MaxIdleConnsPerHost
+	if max == 0 {
+		max = DefaultMaxIdleConnsPerHost
+	}
+	t.idleMu.Lock()
+
+	waitingDialer := t.idleConnCh[key]
+	select {
+	case waitingDialer <- pconn:
+		// We're done with this pconn and somebody else is
+		// currently waiting for a conn of this type (they're
+		// actively dialing, but this conn is ready
+		// first). Chrome calls this socket late binding.  See
+		// https://insouciant.org/tech/connection-management-in-chromium/
+		t.idleMu.Unlock()
+		return true
+	default:
+		if waitingDialer != nil {
+			// They had populated this, but their dial won
+			// first, so we can clean up this map entry.
+			delete(t.idleConnCh, key)
+		}
+	}
+	if t.idleConn == nil {
+		t.idleConn = make(map[connectMethodKey][]*persistConn)
+	}
+	if len(t.idleConn[key]) >= max {
+		t.idleMu.Unlock()
+		pconn.close()
+		return false
+	}
+	for _, exist := range t.idleConn[key] {
+		if exist == pconn {
+			log.Fatalf("dup idle pconn %p in freelist", pconn)
+		}
+	}
+	t.idleConn[key] = append(t.idleConn[key], pconn)
+	t.idleMu.Unlock()
+	return true
+}
+
+// getIdleConnCh returns a channel to receive and return idle
+// persistent connection for the given connectMethod.
+// It may return nil, if persistent connections are not being used.
+func (t *Transport) getIdleConnCh(cm connectMethod) chan *persistConn {
+	if t.DisableKeepAlives {
+		return nil
+	}
+	key := cm.key()
+	t.idleMu.Lock()
+	defer t.idleMu.Unlock()
+	if t.idleConnCh == nil {
+		t.idleConnCh = make(map[connectMethodKey]chan *persistConn)
+	}
+	ch, ok := t.idleConnCh[key]
+	if !ok {
+		ch = make(chan *persistConn)
+		t.idleConnCh[key] = ch
+	}
+	return ch
+}
+
+func (t *Transport) getIdleConn(cm connectMethod) (pconn *persistConn) {
+	key := cm.key()
+	t.idleMu.Lock()
+	defer t.idleMu.Unlock()
+	if t.idleConn == nil {
+		return nil
+	}
+	for {
+		pconns, ok := t.idleConn[key]
+		if !ok {
+			return nil
+		}
+		if len(pconns) == 1 {
+			pconn = pconns[0]
+			delete(t.idleConn, key)
+		} else {
+			// 2 or more cached connections; pop last
+			// TODO: queue?
+			pconn = pconns[len(pconns)-1]
+			t.idleConn[key] = pconns[:len(pconns)-1]
+		}
+		if !pconn.isBroken() {
+			return
+		}
+	}
+}
+
+func (t *Transport) setReqCanceler(r *Request, fn func()) {
+	t.reqMu.Lock()
+	defer t.reqMu.Unlock()
+	if t.reqCanceler == nil {
+		t.reqCanceler = make(map[*Request]func())
+	}
+	if fn != nil {
+		t.reqCanceler[r] = fn
+	} else {
+		delete(t.reqCanceler, r)
+	}
+}
+
+func (t *Transport) dial(network, addr string) (c net.Conn, err error) {
+	if t.Dial != nil {
+		return t.Dial(network, addr)
+	}
+	return net.Dial(network, addr)
+}
+
+// Testing hooks:
+var prePendingDial, postPendingDial func()
+
+// getConn dials and creates a new persistConn to the target as
+// specified in the connectMethod.  This includes doing a proxy CONNECT
+// and/or setting up TLS.  If this doesn't return an error, the persistConn
+// is ready to write requests to.
+func (t *Transport) getConn(req *Request, cm connectMethod) (*persistConn, error) {
+	if pc := t.getIdleConn(cm); pc != nil {
+		return pc, nil
+	}
+
+	type dialRes struct {
+		pc  *persistConn
+		err error
+	}
+	dialc := make(chan dialRes)
+
+	handlePendingDial := func() {
+		if prePendingDial != nil {
+			prePendingDial()
+		}
+		go func() {
+			if v := <-dialc; v.err == nil {
+				t.putIdleConn(v.pc)
+			}
+			if postPendingDial != nil {
+				postPendingDial()
+			}
+		}()
+	}
+
+	cancelc := make(chan struct{})
+	t.setReqCanceler(req, func() { close(cancelc) })
+
+	go func() {
+		pc, err := t.dialConn(cm)
+		dialc <- dialRes{pc, err}
+	}()
+
+	idleConnCh := t.getIdleConnCh(cm)
+	select {
+	case v := <-dialc:
+		// Our dial finished.
+		return v.pc, v.err
+	case pc := <-idleConnCh:
+		// Another request finished first and its net.Conn
+		// became available before our dial. Or somebody
+		// else's dial that they didn't use.
+		// But our dial is still going, so give it away
+		// when it finishes:
+		handlePendingDial()
+		return pc, nil
+	case <-cancelc:
+		handlePendingDial()
+		return nil, errors.New("net/http: request canceled while waiting for connection")
+	}
+}
+
+func (t *Transport) dialConn(cm connectMethod) (*persistConn, error) {
+	pconn := &persistConn{
+		t:          t,
+		cacheKey:   cm.key(),
+		reqch:      make(chan requestAndChan, 1),
+		writech:    make(chan writeRequest, 1),
+		closech:    make(chan struct{}),
+		writeErrCh: make(chan error, 1),
+	}
+	tlsDial := t.DialTLS != nil && cm.targetScheme == "https" && cm.proxyURL == nil
+	if tlsDial {
+		var err error
+		pconn.conn, err = t.DialTLS("tcp", cm.addr())
+		if err != nil {
+			return nil, err
+		}
+		if tc, ok := pconn.conn.(*tls.Conn); ok {
+			cs := tc.ConnectionState()
+			pconn.tlsState = &cs
+		}
+	} else {
+		conn, err := t.dial("tcp", cm.addr())
+		if err != nil {
+			if cm.proxyURL != nil {
+				err = fmt.Errorf("http: error connecting to proxy %s: %v", cm.proxyURL, err)
+			}
+			return nil, err
+		}
+		pconn.conn = conn
+	}
+
+	// Proxy setup.
+	switch {
+	case cm.proxyURL == nil:
+		// Do nothing. Not using a proxy.
+	case cm.targetScheme == "http":
+		pconn.isProxy = true
+		if pa := cm.proxyAuth(); pa != "" {
+			pconn.mutateHeaderFunc = func(h Header) {
+				h.Set("Proxy-Authorization", pa)
+			}
+		}
+	case cm.targetScheme == "https":
+		conn := pconn.conn
+		connectReq := &Request{
+			Method: "CONNECT",
+			URL:    &url.URL{Opaque: cm.targetAddr},
+			Host:   cm.targetAddr,
+			Header: make(Header),
+		}
+		if pa := cm.proxyAuth(); pa != "" {
+			connectReq.Header.Set("Proxy-Authorization", pa)
+		}
+		connectReq.Write(conn)
+
+		// Read response.
+		// Okay to use and discard buffered reader here, because
+		// TLS server will not speak until spoken to.
+		br := bufio.NewReader(conn)
+		resp, err := ReadResponse(br, connectReq)
+		if err != nil {
+			conn.Close()
+			return nil, err
+		}
+		if resp.StatusCode != 200 {
+			f := strings.SplitN(resp.Status, " ", 2)
+			conn.Close()
+			return nil, errors.New(f[1])
+		}
+	}
+
+	if cm.targetScheme == "https" && !tlsDial {
+		// Initiate TLS and check remote host name against certificate.
+		cfg := t.TLSClientConfig
+		if cfg == nil || cfg.ServerName == "" {
+			host := cm.tlsHost()
+			if cfg == nil {
+				cfg = &tls.Config{ServerName: host}
+			} else {
+				clone := *cfg // shallow clone
+				clone.ServerName = host
+				cfg = &clone
+			}
+		}
+		plainConn := pconn.conn
+		tlsConn := tls.Client(plainConn, cfg)
+		errc := make(chan error, 2)
+		var timer *time.Timer // for canceling TLS handshake
+		if d := t.TLSHandshakeTimeout; d != 0 {
+			timer = time.AfterFunc(d, func() {
+				errc <- tlsHandshakeTimeoutError{}
+			})
+		}
+		go func() {
+			err := tlsConn.Handshake()
+			if timer != nil {
+				timer.Stop()
+			}
+			errc <- err
+		}()
+		if err := <-errc; err != nil {
+			plainConn.Close()
+			return nil, err
+		}
+		if !cfg.InsecureSkipVerify {
+			if err := tlsConn.VerifyHostname(cfg.ServerName); err != nil {
+				plainConn.Close()
+				return nil, err
+			}
+		}
+		cs := tlsConn.ConnectionState()
+		pconn.tlsState = &cs
+		pconn.conn = tlsConn
+	}
+
+	pconn.br = bufio.NewReader(noteEOFReader{pconn.conn, &pconn.sawEOF})
+	pconn.bw = bufio.NewWriter(pconn.conn)
+	go pconn.readLoop()
+	go pconn.writeLoop()
+	return pconn, nil
+}
+
+// useProxy returns true if requests to addr should use a proxy,
+// according to the NO_PROXY or no_proxy environment variable.
+// addr is always a canonicalAddr with a host and port.
+func useProxy(addr string) bool {
+	if len(addr) == 0 {
+		return true
+	}
+	host, _, err := net.SplitHostPort(addr)
+	if err != nil {
+		return false
+	}
+	if host == "localhost" {
+		return false
+	}
+	if ip := net.ParseIP(host); ip != nil {
+		if ip.IsLoopback() {
+			return false
+		}
+	}
+
+	no_proxy := noProxyEnv.Get()
+	if no_proxy == "*" {
+		return false
+	}
+
+	addr = strings.ToLower(strings.TrimSpace(addr))
+	if hasPort(addr) {
+		addr = addr[:strings.LastIndex(addr, ":")]
+	}
+
+	for _, p := range strings.Split(no_proxy, ",") {
+		p = strings.ToLower(strings.TrimSpace(p))
+		if len(p) == 0 {
+			continue
+		}
+		if hasPort(p) {
+			p = p[:strings.LastIndex(p, ":")]
+		}
+		if addr == p {
+			return false
+		}
+		if p[0] == '.' && (strings.HasSuffix(addr, p) || addr == p[1:]) {
+			// no_proxy ".foo.com" matches "bar.foo.com" or "foo.com"
+			return false
+		}
+		if p[0] != '.' && strings.HasSuffix(addr, p) && addr[len(addr)-len(p)-1] == '.' {
+			// no_proxy "foo.com" matches "bar.foo.com"
+			return false
+		}
+	}
+	return true
+}
+
+// connectMethod is the map key (in its String form) for keeping persistent
+// TCP connections alive for subsequent HTTP requests.
+//
+// A connect method may be of the following types:
+//
+// Cache key form                Description
+// -----------------             -------------------------
+// |http|foo.com                 http directly to server, no proxy
+// |https|foo.com                https directly to server, no proxy
+// http://proxy.com|https|foo.com  http to proxy, then CONNECT to foo.com
+// http://proxy.com|http           http to proxy, http to anywhere after that
+//
+// Note: no support to https to the proxy yet.
+//
+type connectMethod struct {
+	proxyURL     *url.URL // nil for no proxy, else full proxy URL
+	targetScheme string   // "http" or "https"
+	targetAddr   string   // Not used if proxy + http targetScheme (4th example in table)
+}
+
+func (cm *connectMethod) key() connectMethodKey {
+	proxyStr := ""
+	targetAddr := cm.targetAddr
+	if cm.proxyURL != nil {
+		proxyStr = cm.proxyURL.String()
+		if cm.targetScheme == "http" {
+			targetAddr = ""
+		}
+	}
+	return connectMethodKey{
+		proxy:  proxyStr,
+		scheme: cm.targetScheme,
+		addr:   targetAddr,
+	}
+}
+
+// addr returns the first hop "host:port" to which we need to TCP connect.
+func (cm *connectMethod) addr() string {
+	if cm.proxyURL != nil {
+		return canonicalAddr(cm.proxyURL)
+	}
+	return cm.targetAddr
+}
+
+// tlsHost returns the host name to match against the peer's
+// TLS certificate.
+func (cm *connectMethod) tlsHost() string {
+	h := cm.targetAddr
+	if hasPort(h) {
+		h = h[:strings.LastIndex(h, ":")]
+	}
+	return h
+}
+
+// connectMethodKey is the map key version of connectMethod, with a
+// stringified proxy URL (or the empty string) instead of a pointer to
+// a URL.
+type connectMethodKey struct {
+	proxy, scheme, addr string
+}
+
+func (k connectMethodKey) String() string {
+	// Only used by tests.
+	return fmt.Sprintf("%s|%s|%s", k.proxy, k.scheme, k.addr)
+}
+
+// persistConn wraps a connection, usually a persistent one
+// (but may be used for non-keep-alive requests as well)
+type persistConn struct {
+	t        *Transport
+	cacheKey connectMethodKey
+	conn     net.Conn
+	tlsState *tls.ConnectionState
+	br       *bufio.Reader       // from conn
+	sawEOF   bool                // whether we've seen EOF from conn; owned by readLoop
+	bw       *bufio.Writer       // to conn
+	reqch    chan requestAndChan // written by roundTrip; read by readLoop
+	writech  chan writeRequest   // written by roundTrip; read by writeLoop
+	closech  chan struct{}       // closed when conn closed
+	isProxy  bool
+	// writeErrCh passes the request write error (usually nil)
+	// from the writeLoop goroutine to the readLoop which passes
+	// it off to the res.Body reader, which then uses it to decide
+	// whether or not a connection can be reused. Issue 7569.
+	writeErrCh chan error
+
+	lk                   sync.Mutex // guards following fields
+	numExpectedResponses int
+	closed               bool // whether conn has been closed
+	broken               bool // an error has happened on this connection; marked broken so it's not reused.
+	// mutateHeaderFunc is an optional func to modify extra
+	// headers on each outbound request before it's written. (the
+	// original Request given to RoundTrip is not modified)
+	mutateHeaderFunc func(Header)
+}
+
+// isBroken reports whether this connection is in a known broken state.
+func (pc *persistConn) isBroken() bool {
+	pc.lk.Lock()
+	b := pc.broken
+	pc.lk.Unlock()
+	return b
+}
+
+func (pc *persistConn) cancelRequest() {
+	pc.conn.Close()
+}
+
+var remoteSideClosedFunc func(error) bool // or nil to use default
+
+func remoteSideClosed(err error) bool {
+	if err == io.EOF {
+		return true
+	}
+	if remoteSideClosedFunc != nil {
+		return remoteSideClosedFunc(err)
+	}
+	return false
+}
+
+func (pc *persistConn) readLoop() {
+	alive := true
+
+	for alive {
+		pb, err := pc.br.Peek(1)
+
+		pc.lk.Lock()
+		if pc.numExpectedResponses == 0 {
+			if !pc.closed {
+				pc.closeLocked()
+				if len(pb) > 0 {
+					log.Printf("Unsolicited response received on idle HTTP channel starting with %q; err=%v",
+						string(pb), err)
+				}
+			}
+			pc.lk.Unlock()
+			return
+		}
+		pc.lk.Unlock()
+
+		rc := <-pc.reqch
+
+		var resp *Response
+		if err == nil {
+			resp, err = ReadResponse(pc.br, rc.req)
+			if err == nil && resp.StatusCode == 100 {
+				// Skip any 100-continue for now.
+				// TODO(bradfitz): if rc.req had "Expect: 100-continue",
+				// actually block the request body write and signal the
+				// writeLoop now to begin sending it. (Issue 2184) For now we
+				// eat it, since we're never expecting one.
+				resp, err = ReadResponse(pc.br, rc.req)
+			}
+		}
+
+		if resp != nil {
+			resp.TLS = pc.tlsState
+		}
+
+		hasBody := resp != nil && rc.req.Method != "HEAD" && resp.ContentLength != 0
+
+		if err != nil {
+			pc.close()
+		} else {
+			if rc.addedGzip && hasBody && resp.Header.Get("Content-Encoding") == "gzip" {
+				resp.Header.Del("Content-Encoding")
+				resp.Header.Del("Content-Length")
+				resp.ContentLength = -1
+				resp.Body = &gzipReader{body: resp.Body}
+			}
+			resp.Body = &bodyEOFSignal{body: resp.Body}
+		}
+
+		if err != nil || resp.Close || rc.req.Close || resp.StatusCode <= 199 {
+			// Don't do keep-alive on error if either party requested a close
+			// or we get an unexpected informational (1xx) response.
+			// StatusCode 100 is already handled above.
+			alive = false
+		}
+
+		var waitForBodyRead chan bool
+		if hasBody {
+			waitForBodyRead = make(chan bool, 2)
+			resp.Body.(*bodyEOFSignal).earlyCloseFn = func() error {
+				// Sending false here sets alive to
+				// false and closes the connection
+				// below.
+				waitForBodyRead <- false
+				return nil
+			}
+			resp.Body.(*bodyEOFSignal).fn = func(err error) {
+				waitForBodyRead <- alive &&
+					err == nil &&
+					!pc.sawEOF &&
+					pc.wroteRequest() &&
+					pc.t.putIdleConn(pc)
+			}
+		}
+
+		if alive && !hasBody {
+			alive = !pc.sawEOF &&
+				pc.wroteRequest() &&
+				pc.t.putIdleConn(pc)
+		}
+
+		rc.ch <- responseAndError{resp, err}
+
+		// Wait for the just-returned response body to be fully consumed
+		// before we race and peek on the underlying bufio reader.
+		if waitForBodyRead != nil {
+			select {
+			case alive = <-waitForBodyRead:
+			case <-pc.closech:
+				alive = false
+			}
+		}
+
+		pc.t.setReqCanceler(rc.req, nil)
+
+		if !alive {
+			pc.close()
+		}
+	}
+}
+
+func (pc *persistConn) writeLoop() {
+	for {
+		select {
+		case wr := <-pc.writech:
+			if pc.isBroken() {
+				wr.ch <- errors.New("http: can't write HTTP request on broken connection")
+				continue
+			}
+			err := wr.req.Request.write(pc.bw, pc.isProxy, wr.req.extra)
+			if err == nil {
+				err = pc.bw.Flush()
+			}
+			if err != nil {
+				pc.markBroken()
+				wr.req.Request.closeBody()
+			}
+			pc.writeErrCh <- err // to the body reader, which might recycle us
+			wr.ch <- err         // to the roundTrip function
+		case <-pc.closech:
+			return
+		}
+	}
+}
+
+// wroteRequest is a check before recycling a connection that the previous write
+// (from writeLoop above) happened and was successful.
+func (pc *persistConn) wroteRequest() bool {
+	select {
+	case err := <-pc.writeErrCh:
+		// Common case: the write happened well before the response, so
+		// avoid creating a timer.
+		return err == nil
+	default:
+		// Rare case: the request was written in writeLoop above but
+		// before it could send to pc.writeErrCh, the reader read it
+		// all, processed it, and called us here. In this case, give the
+		// write goroutine a bit of time to finish its send.
+		//
+		// Less rare case: We also get here in the legitimate case of
+		// Issue 7569, where the writer is still writing (or stalled),
+		// but the server has already replied. In this case, we don't
+		// want to wait too long, and we want to return false so this
+		// connection isn't re-used.
+		select {
+		case err := <-pc.writeErrCh:
+			return err == nil
+		case <-time.After(50 * time.Millisecond):
+			return false
+		}
+	}
+}
+
+type responseAndError struct {
+	res *Response
+	err error
+}
+
+type requestAndChan struct {
+	req *Request
+	ch  chan responseAndError
+
+	// did the Transport (as opposed to the client code) add an
+	// Accept-Encoding gzip header? only if it we set it do
+	// we transparently decode the gzip.
+	addedGzip bool
+}
+
+// A writeRequest is sent by the readLoop's goroutine to the
+// writeLoop's goroutine to write a request while the read loop
+// concurrently waits on both the write response and the server's
+// reply.
+type writeRequest struct {
+	req *transportRequest
+	ch  chan<- error
+}
+
+type httpError struct {
+	err     string
+	timeout bool
+}
+
+func (e *httpError) Error() string   { return e.err }
+func (e *httpError) Timeout() bool   { return e.timeout }
+func (e *httpError) Temporary() bool { return true }
+
+var errTimeout error = &httpError{err: "net/http: timeout awaiting response headers", timeout: true}
+var errClosed error = &httpError{err: "net/http: transport closed before response was received"}
+
+func (pc *persistConn) roundTrip(req *transportRequest) (resp *Response, err error) {
+	pc.t.setReqCanceler(req.Request, pc.cancelRequest)
+	pc.lk.Lock()
+	pc.numExpectedResponses++
+	headerFn := pc.mutateHeaderFunc
+	pc.lk.Unlock()
+
+	if headerFn != nil {
+		headerFn(req.extraHeaders())
+	}
+
+	// Ask for a compressed version if the caller didn't set their
+	// own value for Accept-Encoding. We only attempted to
+	// uncompress the gzip stream if we were the layer that
+	// requested it.
+	requestedGzip := false
+	if !pc.t.DisableCompression && req.Header.Get("Accept-Encoding") == "" && req.Method != "HEAD" {
+		// Request gzip only, not deflate. Deflate is ambiguous and
+		// not as universally supported anyway.
+		// See: http://www.gzip.org/zlib/zlib_faq.html#faq38
+		//
+		// Note that we don't request this for HEAD requests,
+		// due to a bug in nginx:
+		//   http://trac.nginx.org/nginx/ticket/358
+		//   http://golang.org/issue/5522
+		requestedGzip = true
+		req.extraHeaders().Set("Accept-Encoding", "gzip")
+	}
+
+	// Write the request concurrently with waiting for a response,
+	// in case the server decides to reply before reading our full
+	// request body.
+	writeErrCh := make(chan error, 1)
+	pc.writech <- writeRequest{req, writeErrCh}
+
+	resc := make(chan responseAndError, 1)
+	pc.reqch <- requestAndChan{req.Request, resc, requestedGzip}
+
+	var re responseAndError
+	var pconnDeadCh = pc.closech
+	var failTicker <-chan time.Time
+	var respHeaderTimer <-chan time.Time
+WaitResponse:
+	for {
+		select {
+		case err := <-writeErrCh:
+			if err != nil {
+				re = responseAndError{nil, err}
+				pc.close()
+				break WaitResponse
+			}
+			if d := pc.t.ResponseHeaderTimeout; d > 0 {
+				respHeaderTimer = time.After(d)
+			}
+		case <-pconnDeadCh:
+			// The persist connection is dead. This shouldn't
+			// usually happen (only with Connection: close responses
+			// with no response bodies), but if it does happen it
+			// means either a) the remote server hung up on us
+			// prematurely, or b) the readLoop sent us a response &
+			// closed its closech at roughly the same time, and we
+			// selected this case first, in which case a response
+			// might still be coming soon.
+			//
+			// We can't avoid the select race in b) by using a unbuffered
+			// resc channel instead, because then goroutines can
+			// leak if we exit due to other errors.
+			pconnDeadCh = nil                               // avoid spinning
+			failTicker = time.After(100 * time.Millisecond) // arbitrary time to wait for resc
+		case <-failTicker:
+			re = responseAndError{err: errClosed}
+			break WaitResponse
+		case <-respHeaderTimer:
+			pc.close()
+			re = responseAndError{err: errTimeout}
+			break WaitResponse
+		case re = <-resc:
+			break WaitResponse
+		}
+	}
+
+	pc.lk.Lock()
+	pc.numExpectedResponses--
+	pc.lk.Unlock()
+
+	if re.err != nil {
+		pc.t.setReqCanceler(req.Request, nil)
+	}
+	return re.res, re.err
+}
+
+// markBroken marks a connection as broken (so it's not reused).
+// It differs from close in that it doesn't close the underlying
+// connection for use when it's still being read.
+func (pc *persistConn) markBroken() {
+	pc.lk.Lock()
+	defer pc.lk.Unlock()
+	pc.broken = true
+}
+
+func (pc *persistConn) close() {
+	pc.lk.Lock()
+	defer pc.lk.Unlock()
+	pc.closeLocked()
+}
+
+func (pc *persistConn) closeLocked() {
+	pc.broken = true
+	if !pc.closed {
+		pc.conn.Close()
+		pc.closed = true
+		close(pc.closech)
+	}
+	pc.mutateHeaderFunc = nil
+}
+
+var portMap = map[string]string{
+	"http":  "80",
+	"https": "443",
+}
+
+// canonicalAddr returns url.Host but always with a ":port" suffix
+func canonicalAddr(url *url.URL) string {
+	addr := url.Host
+	if !hasPort(addr) {
+		return addr + ":" + portMap[url.Scheme]
+	}
+	return addr
+}
+
+// bodyEOFSignal wraps a ReadCloser but runs fn (if non-nil) at most
+// once, right before its final (error-producing) Read or Close call
+// returns. If earlyCloseFn is non-nil and Close is called before
+// io.EOF is seen, earlyCloseFn is called instead of fn, and its
+// return value is the return value from Close.
+type bodyEOFSignal struct {
+	body         io.ReadCloser
+	mu           sync.Mutex   // guards following 4 fields
+	closed       bool         // whether Close has been called
+	rerr         error        // sticky Read error
+	fn           func(error)  // error will be nil on Read io.EOF
+	earlyCloseFn func() error // optional alt Close func used if io.EOF not seen
+}
+
+func (es *bodyEOFSignal) Read(p []byte) (n int, err error) {
+	es.mu.Lock()
+	closed, rerr := es.closed, es.rerr
+	es.mu.Unlock()
+	if closed {
+		return 0, errors.New("http: read on closed response body")
+	}
+	if rerr != nil {
+		return 0, rerr
+	}
+
+	n, err = es.body.Read(p)
+	if err != nil {
+		es.mu.Lock()
+		defer es.mu.Unlock()
+		if es.rerr == nil {
+			es.rerr = err
+		}
+		es.condfn(err)
+	}
+	return
+}
+
+func (es *bodyEOFSignal) Close() error {
+	es.mu.Lock()
+	defer es.mu.Unlock()
+	if es.closed {
+		return nil
+	}
+	es.closed = true
+	if es.earlyCloseFn != nil && es.rerr != io.EOF {
+		return es.earlyCloseFn()
+	}
+	err := es.body.Close()
+	es.condfn(err)
+	return err
+}
+
+// caller must hold es.mu.
+func (es *bodyEOFSignal) condfn(err error) {
+	if es.fn == nil {
+		return
+	}
+	if err == io.EOF {
+		err = nil
+	}
+	es.fn(err)
+	es.fn = nil
+}
+
+// gzipReader wraps a response body so it can lazily
+// call gzip.NewReader on the first call to Read
+type gzipReader struct {
+	body io.ReadCloser // underlying Response.Body
+	zr   io.Reader     // lazily-initialized gzip reader
+}
+
+func (gz *gzipReader) Read(p []byte) (n int, err error) {
+	if gz.zr == nil {
+		gz.zr, err = gzip.NewReader(gz.body)
+		if err != nil {
+			return 0, err
+		}
+	}
+	return gz.zr.Read(p)
+}
+
+func (gz *gzipReader) Close() error {
+	return gz.body.Close()
+}
+
+type readerAndCloser struct {
+	io.Reader
+	io.Closer
+}
+
+type tlsHandshakeTimeoutError struct{}
+
+func (tlsHandshakeTimeoutError) Timeout() bool   { return true }
+func (tlsHandshakeTimeoutError) Temporary() bool { return true }
+func (tlsHandshakeTimeoutError) Error() string   { return "net/http: TLS handshake timeout" }
+
+type noteEOFReader struct {
+	r      io.Reader
+	sawEOF *bool
+}
+
+func (nr noteEOFReader) Read(p []byte) (n int, err error) {
+	n, err = nr.r.Read(p)
+	if err == io.EOF {
+		*nr.sawEOF = true
+	}
+	return
+}
diff --git a/src/net/http/transport_test.go b/src/net/http/transport_test.go
new file mode 100644
index 000000000..3460d690e
--- /dev/null
+++ b/src/net/http/transport_test.go
@@ -0,0 +1,2211 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Tests for transport.go
+
+package http_test
+
+import (
+	"bufio"
+	"bytes"
+	"compress/gzip"
+	"crypto/rand"
+	"crypto/tls"
+	"errors"
+	"fmt"
+	"io"
+	"io/ioutil"
+	"log"
+	"net"
+	"net/http"
+	. "net/http"
+	"net/http/httptest"
+	"net/url"
+	"os"
+	"runtime"
+	"strconv"
+	"strings"
+	"sync"
+	"testing"
+	"time"
+)
+
+// TODO: test 5 pipelined requests with responses: 1) OK, 2) OK, Connection: Close
+//       and then verify that the final 2 responses get errors back.
+
+// hostPortHandler writes back the client's "host:port".
+var hostPortHandler = HandlerFunc(func(w ResponseWriter, r *Request) {
+	if r.FormValue("close") == "true" {
+		w.Header().Set("Connection", "close")
+	}
+	w.Write([]byte(r.RemoteAddr))
+})
+
+// testCloseConn is a net.Conn tracked by a testConnSet.
+type testCloseConn struct {
+	net.Conn
+	set *testConnSet
+}
+
+func (c *testCloseConn) Close() error {
+	c.set.remove(c)
+	return c.Conn.Close()
+}
+
+// testConnSet tracks a set of TCP connections and whether they've
+// been closed.
+type testConnSet struct {
+	t      *testing.T
+	mu     sync.Mutex // guards closed and list
+	closed map[net.Conn]bool
+	list   []net.Conn // in order created
+}
+
+func (tcs *testConnSet) insert(c net.Conn) {
+	tcs.mu.Lock()
+	defer tcs.mu.Unlock()
+	tcs.closed[c] = false
+	tcs.list = append(tcs.list, c)
+}
+
+func (tcs *testConnSet) remove(c net.Conn) {
+	tcs.mu.Lock()
+	defer tcs.mu.Unlock()
+	tcs.closed[c] = true
+}
+
+// some tests use this to manage raw tcp connections for later inspection
+func makeTestDial(t *testing.T) (*testConnSet, func(n, addr string) (net.Conn, error)) {
+	connSet := &testConnSet{
+		t:      t,
+		closed: make(map[net.Conn]bool),
+	}
+	dial := func(n, addr string) (net.Conn, error) {
+		c, err := net.Dial(n, addr)
+		if err != nil {
+			return nil, err
+		}
+		tc := &testCloseConn{c, connSet}
+		connSet.insert(tc)
+		return tc, nil
+	}
+	return connSet, dial
+}
+
+func (tcs *testConnSet) check(t *testing.T) {
+	tcs.mu.Lock()
+	defer tcs.mu.Unlock()
+	for i := 4; i >= 0; i-- {
+		for i, c := range tcs.list {
+			if tcs.closed[c] {
+				continue
+			}
+			if i != 0 {
+				tcs.mu.Unlock()
+				time.Sleep(50 * time.Millisecond)
+				tcs.mu.Lock()
+				continue
+			}
+			t.Errorf("TCP connection #%d, %p (of %d total) was not closed", i+1, c, len(tcs.list))
+		}
+	}
+}
+
+// Two subsequent requests and verify their response is the same.
+// The response from the server is our own IP:port
+func TestTransportKeepAlives(t *testing.T) {
+	defer afterTest(t)
+	ts := httptest.NewServer(hostPortHandler)
+	defer ts.Close()
+
+	for _, disableKeepAlive := range []bool{false, true} {
+		tr := &Transport{DisableKeepAlives: disableKeepAlive}
+		defer tr.CloseIdleConnections()
+		c := &Client{Transport: tr}
+
+		fetch := func(n int) string {
+			res, err := c.Get(ts.URL)
+			if err != nil {
+				t.Fatalf("error in disableKeepAlive=%v, req #%d, GET: %v", disableKeepAlive, n, err)
+			}
+			body, err := ioutil.ReadAll(res.Body)
+			if err != nil {
+				t.Fatalf("error in disableKeepAlive=%v, req #%d, ReadAll: %v", disableKeepAlive, n, err)
+			}
+			return string(body)
+		}
+
+		body1 := fetch(1)
+		body2 := fetch(2)
+
+		bodiesDiffer := body1 != body2
+		if bodiesDiffer != disableKeepAlive {
+			t.Errorf("error in disableKeepAlive=%v. unexpected bodiesDiffer=%v; body1=%q; body2=%q",
+				disableKeepAlive, bodiesDiffer, body1, body2)
+		}
+	}
+}
+
+func TestTransportConnectionCloseOnResponse(t *testing.T) {
+	defer afterTest(t)
+	ts := httptest.NewServer(hostPortHandler)
+	defer ts.Close()
+
+	connSet, testDial := makeTestDial(t)
+
+	for _, connectionClose := range []bool{false, true} {
+		tr := &Transport{
+			Dial: testDial,
+		}
+		c := &Client{Transport: tr}
+
+		fetch := func(n int) string {
+			req := new(Request)
+			var err error
+			req.URL, err = url.Parse(ts.URL + fmt.Sprintf("/?close=%v", connectionClose))
+			if err != nil {
+				t.Fatalf("URL parse error: %v", err)
+			}
+			req.Method = "GET"
+			req.Proto = "HTTP/1.1"
+			req.ProtoMajor = 1
+			req.ProtoMinor = 1
+
+			res, err := c.Do(req)
+			if err != nil {
+				t.Fatalf("error in connectionClose=%v, req #%d, Do: %v", connectionClose, n, err)
+			}
+			defer res.Body.Close()
+			body, err := ioutil.ReadAll(res.Body)
+			if err != nil {
+				t.Fatalf("error in connectionClose=%v, req #%d, ReadAll: %v", connectionClose, n, err)
+			}
+			return string(body)
+		}
+
+		body1 := fetch(1)
+		body2 := fetch(2)
+		bodiesDiffer := body1 != body2
+		if bodiesDiffer != connectionClose {
+			t.Errorf("error in connectionClose=%v. unexpected bodiesDiffer=%v; body1=%q; body2=%q",
+				connectionClose, bodiesDiffer, body1, body2)
+		}
+
+		tr.CloseIdleConnections()
+	}
+
+	connSet.check(t)
+}
+
+func TestTransportConnectionCloseOnRequest(t *testing.T) {
+	defer afterTest(t)
+	ts := httptest.NewServer(hostPortHandler)
+	defer ts.Close()
+
+	connSet, testDial := makeTestDial(t)
+
+	for _, connectionClose := range []bool{false, true} {
+		tr := &Transport{
+			Dial: testDial,
+		}
+		c := &Client{Transport: tr}
+
+		fetch := func(n int) string {
+			req := new(Request)
+			var err error
+			req.URL, err = url.Parse(ts.URL)
+			if err != nil {
+				t.Fatalf("URL parse error: %v", err)
+			}
+			req.Method = "GET"
+			req.Proto = "HTTP/1.1"
+			req.ProtoMajor = 1
+			req.ProtoMinor = 1
+			req.Close = connectionClose
+
+			res, err := c.Do(req)
+			if err != nil {
+				t.Fatalf("error in connectionClose=%v, req #%d, Do: %v", connectionClose, n, err)
+			}
+			body, err := ioutil.ReadAll(res.Body)
+			if err != nil {
+				t.Fatalf("error in connectionClose=%v, req #%d, ReadAll: %v", connectionClose, n, err)
+			}
+			return string(body)
+		}
+
+		body1 := fetch(1)
+		body2 := fetch(2)
+		bodiesDiffer := body1 != body2
+		if bodiesDiffer != connectionClose {
+			t.Errorf("error in connectionClose=%v. unexpected bodiesDiffer=%v; body1=%q; body2=%q",
+				connectionClose, bodiesDiffer, body1, body2)
+		}
+
+		tr.CloseIdleConnections()
+	}
+
+	connSet.check(t)
+}
+
+func TestTransportIdleCacheKeys(t *testing.T) {
+	defer afterTest(t)
+	ts := httptest.NewServer(hostPortHandler)
+	defer ts.Close()
+
+	tr := &Transport{DisableKeepAlives: false}
+	c := &Client{Transport: tr}
+
+	if e, g := 0, len(tr.IdleConnKeysForTesting()); e != g {
+		t.Errorf("After CloseIdleConnections expected %d idle conn cache keys; got %d", e, g)
+	}
+
+	resp, err := c.Get(ts.URL)
+	if err != nil {
+		t.Error(err)
+	}
+	ioutil.ReadAll(resp.Body)
+
+	keys := tr.IdleConnKeysForTesting()
+	if e, g := 1, len(keys); e != g {
+		t.Fatalf("After Get expected %d idle conn cache keys; got %d", e, g)
+	}
+
+	if e := "|http|" + ts.Listener.Addr().String(); keys[0] != e {
+		t.Errorf("Expected idle cache key %q; got %q", e, keys[0])
+	}
+
+	tr.CloseIdleConnections()
+	if e, g := 0, len(tr.IdleConnKeysForTesting()); e != g {
+		t.Errorf("After CloseIdleConnections expected %d idle conn cache keys; got %d", e, g)
+	}
+}
+
+// Tests that the HTTP transport re-uses connections when a client
+// reads to the end of a response Body without closing it.
+func TestTransportReadToEndReusesConn(t *testing.T) {
+	defer afterTest(t)
+	const msg = "foobar"
+
+	var addrSeen map[string]int
+	ts := httptest.NewServer(HandlerFunc(func(w ResponseWriter, r *Request) {
+		addrSeen[r.RemoteAddr]++
+		if r.URL.Path == "/chunked/" {
+			w.WriteHeader(200)
+			w.(http.Flusher).Flush()
+		} else {
+			w.Header().Set("Content-Type", strconv.Itoa(len(msg)))
+			w.WriteHeader(200)
+		}
+		w.Write([]byte(msg))
+	}))
+	defer ts.Close()
+
+	buf := make([]byte, len(msg))
+
+	for pi, path := range []string{"/content-length/", "/chunked/"} {
+		wantLen := []int{len(msg), -1}[pi]
+		addrSeen = make(map[string]int)
+		for i := 0; i < 3; i++ {
+			res, err := http.Get(ts.URL + path)
+			if err != nil {
+				t.Errorf("Get %s: %v", path, err)
+				continue
+			}
+			// We want to close this body eventually (before the
+			// defer afterTest at top runs), but not before the
+			// len(addrSeen) check at the bottom of this test,
+			// since Closing this early in the loop would risk
+			// making connections be re-used for the wrong reason.
+			defer res.Body.Close()
+
+			if res.ContentLength != int64(wantLen) {
+				t.Errorf("%s res.ContentLength = %d; want %d", path, res.ContentLength, wantLen)
+			}
+			n, err := res.Body.Read(buf)
+			if n != len(msg) || err != io.EOF {
+				t.Errorf("%s Read = %v, %v; want %d, EOF", path, n, err, len(msg))
+			}
+		}
+		if len(addrSeen) != 1 {
+			t.Errorf("for %s, server saw %d distinct client addresses; want 1", path, len(addrSeen))
+		}
+	}
+}
+
+func TestTransportMaxPerHostIdleConns(t *testing.T) {
+	defer afterTest(t)
+	resch := make(chan string)
+	gotReq := make(chan bool)
+	ts := httptest.NewServer(HandlerFunc(func(w ResponseWriter, r *Request) {
+		gotReq <- true
+		msg := <-resch
+		_, err := w.Write([]byte(msg))
+		if err != nil {
+			t.Fatalf("Write: %v", err)
+		}
+	}))
+	defer ts.Close()
+	maxIdleConns := 2
+	tr := &Transport{DisableKeepAlives: false, MaxIdleConnsPerHost: maxIdleConns}
+	c := &Client{Transport: tr}
+
+	// Start 3 outstanding requests and wait for the server to get them.
+	// Their responses will hang until we write to resch, though.
+	donech := make(chan bool)
+	doReq := func() {
+		resp, err := c.Get(ts.URL)
+		if err != nil {
+			t.Error(err)
+			return
+		}
+		if _, err := ioutil.ReadAll(resp.Body); err != nil {
+			t.Errorf("ReadAll: %v", err)
+			return
+		}
+		donech <- true
+	}
+	go doReq()
+	<-gotReq
+	go doReq()
+	<-gotReq
+	go doReq()
+	<-gotReq
+
+	if e, g := 0, len(tr.IdleConnKeysForTesting()); e != g {
+		t.Fatalf("Before writes, expected %d idle conn cache keys; got %d", e, g)
+	}
+
+	resch <- "res1"
+	<-donech
+	keys := tr.IdleConnKeysForTesting()
+	if e, g := 1, len(keys); e != g {
+		t.Fatalf("after first response, expected %d idle conn cache keys; got %d", e, g)
+	}
+	cacheKey := "|http|" + ts.Listener.Addr().String()
+	if keys[0] != cacheKey {
+		t.Fatalf("Expected idle cache key %q; got %q", cacheKey, keys[0])
+	}
+	if e, g := 1, tr.IdleConnCountForTesting(cacheKey); e != g {
+		t.Errorf("after first response, expected %d idle conns; got %d", e, g)
+	}
+
+	resch <- "res2"
+	<-donech
+	if e, g := 2, tr.IdleConnCountForTesting(cacheKey); e != g {
+		t.Errorf("after second response, expected %d idle conns; got %d", e, g)
+	}
+
+	resch <- "res3"
+	<-donech
+	if e, g := maxIdleConns, tr.IdleConnCountForTesting(cacheKey); e != g {
+		t.Errorf("after third response, still expected %d idle conns; got %d", e, g)
+	}
+}
+
+func TestTransportServerClosingUnexpectedly(t *testing.T) {
+	defer afterTest(t)
+	ts := httptest.NewServer(hostPortHandler)
+	defer ts.Close()
+
+	tr := &Transport{}
+	c := &Client{Transport: tr}
+
+	fetch := func(n, retries int) string {
+		condFatalf := func(format string, arg ...interface{}) {
+			if retries <= 0 {
+				t.Fatalf(format, arg...)
+			}
+			t.Logf("retrying shortly after expected error: "+format, arg...)
+			time.Sleep(time.Second / time.Duration(retries))
+		}
+		for retries >= 0 {
+			retries--
+			res, err := c.Get(ts.URL)
+			if err != nil {
+				condFatalf("error in req #%d, GET: %v", n, err)
+				continue
+			}
+			body, err := ioutil.ReadAll(res.Body)
+			if err != nil {
+				condFatalf("error in req #%d, ReadAll: %v", n, err)
+				continue
+			}
+			res.Body.Close()
+			return string(body)
+		}
+		panic("unreachable")
+	}
+
+	body1 := fetch(1, 0)
+	body2 := fetch(2, 0)
+
+	ts.CloseClientConnections() // surprise!
+
+	// This test has an expected race. Sleeping for 25 ms prevents
+	// it on most fast machines, causing the next fetch() call to
+	// succeed quickly.  But if we do get errors, fetch() will retry 5
+	// times with some delays between.
+	time.Sleep(25 * time.Millisecond)
+
+	body3 := fetch(3, 5)
+
+	if body1 != body2 {
+		t.Errorf("expected body1 and body2 to be equal")
+	}
+	if body2 == body3 {
+		t.Errorf("expected body2 and body3 to be different")
+	}
+}
+
+// Test for http://golang.org/issue/2616 (appropriate issue number)
+// This fails pretty reliably with GOMAXPROCS=100 or something high.
+func TestStressSurpriseServerCloses(t *testing.T) {
+	defer afterTest(t)
+	if testing.Short() {
+		t.Skip("skipping test in short mode")
+	}
+	ts := httptest.NewServer(HandlerFunc(func(w ResponseWriter, r *Request) {
+		w.Header().Set("Content-Length", "5")
+		w.Header().Set("Content-Type", "text/plain")
+		w.Write([]byte("Hello"))
+		w.(Flusher).Flush()
+		conn, buf, _ := w.(Hijacker).Hijack()
+		buf.Flush()
+		conn.Close()
+	}))
+	defer ts.Close()
+
+	tr := &Transport{DisableKeepAlives: false}
+	c := &Client{Transport: tr}
+
+	// Do a bunch of traffic from different goroutines. Send to activityc
+	// after each request completes, regardless of whether it failed.
+	const (
+		numClients    = 50
+		reqsPerClient = 250
+	)
+	activityc := make(chan bool)
+	for i := 0; i < numClients; i++ {
+		go func() {
+			for i := 0; i < reqsPerClient; i++ {
+				res, err := c.Get(ts.URL)
+				if err == nil {
+					// We expect errors since the server is
+					// hanging up on us after telling us to
+					// send more requests, so we don't
+					// actually care what the error is.
+					// But we want to close the body in cases
+					// where we won the race.
+					res.Body.Close()
+				}
+				activityc <- true
+			}
+		}()
+	}
+
+	// Make sure all the request come back, one way or another.
+	for i := 0; i < numClients*reqsPerClient; i++ {
+		select {
+		case <-activityc:
+		case <-time.After(5 * time.Second):
+			t.Fatalf("presumed deadlock; no HTTP client activity seen in awhile")
+		}
+	}
+}
+
+// TestTransportHeadResponses verifies that we deal with Content-Lengths
+// with no bodies properly
+func TestTransportHeadResponses(t *testing.T) {
+	defer afterTest(t)
+	ts := httptest.NewServer(HandlerFunc(func(w ResponseWriter, r *Request) {
+		if r.Method != "HEAD" {
+			panic("expected HEAD; got " + r.Method)
+		}
+		w.Header().Set("Content-Length", "123")
+		w.WriteHeader(200)
+	}))
+	defer ts.Close()
+
+	tr := &Transport{DisableKeepAlives: false}
+	c := &Client{Transport: tr}
+	for i := 0; i < 2; i++ {
+		res, err := c.Head(ts.URL)
+		if err != nil {
+			t.Errorf("error on loop %d: %v", i, err)
+			continue
+		}
+		if e, g := "123", res.Header.Get("Content-Length"); e != g {
+			t.Errorf("loop %d: expected Content-Length header of %q, got %q", i, e, g)
+		}
+		if e, g := int64(123), res.ContentLength; e != g {
+			t.Errorf("loop %d: expected res.ContentLength of %v, got %v", i, e, g)
+		}
+		if all, err := ioutil.ReadAll(res.Body); err != nil {
+			t.Errorf("loop %d: Body ReadAll: %v", i, err)
+		} else if len(all) != 0 {
+			t.Errorf("Bogus body %q", all)
+		}
+	}
+}
+
+// TestTransportHeadChunkedResponse verifies that we ignore chunked transfer-encoding
+// on responses to HEAD requests.
+func TestTransportHeadChunkedResponse(t *testing.T) {
+	defer afterTest(t)
+	ts := httptest.NewServer(HandlerFunc(func(w ResponseWriter, r *Request) {
+		if r.Method != "HEAD" {
+			panic("expected HEAD; got " + r.Method)
+		}
+		w.Header().Set("Transfer-Encoding", "chunked") // client should ignore
+		w.Header().Set("x-client-ipport", r.RemoteAddr)
+		w.WriteHeader(200)
+	}))
+	defer ts.Close()
+
+	tr := &Transport{DisableKeepAlives: false}
+	c := &Client{Transport: tr}
+
+	res1, err := c.Head(ts.URL)
+	if err != nil {
+		t.Fatalf("request 1 error: %v", err)
+	}
+	res2, err := c.Head(ts.URL)
+	if err != nil {
+		t.Fatalf("request 2 error: %v", err)
+	}
+	if v1, v2 := res1.Header.Get("x-client-ipport"), res2.Header.Get("x-client-ipport"); v1 != v2 {
+		t.Errorf("ip/ports differed between head requests: %q vs %q", v1, v2)
+	}
+}
+
+var roundTripTests = []struct {
+	accept       string
+	expectAccept string
+	compressed   bool
+}{
+	// Requests with no accept-encoding header use transparent compression
+	{"", "gzip", false},
+	// Requests with other accept-encoding should pass through unmodified
+	{"foo", "foo", false},
+	// Requests with accept-encoding == gzip should be passed through
+	{"gzip", "gzip", true},
+}
+
+// Test that the modification made to the Request by the RoundTripper is cleaned up
+func TestRoundTripGzip(t *testing.T) {
+	defer afterTest(t)
+	const responseBody = "test response body"
+	ts := httptest.NewServer(HandlerFunc(func(rw ResponseWriter, req *Request) {
+		accept := req.Header.Get("Accept-Encoding")
+		if expect := req.FormValue("expect_accept"); accept != expect {
+			t.Errorf("in handler, test %v: Accept-Encoding = %q, want %q",
+				req.FormValue("testnum"), accept, expect)
+		}
+		if accept == "gzip" {
+			rw.Header().Set("Content-Encoding", "gzip")
+			gz := gzip.NewWriter(rw)
+			gz.Write([]byte(responseBody))
+			gz.Close()
+		} else {
+			rw.Header().Set("Content-Encoding", accept)
+			rw.Write([]byte(responseBody))
+		}
+	}))
+	defer ts.Close()
+
+	for i, test := range roundTripTests {
+		// Test basic request (no accept-encoding)
+		req, _ := NewRequest("GET", fmt.Sprintf("%s/?testnum=%d&expect_accept=%s", ts.URL, i, test.expectAccept), nil)
+		if test.accept != "" {
+			req.Header.Set("Accept-Encoding", test.accept)
+		}
+		res, err := DefaultTransport.RoundTrip(req)
+		var body []byte
+		if test.compressed {
+			var r *gzip.Reader
+			r, err = gzip.NewReader(res.Body)
+			if err != nil {
+				t.Errorf("%d. gzip NewReader: %v", i, err)
+				continue
+			}
+			body, err = ioutil.ReadAll(r)
+			res.Body.Close()
+		} else {
+			body, err = ioutil.ReadAll(res.Body)
+		}
+		if err != nil {
+			t.Errorf("%d. Error: %q", i, err)
+			continue
+		}
+		if g, e := string(body), responseBody; g != e {
+			t.Errorf("%d. body = %q; want %q", i, g, e)
+		}
+		if g, e := req.Header.Get("Accept-Encoding"), test.accept; g != e {
+			t.Errorf("%d. Accept-Encoding = %q; want %q (it was mutated, in violation of RoundTrip contract)", i, g, e)
+		}
+		if g, e := res.Header.Get("Content-Encoding"), test.accept; g != e {
+			t.Errorf("%d. Content-Encoding = %q; want %q", i, g, e)
+		}
+	}
+
+}
+
+func TestTransportGzip(t *testing.T) {
+	defer afterTest(t)
+	const testString = "The test string aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa"
+	const nRandBytes = 1024 * 1024
+	ts := httptest.NewServer(HandlerFunc(func(rw ResponseWriter, req *Request) {
+		if req.Method == "HEAD" {
+			if g := req.Header.Get("Accept-Encoding"); g != "" {
+				t.Errorf("HEAD request sent with Accept-Encoding of %q; want none", g)
+			}
+			return
+		}
+		if g, e := req.Header.Get("Accept-Encoding"), "gzip"; g != e {
+			t.Errorf("Accept-Encoding = %q, want %q", g, e)
+		}
+		rw.Header().Set("Content-Encoding", "gzip")
+
+		var w io.Writer = rw
+		var buf bytes.Buffer
+		if req.FormValue("chunked") == "0" {
+			w = &buf
+			defer io.Copy(rw, &buf)
+			defer func() {
+				rw.Header().Set("Content-Length", strconv.Itoa(buf.Len()))
+			}()
+		}
+		gz := gzip.NewWriter(w)
+		gz.Write([]byte(testString))
+		if req.FormValue("body") == "large" {
+			io.CopyN(gz, rand.Reader, nRandBytes)
+		}
+		gz.Close()
+	}))
+	defer ts.Close()
+
+	for _, chunked := range []string{"1", "0"} {
+		c := &Client{Transport: &Transport{}}
+
+		// First fetch something large, but only read some of it.
+		res, err := c.Get(ts.URL + "/?body=large&chunked=" + chunked)
+		if err != nil {
+			t.Fatalf("large get: %v", err)
+		}
+		buf := make([]byte, len(testString))
+		n, err := io.ReadFull(res.Body, buf)
+		if err != nil {
+			t.Fatalf("partial read of large response: size=%d, %v", n, err)
+		}
+		if e, g := testString, string(buf); e != g {
+			t.Errorf("partial read got %q, expected %q", g, e)
+		}
+		res.Body.Close()
+		// Read on the body, even though it's closed
+		n, err = res.Body.Read(buf)
+		if n != 0 || err == nil {
+			t.Errorf("expected error post-closed large Read; got = %d, %v", n, err)
+		}
+
+		// Then something small.
+		res, err = c.Get(ts.URL + "/?chunked=" + chunked)
+		if err != nil {
+			t.Fatal(err)
+		}
+		body, err := ioutil.ReadAll(res.Body)
+		if err != nil {
+			t.Fatal(err)
+		}
+		if g, e := string(body), testString; g != e {
+			t.Fatalf("body = %q; want %q", g, e)
+		}
+		if g, e := res.Header.Get("Content-Encoding"), ""; g != e {
+			t.Fatalf("Content-Encoding = %q; want %q", g, e)
+		}
+
+		// Read on the body after it's been fully read:
+		n, err = res.Body.Read(buf)
+		if n != 0 || err == nil {
+			t.Errorf("expected Read error after exhausted reads; got %d, %v", n, err)
+		}
+		res.Body.Close()
+		n, err = res.Body.Read(buf)
+		if n != 0 || err == nil {
+			t.Errorf("expected Read error after Close; got %d, %v", n, err)
+		}
+	}
+
+	// And a HEAD request too, because they're always weird.
+	c := &Client{Transport: &Transport{}}
+	res, err := c.Head(ts.URL)
+	if err != nil {
+		t.Fatalf("Head: %v", err)
+	}
+	if res.StatusCode != 200 {
+		t.Errorf("Head status=%d; want=200", res.StatusCode)
+	}
+}
+
+func TestTransportProxy(t *testing.T) {
+	defer afterTest(t)
+	ch := make(chan string, 1)
+	ts := httptest.NewServer(HandlerFunc(func(w ResponseWriter, r *Request) {
+		ch <- "real server"
+	}))
+	defer ts.Close()
+	proxy := httptest.NewServer(HandlerFunc(func(w ResponseWriter, r *Request) {
+		ch <- "proxy for " + r.URL.String()
+	}))
+	defer proxy.Close()
+
+	pu, err := url.Parse(proxy.URL)
+	if err != nil {
+		t.Fatal(err)
+	}
+	c := &Client{Transport: &Transport{Proxy: ProxyURL(pu)}}
+	c.Head(ts.URL)
+	got := <-ch
+	want := "proxy for " + ts.URL + "/"
+	if got != want {
+		t.Errorf("want %q, got %q", want, got)
+	}
+}
+
+// TestTransportGzipRecursive sends a gzip quine and checks that the
+// client gets the same value back. This is more cute than anything,
+// but checks that we don't recurse forever, and checks that
+// Content-Encoding is removed.
+func TestTransportGzipRecursive(t *testing.T) {
+	defer afterTest(t)
+	ts := httptest.NewServer(HandlerFunc(func(w ResponseWriter, r *Request) {
+		w.Header().Set("Content-Encoding", "gzip")
+		w.Write(rgz)
+	}))
+	defer ts.Close()
+
+	c := &Client{Transport: &Transport{}}
+	res, err := c.Get(ts.URL)
+	if err != nil {
+		t.Fatal(err)
+	}
+	body, err := ioutil.ReadAll(res.Body)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if !bytes.Equal(body, rgz) {
+		t.Fatalf("Incorrect result from recursive gz:\nhave=%x\nwant=%x",
+			body, rgz)
+	}
+	if g, e := res.Header.Get("Content-Encoding"), ""; g != e {
+		t.Fatalf("Content-Encoding = %q; want %q", g, e)
+	}
+}
+
+// golang.org/issue/7750: request fails when server replies with
+// a short gzip body
+func TestTransportGzipShort(t *testing.T) {
+	defer afterTest(t)
+	ts := httptest.NewServer(HandlerFunc(func(w ResponseWriter, r *Request) {
+		w.Header().Set("Content-Encoding", "gzip")
+		w.Write([]byte{0x1f, 0x8b})
+	}))
+	defer ts.Close()
+
+	tr := &Transport{}
+	defer tr.CloseIdleConnections()
+	c := &Client{Transport: tr}
+	res, err := c.Get(ts.URL)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer res.Body.Close()
+	_, err = ioutil.ReadAll(res.Body)
+	if err == nil {
+		t.Fatal("Expect an error from reading a body.")
+	}
+	if err != io.ErrUnexpectedEOF {
+		t.Errorf("ReadAll error = %v; want io.ErrUnexpectedEOF", err)
+	}
+}
+
+// tests that persistent goroutine connections shut down when no longer desired.
+func TestTransportPersistConnLeak(t *testing.T) {
+	if runtime.GOOS == "plan9" {
+		t.Skip("skipping test; see http://golang.org/issue/7237")
+	}
+	defer afterTest(t)
+	gotReqCh := make(chan bool)
+	unblockCh := make(chan bool)
+	ts := httptest.NewServer(HandlerFunc(func(w ResponseWriter, r *Request) {
+		gotReqCh <- true
+		<-unblockCh
+		w.Header().Set("Content-Length", "0")
+		w.WriteHeader(204)
+	}))
+	defer ts.Close()
+
+	tr := &Transport{}
+	c := &Client{Transport: tr}
+
+	n0 := runtime.NumGoroutine()
+
+	const numReq = 25
+	didReqCh := make(chan bool)
+	for i := 0; i < numReq; i++ {
+		go func() {
+			res, err := c.Get(ts.URL)
+			didReqCh <- true
+			if err != nil {
+				t.Errorf("client fetch error: %v", err)
+				return
+			}
+			res.Body.Close()
+		}()
+	}
+
+	// Wait for all goroutines to be stuck in the Handler.
+	for i := 0; i < numReq; i++ {
+		<-gotReqCh
+	}
+
+	nhigh := runtime.NumGoroutine()
+
+	// Tell all handlers to unblock and reply.
+	for i := 0; i < numReq; i++ {
+		unblockCh <- true
+	}
+
+	// Wait for all HTTP clients to be done.
+	for i := 0; i < numReq; i++ {
+		<-didReqCh
+	}
+
+	tr.CloseIdleConnections()
+	time.Sleep(100 * time.Millisecond)
+	runtime.GC()
+	runtime.GC() // even more.
+	nfinal := runtime.NumGoroutine()
+
+	growth := nfinal - n0
+
+	// We expect 0 or 1 extra goroutine, empirically.  Allow up to 5.
+	// Previously we were leaking one per numReq.
+	if int(growth) > 5 {
+		t.Logf("goroutine growth: %d -> %d -> %d (delta: %d)", n0, nhigh, nfinal, growth)
+		t.Error("too many new goroutines")
+	}
+}
+
+// golang.org/issue/4531: Transport leaks goroutines when
+// request.ContentLength is explicitly short
+func TestTransportPersistConnLeakShortBody(t *testing.T) {
+	if runtime.GOOS == "plan9" {
+		t.Skip("skipping test; see http://golang.org/issue/7237")
+	}
+	defer afterTest(t)
+	ts := httptest.NewServer(HandlerFunc(func(w ResponseWriter, r *Request) {
+	}))
+	defer ts.Close()
+
+	tr := &Transport{}
+	c := &Client{Transport: tr}
+
+	n0 := runtime.NumGoroutine()
+	body := []byte("Hello")
+	for i := 0; i < 20; i++ {
+		req, err := NewRequest("POST", ts.URL, bytes.NewReader(body))
+		if err != nil {
+			t.Fatal(err)
+		}
+		req.ContentLength = int64(len(body) - 2) // explicitly short
+		_, err = c.Do(req)
+		if err == nil {
+			t.Fatal("Expect an error from writing too long of a body.")
+		}
+	}
+	nhigh := runtime.NumGoroutine()
+	tr.CloseIdleConnections()
+	time.Sleep(400 * time.Millisecond)
+	runtime.GC()
+	nfinal := runtime.NumGoroutine()
+
+	growth := nfinal - n0
+
+	// We expect 0 or 1 extra goroutine, empirically.  Allow up to 5.
+	// Previously we were leaking one per numReq.
+	t.Logf("goroutine growth: %d -> %d -> %d (delta: %d)", n0, nhigh, nfinal, growth)
+	if int(growth) > 5 {
+		t.Error("too many new goroutines")
+	}
+}
+
+// This used to crash; http://golang.org/issue/3266
+func TestTransportIdleConnCrash(t *testing.T) {
+	defer afterTest(t)
+	tr := &Transport{}
+	c := &Client{Transport: tr}
+
+	unblockCh := make(chan bool, 1)
+	ts := httptest.NewServer(HandlerFunc(func(w ResponseWriter, r *Request) {
+		<-unblockCh
+		tr.CloseIdleConnections()
+	}))
+	defer ts.Close()
+
+	didreq := make(chan bool)
+	go func() {
+		res, err := c.Get(ts.URL)
+		if err != nil {
+			t.Error(err)
+		} else {
+			res.Body.Close() // returns idle conn
+		}
+		didreq <- true
+	}()
+	unblockCh <- true
+	<-didreq
+}
+
+// Test that the transport doesn't close the TCP connection early,
+// before the response body has been read.  This was a regression
+// which sadly lacked a triggering test.  The large response body made
+// the old race easier to trigger.
+func TestIssue3644(t *testing.T) {
+	defer afterTest(t)
+	const numFoos = 5000
+	ts := httptest.NewServer(HandlerFunc(func(w ResponseWriter, r *Request) {
+		w.Header().Set("Connection", "close")
+		for i := 0; i < numFoos; i++ {
+			w.Write([]byte("foo "))
+		}
+	}))
+	defer ts.Close()
+	tr := &Transport{}
+	c := &Client{Transport: tr}
+	res, err := c.Get(ts.URL)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer res.Body.Close()
+	bs, err := ioutil.ReadAll(res.Body)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(bs) != numFoos*len("foo ") {
+		t.Errorf("unexpected response length")
+	}
+}
+
+// Test that a client receives a server's reply, even if the server doesn't read
+// the entire request body.
+func TestIssue3595(t *testing.T) {
+	defer afterTest(t)
+	const deniedMsg = "sorry, denied."
+	ts := httptest.NewServer(HandlerFunc(func(w ResponseWriter, r *Request) {
+		Error(w, deniedMsg, StatusUnauthorized)
+	}))
+	defer ts.Close()
+	tr := &Transport{}
+	c := &Client{Transport: tr}
+	res, err := c.Post(ts.URL, "application/octet-stream", neverEnding('a'))
+	if err != nil {
+		t.Errorf("Post: %v", err)
+		return
+	}
+	got, err := ioutil.ReadAll(res.Body)
+	if err != nil {
+		t.Fatalf("Body ReadAll: %v", err)
+	}
+	if !strings.Contains(string(got), deniedMsg) {
+		t.Errorf("Known bug: response %q does not contain %q", got, deniedMsg)
+	}
+}
+
+// From http://golang.org/issue/4454 ,
+// "client fails to handle requests with no body and chunked encoding"
+func TestChunkedNoContent(t *testing.T) {
+	defer afterTest(t)
+	ts := httptest.NewServer(HandlerFunc(func(w ResponseWriter, r *Request) {
+		w.WriteHeader(StatusNoContent)
+	}))
+	defer ts.Close()
+
+	for _, closeBody := range []bool{true, false} {
+		c := &Client{Transport: &Transport{}}
+		const n = 4
+		for i := 1; i <= n; i++ {
+			res, err := c.Get(ts.URL)
+			if err != nil {
+				t.Errorf("closingBody=%v, req %d/%d: %v", closeBody, i, n, err)
+			} else {
+				if closeBody {
+					res.Body.Close()
+				}
+			}
+		}
+	}
+}
+
+func TestTransportConcurrency(t *testing.T) {
+	defer afterTest(t)
+	maxProcs, numReqs := 16, 500
+	if testing.Short() {
+		maxProcs, numReqs = 4, 50
+	}
+	defer runtime.GOMAXPROCS(runtime.GOMAXPROCS(maxProcs))
+	ts := httptest.NewServer(HandlerFunc(func(w ResponseWriter, r *Request) {
+		fmt.Fprintf(w, "%v", r.FormValue("echo"))
+	}))
+	defer ts.Close()
+
+	var wg sync.WaitGroup
+	wg.Add(numReqs)
+
+	// Due to the Transport's "socket late binding" (see
+	// idleConnCh in transport.go), the numReqs HTTP requests
+	// below can finish with a dial still outstanding.  To keep
+	// the leak checker happy, keep track of pending dials and
+	// wait for them to finish (and be closed or returned to the
+	// idle pool) before we close idle connections.
+	SetPendingDialHooks(func() { wg.Add(1) }, wg.Done)
+	defer SetPendingDialHooks(nil, nil)
+
+	tr := &Transport{}
+	defer tr.CloseIdleConnections()
+
+	c := &Client{Transport: tr}
+	reqs := make(chan string)
+	defer close(reqs)
+
+	for i := 0; i < maxProcs*2; i++ {
+		go func() {
+			for req := range reqs {
+				res, err := c.Get(ts.URL + "/?echo=" + req)
+				if err != nil {
+					t.Errorf("error on req %s: %v", req, err)
+					wg.Done()
+					continue
+				}
+				all, err := ioutil.ReadAll(res.Body)
+				if err != nil {
+					t.Errorf("read error on req %s: %v", req, err)
+					wg.Done()
+					continue
+				}
+				if string(all) != req {
+					t.Errorf("body of req %s = %q; want %q", req, all, req)
+				}
+				res.Body.Close()
+				wg.Done()
+			}
+		}()
+	}
+	for i := 0; i < numReqs; i++ {
+		reqs <- fmt.Sprintf("request-%d", i)
+	}
+	wg.Wait()
+}
+
+func TestIssue4191_InfiniteGetTimeout(t *testing.T) {
+	if runtime.GOOS == "plan9" {
+		t.Skip("skipping test; see http://golang.org/issue/7237")
+	}
+	defer afterTest(t)
+	const debug = false
+	mux := NewServeMux()
+	mux.HandleFunc("/get", func(w ResponseWriter, r *Request) {
+		io.Copy(w, neverEnding('a'))
+	})
+	ts := httptest.NewServer(mux)
+	timeout := 100 * time.Millisecond
+
+	client := &Client{
+		Transport: &Transport{
+			Dial: func(n, addr string) (net.Conn, error) {
+				conn, err := net.Dial(n, addr)
+				if err != nil {
+					return nil, err
+				}
+				conn.SetDeadline(time.Now().Add(timeout))
+				if debug {
+					conn = NewLoggingConn("client", conn)
+				}
+				return conn, nil
+			},
+			DisableKeepAlives: true,
+		},
+	}
+
+	getFailed := false
+	nRuns := 5
+	if testing.Short() {
+		nRuns = 1
+	}
+	for i := 0; i < nRuns; i++ {
+		if debug {
+			println("run", i+1, "of", nRuns)
+		}
+		sres, err := client.Get(ts.URL + "/get")
+		if err != nil {
+			if !getFailed {
+				// Make the timeout longer, once.
+				getFailed = true
+				t.Logf("increasing timeout")
+				i--
+				timeout *= 10
+				continue
+			}
+			t.Errorf("Error issuing GET: %v", err)
+			break
+		}
+		_, err = io.Copy(ioutil.Discard, sres.Body)
+		if err == nil {
+			t.Errorf("Unexpected successful copy")
+			break
+		}
+	}
+	if debug {
+		println("tests complete; waiting for handlers to finish")
+	}
+	ts.Close()
+}
+
+func TestIssue4191_InfiniteGetToPutTimeout(t *testing.T) {
+	if runtime.GOOS == "plan9" {
+		t.Skip("skipping test; see http://golang.org/issue/7237")
+	}
+	defer afterTest(t)
+	const debug = false
+	mux := NewServeMux()
+	mux.HandleFunc("/get", func(w ResponseWriter, r *Request) {
+		io.Copy(w, neverEnding('a'))
+	})
+	mux.HandleFunc("/put", func(w ResponseWriter, r *Request) {
+		defer r.Body.Close()
+		io.Copy(ioutil.Discard, r.Body)
+	})
+	ts := httptest.NewServer(mux)
+	timeout := 100 * time.Millisecond
+
+	client := &Client{
+		Transport: &Transport{
+			Dial: func(n, addr string) (net.Conn, error) {
+				conn, err := net.Dial(n, addr)
+				if err != nil {
+					return nil, err
+				}
+				conn.SetDeadline(time.Now().Add(timeout))
+				if debug {
+					conn = NewLoggingConn("client", conn)
+				}
+				return conn, nil
+			},
+			DisableKeepAlives: true,
+		},
+	}
+
+	getFailed := false
+	nRuns := 5
+	if testing.Short() {
+		nRuns = 1
+	}
+	for i := 0; i < nRuns; i++ {
+		if debug {
+			println("run", i+1, "of", nRuns)
+		}
+		sres, err := client.Get(ts.URL + "/get")
+		if err != nil {
+			if !getFailed {
+				// Make the timeout longer, once.
+				getFailed = true
+				t.Logf("increasing timeout")
+				i--
+				timeout *= 10
+				continue
+			}
+			t.Errorf("Error issuing GET: %v", err)
+			break
+		}
+		req, _ := NewRequest("PUT", ts.URL+"/put", sres.Body)
+		_, err = client.Do(req)
+		if err == nil {
+			sres.Body.Close()
+			t.Errorf("Unexpected successful PUT")
+			break
+		}
+		sres.Body.Close()
+	}
+	if debug {
+		println("tests complete; waiting for handlers to finish")
+	}
+	ts.Close()
+}
+
+func TestTransportResponseHeaderTimeout(t *testing.T) {
+	defer afterTest(t)
+	if testing.Short() {
+		t.Skip("skipping timeout test in -short mode")
+	}
+	inHandler := make(chan bool, 1)
+	mux := NewServeMux()
+	mux.HandleFunc("/fast", func(w ResponseWriter, r *Request) {
+		inHandler <- true
+	})
+	mux.HandleFunc("/slow", func(w ResponseWriter, r *Request) {
+		inHandler <- true
+		time.Sleep(2 * time.Second)
+	})
+	ts := httptest.NewServer(mux)
+	defer ts.Close()
+
+	tr := &Transport{
+		ResponseHeaderTimeout: 500 * time.Millisecond,
+	}
+	defer tr.CloseIdleConnections()
+	c := &Client{Transport: tr}
+
+	tests := []struct {
+		path    string
+		want    int
+		wantErr string
+	}{
+		{path: "/fast", want: 200},
+		{path: "/slow", wantErr: "timeout awaiting response headers"},
+		{path: "/fast", want: 200},
+	}
+	for i, tt := range tests {
+		res, err := c.Get(ts.URL + tt.path)
+		select {
+		case <-inHandler:
+		case <-time.After(5 * time.Second):
+			t.Errorf("never entered handler for test index %d, %s", i, tt.path)
+			continue
+		}
+		if err != nil {
+			uerr, ok := err.(*url.Error)
+			if !ok {
+				t.Errorf("error is not an url.Error; got: %#v", err)
+				continue
+			}
+			nerr, ok := uerr.Err.(net.Error)
+			if !ok {
+				t.Errorf("error does not satisfy net.Error interface; got: %#v", err)
+				continue
+			}
+			if !nerr.Timeout() {
+				t.Errorf("want timeout error; got: %q", nerr)
+				continue
+			}
+			if strings.Contains(err.Error(), tt.wantErr) {
+				continue
+			}
+			t.Errorf("%d. unexpected error: %v", i, err)
+			continue
+		}
+		if tt.wantErr != "" {
+			t.Errorf("%d. no error. expected error: %v", i, tt.wantErr)
+			continue
+		}
+		if res.StatusCode != tt.want {
+			t.Errorf("%d for path %q status = %d; want %d", i, tt.path, res.StatusCode, tt.want)
+		}
+	}
+}
+
+func TestTransportCancelRequest(t *testing.T) {
+	defer afterTest(t)
+	if testing.Short() {
+		t.Skip("skipping test in -short mode")
+	}
+	unblockc := make(chan bool)
+	ts := httptest.NewServer(HandlerFunc(func(w ResponseWriter, r *Request) {
+		fmt.Fprintf(w, "Hello")
+		w.(Flusher).Flush() // send headers and some body
+		<-unblockc
+	}))
+	defer ts.Close()
+	defer close(unblockc)
+
+	tr := &Transport{}
+	defer tr.CloseIdleConnections()
+	c := &Client{Transport: tr}
+
+	req, _ := NewRequest("GET", ts.URL, nil)
+	res, err := c.Do(req)
+	if err != nil {
+		t.Fatal(err)
+	}
+	go func() {
+		time.Sleep(1 * time.Second)
+		tr.CancelRequest(req)
+	}()
+	t0 := time.Now()
+	body, err := ioutil.ReadAll(res.Body)
+	d := time.Since(t0)
+
+	if err == nil {
+		t.Error("expected an error reading the body")
+	}
+	if string(body) != "Hello" {
+		t.Errorf("Body = %q; want Hello", body)
+	}
+	if d < 500*time.Millisecond {
+		t.Errorf("expected ~1 second delay; got %v", d)
+	}
+	// Verify no outstanding requests after readLoop/writeLoop
+	// goroutines shut down.
+	for tries := 3; tries > 0; tries-- {
+		n := tr.NumPendingRequestsForTesting()
+		if n == 0 {
+			break
+		}
+		time.Sleep(100 * time.Millisecond)
+		if tries == 1 {
+			t.Errorf("pending requests = %d; want 0", n)
+		}
+	}
+}
+
+func TestTransportCancelRequestInDial(t *testing.T) {
+	defer afterTest(t)
+	if testing.Short() {
+		t.Skip("skipping test in -short mode")
+	}
+	var logbuf bytes.Buffer
+	eventLog := log.New(&logbuf, "", 0)
+
+	unblockDial := make(chan bool)
+	defer close(unblockDial)
+
+	inDial := make(chan bool)
+	tr := &Transport{
+		Dial: func(network, addr string) (net.Conn, error) {
+			eventLog.Println("dial: blocking")
+			inDial <- true
+			<-unblockDial
+			return nil, errors.New("nope")
+		},
+	}
+	cl := &Client{Transport: tr}
+	gotres := make(chan bool)
+	req, _ := NewRequest("GET", "http://something.no-network.tld/", nil)
+	go func() {
+		_, err := cl.Do(req)
+		eventLog.Printf("Get = %v", err)
+		gotres <- true
+	}()
+
+	select {
+	case <-inDial:
+	case <-time.After(5 * time.Second):
+		t.Fatal("timeout; never saw blocking dial")
+	}
+
+	eventLog.Printf("canceling")
+	tr.CancelRequest(req)
+
+	select {
+	case <-gotres:
+	case <-time.After(5 * time.Second):
+		panic("hang. events are: " + logbuf.String())
+	}
+
+	got := logbuf.String()
+	want := `dial: blocking
+canceling
+Get = Get http://something.no-network.tld/: net/http: request canceled while waiting for connection
+`
+	if got != want {
+		t.Errorf("Got events:\n%s\nWant:\n%s", got, want)
+	}
+}
+
+// golang.org/issue/3672 -- Client can't close HTTP stream
+// Calling Close on a Response.Body used to just read until EOF.
+// Now it actually closes the TCP connection.
+func TestTransportCloseResponseBody(t *testing.T) {
+	defer afterTest(t)
+	writeErr := make(chan error, 1)
+	msg := []byte("young\n")
+	ts := httptest.NewServer(HandlerFunc(func(w ResponseWriter, r *Request) {
+		for {
+			_, err := w.Write(msg)
+			if err != nil {
+				writeErr <- err
+				return
+			}
+			w.(Flusher).Flush()
+		}
+	}))
+	defer ts.Close()
+
+	tr := &Transport{}
+	defer tr.CloseIdleConnections()
+	c := &Client{Transport: tr}
+
+	req, _ := NewRequest("GET", ts.URL, nil)
+	defer tr.CancelRequest(req)
+
+	res, err := c.Do(req)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	const repeats = 3
+	buf := make([]byte, len(msg)*repeats)
+	want := bytes.Repeat(msg, repeats)
+
+	_, err = io.ReadFull(res.Body, buf)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if !bytes.Equal(buf, want) {
+		t.Fatalf("read %q; want %q", buf, want)
+	}
+	didClose := make(chan error, 1)
+	go func() {
+		didClose <- res.Body.Close()
+	}()
+	select {
+	case err := <-didClose:
+		if err != nil {
+			t.Errorf("Close = %v", err)
+		}
+	case <-time.After(10 * time.Second):
+		t.Fatal("too long waiting for close")
+	}
+	select {
+	case err := <-writeErr:
+		if err == nil {
+			t.Errorf("expected non-nil write error")
+		}
+	case <-time.After(10 * time.Second):
+		t.Fatal("too long waiting for write error")
+	}
+}
+
+type fooProto struct{}
+
+func (fooProto) RoundTrip(req *Request) (*Response, error) {
+	res := &Response{
+		Status:     "200 OK",
+		StatusCode: 200,
+		Header:     make(Header),
+		Body:       ioutil.NopCloser(strings.NewReader("You wanted " + req.URL.String())),
+	}
+	return res, nil
+}
+
+func TestTransportAltProto(t *testing.T) {
+	defer afterTest(t)
+	tr := &Transport{}
+	c := &Client{Transport: tr}
+	tr.RegisterProtocol("foo", fooProto{})
+	res, err := c.Get("foo://bar.com/path")
+	if err != nil {
+		t.Fatal(err)
+	}
+	bodyb, err := ioutil.ReadAll(res.Body)
+	if err != nil {
+		t.Fatal(err)
+	}
+	body := string(bodyb)
+	if e := "You wanted foo://bar.com/path"; body != e {
+		t.Errorf("got response %q, want %q", body, e)
+	}
+}
+
+func TestTransportNoHost(t *testing.T) {
+	defer afterTest(t)
+	tr := &Transport{}
+	_, err := tr.RoundTrip(&Request{
+		Header: make(Header),
+		URL: &url.URL{
+			Scheme: "http",
+		},
+	})
+	want := "http: no Host in request URL"
+	if got := fmt.Sprint(err); got != want {
+		t.Errorf("error = %v; want %q", err, want)
+	}
+}
+
+func TestTransportSocketLateBinding(t *testing.T) {
+	defer afterTest(t)
+
+	mux := NewServeMux()
+	fooGate := make(chan bool, 1)
+	mux.HandleFunc("/foo", func(w ResponseWriter, r *Request) {
+		w.Header().Set("foo-ipport", r.RemoteAddr)
+		w.(Flusher).Flush()
+		<-fooGate
+	})
+	mux.HandleFunc("/bar", func(w ResponseWriter, r *Request) {
+		w.Header().Set("bar-ipport", r.RemoteAddr)
+	})
+	ts := httptest.NewServer(mux)
+	defer ts.Close()
+
+	dialGate := make(chan bool, 1)
+	tr := &Transport{
+		Dial: func(n, addr string) (net.Conn, error) {
+			if <-dialGate {
+				return net.Dial(n, addr)
+			}
+			return nil, errors.New("manually closed")
+		},
+		DisableKeepAlives: false,
+	}
+	defer tr.CloseIdleConnections()
+	c := &Client{
+		Transport: tr,
+	}
+
+	dialGate <- true // only allow one dial
+	fooRes, err := c.Get(ts.URL + "/foo")
+	if err != nil {
+		t.Fatal(err)
+	}
+	fooAddr := fooRes.Header.Get("foo-ipport")
+	if fooAddr == "" {
+		t.Fatal("No addr on /foo request")
+	}
+	time.AfterFunc(200*time.Millisecond, func() {
+		// let the foo response finish so we can use its
+		// connection for /bar
+		fooGate <- true
+		io.Copy(ioutil.Discard, fooRes.Body)
+		fooRes.Body.Close()
+	})
+
+	barRes, err := c.Get(ts.URL + "/bar")
+	if err != nil {
+		t.Fatal(err)
+	}
+	barAddr := barRes.Header.Get("bar-ipport")
+	if barAddr != fooAddr {
+		t.Fatalf("/foo came from conn %q; /bar came from %q instead", fooAddr, barAddr)
+	}
+	barRes.Body.Close()
+	dialGate <- false
+}
+
+// Issue 2184
+func TestTransportReading100Continue(t *testing.T) {
+	defer afterTest(t)
+
+	const numReqs = 5
+	reqBody := func(n int) string { return fmt.Sprintf("request body %d", n) }
+	reqID := func(n int) string { return fmt.Sprintf("REQ-ID-%d", n) }
+
+	send100Response := func(w *io.PipeWriter, r *io.PipeReader) {
+		defer w.Close()
+		defer r.Close()
+		br := bufio.NewReader(r)
+		n := 0
+		for {
+			n++
+			req, err := ReadRequest(br)
+			if err == io.EOF {
+				return
+			}
+			if err != nil {
+				t.Error(err)
+				return
+			}
+			slurp, err := ioutil.ReadAll(req.Body)
+			if err != nil {
+				t.Errorf("Server request body slurp: %v", err)
+				return
+			}
+			id := req.Header.Get("Request-Id")
+			resCode := req.Header.Get("X-Want-Response-Code")
+			if resCode == "" {
+				resCode = "100 Continue"
+				if string(slurp) != reqBody(n) {
+					t.Errorf("Server got %q, %v; want %q", slurp, err, reqBody(n))
+				}
+			}
+			body := fmt.Sprintf("Response number %d", n)
+			v := []byte(strings.Replace(fmt.Sprintf(`HTTP/1.1 %s
+Date: Thu, 28 Feb 2013 17:55:41 GMT
+
+HTTP/1.1 200 OK
+Content-Type: text/html
+Echo-Request-Id: %s
+Content-Length: %d
+
+%s`, resCode, id, len(body), body), "\n", "\r\n", -1))
+			w.Write(v)
+			if id == reqID(numReqs) {
+				return
+			}
+		}
+
+	}
+
+	tr := &Transport{
+		Dial: func(n, addr string) (net.Conn, error) {
+			sr, sw := io.Pipe() // server read/write
+			cr, cw := io.Pipe() // client read/write
+			conn := &rwTestConn{
+				Reader: cr,
+				Writer: sw,
+				closeFunc: func() error {
+					sw.Close()
+					cw.Close()
+					return nil
+				},
+			}
+			go send100Response(cw, sr)
+			return conn, nil
+		},
+		DisableKeepAlives: false,
+	}
+	defer tr.CloseIdleConnections()
+	c := &Client{Transport: tr}
+
+	testResponse := func(req *Request, name string, wantCode int) {
+		res, err := c.Do(req)
+		if err != nil {
+			t.Fatalf("%s: Do: %v", name, err)
+		}
+		if res.StatusCode != wantCode {
+			t.Fatalf("%s: Response Statuscode=%d; want %d", name, res.StatusCode, wantCode)
+		}
+		if id, idBack := req.Header.Get("Request-Id"), res.Header.Get("Echo-Request-Id"); id != "" && id != idBack {
+			t.Errorf("%s: response id %q != request id %q", name, idBack, id)
+		}
+		_, err = ioutil.ReadAll(res.Body)
+		if err != nil {
+			t.Fatalf("%s: Slurp error: %v", name, err)
+		}
+	}
+
+	// Few 100 responses, making sure we're not off-by-one.
+	for i := 1; i <= numReqs; i++ {
+		req, _ := NewRequest("POST", "http://dummy.tld/", strings.NewReader(reqBody(i)))
+		req.Header.Set("Request-Id", reqID(i))
+		testResponse(req, fmt.Sprintf("100, %d/%d", i, numReqs), 200)
+	}
+
+	// And some other informational 1xx but non-100 responses, to test
+	// we return them but don't re-use the connection.
+	for i := 1; i <= numReqs; i++ {
+		req, _ := NewRequest("POST", "http://other.tld/", strings.NewReader(reqBody(i)))
+		req.Header.Set("X-Want-Response-Code", "123 Sesame Street")
+		testResponse(req, fmt.Sprintf("123, %d/%d", i, numReqs), 123)
+	}
+}
+
+type proxyFromEnvTest struct {
+	req     string // URL to fetch; blank means "http://example.com"
+	env     string
+	noenv   string
+	want    string
+	wanterr error
+}
+
+func (t proxyFromEnvTest) String() string {
+	var buf bytes.Buffer
+	if t.env != "" {
+		fmt.Fprintf(&buf, "http_proxy=%q", t.env)
+	}
+	if t.noenv != "" {
+		fmt.Fprintf(&buf, " no_proxy=%q", t.noenv)
+	}
+	req := "http://example.com"
+	if t.req != "" {
+		req = t.req
+	}
+	fmt.Fprintf(&buf, " req=%q", req)
+	return strings.TrimSpace(buf.String())
+}
+
+var proxyFromEnvTests = []proxyFromEnvTest{
+	{env: "127.0.0.1:8080", want: "http://127.0.0.1:8080"},
+	{env: "cache.corp.example.com:1234", want: "http://cache.corp.example.com:1234"},
+	{env: "cache.corp.example.com", want: "http://cache.corp.example.com"},
+	{env: "https://cache.corp.example.com", want: "https://cache.corp.example.com"},
+	{env: "http://127.0.0.1:8080", want: "http://127.0.0.1:8080"},
+	{env: "https://127.0.0.1:8080", want: "https://127.0.0.1:8080"},
+	{want: "<nil>"},
+	{noenv: "example.com", req: "http://example.com/", env: "proxy", want: "<nil>"},
+	{noenv: ".example.com", req: "http://example.com/", env: "proxy", want: "<nil>"},
+	{noenv: "ample.com", req: "http://example.com/", env: "proxy", want: "http://proxy"},
+	{noenv: "example.com", req: "http://foo.example.com/", env: "proxy", want: "<nil>"},
+	{noenv: ".foo.com", req: "http://example.com/", env: "proxy", want: "http://proxy"},
+}
+
+func TestProxyFromEnvironment(t *testing.T) {
+	ResetProxyEnv()
+	for _, tt := range proxyFromEnvTests {
+		os.Setenv("HTTP_PROXY", tt.env)
+		os.Setenv("NO_PROXY", tt.noenv)
+		ResetCachedEnvironment()
+		reqURL := tt.req
+		if reqURL == "" {
+			reqURL = "http://example.com"
+		}
+		req, _ := NewRequest("GET", reqURL, nil)
+		url, err := ProxyFromEnvironment(req)
+		if g, e := fmt.Sprintf("%v", err), fmt.Sprintf("%v", tt.wanterr); g != e {
+			t.Errorf("%v: got error = %q, want %q", tt, g, e)
+			continue
+		}
+		if got := fmt.Sprintf("%s", url); got != tt.want {
+			t.Errorf("%v: got URL = %q, want %q", tt, url, tt.want)
+		}
+	}
+}
+
+func TestIdleConnChannelLeak(t *testing.T) {
+	var mu sync.Mutex
+	var n int
+
+	ts := httptest.NewServer(HandlerFunc(func(w ResponseWriter, r *Request) {
+		mu.Lock()
+		n++
+		mu.Unlock()
+	}))
+	defer ts.Close()
+
+	tr := &Transport{
+		Dial: func(netw, addr string) (net.Conn, error) {
+			return net.Dial(netw, ts.Listener.Addr().String())
+		},
+	}
+	defer tr.CloseIdleConnections()
+
+	c := &Client{Transport: tr}
+
+	// First, without keep-alives.
+	for _, disableKeep := range []bool{true, false} {
+		tr.DisableKeepAlives = disableKeep
+		for i := 0; i < 5; i++ {
+			_, err := c.Get(fmt.Sprintf("http://foo-host-%d.tld/", i))
+			if err != nil {
+				t.Fatal(err)
+			}
+		}
+		if got := tr.IdleConnChMapSizeForTesting(); got != 0 {
+			t.Fatalf("ForDisableKeepAlives = %v, map size = %d; want 0", disableKeep, got)
+		}
+	}
+}
+
+// Verify the status quo: that the Client.Post function coerces its
+// body into a ReadCloser if it's a Closer, and that the Transport
+// then closes it.
+func TestTransportClosesRequestBody(t *testing.T) {
+	defer afterTest(t)
+	ts := httptest.NewServer(http.HandlerFunc(func(w ResponseWriter, r *Request) {
+		io.Copy(ioutil.Discard, r.Body)
+	}))
+	defer ts.Close()
+
+	tr := &Transport{}
+	defer tr.CloseIdleConnections()
+	cl := &Client{Transport: tr}
+
+	closes := 0
+
+	res, err := cl.Post(ts.URL, "text/plain", countCloseReader{&closes, strings.NewReader("hello")})
+	if err != nil {
+		t.Fatal(err)
+	}
+	res.Body.Close()
+	if closes != 1 {
+		t.Errorf("closes = %d; want 1", closes)
+	}
+}
+
+func TestTransportTLSHandshakeTimeout(t *testing.T) {
+	defer afterTest(t)
+	if testing.Short() {
+		t.Skip("skipping in short mode")
+	}
+	ln := newLocalListener(t)
+	defer ln.Close()
+	testdonec := make(chan struct{})
+	defer close(testdonec)
+
+	go func() {
+		c, err := ln.Accept()
+		if err != nil {
+			t.Error(err)
+			return
+		}
+		<-testdonec
+		c.Close()
+	}()
+
+	getdonec := make(chan struct{})
+	go func() {
+		defer close(getdonec)
+		tr := &Transport{
+			Dial: func(_, _ string) (net.Conn, error) {
+				return net.Dial("tcp", ln.Addr().String())
+			},
+			TLSHandshakeTimeout: 250 * time.Millisecond,
+		}
+		cl := &Client{Transport: tr}
+		_, err := cl.Get("https://dummy.tld/")
+		if err == nil {
+			t.Error("expected error")
+			return
+		}
+		ue, ok := err.(*url.Error)
+		if !ok {
+			t.Errorf("expected url.Error; got %#v", err)
+			return
+		}
+		ne, ok := ue.Err.(net.Error)
+		if !ok {
+			t.Errorf("expected net.Error; got %#v", err)
+			return
+		}
+		if !ne.Timeout() {
+			t.Errorf("expected timeout error; got %v", err)
+		}
+		if !strings.Contains(err.Error(), "handshake timeout") {
+			t.Errorf("expected 'handshake timeout' in error; got %v", err)
+		}
+	}()
+	select {
+	case <-getdonec:
+	case <-time.After(5 * time.Second):
+		t.Error("test timeout; TLS handshake hung?")
+	}
+}
+
+// Trying to repro golang.org/issue/3514
+func TestTLSServerClosesConnection(t *testing.T) {
+	defer afterTest(t)
+	if runtime.GOOS == "windows" {
+		t.Skip("skipping flaky test on Windows; golang.org/issue/7634")
+	}
+	closedc := make(chan bool, 1)
+	ts := httptest.NewTLSServer(HandlerFunc(func(w ResponseWriter, r *Request) {
+		if strings.Contains(r.URL.Path, "/keep-alive-then-die") {
+			conn, _, _ := w.(Hijacker).Hijack()
+			conn.Write([]byte("HTTP/1.1 200 OK\r\nContent-Length: 3\r\n\r\nfoo"))
+			conn.Close()
+			closedc <- true
+			return
+		}
+		fmt.Fprintf(w, "hello")
+	}))
+	defer ts.Close()
+	tr := &Transport{
+		TLSClientConfig: &tls.Config{
+			InsecureSkipVerify: true,
+		},
+	}
+	defer tr.CloseIdleConnections()
+	client := &Client{Transport: tr}
+
+	var nSuccess = 0
+	var errs []error
+	const trials = 20
+	for i := 0; i < trials; i++ {
+		tr.CloseIdleConnections()
+		res, err := client.Get(ts.URL + "/keep-alive-then-die")
+		if err != nil {
+			t.Fatal(err)
+		}
+		<-closedc
+		slurp, err := ioutil.ReadAll(res.Body)
+		if err != nil {
+			t.Fatal(err)
+		}
+		if string(slurp) != "foo" {
+			t.Errorf("Got %q, want foo", slurp)
+		}
+
+		// Now try again and see if we successfully
+		// pick a new connection.
+		res, err = client.Get(ts.URL + "/")
+		if err != nil {
+			errs = append(errs, err)
+			continue
+		}
+		slurp, err = ioutil.ReadAll(res.Body)
+		if err != nil {
+			errs = append(errs, err)
+			continue
+		}
+		nSuccess++
+	}
+	if nSuccess > 0 {
+		t.Logf("successes = %d of %d", nSuccess, trials)
+	} else {
+		t.Errorf("All runs failed:")
+	}
+	for _, err := range errs {
+		t.Logf("  err: %v", err)
+	}
+}
+
+// byteFromChanReader is an io.Reader that reads a single byte at a
+// time from the channel.  When the channel is closed, the reader
+// returns io.EOF.
+type byteFromChanReader chan byte
+
+func (c byteFromChanReader) Read(p []byte) (n int, err error) {
+	if len(p) == 0 {
+		return
+	}
+	b, ok := <-c
+	if !ok {
+		return 0, io.EOF
+	}
+	p[0] = b
+	return 1, nil
+}
+
+// Verifies that the Transport doesn't reuse a connection in the case
+// where the server replies before the request has been fully
+// written. We still honor that reply (see TestIssue3595), but don't
+// send future requests on the connection because it's then in a
+// questionable state.
+// golang.org/issue/7569
+func TestTransportNoReuseAfterEarlyResponse(t *testing.T) {
+	defer afterTest(t)
+	var sconn struct {
+		sync.Mutex
+		c net.Conn
+	}
+	var getOkay bool
+	closeConn := func() {
+		sconn.Lock()
+		defer sconn.Unlock()
+		if sconn.c != nil {
+			sconn.c.Close()
+			sconn.c = nil
+			if !getOkay {
+				t.Logf("Closed server connection")
+			}
+		}
+	}
+	defer closeConn()
+
+	ts := httptest.NewServer(HandlerFunc(func(w ResponseWriter, r *Request) {
+		if r.Method == "GET" {
+			io.WriteString(w, "bar")
+			return
+		}
+		conn, _, _ := w.(Hijacker).Hijack()
+		sconn.Lock()
+		sconn.c = conn
+		sconn.Unlock()
+		conn.Write([]byte("HTTP/1.1 200 OK\r\nContent-Length: 3\r\n\r\nfoo")) // keep-alive
+		go io.Copy(ioutil.Discard, conn)
+	}))
+	defer ts.Close()
+	tr := &Transport{}
+	defer tr.CloseIdleConnections()
+	client := &Client{Transport: tr}
+
+	const bodySize = 256 << 10
+	finalBit := make(byteFromChanReader, 1)
+	req, _ := NewRequest("POST", ts.URL, io.MultiReader(io.LimitReader(neverEnding('x'), bodySize-1), finalBit))
+	req.ContentLength = bodySize
+	res, err := client.Do(req)
+	if err := wantBody(res, err, "foo"); err != nil {
+		t.Errorf("POST response: %v", err)
+	}
+	donec := make(chan bool)
+	go func() {
+		defer close(donec)
+		res, err = client.Get(ts.URL)
+		if err := wantBody(res, err, "bar"); err != nil {
+			t.Errorf("GET response: %v", err)
+			return
+		}
+		getOkay = true // suppress test noise
+	}()
+	time.AfterFunc(5*time.Second, closeConn)
+	select {
+	case <-donec:
+		finalBit <- 'x' // unblock the writeloop of the first Post
+		close(finalBit)
+	case <-time.After(7 * time.Second):
+		t.Fatal("timeout waiting for GET request to finish")
+	}
+}
+
+type errorReader struct {
+	err error
+}
+
+func (e errorReader) Read(p []byte) (int, error) { return 0, e.err }
+
+type closerFunc func() error
+
+func (f closerFunc) Close() error { return f() }
+
+// Issue 6981
+func TestTransportClosesBodyOnError(t *testing.T) {
+	if runtime.GOOS == "plan9" {
+		t.Skip("skipping test; see http://golang.org/issue/7782")
+	}
+	defer afterTest(t)
+	readBody := make(chan error, 1)
+	ts := httptest.NewServer(HandlerFunc(func(w ResponseWriter, r *Request) {
+		_, err := ioutil.ReadAll(r.Body)
+		readBody <- err
+	}))
+	defer ts.Close()
+	fakeErr := errors.New("fake error")
+	didClose := make(chan bool, 1)
+	req, _ := NewRequest("POST", ts.URL, struct {
+		io.Reader
+		io.Closer
+	}{
+		io.MultiReader(io.LimitReader(neverEnding('x'), 1<<20), errorReader{fakeErr}),
+		closerFunc(func() error {
+			select {
+			case didClose <- true:
+			default:
+			}
+			return nil
+		}),
+	})
+	res, err := DefaultClient.Do(req)
+	if res != nil {
+		defer res.Body.Close()
+	}
+	if err == nil || !strings.Contains(err.Error(), fakeErr.Error()) {
+		t.Fatalf("Do error = %v; want something containing %q", err, fakeErr.Error())
+	}
+	select {
+	case err := <-readBody:
+		if err == nil {
+			t.Errorf("Unexpected success reading request body from handler; want 'unexpected EOF reading trailer'")
+		}
+	case <-time.After(5 * time.Second):
+		t.Error("timeout waiting for server handler to complete")
+	}
+	select {
+	case <-didClose:
+	default:
+		t.Errorf("didn't see Body.Close")
+	}
+}
+
+func TestTransportDialTLS(t *testing.T) {
+	var mu sync.Mutex // guards following
+	var gotReq, didDial bool
+
+	ts := httptest.NewTLSServer(HandlerFunc(func(w ResponseWriter, r *Request) {
+		mu.Lock()
+		gotReq = true
+		mu.Unlock()
+	}))
+	defer ts.Close()
+	tr := &Transport{
+		DialTLS: func(netw, addr string) (net.Conn, error) {
+			mu.Lock()
+			didDial = true
+			mu.Unlock()
+			c, err := tls.Dial(netw, addr, &tls.Config{
+				InsecureSkipVerify: true,
+			})
+			if err != nil {
+				return nil, err
+			}
+			return c, c.Handshake()
+		},
+	}
+	defer tr.CloseIdleConnections()
+	client := &Client{Transport: tr}
+	res, err := client.Get(ts.URL)
+	if err != nil {
+		t.Fatal(err)
+	}
+	res.Body.Close()
+	mu.Lock()
+	if !gotReq {
+		t.Error("didn't get request")
+	}
+	if !didDial {
+		t.Error("didn't use dial hook")
+	}
+}
+
+func wantBody(res *http.Response, err error, want string) error {
+	if err != nil {
+		return err
+	}
+	slurp, err := ioutil.ReadAll(res.Body)
+	if err != nil {
+		return fmt.Errorf("error reading body: %v", err)
+	}
+	if string(slurp) != want {
+		return fmt.Errorf("body = %q; want %q", slurp, want)
+	}
+	if err := res.Body.Close(); err != nil {
+		return fmt.Errorf("body Close = %v", err)
+	}
+	return nil
+}
+
+func newLocalListener(t *testing.T) net.Listener {
+	ln, err := net.Listen("tcp", "127.0.0.1:0")
+	if err != nil {
+		ln, err = net.Listen("tcp6", "[::1]:0")
+	}
+	if err != nil {
+		t.Fatal(err)
+	}
+	return ln
+}
+
+type countCloseReader struct {
+	n *int
+	io.Reader
+}
+
+func (cr countCloseReader) Close() error {
+	(*cr.n)++
+	return nil
+}
+
+// rgz is a gzip quine that uncompresses to itself.
+var rgz = []byte{
+	0x1f, 0x8b, 0x08, 0x08, 0x00, 0x00, 0x00, 0x00,
+	0x00, 0x00, 0x72, 0x65, 0x63, 0x75, 0x72, 0x73,
+	0x69, 0x76, 0x65, 0x00, 0x92, 0xef, 0xe6, 0xe0,
+	0x60, 0x00, 0x83, 0xa2, 0xd4, 0xe4, 0xd2, 0xa2,
+	0xe2, 0xcc, 0xb2, 0x54, 0x06, 0x00, 0x00, 0x17,
+	0x00, 0xe8, 0xff, 0x92, 0xef, 0xe6, 0xe0, 0x60,
+	0x00, 0x83, 0xa2, 0xd4, 0xe4, 0xd2, 0xa2, 0xe2,
+	0xcc, 0xb2, 0x54, 0x06, 0x00, 0x00, 0x17, 0x00,
+	0xe8, 0xff, 0x42, 0x12, 0x46, 0x16, 0x06, 0x00,
+	0x05, 0x00, 0xfa, 0xff, 0x42, 0x12, 0x46, 0x16,
+	0x06, 0x00, 0x05, 0x00, 0xfa, 0xff, 0x00, 0x05,
+	0x00, 0xfa, 0xff, 0x00, 0x14, 0x00, 0xeb, 0xff,
+	0x42, 0x12, 0x46, 0x16, 0x06, 0x00, 0x05, 0x00,
+	0xfa, 0xff, 0x00, 0x05, 0x00, 0xfa, 0xff, 0x00,
+	0x14, 0x00, 0xeb, 0xff, 0x42, 0x88, 0x21, 0xc4,
+	0x00, 0x00, 0x14, 0x00, 0xeb, 0xff, 0x42, 0x88,
+	0x21, 0xc4, 0x00, 0x00, 0x14, 0x00, 0xeb, 0xff,
+	0x42, 0x88, 0x21, 0xc4, 0x00, 0x00, 0x14, 0x00,
+	0xeb, 0xff, 0x42, 0x88, 0x21, 0xc4, 0x00, 0x00,
+	0x14, 0x00, 0xeb, 0xff, 0x42, 0x88, 0x21, 0xc4,
+	0x00, 0x00, 0x00, 0x00, 0xff, 0xff, 0x00, 0x00,
+	0x00, 0xff, 0xff, 0x00, 0x17, 0x00, 0xe8, 0xff,
+	0x42, 0x88, 0x21, 0xc4, 0x00, 0x00, 0x00, 0x00,
+	0xff, 0xff, 0x00, 0x00, 0x00, 0xff, 0xff, 0x00,
+	0x17, 0x00, 0xe8, 0xff, 0x42, 0x12, 0x46, 0x16,
+	0x06, 0x00, 0x00, 0x00, 0xff, 0xff, 0x01, 0x08,
+	0x00, 0xf7, 0xff, 0x3d, 0xb1, 0x20, 0x85, 0xfa,
+	0x00, 0x00, 0x00, 0x42, 0x12, 0x46, 0x16, 0x06,
+	0x00, 0x00, 0x00, 0xff, 0xff, 0x01, 0x08, 0x00,
+	0xf7, 0xff, 0x3d, 0xb1, 0x20, 0x85, 0xfa, 0x00,
+	0x00, 0x00, 0x3d, 0xb1, 0x20, 0x85, 0xfa, 0x00,
+	0x00, 0x00,
+}
diff --git a/src/net/http/triv.go b/src/net/http/triv.go
new file mode 100644
index 000000000..232d65089
--- /dev/null
+++ b/src/net/http/triv.go
@@ -0,0 +1,141 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build ignore
+
+package main
+
+import (
+	"bytes"
+	"expvar"
+	"flag"
+	"fmt"
+	"io"
+	"log"
+	"net/http"
+	"os"
+	"os/exec"
+	"strconv"
+	"sync"
+)
+
+// hello world, the web server
+var helloRequests = expvar.NewInt("hello-requests")
+
+func HelloServer(w http.ResponseWriter, req *http.Request) {
+	helloRequests.Add(1)
+	io.WriteString(w, "hello, world!\n")
+}
+
+// Simple counter server. POSTing to it will set the value.
+type Counter struct {
+	mu sync.Mutex // protects n
+	n  int
+}
+
+// This makes Counter satisfy the expvar.Var interface, so we can export
+// it directly.
+func (ctr *Counter) String() string {
+	ctr.mu.Lock()
+	defer ctr.mu.Unlock()
+	return fmt.Sprintf("%d", ctr.n)
+}
+
+func (ctr *Counter) ServeHTTP(w http.ResponseWriter, req *http.Request) {
+	ctr.mu.Lock()
+	defer ctr.mu.Unlock()
+	switch req.Method {
+	case "GET":
+		ctr.n++
+	case "POST":
+		buf := new(bytes.Buffer)
+		io.Copy(buf, req.Body)
+		body := buf.String()
+		if n, err := strconv.Atoi(body); err != nil {
+			fmt.Fprintf(w, "bad POST: %v\nbody: [%v]\n", err, body)
+		} else {
+			ctr.n = n
+			fmt.Fprint(w, "counter reset\n")
+		}
+	}
+	fmt.Fprintf(w, "counter = %d\n", ctr.n)
+}
+
+// simple flag server
+var booleanflag = flag.Bool("boolean", true, "another flag for testing")
+
+func FlagServer(w http.ResponseWriter, req *http.Request) {
+	w.Header().Set("Content-Type", "text/plain; charset=utf-8")
+	fmt.Fprint(w, "Flags:\n")
+	flag.VisitAll(func(f *flag.Flag) {
+		if f.Value.String() != f.DefValue {
+			fmt.Fprintf(w, "%s = %s [default = %s]\n", f.Name, f.Value.String(), f.DefValue)
+		} else {
+			fmt.Fprintf(w, "%s = %s\n", f.Name, f.Value.String())
+		}
+	})
+}
+
+// simple argument server
+func ArgServer(w http.ResponseWriter, req *http.Request) {
+	for _, s := range os.Args {
+		fmt.Fprint(w, s, " ")
+	}
+}
+
+// a channel (just for the fun of it)
+type Chan chan int
+
+func ChanCreate() Chan {
+	c := make(Chan)
+	go func(c Chan) {
+		for x := 0; ; x++ {
+			c <- x
+		}
+	}(c)
+	return c
+}
+
+func (ch Chan) ServeHTTP(w http.ResponseWriter, req *http.Request) {
+	io.WriteString(w, fmt.Sprintf("channel send #%d\n", <-ch))
+}
+
+// exec a program, redirecting output
+func DateServer(rw http.ResponseWriter, req *http.Request) {
+	rw.Header().Set("Content-Type", "text/plain; charset=utf-8")
+
+	date, err := exec.Command("/bin/date").Output()
+	if err != nil {
+		http.Error(rw, err.Error(), 500)
+		return
+	}
+	rw.Write(date)
+}
+
+func Logger(w http.ResponseWriter, req *http.Request) {
+	log.Print(req.URL)
+	http.Error(w, "oops", 404)
+}
+
+var webroot = flag.String("root", os.Getenv("HOME"), "web root directory")
+
+func main() {
+	flag.Parse()
+
+	// The counter is published as a variable directly.
+	ctr := new(Counter)
+	expvar.Publish("counter", ctr)
+	http.Handle("/counter", ctr)
+	http.Handle("/", http.HandlerFunc(Logger))
+	http.Handle("/go/", http.StripPrefix("/go/", http.FileServer(http.Dir(*webroot))))
+	http.Handle("/chan", ChanCreate())
+	http.HandleFunc("/flags", FlagServer)
+	http.HandleFunc("/args", ArgServer)
+	http.HandleFunc("/go/hello", HelloServer)
+	http.HandleFunc("/date", DateServer)
+	err := http.ListenAndServe(":12345", nil)
+	if err != nil {
+		log.Panicln("ListenAndServe:", err)
+	}
+}
diff --git a/src/net/http/z_last_test.go b/src/net/http/z_last_test.go
new file mode 100644
index 000000000..5a0cc1198
--- /dev/null
+++ b/src/net/http/z_last_test.go
@@ -0,0 +1,97 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package http_test
+
+import (
+	"net/http"
+	"runtime"
+	"sort"
+	"strings"
+	"testing"
+	"time"
+)
+
+func interestingGoroutines() (gs []string) {
+	buf := make([]byte, 2<<20)
+	buf = buf[:runtime.Stack(buf, true)]
+	for _, g := range strings.Split(string(buf), "\n\n") {
+		sl := strings.SplitN(g, "\n", 2)
+		if len(sl) != 2 {
+			continue
+		}
+		stack := strings.TrimSpace(sl[1])
+		if stack == "" ||
+			strings.Contains(stack, "created by net.startServer") ||
+			strings.Contains(stack, "created by testing.RunTests") ||
+			strings.Contains(stack, "closeWriteAndWait") ||
+			strings.Contains(stack, "testing.Main(") ||
+			// These only show up with GOTRACEBACK=2; Issue 5005 (comment 28)
+			strings.Contains(stack, "runtime.goexit") ||
+			strings.Contains(stack, "created by runtime.gc") ||
+			strings.Contains(stack, "runtime.MHeap_Scavenger") {
+			continue
+		}
+		gs = append(gs, stack)
+	}
+	sort.Strings(gs)
+	return
+}
+
+// Verify the other tests didn't leave any goroutines running.
+// This is in a file named z_last_test.go so it sorts at the end.
+func TestGoroutinesRunning(t *testing.T) {
+	if testing.Short() {
+		t.Skip("not counting goroutines for leakage in -short mode")
+	}
+	gs := interestingGoroutines()
+
+	n := 0
+	stackCount := make(map[string]int)
+	for _, g := range gs {
+		stackCount[g]++
+		n++
+	}
+
+	t.Logf("num goroutines = %d", n)
+	if n > 0 {
+		t.Error("Too many goroutines.")
+		for stack, count := range stackCount {
+			t.Logf("%d instances of:\n%s", count, stack)
+		}
+	}
+}
+
+func afterTest(t *testing.T) {
+	http.DefaultTransport.(*http.Transport).CloseIdleConnections()
+	if testing.Short() {
+		return
+	}
+	var bad string
+	badSubstring := map[string]string{
+		").readLoop(":                                  "a Transport",
+		").writeLoop(":                                 "a Transport",
+		"created by net/http/httptest.(*Server).Start": "an httptest.Server",
+		"timeoutHandler":                               "a TimeoutHandler",
+		"net.(*netFD).connect(":                        "a timing out dial",
+		").noteClientGone(":                            "a closenotifier sender",
+	}
+	var stacks string
+	for i := 0; i < 4; i++ {
+		bad = ""
+		stacks = strings.Join(interestingGoroutines(), "\n\n")
+		for substr, what := range badSubstring {
+			if strings.Contains(stacks, substr) {
+				bad = what
+			}
+		}
+		if bad == "" {
+			return
+		}
+		// Bad stuff found, but goroutines might just still be
+		// shutting down, so give it some time.
+		time.Sleep(250 * time.Millisecond)
+	}
+	t.Errorf("Test appears to have leaked %s:\n%s", bad, stacks)
+}
diff --git a/src/net/interface.go b/src/net/interface.go
new file mode 100644
index 000000000..2e9f1ebc6
--- /dev/null
+++ b/src/net/interface.go
@@ -0,0 +1,126 @@
+// Copyright 2011 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package net
+
+import "errors"
+
+var (
+	errInvalidInterface         = errors.New("invalid network interface")
+	errInvalidInterfaceIndex    = errors.New("invalid network interface index")
+	errInvalidInterfaceName     = errors.New("invalid network interface name")
+	errNoSuchInterface          = errors.New("no such network interface")
+	errNoSuchMulticastInterface = errors.New("no such multicast network interface")
+)
+
+// Interface represents a mapping between network interface name
+// and index.  It also represents network interface facility
+// information.
+type Interface struct {
+	Index        int          // positive integer that starts at one, zero is never used
+	MTU          int          // maximum transmission unit
+	Name         string       // e.g., "en0", "lo0", "eth0.100"
+	HardwareAddr HardwareAddr // IEEE MAC-48, EUI-48 and EUI-64 form
+	Flags        Flags        // e.g., FlagUp, FlagLoopback, FlagMulticast
+}
+
+type Flags uint
+
+const (
+	FlagUp           Flags = 1 << iota // interface is up
+	FlagBroadcast                      // interface supports broadcast access capability
+	FlagLoopback                       // interface is a loopback interface
+	FlagPointToPoint                   // interface belongs to a point-to-point link
+	FlagMulticast                      // interface supports multicast access capability
+)
+
+var flagNames = []string{
+	"up",
+	"broadcast",
+	"loopback",
+	"pointtopoint",
+	"multicast",
+}
+
+func (f Flags) String() string {
+	s := ""
+	for i, name := range flagNames {
+		if f&(1<<uint(i)) != 0 {
+			if s != "" {
+				s += "|"
+			}
+			s += name
+		}
+	}
+	if s == "" {
+		s = "0"
+	}
+	return s
+}
+
+// Addrs returns interface addresses for a specific interface.
+func (ifi *Interface) Addrs() ([]Addr, error) {
+	if ifi == nil {
+		return nil, errInvalidInterface
+	}
+	return interfaceAddrTable(ifi)
+}
+
+// MulticastAddrs returns multicast, joined group addresses for
+// a specific interface.
+func (ifi *Interface) MulticastAddrs() ([]Addr, error) {
+	if ifi == nil {
+		return nil, errInvalidInterface
+	}
+	return interfaceMulticastAddrTable(ifi)
+}
+
+// Interfaces returns a list of the system's network interfaces.
+func Interfaces() ([]Interface, error) {
+	return interfaceTable(0)
+}
+
+// InterfaceAddrs returns a list of the system's network interface
+// addresses.
+func InterfaceAddrs() ([]Addr, error) {
+	return interfaceAddrTable(nil)
+}
+
+// InterfaceByIndex returns the interface specified by index.
+func InterfaceByIndex(index int) (*Interface, error) {
+	if index <= 0 {
+		return nil, errInvalidInterfaceIndex
+	}
+	ift, err := interfaceTable(index)
+	if err != nil {
+		return nil, err
+	}
+	return interfaceByIndex(ift, index)
+}
+
+func interfaceByIndex(ift []Interface, index int) (*Interface, error) {
+	for _, ifi := range ift {
+		if index == ifi.Index {
+			return &ifi, nil
+		}
+	}
+	return nil, errNoSuchInterface
+}
+
+// InterfaceByName returns the interface specified by name.
+func InterfaceByName(name string) (*Interface, error) {
+	if name == "" {
+		return nil, errInvalidInterfaceName
+	}
+	ift, err := interfaceTable(0)
+	if err != nil {
+		return nil, err
+	}
+	for _, ifi := range ift {
+		if name == ifi.Name {
+			return &ifi, nil
+		}
+	}
+	return nil, errNoSuchInterface
+}
diff --git a/src/net/interface_bsd.go b/src/net/interface_bsd.go
new file mode 100644
index 000000000..16775579d
--- /dev/null
+++ b/src/net/interface_bsd.go
@@ -0,0 +1,182 @@
+// Copyright 2011 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build darwin dragonfly freebsd netbsd openbsd
+
+package net
+
+import (
+	"os"
+	"syscall"
+	"unsafe"
+)
+
+// If the ifindex is zero, interfaceTable returns mappings of all
+// network interfaces.  Otherwise it returns a mapping of a specific
+// interface.
+func interfaceTable(ifindex int) ([]Interface, error) {
+	tab, err := syscall.RouteRIB(syscall.NET_RT_IFLIST, ifindex)
+	if err != nil {
+		return nil, os.NewSyscallError("route rib", err)
+	}
+	msgs, err := syscall.ParseRoutingMessage(tab)
+	if err != nil {
+		return nil, os.NewSyscallError("route message", err)
+	}
+	return parseInterfaceTable(ifindex, msgs)
+}
+
+func parseInterfaceTable(ifindex int, msgs []syscall.RoutingMessage) ([]Interface, error) {
+	var ift []Interface
+loop:
+	for _, m := range msgs {
+		switch m := m.(type) {
+		case *syscall.InterfaceMessage:
+			if ifindex == 0 || ifindex == int(m.Header.Index) {
+				ifi, err := newLink(m)
+				if err != nil {
+					return nil, err
+				}
+				ift = append(ift, *ifi)
+				if ifindex == int(m.Header.Index) {
+					break loop
+				}
+			}
+		}
+	}
+	return ift, nil
+}
+
+func newLink(m *syscall.InterfaceMessage) (*Interface, error) {
+	sas, err := syscall.ParseRoutingSockaddr(m)
+	if err != nil {
+		return nil, os.NewSyscallError("route sockaddr", err)
+	}
+	ifi := &Interface{Index: int(m.Header.Index), Flags: linkFlags(m.Header.Flags)}
+	for _, sa := range sas {
+		switch sa := sa.(type) {
+		case *syscall.SockaddrDatalink:
+			// NOTE: SockaddrDatalink.Data is minimum work area,
+			// can be larger.
+			m.Data = m.Data[unsafe.Offsetof(sa.Data):]
+			var name [syscall.IFNAMSIZ]byte
+			for i := 0; i < int(sa.Nlen); i++ {
+				name[i] = byte(m.Data[i])
+			}
+			ifi.Name = string(name[:sa.Nlen])
+			ifi.MTU = int(m.Header.Data.Mtu)
+			addr := make([]byte, sa.Alen)
+			for i := 0; i < int(sa.Alen); i++ {
+				addr[i] = byte(m.Data[int(sa.Nlen)+i])
+			}
+			ifi.HardwareAddr = addr[:sa.Alen]
+		}
+	}
+	return ifi, nil
+}
+
+func linkFlags(rawFlags int32) Flags {
+	var f Flags
+	if rawFlags&syscall.IFF_UP != 0 {
+		f |= FlagUp
+	}
+	if rawFlags&syscall.IFF_BROADCAST != 0 {
+		f |= FlagBroadcast
+	}
+	if rawFlags&syscall.IFF_LOOPBACK != 0 {
+		f |= FlagLoopback
+	}
+	if rawFlags&syscall.IFF_POINTOPOINT != 0 {
+		f |= FlagPointToPoint
+	}
+	if rawFlags&syscall.IFF_MULTICAST != 0 {
+		f |= FlagMulticast
+	}
+	return f
+}
+
+// If the ifi is nil, interfaceAddrTable returns addresses for all
+// network interfaces.  Otherwise it returns addresses for a specific
+// interface.
+func interfaceAddrTable(ifi *Interface) ([]Addr, error) {
+	index := 0
+	if ifi != nil {
+		index = ifi.Index
+	}
+	tab, err := syscall.RouteRIB(syscall.NET_RT_IFLIST, index)
+	if err != nil {
+		return nil, os.NewSyscallError("route rib", err)
+	}
+	msgs, err := syscall.ParseRoutingMessage(tab)
+	if err != nil {
+		return nil, os.NewSyscallError("route message", err)
+	}
+	var ift []Interface
+	if index == 0 {
+		ift, err = parseInterfaceTable(index, msgs)
+		if err != nil {
+			return nil, err
+		}
+	}
+	var ifat []Addr
+	for _, m := range msgs {
+		switch m := m.(type) {
+		case *syscall.InterfaceAddrMessage:
+			if index == 0 || index == int(m.Header.Index) {
+				if index == 0 {
+					var err error
+					ifi, err = interfaceByIndex(ift, int(m.Header.Index))
+					if err != nil {
+						return nil, err
+					}
+				}
+				ifa, err := newAddr(ifi, m)
+				if err != nil {
+					return nil, err
+				}
+				if ifa != nil {
+					ifat = append(ifat, ifa)
+				}
+			}
+		}
+	}
+	return ifat, nil
+}
+
+func newAddr(ifi *Interface, m *syscall.InterfaceAddrMessage) (Addr, error) {
+	sas, err := syscall.ParseRoutingSockaddr(m)
+	if err != nil {
+		return nil, os.NewSyscallError("route sockaddr", err)
+	}
+	ifa := &IPNet{}
+	for i, sa := range sas {
+		switch sa := sa.(type) {
+		case *syscall.SockaddrInet4:
+			switch i {
+			case 0:
+				ifa.Mask = IPv4Mask(sa.Addr[0], sa.Addr[1], sa.Addr[2], sa.Addr[3])
+			case 1:
+				ifa.IP = IPv4(sa.Addr[0], sa.Addr[1], sa.Addr[2], sa.Addr[3])
+			}
+		case *syscall.SockaddrInet6:
+			switch i {
+			case 0:
+				ifa.Mask = make(IPMask, IPv6len)
+				copy(ifa.Mask, sa.Addr[:])
+			case 1:
+				ifa.IP = make(IP, IPv6len)
+				copy(ifa.IP, sa.Addr[:])
+				// NOTE: KAME based IPv6 protcol stack usually embeds
+				// the interface index in the interface-local or link-
+				// local address as the kernel-internal form.
+				if ifa.IP.IsLinkLocalUnicast() {
+					ifa.IP[2], ifa.IP[3] = 0, 0
+				}
+			}
+		default: // Sockaddrs contain syscall.SockaddrDatalink on NetBSD
+			return nil, nil
+		}
+	}
+	return ifa, nil
+}
diff --git a/src/net/interface_bsd_test.go b/src/net/interface_bsd_test.go
new file mode 100644
index 000000000..88daf7393
--- /dev/null
+++ b/src/net/interface_bsd_test.go
@@ -0,0 +1,52 @@
+// Copyright 2013 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build darwin dragonfly freebsd netbsd openbsd
+
+package net
+
+import (
+	"fmt"
+	"os/exec"
+)
+
+func (ti *testInterface) setBroadcast(suffix int) error {
+	ti.name = fmt.Sprintf("vlan%d", suffix)
+	xname, err := exec.LookPath("ifconfig")
+	if err != nil {
+		return err
+	}
+	ti.setupCmds = append(ti.setupCmds, &exec.Cmd{
+		Path: xname,
+		Args: []string{"ifconfig", ti.name, "create"},
+	})
+	ti.teardownCmds = append(ti.teardownCmds, &exec.Cmd{
+		Path: xname,
+		Args: []string{"ifconfig", ti.name, "destroy"},
+	})
+	return nil
+}
+
+func (ti *testInterface) setPointToPoint(suffix int, local, remote string) error {
+	ti.name = fmt.Sprintf("gif%d", suffix)
+	ti.local = local
+	ti.remote = remote
+	xname, err := exec.LookPath("ifconfig")
+	if err != nil {
+		return err
+	}
+	ti.setupCmds = append(ti.setupCmds, &exec.Cmd{
+		Path: xname,
+		Args: []string{"ifconfig", ti.name, "create"},
+	})
+	ti.setupCmds = append(ti.setupCmds, &exec.Cmd{
+		Path: xname,
+		Args: []string{"ifconfig", ti.name, "inet", ti.local, ti.remote},
+	})
+	ti.teardownCmds = append(ti.teardownCmds, &exec.Cmd{
+		Path: xname,
+		Args: []string{"ifconfig", ti.name, "destroy"},
+	})
+	return nil
+}
diff --git a/src/net/interface_darwin.go b/src/net/interface_darwin.go
new file mode 100644
index 000000000..ad0937db0
--- /dev/null
+++ b/src/net/interface_darwin.go
@@ -0,0 +1,63 @@
+// Copyright 2011 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package net
+
+import (
+	"os"
+	"syscall"
+)
+
+// interfaceMulticastAddrTable returns addresses for a specific
+// interface.
+func interfaceMulticastAddrTable(ifi *Interface) ([]Addr, error) {
+	tab, err := syscall.RouteRIB(syscall.NET_RT_IFLIST2, ifi.Index)
+	if err != nil {
+		return nil, os.NewSyscallError("route rib", err)
+	}
+	msgs, err := syscall.ParseRoutingMessage(tab)
+	if err != nil {
+		return nil, os.NewSyscallError("route message", err)
+	}
+	var ifmat []Addr
+	for _, m := range msgs {
+		switch m := m.(type) {
+		case *syscall.InterfaceMulticastAddrMessage:
+			if ifi.Index == int(m.Header.Index) {
+				ifma, err := newMulticastAddr(ifi, m)
+				if err != nil {
+					return nil, err
+				}
+				ifmat = append(ifmat, ifma...)
+			}
+		}
+	}
+	return ifmat, nil
+}
+
+func newMulticastAddr(ifi *Interface, m *syscall.InterfaceMulticastAddrMessage) ([]Addr, error) {
+	sas, err := syscall.ParseRoutingSockaddr(m)
+	if err != nil {
+		return nil, os.NewSyscallError("route sockaddr", err)
+	}
+	var ifmat []Addr
+	for _, sa := range sas {
+		switch sa := sa.(type) {
+		case *syscall.SockaddrInet4:
+			ifma := &IPAddr{IP: IPv4(sa.Addr[0], sa.Addr[1], sa.Addr[2], sa.Addr[3])}
+			ifmat = append(ifmat, ifma.toAddr())
+		case *syscall.SockaddrInet6:
+			ifma := &IPAddr{IP: make(IP, IPv6len)}
+			copy(ifma.IP, sa.Addr[:])
+			// NOTE: KAME based IPv6 protocol stack usually embeds
+			// the interface index in the interface-local or link-
+			// local address as the kernel-internal form.
+			if ifma.IP.IsInterfaceLocalMulticast() || ifma.IP.IsLinkLocalMulticast() {
+				ifma.IP[2], ifma.IP[3] = 0, 0
+			}
+			ifmat = append(ifmat, ifma.toAddr())
+		}
+	}
+	return ifmat, nil
+}
diff --git a/src/net/interface_dragonfly.go b/src/net/interface_dragonfly.go
new file mode 100644
index 000000000..c9ce5a7ac
--- /dev/null
+++ b/src/net/interface_dragonfly.go
@@ -0,0 +1,12 @@
+// Copyright 2011 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package net
+
+// interfaceMulticastAddrTable returns addresses for a specific
+// interface.
+func interfaceMulticastAddrTable(ifi *Interface) ([]Addr, error) {
+	// TODO(mikio): Implement this like other platforms.
+	return nil, nil
+}
diff --git a/src/net/interface_freebsd.go b/src/net/interface_freebsd.go
new file mode 100644
index 000000000..5df767910
--- /dev/null
+++ b/src/net/interface_freebsd.go
@@ -0,0 +1,63 @@
+// Copyright 2011 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package net
+
+import (
+	"os"
+	"syscall"
+)
+
+// interfaceMulticastAddrTable returns addresses for a specific
+// interface.
+func interfaceMulticastAddrTable(ifi *Interface) ([]Addr, error) {
+	tab, err := syscall.RouteRIB(syscall.NET_RT_IFMALIST, ifi.Index)
+	if err != nil {
+		return nil, os.NewSyscallError("route rib", err)
+	}
+	msgs, err := syscall.ParseRoutingMessage(tab)
+	if err != nil {
+		return nil, os.NewSyscallError("route message", err)
+	}
+	var ifmat []Addr
+	for _, m := range msgs {
+		switch m := m.(type) {
+		case *syscall.InterfaceMulticastAddrMessage:
+			if ifi.Index == int(m.Header.Index) {
+				ifma, err := newMulticastAddr(ifi, m)
+				if err != nil {
+					return nil, err
+				}
+				ifmat = append(ifmat, ifma...)
+			}
+		}
+	}
+	return ifmat, nil
+}
+
+func newMulticastAddr(ifi *Interface, m *syscall.InterfaceMulticastAddrMessage) ([]Addr, error) {
+	sas, err := syscall.ParseRoutingSockaddr(m)
+	if err != nil {
+		return nil, os.NewSyscallError("route sockaddr", err)
+	}
+	var ifmat []Addr
+	for _, sa := range sas {
+		switch sa := sa.(type) {
+		case *syscall.SockaddrInet4:
+			ifma := &IPAddr{IP: IPv4(sa.Addr[0], sa.Addr[1], sa.Addr[2], sa.Addr[3])}
+			ifmat = append(ifmat, ifma.toAddr())
+		case *syscall.SockaddrInet6:
+			ifma := &IPAddr{IP: make(IP, IPv6len)}
+			copy(ifma.IP, sa.Addr[:])
+			// NOTE: KAME based IPv6 protocol stack usually embeds
+			// the interface index in the interface-local or link-
+			// local address as the kernel-internal form.
+			if ifma.IP.IsInterfaceLocalMulticast() || ifma.IP.IsLinkLocalMulticast() {
+				ifma.IP[2], ifma.IP[3] = 0, 0
+			}
+			ifmat = append(ifmat, ifma.toAddr())
+		}
+	}
+	return ifmat, nil
+}
diff --git a/src/net/interface_linux.go b/src/net/interface_linux.go
new file mode 100644
index 000000000..1115d0fc4
--- /dev/null
+++ b/src/net/interface_linux.go
@@ -0,0 +1,271 @@
+// Copyright 2011 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package net
+
+import (
+	"os"
+	"syscall"
+	"unsafe"
+)
+
+// If the ifindex is zero, interfaceTable returns mappings of all
+// network interfaces.  Otherwise it returns a mapping of a specific
+// interface.
+func interfaceTable(ifindex int) ([]Interface, error) {
+	tab, err := syscall.NetlinkRIB(syscall.RTM_GETLINK, syscall.AF_UNSPEC)
+	if err != nil {
+		return nil, os.NewSyscallError("netlink rib", err)
+	}
+	msgs, err := syscall.ParseNetlinkMessage(tab)
+	if err != nil {
+		return nil, os.NewSyscallError("netlink message", err)
+	}
+	var ift []Interface
+loop:
+	for _, m := range msgs {
+		switch m.Header.Type {
+		case syscall.NLMSG_DONE:
+			break loop
+		case syscall.RTM_NEWLINK:
+			ifim := (*syscall.IfInfomsg)(unsafe.Pointer(&m.Data[0]))
+			if ifindex == 0 || ifindex == int(ifim.Index) {
+				attrs, err := syscall.ParseNetlinkRouteAttr(&m)
+				if err != nil {
+					return nil, os.NewSyscallError("netlink routeattr", err)
+				}
+				ift = append(ift, *newLink(ifim, attrs))
+				if ifindex == int(ifim.Index) {
+					break loop
+				}
+			}
+		}
+	}
+	return ift, nil
+}
+
+const (
+	// See linux/if_arp.h.
+	// Note that Linux doesn't support IPv4 over IPv6 tunneling.
+	sysARPHardwareIPv4IPv4 = 768 // IPv4 over IPv4 tunneling
+	sysARPHardwareIPv6IPv6 = 769 // IPv6 over IPv6 tunneling
+	sysARPHardwareIPv6IPv4 = 776 // IPv6 over IPv4 tunneling
+	sysARPHardwareGREIPv4  = 778 // any over GRE over IPv4 tunneling
+	sysARPHardwareGREIPv6  = 823 // any over GRE over IPv6 tunneling
+)
+
+func newLink(ifim *syscall.IfInfomsg, attrs []syscall.NetlinkRouteAttr) *Interface {
+	ifi := &Interface{Index: int(ifim.Index), Flags: linkFlags(ifim.Flags)}
+	for _, a := range attrs {
+		switch a.Attr.Type {
+		case syscall.IFLA_ADDRESS:
+			// We never return any /32 or /128 IP address
+			// prefix on any IP tunnel interface as the
+			// hardware address.
+			switch len(a.Value) {
+			case IPv4len:
+				switch ifim.Type {
+				case sysARPHardwareIPv4IPv4, sysARPHardwareGREIPv4, sysARPHardwareIPv6IPv4:
+					continue
+				}
+			case IPv6len:
+				switch ifim.Type {
+				case sysARPHardwareIPv6IPv6, sysARPHardwareGREIPv6:
+					continue
+				}
+			}
+			var nonzero bool
+			for _, b := range a.Value {
+				if b != 0 {
+					nonzero = true
+					break
+				}
+			}
+			if nonzero {
+				ifi.HardwareAddr = a.Value[:]
+			}
+		case syscall.IFLA_IFNAME:
+			ifi.Name = string(a.Value[:len(a.Value)-1])
+		case syscall.IFLA_MTU:
+			ifi.MTU = int(*(*uint32)(unsafe.Pointer(&a.Value[:4][0])))
+		}
+	}
+	return ifi
+}
+
+func linkFlags(rawFlags uint32) Flags {
+	var f Flags
+	if rawFlags&syscall.IFF_UP != 0 {
+		f |= FlagUp
+	}
+	if rawFlags&syscall.IFF_BROADCAST != 0 {
+		f |= FlagBroadcast
+	}
+	if rawFlags&syscall.IFF_LOOPBACK != 0 {
+		f |= FlagLoopback
+	}
+	if rawFlags&syscall.IFF_POINTOPOINT != 0 {
+		f |= FlagPointToPoint
+	}
+	if rawFlags&syscall.IFF_MULTICAST != 0 {
+		f |= FlagMulticast
+	}
+	return f
+}
+
+// If the ifi is nil, interfaceAddrTable returns addresses for all
+// network interfaces.  Otherwise it returns addresses for a specific
+// interface.
+func interfaceAddrTable(ifi *Interface) ([]Addr, error) {
+	tab, err := syscall.NetlinkRIB(syscall.RTM_GETADDR, syscall.AF_UNSPEC)
+	if err != nil {
+		return nil, os.NewSyscallError("netlink rib", err)
+	}
+	msgs, err := syscall.ParseNetlinkMessage(tab)
+	if err != nil {
+		return nil, os.NewSyscallError("netlink message", err)
+	}
+	var ift []Interface
+	if ifi == nil {
+		var err error
+		ift, err = interfaceTable(0)
+		if err != nil {
+			return nil, err
+		}
+	}
+	ifat, err := addrTable(ift, ifi, msgs)
+	if err != nil {
+		return nil, err
+	}
+	return ifat, nil
+}
+
+func addrTable(ift []Interface, ifi *Interface, msgs []syscall.NetlinkMessage) ([]Addr, error) {
+	var ifat []Addr
+loop:
+	for _, m := range msgs {
+		switch m.Header.Type {
+		case syscall.NLMSG_DONE:
+			break loop
+		case syscall.RTM_NEWADDR:
+			ifam := (*syscall.IfAddrmsg)(unsafe.Pointer(&m.Data[0]))
+			if len(ift) != 0 || ifi.Index == int(ifam.Index) {
+				if len(ift) != 0 {
+					var err error
+					ifi, err = interfaceByIndex(ift, int(ifam.Index))
+					if err != nil {
+						return nil, err
+					}
+				}
+				attrs, err := syscall.ParseNetlinkRouteAttr(&m)
+				if err != nil {
+					return nil, os.NewSyscallError("netlink routeattr", err)
+				}
+				ifa := newAddr(ifi, ifam, attrs)
+				if ifa != nil {
+					ifat = append(ifat, ifa)
+				}
+			}
+		}
+	}
+	return ifat, nil
+}
+
+func newAddr(ifi *Interface, ifam *syscall.IfAddrmsg, attrs []syscall.NetlinkRouteAttr) Addr {
+	var ipPointToPoint bool
+	// Seems like we need to make sure whether the IP interface
+	// stack consists of IP point-to-point numbered or unnumbered
+	// addressing over point-to-point link encapsulation.
+	if ifi.Flags&FlagPointToPoint != 0 {
+		for _, a := range attrs {
+			if a.Attr.Type == syscall.IFA_LOCAL {
+				ipPointToPoint = true
+				break
+			}
+		}
+	}
+	for _, a := range attrs {
+		if ipPointToPoint && a.Attr.Type == syscall.IFA_ADDRESS || !ipPointToPoint && a.Attr.Type == syscall.IFA_LOCAL {
+			continue
+		}
+		switch ifam.Family {
+		case syscall.AF_INET:
+			return &IPNet{IP: IPv4(a.Value[0], a.Value[1], a.Value[2], a.Value[3]), Mask: CIDRMask(int(ifam.Prefixlen), 8*IPv4len)}
+		case syscall.AF_INET6:
+			ifa := &IPNet{IP: make(IP, IPv6len), Mask: CIDRMask(int(ifam.Prefixlen), 8*IPv6len)}
+			copy(ifa.IP, a.Value[:])
+			return ifa
+		}
+	}
+	return nil
+}
+
+// interfaceMulticastAddrTable returns addresses for a specific
+// interface.
+func interfaceMulticastAddrTable(ifi *Interface) ([]Addr, error) {
+	ifmat4 := parseProcNetIGMP("/proc/net/igmp", ifi)
+	ifmat6 := parseProcNetIGMP6("/proc/net/igmp6", ifi)
+	return append(ifmat4, ifmat6...), nil
+}
+
+func parseProcNetIGMP(path string, ifi *Interface) []Addr {
+	fd, err := open(path)
+	if err != nil {
+		return nil
+	}
+	defer fd.close()
+	var (
+		ifmat []Addr
+		name  string
+	)
+	fd.readLine() // skip first line
+	b := make([]byte, IPv4len)
+	for l, ok := fd.readLine(); ok; l, ok = fd.readLine() {
+		f := splitAtBytes(l, " :\r\t\n")
+		if len(f) < 4 {
+			continue
+		}
+		switch {
+		case l[0] != ' ' && l[0] != '\t': // new interface line
+			name = f[1]
+		case len(f[0]) == 8:
+			if ifi == nil || name == ifi.Name {
+				// The Linux kernel puts the IP
+				// address in /proc/net/igmp in native
+				// endianness.
+				for i := 0; i+1 < len(f[0]); i += 2 {
+					b[i/2], _ = xtoi2(f[0][i:i+2], 0)
+				}
+				i := *(*uint32)(unsafe.Pointer(&b[:4][0]))
+				ifma := IPAddr{IP: IPv4(byte(i>>24), byte(i>>16), byte(i>>8), byte(i))}
+				ifmat = append(ifmat, ifma.toAddr())
+			}
+		}
+	}
+	return ifmat
+}
+
+func parseProcNetIGMP6(path string, ifi *Interface) []Addr {
+	fd, err := open(path)
+	if err != nil {
+		return nil
+	}
+	defer fd.close()
+	var ifmat []Addr
+	b := make([]byte, IPv6len)
+	for l, ok := fd.readLine(); ok; l, ok = fd.readLine() {
+		f := splitAtBytes(l, " \r\t\n")
+		if len(f) < 6 {
+			continue
+		}
+		if ifi == nil || f[1] == ifi.Name {
+			for i := 0; i+1 < len(f[2]); i += 2 {
+				b[i/2], _ = xtoi2(f[2][i:i+2], 0)
+			}
+			ifma := IPAddr{IP: IP{b[0], b[1], b[2], b[3], b[4], b[5], b[6], b[7], b[8], b[9], b[10], b[11], b[12], b[13], b[14], b[15]}}
+			ifmat = append(ifmat, ifma.toAddr())
+		}
+	}
+	return ifmat
+}
diff --git a/src/net/interface_linux_test.go b/src/net/interface_linux_test.go
new file mode 100644
index 000000000..d8800bd0c
--- /dev/null
+++ b/src/net/interface_linux_test.go
@@ -0,0 +1,102 @@
+// Copyright 2012 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package net
+
+import (
+	"fmt"
+	"os/exec"
+	"testing"
+)
+
+func (ti *testInterface) setBroadcast(suffix int) error {
+	ti.name = fmt.Sprintf("gotest%d", suffix)
+	xname, err := exec.LookPath("ip")
+	if err != nil {
+		return err
+	}
+	ti.setupCmds = append(ti.setupCmds, &exec.Cmd{
+		Path: xname,
+		Args: []string{"ip", "link", "add", ti.name, "type", "dummy"},
+	})
+	ti.teardownCmds = append(ti.teardownCmds, &exec.Cmd{
+		Path: xname,
+		Args: []string{"ip", "link", "delete", ti.name, "type", "dummy"},
+	})
+	return nil
+}
+
+func (ti *testInterface) setPointToPoint(suffix int, local, remote string) error {
+	ti.name = fmt.Sprintf("gotest%d", suffix)
+	ti.local = local
+	ti.remote = remote
+	xname, err := exec.LookPath("ip")
+	if err != nil {
+		return err
+	}
+	ti.setupCmds = append(ti.setupCmds, &exec.Cmd{
+		Path: xname,
+		Args: []string{"ip", "tunnel", "add", ti.name, "mode", "gre", "local", local, "remote", remote},
+	})
+	ti.teardownCmds = append(ti.teardownCmds, &exec.Cmd{
+		Path: xname,
+		Args: []string{"ip", "tunnel", "del", ti.name, "mode", "gre", "local", local, "remote", remote},
+	})
+	xname, err = exec.LookPath("ifconfig")
+	if err != nil {
+		return err
+	}
+	ti.setupCmds = append(ti.setupCmds, &exec.Cmd{
+		Path: xname,
+		Args: []string{"ifconfig", ti.name, "inet", local, "dstaddr", remote},
+	})
+	return nil
+}
+
+const (
+	numOfTestIPv4MCAddrs = 14
+	numOfTestIPv6MCAddrs = 18
+)
+
+var (
+	igmpInterfaceTable = []Interface{
+		{Name: "lo"},
+		{Name: "eth0"}, {Name: "eth1"}, {Name: "eth2"},
+		{Name: "eth0.100"}, {Name: "eth0.101"}, {Name: "eth0.102"}, {Name: "eth0.103"},
+		{Name: "device1tap2"},
+	}
+	igmp6InterfaceTable = []Interface{
+		{Name: "lo"},
+		{Name: "eth0"}, {Name: "eth1"}, {Name: "eth2"},
+		{Name: "eth0.100"}, {Name: "eth0.101"}, {Name: "eth0.102"}, {Name: "eth0.103"},
+		{Name: "device1tap2"},
+		{Name: "pan0"},
+	}
+)
+
+func TestParseProcNet(t *testing.T) {
+	defer func() {
+		if p := recover(); p != nil {
+			t.Fatalf("parseProcNetIGMP or parseProtNetIGMP6 panicked: %v", p)
+		}
+	}()
+
+	var ifmat4 []Addr
+	for _, ifi := range igmpInterfaceTable {
+		ifmat := parseProcNetIGMP("testdata/igmp", &ifi)
+		ifmat4 = append(ifmat4, ifmat...)
+	}
+	if len(ifmat4) != numOfTestIPv4MCAddrs {
+		t.Fatalf("parseProcNetIGMP returns %v addresses, expected %v", len(ifmat4), numOfTestIPv4MCAddrs)
+	}
+
+	var ifmat6 []Addr
+	for _, ifi := range igmp6InterfaceTable {
+		ifmat := parseProcNetIGMP6("testdata/igmp6", &ifi)
+		ifmat6 = append(ifmat6, ifmat...)
+	}
+	if len(ifmat6) != numOfTestIPv6MCAddrs {
+		t.Fatalf("parseProcNetIGMP6 returns %v addresses, expected %v", len(ifmat6), numOfTestIPv6MCAddrs)
+	}
+}
diff --git a/src/net/interface_netbsd.go b/src/net/interface_netbsd.go
new file mode 100644
index 000000000..c9ce5a7ac
--- /dev/null
+++ b/src/net/interface_netbsd.go
@@ -0,0 +1,12 @@
+// Copyright 2011 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package net
+
+// interfaceMulticastAddrTable returns addresses for a specific
+// interface.
+func interfaceMulticastAddrTable(ifi *Interface) ([]Addr, error) {
+	// TODO(mikio): Implement this like other platforms.
+	return nil, nil
+}
diff --git a/src/net/interface_openbsd.go b/src/net/interface_openbsd.go
new file mode 100644
index 000000000..c9ce5a7ac
--- /dev/null
+++ b/src/net/interface_openbsd.go
@@ -0,0 +1,12 @@
+// Copyright 2011 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package net
+
+// interfaceMulticastAddrTable returns addresses for a specific
+// interface.
+func interfaceMulticastAddrTable(ifi *Interface) ([]Addr, error) {
+	// TODO(mikio): Implement this like other platforms.
+	return nil, nil
+}
diff --git a/src/net/interface_stub.go b/src/net/interface_stub.go
new file mode 100644
index 000000000..c38fb7f76
--- /dev/null
+++ b/src/net/interface_stub.go
@@ -0,0 +1,27 @@
+// Copyright 2011 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build nacl plan9 solaris
+
+package net
+
+// If the ifindex is zero, interfaceTable returns mappings of all
+// network interfaces.  Otherwise it returns a mapping of a specific
+// interface.
+func interfaceTable(ifindex int) ([]Interface, error) {
+	return nil, nil
+}
+
+// If the ifi is nil, interfaceAddrTable returns addresses for all
+// network interfaces.  Otherwise it returns addresses for a specific
+// interface.
+func interfaceAddrTable(ifi *Interface) ([]Addr, error) {
+	return nil, nil
+}
+
+// interfaceMulticastAddrTable returns addresses for a specific
+// interface.
+func interfaceMulticastAddrTable(ifi *Interface) ([]Addr, error) {
+	return nil, nil
+}
diff --git a/src/net/interface_test.go b/src/net/interface_test.go
new file mode 100644
index 000000000..efabb5f3c
--- /dev/null
+++ b/src/net/interface_test.go
@@ -0,0 +1,211 @@
+// Copyright 2011 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package net
+
+import (
+	"reflect"
+	"testing"
+)
+
+// loopbackInterface returns an available logical network interface
+// for loopback tests.  It returns nil if no suitable interface is
+// found.
+func loopbackInterface() *Interface {
+	ift, err := Interfaces()
+	if err != nil {
+		return nil
+	}
+	for _, ifi := range ift {
+		if ifi.Flags&FlagLoopback != 0 && ifi.Flags&FlagUp != 0 {
+			return &ifi
+		}
+	}
+	return nil
+}
+
+// ipv6LinkLocalUnicastAddr returns an IPv6 link-local unicast address
+// on the given network interface for tests. It returns "" if no
+// suitable address is found.
+func ipv6LinkLocalUnicastAddr(ifi *Interface) string {
+	if ifi == nil {
+		return ""
+	}
+	ifat, err := ifi.Addrs()
+	if err != nil {
+		return ""
+	}
+	for _, ifa := range ifat {
+		switch ifa := ifa.(type) {
+		case *IPAddr:
+			if ifa.IP.To4() == nil && ifa.IP.IsLinkLocalUnicast() {
+				return ifa.IP.String()
+			}
+		case *IPNet:
+			if ifa.IP.To4() == nil && ifa.IP.IsLinkLocalUnicast() {
+				return ifa.IP.String()
+			}
+		}
+	}
+	return ""
+}
+
+func TestInterfaces(t *testing.T) {
+	ift, err := Interfaces()
+	if err != nil {
+		t.Fatalf("Interfaces failed: %v", err)
+	}
+	t.Logf("table: len/cap = %v/%v", len(ift), cap(ift))
+
+	for _, ifi := range ift {
+		ifxi, err := InterfaceByIndex(ifi.Index)
+		if err != nil {
+			t.Fatalf("InterfaceByIndex(%v) failed: %v", ifi.Index, err)
+		}
+		if !reflect.DeepEqual(ifxi, &ifi) {
+			t.Fatalf("InterfaceByIndex(%v) = %v, want %v", ifi.Index, ifxi, ifi)
+		}
+		ifxn, err := InterfaceByName(ifi.Name)
+		if err != nil {
+			t.Fatalf("InterfaceByName(%q) failed: %v", ifi.Name, err)
+		}
+		if !reflect.DeepEqual(ifxn, &ifi) {
+			t.Fatalf("InterfaceByName(%q) = %v, want %v", ifi.Name, ifxn, ifi)
+		}
+		t.Logf("%q: flags %q, ifindex %v, mtu %v", ifi.Name, ifi.Flags.String(), ifi.Index, ifi.MTU)
+		t.Logf("\thardware address %q", ifi.HardwareAddr.String())
+		testInterfaceAddrs(t, &ifi)
+		testInterfaceMulticastAddrs(t, &ifi)
+	}
+}
+
+func TestInterfaceAddrs(t *testing.T) {
+	ifat, err := InterfaceAddrs()
+	if err != nil {
+		t.Fatalf("InterfaceAddrs failed: %v", err)
+	}
+	t.Logf("table: len/cap = %v/%v", len(ifat), cap(ifat))
+	testAddrs(t, ifat)
+}
+
+func testInterfaceAddrs(t *testing.T, ifi *Interface) {
+	ifat, err := ifi.Addrs()
+	if err != nil {
+		t.Fatalf("Interface.Addrs failed: %v", err)
+	}
+	testAddrs(t, ifat)
+}
+
+func testInterfaceMulticastAddrs(t *testing.T, ifi *Interface) {
+	ifmat, err := ifi.MulticastAddrs()
+	if err != nil {
+		t.Fatalf("Interface.MulticastAddrs failed: %v", err)
+	}
+	testMulticastAddrs(t, ifmat)
+}
+
+func testAddrs(t *testing.T, ifat []Addr) {
+	for _, ifa := range ifat {
+		switch ifa := ifa.(type) {
+		case *IPAddr:
+			if ifa == nil || ifa.IP == nil {
+				t.Errorf("\tunexpected value: %v, %v", ifa, ifa.IP)
+			} else {
+				t.Logf("\tinterface address %q", ifa.String())
+			}
+		case *IPNet:
+			if ifa == nil || ifa.IP == nil || ifa.Mask == nil {
+				t.Errorf("\tunexpected value: %v, %v, %v", ifa, ifa.IP, ifa.Mask)
+			} else {
+				_, prefixLen := ifa.Mask.Size()
+				if ifa.IP.To4() != nil && prefixLen != 8*IPv4len || ifa.IP.To16() != nil && ifa.IP.To4() == nil && prefixLen != 8*IPv6len {
+					t.Errorf("\tunexpected value: %v, %v, %v, %v", ifa, ifa.IP, ifa.Mask, prefixLen)
+				} else {
+					t.Logf("\tinterface address %q", ifa.String())
+				}
+			}
+		default:
+			t.Errorf("\tunexpected type: %T", ifa)
+		}
+	}
+}
+
+func testMulticastAddrs(t *testing.T, ifmat []Addr) {
+	for _, ifma := range ifmat {
+		switch ifma := ifma.(type) {
+		case *IPAddr:
+			if ifma == nil {
+				t.Errorf("\tunexpected value: %v", ifma)
+			} else {
+				t.Logf("\tjoined group address %q", ifma.String())
+			}
+		default:
+			t.Errorf("\tunexpected type: %T", ifma)
+		}
+	}
+}
+
+func BenchmarkInterfaces(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		if _, err := Interfaces(); err != nil {
+			b.Fatalf("Interfaces failed: %v", err)
+		}
+	}
+}
+
+func BenchmarkInterfaceByIndex(b *testing.B) {
+	ifi := loopbackInterface()
+	if ifi == nil {
+		b.Skip("loopback interface not found")
+	}
+	for i := 0; i < b.N; i++ {
+		if _, err := InterfaceByIndex(ifi.Index); err != nil {
+			b.Fatalf("InterfaceByIndex failed: %v", err)
+		}
+	}
+}
+
+func BenchmarkInterfaceByName(b *testing.B) {
+	ifi := loopbackInterface()
+	if ifi == nil {
+		b.Skip("loopback interface not found")
+	}
+	for i := 0; i < b.N; i++ {
+		if _, err := InterfaceByName(ifi.Name); err != nil {
+			b.Fatalf("InterfaceByName failed: %v", err)
+		}
+	}
+}
+
+func BenchmarkInterfaceAddrs(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		if _, err := InterfaceAddrs(); err != nil {
+			b.Fatalf("InterfaceAddrs failed: %v", err)
+		}
+	}
+}
+
+func BenchmarkInterfacesAndAddrs(b *testing.B) {
+	ifi := loopbackInterface()
+	if ifi == nil {
+		b.Skip("loopback interface not found")
+	}
+	for i := 0; i < b.N; i++ {
+		if _, err := ifi.Addrs(); err != nil {
+			b.Fatalf("Interface.Addrs failed: %v", err)
+		}
+	}
+}
+
+func BenchmarkInterfacesAndMulticastAddrs(b *testing.B) {
+	ifi := loopbackInterface()
+	if ifi == nil {
+		b.Skip("loopback interface not found")
+	}
+	for i := 0; i < b.N; i++ {
+		if _, err := ifi.MulticastAddrs(); err != nil {
+			b.Fatalf("Interface.MulticastAddrs failed: %v", err)
+		}
+	}
+}
diff --git a/src/net/interface_unix_test.go b/src/net/interface_unix_test.go
new file mode 100644
index 000000000..01f609f15
--- /dev/null
+++ b/src/net/interface_unix_test.go
@@ -0,0 +1,151 @@
+// Copyright 2013 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build darwin dragonfly freebsd linux netbsd openbsd
+
+package net
+
+import (
+	"os"
+	"os/exec"
+	"runtime"
+	"testing"
+	"time"
+)
+
+type testInterface struct {
+	name         string
+	local        string
+	remote       string
+	setupCmds    []*exec.Cmd
+	teardownCmds []*exec.Cmd
+}
+
+func (ti *testInterface) setup() error {
+	for _, cmd := range ti.setupCmds {
+		if err := cmd.Run(); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+func (ti *testInterface) teardown() error {
+	for _, cmd := range ti.teardownCmds {
+		if err := cmd.Run(); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+func TestPointToPointInterface(t *testing.T) {
+	if testing.Short() {
+		t.Skip("skipping test in short mode")
+	}
+	switch {
+	case runtime.GOOS == "darwin":
+		t.Skipf("skipping read test on %q", runtime.GOOS)
+	}
+	if os.Getuid() != 0 {
+		t.Skip("skipping test; must be root")
+	}
+
+	local, remote := "169.254.0.1", "169.254.0.254"
+	ip := ParseIP(remote)
+	for i := 0; i < 3; i++ {
+		ti := &testInterface{}
+		if err := ti.setPointToPoint(5963+i, local, remote); err != nil {
+			t.Skipf("test requries external command: %v", err)
+		}
+		if err := ti.setup(); err != nil {
+			t.Fatalf("testInterface.setup failed: %v", err)
+		} else {
+			time.Sleep(3 * time.Millisecond)
+		}
+		ift, err := Interfaces()
+		if err != nil {
+			ti.teardown()
+			t.Fatalf("Interfaces failed: %v", err)
+		}
+		for _, ifi := range ift {
+			if ti.name == ifi.Name {
+				ifat, err := ifi.Addrs()
+				if err != nil {
+					ti.teardown()
+					t.Fatalf("Interface.Addrs failed: %v", err)
+				}
+				for _, ifa := range ifat {
+					if ip.Equal(ifa.(*IPNet).IP) {
+						ti.teardown()
+						t.Fatalf("got %v; want %v", ip, local)
+					}
+				}
+			}
+		}
+		if err := ti.teardown(); err != nil {
+			t.Fatalf("testInterface.teardown failed: %v", err)
+		} else {
+			time.Sleep(3 * time.Millisecond)
+		}
+	}
+}
+
+func TestInterfaceArrivalAndDeparture(t *testing.T) {
+	if testing.Short() {
+		t.Skip("skipping test in short mode")
+	}
+	if os.Getuid() != 0 {
+		t.Skip("skipping test; must be root")
+	}
+
+	for i := 0; i < 3; i++ {
+		ift1, err := Interfaces()
+		if err != nil {
+			t.Fatalf("Interfaces failed: %v", err)
+		}
+		ti := &testInterface{}
+		if err := ti.setBroadcast(5682 + i); err != nil {
+			t.Skipf("test requires external command: %v", err)
+		}
+		if err := ti.setup(); err != nil {
+			t.Fatalf("testInterface.setup failed: %v", err)
+		} else {
+			time.Sleep(3 * time.Millisecond)
+		}
+		ift2, err := Interfaces()
+		if err != nil {
+			ti.teardown()
+			t.Fatalf("Interfaces failed: %v", err)
+		}
+		if len(ift2) <= len(ift1) {
+			for _, ifi := range ift1 {
+				t.Logf("before: %v", ifi)
+			}
+			for _, ifi := range ift2 {
+				t.Logf("after: %v", ifi)
+			}
+			ti.teardown()
+			t.Fatalf("got %v; want gt %v", len(ift2), len(ift1))
+		}
+		if err := ti.teardown(); err != nil {
+			t.Fatalf("testInterface.teardown failed: %v", err)
+		} else {
+			time.Sleep(3 * time.Millisecond)
+		}
+		ift3, err := Interfaces()
+		if err != nil {
+			t.Fatalf("Interfaces failed: %v", err)
+		}
+		if len(ift3) >= len(ift2) {
+			for _, ifi := range ift2 {
+				t.Logf("before: %v", ifi)
+			}
+			for _, ifi := range ift3 {
+				t.Logf("after: %v", ifi)
+			}
+			t.Fatalf("got %v; want lt %v", len(ift3), len(ift2))
+		}
+	}
+}
diff --git a/src/net/interface_windows.go b/src/net/interface_windows.go
new file mode 100644
index 000000000..0759dc255
--- /dev/null
+++ b/src/net/interface_windows.go
@@ -0,0 +1,158 @@
+// Copyright 2011 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package net
+
+import (
+	"os"
+	"syscall"
+	"unsafe"
+)
+
+func bytePtrToString(p *uint8) string {
+	a := (*[10000]uint8)(unsafe.Pointer(p))
+	i := 0
+	for a[i] != 0 {
+		i++
+	}
+	return string(a[:i])
+}
+
+func getAdapterList() (*syscall.IpAdapterInfo, error) {
+	b := make([]byte, 1000)
+	l := uint32(len(b))
+	a := (*syscall.IpAdapterInfo)(unsafe.Pointer(&b[0]))
+	// TODO(mikio): GetAdaptersInfo returns IP_ADAPTER_INFO that
+	// contains IPv4 address list only. We should use another API
+	// for fetching IPv6 stuff from the kernel.
+	err := syscall.GetAdaptersInfo(a, &l)
+	if err == syscall.ERROR_BUFFER_OVERFLOW {
+		b = make([]byte, l)
+		a = (*syscall.IpAdapterInfo)(unsafe.Pointer(&b[0]))
+		err = syscall.GetAdaptersInfo(a, &l)
+	}
+	if err != nil {
+		return nil, os.NewSyscallError("GetAdaptersInfo", err)
+	}
+	return a, nil
+}
+
+func getInterfaceList() ([]syscall.InterfaceInfo, error) {
+	s, err := sysSocket(syscall.AF_INET, syscall.SOCK_DGRAM, syscall.IPPROTO_UDP)
+	if err != nil {
+		return nil, os.NewSyscallError("Socket", err)
+	}
+	defer syscall.Closesocket(s)
+
+	ii := [20]syscall.InterfaceInfo{}
+	ret := uint32(0)
+	size := uint32(unsafe.Sizeof(ii))
+	err = syscall.WSAIoctl(s, syscall.SIO_GET_INTERFACE_LIST, nil, 0, (*byte)(unsafe.Pointer(&ii[0])), size, &ret, nil, 0)
+	if err != nil {
+		return nil, os.NewSyscallError("WSAIoctl", err)
+	}
+	c := ret / uint32(unsafe.Sizeof(ii[0]))
+	return ii[:c-1], nil
+}
+
+// If the ifindex is zero, interfaceTable returns mappings of all
+// network interfaces.  Otherwise it returns a mapping of a specific
+// interface.
+func interfaceTable(ifindex int) ([]Interface, error) {
+	ai, err := getAdapterList()
+	if err != nil {
+		return nil, err
+	}
+
+	ii, err := getInterfaceList()
+	if err != nil {
+		return nil, err
+	}
+
+	var ift []Interface
+	for ; ai != nil; ai = ai.Next {
+		index := ai.Index
+		if ifindex == 0 || ifindex == int(index) {
+			var flags Flags
+
+			row := syscall.MibIfRow{Index: index}
+			e := syscall.GetIfEntry(&row)
+			if e != nil {
+				return nil, os.NewSyscallError("GetIfEntry", e)
+			}
+
+			for _, ii := range ii {
+				ip := (*syscall.RawSockaddrInet4)(unsafe.Pointer(&ii.Address)).Addr
+				ipv4 := IPv4(ip[0], ip[1], ip[2], ip[3])
+				ipl := &ai.IpAddressList
+				for ipl != nil {
+					ips := bytePtrToString(&ipl.IpAddress.String[0])
+					if ipv4.Equal(parseIPv4(ips)) {
+						break
+					}
+					ipl = ipl.Next
+				}
+				if ipl == nil {
+					continue
+				}
+				if ii.Flags&syscall.IFF_UP != 0 {
+					flags |= FlagUp
+				}
+				if ii.Flags&syscall.IFF_LOOPBACK != 0 {
+					flags |= FlagLoopback
+				}
+				if ii.Flags&syscall.IFF_BROADCAST != 0 {
+					flags |= FlagBroadcast
+				}
+				if ii.Flags&syscall.IFF_POINTTOPOINT != 0 {
+					flags |= FlagPointToPoint
+				}
+				if ii.Flags&syscall.IFF_MULTICAST != 0 {
+					flags |= FlagMulticast
+				}
+			}
+
+			name := bytePtrToString(&ai.AdapterName[0])
+
+			ifi := Interface{
+				Index:        int(index),
+				MTU:          int(row.Mtu),
+				Name:         name,
+				HardwareAddr: HardwareAddr(row.PhysAddr[:row.PhysAddrLen]),
+				Flags:        flags}
+			ift = append(ift, ifi)
+		}
+	}
+	return ift, nil
+}
+
+// If the ifi is nil, interfaceAddrTable returns addresses for all
+// network interfaces.  Otherwise it returns addresses for a specific
+// interface.
+func interfaceAddrTable(ifi *Interface) ([]Addr, error) {
+	ai, err := getAdapterList()
+	if err != nil {
+		return nil, err
+	}
+
+	var ifat []Addr
+	for ; ai != nil; ai = ai.Next {
+		index := ai.Index
+		if ifi == nil || ifi.Index == int(index) {
+			ipl := &ai.IpAddressList
+			for ; ipl != nil; ipl = ipl.Next {
+				ifa := IPAddr{IP: parseIPv4(bytePtrToString(&ipl.IpAddress.String[0]))}
+				ifat = append(ifat, ifa.toAddr())
+			}
+		}
+	}
+	return ifat, nil
+}
+
+// interfaceMulticastAddrTable returns addresses for a specific
+// interface.
+func interfaceMulticastAddrTable(ifi *Interface) ([]Addr, error) {
+	// TODO(mikio): Implement this like other platforms.
+	return nil, nil
+}
diff --git a/src/net/ip.go b/src/net/ip.go
new file mode 100644
index 000000000..4a93e97b3
--- /dev/null
+++ b/src/net/ip.go
@@ -0,0 +1,689 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// IP address manipulations
+//
+// IPv4 addresses are 4 bytes; IPv6 addresses are 16 bytes.
+// An IPv4 address can be converted to an IPv6 address by
+// adding a canonical prefix (10 zeros, 2 0xFFs).
+// This library accepts either size of byte slice but always
+// returns 16-byte addresses.
+
+package net
+
+import "errors"
+
+// IP address lengths (bytes).
+const (
+	IPv4len = 4
+	IPv6len = 16
+)
+
+// An IP is a single IP address, a slice of bytes.
+// Functions in this package accept either 4-byte (IPv4)
+// or 16-byte (IPv6) slices as input.
+//
+// Note that in this documentation, referring to an
+// IP address as an IPv4 address or an IPv6 address
+// is a semantic property of the address, not just the
+// length of the byte slice: a 16-byte slice can still
+// be an IPv4 address.
+type IP []byte
+
+// An IP mask is an IP address.
+type IPMask []byte
+
+// An IPNet represents an IP network.
+type IPNet struct {
+	IP   IP     // network number
+	Mask IPMask // network mask
+}
+
+// IPv4 returns the IP address (in 16-byte form) of the
+// IPv4 address a.b.c.d.
+func IPv4(a, b, c, d byte) IP {
+	p := make(IP, IPv6len)
+	copy(p, v4InV6Prefix)
+	p[12] = a
+	p[13] = b
+	p[14] = c
+	p[15] = d
+	return p
+}
+
+var v4InV6Prefix = []byte{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0xff, 0xff}
+
+// IPv4Mask returns the IP mask (in 4-byte form) of the
+// IPv4 mask a.b.c.d.
+func IPv4Mask(a, b, c, d byte) IPMask {
+	p := make(IPMask, IPv4len)
+	p[0] = a
+	p[1] = b
+	p[2] = c
+	p[3] = d
+	return p
+}
+
+// CIDRMask returns an IPMask consisting of `ones' 1 bits
+// followed by 0s up to a total length of `bits' bits.
+// For a mask of this form, CIDRMask is the inverse of IPMask.Size.
+func CIDRMask(ones, bits int) IPMask {
+	if bits != 8*IPv4len && bits != 8*IPv6len {
+		return nil
+	}
+	if ones < 0 || ones > bits {
+		return nil
+	}
+	l := bits / 8
+	m := make(IPMask, l)
+	n := uint(ones)
+	for i := 0; i < l; i++ {
+		if n >= 8 {
+			m[i] = 0xff
+			n -= 8
+			continue
+		}
+		m[i] = ^byte(0xff >> n)
+		n = 0
+	}
+	return m
+}
+
+// Well-known IPv4 addresses
+var (
+	IPv4bcast     = IPv4(255, 255, 255, 255) // broadcast
+	IPv4allsys    = IPv4(224, 0, 0, 1)       // all systems
+	IPv4allrouter = IPv4(224, 0, 0, 2)       // all routers
+	IPv4zero      = IPv4(0, 0, 0, 0)         // all zeros
+)
+
+// Well-known IPv6 addresses
+var (
+	IPv6zero                   = IP{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}
+	IPv6unspecified            = IP{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}
+	IPv6loopback               = IP{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1}
+	IPv6interfacelocalallnodes = IP{0xff, 0x01, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0x01}
+	IPv6linklocalallnodes      = IP{0xff, 0x02, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0x01}
+	IPv6linklocalallrouters    = IP{0xff, 0x02, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0x02}
+)
+
+// IsUnspecified returns true if ip is an unspecified address.
+func (ip IP) IsUnspecified() bool {
+	if ip.Equal(IPv4zero) || ip.Equal(IPv6unspecified) {
+		return true
+	}
+	return false
+}
+
+// IsLoopback returns true if ip is a loopback address.
+func (ip IP) IsLoopback() bool {
+	if ip4 := ip.To4(); ip4 != nil && ip4[0] == 127 {
+		return true
+	}
+	return ip.Equal(IPv6loopback)
+}
+
+// IsMulticast returns true if ip is a multicast address.
+func (ip IP) IsMulticast() bool {
+	if ip4 := ip.To4(); ip4 != nil && ip4[0]&0xf0 == 0xe0 {
+		return true
+	}
+	return ip[0] == 0xff
+}
+
+// IsInterfaceLinkLocalMulticast returns true if ip is
+// an interface-local multicast address.
+func (ip IP) IsInterfaceLocalMulticast() bool {
+	return len(ip) == IPv6len && ip[0] == 0xff && ip[1]&0x0f == 0x01
+}
+
+// IsLinkLocalMulticast returns true if ip is a link-local
+// multicast address.
+func (ip IP) IsLinkLocalMulticast() bool {
+	if ip4 := ip.To4(); ip4 != nil && ip4[0] == 224 && ip4[1] == 0 && ip4[2] == 0 {
+		return true
+	}
+	return ip[0] == 0xff && ip[1]&0x0f == 0x02
+}
+
+// IsLinkLocalUnicast returns true if ip is a link-local
+// unicast address.
+func (ip IP) IsLinkLocalUnicast() bool {
+	if ip4 := ip.To4(); ip4 != nil && ip4[0] == 169 && ip4[1] == 254 {
+		return true
+	}
+	return ip[0] == 0xfe && ip[1]&0xc0 == 0x80
+}
+
+// IsGlobalUnicast returns true if ip is a global unicast
+// address.
+func (ip IP) IsGlobalUnicast() bool {
+	return !ip.IsUnspecified() &&
+		!ip.IsLoopback() &&
+		!ip.IsMulticast() &&
+		!ip.IsLinkLocalUnicast()
+}
+
+// Is p all zeros?
+func isZeros(p IP) bool {
+	for i := 0; i < len(p); i++ {
+		if p[i] != 0 {
+			return false
+		}
+	}
+	return true
+}
+
+// To4 converts the IPv4 address ip to a 4-byte representation.
+// If ip is not an IPv4 address, To4 returns nil.
+func (ip IP) To4() IP {
+	if len(ip) == IPv4len {
+		return ip
+	}
+	if len(ip) == IPv6len &&
+		isZeros(ip[0:10]) &&
+		ip[10] == 0xff &&
+		ip[11] == 0xff {
+		return ip[12:16]
+	}
+	return nil
+}
+
+// To16 converts the IP address ip to a 16-byte representation.
+// If ip is not an IP address (it is the wrong length), To16 returns nil.
+func (ip IP) To16() IP {
+	if len(ip) == IPv4len {
+		return IPv4(ip[0], ip[1], ip[2], ip[3])
+	}
+	if len(ip) == IPv6len {
+		return ip
+	}
+	return nil
+}
+
+// Default route masks for IPv4.
+var (
+	classAMask = IPv4Mask(0xff, 0, 0, 0)
+	classBMask = IPv4Mask(0xff, 0xff, 0, 0)
+	classCMask = IPv4Mask(0xff, 0xff, 0xff, 0)
+)
+
+// DefaultMask returns the default IP mask for the IP address ip.
+// Only IPv4 addresses have default masks; DefaultMask returns
+// nil if ip is not a valid IPv4 address.
+func (ip IP) DefaultMask() IPMask {
+	if ip = ip.To4(); ip == nil {
+		return nil
+	}
+	switch true {
+	case ip[0] < 0x80:
+		return classAMask
+	case ip[0] < 0xC0:
+		return classBMask
+	default:
+		return classCMask
+	}
+}
+
+func allFF(b []byte) bool {
+	for _, c := range b {
+		if c != 0xff {
+			return false
+		}
+	}
+	return true
+}
+
+// Mask returns the result of masking the IP address ip with mask.
+func (ip IP) Mask(mask IPMask) IP {
+	if len(mask) == IPv6len && len(ip) == IPv4len && allFF(mask[:12]) {
+		mask = mask[12:]
+	}
+	if len(mask) == IPv4len && len(ip) == IPv6len && bytesEqual(ip[:12], v4InV6Prefix) {
+		ip = ip[12:]
+	}
+	n := len(ip)
+	if n != len(mask) {
+		return nil
+	}
+	out := make(IP, n)
+	for i := 0; i < n; i++ {
+		out[i] = ip[i] & mask[i]
+	}
+	return out
+}
+
+// String returns the string form of the IP address ip.
+// If the address is an IPv4 address, the string representation
+// is dotted decimal ("74.125.19.99").  Otherwise the representation
+// is IPv6 ("2001:4860:0:2001::68").
+func (ip IP) String() string {
+	p := ip
+
+	if len(ip) == 0 {
+		return "<nil>"
+	}
+
+	// If IPv4, use dotted notation.
+	if p4 := p.To4(); len(p4) == IPv4len {
+		return itod(uint(p4[0])) + "." +
+			itod(uint(p4[1])) + "." +
+			itod(uint(p4[2])) + "." +
+			itod(uint(p4[3]))
+	}
+	if len(p) != IPv6len {
+		return "?"
+	}
+
+	// Find longest run of zeros.
+	e0 := -1
+	e1 := -1
+	for i := 0; i < IPv6len; i += 2 {
+		j := i
+		for j < IPv6len && p[j] == 0 && p[j+1] == 0 {
+			j += 2
+		}
+		if j > i && j-i > e1-e0 {
+			e0 = i
+			e1 = j
+			i = j
+		}
+	}
+	// The symbol "::" MUST NOT be used to shorten just one 16 bit 0 field.
+	if e1-e0 <= 2 {
+		e0 = -1
+		e1 = -1
+	}
+
+	const maxLen = len("ffff:ffff:ffff:ffff:ffff:ffff:ffff:ffff")
+	b := make([]byte, 0, maxLen)
+
+	// Print with possible :: in place of run of zeros
+	for i := 0; i < IPv6len; i += 2 {
+		if i == e0 {
+			b = append(b, ':', ':')
+			i = e1
+			if i >= IPv6len {
+				break
+			}
+		} else if i > 0 {
+			b = append(b, ':')
+		}
+		b = appendHex(b, (uint32(p[i])<<8)|uint32(p[i+1]))
+	}
+	return string(b)
+}
+
+// ipEmptyString is like ip.String except that it returns
+// an empty string when ip is unset.
+func ipEmptyString(ip IP) string {
+	if len(ip) == 0 {
+		return ""
+	}
+	return ip.String()
+}
+
+// MarshalText implements the encoding.TextMarshaler interface.
+// The encoding is the same as returned by String.
+func (ip IP) MarshalText() ([]byte, error) {
+	if len(ip) == 0 {
+		return []byte(""), nil
+	}
+	if len(ip) != IPv4len && len(ip) != IPv6len {
+		return nil, errors.New("invalid IP address")
+	}
+	return []byte(ip.String()), nil
+}
+
+// UnmarshalText implements the encoding.TextUnmarshaler interface.
+// The IP address is expected in a form accepted by ParseIP.
+func (ip *IP) UnmarshalText(text []byte) error {
+	if len(text) == 0 {
+		*ip = nil
+		return nil
+	}
+	s := string(text)
+	x := ParseIP(s)
+	if x == nil {
+		return &ParseError{"IP address", s}
+	}
+	*ip = x
+	return nil
+}
+
+// Equal returns true if ip and x are the same IP address.
+// An IPv4 address and that same address in IPv6 form are
+// considered to be equal.
+func (ip IP) Equal(x IP) bool {
+	if len(ip) == len(x) {
+		return bytesEqual(ip, x)
+	}
+	if len(ip) == IPv4len && len(x) == IPv6len {
+		return bytesEqual(x[0:12], v4InV6Prefix) && bytesEqual(ip, x[12:])
+	}
+	if len(ip) == IPv6len && len(x) == IPv4len {
+		return bytesEqual(ip[0:12], v4InV6Prefix) && bytesEqual(ip[12:], x)
+	}
+	return false
+}
+
+func bytesEqual(x, y []byte) bool {
+	if len(x) != len(y) {
+		return false
+	}
+	for i, b := range x {
+		if y[i] != b {
+			return false
+		}
+	}
+	return true
+}
+
+// If mask is a sequence of 1 bits followed by 0 bits,
+// return the number of 1 bits.
+func simpleMaskLength(mask IPMask) int {
+	var n int
+	for i, v := range mask {
+		if v == 0xff {
+			n += 8
+			continue
+		}
+		// found non-ff byte
+		// count 1 bits
+		for v&0x80 != 0 {
+			n++
+			v <<= 1
+		}
+		// rest must be 0 bits
+		if v != 0 {
+			return -1
+		}
+		for i++; i < len(mask); i++ {
+			if mask[i] != 0 {
+				return -1
+			}
+		}
+		break
+	}
+	return n
+}
+
+// Size returns the number of leading ones and total bits in the mask.
+// If the mask is not in the canonical form--ones followed by zeros--then
+// Size returns 0, 0.
+func (m IPMask) Size() (ones, bits int) {
+	ones, bits = simpleMaskLength(m), len(m)*8
+	if ones == -1 {
+		return 0, 0
+	}
+	return
+}
+
+// String returns the hexadecimal form of m, with no punctuation.
+func (m IPMask) String() string {
+	if len(m) == 0 {
+		return "<nil>"
+	}
+	buf := make([]byte, len(m)*2)
+	for i, b := range m {
+		buf[i*2], buf[i*2+1] = hexDigit[b>>4], hexDigit[b&0xf]
+	}
+	return string(buf)
+}
+
+func networkNumberAndMask(n *IPNet) (ip IP, m IPMask) {
+	if ip = n.IP.To4(); ip == nil {
+		ip = n.IP
+		if len(ip) != IPv6len {
+			return nil, nil
+		}
+	}
+	m = n.Mask
+	switch len(m) {
+	case IPv4len:
+		if len(ip) != IPv4len {
+			return nil, nil
+		}
+	case IPv6len:
+		if len(ip) == IPv4len {
+			m = m[12:]
+		}
+	default:
+		return nil, nil
+	}
+	return
+}
+
+// Contains reports whether the network includes ip.
+func (n *IPNet) Contains(ip IP) bool {
+	nn, m := networkNumberAndMask(n)
+	if x := ip.To4(); x != nil {
+		ip = x
+	}
+	l := len(ip)
+	if l != len(nn) {
+		return false
+	}
+	for i := 0; i < l; i++ {
+		if nn[i]&m[i] != ip[i]&m[i] {
+			return false
+		}
+	}
+	return true
+}
+
+// Network returns the address's network name, "ip+net".
+func (n *IPNet) Network() string { return "ip+net" }
+
+// String returns the CIDR notation of n like "192.168.100.1/24"
+// or "2001:DB8::/48" as defined in RFC 4632 and RFC 4291.
+// If the mask is not in the canonical form, it returns the
+// string which consists of an IP address, followed by a slash
+// character and a mask expressed as hexadecimal form with no
+// punctuation like "192.168.100.1/c000ff00".
+func (n *IPNet) String() string {
+	nn, m := networkNumberAndMask(n)
+	if nn == nil || m == nil {
+		return "<nil>"
+	}
+	l := simpleMaskLength(m)
+	if l == -1 {
+		return nn.String() + "/" + m.String()
+	}
+	return nn.String() + "/" + itod(uint(l))
+}
+
+// Parse IPv4 address (d.d.d.d).
+func parseIPv4(s string) IP {
+	var p [IPv4len]byte
+	i := 0
+	for j := 0; j < IPv4len; j++ {
+		if i >= len(s) {
+			// Missing octets.
+			return nil
+		}
+		if j > 0 {
+			if s[i] != '.' {
+				return nil
+			}
+			i++
+		}
+		var (
+			n  int
+			ok bool
+		)
+		n, i, ok = dtoi(s, i)
+		if !ok || n > 0xFF {
+			return nil
+		}
+		p[j] = byte(n)
+	}
+	if i != len(s) {
+		return nil
+	}
+	return IPv4(p[0], p[1], p[2], p[3])
+}
+
+// parseIPv6 parses s as a literal IPv6 address described in RFC 4291
+// and RFC 5952.  It can also parse a literal scoped IPv6 address with
+// zone identifier which is described in RFC 4007 when zoneAllowed is
+// true.
+func parseIPv6(s string, zoneAllowed bool) (ip IP, zone string) {
+	ip = make(IP, IPv6len)
+	ellipsis := -1 // position of ellipsis in p
+	i := 0         // index in string s
+
+	if zoneAllowed {
+		s, zone = splitHostZone(s)
+	}
+
+	// Might have leading ellipsis
+	if len(s) >= 2 && s[0] == ':' && s[1] == ':' {
+		ellipsis = 0
+		i = 2
+		// Might be only ellipsis
+		if i == len(s) {
+			return ip, zone
+		}
+	}
+
+	// Loop, parsing hex numbers followed by colon.
+	j := 0
+	for j < IPv6len {
+		// Hex number.
+		n, i1, ok := xtoi(s, i)
+		if !ok || n > 0xFFFF {
+			return nil, zone
+		}
+
+		// If followed by dot, might be in trailing IPv4.
+		if i1 < len(s) && s[i1] == '.' {
+			if ellipsis < 0 && j != IPv6len-IPv4len {
+				// Not the right place.
+				return nil, zone
+			}
+			if j+IPv4len > IPv6len {
+				// Not enough room.
+				return nil, zone
+			}
+			ip4 := parseIPv4(s[i:])
+			if ip4 == nil {
+				return nil, zone
+			}
+			ip[j] = ip4[12]
+			ip[j+1] = ip4[13]
+			ip[j+2] = ip4[14]
+			ip[j+3] = ip4[15]
+			i = len(s)
+			j += IPv4len
+			break
+		}
+
+		// Save this 16-bit chunk.
+		ip[j] = byte(n >> 8)
+		ip[j+1] = byte(n)
+		j += 2
+
+		// Stop at end of string.
+		i = i1
+		if i == len(s) {
+			break
+		}
+
+		// Otherwise must be followed by colon and more.
+		if s[i] != ':' || i+1 == len(s) {
+			return nil, zone
+		}
+		i++
+
+		// Look for ellipsis.
+		if s[i] == ':' {
+			if ellipsis >= 0 { // already have one
+				return nil, zone
+			}
+			ellipsis = j
+			if i++; i == len(s) { // can be at end
+				break
+			}
+		}
+	}
+
+	// Must have used entire string.
+	if i != len(s) {
+		return nil, zone
+	}
+
+	// If didn't parse enough, expand ellipsis.
+	if j < IPv6len {
+		if ellipsis < 0 {
+			return nil, zone
+		}
+		n := IPv6len - j
+		for k := j - 1; k >= ellipsis; k-- {
+			ip[k+n] = ip[k]
+		}
+		for k := ellipsis + n - 1; k >= ellipsis; k-- {
+			ip[k] = 0
+		}
+	} else if ellipsis >= 0 {
+		// Ellipsis must represent at least one 0 group.
+		return nil, zone
+	}
+	return ip, zone
+}
+
+// A ParseError represents a malformed text string and the type of string that was expected.
+type ParseError struct {
+	Type string
+	Text string
+}
+
+func (e *ParseError) Error() string {
+	return "invalid " + e.Type + ": " + e.Text
+}
+
+// ParseIP parses s as an IP address, returning the result.
+// The string s can be in dotted decimal ("74.125.19.99")
+// or IPv6 ("2001:4860:0:2001::68") form.
+// If s is not a valid textual representation of an IP address,
+// ParseIP returns nil.
+func ParseIP(s string) IP {
+	for i := 0; i < len(s); i++ {
+		switch s[i] {
+		case '.':
+			return parseIPv4(s)
+		case ':':
+			ip, _ := parseIPv6(s, false)
+			return ip
+		}
+	}
+	return nil
+}
+
+// ParseCIDR parses s as a CIDR notation IP address and mask,
+// like "192.168.100.1/24" or "2001:DB8::/48", as defined in
+// RFC 4632 and RFC 4291.
+//
+// It returns the IP address and the network implied by the IP
+// and mask.  For example, ParseCIDR("192.168.100.1/16") returns
+// the IP address 192.168.100.1 and the network 192.168.0.0/16.
+func ParseCIDR(s string) (IP, *IPNet, error) {
+	i := byteIndex(s, '/')
+	if i < 0 {
+		return nil, nil, &ParseError{"CIDR address", s}
+	}
+	addr, mask := s[:i], s[i+1:]
+	iplen := IPv4len
+	ip := parseIPv4(addr)
+	if ip == nil {
+		iplen = IPv6len
+		ip, _ = parseIPv6(addr, false)
+	}
+	n, i, ok := dtoi(mask, 0)
+	if ip == nil || !ok || i != len(mask) || n < 0 || n > 8*iplen {
+		return nil, nil, &ParseError{"CIDR address", s}
+	}
+	m := CIDRMask(n, 8*iplen)
+	return ip, &IPNet{IP: ip.Mask(m), Mask: m}, nil
+}
diff --git a/src/net/ip_test.go b/src/net/ip_test.go
new file mode 100644
index 000000000..485ff5115
--- /dev/null
+++ b/src/net/ip_test.go
@@ -0,0 +1,465 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package net
+
+import (
+	"reflect"
+	"runtime"
+	"testing"
+)
+
+var parseIPTests = []struct {
+	in  string
+	out IP
+}{
+	{"127.0.1.2", IPv4(127, 0, 1, 2)},
+	{"127.0.0.1", IPv4(127, 0, 0, 1)},
+	{"127.0.0.256", nil},
+	{"abc", nil},
+	{"123:", nil},
+	{"::ffff:127.0.0.1", IPv4(127, 0, 0, 1)},
+	{"2001:4860:0:2001::68", IP{0x20, 0x01, 0x48, 0x60, 0, 0, 0x20, 0x01, 0, 0, 0, 0, 0, 0, 0x00, 0x68}},
+	{"::ffff:4a7d:1363", IPv4(74, 125, 19, 99)},
+	{"fe80::1%lo0", nil},
+	{"fe80::1%911", nil},
+	{"", nil},
+	{"a1:a2:a3:a4::b1:b2:b3:b4", nil}, // Issue 6628
+}
+
+func TestParseIP(t *testing.T) {
+	for _, tt := range parseIPTests {
+		if out := ParseIP(tt.in); !reflect.DeepEqual(out, tt.out) {
+			t.Errorf("ParseIP(%q) = %v, want %v", tt.in, out, tt.out)
+		}
+		if tt.in == "" {
+			// Tested in TestMarshalEmptyIP below.
+			continue
+		}
+		var out IP
+		if err := out.UnmarshalText([]byte(tt.in)); !reflect.DeepEqual(out, tt.out) || (tt.out == nil) != (err != nil) {
+			t.Errorf("IP.UnmarshalText(%q) = %v, %v, want %v", tt.in, out, err, tt.out)
+		}
+	}
+}
+
+func BenchmarkParseIP(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		for _, tt := range parseIPTests {
+			ParseIP(tt.in)
+		}
+	}
+}
+
+// Issue 6339
+func TestMarshalEmptyIP(t *testing.T) {
+	for _, in := range [][]byte{nil, []byte("")} {
+		var out = IP{1, 2, 3, 4}
+		if err := out.UnmarshalText(in); err != nil || out != nil {
+			t.Errorf("UnmarshalText(%v) = %v, %v; want nil, nil", in, out, err)
+		}
+	}
+	var ip IP
+	got, err := ip.MarshalText()
+	if err != nil {
+		t.Fatal(err)
+	}
+	if !reflect.DeepEqual(got, []byte("")) {
+		t.Errorf(`got %#v, want []byte("")`, got)
+	}
+}
+
+var ipStringTests = []struct {
+	in  IP
+	out string // see RFC 5952
+}{
+	{IP{0x20, 0x1, 0xd, 0xb8, 0, 0, 0, 0, 0, 0, 0x1, 0x23, 0, 0x12, 0, 0x1}, "2001:db8::123:12:1"},
+	{IP{0x20, 0x1, 0xd, 0xb8, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0x1}, "2001:db8::1"},
+	{IP{0x20, 0x1, 0xd, 0xb8, 0, 0, 0, 0x1, 0, 0, 0, 0x1, 0, 0, 0, 0x1}, "2001:db8:0:1:0:1:0:1"},
+	{IP{0x20, 0x1, 0xd, 0xb8, 0, 0x1, 0, 0, 0, 0x1, 0, 0, 0, 0x1, 0, 0}, "2001:db8:1:0:1:0:1:0"},
+	{IP{0x20, 0x1, 0, 0, 0, 0, 0, 0, 0, 0x1, 0, 0, 0, 0, 0, 0x1}, "2001::1:0:0:1"},
+	{IP{0x20, 0x1, 0xd, 0xb8, 0, 0, 0, 0, 0, 0x1, 0, 0, 0, 0, 0, 0}, "2001:db8:0:0:1::"},
+	{IP{0x20, 0x1, 0xd, 0xb8, 0, 0, 0, 0, 0, 0x1, 0, 0, 0, 0, 0, 0x1}, "2001:db8::1:0:0:1"},
+	{IP{0x20, 0x1, 0xD, 0xB8, 0, 0, 0, 0, 0, 0xA, 0, 0xB, 0, 0xC, 0, 0xD}, "2001:db8::a:b:c:d"},
+	{IPv4(192, 168, 0, 1), "192.168.0.1"},
+	{nil, ""},
+}
+
+func TestIPString(t *testing.T) {
+	for _, tt := range ipStringTests {
+		if tt.in != nil {
+			if out := tt.in.String(); out != tt.out {
+				t.Errorf("IP.String(%v) = %q, want %q", tt.in, out, tt.out)
+			}
+		}
+		if out, err := tt.in.MarshalText(); string(out) != tt.out || err != nil {
+			t.Errorf("IP.MarshalText(%v) = %q, %v, want %q, nil", tt.in, out, err, tt.out)
+		}
+	}
+}
+
+func BenchmarkIPString(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		for _, tt := range ipStringTests {
+			if tt.in != nil {
+				tt.in.String()
+			}
+		}
+	}
+}
+
+var ipMaskTests = []struct {
+	in   IP
+	mask IPMask
+	out  IP
+}{
+	{IPv4(192, 168, 1, 127), IPv4Mask(255, 255, 255, 128), IPv4(192, 168, 1, 0)},
+	{IPv4(192, 168, 1, 127), IPMask(ParseIP("255.255.255.192")), IPv4(192, 168, 1, 64)},
+	{IPv4(192, 168, 1, 127), IPMask(ParseIP("ffff:ffff:ffff:ffff:ffff:ffff:ffff:ffe0")), IPv4(192, 168, 1, 96)},
+	{IPv4(192, 168, 1, 127), IPv4Mask(255, 0, 255, 0), IPv4(192, 0, 1, 0)},
+	{ParseIP("2001:db8::1"), IPMask(ParseIP("ffff:ff80::")), ParseIP("2001:d80::")},
+	{ParseIP("2001:db8::1"), IPMask(ParseIP("f0f0:0f0f::")), ParseIP("2000:d08::")},
+}
+
+func TestIPMask(t *testing.T) {
+	for _, tt := range ipMaskTests {
+		if out := tt.in.Mask(tt.mask); out == nil || !tt.out.Equal(out) {
+			t.Errorf("IP(%v).Mask(%v) = %v, want %v", tt.in, tt.mask, out, tt.out)
+		}
+	}
+}
+
+var ipMaskStringTests = []struct {
+	in  IPMask
+	out string
+}{
+	{IPv4Mask(255, 255, 255, 240), "fffffff0"},
+	{IPv4Mask(255, 0, 128, 0), "ff008000"},
+	{IPMask(ParseIP("ffff:ff80::")), "ffffff80000000000000000000000000"},
+	{IPMask(ParseIP("ef00:ff80::cafe:0")), "ef00ff800000000000000000cafe0000"},
+	{nil, "<nil>"},
+}
+
+func TestIPMaskString(t *testing.T) {
+	for _, tt := range ipMaskStringTests {
+		if out := tt.in.String(); out != tt.out {
+			t.Errorf("IPMask.String(%v) = %q, want %q", tt.in, out, tt.out)
+		}
+	}
+}
+
+func BenchmarkIPMaskString(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		for _, tt := range ipMaskStringTests {
+			tt.in.String()
+		}
+	}
+}
+
+var parseCIDRTests = []struct {
+	in  string
+	ip  IP
+	net *IPNet
+	err error
+}{
+	{"135.104.0.0/32", IPv4(135, 104, 0, 0), &IPNet{IP: IPv4(135, 104, 0, 0), Mask: IPv4Mask(255, 255, 255, 255)}, nil},
+	{"0.0.0.0/24", IPv4(0, 0, 0, 0), &IPNet{IP: IPv4(0, 0, 0, 0), Mask: IPv4Mask(255, 255, 255, 0)}, nil},
+	{"135.104.0.0/24", IPv4(135, 104, 0, 0), &IPNet{IP: IPv4(135, 104, 0, 0), Mask: IPv4Mask(255, 255, 255, 0)}, nil},
+	{"135.104.0.1/32", IPv4(135, 104, 0, 1), &IPNet{IP: IPv4(135, 104, 0, 1), Mask: IPv4Mask(255, 255, 255, 255)}, nil},
+	{"135.104.0.1/24", IPv4(135, 104, 0, 1), &IPNet{IP: IPv4(135, 104, 0, 0), Mask: IPv4Mask(255, 255, 255, 0)}, nil},
+	{"::1/128", ParseIP("::1"), &IPNet{IP: ParseIP("::1"), Mask: IPMask(ParseIP("ffff:ffff:ffff:ffff:ffff:ffff:ffff:ffff"))}, nil},
+	{"abcd:2345::/127", ParseIP("abcd:2345::"), &IPNet{IP: ParseIP("abcd:2345::"), Mask: IPMask(ParseIP("ffff:ffff:ffff:ffff:ffff:ffff:ffff:fffe"))}, nil},
+	{"abcd:2345::/65", ParseIP("abcd:2345::"), &IPNet{IP: ParseIP("abcd:2345::"), Mask: IPMask(ParseIP("ffff:ffff:ffff:ffff:8000::"))}, nil},
+	{"abcd:2345::/64", ParseIP("abcd:2345::"), &IPNet{IP: ParseIP("abcd:2345::"), Mask: IPMask(ParseIP("ffff:ffff:ffff:ffff::"))}, nil},
+	{"abcd:2345::/63", ParseIP("abcd:2345::"), &IPNet{IP: ParseIP("abcd:2345::"), Mask: IPMask(ParseIP("ffff:ffff:ffff:fffe::"))}, nil},
+	{"abcd:2345::/33", ParseIP("abcd:2345::"), &IPNet{IP: ParseIP("abcd:2345::"), Mask: IPMask(ParseIP("ffff:ffff:8000::"))}, nil},
+	{"abcd:2345::/32", ParseIP("abcd:2345::"), &IPNet{IP: ParseIP("abcd:2345::"), Mask: IPMask(ParseIP("ffff:ffff::"))}, nil},
+	{"abcd:2344::/31", ParseIP("abcd:2344::"), &IPNet{IP: ParseIP("abcd:2344::"), Mask: IPMask(ParseIP("ffff:fffe::"))}, nil},
+	{"abcd:2300::/24", ParseIP("abcd:2300::"), &IPNet{IP: ParseIP("abcd:2300::"), Mask: IPMask(ParseIP("ffff:ff00::"))}, nil},
+	{"abcd:2345::/24", ParseIP("abcd:2345::"), &IPNet{IP: ParseIP("abcd:2300::"), Mask: IPMask(ParseIP("ffff:ff00::"))}, nil},
+	{"2001:DB8::/48", ParseIP("2001:DB8::"), &IPNet{IP: ParseIP("2001:DB8::"), Mask: IPMask(ParseIP("ffff:ffff:ffff::"))}, nil},
+	{"2001:DB8::1/48", ParseIP("2001:DB8::1"), &IPNet{IP: ParseIP("2001:DB8::"), Mask: IPMask(ParseIP("ffff:ffff:ffff::"))}, nil},
+	{"192.168.1.1/255.255.255.0", nil, nil, &ParseError{"CIDR address", "192.168.1.1/255.255.255.0"}},
+	{"192.168.1.1/35", nil, nil, &ParseError{"CIDR address", "192.168.1.1/35"}},
+	{"2001:db8::1/-1", nil, nil, &ParseError{"CIDR address", "2001:db8::1/-1"}},
+	{"", nil, nil, &ParseError{"CIDR address", ""}},
+}
+
+func TestParseCIDR(t *testing.T) {
+	for _, tt := range parseCIDRTests {
+		ip, net, err := ParseCIDR(tt.in)
+		if !reflect.DeepEqual(err, tt.err) {
+			t.Errorf("ParseCIDR(%q) = %v, %v; want %v, %v", tt.in, ip, net, tt.ip, tt.net)
+		}
+		if err == nil && (!tt.ip.Equal(ip) || !tt.net.IP.Equal(net.IP) || !reflect.DeepEqual(net.Mask, tt.net.Mask)) {
+			t.Errorf("ParseCIDR(%q) = %v, {%v, %v}; want %v, {%v, %v}", tt.in, ip, net.IP, net.Mask, tt.ip, tt.net.IP, tt.net.Mask)
+		}
+	}
+}
+
+var ipNetContainsTests = []struct {
+	ip  IP
+	net *IPNet
+	ok  bool
+}{
+	{IPv4(172, 16, 1, 1), &IPNet{IP: IPv4(172, 16, 0, 0), Mask: CIDRMask(12, 32)}, true},
+	{IPv4(172, 24, 0, 1), &IPNet{IP: IPv4(172, 16, 0, 0), Mask: CIDRMask(13, 32)}, false},
+	{IPv4(192, 168, 0, 3), &IPNet{IP: IPv4(192, 168, 0, 0), Mask: IPv4Mask(0, 0, 255, 252)}, true},
+	{IPv4(192, 168, 0, 4), &IPNet{IP: IPv4(192, 168, 0, 0), Mask: IPv4Mask(0, 255, 0, 252)}, false},
+	{ParseIP("2001:db8:1:2::1"), &IPNet{IP: ParseIP("2001:db8:1::"), Mask: CIDRMask(47, 128)}, true},
+	{ParseIP("2001:db8:1:2::1"), &IPNet{IP: ParseIP("2001:db8:2::"), Mask: CIDRMask(47, 128)}, false},
+	{ParseIP("2001:db8:1:2::1"), &IPNet{IP: ParseIP("2001:db8:1::"), Mask: IPMask(ParseIP("ffff:0:ffff::"))}, true},
+	{ParseIP("2001:db8:1:2::1"), &IPNet{IP: ParseIP("2001:db8:1::"), Mask: IPMask(ParseIP("0:0:0:ffff::"))}, false},
+}
+
+func TestIPNetContains(t *testing.T) {
+	for _, tt := range ipNetContainsTests {
+		if ok := tt.net.Contains(tt.ip); ok != tt.ok {
+			t.Errorf("IPNet(%v).Contains(%v) = %v, want %v", tt.net, tt.ip, ok, tt.ok)
+		}
+	}
+}
+
+var ipNetStringTests = []struct {
+	in  *IPNet
+	out string
+}{
+	{&IPNet{IP: IPv4(192, 168, 1, 0), Mask: CIDRMask(26, 32)}, "192.168.1.0/26"},
+	{&IPNet{IP: IPv4(192, 168, 1, 0), Mask: IPv4Mask(255, 0, 255, 0)}, "192.168.1.0/ff00ff00"},
+	{&IPNet{IP: ParseIP("2001:db8::"), Mask: CIDRMask(55, 128)}, "2001:db8::/55"},
+	{&IPNet{IP: ParseIP("2001:db8::"), Mask: IPMask(ParseIP("8000:f123:0:cafe::"))}, "2001:db8::/8000f1230000cafe0000000000000000"},
+}
+
+func TestIPNetString(t *testing.T) {
+	for _, tt := range ipNetStringTests {
+		if out := tt.in.String(); out != tt.out {
+			t.Errorf("IPNet.String(%v) = %q, want %q", tt.in, out, tt.out)
+		}
+	}
+}
+
+var cidrMaskTests = []struct {
+	ones int
+	bits int
+	out  IPMask
+}{
+	{0, 32, IPv4Mask(0, 0, 0, 0)},
+	{12, 32, IPv4Mask(255, 240, 0, 0)},
+	{24, 32, IPv4Mask(255, 255, 255, 0)},
+	{32, 32, IPv4Mask(255, 255, 255, 255)},
+	{0, 128, IPMask{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}},
+	{4, 128, IPMask{0xf0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}},
+	{48, 128, IPMask{0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}},
+	{128, 128, IPMask{0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff}},
+	{33, 32, nil},
+	{32, 33, nil},
+	{-1, 128, nil},
+	{128, -1, nil},
+}
+
+func TestCIDRMask(t *testing.T) {
+	for _, tt := range cidrMaskTests {
+		if out := CIDRMask(tt.ones, tt.bits); !reflect.DeepEqual(out, tt.out) {
+			t.Errorf("CIDRMask(%v, %v) = %v, want %v", tt.ones, tt.bits, out, tt.out)
+		}
+	}
+}
+
+var (
+	v4addr         = IP{192, 168, 0, 1}
+	v4mappedv6addr = IP{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0xff, 0xff, 192, 168, 0, 1}
+	v6addr         = IP{0x20, 0x1, 0xd, 0xb8, 0, 0, 0, 0, 0, 0, 0x1, 0x23, 0, 0x12, 0, 0x1}
+	v4mask         = IPMask{255, 255, 255, 0}
+	v4mappedv6mask = IPMask{0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 255, 255, 255, 0}
+	v6mask         = IPMask{0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0, 0, 0, 0, 0, 0, 0, 0}
+	badaddr        = IP{192, 168, 0}
+	badmask        = IPMask{255, 255, 0}
+	v4maskzero     = IPMask{0, 0, 0, 0}
+)
+
+var networkNumberAndMaskTests = []struct {
+	in  IPNet
+	out IPNet
+}{
+	{IPNet{IP: v4addr, Mask: v4mask}, IPNet{IP: v4addr, Mask: v4mask}},
+	{IPNet{IP: v4addr, Mask: v4mappedv6mask}, IPNet{IP: v4addr, Mask: v4mask}},
+	{IPNet{IP: v4mappedv6addr, Mask: v4mappedv6mask}, IPNet{IP: v4addr, Mask: v4mask}},
+	{IPNet{IP: v4mappedv6addr, Mask: v6mask}, IPNet{IP: v4addr, Mask: v4maskzero}},
+	{IPNet{IP: v4addr, Mask: v6mask}, IPNet{IP: v4addr, Mask: v4maskzero}},
+	{IPNet{IP: v6addr, Mask: v6mask}, IPNet{IP: v6addr, Mask: v6mask}},
+	{IPNet{IP: v6addr, Mask: v4mappedv6mask}, IPNet{IP: v6addr, Mask: v4mappedv6mask}},
+	{in: IPNet{IP: v6addr, Mask: v4mask}},
+	{in: IPNet{IP: v4addr, Mask: badmask}},
+	{in: IPNet{IP: v4mappedv6addr, Mask: badmask}},
+	{in: IPNet{IP: v6addr, Mask: badmask}},
+	{in: IPNet{IP: badaddr, Mask: v4mask}},
+	{in: IPNet{IP: badaddr, Mask: v4mappedv6mask}},
+	{in: IPNet{IP: badaddr, Mask: v6mask}},
+	{in: IPNet{IP: badaddr, Mask: badmask}},
+}
+
+func TestNetworkNumberAndMask(t *testing.T) {
+	for _, tt := range networkNumberAndMaskTests {
+		ip, m := networkNumberAndMask(&tt.in)
+		out := &IPNet{IP: ip, Mask: m}
+		if !reflect.DeepEqual(&tt.out, out) {
+			t.Errorf("networkNumberAndMask(%v) = %v, want %v", tt.in, out, &tt.out)
+		}
+	}
+}
+
+var splitJoinTests = []struct {
+	host string
+	port string
+	join string
+}{
+	{"www.google.com", "80", "www.google.com:80"},
+	{"127.0.0.1", "1234", "127.0.0.1:1234"},
+	{"::1", "80", "[::1]:80"},
+	{"fe80::1%lo0", "80", "[fe80::1%lo0]:80"},
+	{"localhost%lo0", "80", "[localhost%lo0]:80"},
+	{"", "0", ":0"},
+
+	{"google.com", "https%foo", "google.com:https%foo"}, // Go 1.0 behavior
+	{"127.0.0.1", "", "127.0.0.1:"},                     // Go 1.0 behaviour
+	{"www.google.com", "", "www.google.com:"},           // Go 1.0 behaviour
+}
+
+var splitFailureTests = []struct {
+	hostPort string
+	err      string
+}{
+	{"www.google.com", "missing port in address"},
+	{"127.0.0.1", "missing port in address"},
+	{"[::1]", "missing port in address"},
+	{"[fe80::1%lo0]", "missing port in address"},
+	{"[localhost%lo0]", "missing port in address"},
+	{"localhost%lo0", "missing port in address"},
+
+	{"::1", "too many colons in address"},
+	{"fe80::1%lo0", "too many colons in address"},
+	{"fe80::1%lo0:80", "too many colons in address"},
+
+	{"localhost%lo0:80", "missing brackets in address"},
+
+	// Test cases that didn't fail in Go 1.0
+
+	{"[foo:bar]", "missing port in address"},
+	{"[foo:bar]baz", "missing port in address"},
+	{"[foo]bar:baz", "missing port in address"},
+
+	{"[foo]:[bar]:baz", "too many colons in address"},
+
+	{"[foo]:[bar]baz", "unexpected '[' in address"},
+	{"foo[bar]:baz", "unexpected '[' in address"},
+
+	{"foo]bar:baz", "unexpected ']' in address"},
+}
+
+func TestSplitHostPort(t *testing.T) {
+	for _, tt := range splitJoinTests {
+		if host, port, err := SplitHostPort(tt.join); host != tt.host || port != tt.port || err != nil {
+			t.Errorf("SplitHostPort(%q) = %q, %q, %v; want %q, %q, nil", tt.join, host, port, err, tt.host, tt.port)
+		}
+	}
+	for _, tt := range splitFailureTests {
+		if _, _, err := SplitHostPort(tt.hostPort); err == nil {
+			t.Errorf("SplitHostPort(%q) should have failed", tt.hostPort)
+		} else {
+			e := err.(*AddrError)
+			if e.Err != tt.err {
+				t.Errorf("SplitHostPort(%q) = _, _, %q; want %q", tt.hostPort, e.Err, tt.err)
+			}
+		}
+	}
+}
+
+func TestJoinHostPort(t *testing.T) {
+	for _, tt := range splitJoinTests {
+		if join := JoinHostPort(tt.host, tt.port); join != tt.join {
+			t.Errorf("JoinHostPort(%q, %q) = %q; want %q", tt.host, tt.port, join, tt.join)
+		}
+	}
+}
+
+var ipAddrFamilyTests = []struct {
+	in  IP
+	af4 bool
+	af6 bool
+}{
+	{IPv4bcast, true, false},
+	{IPv4allsys, true, false},
+	{IPv4allrouter, true, false},
+	{IPv4zero, true, false},
+	{IPv4(224, 0, 0, 1), true, false},
+	{IPv4(127, 0, 0, 1), true, false},
+	{IPv4(240, 0, 0, 1), true, false},
+	{IPv6unspecified, false, true},
+	{IPv6loopback, false, true},
+	{IPv6interfacelocalallnodes, false, true},
+	{IPv6linklocalallnodes, false, true},
+	{IPv6linklocalallrouters, false, true},
+	{ParseIP("ff05::a:b:c:d"), false, true},
+	{ParseIP("fe80::1:2:3:4"), false, true},
+	{ParseIP("2001:db8::123:12:1"), false, true},
+}
+
+func TestIPAddrFamily(t *testing.T) {
+	for _, tt := range ipAddrFamilyTests {
+		if af := tt.in.To4() != nil; af != tt.af4 {
+			t.Errorf("verifying IPv4 address family for %q = %v, want %v", tt.in, af, tt.af4)
+		}
+		if af := len(tt.in) == IPv6len && tt.in.To4() == nil; af != tt.af6 {
+			t.Errorf("verifying IPv6 address family for %q = %v, want %v", tt.in, af, tt.af6)
+		}
+	}
+}
+
+var ipAddrScopeTests = []struct {
+	scope func(IP) bool
+	in    IP
+	ok    bool
+}{
+	{IP.IsUnspecified, IPv4zero, true},
+	{IP.IsUnspecified, IPv4(127, 0, 0, 1), false},
+	{IP.IsUnspecified, IPv6unspecified, true},
+	{IP.IsUnspecified, IPv6interfacelocalallnodes, false},
+	{IP.IsLoopback, IPv4(127, 0, 0, 1), true},
+	{IP.IsLoopback, IPv4(127, 255, 255, 254), true},
+	{IP.IsLoopback, IPv4(128, 1, 2, 3), false},
+	{IP.IsLoopback, IPv6loopback, true},
+	{IP.IsLoopback, IPv6linklocalallrouters, false},
+	{IP.IsMulticast, IPv4(224, 0, 0, 0), true},
+	{IP.IsMulticast, IPv4(239, 0, 0, 0), true},
+	{IP.IsMulticast, IPv4(240, 0, 0, 0), false},
+	{IP.IsMulticast, IPv6linklocalallnodes, true},
+	{IP.IsMulticast, IP{0xff, 0x05, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}, true},
+	{IP.IsMulticast, IP{0xfe, 0x80, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}, false},
+	{IP.IsLinkLocalMulticast, IPv4(224, 0, 0, 0), true},
+	{IP.IsLinkLocalMulticast, IPv4(239, 0, 0, 0), false},
+	{IP.IsLinkLocalMulticast, IPv6linklocalallrouters, true},
+	{IP.IsLinkLocalMulticast, IP{0xff, 0x05, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}, false},
+	{IP.IsLinkLocalUnicast, IPv4(169, 254, 0, 0), true},
+	{IP.IsLinkLocalUnicast, IPv4(169, 255, 0, 0), false},
+	{IP.IsLinkLocalUnicast, IP{0xfe, 0x80, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}, true},
+	{IP.IsLinkLocalUnicast, IP{0xfe, 0xc0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}, false},
+	{IP.IsGlobalUnicast, IPv4(240, 0, 0, 0), true},
+	{IP.IsGlobalUnicast, IPv4(232, 0, 0, 0), false},
+	{IP.IsGlobalUnicast, IPv4(169, 254, 0, 0), false},
+	{IP.IsGlobalUnicast, IP{0x20, 0x1, 0xd, 0xb8, 0, 0, 0, 0, 0, 0, 0x1, 0x23, 0, 0x12, 0, 0x1}, true},
+	{IP.IsGlobalUnicast, IP{0xfe, 0x80, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}, false},
+	{IP.IsGlobalUnicast, IP{0xff, 0x05, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}, false},
+}
+
+func name(f interface{}) string {
+	return runtime.FuncForPC(reflect.ValueOf(f).Pointer()).Name()
+}
+
+func TestIPAddrScope(t *testing.T) {
+	for _, tt := range ipAddrScopeTests {
+		if ok := tt.scope(tt.in); ok != tt.ok {
+			t.Errorf("%s(%q) = %v, want %v", name(tt.scope), tt.in, ok, tt.ok)
+		}
+	}
+}
diff --git a/src/net/ipraw_test.go b/src/net/ipraw_test.go
new file mode 100644
index 000000000..0632dafc6
--- /dev/null
+++ b/src/net/ipraw_test.go
@@ -0,0 +1,289 @@
+// Copyright 2009 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package net
+
+import (
+	"bytes"
+	"fmt"
+	"os"
+	"reflect"
+	"runtime"
+	"testing"
+	"time"
+)
+
+type resolveIPAddrTest struct {
+	net           string
+	litAddrOrName string
+	addr          *IPAddr
+	err           error
+}
+
+var resolveIPAddrTests = []resolveIPAddrTest{
+	{"ip", "127.0.0.1", &IPAddr{IP: IPv4(127, 0, 0, 1)}, nil},
+	{"ip4", "127.0.0.1", &IPAddr{IP: IPv4(127, 0, 0, 1)}, nil},
+	{"ip4:icmp", "127.0.0.1", &IPAddr{IP: IPv4(127, 0, 0, 1)}, nil},
+
+	{"ip", "::1", &IPAddr{IP: ParseIP("::1")}, nil},
+	{"ip6", "::1", &IPAddr{IP: ParseIP("::1")}, nil},
+	{"ip6:ipv6-icmp", "::1", &IPAddr{IP: ParseIP("::1")}, nil},
+	{"ip6:IPv6-ICMP", "::1", &IPAddr{IP: ParseIP("::1")}, nil},
+
+	{"ip", "::1%en0", &IPAddr{IP: ParseIP("::1"), Zone: "en0"}, nil},
+	{"ip6", "::1%911", &IPAddr{IP: ParseIP("::1"), Zone: "911"}, nil},
+
+	{"", "127.0.0.1", &IPAddr{IP: IPv4(127, 0, 0, 1)}, nil}, // Go 1.0 behavior
+	{"", "::1", &IPAddr{IP: ParseIP("::1")}, nil},           // Go 1.0 behavior
+
+	{"l2tp", "127.0.0.1", nil, UnknownNetworkError("l2tp")},
+	{"l2tp:gre", "127.0.0.1", nil, UnknownNetworkError("l2tp:gre")},
+	{"tcp", "1.2.3.4:123", nil, UnknownNetworkError("tcp")},
+}
+
+func init() {
+	if ifi := loopbackInterface(); ifi != nil {
+		index := fmt.Sprintf("%v", ifi.Index)
+		resolveIPAddrTests = append(resolveIPAddrTests, []resolveIPAddrTest{
+			{"ip6", "fe80::1%" + ifi.Name, &IPAddr{IP: ParseIP("fe80::1"), Zone: zoneToString(ifi.Index)}, nil},
+			{"ip6", "fe80::1%" + index, &IPAddr{IP: ParseIP("fe80::1"), Zone: index}, nil},
+		}...)
+	}
+	if ips, err := LookupIP("localhost"); err == nil && len(ips) > 1 && supportsIPv4 && supportsIPv6 {
+		resolveIPAddrTests = append(resolveIPAddrTests, []resolveIPAddrTest{
+			{"ip", "localhost", &IPAddr{IP: IPv4(127, 0, 0, 1)}, nil},
+			{"ip4", "localhost", &IPAddr{IP: IPv4(127, 0, 0, 1)}, nil},
+			{"ip6", "localhost", &IPAddr{IP: IPv6loopback}, nil},
+		}...)
+	}
+}
+
+func skipRawSocketTest(t *testing.T) (skip bool, skipmsg string) {
+	skip, skipmsg, err := skipRawSocketTests()
+	if err != nil {
+		t.Fatal(err)
+	}
+	return skip, skipmsg
+}
+
+func TestResolveIPAddr(t *testing.T) {
+	for _, tt := range resolveIPAddrTests {
+		addr, err := ResolveIPAddr(tt.net, tt.litAddrOrName)
+		if err != tt.err {
+			t.Fatalf("ResolveIPAddr(%v, %v) failed: %v", tt.net, tt.litAddrOrName, err)
+		} else if !reflect.DeepEqual(addr, tt.addr) {
+			t.Fatalf("got %#v; expected %#v", addr, tt.addr)
+		}
+	}
+}
+
+var icmpEchoTests = []struct {
+	net   string
+	laddr string
+	raddr string
+}{
+	{"ip4:icmp", "0.0.0.0", "127.0.0.1"},
+	{"ip6:ipv6-icmp", "::", "::1"},
+}
+
+func TestConnICMPEcho(t *testing.T) {
+	if skip, skipmsg := skipRawSocketTest(t); skip {
+		t.Skip(skipmsg)
+	}
+
+	for i, tt := range icmpEchoTests {
+		net, _, err := parseNetwork(tt.net)
+		if err != nil {
+			t.Fatalf("parseNetwork failed: %v", err)
+		}
+		if net == "ip6" && !supportsIPv6 {
+			continue
+		}
+
+		c, err := Dial(tt.net, tt.raddr)
+		if err != nil {
+			t.Fatalf("Dial failed: %v", err)
+		}
+		c.SetDeadline(time.Now().Add(100 * time.Millisecond))
+		defer c.Close()
+
+		typ := icmpv4EchoRequest
+		if net == "ip6" {
+			typ = icmpv6EchoRequest
+		}
+		xid, xseq := os.Getpid()&0xffff, i+1
+		wb, err := (&icmpMessage{
+			Type: typ, Code: 0,
+			Body: &icmpEcho{
+				ID: xid, Seq: xseq,
+				Data: bytes.Repeat([]byte("Go Go Gadget Ping!!!"), 3),
+			},
+		}).Marshal()
+		if err != nil {
+			t.Fatalf("icmpMessage.Marshal failed: %v", err)
+		}
+		if _, err := c.Write(wb); err != nil {
+			t.Fatalf("Conn.Write failed: %v", err)
+		}
+		var m *icmpMessage
+		rb := make([]byte, 20+len(wb))
+		for {
+			if _, err := c.Read(rb); err != nil {
+				t.Fatalf("Conn.Read failed: %v", err)
+			}
+			if net == "ip4" {
+				rb = ipv4Payload(rb)
+			}
+			if m, err = parseICMPMessage(rb); err != nil {
+				t.Fatalf("parseICMPMessage failed: %v", err)
+			}
+			switch m.Type {
+			case icmpv4EchoRequest, icmpv6EchoRequest:
+				continue
+			}
+			break
+		}
+		switch p := m.Body.(type) {
+		case *icmpEcho:
+			if p.ID != xid || p.Seq != xseq {
+				t.Fatalf("got id=%v, seqnum=%v; expected id=%v, seqnum=%v", p.ID, p.Seq, xid, xseq)
+			}
+		default:
+			t.Fatalf("got type=%v, code=%v; expected type=%v, code=%v", m.Type, m.Code, typ, 0)
+		}
+	}
+}
+
+func TestPacketConnICMPEcho(t *testing.T) {
+	if skip, skipmsg := skipRawSocketTest(t); skip {
+		t.Skip(skipmsg)
+	}
+
+	for i, tt := range icmpEchoTests {
+		net, _, err := parseNetwork(tt.net)
+		if err != nil {
+			t.Fatalf("parseNetwork failed: %v", err)
+		}
+		if net == "ip6" && !supportsIPv6 {
+			continue
+		}
+
+		c, err := ListenPacket(tt.net, tt.laddr)
+		if err != nil {
+			t.Fatalf("ListenPacket failed: %v", err)
+		}
+		c.SetDeadline(time.Now().Add(100 * time.Millisecond))
+		defer c.Close()
+
+		ra, err := ResolveIPAddr(tt.net, tt.raddr)
+		if err != nil {
+			t.Fatalf("ResolveIPAddr failed: %v", err)
+		}
+		typ := icmpv4EchoRequest
+		if net == "ip6" {
+			typ = icmpv6EchoRequest
+		}
+		xid, xseq := os.Getpid()&0xffff, i+1
+		wb, err := (&icmpMessage{
+			Type: typ, Code: 0,
+			Body: &icmpEcho{
+				ID: xid, Seq: xseq,
+				Data: bytes.Repeat([]byte("Go Go Gadget Ping!!!"), 3),
+			},
+		}).Marshal()
+		if err != nil {
+			t.Fatalf("icmpMessage.Marshal failed: %v", err)
+		}
+		if _, err := c.WriteTo(wb, ra); err != nil {
+			t.Fatalf("PacketConn.WriteTo failed: %v", err)
+		}
+		var m *icmpMessage
+		rb := make([]byte, 20+len(wb))
+		for {
+			if _, _, err := c.ReadFrom(rb); err != nil {
+				t.Fatalf("PacketConn.ReadFrom failed: %v", err)
+			}
+			// See BUG section.
+			//if net == "ip4" {
+			//	rb = ipv4Payload(rb)
+			//}
+			if m, err = parseICMPMessage(rb); err != nil {
+				t.Fatalf("parseICMPMessage failed: %v", err)
+			}
+			switch m.Type {
+			case icmpv4EchoRequest, icmpv6EchoRequest:
+				continue
+			}
+			break
+		}
+		switch p := m.Body.(type) {
+		case *icmpEcho:
+			if p.ID != xid || p.Seq != xseq {
+				t.Fatalf("got id=%v, seqnum=%v; expected id=%v, seqnum=%v", p.ID, p.Seq, xid, xseq)
+			}
+		default:
+			t.Fatalf("got type=%v, code=%v; expected type=%v, code=%v", m.Type, m.Code, typ, 0)
+		}
+	}
+}
+
+func ipv4Payload(b []byte) []byte {
+	if len(b) < 20 {
+		return b
+	}
+	hdrlen := int(b[0]&0x0f) << 2
+	return b[hdrlen:]
+}
+
+var ipConnLocalNameTests = []struct {
+	net   string
+	laddr *IPAddr
+}{
+	{"ip4:icmp", &IPAddr{IP: IPv4(127, 0, 0, 1)}},
+	{"ip4:icmp", &IPAddr{}},
+	{"ip4:icmp", nil},
+}
+
+func TestIPConnLocalName(t *testing.T) {
+	switch runtime.GOOS {
+	case "nacl", "plan9", "windows":
+		t.Skipf("skipping test on %q", runtime.GOOS)
+	default:
+		if os.Getuid() != 0 {
+			t.Skip("skipping test; must be root")
+		}
+	}
+
+	for _, tt := range ipConnLocalNameTests {
+		c, err := ListenIP(tt.net, tt.laddr)
+		if err != nil {
+			t.Fatalf("ListenIP failed: %v", err)
+		}
+		defer c.Close()
+		if la := c.LocalAddr(); la == nil {
+			t.Fatal("IPConn.LocalAddr failed")
+		}
+	}
+}
+
+func TestIPConnRemoteName(t *testing.T) {
+	switch runtime.GOOS {
+	case "plan9", "windows":
+		t.Skipf("skipping test on %q", runtime.GOOS)
+	default:
+		if os.Getuid() != 0 {
+			t.Skip("skipping test; must be root")
+		}
+	}
+
+	raddr := &IPAddr{IP: IPv4(127, 0, 0, 1).To4()}
+	c, err := DialIP("ip:tcp", &IPAddr{IP: IPv4(127, 0, 0, 1)}, raddr)
+	if err != nil {
+		t.Fatalf("DialIP failed: %v", err)
+	}
+	defer c.Close()
+	if !reflect.DeepEqual(raddr, c.RemoteAddr()) {
+		t.Fatalf("got %#v, expected %#v", c.RemoteAddr(), raddr)
+	}
+}
diff --git a/src/net/iprawsock.go b/src/net/iprawsock.go
new file mode 100644
index 000000000..5cc361390
--- /dev/null
+++ b/src/net/iprawsock.go
@@ -0,0 +1,54 @@
+// Copyright 2010 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package net
+
+// IPAddr represents the address of an IP end point.
+type IPAddr struct {
+	IP   IP
+	Zone string // IPv6 scoped addressing zone
+}
+
+// Network returns the address's network name, "ip".
+func (a *IPAddr) Network() string { return "ip" }
+
+func (a *IPAddr) String() string {
+	if a == nil {
+		return "<nil>"
+	}
+	if a.Zone != "" {
+		return a.IP.String() + "%" + a.Zone
+	}
+	return a.IP.String()
+}
+
+func (a *IPAddr) toAddr() Addr {
+	if a == nil {
+		return nil
+	}
+	return a
+}
+
+// ResolveIPAddr parses addr as an IP address of the form "host" or
+// "ipv6-host%zone" and resolves the domain name on the network net,
+// which must be "ip", "ip4" or "ip6".
+func ResolveIPAddr(net, addr string) (*IPAddr, error) {
+	if net == "" { // a hint wildcard for Go 1.0 undocumented behavior
+		net = "ip"
+	}
+	afnet, _, err := parseNetwork(net)
+	if err != nil {
+		return nil, err
+	}
+	switch afnet {
+	case "ip", "ip4", "ip6":
+	default:
+		return nil, UnknownNetworkError(net)
+	}
+	a, err := resolveInternetAddr(afnet, addr, noDeadline)
+	if err != nil {
+		return nil, err
+	}
+	return a.toAddr().(*IPAddr), nil
+}
diff --git a/src/net/iprawsock_plan9.go b/src/net/iprawsock_plan9.go
new file mode 100644
index 000000000..e62d116b8
--- /dev/null
+++ b/src/net/iprawsock_plan9.go
@@ -0,0 +1,82 @@
+// Copyright 2010 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package net
+
+import (
+	"syscall"
+	"time"
+)
+
+// IPConn is the implementation of the Conn and PacketConn interfaces
+// for IP network connections.
+type IPConn struct {
+	conn
+}
+
+// ReadFromIP reads an IP packet from c, copying the payload into b.
+// It returns the number of bytes copied into b and the return address
+// that was on the packet.
+//
+// ReadFromIP can be made to time out and return an error with
+// Timeout() == true after a fixed time limit; see SetDeadline and
+// SetReadDeadline.
+func (c *IPConn) ReadFromIP(b []byte) (int, *IPAddr, error) {
+	return 0, nil, syscall.EPLAN9
+}
+
+// ReadFrom implements the PacketConn ReadFrom method.
+func (c *IPConn) ReadFrom(b []byte) (int, Addr, error) {
+	return 0, nil, syscall.EPLAN9
+}
+
+// ReadMsgIP reads a packet from c, copying the payload into b and the
+// associated out-of-band data into oob.  It returns the number of
+// bytes copied into b, the number of bytes copied into oob, the flags
+// that were set on the packet and the source address of the packet.
+func (c *IPConn) ReadMsgIP(b, oob []byte) (n, oobn, flags int, addr *IPAddr, err error) {
+	return 0, 0, 0, nil, syscall.EPLAN9
+}
+
+// WriteToIP writes an IP packet to addr via c, copying the payload
+// from b.
+//
+// WriteToIP can be made to time out and return an error with
+// Timeout() == true after a fixed time limit; see SetDeadline and
+// SetWriteDeadline.  On packet-oriented connections, write timeouts
+// are rare.
+func (c *IPConn) WriteToIP(b []byte, addr *IPAddr) (int, error) {
+	return 0, syscall.EPLAN9
+}
+
+// WriteTo implements the PacketConn WriteTo method.
+func (c *IPConn) WriteTo(b []byte, addr Addr) (int, error) {
+	return 0, syscall.EPLAN9
+}
+
+// WriteMsgIP writes a packet to addr via c, copying the payload from
+// b and the associated out-of-band data from oob.  It returns the
+// number of payload and out-of-band bytes written.
+func (c *IPConn) WriteMsgIP(b, oob []byte, addr *IPAddr) (n, oobn int, err error) {
+	return 0, 0, syscall.EPLAN9
+}
+
+// DialIP connects to the remote address raddr on the network protocol
+// netProto, which must be "ip", "ip4", or "ip6" followed by a colon
+// and a protocol number or name.
+func DialIP(netProto string, laddr, raddr *IPAddr) (*IPConn, error) {
+	return dialIP(netProto, laddr, raddr, noDeadline)
+}
+
+func dialIP(netProto string, laddr, raddr *IPAddr, deadline time.Time) (*IPConn, error) {
+	return nil, syscall.EPLAN9
+}
+
+// ListenIP listens for incoming IP packets addressed to the local
+// address laddr.  The returned connection's ReadFrom and WriteTo
+// methods can be used to receive and send IP packets with per-packet
+// addressing.
+func ListenIP(netProto string, laddr *IPAddr) (*IPConn, error) {
+	return nil, syscall.EPLAN9
+}
diff --git a/src/net/iprawsock_posix.go b/src/net/iprawsock_posix.go
new file mode 100644
index 000000000..99b081ba8
--- /dev/null
+++ b/src/net/iprawsock_posix.go
@@ -0,0 +1,227 @@
+// Copyright 2010 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build darwin dragonfly freebsd linux nacl netbsd openbsd solaris windows
+
+package net
+
+import (
+	"syscall"
+	"time"
+)
+
+// BUG(mikio): On every POSIX platform, reads from the "ip4" network
+// using the ReadFrom or ReadFromIP method might not return a complete
+// IPv4 packet, including its header, even if there is space
+// available. This can occur even in cases where Read or ReadMsgIP
+// could return a complete packet. For this reason, it is recommended
+// that you do not uses these methods if it is important to receive a
+// full packet.
+//
+// The Go 1 compatibility guidelines make it impossible for us to
+// change the behavior of these methods; use Read or ReadMsgIP
+// instead.
+
+func sockaddrToIP(sa syscall.Sockaddr) Addr {
+	switch sa := sa.(type) {
+	case *syscall.SockaddrInet4:
+		return &IPAddr{IP: sa.Addr[0:]}
+	case *syscall.SockaddrInet6:
+		return &IPAddr{IP: sa.Addr[0:], Zone: zoneToString(int(sa.ZoneId))}
+	}
+	return nil
+}
+
+func (a *IPAddr) family() int {
+	if a == nil || len(a.IP) <= IPv4len {
+		return syscall.AF_INET
+	}
+	if a.IP.To4() != nil {
+		return syscall.AF_INET
+	}
+	return syscall.AF_INET6
+}
+
+func (a *IPAddr) isWildcard() bool {
+	if a == nil || a.IP == nil {
+		return true
+	}
+	return a.IP.IsUnspecified()
+}
+
+func (a *IPAddr) sockaddr(family int) (syscall.Sockaddr, error) {
+	if a == nil {
+		return nil, nil
+	}
+	return ipToSockaddr(family, a.IP, 0, a.Zone)
+}
+
+// IPConn is the implementation of the Conn and PacketConn interfaces
+// for IP network connections.
+type IPConn struct {
+	conn
+}
+
+func newIPConn(fd *netFD) *IPConn { return &IPConn{conn{fd}} }
+
+// ReadFromIP reads an IP packet from c, copying the payload into b.
+// It returns the number of bytes copied into b and the return address
+// that was on the packet.
+//
+// ReadFromIP can be made to time out and return an error with
+// Timeout() == true after a fixed time limit; see SetDeadline and
+// SetReadDeadline.
+func (c *IPConn) ReadFromIP(b []byte) (int, *IPAddr, error) {
+	if !c.ok() {
+		return 0, nil, syscall.EINVAL
+	}
+	// TODO(cw,rsc): consider using readv if we know the family
+	// type to avoid the header trim/copy
+	var addr *IPAddr
+	n, sa, err := c.fd.readFrom(b)
+	switch sa := sa.(type) {
+	case *syscall.SockaddrInet4:
+		addr = &IPAddr{IP: sa.Addr[0:]}
+		if len(b) >= IPv4len { // discard ipv4 header
+			hsize := (int(b[0]) & 0xf) * 4
+			copy(b, b[hsize:])
+			n -= hsize
+		}
+	case *syscall.SockaddrInet6:
+		addr = &IPAddr{IP: sa.Addr[0:], Zone: zoneToString(int(sa.ZoneId))}
+	}
+	return n, addr, err
+}
+
+// ReadFrom implements the PacketConn ReadFrom method.
+func (c *IPConn) ReadFrom(b []byte) (int, Addr, error) {
+	if !c.ok() {
+		return 0, nil, syscall.EINVAL
+	}
+	n, addr, err := c.ReadFromIP(b)
+	return n, addr.toAddr(), err
+}
+
+// ReadMsgIP reads a packet from c, copying the payload into b and the
+// associated out-of-band data into oob.  It returns the number of
+// bytes copied into b, the number of bytes copied into oob, the flags
+// that were set on the packet and the source address of the packet.
+func (c *IPConn) ReadMsgIP(b, oob []byte) (n, oobn, flags int, addr *IPAddr, err error) {
+	if !c.ok() {
+		return 0, 0, 0, nil, syscall.EINVAL
+	}
+	var sa syscall.Sockaddr
+	n, oobn, flags, sa, err = c.fd.readMsg(b, oob)
+	switch sa := sa.(type) {
+	case *syscall.SockaddrInet4:
+		addr = &IPAddr{IP: sa.Addr[0:]}
+	case *syscall.SockaddrInet6:
+		addr = &IPAddr{IP: sa.Addr[0:], Zone: zoneToString(int(sa.ZoneId))}
+	}
+	return
+}
+
+// WriteToIP writes an IP packet to addr via c, copying the payload
+// from b.
+//
+// WriteToIP can be made to time out and return an error with
+// Timeout() == true after a fixed time limit; see SetDeadline and
+// SetWriteDeadline.  On packet-oriented connections, write timeouts
+// are rare.
+func (c *IPConn) WriteToIP(b []byte, addr *IPAddr) (int, error) {
+	if !c.ok() {
+		return 0, syscall.EINVAL
+	}
+	if c.fd.isConnected {
+		return 0, &OpError{Op: "write", Net: c.fd.net, Addr: addr, Err: ErrWriteToConnected}
+	}
+	if addr == nil {
+		return 0, &OpError{Op: "write", Net: c.fd.net, Addr: nil, Err: errMissingAddress}
+	}
+	sa, err := addr.sockaddr(c.fd.family)
+	if err != nil {
+		return 0, &OpError{"write", c.fd.net, addr, err}
+	}
+	return c.fd.writeTo(b, sa)
+}
+
+// WriteTo implements the PacketConn WriteTo method.
+func (c *IPConn) WriteTo(b []byte, addr Addr) (int, error) {
+	if !c.ok() {
+		return 0, syscall.EINVAL
+	}
+	a, ok := addr.(*IPAddr)
+	if !ok {
+		return 0, &OpError{"write", c.fd.net, addr, syscall.EINVAL}
+	}
+	return c.WriteToIP(b, a)
+}
+
+// WriteMsgIP writes a packet to addr via c, copying the payload from
+// b and the associated out-of-band data from oob.  It returns the
+// number of payload and out-of-band bytes written.
+func (c *IPConn) WriteMsgIP(b, oob []byte, addr *IPAddr) (n, oobn int, err error) {
+	if !c.ok() {
+		return 0, 0, syscall.EINVAL
+	}
+	if c.fd.isConnected {
+		return 0, 0, &OpError{Op: "write", Net: c.fd.net, Addr: addr, Err: ErrWriteToConnected}
+	}
+	if addr == nil {
+		return 0, 0, &OpError{Op: "write", Net: c.fd.net, Addr: nil, Err: errMissingAddress}
+	}
+	sa, err := addr.sockaddr(c.fd.family)
+	if err != nil {
+		return 0, 0, &OpError{"write", c.fd.net, addr, err}
+	}
+	return c.fd.writeMsg(b, oob, sa)
+}
+
+// DialIP connects to the remote address raddr on the network protocol
+// netProto, which must be "ip", "ip4", or "ip6" followed by a colon
+// and a protocol number or name.
+func DialIP(netProto string, laddr, raddr *IPAddr) (*IPConn, error) {
+	return dialIP(netProto, laddr, raddr, noDeadline)
+}
+
+func dialIP(netProto string, laddr, raddr *IPAddr, deadline time.Time) (*IPConn, error) {
+	net, proto, err := parseNetwork(netProto)
+	if err != nil {
+		return nil, &OpError{Op: "dial", Net: netProto, Addr: raddr, Err: err}
+	}
+	switch net {
+	case "ip", "ip4", "ip6":
+	default:
+		return nil, &OpError{Op: "dial", Net: netProto, Addr: raddr, Err: UnknownNetworkError(netProto)}
+	}
+	if raddr == nil {
+		return nil, &OpError{Op: "dial", Net: netProto, Addr: nil, Err: errMissingAddress}
+	}
+	fd, err := internetSocket(net, laddr, raddr, deadline, syscall.SOCK_RAW, proto, "dial")
+	if err != nil {
+		return nil, &OpError{Op: "dial", Net: netProto, Addr: raddr, Err: err}
+	}
+	return newIPConn(fd), nil
+}
+
+// ListenIP listens for incoming IP packets addressed to the local
+// address laddr.  The returned connection's ReadFrom and WriteTo
+// methods can be used to receive and send IP packets with per-packet
+// addressing.
+func ListenIP(netProto string, laddr *IPAddr) (*IPConn, error) {
+	net, proto, err := parseNetwork(netProto)
+	if err != nil {
+		return nil, &OpError{Op: "dial", Net: netProto, Addr: laddr, Err: err}
+	}
+	switch net {
+	case "ip", "ip4", "ip6":
+	default:
+		return nil, &OpError{Op: "listen", Net: netProto, Addr: laddr, Err: UnknownNetworkError(netProto)}
+	}
+	fd, err := internetSocket(net, laddr, nil, noDeadline, syscall.SOCK_RAW, proto, "listen")
+	if err != nil {
+		return nil, &OpError{Op: "listen", Net: netProto, Addr: laddr, Err: err}
+	}
+	return newIPConn(fd), nil
+}
diff --git a/src/net/ipsock.go b/src/net/ipsock.go
new file mode 100644
index 000000000..dda857803
--- /dev/null
+++ b/src/net/ipsock.go
@@ -0,0 +1,318 @@
+// Copyright 2009 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Internet protocol family sockets
+
+package net
+
+import (
+	"errors"
+	"time"
+)
+
+var (
+	// supportsIPv4 reports whether the platform supports IPv4
+	// networking functionality.
+	supportsIPv4 bool
+
+	// supportsIPv6 reports whether the platform supports IPv6
+	// networking functionality.
+	supportsIPv6 bool
+
+	// supportsIPv4map reports whether the platform supports
+	// mapping an IPv4 address inside an IPv6 address at transport
+	// layer protocols.  See RFC 4291, RFC 4038 and RFC 3493.
+	supportsIPv4map bool
+)
+
+func init() {
+	sysInit()
+	supportsIPv4 = probeIPv4Stack()
+	supportsIPv6, supportsIPv4map = probeIPv6Stack()
+}
+
+// A netaddr represents a network endpoint address or a list of
+// network endpoint addresses.
+type netaddr interface {
+	// toAddr returns the address represented in Addr interface.
+	// It returns a nil interface when the address is nil.
+	toAddr() Addr
+}
+
+// An addrList represents a list of network endpoint addresses.
+type addrList []netaddr
+
+func (al addrList) toAddr() Addr {
+	switch len(al) {
+	case 0:
+		return nil
+	case 1:
+		return al[0].toAddr()
+	default:
+		// For now, we'll roughly pick first one without
+		// considering dealing with any preferences such as
+		// DNS TTL, transport path quality, network routing
+		// information.
+		return al[0].toAddr()
+	}
+}
+
+var errNoSuitableAddress = errors.New("no suitable address found")
+
+// firstFavoriteAddr returns an address or a list of addresses that
+// implement the netaddr interface. Known filters are nil, ipv4only
+// and ipv6only. It returns any address when filter is nil. The result
+// contains at least one address when error is nil.
+func firstFavoriteAddr(filter func(IP) IP, ips []IP, inetaddr func(IP) netaddr) (netaddr, error) {
+	if filter != nil {
+		return firstSupportedAddr(filter, ips, inetaddr)
+	}
+	var (
+		ipv4, ipv6, swap bool
+		list             addrList
+	)
+	for _, ip := range ips {
+		// We'll take any IP address, but since the dialing
+		// code does not yet try multiple addresses
+		// effectively, prefer to use an IPv4 address if
+		// possible. This is especially relevant if localhost
+		// resolves to [ipv6-localhost, ipv4-localhost]. Too
+		// much code assumes localhost == ipv4-localhost.
+		if ip4 := ipv4only(ip); ip4 != nil && !ipv4 {
+			list = append(list, inetaddr(ip4))
+			ipv4 = true
+			if ipv6 {
+				swap = true
+			}
+		} else if ip6 := ipv6only(ip); ip6 != nil && !ipv6 {
+			list = append(list, inetaddr(ip6))
+			ipv6 = true
+		}
+		if ipv4 && ipv6 {
+			if swap {
+				list[0], list[1] = list[1], list[0]
+			}
+			break
+		}
+	}
+	switch len(list) {
+	case 0:
+		return nil, errNoSuitableAddress
+	case 1:
+		return list[0], nil
+	default:
+		return list, nil
+	}
+}
+
+func firstSupportedAddr(filter func(IP) IP, ips []IP, inetaddr func(IP) netaddr) (netaddr, error) {
+	for _, ip := range ips {
+		if ip := filter(ip); ip != nil {
+			return inetaddr(ip), nil
+		}
+	}
+	return nil, errNoSuitableAddress
+}
+
+// ipv4only returns IPv4 addresses that we can use with the kernel's
+// IPv4 addressing modes. If ip is an IPv4 address, ipv4only returns ip.
+// Otherwise it returns nil.
+func ipv4only(ip IP) IP {
+	if supportsIPv4 && ip.To4() != nil {
+		return ip
+	}
+	return nil
+}
+
+// ipv6only returns IPv6 addresses that we can use with the kernel's
+// IPv6 addressing modes.  It returns IPv4-mapped IPv6 addresses as
+// nils and returns other IPv6 address types as IPv6 addresses.
+func ipv6only(ip IP) IP {
+	if supportsIPv6 && len(ip) == IPv6len && ip.To4() == nil {
+		return ip
+	}
+	return nil
+}
+
+// SplitHostPort splits a network address of the form "host:port",
+// "[host]:port" or "[ipv6-host%zone]:port" into host or
+// ipv6-host%zone and port.  A literal address or host name for IPv6
+// must be enclosed in square brackets, as in "[::1]:80",
+// "[ipv6-host]:http" or "[ipv6-host%zone]:80".
+func SplitHostPort(hostport string) (host, port string, err error) {
+	j, k := 0, 0
+
+	// The port starts after the last colon.
+	i := last(hostport, ':')
+	if i < 0 {
+		goto missingPort
+	}
+
+	if hostport[0] == '[' {
+		// Expect the first ']' just before the last ':'.
+		end := byteIndex(hostport, ']')
+		if end < 0 {
+			err = &AddrError{"missing ']' in address", hostport}
+			return
+		}
+		switch end + 1 {
+		case len(hostport):
+			// There can't be a ':' behind the ']' now.
+			goto missingPort
+		case i:
+			// The expected result.
+		default:
+			// Either ']' isn't followed by a colon, or it is
+			// followed by a colon that is not the last one.
+			if hostport[end+1] == ':' {
+				goto tooManyColons
+			}
+			goto missingPort
+		}
+		host = hostport[1:end]
+		j, k = 1, end+1 // there can't be a '[' resp. ']' before these positions
+	} else {
+		host = hostport[:i]
+		if byteIndex(host, ':') >= 0 {
+			goto tooManyColons
+		}
+		if byteIndex(host, '%') >= 0 {
+			goto missingBrackets
+		}
+	}
+	if byteIndex(hostport[j:], '[') >= 0 {
+		err = &AddrError{"unexpected '[' in address", hostport}
+		return
+	}
+	if byteIndex(hostport[k:], ']') >= 0 {
+		err = &AddrError{"unexpected ']' in address", hostport}
+		return
+	}
+
+	port = hostport[i+1:]
+	return
+
+missingPort:
+	err = &AddrError{"missing port in address", hostport}
+	return
+
+tooManyColons:
+	err = &AddrError{"too many colons in address", hostport}
+	return
+
+missingBrackets:
+	err = &AddrError{"missing brackets in address", hostport}
+	return
+}
+
+func splitHostZone(s string) (host, zone string) {
+	// The IPv6 scoped addressing zone identifier starts after the
+	// last percent sign.
+	if i := last(s, '%'); i > 0 {
+		host, zone = s[:i], s[i+1:]
+	} else {
+		host = s
+	}
+	return
+}
+
+// JoinHostPort combines host and port into a network address of the
+// form "host:port" or, if host contains a colon or a percent sign,
+// "[host]:port".
+func JoinHostPort(host, port string) string {
+	// If host has colons or a percent sign, have to bracket it.
+	if byteIndex(host, ':') >= 0 || byteIndex(host, '%') >= 0 {
+		return "[" + host + "]:" + port
+	}
+	return host + ":" + port
+}
+
+// resolveInternetAddr resolves addr that is either a literal IP
+// address or a DNS name and returns an internet protocol family
+// address. It returns a list that contains a pair of different
+// address family addresses when addr is a DNS name and the name has
+// multiple address family records. The result contains at least one
+// address when error is nil.
+func resolveInternetAddr(net, addr string, deadline time.Time) (netaddr, error) {
+	var (
+		err              error
+		host, port, zone string
+		portnum          int
+	)
+	switch net {
+	case "tcp", "tcp4", "tcp6", "udp", "udp4", "udp6":
+		if addr != "" {
+			if host, port, err = SplitHostPort(addr); err != nil {
+				return nil, err
+			}
+			if portnum, err = parsePort(net, port); err != nil {
+				return nil, err
+			}
+		}
+	case "ip", "ip4", "ip6":
+		if addr != "" {
+			host = addr
+		}
+	default:
+		return nil, UnknownNetworkError(net)
+	}
+	inetaddr := func(ip IP) netaddr {
+		switch net {
+		case "tcp", "tcp4", "tcp6":
+			return &TCPAddr{IP: ip, Port: portnum, Zone: zone}
+		case "udp", "udp4", "udp6":
+			return &UDPAddr{IP: ip, Port: portnum, Zone: zone}
+		case "ip", "ip4", "ip6":
+			return &IPAddr{IP: ip, Zone: zone}
+		default:
+			panic("unexpected network: " + net)
+		}
+	}
+	if host == "" {
+		return inetaddr(nil), nil
+	}
+	// Try as a literal IP address.
+	var ip IP
+	if ip = parseIPv4(host); ip != nil {
+		return inetaddr(ip), nil
+	}
+	if ip, zone = parseIPv6(host, true); ip != nil {
+		return inetaddr(ip), nil
+	}
+	// Try as a DNS name.
+	host, zone = splitHostZone(host)
+	ips, err := lookupIPDeadline(host, deadline)
+	if err != nil {
+		return nil, err
+	}
+	var filter func(IP) IP
+	if net != "" && net[len(net)-1] == '4' {
+		filter = ipv4only
+	}
+	if net != "" && net[len(net)-1] == '6' || zone != "" {
+		filter = ipv6only
+	}
+	return firstFavoriteAddr(filter, ips, inetaddr)
+}
+
+func zoneToString(zone int) string {
+	if zone == 0 {
+		return ""
+	}
+	if ifi, err := InterfaceByIndex(zone); err == nil {
+		return ifi.Name
+	}
+	return itod(uint(zone))
+}
+
+func zoneToInt(zone string) int {
+	if zone == "" {
+		return 0
+	}
+	if ifi, err := InterfaceByName(zone); err == nil {
+		return ifi.Index
+	}
+	n, _, _ := dtoi(zone, 0)
+	return n
+}
diff --git a/src/net/ipsock_plan9.go b/src/net/ipsock_plan9.go
new file mode 100644
index 000000000..94ceea31b
--- /dev/null
+++ b/src/net/ipsock_plan9.go
@@ -0,0 +1,228 @@
+// Copyright 2009 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Internet protocol family sockets for Plan 9
+
+package net
+
+import (
+	"errors"
+	"os"
+	"syscall"
+)
+
+func probe(filename, query string) bool {
+	var file *file
+	var err error
+	if file, err = open(filename); err != nil {
+		return false
+	}
+
+	r := false
+	for line, ok := file.readLine(); ok && !r; line, ok = file.readLine() {
+		f := getFields(line)
+		if len(f) < 3 {
+			continue
+		}
+		for i := 0; i < len(f); i++ {
+			if query == f[i] {
+				r = true
+				break
+			}
+		}
+	}
+	file.close()
+	return r
+}
+
+func probeIPv4Stack() bool {
+	return probe(netdir+"/iproute", "4i")
+}
+
+// probeIPv6Stack returns two boolean values.  If the first boolean
+// value is true, kernel supports basic IPv6 functionality.  If the
+// second boolean value is true, kernel supports IPv6 IPv4-mapping.
+func probeIPv6Stack() (supportsIPv6, supportsIPv4map bool) {
+	// Plan 9 uses IPv6 natively, see ip(3).
+	r := probe(netdir+"/iproute", "6i")
+	v := false
+	if r {
+		v = probe(netdir+"/iproute", "4i")
+	}
+	return r, v
+}
+
+// parsePlan9Addr parses address of the form [ip!]port (e.g. 127.0.0.1!80).
+func parsePlan9Addr(s string) (ip IP, iport int, err error) {
+	addr := IPv4zero // address contains port only
+	i := byteIndex(s, '!')
+	if i >= 0 {
+		addr = ParseIP(s[:i])
+		if addr == nil {
+			return nil, 0, errors.New("parsing IP failed")
+		}
+	}
+	p, _, ok := dtoi(s[i+1:], 0)
+	if !ok {
+		return nil, 0, errors.New("parsing port failed")
+	}
+	if p < 0 || p > 0xFFFF {
+		return nil, 0, &AddrError{"invalid port", string(p)}
+	}
+	return addr, p, nil
+}
+
+func readPlan9Addr(proto, filename string) (addr Addr, err error) {
+	var buf [128]byte
+
+	f, err := os.Open(filename)
+	if err != nil {
+		return
+	}
+	defer f.Close()
+	n, err := f.Read(buf[:])
+	if err != nil {
+		return
+	}
+	ip, port, err := parsePlan9Addr(string(buf[:n]))
+	if err != nil {
+		return
+	}
+	switch proto {
+	case "tcp":
+		addr = &TCPAddr{IP: ip, Port: port}
+	case "udp":
+		addr = &UDPAddr{IP: ip, Port: port}
+	default:
+		return nil, errors.New("unknown protocol " + proto)
+	}
+	return addr, nil
+}
+
+func startPlan9(net string, addr Addr) (ctl *os.File, dest, proto, name string, err error) {
+	var (
+		ip   IP
+		port int
+	)
+	switch a := addr.(type) {
+	case *TCPAddr:
+		proto = "tcp"
+		ip = a.IP
+		port = a.Port
+	case *UDPAddr:
+		proto = "udp"
+		ip = a.IP
+		port = a.Port
+	default:
+		err = UnknownNetworkError(net)
+		return
+	}
+
+	clone, dest, err := queryCS1(proto, ip, port)
+	if err != nil {
+		return
+	}
+	f, err := os.OpenFile(clone, os.O_RDWR, 0)
+	if err != nil {
+		return
+	}
+	var buf [16]byte
+	n, err := f.Read(buf[:])
+	if err != nil {
+		f.Close()
+		return
+	}
+	return f, dest, proto, string(buf[:n]), nil
+}
+
+func netErr(e error) {
+	oe, ok := e.(*OpError)
+	if !ok {
+		return
+	}
+	if pe, ok := oe.Err.(*os.PathError); ok {
+		if _, ok = pe.Err.(syscall.ErrorString); ok {
+			oe.Err = pe.Err
+		}
+	}
+}
+
+func dialPlan9(net string, laddr, raddr Addr) (fd *netFD, err error) {
+	defer func() { netErr(err) }()
+	f, dest, proto, name, err := startPlan9(net, raddr)
+	if err != nil {
+		return nil, &OpError{"dial", net, raddr, err}
+	}
+	_, err = f.WriteString("connect " + dest)
+	if err != nil {
+		f.Close()
+		return nil, &OpError{"dial", f.Name(), raddr, err}
+	}
+	data, err := os.OpenFile(netdir+"/"+proto+"/"+name+"/data", os.O_RDWR, 0)
+	if err != nil {
+		f.Close()
+		return nil, &OpError{"dial", net, raddr, err}
+	}
+	laddr, err = readPlan9Addr(proto, netdir+"/"+proto+"/"+name+"/local")
+	if err != nil {
+		data.Close()
+		f.Close()
+		return nil, &OpError{"dial", proto, raddr, err}
+	}
+	return newFD(proto, name, f, data, laddr, raddr)
+}
+
+func listenPlan9(net string, laddr Addr) (fd *netFD, err error) {
+	defer func() { netErr(err) }()
+	f, dest, proto, name, err := startPlan9(net, laddr)
+	if err != nil {
+		return nil, &OpError{"listen", net, laddr, err}
+	}
+	_, err = f.WriteString("announce " + dest)
+	if err != nil {
+		f.Close()
+		return nil, &OpError{"announce", proto, laddr, err}
+	}
+	laddr, err = readPlan9Addr(proto, netdir+"/"+proto+"/"+name+"/local")
+	if err != nil {
+		f.Close()
+		return nil, &OpError{Op: "listen", Net: net, Err: err}
+	}
+	return newFD(proto, name, f, nil, laddr, nil)
+}
+
+func (l *netFD) netFD() (*netFD, error) {
+	return newFD(l.proto, l.n, l.ctl, l.data, l.laddr, l.raddr)
+}
+
+func (l *netFD) acceptPlan9() (fd *netFD, err error) {
+	defer func() { netErr(err) }()
+	if err := l.readLock(); err != nil {
+		return nil, err
+	}
+	defer l.readUnlock()
+	f, err := os.Open(l.dir + "/listen")
+	if err != nil {
+		return nil, &OpError{"accept", l.dir + "/listen", l.laddr, err}
+	}
+	var buf [16]byte
+	n, err := f.Read(buf[:])
+	if err != nil {
+		f.Close()
+		return nil, &OpError{"accept", l.dir + "/listen", l.laddr, err}
+	}
+	name := string(buf[:n])
+	data, err := os.OpenFile(netdir+"/"+l.proto+"/"+name+"/data", os.O_RDWR, 0)
+	if err != nil {
+		f.Close()
+		return nil, &OpError{"accept", l.proto, l.laddr, err}
+	}
+	raddr, err := readPlan9Addr(l.proto, netdir+"/"+l.proto+"/"+name+"/remote")
+	if err != nil {
+		data.Close()
+		f.Close()
+		return nil, &OpError{"accept", l.proto, l.laddr, err}
+	}
+	return newFD(l.proto, name, f, data, l.laddr, raddr)
+}
diff --git a/src/net/ipsock_posix.go b/src/net/ipsock_posix.go
new file mode 100644
index 000000000..f9ebe40a2
--- /dev/null
+++ b/src/net/ipsock_posix.go
@@ -0,0 +1,177 @@
+// Copyright 2009 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build darwin dragonfly freebsd linux nacl netbsd openbsd solaris windows
+
+// Internet protocol family sockets for POSIX
+
+package net
+
+import (
+	"syscall"
+	"time"
+)
+
+func probeIPv4Stack() bool {
+	s, err := syscall.Socket(syscall.AF_INET, syscall.SOCK_STREAM, syscall.IPPROTO_TCP)
+	switch err {
+	case syscall.EAFNOSUPPORT, syscall.EPROTONOSUPPORT:
+		return false
+	case nil:
+		closesocket(s)
+	}
+	return true
+}
+
+// Should we try to use the IPv4 socket interface if we're
+// only dealing with IPv4 sockets?  As long as the host system
+// understands IPv6, it's okay to pass IPv4 addresses to the IPv6
+// interface.  That simplifies our code and is most general.
+// Unfortunately, we need to run on kernels built without IPv6
+// support too.  So probe the kernel to figure it out.
+//
+// probeIPv6Stack probes both basic IPv6 capability and IPv6 IPv4-
+// mapping capability which is controlled by IPV6_V6ONLY socket
+// option and/or kernel state "net.inet6.ip6.v6only".
+// It returns two boolean values.  If the first boolean value is
+// true, kernel supports basic IPv6 functionality.  If the second
+// boolean value is true, kernel supports IPv6 IPv4-mapping.
+func probeIPv6Stack() (supportsIPv6, supportsIPv4map bool) {
+	var probes = []struct {
+		laddr TCPAddr
+		value int
+		ok    bool
+	}{
+		// IPv6 communication capability
+		{laddr: TCPAddr{IP: ParseIP("::1")}, value: 1},
+		// IPv6 IPv4-mapped address communication capability
+		{laddr: TCPAddr{IP: IPv4(127, 0, 0, 1)}, value: 0},
+	}
+
+	for i := range probes {
+		s, err := syscall.Socket(syscall.AF_INET6, syscall.SOCK_STREAM, syscall.IPPROTO_TCP)
+		if err != nil {
+			continue
+		}
+		defer closesocket(s)
+		syscall.SetsockoptInt(s, syscall.IPPROTO_IPV6, syscall.IPV6_V6ONLY, probes[i].value)
+		sa, err := probes[i].laddr.sockaddr(syscall.AF_INET6)
+		if err != nil {
+			continue
+		}
+		if err := syscall.Bind(s, sa); err != nil {
+			continue
+		}
+		probes[i].ok = true
+	}
+
+	return probes[0].ok, probes[1].ok
+}
+
+// favoriteAddrFamily returns the appropriate address family to
+// the given net, laddr, raddr and mode.  At first it figures
+// address family out from the net.  If mode indicates "listen"
+// and laddr is a wildcard, it assumes that the user wants to
+// make a passive connection with a wildcard address family, both
+// AF_INET and AF_INET6, and a wildcard address like following:
+//
+//	1. A wild-wild listen, "tcp" + ""
+//	If the platform supports both IPv6 and IPv6 IPv4-mapping
+//	capabilities, we assume that the user want to listen on
+//	both IPv4 and IPv6 wildcard address over an AF_INET6
+//	socket with IPV6_V6ONLY=0.  Otherwise we prefer an IPv4
+//	wildcard address listen over an AF_INET socket.
+//
+//	2. A wild-ipv4wild listen, "tcp" + "0.0.0.0"
+//	Same as 1.
+//
+//	3. A wild-ipv6wild listen, "tcp" + "[::]"
+//	Almost same as 1 but we prefer an IPv6 wildcard address
+//	listen over an AF_INET6 socket with IPV6_V6ONLY=0 when
+//	the platform supports IPv6 capability but not IPv6 IPv4-
+//	mapping capability.
+//
+//	4. A ipv4-ipv4wild listen, "tcp4" + "" or "0.0.0.0"
+//	We use an IPv4 (AF_INET) wildcard address listen.
+//
+//	5. A ipv6-ipv6wild listen, "tcp6" + "" or "[::]"
+//	We use an IPv6 (AF_INET6, IPV6_V6ONLY=1) wildcard address
+//	listen.
+//
+// Otherwise guess: if the addresses are IPv4 then returns AF_INET,
+// or else returns AF_INET6.  It also returns a boolean value what
+// designates IPV6_V6ONLY option.
+//
+// Note that OpenBSD allows neither "net.inet6.ip6.v6only=1" change
+// nor IPPROTO_IPV6 level IPV6_V6ONLY socket option setting.
+func favoriteAddrFamily(net string, laddr, raddr sockaddr, mode string) (family int, ipv6only bool) {
+	switch net[len(net)-1] {
+	case '4':
+		return syscall.AF_INET, false
+	case '6':
+		return syscall.AF_INET6, true
+	}
+
+	if mode == "listen" && (laddr == nil || laddr.isWildcard()) {
+		if supportsIPv4map {
+			return syscall.AF_INET6, false
+		}
+		if laddr == nil {
+			return syscall.AF_INET, false
+		}
+		return laddr.family(), false
+	}
+
+	if (laddr == nil || laddr.family() == syscall.AF_INET) &&
+		(raddr == nil || raddr.family() == syscall.AF_INET) {
+		return syscall.AF_INET, false
+	}
+	return syscall.AF_INET6, false
+}
+
+// Internet sockets (TCP, UDP, IP)
+
+func internetSocket(net string, laddr, raddr sockaddr, deadline time.Time, sotype, proto int, mode string) (fd *netFD, err error) {
+	family, ipv6only := favoriteAddrFamily(net, laddr, raddr, mode)
+	return socket(net, family, sotype, proto, ipv6only, laddr, raddr, deadline)
+}
+
+func ipToSockaddr(family int, ip IP, port int, zone string) (syscall.Sockaddr, error) {
+	switch family {
+	case syscall.AF_INET:
+		if len(ip) == 0 {
+			ip = IPv4zero
+		}
+		if ip = ip.To4(); ip == nil {
+			return nil, InvalidAddrError("non-IPv4 address")
+		}
+		sa := new(syscall.SockaddrInet4)
+		for i := 0; i < IPv4len; i++ {
+			sa.Addr[i] = ip[i]
+		}
+		sa.Port = port
+		return sa, nil
+	case syscall.AF_INET6:
+		if len(ip) == 0 {
+			ip = IPv6zero
+		}
+		// IPv4 callers use 0.0.0.0 to mean "announce on any available address".
+		// In IPv6 mode, Linux treats that as meaning "announce on 0.0.0.0",
+		// which it refuses to do.  Rewrite to the IPv6 unspecified address.
+		if ip.Equal(IPv4zero) {
+			ip = IPv6zero
+		}
+		if ip = ip.To16(); ip == nil {
+			return nil, InvalidAddrError("non-IPv6 address")
+		}
+		sa := new(syscall.SockaddrInet6)
+		for i := 0; i < IPv6len; i++ {
+			sa.Addr[i] = ip[i]
+		}
+		sa.Port = port
+		sa.ZoneId = uint32(zoneToInt(zone))
+		return sa, nil
+	}
+	return nil, InvalidAddrError("unexpected socket family")
+}
diff --git a/src/net/ipsock_test.go b/src/net/ipsock_test.go
new file mode 100644
index 000000000..9ecaaec69
--- /dev/null
+++ b/src/net/ipsock_test.go
@@ -0,0 +1,193 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package net
+
+import (
+	"reflect"
+	"testing"
+)
+
+var testInetaddr = func(ip IP) netaddr { return &TCPAddr{IP: ip, Port: 5682} }
+
+var firstFavoriteAddrTests = []struct {
+	filter   func(IP) IP
+	ips      []IP
+	inetaddr func(IP) netaddr
+	addr     netaddr
+	err      error
+}{
+	{
+		nil,
+		[]IP{
+			IPv4(127, 0, 0, 1),
+			IPv6loopback,
+		},
+		testInetaddr,
+		addrList{
+			&TCPAddr{IP: IPv4(127, 0, 0, 1), Port: 5682},
+			&TCPAddr{IP: IPv6loopback, Port: 5682},
+		},
+		nil,
+	},
+	{
+		nil,
+		[]IP{
+			IPv6loopback,
+			IPv4(127, 0, 0, 1),
+		},
+		testInetaddr,
+		addrList{
+			&TCPAddr{IP: IPv4(127, 0, 0, 1), Port: 5682},
+			&TCPAddr{IP: IPv6loopback, Port: 5682},
+		},
+		nil,
+	},
+	{
+		nil,
+		[]IP{
+			IPv4(127, 0, 0, 1),
+			IPv4(192, 168, 0, 1),
+		},
+		testInetaddr,
+		&TCPAddr{IP: IPv4(127, 0, 0, 1), Port: 5682},
+		nil,
+	},
+	{
+		nil,
+		[]IP{
+			IPv6loopback,
+			ParseIP("fe80::1"),
+		},
+		testInetaddr,
+		&TCPAddr{IP: IPv6loopback, Port: 5682},
+		nil,
+	},
+	{
+		nil,
+		[]IP{
+			IPv4(127, 0, 0, 1),
+			IPv4(192, 168, 0, 1),
+			IPv6loopback,
+			ParseIP("fe80::1"),
+		},
+		testInetaddr,
+		addrList{
+			&TCPAddr{IP: IPv4(127, 0, 0, 1), Port: 5682},
+			&TCPAddr{IP: IPv6loopback, Port: 5682},
+		},
+		nil,
+	},
+	{
+		nil,
+		[]IP{
+			IPv6loopback,
+			ParseIP("fe80::1"),
+			IPv4(127, 0, 0, 1),
+			IPv4(192, 168, 0, 1),
+		},
+		testInetaddr,
+		addrList{
+			&TCPAddr{IP: IPv4(127, 0, 0, 1), Port: 5682},
+			&TCPAddr{IP: IPv6loopback, Port: 5682},
+		},
+		nil,
+	},
+	{
+		nil,
+		[]IP{
+			IPv4(127, 0, 0, 1),
+			IPv6loopback,
+			IPv4(192, 168, 0, 1),
+			ParseIP("fe80::1"),
+		},
+		testInetaddr,
+		addrList{
+			&TCPAddr{IP: IPv4(127, 0, 0, 1), Port: 5682},
+			&TCPAddr{IP: IPv6loopback, Port: 5682},
+		},
+		nil,
+	},
+	{
+		nil,
+		[]IP{
+			IPv6loopback,
+			IPv4(127, 0, 0, 1),
+			ParseIP("fe80::1"),
+			IPv4(192, 168, 0, 1),
+		},
+		testInetaddr,
+		addrList{
+			&TCPAddr{IP: IPv4(127, 0, 0, 1), Port: 5682},
+			&TCPAddr{IP: IPv6loopback, Port: 5682},
+		},
+		nil,
+	},
+
+	{
+		ipv4only,
+		[]IP{
+			IPv4(127, 0, 0, 1),
+			IPv6loopback,
+		},
+		testInetaddr,
+		&TCPAddr{IP: IPv4(127, 0, 0, 1), Port: 5682},
+		nil,
+	},
+	{
+		ipv4only,
+		[]IP{
+			IPv6loopback,
+			IPv4(127, 0, 0, 1),
+		},
+		testInetaddr,
+		&TCPAddr{IP: IPv4(127, 0, 0, 1), Port: 5682},
+		nil,
+	},
+
+	{
+		ipv6only,
+		[]IP{
+			IPv4(127, 0, 0, 1),
+			IPv6loopback,
+		},
+		testInetaddr,
+		&TCPAddr{IP: IPv6loopback, Port: 5682},
+		nil,
+	},
+	{
+		ipv6only,
+		[]IP{
+			IPv6loopback,
+			IPv4(127, 0, 0, 1),
+		},
+		testInetaddr,
+		&TCPAddr{IP: IPv6loopback, Port: 5682},
+		nil,
+	},
+
+	{nil, nil, testInetaddr, nil, errNoSuitableAddress},
+
+	{ipv4only, nil, testInetaddr, nil, errNoSuitableAddress},
+	{ipv4only, []IP{IPv6loopback}, testInetaddr, nil, errNoSuitableAddress},
+
+	{ipv6only, nil, testInetaddr, nil, errNoSuitableAddress},
+	{ipv6only, []IP{IPv4(127, 0, 0, 1)}, testInetaddr, nil, errNoSuitableAddress},
+}
+
+func TestFirstFavoriteAddr(t *testing.T) {
+	if !supportsIPv4 || !supportsIPv6 {
+		t.Skip("ipv4 or ipv6 is not supported")
+	}
+
+	for i, tt := range firstFavoriteAddrTests {
+		addr, err := firstFavoriteAddr(tt.filter, tt.ips, tt.inetaddr)
+		if err != tt.err {
+			t.Errorf("#%v: got %v; expected %v", i, err, tt.err)
+		}
+		if !reflect.DeepEqual(addr, tt.addr) {
+			t.Errorf("#%v: got %v; expected %v", i, addr, tt.addr)
+		}
+	}
+}
diff --git a/src/net/lookup.go b/src/net/lookup.go
new file mode 100644
index 000000000..20f20578c
--- /dev/null
+++ b/src/net/lookup.go
@@ -0,0 +1,137 @@
+// Copyright 2012 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package net
+
+import "time"
+
+// protocols contains minimal mappings between internet protocol
+// names and numbers for platforms that don't have a complete list of
+// protocol numbers.
+//
+// See http://www.iana.org/assignments/protocol-numbers
+var protocols = map[string]int{
+	"icmp": 1, "ICMP": 1,
+	"igmp": 2, "IGMP": 2,
+	"tcp": 6, "TCP": 6,
+	"udp": 17, "UDP": 17,
+	"ipv6-icmp": 58, "IPV6-ICMP": 58, "IPv6-ICMP": 58,
+}
+
+// LookupHost looks up the given host using the local resolver.
+// It returns an array of that host's addresses.
+func LookupHost(host string) (addrs []string, err error) {
+	return lookupHost(host)
+}
+
+// LookupIP looks up host using the local resolver.
+// It returns an array of that host's IPv4 and IPv6 addresses.
+func LookupIP(host string) (addrs []IP, err error) {
+	return lookupIPMerge(host)
+}
+
+var lookupGroup singleflight
+
+// lookupIPMerge wraps lookupIP, but makes sure that for any given
+// host, only one lookup is in-flight at a time. The returned memory
+// is always owned by the caller.
+func lookupIPMerge(host string) (addrs []IP, err error) {
+	addrsi, err, shared := lookupGroup.Do(host, func() (interface{}, error) {
+		return lookupIP(host)
+	})
+	if err != nil {
+		return nil, err
+	}
+	addrs = addrsi.([]IP)
+	if shared {
+		clone := make([]IP, len(addrs))
+		copy(clone, addrs)
+		addrs = clone
+	}
+	return addrs, nil
+}
+
+func lookupIPDeadline(host string, deadline time.Time) (addrs []IP, err error) {
+	if deadline.IsZero() {
+		return lookupIPMerge(host)
+	}
+
+	// TODO(bradfitz): consider pushing the deadline down into the
+	// name resolution functions. But that involves fixing it for
+	// the native Go resolver, cgo, Windows, etc.
+	//
+	// In the meantime, just use a goroutine. Most users affected
+	// by http://golang.org/issue/2631 are due to TCP connections
+	// to unresponsive hosts, not DNS.
+	timeout := deadline.Sub(time.Now())
+	if timeout <= 0 {
+		err = errTimeout
+		return
+	}
+	t := time.NewTimer(timeout)
+	defer t.Stop()
+	type res struct {
+		addrs []IP
+		err   error
+	}
+	resc := make(chan res, 1)
+	go func() {
+		a, err := lookupIPMerge(host)
+		resc <- res{a, err}
+	}()
+	select {
+	case <-t.C:
+		err = errTimeout
+	case r := <-resc:
+		addrs, err = r.addrs, r.err
+	}
+	return
+}
+
+// LookupPort looks up the port for the given network and service.
+func LookupPort(network, service string) (port int, err error) {
+	return lookupPort(network, service)
+}
+
+// LookupCNAME returns the canonical DNS host for the given name.
+// Callers that do not care about the canonical name can call
+// LookupHost or LookupIP directly; both take care of resolving
+// the canonical name as part of the lookup.
+func LookupCNAME(name string) (cname string, err error) {
+	return lookupCNAME(name)
+}
+
+// LookupSRV tries to resolve an SRV query of the given service,
+// protocol, and domain name.  The proto is "tcp" or "udp".
+// The returned records are sorted by priority and randomized
+// by weight within a priority.
+//
+// LookupSRV constructs the DNS name to look up following RFC 2782.
+// That is, it looks up _service._proto.name.  To accommodate services
+// publishing SRV records under non-standard names, if both service
+// and proto are empty strings, LookupSRV looks up name directly.
+func LookupSRV(service, proto, name string) (cname string, addrs []*SRV, err error) {
+	return lookupSRV(service, proto, name)
+}
+
+// LookupMX returns the DNS MX records for the given domain name sorted by preference.
+func LookupMX(name string) (mx []*MX, err error) {
+	return lookupMX(name)
+}
+
+// LookupNS returns the DNS NS records for the given domain name.
+func LookupNS(name string) (ns []*NS, err error) {
+	return lookupNS(name)
+}
+
+// LookupTXT returns the DNS TXT records for the given domain name.
+func LookupTXT(name string) (txt []string, err error) {
+	return lookupTXT(name)
+}
+
+// LookupAddr performs a reverse lookup for the given address, returning a list
+// of names mapping to that address.
+func LookupAddr(addr string) (name []string, err error) {
+	return lookupAddr(addr)
+}
diff --git a/src/net/lookup_plan9.go b/src/net/lookup_plan9.go
new file mode 100644
index 000000000..b80ac10e0
--- /dev/null
+++ b/src/net/lookup_plan9.go
@@ -0,0 +1,297 @@
+// Copyright 2011 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package net
+
+import (
+	"errors"
+	"os"
+)
+
+func query(filename, query string, bufSize int) (res []string, err error) {
+	file, err := os.OpenFile(filename, os.O_RDWR, 0)
+	if err != nil {
+		return
+	}
+	defer file.Close()
+
+	_, err = file.Seek(0, 0)
+	if err != nil {
+		return
+	}
+	_, err = file.WriteString(query)
+	if err != nil {
+		return
+	}
+	_, err = file.Seek(0, 0)
+	if err != nil {
+		return
+	}
+	buf := make([]byte, bufSize)
+	for {
+		n, _ := file.Read(buf)
+		if n <= 0 {
+			break
+		}
+		res = append(res, string(buf[:n]))
+	}
+	return
+}
+
+func queryCS(net, host, service string) (res []string, err error) {
+	switch net {
+	case "tcp4", "tcp6":
+		net = "tcp"
+	case "udp4", "udp6":
+		net = "udp"
+	}
+	if host == "" {
+		host = "*"
+	}
+	return query(netdir+"/cs", net+"!"+host+"!"+service, 128)
+}
+
+func queryCS1(net string, ip IP, port int) (clone, dest string, err error) {
+	ips := "*"
+	if len(ip) != 0 && !ip.IsUnspecified() {
+		ips = ip.String()
+	}
+	lines, err := queryCS(net, ips, itoa(port))
+	if err != nil {
+		return
+	}
+	f := getFields(lines[0])
+	if len(f) < 2 {
+		return "", "", errors.New("bad response from ndb/cs")
+	}
+	clone, dest = f[0], f[1]
+	return
+}
+
+func queryDNS(addr string, typ string) (res []string, err error) {
+	return query(netdir+"/dns", addr+" "+typ, 1024)
+}
+
+// toLower returns a lower-case version of in. Restricting us to
+// ASCII is sufficient to handle the IP protocol names and allow
+// us to not depend on the strings and unicode packages.
+func toLower(in string) string {
+	for _, c := range in {
+		if 'A' <= c && c <= 'Z' {
+			// Has upper case; need to fix.
+			out := []byte(in)
+			for i := 0; i < len(in); i++ {
+				c := in[i]
+				if 'A' <= c && c <= 'Z' {
+					c += 'a' - 'A'
+				}
+				out[i] = c
+			}
+			return string(out)
+		}
+	}
+	return in
+}
+
+// lookupProtocol looks up IP protocol name and returns
+// the corresponding protocol number.
+func lookupProtocol(name string) (proto int, err error) {
+	lines, err := query(netdir+"/cs", "!protocol="+toLower(name), 128)
+	if err != nil {
+		return 0, err
+	}
+	unknownProtoError := errors.New("unknown IP protocol specified: " + name)
+	if len(lines) == 0 {
+		return 0, unknownProtoError
+	}
+	f := getFields(lines[0])
+	if len(f) < 2 {
+		return 0, unknownProtoError
+	}
+	s := f[1]
+	if n, _, ok := dtoi(s, byteIndex(s, '=')+1); ok {
+		return n, nil
+	}
+	return 0, unknownProtoError
+}
+
+func lookupHost(host string) (addrs []string, err error) {
+	// Use netdir/cs instead of netdir/dns because cs knows about
+	// host names in local network (e.g. from /lib/ndb/local)
+	lines, err := queryCS("net", host, "1")
+	if err != nil {
+		return
+	}
+loop:
+	for _, line := range lines {
+		f := getFields(line)
+		if len(f) < 2 {
+			continue
+		}
+		addr := f[1]
+		if i := byteIndex(addr, '!'); i >= 0 {
+			addr = addr[:i] // remove port
+		}
+		if ParseIP(addr) == nil {
+			continue
+		}
+		// only return unique addresses
+		for _, a := range addrs {
+			if a == addr {
+				continue loop
+			}
+		}
+		addrs = append(addrs, addr)
+	}
+	return
+}
+
+func lookupIP(host string) (ips []IP, err error) {
+	addrs, err := LookupHost(host)
+	if err != nil {
+		return
+	}
+	for _, addr := range addrs {
+		if ip := ParseIP(addr); ip != nil {
+			ips = append(ips, ip)
+		}
+	}
+	return
+}
+
+func lookupPort(network, service string) (port int, err error) {
+	switch network {
+	case "tcp4", "tcp6":
+		network = "tcp"
+	case "udp4", "udp6":
+		network = "udp"
+	}
+	lines, err := queryCS(network, "127.0.0.1", service)
+	if err != nil {
+		return
+	}
+	unknownPortError := &AddrError{"unknown port", network + "/" + service}
+	if len(lines) == 0 {
+		return 0, unknownPortError
+	}
+	f := getFields(lines[0])
+	if len(f) < 2 {
+		return 0, unknownPortError
+	}
+	s := f[1]
+	if i := byteIndex(s, '!'); i >= 0 {
+		s = s[i+1:] // remove address
+	}
+	if n, _, ok := dtoi(s, 0); ok {
+		return n, nil
+	}
+	return 0, unknownPortError
+}
+
+func lookupCNAME(name string) (cname string, err error) {
+	lines, err := queryDNS(name, "cname")
+	if err != nil {
+		return
+	}
+	if len(lines) > 0 {
+		if f := getFields(lines[0]); len(f) >= 3 {
+			return f[2] + ".", nil
+		}
+	}
+	return "", errors.New("bad response from ndb/dns")
+}
+
+func lookupSRV(service, proto, name string) (cname string, addrs []*SRV, err error) {
+	var target string
+	if service == "" && proto == "" {
+		target = name
+	} else {
+		target = "_" + service + "._" + proto + "." + name
+	}
+	lines, err := queryDNS(target, "srv")
+	if err != nil {
+		return
+	}
+	for _, line := range lines {
+		f := getFields(line)
+		if len(f) < 6 {
+			continue
+		}
+		port, _, portOk := dtoi(f[4], 0)
+		priority, _, priorityOk := dtoi(f[3], 0)
+		weight, _, weightOk := dtoi(f[2], 0)
+		if !(portOk && priorityOk && weightOk) {
+			continue
+		}
+		addrs = append(addrs, &SRV{f[5], uint16(port), uint16(priority), uint16(weight)})
+		cname = f[0]
+	}
+	byPriorityWeight(addrs).sort()
+	return
+}
+
+func lookupMX(name string) (mx []*MX, err error) {
+	lines, err := queryDNS(name, "mx")
+	if err != nil {
+		return
+	}
+	for _, line := range lines {
+		f := getFields(line)
+		if len(f) < 4 {
+			continue
+		}
+		if pref, _, ok := dtoi(f[2], 0); ok {
+			mx = append(mx, &MX{f[3], uint16(pref)})
+		}
+	}
+	byPref(mx).sort()
+	return
+}
+
+func lookupNS(name string) (ns []*NS, err error) {
+	lines, err := queryDNS(name, "ns")
+	if err != nil {
+		return
+	}
+	for _, line := range lines {
+		f := getFields(line)
+		if len(f) < 3 {
+			continue
+		}
+		ns = append(ns, &NS{f[2]})
+	}
+	return
+}
+
+func lookupTXT(name string) (txt []string, err error) {
+	lines, err := queryDNS(name, "txt")
+	if err != nil {
+		return
+	}
+	for _, line := range lines {
+		if i := byteIndex(line, '\t'); i >= 0 {
+			txt = append(txt, line[i+1:])
+		}
+	}
+	return
+}
+
+func lookupAddr(addr string) (name []string, err error) {
+	arpa, err := reverseaddr(addr)
+	if err != nil {
+		return
+	}
+	lines, err := queryDNS(arpa, "ptr")
+	if err != nil {
+		return
+	}
+	for _, line := range lines {
+		f := getFields(line)
+		if len(f) < 3 {
+			continue
+		}
+		name = append(name, f[2])
+	}
+	return
+}
diff --git a/src/net/lookup_test.go b/src/net/lookup_test.go
new file mode 100644
index 000000000..057e1322b
--- /dev/null
+++ b/src/net/lookup_test.go
@@ -0,0 +1,231 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// TODO It would be nice to use a mock DNS server, to eliminate
+// external dependencies.
+
+package net
+
+import (
+	"flag"
+	"strings"
+	"testing"
+)
+
+var testExternal = flag.Bool("external", true, "allow use of external networks during long test")
+
+var lookupGoogleSRVTests = []struct {
+	service, proto, name string
+	cname, target        string
+}{
+	{
+		"xmpp-server", "tcp", "google.com",
+		".google.com", ".google.com",
+	},
+	{
+		"", "", "_xmpp-server._tcp.google.com", // non-standard back door
+		".google.com", ".google.com",
+	},
+}
+
+func TestLookupGoogleSRV(t *testing.T) {
+	if testing.Short() || !*testExternal {
+		t.Skip("skipping test to avoid external network")
+	}
+
+	for _, tt := range lookupGoogleSRVTests {
+		cname, srvs, err := LookupSRV(tt.service, tt.proto, tt.name)
+		if err != nil {
+			t.Fatal(err)
+		}
+		if len(srvs) == 0 {
+			t.Error("got no record")
+		}
+		if !strings.Contains(cname, tt.cname) {
+			t.Errorf("got %q; want %q", cname, tt.cname)
+		}
+		for _, srv := range srvs {
+			if !strings.Contains(srv.Target, tt.target) {
+				t.Errorf("got %v; want a record containing %q", srv, tt.target)
+			}
+		}
+	}
+}
+
+func TestLookupGmailMX(t *testing.T) {
+	if testing.Short() || !*testExternal {
+		t.Skip("skipping test to avoid external network")
+	}
+
+	mxs, err := LookupMX("gmail.com")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(mxs) == 0 {
+		t.Error("got no record")
+	}
+	for _, mx := range mxs {
+		if !strings.Contains(mx.Host, ".google.com") {
+			t.Errorf("got %v; want a record containing .google.com.", mx)
+		}
+	}
+}
+
+func TestLookupGmailNS(t *testing.T) {
+	if testing.Short() || !*testExternal {
+		t.Skip("skipping test to avoid external network")
+	}
+
+	nss, err := LookupNS("gmail.com")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(nss) == 0 {
+		t.Error("got no record")
+	}
+	for _, ns := range nss {
+		if !strings.Contains(ns.Host, ".google.com") {
+			t.Errorf("got %v; want a record containing .google.com.", ns)
+		}
+	}
+}
+
+func TestLookupGmailTXT(t *testing.T) {
+	if testing.Short() || !*testExternal {
+		t.Skip("skipping test to avoid external network")
+	}
+
+	txts, err := LookupTXT("gmail.com")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(txts) == 0 {
+		t.Error("got no record")
+	}
+	for _, txt := range txts {
+		if !strings.Contains(txt, "spf") {
+			t.Errorf("got %q; want a spf record", txt)
+		}
+	}
+}
+
+var lookupGooglePublicDNSAddrs = []struct {
+	addr string
+	name string
+}{
+	{"8.8.8.8", ".google.com."},
+	{"8.8.4.4", ".google.com."},
+	{"2001:4860:4860::8888", ".google.com."},
+	{"2001:4860:4860::8844", ".google.com."},
+}
+
+func TestLookupGooglePublicDNSAddr(t *testing.T) {
+	if testing.Short() || !*testExternal {
+		t.Skip("skipping test to avoid external network")
+	}
+
+	for _, tt := range lookupGooglePublicDNSAddrs {
+		names, err := LookupAddr(tt.addr)
+		if err != nil {
+			t.Fatal(err)
+		}
+		if len(names) == 0 {
+			t.Error("got no record")
+		}
+		for _, name := range names {
+			if !strings.HasSuffix(name, tt.name) {
+				t.Errorf("got %q; want a record containing %q", name, tt.name)
+			}
+		}
+	}
+}
+
+func TestLookupIANACNAME(t *testing.T) {
+	if testing.Short() || !*testExternal {
+		t.Skip("skipping test to avoid external network")
+	}
+
+	cname, err := LookupCNAME("www.iana.org")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if !strings.HasSuffix(cname, ".icann.org.") {
+		t.Errorf("got %q; want a record containing .icann.org.", cname)
+	}
+}
+
+func TestLookupGoogleHost(t *testing.T) {
+	if testing.Short() || !*testExternal {
+		t.Skip("skipping test to avoid external network")
+	}
+
+	addrs, err := LookupHost("google.com")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(addrs) == 0 {
+		t.Error("got no record")
+	}
+	for _, addr := range addrs {
+		if ParseIP(addr) == nil {
+			t.Errorf("got %q; want a literal ip address", addr)
+		}
+	}
+}
+
+func TestLookupGoogleIP(t *testing.T) {
+	if testing.Short() || !*testExternal {
+		t.Skip("skipping test to avoid external network")
+	}
+
+	ips, err := LookupIP("google.com")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(ips) == 0 {
+		t.Error("got no record")
+	}
+	for _, ip := range ips {
+		if ip.To4() == nil && ip.To16() == nil {
+			t.Errorf("got %v; want an ip address", ip)
+		}
+	}
+}
+
+var revAddrTests = []struct {
+	Addr      string
+	Reverse   string
+	ErrPrefix string
+}{
+	{"1.2.3.4", "4.3.2.1.in-addr.arpa.", ""},
+	{"245.110.36.114", "114.36.110.245.in-addr.arpa.", ""},
+	{"::ffff:12.34.56.78", "78.56.34.12.in-addr.arpa.", ""},
+	{"::1", "1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.ip6.arpa.", ""},
+	{"1::", "0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.1.0.0.0.ip6.arpa.", ""},
+	{"1234:567::89a:bcde", "e.d.c.b.a.9.8.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.7.6.5.0.4.3.2.1.ip6.arpa.", ""},
+	{"1234:567:fefe:bcbc:adad:9e4a:89a:bcde", "e.d.c.b.a.9.8.0.a.4.e.9.d.a.d.a.c.b.c.b.e.f.e.f.7.6.5.0.4.3.2.1.ip6.arpa.", ""},
+	{"1.2.3", "", "unrecognized address"},
+	{"1.2.3.4.5", "", "unrecognized address"},
+	{"1234:567:bcbca::89a:bcde", "", "unrecognized address"},
+	{"1234:567::bcbc:adad::89a:bcde", "", "unrecognized address"},
+}
+
+func TestReverseAddress(t *testing.T) {
+	for i, tt := range revAddrTests {
+		a, err := reverseaddr(tt.Addr)
+		if len(tt.ErrPrefix) > 0 && err == nil {
+			t.Errorf("#%d: expected %q, got <nil> (error)", i, tt.ErrPrefix)
+			continue
+		}
+		if len(tt.ErrPrefix) == 0 && err != nil {
+			t.Errorf("#%d: expected <nil>, got %q (error)", i, err)
+		}
+		if err != nil && err.(*DNSError).Err != tt.ErrPrefix {
+			t.Errorf("#%d: expected %q, got %q (mismatched error)", i, tt.ErrPrefix, err.(*DNSError).Err)
+		}
+		if a != tt.Reverse {
+			t.Errorf("#%d: expected %q, got %q (reverse address)", i, tt.Reverse, a)
+		}
+	}
+}
diff --git a/src/net/lookup_unix.go b/src/net/lookup_unix.go
new file mode 100644
index 000000000..b1d2f8f31
--- /dev/null
+++ b/src/net/lookup_unix.go
@@ -0,0 +1,168 @@
+// Copyright 2011 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build darwin dragonfly freebsd linux nacl netbsd openbsd solaris
+
+package net
+
+import (
+	"errors"
+	"sync"
+)
+
+var onceReadProtocols sync.Once
+
+// readProtocols loads contents of /etc/protocols into protocols map
+// for quick access.
+func readProtocols() {
+	if file, err := open("/etc/protocols"); err == nil {
+		for line, ok := file.readLine(); ok; line, ok = file.readLine() {
+			// tcp    6   TCP    # transmission control protocol
+			if i := byteIndex(line, '#'); i >= 0 {
+				line = line[0:i]
+			}
+			f := getFields(line)
+			if len(f) < 2 {
+				continue
+			}
+			if proto, _, ok := dtoi(f[1], 0); ok {
+				if _, ok := protocols[f[0]]; !ok {
+					protocols[f[0]] = proto
+				}
+				for _, alias := range f[2:] {
+					if _, ok := protocols[alias]; !ok {
+						protocols[alias] = proto
+					}
+				}
+			}
+		}
+		file.close()
+	}
+}
+
+// lookupProtocol looks up IP protocol name in /etc/protocols and
+// returns correspondent protocol number.
+func lookupProtocol(name string) (proto int, err error) {
+	onceReadProtocols.Do(readProtocols)
+	proto, found := protocols[name]
+	if !found {
+		return 0, errors.New("unknown IP protocol specified: " + name)
+	}
+	return
+}
+
+func lookupHost(host string) (addrs []string, err error) {
+	addrs, err, ok := cgoLookupHost(host)
+	if !ok {
+		addrs, err = goLookupHost(host)
+	}
+	return
+}
+
+func lookupIP(host string) (addrs []IP, err error) {
+	addrs, err, ok := cgoLookupIP(host)
+	if !ok {
+		addrs, err = goLookupIP(host)
+	}
+	return
+}
+
+func lookupPort(network, service string) (port int, err error) {
+	port, err, ok := cgoLookupPort(network, service)
+	if !ok {
+		port, err = goLookupPort(network, service)
+	}
+	return
+}
+
+func lookupCNAME(name string) (cname string, err error) {
+	cname, err, ok := cgoLookupCNAME(name)
+	if !ok {
+		cname, err = goLookupCNAME(name)
+	}
+	return
+}
+
+func lookupSRV(service, proto, name string) (cname string, addrs []*SRV, err error) {
+	var target string
+	if service == "" && proto == "" {
+		target = name
+	} else {
+		target = "_" + service + "._" + proto + "." + name
+	}
+	var records []dnsRR
+	cname, records, err = lookup(target, dnsTypeSRV)
+	if err != nil {
+		return
+	}
+	addrs = make([]*SRV, len(records))
+	for i, rr := range records {
+		r := rr.(*dnsRR_SRV)
+		addrs[i] = &SRV{r.Target, r.Port, r.Priority, r.Weight}
+	}
+	byPriorityWeight(addrs).sort()
+	return
+}
+
+func lookupMX(name string) (mx []*MX, err error) {
+	_, records, err := lookup(name, dnsTypeMX)
+	if err != nil {
+		return
+	}
+	mx = make([]*MX, len(records))
+	for i, rr := range records {
+		r := rr.(*dnsRR_MX)
+		mx[i] = &MX{r.Mx, r.Pref}
+	}
+	byPref(mx).sort()
+	return
+}
+
+func lookupNS(name string) (ns []*NS, err error) {
+	_, records, err := lookup(name, dnsTypeNS)
+	if err != nil {
+		return
+	}
+	ns = make([]*NS, len(records))
+	for i, r := range records {
+		r := r.(*dnsRR_NS)
+		ns[i] = &NS{r.Ns}
+	}
+	return
+}
+
+func lookupTXT(name string) (txt []string, err error) {
+	_, records, err := lookup(name, dnsTypeTXT)
+	if err != nil {
+		return
+	}
+	txt = make([]string, len(records))
+	for i, r := range records {
+		txt[i] = r.(*dnsRR_TXT).Txt
+	}
+	return
+}
+
+func lookupAddr(addr string) (name []string, err error) {
+	name = lookupStaticAddr(addr)
+	if len(name) > 0 {
+		return
+	}
+	var arpa string
+	arpa, err = reverseaddr(addr)
+	if err != nil {
+		return
+	}
+	var records []dnsRR
+	_, records, err = lookup(arpa, dnsTypePTR)
+	if err != nil {
+		return
+	}
+	name = make([]string, len(records))
+	for i := range records {
+		r := records[i].(*dnsRR_PTR)
+		name[i] = r.Ptr
+	}
+	return
+}
diff --git a/src/net/lookup_windows.go b/src/net/lookup_windows.go
new file mode 100644
index 000000000..6a925b0a7
--- /dev/null
+++ b/src/net/lookup_windows.go
@@ -0,0 +1,381 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package net
+
+import (
+	"os"
+	"runtime"
+	"syscall"
+	"unsafe"
+)
+
+var (
+	lookupPort = oldLookupPort
+	lookupIP   = oldLookupIP
+)
+
+func getprotobyname(name string) (proto int, err error) {
+	p, err := syscall.GetProtoByName(name)
+	if err != nil {
+		return 0, os.NewSyscallError("GetProtoByName", err)
+	}
+	return int(p.Proto), nil
+}
+
+// lookupProtocol looks up IP protocol name and returns correspondent protocol number.
+func lookupProtocol(name string) (proto int, err error) {
+	// GetProtoByName return value is stored in thread local storage.
+	// Start new os thread before the call to prevent races.
+	type result struct {
+		proto int
+		err   error
+	}
+	ch := make(chan result)
+	go func() {
+		acquireThread()
+		defer releaseThread()
+		runtime.LockOSThread()
+		defer runtime.UnlockOSThread()
+		proto, err := getprotobyname(name)
+		ch <- result{proto: proto, err: err}
+	}()
+	r := <-ch
+	if r.err != nil {
+		if proto, ok := protocols[name]; ok {
+			return proto, nil
+		}
+	}
+	return r.proto, r.err
+}
+
+func lookupHost(name string) (addrs []string, err error) {
+	ips, err := LookupIP(name)
+	if err != nil {
+		return
+	}
+	addrs = make([]string, 0, len(ips))
+	for _, ip := range ips {
+		addrs = append(addrs, ip.String())
+	}
+	return
+}
+
+func gethostbyname(name string) (addrs []IP, err error) {
+	// caller already acquired thread
+	h, err := syscall.GetHostByName(name)
+	if err != nil {
+		return nil, os.NewSyscallError("GetHostByName", err)
+	}
+	switch h.AddrType {
+	case syscall.AF_INET:
+		i := 0
+		addrs = make([]IP, 100) // plenty of room to grow
+		for p := (*[100](*[4]byte))(unsafe.Pointer(h.AddrList)); i < cap(addrs) && p[i] != nil; i++ {
+			addrs[i] = IPv4(p[i][0], p[i][1], p[i][2], p[i][3])
+		}
+		addrs = addrs[0:i]
+	default: // TODO(vcc): Implement non IPv4 address lookups.
+		return nil, os.NewSyscallError("LookupIP", syscall.EWINDOWS)
+	}
+	return addrs, nil
+}
+
+func oldLookupIP(name string) (addrs []IP, err error) {
+	// GetHostByName return value is stored in thread local storage.
+	// Start new os thread before the call to prevent races.
+	type result struct {
+		addrs []IP
+		err   error
+	}
+	ch := make(chan result)
+	go func() {
+		acquireThread()
+		defer releaseThread()
+		runtime.LockOSThread()
+		defer runtime.UnlockOSThread()
+		addrs, err := gethostbyname(name)
+		ch <- result{addrs: addrs, err: err}
+	}()
+	r := <-ch
+	return r.addrs, r.err
+}
+
+func newLookupIP(name string) (addrs []IP, err error) {
+	acquireThread()
+	defer releaseThread()
+	hints := syscall.AddrinfoW{
+		Family:   syscall.AF_UNSPEC,
+		Socktype: syscall.SOCK_STREAM,
+		Protocol: syscall.IPPROTO_IP,
+	}
+	var result *syscall.AddrinfoW
+	e := syscall.GetAddrInfoW(syscall.StringToUTF16Ptr(name), nil, &hints, &result)
+	if e != nil {
+		return nil, os.NewSyscallError("GetAddrInfoW", e)
+	}
+	defer syscall.FreeAddrInfoW(result)
+	addrs = make([]IP, 0, 5)
+	for ; result != nil; result = result.Next {
+		addr := unsafe.Pointer(result.Addr)
+		switch result.Family {
+		case syscall.AF_INET:
+			a := (*syscall.RawSockaddrInet4)(addr).Addr
+			addrs = append(addrs, IPv4(a[0], a[1], a[2], a[3]))
+		case syscall.AF_INET6:
+			a := (*syscall.RawSockaddrInet6)(addr).Addr
+			addrs = append(addrs, IP{a[0], a[1], a[2], a[3], a[4], a[5], a[6], a[7], a[8], a[9], a[10], a[11], a[12], a[13], a[14], a[15]})
+		default:
+			return nil, os.NewSyscallError("LookupIP", syscall.EWINDOWS)
+		}
+	}
+	return addrs, nil
+}
+
+func getservbyname(network, service string) (port int, err error) {
+	acquireThread()
+	defer releaseThread()
+	switch network {
+	case "tcp4", "tcp6":
+		network = "tcp"
+	case "udp4", "udp6":
+		network = "udp"
+	}
+	s, err := syscall.GetServByName(service, network)
+	if err != nil {
+		return 0, os.NewSyscallError("GetServByName", err)
+	}
+	return int(syscall.Ntohs(s.Port)), nil
+}
+
+func oldLookupPort(network, service string) (port int, err error) {
+	// GetServByName return value is stored in thread local storage.
+	// Start new os thread before the call to prevent races.
+	type result struct {
+		port int
+		err  error
+	}
+	ch := make(chan result)
+	go func() {
+		acquireThread()
+		defer releaseThread()
+		runtime.LockOSThread()
+		defer runtime.UnlockOSThread()
+		port, err := getservbyname(network, service)
+		ch <- result{port: port, err: err}
+	}()
+	r := <-ch
+	return r.port, r.err
+}
+
+func newLookupPort(network, service string) (port int, err error) {
+	acquireThread()
+	defer releaseThread()
+	var stype int32
+	switch network {
+	case "tcp4", "tcp6":
+		stype = syscall.SOCK_STREAM
+	case "udp4", "udp6":
+		stype = syscall.SOCK_DGRAM
+	}
+	hints := syscall.AddrinfoW{
+		Family:   syscall.AF_UNSPEC,
+		Socktype: stype,
+		Protocol: syscall.IPPROTO_IP,
+	}
+	var result *syscall.AddrinfoW
+	e := syscall.GetAddrInfoW(nil, syscall.StringToUTF16Ptr(service), &hints, &result)
+	if e != nil {
+		return 0, os.NewSyscallError("GetAddrInfoW", e)
+	}
+	defer syscall.FreeAddrInfoW(result)
+	if result == nil {
+		return 0, os.NewSyscallError("LookupPort", syscall.EINVAL)
+	}
+	addr := unsafe.Pointer(result.Addr)
+	switch result.Family {
+	case syscall.AF_INET:
+		a := (*syscall.RawSockaddrInet4)(addr)
+		return int(syscall.Ntohs(a.Port)), nil
+	case syscall.AF_INET6:
+		a := (*syscall.RawSockaddrInet6)(addr)
+		return int(syscall.Ntohs(a.Port)), nil
+	}
+	return 0, os.NewSyscallError("LookupPort", syscall.EINVAL)
+}
+
+func lookupCNAME(name string) (cname string, err error) {
+	acquireThread()
+	defer releaseThread()
+	var r *syscall.DNSRecord
+	e := syscall.DnsQuery(name, syscall.DNS_TYPE_CNAME, 0, nil, &r, nil)
+	// windows returns DNS_INFO_NO_RECORDS if there are no CNAME-s
+	if errno, ok := e.(syscall.Errno); ok && errno == syscall.DNS_INFO_NO_RECORDS {
+		// if there are no aliases, the canonical name is the input name
+		if name == "" || name[len(name)-1] != '.' {
+			return name + ".", nil
+		}
+		return name, nil
+	}
+	if e != nil {
+		return "", os.NewSyscallError("LookupCNAME", e)
+	}
+	defer syscall.DnsRecordListFree(r, 1)
+
+	resolved := resolveCNAME(syscall.StringToUTF16Ptr(name), r)
+	cname = syscall.UTF16ToString((*[256]uint16)(unsafe.Pointer(resolved))[:]) + "."
+	return
+}
+
+func lookupSRV(service, proto, name string) (cname string, addrs []*SRV, err error) {
+	acquireThread()
+	defer releaseThread()
+	var target string
+	if service == "" && proto == "" {
+		target = name
+	} else {
+		target = "_" + service + "._" + proto + "." + name
+	}
+	var r *syscall.DNSRecord
+	e := syscall.DnsQuery(target, syscall.DNS_TYPE_SRV, 0, nil, &r, nil)
+	if e != nil {
+		return "", nil, os.NewSyscallError("LookupSRV", e)
+	}
+	defer syscall.DnsRecordListFree(r, 1)
+
+	addrs = make([]*SRV, 0, 10)
+	for _, p := range validRecs(r, syscall.DNS_TYPE_SRV, target) {
+		v := (*syscall.DNSSRVData)(unsafe.Pointer(&p.Data[0]))
+		addrs = append(addrs, &SRV{syscall.UTF16ToString((*[256]uint16)(unsafe.Pointer(v.Target))[:]), v.Port, v.Priority, v.Weight})
+	}
+	byPriorityWeight(addrs).sort()
+	return name, addrs, nil
+}
+
+func lookupMX(name string) (mx []*MX, err error) {
+	acquireThread()
+	defer releaseThread()
+	var r *syscall.DNSRecord
+	e := syscall.DnsQuery(name, syscall.DNS_TYPE_MX, 0, nil, &r, nil)
+	if e != nil {
+		return nil, os.NewSyscallError("LookupMX", e)
+	}
+	defer syscall.DnsRecordListFree(r, 1)
+
+	mx = make([]*MX, 0, 10)
+	for _, p := range validRecs(r, syscall.DNS_TYPE_MX, name) {
+		v := (*syscall.DNSMXData)(unsafe.Pointer(&p.Data[0]))
+		mx = append(mx, &MX{syscall.UTF16ToString((*[256]uint16)(unsafe.Pointer(v.NameExchange))[:]) + ".", v.Preference})
+	}
+	byPref(mx).sort()
+	return mx, nil
+}
+
+func lookupNS(name string) (ns []*NS, err error) {
+	acquireThread()
+	defer releaseThread()
+	var r *syscall.DNSRecord
+	e := syscall.DnsQuery(name, syscall.DNS_TYPE_NS, 0, nil, &r, nil)
+	if e != nil {
+		return nil, os.NewSyscallError("LookupNS", e)
+	}
+	defer syscall.DnsRecordListFree(r, 1)
+
+	ns = make([]*NS, 0, 10)
+	for _, p := range validRecs(r, syscall.DNS_TYPE_NS, name) {
+		v := (*syscall.DNSPTRData)(unsafe.Pointer(&p.Data[0]))
+		ns = append(ns, &NS{syscall.UTF16ToString((*[256]uint16)(unsafe.Pointer(v.Host))[:]) + "."})
+	}
+	return ns, nil
+}
+
+func lookupTXT(name string) (txt []string, err error) {
+	acquireThread()
+	defer releaseThread()
+	var r *syscall.DNSRecord
+	e := syscall.DnsQuery(name, syscall.DNS_TYPE_TEXT, 0, nil, &r, nil)
+	if e != nil {
+		return nil, os.NewSyscallError("LookupTXT", e)
+	}
+	defer syscall.DnsRecordListFree(r, 1)
+
+	txt = make([]string, 0, 10)
+	for _, p := range validRecs(r, syscall.DNS_TYPE_TEXT, name) {
+		d := (*syscall.DNSTXTData)(unsafe.Pointer(&p.Data[0]))
+		for _, v := range (*[1 << 10]*uint16)(unsafe.Pointer(&(d.StringArray[0])))[:d.StringCount] {
+			s := syscall.UTF16ToString((*[1 << 20]uint16)(unsafe.Pointer(v))[:])
+			txt = append(txt, s)
+		}
+	}
+	return
+}
+
+func lookupAddr(addr string) (name []string, err error) {
+	acquireThread()
+	defer releaseThread()
+	arpa, err := reverseaddr(addr)
+	if err != nil {
+		return nil, err
+	}
+	var r *syscall.DNSRecord
+	e := syscall.DnsQuery(arpa, syscall.DNS_TYPE_PTR, 0, nil, &r, nil)
+	if e != nil {
+		return nil, os.NewSyscallError("LookupAddr", e)
+	}
+	defer syscall.DnsRecordListFree(r, 1)
+
+	name = make([]string, 0, 10)
+	for _, p := range validRecs(r, syscall.DNS_TYPE_PTR, arpa) {
+		v := (*syscall.DNSPTRData)(unsafe.Pointer(&p.Data[0]))
+		name = append(name, syscall.UTF16ToString((*[256]uint16)(unsafe.Pointer(v.Host))[:]))
+	}
+	return name, nil
+}
+
+const dnsSectionMask = 0x0003
+
+// returns only results applicable to name and resolves CNAME entries
+func validRecs(r *syscall.DNSRecord, dnstype uint16, name string) []*syscall.DNSRecord {
+	cname := syscall.StringToUTF16Ptr(name)
+	if dnstype != syscall.DNS_TYPE_CNAME {
+		cname = resolveCNAME(cname, r)
+	}
+	rec := make([]*syscall.DNSRecord, 0, 10)
+	for p := r; p != nil; p = p.Next {
+		if p.Dw&dnsSectionMask != syscall.DnsSectionAnswer {
+			continue
+		}
+		if p.Type != dnstype {
+			continue
+		}
+		if !syscall.DnsNameCompare(cname, p.Name) {
+			continue
+		}
+		rec = append(rec, p)
+	}
+	return rec
+}
+
+// returns the last CNAME in chain
+func resolveCNAME(name *uint16, r *syscall.DNSRecord) *uint16 {
+	// limit cname resolving to 10 in case of a infinite CNAME loop
+Cname:
+	for cnameloop := 0; cnameloop < 10; cnameloop++ {
+		for p := r; p != nil; p = p.Next {
+			if p.Dw&dnsSectionMask != syscall.DnsSectionAnswer {
+				continue
+			}
+			if p.Type != syscall.DNS_TYPE_CNAME {
+				continue
+			}
+			if !syscall.DnsNameCompare(name, p.Name) {
+				continue
+			}
+			name = (*syscall.DNSPTRData)(unsafe.Pointer(&r.Data[0])).Host
+			continue Cname
+		}
+		break
+	}
+	return name
+}
diff --git a/src/net/lookup_windows_test.go b/src/net/lookup_windows_test.go
new file mode 100644
index 000000000..7495b5b57
--- /dev/null
+++ b/src/net/lookup_windows_test.go
@@ -0,0 +1,243 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package net
+
+import (
+	"bytes"
+	"encoding/json"
+	"errors"
+	"os/exec"
+	"reflect"
+	"regexp"
+	"sort"
+	"strconv"
+	"strings"
+	"testing"
+)
+
+var nslookupTestServers = []string{"mail.golang.com", "gmail.com"}
+
+func toJson(v interface{}) string {
+	data, _ := json.Marshal(v)
+	return string(data)
+}
+
+func TestLookupMX(t *testing.T) {
+	if testing.Short() || !*testExternal {
+		t.Skip("skipping test to avoid external network")
+	}
+	for _, server := range nslookupTestServers {
+		mx, err := LookupMX(server)
+		if err != nil {
+			t.Errorf("failed %s: %s", server, err)
+			continue
+		}
+		if len(mx) == 0 {
+			t.Errorf("no results")
+			continue
+		}
+		expected, err := nslookupMX(server)
+		if err != nil {
+			t.Logf("skipping failed nslookup %s test: %s", server, err)
+		}
+		sort.Sort(byPrefAndHost(expected))
+		sort.Sort(byPrefAndHost(mx))
+		if !reflect.DeepEqual(expected, mx) {
+			t.Errorf("different results %s:\texp:%v\tgot:%v", server, toJson(expected), toJson(mx))
+		}
+	}
+}
+
+func TestLookupCNAME(t *testing.T) {
+	if testing.Short() || !*testExternal {
+		t.Skip("skipping test to avoid external network")
+	}
+	for _, server := range nslookupTestServers {
+		cname, err := LookupCNAME(server)
+		if err != nil {
+			t.Errorf("failed %s: %s", server, err)
+			continue
+		}
+		if cname == "" {
+			t.Errorf("no result %s", server)
+		}
+		expected, err := nslookupCNAME(server)
+		if err != nil {
+			t.Logf("skipping failed nslookup %s test: %s", server, err)
+			continue
+		}
+		if expected != cname {
+			t.Errorf("different results %s:\texp:%v\tgot:%v", server, expected, cname)
+		}
+	}
+}
+
+func TestLookupNS(t *testing.T) {
+	if testing.Short() || !*testExternal {
+		t.Skip("skipping test to avoid external network")
+	}
+	for _, server := range nslookupTestServers {
+		ns, err := LookupNS(server)
+		if err != nil {
+			t.Errorf("failed %s: %s", server, err)
+			continue
+		}
+		if len(ns) == 0 {
+			t.Errorf("no results")
+			continue
+		}
+		expected, err := nslookupNS(server)
+		if err != nil {
+			t.Logf("skipping failed nslookup %s test: %s", server, err)
+			continue
+		}
+		sort.Sort(byHost(expected))
+		sort.Sort(byHost(ns))
+		if !reflect.DeepEqual(expected, ns) {
+			t.Errorf("different results %s:\texp:%v\tgot:%v", toJson(server), toJson(expected), ns)
+		}
+	}
+}
+
+func TestLookupTXT(t *testing.T) {
+	if testing.Short() || !*testExternal {
+		t.Skip("skipping test to avoid external network")
+	}
+	for _, server := range nslookupTestServers {
+		txt, err := LookupTXT(server)
+		if err != nil {
+			t.Errorf("failed %s: %s", server, err)
+			continue
+		}
+		if len(txt) == 0 {
+			t.Errorf("no results")
+			continue
+		}
+		expected, err := nslookupTXT(server)
+		if err != nil {
+			t.Logf("skipping failed nslookup %s test: %s", server, err)
+			continue
+		}
+		sort.Strings(expected)
+		sort.Strings(txt)
+		if !reflect.DeepEqual(expected, txt) {
+			t.Errorf("different results %s:\texp:%v\tgot:%v", server, toJson(expected), toJson(txt))
+		}
+	}
+}
+
+type byPrefAndHost []*MX
+
+func (s byPrefAndHost) Len() int { return len(s) }
+func (s byPrefAndHost) Less(i, j int) bool {
+	if s[i].Pref != s[j].Pref {
+		return s[i].Pref < s[j].Pref
+	}
+	return s[i].Host < s[j].Host
+}
+func (s byPrefAndHost) Swap(i, j int) { s[i], s[j] = s[j], s[i] }
+
+type byHost []*NS
+
+func (s byHost) Len() int           { return len(s) }
+func (s byHost) Less(i, j int) bool { return s[i].Host < s[j].Host }
+func (s byHost) Swap(i, j int)      { s[i], s[j] = s[j], s[i] }
+
+func fqdn(s string) string {
+	if len(s) == 0 || s[len(s)-1] != '.' {
+		return s + "."
+	}
+	return s
+}
+
+func nslookup(qtype, name string) (string, error) {
+	var out bytes.Buffer
+	var err bytes.Buffer
+	cmd := exec.Command("nslookup", "-querytype="+qtype, name)
+	cmd.Stdout = &out
+	cmd.Stderr = &err
+	if err := cmd.Run(); err != nil {
+		return "", err
+	}
+	r := strings.Replace(out.String(), "\r\n", "\n", -1)
+	// nslookup stderr output contains also debug information such as
+	// "Non-authoritative answer" and it doesn't return the correct errcode
+	if strings.Contains(err.String(), "can't find") {
+		return r, errors.New(err.String())
+	}
+	return r, nil
+}
+
+func nslookupMX(name string) (mx []*MX, err error) {
+	var r string
+	if r, err = nslookup("mx", name); err != nil {
+		return
+	}
+	mx = make([]*MX, 0, 10)
+	// linux nslookup syntax
+	// golang.org      mail exchanger = 2 alt1.aspmx.l.google.com.
+	rx := regexp.MustCompile(`(?m)^([a-z0-9.\-]+)\s+mail exchanger\s*=\s*([0-9]+)\s*([a-z0-9.\-]+)$`)
+	for _, ans := range rx.FindAllStringSubmatch(r, -1) {
+		pref, _ := strconv.Atoi(ans[2])
+		mx = append(mx, &MX{fqdn(ans[3]), uint16(pref)})
+	}
+	// windows nslookup syntax
+	// gmail.com       MX preference = 30, mail exchanger = alt3.gmail-smtp-in.l.google.com
+	rx = regexp.MustCompile(`(?m)^([a-z0-9.\-]+)\s+MX preference\s*=\s*([0-9]+)\s*,\s*mail exchanger\s*=\s*([a-z0-9.\-]+)$`)
+	for _, ans := range rx.FindAllStringSubmatch(r, -1) {
+		pref, _ := strconv.Atoi(ans[2])
+		mx = append(mx, &MX{fqdn(ans[3]), uint16(pref)})
+	}
+	return
+}
+
+func nslookupNS(name string) (ns []*NS, err error) {
+	var r string
+	if r, err = nslookup("ns", name); err != nil {
+		return
+	}
+	ns = make([]*NS, 0, 10)
+	// golang.org      nameserver = ns1.google.com.
+	rx := regexp.MustCompile(`(?m)^([a-z0-9.\-]+)\s+nameserver\s*=\s*([a-z0-9.\-]+)$`)
+	for _, ans := range rx.FindAllStringSubmatch(r, -1) {
+		ns = append(ns, &NS{fqdn(ans[2])})
+	}
+	return
+}
+
+func nslookupCNAME(name string) (cname string, err error) {
+	var r string
+	if r, err = nslookup("cname", name); err != nil {
+		return
+	}
+	// mail.golang.com canonical name = golang.org.
+	rx := regexp.MustCompile(`(?m)^([a-z0-9.\-]+)\s+canonical name\s*=\s*([a-z0-9.\-]+)$`)
+	// assumes the last CNAME is the correct one
+	last := name
+	for _, ans := range rx.FindAllStringSubmatch(r, -1) {
+		last = ans[2]
+	}
+	return fqdn(last), nil
+}
+
+func nslookupTXT(name string) (txt []string, err error) {
+	var r string
+	if r, err = nslookup("txt", name); err != nil {
+		return
+	}
+	txt = make([]string, 0, 10)
+	// linux
+	// golang.org      text = "v=spf1 redirect=_spf.google.com"
+
+	// windows
+	// golang.org      text =
+	//
+	//    "v=spf1 redirect=_spf.google.com"
+	rx := regexp.MustCompile(`(?m)^([a-z0-9.\-]+)\s+text\s*=\s*"(.*)"$`)
+	for _, ans := range rx.FindAllStringSubmatch(r, -1) {
+		txt = append(txt, ans[2])
+	}
+	return
+}
diff --git a/src/net/mac.go b/src/net/mac.go
new file mode 100644
index 000000000..d616b1f68
--- /dev/null
+++ b/src/net/mac.go
@@ -0,0 +1,86 @@
+// Copyright 2011 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// MAC address manipulations
+
+package net
+
+import "errors"
+
+const hexDigit = "0123456789abcdef"
+
+// A HardwareAddr represents a physical hardware address.
+type HardwareAddr []byte
+
+func (a HardwareAddr) String() string {
+	if len(a) == 0 {
+		return ""
+	}
+	buf := make([]byte, 0, len(a)*3-1)
+	for i, b := range a {
+		if i > 0 {
+			buf = append(buf, ':')
+		}
+		buf = append(buf, hexDigit[b>>4])
+		buf = append(buf, hexDigit[b&0xF])
+	}
+	return string(buf)
+}
+
+// ParseMAC parses s as an IEEE 802 MAC-48, EUI-48, or EUI-64 using one of the
+// following formats:
+//   01:23:45:67:89:ab
+//   01:23:45:67:89:ab:cd:ef
+//   01-23-45-67-89-ab
+//   01-23-45-67-89-ab-cd-ef
+//   0123.4567.89ab
+//   0123.4567.89ab.cdef
+func ParseMAC(s string) (hw HardwareAddr, err error) {
+	if len(s) < 14 {
+		goto error
+	}
+
+	if s[2] == ':' || s[2] == '-' {
+		if (len(s)+1)%3 != 0 {
+			goto error
+		}
+		n := (len(s) + 1) / 3
+		if n != 6 && n != 8 {
+			goto error
+		}
+		hw = make(HardwareAddr, n)
+		for x, i := 0, 0; i < n; i++ {
+			var ok bool
+			if hw[i], ok = xtoi2(s[x:], s[2]); !ok {
+				goto error
+			}
+			x += 3
+		}
+	} else if s[4] == '.' {
+		if (len(s)+1)%5 != 0 {
+			goto error
+		}
+		n := 2 * (len(s) + 1) / 5
+		if n != 6 && n != 8 {
+			goto error
+		}
+		hw = make(HardwareAddr, n)
+		for x, i := 0, 0; i < n; i += 2 {
+			var ok bool
+			if hw[i], ok = xtoi2(s[x:x+2], 0); !ok {
+				goto error
+			}
+			if hw[i+1], ok = xtoi2(s[x+2:], s[4]); !ok {
+				goto error
+			}
+			x += 5
+		}
+	} else {
+		goto error
+	}
+	return hw, nil
+
+error:
+	return nil, errors.New("invalid MAC address: " + s)
+}
diff --git a/src/net/mac_test.go b/src/net/mac_test.go
new file mode 100644
index 000000000..8f9dc6685
--- /dev/null
+++ b/src/net/mac_test.go
@@ -0,0 +1,66 @@
+// Copyright 2011 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package net
+
+import (
+	"reflect"
+	"strings"
+	"testing"
+)
+
+var mactests = []struct {
+	in  string
+	out HardwareAddr
+	err string
+}{
+	{"01:23:45:67:89:AB", HardwareAddr{1, 0x23, 0x45, 0x67, 0x89, 0xab}, ""},
+	{"01-23-45-67-89-AB", HardwareAddr{1, 0x23, 0x45, 0x67, 0x89, 0xab}, ""},
+	{"0123.4567.89AB", HardwareAddr{1, 0x23, 0x45, 0x67, 0x89, 0xab}, ""},
+	{"ab:cd:ef:AB:CD:EF", HardwareAddr{0xab, 0xcd, 0xef, 0xab, 0xcd, 0xef}, ""},
+	{"01.02.03.04.05.06", nil, "invalid MAC address"},
+	{"01:02:03:04:05:06:", nil, "invalid MAC address"},
+	{"x1:02:03:04:05:06", nil, "invalid MAC address"},
+	{"01002:03:04:05:06", nil, "invalid MAC address"},
+	{"01:02003:04:05:06", nil, "invalid MAC address"},
+	{"01:02:03004:05:06", nil, "invalid MAC address"},
+	{"01:02:03:04005:06", nil, "invalid MAC address"},
+	{"01:02:03:04:05006", nil, "invalid MAC address"},
+	{"01-02:03:04:05:06", nil, "invalid MAC address"},
+	{"01:02-03-04-05-06", nil, "invalid MAC address"},
+	{"0123:4567:89AF", nil, "invalid MAC address"},
+	{"0123-4567-89AF", nil, "invalid MAC address"},
+	{"01:23:45:67:89:AB:CD:EF", HardwareAddr{1, 0x23, 0x45, 0x67, 0x89, 0xab, 0xcd, 0xef}, ""},
+	{"01-23-45-67-89-AB-CD-EF", HardwareAddr{1, 0x23, 0x45, 0x67, 0x89, 0xab, 0xcd, 0xef}, ""},
+	{"0123.4567.89AB.CDEF", HardwareAddr{1, 0x23, 0x45, 0x67, 0x89, 0xab, 0xcd, 0xef}, ""},
+}
+
+func match(err error, s string) bool {
+	if s == "" {
+		return err == nil
+	}
+	return err != nil && strings.Contains(err.Error(), s)
+}
+
+func TestMACParseString(t *testing.T) {
+	for i, tt := range mactests {
+		out, err := ParseMAC(tt.in)
+		if !reflect.DeepEqual(out, tt.out) || !match(err, tt.err) {
+			t.Errorf("ParseMAC(%q) = %v, %v, want %v, %v", tt.in, out, err, tt.out,
+				tt.err)
+		}
+		if tt.err == "" {
+			// Verify that serialization works too, and that it round-trips.
+			s := out.String()
+			out2, err := ParseMAC(s)
+			if err != nil {
+				t.Errorf("%d. ParseMAC(%q) = %v", i, s, err)
+				continue
+			}
+			if !reflect.DeepEqual(out2, out) {
+				t.Errorf("%d. ParseMAC(%q) = %v, want %v", i, s, out2, out)
+			}
+		}
+	}
+}
diff --git a/src/net/mail/message.go b/src/net/mail/message.go
new file mode 100644
index 000000000..ba0778caa
--- /dev/null
+++ b/src/net/mail/message.go
@@ -0,0 +1,545 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+/*
+Package mail implements parsing of mail messages.
+
+For the most part, this package follows the syntax as specified by RFC 5322.
+Notable divergences:
+	* Obsolete address formats are not parsed, including addresses with
+	  embedded route information.
+	* Group addresses are not parsed.
+	* The full range of spacing (the CFWS syntax element) is not supported,
+	  such as breaking addresses across lines.
+*/
+package mail
+
+import (
+	"bufio"
+	"bytes"
+	"encoding/base64"
+	"errors"
+	"fmt"
+	"io"
+	"io/ioutil"
+	"log"
+	"net/textproto"
+	"strconv"
+	"strings"
+	"time"
+)
+
+var debug = debugT(false)
+
+type debugT bool
+
+func (d debugT) Printf(format string, args ...interface{}) {
+	if d {
+		log.Printf(format, args...)
+	}
+}
+
+// A Message represents a parsed mail message.
+type Message struct {
+	Header Header
+	Body   io.Reader
+}
+
+// ReadMessage reads a message from r.
+// The headers are parsed, and the body of the message will be available
+// for reading from r.
+func ReadMessage(r io.Reader) (msg *Message, err error) {
+	tp := textproto.NewReader(bufio.NewReader(r))
+
+	hdr, err := tp.ReadMIMEHeader()
+	if err != nil {
+		return nil, err
+	}
+
+	return &Message{
+		Header: Header(hdr),
+		Body:   tp.R,
+	}, nil
+}
+
+// Layouts suitable for passing to time.Parse.
+// These are tried in order.
+var dateLayouts []string
+
+func init() {
+	// Generate layouts based on RFC 5322, section 3.3.
+
+	dows := [...]string{"", "Mon, "}   // day-of-week
+	days := [...]string{"2", "02"}     // day = 1*2DIGIT
+	years := [...]string{"2006", "06"} // year = 4*DIGIT / 2*DIGIT
+	seconds := [...]string{":05", ""}  // second
+	// "-0700 (MST)" is not in RFC 5322, but is common.
+	zones := [...]string{"-0700", "MST", "-0700 (MST)"} // zone = (("+" / "-") 4DIGIT) / "GMT" / ...
+
+	for _, dow := range dows {
+		for _, day := range days {
+			for _, year := range years {
+				for _, second := range seconds {
+					for _, zone := range zones {
+						s := dow + day + " Jan " + year + " 15:04" + second + " " + zone
+						dateLayouts = append(dateLayouts, s)
+					}
+				}
+			}
+		}
+	}
+}
+
+func parseDate(date string) (time.Time, error) {
+	for _, layout := range dateLayouts {
+		t, err := time.Parse(layout, date)
+		if err == nil {
+			return t, nil
+		}
+	}
+	return time.Time{}, errors.New("mail: header could not be parsed")
+}
+
+// A Header represents the key-value pairs in a mail message header.
+type Header map[string][]string
+
+// Get gets the first value associated with the given key.
+// If there are no values associated with the key, Get returns "".
+func (h Header) Get(key string) string {
+	return textproto.MIMEHeader(h).Get(key)
+}
+
+var ErrHeaderNotPresent = errors.New("mail: header not in message")
+
+// Date parses the Date header field.
+func (h Header) Date() (time.Time, error) {
+	hdr := h.Get("Date")
+	if hdr == "" {
+		return time.Time{}, ErrHeaderNotPresent
+	}
+	return parseDate(hdr)
+}
+
+// AddressList parses the named header field as a list of addresses.
+func (h Header) AddressList(key string) ([]*Address, error) {
+	hdr := h.Get(key)
+	if hdr == "" {
+		return nil, ErrHeaderNotPresent
+	}
+	return ParseAddressList(hdr)
+}
+
+// Address represents a single mail address.
+// An address such as "Barry Gibbs <bg@example.com>" is represented
+// as Address{Name: "Barry Gibbs", Address: "bg@example.com"}.
+type Address struct {
+	Name    string // Proper name; may be empty.
+	Address string // user@domain
+}
+
+// Parses a single RFC 5322 address, e.g. "Barry Gibbs <bg@example.com>"
+func ParseAddress(address string) (*Address, error) {
+	return newAddrParser(address).parseAddress()
+}
+
+// ParseAddressList parses the given string as a list of addresses.
+func ParseAddressList(list string) ([]*Address, error) {
+	return newAddrParser(list).parseAddressList()
+}
+
+// String formats the address as a valid RFC 5322 address.
+// If the address's name contains non-ASCII characters
+// the name will be rendered according to RFC 2047.
+func (a *Address) String() string {
+	s := "<" + a.Address + ">"
+	if a.Name == "" {
+		return s
+	}
+	// If every character is printable ASCII, quoting is simple.
+	allPrintable := true
+	for i := 0; i < len(a.Name); i++ {
+		// isWSP here should actually be isFWS,
+		// but we don't support folding yet.
+		if !isVchar(a.Name[i]) && !isWSP(a.Name[i]) {
+			allPrintable = false
+			break
+		}
+	}
+	if allPrintable {
+		b := bytes.NewBufferString(`"`)
+		for i := 0; i < len(a.Name); i++ {
+			if !isQtext(a.Name[i]) && !isWSP(a.Name[i]) {
+				b.WriteByte('\\')
+			}
+			b.WriteByte(a.Name[i])
+		}
+		b.WriteString(`" `)
+		b.WriteString(s)
+		return b.String()
+	}
+
+	// UTF-8 "Q" encoding
+	b := bytes.NewBufferString("=?utf-8?q?")
+	for i := 0; i < len(a.Name); i++ {
+		switch c := a.Name[i]; {
+		case c == ' ':
+			b.WriteByte('_')
+		case isVchar(c) && c != '=' && c != '?' && c != '_':
+			b.WriteByte(c)
+		default:
+			fmt.Fprintf(b, "=%02X", c)
+		}
+	}
+	b.WriteString("?= ")
+	b.WriteString(s)
+	return b.String()
+}
+
+type addrParser []byte
+
+func newAddrParser(s string) *addrParser {
+	p := addrParser(s)
+	return &p
+}
+
+func (p *addrParser) parseAddressList() ([]*Address, error) {
+	var list []*Address
+	for {
+		p.skipSpace()
+		addr, err := p.parseAddress()
+		if err != nil {
+			return nil, err
+		}
+		list = append(list, addr)
+
+		p.skipSpace()
+		if p.empty() {
+			break
+		}
+		if !p.consume(',') {
+			return nil, errors.New("mail: expected comma")
+		}
+	}
+	return list, nil
+}
+
+// parseAddress parses a single RFC 5322 address at the start of p.
+func (p *addrParser) parseAddress() (addr *Address, err error) {
+	debug.Printf("parseAddress: %q", *p)
+	p.skipSpace()
+	if p.empty() {
+		return nil, errors.New("mail: no address")
+	}
+
+	// address = name-addr / addr-spec
+	// TODO(dsymonds): Support parsing group address.
+
+	// addr-spec has a more restricted grammar than name-addr,
+	// so try parsing it first, and fallback to name-addr.
+	// TODO(dsymonds): Is this really correct?
+	spec, err := p.consumeAddrSpec()
+	if err == nil {
+		return &Address{
+			Address: spec,
+		}, err
+	}
+	debug.Printf("parseAddress: not an addr-spec: %v", err)
+	debug.Printf("parseAddress: state is now %q", *p)
+
+	// display-name
+	var displayName string
+	if p.peek() != '<' {
+		displayName, err = p.consumePhrase()
+		if err != nil {
+			return nil, err
+		}
+	}
+	debug.Printf("parseAddress: displayName=%q", displayName)
+
+	// angle-addr = "<" addr-spec ">"
+	p.skipSpace()
+	if !p.consume('<') {
+		return nil, errors.New("mail: no angle-addr")
+	}
+	spec, err = p.consumeAddrSpec()
+	if err != nil {
+		return nil, err
+	}
+	if !p.consume('>') {
+		return nil, errors.New("mail: unclosed angle-addr")
+	}
+	debug.Printf("parseAddress: spec=%q", spec)
+
+	return &Address{
+		Name:    displayName,
+		Address: spec,
+	}, nil
+}
+
+// consumeAddrSpec parses a single RFC 5322 addr-spec at the start of p.
+func (p *addrParser) consumeAddrSpec() (spec string, err error) {
+	debug.Printf("consumeAddrSpec: %q", *p)
+
+	orig := *p
+	defer func() {
+		if err != nil {
+			*p = orig
+		}
+	}()
+
+	// local-part = dot-atom / quoted-string
+	var localPart string
+	p.skipSpace()
+	if p.empty() {
+		return "", errors.New("mail: no addr-spec")
+	}
+	if p.peek() == '"' {
+		// quoted-string
+		debug.Printf("consumeAddrSpec: parsing quoted-string")
+		localPart, err = p.consumeQuotedString()
+	} else {
+		// dot-atom
+		debug.Printf("consumeAddrSpec: parsing dot-atom")
+		localPart, err = p.consumeAtom(true)
+	}
+	if err != nil {
+		debug.Printf("consumeAddrSpec: failed: %v", err)
+		return "", err
+	}
+
+	if !p.consume('@') {
+		return "", errors.New("mail: missing @ in addr-spec")
+	}
+
+	// domain = dot-atom / domain-literal
+	var domain string
+	p.skipSpace()
+	if p.empty() {
+		return "", errors.New("mail: no domain in addr-spec")
+	}
+	// TODO(dsymonds): Handle domain-literal
+	domain, err = p.consumeAtom(true)
+	if err != nil {
+		return "", err
+	}
+
+	return localPart + "@" + domain, nil
+}
+
+// consumePhrase parses the RFC 5322 phrase at the start of p.
+func (p *addrParser) consumePhrase() (phrase string, err error) {
+	debug.Printf("consumePhrase: [%s]", *p)
+	// phrase = 1*word
+	var words []string
+	for {
+		// word = atom / quoted-string
+		var word string
+		p.skipSpace()
+		if p.empty() {
+			return "", errors.New("mail: missing phrase")
+		}
+		if p.peek() == '"' {
+			// quoted-string
+			word, err = p.consumeQuotedString()
+		} else {
+			// atom
+			// We actually parse dot-atom here to be more permissive
+			// than what RFC 5322 specifies.
+			word, err = p.consumeAtom(true)
+		}
+
+		// RFC 2047 encoded-word starts with =?, ends with ?=, and has two other ?s.
+		if err == nil && strings.HasPrefix(word, "=?") && strings.HasSuffix(word, "?=") && strings.Count(word, "?") == 4 {
+			word, err = decodeRFC2047Word(word)
+		}
+
+		if err != nil {
+			break
+		}
+		debug.Printf("consumePhrase: consumed %q", word)
+		words = append(words, word)
+	}
+	// Ignore any error if we got at least one word.
+	if err != nil && len(words) == 0 {
+		debug.Printf("consumePhrase: hit err: %v", err)
+		return "", fmt.Errorf("mail: missing word in phrase: %v", err)
+	}
+	phrase = strings.Join(words, " ")
+	return phrase, nil
+}
+
+// consumeQuotedString parses the quoted string at the start of p.
+func (p *addrParser) consumeQuotedString() (qs string, err error) {
+	// Assume first byte is '"'.
+	i := 1
+	qsb := make([]byte, 0, 10)
+Loop:
+	for {
+		if i >= p.len() {
+			return "", errors.New("mail: unclosed quoted-string")
+		}
+		switch c := (*p)[i]; {
+		case c == '"':
+			break Loop
+		case c == '\\':
+			if i+1 == p.len() {
+				return "", errors.New("mail: unclosed quoted-string")
+			}
+			qsb = append(qsb, (*p)[i+1])
+			i += 2
+		case isQtext(c), c == ' ' || c == '\t':
+			// qtext (printable US-ASCII excluding " and \), or
+			// FWS (almost; we're ignoring CRLF)
+			qsb = append(qsb, c)
+			i++
+		default:
+			return "", fmt.Errorf("mail: bad character in quoted-string: %q", c)
+		}
+	}
+	*p = (*p)[i+1:]
+	return string(qsb), nil
+}
+
+// consumeAtom parses an RFC 5322 atom at the start of p.
+// If dot is true, consumeAtom parses an RFC 5322 dot-atom instead.
+func (p *addrParser) consumeAtom(dot bool) (atom string, err error) {
+	if !isAtext(p.peek(), false) {
+		return "", errors.New("mail: invalid string")
+	}
+	i := 1
+	for ; i < p.len() && isAtext((*p)[i], dot); i++ {
+	}
+	atom, *p = string((*p)[:i]), (*p)[i:]
+	return atom, nil
+}
+
+func (p *addrParser) consume(c byte) bool {
+	if p.empty() || p.peek() != c {
+		return false
+	}
+	*p = (*p)[1:]
+	return true
+}
+
+// skipSpace skips the leading space and tab characters.
+func (p *addrParser) skipSpace() {
+	*p = bytes.TrimLeft(*p, " \t")
+}
+
+func (p *addrParser) peek() byte {
+	return (*p)[0]
+}
+
+func (p *addrParser) empty() bool {
+	return p.len() == 0
+}
+
+func (p *addrParser) len() int {
+	return len(*p)
+}
+
+func decodeRFC2047Word(s string) (string, error) {
+	fields := strings.Split(s, "?")
+	if len(fields) != 5 || fields[0] != "=" || fields[4] != "=" {
+		return "", errors.New("address not RFC 2047 encoded")
+	}
+	charset, enc := strings.ToLower(fields[1]), strings.ToLower(fields[2])
+	if charset != "iso-8859-1" && charset != "utf-8" {
+		return "", fmt.Errorf("charset not supported: %q", charset)
+	}
+
+	in := bytes.NewBufferString(fields[3])
+	var r io.Reader
+	switch enc {
+	case "b":
+		r = base64.NewDecoder(base64.StdEncoding, in)
+	case "q":
+		r = qDecoder{r: in}
+	default:
+		return "", fmt.Errorf("RFC 2047 encoding not supported: %q", enc)
+	}
+
+	dec, err := ioutil.ReadAll(r)
+	if err != nil {
+		return "", err
+	}
+
+	switch charset {
+	case "iso-8859-1":
+		b := new(bytes.Buffer)
+		for _, c := range dec {
+			b.WriteRune(rune(c))
+		}
+		return b.String(), nil
+	case "utf-8":
+		return string(dec), nil
+	}
+	panic("unreachable")
+}
+
+type qDecoder struct {
+	r       io.Reader
+	scratch [2]byte
+}
+
+func (qd qDecoder) Read(p []byte) (n int, err error) {
+	// This method writes at most one byte into p.
+	if len(p) == 0 {
+		return 0, nil
+	}
+	if _, err := qd.r.Read(qd.scratch[:1]); err != nil {
+		return 0, err
+	}
+	switch c := qd.scratch[0]; {
+	case c == '=':
+		if _, err := io.ReadFull(qd.r, qd.scratch[:2]); err != nil {
+			return 0, err
+		}
+		x, err := strconv.ParseInt(string(qd.scratch[:2]), 16, 64)
+		if err != nil {
+			return 0, fmt.Errorf("mail: invalid RFC 2047 encoding: %q", qd.scratch[:2])
+		}
+		p[0] = byte(x)
+	case c == '_':
+		p[0] = ' '
+	default:
+		p[0] = c
+	}
+	return 1, nil
+}
+
+var atextChars = []byte("ABCDEFGHIJKLMNOPQRSTUVWXYZ" +
+	"abcdefghijklmnopqrstuvwxyz" +
+	"0123456789" +
+	"!#$%&'*+-/=?^_`{|}~")
+
+// isAtext returns true if c is an RFC 5322 atext character.
+// If dot is true, period is included.
+func isAtext(c byte, dot bool) bool {
+	if dot && c == '.' {
+		return true
+	}
+	return bytes.IndexByte(atextChars, c) >= 0
+}
+
+// isQtext returns true if c is an RFC 5322 qtext character.
+func isQtext(c byte) bool {
+	// Printable US-ASCII, excluding backslash or quote.
+	if c == '\\' || c == '"' {
+		return false
+	}
+	return '!' <= c && c <= '~'
+}
+
+// isVchar returns true if c is an RFC 5322 VCHAR character.
+func isVchar(c byte) bool {
+	// Visible (printing) characters.
+	return '!' <= c && c <= '~'
+}
+
+// isWSP returns true if c is a WSP (white space).
+// WSP is a space or horizontal tab (RFC5234 Appendix B).
+func isWSP(c byte) bool {
+	return c == ' ' || c == '\t'
+}
diff --git a/src/net/mail/message_test.go b/src/net/mail/message_test.go
new file mode 100644
index 000000000..eb9c8cbdc
--- /dev/null
+++ b/src/net/mail/message_test.go
@@ -0,0 +1,304 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package mail
+
+import (
+	"bytes"
+	"io/ioutil"
+	"reflect"
+	"strings"
+	"testing"
+	"time"
+)
+
+var parseTests = []struct {
+	in     string
+	header Header
+	body   string
+}{
+	{
+		// RFC 5322, Appendix A.1.1
+		in: `From: John Doe <jdoe@machine.example>
+To: Mary Smith <mary@example.net>
+Subject: Saying Hello
+Date: Fri, 21 Nov 1997 09:55:06 -0600
+Message-ID: <1234@local.machine.example>
+
+This is a message just to say hello.
+So, "Hello".
+`,
+		header: Header{
+			"From":       []string{"John Doe <jdoe@machine.example>"},
+			"To":         []string{"Mary Smith <mary@example.net>"},
+			"Subject":    []string{"Saying Hello"},
+			"Date":       []string{"Fri, 21 Nov 1997 09:55:06 -0600"},
+			"Message-Id": []string{"<1234@local.machine.example>"},
+		},
+		body: "This is a message just to say hello.\nSo, \"Hello\".\n",
+	},
+}
+
+func TestParsing(t *testing.T) {
+	for i, test := range parseTests {
+		msg, err := ReadMessage(bytes.NewBuffer([]byte(test.in)))
+		if err != nil {
+			t.Errorf("test #%d: Failed parsing message: %v", i, err)
+			continue
+		}
+		if !headerEq(msg.Header, test.header) {
+			t.Errorf("test #%d: Incorrectly parsed message header.\nGot:\n%+v\nWant:\n%+v",
+				i, msg.Header, test.header)
+		}
+		body, err := ioutil.ReadAll(msg.Body)
+		if err != nil {
+			t.Errorf("test #%d: Failed reading body: %v", i, err)
+			continue
+		}
+		bodyStr := string(body)
+		if bodyStr != test.body {
+			t.Errorf("test #%d: Incorrectly parsed message body.\nGot:\n%+v\nWant:\n%+v",
+				i, bodyStr, test.body)
+		}
+	}
+}
+
+func headerEq(a, b Header) bool {
+	if len(a) != len(b) {
+		return false
+	}
+	for k, as := range a {
+		bs, ok := b[k]
+		if !ok {
+			return false
+		}
+		if !reflect.DeepEqual(as, bs) {
+			return false
+		}
+	}
+	return true
+}
+
+func TestDateParsing(t *testing.T) {
+	tests := []struct {
+		dateStr string
+		exp     time.Time
+	}{
+		// RFC 5322, Appendix A.1.1
+		{
+			"Fri, 21 Nov 1997 09:55:06 -0600",
+			time.Date(1997, 11, 21, 9, 55, 6, 0, time.FixedZone("", -6*60*60)),
+		},
+		// RFC5322, Appendix A.6.2
+		// Obsolete date.
+		{
+			"21 Nov 97 09:55:06 GMT",
+			time.Date(1997, 11, 21, 9, 55, 6, 0, time.FixedZone("GMT", 0)),
+		},
+		// Commonly found format not specified by RFC 5322.
+		{
+			"Fri, 21 Nov 1997 09:55:06 -0600 (MDT)",
+			time.Date(1997, 11, 21, 9, 55, 6, 0, time.FixedZone("", -6*60*60)),
+		},
+	}
+	for _, test := range tests {
+		hdr := Header{
+			"Date": []string{test.dateStr},
+		}
+		date, err := hdr.Date()
+		if err != nil {
+			t.Errorf("Failed parsing %q: %v", test.dateStr, err)
+			continue
+		}
+		if !date.Equal(test.exp) {
+			t.Errorf("Parse of %q: got %+v, want %+v", test.dateStr, date, test.exp)
+		}
+	}
+}
+
+func TestAddressParsingError(t *testing.T) {
+	const txt = "=?iso-8859-2?Q?Bogl=E1rka_Tak=E1cs?= <unknown@gmail.com>"
+	_, err := ParseAddress(txt)
+	if err == nil || !strings.Contains(err.Error(), "charset not supported") {
+		t.Errorf(`mail.ParseAddress(%q) err: %q, want ".*charset not supported.*"`, txt, err)
+	}
+}
+
+func TestAddressParsing(t *testing.T) {
+	tests := []struct {
+		addrsStr string
+		exp      []*Address
+	}{
+		// Bare address
+		{
+			`jdoe@machine.example`,
+			[]*Address{{
+				Address: "jdoe@machine.example",
+			}},
+		},
+		// RFC 5322, Appendix A.1.1
+		{
+			`John Doe <jdoe@machine.example>`,
+			[]*Address{{
+				Name:    "John Doe",
+				Address: "jdoe@machine.example",
+			}},
+		},
+		// RFC 5322, Appendix A.1.2
+		{
+			`"Joe Q. Public" <john.q.public@example.com>`,
+			[]*Address{{
+				Name:    "Joe Q. Public",
+				Address: "john.q.public@example.com",
+			}},
+		},
+		{
+			`Mary Smith <mary@x.test>, jdoe@example.org, Who? <one@y.test>`,
+			[]*Address{
+				{
+					Name:    "Mary Smith",
+					Address: "mary@x.test",
+				},
+				{
+					Address: "jdoe@example.org",
+				},
+				{
+					Name:    "Who?",
+					Address: "one@y.test",
+				},
+			},
+		},
+		{
+			`<boss@nil.test>, "Giant; \"Big\" Box" <sysservices@example.net>`,
+			[]*Address{
+				{
+					Address: "boss@nil.test",
+				},
+				{
+					Name:    `Giant; "Big" Box`,
+					Address: "sysservices@example.net",
+				},
+			},
+		},
+		// RFC 5322, Appendix A.1.3
+		// TODO(dsymonds): Group addresses.
+
+		// RFC 2047 "Q"-encoded ISO-8859-1 address.
+		{
+			`=?iso-8859-1?q?J=F6rg_Doe?= <joerg@example.com>`,
+			[]*Address{
+				{
+					Name:    `Jörg Doe`,
+					Address: "joerg@example.com",
+				},
+			},
+		},
+		// RFC 2047 "Q"-encoded UTF-8 address.
+		{
+			`=?utf-8?q?J=C3=B6rg_Doe?= <joerg@example.com>`,
+			[]*Address{
+				{
+					Name:    `Jörg Doe`,
+					Address: "joerg@example.com",
+				},
+			},
+		},
+		// RFC 2047, Section 8.
+		{
+			`=?ISO-8859-1?Q?Andr=E9?= Pirard <PIRARD@vm1.ulg.ac.be>`,
+			[]*Address{
+				{
+					Name:    `André Pirard`,
+					Address: "PIRARD@vm1.ulg.ac.be",
+				},
+			},
+		},
+		// Custom example of RFC 2047 "B"-encoded ISO-8859-1 address.
+		{
+			`=?ISO-8859-1?B?SvZyZw==?= <joerg@example.com>`,
+			[]*Address{
+				{
+					Name:    `Jörg`,
+					Address: "joerg@example.com",
+				},
+			},
+		},
+		// Custom example of RFC 2047 "B"-encoded UTF-8 address.
+		{
+			`=?UTF-8?B?SsO2cmc=?= <joerg@example.com>`,
+			[]*Address{
+				{
+					Name:    `Jörg`,
+					Address: "joerg@example.com",
+				},
+			},
+		},
+		// Custom example with "." in name. For issue 4938
+		{
+			`Asem H. <noreply@example.com>`,
+			[]*Address{
+				{
+					Name:    `Asem H.`,
+					Address: "noreply@example.com",
+				},
+			},
+		},
+	}
+	for _, test := range tests {
+		if len(test.exp) == 1 {
+			addr, err := ParseAddress(test.addrsStr)
+			if err != nil {
+				t.Errorf("Failed parsing (single) %q: %v", test.addrsStr, err)
+				continue
+			}
+			if !reflect.DeepEqual([]*Address{addr}, test.exp) {
+				t.Errorf("Parse (single) of %q: got %+v, want %+v", test.addrsStr, addr, test.exp)
+			}
+		}
+
+		addrs, err := ParseAddressList(test.addrsStr)
+		if err != nil {
+			t.Errorf("Failed parsing (list) %q: %v", test.addrsStr, err)
+			continue
+		}
+		if !reflect.DeepEqual(addrs, test.exp) {
+			t.Errorf("Parse (list) of %q: got %+v, want %+v", test.addrsStr, addrs, test.exp)
+		}
+	}
+}
+
+func TestAddressFormatting(t *testing.T) {
+	tests := []struct {
+		addr *Address
+		exp  string
+	}{
+		{
+			&Address{Address: "bob@example.com"},
+			"<bob@example.com>",
+		},
+		{
+			&Address{Name: "Bob", Address: "bob@example.com"},
+			`"Bob" <bob@example.com>`,
+		},
+		{
+			// note the ö (o with an umlaut)
+			&Address{Name: "Böb", Address: "bob@example.com"},
+			`=?utf-8?q?B=C3=B6b?= <bob@example.com>`,
+		},
+		{
+			&Address{Name: "Bob Jane", Address: "bob@example.com"},
+			`"Bob Jane" <bob@example.com>`,
+		},
+		{
+			&Address{Name: "Böb Jacöb", Address: "bob@example.com"},
+			`=?utf-8?q?B=C3=B6b_Jac=C3=B6b?= <bob@example.com>`,
+		},
+	}
+	for _, test := range tests {
+		s := test.addr.String()
+		if s != test.exp {
+			t.Errorf("Address%+v.String() = %v, want %v", *test.addr, s, test.exp)
+		}
+	}
+}
diff --git a/src/net/mockicmp_test.go b/src/net/mockicmp_test.go
new file mode 100644
index 000000000..e742365ea
--- /dev/null
+++ b/src/net/mockicmp_test.go
@@ -0,0 +1,116 @@
+// Copyright 2009 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package net
+
+import "errors"
+
+const (
+	icmpv4EchoRequest = 8
+	icmpv4EchoReply   = 0
+	icmpv6EchoRequest = 128
+	icmpv6EchoReply   = 129
+)
+
+// icmpMessage represents an ICMP message.
+type icmpMessage struct {
+	Type     int             // type
+	Code     int             // code
+	Checksum int             // checksum
+	Body     icmpMessageBody // body
+}
+
+// icmpMessageBody represents an ICMP message body.
+type icmpMessageBody interface {
+	Len() int
+	Marshal() ([]byte, error)
+}
+
+// Marshal returns the binary enconding of the ICMP echo request or
+// reply message m.
+func (m *icmpMessage) Marshal() ([]byte, error) {
+	b := []byte{byte(m.Type), byte(m.Code), 0, 0}
+	if m.Body != nil && m.Body.Len() != 0 {
+		mb, err := m.Body.Marshal()
+		if err != nil {
+			return nil, err
+		}
+		b = append(b, mb...)
+	}
+	switch m.Type {
+	case icmpv6EchoRequest, icmpv6EchoReply:
+		return b, nil
+	}
+	csumcv := len(b) - 1 // checksum coverage
+	s := uint32(0)
+	for i := 0; i < csumcv; i += 2 {
+		s += uint32(b[i+1])<<8 | uint32(b[i])
+	}
+	if csumcv&1 == 0 {
+		s += uint32(b[csumcv])
+	}
+	s = s>>16 + s&0xffff
+	s = s + s>>16
+	// Place checksum back in header; using ^= avoids the
+	// assumption the checksum bytes are zero.
+	b[2] ^= byte(^s)
+	b[3] ^= byte(^s >> 8)
+	return b, nil
+}
+
+// parseICMPMessage parses b as an ICMP message.
+func parseICMPMessage(b []byte) (*icmpMessage, error) {
+	msglen := len(b)
+	if msglen < 4 {
+		return nil, errors.New("message too short")
+	}
+	m := &icmpMessage{Type: int(b[0]), Code: int(b[1]), Checksum: int(b[2])<<8 | int(b[3])}
+	if msglen > 4 {
+		var err error
+		switch m.Type {
+		case icmpv4EchoRequest, icmpv4EchoReply, icmpv6EchoRequest, icmpv6EchoReply:
+			m.Body, err = parseICMPEcho(b[4:])
+			if err != nil {
+				return nil, err
+			}
+		}
+	}
+	return m, nil
+}
+
+// imcpEcho represenets an ICMP echo request or reply message body.
+type icmpEcho struct {
+	ID   int    // identifier
+	Seq  int    // sequence number
+	Data []byte // data
+}
+
+func (p *icmpEcho) Len() int {
+	if p == nil {
+		return 0
+	}
+	return 4 + len(p.Data)
+}
+
+// Marshal returns the binary enconding of the ICMP echo request or
+// reply message body p.
+func (p *icmpEcho) Marshal() ([]byte, error) {
+	b := make([]byte, 4+len(p.Data))
+	b[0], b[1] = byte(p.ID>>8), byte(p.ID)
+	b[2], b[3] = byte(p.Seq>>8), byte(p.Seq)
+	copy(b[4:], p.Data)
+	return b, nil
+}
+
+// parseICMPEcho parses b as an ICMP echo request or reply message
+// body.
+func parseICMPEcho(b []byte) (*icmpEcho, error) {
+	bodylen := len(b)
+	p := &icmpEcho{ID: int(b[0])<<8 | int(b[1]), Seq: int(b[2])<<8 | int(b[3])}
+	if bodylen > 4 {
+		p.Data = make([]byte, bodylen-4)
+		copy(p.Data, b[4:])
+	}
+	return p, nil
+}
diff --git a/src/net/mockserver_test.go b/src/net/mockserver_test.go
new file mode 100644
index 000000000..68ded5d75
--- /dev/null
+++ b/src/net/mockserver_test.go
@@ -0,0 +1,82 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package net
+
+import "sync"
+
+type streamListener struct {
+	net, addr string
+	ln        Listener
+}
+
+type dualStackServer struct {
+	lnmu sync.RWMutex
+	lns  []streamListener
+	port string
+
+	cmu sync.RWMutex
+	cs  []Conn // established connections at the passive open side
+}
+
+func (dss *dualStackServer) buildup(server func(*dualStackServer, Listener)) error {
+	for i := range dss.lns {
+		go server(dss, dss.lns[i].ln)
+	}
+	return nil
+}
+
+func (dss *dualStackServer) putConn(c Conn) error {
+	dss.cmu.Lock()
+	dss.cs = append(dss.cs, c)
+	dss.cmu.Unlock()
+	return nil
+}
+
+func (dss *dualStackServer) teardownNetwork(net string) error {
+	dss.lnmu.Lock()
+	for i := range dss.lns {
+		if net == dss.lns[i].net && dss.lns[i].ln != nil {
+			dss.lns[i].ln.Close()
+			dss.lns[i].ln = nil
+		}
+	}
+	dss.lnmu.Unlock()
+	return nil
+}
+
+func (dss *dualStackServer) teardown() error {
+	dss.lnmu.Lock()
+	for i := range dss.lns {
+		if dss.lns[i].ln != nil {
+			dss.lns[i].ln.Close()
+		}
+	}
+	dss.lnmu.Unlock()
+	dss.cmu.Lock()
+	for _, c := range dss.cs {
+		c.Close()
+	}
+	dss.cmu.Unlock()
+	return nil
+}
+
+func newDualStackServer(lns []streamListener) (*dualStackServer, error) {
+	dss := &dualStackServer{lns: lns, port: "0"}
+	for i := range dss.lns {
+		ln, err := Listen(dss.lns[i].net, dss.lns[i].addr+":"+dss.port)
+		if err != nil {
+			dss.teardown()
+			return nil, err
+		}
+		dss.lns[i].ln = ln
+		if dss.port == "0" {
+			if _, dss.port, err = SplitHostPort(ln.Addr().String()); err != nil {
+				dss.teardown()
+				return nil, err
+			}
+		}
+	}
+	return dss, nil
+}
diff --git a/src/net/multicast_test.go b/src/net/multicast_test.go
new file mode 100644
index 000000000..5f253f44a
--- /dev/null
+++ b/src/net/multicast_test.go
@@ -0,0 +1,188 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package net
+
+import (
+	"fmt"
+	"os"
+	"runtime"
+	"testing"
+)
+
+var ipv4MulticastListenerTests = []struct {
+	net   string
+	gaddr *UDPAddr // see RFC 4727
+}{
+	{"udp", &UDPAddr{IP: IPv4(224, 0, 0, 254), Port: 12345}},
+
+	{"udp4", &UDPAddr{IP: IPv4(224, 0, 0, 254), Port: 12345}},
+}
+
+// TestIPv4MulticastListener tests both single and double listen to a
+// test listener with same address family, same group address and same
+// port.
+func TestIPv4MulticastListener(t *testing.T) {
+	switch runtime.GOOS {
+	case "android", "nacl", "plan9":
+		t.Skipf("skipping test on %q", runtime.GOOS)
+	case "solaris":
+		t.Skipf("skipping test on solaris, see issue 7399")
+	}
+
+	closer := func(cs []*UDPConn) {
+		for _, c := range cs {
+			if c != nil {
+				c.Close()
+			}
+		}
+	}
+
+	for _, ifi := range []*Interface{loopbackInterface(), nil} {
+		// Note that multicast interface assignment by system
+		// is not recommended because it usually relies on
+		// routing stuff for finding out an appropriate
+		// nexthop containing both network and link layer
+		// adjacencies.
+		if ifi == nil && !*testExternal {
+			continue
+		}
+		for _, tt := range ipv4MulticastListenerTests {
+			var err error
+			cs := make([]*UDPConn, 2)
+			if cs[0], err = ListenMulticastUDP(tt.net, ifi, tt.gaddr); err != nil {
+				t.Fatalf("First ListenMulticastUDP on %v failed: %v", ifi, err)
+			}
+			if err := checkMulticastListener(cs[0], tt.gaddr.IP); err != nil {
+				closer(cs)
+				t.Fatal(err)
+			}
+			if cs[1], err = ListenMulticastUDP(tt.net, ifi, tt.gaddr); err != nil {
+				closer(cs)
+				t.Fatalf("Second ListenMulticastUDP on %v failed: %v", ifi, err)
+			}
+			if err := checkMulticastListener(cs[1], tt.gaddr.IP); err != nil {
+				closer(cs)
+				t.Fatal(err)
+			}
+			closer(cs)
+		}
+	}
+}
+
+var ipv6MulticastListenerTests = []struct {
+	net   string
+	gaddr *UDPAddr // see RFC 4727
+}{
+	{"udp", &UDPAddr{IP: ParseIP("ff01::114"), Port: 12345}},
+	{"udp", &UDPAddr{IP: ParseIP("ff02::114"), Port: 12345}},
+	{"udp", &UDPAddr{IP: ParseIP("ff04::114"), Port: 12345}},
+	{"udp", &UDPAddr{IP: ParseIP("ff05::114"), Port: 12345}},
+	{"udp", &UDPAddr{IP: ParseIP("ff08::114"), Port: 12345}},
+	{"udp", &UDPAddr{IP: ParseIP("ff0e::114"), Port: 12345}},
+
+	{"udp6", &UDPAddr{IP: ParseIP("ff01::114"), Port: 12345}},
+	{"udp6", &UDPAddr{IP: ParseIP("ff02::114"), Port: 12345}},
+	{"udp6", &UDPAddr{IP: ParseIP("ff04::114"), Port: 12345}},
+	{"udp6", &UDPAddr{IP: ParseIP("ff05::114"), Port: 12345}},
+	{"udp6", &UDPAddr{IP: ParseIP("ff08::114"), Port: 12345}},
+	{"udp6", &UDPAddr{IP: ParseIP("ff0e::114"), Port: 12345}},
+}
+
+// TestIPv6MulticastListener tests both single and double listen to a
+// test listener with same address family, same group address and same
+// port.
+func TestIPv6MulticastListener(t *testing.T) {
+	switch runtime.GOOS {
+	case "plan9":
+		t.Skipf("skipping test on %q", runtime.GOOS)
+	case "solaris":
+		t.Skipf("skipping test on solaris, see issue 7399")
+	}
+	if !supportsIPv6 {
+		t.Skip("ipv6 is not supported")
+	}
+	if os.Getuid() != 0 {
+		t.Skip("skipping test; must be root")
+	}
+
+	closer := func(cs []*UDPConn) {
+		for _, c := range cs {
+			if c != nil {
+				c.Close()
+			}
+		}
+	}
+
+	for _, ifi := range []*Interface{loopbackInterface(), nil} {
+		// Note that multicast interface assignment by system
+		// is not recommended because it usually relies on
+		// routing stuff for finding out an appropriate
+		// nexthop containing both network and link layer
+		// adjacencies.
+		if ifi == nil && (!*testExternal || !*testIPv6) {
+			continue
+		}
+		for _, tt := range ipv6MulticastListenerTests {
+			var err error
+			cs := make([]*UDPConn, 2)
+			if cs[0], err = ListenMulticastUDP(tt.net, ifi, tt.gaddr); err != nil {
+				t.Fatalf("First ListenMulticastUDP on %v failed: %v", ifi, err)
+			}
+			if err := checkMulticastListener(cs[0], tt.gaddr.IP); err != nil {
+				closer(cs)
+				t.Fatal(err)
+			}
+			if cs[1], err = ListenMulticastUDP(tt.net, ifi, tt.gaddr); err != nil {
+				closer(cs)
+				t.Fatalf("Second ListenMulticastUDP on %v failed: %v", ifi, err)
+			}
+			if err := checkMulticastListener(cs[1], tt.gaddr.IP); err != nil {
+				closer(cs)
+				t.Fatal(err)
+			}
+			closer(cs)
+		}
+	}
+}
+
+func checkMulticastListener(c *UDPConn, ip IP) error {
+	if ok, err := multicastRIBContains(ip); err != nil {
+		return err
+	} else if !ok {
+		return fmt.Errorf("%q not found in multicast RIB", ip.String())
+	}
+	la := c.LocalAddr()
+	if la, ok := la.(*UDPAddr); !ok || la.Port == 0 {
+		return fmt.Errorf("got %v; expected a proper address with non-zero port number", la)
+	}
+	return nil
+}
+
+func multicastRIBContains(ip IP) (bool, error) {
+	switch runtime.GOOS {
+	case "dragonfly", "netbsd", "openbsd", "plan9", "solaris", "windows":
+		return true, nil // not implemented yet
+	case "linux":
+		if runtime.GOARCH == "arm" || runtime.GOARCH == "alpha" {
+			return true, nil // not implemented yet
+		}
+	}
+	ift, err := Interfaces()
+	if err != nil {
+		return false, err
+	}
+	for _, ifi := range ift {
+		ifmat, err := ifi.MulticastAddrs()
+		if err != nil {
+			return false, err
+		}
+		for _, ifma := range ifmat {
+			if ifma.(*IPAddr).IP.Equal(ip) {
+				return true, nil
+			}
+		}
+	}
+	return false, nil
+}
diff --git a/src/net/net.go b/src/net/net.go
new file mode 100644
index 000000000..ca56af54f
--- /dev/null
+++ b/src/net/net.go
@@ -0,0 +1,426 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+/*
+Package net provides a portable interface for network I/O, including
+TCP/IP, UDP, domain name resolution, and Unix domain sockets.
+
+Although the package provides access to low-level networking
+primitives, most clients will need only the basic interface provided
+by the Dial, Listen, and Accept functions and the associated
+Conn and Listener interfaces. The crypto/tls package uses
+the same interfaces and similar Dial and Listen functions.
+
+The Dial function connects to a server:
+
+	conn, err := net.Dial("tcp", "google.com:80")
+	if err != nil {
+		// handle error
+	}
+	fmt.Fprintf(conn, "GET / HTTP/1.0\r\n\r\n")
+	status, err := bufio.NewReader(conn).ReadString('\n')
+	// ...
+
+The Listen function creates servers:
+
+	ln, err := net.Listen("tcp", ":8080")
+	if err != nil {
+		// handle error
+	}
+	for {
+		conn, err := ln.Accept()
+		if err != nil {
+			// handle error
+			continue
+		}
+		go handleConnection(conn)
+	}
+*/
+package net
+
+// TODO(rsc):
+//	support for raw ethernet sockets
+
+import (
+	"errors"
+	"io"
+	"os"
+	"syscall"
+	"time"
+)
+
+// Addr represents a network end point address.
+type Addr interface {
+	Network() string // name of the network
+	String() string  // string form of address
+}
+
+// Conn is a generic stream-oriented network connection.
+//
+// Multiple goroutines may invoke methods on a Conn simultaneously.
+type Conn interface {
+	// Read reads data from the connection.
+	// Read can be made to time out and return a Error with Timeout() == true
+	// after a fixed time limit; see SetDeadline and SetReadDeadline.
+	Read(b []byte) (n int, err error)
+
+	// Write writes data to the connection.
+	// Write can be made to time out and return a Error with Timeout() == true
+	// after a fixed time limit; see SetDeadline and SetWriteDeadline.
+	Write(b []byte) (n int, err error)
+
+	// Close closes the connection.
+	// Any blocked Read or Write operations will be unblocked and return errors.
+	Close() error
+
+	// LocalAddr returns the local network address.
+	LocalAddr() Addr
+
+	// RemoteAddr returns the remote network address.
+	RemoteAddr() Addr
+
+	// SetDeadline sets the read and write deadlines associated
+	// with the connection. It is equivalent to calling both
+	// SetReadDeadline and SetWriteDeadline.
+	//
+	// A deadline is an absolute time after which I/O operations
+	// fail with a timeout (see type Error) instead of
+	// blocking. The deadline applies to all future I/O, not just
+	// the immediately following call to Read or Write.
+	//
+	// An idle timeout can be implemented by repeatedly extending
+	// the deadline after successful Read or Write calls.
+	//
+	// A zero value for t means I/O operations will not time out.
+	SetDeadline(t time.Time) error
+
+	// SetReadDeadline sets the deadline for future Read calls.
+	// A zero value for t means Read will not time out.
+	SetReadDeadline(t time.Time) error
+
+	// SetWriteDeadline sets the deadline for future Write calls.
+	// Even if write times out, it may return n > 0, indicating that
+	// some of the data was successfully written.
+	// A zero value for t means Write will not time out.
+	SetWriteDeadline(t time.Time) error
+}
+
+type conn struct {
+	fd *netFD
+}
+
+func (c *conn) ok() bool { return c != nil && c.fd != nil }
+
+// Implementation of the Conn interface.
+
+// Read implements the Conn Read method.
+func (c *conn) Read(b []byte) (int, error) {
+	if !c.ok() {
+		return 0, syscall.EINVAL
+	}
+	return c.fd.Read(b)
+}
+
+// Write implements the Conn Write method.
+func (c *conn) Write(b []byte) (int, error) {
+	if !c.ok() {
+		return 0, syscall.EINVAL
+	}
+	return c.fd.Write(b)
+}
+
+// Close closes the connection.
+func (c *conn) Close() error {
+	if !c.ok() {
+		return syscall.EINVAL
+	}
+	return c.fd.Close()
+}
+
+// LocalAddr returns the local network address.
+func (c *conn) LocalAddr() Addr {
+	if !c.ok() {
+		return nil
+	}
+	return c.fd.laddr
+}
+
+// RemoteAddr returns the remote network address.
+func (c *conn) RemoteAddr() Addr {
+	if !c.ok() {
+		return nil
+	}
+	return c.fd.raddr
+}
+
+// SetDeadline implements the Conn SetDeadline method.
+func (c *conn) SetDeadline(t time.Time) error {
+	if !c.ok() {
+		return syscall.EINVAL
+	}
+	return c.fd.setDeadline(t)
+}
+
+// SetReadDeadline implements the Conn SetReadDeadline method.
+func (c *conn) SetReadDeadline(t time.Time) error {
+	if !c.ok() {
+		return syscall.EINVAL
+	}
+	return c.fd.setReadDeadline(t)
+}
+
+// SetWriteDeadline implements the Conn SetWriteDeadline method.
+func (c *conn) SetWriteDeadline(t time.Time) error {
+	if !c.ok() {
+		return syscall.EINVAL
+	}
+	return c.fd.setWriteDeadline(t)
+}
+
+// SetReadBuffer sets the size of the operating system's
+// receive buffer associated with the connection.
+func (c *conn) SetReadBuffer(bytes int) error {
+	if !c.ok() {
+		return syscall.EINVAL
+	}
+	return setReadBuffer(c.fd, bytes)
+}
+
+// SetWriteBuffer sets the size of the operating system's
+// transmit buffer associated with the connection.
+func (c *conn) SetWriteBuffer(bytes int) error {
+	if !c.ok() {
+		return syscall.EINVAL
+	}
+	return setWriteBuffer(c.fd, bytes)
+}
+
+// File sets the underlying os.File to blocking mode and returns a copy.
+// It is the caller's responsibility to close f when finished.
+// Closing c does not affect f, and closing f does not affect c.
+//
+// The returned os.File's file descriptor is different from the connection's.
+// Attempting to change properties of the original using this duplicate
+// may or may not have the desired effect.
+func (c *conn) File() (f *os.File, err error) { return c.fd.dup() }
+
+// An Error represents a network error.
+type Error interface {
+	error
+	Timeout() bool   // Is the error a timeout?
+	Temporary() bool // Is the error temporary?
+}
+
+// PacketConn is a generic packet-oriented network connection.
+//
+// Multiple goroutines may invoke methods on a PacketConn simultaneously.
+type PacketConn interface {
+	// ReadFrom reads a packet from the connection,
+	// copying the payload into b.  It returns the number of
+	// bytes copied into b and the return address that
+	// was on the packet.
+	// ReadFrom can be made to time out and return
+	// an error with Timeout() == true after a fixed time limit;
+	// see SetDeadline and SetReadDeadline.
+	ReadFrom(b []byte) (n int, addr Addr, err error)
+
+	// WriteTo writes a packet with payload b to addr.
+	// WriteTo can be made to time out and return
+	// an error with Timeout() == true after a fixed time limit;
+	// see SetDeadline and SetWriteDeadline.
+	// On packet-oriented connections, write timeouts are rare.
+	WriteTo(b []byte, addr Addr) (n int, err error)
+
+	// Close closes the connection.
+	// Any blocked ReadFrom or WriteTo operations will be unblocked and return errors.
+	Close() error
+
+	// LocalAddr returns the local network address.
+	LocalAddr() Addr
+
+	// SetDeadline sets the read and write deadlines associated
+	// with the connection.
+	SetDeadline(t time.Time) error
+
+	// SetReadDeadline sets the deadline for future Read calls.
+	// If the deadline is reached, Read will fail with a timeout
+	// (see type Error) instead of blocking.
+	// A zero value for t means Read will not time out.
+	SetReadDeadline(t time.Time) error
+
+	// SetWriteDeadline sets the deadline for future Write calls.
+	// If the deadline is reached, Write will fail with a timeout
+	// (see type Error) instead of blocking.
+	// A zero value for t means Write will not time out.
+	// Even if write times out, it may return n > 0, indicating that
+	// some of the data was successfully written.
+	SetWriteDeadline(t time.Time) error
+}
+
+var listenerBacklog = maxListenerBacklog()
+
+// A Listener is a generic network listener for stream-oriented protocols.
+//
+// Multiple goroutines may invoke methods on a Listener simultaneously.
+type Listener interface {
+	// Accept waits for and returns the next connection to the listener.
+	Accept() (c Conn, err error)
+
+	// Close closes the listener.
+	// Any blocked Accept operations will be unblocked and return errors.
+	Close() error
+
+	// Addr returns the listener's network address.
+	Addr() Addr
+}
+
+// Various errors contained in OpError.
+var (
+	// For connection setup and write operations.
+	errMissingAddress = errors.New("missing address")
+
+	// For both read and write operations.
+	errTimeout          error = &timeoutError{}
+	errClosing                = errors.New("use of closed network connection")
+	ErrWriteToConnected       = errors.New("use of WriteTo with pre-connected connection")
+)
+
+// OpError is the error type usually returned by functions in the net
+// package. It describes the operation, network type, and address of
+// an error.
+type OpError struct {
+	// Op is the operation which caused the error, such as
+	// "read" or "write".
+	Op string
+
+	// Net is the network type on which this error occurred,
+	// such as "tcp" or "udp6".
+	Net string
+
+	// Addr is the network address on which this error occurred.
+	Addr Addr
+
+	// Err is the error that occurred during the operation.
+	Err error
+}
+
+func (e *OpError) Error() string {
+	if e == nil {
+		return "<nil>"
+	}
+	s := e.Op
+	if e.Net != "" {
+		s += " " + e.Net
+	}
+	if e.Addr != nil {
+		s += " " + e.Addr.String()
+	}
+	s += ": " + e.Err.Error()
+	return s
+}
+
+type temporary interface {
+	Temporary() bool
+}
+
+func (e *OpError) Temporary() bool {
+	t, ok := e.Err.(temporary)
+	return ok && t.Temporary()
+}
+
+var noDeadline = time.Time{}
+
+type timeout interface {
+	Timeout() bool
+}
+
+func (e *OpError) Timeout() bool {
+	t, ok := e.Err.(timeout)
+	return ok && t.Timeout()
+}
+
+type timeoutError struct{}
+
+func (e *timeoutError) Error() string   { return "i/o timeout" }
+func (e *timeoutError) Timeout() bool   { return true }
+func (e *timeoutError) Temporary() bool { return true }
+
+type AddrError struct {
+	Err  string
+	Addr string
+}
+
+func (e *AddrError) Error() string {
+	if e == nil {
+		return "<nil>"
+	}
+	s := e.Err
+	if e.Addr != "" {
+		s += " " + e.Addr
+	}
+	return s
+}
+
+func (e *AddrError) Temporary() bool {
+	return false
+}
+
+func (e *AddrError) Timeout() bool {
+	return false
+}
+
+type UnknownNetworkError string
+
+func (e UnknownNetworkError) Error() string   { return "unknown network " + string(e) }
+func (e UnknownNetworkError) Temporary() bool { return false }
+func (e UnknownNetworkError) Timeout() bool   { return false }
+
+type InvalidAddrError string
+
+func (e InvalidAddrError) Error() string   { return string(e) }
+func (e InvalidAddrError) Timeout() bool   { return false }
+func (e InvalidAddrError) Temporary() bool { return false }
+
+// DNSConfigError represents an error reading the machine's DNS configuration.
+type DNSConfigError struct {
+	Err error
+}
+
+func (e *DNSConfigError) Error() string {
+	return "error reading DNS config: " + e.Err.Error()
+}
+
+func (e *DNSConfigError) Timeout() bool   { return false }
+func (e *DNSConfigError) Temporary() bool { return false }
+
+type writerOnly struct {
+	io.Writer
+}
+
+// Fallback implementation of io.ReaderFrom's ReadFrom, when sendfile isn't
+// applicable.
+func genericReadFrom(w io.Writer, r io.Reader) (n int64, err error) {
+	// Use wrapper to hide existing r.ReadFrom from io.Copy.
+	return io.Copy(writerOnly{w}, r)
+}
+
+// Limit the number of concurrent cgo-using goroutines, because
+// each will block an entire operating system thread. The usual culprit
+// is resolving many DNS names in separate goroutines but the DNS
+// server is not responding. Then the many lookups each use a different
+// thread, and the system or the program runs out of threads.
+
+var threadLimit = make(chan struct{}, 500)
+
+// Using send for acquire is fine here because we are not using this
+// to protect any memory. All we care about is the number of goroutines
+// making calls at a time.
+
+func acquireThread() {
+	threadLimit <- struct{}{}
+}
+
+func releaseThread() {
+	<-threadLimit
+}
diff --git a/src/net/net_test.go b/src/net/net_test.go
new file mode 100644
index 000000000..bfed4d657
--- /dev/null
+++ b/src/net/net_test.go
@@ -0,0 +1,263 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package net
+
+import (
+	"io"
+	"io/ioutil"
+	"os"
+	"runtime"
+	"testing"
+	"time"
+)
+
+func TestShutdown(t *testing.T) {
+	if runtime.GOOS == "plan9" {
+		t.Skipf("skipping test on %q", runtime.GOOS)
+	}
+	ln, err := Listen("tcp", "127.0.0.1:0")
+	if err != nil {
+		if ln, err = Listen("tcp6", "[::1]:0"); err != nil {
+			t.Fatalf("ListenTCP on :0: %v", err)
+		}
+	}
+
+	go func() {
+		defer ln.Close()
+		c, err := ln.Accept()
+		if err != nil {
+			t.Errorf("Accept: %v", err)
+			return
+		}
+		var buf [10]byte
+		n, err := c.Read(buf[:])
+		if n != 0 || err != io.EOF {
+			t.Errorf("server Read = %d, %v; want 0, io.EOF", n, err)
+			return
+		}
+		c.Write([]byte("response"))
+		c.Close()
+	}()
+
+	c, err := Dial("tcp", ln.Addr().String())
+	if err != nil {
+		t.Fatalf("Dial: %v", err)
+	}
+	defer c.Close()
+
+	err = c.(*TCPConn).CloseWrite()
+	if err != nil {
+		t.Fatalf("CloseWrite: %v", err)
+	}
+	var buf [10]byte
+	n, err := c.Read(buf[:])
+	if err != nil {
+		t.Fatalf("client Read: %d, %v", n, err)
+	}
+	got := string(buf[:n])
+	if got != "response" {
+		t.Errorf("read = %q, want \"response\"", got)
+	}
+}
+
+func TestShutdownUnix(t *testing.T) {
+	switch runtime.GOOS {
+	case "nacl", "plan9", "windows":
+		t.Skipf("skipping test on %q", runtime.GOOS)
+	}
+	f, err := ioutil.TempFile("", "go_net_unixtest")
+	if err != nil {
+		t.Fatalf("TempFile: %s", err)
+	}
+	f.Close()
+	tmpname := f.Name()
+	os.Remove(tmpname)
+	ln, err := Listen("unix", tmpname)
+	if err != nil {
+		t.Fatalf("ListenUnix on %s: %s", tmpname, err)
+	}
+	defer func() {
+		ln.Close()
+		os.Remove(tmpname)
+	}()
+
+	go func() {
+		c, err := ln.Accept()
+		if err != nil {
+			t.Errorf("Accept: %v", err)
+			return
+		}
+		var buf [10]byte
+		n, err := c.Read(buf[:])
+		if n != 0 || err != io.EOF {
+			t.Errorf("server Read = %d, %v; want 0, io.EOF", n, err)
+			return
+		}
+		c.Write([]byte("response"))
+		c.Close()
+	}()
+
+	c, err := Dial("unix", tmpname)
+	if err != nil {
+		t.Fatalf("Dial: %v", err)
+	}
+	defer c.Close()
+
+	err = c.(*UnixConn).CloseWrite()
+	if err != nil {
+		t.Fatalf("CloseWrite: %v", err)
+	}
+	var buf [10]byte
+	n, err := c.Read(buf[:])
+	if err != nil {
+		t.Fatalf("client Read: %d, %v", n, err)
+	}
+	got := string(buf[:n])
+	if got != "response" {
+		t.Errorf("read = %q, want \"response\"", got)
+	}
+}
+
+func TestTCPListenClose(t *testing.T) {
+	ln, err := Listen("tcp", "127.0.0.1:0")
+	if err != nil {
+		t.Fatalf("Listen failed: %v", err)
+	}
+
+	done := make(chan bool, 1)
+	go func() {
+		time.Sleep(100 * time.Millisecond)
+		ln.Close()
+	}()
+	go func() {
+		c, err := ln.Accept()
+		if err == nil {
+			c.Close()
+			t.Error("Accept succeeded")
+		} else {
+			t.Logf("Accept timeout error: %s (any error is fine)", err)
+		}
+		done <- true
+	}()
+	select {
+	case <-done:
+	case <-time.After(2 * time.Second):
+		t.Fatal("timeout waiting for TCP close")
+	}
+}
+
+func TestUDPListenClose(t *testing.T) {
+	switch runtime.GOOS {
+	case "plan9":
+		t.Skipf("skipping test on %q", runtime.GOOS)
+	}
+	ln, err := ListenPacket("udp", "127.0.0.1:0")
+	if err != nil {
+		t.Fatalf("Listen failed: %v", err)
+	}
+
+	buf := make([]byte, 1000)
+	done := make(chan bool, 1)
+	go func() {
+		time.Sleep(100 * time.Millisecond)
+		ln.Close()
+	}()
+	go func() {
+		_, _, err = ln.ReadFrom(buf)
+		if err == nil {
+			t.Error("ReadFrom succeeded")
+		} else {
+			t.Logf("ReadFrom timeout error: %s (any error is fine)", err)
+		}
+		done <- true
+	}()
+	select {
+	case <-done:
+	case <-time.After(2 * time.Second):
+		t.Fatal("timeout waiting for UDP close")
+	}
+}
+
+func TestTCPClose(t *testing.T) {
+	switch runtime.GOOS {
+	case "plan9":
+		t.Skipf("skipping test on %q", runtime.GOOS)
+	}
+	l, err := Listen("tcp", "127.0.0.1:0")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer l.Close()
+
+	read := func(r io.Reader) error {
+		var m [1]byte
+		_, err := r.Read(m[:])
+		return err
+	}
+
+	go func() {
+		c, err := Dial("tcp", l.Addr().String())
+		if err != nil {
+			t.Errorf("Dial: %v", err)
+			return
+		}
+
+		go read(c)
+
+		time.Sleep(10 * time.Millisecond)
+		c.Close()
+	}()
+
+	c, err := l.Accept()
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer c.Close()
+
+	for err == nil {
+		err = read(c)
+	}
+	if err != nil && err != io.EOF {
+		t.Fatal(err)
+	}
+}
+
+func TestErrorNil(t *testing.T) {
+	c, err := Dial("tcp", "127.0.0.1:65535")
+	if err == nil {
+		t.Fatal("Dial 127.0.0.1:65535 succeeded")
+	}
+	if c != nil {
+		t.Fatalf("Dial returned non-nil interface %T(%v) with err != nil", c, c)
+	}
+
+	// Make Listen fail by relistening on the same address.
+	l, err := Listen("tcp", "127.0.0.1:0")
+	if err != nil {
+		t.Fatalf("Listen 127.0.0.1:0: %v", err)
+	}
+	defer l.Close()
+	l1, err := Listen("tcp", l.Addr().String())
+	if err == nil {
+		t.Fatalf("second Listen %v: %v", l.Addr(), err)
+	}
+	if l1 != nil {
+		t.Fatalf("Listen returned non-nil interface %T(%v) with err != nil", l1, l1)
+	}
+
+	// Make ListenPacket fail by relistening on the same address.
+	lp, err := ListenPacket("udp", "127.0.0.1:0")
+	if err != nil {
+		t.Fatalf("Listen 127.0.0.1:0: %v", err)
+	}
+	defer lp.Close()
+	lp1, err := ListenPacket("udp", lp.LocalAddr().String())
+	if err == nil {
+		t.Fatalf("second Listen %v: %v", lp.LocalAddr(), err)
+	}
+	if lp1 != nil {
+		t.Fatalf("ListenPacket returned non-nil interface %T(%v) with err != nil", lp1, lp1)
+	}
+}
diff --git a/src/net/net_windows_test.go b/src/net/net_windows_test.go
new file mode 100644
index 000000000..750a4304b
--- /dev/null
+++ b/src/net/net_windows_test.go
@@ -0,0 +1,148 @@
+// Copyright 2014 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package net
+
+import (
+	"bufio"
+	"fmt"
+	"io"
+	"os"
+	"os/exec"
+	"syscall"
+	"testing"
+	"time"
+)
+
+func TestAcceptIgnoreSomeErrors(t *testing.T) {
+	t.Skip("skipping temporarily, see issue 8662")
+
+	recv := func(ln Listener) (string, error) {
+		c, err := ln.Accept()
+		if err != nil {
+			// Display windows errno in error message.
+			operr, ok := err.(*OpError)
+			if !ok {
+				return "", err
+			}
+			errno, ok := operr.Err.(syscall.Errno)
+			if !ok {
+				return "", err
+			}
+			return "", fmt.Errorf("%v (windows errno=%d)", err, errno)
+		}
+		defer c.Close()
+
+		b := make([]byte, 100)
+		n, err := c.Read(b)
+		if err != nil && err != io.EOF {
+			return "", err
+		}
+		return string(b[:n]), nil
+	}
+
+	send := func(addr string, data string) error {
+		c, err := Dial("tcp", addr)
+		if err != nil {
+			return err
+		}
+		defer c.Close()
+
+		b := []byte(data)
+		n, err := c.Write(b)
+		if err != nil {
+			return err
+		}
+		if n != len(b) {
+			return fmt.Errorf(`Only %d chars of string "%s" sent`, n, data)
+		}
+		return nil
+	}
+
+	if envaddr := os.Getenv("GOTEST_DIAL_ADDR"); envaddr != "" {
+		// In child process.
+		c, err := Dial("tcp", envaddr)
+		if err != nil {
+			t.Fatalf("Dial failed: %v", err)
+		}
+		fmt.Printf("sleeping\n")
+		time.Sleep(time.Minute) // process will be killed here
+		c.Close()
+	}
+
+	ln, err := Listen("tcp", "127.0.0.1:0")
+	if err != nil {
+		t.Fatalf("Listen failed: %v", err)
+	}
+	defer ln.Close()
+
+	// Start child process that connects to our listener.
+	cmd := exec.Command(os.Args[0], "-test.run=TestAcceptIgnoreSomeErrors")
+	cmd.Env = append(os.Environ(), "GOTEST_DIAL_ADDR="+ln.Addr().String())
+	stdout, err := cmd.StdoutPipe()
+	if err != nil {
+		t.Fatalf("cmd.StdoutPipe failed: %v", err)
+	}
+	err = cmd.Start()
+	if err != nil {
+		t.Fatalf("cmd.Start failed: %v\n", err)
+	}
+	outReader := bufio.NewReader(stdout)
+	for {
+		s, err := outReader.ReadString('\n')
+		if err != nil {
+			t.Fatalf("reading stdout failed: %v", err)
+		}
+		if s == "sleeping\n" {
+			break
+		}
+	}
+	defer cmd.Wait() // ignore error - we know it is getting killed
+
+	const alittle = 100 * time.Millisecond
+	time.Sleep(alittle)
+	cmd.Process.Kill() // the only way to trigger the errors
+	time.Sleep(alittle)
+
+	// Send second connection data (with delay in a separate goroutine).
+	result := make(chan error)
+	go func() {
+		time.Sleep(alittle)
+		err := send(ln.Addr().String(), "abc")
+		if err != nil {
+			result <- err
+		}
+		result <- nil
+	}()
+	defer func() {
+		err := <-result
+		if err != nil {
+			t.Fatalf("send failed: %v", err)
+		}
+	}()
+
+	// Receive first or second connection.
+	s, err := recv(ln)
+	if err != nil {
+		t.Fatalf("recv failed: %v", err)
+	}
+	switch s {
+	case "":
+		// First connection data is received, lets get second connection data.
+	case "abc":
+		// First connection is lost forever, but that is ok.
+		return
+	default:
+		t.Fatalf(`"%s" received from recv, but "" or "abc" expected`, s)
+	}
+
+	// Get second connection data.
+	s, err = recv(ln)
+	if err != nil {
+		t.Fatalf("recv failed: %v", err)
+	}
+	if s != "abc" {
+		t.Fatalf(`"%s" received from recv, but "abc" expected`, s)
+	}
+}
diff --git a/src/net/netgo_unix_test.go b/src/net/netgo_unix_test.go
new file mode 100644
index 000000000..9fb2a567d
--- /dev/null
+++ b/src/net/netgo_unix_test.go
@@ -0,0 +1,24 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build !cgo netgo
+// +build darwin dragonfly freebsd linux netbsd openbsd solaris
+
+package net
+
+import "testing"
+
+func TestGoLookupIP(t *testing.T) {
+	host := "localhost"
+	_, err, ok := cgoLookupIP(host)
+	if ok {
+		t.Errorf("cgoLookupIP must be a placeholder")
+	}
+	if err != nil {
+		t.Errorf("cgoLookupIP failed: %v", err)
+	}
+	if _, err := goLookupIP(host); err != nil {
+		t.Errorf("goLookupIP failed: %v", err)
+	}
+}
diff --git a/src/net/packetconn_test.go b/src/net/packetconn_test.go
new file mode 100644
index 000000000..b6e4e76f9
--- /dev/null
+++ b/src/net/packetconn_test.go
@@ -0,0 +1,186 @@
+// Copyright 2012 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// This file implements API tests across platforms and will never have a build
+// tag.
+
+package net
+
+import (
+	"os"
+	"runtime"
+	"strings"
+	"testing"
+	"time"
+)
+
+func packetConnTestData(t *testing.T, net string, i int) ([]byte, func()) {
+	switch net {
+	case "udp":
+		return []byte("UDP PACKETCONN TEST"), nil
+	case "ip":
+		if skip, skipmsg := skipRawSocketTest(t); skip {
+			return nil, func() {
+				t.Logf(skipmsg)
+			}
+		}
+		b, err := (&icmpMessage{
+			Type: icmpv4EchoRequest, Code: 0,
+			Body: &icmpEcho{
+				ID: os.Getpid() & 0xffff, Seq: i + 1,
+				Data: []byte("IP PACKETCONN TEST"),
+			},
+		}).Marshal()
+		if err != nil {
+			return nil, func() {
+				t.Fatalf("icmpMessage.Marshal failed: %v", err)
+			}
+		}
+		return b, nil
+	case "unixgram":
+		switch runtime.GOOS {
+		case "nacl", "plan9", "windows":
+			return nil, func() {
+				t.Logf("skipping %q test on %q", net, runtime.GOOS)
+			}
+		default:
+			return []byte("UNIXGRAM PACKETCONN TEST"), nil
+		}
+	default:
+		return nil, func() {
+			t.Logf("skipping %q test", net)
+		}
+	}
+}
+
+var packetConnTests = []struct {
+	net   string
+	addr1 string
+	addr2 string
+}{
+	{"udp", "127.0.0.1:0", "127.0.0.1:0"},
+	{"ip:icmp", "127.0.0.1", "127.0.0.1"},
+	{"unixgram", testUnixAddr(), testUnixAddr()},
+}
+
+func TestPacketConn(t *testing.T) {
+	closer := func(c PacketConn, net, addr1, addr2 string) {
+		c.Close()
+		switch net {
+		case "unixgram":
+			os.Remove(addr1)
+			os.Remove(addr2)
+		}
+	}
+
+	for i, tt := range packetConnTests {
+		netstr := strings.Split(tt.net, ":")
+		wb, skipOrFatalFn := packetConnTestData(t, netstr[0], i)
+		if skipOrFatalFn != nil {
+			skipOrFatalFn()
+			continue
+		}
+
+		c1, err := ListenPacket(tt.net, tt.addr1)
+		if err != nil {
+			t.Fatalf("ListenPacket failed: %v", err)
+		}
+		defer closer(c1, netstr[0], tt.addr1, tt.addr2)
+		c1.LocalAddr()
+		c1.SetDeadline(time.Now().Add(100 * time.Millisecond))
+		c1.SetReadDeadline(time.Now().Add(100 * time.Millisecond))
+		c1.SetWriteDeadline(time.Now().Add(100 * time.Millisecond))
+
+		c2, err := ListenPacket(tt.net, tt.addr2)
+		if err != nil {
+			t.Fatalf("ListenPacket failed: %v", err)
+		}
+		defer closer(c2, netstr[0], tt.addr1, tt.addr2)
+		c2.LocalAddr()
+		c2.SetDeadline(time.Now().Add(100 * time.Millisecond))
+		c2.SetReadDeadline(time.Now().Add(100 * time.Millisecond))
+		c2.SetWriteDeadline(time.Now().Add(100 * time.Millisecond))
+
+		if _, err := c1.WriteTo(wb, c2.LocalAddr()); err != nil {
+			t.Fatalf("PacketConn.WriteTo failed: %v", err)
+		}
+		rb2 := make([]byte, 128)
+		if _, _, err := c2.ReadFrom(rb2); err != nil {
+			t.Fatalf("PacketConn.ReadFrom failed: %v", err)
+		}
+		if _, err := c2.WriteTo(wb, c1.LocalAddr()); err != nil {
+			t.Fatalf("PacketConn.WriteTo failed: %v", err)
+		}
+		rb1 := make([]byte, 128)
+		if _, _, err := c1.ReadFrom(rb1); err != nil {
+			t.Fatalf("PacketConn.ReadFrom failed: %v", err)
+		}
+	}
+}
+
+func TestConnAndPacketConn(t *testing.T) {
+	closer := func(c PacketConn, net, addr1, addr2 string) {
+		c.Close()
+		switch net {
+		case "unixgram":
+			os.Remove(addr1)
+			os.Remove(addr2)
+		}
+	}
+
+	for i, tt := range packetConnTests {
+		var wb []byte
+		netstr := strings.Split(tt.net, ":")
+		wb, skipOrFatalFn := packetConnTestData(t, netstr[0], i)
+		if skipOrFatalFn != nil {
+			skipOrFatalFn()
+			continue
+		}
+
+		c1, err := ListenPacket(tt.net, tt.addr1)
+		if err != nil {
+			t.Fatalf("ListenPacket failed: %v", err)
+		}
+		defer closer(c1, netstr[0], tt.addr1, tt.addr2)
+		c1.LocalAddr()
+		c1.SetDeadline(time.Now().Add(100 * time.Millisecond))
+		c1.SetReadDeadline(time.Now().Add(100 * time.Millisecond))
+		c1.SetWriteDeadline(time.Now().Add(100 * time.Millisecond))
+
+		c2, err := Dial(tt.net, c1.LocalAddr().String())
+		if err != nil {
+			t.Fatalf("Dial failed: %v", err)
+		}
+		defer c2.Close()
+		c2.LocalAddr()
+		c2.RemoteAddr()
+		c2.SetDeadline(time.Now().Add(100 * time.Millisecond))
+		c2.SetReadDeadline(time.Now().Add(100 * time.Millisecond))
+		c2.SetWriteDeadline(time.Now().Add(100 * time.Millisecond))
+
+		if _, err := c2.Write(wb); err != nil {
+			t.Fatalf("Conn.Write failed: %v", err)
+		}
+		rb1 := make([]byte, 128)
+		if _, _, err := c1.ReadFrom(rb1); err != nil {
+			t.Fatalf("PacketConn.ReadFrom failed: %v", err)
+		}
+		var dst Addr
+		switch netstr[0] {
+		case "ip":
+			dst = &IPAddr{IP: IPv4(127, 0, 0, 1)}
+		case "unixgram":
+			continue
+		default:
+			dst = c2.LocalAddr()
+		}
+		if _, err := c1.WriteTo(wb, dst); err != nil {
+			t.Fatalf("PacketConn.WriteTo failed: %v", err)
+		}
+		rb2 := make([]byte, 128)
+		if _, err := c2.Read(rb2); err != nil {
+			t.Fatalf("Conn.Read failed: %v", err)
+		}
+	}
+}
diff --git a/src/net/parse.go b/src/net/parse.go
new file mode 100644
index 000000000..e1d0130c9
--- /dev/null
+++ b/src/net/parse.go
@@ -0,0 +1,247 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Simple file i/o and string manipulation, to avoid
+// depending on strconv and bufio and strings.
+
+package net
+
+import (
+	"io"
+	"os"
+)
+
+type file struct {
+	file  *os.File
+	data  []byte
+	atEOF bool
+}
+
+func (f *file) close() { f.file.Close() }
+
+func (f *file) getLineFromData() (s string, ok bool) {
+	data := f.data
+	i := 0
+	for i = 0; i < len(data); i++ {
+		if data[i] == '\n' {
+			s = string(data[0:i])
+			ok = true
+			// move data
+			i++
+			n := len(data) - i
+			copy(data[0:], data[i:])
+			f.data = data[0:n]
+			return
+		}
+	}
+	if f.atEOF && len(f.data) > 0 {
+		// EOF, return all we have
+		s = string(data)
+		f.data = f.data[0:0]
+		ok = true
+	}
+	return
+}
+
+func (f *file) readLine() (s string, ok bool) {
+	if s, ok = f.getLineFromData(); ok {
+		return
+	}
+	if len(f.data) < cap(f.data) {
+		ln := len(f.data)
+		n, err := io.ReadFull(f.file, f.data[ln:cap(f.data)])
+		if n >= 0 {
+			f.data = f.data[0 : ln+n]
+		}
+		if err == io.EOF || err == io.ErrUnexpectedEOF {
+			f.atEOF = true
+		}
+	}
+	s, ok = f.getLineFromData()
+	return
+}
+
+func open(name string) (*file, error) {
+	fd, err := os.Open(name)
+	if err != nil {
+		return nil, err
+	}
+	return &file{fd, make([]byte, 0, os.Getpagesize()), false}, nil
+}
+
+func byteIndex(s string, c byte) int {
+	for i := 0; i < len(s); i++ {
+		if s[i] == c {
+			return i
+		}
+	}
+	return -1
+}
+
+// Count occurrences in s of any bytes in t.
+func countAnyByte(s string, t string) int {
+	n := 0
+	for i := 0; i < len(s); i++ {
+		if byteIndex(t, s[i]) >= 0 {
+			n++
+		}
+	}
+	return n
+}
+
+// Split s at any bytes in t.
+func splitAtBytes(s string, t string) []string {
+	a := make([]string, 1+countAnyByte(s, t))
+	n := 0
+	last := 0
+	for i := 0; i < len(s); i++ {
+		if byteIndex(t, s[i]) >= 0 {
+			if last < i {
+				a[n] = string(s[last:i])
+				n++
+			}
+			last = i + 1
+		}
+	}
+	if last < len(s) {
+		a[n] = string(s[last:])
+		n++
+	}
+	return a[0:n]
+}
+
+func getFields(s string) []string { return splitAtBytes(s, " \r\t\n") }
+
+// Bigger than we need, not too big to worry about overflow
+const big = 0xFFFFFF
+
+// Decimal to integer starting at &s[i0].
+// Returns number, new offset, success.
+func dtoi(s string, i0 int) (n int, i int, ok bool) {
+	n = 0
+	for i = i0; i < len(s) && '0' <= s[i] && s[i] <= '9'; i++ {
+		n = n*10 + int(s[i]-'0')
+		if n >= big {
+			return 0, i, false
+		}
+	}
+	if i == i0 {
+		return 0, i, false
+	}
+	return n, i, true
+}
+
+// Hexadecimal to integer starting at &s[i0].
+// Returns number, new offset, success.
+func xtoi(s string, i0 int) (n int, i int, ok bool) {
+	n = 0
+	for i = i0; i < len(s); i++ {
+		if '0' <= s[i] && s[i] <= '9' {
+			n *= 16
+			n += int(s[i] - '0')
+		} else if 'a' <= s[i] && s[i] <= 'f' {
+			n *= 16
+			n += int(s[i]-'a') + 10
+		} else if 'A' <= s[i] && s[i] <= 'F' {
+			n *= 16
+			n += int(s[i]-'A') + 10
+		} else {
+			break
+		}
+		if n >= big {
+			return 0, i, false
+		}
+	}
+	if i == i0 {
+		return 0, i, false
+	}
+	return n, i, true
+}
+
+// xtoi2 converts the next two hex digits of s into a byte.
+// If s is longer than 2 bytes then the third byte must be e.
+// If the first two bytes of s are not hex digits or the third byte
+// does not match e, false is returned.
+func xtoi2(s string, e byte) (byte, bool) {
+	if len(s) > 2 && s[2] != e {
+		return 0, false
+	}
+	n, ei, ok := xtoi(s[:2], 0)
+	return byte(n), ok && ei == 2
+}
+
+// Integer to decimal.
+func itoa(i int) string {
+	var buf [30]byte
+	n := len(buf)
+	neg := false
+	if i < 0 {
+		i = -i
+		neg = true
+	}
+	ui := uint(i)
+	for ui > 0 || n == len(buf) {
+		n--
+		buf[n] = byte('0' + ui%10)
+		ui /= 10
+	}
+	if neg {
+		n--
+		buf[n] = '-'
+	}
+	return string(buf[n:])
+}
+
+// Convert i to decimal string.
+func itod(i uint) string {
+	if i == 0 {
+		return "0"
+	}
+
+	// Assemble decimal in reverse order.
+	var b [32]byte
+	bp := len(b)
+	for ; i > 0; i /= 10 {
+		bp--
+		b[bp] = byte(i%10) + '0'
+	}
+
+	return string(b[bp:])
+}
+
+// Convert i to a hexadecimal string. Leading zeros are not printed.
+func appendHex(dst []byte, i uint32) []byte {
+	if i == 0 {
+		return append(dst, '0')
+	}
+	for j := 7; j >= 0; j-- {
+		v := i >> uint(j*4)
+		if v > 0 {
+			dst = append(dst, hexDigit[v&0xf])
+		}
+	}
+	return dst
+}
+
+// Number of occurrences of b in s.
+func count(s string, b byte) int {
+	n := 0
+	for i := 0; i < len(s); i++ {
+		if s[i] == b {
+			n++
+		}
+	}
+	return n
+}
+
+// Index of rightmost occurrence of b in s.
+func last(s string, b byte) int {
+	i := len(s)
+	for i--; i >= 0; i-- {
+		if s[i] == b {
+			break
+		}
+	}
+	return i
+}
diff --git a/src/net/parse_test.go b/src/net/parse_test.go
new file mode 100644
index 000000000..7b213b75b
--- /dev/null
+++ b/src/net/parse_test.go
@@ -0,0 +1,53 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package net
+
+import (
+	"bufio"
+	"os"
+	"runtime"
+	"testing"
+)
+
+func TestReadLine(t *testing.T) {
+	// /etc/services file does not exist on android, plan9, windows.
+	switch runtime.GOOS {
+	case "android", "plan9", "windows":
+		t.Skipf("skipping test on %q", runtime.GOOS)
+	}
+	filename := "/etc/services" // a nice big file
+
+	fd, err := os.Open(filename)
+	if err != nil {
+		t.Fatalf("open %s: %v", filename, err)
+	}
+	defer fd.Close()
+	br := bufio.NewReader(fd)
+
+	file, err := open(filename)
+	if file == nil {
+		t.Fatalf("net.open(%s) = nil", filename)
+	}
+	defer file.close()
+
+	lineno := 1
+	byteno := 0
+	for {
+		bline, berr := br.ReadString('\n')
+		if n := len(bline); n > 0 {
+			bline = bline[0 : n-1]
+		}
+		line, ok := file.readLine()
+		if (berr != nil) != !ok || bline != line {
+			t.Fatalf("%s:%d (#%d)\nbufio => %q, %v\nnet => %q, %v",
+				filename, lineno, byteno, bline, berr, line, ok)
+		}
+		if !ok {
+			break
+		}
+		lineno++
+		byteno += len(line) + 1
+	}
+}
diff --git a/src/net/pipe.go b/src/net/pipe.go
new file mode 100644
index 000000000..f1a2eca4e
--- /dev/null
+++ b/src/net/pipe.go
@@ -0,0 +1,67 @@
+// Copyright 2010 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package net
+
+import (
+	"errors"
+	"io"
+	"time"
+)
+
+// Pipe creates a synchronous, in-memory, full duplex
+// network connection; both ends implement the Conn interface.
+// Reads on one end are matched with writes on the other,
+// copying data directly between the two; there is no internal
+// buffering.
+func Pipe() (Conn, Conn) {
+	r1, w1 := io.Pipe()
+	r2, w2 := io.Pipe()
+
+	return &pipe{r1, w2}, &pipe{r2, w1}
+}
+
+type pipe struct {
+	*io.PipeReader
+	*io.PipeWriter
+}
+
+type pipeAddr int
+
+func (pipeAddr) Network() string {
+	return "pipe"
+}
+
+func (pipeAddr) String() string {
+	return "pipe"
+}
+
+func (p *pipe) Close() error {
+	err := p.PipeReader.Close()
+	err1 := p.PipeWriter.Close()
+	if err == nil {
+		err = err1
+	}
+	return err
+}
+
+func (p *pipe) LocalAddr() Addr {
+	return pipeAddr(0)
+}
+
+func (p *pipe) RemoteAddr() Addr {
+	return pipeAddr(0)
+}
+
+func (p *pipe) SetDeadline(t time.Time) error {
+	return errors.New("net.Pipe does not support deadlines")
+}
+
+func (p *pipe) SetReadDeadline(t time.Time) error {
+	return errors.New("net.Pipe does not support deadlines")
+}
+
+func (p *pipe) SetWriteDeadline(t time.Time) error {
+	return errors.New("net.Pipe does not support deadlines")
+}
diff --git a/src/net/pipe_test.go b/src/net/pipe_test.go
new file mode 100644
index 000000000..afe4f2408
--- /dev/null
+++ b/src/net/pipe_test.go
@@ -0,0 +1,56 @@
+// Copyright 2010 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package net
+
+import (
+	"bytes"
+	"io"
+	"testing"
+)
+
+func checkWrite(t *testing.T, w io.Writer, data []byte, c chan int) {
+	n, err := w.Write(data)
+	if err != nil {
+		t.Errorf("write: %v", err)
+	}
+	if n != len(data) {
+		t.Errorf("short write: %d != %d", n, len(data))
+	}
+	c <- 0
+}
+
+func checkRead(t *testing.T, r io.Reader, data []byte, wantErr error) {
+	buf := make([]byte, len(data)+10)
+	n, err := r.Read(buf)
+	if err != wantErr {
+		t.Errorf("read: %v", err)
+		return
+	}
+	if n != len(data) || !bytes.Equal(buf[0:n], data) {
+		t.Errorf("bad read: got %q", buf[0:n])
+		return
+	}
+}
+
+// Test a simple read/write/close sequence.
+// Assumes that the underlying io.Pipe implementation
+// is solid and we're just testing the net wrapping.
+
+func TestPipe(t *testing.T) {
+	c := make(chan int)
+	cli, srv := Pipe()
+	go checkWrite(t, cli, []byte("hello, world"), c)
+	checkRead(t, srv, []byte("hello, world"), nil)
+	<-c
+	go checkWrite(t, srv, []byte("line 2"), c)
+	checkRead(t, cli, []byte("line 2"), nil)
+	<-c
+	go checkWrite(t, cli, []byte("a third line"), c)
+	checkRead(t, srv, []byte("a third line"), nil)
+	<-c
+	go srv.Close()
+	checkRead(t, cli, nil, io.EOF)
+	cli.Close()
+}
diff --git a/src/net/port.go b/src/net/port.go
new file mode 100644
index 000000000..c24f4ed5b
--- /dev/null
+++ b/src/net/port.go
@@ -0,0 +1,24 @@
+// Copyright 2012 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Network service port manipulations
+
+package net
+
+// parsePort parses port as a network service port number for both
+// TCP and UDP.
+func parsePort(net, port string) (int, error) {
+	p, i, ok := dtoi(port, 0)
+	if !ok || i != len(port) {
+		var err error
+		p, err = LookupPort(net, port)
+		if err != nil {
+			return 0, err
+		}
+	}
+	if p < 0 || p > 0xFFFF {
+		return 0, &AddrError{"invalid port", port}
+	}
+	return p, nil
+}
diff --git a/src/net/port_test.go b/src/net/port_test.go
new file mode 100644
index 000000000..9e8968f35
--- /dev/null
+++ b/src/net/port_test.go
@@ -0,0 +1,53 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package net
+
+import (
+	"testing"
+)
+
+type portTest struct {
+	netw string
+	name string
+	port int
+	ok   bool
+}
+
+var porttests = []portTest{
+	{"tcp", "echo", 7, true},
+	{"tcp", "discard", 9, true},
+	{"tcp", "systat", 11, true},
+	{"tcp", "daytime", 13, true},
+	{"tcp", "chargen", 19, true},
+	{"tcp", "ftp-data", 20, true},
+	{"tcp", "ftp", 21, true},
+	{"tcp", "telnet", 23, true},
+	{"tcp", "smtp", 25, true},
+	{"tcp", "time", 37, true},
+	{"tcp", "domain", 53, true},
+	{"tcp", "finger", 79, true},
+
+	{"udp", "echo", 7, true},
+	{"udp", "tftp", 69, true},
+	{"udp", "bootpc", 68, true},
+	{"udp", "bootps", 67, true},
+	{"udp", "domain", 53, true},
+	{"udp", "ntp", 123, true},
+	{"udp", "snmp", 161, true},
+	{"udp", "syslog", 514, true},
+
+	{"--badnet--", "zzz", 0, false},
+	{"tcp", "--badport--", 0, false},
+}
+
+func TestLookupPort(t *testing.T) {
+	for i := 0; i < len(porttests); i++ {
+		tt := porttests[i]
+		if port, err := LookupPort(tt.netw, tt.name); port != tt.port || (err == nil) != tt.ok {
+			t.Errorf("LookupPort(%q, %q) = %v, %v; want %v",
+				tt.netw, tt.name, port, err, tt.port)
+		}
+	}
+}
diff --git a/src/net/port_unix.go b/src/net/port_unix.go
new file mode 100644
index 000000000..89558c1f0
--- /dev/null
+++ b/src/net/port_unix.go
@@ -0,0 +1,73 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build darwin dragonfly freebsd linux nacl netbsd openbsd solaris
+
+// Read system port mappings from /etc/services
+
+package net
+
+import "sync"
+
+// services contains minimal mappings between services names and port
+// numbers for platforms that don't have a complete list of port numbers
+// (some Solaris distros).
+var services = map[string]map[string]int{
+	"tcp": {"http": 80},
+}
+var servicesError error
+var onceReadServices sync.Once
+
+func readServices() {
+	var file *file
+	if file, servicesError = open("/etc/services"); servicesError != nil {
+		return
+	}
+	for line, ok := file.readLine(); ok; line, ok = file.readLine() {
+		// "http 80/tcp www www-http # World Wide Web HTTP"
+		if i := byteIndex(line, '#'); i >= 0 {
+			line = line[0:i]
+		}
+		f := getFields(line)
+		if len(f) < 2 {
+			continue
+		}
+		portnet := f[1] // "80/tcp"
+		port, j, ok := dtoi(portnet, 0)
+		if !ok || port <= 0 || j >= len(portnet) || portnet[j] != '/' {
+			continue
+		}
+		netw := portnet[j+1:] // "tcp"
+		m, ok1 := services[netw]
+		if !ok1 {
+			m = make(map[string]int)
+			services[netw] = m
+		}
+		for i := 0; i < len(f); i++ {
+			if i != 1 { // f[1] was port/net
+				m[f[i]] = port
+			}
+		}
+	}
+	file.close()
+}
+
+// goLookupPort is the native Go implementation of LookupPort.
+func goLookupPort(network, service string) (port int, err error) {
+	onceReadServices.Do(readServices)
+
+	switch network {
+	case "tcp4", "tcp6":
+		network = "tcp"
+	case "udp4", "udp6":
+		network = "udp"
+	}
+
+	if m, ok := services[network]; ok {
+		if port, ok = m[service]; ok {
+			return
+		}
+	}
+	return 0, &AddrError{"unknown port", network + "/" + service}
+}
diff --git a/src/net/protoconn_test.go b/src/net/protoconn_test.go
new file mode 100644
index 000000000..12856b6c3
--- /dev/null
+++ b/src/net/protoconn_test.go
@@ -0,0 +1,386 @@
+// Copyright 2012 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// This file implements API tests across platforms and will never have a build
+// tag.
+
+package net
+
+import (
+	"io/ioutil"
+	"os"
+	"runtime"
+	"testing"
+	"time"
+)
+
+// testUnixAddr uses ioutil.TempFile to get a name that is unique. It
+// also uses /tmp directory in case it is prohibited to create UNIX
+// sockets in TMPDIR.
+func testUnixAddr() string {
+	f, err := ioutil.TempFile("", "nettest")
+	if err != nil {
+		panic(err)
+	}
+	addr := f.Name()
+	f.Close()
+	os.Remove(addr)
+	return addr
+}
+
+var condFatalf = func() func(*testing.T, string, ...interface{}) {
+	// A few APIs are not implemented yet on both Plan 9 and Windows.
+	switch runtime.GOOS {
+	case "plan9", "windows":
+		return (*testing.T).Logf
+	}
+	return (*testing.T).Fatalf
+}()
+
+func TestTCPListenerSpecificMethods(t *testing.T) {
+	switch runtime.GOOS {
+	case "plan9":
+		t.Skipf("skipping test on %q", runtime.GOOS)
+	}
+
+	la, err := ResolveTCPAddr("tcp4", "127.0.0.1:0")
+	if err != nil {
+		t.Fatalf("ResolveTCPAddr failed: %v", err)
+	}
+	ln, err := ListenTCP("tcp4", la)
+	if err != nil {
+		t.Fatalf("ListenTCP failed: %v", err)
+	}
+	defer ln.Close()
+	ln.Addr()
+	ln.SetDeadline(time.Now().Add(30 * time.Nanosecond))
+
+	if c, err := ln.Accept(); err != nil {
+		if !err.(Error).Timeout() {
+			t.Fatalf("TCPListener.Accept failed: %v", err)
+		}
+	} else {
+		c.Close()
+	}
+	if c, err := ln.AcceptTCP(); err != nil {
+		if !err.(Error).Timeout() {
+			t.Fatalf("TCPListener.AcceptTCP failed: %v", err)
+		}
+	} else {
+		c.Close()
+	}
+
+	if f, err := ln.File(); err != nil {
+		condFatalf(t, "TCPListener.File failed: %v", err)
+	} else {
+		f.Close()
+	}
+}
+
+func TestTCPConnSpecificMethods(t *testing.T) {
+	la, err := ResolveTCPAddr("tcp4", "127.0.0.1:0")
+	if err != nil {
+		t.Fatalf("ResolveTCPAddr failed: %v", err)
+	}
+	ln, err := ListenTCP("tcp4", la)
+	if err != nil {
+		t.Fatalf("ListenTCP failed: %v", err)
+	}
+	defer ln.Close()
+	ln.Addr()
+
+	done := make(chan int)
+	go transponder(t, ln, done)
+
+	ra, err := ResolveTCPAddr("tcp4", ln.Addr().String())
+	if err != nil {
+		t.Fatalf("ResolveTCPAddr failed: %v", err)
+	}
+	c, err := DialTCP("tcp4", nil, ra)
+	if err != nil {
+		t.Fatalf("DialTCP failed: %v", err)
+	}
+	defer c.Close()
+	c.SetKeepAlive(false)
+	c.SetKeepAlivePeriod(3 * time.Second)
+	c.SetLinger(0)
+	c.SetNoDelay(false)
+	c.LocalAddr()
+	c.RemoteAddr()
+	c.SetDeadline(time.Now().Add(someTimeout))
+	c.SetReadDeadline(time.Now().Add(someTimeout))
+	c.SetWriteDeadline(time.Now().Add(someTimeout))
+
+	if _, err := c.Write([]byte("TCPCONN TEST")); err != nil {
+		t.Fatalf("TCPConn.Write failed: %v", err)
+	}
+	rb := make([]byte, 128)
+	if _, err := c.Read(rb); err != nil {
+		t.Fatalf("TCPConn.Read failed: %v", err)
+	}
+
+	<-done
+}
+
+func TestUDPConnSpecificMethods(t *testing.T) {
+	la, err := ResolveUDPAddr("udp4", "127.0.0.1:0")
+	if err != nil {
+		t.Fatalf("ResolveUDPAddr failed: %v", err)
+	}
+	c, err := ListenUDP("udp4", la)
+	if err != nil {
+		t.Fatalf("ListenUDP failed: %v", err)
+	}
+	defer c.Close()
+	c.LocalAddr()
+	c.RemoteAddr()
+	c.SetDeadline(time.Now().Add(someTimeout))
+	c.SetReadDeadline(time.Now().Add(someTimeout))
+	c.SetWriteDeadline(time.Now().Add(someTimeout))
+	c.SetReadBuffer(2048)
+	c.SetWriteBuffer(2048)
+
+	wb := []byte("UDPCONN TEST")
+	rb := make([]byte, 128)
+	if _, err := c.WriteToUDP(wb, c.LocalAddr().(*UDPAddr)); err != nil {
+		t.Fatalf("UDPConn.WriteToUDP failed: %v", err)
+	}
+	if _, _, err := c.ReadFromUDP(rb); err != nil {
+		t.Fatalf("UDPConn.ReadFromUDP failed: %v", err)
+	}
+	if _, _, err := c.WriteMsgUDP(wb, nil, c.LocalAddr().(*UDPAddr)); err != nil {
+		condFatalf(t, "UDPConn.WriteMsgUDP failed: %v", err)
+	}
+	if _, _, _, _, err := c.ReadMsgUDP(rb, nil); err != nil {
+		condFatalf(t, "UDPConn.ReadMsgUDP failed: %v", err)
+	}
+
+	if f, err := c.File(); err != nil {
+		condFatalf(t, "UDPConn.File failed: %v", err)
+	} else {
+		f.Close()
+	}
+
+	defer func() {
+		if p := recover(); p != nil {
+			t.Fatalf("UDPConn.WriteToUDP or WriteMsgUDP panicked: %v", p)
+		}
+	}()
+
+	c.WriteToUDP(wb, nil)
+	c.WriteMsgUDP(wb, nil, nil)
+}
+
+func TestIPConnSpecificMethods(t *testing.T) {
+	if skip, skipmsg := skipRawSocketTest(t); skip {
+		t.Skip(skipmsg)
+	}
+
+	la, err := ResolveIPAddr("ip4", "127.0.0.1")
+	if err != nil {
+		t.Fatalf("ResolveIPAddr failed: %v", err)
+	}
+	c, err := ListenIP("ip4:icmp", la)
+	if err != nil {
+		t.Fatalf("ListenIP failed: %v", err)
+	}
+	defer c.Close()
+	c.LocalAddr()
+	c.RemoteAddr()
+	c.SetDeadline(time.Now().Add(someTimeout))
+	c.SetReadDeadline(time.Now().Add(someTimeout))
+	c.SetWriteDeadline(time.Now().Add(someTimeout))
+	c.SetReadBuffer(2048)
+	c.SetWriteBuffer(2048)
+
+	wb, err := (&icmpMessage{
+		Type: icmpv4EchoRequest, Code: 0,
+		Body: &icmpEcho{
+			ID: os.Getpid() & 0xffff, Seq: 1,
+			Data: []byte("IPCONN TEST "),
+		},
+	}).Marshal()
+	if err != nil {
+		t.Fatalf("icmpMessage.Marshal failed: %v", err)
+	}
+	rb := make([]byte, 20+len(wb))
+	if _, err := c.WriteToIP(wb, c.LocalAddr().(*IPAddr)); err != nil {
+		t.Fatalf("IPConn.WriteToIP failed: %v", err)
+	}
+	if _, _, err := c.ReadFromIP(rb); err != nil {
+		t.Fatalf("IPConn.ReadFromIP failed: %v", err)
+	}
+	if _, _, err := c.WriteMsgIP(wb, nil, c.LocalAddr().(*IPAddr)); err != nil {
+		condFatalf(t, "IPConn.WriteMsgIP failed: %v", err)
+	}
+	if _, _, _, _, err := c.ReadMsgIP(rb, nil); err != nil {
+		condFatalf(t, "IPConn.ReadMsgIP failed: %v", err)
+	}
+
+	if f, err := c.File(); err != nil {
+		condFatalf(t, "IPConn.File failed: %v", err)
+	} else {
+		f.Close()
+	}
+
+	defer func() {
+		if p := recover(); p != nil {
+			t.Fatalf("IPConn.WriteToIP or WriteMsgIP panicked: %v", p)
+		}
+	}()
+
+	c.WriteToIP(wb, nil)
+	c.WriteMsgIP(wb, nil, nil)
+}
+
+func TestUnixListenerSpecificMethods(t *testing.T) {
+	switch runtime.GOOS {
+	case "nacl", "plan9", "windows":
+		t.Skipf("skipping test on %q", runtime.GOOS)
+	}
+
+	addr := testUnixAddr()
+	la, err := ResolveUnixAddr("unix", addr)
+	if err != nil {
+		t.Fatalf("ResolveUnixAddr failed: %v", err)
+	}
+	ln, err := ListenUnix("unix", la)
+	if err != nil {
+		t.Fatalf("ListenUnix failed: %v", err)
+	}
+	defer ln.Close()
+	defer os.Remove(addr)
+	ln.Addr()
+	ln.SetDeadline(time.Now().Add(30 * time.Nanosecond))
+
+	if c, err := ln.Accept(); err != nil {
+		if !err.(Error).Timeout() {
+			t.Fatalf("UnixListener.Accept failed: %v", err)
+		}
+	} else {
+		c.Close()
+	}
+	if c, err := ln.AcceptUnix(); err != nil {
+		if !err.(Error).Timeout() {
+			t.Fatalf("UnixListener.AcceptUnix failed: %v", err)
+		}
+	} else {
+		c.Close()
+	}
+
+	if f, err := ln.File(); err != nil {
+		t.Fatalf("UnixListener.File failed: %v", err)
+	} else {
+		f.Close()
+	}
+}
+
+func TestUnixConnSpecificMethods(t *testing.T) {
+	switch runtime.GOOS {
+	case "nacl", "plan9", "windows":
+		t.Skipf("skipping test on %q", runtime.GOOS)
+	}
+
+	addr1, addr2, addr3 := testUnixAddr(), testUnixAddr(), testUnixAddr()
+
+	a1, err := ResolveUnixAddr("unixgram", addr1)
+	if err != nil {
+		t.Fatalf("ResolveUnixAddr failed: %v", err)
+	}
+	c1, err := DialUnix("unixgram", a1, nil)
+	if err != nil {
+		t.Fatalf("DialUnix failed: %v", err)
+	}
+	defer c1.Close()
+	defer os.Remove(addr1)
+	c1.LocalAddr()
+	c1.RemoteAddr()
+	c1.SetDeadline(time.Now().Add(someTimeout))
+	c1.SetReadDeadline(time.Now().Add(someTimeout))
+	c1.SetWriteDeadline(time.Now().Add(someTimeout))
+	c1.SetReadBuffer(2048)
+	c1.SetWriteBuffer(2048)
+
+	a2, err := ResolveUnixAddr("unixgram", addr2)
+	if err != nil {
+		t.Fatalf("ResolveUnixAddr failed: %v", err)
+	}
+	c2, err := DialUnix("unixgram", a2, nil)
+	if err != nil {
+		t.Fatalf("DialUnix failed: %v", err)
+	}
+	defer c2.Close()
+	defer os.Remove(addr2)
+	c2.LocalAddr()
+	c2.RemoteAddr()
+	c2.SetDeadline(time.Now().Add(someTimeout))
+	c2.SetReadDeadline(time.Now().Add(someTimeout))
+	c2.SetWriteDeadline(time.Now().Add(someTimeout))
+	c2.SetReadBuffer(2048)
+	c2.SetWriteBuffer(2048)
+
+	a3, err := ResolveUnixAddr("unixgram", addr3)
+	if err != nil {
+		t.Fatalf("ResolveUnixAddr failed: %v", err)
+	}
+	c3, err := ListenUnixgram("unixgram", a3)
+	if err != nil {
+		t.Fatalf("ListenUnixgram failed: %v", err)
+	}
+	defer c3.Close()
+	defer os.Remove(addr3)
+	c3.LocalAddr()
+	c3.RemoteAddr()
+	c3.SetDeadline(time.Now().Add(someTimeout))
+	c3.SetReadDeadline(time.Now().Add(someTimeout))
+	c3.SetWriteDeadline(time.Now().Add(someTimeout))
+	c3.SetReadBuffer(2048)
+	c3.SetWriteBuffer(2048)
+
+	wb := []byte("UNIXCONN TEST")
+	rb1 := make([]byte, 128)
+	rb2 := make([]byte, 128)
+	rb3 := make([]byte, 128)
+	if _, _, err := c1.WriteMsgUnix(wb, nil, a2); err != nil {
+		t.Fatalf("UnixConn.WriteMsgUnix failed: %v", err)
+	}
+	if _, _, _, _, err := c2.ReadMsgUnix(rb2, nil); err != nil {
+		t.Fatalf("UnixConn.ReadMsgUnix failed: %v", err)
+	}
+	if _, err := c2.WriteToUnix(wb, a1); err != nil {
+		t.Fatalf("UnixConn.WriteToUnix failed: %v", err)
+	}
+	if _, _, err := c1.ReadFromUnix(rb1); err != nil {
+		t.Fatalf("UnixConn.ReadFromUnix failed: %v", err)
+	}
+	if _, err := c3.WriteToUnix(wb, a1); err != nil {
+		t.Fatalf("UnixConn.WriteToUnix failed: %v", err)
+	}
+	if _, _, err := c1.ReadFromUnix(rb1); err != nil {
+		t.Fatalf("UnixConn.ReadFromUnix failed: %v", err)
+	}
+	if _, err := c2.WriteToUnix(wb, a3); err != nil {
+		t.Fatalf("UnixConn.WriteToUnix failed: %v", err)
+	}
+	if _, _, err := c3.ReadFromUnix(rb3); err != nil {
+		t.Fatalf("UnixConn.ReadFromUnix failed: %v", err)
+	}
+
+	if f, err := c1.File(); err != nil {
+		t.Fatalf("UnixConn.File failed: %v", err)
+	} else {
+		f.Close()
+	}
+
+	defer func() {
+		if p := recover(); p != nil {
+			t.Fatalf("UnixConn.WriteToUnix or WriteMsgUnix panicked: %v", p)
+		}
+	}()
+
+	c1.WriteToUnix(wb, nil)
+	c1.WriteMsgUnix(wb, nil, nil)
+	c3.WriteToUnix(wb, nil)
+	c3.WriteMsgUnix(wb, nil, nil)
+}
diff --git a/src/net/race.go b/src/net/race.go
new file mode 100644
index 000000000..2f02a6c22
--- /dev/null
+++ b/src/net/race.go
@@ -0,0 +1,31 @@
+// Copyright 2013 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build race
+// +build windows
+
+package net
+
+import (
+	"runtime"
+	"unsafe"
+)
+
+const raceenabled = true
+
+func raceAcquire(addr unsafe.Pointer) {
+	runtime.RaceAcquire(addr)
+}
+
+func raceReleaseMerge(addr unsafe.Pointer) {
+	runtime.RaceReleaseMerge(addr)
+}
+
+func raceReadRange(addr unsafe.Pointer, len int) {
+	runtime.RaceReadRange(addr, len)
+}
+
+func raceWriteRange(addr unsafe.Pointer, len int) {
+	runtime.RaceWriteRange(addr, len)
+}
diff --git a/src/net/race0.go b/src/net/race0.go
new file mode 100644
index 000000000..f50429779
--- /dev/null
+++ b/src/net/race0.go
@@ -0,0 +1,26 @@
+// Copyright 2013 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build !race
+// +build windows
+
+package net
+
+import (
+	"unsafe"
+)
+
+const raceenabled = false
+
+func raceAcquire(addr unsafe.Pointer) {
+}
+
+func raceReleaseMerge(addr unsafe.Pointer) {
+}
+
+func raceReadRange(addr unsafe.Pointer, len int) {
+}
+
+func raceWriteRange(addr unsafe.Pointer, len int) {
+}
diff --git a/src/net/rpc/client.go b/src/net/rpc/client.go
new file mode 100644
index 000000000..21f79b068
--- /dev/null
+++ b/src/net/rpc/client.go
@@ -0,0 +1,317 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package rpc
+
+import (
+	"bufio"
+	"encoding/gob"
+	"errors"
+	"io"
+	"log"
+	"net"
+	"net/http"
+	"sync"
+)
+
+// ServerError represents an error that has been returned from
+// the remote side of the RPC connection.
+type ServerError string
+
+func (e ServerError) Error() string {
+	return string(e)
+}
+
+var ErrShutdown = errors.New("connection is shut down")
+
+// Call represents an active RPC.
+type Call struct {
+	ServiceMethod string      // The name of the service and method to call.
+	Args          interface{} // The argument to the function (*struct).
+	Reply         interface{} // The reply from the function (*struct).
+	Error         error       // After completion, the error status.
+	Done          chan *Call  // Strobes when call is complete.
+}
+
+// Client represents an RPC Client.
+// There may be multiple outstanding Calls associated
+// with a single Client, and a Client may be used by
+// multiple goroutines simultaneously.
+type Client struct {
+	codec ClientCodec
+
+	sending sync.Mutex
+
+	mutex    sync.Mutex // protects following
+	request  Request
+	seq      uint64
+	pending  map[uint64]*Call
+	closing  bool // user has called Close
+	shutdown bool // server has told us to stop
+}
+
+// A ClientCodec implements writing of RPC requests and
+// reading of RPC responses for the client side of an RPC session.
+// The client calls WriteRequest to write a request to the connection
+// and calls ReadResponseHeader and ReadResponseBody in pairs
+// to read responses.  The client calls Close when finished with the
+// connection. ReadResponseBody may be called with a nil
+// argument to force the body of the response to be read and then
+// discarded.
+type ClientCodec interface {
+	// WriteRequest must be safe for concurrent use by multiple goroutines.
+	WriteRequest(*Request, interface{}) error
+	ReadResponseHeader(*Response) error
+	ReadResponseBody(interface{}) error
+
+	Close() error
+}
+
+func (client *Client) send(call *Call) {
+	client.sending.Lock()
+	defer client.sending.Unlock()
+
+	// Register this call.
+	client.mutex.Lock()
+	if client.shutdown || client.closing {
+		call.Error = ErrShutdown
+		client.mutex.Unlock()
+		call.done()
+		return
+	}
+	seq := client.seq
+	client.seq++
+	client.pending[seq] = call
+	client.mutex.Unlock()
+
+	// Encode and send the request.
+	client.request.Seq = seq
+	client.request.ServiceMethod = call.ServiceMethod
+	err := client.codec.WriteRequest(&client.request, call.Args)
+	if err != nil {
+		client.mutex.Lock()
+		call = client.pending[seq]
+		delete(client.pending, seq)
+		client.mutex.Unlock()
+		if call != nil {
+			call.Error = err
+			call.done()
+		}
+	}
+}
+
+func (client *Client) input() {
+	var err error
+	var response Response
+	for err == nil {
+		response = Response{}
+		err = client.codec.ReadResponseHeader(&response)
+		if err != nil {
+			break
+		}
+		seq := response.Seq
+		client.mutex.Lock()
+		call := client.pending[seq]
+		delete(client.pending, seq)
+		client.mutex.Unlock()
+
+		switch {
+		case call == nil:
+			// We've got no pending call. That usually means that
+			// WriteRequest partially failed, and call was already
+			// removed; response is a server telling us about an
+			// error reading request body. We should still attempt
+			// to read error body, but there's no one to give it to.
+			err = client.codec.ReadResponseBody(nil)
+			if err != nil {
+				err = errors.New("reading error body: " + err.Error())
+			}
+		case response.Error != "":
+			// We've got an error response. Give this to the request;
+			// any subsequent requests will get the ReadResponseBody
+			// error if there is one.
+			call.Error = ServerError(response.Error)
+			err = client.codec.ReadResponseBody(nil)
+			if err != nil {
+				err = errors.New("reading error body: " + err.Error())
+			}
+			call.done()
+		default:
+			err = client.codec.ReadResponseBody(call.Reply)
+			if err != nil {
+				call.Error = errors.New("reading body " + err.Error())
+			}
+			call.done()
+		}
+	}
+	// Terminate pending calls.
+	client.sending.Lock()
+	client.mutex.Lock()
+	client.shutdown = true
+	closing := client.closing
+	if err == io.EOF {
+		if closing {
+			err = ErrShutdown
+		} else {
+			err = io.ErrUnexpectedEOF
+		}
+	}
+	for _, call := range client.pending {
+		call.Error = err
+		call.done()
+	}
+	client.mutex.Unlock()
+	client.sending.Unlock()
+	if debugLog && err != io.EOF && !closing {
+		log.Println("rpc: client protocol error:", err)
+	}
+}
+
+func (call *Call) done() {
+	select {
+	case call.Done <- call:
+		// ok
+	default:
+		// We don't want to block here.  It is the caller's responsibility to make
+		// sure the channel has enough buffer space. See comment in Go().
+		if debugLog {
+			log.Println("rpc: discarding Call reply due to insufficient Done chan capacity")
+		}
+	}
+}
+
+// NewClient returns a new Client to handle requests to the
+// set of services at the other end of the connection.
+// It adds a buffer to the write side of the connection so
+// the header and payload are sent as a unit.
+func NewClient(conn io.ReadWriteCloser) *Client {
+	encBuf := bufio.NewWriter(conn)
+	client := &gobClientCodec{conn, gob.NewDecoder(conn), gob.NewEncoder(encBuf), encBuf}
+	return NewClientWithCodec(client)
+}
+
+// NewClientWithCodec is like NewClient but uses the specified
+// codec to encode requests and decode responses.
+func NewClientWithCodec(codec ClientCodec) *Client {
+	client := &Client{
+		codec:   codec,
+		pending: make(map[uint64]*Call),
+	}
+	go client.input()
+	return client
+}
+
+type gobClientCodec struct {
+	rwc    io.ReadWriteCloser
+	dec    *gob.Decoder
+	enc    *gob.Encoder
+	encBuf *bufio.Writer
+}
+
+func (c *gobClientCodec) WriteRequest(r *Request, body interface{}) (err error) {
+	if err = c.enc.Encode(r); err != nil {
+		return
+	}
+	if err = c.enc.Encode(body); err != nil {
+		return
+	}
+	return c.encBuf.Flush()
+}
+
+func (c *gobClientCodec) ReadResponseHeader(r *Response) error {
+	return c.dec.Decode(r)
+}
+
+func (c *gobClientCodec) ReadResponseBody(body interface{}) error {
+	return c.dec.Decode(body)
+}
+
+func (c *gobClientCodec) Close() error {
+	return c.rwc.Close()
+}
+
+// DialHTTP connects to an HTTP RPC server at the specified network address
+// listening on the default HTTP RPC path.
+func DialHTTP(network, address string) (*Client, error) {
+	return DialHTTPPath(network, address, DefaultRPCPath)
+}
+
+// DialHTTPPath connects to an HTTP RPC server
+// at the specified network address and path.
+func DialHTTPPath(network, address, path string) (*Client, error) {
+	var err error
+	conn, err := net.Dial(network, address)
+	if err != nil {
+		return nil, err
+	}
+	io.WriteString(conn, "CONNECT "+path+" HTTP/1.0\n\n")
+
+	// Require successful HTTP response
+	// before switching to RPC protocol.
+	resp, err := http.ReadResponse(bufio.NewReader(conn), &http.Request{Method: "CONNECT"})
+	if err == nil && resp.Status == connected {
+		return NewClient(conn), nil
+	}
+	if err == nil {
+		err = errors.New("unexpected HTTP response: " + resp.Status)
+	}
+	conn.Close()
+	return nil, &net.OpError{
+		Op:   "dial-http",
+		Net:  network + " " + address,
+		Addr: nil,
+		Err:  err,
+	}
+}
+
+// Dial connects to an RPC server at the specified network address.
+func Dial(network, address string) (*Client, error) {
+	conn, err := net.Dial(network, address)
+	if err != nil {
+		return nil, err
+	}
+	return NewClient(conn), nil
+}
+
+func (client *Client) Close() error {
+	client.mutex.Lock()
+	if client.closing {
+		client.mutex.Unlock()
+		return ErrShutdown
+	}
+	client.closing = true
+	client.mutex.Unlock()
+	return client.codec.Close()
+}
+
+// Go invokes the function asynchronously.  It returns the Call structure representing
+// the invocation.  The done channel will signal when the call is complete by returning
+// the same Call object.  If done is nil, Go will allocate a new channel.
+// If non-nil, done must be buffered or Go will deliberately crash.
+func (client *Client) Go(serviceMethod string, args interface{}, reply interface{}, done chan *Call) *Call {
+	call := new(Call)
+	call.ServiceMethod = serviceMethod
+	call.Args = args
+	call.Reply = reply
+	if done == nil {
+		done = make(chan *Call, 10) // buffered.
+	} else {
+		// If caller passes done != nil, it must arrange that
+		// done has enough buffer for the number of simultaneous
+		// RPCs that will be using that channel.  If the channel
+		// is totally unbuffered, it's best not to run at all.
+		if cap(done) == 0 {
+			log.Panic("rpc: done channel is unbuffered")
+		}
+	}
+	call.Done = done
+	client.send(call)
+	return call
+}
+
+// Call invokes the named function, waits for it to complete, and returns its error status.
+func (client *Client) Call(serviceMethod string, args interface{}, reply interface{}) error {
+	call := <-client.Go(serviceMethod, args, reply, make(chan *Call, 1)).Done
+	return call.Error
+}
diff --git a/src/net/rpc/client_test.go b/src/net/rpc/client_test.go
new file mode 100644
index 000000000..bbfc1ec3a
--- /dev/null
+++ b/src/net/rpc/client_test.go
@@ -0,0 +1,36 @@
+// Copyright 2014 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package rpc
+
+import (
+	"errors"
+	"testing"
+)
+
+type shutdownCodec struct {
+	responded chan int
+	closed    bool
+}
+
+func (c *shutdownCodec) WriteRequest(*Request, interface{}) error { return nil }
+func (c *shutdownCodec) ReadResponseBody(interface{}) error       { return nil }
+func (c *shutdownCodec) ReadResponseHeader(*Response) error {
+	c.responded <- 1
+	return errors.New("shutdownCodec ReadResponseHeader")
+}
+func (c *shutdownCodec) Close() error {
+	c.closed = true
+	return nil
+}
+
+func TestCloseCodec(t *testing.T) {
+	codec := &shutdownCodec{responded: make(chan int)}
+	client := NewClientWithCodec(codec)
+	<-codec.responded
+	client.Close()
+	if !codec.closed {
+		t.Error("client.Close did not close codec")
+	}
+}
diff --git a/src/net/rpc/debug.go b/src/net/rpc/debug.go
new file mode 100644
index 000000000..98b2c1c6c
--- /dev/null
+++ b/src/net/rpc/debug.go
@@ -0,0 +1,93 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package rpc
+
+/*
+	Some HTML presented at http://machine:port/debug/rpc
+	Lists services, their methods, and some statistics, still rudimentary.
+*/
+
+import (
+	"fmt"
+	"html/template"
+	"net/http"
+	"sort"
+)
+
+const debugText = `<html>
+	<body>
+	<title>Services</title>
+	{{range .}}
+	<hr>
+	Service {{.Name}}
+	<hr>
+		<table>
+		<th align=center>Method</th><th align=center>Calls</th>
+		{{range .Method}}
+			<tr>
+			<td align=left font=fixed>{{.Name}}({{.Type.ArgType}}, {{.Type.ReplyType}}) error</td>
+			<td align=center>{{.Type.NumCalls}}</td>
+			</tr>
+		{{end}}
+		</table>
+	{{end}}
+	</body>
+	</html>`
+
+var debug = template.Must(template.New("RPC debug").Parse(debugText))
+
+// If set, print log statements for internal and I/O errors.
+var debugLog = false
+
+type debugMethod struct {
+	Type *methodType
+	Name string
+}
+
+type methodArray []debugMethod
+
+type debugService struct {
+	Service *service
+	Name    string
+	Method  methodArray
+}
+
+type serviceArray []debugService
+
+func (s serviceArray) Len() int           { return len(s) }
+func (s serviceArray) Less(i, j int) bool { return s[i].Name < s[j].Name }
+func (s serviceArray) Swap(i, j int)      { s[i], s[j] = s[j], s[i] }
+
+func (m methodArray) Len() int           { return len(m) }
+func (m methodArray) Less(i, j int) bool { return m[i].Name < m[j].Name }
+func (m methodArray) Swap(i, j int)      { m[i], m[j] = m[j], m[i] }
+
+type debugHTTP struct {
+	*Server
+}
+
+// Runs at /debug/rpc
+func (server debugHTTP) ServeHTTP(w http.ResponseWriter, req *http.Request) {
+	// Build a sorted version of the data.
+	var services = make(serviceArray, len(server.serviceMap))
+	i := 0
+	server.mu.Lock()
+	for sname, service := range server.serviceMap {
+		services[i] = debugService{service, sname, make(methodArray, len(service.method))}
+		j := 0
+		for mname, method := range service.method {
+			services[i].Method[j] = debugMethod{method, mname}
+			j++
+		}
+		sort.Sort(services[i].Method)
+		i++
+	}
+	server.mu.Unlock()
+	sort.Sort(services)
+	err := debug.Execute(w, services)
+	if err != nil {
+		fmt.Fprintln(w, "rpc: error executing template:", err.Error())
+	}
+}
diff --git a/src/net/rpc/jsonrpc/all_test.go b/src/net/rpc/jsonrpc/all_test.go
new file mode 100644
index 000000000..a433a365e
--- /dev/null
+++ b/src/net/rpc/jsonrpc/all_test.go
@@ -0,0 +1,296 @@
+// Copyright 2010 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package jsonrpc
+
+import (
+	"bytes"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"io"
+	"io/ioutil"
+	"net"
+	"net/rpc"
+	"strings"
+	"testing"
+)
+
+type Args struct {
+	A, B int
+}
+
+type Reply struct {
+	C int
+}
+
+type Arith int
+
+type ArithAddResp struct {
+	Id     interface{} `json:"id"`
+	Result Reply       `json:"result"`
+	Error  interface{} `json:"error"`
+}
+
+func (t *Arith) Add(args *Args, reply *Reply) error {
+	reply.C = args.A + args.B
+	return nil
+}
+
+func (t *Arith) Mul(args *Args, reply *Reply) error {
+	reply.C = args.A * args.B
+	return nil
+}
+
+func (t *Arith) Div(args *Args, reply *Reply) error {
+	if args.B == 0 {
+		return errors.New("divide by zero")
+	}
+	reply.C = args.A / args.B
+	return nil
+}
+
+func (t *Arith) Error(args *Args, reply *Reply) error {
+	panic("ERROR")
+}
+
+func init() {
+	rpc.Register(new(Arith))
+}
+
+func TestServerNoParams(t *testing.T) {
+	cli, srv := net.Pipe()
+	defer cli.Close()
+	go ServeConn(srv)
+	dec := json.NewDecoder(cli)
+
+	fmt.Fprintf(cli, `{"method": "Arith.Add", "id": "123"}`)
+	var resp ArithAddResp
+	if err := dec.Decode(&resp); err != nil {
+		t.Fatalf("Decode after no params: %s", err)
+	}
+	if resp.Error == nil {
+		t.Fatalf("Expected error, got nil")
+	}
+}
+
+func TestServerEmptyMessage(t *testing.T) {
+	cli, srv := net.Pipe()
+	defer cli.Close()
+	go ServeConn(srv)
+	dec := json.NewDecoder(cli)
+
+	fmt.Fprintf(cli, "{}")
+	var resp ArithAddResp
+	if err := dec.Decode(&resp); err != nil {
+		t.Fatalf("Decode after empty: %s", err)
+	}
+	if resp.Error == nil {
+		t.Fatalf("Expected error, got nil")
+	}
+}
+
+func TestServer(t *testing.T) {
+	cli, srv := net.Pipe()
+	defer cli.Close()
+	go ServeConn(srv)
+	dec := json.NewDecoder(cli)
+
+	// Send hand-coded requests to server, parse responses.
+	for i := 0; i < 10; i++ {
+		fmt.Fprintf(cli, `{"method": "Arith.Add", "id": "\u%04d", "params": [{"A": %d, "B": %d}]}`, i, i, i+1)
+		var resp ArithAddResp
+		err := dec.Decode(&resp)
+		if err != nil {
+			t.Fatalf("Decode: %s", err)
+		}
+		if resp.Error != nil {
+			t.Fatalf("resp.Error: %s", resp.Error)
+		}
+		if resp.Id.(string) != string(i) {
+			t.Fatalf("resp: bad id %q want %q", resp.Id.(string), string(i))
+		}
+		if resp.Result.C != 2*i+1 {
+			t.Fatalf("resp: bad result: %d+%d=%d", i, i+1, resp.Result.C)
+		}
+	}
+}
+
+func TestClient(t *testing.T) {
+	// Assume server is okay (TestServer is above).
+	// Test client against server.
+	cli, srv := net.Pipe()
+	go ServeConn(srv)
+
+	client := NewClient(cli)
+	defer client.Close()
+
+	// Synchronous calls
+	args := &Args{7, 8}
+	reply := new(Reply)
+	err := client.Call("Arith.Add", args, reply)
+	if err != nil {
+		t.Errorf("Add: expected no error but got string %q", err.Error())
+	}
+	if reply.C != args.A+args.B {
+		t.Errorf("Add: got %d expected %d", reply.C, args.A+args.B)
+	}
+
+	args = &Args{7, 8}
+	reply = new(Reply)
+	err = client.Call("Arith.Mul", args, reply)
+	if err != nil {
+		t.Errorf("Mul: expected no error but got string %q", err.Error())
+	}
+	if reply.C != args.A*args.B {
+		t.Errorf("Mul: got %d expected %d", reply.C, args.A*args.B)
+	}
+
+	// Out of order.
+	args = &Args{7, 8}
+	mulReply := new(Reply)
+	mulCall := client.Go("Arith.Mul", args, mulReply, nil)
+	addReply := new(Reply)
+	addCall := client.Go("Arith.Add", args, addReply, nil)
+
+	addCall = <-addCall.Done
+	if addCall.Error != nil {
+		t.Errorf("Add: expected no error but got string %q", addCall.Error.Error())
+	}
+	if addReply.C != args.A+args.B {
+		t.Errorf("Add: got %d expected %d", addReply.C, args.A+args.B)
+	}
+
+	mulCall = <-mulCall.Done
+	if mulCall.Error != nil {
+		t.Errorf("Mul: expected no error but got string %q", mulCall.Error.Error())
+	}
+	if mulReply.C != args.A*args.B {
+		t.Errorf("Mul: got %d expected %d", mulReply.C, args.A*args.B)
+	}
+
+	// Error test
+	args = &Args{7, 0}
+	reply = new(Reply)
+	err = client.Call("Arith.Div", args, reply)
+	// expect an error: zero divide
+	if err == nil {
+		t.Error("Div: expected error")
+	} else if err.Error() != "divide by zero" {
+		t.Error("Div: expected divide by zero error; got", err)
+	}
+}
+
+func TestMalformedInput(t *testing.T) {
+	cli, srv := net.Pipe()
+	go cli.Write([]byte(`{id:1}`)) // invalid json
+	ServeConn(srv)                 // must return, not loop
+}
+
+func TestMalformedOutput(t *testing.T) {
+	cli, srv := net.Pipe()
+	go srv.Write([]byte(`{"id":0,"result":null,"error":null}`))
+	go ioutil.ReadAll(srv)
+
+	client := NewClient(cli)
+	defer client.Close()
+
+	args := &Args{7, 8}
+	reply := new(Reply)
+	err := client.Call("Arith.Add", args, reply)
+	if err == nil {
+		t.Error("expected error")
+	}
+}
+
+func TestServerErrorHasNullResult(t *testing.T) {
+	var out bytes.Buffer
+	sc := NewServerCodec(struct {
+		io.Reader
+		io.Writer
+		io.Closer
+	}{
+		Reader: strings.NewReader(`{"method": "Arith.Add", "id": "123", "params": []}`),
+		Writer: &out,
+		Closer: ioutil.NopCloser(nil),
+	})
+	r := new(rpc.Request)
+	if err := sc.ReadRequestHeader(r); err != nil {
+		t.Fatal(err)
+	}
+	const valueText = "the value we don't want to see"
+	const errorText = "some error"
+	err := sc.WriteResponse(&rpc.Response{
+		ServiceMethod: "Method",
+		Seq:           1,
+		Error:         errorText,
+	}, valueText)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if !strings.Contains(out.String(), errorText) {
+		t.Fatalf("Response didn't contain expected error %q: %s", errorText, &out)
+	}
+	if strings.Contains(out.String(), valueText) {
+		t.Errorf("Response contains both an error and value: %s", &out)
+	}
+}
+
+func TestUnexpectedError(t *testing.T) {
+	cli, srv := myPipe()
+	go cli.PipeWriter.CloseWithError(errors.New("unexpected error!")) // reader will get this error
+	ServeConn(srv)                                                    // must return, not loop
+}
+
+// Copied from package net.
+func myPipe() (*pipe, *pipe) {
+	r1, w1 := io.Pipe()
+	r2, w2 := io.Pipe()
+
+	return &pipe{r1, w2}, &pipe{r2, w1}
+}
+
+type pipe struct {
+	*io.PipeReader
+	*io.PipeWriter
+}
+
+type pipeAddr int
+
+func (pipeAddr) Network() string {
+	return "pipe"
+}
+
+func (pipeAddr) String() string {
+	return "pipe"
+}
+
+func (p *pipe) Close() error {
+	err := p.PipeReader.Close()
+	err1 := p.PipeWriter.Close()
+	if err == nil {
+		err = err1
+	}
+	return err
+}
+
+func (p *pipe) LocalAddr() net.Addr {
+	return pipeAddr(0)
+}
+
+func (p *pipe) RemoteAddr() net.Addr {
+	return pipeAddr(0)
+}
+
+func (p *pipe) SetTimeout(nsec int64) error {
+	return errors.New("net.Pipe does not support timeouts")
+}
+
+func (p *pipe) SetReadTimeout(nsec int64) error {
+	return errors.New("net.Pipe does not support timeouts")
+}
+
+func (p *pipe) SetWriteTimeout(nsec int64) error {
+	return errors.New("net.Pipe does not support timeouts")
+}
diff --git a/src/net/rpc/jsonrpc/client.go b/src/net/rpc/jsonrpc/client.go
new file mode 100644
index 000000000..2194f2125
--- /dev/null
+++ b/src/net/rpc/jsonrpc/client.go
@@ -0,0 +1,123 @@
+// Copyright 2010 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package jsonrpc implements a JSON-RPC ClientCodec and ServerCodec
+// for the rpc package.
+package jsonrpc
+
+import (
+	"encoding/json"
+	"fmt"
+	"io"
+	"net"
+	"net/rpc"
+	"sync"
+)
+
+type clientCodec struct {
+	dec *json.Decoder // for reading JSON values
+	enc *json.Encoder // for writing JSON values
+	c   io.Closer
+
+	// temporary work space
+	req  clientRequest
+	resp clientResponse
+
+	// JSON-RPC responses include the request id but not the request method.
+	// Package rpc expects both.
+	// We save the request method in pending when sending a request
+	// and then look it up by request ID when filling out the rpc Response.
+	mutex   sync.Mutex        // protects pending
+	pending map[uint64]string // map request id to method name
+}
+
+// NewClientCodec returns a new rpc.ClientCodec using JSON-RPC on conn.
+func NewClientCodec(conn io.ReadWriteCloser) rpc.ClientCodec {
+	return &clientCodec{
+		dec:     json.NewDecoder(conn),
+		enc:     json.NewEncoder(conn),
+		c:       conn,
+		pending: make(map[uint64]string),
+	}
+}
+
+type clientRequest struct {
+	Method string         `json:"method"`
+	Params [1]interface{} `json:"params"`
+	Id     uint64         `json:"id"`
+}
+
+func (c *clientCodec) WriteRequest(r *rpc.Request, param interface{}) error {
+	c.mutex.Lock()
+	c.pending[r.Seq] = r.ServiceMethod
+	c.mutex.Unlock()
+	c.req.Method = r.ServiceMethod
+	c.req.Params[0] = param
+	c.req.Id = r.Seq
+	return c.enc.Encode(&c.req)
+}
+
+type clientResponse struct {
+	Id     uint64           `json:"id"`
+	Result *json.RawMessage `json:"result"`
+	Error  interface{}      `json:"error"`
+}
+
+func (r *clientResponse) reset() {
+	r.Id = 0
+	r.Result = nil
+	r.Error = nil
+}
+
+func (c *clientCodec) ReadResponseHeader(r *rpc.Response) error {
+	c.resp.reset()
+	if err := c.dec.Decode(&c.resp); err != nil {
+		return err
+	}
+
+	c.mutex.Lock()
+	r.ServiceMethod = c.pending[c.resp.Id]
+	delete(c.pending, c.resp.Id)
+	c.mutex.Unlock()
+
+	r.Error = ""
+	r.Seq = c.resp.Id
+	if c.resp.Error != nil || c.resp.Result == nil {
+		x, ok := c.resp.Error.(string)
+		if !ok {
+			return fmt.Errorf("invalid error %v", c.resp.Error)
+		}
+		if x == "" {
+			x = "unspecified error"
+		}
+		r.Error = x
+	}
+	return nil
+}
+
+func (c *clientCodec) ReadResponseBody(x interface{}) error {
+	if x == nil {
+		return nil
+	}
+	return json.Unmarshal(*c.resp.Result, x)
+}
+
+func (c *clientCodec) Close() error {
+	return c.c.Close()
+}
+
+// NewClient returns a new rpc.Client to handle requests to the
+// set of services at the other end of the connection.
+func NewClient(conn io.ReadWriteCloser) *rpc.Client {
+	return rpc.NewClientWithCodec(NewClientCodec(conn))
+}
+
+// Dial connects to a JSON-RPC server at the specified network address.
+func Dial(network, address string) (*rpc.Client, error) {
+	conn, err := net.Dial(network, address)
+	if err != nil {
+		return nil, err
+	}
+	return NewClient(conn), err
+}
diff --git a/src/net/rpc/jsonrpc/server.go b/src/net/rpc/jsonrpc/server.go
new file mode 100644
index 000000000..e6d37cfa6
--- /dev/null
+++ b/src/net/rpc/jsonrpc/server.go
@@ -0,0 +1,134 @@
+// Copyright 2010 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package jsonrpc
+
+import (
+	"encoding/json"
+	"errors"
+	"io"
+	"net/rpc"
+	"sync"
+)
+
+var errMissingParams = errors.New("jsonrpc: request body missing params")
+
+type serverCodec struct {
+	dec *json.Decoder // for reading JSON values
+	enc *json.Encoder // for writing JSON values
+	c   io.Closer
+
+	// temporary work space
+	req serverRequest
+
+	// JSON-RPC clients can use arbitrary json values as request IDs.
+	// Package rpc expects uint64 request IDs.
+	// We assign uint64 sequence numbers to incoming requests
+	// but save the original request ID in the pending map.
+	// When rpc responds, we use the sequence number in
+	// the response to find the original request ID.
+	mutex   sync.Mutex // protects seq, pending
+	seq     uint64
+	pending map[uint64]*json.RawMessage
+}
+
+// NewServerCodec returns a new rpc.ServerCodec using JSON-RPC on conn.
+func NewServerCodec(conn io.ReadWriteCloser) rpc.ServerCodec {
+	return &serverCodec{
+		dec:     json.NewDecoder(conn),
+		enc:     json.NewEncoder(conn),
+		c:       conn,
+		pending: make(map[uint64]*json.RawMessage),
+	}
+}
+
+type serverRequest struct {
+	Method string           `json:"method"`
+	Params *json.RawMessage `json:"params"`
+	Id     *json.RawMessage `json:"id"`
+}
+
+func (r *serverRequest) reset() {
+	r.Method = ""
+	r.Params = nil
+	r.Id = nil
+}
+
+type serverResponse struct {
+	Id     *json.RawMessage `json:"id"`
+	Result interface{}      `json:"result"`
+	Error  interface{}      `json:"error"`
+}
+
+func (c *serverCodec) ReadRequestHeader(r *rpc.Request) error {
+	c.req.reset()
+	if err := c.dec.Decode(&c.req); err != nil {
+		return err
+	}
+	r.ServiceMethod = c.req.Method
+
+	// JSON request id can be any JSON value;
+	// RPC package expects uint64.  Translate to
+	// internal uint64 and save JSON on the side.
+	c.mutex.Lock()
+	c.seq++
+	c.pending[c.seq] = c.req.Id
+	c.req.Id = nil
+	r.Seq = c.seq
+	c.mutex.Unlock()
+
+	return nil
+}
+
+func (c *serverCodec) ReadRequestBody(x interface{}) error {
+	if x == nil {
+		return nil
+	}
+	if c.req.Params == nil {
+		return errMissingParams
+	}
+	// JSON params is array value.
+	// RPC params is struct.
+	// Unmarshal into array containing struct for now.
+	// Should think about making RPC more general.
+	var params [1]interface{}
+	params[0] = x
+	return json.Unmarshal(*c.req.Params, &params)
+}
+
+var null = json.RawMessage([]byte("null"))
+
+func (c *serverCodec) WriteResponse(r *rpc.Response, x interface{}) error {
+	c.mutex.Lock()
+	b, ok := c.pending[r.Seq]
+	if !ok {
+		c.mutex.Unlock()
+		return errors.New("invalid sequence number in response")
+	}
+	delete(c.pending, r.Seq)
+	c.mutex.Unlock()
+
+	if b == nil {
+		// Invalid request so no id.  Use JSON null.
+		b = &null
+	}
+	resp := serverResponse{Id: b}
+	if r.Error == "" {
+		resp.Result = x
+	} else {
+		resp.Error = r.Error
+	}
+	return c.enc.Encode(resp)
+}
+
+func (c *serverCodec) Close() error {
+	return c.c.Close()
+}
+
+// ServeConn runs the JSON-RPC server on a single connection.
+// ServeConn blocks, serving the connection until the client hangs up.
+// The caller typically invokes ServeConn in a go statement.
+func ServeConn(conn io.ReadWriteCloser) {
+	rpc.ServeCodec(NewServerCodec(conn))
+}
diff --git a/src/net/rpc/server.go b/src/net/rpc/server.go
new file mode 100644
index 000000000..6b264b46b
--- /dev/null
+++ b/src/net/rpc/server.go
@@ -0,0 +1,686 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+/*
+	Package rpc provides access to the exported methods of an object across a
+	network or other I/O connection.  A server registers an object, making it visible
+	as a service with the name of the type of the object.  After registration, exported
+	methods of the object will be accessible remotely.  A server may register multiple
+	objects (services) of different types but it is an error to register multiple
+	objects of the same type.
+
+	Only methods that satisfy these criteria will be made available for remote access;
+	other methods will be ignored:
+
+		- the method is exported.
+		- the method has two arguments, both exported (or builtin) types.
+		- the method's second argument is a pointer.
+		- the method has return type error.
+
+	In effect, the method must look schematically like
+
+		func (t *T) MethodName(argType T1, replyType *T2) error
+
+	where T, T1 and T2 can be marshaled by encoding/gob.
+	These requirements apply even if a different codec is used.
+	(In the future, these requirements may soften for custom codecs.)
+
+	The method's first argument represents the arguments provided by the caller; the
+	second argument represents the result parameters to be returned to the caller.
+	The method's return value, if non-nil, is passed back as a string that the client
+	sees as if created by errors.New.  If an error is returned, the reply parameter
+	will not be sent back to the client.
+
+	The server may handle requests on a single connection by calling ServeConn.  More
+	typically it will create a network listener and call Accept or, for an HTTP
+	listener, HandleHTTP and http.Serve.
+
+	A client wishing to use the service establishes a connection and then invokes
+	NewClient on the connection.  The convenience function Dial (DialHTTP) performs
+	both steps for a raw network connection (an HTTP connection).  The resulting
+	Client object has two methods, Call and Go, that specify the service and method to
+	call, a pointer containing the arguments, and a pointer to receive the result
+	parameters.
+
+	The Call method waits for the remote call to complete while the Go method
+	launches the call asynchronously and signals completion using the Call
+	structure's Done channel.
+
+	Unless an explicit codec is set up, package encoding/gob is used to
+	transport the data.
+
+	Here is a simple example.  A server wishes to export an object of type Arith:
+
+		package server
+
+		type Args struct {
+			A, B int
+		}
+
+		type Quotient struct {
+			Quo, Rem int
+		}
+
+		type Arith int
+
+		func (t *Arith) Multiply(args *Args, reply *int) error {
+			*reply = args.A * args.B
+			return nil
+		}
+
+		func (t *Arith) Divide(args *Args, quo *Quotient) error {
+			if args.B == 0 {
+				return errors.New("divide by zero")
+			}
+			quo.Quo = args.A / args.B
+			quo.Rem = args.A % args.B
+			return nil
+		}
+
+	The server calls (for HTTP service):
+
+		arith := new(Arith)
+		rpc.Register(arith)
+		rpc.HandleHTTP()
+		l, e := net.Listen("tcp", ":1234")
+		if e != nil {
+			log.Fatal("listen error:", e)
+		}
+		go http.Serve(l, nil)
+
+	At this point, clients can see a service "Arith" with methods "Arith.Multiply" and
+	"Arith.Divide".  To invoke one, a client first dials the server:
+
+		client, err := rpc.DialHTTP("tcp", serverAddress + ":1234")
+		if err != nil {
+			log.Fatal("dialing:", err)
+		}
+
+	Then it can make a remote call:
+
+		// Synchronous call
+		args := &server.Args{7,8}
+		var reply int
+		err = client.Call("Arith.Multiply", args, &reply)
+		if err != nil {
+			log.Fatal("arith error:", err)
+		}
+		fmt.Printf("Arith: %d*%d=%d", args.A, args.B, reply)
+
+	or
+
+		// Asynchronous call
+		quotient := new(Quotient)
+		divCall := client.Go("Arith.Divide", args, quotient, nil)
+		replyCall := <-divCall.Done	// will be equal to divCall
+		// check errors, print, etc.
+
+	A server implementation will often provide a simple, type-safe wrapper for the
+	client.
+*/
+package rpc
+
+import (
+	"bufio"
+	"encoding/gob"
+	"errors"
+	"io"
+	"log"
+	"net"
+	"net/http"
+	"reflect"
+	"strings"
+	"sync"
+	"unicode"
+	"unicode/utf8"
+)
+
+const (
+	// Defaults used by HandleHTTP
+	DefaultRPCPath   = "/_goRPC_"
+	DefaultDebugPath = "/debug/rpc"
+)
+
+// Precompute the reflect type for error.  Can't use error directly
+// because Typeof takes an empty interface value.  This is annoying.
+var typeOfError = reflect.TypeOf((*error)(nil)).Elem()
+
+type methodType struct {
+	sync.Mutex // protects counters
+	method     reflect.Method
+	ArgType    reflect.Type
+	ReplyType  reflect.Type
+	numCalls   uint
+}
+
+type service struct {
+	name   string                 // name of service
+	rcvr   reflect.Value          // receiver of methods for the service
+	typ    reflect.Type           // type of the receiver
+	method map[string]*methodType // registered methods
+}
+
+// Request is a header written before every RPC call.  It is used internally
+// but documented here as an aid to debugging, such as when analyzing
+// network traffic.
+type Request struct {
+	ServiceMethod string   // format: "Service.Method"
+	Seq           uint64   // sequence number chosen by client
+	next          *Request // for free list in Server
+}
+
+// Response is a header written before every RPC return.  It is used internally
+// but documented here as an aid to debugging, such as when analyzing
+// network traffic.
+type Response struct {
+	ServiceMethod string    // echoes that of the Request
+	Seq           uint64    // echoes that of the request
+	Error         string    // error, if any.
+	next          *Response // for free list in Server
+}
+
+// Server represents an RPC Server.
+type Server struct {
+	mu         sync.RWMutex // protects the serviceMap
+	serviceMap map[string]*service
+	reqLock    sync.Mutex // protects freeReq
+	freeReq    *Request
+	respLock   sync.Mutex // protects freeResp
+	freeResp   *Response
+}
+
+// NewServer returns a new Server.
+func NewServer() *Server {
+	return &Server{serviceMap: make(map[string]*service)}
+}
+
+// DefaultServer is the default instance of *Server.
+var DefaultServer = NewServer()
+
+// Is this an exported - upper case - name?
+func isExported(name string) bool {
+	rune, _ := utf8.DecodeRuneInString(name)
+	return unicode.IsUpper(rune)
+}
+
+// Is this type exported or a builtin?
+func isExportedOrBuiltinType(t reflect.Type) bool {
+	for t.Kind() == reflect.Ptr {
+		t = t.Elem()
+	}
+	// PkgPath will be non-empty even for an exported type,
+	// so we need to check the type name as well.
+	return isExported(t.Name()) || t.PkgPath() == ""
+}
+
+// Register publishes in the server the set of methods of the
+// receiver value that satisfy the following conditions:
+//	- exported method
+//	- two arguments, both of exported type
+//	- the second argument is a pointer
+//	- one return value, of type error
+// It returns an error if the receiver is not an exported type or has
+// no suitable methods. It also logs the error using package log.
+// The client accesses each method using a string of the form "Type.Method",
+// where Type is the receiver's concrete type.
+func (server *Server) Register(rcvr interface{}) error {
+	return server.register(rcvr, "", false)
+}
+
+// RegisterName is like Register but uses the provided name for the type
+// instead of the receiver's concrete type.
+func (server *Server) RegisterName(name string, rcvr interface{}) error {
+	return server.register(rcvr, name, true)
+}
+
+func (server *Server) register(rcvr interface{}, name string, useName bool) error {
+	server.mu.Lock()
+	defer server.mu.Unlock()
+	if server.serviceMap == nil {
+		server.serviceMap = make(map[string]*service)
+	}
+	s := new(service)
+	s.typ = reflect.TypeOf(rcvr)
+	s.rcvr = reflect.ValueOf(rcvr)
+	sname := reflect.Indirect(s.rcvr).Type().Name()
+	if useName {
+		sname = name
+	}
+	if sname == "" {
+		s := "rpc.Register: no service name for type " + s.typ.String()
+		log.Print(s)
+		return errors.New(s)
+	}
+	if !isExported(sname) && !useName {
+		s := "rpc.Register: type " + sname + " is not exported"
+		log.Print(s)
+		return errors.New(s)
+	}
+	if _, present := server.serviceMap[sname]; present {
+		return errors.New("rpc: service already defined: " + sname)
+	}
+	s.name = sname
+
+	// Install the methods
+	s.method = suitableMethods(s.typ, true)
+
+	if len(s.method) == 0 {
+		str := ""
+
+		// To help the user, see if a pointer receiver would work.
+		method := suitableMethods(reflect.PtrTo(s.typ), false)
+		if len(method) != 0 {
+			str = "rpc.Register: type " + sname + " has no exported methods of suitable type (hint: pass a pointer to value of that type)"
+		} else {
+			str = "rpc.Register: type " + sname + " has no exported methods of suitable type"
+		}
+		log.Print(str)
+		return errors.New(str)
+	}
+	server.serviceMap[s.name] = s
+	return nil
+}
+
+// suitableMethods returns suitable Rpc methods of typ, it will report
+// error using log if reportErr is true.
+func suitableMethods(typ reflect.Type, reportErr bool) map[string]*methodType {
+	methods := make(map[string]*methodType)
+	for m := 0; m < typ.NumMethod(); m++ {
+		method := typ.Method(m)
+		mtype := method.Type
+		mname := method.Name
+		// Method must be exported.
+		if method.PkgPath != "" {
+			continue
+		}
+		// Method needs three ins: receiver, *args, *reply.
+		if mtype.NumIn() != 3 {
+			if reportErr {
+				log.Println("method", mname, "has wrong number of ins:", mtype.NumIn())
+			}
+			continue
+		}
+		// First arg need not be a pointer.
+		argType := mtype.In(1)
+		if !isExportedOrBuiltinType(argType) {
+			if reportErr {
+				log.Println(mname, "argument type not exported:", argType)
+			}
+			continue
+		}
+		// Second arg must be a pointer.
+		replyType := mtype.In(2)
+		if replyType.Kind() != reflect.Ptr {
+			if reportErr {
+				log.Println("method", mname, "reply type not a pointer:", replyType)
+			}
+			continue
+		}
+		// Reply type must be exported.
+		if !isExportedOrBuiltinType(replyType) {
+			if reportErr {
+				log.Println("method", mname, "reply type not exported:", replyType)
+			}
+			continue
+		}
+		// Method needs one out.
+		if mtype.NumOut() != 1 {
+			if reportErr {
+				log.Println("method", mname, "has wrong number of outs:", mtype.NumOut())
+			}
+			continue
+		}
+		// The return type of the method must be error.
+		if returnType := mtype.Out(0); returnType != typeOfError {
+			if reportErr {
+				log.Println("method", mname, "returns", returnType.String(), "not error")
+			}
+			continue
+		}
+		methods[mname] = &methodType{method: method, ArgType: argType, ReplyType: replyType}
+	}
+	return methods
+}
+
+// A value sent as a placeholder for the server's response value when the server
+// receives an invalid request. It is never decoded by the client since the Response
+// contains an error when it is used.
+var invalidRequest = struct{}{}
+
+func (server *Server) sendResponse(sending *sync.Mutex, req *Request, reply interface{}, codec ServerCodec, errmsg string) {
+	resp := server.getResponse()
+	// Encode the response header
+	resp.ServiceMethod = req.ServiceMethod
+	if errmsg != "" {
+		resp.Error = errmsg
+		reply = invalidRequest
+	}
+	resp.Seq = req.Seq
+	sending.Lock()
+	err := codec.WriteResponse(resp, reply)
+	if debugLog && err != nil {
+		log.Println("rpc: writing response:", err)
+	}
+	sending.Unlock()
+	server.freeResponse(resp)
+}
+
+func (m *methodType) NumCalls() (n uint) {
+	m.Lock()
+	n = m.numCalls
+	m.Unlock()
+	return n
+}
+
+func (s *service) call(server *Server, sending *sync.Mutex, mtype *methodType, req *Request, argv, replyv reflect.Value, codec ServerCodec) {
+	mtype.Lock()
+	mtype.numCalls++
+	mtype.Unlock()
+	function := mtype.method.Func
+	// Invoke the method, providing a new value for the reply.
+	returnValues := function.Call([]reflect.Value{s.rcvr, argv, replyv})
+	// The return value for the method is an error.
+	errInter := returnValues[0].Interface()
+	errmsg := ""
+	if errInter != nil {
+		errmsg = errInter.(error).Error()
+	}
+	server.sendResponse(sending, req, replyv.Interface(), codec, errmsg)
+	server.freeRequest(req)
+}
+
+type gobServerCodec struct {
+	rwc    io.ReadWriteCloser
+	dec    *gob.Decoder
+	enc    *gob.Encoder
+	encBuf *bufio.Writer
+}
+
+func (c *gobServerCodec) ReadRequestHeader(r *Request) error {
+	return c.dec.Decode(r)
+}
+
+func (c *gobServerCodec) ReadRequestBody(body interface{}) error {
+	return c.dec.Decode(body)
+}
+
+func (c *gobServerCodec) WriteResponse(r *Response, body interface{}) (err error) {
+	if err = c.enc.Encode(r); err != nil {
+		return
+	}
+	if err = c.enc.Encode(body); err != nil {
+		return
+	}
+	return c.encBuf.Flush()
+}
+
+func (c *gobServerCodec) Close() error {
+	return c.rwc.Close()
+}
+
+// ServeConn runs the server on a single connection.
+// ServeConn blocks, serving the connection until the client hangs up.
+// The caller typically invokes ServeConn in a go statement.
+// ServeConn uses the gob wire format (see package gob) on the
+// connection.  To use an alternate codec, use ServeCodec.
+func (server *Server) ServeConn(conn io.ReadWriteCloser) {
+	buf := bufio.NewWriter(conn)
+	srv := &gobServerCodec{conn, gob.NewDecoder(conn), gob.NewEncoder(buf), buf}
+	server.ServeCodec(srv)
+}
+
+// ServeCodec is like ServeConn but uses the specified codec to
+// decode requests and encode responses.
+func (server *Server) ServeCodec(codec ServerCodec) {
+	sending := new(sync.Mutex)
+	for {
+		service, mtype, req, argv, replyv, keepReading, err := server.readRequest(codec)
+		if err != nil {
+			if debugLog && err != io.EOF {
+				log.Println("rpc:", err)
+			}
+			if !keepReading {
+				break
+			}
+			// send a response if we actually managed to read a header.
+			if req != nil {
+				server.sendResponse(sending, req, invalidRequest, codec, err.Error())
+				server.freeRequest(req)
+			}
+			continue
+		}
+		go service.call(server, sending, mtype, req, argv, replyv, codec)
+	}
+	codec.Close()
+}
+
+// ServeRequest is like ServeCodec but synchronously serves a single request.
+// It does not close the codec upon completion.
+func (server *Server) ServeRequest(codec ServerCodec) error {
+	sending := new(sync.Mutex)
+	service, mtype, req, argv, replyv, keepReading, err := server.readRequest(codec)
+	if err != nil {
+		if !keepReading {
+			return err
+		}
+		// send a response if we actually managed to read a header.
+		if req != nil {
+			server.sendResponse(sending, req, invalidRequest, codec, err.Error())
+			server.freeRequest(req)
+		}
+		return err
+	}
+	service.call(server, sending, mtype, req, argv, replyv, codec)
+	return nil
+}
+
+func (server *Server) getRequest() *Request {
+	server.reqLock.Lock()
+	req := server.freeReq
+	if req == nil {
+		req = new(Request)
+	} else {
+		server.freeReq = req.next
+		*req = Request{}
+	}
+	server.reqLock.Unlock()
+	return req
+}
+
+func (server *Server) freeRequest(req *Request) {
+	server.reqLock.Lock()
+	req.next = server.freeReq
+	server.freeReq = req
+	server.reqLock.Unlock()
+}
+
+func (server *Server) getResponse() *Response {
+	server.respLock.Lock()
+	resp := server.freeResp
+	if resp == nil {
+		resp = new(Response)
+	} else {
+		server.freeResp = resp.next
+		*resp = Response{}
+	}
+	server.respLock.Unlock()
+	return resp
+}
+
+func (server *Server) freeResponse(resp *Response) {
+	server.respLock.Lock()
+	resp.next = server.freeResp
+	server.freeResp = resp
+	server.respLock.Unlock()
+}
+
+func (server *Server) readRequest(codec ServerCodec) (service *service, mtype *methodType, req *Request, argv, replyv reflect.Value, keepReading bool, err error) {
+	service, mtype, req, keepReading, err = server.readRequestHeader(codec)
+	if err != nil {
+		if !keepReading {
+			return
+		}
+		// discard body
+		codec.ReadRequestBody(nil)
+		return
+	}
+
+	// Decode the argument value.
+	argIsValue := false // if true, need to indirect before calling.
+	if mtype.ArgType.Kind() == reflect.Ptr {
+		argv = reflect.New(mtype.ArgType.Elem())
+	} else {
+		argv = reflect.New(mtype.ArgType)
+		argIsValue = true
+	}
+	// argv guaranteed to be a pointer now.
+	if err = codec.ReadRequestBody(argv.Interface()); err != nil {
+		return
+	}
+	if argIsValue {
+		argv = argv.Elem()
+	}
+
+	replyv = reflect.New(mtype.ReplyType.Elem())
+	return
+}
+
+func (server *Server) readRequestHeader(codec ServerCodec) (service *service, mtype *methodType, req *Request, keepReading bool, err error) {
+	// Grab the request header.
+	req = server.getRequest()
+	err = codec.ReadRequestHeader(req)
+	if err != nil {
+		req = nil
+		if err == io.EOF || err == io.ErrUnexpectedEOF {
+			return
+		}
+		err = errors.New("rpc: server cannot decode request: " + err.Error())
+		return
+	}
+
+	// We read the header successfully.  If we see an error now,
+	// we can still recover and move on to the next request.
+	keepReading = true
+
+	dot := strings.LastIndex(req.ServiceMethod, ".")
+	if dot < 0 {
+		err = errors.New("rpc: service/method request ill-formed: " + req.ServiceMethod)
+		return
+	}
+	serviceName := req.ServiceMethod[:dot]
+	methodName := req.ServiceMethod[dot+1:]
+
+	// Look up the request.
+	server.mu.RLock()
+	service = server.serviceMap[serviceName]
+	server.mu.RUnlock()
+	if service == nil {
+		err = errors.New("rpc: can't find service " + req.ServiceMethod)
+		return
+	}
+	mtype = service.method[methodName]
+	if mtype == nil {
+		err = errors.New("rpc: can't find method " + req.ServiceMethod)
+	}
+	return
+}
+
+// Accept accepts connections on the listener and serves requests
+// for each incoming connection.  Accept blocks; the caller typically
+// invokes it in a go statement.
+func (server *Server) Accept(lis net.Listener) {
+	for {
+		conn, err := lis.Accept()
+		if err != nil {
+			log.Fatal("rpc.Serve: accept:", err.Error()) // TODO(r): exit?
+		}
+		go server.ServeConn(conn)
+	}
+}
+
+// Register publishes the receiver's methods in the DefaultServer.
+func Register(rcvr interface{}) error { return DefaultServer.Register(rcvr) }
+
+// RegisterName is like Register but uses the provided name for the type
+// instead of the receiver's concrete type.
+func RegisterName(name string, rcvr interface{}) error {
+	return DefaultServer.RegisterName(name, rcvr)
+}
+
+// A ServerCodec implements reading of RPC requests and writing of
+// RPC responses for the server side of an RPC session.
+// The server calls ReadRequestHeader and ReadRequestBody in pairs
+// to read requests from the connection, and it calls WriteResponse to
+// write a response back.  The server calls Close when finished with the
+// connection. ReadRequestBody may be called with a nil
+// argument to force the body of the request to be read and discarded.
+type ServerCodec interface {
+	ReadRequestHeader(*Request) error
+	ReadRequestBody(interface{}) error
+	// WriteResponse must be safe for concurrent use by multiple goroutines.
+	WriteResponse(*Response, interface{}) error
+
+	Close() error
+}
+
+// ServeConn runs the DefaultServer on a single connection.
+// ServeConn blocks, serving the connection until the client hangs up.
+// The caller typically invokes ServeConn in a go statement.
+// ServeConn uses the gob wire format (see package gob) on the
+// connection.  To use an alternate codec, use ServeCodec.
+func ServeConn(conn io.ReadWriteCloser) {
+	DefaultServer.ServeConn(conn)
+}
+
+// ServeCodec is like ServeConn but uses the specified codec to
+// decode requests and encode responses.
+func ServeCodec(codec ServerCodec) {
+	DefaultServer.ServeCodec(codec)
+}
+
+// ServeRequest is like ServeCodec but synchronously serves a single request.
+// It does not close the codec upon completion.
+func ServeRequest(codec ServerCodec) error {
+	return DefaultServer.ServeRequest(codec)
+}
+
+// Accept accepts connections on the listener and serves requests
+// to DefaultServer for each incoming connection.
+// Accept blocks; the caller typically invokes it in a go statement.
+func Accept(lis net.Listener) { DefaultServer.Accept(lis) }
+
+// Can connect to RPC service using HTTP CONNECT to rpcPath.
+var connected = "200 Connected to Go RPC"
+
+// ServeHTTP implements an http.Handler that answers RPC requests.
+func (server *Server) ServeHTTP(w http.ResponseWriter, req *http.Request) {
+	if req.Method != "CONNECT" {
+		w.Header().Set("Content-Type", "text/plain; charset=utf-8")
+		w.WriteHeader(http.StatusMethodNotAllowed)
+		io.WriteString(w, "405 must CONNECT\n")
+		return
+	}
+	conn, _, err := w.(http.Hijacker).Hijack()
+	if err != nil {
+		log.Print("rpc hijacking ", req.RemoteAddr, ": ", err.Error())
+		return
+	}
+	io.WriteString(conn, "HTTP/1.0 "+connected+"\n\n")
+	server.ServeConn(conn)
+}
+
+// HandleHTTP registers an HTTP handler for RPC messages on rpcPath,
+// and a debugging handler on debugPath.
+// It is still necessary to invoke http.Serve(), typically in a go statement.
+func (server *Server) HandleHTTP(rpcPath, debugPath string) {
+	http.Handle(rpcPath, server)
+	http.Handle(debugPath, debugHTTP{server})
+}
+
+// HandleHTTP registers an HTTP handler for RPC messages to DefaultServer
+// on DefaultRPCPath and a debugging handler on DefaultDebugPath.
+// It is still necessary to invoke http.Serve(), typically in a go statement.
+func HandleHTTP() {
+	DefaultServer.HandleHTTP(DefaultRPCPath, DefaultDebugPath)
+}
diff --git a/src/net/rpc/server_test.go b/src/net/rpc/server_test.go
new file mode 100644
index 000000000..0dc4ddc2d
--- /dev/null
+++ b/src/net/rpc/server_test.go
@@ -0,0 +1,683 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package rpc
+
+import (
+	"errors"
+	"fmt"
+	"io"
+	"log"
+	"net"
+	"net/http/httptest"
+	"runtime"
+	"strings"
+	"sync"
+	"sync/atomic"
+	"testing"
+	"time"
+)
+
+var (
+	newServer                 *Server
+	serverAddr, newServerAddr string
+	httpServerAddr            string
+	once, newOnce, httpOnce   sync.Once
+)
+
+const (
+	newHttpPath = "/foo"
+)
+
+type Args struct {
+	A, B int
+}
+
+type Reply struct {
+	C int
+}
+
+type Arith int
+
+// Some of Arith's methods have value args, some have pointer args. That's deliberate.
+
+func (t *Arith) Add(args Args, reply *Reply) error {
+	reply.C = args.A + args.B
+	return nil
+}
+
+func (t *Arith) Mul(args *Args, reply *Reply) error {
+	reply.C = args.A * args.B
+	return nil
+}
+
+func (t *Arith) Div(args Args, reply *Reply) error {
+	if args.B == 0 {
+		return errors.New("divide by zero")
+	}
+	reply.C = args.A / args.B
+	return nil
+}
+
+func (t *Arith) String(args *Args, reply *string) error {
+	*reply = fmt.Sprintf("%d+%d=%d", args.A, args.B, args.A+args.B)
+	return nil
+}
+
+func (t *Arith) Scan(args string, reply *Reply) (err error) {
+	_, err = fmt.Sscan(args, &reply.C)
+	return
+}
+
+func (t *Arith) Error(args *Args, reply *Reply) error {
+	panic("ERROR")
+}
+
+func listenTCP() (net.Listener, string) {
+	l, e := net.Listen("tcp", "127.0.0.1:0") // any available address
+	if e != nil {
+		log.Fatalf("net.Listen tcp :0: %v", e)
+	}
+	return l, l.Addr().String()
+}
+
+func startServer() {
+	Register(new(Arith))
+	RegisterName("net.rpc.Arith", new(Arith))
+
+	var l net.Listener
+	l, serverAddr = listenTCP()
+	log.Println("Test RPC server listening on", serverAddr)
+	go Accept(l)
+
+	HandleHTTP()
+	httpOnce.Do(startHttpServer)
+}
+
+func startNewServer() {
+	newServer = NewServer()
+	newServer.Register(new(Arith))
+	newServer.RegisterName("net.rpc.Arith", new(Arith))
+	newServer.RegisterName("newServer.Arith", new(Arith))
+
+	var l net.Listener
+	l, newServerAddr = listenTCP()
+	log.Println("NewServer test RPC server listening on", newServerAddr)
+	go newServer.Accept(l)
+
+	newServer.HandleHTTP(newHttpPath, "/bar")
+	httpOnce.Do(startHttpServer)
+}
+
+func startHttpServer() {
+	server := httptest.NewServer(nil)
+	httpServerAddr = server.Listener.Addr().String()
+	log.Println("Test HTTP RPC server listening on", httpServerAddr)
+}
+
+func TestRPC(t *testing.T) {
+	once.Do(startServer)
+	testRPC(t, serverAddr)
+	newOnce.Do(startNewServer)
+	testRPC(t, newServerAddr)
+	testNewServerRPC(t, newServerAddr)
+}
+
+func testRPC(t *testing.T, addr string) {
+	client, err := Dial("tcp", addr)
+	if err != nil {
+		t.Fatal("dialing", err)
+	}
+	defer client.Close()
+
+	// Synchronous calls
+	args := &Args{7, 8}
+	reply := new(Reply)
+	err = client.Call("Arith.Add", args, reply)
+	if err != nil {
+		t.Errorf("Add: expected no error but got string %q", err.Error())
+	}
+	if reply.C != args.A+args.B {
+		t.Errorf("Add: expected %d got %d", reply.C, args.A+args.B)
+	}
+
+	// Nonexistent method
+	args = &Args{7, 0}
+	reply = new(Reply)
+	err = client.Call("Arith.BadOperation", args, reply)
+	// expect an error
+	if err == nil {
+		t.Error("BadOperation: expected error")
+	} else if !strings.HasPrefix(err.Error(), "rpc: can't find method ") {
+		t.Errorf("BadOperation: expected can't find method error; got %q", err)
+	}
+
+	// Unknown service
+	args = &Args{7, 8}
+	reply = new(Reply)
+	err = client.Call("Arith.Unknown", args, reply)
+	if err == nil {
+		t.Error("expected error calling unknown service")
+	} else if strings.Index(err.Error(), "method") < 0 {
+		t.Error("expected error about method; got", err)
+	}
+
+	// Out of order.
+	args = &Args{7, 8}
+	mulReply := new(Reply)
+	mulCall := client.Go("Arith.Mul", args, mulReply, nil)
+	addReply := new(Reply)
+	addCall := client.Go("Arith.Add", args, addReply, nil)
+
+	addCall = <-addCall.Done
+	if addCall.Error != nil {
+		t.Errorf("Add: expected no error but got string %q", addCall.Error.Error())
+	}
+	if addReply.C != args.A+args.B {
+		t.Errorf("Add: expected %d got %d", addReply.C, args.A+args.B)
+	}
+
+	mulCall = <-mulCall.Done
+	if mulCall.Error != nil {
+		t.Errorf("Mul: expected no error but got string %q", mulCall.Error.Error())
+	}
+	if mulReply.C != args.A*args.B {
+		t.Errorf("Mul: expected %d got %d", mulReply.C, args.A*args.B)
+	}
+
+	// Error test
+	args = &Args{7, 0}
+	reply = new(Reply)
+	err = client.Call("Arith.Div", args, reply)
+	// expect an error: zero divide
+	if err == nil {
+		t.Error("Div: expected error")
+	} else if err.Error() != "divide by zero" {
+		t.Error("Div: expected divide by zero error; got", err)
+	}
+
+	// Bad type.
+	reply = new(Reply)
+	err = client.Call("Arith.Add", reply, reply) // args, reply would be the correct thing to use
+	if err == nil {
+		t.Error("expected error calling Arith.Add with wrong arg type")
+	} else if strings.Index(err.Error(), "type") < 0 {
+		t.Error("expected error about type; got", err)
+	}
+
+	// Non-struct argument
+	const Val = 12345
+	str := fmt.Sprint(Val)
+	reply = new(Reply)
+	err = client.Call("Arith.Scan", &str, reply)
+	if err != nil {
+		t.Errorf("Scan: expected no error but got string %q", err.Error())
+	} else if reply.C != Val {
+		t.Errorf("Scan: expected %d got %d", Val, reply.C)
+	}
+
+	// Non-struct reply
+	args = &Args{27, 35}
+	str = ""
+	err = client.Call("Arith.String", args, &str)
+	if err != nil {
+		t.Errorf("String: expected no error but got string %q", err.Error())
+	}
+	expect := fmt.Sprintf("%d+%d=%d", args.A, args.B, args.A+args.B)
+	if str != expect {
+		t.Errorf("String: expected %s got %s", expect, str)
+	}
+
+	args = &Args{7, 8}
+	reply = new(Reply)
+	err = client.Call("Arith.Mul", args, reply)
+	if err != nil {
+		t.Errorf("Mul: expected no error but got string %q", err.Error())
+	}
+	if reply.C != args.A*args.B {
+		t.Errorf("Mul: expected %d got %d", reply.C, args.A*args.B)
+	}
+
+	// ServiceName contain "." character
+	args = &Args{7, 8}
+	reply = new(Reply)
+	err = client.Call("net.rpc.Arith.Add", args, reply)
+	if err != nil {
+		t.Errorf("Add: expected no error but got string %q", err.Error())
+	}
+	if reply.C != args.A+args.B {
+		t.Errorf("Add: expected %d got %d", reply.C, args.A+args.B)
+	}
+}
+
+func testNewServerRPC(t *testing.T, addr string) {
+	client, err := Dial("tcp", addr)
+	if err != nil {
+		t.Fatal("dialing", err)
+	}
+	defer client.Close()
+
+	// Synchronous calls
+	args := &Args{7, 8}
+	reply := new(Reply)
+	err = client.Call("newServer.Arith.Add", args, reply)
+	if err != nil {
+		t.Errorf("Add: expected no error but got string %q", err.Error())
+	}
+	if reply.C != args.A+args.B {
+		t.Errorf("Add: expected %d got %d", reply.C, args.A+args.B)
+	}
+}
+
+func TestHTTP(t *testing.T) {
+	once.Do(startServer)
+	testHTTPRPC(t, "")
+	newOnce.Do(startNewServer)
+	testHTTPRPC(t, newHttpPath)
+}
+
+func testHTTPRPC(t *testing.T, path string) {
+	var client *Client
+	var err error
+	if path == "" {
+		client, err = DialHTTP("tcp", httpServerAddr)
+	} else {
+		client, err = DialHTTPPath("tcp", httpServerAddr, path)
+	}
+	if err != nil {
+		t.Fatal("dialing", err)
+	}
+	defer client.Close()
+
+	// Synchronous calls
+	args := &Args{7, 8}
+	reply := new(Reply)
+	err = client.Call("Arith.Add", args, reply)
+	if err != nil {
+		t.Errorf("Add: expected no error but got string %q", err.Error())
+	}
+	if reply.C != args.A+args.B {
+		t.Errorf("Add: expected %d got %d", reply.C, args.A+args.B)
+	}
+}
+
+// CodecEmulator provides a client-like api and a ServerCodec interface.
+// Can be used to test ServeRequest.
+type CodecEmulator struct {
+	server        *Server
+	serviceMethod string
+	args          *Args
+	reply         *Reply
+	err           error
+}
+
+func (codec *CodecEmulator) Call(serviceMethod string, args *Args, reply *Reply) error {
+	codec.serviceMethod = serviceMethod
+	codec.args = args
+	codec.reply = reply
+	codec.err = nil
+	var serverError error
+	if codec.server == nil {
+		serverError = ServeRequest(codec)
+	} else {
+		serverError = codec.server.ServeRequest(codec)
+	}
+	if codec.err == nil && serverError != nil {
+		codec.err = serverError
+	}
+	return codec.err
+}
+
+func (codec *CodecEmulator) ReadRequestHeader(req *Request) error {
+	req.ServiceMethod = codec.serviceMethod
+	req.Seq = 0
+	return nil
+}
+
+func (codec *CodecEmulator) ReadRequestBody(argv interface{}) error {
+	if codec.args == nil {
+		return io.ErrUnexpectedEOF
+	}
+	*(argv.(*Args)) = *codec.args
+	return nil
+}
+
+func (codec *CodecEmulator) WriteResponse(resp *Response, reply interface{}) error {
+	if resp.Error != "" {
+		codec.err = errors.New(resp.Error)
+	} else {
+		*codec.reply = *(reply.(*Reply))
+	}
+	return nil
+}
+
+func (codec *CodecEmulator) Close() error {
+	return nil
+}
+
+func TestServeRequest(t *testing.T) {
+	once.Do(startServer)
+	testServeRequest(t, nil)
+	newOnce.Do(startNewServer)
+	testServeRequest(t, newServer)
+}
+
+func testServeRequest(t *testing.T, server *Server) {
+	client := CodecEmulator{server: server}
+	defer client.Close()
+
+	args := &Args{7, 8}
+	reply := new(Reply)
+	err := client.Call("Arith.Add", args, reply)
+	if err != nil {
+		t.Errorf("Add: expected no error but got string %q", err.Error())
+	}
+	if reply.C != args.A+args.B {
+		t.Errorf("Add: expected %d got %d", reply.C, args.A+args.B)
+	}
+
+	err = client.Call("Arith.Add", nil, reply)
+	if err == nil {
+		t.Errorf("expected error calling Arith.Add with nil arg")
+	}
+}
+
+type ReplyNotPointer int
+type ArgNotPublic int
+type ReplyNotPublic int
+type NeedsPtrType int
+type local struct{}
+
+func (t *ReplyNotPointer) ReplyNotPointer(args *Args, reply Reply) error {
+	return nil
+}
+
+func (t *ArgNotPublic) ArgNotPublic(args *local, reply *Reply) error {
+	return nil
+}
+
+func (t *ReplyNotPublic) ReplyNotPublic(args *Args, reply *local) error {
+	return nil
+}
+
+func (t *NeedsPtrType) NeedsPtrType(args *Args, reply *Reply) error {
+	return nil
+}
+
+// Check that registration handles lots of bad methods and a type with no suitable methods.
+func TestRegistrationError(t *testing.T) {
+	err := Register(new(ReplyNotPointer))
+	if err == nil {
+		t.Error("expected error registering ReplyNotPointer")
+	}
+	err = Register(new(ArgNotPublic))
+	if err == nil {
+		t.Error("expected error registering ArgNotPublic")
+	}
+	err = Register(new(ReplyNotPublic))
+	if err == nil {
+		t.Error("expected error registering ReplyNotPublic")
+	}
+	err = Register(NeedsPtrType(0))
+	if err == nil {
+		t.Error("expected error registering NeedsPtrType")
+	} else if !strings.Contains(err.Error(), "pointer") {
+		t.Error("expected hint when registering NeedsPtrType")
+	}
+}
+
+type WriteFailCodec int
+
+func (WriteFailCodec) WriteRequest(*Request, interface{}) error {
+	// the panic caused by this error used to not unlock a lock.
+	return errors.New("fail")
+}
+
+func (WriteFailCodec) ReadResponseHeader(*Response) error {
+	select {}
+}
+
+func (WriteFailCodec) ReadResponseBody(interface{}) error {
+	select {}
+}
+
+func (WriteFailCodec) Close() error {
+	return nil
+}
+
+func TestSendDeadlock(t *testing.T) {
+	client := NewClientWithCodec(WriteFailCodec(0))
+	defer client.Close()
+
+	done := make(chan bool)
+	go func() {
+		testSendDeadlock(client)
+		testSendDeadlock(client)
+		done <- true
+	}()
+	select {
+	case <-done:
+		return
+	case <-time.After(5 * time.Second):
+		t.Fatal("deadlock")
+	}
+}
+
+func testSendDeadlock(client *Client) {
+	defer func() {
+		recover()
+	}()
+	args := &Args{7, 8}
+	reply := new(Reply)
+	client.Call("Arith.Add", args, reply)
+}
+
+func dialDirect() (*Client, error) {
+	return Dial("tcp", serverAddr)
+}
+
+func dialHTTP() (*Client, error) {
+	return DialHTTP("tcp", httpServerAddr)
+}
+
+func countMallocs(dial func() (*Client, error), t *testing.T) float64 {
+	once.Do(startServer)
+	client, err := dial()
+	if err != nil {
+		t.Fatal("error dialing", err)
+	}
+	defer client.Close()
+
+	args := &Args{7, 8}
+	reply := new(Reply)
+	return testing.AllocsPerRun(100, func() {
+		err := client.Call("Arith.Add", args, reply)
+		if err != nil {
+			t.Errorf("Add: expected no error but got string %q", err.Error())
+		}
+		if reply.C != args.A+args.B {
+			t.Errorf("Add: expected %d got %d", reply.C, args.A+args.B)
+		}
+	})
+}
+
+func TestCountMallocs(t *testing.T) {
+	if testing.Short() {
+		t.Skip("skipping malloc count in short mode")
+	}
+	if runtime.GOMAXPROCS(0) > 1 {
+		t.Skip("skipping; GOMAXPROCS>1")
+	}
+	fmt.Printf("mallocs per rpc round trip: %v\n", countMallocs(dialDirect, t))
+}
+
+func TestCountMallocsOverHTTP(t *testing.T) {
+	if testing.Short() {
+		t.Skip("skipping malloc count in short mode")
+	}
+	if runtime.GOMAXPROCS(0) > 1 {
+		t.Skip("skipping; GOMAXPROCS>1")
+	}
+	fmt.Printf("mallocs per HTTP rpc round trip: %v\n", countMallocs(dialHTTP, t))
+}
+
+type writeCrasher struct {
+	done chan bool
+}
+
+func (writeCrasher) Close() error {
+	return nil
+}
+
+func (w *writeCrasher) Read(p []byte) (int, error) {
+	<-w.done
+	return 0, io.EOF
+}
+
+func (writeCrasher) Write(p []byte) (int, error) {
+	return 0, errors.New("fake write failure")
+}
+
+func TestClientWriteError(t *testing.T) {
+	w := &writeCrasher{done: make(chan bool)}
+	c := NewClient(w)
+	defer c.Close()
+
+	res := false
+	err := c.Call("foo", 1, &res)
+	if err == nil {
+		t.Fatal("expected error")
+	}
+	if err.Error() != "fake write failure" {
+		t.Error("unexpected value of error:", err)
+	}
+	w.done <- true
+}
+
+func TestTCPClose(t *testing.T) {
+	once.Do(startServer)
+
+	client, err := dialHTTP()
+	if err != nil {
+		t.Fatalf("dialing: %v", err)
+	}
+	defer client.Close()
+
+	args := Args{17, 8}
+	var reply Reply
+	err = client.Call("Arith.Mul", args, &reply)
+	if err != nil {
+		t.Fatal("arith error:", err)
+	}
+	t.Logf("Arith: %d*%d=%d\n", args.A, args.B, reply)
+	if reply.C != args.A*args.B {
+		t.Errorf("Add: expected %d got %d", reply.C, args.A*args.B)
+	}
+}
+
+func TestErrorAfterClientClose(t *testing.T) {
+	once.Do(startServer)
+
+	client, err := dialHTTP()
+	if err != nil {
+		t.Fatalf("dialing: %v", err)
+	}
+	err = client.Close()
+	if err != nil {
+		t.Fatal("close error:", err)
+	}
+	err = client.Call("Arith.Add", &Args{7, 9}, new(Reply))
+	if err != ErrShutdown {
+		t.Errorf("Forever: expected ErrShutdown got %v", err)
+	}
+}
+
+func benchmarkEndToEnd(dial func() (*Client, error), b *testing.B) {
+	once.Do(startServer)
+	client, err := dial()
+	if err != nil {
+		b.Fatal("error dialing:", err)
+	}
+	defer client.Close()
+
+	// Synchronous calls
+	args := &Args{7, 8}
+	b.ResetTimer()
+
+	b.RunParallel(func(pb *testing.PB) {
+		reply := new(Reply)
+		for pb.Next() {
+			err := client.Call("Arith.Add", args, reply)
+			if err != nil {
+				b.Fatalf("rpc error: Add: expected no error but got string %q", err.Error())
+			}
+			if reply.C != args.A+args.B {
+				b.Fatalf("rpc error: Add: expected %d got %d", reply.C, args.A+args.B)
+			}
+		}
+	})
+}
+
+func benchmarkEndToEndAsync(dial func() (*Client, error), b *testing.B) {
+	const MaxConcurrentCalls = 100
+	once.Do(startServer)
+	client, err := dial()
+	if err != nil {
+		b.Fatal("error dialing:", err)
+	}
+	defer client.Close()
+
+	// Asynchronous calls
+	args := &Args{7, 8}
+	procs := 4 * runtime.GOMAXPROCS(-1)
+	send := int32(b.N)
+	recv := int32(b.N)
+	var wg sync.WaitGroup
+	wg.Add(procs)
+	gate := make(chan bool, MaxConcurrentCalls)
+	res := make(chan *Call, MaxConcurrentCalls)
+	b.ResetTimer()
+
+	for p := 0; p < procs; p++ {
+		go func() {
+			for atomic.AddInt32(&send, -1) >= 0 {
+				gate <- true
+				reply := new(Reply)
+				client.Go("Arith.Add", args, reply, res)
+			}
+		}()
+		go func() {
+			for call := range res {
+				A := call.Args.(*Args).A
+				B := call.Args.(*Args).B
+				C := call.Reply.(*Reply).C
+				if A+B != C {
+					b.Fatalf("incorrect reply: Add: expected %d got %d", A+B, C)
+				}
+				<-gate
+				if atomic.AddInt32(&recv, -1) == 0 {
+					close(res)
+				}
+			}
+			wg.Done()
+		}()
+	}
+	wg.Wait()
+}
+
+func BenchmarkEndToEnd(b *testing.B) {
+	benchmarkEndToEnd(dialDirect, b)
+}
+
+func BenchmarkEndToEndHTTP(b *testing.B) {
+	benchmarkEndToEnd(dialHTTP, b)
+}
+
+func BenchmarkEndToEndAsync(b *testing.B) {
+	benchmarkEndToEndAsync(dialDirect, b)
+}
+
+func BenchmarkEndToEndAsyncHTTP(b *testing.B) {
+	benchmarkEndToEndAsync(dialHTTP, b)
+}
diff --git a/src/net/sendfile_dragonfly.go b/src/net/sendfile_dragonfly.go
new file mode 100644
index 000000000..bc88fd3b9
--- /dev/null
+++ b/src/net/sendfile_dragonfly.go
@@ -0,0 +1,103 @@
+// Copyright 2011 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package net
+
+import (
+	"io"
+	"os"
+	"syscall"
+)
+
+// maxSendfileSize is the largest chunk size we ask the kernel to copy
+// at a time.
+const maxSendfileSize int = 4 << 20
+
+// sendFile copies the contents of r to c using the sendfile
+// system call to minimize copies.
+//
+// if handled == true, sendFile returns the number of bytes copied and any
+// non-EOF error.
+//
+// if handled == false, sendFile performed no work.
+func sendFile(c *netFD, r io.Reader) (written int64, err error, handled bool) {
+	// DragonFly uses 0 as the "until EOF" value. If you pass in more bytes than the
+	// file contains, it will loop back to the beginning ad nauseam until it's sent
+	// exactly the number of bytes told to. As such, we need to know exactly how many
+	// bytes to send.
+	var remain int64 = 0
+
+	lr, ok := r.(*io.LimitedReader)
+	if ok {
+		remain, r = lr.N, lr.R
+		if remain <= 0 {
+			return 0, nil, true
+		}
+	}
+	f, ok := r.(*os.File)
+	if !ok {
+		return 0, nil, false
+	}
+
+	if remain == 0 {
+		fi, err := f.Stat()
+		if err != nil {
+			return 0, err, false
+		}
+
+		remain = fi.Size()
+	}
+
+	// The other quirk with DragonFly's sendfile implementation is that it doesn't
+	// use the current position of the file -- if you pass it offset 0, it starts
+	// from offset 0. There's no way to tell it "start from current position", so
+	// we have to manage that explicitly.
+	pos, err := f.Seek(0, os.SEEK_CUR)
+	if err != nil {
+		return 0, err, false
+	}
+
+	if err := c.writeLock(); err != nil {
+		return 0, err, true
+	}
+	defer c.writeUnlock()
+
+	dst := c.sysfd
+	src := int(f.Fd())
+	for remain > 0 {
+		n := maxSendfileSize
+		if int64(n) > remain {
+			n = int(remain)
+		}
+		pos1 := pos
+		n, err1 := syscall.Sendfile(dst, src, &pos1, n)
+		if n > 0 {
+			pos += int64(n)
+			written += int64(n)
+			remain -= int64(n)
+		}
+		if n == 0 && err1 == nil {
+			break
+		}
+		if err1 == syscall.EAGAIN {
+			if err1 = c.pd.WaitWrite(); err1 == nil {
+				continue
+			}
+		}
+		if err1 == syscall.EINTR {
+			continue
+		}
+		if err1 != nil {
+			// This includes syscall.ENOSYS (no kernel
+			// support) and syscall.EINVAL (fd types which
+			// don't implement sendfile together)
+			err = &OpError{"sendfile", c.net, c.raddr, err1}
+			break
+		}
+	}
+	if lr != nil {
+		lr.N = remain
+	}
+	return written, err, written > 0
+}
diff --git a/src/net/sendfile_freebsd.go b/src/net/sendfile_freebsd.go
new file mode 100644
index 000000000..ffc147262
--- /dev/null
+++ b/src/net/sendfile_freebsd.go
@@ -0,0 +1,103 @@
+// Copyright 2011 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package net
+
+import (
+	"io"
+	"os"
+	"syscall"
+)
+
+// maxSendfileSize is the largest chunk size we ask the kernel to copy
+// at a time.
+const maxSendfileSize int = 4 << 20
+
+// sendFile copies the contents of r to c using the sendfile
+// system call to minimize copies.
+//
+// if handled == true, sendFile returns the number of bytes copied and any
+// non-EOF error.
+//
+// if handled == false, sendFile performed no work.
+func sendFile(c *netFD, r io.Reader) (written int64, err error, handled bool) {
+	// FreeBSD uses 0 as the "until EOF" value. If you pass in more bytes than the
+	// file contains, it will loop back to the beginning ad nauseam until it's sent
+	// exactly the number of bytes told to. As such, we need to know exactly how many
+	// bytes to send.
+	var remain int64 = 0
+
+	lr, ok := r.(*io.LimitedReader)
+	if ok {
+		remain, r = lr.N, lr.R
+		if remain <= 0 {
+			return 0, nil, true
+		}
+	}
+	f, ok := r.(*os.File)
+	if !ok {
+		return 0, nil, false
+	}
+
+	if remain == 0 {
+		fi, err := f.Stat()
+		if err != nil {
+			return 0, err, false
+		}
+
+		remain = fi.Size()
+	}
+
+	// The other quirk with FreeBSD's sendfile implementation is that it doesn't
+	// use the current position of the file -- if you pass it offset 0, it starts
+	// from offset 0. There's no way to tell it "start from current position", so
+	// we have to manage that explicitly.
+	pos, err := f.Seek(0, os.SEEK_CUR)
+	if err != nil {
+		return 0, err, false
+	}
+
+	if err := c.writeLock(); err != nil {
+		return 0, err, true
+	}
+	defer c.writeUnlock()
+
+	dst := c.sysfd
+	src := int(f.Fd())
+	for remain > 0 {
+		n := maxSendfileSize
+		if int64(n) > remain {
+			n = int(remain)
+		}
+		pos1 := pos
+		n, err1 := syscall.Sendfile(dst, src, &pos1, n)
+		if n > 0 {
+			pos += int64(n)
+			written += int64(n)
+			remain -= int64(n)
+		}
+		if n == 0 && err1 == nil {
+			break
+		}
+		if err1 == syscall.EAGAIN {
+			if err1 = c.pd.WaitWrite(); err1 == nil {
+				continue
+			}
+		}
+		if err1 == syscall.EINTR {
+			continue
+		}
+		if err1 != nil {
+			// This includes syscall.ENOSYS (no kernel
+			// support) and syscall.EINVAL (fd types which
+			// don't implement sendfile together)
+			err = &OpError{"sendfile", c.net, c.raddr, err1}
+			break
+		}
+	}
+	if lr != nil {
+		lr.N = remain
+	}
+	return written, err, written > 0
+}
diff --git a/src/net/sendfile_linux.go b/src/net/sendfile_linux.go
new file mode 100644
index 000000000..5e117636a
--- /dev/null
+++ b/src/net/sendfile_linux.go
@@ -0,0 +1,76 @@
+// Copyright 2011 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package net
+
+import (
+	"io"
+	"os"
+	"syscall"
+)
+
+// maxSendfileSize is the largest chunk size we ask the kernel to copy
+// at a time.
+const maxSendfileSize int = 4 << 20
+
+// sendFile copies the contents of r to c using the sendfile
+// system call to minimize copies.
+//
+// if handled == true, sendFile returns the number of bytes copied and any
+// non-EOF error.
+//
+// if handled == false, sendFile performed no work.
+func sendFile(c *netFD, r io.Reader) (written int64, err error, handled bool) {
+	var remain int64 = 1 << 62 // by default, copy until EOF
+
+	lr, ok := r.(*io.LimitedReader)
+	if ok {
+		remain, r = lr.N, lr.R
+		if remain <= 0 {
+			return 0, nil, true
+		}
+	}
+	f, ok := r.(*os.File)
+	if !ok {
+		return 0, nil, false
+	}
+
+	if err := c.writeLock(); err != nil {
+		return 0, err, true
+	}
+	defer c.writeUnlock()
+
+	dst := c.sysfd
+	src := int(f.Fd())
+	for remain > 0 {
+		n := maxSendfileSize
+		if int64(n) > remain {
+			n = int(remain)
+		}
+		n, err1 := syscall.Sendfile(dst, src, nil, n)
+		if n > 0 {
+			written += int64(n)
+			remain -= int64(n)
+		}
+		if n == 0 && err1 == nil {
+			break
+		}
+		if err1 == syscall.EAGAIN {
+			if err1 = c.pd.WaitWrite(); err1 == nil {
+				continue
+			}
+		}
+		if err1 != nil {
+			// This includes syscall.ENOSYS (no kernel
+			// support) and syscall.EINVAL (fd types which
+			// don't implement sendfile together)
+			err = &OpError{"sendfile", c.net, c.raddr, err1}
+			break
+		}
+	}
+	if lr != nil {
+		lr.N = remain
+	}
+	return written, err, written > 0
+}
diff --git a/src/net/sendfile_stub.go b/src/net/sendfile_stub.go
new file mode 100644
index 000000000..03426ef0d
--- /dev/null
+++ b/src/net/sendfile_stub.go
@@ -0,0 +1,13 @@
+// Copyright 2011 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build darwin nacl netbsd openbsd solaris
+
+package net
+
+import "io"
+
+func sendFile(c *netFD, r io.Reader) (n int64, err error, handled bool) {
+	return 0, nil, false
+}
diff --git a/src/net/sendfile_windows.go b/src/net/sendfile_windows.go
new file mode 100644
index 000000000..b128ba27b
--- /dev/null
+++ b/src/net/sendfile_windows.go
@@ -0,0 +1,55 @@
+// Copyright 2011 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package net
+
+import (
+	"io"
+	"os"
+	"syscall"
+)
+
+// sendFile copies the contents of r to c using the TransmitFile
+// system call to minimize copies.
+//
+// if handled == true, sendFile returns the number of bytes copied and any
+// non-EOF error.
+//
+// if handled == false, sendFile performed no work.
+//
+// Note that sendfile for windows does not suppport >2GB file.
+func sendFile(fd *netFD, r io.Reader) (written int64, err error, handled bool) {
+	var n int64 = 0 // by default, copy until EOF
+
+	lr, ok := r.(*io.LimitedReader)
+	if ok {
+		n, r = lr.N, lr.R
+		if n <= 0 {
+			return 0, nil, true
+		}
+	}
+	f, ok := r.(*os.File)
+	if !ok {
+		return 0, nil, false
+	}
+
+	if err := fd.writeLock(); err != nil {
+		return 0, err, true
+	}
+	defer fd.writeUnlock()
+
+	o := &fd.wop
+	o.qty = uint32(n)
+	o.handle = syscall.Handle(f.Fd())
+	done, err := wsrv.ExecIO(o, "TransmitFile", func(o *operation) error {
+		return syscall.TransmitFile(o.fd.sysfd, o.handle, o.qty, 0, &o.o, nil, syscall.TF_WRITE_BEHIND)
+	})
+	if err != nil {
+		return 0, err, false
+	}
+	if lr != nil {
+		lr.N -= int64(done)
+	}
+	return int64(done), nil, true
+}
diff --git a/src/net/server_test.go b/src/net/server_test.go
new file mode 100644
index 000000000..6a2bb9243
--- /dev/null
+++ b/src/net/server_test.go
@@ -0,0 +1,461 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package net
+
+import (
+	"flag"
+	"io"
+	"os"
+	"runtime"
+	"testing"
+	"time"
+)
+
+func skipServerTest(net, unixsotype, addr string, ipv6, ipv4map, linuxOnly bool) bool {
+	switch runtime.GOOS {
+	case "linux":
+	case "nacl", "plan9", "windows":
+		// "unix" sockets are not supported on Windows and Plan 9.
+		if net == unixsotype {
+			return true
+		}
+	default:
+		if net == unixsotype && linuxOnly {
+			return true
+		}
+	}
+	switch addr {
+	case "", "0.0.0.0", "[::ffff:0.0.0.0]", "[::]":
+		if testing.Short() || !*testExternal {
+			return true
+		}
+	}
+	if ipv6 && !supportsIPv6 {
+		return true
+	}
+	if ipv4map && !supportsIPv4map {
+		return true
+	}
+	return false
+}
+
+var streamConnServerTests = []struct {
+	snet      string // server side
+	saddr     string
+	cnet      string // client side
+	caddr     string
+	ipv6      bool // test with underlying AF_INET6 socket
+	ipv4map   bool // test with IPv6 IPv4-mapping functionality
+	empty     bool // test with empty data
+	linuxOnly bool // test with abstract unix domain socket, a Linux-ism
+}{
+	{snet: "tcp", saddr: "", cnet: "tcp", caddr: "127.0.0.1"},
+	{snet: "tcp", saddr: "0.0.0.0", cnet: "tcp", caddr: "127.0.0.1"},
+	{snet: "tcp", saddr: "[::ffff:0.0.0.0]", cnet: "tcp", caddr: "127.0.0.1"},
+	{snet: "tcp", saddr: "[::]", cnet: "tcp", caddr: "[::1]", ipv6: true},
+
+	{snet: "tcp", saddr: "", cnet: "tcp", caddr: "[::1]", ipv4map: true},
+	{snet: "tcp", saddr: "0.0.0.0", cnet: "tcp", caddr: "[::1]", ipv4map: true},
+	{snet: "tcp", saddr: "[::ffff:0.0.0.0]", cnet: "tcp", caddr: "[::1]", ipv4map: true},
+	{snet: "tcp", saddr: "[::]", cnet: "tcp", caddr: "127.0.0.1", ipv4map: true},
+
+	{snet: "tcp", saddr: "", cnet: "tcp4", caddr: "127.0.0.1"},
+	{snet: "tcp", saddr: "0.0.0.0", cnet: "tcp4", caddr: "127.0.0.1"},
+	{snet: "tcp", saddr: "[::ffff:0.0.0.0]", cnet: "tcp4", caddr: "127.0.0.1"},
+	{snet: "tcp", saddr: "[::]", cnet: "tcp6", caddr: "[::1]", ipv6: true},
+
+	{snet: "tcp", saddr: "", cnet: "tcp6", caddr: "[::1]", ipv4map: true},
+	{snet: "tcp", saddr: "0.0.0.0", cnet: "tcp6", caddr: "[::1]", ipv4map: true},
+	{snet: "tcp", saddr: "[::ffff:0.0.0.0]", cnet: "tcp6", caddr: "[::1]", ipv4map: true},
+	{snet: "tcp", saddr: "[::]", cnet: "tcp4", caddr: "127.0.0.1", ipv4map: true},
+
+	{snet: "tcp", saddr: "127.0.0.1", cnet: "tcp", caddr: "127.0.0.1"},
+	{snet: "tcp", saddr: "[::ffff:127.0.0.1]", cnet: "tcp", caddr: "127.0.0.1"},
+	{snet: "tcp", saddr: "[::1]", cnet: "tcp", caddr: "[::1]", ipv6: true},
+
+	{snet: "tcp4", saddr: "", cnet: "tcp4", caddr: "127.0.0.1"},
+	{snet: "tcp4", saddr: "0.0.0.0", cnet: "tcp4", caddr: "127.0.0.1"},
+	{snet: "tcp4", saddr: "[::ffff:0.0.0.0]", cnet: "tcp4", caddr: "127.0.0.1"},
+
+	{snet: "tcp4", saddr: "127.0.0.1", cnet: "tcp4", caddr: "127.0.0.1"},
+
+	{snet: "tcp6", saddr: "", cnet: "tcp6", caddr: "[::1]", ipv6: true},
+	{snet: "tcp6", saddr: "[::]", cnet: "tcp6", caddr: "[::1]", ipv6: true},
+
+	{snet: "tcp6", saddr: "[::1]", cnet: "tcp6", caddr: "[::1]", ipv6: true},
+
+	{snet: "unix", saddr: testUnixAddr(), cnet: "unix", caddr: testUnixAddr()},
+	{snet: "unix", saddr: "@gotest2/net", cnet: "unix", caddr: "@gotest2/net.local", linuxOnly: true},
+}
+
+func TestStreamConnServer(t *testing.T) {
+	for _, tt := range streamConnServerTests {
+		if skipServerTest(tt.snet, "unix", tt.saddr, tt.ipv6, tt.ipv4map, tt.linuxOnly) {
+			continue
+		}
+
+		listening := make(chan string)
+		done := make(chan int)
+		switch tt.snet {
+		case "tcp", "tcp4", "tcp6":
+			tt.saddr += ":0"
+		case "unix":
+			os.Remove(tt.saddr)
+			os.Remove(tt.caddr)
+		}
+
+		go runStreamConnServer(t, tt.snet, tt.saddr, listening, done)
+		taddr := <-listening // wait for server to start
+
+		switch tt.cnet {
+		case "tcp", "tcp4", "tcp6":
+			_, port, err := SplitHostPort(taddr)
+			if err != nil {
+				t.Fatalf("SplitHostPort(%q) failed: %v", taddr, err)
+			}
+			taddr = tt.caddr + ":" + port
+		}
+
+		runStreamConnClient(t, tt.cnet, taddr, tt.empty)
+		<-done // make sure server stopped
+
+		switch tt.snet {
+		case "unix":
+			os.Remove(tt.saddr)
+			os.Remove(tt.caddr)
+		}
+	}
+}
+
+var seqpacketConnServerTests = []struct {
+	net       string
+	saddr     string // server address
+	caddr     string // client address
+	empty     bool   // test with empty data
+	linuxOnly bool   // test with abstract unix domain socket, a Linux-ism
+}{
+	{net: "unixpacket", saddr: testUnixAddr(), caddr: testUnixAddr()},
+	{net: "unixpacket", saddr: "@gotest4/net", caddr: "@gotest4/net.local", linuxOnly: true},
+}
+
+func TestSeqpacketConnServer(t *testing.T) {
+	switch runtime.GOOS {
+	case "darwin", "nacl", "openbsd", "plan9", "windows":
+		fallthrough
+	case "freebsd": // FreeBSD 8 doesn't support unixpacket
+		t.Skipf("skipping test on %q", runtime.GOOS)
+	}
+
+	for _, tt := range seqpacketConnServerTests {
+		if runtime.GOOS != "linux" && tt.linuxOnly {
+			continue
+		}
+		listening := make(chan string)
+		done := make(chan int)
+		switch tt.net {
+		case "unixpacket":
+			os.Remove(tt.saddr)
+			os.Remove(tt.caddr)
+		}
+
+		go runStreamConnServer(t, tt.net, tt.saddr, listening, done)
+		taddr := <-listening // wait for server to start
+
+		runStreamConnClient(t, tt.net, taddr, tt.empty)
+		<-done // make sure server stopped
+
+		switch tt.net {
+		case "unixpacket":
+			os.Remove(tt.saddr)
+			os.Remove(tt.caddr)
+		}
+	}
+}
+
+func runStreamConnServer(t *testing.T, net, laddr string, listening chan<- string, done chan<- int) {
+	defer close(done)
+	l, err := Listen(net, laddr)
+	if err != nil {
+		t.Errorf("Listen(%q, %q) failed: %v", net, laddr, err)
+		listening <- "<nil>"
+		return
+	}
+	defer l.Close()
+	listening <- l.Addr().String()
+
+	echo := func(rw io.ReadWriter, done chan<- int) {
+		buf := make([]byte, 1024)
+		for {
+			n, err := rw.Read(buf[0:])
+			if err != nil || n == 0 || string(buf[:n]) == "END" {
+				break
+			}
+			rw.Write(buf[0:n])
+		}
+		close(done)
+	}
+
+run:
+	for {
+		c, err := l.Accept()
+		if err != nil {
+			t.Logf("Accept failed: %v", err)
+			continue run
+		}
+		echodone := make(chan int)
+		go echo(c, echodone)
+		<-echodone // make sure echo stopped
+		c.Close()
+		break run
+	}
+}
+
+func runStreamConnClient(t *testing.T, net, taddr string, isEmpty bool) {
+	c, err := Dial(net, taddr)
+	if err != nil {
+		t.Fatalf("Dial(%q, %q) failed: %v", net, taddr, err)
+	}
+	defer c.Close()
+	c.SetReadDeadline(time.Now().Add(1 * time.Second))
+
+	var wb []byte
+	if !isEmpty {
+		wb = []byte("StreamConnClient by Dial\n")
+	}
+	if n, err := c.Write(wb); err != nil || n != len(wb) {
+		t.Fatalf("Write failed: %v, %v; want %v, <nil>", n, err, len(wb))
+	}
+
+	rb := make([]byte, 1024)
+	if n, err := c.Read(rb[0:]); err != nil || n != len(wb) {
+		t.Fatalf("Read failed: %v, %v; want %v, <nil>", n, err, len(wb))
+	}
+
+	// Send explicit ending for unixpacket.
+	// Older Linux kernels do not stop reads on close.
+	switch net {
+	case "unixpacket":
+		c.Write([]byte("END"))
+	}
+}
+
+// Do not test empty datagrams by default.
+// It causes unexplained timeouts on some systems,
+// including Snow Leopard.  I think that the kernel
+// doesn't quite expect them.
+var testDatagram = flag.Bool("datagram", false, "whether to test udp and unixgram")
+
+var datagramPacketConnServerTests = []struct {
+	snet      string // server side
+	saddr     string
+	cnet      string // client side
+	caddr     string
+	ipv6      bool // test with underlying AF_INET6 socket
+	ipv4map   bool // test with IPv6 IPv4-mapping functionality
+	dial      bool // test with Dial or DialUnix
+	empty     bool // test with empty data
+	linuxOnly bool // test with abstract unix domain socket, a Linux-ism
+}{
+	{snet: "udp", saddr: "", cnet: "udp", caddr: "127.0.0.1"},
+	{snet: "udp", saddr: "0.0.0.0", cnet: "udp", caddr: "127.0.0.1"},
+	{snet: "udp", saddr: "[::ffff:0.0.0.0]", cnet: "udp", caddr: "127.0.0.1"},
+	{snet: "udp", saddr: "[::]", cnet: "udp", caddr: "[::1]", ipv6: true},
+
+	{snet: "udp", saddr: "", cnet: "udp", caddr: "[::1]", ipv4map: true},
+	{snet: "udp", saddr: "0.0.0.0", cnet: "udp", caddr: "[::1]", ipv4map: true},
+	{snet: "udp", saddr: "[::ffff:0.0.0.0]", cnet: "udp", caddr: "[::1]", ipv4map: true},
+	{snet: "udp", saddr: "[::]", cnet: "udp", caddr: "127.0.0.1", ipv4map: true},
+
+	{snet: "udp", saddr: "", cnet: "udp4", caddr: "127.0.0.1"},
+	{snet: "udp", saddr: "0.0.0.0", cnet: "udp4", caddr: "127.0.0.1"},
+	{snet: "udp", saddr: "[::ffff:0.0.0.0]", cnet: "udp4", caddr: "127.0.0.1"},
+	{snet: "udp", saddr: "[::]", cnet: "udp6", caddr: "[::1]", ipv6: true},
+
+	{snet: "udp", saddr: "", cnet: "udp6", caddr: "[::1]", ipv4map: true},
+	{snet: "udp", saddr: "0.0.0.0", cnet: "udp6", caddr: "[::1]", ipv4map: true},
+	{snet: "udp", saddr: "[::ffff:0.0.0.0]", cnet: "udp6", caddr: "[::1]", ipv4map: true},
+	{snet: "udp", saddr: "[::]", cnet: "udp4", caddr: "127.0.0.1", ipv4map: true},
+
+	{snet: "udp", saddr: "127.0.0.1", cnet: "udp", caddr: "127.0.0.1"},
+	{snet: "udp", saddr: "[::ffff:127.0.0.1]", cnet: "udp", caddr: "127.0.0.1"},
+	{snet: "udp", saddr: "[::1]", cnet: "udp", caddr: "[::1]", ipv6: true},
+
+	{snet: "udp4", saddr: "", cnet: "udp4", caddr: "127.0.0.1"},
+	{snet: "udp4", saddr: "0.0.0.0", cnet: "udp4", caddr: "127.0.0.1"},
+	{snet: "udp4", saddr: "[::ffff:0.0.0.0]", cnet: "udp4", caddr: "127.0.0.1"},
+
+	{snet: "udp4", saddr: "127.0.0.1", cnet: "udp4", caddr: "127.0.0.1"},
+
+	{snet: "udp6", saddr: "", cnet: "udp6", caddr: "[::1]", ipv6: true},
+	{snet: "udp6", saddr: "[::]", cnet: "udp6", caddr: "[::1]", ipv6: true},
+
+	{snet: "udp6", saddr: "[::1]", cnet: "udp6", caddr: "[::1]", ipv6: true},
+
+	{snet: "udp", saddr: "127.0.0.1", cnet: "udp", caddr: "127.0.0.1", dial: true},
+	{snet: "udp", saddr: "127.0.0.1", cnet: "udp", caddr: "127.0.0.1", empty: true},
+	{snet: "udp", saddr: "127.0.0.1", cnet: "udp", caddr: "127.0.0.1", dial: true, empty: true},
+
+	{snet: "udp", saddr: "[::1]", cnet: "udp", caddr: "[::1]", ipv6: true, dial: true},
+	{snet: "udp", saddr: "[::1]", cnet: "udp", caddr: "[::1]", ipv6: true, empty: true},
+	{snet: "udp", saddr: "[::1]", cnet: "udp", caddr: "[::1]", ipv6: true, dial: true, empty: true},
+
+	{snet: "unixgram", saddr: testUnixAddr(), cnet: "unixgram", caddr: testUnixAddr()},
+	{snet: "unixgram", saddr: testUnixAddr(), cnet: "unixgram", caddr: testUnixAddr(), dial: true},
+	{snet: "unixgram", saddr: testUnixAddr(), cnet: "unixgram", caddr: testUnixAddr(), empty: true},
+	{snet: "unixgram", saddr: testUnixAddr(), cnet: "unixgram", caddr: testUnixAddr(), dial: true, empty: true},
+
+	{snet: "unixgram", saddr: "@gotest6/net", cnet: "unixgram", caddr: "@gotest6/net.local", linuxOnly: true},
+}
+
+func TestDatagramPacketConnServer(t *testing.T) {
+	if !*testDatagram {
+		return
+	}
+
+	for _, tt := range datagramPacketConnServerTests {
+		if skipServerTest(tt.snet, "unixgram", tt.saddr, tt.ipv6, tt.ipv4map, tt.linuxOnly) {
+			continue
+		}
+
+		listening := make(chan string)
+		done := make(chan int)
+		switch tt.snet {
+		case "udp", "udp4", "udp6":
+			tt.saddr += ":0"
+		case "unixgram":
+			os.Remove(tt.saddr)
+			os.Remove(tt.caddr)
+		}
+
+		go runDatagramPacketConnServer(t, tt.snet, tt.saddr, listening, done)
+		taddr := <-listening // wait for server to start
+
+		switch tt.cnet {
+		case "udp", "udp4", "udp6":
+			_, port, err := SplitHostPort(taddr)
+			if err != nil {
+				t.Fatalf("SplitHostPort(%q) failed: %v", taddr, err)
+			}
+			taddr = tt.caddr + ":" + port
+			tt.caddr += ":0"
+		}
+		if tt.dial {
+			runDatagramConnClient(t, tt.cnet, tt.caddr, taddr, tt.empty)
+		} else {
+			runDatagramPacketConnClient(t, tt.cnet, tt.caddr, taddr, tt.empty)
+		}
+		<-done // tell server to stop
+		<-done // make sure server stopped
+
+		switch tt.snet {
+		case "unixgram":
+			os.Remove(tt.saddr)
+			os.Remove(tt.caddr)
+		}
+	}
+}
+
+func runDatagramPacketConnServer(t *testing.T, net, laddr string, listening chan<- string, done chan<- int) {
+	c, err := ListenPacket(net, laddr)
+	if err != nil {
+		t.Errorf("ListenPacket(%q, %q) failed: %v", net, laddr, err)
+		listening <- "<nil>"
+		done <- 1
+		return
+	}
+	defer c.Close()
+	listening <- c.LocalAddr().String()
+
+	buf := make([]byte, 1024)
+run:
+	for {
+		c.SetReadDeadline(time.Now().Add(10 * time.Millisecond))
+		n, ra, err := c.ReadFrom(buf[0:])
+		if nerr, ok := err.(Error); ok && nerr.Timeout() {
+			select {
+			case done <- 1:
+				break run
+			default:
+				continue run
+			}
+		}
+		if err != nil {
+			break run
+		}
+		if _, err = c.WriteTo(buf[0:n], ra); err != nil {
+			t.Errorf("WriteTo(%v) failed: %v", ra, err)
+			break run
+		}
+	}
+	done <- 1
+}
+
+func runDatagramConnClient(t *testing.T, net, laddr, taddr string, isEmpty bool) {
+	var c Conn
+	var err error
+	switch net {
+	case "udp", "udp4", "udp6":
+		c, err = Dial(net, taddr)
+		if err != nil {
+			t.Fatalf("Dial(%q, %q) failed: %v", net, taddr, err)
+		}
+	case "unixgram":
+		c, err = DialUnix(net, &UnixAddr{Name: laddr, Net: net}, &UnixAddr{Name: taddr, Net: net})
+		if err != nil {
+			t.Fatalf("DialUnix(%q, {%q, %q}) failed: %v", net, laddr, taddr, err)
+		}
+	}
+	defer c.Close()
+	c.SetReadDeadline(time.Now().Add(1 * time.Second))
+
+	var wb []byte
+	if !isEmpty {
+		wb = []byte("DatagramConnClient by Dial\n")
+	}
+	if n, err := c.Write(wb[0:]); err != nil || n != len(wb) {
+		t.Fatalf("Write failed: %v, %v; want %v, <nil>", n, err, len(wb))
+	}
+
+	rb := make([]byte, 1024)
+	if n, err := c.Read(rb[0:]); err != nil || n != len(wb) {
+		t.Fatalf("Read failed: %v, %v; want %v, <nil>", n, err, len(wb))
+	}
+}
+
+func runDatagramPacketConnClient(t *testing.T, net, laddr, taddr string, isEmpty bool) {
+	var ra Addr
+	var err error
+	switch net {
+	case "udp", "udp4", "udp6":
+		ra, err = ResolveUDPAddr(net, taddr)
+		if err != nil {
+			t.Fatalf("ResolveUDPAddr(%q, %q) failed: %v", net, taddr, err)
+		}
+	case "unixgram":
+		ra, err = ResolveUnixAddr(net, taddr)
+		if err != nil {
+			t.Fatalf("ResolveUxixAddr(%q, %q) failed: %v", net, taddr, err)
+		}
+	}
+	c, err := ListenPacket(net, laddr)
+	if err != nil {
+		t.Fatalf("ListenPacket(%q, %q) faild: %v", net, laddr, err)
+	}
+	defer c.Close()
+	c.SetReadDeadline(time.Now().Add(1 * time.Second))
+
+	var wb []byte
+	if !isEmpty {
+		wb = []byte("DatagramPacketConnClient by ListenPacket\n")
+	}
+	if n, err := c.WriteTo(wb[0:], ra); err != nil || n != len(wb) {
+		t.Fatalf("WriteTo(%v) failed: %v, %v; want %v, <nil>", ra, n, err, len(wb))
+	}
+
+	rb := make([]byte, 1024)
+	if n, _, err := c.ReadFrom(rb[0:]); err != nil || n != len(wb) {
+		t.Fatalf("ReadFrom failed: %v, %v; want %v, <nil>", n, err, len(wb))
+	}
+}
diff --git a/src/net/singleflight.go b/src/net/singleflight.go
new file mode 100644
index 000000000..dc58affda
--- /dev/null
+++ b/src/net/singleflight.go
@@ -0,0 +1,53 @@
+// Copyright 2013 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package net
+
+import "sync"
+
+// call is an in-flight or completed singleflight.Do call
+type call struct {
+	wg   sync.WaitGroup
+	val  interface{}
+	err  error
+	dups int
+}
+
+// singleflight represents a class of work and forms a namespace in
+// which units of work can be executed with duplicate suppression.
+type singleflight struct {
+	mu sync.Mutex       // protects m
+	m  map[string]*call // lazily initialized
+}
+
+// Do executes and returns the results of the given function, making
+// sure that only one execution is in-flight for a given key at a
+// time. If a duplicate comes in, the duplicate caller waits for the
+// original to complete and receives the same results.
+// The return value shared indicates whether v was given to multiple callers.
+func (g *singleflight) Do(key string, fn func() (interface{}, error)) (v interface{}, err error, shared bool) {
+	g.mu.Lock()
+	if g.m == nil {
+		g.m = make(map[string]*call)
+	}
+	if c, ok := g.m[key]; ok {
+		c.dups++
+		g.mu.Unlock()
+		c.wg.Wait()
+		return c.val, c.err, true
+	}
+	c := new(call)
+	c.wg.Add(1)
+	g.m[key] = c
+	g.mu.Unlock()
+
+	c.val, c.err = fn()
+	c.wg.Done()
+
+	g.mu.Lock()
+	delete(g.m, key)
+	g.mu.Unlock()
+
+	return c.val, c.err, c.dups > 0
+}
diff --git a/src/net/smtp/auth.go b/src/net/smtp/auth.go
new file mode 100644
index 000000000..3f1339ebc
--- /dev/null
+++ b/src/net/smtp/auth.go
@@ -0,0 +1,107 @@
+// Copyright 2010 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package smtp
+
+import (
+	"crypto/hmac"
+	"crypto/md5"
+	"errors"
+	"fmt"
+)
+
+// Auth is implemented by an SMTP authentication mechanism.
+type Auth interface {
+	// Start begins an authentication with a server.
+	// It returns the name of the authentication protocol
+	// and optionally data to include in the initial AUTH message
+	// sent to the server. It can return proto == "" to indicate
+	// that the authentication should be skipped.
+	// If it returns a non-nil error, the SMTP client aborts
+	// the authentication attempt and closes the connection.
+	Start(server *ServerInfo) (proto string, toServer []byte, err error)
+
+	// Next continues the authentication. The server has just sent
+	// the fromServer data. If more is true, the server expects a
+	// response, which Next should return as toServer; otherwise
+	// Next should return toServer == nil.
+	// If Next returns a non-nil error, the SMTP client aborts
+	// the authentication attempt and closes the connection.
+	Next(fromServer []byte, more bool) (toServer []byte, err error)
+}
+
+// ServerInfo records information about an SMTP server.
+type ServerInfo struct {
+	Name string   // SMTP server name
+	TLS  bool     // using TLS, with valid certificate for Name
+	Auth []string // advertised authentication mechanisms
+}
+
+type plainAuth struct {
+	identity, username, password string
+	host                         string
+}
+
+// PlainAuth returns an Auth that implements the PLAIN authentication
+// mechanism as defined in RFC 4616.
+// The returned Auth uses the given username and password to authenticate
+// on TLS connections to host and act as identity. Usually identity will be
+// left blank to act as username.
+func PlainAuth(identity, username, password, host string) Auth {
+	return &plainAuth{identity, username, password, host}
+}
+
+func (a *plainAuth) Start(server *ServerInfo) (string, []byte, error) {
+	if !server.TLS {
+		advertised := false
+		for _, mechanism := range server.Auth {
+			if mechanism == "PLAIN" {
+				advertised = true
+				break
+			}
+		}
+		if !advertised {
+			return "", nil, errors.New("unencrypted connection")
+		}
+	}
+	if server.Name != a.host {
+		return "", nil, errors.New("wrong host name")
+	}
+	resp := []byte(a.identity + "\x00" + a.username + "\x00" + a.password)
+	return "PLAIN", resp, nil
+}
+
+func (a *plainAuth) Next(fromServer []byte, more bool) ([]byte, error) {
+	if more {
+		// We've already sent everything.
+		return nil, errors.New("unexpected server challenge")
+	}
+	return nil, nil
+}
+
+type cramMD5Auth struct {
+	username, secret string
+}
+
+// CRAMMD5Auth returns an Auth that implements the CRAM-MD5 authentication
+// mechanism as defined in RFC 2195.
+// The returned Auth uses the given username and secret to authenticate
+// to the server using the challenge-response mechanism.
+func CRAMMD5Auth(username, secret string) Auth {
+	return &cramMD5Auth{username, secret}
+}
+
+func (a *cramMD5Auth) Start(server *ServerInfo) (string, []byte, error) {
+	return "CRAM-MD5", nil, nil
+}
+
+func (a *cramMD5Auth) Next(fromServer []byte, more bool) ([]byte, error) {
+	if more {
+		d := hmac.New(md5.New, []byte(a.secret))
+		d.Write(fromServer)
+		s := make([]byte, 0, d.Size())
+		return []byte(fmt.Sprintf("%s %x", a.username, d.Sum(s))), nil
+	}
+	return nil, nil
+}
diff --git a/src/net/smtp/example_test.go b/src/net/smtp/example_test.go
new file mode 100644
index 000000000..d551e365a
--- /dev/null
+++ b/src/net/smtp/example_test.go
@@ -0,0 +1,61 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package smtp_test
+
+import (
+	"fmt"
+	"log"
+	"net/smtp"
+)
+
+func Example() {
+	// Connect to the remote SMTP server.
+	c, err := smtp.Dial("mail.example.com:25")
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	// Set the sender and recipient first
+	if err := c.Mail("sender@example.org"); err != nil {
+		log.Fatal(err)
+	}
+	if err := c.Rcpt("recipient@example.net"); err != nil {
+		log.Fatal(err)
+	}
+
+	// Send the email body.
+	wc, err := c.Data()
+	if err != nil {
+		log.Fatal(err)
+	}
+	_, err = fmt.Fprintf(wc, "This is the email body")
+	if err != nil {
+		log.Fatal(err)
+	}
+	err = wc.Close()
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	// Send the QUIT command and close the connection.
+	err = c.Quit()
+	if err != nil {
+		log.Fatal(err)
+	}
+}
+
+func ExamplePlainAuth() {
+	// Set up authentication information.
+	auth := smtp.PlainAuth("", "user@example.com", "password", "mail.example.com")
+
+	// Connect to the server, authenticate, set the sender and recipient,
+	// and send the email all in one step.
+	to := []string{"recipient@example.net"}
+	msg := []byte("This is the email body.")
+	err := smtp.SendMail("mail.example.com:25", auth, "sender@example.org", to, msg)
+	if err != nil {
+		log.Fatal(err)
+	}
+}
diff --git a/src/net/smtp/smtp.go b/src/net/smtp/smtp.go
new file mode 100644
index 000000000..87dea442c
--- /dev/null
+++ b/src/net/smtp/smtp.go
@@ -0,0 +1,357 @@
+// Copyright 2010 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package smtp implements the Simple Mail Transfer Protocol as defined in RFC 5321.
+// It also implements the following extensions:
+//	8BITMIME  RFC 1652
+//	AUTH      RFC 2554
+//	STARTTLS  RFC 3207
+// Additional extensions may be handled by clients.
+package smtp
+
+import (
+	"crypto/tls"
+	"encoding/base64"
+	"errors"
+	"io"
+	"net"
+	"net/textproto"
+	"strings"
+)
+
+// A Client represents a client connection to an SMTP server.
+type Client struct {
+	// Text is the textproto.Conn used by the Client. It is exported to allow for
+	// clients to add extensions.
+	Text *textproto.Conn
+	// keep a reference to the connection so it can be used to create a TLS
+	// connection later
+	conn net.Conn
+	// whether the Client is using TLS
+	tls        bool
+	serverName string
+	// map of supported extensions
+	ext map[string]string
+	// supported auth mechanisms
+	auth       []string
+	localName  string // the name to use in HELO/EHLO
+	didHello   bool   // whether we've said HELO/EHLO
+	helloError error  // the error from the hello
+}
+
+// Dial returns a new Client connected to an SMTP server at addr.
+// The addr must include a port number.
+func Dial(addr string) (*Client, error) {
+	conn, err := net.Dial("tcp", addr)
+	if err != nil {
+		return nil, err
+	}
+	host, _, _ := net.SplitHostPort(addr)
+	return NewClient(conn, host)
+}
+
+// NewClient returns a new Client using an existing connection and host as a
+// server name to be used when authenticating.
+func NewClient(conn net.Conn, host string) (*Client, error) {
+	text := textproto.NewConn(conn)
+	_, _, err := text.ReadResponse(220)
+	if err != nil {
+		text.Close()
+		return nil, err
+	}
+	c := &Client{Text: text, conn: conn, serverName: host, localName: "localhost"}
+	return c, nil
+}
+
+// Close closes the connection.
+func (c *Client) Close() error {
+	return c.Text.Close()
+}
+
+// hello runs a hello exchange if needed.
+func (c *Client) hello() error {
+	if !c.didHello {
+		c.didHello = true
+		err := c.ehlo()
+		if err != nil {
+			c.helloError = c.helo()
+		}
+	}
+	return c.helloError
+}
+
+// Hello sends a HELO or EHLO to the server as the given host name.
+// Calling this method is only necessary if the client needs control
+// over the host name used.  The client will introduce itself as "localhost"
+// automatically otherwise.  If Hello is called, it must be called before
+// any of the other methods.
+func (c *Client) Hello(localName string) error {
+	if c.didHello {
+		return errors.New("smtp: Hello called after other methods")
+	}
+	c.localName = localName
+	return c.hello()
+}
+
+// cmd is a convenience function that sends a command and returns the response
+func (c *Client) cmd(expectCode int, format string, args ...interface{}) (int, string, error) {
+	id, err := c.Text.Cmd(format, args...)
+	if err != nil {
+		return 0, "", err
+	}
+	c.Text.StartResponse(id)
+	defer c.Text.EndResponse(id)
+	code, msg, err := c.Text.ReadResponse(expectCode)
+	return code, msg, err
+}
+
+// helo sends the HELO greeting to the server. It should be used only when the
+// server does not support ehlo.
+func (c *Client) helo() error {
+	c.ext = nil
+	_, _, err := c.cmd(250, "HELO %s", c.localName)
+	return err
+}
+
+// ehlo sends the EHLO (extended hello) greeting to the server. It
+// should be the preferred greeting for servers that support it.
+func (c *Client) ehlo() error {
+	_, msg, err := c.cmd(250, "EHLO %s", c.localName)
+	if err != nil {
+		return err
+	}
+	ext := make(map[string]string)
+	extList := strings.Split(msg, "\n")
+	if len(extList) > 1 {
+		extList = extList[1:]
+		for _, line := range extList {
+			args := strings.SplitN(line, " ", 2)
+			if len(args) > 1 {
+				ext[args[0]] = args[1]
+			} else {
+				ext[args[0]] = ""
+			}
+		}
+	}
+	if mechs, ok := ext["AUTH"]; ok {
+		c.auth = strings.Split(mechs, " ")
+	}
+	c.ext = ext
+	return err
+}
+
+// StartTLS sends the STARTTLS command and encrypts all further communication.
+// Only servers that advertise the STARTTLS extension support this function.
+func (c *Client) StartTLS(config *tls.Config) error {
+	if err := c.hello(); err != nil {
+		return err
+	}
+	_, _, err := c.cmd(220, "STARTTLS")
+	if err != nil {
+		return err
+	}
+	c.conn = tls.Client(c.conn, config)
+	c.Text = textproto.NewConn(c.conn)
+	c.tls = true
+	return c.ehlo()
+}
+
+// Verify checks the validity of an email address on the server.
+// If Verify returns nil, the address is valid. A non-nil return
+// does not necessarily indicate an invalid address. Many servers
+// will not verify addresses for security reasons.
+func (c *Client) Verify(addr string) error {
+	if err := c.hello(); err != nil {
+		return err
+	}
+	_, _, err := c.cmd(250, "VRFY %s", addr)
+	return err
+}
+
+// Auth authenticates a client using the provided authentication mechanism.
+// A failed authentication closes the connection.
+// Only servers that advertise the AUTH extension support this function.
+func (c *Client) Auth(a Auth) error {
+	if err := c.hello(); err != nil {
+		return err
+	}
+	encoding := base64.StdEncoding
+	mech, resp, err := a.Start(&ServerInfo{c.serverName, c.tls, c.auth})
+	if err != nil {
+		c.Quit()
+		return err
+	}
+	resp64 := make([]byte, encoding.EncodedLen(len(resp)))
+	encoding.Encode(resp64, resp)
+	code, msg64, err := c.cmd(0, "AUTH %s %s", mech, resp64)
+	for err == nil {
+		var msg []byte
+		switch code {
+		case 334:
+			msg, err = encoding.DecodeString(msg64)
+		case 235:
+			// the last message isn't base64 because it isn't a challenge
+			msg = []byte(msg64)
+		default:
+			err = &textproto.Error{Code: code, Msg: msg64}
+		}
+		if err == nil {
+			resp, err = a.Next(msg, code == 334)
+		}
+		if err != nil {
+			// abort the AUTH
+			c.cmd(501, "*")
+			c.Quit()
+			break
+		}
+		if resp == nil {
+			break
+		}
+		resp64 = make([]byte, encoding.EncodedLen(len(resp)))
+		encoding.Encode(resp64, resp)
+		code, msg64, err = c.cmd(0, string(resp64))
+	}
+	return err
+}
+
+// Mail issues a MAIL command to the server using the provided email address.
+// If the server supports the 8BITMIME extension, Mail adds the BODY=8BITMIME
+// parameter.
+// This initiates a mail transaction and is followed by one or more Rcpt calls.
+func (c *Client) Mail(from string) error {
+	if err := c.hello(); err != nil {
+		return err
+	}
+	cmdStr := "MAIL FROM:<%s>"
+	if c.ext != nil {
+		if _, ok := c.ext["8BITMIME"]; ok {
+			cmdStr += " BODY=8BITMIME"
+		}
+	}
+	_, _, err := c.cmd(250, cmdStr, from)
+	return err
+}
+
+// Rcpt issues a RCPT command to the server using the provided email address.
+// A call to Rcpt must be preceded by a call to Mail and may be followed by
+// a Data call or another Rcpt call.
+func (c *Client) Rcpt(to string) error {
+	_, _, err := c.cmd(25, "RCPT TO:<%s>", to)
+	return err
+}
+
+type dataCloser struct {
+	c *Client
+	io.WriteCloser
+}
+
+func (d *dataCloser) Close() error {
+	d.WriteCloser.Close()
+	_, _, err := d.c.Text.ReadResponse(250)
+	return err
+}
+
+// Data issues a DATA command to the server and returns a writer that
+// can be used to write the data. The caller should close the writer
+// before calling any more methods on c.
+// A call to Data must be preceded by one or more calls to Rcpt.
+func (c *Client) Data() (io.WriteCloser, error) {
+	_, _, err := c.cmd(354, "DATA")
+	if err != nil {
+		return nil, err
+	}
+	return &dataCloser{c, c.Text.DotWriter()}, nil
+}
+
+var testHookStartTLS func(*tls.Config) // nil, except for tests
+
+// SendMail connects to the server at addr, switches to TLS if
+// possible, authenticates with the optional mechanism a if possible,
+// and then sends an email from address from, to addresses to, with
+// message msg.
+func SendMail(addr string, a Auth, from string, to []string, msg []byte) error {
+	c, err := Dial(addr)
+	if err != nil {
+		return err
+	}
+	defer c.Close()
+	if err = c.hello(); err != nil {
+		return err
+	}
+	if ok, _ := c.Extension("STARTTLS"); ok {
+		config := &tls.Config{ServerName: c.serverName}
+		if testHookStartTLS != nil {
+			testHookStartTLS(config)
+		}
+		if err = c.StartTLS(config); err != nil {
+			return err
+		}
+	}
+	if a != nil && c.ext != nil {
+		if _, ok := c.ext["AUTH"]; ok {
+			if err = c.Auth(a); err != nil {
+				return err
+			}
+		}
+	}
+	if err = c.Mail(from); err != nil {
+		return err
+	}
+	for _, addr := range to {
+		if err = c.Rcpt(addr); err != nil {
+			return err
+		}
+	}
+	w, err := c.Data()
+	if err != nil {
+		return err
+	}
+	_, err = w.Write(msg)
+	if err != nil {
+		return err
+	}
+	err = w.Close()
+	if err != nil {
+		return err
+	}
+	return c.Quit()
+}
+
+// Extension reports whether an extension is support by the server.
+// The extension name is case-insensitive. If the extension is supported,
+// Extension also returns a string that contains any parameters the
+// server specifies for the extension.
+func (c *Client) Extension(ext string) (bool, string) {
+	if err := c.hello(); err != nil {
+		return false, ""
+	}
+	if c.ext == nil {
+		return false, ""
+	}
+	ext = strings.ToUpper(ext)
+	param, ok := c.ext[ext]
+	return ok, param
+}
+
+// Reset sends the RSET command to the server, aborting the current mail
+// transaction.
+func (c *Client) Reset() error {
+	if err := c.hello(); err != nil {
+		return err
+	}
+	_, _, err := c.cmd(250, "RSET")
+	return err
+}
+
+// Quit sends the QUIT command and closes the connection to the server.
+func (c *Client) Quit() error {
+	if err := c.hello(); err != nil {
+		return err
+	}
+	_, _, err := c.cmd(221, "QUIT")
+	if err != nil {
+		return err
+	}
+	return c.Text.Close()
+}
diff --git a/src/net/smtp/smtp_test.go b/src/net/smtp/smtp_test.go
new file mode 100644
index 000000000..5c659e8a0
--- /dev/null
+++ b/src/net/smtp/smtp_test.go
@@ -0,0 +1,694 @@
+// Copyright 2010 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package smtp
+
+import (
+	"bufio"
+	"bytes"
+	"crypto/tls"
+	"crypto/x509"
+	"io"
+	"net"
+	"net/textproto"
+	"strings"
+	"testing"
+	"time"
+)
+
+type authTest struct {
+	auth       Auth
+	challenges []string
+	name       string
+	responses  []string
+}
+
+var authTests = []authTest{
+	{PlainAuth("", "user", "pass", "testserver"), []string{}, "PLAIN", []string{"\x00user\x00pass"}},
+	{PlainAuth("foo", "bar", "baz", "testserver"), []string{}, "PLAIN", []string{"foo\x00bar\x00baz"}},
+	{CRAMMD5Auth("user", "pass"), []string{"<123456.1322876914@testserver>"}, "CRAM-MD5", []string{"", "user 287eb355114cf5c471c26a875f1ca4ae"}},
+}
+
+func TestAuth(t *testing.T) {
+testLoop:
+	for i, test := range authTests {
+		name, resp, err := test.auth.Start(&ServerInfo{"testserver", true, nil})
+		if name != test.name {
+			t.Errorf("#%d got name %s, expected %s", i, name, test.name)
+		}
+		if !bytes.Equal(resp, []byte(test.responses[0])) {
+			t.Errorf("#%d got response %s, expected %s", i, resp, test.responses[0])
+		}
+		if err != nil {
+			t.Errorf("#%d error: %s", i, err)
+		}
+		for j := range test.challenges {
+			challenge := []byte(test.challenges[j])
+			expected := []byte(test.responses[j+1])
+			resp, err := test.auth.Next(challenge, true)
+			if err != nil {
+				t.Errorf("#%d error: %s", i, err)
+				continue testLoop
+			}
+			if !bytes.Equal(resp, expected) {
+				t.Errorf("#%d got %s, expected %s", i, resp, expected)
+				continue testLoop
+			}
+		}
+	}
+}
+
+func TestAuthPlain(t *testing.T) {
+	auth := PlainAuth("foo", "bar", "baz", "servername")
+
+	tests := []struct {
+		server *ServerInfo
+		err    string
+	}{
+		{
+			server: &ServerInfo{Name: "servername", TLS: true},
+		},
+		{
+			// Okay; explicitly advertised by server.
+			server: &ServerInfo{Name: "servername", Auth: []string{"PLAIN"}},
+		},
+		{
+			server: &ServerInfo{Name: "servername", Auth: []string{"CRAM-MD5"}},
+			err:    "unencrypted connection",
+		},
+		{
+			server: &ServerInfo{Name: "attacker", TLS: true},
+			err:    "wrong host name",
+		},
+	}
+	for i, tt := range tests {
+		_, _, err := auth.Start(tt.server)
+		got := ""
+		if err != nil {
+			got = err.Error()
+		}
+		if got != tt.err {
+			t.Errorf("%d. got error = %q; want %q", i, got, tt.err)
+		}
+	}
+}
+
+type faker struct {
+	io.ReadWriter
+}
+
+func (f faker) Close() error                     { return nil }
+func (f faker) LocalAddr() net.Addr              { return nil }
+func (f faker) RemoteAddr() net.Addr             { return nil }
+func (f faker) SetDeadline(time.Time) error      { return nil }
+func (f faker) SetReadDeadline(time.Time) error  { return nil }
+func (f faker) SetWriteDeadline(time.Time) error { return nil }
+
+func TestBasic(t *testing.T) {
+	server := strings.Join(strings.Split(basicServer, "\n"), "\r\n")
+	client := strings.Join(strings.Split(basicClient, "\n"), "\r\n")
+
+	var cmdbuf bytes.Buffer
+	bcmdbuf := bufio.NewWriter(&cmdbuf)
+	var fake faker
+	fake.ReadWriter = bufio.NewReadWriter(bufio.NewReader(strings.NewReader(server)), bcmdbuf)
+	c := &Client{Text: textproto.NewConn(fake), localName: "localhost"}
+
+	if err := c.helo(); err != nil {
+		t.Fatalf("HELO failed: %s", err)
+	}
+	if err := c.ehlo(); err == nil {
+		t.Fatalf("Expected first EHLO to fail")
+	}
+	if err := c.ehlo(); err != nil {
+		t.Fatalf("Second EHLO failed: %s", err)
+	}
+
+	c.didHello = true
+	if ok, args := c.Extension("aUtH"); !ok || args != "LOGIN PLAIN" {
+		t.Fatalf("Expected AUTH supported")
+	}
+	if ok, _ := c.Extension("DSN"); ok {
+		t.Fatalf("Shouldn't support DSN")
+	}
+
+	if err := c.Mail("user@gmail.com"); err == nil {
+		t.Fatalf("MAIL should require authentication")
+	}
+
+	if err := c.Verify("user1@gmail.com"); err == nil {
+		t.Fatalf("First VRFY: expected no verification")
+	}
+	if err := c.Verify("user2@gmail.com"); err != nil {
+		t.Fatalf("Second VRFY: expected verification, got %s", err)
+	}
+
+	// fake TLS so authentication won't complain
+	c.tls = true
+	c.serverName = "smtp.google.com"
+	if err := c.Auth(PlainAuth("", "user", "pass", "smtp.google.com")); err != nil {
+		t.Fatalf("AUTH failed: %s", err)
+	}
+
+	if err := c.Mail("user@gmail.com"); err != nil {
+		t.Fatalf("MAIL failed: %s", err)
+	}
+	if err := c.Rcpt("golang-nuts@googlegroups.com"); err != nil {
+		t.Fatalf("RCPT failed: %s", err)
+	}
+	msg := `From: user@gmail.com
+To: golang-nuts@googlegroups.com
+Subject: Hooray for Go
+
+Line 1
+.Leading dot line .
+Goodbye.`
+	w, err := c.Data()
+	if err != nil {
+		t.Fatalf("DATA failed: %s", err)
+	}
+	if _, err := w.Write([]byte(msg)); err != nil {
+		t.Fatalf("Data write failed: %s", err)
+	}
+	if err := w.Close(); err != nil {
+		t.Fatalf("Bad data response: %s", err)
+	}
+
+	if err := c.Quit(); err != nil {
+		t.Fatalf("QUIT failed: %s", err)
+	}
+
+	bcmdbuf.Flush()
+	actualcmds := cmdbuf.String()
+	if client != actualcmds {
+		t.Fatalf("Got:\n%s\nExpected:\n%s", actualcmds, client)
+	}
+}
+
+var basicServer = `250 mx.google.com at your service
+502 Unrecognized command.
+250-mx.google.com at your service
+250-SIZE 35651584
+250-AUTH LOGIN PLAIN
+250 8BITMIME
+530 Authentication required
+252 Send some mail, I'll try my best
+250 User is valid
+235 Accepted
+250 Sender OK
+250 Receiver OK
+354 Go ahead
+250 Data OK
+221 OK
+`
+
+var basicClient = `HELO localhost
+EHLO localhost
+EHLO localhost
+MAIL FROM:<user@gmail.com> BODY=8BITMIME
+VRFY user1@gmail.com
+VRFY user2@gmail.com
+AUTH PLAIN AHVzZXIAcGFzcw==
+MAIL FROM:<user@gmail.com> BODY=8BITMIME
+RCPT TO:<golang-nuts@googlegroups.com>
+DATA
+From: user@gmail.com
+To: golang-nuts@googlegroups.com
+Subject: Hooray for Go
+
+Line 1
+..Leading dot line .
+Goodbye.
+.
+QUIT
+`
+
+func TestNewClient(t *testing.T) {
+	server := strings.Join(strings.Split(newClientServer, "\n"), "\r\n")
+	client := strings.Join(strings.Split(newClientClient, "\n"), "\r\n")
+
+	var cmdbuf bytes.Buffer
+	bcmdbuf := bufio.NewWriter(&cmdbuf)
+	out := func() string {
+		bcmdbuf.Flush()
+		return cmdbuf.String()
+	}
+	var fake faker
+	fake.ReadWriter = bufio.NewReadWriter(bufio.NewReader(strings.NewReader(server)), bcmdbuf)
+	c, err := NewClient(fake, "fake.host")
+	if err != nil {
+		t.Fatalf("NewClient: %v\n(after %v)", err, out())
+	}
+	defer c.Close()
+	if ok, args := c.Extension("aUtH"); !ok || args != "LOGIN PLAIN" {
+		t.Fatalf("Expected AUTH supported")
+	}
+	if ok, _ := c.Extension("DSN"); ok {
+		t.Fatalf("Shouldn't support DSN")
+	}
+	if err := c.Quit(); err != nil {
+		t.Fatalf("QUIT failed: %s", err)
+	}
+
+	actualcmds := out()
+	if client != actualcmds {
+		t.Fatalf("Got:\n%s\nExpected:\n%s", actualcmds, client)
+	}
+}
+
+var newClientServer = `220 hello world
+250-mx.google.com at your service
+250-SIZE 35651584
+250-AUTH LOGIN PLAIN
+250 8BITMIME
+221 OK
+`
+
+var newClientClient = `EHLO localhost
+QUIT
+`
+
+func TestNewClient2(t *testing.T) {
+	server := strings.Join(strings.Split(newClient2Server, "\n"), "\r\n")
+	client := strings.Join(strings.Split(newClient2Client, "\n"), "\r\n")
+
+	var cmdbuf bytes.Buffer
+	bcmdbuf := bufio.NewWriter(&cmdbuf)
+	var fake faker
+	fake.ReadWriter = bufio.NewReadWriter(bufio.NewReader(strings.NewReader(server)), bcmdbuf)
+	c, err := NewClient(fake, "fake.host")
+	if err != nil {
+		t.Fatalf("NewClient: %v", err)
+	}
+	defer c.Close()
+	if ok, _ := c.Extension("DSN"); ok {
+		t.Fatalf("Shouldn't support DSN")
+	}
+	if err := c.Quit(); err != nil {
+		t.Fatalf("QUIT failed: %s", err)
+	}
+
+	bcmdbuf.Flush()
+	actualcmds := cmdbuf.String()
+	if client != actualcmds {
+		t.Fatalf("Got:\n%s\nExpected:\n%s", actualcmds, client)
+	}
+}
+
+var newClient2Server = `220 hello world
+502 EH?
+250-mx.google.com at your service
+250-SIZE 35651584
+250-AUTH LOGIN PLAIN
+250 8BITMIME
+221 OK
+`
+
+var newClient2Client = `EHLO localhost
+HELO localhost
+QUIT
+`
+
+func TestHello(t *testing.T) {
+
+	if len(helloServer) != len(helloClient) {
+		t.Fatalf("Hello server and client size mismatch")
+	}
+
+	for i := 0; i < len(helloServer); i++ {
+		server := strings.Join(strings.Split(baseHelloServer+helloServer[i], "\n"), "\r\n")
+		client := strings.Join(strings.Split(baseHelloClient+helloClient[i], "\n"), "\r\n")
+		var cmdbuf bytes.Buffer
+		bcmdbuf := bufio.NewWriter(&cmdbuf)
+		var fake faker
+		fake.ReadWriter = bufio.NewReadWriter(bufio.NewReader(strings.NewReader(server)), bcmdbuf)
+		c, err := NewClient(fake, "fake.host")
+		if err != nil {
+			t.Fatalf("NewClient: %v", err)
+		}
+		defer c.Close()
+		c.localName = "customhost"
+		err = nil
+
+		switch i {
+		case 0:
+			err = c.Hello("customhost")
+		case 1:
+			err = c.StartTLS(nil)
+			if err.Error() == "502 Not implemented" {
+				err = nil
+			}
+		case 2:
+			err = c.Verify("test@example.com")
+		case 3:
+			c.tls = true
+			c.serverName = "smtp.google.com"
+			err = c.Auth(PlainAuth("", "user", "pass", "smtp.google.com"))
+		case 4:
+			err = c.Mail("test@example.com")
+		case 5:
+			ok, _ := c.Extension("feature")
+			if ok {
+				t.Errorf("Expected FEATURE not to be supported")
+			}
+		case 6:
+			err = c.Reset()
+		case 7:
+			err = c.Quit()
+		case 8:
+			err = c.Verify("test@example.com")
+			if err != nil {
+				err = c.Hello("customhost")
+				if err != nil {
+					t.Errorf("Want error, got none")
+				}
+			}
+		default:
+			t.Fatalf("Unhandled command")
+		}
+
+		if err != nil {
+			t.Errorf("Command %d failed: %v", i, err)
+		}
+
+		bcmdbuf.Flush()
+		actualcmds := cmdbuf.String()
+		if client != actualcmds {
+			t.Errorf("Got:\n%s\nExpected:\n%s", actualcmds, client)
+		}
+	}
+}
+
+var baseHelloServer = `220 hello world
+502 EH?
+250-mx.google.com at your service
+250 FEATURE
+`
+
+var helloServer = []string{
+	"",
+	"502 Not implemented\n",
+	"250 User is valid\n",
+	"235 Accepted\n",
+	"250 Sender ok\n",
+	"",
+	"250 Reset ok\n",
+	"221 Goodbye\n",
+	"250 Sender ok\n",
+}
+
+var baseHelloClient = `EHLO customhost
+HELO customhost
+`
+
+var helloClient = []string{
+	"",
+	"STARTTLS\n",
+	"VRFY test@example.com\n",
+	"AUTH PLAIN AHVzZXIAcGFzcw==\n",
+	"MAIL FROM:<test@example.com>\n",
+	"",
+	"RSET\n",
+	"QUIT\n",
+	"VRFY test@example.com\n",
+}
+
+func TestSendMail(t *testing.T) {
+	server := strings.Join(strings.Split(sendMailServer, "\n"), "\r\n")
+	client := strings.Join(strings.Split(sendMailClient, "\n"), "\r\n")
+	var cmdbuf bytes.Buffer
+	bcmdbuf := bufio.NewWriter(&cmdbuf)
+	l, err := net.Listen("tcp", "127.0.0.1:0")
+	if err != nil {
+		t.Fatalf("Unable to to create listener: %v", err)
+	}
+	defer l.Close()
+
+	// prevent data race on bcmdbuf
+	var done = make(chan struct{})
+	go func(data []string) {
+
+		defer close(done)
+
+		conn, err := l.Accept()
+		if err != nil {
+			t.Errorf("Accept error: %v", err)
+			return
+		}
+		defer conn.Close()
+
+		tc := textproto.NewConn(conn)
+		for i := 0; i < len(data) && data[i] != ""; i++ {
+			tc.PrintfLine(data[i])
+			for len(data[i]) >= 4 && data[i][3] == '-' {
+				i++
+				tc.PrintfLine(data[i])
+			}
+			if data[i] == "221 Goodbye" {
+				return
+			}
+			read := false
+			for !read || data[i] == "354 Go ahead" {
+				msg, err := tc.ReadLine()
+				bcmdbuf.Write([]byte(msg + "\r\n"))
+				read = true
+				if err != nil {
+					t.Errorf("Read error: %v", err)
+					return
+				}
+				if data[i] == "354 Go ahead" && msg == "." {
+					break
+				}
+			}
+		}
+	}(strings.Split(server, "\r\n"))
+
+	err = SendMail(l.Addr().String(), nil, "test@example.com", []string{"other@example.com"}, []byte(strings.Replace(`From: test@example.com
+To: other@example.com
+Subject: SendMail test
+
+SendMail is working for me.
+`, "\n", "\r\n", -1)))
+
+	if err != nil {
+		t.Errorf("%v", err)
+	}
+
+	<-done
+	bcmdbuf.Flush()
+	actualcmds := cmdbuf.String()
+	if client != actualcmds {
+		t.Errorf("Got:\n%s\nExpected:\n%s", actualcmds, client)
+	}
+}
+
+var sendMailServer = `220 hello world
+502 EH?
+250 mx.google.com at your service
+250 Sender ok
+250 Receiver ok
+354 Go ahead
+250 Data ok
+221 Goodbye
+`
+
+var sendMailClient = `EHLO localhost
+HELO localhost
+MAIL FROM:<test@example.com>
+RCPT TO:<other@example.com>
+DATA
+From: test@example.com
+To: other@example.com
+Subject: SendMail test
+
+SendMail is working for me.
+.
+QUIT
+`
+
+func TestAuthFailed(t *testing.T) {
+	server := strings.Join(strings.Split(authFailedServer, "\n"), "\r\n")
+	client := strings.Join(strings.Split(authFailedClient, "\n"), "\r\n")
+	var cmdbuf bytes.Buffer
+	bcmdbuf := bufio.NewWriter(&cmdbuf)
+	var fake faker
+	fake.ReadWriter = bufio.NewReadWriter(bufio.NewReader(strings.NewReader(server)), bcmdbuf)
+	c, err := NewClient(fake, "fake.host")
+	if err != nil {
+		t.Fatalf("NewClient: %v", err)
+	}
+	defer c.Close()
+
+	c.tls = true
+	c.serverName = "smtp.google.com"
+	err = c.Auth(PlainAuth("", "user", "pass", "smtp.google.com"))
+
+	if err == nil {
+		t.Error("Auth: expected error; got none")
+	} else if err.Error() != "535 Invalid credentials\nplease see www.example.com" {
+		t.Errorf("Auth: got error: %v, want: %s", err, "535 Invalid credentials\nplease see www.example.com")
+	}
+
+	bcmdbuf.Flush()
+	actualcmds := cmdbuf.String()
+	if client != actualcmds {
+		t.Errorf("Got:\n%s\nExpected:\n%s", actualcmds, client)
+	}
+}
+
+var authFailedServer = `220 hello world
+250-mx.google.com at your service
+250 AUTH LOGIN PLAIN
+535-Invalid credentials
+535 please see www.example.com
+221 Goodbye
+`
+
+var authFailedClient = `EHLO localhost
+AUTH PLAIN AHVzZXIAcGFzcw==
+*
+QUIT
+`
+
+func TestTLSClient(t *testing.T) {
+	ln := newLocalListener(t)
+	defer ln.Close()
+	errc := make(chan error)
+	go func() {
+		errc <- sendMail(ln.Addr().String())
+	}()
+	conn, err := ln.Accept()
+	if err != nil {
+		t.Fatalf("failed to accept connection: %v", err)
+	}
+	defer conn.Close()
+	if err := serverHandle(conn, t); err != nil {
+		t.Fatalf("failed to handle connection: %v", err)
+	}
+	if err := <-errc; err != nil {
+		t.Fatalf("client error: %v", err)
+	}
+}
+
+func newLocalListener(t *testing.T) net.Listener {
+	ln, err := net.Listen("tcp", "127.0.0.1:0")
+	if err != nil {
+		ln, err = net.Listen("tcp6", "[::1]:0")
+	}
+	if err != nil {
+		t.Fatal(err)
+	}
+	return ln
+}
+
+type smtpSender struct {
+	w io.Writer
+}
+
+func (s smtpSender) send(f string) {
+	s.w.Write([]byte(f + "\r\n"))
+}
+
+// smtp server, finely tailored to deal with our own client only!
+func serverHandle(c net.Conn, t *testing.T) error {
+	send := smtpSender{c}.send
+	send("220 127.0.0.1 ESMTP service ready")
+	s := bufio.NewScanner(c)
+	for s.Scan() {
+		switch s.Text() {
+		case "EHLO localhost":
+			send("250-127.0.0.1 ESMTP offers a warm hug of welcome")
+			send("250-STARTTLS")
+			send("250 Ok")
+		case "STARTTLS":
+			send("220 Go ahead")
+			keypair, err := tls.X509KeyPair(localhostCert, localhostKey)
+			if err != nil {
+				return err
+			}
+			config := &tls.Config{Certificates: []tls.Certificate{keypair}}
+			c = tls.Server(c, config)
+			defer c.Close()
+			return serverHandleTLS(c, t)
+		default:
+			t.Fatalf("unrecognized command: %q", s.Text())
+		}
+	}
+	return s.Err()
+}
+
+func serverHandleTLS(c net.Conn, t *testing.T) error {
+	send := smtpSender{c}.send
+	s := bufio.NewScanner(c)
+	for s.Scan() {
+		switch s.Text() {
+		case "EHLO localhost":
+			send("250 Ok")
+		case "MAIL FROM:<joe1@example.com>":
+			send("250 Ok")
+		case "RCPT TO:<joe2@example.com>":
+			send("250 Ok")
+		case "DATA":
+			send("354 send the mail data, end with .")
+			send("250 Ok")
+		case "Subject: test":
+		case "":
+		case "howdy!":
+		case ".":
+		case "QUIT":
+			send("221 127.0.0.1 Service closing transmission channel")
+			return nil
+		default:
+			t.Fatalf("unrecognized command during TLS: %q", s.Text())
+		}
+	}
+	return s.Err()
+}
+
+func init() {
+	testRootCAs := x509.NewCertPool()
+	testRootCAs.AppendCertsFromPEM(localhostCert)
+	testHookStartTLS = func(config *tls.Config) {
+		config.RootCAs = testRootCAs
+	}
+}
+
+func sendMail(hostPort string) error {
+	host, _, err := net.SplitHostPort(hostPort)
+	if err != nil {
+		return err
+	}
+	auth := PlainAuth("", "", "", host)
+	from := "joe1@example.com"
+	to := []string{"joe2@example.com"}
+	return SendMail(hostPort, auth, from, to, []byte("Subject: test\n\nhowdy!"))
+}
+
+// (copied from net/http/httptest)
+// localhostCert is a PEM-encoded TLS cert with SAN IPs
+// "127.0.0.1" and "[::1]", expiring at the last second of 2049 (the end
+// of ASN.1 time).
+// generated from src/crypto/tls:
+// go run generate_cert.go  --rsa-bits 512 --host 127.0.0.1,::1,example.com --ca --start-date "Jan 1 00:00:00 1970" --duration=1000000h
+var localhostCert = []byte(`-----BEGIN CERTIFICATE-----
+MIIBdzCCASOgAwIBAgIBADALBgkqhkiG9w0BAQUwEjEQMA4GA1UEChMHQWNtZSBD
+bzAeFw03MDAxMDEwMDAwMDBaFw00OTEyMzEyMzU5NTlaMBIxEDAOBgNVBAoTB0Fj
+bWUgQ28wWjALBgkqhkiG9w0BAQEDSwAwSAJBAN55NcYKZeInyTuhcCwFMhDHCmwa
+IUSdtXdcbItRB/yfXGBhiex00IaLXQnSU+QZPRZWYqeTEbFSgihqi1PUDy8CAwEA
+AaNoMGYwDgYDVR0PAQH/BAQDAgCkMBMGA1UdJQQMMAoGCCsGAQUFBwMBMA8GA1Ud
+EwEB/wQFMAMBAf8wLgYDVR0RBCcwJYILZXhhbXBsZS5jb22HBH8AAAGHEAAAAAAA
+AAAAAAAAAAAAAAEwCwYJKoZIhvcNAQEFA0EAAoQn/ytgqpiLcZu9XKbCJsJcvkgk
+Se6AbGXgSlq+ZCEVo0qIwSgeBqmsJxUu7NCSOwVJLYNEBO2DtIxoYVk+MA==
+-----END CERTIFICATE-----`)
+
+// localhostKey is the private key for localhostCert.
+var localhostKey = []byte(`-----BEGIN RSA PRIVATE KEY-----
+MIIBPAIBAAJBAN55NcYKZeInyTuhcCwFMhDHCmwaIUSdtXdcbItRB/yfXGBhiex0
+0IaLXQnSU+QZPRZWYqeTEbFSgihqi1PUDy8CAwEAAQJBAQdUx66rfh8sYsgfdcvV
+NoafYpnEcB5s4m/vSVe6SU7dCK6eYec9f9wpT353ljhDUHq3EbmE4foNzJngh35d
+AekCIQDhRQG5Li0Wj8TM4obOnnXUXf1jRv0UkzE9AHWLG5q3AwIhAPzSjpYUDjVW
+MCUXgckTpKCuGwbJk7424Nb8bLzf3kllAiA5mUBgjfr/WtFSJdWcPQ4Zt9KTMNKD
+EUO0ukpTwEIl6wIhAMbGqZK3zAAFdq8DD2jPx+UJXnh0rnOkZBzDtJ6/iN69AiEA
+1Aq8MJgTaYsDQWyU/hDq5YkDJc9e9DSCvUIzqxQWMQE=
+-----END RSA PRIVATE KEY-----`)
diff --git a/src/net/sock_bsd.go b/src/net/sock_bsd.go
new file mode 100644
index 000000000..48fb78527
--- /dev/null
+++ b/src/net/sock_bsd.go
@@ -0,0 +1,37 @@
+// Copyright 2009 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build darwin dragonfly freebsd nacl netbsd openbsd
+
+package net
+
+import (
+	"runtime"
+	"syscall"
+)
+
+func maxListenerBacklog() int {
+	var (
+		n   uint32
+		err error
+	)
+	switch runtime.GOOS {
+	case "darwin", "freebsd":
+		n, err = syscall.SysctlUint32("kern.ipc.somaxconn")
+	case "netbsd":
+		// NOTE: NetBSD has no somaxconn-like kernel state so far
+	case "openbsd":
+		n, err = syscall.SysctlUint32("kern.somaxconn")
+	}
+	if n == 0 || err != nil {
+		return syscall.SOMAXCONN
+	}
+	// FreeBSD stores the backlog in a uint16, as does Linux.
+	// Assume the other BSDs do too. Truncate number to avoid wrapping.
+	// See issue 5030.
+	if n > 1<<16-1 {
+		n = 1<<16 - 1
+	}
+	return int(n)
+}
diff --git a/src/net/sock_cloexec.go b/src/net/sock_cloexec.go
new file mode 100644
index 000000000..dec81855b
--- /dev/null
+++ b/src/net/sock_cloexec.go
@@ -0,0 +1,78 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// This file implements sysSocket and accept for platforms that
+// provide a fast path for setting SetNonblock and CloseOnExec.
+
+// +build freebsd linux
+
+package net
+
+import "syscall"
+
+// Wrapper around the socket system call that marks the returned file
+// descriptor as nonblocking and close-on-exec.
+func sysSocket(family, sotype, proto int) (int, error) {
+	s, err := syscall.Socket(family, sotype|syscall.SOCK_NONBLOCK|syscall.SOCK_CLOEXEC, proto)
+	// On Linux the SOCK_NONBLOCK and SOCK_CLOEXEC flags were
+	// introduced in 2.6.27 kernel and on FreeBSD both flags were
+	// introduced in 10 kernel. If we get an EINVAL error on Linux
+	// or EPROTONOSUPPORT error on FreeBSD, fall back to using
+	// socket without them.
+	if err == nil || (err != syscall.EPROTONOSUPPORT && err != syscall.EINVAL) {
+		return s, err
+	}
+
+	// See ../syscall/exec_unix.go for description of ForkLock.
+	syscall.ForkLock.RLock()
+	s, err = syscall.Socket(family, sotype, proto)
+	if err == nil {
+		syscall.CloseOnExec(s)
+	}
+	syscall.ForkLock.RUnlock()
+	if err != nil {
+		return -1, err
+	}
+	if err = syscall.SetNonblock(s, true); err != nil {
+		syscall.Close(s)
+		return -1, err
+	}
+	return s, nil
+}
+
+// Wrapper around the accept system call that marks the returned file
+// descriptor as nonblocking and close-on-exec.
+func accept(s int) (int, syscall.Sockaddr, error) {
+	ns, sa, err := syscall.Accept4(s, syscall.SOCK_NONBLOCK|syscall.SOCK_CLOEXEC)
+	// On Linux the accept4 system call was introduced in 2.6.28
+	// kernel and on FreeBSD it was introduced in 10 kernel. If we
+	// get an ENOSYS error on both Linux and FreeBSD, or EINVAL
+	// error on Linux, fall back to using accept.
+	switch err {
+	default: // nil and errors other than the ones listed
+		return ns, sa, err
+	case syscall.ENOSYS: // syscall missing
+	case syscall.EINVAL: // some Linux use this instead of ENOSYS
+	case syscall.EACCES: // some Linux use this instead of ENOSYS
+	case syscall.EFAULT: // some Linux use this instead of ENOSYS
+	}
+
+	// See ../syscall/exec_unix.go for description of ForkLock.
+	// It is probably okay to hold the lock across syscall.Accept
+	// because we have put fd.sysfd into non-blocking mode.
+	// However, a call to the File method will put it back into
+	// blocking mode. We can't take that risk, so no use of ForkLock here.
+	ns, sa, err = syscall.Accept(s)
+	if err == nil {
+		syscall.CloseOnExec(ns)
+	}
+	if err != nil {
+		return -1, nil, err
+	}
+	if err = syscall.SetNonblock(ns, true); err != nil {
+		syscall.Close(ns)
+		return -1, nil, err
+	}
+	return ns, sa, nil
+}
diff --git a/src/net/sock_linux.go b/src/net/sock_linux.go
new file mode 100644
index 000000000..cc5ce153b
--- /dev/null
+++ b/src/net/sock_linux.go
@@ -0,0 +1,31 @@
+// Copyright 2009 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package net
+
+import "syscall"
+
+func maxListenerBacklog() int {
+	fd, err := open("/proc/sys/net/core/somaxconn")
+	if err != nil {
+		return syscall.SOMAXCONN
+	}
+	defer fd.close()
+	l, ok := fd.readLine()
+	if !ok {
+		return syscall.SOMAXCONN
+	}
+	f := getFields(l)
+	n, _, ok := dtoi(f[0], 0)
+	if n == 0 || !ok {
+		return syscall.SOMAXCONN
+	}
+	// Linux stores the backlog in a uint16.
+	// Truncate number to avoid wrapping.
+	// See issue 5030.
+	if n > 1<<16-1 {
+		n = 1<<16 - 1
+	}
+	return n
+}
diff --git a/src/net/sock_plan9.go b/src/net/sock_plan9.go
new file mode 100644
index 000000000..88d9ed15c
--- /dev/null
+++ b/src/net/sock_plan9.go
@@ -0,0 +1,10 @@
+// Copyright 2013 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package net
+
+func maxListenerBacklog() int {
+	// /sys/include/ape/sys/socket.h:/SOMAXCONN
+	return 5
+}
diff --git a/src/net/sock_posix.go b/src/net/sock_posix.go
new file mode 100644
index 000000000..3f956df65
--- /dev/null
+++ b/src/net/sock_posix.go
@@ -0,0 +1,216 @@
+// Copyright 2009 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build darwin dragonfly freebsd linux nacl netbsd openbsd solaris windows
+
+package net
+
+import (
+	"os"
+	"syscall"
+	"time"
+)
+
+// A sockaddr represents a TCP, UDP, IP or Unix network endpoint
+// address that can be converted into a syscall.Sockaddr.
+type sockaddr interface {
+	Addr
+
+	netaddr
+
+	// family returns the platform-dependent address family
+	// identifier.
+	family() int
+
+	// isWildcard reports whether the address is a wildcard
+	// address.
+	isWildcard() bool
+
+	// sockaddr returns the address converted into a syscall
+	// sockaddr type that implements syscall.Sockaddr
+	// interface. It returns a nil interface when the address is
+	// nil.
+	sockaddr(family int) (syscall.Sockaddr, error)
+}
+
+// socket returns a network file descriptor that is ready for
+// asynchronous I/O using the network poller.
+func socket(net string, family, sotype, proto int, ipv6only bool, laddr, raddr sockaddr, deadline time.Time) (fd *netFD, err error) {
+	s, err := sysSocket(family, sotype, proto)
+	if err != nil {
+		return nil, err
+	}
+	if err = setDefaultSockopts(s, family, sotype, ipv6only); err != nil {
+		closesocket(s)
+		return nil, err
+	}
+	if fd, err = newFD(s, family, sotype, net); err != nil {
+		closesocket(s)
+		return nil, err
+	}
+
+	// This function makes a network file descriptor for the
+	// following applications:
+	//
+	// - An endpoint holder that opens a passive stream
+	//   connenction, known as a stream listener
+	//
+	// - An endpoint holder that opens a destination-unspecific
+	//   datagram connection, known as a datagram listener
+	//
+	// - An endpoint holder that opens an active stream or a
+	//   destination-specific datagram connection, known as a
+	//   dialer
+	//
+	// - An endpoint holder that opens the other connection, such
+	//   as talking to the protocol stack inside the kernel
+	//
+	// For stream and datagram listeners, they will only require
+	// named sockets, so we can assume that it's just a request
+	// from stream or datagram listeners when laddr is not nil but
+	// raddr is nil. Otherwise we assume it's just for dialers or
+	// the other connection holders.
+
+	if laddr != nil && raddr == nil {
+		switch sotype {
+		case syscall.SOCK_STREAM, syscall.SOCK_SEQPACKET:
+			if err := fd.listenStream(laddr, listenerBacklog); err != nil {
+				fd.Close()
+				return nil, err
+			}
+			return fd, nil
+		case syscall.SOCK_DGRAM:
+			if err := fd.listenDatagram(laddr); err != nil {
+				fd.Close()
+				return nil, err
+			}
+			return fd, nil
+		}
+	}
+	if err := fd.dial(laddr, raddr, deadline); err != nil {
+		fd.Close()
+		return nil, err
+	}
+	return fd, nil
+}
+
+func (fd *netFD) addrFunc() func(syscall.Sockaddr) Addr {
+	switch fd.family {
+	case syscall.AF_INET, syscall.AF_INET6:
+		switch fd.sotype {
+		case syscall.SOCK_STREAM:
+			return sockaddrToTCP
+		case syscall.SOCK_DGRAM:
+			return sockaddrToUDP
+		case syscall.SOCK_RAW:
+			return sockaddrToIP
+		}
+	case syscall.AF_UNIX:
+		switch fd.sotype {
+		case syscall.SOCK_STREAM:
+			return sockaddrToUnix
+		case syscall.SOCK_DGRAM:
+			return sockaddrToUnixgram
+		case syscall.SOCK_SEQPACKET:
+			return sockaddrToUnixpacket
+		}
+	}
+	return func(syscall.Sockaddr) Addr { return nil }
+}
+
+func (fd *netFD) dial(laddr, raddr sockaddr, deadline time.Time) error {
+	var err error
+	var lsa syscall.Sockaddr
+	if laddr != nil {
+		if lsa, err = laddr.sockaddr(fd.family); err != nil {
+			return err
+		} else if lsa != nil {
+			if err := syscall.Bind(fd.sysfd, lsa); err != nil {
+				return os.NewSyscallError("bind", err)
+			}
+		}
+	}
+	var rsa syscall.Sockaddr
+	if raddr != nil {
+		if rsa, err = raddr.sockaddr(fd.family); err != nil {
+			return err
+		}
+		if err := fd.connect(lsa, rsa, deadline); err != nil {
+			return err
+		}
+		fd.isConnected = true
+	} else {
+		if err := fd.init(); err != nil {
+			return err
+		}
+	}
+	lsa, _ = syscall.Getsockname(fd.sysfd)
+	if rsa, _ = syscall.Getpeername(fd.sysfd); rsa != nil {
+		fd.setAddr(fd.addrFunc()(lsa), fd.addrFunc()(rsa))
+	} else {
+		fd.setAddr(fd.addrFunc()(lsa), raddr)
+	}
+	return nil
+}
+
+func (fd *netFD) listenStream(laddr sockaddr, backlog int) error {
+	if err := setDefaultListenerSockopts(fd.sysfd); err != nil {
+		return err
+	}
+	if lsa, err := laddr.sockaddr(fd.family); err != nil {
+		return err
+	} else if lsa != nil {
+		if err := syscall.Bind(fd.sysfd, lsa); err != nil {
+			return os.NewSyscallError("bind", err)
+		}
+	}
+	if err := syscall.Listen(fd.sysfd, backlog); err != nil {
+		return os.NewSyscallError("listen", err)
+	}
+	if err := fd.init(); err != nil {
+		return err
+	}
+	lsa, _ := syscall.Getsockname(fd.sysfd)
+	fd.setAddr(fd.addrFunc()(lsa), nil)
+	return nil
+}
+
+func (fd *netFD) listenDatagram(laddr sockaddr) error {
+	switch addr := laddr.(type) {
+	case *UDPAddr:
+		// We provide a socket that listens to a wildcard
+		// address with reusable UDP port when the given laddr
+		// is an appropriate UDP multicast address prefix.
+		// This makes it possible for a single UDP listener to
+		// join multiple different group addresses, for
+		// multiple UDP listeners that listen on the same UDP
+		// port to join the same group address.
+		if addr.IP != nil && addr.IP.IsMulticast() {
+			if err := setDefaultMulticastSockopts(fd.sysfd); err != nil {
+				return err
+			}
+			addr := *addr
+			switch fd.family {
+			case syscall.AF_INET:
+				addr.IP = IPv4zero
+			case syscall.AF_INET6:
+				addr.IP = IPv6unspecified
+			}
+			laddr = &addr
+		}
+	}
+	if lsa, err := laddr.sockaddr(fd.family); err != nil {
+		return err
+	} else if lsa != nil {
+		if err := syscall.Bind(fd.sysfd, lsa); err != nil {
+			return os.NewSyscallError("bind", err)
+		}
+	}
+	if err := fd.init(); err != nil {
+		return err
+	}
+	lsa, _ := syscall.Getsockname(fd.sysfd)
+	fd.setAddr(fd.addrFunc()(lsa), nil)
+	return nil
+}
diff --git a/src/net/sock_solaris.go b/src/net/sock_solaris.go
new file mode 100644
index 000000000..90fe9de89
--- /dev/null
+++ b/src/net/sock_solaris.go
@@ -0,0 +1,13 @@
+// Copyright 2009 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package net
+
+import "syscall"
+
+func maxListenerBacklog() int {
+	// TODO: Implement this
+	// NOTE: Never return a number bigger than 1<<16 - 1. See issue 5030.
+	return syscall.SOMAXCONN
+}
diff --git a/src/net/sock_windows.go b/src/net/sock_windows.go
new file mode 100644
index 000000000..6ccde3a24
--- /dev/null
+++ b/src/net/sock_windows.go
@@ -0,0 +1,24 @@
+// Copyright 2009 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package net
+
+import "syscall"
+
+func maxListenerBacklog() int {
+	// TODO: Implement this
+	// NOTE: Never return a number bigger than 1<<16 - 1. See issue 5030.
+	return syscall.SOMAXCONN
+}
+
+func sysSocket(f, t, p int) (syscall.Handle, error) {
+	// See ../syscall/exec_unix.go for description of ForkLock.
+	syscall.ForkLock.RLock()
+	s, err := syscall.Socket(f, t, p)
+	if err == nil {
+		syscall.CloseOnExec(s)
+	}
+	syscall.ForkLock.RUnlock()
+	return s, err
+}
diff --git a/src/net/sockopt_bsd.go b/src/net/sockopt_bsd.go
new file mode 100644
index 000000000..2d36a5595
--- /dev/null
+++ b/src/net/sockopt_bsd.go
@@ -0,0 +1,54 @@
+// Copyright 2011 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build darwin dragonfly freebsd nacl netbsd openbsd
+
+package net
+
+import (
+	"os"
+	"runtime"
+	"syscall"
+)
+
+func setDefaultSockopts(s, family, sotype int, ipv6only bool) error {
+	if runtime.GOOS == "dragonfly" && sotype != syscall.SOCK_RAW {
+		// On DragonFly BSD, we adjust the ephemeral port
+		// range because unlike other BSD systems its default
+		// port range doesn't conform to IANA recommendation
+		// as described in RFC 6056 and is pretty narrow.
+		switch family {
+		case syscall.AF_INET:
+			syscall.SetsockoptInt(s, syscall.IPPROTO_IP, syscall.IP_PORTRANGE, syscall.IP_PORTRANGE_HIGH)
+		case syscall.AF_INET6:
+			syscall.SetsockoptInt(s, syscall.IPPROTO_IPV6, syscall.IPV6_PORTRANGE, syscall.IPV6_PORTRANGE_HIGH)
+		}
+	}
+	if family == syscall.AF_INET6 && sotype != syscall.SOCK_RAW {
+		// Allow both IP versions even if the OS default
+		// is otherwise.  Note that some operating systems
+		// never admit this option.
+		syscall.SetsockoptInt(s, syscall.IPPROTO_IPV6, syscall.IPV6_V6ONLY, boolint(ipv6only))
+	}
+	// Allow broadcast.
+	return os.NewSyscallError("setsockopt", syscall.SetsockoptInt(s, syscall.SOL_SOCKET, syscall.SO_BROADCAST, 1))
+}
+
+func setDefaultListenerSockopts(s int) error {
+	// Allow reuse of recently-used addresses.
+	return os.NewSyscallError("setsockopt", syscall.SetsockoptInt(s, syscall.SOL_SOCKET, syscall.SO_REUSEADDR, 1))
+}
+
+func setDefaultMulticastSockopts(s int) error {
+	// Allow multicast UDP and raw IP datagram sockets to listen
+	// concurrently across multiple listeners.
+	if err := syscall.SetsockoptInt(s, syscall.SOL_SOCKET, syscall.SO_REUSEADDR, 1); err != nil {
+		return os.NewSyscallError("setsockopt", err)
+	}
+	// Allow reuse of recently-used ports.
+	// This option is supported only in descendants of 4.4BSD,
+	// to make an effective multicast application that requires
+	// quick draw possible.
+	return os.NewSyscallError("setsockopt", syscall.SetsockoptInt(s, syscall.SOL_SOCKET, syscall.SO_REUSEPORT, 1))
+}
diff --git a/src/net/sockopt_linux.go b/src/net/sockopt_linux.go
new file mode 100644
index 000000000..54c20b140
--- /dev/null
+++ b/src/net/sockopt_linux.go
@@ -0,0 +1,32 @@
+// Copyright 2011 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package net
+
+import (
+	"os"
+	"syscall"
+)
+
+func setDefaultSockopts(s, family, sotype int, ipv6only bool) error {
+	if family == syscall.AF_INET6 && sotype != syscall.SOCK_RAW {
+		// Allow both IP versions even if the OS default
+		// is otherwise.  Note that some operating systems
+		// never admit this option.
+		syscall.SetsockoptInt(s, syscall.IPPROTO_IPV6, syscall.IPV6_V6ONLY, boolint(ipv6only))
+	}
+	// Allow broadcast.
+	return os.NewSyscallError("setsockopt", syscall.SetsockoptInt(s, syscall.SOL_SOCKET, syscall.SO_BROADCAST, 1))
+}
+
+func setDefaultListenerSockopts(s int) error {
+	// Allow reuse of recently-used addresses.
+	return os.NewSyscallError("setsockopt", syscall.SetsockoptInt(s, syscall.SOL_SOCKET, syscall.SO_REUSEADDR, 1))
+}
+
+func setDefaultMulticastSockopts(s int) error {
+	// Allow multicast UDP and raw IP datagram sockets to listen
+	// concurrently across multiple listeners.
+	return os.NewSyscallError("setsockopt", syscall.SetsockoptInt(s, syscall.SOL_SOCKET, syscall.SO_REUSEADDR, 1))
+}
diff --git a/src/net/sockopt_plan9.go b/src/net/sockopt_plan9.go
new file mode 100644
index 000000000..8bc689b6c
--- /dev/null
+++ b/src/net/sockopt_plan9.go
@@ -0,0 +1,13 @@
+// Copyright 2014 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package net
+
+func setKeepAlive(fd *netFD, keepalive bool) error {
+	if keepalive {
+		_, e := fd.ctl.WriteAt([]byte("keepalive"), 0)
+		return e
+	}
+	return nil
+}
diff --git a/src/net/sockopt_posix.go b/src/net/sockopt_posix.go
new file mode 100644
index 000000000..921918c37
--- /dev/null
+++ b/src/net/sockopt_posix.go
@@ -0,0 +1,141 @@
+// Copyright 2009 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build darwin dragonfly freebsd linux nacl netbsd openbsd solaris windows
+
+package net
+
+import (
+	"os"
+	"syscall"
+)
+
+// Boolean to int.
+func boolint(b bool) int {
+	if b {
+		return 1
+	}
+	return 0
+}
+
+func ipv4AddrToInterface(ip IP) (*Interface, error) {
+	ift, err := Interfaces()
+	if err != nil {
+		return nil, err
+	}
+	for _, ifi := range ift {
+		ifat, err := ifi.Addrs()
+		if err != nil {
+			return nil, err
+		}
+		for _, ifa := range ifat {
+			switch v := ifa.(type) {
+			case *IPAddr:
+				if ip.Equal(v.IP) {
+					return &ifi, nil
+				}
+			case *IPNet:
+				if ip.Equal(v.IP) {
+					return &ifi, nil
+				}
+			}
+		}
+	}
+	if ip.Equal(IPv4zero) {
+		return nil, nil
+	}
+	return nil, errNoSuchInterface
+}
+
+func interfaceToIPv4Addr(ifi *Interface) (IP, error) {
+	if ifi == nil {
+		return IPv4zero, nil
+	}
+	ifat, err := ifi.Addrs()
+	if err != nil {
+		return nil, err
+	}
+	for _, ifa := range ifat {
+		switch v := ifa.(type) {
+		case *IPAddr:
+			if v.IP.To4() != nil {
+				return v.IP, nil
+			}
+		case *IPNet:
+			if v.IP.To4() != nil {
+				return v.IP, nil
+			}
+		}
+	}
+	return nil, errNoSuchInterface
+}
+
+func setIPv4MreqToInterface(mreq *syscall.IPMreq, ifi *Interface) error {
+	if ifi == nil {
+		return nil
+	}
+	ifat, err := ifi.Addrs()
+	if err != nil {
+		return err
+	}
+	for _, ifa := range ifat {
+		switch v := ifa.(type) {
+		case *IPAddr:
+			if a := v.IP.To4(); a != nil {
+				copy(mreq.Interface[:], a)
+				goto done
+			}
+		case *IPNet:
+			if a := v.IP.To4(); a != nil {
+				copy(mreq.Interface[:], a)
+				goto done
+			}
+		}
+	}
+done:
+	if bytesEqual(mreq.Multiaddr[:], IPv4zero.To4()) {
+		return errNoSuchMulticastInterface
+	}
+	return nil
+}
+
+func setReadBuffer(fd *netFD, bytes int) error {
+	if err := fd.incref(); err != nil {
+		return err
+	}
+	defer fd.decref()
+	return os.NewSyscallError("setsockopt", syscall.SetsockoptInt(fd.sysfd, syscall.SOL_SOCKET, syscall.SO_RCVBUF, bytes))
+}
+
+func setWriteBuffer(fd *netFD, bytes int) error {
+	if err := fd.incref(); err != nil {
+		return err
+	}
+	defer fd.decref()
+	return os.NewSyscallError("setsockopt", syscall.SetsockoptInt(fd.sysfd, syscall.SOL_SOCKET, syscall.SO_SNDBUF, bytes))
+}
+
+func setKeepAlive(fd *netFD, keepalive bool) error {
+	if err := fd.incref(); err != nil {
+		return err
+	}
+	defer fd.decref()
+	return os.NewSyscallError("setsockopt", syscall.SetsockoptInt(fd.sysfd, syscall.SOL_SOCKET, syscall.SO_KEEPALIVE, boolint(keepalive)))
+}
+
+func setLinger(fd *netFD, sec int) error {
+	var l syscall.Linger
+	if sec >= 0 {
+		l.Onoff = 1
+		l.Linger = int32(sec)
+	} else {
+		l.Onoff = 0
+		l.Linger = 0
+	}
+	if err := fd.incref(); err != nil {
+		return err
+	}
+	defer fd.decref()
+	return os.NewSyscallError("setsockopt", syscall.SetsockoptLinger(fd.sysfd, syscall.SOL_SOCKET, syscall.SO_LINGER, &l))
+}
diff --git a/src/net/sockopt_solaris.go b/src/net/sockopt_solaris.go
new file mode 100644
index 000000000..54c20b140
--- /dev/null
+++ b/src/net/sockopt_solaris.go
@@ -0,0 +1,32 @@
+// Copyright 2011 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package net
+
+import (
+	"os"
+	"syscall"
+)
+
+func setDefaultSockopts(s, family, sotype int, ipv6only bool) error {
+	if family == syscall.AF_INET6 && sotype != syscall.SOCK_RAW {
+		// Allow both IP versions even if the OS default
+		// is otherwise.  Note that some operating systems
+		// never admit this option.
+		syscall.SetsockoptInt(s, syscall.IPPROTO_IPV6, syscall.IPV6_V6ONLY, boolint(ipv6only))
+	}
+	// Allow broadcast.
+	return os.NewSyscallError("setsockopt", syscall.SetsockoptInt(s, syscall.SOL_SOCKET, syscall.SO_BROADCAST, 1))
+}
+
+func setDefaultListenerSockopts(s int) error {
+	// Allow reuse of recently-used addresses.
+	return os.NewSyscallError("setsockopt", syscall.SetsockoptInt(s, syscall.SOL_SOCKET, syscall.SO_REUSEADDR, 1))
+}
+
+func setDefaultMulticastSockopts(s int) error {
+	// Allow multicast UDP and raw IP datagram sockets to listen
+	// concurrently across multiple listeners.
+	return os.NewSyscallError("setsockopt", syscall.SetsockoptInt(s, syscall.SOL_SOCKET, syscall.SO_REUSEADDR, 1))
+}
diff --git a/src/net/sockopt_windows.go b/src/net/sockopt_windows.go
new file mode 100644
index 000000000..cb64a40c6
--- /dev/null
+++ b/src/net/sockopt_windows.go
@@ -0,0 +1,38 @@
+// Copyright 2011 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package net
+
+import (
+	"os"
+	"syscall"
+)
+
+func setDefaultSockopts(s syscall.Handle, family, sotype int, ipv6only bool) error {
+	if family == syscall.AF_INET6 && sotype != syscall.SOCK_RAW {
+		// Allow both IP versions even if the OS default
+		// is otherwise.  Note that some operating systems
+		// never admit this option.
+		syscall.SetsockoptInt(s, syscall.IPPROTO_IPV6, syscall.IPV6_V6ONLY, boolint(ipv6only))
+	}
+	// Allow broadcast.
+	syscall.SetsockoptInt(s, syscall.SOL_SOCKET, syscall.SO_BROADCAST, 1)
+	return nil
+}
+
+func setDefaultListenerSockopts(s syscall.Handle) error {
+	// Windows will reuse recently-used addresses by default.
+	// SO_REUSEADDR should not be used here, as it allows
+	// a socket to forcibly bind to a port in use by another socket.
+	// This could lead to a non-deterministic behavior, where
+	// connection requests over the port cannot be guaranteed
+	// to be handled by the correct socket.
+	return nil
+}
+
+func setDefaultMulticastSockopts(s syscall.Handle) error {
+	// Allow multicast UDP and raw IP datagram sockets to listen
+	// concurrently across multiple listeners.
+	return os.NewSyscallError("setsockopt", syscall.SetsockoptInt(s, syscall.SOL_SOCKET, syscall.SO_REUSEADDR, 1))
+}
diff --git a/src/net/sockoptip_bsd.go b/src/net/sockoptip_bsd.go
new file mode 100644
index 000000000..87132f0f4
--- /dev/null
+++ b/src/net/sockoptip_bsd.go
@@ -0,0 +1,34 @@
+// Copyright 2011 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build darwin dragonfly freebsd nacl netbsd openbsd
+
+package net
+
+import (
+	"os"
+	"syscall"
+)
+
+func setIPv4MulticastInterface(fd *netFD, ifi *Interface) error {
+	ip, err := interfaceToIPv4Addr(ifi)
+	if err != nil {
+		return os.NewSyscallError("setsockopt", err)
+	}
+	var a [4]byte
+	copy(a[:], ip.To4())
+	if err := fd.incref(); err != nil {
+		return err
+	}
+	defer fd.decref()
+	return os.NewSyscallError("setsockopt", syscall.SetsockoptInet4Addr(fd.sysfd, syscall.IPPROTO_IP, syscall.IP_MULTICAST_IF, a))
+}
+
+func setIPv4MulticastLoopback(fd *netFD, v bool) error {
+	if err := fd.incref(); err != nil {
+		return err
+	}
+	defer fd.decref()
+	return os.NewSyscallError("setsockopt", syscall.SetsockoptByte(fd.sysfd, syscall.IPPROTO_IP, syscall.IP_MULTICAST_LOOP, byte(boolint(v))))
+}
diff --git a/src/net/sockoptip_linux.go b/src/net/sockoptip_linux.go
new file mode 100644
index 000000000..a69b778e4
--- /dev/null
+++ b/src/net/sockoptip_linux.go
@@ -0,0 +1,31 @@
+// Copyright 2011 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package net
+
+import (
+	"os"
+	"syscall"
+)
+
+func setIPv4MulticastInterface(fd *netFD, ifi *Interface) error {
+	var v int32
+	if ifi != nil {
+		v = int32(ifi.Index)
+	}
+	mreq := &syscall.IPMreqn{Ifindex: v}
+	if err := fd.incref(); err != nil {
+		return err
+	}
+	defer fd.decref()
+	return os.NewSyscallError("setsockopt", syscall.SetsockoptIPMreqn(fd.sysfd, syscall.IPPROTO_IP, syscall.IP_MULTICAST_IF, mreq))
+}
+
+func setIPv4MulticastLoopback(fd *netFD, v bool) error {
+	if err := fd.incref(); err != nil {
+		return err
+	}
+	defer fd.decref()
+	return os.NewSyscallError("setsockopt", syscall.SetsockoptInt(fd.sysfd, syscall.IPPROTO_IP, syscall.IP_MULTICAST_LOOP, boolint(v)))
+}
diff --git a/src/net/sockoptip_posix.go b/src/net/sockoptip_posix.go
new file mode 100644
index 000000000..b5c80e449
--- /dev/null
+++ b/src/net/sockoptip_posix.go
@@ -0,0 +1,57 @@
+// Copyright 2011 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build darwin dragonfly freebsd linux nacl netbsd openbsd windows
+
+package net
+
+import (
+	"os"
+	"syscall"
+)
+
+func joinIPv4Group(fd *netFD, ifi *Interface, ip IP) error {
+	mreq := &syscall.IPMreq{Multiaddr: [4]byte{ip[0], ip[1], ip[2], ip[3]}}
+	if err := setIPv4MreqToInterface(mreq, ifi); err != nil {
+		return err
+	}
+	if err := fd.incref(); err != nil {
+		return err
+	}
+	defer fd.decref()
+	return os.NewSyscallError("setsockopt", syscall.SetsockoptIPMreq(fd.sysfd, syscall.IPPROTO_IP, syscall.IP_ADD_MEMBERSHIP, mreq))
+}
+
+func setIPv6MulticastInterface(fd *netFD, ifi *Interface) error {
+	var v int
+	if ifi != nil {
+		v = ifi.Index
+	}
+	if err := fd.incref(); err != nil {
+		return err
+	}
+	defer fd.decref()
+	return os.NewSyscallError("setsockopt", syscall.SetsockoptInt(fd.sysfd, syscall.IPPROTO_IPV6, syscall.IPV6_MULTICAST_IF, v))
+}
+
+func setIPv6MulticastLoopback(fd *netFD, v bool) error {
+	if err := fd.incref(); err != nil {
+		return err
+	}
+	defer fd.decref()
+	return os.NewSyscallError("setsockopt", syscall.SetsockoptInt(fd.sysfd, syscall.IPPROTO_IPV6, syscall.IPV6_MULTICAST_LOOP, boolint(v)))
+}
+
+func joinIPv6Group(fd *netFD, ifi *Interface, ip IP) error {
+	mreq := &syscall.IPv6Mreq{}
+	copy(mreq.Multiaddr[:], ip)
+	if ifi != nil {
+		mreq.Interface = uint32(ifi.Index)
+	}
+	if err := fd.incref(); err != nil {
+		return err
+	}
+	defer fd.decref()
+	return os.NewSyscallError("setsockopt", syscall.SetsockoptIPv6Mreq(fd.sysfd, syscall.IPPROTO_IPV6, syscall.IPV6_JOIN_GROUP, mreq))
+}
diff --git a/src/net/sockoptip_stub.go b/src/net/sockoptip_stub.go
new file mode 100644
index 000000000..dcd3a22b5
--- /dev/null
+++ b/src/net/sockoptip_stub.go
@@ -0,0 +1,39 @@
+// Copyright 2011 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build solaris
+
+package net
+
+import "syscall"
+
+func setIPv4MulticastInterface(fd *netFD, ifi *Interface) error {
+	// See golang.org/issue/7399.
+	return syscall.EINVAL
+}
+
+func setIPv4MulticastLoopback(fd *netFD, v bool) error {
+	// See golang.org/issue/7399.
+	return syscall.EINVAL
+}
+
+func joinIPv4Group(fd *netFD, ifi *Interface, ip IP) error {
+	// See golang.org/issue/7399.
+	return syscall.EINVAL
+}
+
+func setIPv6MulticastInterface(fd *netFD, ifi *Interface) error {
+	// See golang.org/issue/7399.
+	return syscall.EINVAL
+}
+
+func setIPv6MulticastLoopback(fd *netFD, v bool) error {
+	// See golang.org/issue/7399.
+	return syscall.EINVAL
+}
+
+func joinIPv6Group(fd *netFD, ifi *Interface, ip IP) error {
+	// See golang.org/issue/7399.
+	return syscall.EINVAL
+}
diff --git a/src/net/sockoptip_windows.go b/src/net/sockoptip_windows.go
new file mode 100644
index 000000000..7b11f207a
--- /dev/null
+++ b/src/net/sockoptip_windows.go
@@ -0,0 +1,33 @@
+// Copyright 2011 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package net
+
+import (
+	"os"
+	"syscall"
+	"unsafe"
+)
+
+func setIPv4MulticastInterface(fd *netFD, ifi *Interface) error {
+	ip, err := interfaceToIPv4Addr(ifi)
+	if err != nil {
+		return os.NewSyscallError("setsockopt", err)
+	}
+	var a [4]byte
+	copy(a[:], ip.To4())
+	if err := fd.incref(); err != nil {
+		return err
+	}
+	defer fd.decref()
+	return os.NewSyscallError("setsockopt", syscall.Setsockopt(fd.sysfd, syscall.IPPROTO_IP, syscall.IP_MULTICAST_IF, (*byte)(unsafe.Pointer(&a[0])), 4))
+}
+
+func setIPv4MulticastLoopback(fd *netFD, v bool) error {
+	if err := fd.incref(); err != nil {
+		return err
+	}
+	defer fd.decref()
+	return os.NewSyscallError("setsockopt", syscall.SetsockoptInt(fd.sysfd, syscall.IPPROTO_IP, syscall.IP_MULTICAST_LOOP, boolint(v)))
+}
diff --git a/src/net/sys_cloexec.go b/src/net/sys_cloexec.go
new file mode 100644
index 000000000..898fb7c0c
--- /dev/null
+++ b/src/net/sys_cloexec.go
@@ -0,0 +1,54 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// This file implements sysSocket and accept for platforms that do not
+// provide a fast path for setting SetNonblock and CloseOnExec.
+
+// +build darwin dragonfly nacl netbsd openbsd solaris
+
+package net
+
+import "syscall"
+
+// Wrapper around the socket system call that marks the returned file
+// descriptor as nonblocking and close-on-exec.
+func sysSocket(family, sotype, proto int) (int, error) {
+	// See ../syscall/exec_unix.go for description of ForkLock.
+	syscall.ForkLock.RLock()
+	s, err := syscall.Socket(family, sotype, proto)
+	if err == nil {
+		syscall.CloseOnExec(s)
+	}
+	syscall.ForkLock.RUnlock()
+	if err != nil {
+		return -1, err
+	}
+	if err = syscall.SetNonblock(s, true); err != nil {
+		syscall.Close(s)
+		return -1, err
+	}
+	return s, nil
+}
+
+// Wrapper around the accept system call that marks the returned file
+// descriptor as nonblocking and close-on-exec.
+func accept(s int) (int, syscall.Sockaddr, error) {
+	// See ../syscall/exec_unix.go for description of ForkLock.
+	// It is probably okay to hold the lock across syscall.Accept
+	// because we have put fd.sysfd into non-blocking mode.
+	// However, a call to the File method will put it back into
+	// blocking mode. We can't take that risk, so no use of ForkLock here.
+	ns, sa, err := syscall.Accept(s)
+	if err == nil {
+		syscall.CloseOnExec(ns)
+	}
+	if err != nil {
+		return -1, nil, err
+	}
+	if err = syscall.SetNonblock(ns, true); err != nil {
+		syscall.Close(ns)
+		return -1, nil, err
+	}
+	return ns, sa, nil
+}
diff --git a/src/net/tcp_test.go b/src/net/tcp_test.go
new file mode 100644
index 000000000..c04198ea0
--- /dev/null
+++ b/src/net/tcp_test.go
@@ -0,0 +1,611 @@
+// Copyright 2012 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package net
+
+import (
+	"fmt"
+	"io"
+	"reflect"
+	"runtime"
+	"sync"
+	"testing"
+	"time"
+)
+
+func BenchmarkTCP4OneShot(b *testing.B) {
+	benchmarkTCP(b, false, false, "127.0.0.1:0")
+}
+
+func BenchmarkTCP4OneShotTimeout(b *testing.B) {
+	benchmarkTCP(b, false, true, "127.0.0.1:0")
+}
+
+func BenchmarkTCP4Persistent(b *testing.B) {
+	benchmarkTCP(b, true, false, "127.0.0.1:0")
+}
+
+func BenchmarkTCP4PersistentTimeout(b *testing.B) {
+	benchmarkTCP(b, true, true, "127.0.0.1:0")
+}
+
+func BenchmarkTCP6OneShot(b *testing.B) {
+	if !supportsIPv6 {
+		b.Skip("ipv6 is not supported")
+	}
+	benchmarkTCP(b, false, false, "[::1]:0")
+}
+
+func BenchmarkTCP6OneShotTimeout(b *testing.B) {
+	if !supportsIPv6 {
+		b.Skip("ipv6 is not supported")
+	}
+	benchmarkTCP(b, false, true, "[::1]:0")
+}
+
+func BenchmarkTCP6Persistent(b *testing.B) {
+	if !supportsIPv6 {
+		b.Skip("ipv6 is not supported")
+	}
+	benchmarkTCP(b, true, false, "[::1]:0")
+}
+
+func BenchmarkTCP6PersistentTimeout(b *testing.B) {
+	if !supportsIPv6 {
+		b.Skip("ipv6 is not supported")
+	}
+	benchmarkTCP(b, true, true, "[::1]:0")
+}
+
+func benchmarkTCP(b *testing.B, persistent, timeout bool, laddr string) {
+	const msgLen = 512
+	conns := b.N
+	numConcurrent := runtime.GOMAXPROCS(-1) * 2
+	msgs := 1
+	if persistent {
+		conns = numConcurrent
+		msgs = b.N / conns
+		if msgs == 0 {
+			msgs = 1
+		}
+		if conns > b.N {
+			conns = b.N
+		}
+	}
+	sendMsg := func(c Conn, buf []byte) bool {
+		n, err := c.Write(buf)
+		if n != len(buf) || err != nil {
+			b.Logf("Write failed: %v", err)
+			return false
+		}
+		return true
+	}
+	recvMsg := func(c Conn, buf []byte) bool {
+		for read := 0; read != len(buf); {
+			n, err := c.Read(buf)
+			read += n
+			if err != nil {
+				b.Logf("Read failed: %v", err)
+				return false
+			}
+		}
+		return true
+	}
+	ln, err := Listen("tcp", laddr)
+	if err != nil {
+		b.Fatalf("Listen failed: %v", err)
+	}
+	defer ln.Close()
+	serverSem := make(chan bool, numConcurrent)
+	// Acceptor.
+	go func() {
+		for {
+			c, err := ln.Accept()
+			if err != nil {
+				break
+			}
+			serverSem <- true
+			// Server connection.
+			go func(c Conn) {
+				defer func() {
+					c.Close()
+					<-serverSem
+				}()
+				if timeout {
+					c.SetDeadline(time.Now().Add(time.Hour)) // Not intended to fire.
+				}
+				var buf [msgLen]byte
+				for m := 0; m < msgs; m++ {
+					if !recvMsg(c, buf[:]) || !sendMsg(c, buf[:]) {
+						break
+					}
+				}
+			}(c)
+		}
+	}()
+	clientSem := make(chan bool, numConcurrent)
+	for i := 0; i < conns; i++ {
+		clientSem <- true
+		// Client connection.
+		go func() {
+			defer func() {
+				<-clientSem
+			}()
+			c, err := Dial("tcp", ln.Addr().String())
+			if err != nil {
+				b.Logf("Dial failed: %v", err)
+				return
+			}
+			defer c.Close()
+			if timeout {
+				c.SetDeadline(time.Now().Add(time.Hour)) // Not intended to fire.
+			}
+			var buf [msgLen]byte
+			for m := 0; m < msgs; m++ {
+				if !sendMsg(c, buf[:]) || !recvMsg(c, buf[:]) {
+					break
+				}
+			}
+		}()
+	}
+	for i := 0; i < numConcurrent; i++ {
+		clientSem <- true
+		serverSem <- true
+	}
+}
+
+func BenchmarkTCP4ConcurrentReadWrite(b *testing.B) {
+	benchmarkTCPConcurrentReadWrite(b, "127.0.0.1:0")
+}
+
+func BenchmarkTCP6ConcurrentReadWrite(b *testing.B) {
+	if !supportsIPv6 {
+		b.Skip("ipv6 is not supported")
+	}
+	benchmarkTCPConcurrentReadWrite(b, "[::1]:0")
+}
+
+func benchmarkTCPConcurrentReadWrite(b *testing.B, laddr string) {
+	// The benchmark creates GOMAXPROCS client/server pairs.
+	// Each pair creates 4 goroutines: client reader/writer and server reader/writer.
+	// The benchmark stresses concurrent reading and writing to the same connection.
+	// Such pattern is used in net/http and net/rpc.
+
+	b.StopTimer()
+
+	P := runtime.GOMAXPROCS(0)
+	N := b.N / P
+	W := 1000
+
+	// Setup P client/server connections.
+	clients := make([]Conn, P)
+	servers := make([]Conn, P)
+	ln, err := Listen("tcp", laddr)
+	if err != nil {
+		b.Fatalf("Listen failed: %v", err)
+	}
+	defer ln.Close()
+	done := make(chan bool)
+	go func() {
+		for p := 0; p < P; p++ {
+			s, err := ln.Accept()
+			if err != nil {
+				b.Errorf("Accept failed: %v", err)
+				return
+			}
+			servers[p] = s
+		}
+		done <- true
+	}()
+	for p := 0; p < P; p++ {
+		c, err := Dial("tcp", ln.Addr().String())
+		if err != nil {
+			b.Fatalf("Dial failed: %v", err)
+		}
+		clients[p] = c
+	}
+	<-done
+
+	b.StartTimer()
+
+	var wg sync.WaitGroup
+	wg.Add(4 * P)
+	for p := 0; p < P; p++ {
+		// Client writer.
+		go func(c Conn) {
+			defer wg.Done()
+			var buf [1]byte
+			for i := 0; i < N; i++ {
+				v := byte(i)
+				for w := 0; w < W; w++ {
+					v *= v
+				}
+				buf[0] = v
+				_, err := c.Write(buf[:])
+				if err != nil {
+					b.Errorf("Write failed: %v", err)
+					return
+				}
+			}
+		}(clients[p])
+
+		// Pipe between server reader and server writer.
+		pipe := make(chan byte, 128)
+
+		// Server reader.
+		go func(s Conn) {
+			defer wg.Done()
+			var buf [1]byte
+			for i := 0; i < N; i++ {
+				_, err := s.Read(buf[:])
+				if err != nil {
+					b.Errorf("Read failed: %v", err)
+					return
+				}
+				pipe <- buf[0]
+			}
+		}(servers[p])
+
+		// Server writer.
+		go func(s Conn) {
+			defer wg.Done()
+			var buf [1]byte
+			for i := 0; i < N; i++ {
+				v := <-pipe
+				for w := 0; w < W; w++ {
+					v *= v
+				}
+				buf[0] = v
+				_, err := s.Write(buf[:])
+				if err != nil {
+					b.Errorf("Write failed: %v", err)
+					return
+				}
+			}
+			s.Close()
+		}(servers[p])
+
+		// Client reader.
+		go func(c Conn) {
+			defer wg.Done()
+			var buf [1]byte
+			for i := 0; i < N; i++ {
+				_, err := c.Read(buf[:])
+				if err != nil {
+					b.Errorf("Read failed: %v", err)
+					return
+				}
+			}
+			c.Close()
+		}(clients[p])
+	}
+	wg.Wait()
+}
+
+type resolveTCPAddrTest struct {
+	net           string
+	litAddrOrName string
+	addr          *TCPAddr
+	err           error
+}
+
+var resolveTCPAddrTests = []resolveTCPAddrTest{
+	{"tcp", "127.0.0.1:0", &TCPAddr{IP: IPv4(127, 0, 0, 1), Port: 0}, nil},
+	{"tcp4", "127.0.0.1:65535", &TCPAddr{IP: IPv4(127, 0, 0, 1), Port: 65535}, nil},
+
+	{"tcp", "[::1]:1", &TCPAddr{IP: ParseIP("::1"), Port: 1}, nil},
+	{"tcp6", "[::1]:65534", &TCPAddr{IP: ParseIP("::1"), Port: 65534}, nil},
+
+	{"tcp", "[::1%en0]:1", &TCPAddr{IP: ParseIP("::1"), Port: 1, Zone: "en0"}, nil},
+	{"tcp6", "[::1%911]:2", &TCPAddr{IP: ParseIP("::1"), Port: 2, Zone: "911"}, nil},
+
+	{"", "127.0.0.1:0", &TCPAddr{IP: IPv4(127, 0, 0, 1), Port: 0}, nil}, // Go 1.0 behavior
+	{"", "[::1]:0", &TCPAddr{IP: ParseIP("::1"), Port: 0}, nil},         // Go 1.0 behavior
+
+	{"tcp", ":12345", &TCPAddr{Port: 12345}, nil},
+
+	{"http", "127.0.0.1:0", nil, UnknownNetworkError("http")},
+}
+
+func init() {
+	if ifi := loopbackInterface(); ifi != nil {
+		index := fmt.Sprintf("%v", ifi.Index)
+		resolveTCPAddrTests = append(resolveTCPAddrTests, []resolveTCPAddrTest{
+			{"tcp6", "[fe80::1%" + ifi.Name + "]:3", &TCPAddr{IP: ParseIP("fe80::1"), Port: 3, Zone: zoneToString(ifi.Index)}, nil},
+			{"tcp6", "[fe80::1%" + index + "]:4", &TCPAddr{IP: ParseIP("fe80::1"), Port: 4, Zone: index}, nil},
+		}...)
+	}
+	if ips, err := LookupIP("localhost"); err == nil && len(ips) > 1 && supportsIPv4 && supportsIPv6 {
+		resolveTCPAddrTests = append(resolveTCPAddrTests, []resolveTCPAddrTest{
+			{"tcp", "localhost:5", &TCPAddr{IP: IPv4(127, 0, 0, 1), Port: 5}, nil},
+			{"tcp4", "localhost:6", &TCPAddr{IP: IPv4(127, 0, 0, 1), Port: 6}, nil},
+			{"tcp6", "localhost:7", &TCPAddr{IP: IPv6loopback, Port: 7}, nil},
+		}...)
+	}
+}
+
+func TestResolveTCPAddr(t *testing.T) {
+	for _, tt := range resolveTCPAddrTests {
+		addr, err := ResolveTCPAddr(tt.net, tt.litAddrOrName)
+		if err != tt.err {
+			t.Fatalf("ResolveTCPAddr(%q, %q) failed: %v", tt.net, tt.litAddrOrName, err)
+		}
+		if !reflect.DeepEqual(addr, tt.addr) {
+			t.Fatalf("ResolveTCPAddr(%q, %q) = %#v, want %#v", tt.net, tt.litAddrOrName, addr, tt.addr)
+		}
+		if err == nil {
+			str := addr.String()
+			addr1, err := ResolveTCPAddr(tt.net, str)
+			if err != nil {
+				t.Fatalf("ResolveTCPAddr(%q, %q) [from %q]: %v", tt.net, str, tt.litAddrOrName, err)
+			}
+			if !reflect.DeepEqual(addr1, addr) {
+				t.Fatalf("ResolveTCPAddr(%q, %q) [from %q] = %#v, want %#v", tt.net, str, tt.litAddrOrName, addr1, addr)
+			}
+		}
+	}
+}
+
+var tcpListenerNameTests = []struct {
+	net   string
+	laddr *TCPAddr
+}{
+	{"tcp4", &TCPAddr{IP: IPv4(127, 0, 0, 1)}},
+	{"tcp4", &TCPAddr{}},
+	{"tcp4", nil},
+}
+
+func TestTCPListenerName(t *testing.T) {
+	if testing.Short() || !*testExternal {
+		t.Skip("skipping test to avoid external network")
+	}
+
+	for _, tt := range tcpListenerNameTests {
+		ln, err := ListenTCP(tt.net, tt.laddr)
+		if err != nil {
+			t.Fatalf("ListenTCP failed: %v", err)
+		}
+		defer ln.Close()
+		la := ln.Addr()
+		if a, ok := la.(*TCPAddr); !ok || a.Port == 0 {
+			t.Fatalf("got %v; expected a proper address with non-zero port number", la)
+		}
+	}
+}
+
+func TestIPv6LinkLocalUnicastTCP(t *testing.T) {
+	if testing.Short() || !*testExternal {
+		t.Skip("skipping test to avoid external network")
+	}
+	if !supportsIPv6 {
+		t.Skip("ipv6 is not supported")
+	}
+	ifi := loopbackInterface()
+	if ifi == nil {
+		t.Skip("loopback interface not found")
+	}
+	laddr := ipv6LinkLocalUnicastAddr(ifi)
+	if laddr == "" {
+		t.Skip("ipv6 unicast address on loopback not found")
+	}
+
+	type test struct {
+		net, addr  string
+		nameLookup bool
+	}
+	var tests = []test{
+		{"tcp", "[" + laddr + "%" + ifi.Name + "]:0", false},
+		{"tcp6", "[" + laddr + "%" + ifi.Name + "]:0", false},
+	}
+	switch runtime.GOOS {
+	case "darwin", "freebsd", "openbsd", "netbsd":
+		tests = append(tests, []test{
+			{"tcp", "[localhost%" + ifi.Name + "]:0", true},
+			{"tcp6", "[localhost%" + ifi.Name + "]:0", true},
+		}...)
+	case "linux":
+		tests = append(tests, []test{
+			{"tcp", "[ip6-localhost%" + ifi.Name + "]:0", true},
+			{"tcp6", "[ip6-localhost%" + ifi.Name + "]:0", true},
+		}...)
+	}
+	for _, tt := range tests {
+		ln, err := Listen(tt.net, tt.addr)
+		if err != nil {
+			// It might return "LookupHost returned no
+			// suitable address" error on some platforms.
+			t.Logf("Listen failed: %v", err)
+			continue
+		}
+		defer ln.Close()
+		if la, ok := ln.Addr().(*TCPAddr); !ok || !tt.nameLookup && la.Zone == "" {
+			t.Fatalf("got %v; expected a proper address with zone identifier", la)
+		}
+
+		done := make(chan int)
+		go transponder(t, ln, done)
+
+		c, err := Dial(tt.net, ln.Addr().String())
+		if err != nil {
+			t.Fatalf("Dial failed: %v", err)
+		}
+		defer c.Close()
+		if la, ok := c.LocalAddr().(*TCPAddr); !ok || !tt.nameLookup && la.Zone == "" {
+			t.Fatalf("got %v; expected a proper address with zone identifier", la)
+		}
+		if ra, ok := c.RemoteAddr().(*TCPAddr); !ok || !tt.nameLookup && ra.Zone == "" {
+			t.Fatalf("got %v; expected a proper address with zone identifier", ra)
+		}
+
+		if _, err := c.Write([]byte("TCP OVER IPV6 LINKLOCAL TEST")); err != nil {
+			t.Fatalf("Conn.Write failed: %v", err)
+		}
+		b := make([]byte, 32)
+		if _, err := c.Read(b); err != nil {
+			t.Fatalf("Conn.Read failed: %v", err)
+		}
+
+		<-done
+	}
+}
+
+func TestTCPConcurrentAccept(t *testing.T) {
+	defer runtime.GOMAXPROCS(runtime.GOMAXPROCS(4))
+	ln, err := Listen("tcp", "127.0.0.1:0")
+	if err != nil {
+		t.Fatalf("Listen failed: %v", err)
+	}
+	const N = 10
+	var wg sync.WaitGroup
+	wg.Add(N)
+	for i := 0; i < N; i++ {
+		go func() {
+			for {
+				c, err := ln.Accept()
+				if err != nil {
+					break
+				}
+				c.Close()
+			}
+			wg.Done()
+		}()
+	}
+	attempts := 10 * N
+	fails := 0
+	d := &Dialer{Timeout: 200 * time.Millisecond}
+	for i := 0; i < attempts; i++ {
+		c, err := d.Dial("tcp", ln.Addr().String())
+		if err != nil {
+			fails++
+		} else {
+			c.Close()
+		}
+	}
+	ln.Close()
+	wg.Wait()
+	if fails > attempts/9 { // see issues 7400 and 7541
+		t.Fatalf("too many Dial failed: %v", fails)
+	}
+	if fails > 0 {
+		t.Logf("# of failed Dials: %v", fails)
+	}
+}
+
+func TestTCPReadWriteMallocs(t *testing.T) {
+	if testing.Short() {
+		t.Skip("skipping malloc count in short mode")
+	}
+	ln, err := Listen("tcp", "127.0.0.1:0")
+	if err != nil {
+		t.Fatalf("Listen failed: %v", err)
+	}
+	defer ln.Close()
+	var server Conn
+	errc := make(chan error)
+	go func() {
+		var err error
+		server, err = ln.Accept()
+		errc <- err
+	}()
+	client, err := Dial("tcp", ln.Addr().String())
+	if err != nil {
+		t.Fatalf("Dial failed: %v", err)
+	}
+	if err := <-errc; err != nil {
+		t.Fatalf("Accept failed: %v", err)
+	}
+	defer server.Close()
+	var buf [128]byte
+	mallocs := testing.AllocsPerRun(1000, func() {
+		_, err := server.Write(buf[:])
+		if err != nil {
+			t.Fatalf("Write failed: %v", err)
+		}
+		_, err = io.ReadFull(client, buf[:])
+		if err != nil {
+			t.Fatalf("Read failed: %v", err)
+		}
+	})
+	if mallocs > 0 {
+		t.Fatalf("Got %v allocs, want 0", mallocs)
+	}
+}
+
+func TestTCPStress(t *testing.T) {
+	const conns = 2
+	const msgLen = 512
+	msgs := int(1e4)
+	if testing.Short() {
+		msgs = 1e2
+	}
+
+	sendMsg := func(c Conn, buf []byte) bool {
+		n, err := c.Write(buf)
+		if n != len(buf) || err != nil {
+			t.Logf("Write failed: %v", err)
+			return false
+		}
+		return true
+	}
+	recvMsg := func(c Conn, buf []byte) bool {
+		for read := 0; read != len(buf); {
+			n, err := c.Read(buf)
+			read += n
+			if err != nil {
+				t.Logf("Read failed: %v", err)
+				return false
+			}
+		}
+		return true
+	}
+
+	ln, err := Listen("tcp", "127.0.0.1:0")
+	if err != nil {
+		t.Fatalf("Listen failed: %v", err)
+	}
+	defer ln.Close()
+	// Acceptor.
+	go func() {
+		for {
+			c, err := ln.Accept()
+			if err != nil {
+				break
+			}
+			// Server connection.
+			go func(c Conn) {
+				defer c.Close()
+				var buf [msgLen]byte
+				for m := 0; m < msgs; m++ {
+					if !recvMsg(c, buf[:]) || !sendMsg(c, buf[:]) {
+						break
+					}
+				}
+			}(c)
+		}
+	}()
+	done := make(chan bool)
+	for i := 0; i < conns; i++ {
+		// Client connection.
+		go func() {
+			defer func() {
+				done <- true
+			}()
+			c, err := Dial("tcp", ln.Addr().String())
+			if err != nil {
+				t.Logf("Dial failed: %v", err)
+				return
+			}
+			defer c.Close()
+			var buf [msgLen]byte
+			for m := 0; m < msgs; m++ {
+				if !sendMsg(c, buf[:]) || !recvMsg(c, buf[:]) {
+					break
+				}
+			}
+		}()
+	}
+	for i := 0; i < conns; i++ {
+		<-done
+	}
+}
diff --git a/src/net/tcpsock.go b/src/net/tcpsock.go
new file mode 100644
index 000000000..f3dfbd23d
--- /dev/null
+++ b/src/net/tcpsock.go
@@ -0,0 +1,54 @@
+// Copyright 2009 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package net
+
+// TCPAddr represents the address of a TCP end point.
+type TCPAddr struct {
+	IP   IP
+	Port int
+	Zone string // IPv6 scoped addressing zone
+}
+
+// Network returns the address's network name, "tcp".
+func (a *TCPAddr) Network() string { return "tcp" }
+
+func (a *TCPAddr) String() string {
+	if a == nil {
+		return "<nil>"
+	}
+	ip := ipEmptyString(a.IP)
+	if a.Zone != "" {
+		return JoinHostPort(ip+"%"+a.Zone, itoa(a.Port))
+	}
+	return JoinHostPort(ip, itoa(a.Port))
+}
+
+func (a *TCPAddr) toAddr() Addr {
+	if a == nil {
+		return nil
+	}
+	return a
+}
+
+// ResolveTCPAddr parses addr as a TCP address of the form "host:port"
+// or "[ipv6-host%zone]:port" and resolves a pair of domain name and
+// port name on the network net, which must be "tcp", "tcp4" or
+// "tcp6".  A literal address or host name for IPv6 must be enclosed
+// in square brackets, as in "[::1]:80", "[ipv6-host]:http" or
+// "[ipv6-host%zone]:80".
+func ResolveTCPAddr(net, addr string) (*TCPAddr, error) {
+	switch net {
+	case "tcp", "tcp4", "tcp6":
+	case "": // a hint wildcard for Go 1.0 undocumented behavior
+		net = "tcp"
+	default:
+		return nil, UnknownNetworkError(net)
+	}
+	a, err := resolveInternetAddr(net, addr, noDeadline)
+	if err != nil {
+		return nil, err
+	}
+	return a.toAddr().(*TCPAddr), nil
+}
diff --git a/src/net/tcpsock_plan9.go b/src/net/tcpsock_plan9.go
new file mode 100644
index 000000000..52019d7b4
--- /dev/null
+++ b/src/net/tcpsock_plan9.go
@@ -0,0 +1,198 @@
+// Copyright 2009 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package net
+
+import (
+	"io"
+	"os"
+	"syscall"
+	"time"
+)
+
+// TCPConn is an implementation of the Conn interface for TCP network
+// connections.
+type TCPConn struct {
+	conn
+}
+
+func newTCPConn(fd *netFD) *TCPConn {
+	return &TCPConn{conn{fd}}
+}
+
+// ReadFrom implements the io.ReaderFrom ReadFrom method.
+func (c *TCPConn) ReadFrom(r io.Reader) (int64, error) {
+	return genericReadFrom(c, r)
+}
+
+// CloseRead shuts down the reading side of the TCP connection.
+// Most callers should just use Close.
+func (c *TCPConn) CloseRead() error {
+	if !c.ok() {
+		return syscall.EINVAL
+	}
+	return c.fd.closeRead()
+}
+
+// CloseWrite shuts down the writing side of the TCP connection.
+// Most callers should just use Close.
+func (c *TCPConn) CloseWrite() error {
+	if !c.ok() {
+		return syscall.EINVAL
+	}
+	return c.fd.closeWrite()
+}
+
+// SetLinger sets the behavior of Close on a connection which still
+// has data waiting to be sent or to be acknowledged.
+//
+// If sec < 0 (the default), the operating system finishes sending the
+// data in the background.
+//
+// If sec == 0, the operating system discards any unsent or
+// unacknowledged data.
+//
+// If sec > 0, the data is sent in the background as with sec < 0. On
+// some operating systems after sec seconds have elapsed any remaining
+// unsent data may be discarded.
+func (c *TCPConn) SetLinger(sec int) error {
+	return syscall.EPLAN9
+}
+
+// SetKeepAlive sets whether the operating system should send
+// keepalive messages on the connection.
+func (c *TCPConn) SetKeepAlive(keepalive bool) error {
+	if !c.ok() {
+		return syscall.EPLAN9
+	}
+	return setKeepAlive(c.fd, keepalive)
+}
+
+// SetKeepAlivePeriod sets period between keep alives.
+func (c *TCPConn) SetKeepAlivePeriod(d time.Duration) error {
+	if !c.ok() {
+		return syscall.EPLAN9
+	}
+	return setKeepAlivePeriod(c.fd, d)
+}
+
+// SetNoDelay controls whether the operating system should delay
+// packet transmission in hopes of sending fewer packets (Nagle's
+// algorithm).  The default is true (no delay), meaning that data is
+// sent as soon as possible after a Write.
+func (c *TCPConn) SetNoDelay(noDelay bool) error {
+	return syscall.EPLAN9
+}
+
+// DialTCP connects to the remote address raddr on the network net,
+// which must be "tcp", "tcp4", or "tcp6".  If laddr is not nil, it is
+// used as the local address for the connection.
+func DialTCP(net string, laddr, raddr *TCPAddr) (*TCPConn, error) {
+	return dialTCP(net, laddr, raddr, noDeadline)
+}
+
+func dialTCP(net string, laddr, raddr *TCPAddr, deadline time.Time) (*TCPConn, error) {
+	if !deadline.IsZero() {
+		panic("net.dialTCP: deadline not implemented on Plan 9")
+	}
+	switch net {
+	case "tcp", "tcp4", "tcp6":
+	default:
+		return nil, &OpError{"dial", net, raddr, UnknownNetworkError(net)}
+	}
+	if raddr == nil {
+		return nil, &OpError{"dial", net, nil, errMissingAddress}
+	}
+	fd, err := dialPlan9(net, laddr, raddr)
+	if err != nil {
+		return nil, err
+	}
+	return newTCPConn(fd), nil
+}
+
+// TCPListener is a TCP network listener.  Clients should typically
+// use variables of type Listener instead of assuming TCP.
+type TCPListener struct {
+	fd *netFD
+}
+
+// AcceptTCP accepts the next incoming call and returns the new
+// connection.
+func (l *TCPListener) AcceptTCP() (*TCPConn, error) {
+	if l == nil || l.fd == nil || l.fd.ctl == nil {
+		return nil, syscall.EINVAL
+	}
+	fd, err := l.fd.acceptPlan9()
+	if err != nil {
+		return nil, err
+	}
+	return newTCPConn(fd), nil
+}
+
+// Accept implements the Accept method in the Listener interface; it
+// waits for the next call and returns a generic Conn.
+func (l *TCPListener) Accept() (Conn, error) {
+	if l == nil || l.fd == nil || l.fd.ctl == nil {
+		return nil, syscall.EINVAL
+	}
+	c, err := l.AcceptTCP()
+	if err != nil {
+		return nil, err
+	}
+	return c, nil
+}
+
+// Close stops listening on the TCP address.
+// Already Accepted connections are not closed.
+func (l *TCPListener) Close() error {
+	if l == nil || l.fd == nil || l.fd.ctl == nil {
+		return syscall.EINVAL
+	}
+	if _, err := l.fd.ctl.WriteString("hangup"); err != nil {
+		l.fd.ctl.Close()
+		return &OpError{"close", l.fd.ctl.Name(), l.fd.laddr, err}
+	}
+	return l.fd.ctl.Close()
+}
+
+// Addr returns the listener's network address, a *TCPAddr.
+func (l *TCPListener) Addr() Addr { return l.fd.laddr }
+
+// SetDeadline sets the deadline associated with the listener.
+// A zero time value disables the deadline.
+func (l *TCPListener) SetDeadline(t time.Time) error {
+	if l == nil || l.fd == nil || l.fd.ctl == nil {
+		return syscall.EINVAL
+	}
+	return l.fd.setDeadline(t)
+}
+
+// File returns a copy of the underlying os.File, set to blocking
+// mode.  It is the caller's responsibility to close f when finished.
+// Closing l does not affect f, and closing f does not affect l.
+//
+// The returned os.File's file descriptor is different from the
+// connection's.  Attempting to change properties of the original
+// using this duplicate may or may not have the desired effect.
+func (l *TCPListener) File() (f *os.File, err error) { return l.dup() }
+
+// ListenTCP announces on the TCP address laddr and returns a TCP
+// listener.  Net must be "tcp", "tcp4", or "tcp6".  If laddr has a
+// port of 0, ListenTCP will choose an available port.  The caller can
+// use the Addr method of TCPListener to retrieve the chosen address.
+func ListenTCP(net string, laddr *TCPAddr) (*TCPListener, error) {
+	switch net {
+	case "tcp", "tcp4", "tcp6":
+	default:
+		return nil, &OpError{"listen", net, laddr, UnknownNetworkError(net)}
+	}
+	if laddr == nil {
+		laddr = &TCPAddr{}
+	}
+	fd, err := listenPlan9(net, laddr)
+	if err != nil {
+		return nil, err
+	}
+	return &TCPListener{fd}, nil
+}
diff --git a/src/net/tcpsock_posix.go b/src/net/tcpsock_posix.go
new file mode 100644
index 000000000..dd78aefa7
--- /dev/null
+++ b/src/net/tcpsock_posix.go
@@ -0,0 +1,299 @@
+// Copyright 2009 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build darwin dragonfly freebsd linux nacl netbsd openbsd solaris windows
+
+package net
+
+import (
+	"io"
+	"os"
+	"syscall"
+	"time"
+)
+
+// BUG(rsc): On OpenBSD, listening on the "tcp" network does not listen for
+// both IPv4 and IPv6 connections. This is due to the fact that IPv4 traffic
+// will not be routed to an IPv6 socket - two separate sockets are required
+// if both AFs are to be supported. See inet6(4) on OpenBSD for details.
+
+func sockaddrToTCP(sa syscall.Sockaddr) Addr {
+	switch sa := sa.(type) {
+	case *syscall.SockaddrInet4:
+		return &TCPAddr{IP: sa.Addr[0:], Port: sa.Port}
+	case *syscall.SockaddrInet6:
+		return &TCPAddr{IP: sa.Addr[0:], Port: sa.Port, Zone: zoneToString(int(sa.ZoneId))}
+	}
+	return nil
+}
+
+func (a *TCPAddr) family() int {
+	if a == nil || len(a.IP) <= IPv4len {
+		return syscall.AF_INET
+	}
+	if a.IP.To4() != nil {
+		return syscall.AF_INET
+	}
+	return syscall.AF_INET6
+}
+
+func (a *TCPAddr) isWildcard() bool {
+	if a == nil || a.IP == nil {
+		return true
+	}
+	return a.IP.IsUnspecified()
+}
+
+func (a *TCPAddr) sockaddr(family int) (syscall.Sockaddr, error) {
+	if a == nil {
+		return nil, nil
+	}
+	return ipToSockaddr(family, a.IP, a.Port, a.Zone)
+}
+
+// TCPConn is an implementation of the Conn interface for TCP network
+// connections.
+type TCPConn struct {
+	conn
+}
+
+func newTCPConn(fd *netFD) *TCPConn {
+	c := &TCPConn{conn{fd}}
+	c.SetNoDelay(true)
+	return c
+}
+
+// ReadFrom implements the io.ReaderFrom ReadFrom method.
+func (c *TCPConn) ReadFrom(r io.Reader) (int64, error) {
+	if n, err, handled := sendFile(c.fd, r); handled {
+		return n, err
+	}
+	return genericReadFrom(c, r)
+}
+
+// CloseRead shuts down the reading side of the TCP connection.
+// Most callers should just use Close.
+func (c *TCPConn) CloseRead() error {
+	if !c.ok() {
+		return syscall.EINVAL
+	}
+	return c.fd.closeRead()
+}
+
+// CloseWrite shuts down the writing side of the TCP connection.
+// Most callers should just use Close.
+func (c *TCPConn) CloseWrite() error {
+	if !c.ok() {
+		return syscall.EINVAL
+	}
+	return c.fd.closeWrite()
+}
+
+// SetLinger sets the behavior of Close on a connection which still
+// has data waiting to be sent or to be acknowledged.
+//
+// If sec < 0 (the default), the operating system finishes sending the
+// data in the background.
+//
+// If sec == 0, the operating system discards any unsent or
+// unacknowledged data.
+//
+// If sec > 0, the data is sent in the background as with sec < 0. On
+// some operating systems after sec seconds have elapsed any remaining
+// unsent data may be discarded.
+func (c *TCPConn) SetLinger(sec int) error {
+	if !c.ok() {
+		return syscall.EINVAL
+	}
+	return setLinger(c.fd, sec)
+}
+
+// SetKeepAlive sets whether the operating system should send
+// keepalive messages on the connection.
+func (c *TCPConn) SetKeepAlive(keepalive bool) error {
+	if !c.ok() {
+		return syscall.EINVAL
+	}
+	return setKeepAlive(c.fd, keepalive)
+}
+
+// SetKeepAlivePeriod sets period between keep alives.
+func (c *TCPConn) SetKeepAlivePeriod(d time.Duration) error {
+	if !c.ok() {
+		return syscall.EINVAL
+	}
+	return setKeepAlivePeriod(c.fd, d)
+}
+
+// SetNoDelay controls whether the operating system should delay
+// packet transmission in hopes of sending fewer packets (Nagle's
+// algorithm).  The default is true (no delay), meaning that data is
+// sent as soon as possible after a Write.
+func (c *TCPConn) SetNoDelay(noDelay bool) error {
+	if !c.ok() {
+		return syscall.EINVAL
+	}
+	return setNoDelay(c.fd, noDelay)
+}
+
+// DialTCP connects to the remote address raddr on the network net,
+// which must be "tcp", "tcp4", or "tcp6".  If laddr is not nil, it is
+// used as the local address for the connection.
+func DialTCP(net string, laddr, raddr *TCPAddr) (*TCPConn, error) {
+	switch net {
+	case "tcp", "tcp4", "tcp6":
+	default:
+		return nil, &OpError{Op: "dial", Net: net, Addr: raddr, Err: UnknownNetworkError(net)}
+	}
+	if raddr == nil {
+		return nil, &OpError{Op: "dial", Net: net, Addr: nil, Err: errMissingAddress}
+	}
+	return dialTCP(net, laddr, raddr, noDeadline)
+}
+
+func dialTCP(net string, laddr, raddr *TCPAddr, deadline time.Time) (*TCPConn, error) {
+	fd, err := internetSocket(net, laddr, raddr, deadline, syscall.SOCK_STREAM, 0, "dial")
+
+	// TCP has a rarely used mechanism called a 'simultaneous connection' in
+	// which Dial("tcp", addr1, addr2) run on the machine at addr1 can
+	// connect to a simultaneous Dial("tcp", addr2, addr1) run on the machine
+	// at addr2, without either machine executing Listen.  If laddr == nil,
+	// it means we want the kernel to pick an appropriate originating local
+	// address.  Some Linux kernels cycle blindly through a fixed range of
+	// local ports, regardless of destination port.  If a kernel happens to
+	// pick local port 50001 as the source for a Dial("tcp", "", "localhost:50001"),
+	// then the Dial will succeed, having simultaneously connected to itself.
+	// This can only happen when we are letting the kernel pick a port (laddr == nil)
+	// and when there is no listener for the destination address.
+	// It's hard to argue this is anything other than a kernel bug.  If we
+	// see this happen, rather than expose the buggy effect to users, we
+	// close the fd and try again.  If it happens twice more, we relent and
+	// use the result.  See also:
+	//	http://golang.org/issue/2690
+	//	http://stackoverflow.com/questions/4949858/
+	//
+	// The opposite can also happen: if we ask the kernel to pick an appropriate
+	// originating local address, sometimes it picks one that is already in use.
+	// So if the error is EADDRNOTAVAIL, we have to try again too, just for
+	// a different reason.
+	//
+	// The kernel socket code is no doubt enjoying watching us squirm.
+	for i := 0; i < 2 && (laddr == nil || laddr.Port == 0) && (selfConnect(fd, err) || spuriousENOTAVAIL(err)); i++ {
+		if err == nil {
+			fd.Close()
+		}
+		fd, err = internetSocket(net, laddr, raddr, deadline, syscall.SOCK_STREAM, 0, "dial")
+	}
+
+	if err != nil {
+		return nil, &OpError{Op: "dial", Net: net, Addr: raddr, Err: err}
+	}
+	return newTCPConn(fd), nil
+}
+
+func selfConnect(fd *netFD, err error) bool {
+	// If the connect failed, we clearly didn't connect to ourselves.
+	if err != nil {
+		return false
+	}
+
+	// The socket constructor can return an fd with raddr nil under certain
+	// unknown conditions. The errors in the calls there to Getpeername
+	// are discarded, but we can't catch the problem there because those
+	// calls are sometimes legally erroneous with a "socket not connected".
+	// Since this code (selfConnect) is already trying to work around
+	// a problem, we make sure if this happens we recognize trouble and
+	// ask the DialTCP routine to try again.
+	// TODO: try to understand what's really going on.
+	if fd.laddr == nil || fd.raddr == nil {
+		return true
+	}
+	l := fd.laddr.(*TCPAddr)
+	r := fd.raddr.(*TCPAddr)
+	return l.Port == r.Port && l.IP.Equal(r.IP)
+}
+
+func spuriousENOTAVAIL(err error) bool {
+	e, ok := err.(*OpError)
+	return ok && e.Err == syscall.EADDRNOTAVAIL
+}
+
+// TCPListener is a TCP network listener.  Clients should typically
+// use variables of type Listener instead of assuming TCP.
+type TCPListener struct {
+	fd *netFD
+}
+
+// AcceptTCP accepts the next incoming call and returns the new
+// connection.
+func (l *TCPListener) AcceptTCP() (*TCPConn, error) {
+	if l == nil || l.fd == nil {
+		return nil, syscall.EINVAL
+	}
+	fd, err := l.fd.accept()
+	if err != nil {
+		return nil, err
+	}
+	return newTCPConn(fd), nil
+}
+
+// Accept implements the Accept method in the Listener interface; it
+// waits for the next call and returns a generic Conn.
+func (l *TCPListener) Accept() (Conn, error) {
+	c, err := l.AcceptTCP()
+	if err != nil {
+		return nil, err
+	}
+	return c, nil
+}
+
+// Close stops listening on the TCP address.
+// Already Accepted connections are not closed.
+func (l *TCPListener) Close() error {
+	if l == nil || l.fd == nil {
+		return syscall.EINVAL
+	}
+	return l.fd.Close()
+}
+
+// Addr returns the listener's network address, a *TCPAddr.
+func (l *TCPListener) Addr() Addr { return l.fd.laddr }
+
+// SetDeadline sets the deadline associated with the listener.
+// A zero time value disables the deadline.
+func (l *TCPListener) SetDeadline(t time.Time) error {
+	if l == nil || l.fd == nil {
+		return syscall.EINVAL
+	}
+	return l.fd.setDeadline(t)
+}
+
+// File returns a copy of the underlying os.File, set to blocking
+// mode.  It is the caller's responsibility to close f when finished.
+// Closing l does not affect f, and closing f does not affect l.
+//
+// The returned os.File's file descriptor is different from the
+// connection's.  Attempting to change properties of the original
+// using this duplicate may or may not have the desired effect.
+func (l *TCPListener) File() (f *os.File, err error) { return l.fd.dup() }
+
+// ListenTCP announces on the TCP address laddr and returns a TCP
+// listener.  Net must be "tcp", "tcp4", or "tcp6".  If laddr has a
+// port of 0, ListenTCP will choose an available port.  The caller can
+// use the Addr method of TCPListener to retrieve the chosen address.
+func ListenTCP(net string, laddr *TCPAddr) (*TCPListener, error) {
+	switch net {
+	case "tcp", "tcp4", "tcp6":
+	default:
+		return nil, &OpError{Op: "listen", Net: net, Addr: laddr, Err: UnknownNetworkError(net)}
+	}
+	if laddr == nil {
+		laddr = &TCPAddr{}
+	}
+	fd, err := internetSocket(net, laddr, nil, noDeadline, syscall.SOCK_STREAM, 0, "listen")
+	if err != nil {
+		return nil, &OpError{Op: "listen", Net: net, Addr: laddr, Err: err}
+	}
+	return &TCPListener{fd}, nil
+}
diff --git a/src/net/tcpsockopt_darwin.go b/src/net/tcpsockopt_darwin.go
new file mode 100644
index 000000000..33140849c
--- /dev/null
+++ b/src/net/tcpsockopt_darwin.go
@@ -0,0 +1,27 @@
+// Copyright 2009 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// TCP socket options for darwin
+
+package net
+
+import (
+	"os"
+	"syscall"
+	"time"
+)
+
+// Set keep alive period.
+func setKeepAlivePeriod(fd *netFD, d time.Duration) error {
+	if err := fd.incref(); err != nil {
+		return err
+	}
+	defer fd.decref()
+
+	// The kernel expects seconds so round to next highest second.
+	d += (time.Second - time.Nanosecond)
+	secs := int(d.Seconds())
+
+	return os.NewSyscallError("setsockopt", syscall.SetsockoptInt(fd.sysfd, syscall.IPPROTO_TCP, syscall.TCP_KEEPALIVE, secs))
+}
diff --git a/src/net/tcpsockopt_dragonfly.go b/src/net/tcpsockopt_dragonfly.go
new file mode 100644
index 000000000..d10a77773
--- /dev/null
+++ b/src/net/tcpsockopt_dragonfly.go
@@ -0,0 +1,29 @@
+// Copyright 2009 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package net
+
+import (
+	"os"
+	"syscall"
+	"time"
+)
+
+// Set keep alive period.
+func setKeepAlivePeriod(fd *netFD, d time.Duration) error {
+	if err := fd.incref(); err != nil {
+		return err
+	}
+	defer fd.decref()
+
+	// The kernel expects milliseconds so round to next highest millisecond.
+	d += (time.Millisecond - time.Nanosecond)
+	msecs := int(time.Duration(d.Nanoseconds()) / time.Millisecond)
+
+	err := os.NewSyscallError("setsockopt", syscall.SetsockoptInt(fd.sysfd, syscall.IPPROTO_TCP, syscall.TCP_KEEPINTVL, msecs))
+	if err != nil {
+		return err
+	}
+	return os.NewSyscallError("setsockopt", syscall.SetsockoptInt(fd.sysfd, syscall.IPPROTO_TCP, syscall.TCP_KEEPIDLE, msecs))
+}
diff --git a/src/net/tcpsockopt_openbsd.go b/src/net/tcpsockopt_openbsd.go
new file mode 100644
index 000000000..3480f932c
--- /dev/null
+++ b/src/net/tcpsockopt_openbsd.go
@@ -0,0 +1,27 @@
+// Copyright 2009 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// TCP socket options for openbsd
+
+package net
+
+import (
+	"os"
+	"syscall"
+	"time"
+)
+
+// Set keep alive period.
+func setKeepAlivePeriod(fd *netFD, d time.Duration) error {
+	if err := fd.incref(); err != nil {
+		return err
+	}
+	defer fd.decref()
+
+	// The kernel expects seconds so round to next highest second.
+	d += (time.Second - time.Nanosecond)
+	secs := int(d.Seconds())
+
+	return os.NewSyscallError("setsockopt", syscall.SetsockoptInt(fd.sysfd, syscall.IPPROTO_TCP, syscall.SO_KEEPALIVE, secs))
+}
diff --git a/src/net/tcpsockopt_plan9.go b/src/net/tcpsockopt_plan9.go
new file mode 100644
index 000000000..0e7a6647c
--- /dev/null
+++ b/src/net/tcpsockopt_plan9.go
@@ -0,0 +1,18 @@
+// Copyright 2014 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// TCP socket options for plan9
+
+package net
+
+import (
+	"time"
+)
+
+// Set keep alive period.
+func setKeepAlivePeriod(fd *netFD, d time.Duration) error {
+	cmd := "keepalive " + string(int64(d/time.Millisecond))
+	_, e := fd.ctl.WriteAt([]byte(cmd), 0)
+	return e
+}
diff --git a/src/net/tcpsockopt_posix.go b/src/net/tcpsockopt_posix.go
new file mode 100644
index 000000000..6484bad4b
--- /dev/null
+++ b/src/net/tcpsockopt_posix.go
@@ -0,0 +1,20 @@
+// Copyright 2009 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build darwin dragonfly freebsd linux nacl netbsd openbsd solaris windows
+
+package net
+
+import (
+	"os"
+	"syscall"
+)
+
+func setNoDelay(fd *netFD, noDelay bool) error {
+	if err := fd.incref(); err != nil {
+		return err
+	}
+	defer fd.decref()
+	return os.NewSyscallError("setsockopt", syscall.SetsockoptInt(fd.sysfd, syscall.IPPROTO_TCP, syscall.TCP_NODELAY, boolint(noDelay)))
+}
diff --git a/src/net/tcpsockopt_solaris.go b/src/net/tcpsockopt_solaris.go
new file mode 100644
index 000000000..eaab6b678
--- /dev/null
+++ b/src/net/tcpsockopt_solaris.go
@@ -0,0 +1,27 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// TCP socket options for solaris
+
+package net
+
+import (
+	"os"
+	"syscall"
+	"time"
+)
+
+// Set keep alive period.
+func setKeepAlivePeriod(fd *netFD, d time.Duration) error {
+	if err := fd.incref(); err != nil {
+		return err
+	}
+	defer fd.decref()
+
+	// The kernel expects seconds so round to next highest second.
+	d += (time.Second - time.Nanosecond)
+	secs := int(d.Seconds())
+
+	return os.NewSyscallError("setsockopt", syscall.SetsockoptInt(fd.sysfd, syscall.IPPROTO_TCP, syscall.SO_KEEPALIVE, secs))
+}
diff --git a/src/net/tcpsockopt_unix.go b/src/net/tcpsockopt_unix.go
new file mode 100644
index 000000000..2693a541d
--- /dev/null
+++ b/src/net/tcpsockopt_unix.go
@@ -0,0 +1,31 @@
+// Copyright 2009 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build freebsd linux nacl netbsd
+
+package net
+
+import (
+	"os"
+	"syscall"
+	"time"
+)
+
+// Set keep alive period.
+func setKeepAlivePeriod(fd *netFD, d time.Duration) error {
+	if err := fd.incref(); err != nil {
+		return err
+	}
+	defer fd.decref()
+
+	// The kernel expects seconds so round to next highest second.
+	d += (time.Second - time.Nanosecond)
+	secs := int(d.Seconds())
+
+	err := os.NewSyscallError("setsockopt", syscall.SetsockoptInt(fd.sysfd, syscall.IPPROTO_TCP, syscall.TCP_KEEPINTVL, secs))
+	if err != nil {
+		return err
+	}
+	return os.NewSyscallError("setsockopt", syscall.SetsockoptInt(fd.sysfd, syscall.IPPROTO_TCP, syscall.TCP_KEEPIDLE, secs))
+}
diff --git a/src/net/tcpsockopt_windows.go b/src/net/tcpsockopt_windows.go
new file mode 100644
index 000000000..8ef140797
--- /dev/null
+++ b/src/net/tcpsockopt_windows.go
@@ -0,0 +1,34 @@
+// Copyright 2009 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// TCP socket options for windows
+
+package net
+
+import (
+	"os"
+	"syscall"
+	"time"
+	"unsafe"
+)
+
+func setKeepAlivePeriod(fd *netFD, d time.Duration) error {
+	if err := fd.incref(); err != nil {
+		return err
+	}
+	defer fd.decref()
+
+	// Windows expects milliseconds so round to next highest millisecond.
+	d += (time.Millisecond - time.Nanosecond)
+	millis := uint32(d / time.Millisecond)
+	ka := syscall.TCPKeepalive{
+		OnOff:    1,
+		Time:     millis,
+		Interval: millis,
+	}
+	ret := uint32(0)
+	size := uint32(unsafe.Sizeof(ka))
+	err := syscall.WSAIoctl(fd.sysfd, syscall.SIO_KEEPALIVE_VALS, (*byte)(unsafe.Pointer(&ka)), size, nil, 0, &ret, nil, 0)
+	return os.NewSyscallError("WSAIoctl", err)
+}
diff --git a/src/net/testdata/domain-resolv.conf b/src/net/testdata/domain-resolv.conf
new file mode 100644
index 000000000..ff269180f
--- /dev/null
+++ b/src/net/testdata/domain-resolv.conf
@@ -0,0 +1,5 @@
+# /etc/resolv.conf
+
+search test invalid
+domain localdomain
+nameserver 8.8.8.8
diff --git a/src/net/testdata/empty-resolv.conf b/src/net/testdata/empty-resolv.conf
new file mode 100644
index 000000000..c4b2b5765
--- /dev/null
+++ b/src/net/testdata/empty-resolv.conf
@@ -0,0 +1 @@
+# /etc/resolv.conf
diff --git a/src/net/testdata/hosts b/src/net/testdata/hosts
new file mode 100644
index 000000000..b60176389
--- /dev/null
+++ b/src/net/testdata/hosts
@@ -0,0 +1,12 @@
+255.255.255.255	broadcasthost
+127.0.0.2	odin
+127.0.0.3	odin  # inline comment 
+::2             odin
+127.1.1.1	thor
+# aliases
+127.1.1.2	ullr ullrhost
+# Bogus entries that must be ignored.
+123.123.123	loki
+321.321.321.321
+# TODO(yvesj): Should we be able to parse this? From a Darwin system.
+fe80::1%lo0	localhost
diff --git a/src/net/testdata/hosts_singleline b/src/net/testdata/hosts_singleline
new file mode 100644
index 000000000..5f5f74a3f
--- /dev/null
+++ b/src/net/testdata/hosts_singleline
@@ -0,0 +1 @@
+127.0.0.2	odin
\ No newline at end of file
diff --git a/src/net/testdata/igmp b/src/net/testdata/igmp
new file mode 100644
index 000000000..5f380a2c7
--- /dev/null
+++ b/src/net/testdata/igmp
@@ -0,0 +1,24 @@
+Idx	Device    : Count Querier	Group    Users Timer	Reporter
+1	lo        :     1      V3
+				010000E0     1 0:00000000		0
+2	eth0      :     2      V2
+				FB0000E0     1 0:00000000		1
+				010000E0     1 0:00000000		0
+3	eth1      :     1      V3
+				010000E0     1 0:00000000		0
+4	eth2      :     1      V3
+				010000E0     1 0:00000000		0
+5	eth0.100  :     2      V3
+				FB0000E0     1 0:00000000		0
+				010000E0     1 0:00000000		0
+6	eth0.101  :     2      V3
+				FB0000E0     1 0:00000000		0
+				010000E0     1 0:00000000		0
+7	eth0.102  :     2      V3
+				FB0000E0     1 0:00000000		0
+				010000E0     1 0:00000000		0
+8	eth0.103  :     2      V3
+				FB0000E0     1 0:00000000		0
+				010000E0     1 0:00000000		0
+9	device1tap2:     1      V3
+				010000E0     1 0:00000000		0
diff --git a/src/net/testdata/igmp6 b/src/net/testdata/igmp6
new file mode 100644
index 000000000..6cd5a2d4d
--- /dev/null
+++ b/src/net/testdata/igmp6
@@ -0,0 +1,18 @@
+1    lo              ff020000000000000000000000000001     1 0000000C 0
+2    eth0            ff0200000000000000000001ffac891e     1 00000006 0
+2    eth0            ff020000000000000000000000000001     1 0000000C 0
+3    eth1            ff0200000000000000000001ffac8928     2 00000006 0
+3    eth1            ff020000000000000000000000000001     1 0000000C 0
+4    eth2            ff0200000000000000000001ffac8932     2 00000006 0
+4    eth2            ff020000000000000000000000000001     1 0000000C 0
+5    eth0.100        ff0200000000000000000001ffac891e     1 00000004 0
+5    eth0.100        ff020000000000000000000000000001     1 0000000C 0
+6    pan0            ff020000000000000000000000000001     1 0000000C 0
+7    eth0.101        ff0200000000000000000001ffac891e     1 00000004 0
+7    eth0.101        ff020000000000000000000000000001     1 0000000C 0
+8    eth0.102        ff0200000000000000000001ffac891e     1 00000004 0
+8    eth0.102        ff020000000000000000000000000001     1 0000000C 0
+9    eth0.103        ff0200000000000000000001ffac891e     1 00000004 0
+9    eth0.103        ff020000000000000000000000000001     1 0000000C 0
+10   device1tap2     ff0200000000000000000001ff4cc3a3     1 00000004 0
+10   device1tap2     ff020000000000000000000000000001     1 0000000C 0
diff --git a/src/net/testdata/resolv.conf b/src/net/testdata/resolv.conf
new file mode 100644
index 000000000..04e87eed0
--- /dev/null
+++ b/src/net/testdata/resolv.conf
@@ -0,0 +1,8 @@
+# /etc/resolv.conf
+
+domain localdomain
+nameserver 8.8.8.8
+nameserver 2001:4860:4860::8888
+nameserver fe80::1%lo0
+options ndots:5 timeout:10 attempts:3 rotate
+options attempts 3
diff --git a/src/net/testdata/search-resolv.conf b/src/net/testdata/search-resolv.conf
new file mode 100644
index 000000000..1c846bfaf
--- /dev/null
+++ b/src/net/testdata/search-resolv.conf
@@ -0,0 +1,5 @@
+# /etc/resolv.conf
+
+domain localdomain
+search test invalid
+nameserver 8.8.8.8
diff --git a/src/net/textproto/header.go b/src/net/textproto/header.go
new file mode 100644
index 000000000..7fb32f804
--- /dev/null
+++ b/src/net/textproto/header.go
@@ -0,0 +1,43 @@
+// Copyright 2010 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package textproto
+
+// A MIMEHeader represents a MIME-style header mapping
+// keys to sets of values.
+type MIMEHeader map[string][]string
+
+// Add adds the key, value pair to the header.
+// It appends to any existing values associated with key.
+func (h MIMEHeader) Add(key, value string) {
+	key = CanonicalMIMEHeaderKey(key)
+	h[key] = append(h[key], value)
+}
+
+// Set sets the header entries associated with key to
+// the single element value.  It replaces any existing
+// values associated with key.
+func (h MIMEHeader) Set(key, value string) {
+	h[CanonicalMIMEHeaderKey(key)] = []string{value}
+}
+
+// Get gets the first value associated with the given key.
+// If there are no values associated with the key, Get returns "".
+// Get is a convenience method.  For more complex queries,
+// access the map directly.
+func (h MIMEHeader) Get(key string) string {
+	if h == nil {
+		return ""
+	}
+	v := h[CanonicalMIMEHeaderKey(key)]
+	if len(v) == 0 {
+		return ""
+	}
+	return v[0]
+}
+
+// Del deletes the values associated with key.
+func (h MIMEHeader) Del(key string) {
+	delete(h, CanonicalMIMEHeaderKey(key))
+}
diff --git a/src/net/textproto/pipeline.go b/src/net/textproto/pipeline.go
new file mode 100644
index 000000000..ca50eddac
--- /dev/null
+++ b/src/net/textproto/pipeline.go
@@ -0,0 +1,117 @@
+// Copyright 2010 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package textproto
+
+import (
+	"sync"
+)
+
+// A Pipeline manages a pipelined in-order request/response sequence.
+//
+// To use a Pipeline p to manage multiple clients on a connection,
+// each client should run:
+//
+//	id := p.Next()	// take a number
+//
+//	p.StartRequest(id)	// wait for turn to send request
+//	«send request»
+//	p.EndRequest(id)	// notify Pipeline that request is sent
+//
+//	p.StartResponse(id)	// wait for turn to read response
+//	«read response»
+//	p.EndResponse(id)	// notify Pipeline that response is read
+//
+// A pipelined server can use the same calls to ensure that
+// responses computed in parallel are written in the correct order.
+type Pipeline struct {
+	mu       sync.Mutex
+	id       uint
+	request  sequencer
+	response sequencer
+}
+
+// Next returns the next id for a request/response pair.
+func (p *Pipeline) Next() uint {
+	p.mu.Lock()
+	id := p.id
+	p.id++
+	p.mu.Unlock()
+	return id
+}
+
+// StartRequest blocks until it is time to send (or, if this is a server, receive)
+// the request with the given id.
+func (p *Pipeline) StartRequest(id uint) {
+	p.request.Start(id)
+}
+
+// EndRequest notifies p that the request with the given id has been sent
+// (or, if this is a server, received).
+func (p *Pipeline) EndRequest(id uint) {
+	p.request.End(id)
+}
+
+// StartResponse blocks until it is time to receive (or, if this is a server, send)
+// the request with the given id.
+func (p *Pipeline) StartResponse(id uint) {
+	p.response.Start(id)
+}
+
+// EndResponse notifies p that the response with the given id has been received
+// (or, if this is a server, sent).
+func (p *Pipeline) EndResponse(id uint) {
+	p.response.End(id)
+}
+
+// A sequencer schedules a sequence of numbered events that must
+// happen in order, one after the other.  The event numbering must start
+// at 0 and increment without skipping.  The event number wraps around
+// safely as long as there are not 2^32 simultaneous events pending.
+type sequencer struct {
+	mu   sync.Mutex
+	id   uint
+	wait map[uint]chan uint
+}
+
+// Start waits until it is time for the event numbered id to begin.
+// That is, except for the first event, it waits until End(id-1) has
+// been called.
+func (s *sequencer) Start(id uint) {
+	s.mu.Lock()
+	if s.id == id {
+		s.mu.Unlock()
+		return
+	}
+	c := make(chan uint)
+	if s.wait == nil {
+		s.wait = make(map[uint]chan uint)
+	}
+	s.wait[id] = c
+	s.mu.Unlock()
+	<-c
+}
+
+// End notifies the sequencer that the event numbered id has completed,
+// allowing it to schedule the event numbered id+1.  It is a run-time error
+// to call End with an id that is not the number of the active event.
+func (s *sequencer) End(id uint) {
+	s.mu.Lock()
+	if s.id != id {
+		panic("out of sync")
+	}
+	id++
+	s.id = id
+	if s.wait == nil {
+		s.wait = make(map[uint]chan uint)
+	}
+	c, ok := s.wait[id]
+	if ok {
+		delete(s.wait, id)
+	}
+	s.mu.Unlock()
+	if ok {
+		c <- 1
+	}
+}
diff --git a/src/net/textproto/reader.go b/src/net/textproto/reader.go
new file mode 100644
index 000000000..eea9207f2
--- /dev/null
+++ b/src/net/textproto/reader.go
@@ -0,0 +1,637 @@
+// Copyright 2010 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package textproto
+
+import (
+	"bufio"
+	"bytes"
+	"io"
+	"io/ioutil"
+	"strconv"
+	"strings"
+)
+
+// BUG(rsc): To let callers manage exposure to denial of service
+// attacks, Reader should allow them to set and reset a limit on
+// the number of bytes read from the connection.
+
+// A Reader implements convenience methods for reading requests
+// or responses from a text protocol network connection.
+type Reader struct {
+	R   *bufio.Reader
+	dot *dotReader
+	buf []byte // a re-usable buffer for readContinuedLineSlice
+}
+
+// NewReader returns a new Reader reading from r.
+func NewReader(r *bufio.Reader) *Reader {
+	return &Reader{R: r}
+}
+
+// ReadLine reads a single line from r,
+// eliding the final \n or \r\n from the returned string.
+func (r *Reader) ReadLine() (string, error) {
+	line, err := r.readLineSlice()
+	return string(line), err
+}
+
+// ReadLineBytes is like ReadLine but returns a []byte instead of a string.
+func (r *Reader) ReadLineBytes() ([]byte, error) {
+	line, err := r.readLineSlice()
+	if line != nil {
+		buf := make([]byte, len(line))
+		copy(buf, line)
+		line = buf
+	}
+	return line, err
+}
+
+func (r *Reader) readLineSlice() ([]byte, error) {
+	r.closeDot()
+	var line []byte
+	for {
+		l, more, err := r.R.ReadLine()
+		if err != nil {
+			return nil, err
+		}
+		// Avoid the copy if the first call produced a full line.
+		if line == nil && !more {
+			return l, nil
+		}
+		line = append(line, l...)
+		if !more {
+			break
+		}
+	}
+	return line, nil
+}
+
+// ReadContinuedLine reads a possibly continued line from r,
+// eliding the final trailing ASCII white space.
+// Lines after the first are considered continuations if they
+// begin with a space or tab character.  In the returned data,
+// continuation lines are separated from the previous line
+// only by a single space: the newline and leading white space
+// are removed.
+//
+// For example, consider this input:
+//
+//	Line 1
+//	  continued...
+//	Line 2
+//
+// The first call to ReadContinuedLine will return "Line 1 continued..."
+// and the second will return "Line 2".
+//
+// A line consisting of only white space is never continued.
+//
+func (r *Reader) ReadContinuedLine() (string, error) {
+	line, err := r.readContinuedLineSlice()
+	return string(line), err
+}
+
+// trim returns s with leading and trailing spaces and tabs removed.
+// It does not assume Unicode or UTF-8.
+func trim(s []byte) []byte {
+	i := 0
+	for i < len(s) && (s[i] == ' ' || s[i] == '\t') {
+		i++
+	}
+	n := len(s)
+	for n > i && (s[n-1] == ' ' || s[n-1] == '\t') {
+		n--
+	}
+	return s[i:n]
+}
+
+// ReadContinuedLineBytes is like ReadContinuedLine but
+// returns a []byte instead of a string.
+func (r *Reader) ReadContinuedLineBytes() ([]byte, error) {
+	line, err := r.readContinuedLineSlice()
+	if line != nil {
+		buf := make([]byte, len(line))
+		copy(buf, line)
+		line = buf
+	}
+	return line, err
+}
+
+func (r *Reader) readContinuedLineSlice() ([]byte, error) {
+	// Read the first line.
+	line, err := r.readLineSlice()
+	if err != nil {
+		return nil, err
+	}
+	if len(line) == 0 { // blank line - no continuation
+		return line, nil
+	}
+
+	// Optimistically assume that we have started to buffer the next line
+	// and it starts with an ASCII letter (the next header key), so we can
+	// avoid copying that buffered data around in memory and skipping over
+	// non-existent whitespace.
+	if r.R.Buffered() > 1 {
+		peek, err := r.R.Peek(1)
+		if err == nil && isASCIILetter(peek[0]) {
+			return trim(line), nil
+		}
+	}
+
+	// ReadByte or the next readLineSlice will flush the read buffer;
+	// copy the slice into buf.
+	r.buf = append(r.buf[:0], trim(line)...)
+
+	// Read continuation lines.
+	for r.skipSpace() > 0 {
+		line, err := r.readLineSlice()
+		if err != nil {
+			break
+		}
+		r.buf = append(r.buf, ' ')
+		r.buf = append(r.buf, line...)
+	}
+	return r.buf, nil
+}
+
+// skipSpace skips R over all spaces and returns the number of bytes skipped.
+func (r *Reader) skipSpace() int {
+	n := 0
+	for {
+		c, err := r.R.ReadByte()
+		if err != nil {
+			// Bufio will keep err until next read.
+			break
+		}
+		if c != ' ' && c != '\t' {
+			r.R.UnreadByte()
+			break
+		}
+		n++
+	}
+	return n
+}
+
+func (r *Reader) readCodeLine(expectCode int) (code int, continued bool, message string, err error) {
+	line, err := r.ReadLine()
+	if err != nil {
+		return
+	}
+	return parseCodeLine(line, expectCode)
+}
+
+func parseCodeLine(line string, expectCode int) (code int, continued bool, message string, err error) {
+	if len(line) < 4 || line[3] != ' ' && line[3] != '-' {
+		err = ProtocolError("short response: " + line)
+		return
+	}
+	continued = line[3] == '-'
+	code, err = strconv.Atoi(line[0:3])
+	if err != nil || code < 100 {
+		err = ProtocolError("invalid response code: " + line)
+		return
+	}
+	message = line[4:]
+	if 1 <= expectCode && expectCode < 10 && code/100 != expectCode ||
+		10 <= expectCode && expectCode < 100 && code/10 != expectCode ||
+		100 <= expectCode && expectCode < 1000 && code != expectCode {
+		err = &Error{code, message}
+	}
+	return
+}
+
+// ReadCodeLine reads a response code line of the form
+//	code message
+// where code is a three-digit status code and the message
+// extends to the rest of the line.  An example of such a line is:
+//	220 plan9.bell-labs.com ESMTP
+//
+// If the prefix of the status does not match the digits in expectCode,
+// ReadCodeLine returns with err set to &Error{code, message}.
+// For example, if expectCode is 31, an error will be returned if
+// the status is not in the range [310,319].
+//
+// If the response is multi-line, ReadCodeLine returns an error.
+//
+// An expectCode <= 0 disables the check of the status code.
+//
+func (r *Reader) ReadCodeLine(expectCode int) (code int, message string, err error) {
+	code, continued, message, err := r.readCodeLine(expectCode)
+	if err == nil && continued {
+		err = ProtocolError("unexpected multi-line response: " + message)
+	}
+	return
+}
+
+// ReadResponse reads a multi-line response of the form:
+//
+//	code-message line 1
+//	code-message line 2
+//	...
+//	code message line n
+//
+// where code is a three-digit status code. The first line starts with the
+// code and a hyphen. The response is terminated by a line that starts
+// with the same code followed by a space. Each line in message is
+// separated by a newline (\n).
+//
+// See page 36 of RFC 959 (http://www.ietf.org/rfc/rfc959.txt) for
+// details.
+//
+// If the prefix of the status does not match the digits in expectCode,
+// ReadResponse returns with err set to &Error{code, message}.
+// For example, if expectCode is 31, an error will be returned if
+// the status is not in the range [310,319].
+//
+// An expectCode <= 0 disables the check of the status code.
+//
+func (r *Reader) ReadResponse(expectCode int) (code int, message string, err error) {
+	code, continued, message, err := r.readCodeLine(expectCode)
+	for err == nil && continued {
+		line, err := r.ReadLine()
+		if err != nil {
+			return 0, "", err
+		}
+
+		var code2 int
+		var moreMessage string
+		code2, continued, moreMessage, err = parseCodeLine(line, expectCode)
+		if err != nil || code2 != code {
+			message += "\n" + strings.TrimRight(line, "\r\n")
+			continued = true
+			continue
+		}
+		message += "\n" + moreMessage
+	}
+	return
+}
+
+// DotReader returns a new Reader that satisfies Reads using the
+// decoded text of a dot-encoded block read from r.
+// The returned Reader is only valid until the next call
+// to a method on r.
+//
+// Dot encoding is a common framing used for data blocks
+// in text protocols such as SMTP.  The data consists of a sequence
+// of lines, each of which ends in "\r\n".  The sequence itself
+// ends at a line containing just a dot: ".\r\n".  Lines beginning
+// with a dot are escaped with an additional dot to avoid
+// looking like the end of the sequence.
+//
+// The decoded form returned by the Reader's Read method
+// rewrites the "\r\n" line endings into the simpler "\n",
+// removes leading dot escapes if present, and stops with error io.EOF
+// after consuming (and discarding) the end-of-sequence line.
+func (r *Reader) DotReader() io.Reader {
+	r.closeDot()
+	r.dot = &dotReader{r: r}
+	return r.dot
+}
+
+type dotReader struct {
+	r     *Reader
+	state int
+}
+
+// Read satisfies reads by decoding dot-encoded data read from d.r.
+func (d *dotReader) Read(b []byte) (n int, err error) {
+	// Run data through a simple state machine to
+	// elide leading dots, rewrite trailing \r\n into \n,
+	// and detect ending .\r\n line.
+	const (
+		stateBeginLine = iota // beginning of line; initial state; must be zero
+		stateDot              // read . at beginning of line
+		stateDotCR            // read .\r at beginning of line
+		stateCR               // read \r (possibly at end of line)
+		stateData             // reading data in middle of line
+		stateEOF              // reached .\r\n end marker line
+	)
+	br := d.r.R
+	for n < len(b) && d.state != stateEOF {
+		var c byte
+		c, err = br.ReadByte()
+		if err != nil {
+			if err == io.EOF {
+				err = io.ErrUnexpectedEOF
+			}
+			break
+		}
+		switch d.state {
+		case stateBeginLine:
+			if c == '.' {
+				d.state = stateDot
+				continue
+			}
+			if c == '\r' {
+				d.state = stateCR
+				continue
+			}
+			d.state = stateData
+
+		case stateDot:
+			if c == '\r' {
+				d.state = stateDotCR
+				continue
+			}
+			if c == '\n' {
+				d.state = stateEOF
+				continue
+			}
+			d.state = stateData
+
+		case stateDotCR:
+			if c == '\n' {
+				d.state = stateEOF
+				continue
+			}
+			// Not part of .\r\n.
+			// Consume leading dot and emit saved \r.
+			br.UnreadByte()
+			c = '\r'
+			d.state = stateData
+
+		case stateCR:
+			if c == '\n' {
+				d.state = stateBeginLine
+				break
+			}
+			// Not part of \r\n.  Emit saved \r
+			br.UnreadByte()
+			c = '\r'
+			d.state = stateData
+
+		case stateData:
+			if c == '\r' {
+				d.state = stateCR
+				continue
+			}
+			if c == '\n' {
+				d.state = stateBeginLine
+			}
+		}
+		b[n] = c
+		n++
+	}
+	if err == nil && d.state == stateEOF {
+		err = io.EOF
+	}
+	if err != nil && d.r.dot == d {
+		d.r.dot = nil
+	}
+	return
+}
+
+// closeDot drains the current DotReader if any,
+// making sure that it reads until the ending dot line.
+func (r *Reader) closeDot() {
+	if r.dot == nil {
+		return
+	}
+	buf := make([]byte, 128)
+	for r.dot != nil {
+		// When Read reaches EOF or an error,
+		// it will set r.dot == nil.
+		r.dot.Read(buf)
+	}
+}
+
+// ReadDotBytes reads a dot-encoding and returns the decoded data.
+//
+// See the documentation for the DotReader method for details about dot-encoding.
+func (r *Reader) ReadDotBytes() ([]byte, error) {
+	return ioutil.ReadAll(r.DotReader())
+}
+
+// ReadDotLines reads a dot-encoding and returns a slice
+// containing the decoded lines, with the final \r\n or \n elided from each.
+//
+// See the documentation for the DotReader method for details about dot-encoding.
+func (r *Reader) ReadDotLines() ([]string, error) {
+	// We could use ReadDotBytes and then Split it,
+	// but reading a line at a time avoids needing a
+	// large contiguous block of memory and is simpler.
+	var v []string
+	var err error
+	for {
+		var line string
+		line, err = r.ReadLine()
+		if err != nil {
+			if err == io.EOF {
+				err = io.ErrUnexpectedEOF
+			}
+			break
+		}
+
+		// Dot by itself marks end; otherwise cut one dot.
+		if len(line) > 0 && line[0] == '.' {
+			if len(line) == 1 {
+				break
+			}
+			line = line[1:]
+		}
+		v = append(v, line)
+	}
+	return v, err
+}
+
+// ReadMIMEHeader reads a MIME-style header from r.
+// The header is a sequence of possibly continued Key: Value lines
+// ending in a blank line.
+// The returned map m maps CanonicalMIMEHeaderKey(key) to a
+// sequence of values in the same order encountered in the input.
+//
+// For example, consider this input:
+//
+//	My-Key: Value 1
+//	Long-Key: Even
+//	       Longer Value
+//	My-Key: Value 2
+//
+// Given that input, ReadMIMEHeader returns the map:
+//
+//	map[string][]string{
+//		"My-Key": {"Value 1", "Value 2"},
+//		"Long-Key": {"Even Longer Value"},
+//	}
+//
+func (r *Reader) ReadMIMEHeader() (MIMEHeader, error) {
+	// Avoid lots of small slice allocations later by allocating one
+	// large one ahead of time which we'll cut up into smaller
+	// slices. If this isn't big enough later, we allocate small ones.
+	var strs []string
+	hint := r.upcomingHeaderNewlines()
+	if hint > 0 {
+		strs = make([]string, hint)
+	}
+
+	m := make(MIMEHeader, hint)
+	for {
+		kv, err := r.readContinuedLineSlice()
+		if len(kv) == 0 {
+			return m, err
+		}
+
+		// Key ends at first colon; should not have spaces but
+		// they appear in the wild, violating specs, so we
+		// remove them if present.
+		i := bytes.IndexByte(kv, ':')
+		if i < 0 {
+			return m, ProtocolError("malformed MIME header line: " + string(kv))
+		}
+		endKey := i
+		for endKey > 0 && kv[endKey-1] == ' ' {
+			endKey--
+		}
+		key := canonicalMIMEHeaderKey(kv[:endKey])
+
+		// Skip initial spaces in value.
+		i++ // skip colon
+		for i < len(kv) && (kv[i] == ' ' || kv[i] == '\t') {
+			i++
+		}
+		value := string(kv[i:])
+
+		vv := m[key]
+		if vv == nil && len(strs) > 0 {
+			// More than likely this will be a single-element key.
+			// Most headers aren't multi-valued.
+			// Set the capacity on strs[0] to 1, so any future append
+			// won't extend the slice into the other strings.
+			vv, strs = strs[:1:1], strs[1:]
+			vv[0] = value
+			m[key] = vv
+		} else {
+			m[key] = append(vv, value)
+		}
+
+		if err != nil {
+			return m, err
+		}
+	}
+}
+
+// upcomingHeaderNewlines returns an approximation of the number of newlines
+// that will be in this header. If it gets confused, it returns 0.
+func (r *Reader) upcomingHeaderNewlines() (n int) {
+	// Try to determine the 'hint' size.
+	r.R.Peek(1) // force a buffer load if empty
+	s := r.R.Buffered()
+	if s == 0 {
+		return
+	}
+	peek, _ := r.R.Peek(s)
+	for len(peek) > 0 {
+		i := bytes.IndexByte(peek, '\n')
+		if i < 3 {
+			// Not present (-1) or found within the next few bytes,
+			// implying we're at the end ("\r\n\r\n" or "\n\n")
+			return
+		}
+		n++
+		peek = peek[i+1:]
+	}
+	return
+}
+
+// CanonicalMIMEHeaderKey returns the canonical format of the
+// MIME header key s.  The canonicalization converts the first
+// letter and any letter following a hyphen to upper case;
+// the rest are converted to lowercase.  For example, the
+// canonical key for "accept-encoding" is "Accept-Encoding".
+// MIME header keys are assumed to be ASCII only.
+func CanonicalMIMEHeaderKey(s string) string {
+	// Quick check for canonical encoding.
+	upper := true
+	for i := 0; i < len(s); i++ {
+		c := s[i]
+		if upper && 'a' <= c && c <= 'z' {
+			return canonicalMIMEHeaderKey([]byte(s))
+		}
+		if !upper && 'A' <= c && c <= 'Z' {
+			return canonicalMIMEHeaderKey([]byte(s))
+		}
+		upper = c == '-'
+	}
+	return s
+}
+
+const toLower = 'a' - 'A'
+
+// canonicalMIMEHeaderKey is like CanonicalMIMEHeaderKey but is
+// allowed to mutate the provided byte slice before returning the
+// string.
+func canonicalMIMEHeaderKey(a []byte) string {
+	upper := true
+	for i, c := range a {
+		// Canonicalize: first letter upper case
+		// and upper case after each dash.
+		// (Host, User-Agent, If-Modified-Since).
+		// MIME headers are ASCII only, so no Unicode issues.
+		if c == ' ' {
+			c = '-'
+		} else if upper && 'a' <= c && c <= 'z' {
+			c -= toLower
+		} else if !upper && 'A' <= c && c <= 'Z' {
+			c += toLower
+		}
+		a[i] = c
+		upper = c == '-' // for next time
+	}
+	// The compiler recognizes m[string(byteSlice)] as a special
+	// case, so a copy of a's bytes into a new string does not
+	// happen in this map lookup:
+	if v := commonHeader[string(a)]; v != "" {
+		return v
+	}
+	return string(a)
+}
+
+// commonHeader interns common header strings.
+var commonHeader = make(map[string]string)
+
+func init() {
+	for _, v := range []string{
+		"Accept",
+		"Accept-Charset",
+		"Accept-Encoding",
+		"Accept-Language",
+		"Accept-Ranges",
+		"Cache-Control",
+		"Cc",
+		"Connection",
+		"Content-Id",
+		"Content-Language",
+		"Content-Length",
+		"Content-Transfer-Encoding",
+		"Content-Type",
+		"Cookie",
+		"Date",
+		"Dkim-Signature",
+		"Etag",
+		"Expires",
+		"From",
+		"Host",
+		"If-Modified-Since",
+		"If-None-Match",
+		"In-Reply-To",
+		"Last-Modified",
+		"Location",
+		"Message-Id",
+		"Mime-Version",
+		"Pragma",
+		"Received",
+		"Return-Path",
+		"Server",
+		"Set-Cookie",
+		"Subject",
+		"To",
+		"User-Agent",
+		"Via",
+		"X-Forwarded-For",
+		"X-Imforwards",
+		"X-Powered-By",
+	} {
+		commonHeader[v] = v
+	}
+}
diff --git a/src/net/textproto/reader_test.go b/src/net/textproto/reader_test.go
new file mode 100644
index 000000000..cbc0ed183
--- /dev/null
+++ b/src/net/textproto/reader_test.go
@@ -0,0 +1,337 @@
+// Copyright 2010 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package textproto
+
+import (
+	"bufio"
+	"bytes"
+	"io"
+	"reflect"
+	"strings"
+	"testing"
+)
+
+type canonicalHeaderKeyTest struct {
+	in, out string
+}
+
+var canonicalHeaderKeyTests = []canonicalHeaderKeyTest{
+	{"a-b-c", "A-B-C"},
+	{"a-1-c", "A-1-C"},
+	{"User-Agent", "User-Agent"},
+	{"uSER-aGENT", "User-Agent"},
+	{"user-agent", "User-Agent"},
+	{"USER-AGENT", "User-Agent"},
+	{"üser-agenT", "üser-Agent"}, // non-ASCII unchanged
+
+	// This caused a panic due to mishandling of a space:
+	{"C Ontent-Transfer-Encoding", "C-Ontent-Transfer-Encoding"},
+	{"foo bar", "Foo-Bar"},
+}
+
+func TestCanonicalMIMEHeaderKey(t *testing.T) {
+	for _, tt := range canonicalHeaderKeyTests {
+		if s := CanonicalMIMEHeaderKey(tt.in); s != tt.out {
+			t.Errorf("CanonicalMIMEHeaderKey(%q) = %q, want %q", tt.in, s, tt.out)
+		}
+	}
+}
+
+func reader(s string) *Reader {
+	return NewReader(bufio.NewReader(strings.NewReader(s)))
+}
+
+func TestReadLine(t *testing.T) {
+	r := reader("line1\nline2\n")
+	s, err := r.ReadLine()
+	if s != "line1" || err != nil {
+		t.Fatalf("Line 1: %s, %v", s, err)
+	}
+	s, err = r.ReadLine()
+	if s != "line2" || err != nil {
+		t.Fatalf("Line 2: %s, %v", s, err)
+	}
+	s, err = r.ReadLine()
+	if s != "" || err != io.EOF {
+		t.Fatalf("EOF: %s, %v", s, err)
+	}
+}
+
+func TestReadContinuedLine(t *testing.T) {
+	r := reader("line1\nline\n 2\nline3\n")
+	s, err := r.ReadContinuedLine()
+	if s != "line1" || err != nil {
+		t.Fatalf("Line 1: %s, %v", s, err)
+	}
+	s, err = r.ReadContinuedLine()
+	if s != "line 2" || err != nil {
+		t.Fatalf("Line 2: %s, %v", s, err)
+	}
+	s, err = r.ReadContinuedLine()
+	if s != "line3" || err != nil {
+		t.Fatalf("Line 3: %s, %v", s, err)
+	}
+	s, err = r.ReadContinuedLine()
+	if s != "" || err != io.EOF {
+		t.Fatalf("EOF: %s, %v", s, err)
+	}
+}
+
+func TestReadCodeLine(t *testing.T) {
+	r := reader("123 hi\n234 bye\n345 no way\n")
+	code, msg, err := r.ReadCodeLine(0)
+	if code != 123 || msg != "hi" || err != nil {
+		t.Fatalf("Line 1: %d, %s, %v", code, msg, err)
+	}
+	code, msg, err = r.ReadCodeLine(23)
+	if code != 234 || msg != "bye" || err != nil {
+		t.Fatalf("Line 2: %d, %s, %v", code, msg, err)
+	}
+	code, msg, err = r.ReadCodeLine(346)
+	if code != 345 || msg != "no way" || err == nil {
+		t.Fatalf("Line 3: %d, %s, %v", code, msg, err)
+	}
+	if e, ok := err.(*Error); !ok || e.Code != code || e.Msg != msg {
+		t.Fatalf("Line 3: wrong error %v\n", err)
+	}
+	code, msg, err = r.ReadCodeLine(1)
+	if code != 0 || msg != "" || err != io.EOF {
+		t.Fatalf("EOF: %d, %s, %v", code, msg, err)
+	}
+}
+
+func TestReadDotLines(t *testing.T) {
+	r := reader("dotlines\r\n.foo\r\n..bar\n...baz\nquux\r\n\r\n.\r\nanother\n")
+	s, err := r.ReadDotLines()
+	want := []string{"dotlines", "foo", ".bar", "..baz", "quux", ""}
+	if !reflect.DeepEqual(s, want) || err != nil {
+		t.Fatalf("ReadDotLines: %v, %v", s, err)
+	}
+
+	s, err = r.ReadDotLines()
+	want = []string{"another"}
+	if !reflect.DeepEqual(s, want) || err != io.ErrUnexpectedEOF {
+		t.Fatalf("ReadDotLines2: %v, %v", s, err)
+	}
+}
+
+func TestReadDotBytes(t *testing.T) {
+	r := reader("dotlines\r\n.foo\r\n..bar\n...baz\nquux\r\n\r\n.\r\nanot.her\r\n")
+	b, err := r.ReadDotBytes()
+	want := []byte("dotlines\nfoo\n.bar\n..baz\nquux\n\n")
+	if !reflect.DeepEqual(b, want) || err != nil {
+		t.Fatalf("ReadDotBytes: %q, %v", b, err)
+	}
+
+	b, err = r.ReadDotBytes()
+	want = []byte("anot.her\n")
+	if !reflect.DeepEqual(b, want) || err != io.ErrUnexpectedEOF {
+		t.Fatalf("ReadDotBytes2: %q, %v", b, err)
+	}
+}
+
+func TestReadMIMEHeader(t *testing.T) {
+	r := reader("my-key: Value 1  \r\nLong-key: Even \n Longer Value\r\nmy-Key: Value 2\r\n\n")
+	m, err := r.ReadMIMEHeader()
+	want := MIMEHeader{
+		"My-Key":   {"Value 1", "Value 2"},
+		"Long-Key": {"Even Longer Value"},
+	}
+	if !reflect.DeepEqual(m, want) || err != nil {
+		t.Fatalf("ReadMIMEHeader: %v, %v; want %v", m, err, want)
+	}
+}
+
+func TestReadMIMEHeaderSingle(t *testing.T) {
+	r := reader("Foo: bar\n\n")
+	m, err := r.ReadMIMEHeader()
+	want := MIMEHeader{"Foo": {"bar"}}
+	if !reflect.DeepEqual(m, want) || err != nil {
+		t.Fatalf("ReadMIMEHeader: %v, %v; want %v", m, err, want)
+	}
+}
+
+func TestLargeReadMIMEHeader(t *testing.T) {
+	data := make([]byte, 16*1024)
+	for i := 0; i < len(data); i++ {
+		data[i] = 'x'
+	}
+	sdata := string(data)
+	r := reader("Cookie: " + sdata + "\r\n\n")
+	m, err := r.ReadMIMEHeader()
+	if err != nil {
+		t.Fatalf("ReadMIMEHeader: %v", err)
+	}
+	cookie := m.Get("Cookie")
+	if cookie != sdata {
+		t.Fatalf("ReadMIMEHeader: %v bytes, want %v bytes", len(cookie), len(sdata))
+	}
+}
+
+// Test that we read slightly-bogus MIME headers seen in the wild,
+// with spaces before colons, and spaces in keys.
+func TestReadMIMEHeaderNonCompliant(t *testing.T) {
+	// Invalid HTTP response header as sent by an Axis security
+	// camera: (this is handled by IE, Firefox, Chrome, curl, etc.)
+	r := reader("Foo: bar\r\n" +
+		"Content-Language: en\r\n" +
+		"SID : 0\r\n" +
+		"Audio Mode : None\r\n" +
+		"Privilege : 127\r\n\r\n")
+	m, err := r.ReadMIMEHeader()
+	want := MIMEHeader{
+		"Foo":              {"bar"},
+		"Content-Language": {"en"},
+		"Sid":              {"0"},
+		"Audio-Mode":       {"None"},
+		"Privilege":        {"127"},
+	}
+	if !reflect.DeepEqual(m, want) || err != nil {
+		t.Fatalf("ReadMIMEHeader =\n%v, %v; want:\n%v", m, err, want)
+	}
+}
+
+type readResponseTest struct {
+	in       string
+	inCode   int
+	wantCode int
+	wantMsg  string
+}
+
+var readResponseTests = []readResponseTest{
+	{"230-Anonymous access granted, restrictions apply\n" +
+		"Read the file README.txt,\n" +
+		"230  please",
+		23,
+		230,
+		"Anonymous access granted, restrictions apply\nRead the file README.txt,\n please",
+	},
+
+	{"230 Anonymous access granted, restrictions apply\n",
+		23,
+		230,
+		"Anonymous access granted, restrictions apply",
+	},
+
+	{"400-A\n400-B\n400 C",
+		4,
+		400,
+		"A\nB\nC",
+	},
+
+	{"400-A\r\n400-B\r\n400 C\r\n",
+		4,
+		400,
+		"A\nB\nC",
+	},
+}
+
+// See http://www.ietf.org/rfc/rfc959.txt page 36.
+func TestRFC959Lines(t *testing.T) {
+	for i, tt := range readResponseTests {
+		r := reader(tt.in + "\nFOLLOWING DATA")
+		code, msg, err := r.ReadResponse(tt.inCode)
+		if err != nil {
+			t.Errorf("#%d: ReadResponse: %v", i, err)
+			continue
+		}
+		if code != tt.wantCode {
+			t.Errorf("#%d: code=%d, want %d", i, code, tt.wantCode)
+		}
+		if msg != tt.wantMsg {
+			t.Errorf("#%d: msg=%q, want %q", i, msg, tt.wantMsg)
+		}
+	}
+}
+
+func TestCommonHeaders(t *testing.T) {
+	for h := range commonHeader {
+		if h != CanonicalMIMEHeaderKey(h) {
+			t.Errorf("Non-canonical header %q in commonHeader", h)
+		}
+	}
+	b := []byte("content-Length")
+	want := "Content-Length"
+	n := testing.AllocsPerRun(200, func() {
+		if x := canonicalMIMEHeaderKey(b); x != want {
+			t.Fatalf("canonicalMIMEHeaderKey(%q) = %q; want %q", b, x, want)
+		}
+	})
+	if n > 0 {
+		t.Errorf("canonicalMIMEHeaderKey allocs = %v; want 0", n)
+	}
+}
+
+var clientHeaders = strings.Replace(`Host: golang.org
+Connection: keep-alive
+Cache-Control: max-age=0
+Accept: application/xml,application/xhtml+xml,text/html;q=0.9,text/plain;q=0.8,image/png,*/*;q=0.5
+User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US) AppleWebKit/534.3 (KHTML, like Gecko) Chrome/6.0.472.63 Safari/534.3
+Accept-Encoding: gzip,deflate,sdch
+Accept-Language: en-US,en;q=0.8,fr-CH;q=0.6
+Accept-Charset: ISO-8859-1,utf-8;q=0.7,*;q=0.3
+COOKIE: __utma=000000000.0000000000.0000000000.0000000000.0000000000.00; __utmb=000000000.0.00.0000000000; __utmc=000000000; __utmz=000000000.0000000000.00.0.utmcsr=code.google.com|utmccn=(referral)|utmcmd=referral|utmcct=/p/go/issues/detail
+Non-Interned: test
+
+`, "\n", "\r\n", -1)
+
+var serverHeaders = strings.Replace(`Content-Type: text/html; charset=utf-8
+Content-Encoding: gzip
+Date: Thu, 27 Sep 2012 09:03:33 GMT
+Server: Google Frontend
+Cache-Control: private
+Content-Length: 2298
+VIA: 1.1 proxy.example.com:80 (XXX/n.n.n-nnn)
+Connection: Close
+Non-Interned: test
+
+`, "\n", "\r\n", -1)
+
+func BenchmarkReadMIMEHeader(b *testing.B) {
+	b.ReportAllocs()
+	var buf bytes.Buffer
+	br := bufio.NewReader(&buf)
+	r := NewReader(br)
+	for i := 0; i < b.N; i++ {
+		var want int
+		var find string
+		if (i & 1) == 1 {
+			buf.WriteString(clientHeaders)
+			want = 10
+			find = "Cookie"
+		} else {
+			buf.WriteString(serverHeaders)
+			want = 9
+			find = "Via"
+		}
+		h, err := r.ReadMIMEHeader()
+		if err != nil {
+			b.Fatal(err)
+		}
+		if len(h) != want {
+			b.Fatalf("wrong number of headers: got %d, want %d", len(h), want)
+		}
+		if _, ok := h[find]; !ok {
+			b.Fatalf("did not find key %s", find)
+		}
+	}
+}
+
+func BenchmarkUncommon(b *testing.B) {
+	b.ReportAllocs()
+	var buf bytes.Buffer
+	br := bufio.NewReader(&buf)
+	r := NewReader(br)
+	for i := 0; i < b.N; i++ {
+		buf.WriteString("uncommon-header-for-benchmark: foo\r\n\r\n")
+		h, err := r.ReadMIMEHeader()
+		if err != nil {
+			b.Fatal(err)
+		}
+		if _, ok := h["Uncommon-Header-For-Benchmark"]; !ok {
+			b.Fatal("Missing result header.")
+		}
+	}
+}
diff --git a/src/net/textproto/textproto.go b/src/net/textproto/textproto.go
new file mode 100644
index 000000000..026eb026b
--- /dev/null
+++ b/src/net/textproto/textproto.go
@@ -0,0 +1,154 @@
+// Copyright 2010 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package textproto implements generic support for text-based request/response
+// protocols in the style of HTTP, NNTP, and SMTP.
+//
+// The package provides:
+//
+// Error, which represents a numeric error response from
+// a server.
+//
+// Pipeline, to manage pipelined requests and responses
+// in a client.
+//
+// Reader, to read numeric response code lines,
+// key: value headers, lines wrapped with leading spaces
+// on continuation lines, and whole text blocks ending
+// with a dot on a line by itself.
+//
+// Writer, to write dot-encoded text blocks.
+//
+// Conn, a convenient packaging of Reader, Writer, and Pipeline for use
+// with a single network connection.
+//
+package textproto
+
+import (
+	"bufio"
+	"fmt"
+	"io"
+	"net"
+)
+
+// An Error represents a numeric error response from a server.
+type Error struct {
+	Code int
+	Msg  string
+}
+
+func (e *Error) Error() string {
+	return fmt.Sprintf("%03d %s", e.Code, e.Msg)
+}
+
+// A ProtocolError describes a protocol violation such
+// as an invalid response or a hung-up connection.
+type ProtocolError string
+
+func (p ProtocolError) Error() string {
+	return string(p)
+}
+
+// A Conn represents a textual network protocol connection.
+// It consists of a Reader and Writer to manage I/O
+// and a Pipeline to sequence concurrent requests on the connection.
+// These embedded types carry methods with them;
+// see the documentation of those types for details.
+type Conn struct {
+	Reader
+	Writer
+	Pipeline
+	conn io.ReadWriteCloser
+}
+
+// NewConn returns a new Conn using conn for I/O.
+func NewConn(conn io.ReadWriteCloser) *Conn {
+	return &Conn{
+		Reader: Reader{R: bufio.NewReader(conn)},
+		Writer: Writer{W: bufio.NewWriter(conn)},
+		conn:   conn,
+	}
+}
+
+// Close closes the connection.
+func (c *Conn) Close() error {
+	return c.conn.Close()
+}
+
+// Dial connects to the given address on the given network using net.Dial
+// and then returns a new Conn for the connection.
+func Dial(network, addr string) (*Conn, error) {
+	c, err := net.Dial(network, addr)
+	if err != nil {
+		return nil, err
+	}
+	return NewConn(c), nil
+}
+
+// Cmd is a convenience method that sends a command after
+// waiting its turn in the pipeline.  The command text is the
+// result of formatting format with args and appending \r\n.
+// Cmd returns the id of the command, for use with StartResponse and EndResponse.
+//
+// For example, a client might run a HELP command that returns a dot-body
+// by using:
+//
+//	id, err := c.Cmd("HELP")
+//	if err != nil {
+//		return nil, err
+//	}
+//
+//	c.StartResponse(id)
+//	defer c.EndResponse(id)
+//
+//	if _, _, err = c.ReadCodeLine(110); err != nil {
+//		return nil, err
+//	}
+//	text, err := c.ReadDotBytes()
+//	if err != nil {
+//		return nil, err
+//	}
+//	return c.ReadCodeLine(250)
+//
+func (c *Conn) Cmd(format string, args ...interface{}) (id uint, err error) {
+	id = c.Next()
+	c.StartRequest(id)
+	err = c.PrintfLine(format, args...)
+	c.EndRequest(id)
+	if err != nil {
+		return 0, err
+	}
+	return id, nil
+}
+
+// TrimString returns s without leading and trailing ASCII space.
+func TrimString(s string) string {
+	for len(s) > 0 && isASCIISpace(s[0]) {
+		s = s[1:]
+	}
+	for len(s) > 0 && isASCIISpace(s[len(s)-1]) {
+		s = s[:len(s)-1]
+	}
+	return s
+}
+
+// TrimBytes returns b without leading and trailing ASCII space.
+func TrimBytes(b []byte) []byte {
+	for len(b) > 0 && isASCIISpace(b[0]) {
+		b = b[1:]
+	}
+	for len(b) > 0 && isASCIISpace(b[len(b)-1]) {
+		b = b[:len(b)-1]
+	}
+	return b
+}
+
+func isASCIISpace(b byte) bool {
+	return b == ' ' || b == '\t' || b == '\n' || b == '\r'
+}
+
+func isASCIILetter(b byte) bool {
+	b |= 0x20 // make lower case
+	return 'a' <= b && b <= 'z'
+}
diff --git a/src/net/textproto/writer.go b/src/net/textproto/writer.go
new file mode 100644
index 000000000..03e2fd658
--- /dev/null
+++ b/src/net/textproto/writer.go
@@ -0,0 +1,118 @@
+// Copyright 2010 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package textproto
+
+import (
+	"bufio"
+	"fmt"
+	"io"
+)
+
+// A Writer implements convenience methods for writing
+// requests or responses to a text protocol network connection.
+type Writer struct {
+	W   *bufio.Writer
+	dot *dotWriter
+}
+
+// NewWriter returns a new Writer writing to w.
+func NewWriter(w *bufio.Writer) *Writer {
+	return &Writer{W: w}
+}
+
+var crnl = []byte{'\r', '\n'}
+var dotcrnl = []byte{'.', '\r', '\n'}
+
+// PrintfLine writes the formatted output followed by \r\n.
+func (w *Writer) PrintfLine(format string, args ...interface{}) error {
+	w.closeDot()
+	fmt.Fprintf(w.W, format, args...)
+	w.W.Write(crnl)
+	return w.W.Flush()
+}
+
+// DotWriter returns a writer that can be used to write a dot-encoding to w.
+// It takes care of inserting leading dots when necessary,
+// translating line-ending \n into \r\n, and adding the final .\r\n line
+// when the DotWriter is closed.  The caller should close the
+// DotWriter before the next call to a method on w.
+//
+// See the documentation for Reader's DotReader method for details about dot-encoding.
+func (w *Writer) DotWriter() io.WriteCloser {
+	w.closeDot()
+	w.dot = &dotWriter{w: w}
+	return w.dot
+}
+
+func (w *Writer) closeDot() {
+	if w.dot != nil {
+		w.dot.Close() // sets w.dot = nil
+	}
+}
+
+type dotWriter struct {
+	w     *Writer
+	state int
+}
+
+const (
+	wstateBeginLine = iota // beginning of line; initial state; must be zero
+	wstateCR               // wrote \r (possibly at end of line)
+	wstateData             // writing data in middle of line
+)
+
+func (d *dotWriter) Write(b []byte) (n int, err error) {
+	bw := d.w.W
+	for n < len(b) {
+		c := b[n]
+		switch d.state {
+		case wstateBeginLine:
+			d.state = wstateData
+			if c == '.' {
+				// escape leading dot
+				bw.WriteByte('.')
+			}
+			fallthrough
+
+		case wstateData:
+			if c == '\r' {
+				d.state = wstateCR
+			}
+			if c == '\n' {
+				bw.WriteByte('\r')
+				d.state = wstateBeginLine
+			}
+
+		case wstateCR:
+			d.state = wstateData
+			if c == '\n' {
+				d.state = wstateBeginLine
+			}
+		}
+		if err = bw.WriteByte(c); err != nil {
+			break
+		}
+		n++
+	}
+	return
+}
+
+func (d *dotWriter) Close() error {
+	if d.w.dot == d {
+		d.w.dot = nil
+	}
+	bw := d.w.W
+	switch d.state {
+	default:
+		bw.WriteByte('\r')
+		fallthrough
+	case wstateCR:
+		bw.WriteByte('\n')
+		fallthrough
+	case wstateBeginLine:
+		bw.Write(dotcrnl)
+	}
+	return bw.Flush()
+}
diff --git a/src/net/textproto/writer_test.go b/src/net/textproto/writer_test.go
new file mode 100644
index 000000000..e03ab5e15
--- /dev/null
+++ b/src/net/textproto/writer_test.go
@@ -0,0 +1,35 @@
+// Copyright 2010 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package textproto
+
+import (
+	"bufio"
+	"bytes"
+	"testing"
+)
+
+func TestPrintfLine(t *testing.T) {
+	var buf bytes.Buffer
+	w := NewWriter(bufio.NewWriter(&buf))
+	err := w.PrintfLine("foo %d", 123)
+	if s := buf.String(); s != "foo 123\r\n" || err != nil {
+		t.Fatalf("s=%q; err=%s", s, err)
+	}
+}
+
+func TestDotWriter(t *testing.T) {
+	var buf bytes.Buffer
+	w := NewWriter(bufio.NewWriter(&buf))
+	d := w.DotWriter()
+	n, err := d.Write([]byte("abc\n.def\n..ghi\n.jkl\n."))
+	if n != 21 || err != nil {
+		t.Fatalf("Write: %d, %s", n, err)
+	}
+	d.Close()
+	want := "abc\r\n..def\r\n...ghi\r\n..jkl\r\n..\r\n.\r\n"
+	if s := buf.String(); s != want {
+		t.Fatalf("wrote %q", s)
+	}
+}
diff --git a/src/net/timeout_test.go b/src/net/timeout_test.go
new file mode 100644
index 000000000..9ef0c4d15
--- /dev/null
+++ b/src/net/timeout_test.go
@@ -0,0 +1,747 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package net
+
+import (
+	"fmt"
+	"io"
+	"io/ioutil"
+	"runtime"
+	"testing"
+	"time"
+)
+
+func isTimeout(err error) bool {
+	e, ok := err.(Error)
+	return ok && e.Timeout()
+}
+
+type copyRes struct {
+	n   int64
+	err error
+	d   time.Duration
+}
+
+func TestAcceptTimeout(t *testing.T) {
+	switch runtime.GOOS {
+	case "plan9":
+		t.Skipf("skipping test on %q", runtime.GOOS)
+	}
+
+	ln := newLocalListener(t).(*TCPListener)
+	defer ln.Close()
+	ln.SetDeadline(time.Now().Add(-1 * time.Second))
+	if _, err := ln.Accept(); !isTimeout(err) {
+		t.Fatalf("Accept: expected err %v, got %v", errTimeout, err)
+	}
+	if _, err := ln.Accept(); !isTimeout(err) {
+		t.Fatalf("Accept: expected err %v, got %v", errTimeout, err)
+	}
+	ln.SetDeadline(time.Now().Add(100 * time.Millisecond))
+	if _, err := ln.Accept(); !isTimeout(err) {
+		t.Fatalf("Accept: expected err %v, got %v", errTimeout, err)
+	}
+	if _, err := ln.Accept(); !isTimeout(err) {
+		t.Fatalf("Accept: expected err %v, got %v", errTimeout, err)
+	}
+	ln.SetDeadline(noDeadline)
+	errc := make(chan error)
+	go func() {
+		_, err := ln.Accept()
+		errc <- err
+	}()
+	time.Sleep(100 * time.Millisecond)
+	select {
+	case err := <-errc:
+		t.Fatalf("Expected Accept() to not return, but it returned with %v\n", err)
+	default:
+	}
+	ln.Close()
+	switch nerr := <-errc; err := nerr.(type) {
+	case *OpError:
+		if err.Err != errClosing {
+			t.Fatalf("Accept: expected err %v, got %v", errClosing, err)
+		}
+	default:
+		if err != errClosing {
+			t.Fatalf("Accept: expected err %v, got %v", errClosing, err)
+		}
+	}
+}
+
+func TestReadTimeout(t *testing.T) {
+	switch runtime.GOOS {
+	case "plan9":
+		t.Skipf("skipping test on %q", runtime.GOOS)
+	}
+
+	ln := newLocalListener(t)
+	defer ln.Close()
+	c, err := DialTCP("tcp", nil, ln.Addr().(*TCPAddr))
+	if err != nil {
+		t.Fatalf("Connect: %v", err)
+	}
+	defer c.Close()
+	c.SetDeadline(time.Now().Add(time.Hour))
+	c.SetReadDeadline(time.Now().Add(-1 * time.Second))
+	buf := make([]byte, 1)
+	if _, err = c.Read(buf); !isTimeout(err) {
+		t.Fatalf("Read: expected err %v, got %v", errTimeout, err)
+	}
+	if _, err = c.Read(buf); !isTimeout(err) {
+		t.Fatalf("Read: expected err %v, got %v", errTimeout, err)
+	}
+	c.SetDeadline(time.Now().Add(100 * time.Millisecond))
+	if _, err = c.Read(buf); !isTimeout(err) {
+		t.Fatalf("Read: expected err %v, got %v", errTimeout, err)
+	}
+	if _, err = c.Read(buf); !isTimeout(err) {
+		t.Fatalf("Read: expected err %v, got %v", errTimeout, err)
+	}
+	c.SetReadDeadline(noDeadline)
+	c.SetWriteDeadline(time.Now().Add(-1 * time.Second))
+	errc := make(chan error)
+	go func() {
+		_, err := c.Read(buf)
+		errc <- err
+	}()
+	time.Sleep(100 * time.Millisecond)
+	select {
+	case err := <-errc:
+		t.Fatalf("Expected Read() to not return, but it returned with %v\n", err)
+	default:
+	}
+	c.Close()
+	switch nerr := <-errc; err := nerr.(type) {
+	case *OpError:
+		if err.Err != errClosing {
+			t.Fatalf("Read: expected err %v, got %v", errClosing, err)
+		}
+	default:
+		if err == io.EOF && runtime.GOOS == "nacl" { // close enough; golang.org/issue/8044
+			break
+		}
+		if err != errClosing {
+			t.Fatalf("Read: expected err %v, got %v", errClosing, err)
+		}
+	}
+}
+
+func TestWriteTimeout(t *testing.T) {
+	switch runtime.GOOS {
+	case "plan9":
+		t.Skipf("skipping test on %q", runtime.GOOS)
+	}
+
+	ln := newLocalListener(t)
+	defer ln.Close()
+	c, err := DialTCP("tcp", nil, ln.Addr().(*TCPAddr))
+	if err != nil {
+		t.Fatalf("Connect: %v", err)
+	}
+	defer c.Close()
+	c.SetDeadline(time.Now().Add(time.Hour))
+	c.SetWriteDeadline(time.Now().Add(-1 * time.Second))
+	buf := make([]byte, 4096)
+	writeUntilTimeout := func() {
+		for {
+			_, err := c.Write(buf)
+			if err != nil {
+				if isTimeout(err) {
+					return
+				}
+				t.Fatalf("Write: expected err %v, got %v", errTimeout, err)
+			}
+		}
+	}
+	writeUntilTimeout()
+	c.SetDeadline(time.Now().Add(10 * time.Millisecond))
+	writeUntilTimeout()
+	writeUntilTimeout()
+	c.SetWriteDeadline(noDeadline)
+	c.SetReadDeadline(time.Now().Add(-1 * time.Second))
+	errc := make(chan error)
+	go func() {
+		for {
+			_, err := c.Write(buf)
+			if err != nil {
+				errc <- err
+			}
+		}
+	}()
+	time.Sleep(100 * time.Millisecond)
+	select {
+	case err := <-errc:
+		t.Fatalf("Expected Write() to not return, but it returned with %v\n", err)
+	default:
+	}
+	c.Close()
+	switch nerr := <-errc; err := nerr.(type) {
+	case *OpError:
+		if err.Err != errClosing {
+			t.Fatalf("Write: expected err %v, got %v", errClosing, err)
+		}
+	default:
+		if err != errClosing {
+			t.Fatalf("Write: expected err %v, got %v", errClosing, err)
+		}
+	}
+}
+
+func testTimeout(t *testing.T, net, addr string, readFrom bool) {
+	c, err := Dial(net, addr)
+	if err != nil {
+		t.Errorf("Dial(%q, %q) failed: %v", net, addr, err)
+		return
+	}
+	defer c.Close()
+	what := "Read"
+	if readFrom {
+		what = "ReadFrom"
+	}
+
+	errc := make(chan error, 1)
+	go func() {
+		t0 := time.Now()
+		c.SetReadDeadline(time.Now().Add(100 * time.Millisecond))
+		var b [100]byte
+		var n int
+		var err error
+		if readFrom {
+			n, _, err = c.(PacketConn).ReadFrom(b[0:])
+		} else {
+			n, err = c.Read(b[0:])
+		}
+		t1 := time.Now()
+		if n != 0 || err == nil || !err.(Error).Timeout() {
+			errc <- fmt.Errorf("%s(%q, %q) did not return 0, timeout: %v, %v", what, net, addr, n, err)
+			return
+		}
+		if dt := t1.Sub(t0); dt < 50*time.Millisecond || !testing.Short() && dt > 250*time.Millisecond {
+			errc <- fmt.Errorf("%s(%q, %q) took %s, expected 0.1s", what, net, addr, dt)
+			return
+		}
+		errc <- nil
+	}()
+	select {
+	case err := <-errc:
+		if err != nil {
+			t.Error(err)
+		}
+	case <-time.After(1 * time.Second):
+		t.Errorf("%s(%q, %q) took over 1 second, expected 0.1s", what, net, addr)
+	}
+}
+
+func TestTimeoutUDP(t *testing.T) {
+	switch runtime.GOOS {
+	case "plan9":
+		t.Skipf("skipping test on %q", runtime.GOOS)
+	}
+
+	// set up a listener that won't talk back
+	listening := make(chan string)
+	done := make(chan int)
+	go runDatagramPacketConnServer(t, "udp", "127.0.0.1:0", listening, done)
+	addr := <-listening
+
+	testTimeout(t, "udp", addr, false)
+	testTimeout(t, "udp", addr, true)
+	<-done
+}
+
+func TestTimeoutTCP(t *testing.T) {
+	switch runtime.GOOS {
+	case "plan9":
+		t.Skipf("skipping test on %q", runtime.GOOS)
+	}
+
+	// set up a listener that won't talk back
+	listening := make(chan string)
+	done := make(chan int)
+	go runStreamConnServer(t, "tcp", "127.0.0.1:0", listening, done)
+	addr := <-listening
+
+	testTimeout(t, "tcp", addr, false)
+	<-done
+}
+
+func TestDeadlineReset(t *testing.T) {
+	switch runtime.GOOS {
+	case "plan9":
+		t.Skipf("skipping test on %q", runtime.GOOS)
+	}
+	ln, err := Listen("tcp", "127.0.0.1:0")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer ln.Close()
+	tl := ln.(*TCPListener)
+	tl.SetDeadline(time.Now().Add(1 * time.Minute))
+	tl.SetDeadline(noDeadline) // reset it
+	errc := make(chan error, 1)
+	go func() {
+		_, err := ln.Accept()
+		errc <- err
+	}()
+	select {
+	case <-time.After(50 * time.Millisecond):
+		// Pass.
+	case err := <-errc:
+		// Accept should never return; we never
+		// connected to it.
+		t.Errorf("unexpected return from Accept; err=%v", err)
+	}
+}
+
+func TestTimeoutAccept(t *testing.T) {
+	switch runtime.GOOS {
+	case "plan9":
+		t.Skipf("skipping test on %q", runtime.GOOS)
+	}
+	ln, err := Listen("tcp", "127.0.0.1:0")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer ln.Close()
+	tl := ln.(*TCPListener)
+	tl.SetDeadline(time.Now().Add(100 * time.Millisecond))
+	errc := make(chan error, 1)
+	go func() {
+		_, err := ln.Accept()
+		errc <- err
+	}()
+	select {
+	case <-time.After(1 * time.Second):
+		// Accept shouldn't block indefinitely
+		t.Errorf("Accept didn't return in an expected time")
+	case <-errc:
+		// Pass.
+	}
+}
+
+func TestReadWriteDeadline(t *testing.T) {
+	switch runtime.GOOS {
+	case "plan9":
+		t.Skipf("skipping test on %q", runtime.GOOS)
+	}
+
+	const (
+		readTimeout  = 50 * time.Millisecond
+		writeTimeout = 250 * time.Millisecond
+	)
+	checkTimeout := func(command string, start time.Time, should time.Duration) {
+		is := time.Now().Sub(start)
+		d := is - should
+		if d < -30*time.Millisecond || !testing.Short() && 150*time.Millisecond < d {
+			t.Errorf("%s timeout test failed: is=%v should=%v\n", command, is, should)
+		}
+	}
+
+	ln, err := Listen("tcp", "127.0.0.1:0")
+	if err != nil {
+		t.Fatalf("ListenTCP on :0: %v", err)
+	}
+	defer ln.Close()
+
+	lnquit := make(chan bool)
+
+	go func() {
+		c, err := ln.Accept()
+		if err != nil {
+			t.Errorf("Accept: %v", err)
+			return
+		}
+		defer c.Close()
+		lnquit <- true
+	}()
+
+	c, err := Dial("tcp", ln.Addr().String())
+	if err != nil {
+		t.Fatalf("Dial: %v", err)
+	}
+	defer c.Close()
+
+	start := time.Now()
+	err = c.SetReadDeadline(start.Add(readTimeout))
+	if err != nil {
+		t.Fatalf("SetReadDeadline: %v", err)
+	}
+	err = c.SetWriteDeadline(start.Add(writeTimeout))
+	if err != nil {
+		t.Fatalf("SetWriteDeadline: %v", err)
+	}
+
+	quit := make(chan bool)
+
+	go func() {
+		var buf [10]byte
+		_, err := c.Read(buf[:])
+		if err == nil {
+			t.Errorf("Read should not succeed")
+		}
+		checkTimeout("Read", start, readTimeout)
+		quit <- true
+	}()
+
+	go func() {
+		var buf [10000]byte
+		for {
+			_, err := c.Write(buf[:])
+			if err != nil {
+				break
+			}
+		}
+		checkTimeout("Write", start, writeTimeout)
+		quit <- true
+	}()
+
+	<-quit
+	<-quit
+	<-lnquit
+}
+
+type neverEnding byte
+
+func (b neverEnding) Read(p []byte) (n int, err error) {
+	for i := range p {
+		p[i] = byte(b)
+	}
+	return len(p), nil
+}
+
+func TestVariousDeadlines1Proc(t *testing.T) {
+	testVariousDeadlines(t, 1)
+}
+
+func TestVariousDeadlines4Proc(t *testing.T) {
+	testVariousDeadlines(t, 4)
+}
+
+func testVariousDeadlines(t *testing.T, maxProcs int) {
+	switch runtime.GOOS {
+	case "plan9":
+		t.Skipf("skipping test on %q", runtime.GOOS)
+	}
+
+	defer runtime.GOMAXPROCS(runtime.GOMAXPROCS(maxProcs))
+	ln := newLocalListener(t)
+	defer ln.Close()
+	acceptc := make(chan error, 1)
+
+	// The server, with no timeouts of its own, sending bytes to clients
+	// as fast as it can.
+	servec := make(chan copyRes)
+	go func() {
+		for {
+			c, err := ln.Accept()
+			if err != nil {
+				acceptc <- err
+				return
+			}
+			go func() {
+				t0 := time.Now()
+				n, err := io.Copy(c, neverEnding('a'))
+				d := time.Since(t0)
+				c.Close()
+				servec <- copyRes{n, err, d}
+			}()
+		}
+	}()
+
+	for _, timeout := range []time.Duration{
+		1 * time.Nanosecond,
+		2 * time.Nanosecond,
+		5 * time.Nanosecond,
+		50 * time.Nanosecond,
+		100 * time.Nanosecond,
+		200 * time.Nanosecond,
+		500 * time.Nanosecond,
+		750 * time.Nanosecond,
+		1 * time.Microsecond,
+		5 * time.Microsecond,
+		25 * time.Microsecond,
+		250 * time.Microsecond,
+		500 * time.Microsecond,
+		1 * time.Millisecond,
+		5 * time.Millisecond,
+		100 * time.Millisecond,
+		250 * time.Millisecond,
+		500 * time.Millisecond,
+		1 * time.Second,
+	} {
+		numRuns := 3
+		if testing.Short() {
+			numRuns = 1
+			if timeout > 500*time.Microsecond {
+				continue
+			}
+		}
+		for run := 0; run < numRuns; run++ {
+			name := fmt.Sprintf("%v run %d/%d", timeout, run+1, numRuns)
+			t.Log(name)
+
+			c, err := Dial("tcp", ln.Addr().String())
+			if err != nil {
+				t.Fatalf("Dial: %v", err)
+			}
+			clientc := make(chan copyRes)
+			go func() {
+				t0 := time.Now()
+				c.SetDeadline(t0.Add(timeout))
+				n, err := io.Copy(ioutil.Discard, c)
+				d := time.Since(t0)
+				c.Close()
+				clientc <- copyRes{n, err, d}
+			}()
+
+			tooLong := 5 * time.Second
+			select {
+			case res := <-clientc:
+				if isTimeout(res.err) {
+					t.Logf("for %v, good client timeout after %v, reading %d bytes", name, res.d, res.n)
+				} else {
+					t.Fatalf("for %v: client Copy = %d, %v (want timeout)", name, res.n, res.err)
+				}
+			case <-time.After(tooLong):
+				t.Fatalf("for %v: timeout (%v) waiting for client to timeout (%v) reading", name, tooLong, timeout)
+			}
+
+			select {
+			case res := <-servec:
+				t.Logf("for %v: server in %v wrote %d, %v", name, res.d, res.n, res.err)
+			case err := <-acceptc:
+				t.Fatalf("for %v: server Accept = %v", name, err)
+			case <-time.After(tooLong):
+				t.Fatalf("for %v, timeout waiting for server to finish writing", name)
+			}
+		}
+	}
+}
+
+// TestReadDeadlineDataAvailable tests that read deadlines work, even
+// if there's data ready to be read.
+func TestReadDeadlineDataAvailable(t *testing.T) {
+	switch runtime.GOOS {
+	case "plan9":
+		t.Skipf("skipping test on %q", runtime.GOOS)
+	}
+
+	ln := newLocalListener(t)
+	defer ln.Close()
+
+	servec := make(chan copyRes)
+	const msg = "data client shouldn't read, even though it'll be waiting"
+	go func() {
+		c, err := ln.Accept()
+		if err != nil {
+			t.Errorf("Accept: %v", err)
+			return
+		}
+		defer c.Close()
+		n, err := c.Write([]byte(msg))
+		servec <- copyRes{n: int64(n), err: err}
+	}()
+
+	c, err := Dial("tcp", ln.Addr().String())
+	if err != nil {
+		t.Fatalf("Dial: %v", err)
+	}
+	defer c.Close()
+	if res := <-servec; res.err != nil || res.n != int64(len(msg)) {
+		t.Fatalf("unexpected server Write: n=%d, err=%v; want n=%d, err=nil", res.n, res.err, len(msg))
+	}
+	c.SetReadDeadline(time.Now().Add(-5 * time.Second)) // in the psat.
+	buf := make([]byte, len(msg)/2)
+	n, err := c.Read(buf)
+	if n > 0 || !isTimeout(err) {
+		t.Fatalf("client read = %d (%q) err=%v; want 0, timeout", n, buf[:n], err)
+	}
+}
+
+// TestWriteDeadlineBufferAvailable tests that write deadlines work, even
+// if there's buffer space available to write.
+func TestWriteDeadlineBufferAvailable(t *testing.T) {
+	switch runtime.GOOS {
+	case "plan9":
+		t.Skipf("skipping test on %q", runtime.GOOS)
+	}
+
+	ln := newLocalListener(t)
+	defer ln.Close()
+
+	servec := make(chan copyRes)
+	go func() {
+		c, err := ln.Accept()
+		if err != nil {
+			t.Errorf("Accept: %v", err)
+			return
+		}
+		defer c.Close()
+		c.SetWriteDeadline(time.Now().Add(-5 * time.Second)) // in the past
+		n, err := c.Write([]byte{'x'})
+		servec <- copyRes{n: int64(n), err: err}
+	}()
+
+	c, err := Dial("tcp", ln.Addr().String())
+	if err != nil {
+		t.Fatalf("Dial: %v", err)
+	}
+	defer c.Close()
+	res := <-servec
+	if res.n != 0 {
+		t.Errorf("Write = %d; want 0", res.n)
+	}
+	if !isTimeout(res.err) {
+		t.Errorf("Write error = %v; want timeout", res.err)
+	}
+}
+
+// TestAcceptDeadlineConnectionAvailable tests that accept deadlines work, even
+// if there's incoming connections available.
+func TestAcceptDeadlineConnectionAvailable(t *testing.T) {
+	switch runtime.GOOS {
+	case "plan9":
+		t.Skipf("skipping test on %q", runtime.GOOS)
+	}
+
+	ln := newLocalListener(t).(*TCPListener)
+	defer ln.Close()
+
+	go func() {
+		c, err := Dial("tcp", ln.Addr().String())
+		if err != nil {
+			t.Errorf("Dial: %v", err)
+			return
+		}
+		defer c.Close()
+		var buf [1]byte
+		c.Read(buf[:]) // block until the connection or listener is closed
+	}()
+	time.Sleep(10 * time.Millisecond)
+	ln.SetDeadline(time.Now().Add(-5 * time.Second)) // in the past
+	c, err := ln.Accept()
+	if err == nil {
+		defer c.Close()
+	}
+	if !isTimeout(err) {
+		t.Fatalf("Accept: got %v; want timeout", err)
+	}
+}
+
+// TestConnectDeadlineInThePast tests that connect deadlines work, even
+// if the connection can be established w/o blocking.
+func TestConnectDeadlineInThePast(t *testing.T) {
+	switch runtime.GOOS {
+	case "plan9":
+		t.Skipf("skipping test on %q", runtime.GOOS)
+	}
+
+	ln := newLocalListener(t).(*TCPListener)
+	defer ln.Close()
+
+	go func() {
+		c, err := ln.Accept()
+		if err == nil {
+			defer c.Close()
+		}
+	}()
+	time.Sleep(10 * time.Millisecond)
+	c, err := DialTimeout("tcp", ln.Addr().String(), -5*time.Second) // in the past
+	if err == nil {
+		defer c.Close()
+	}
+	if !isTimeout(err) {
+		t.Fatalf("DialTimeout: got %v; want timeout", err)
+	}
+}
+
+// TestProlongTimeout tests concurrent deadline modification.
+// Known to cause data races in the past.
+func TestProlongTimeout(t *testing.T) {
+	switch runtime.GOOS {
+	case "plan9":
+		t.Skipf("skipping test on %q", runtime.GOOS)
+	}
+
+	ln := newLocalListener(t)
+	defer ln.Close()
+	connected := make(chan bool)
+	go func() {
+		s, err := ln.Accept()
+		connected <- true
+		if err != nil {
+			t.Errorf("ln.Accept: %v", err)
+			return
+		}
+		defer s.Close()
+		s.SetDeadline(time.Now().Add(time.Hour))
+		go func() {
+			var buf [4096]byte
+			for {
+				_, err := s.Write(buf[:])
+				if err != nil {
+					break
+				}
+				s.SetDeadline(time.Now().Add(time.Hour))
+			}
+		}()
+		buf := make([]byte, 1)
+		for {
+			_, err := s.Read(buf)
+			if err != nil {
+				break
+			}
+			s.SetDeadline(time.Now().Add(time.Hour))
+		}
+	}()
+	c, err := Dial("tcp", ln.Addr().String())
+	if err != nil {
+		t.Fatalf("DialTCP: %v", err)
+	}
+	defer c.Close()
+	<-connected
+	for i := 0; i < 1024; i++ {
+		var buf [1]byte
+		c.Write(buf[:])
+	}
+}
+
+func TestDeadlineRace(t *testing.T) {
+	switch runtime.GOOS {
+	case "nacl", "plan9":
+		t.Skipf("skipping test on %q", runtime.GOOS)
+	}
+
+	N := 1000
+	if testing.Short() {
+		N = 50
+	}
+	defer runtime.GOMAXPROCS(runtime.GOMAXPROCS(4))
+	ln := newLocalListener(t)
+	defer ln.Close()
+	c, err := Dial("tcp", ln.Addr().String())
+	if err != nil {
+		t.Fatalf("Dial: %v", err)
+	}
+	defer c.Close()
+	done := make(chan bool)
+	go func() {
+		t := time.NewTicker(2 * time.Microsecond).C
+		for i := 0; i < N; i++ {
+			if err := c.SetDeadline(time.Now().Add(2 * time.Microsecond)); err != nil {
+				break
+			}
+			<-t
+		}
+		done <- true
+	}()
+	var buf [1]byte
+	for i := 0; i < N; i++ {
+		c.Read(buf[:]) // ignore possible timeout errors
+	}
+	c.Close()
+	<-done
+}
diff --git a/src/net/udp_test.go b/src/net/udp_test.go
new file mode 100644
index 000000000..e1778779c
--- /dev/null
+++ b/src/net/udp_test.go
@@ -0,0 +1,257 @@
+// Copyright 2012 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package net
+
+import (
+	"reflect"
+	"runtime"
+	"strings"
+	"testing"
+)
+
+func TestResolveUDPAddr(t *testing.T) {
+	for _, tt := range resolveTCPAddrTests {
+		net := strings.Replace(tt.net, "tcp", "udp", -1)
+		addr, err := ResolveUDPAddr(net, tt.litAddrOrName)
+		if err != tt.err {
+			t.Fatalf("ResolveUDPAddr(%q, %q) failed: %v", net, tt.litAddrOrName, err)
+		}
+		if !reflect.DeepEqual(addr, (*UDPAddr)(tt.addr)) {
+			t.Fatalf("ResolveUDPAddr(%q, %q) = %#v, want %#v", net, tt.litAddrOrName, addr, tt.addr)
+		}
+		if err == nil {
+			str := addr.String()
+			addr1, err := ResolveUDPAddr(net, str)
+			if err != nil {
+				t.Fatalf("ResolveUDPAddr(%q, %q) [from %q]: %v", net, str, tt.litAddrOrName, err)
+			}
+			if !reflect.DeepEqual(addr1, addr) {
+				t.Fatalf("ResolveUDPAddr(%q, %q) [from %q] = %#v, want %#v", net, str, tt.litAddrOrName, addr1, addr)
+			}
+		}
+	}
+}
+
+func TestWriteToUDP(t *testing.T) {
+	switch runtime.GOOS {
+	case "plan9":
+		t.Skipf("skipping test on %q", runtime.GOOS)
+	}
+
+	l, err := ListenPacket("udp", "127.0.0.1:0")
+	if err != nil {
+		t.Fatalf("Listen failed: %v", err)
+	}
+	defer l.Close()
+
+	testWriteToConn(t, l.LocalAddr().String())
+	testWriteToPacketConn(t, l.LocalAddr().String())
+}
+
+func testWriteToConn(t *testing.T, raddr string) {
+	c, err := Dial("udp", raddr)
+	if err != nil {
+		t.Fatalf("Dial failed: %v", err)
+	}
+	defer c.Close()
+
+	ra, err := ResolveUDPAddr("udp", raddr)
+	if err != nil {
+		t.Fatalf("ResolveUDPAddr failed: %v", err)
+	}
+
+	_, err = c.(*UDPConn).WriteToUDP([]byte("Connection-oriented mode socket"), ra)
+	if err == nil {
+		t.Fatal("WriteToUDP should fail")
+	}
+	if err != nil && err.(*OpError).Err != ErrWriteToConnected {
+		t.Fatalf("WriteToUDP should fail as ErrWriteToConnected: %v", err)
+	}
+
+	_, err = c.(*UDPConn).WriteTo([]byte("Connection-oriented mode socket"), ra)
+	if err == nil {
+		t.Fatal("WriteTo should fail")
+	}
+	if err != nil && err.(*OpError).Err != ErrWriteToConnected {
+		t.Fatalf("WriteTo should fail as ErrWriteToConnected: %v", err)
+	}
+
+	_, err = c.Write([]byte("Connection-oriented mode socket"))
+	if err != nil {
+		t.Fatalf("Write failed: %v", err)
+	}
+}
+
+func testWriteToPacketConn(t *testing.T, raddr string) {
+	c, err := ListenPacket("udp", "127.0.0.1:0")
+	if err != nil {
+		t.Fatalf("ListenPacket failed: %v", err)
+	}
+	defer c.Close()
+
+	ra, err := ResolveUDPAddr("udp", raddr)
+	if err != nil {
+		t.Fatalf("ResolveUDPAddr failed: %v", err)
+	}
+
+	_, err = c.(*UDPConn).WriteToUDP([]byte("Connection-less mode socket"), ra)
+	if err != nil {
+		t.Fatalf("WriteToUDP failed: %v", err)
+	}
+
+	_, err = c.WriteTo([]byte("Connection-less mode socket"), ra)
+	if err != nil {
+		t.Fatalf("WriteTo failed: %v", err)
+	}
+
+	_, err = c.(*UDPConn).Write([]byte("Connection-less mode socket"))
+	if err == nil {
+		t.Fatal("Write should fail")
+	}
+}
+
+var udpConnLocalNameTests = []struct {
+	net   string
+	laddr *UDPAddr
+}{
+	{"udp4", &UDPAddr{IP: IPv4(127, 0, 0, 1)}},
+	{"udp4", &UDPAddr{}},
+	{"udp4", nil},
+}
+
+func TestUDPConnLocalName(t *testing.T) {
+	if testing.Short() || !*testExternal {
+		t.Skip("skipping test to avoid external network")
+	}
+
+	for _, tt := range udpConnLocalNameTests {
+		c, err := ListenUDP(tt.net, tt.laddr)
+		if err != nil {
+			t.Fatalf("ListenUDP failed: %v", err)
+		}
+		defer c.Close()
+		la := c.LocalAddr()
+		if a, ok := la.(*UDPAddr); !ok || a.Port == 0 {
+			t.Fatalf("got %v; expected a proper address with non-zero port number", la)
+		}
+	}
+}
+
+func TestUDPConnLocalAndRemoteNames(t *testing.T) {
+	for _, laddr := range []string{"", "127.0.0.1:0"} {
+		c1, err := ListenPacket("udp", "127.0.0.1:0")
+		if err != nil {
+			t.Fatalf("ListenUDP failed: %v", err)
+		}
+		defer c1.Close()
+
+		var la *UDPAddr
+		if laddr != "" {
+			var err error
+			if la, err = ResolveUDPAddr("udp", laddr); err != nil {
+				t.Fatalf("ResolveUDPAddr failed: %v", err)
+			}
+		}
+		c2, err := DialUDP("udp", la, c1.LocalAddr().(*UDPAddr))
+		if err != nil {
+			t.Fatalf("DialUDP failed: %v", err)
+		}
+		defer c2.Close()
+
+		var connAddrs = [4]struct {
+			got Addr
+			ok  bool
+		}{
+			{c1.LocalAddr(), true},
+			{c1.(*UDPConn).RemoteAddr(), false},
+			{c2.LocalAddr(), true},
+			{c2.RemoteAddr(), true},
+		}
+		for _, ca := range connAddrs {
+			if a, ok := ca.got.(*UDPAddr); ok != ca.ok || ok && a.Port == 0 {
+				t.Fatalf("got %v; expected a proper address with non-zero port number", ca.got)
+			}
+		}
+	}
+}
+
+func TestIPv6LinkLocalUnicastUDP(t *testing.T) {
+	if testing.Short() || !*testExternal {
+		t.Skip("skipping test to avoid external network")
+	}
+	if !supportsIPv6 {
+		t.Skip("ipv6 is not supported")
+	}
+	ifi := loopbackInterface()
+	if ifi == nil {
+		t.Skip("loopback interface not found")
+	}
+	laddr := ipv6LinkLocalUnicastAddr(ifi)
+	if laddr == "" {
+		t.Skip("ipv6 unicast address on loopback not found")
+	}
+
+	type test struct {
+		net, addr  string
+		nameLookup bool
+	}
+	var tests = []test{
+		{"udp", "[" + laddr + "%" + ifi.Name + "]:0", false},
+		{"udp6", "[" + laddr + "%" + ifi.Name + "]:0", false},
+	}
+	// The first udp test fails on DragonFly - see issue 7473.
+	if runtime.GOOS == "dragonfly" {
+		tests = tests[1:]
+	}
+	switch runtime.GOOS {
+	case "darwin", "dragonfly", "freebsd", "openbsd", "netbsd":
+		tests = append(tests, []test{
+			{"udp", "[localhost%" + ifi.Name + "]:0", true},
+			{"udp6", "[localhost%" + ifi.Name + "]:0", true},
+		}...)
+	case "linux":
+		tests = append(tests, []test{
+			{"udp", "[ip6-localhost%" + ifi.Name + "]:0", true},
+			{"udp6", "[ip6-localhost%" + ifi.Name + "]:0", true},
+		}...)
+	}
+	for _, tt := range tests {
+		c1, err := ListenPacket(tt.net, tt.addr)
+		if err != nil {
+			// It might return "LookupHost returned no
+			// suitable address" error on some platforms.
+			t.Logf("ListenPacket failed: %v", err)
+			continue
+		}
+		defer c1.Close()
+		if la, ok := c1.LocalAddr().(*UDPAddr); !ok || !tt.nameLookup && la.Zone == "" {
+			t.Fatalf("got %v; expected a proper address with zone identifier", la)
+		}
+
+		c2, err := Dial(tt.net, c1.LocalAddr().String())
+		if err != nil {
+			t.Fatalf("Dial failed: %v", err)
+		}
+		defer c2.Close()
+		if la, ok := c2.LocalAddr().(*UDPAddr); !ok || !tt.nameLookup && la.Zone == "" {
+			t.Fatalf("got %v; expected a proper address with zone identifier", la)
+		}
+		if ra, ok := c2.RemoteAddr().(*UDPAddr); !ok || !tt.nameLookup && ra.Zone == "" {
+			t.Fatalf("got %v; expected a proper address with zone identifier", ra)
+		}
+
+		if _, err := c2.Write([]byte("UDP OVER IPV6 LINKLOCAL TEST")); err != nil {
+			t.Fatalf("Conn.Write failed: %v", err)
+		}
+		b := make([]byte, 32)
+		if _, from, err := c1.ReadFrom(b); err != nil {
+			t.Fatalf("PacketConn.ReadFrom failed: %v", err)
+		} else {
+			if ra, ok := from.(*UDPAddr); !ok || !tt.nameLookup && ra.Zone == "" {
+				t.Fatalf("got %v; expected a proper address with zone identifier", ra)
+			}
+		}
+	}
+}
diff --git a/src/net/udpsock.go b/src/net/udpsock.go
new file mode 100644
index 000000000..4c99ae4af
--- /dev/null
+++ b/src/net/udpsock.go
@@ -0,0 +1,54 @@
+// Copyright 2009 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package net
+
+// UDPAddr represents the address of a UDP end point.
+type UDPAddr struct {
+	IP   IP
+	Port int
+	Zone string // IPv6 scoped addressing zone
+}
+
+// Network returns the address's network name, "udp".
+func (a *UDPAddr) Network() string { return "udp" }
+
+func (a *UDPAddr) String() string {
+	if a == nil {
+		return "<nil>"
+	}
+	ip := ipEmptyString(a.IP)
+	if a.Zone != "" {
+		return JoinHostPort(ip+"%"+a.Zone, itoa(a.Port))
+	}
+	return JoinHostPort(ip, itoa(a.Port))
+}
+
+func (a *UDPAddr) toAddr() Addr {
+	if a == nil {
+		return nil
+	}
+	return a
+}
+
+// ResolveUDPAddr parses addr as a UDP address of the form "host:port"
+// or "[ipv6-host%zone]:port" and resolves a pair of domain name and
+// port name on the network net, which must be "udp", "udp4" or
+// "udp6".  A literal address or host name for IPv6 must be enclosed
+// in square brackets, as in "[::1]:80", "[ipv6-host]:http" or
+// "[ipv6-host%zone]:80".
+func ResolveUDPAddr(net, addr string) (*UDPAddr, error) {
+	switch net {
+	case "udp", "udp4", "udp6":
+	case "": // a hint wildcard for Go 1.0 undocumented behavior
+		net = "udp"
+	default:
+		return nil, UnknownNetworkError(net)
+	}
+	a, err := resolveInternetAddr(net, addr, noDeadline)
+	if err != nil {
+		return nil, err
+	}
+	return a.toAddr().(*UDPAddr), nil
+}
diff --git a/src/net/udpsock_plan9.go b/src/net/udpsock_plan9.go
new file mode 100644
index 000000000..510ac5e4a
--- /dev/null
+++ b/src/net/udpsock_plan9.go
@@ -0,0 +1,203 @@
+// Copyright 2009 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package net
+
+import (
+	"errors"
+	"os"
+	"syscall"
+	"time"
+)
+
+// UDPConn is the implementation of the Conn and PacketConn interfaces
+// for UDP network connections.
+type UDPConn struct {
+	conn
+}
+
+func newUDPConn(fd *netFD) *UDPConn { return &UDPConn{conn{fd}} }
+
+// ReadFromUDP reads a UDP packet from c, copying the payload into b.
+// It returns the number of bytes copied into b and the return address
+// that was on the packet.
+//
+// ReadFromUDP can be made to time out and return an error with
+// Timeout() == true after a fixed time limit; see SetDeadline and
+// SetReadDeadline.
+func (c *UDPConn) ReadFromUDP(b []byte) (n int, addr *UDPAddr, err error) {
+	if !c.ok() || c.fd.data == nil {
+		return 0, nil, syscall.EINVAL
+	}
+	buf := make([]byte, udpHeaderSize+len(b))
+	m, err := c.fd.data.Read(buf)
+	if err != nil {
+		return
+	}
+	if m < udpHeaderSize {
+		return 0, nil, errors.New("short read reading UDP header")
+	}
+	buf = buf[:m]
+
+	h, buf := unmarshalUDPHeader(buf)
+	n = copy(b, buf)
+	return n, &UDPAddr{IP: h.raddr, Port: int(h.rport)}, nil
+}
+
+// ReadFrom implements the PacketConn ReadFrom method.
+func (c *UDPConn) ReadFrom(b []byte) (int, Addr, error) {
+	if !c.ok() {
+		return 0, nil, syscall.EINVAL
+	}
+	return c.ReadFromUDP(b)
+}
+
+// ReadMsgUDP reads a packet from c, copying the payload into b and
+// the associated out-of-band data into oob.  It returns the number
+// of bytes copied into b, the number of bytes copied into oob, the
+// flags that were set on the packet and the source address of the
+// packet.
+func (c *UDPConn) ReadMsgUDP(b, oob []byte) (n, oobn, flags int, addr *UDPAddr, err error) {
+	return 0, 0, 0, nil, syscall.EPLAN9
+}
+
+// WriteToUDP writes a UDP packet to addr via c, copying the payload
+// from b.
+//
+// WriteToUDP can be made to time out and return an error with
+// Timeout() == true after a fixed time limit; see SetDeadline and
+// SetWriteDeadline.  On packet-oriented connections, write timeouts
+// are rare.
+func (c *UDPConn) WriteToUDP(b []byte, addr *UDPAddr) (int, error) {
+	if !c.ok() || c.fd.data == nil {
+		return 0, syscall.EINVAL
+	}
+	if addr == nil {
+		return 0, &OpError{Op: "write", Net: c.fd.dir, Addr: nil, Err: errMissingAddress}
+	}
+	h := new(udpHeader)
+	h.raddr = addr.IP.To16()
+	h.laddr = c.fd.laddr.(*UDPAddr).IP.To16()
+	h.ifcaddr = IPv6zero // ignored (receive only)
+	h.rport = uint16(addr.Port)
+	h.lport = uint16(c.fd.laddr.(*UDPAddr).Port)
+
+	buf := make([]byte, udpHeaderSize+len(b))
+	i := copy(buf, h.Bytes())
+	copy(buf[i:], b)
+	return c.fd.data.Write(buf)
+}
+
+// WriteTo implements the PacketConn WriteTo method.
+func (c *UDPConn) WriteTo(b []byte, addr Addr) (int, error) {
+	if !c.ok() {
+		return 0, syscall.EINVAL
+	}
+	a, ok := addr.(*UDPAddr)
+	if !ok {
+		return 0, &OpError{"write", c.fd.dir, addr, syscall.EINVAL}
+	}
+	return c.WriteToUDP(b, a)
+}
+
+// WriteMsgUDP writes a packet to addr via c, copying the payload from
+// b and the associated out-of-band data from oob.  It returns the
+// number of payload and out-of-band bytes written.
+func (c *UDPConn) WriteMsgUDP(b, oob []byte, addr *UDPAddr) (n, oobn int, err error) {
+	return 0, 0, syscall.EPLAN9
+}
+
+// DialUDP connects to the remote address raddr on the network net,
+// which must be "udp", "udp4", or "udp6".  If laddr is not nil, it is
+// used as the local address for the connection.
+func DialUDP(net string, laddr, raddr *UDPAddr) (*UDPConn, error) {
+	return dialUDP(net, laddr, raddr, noDeadline)
+}
+
+func dialUDP(net string, laddr, raddr *UDPAddr, deadline time.Time) (*UDPConn, error) {
+	if !deadline.IsZero() {
+		panic("net.dialUDP: deadline not implemented on Plan 9")
+	}
+	switch net {
+	case "udp", "udp4", "udp6":
+	default:
+		return nil, UnknownNetworkError(net)
+	}
+	if raddr == nil {
+		return nil, &OpError{"dial", net, nil, errMissingAddress}
+	}
+	fd, err := dialPlan9(net, laddr, raddr)
+	if err != nil {
+		return nil, err
+	}
+	return newUDPConn(fd), nil
+}
+
+const udpHeaderSize = 16*3 + 2*2
+
+type udpHeader struct {
+	raddr, laddr, ifcaddr IP
+	rport, lport          uint16
+}
+
+func (h *udpHeader) Bytes() []byte {
+	b := make([]byte, udpHeaderSize)
+	i := 0
+	i += copy(b[i:i+16], h.raddr)
+	i += copy(b[i:i+16], h.laddr)
+	i += copy(b[i:i+16], h.ifcaddr)
+	b[i], b[i+1], i = byte(h.rport>>8), byte(h.rport), i+2
+	b[i], b[i+1], i = byte(h.lport>>8), byte(h.lport), i+2
+	return b
+}
+
+func unmarshalUDPHeader(b []byte) (*udpHeader, []byte) {
+	h := new(udpHeader)
+	h.raddr, b = IP(b[:16]), b[16:]
+	h.laddr, b = IP(b[:16]), b[16:]
+	h.ifcaddr, b = IP(b[:16]), b[16:]
+	h.rport, b = uint16(b[0])<<8|uint16(b[1]), b[2:]
+	h.lport, b = uint16(b[0])<<8|uint16(b[1]), b[2:]
+	return h, b
+}
+
+// ListenUDP listens for incoming UDP packets addressed to the local
+// address laddr.  Net must be "udp", "udp4", or "udp6".  If laddr has
+// a port of 0, ListenUDP will choose an available port.
+// The LocalAddr method of the returned UDPConn can be used to
+// discover the port.  The returned connection's ReadFrom and WriteTo
+// methods can be used to receive and send UDP packets with per-packet
+// addressing.
+func ListenUDP(net string, laddr *UDPAddr) (*UDPConn, error) {
+	switch net {
+	case "udp", "udp4", "udp6":
+	default:
+		return nil, UnknownNetworkError(net)
+	}
+	if laddr == nil {
+		laddr = &UDPAddr{}
+	}
+	l, err := listenPlan9(net, laddr)
+	if err != nil {
+		return nil, err
+	}
+	_, err = l.ctl.WriteString("headers")
+	if err != nil {
+		return nil, err
+	}
+	l.data, err = os.OpenFile(l.dir+"/data", os.O_RDWR, 0)
+	if err != nil {
+		return nil, err
+	}
+	fd, err := l.netFD()
+	return newUDPConn(fd), err
+}
+
+// ListenMulticastUDP listens for incoming multicast UDP packets
+// addressed to the group address gaddr on ifi, which specifies the
+// interface to join.  ListenMulticastUDP uses default multicast
+// interface if ifi is nil.
+func ListenMulticastUDP(net string, ifi *Interface, gaddr *UDPAddr) (*UDPConn, error) {
+	return nil, syscall.EPLAN9
+}
diff --git a/src/net/udpsock_posix.go b/src/net/udpsock_posix.go
new file mode 100644
index 000000000..a0533366a
--- /dev/null
+++ b/src/net/udpsock_posix.go
@@ -0,0 +1,268 @@
+// Copyright 2009 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build darwin dragonfly freebsd linux nacl netbsd openbsd solaris windows
+
+package net
+
+import (
+	"syscall"
+	"time"
+)
+
+func sockaddrToUDP(sa syscall.Sockaddr) Addr {
+	switch sa := sa.(type) {
+	case *syscall.SockaddrInet4:
+		return &UDPAddr{IP: sa.Addr[0:], Port: sa.Port}
+	case *syscall.SockaddrInet6:
+		return &UDPAddr{IP: sa.Addr[0:], Port: sa.Port, Zone: zoneToString(int(sa.ZoneId))}
+	}
+	return nil
+}
+
+func (a *UDPAddr) family() int {
+	if a == nil || len(a.IP) <= IPv4len {
+		return syscall.AF_INET
+	}
+	if a.IP.To4() != nil {
+		return syscall.AF_INET
+	}
+	return syscall.AF_INET6
+}
+
+func (a *UDPAddr) isWildcard() bool {
+	if a == nil || a.IP == nil {
+		return true
+	}
+	return a.IP.IsUnspecified()
+}
+
+func (a *UDPAddr) sockaddr(family int) (syscall.Sockaddr, error) {
+	if a == nil {
+		return nil, nil
+	}
+	return ipToSockaddr(family, a.IP, a.Port, a.Zone)
+}
+
+// UDPConn is the implementation of the Conn and PacketConn interfaces
+// for UDP network connections.
+type UDPConn struct {
+	conn
+}
+
+func newUDPConn(fd *netFD) *UDPConn { return &UDPConn{conn{fd}} }
+
+// ReadFromUDP reads a UDP packet from c, copying the payload into b.
+// It returns the number of bytes copied into b and the return address
+// that was on the packet.
+//
+// ReadFromUDP can be made to time out and return an error with
+// Timeout() == true after a fixed time limit; see SetDeadline and
+// SetReadDeadline.
+func (c *UDPConn) ReadFromUDP(b []byte) (n int, addr *UDPAddr, err error) {
+	if !c.ok() {
+		return 0, nil, syscall.EINVAL
+	}
+	n, sa, err := c.fd.readFrom(b)
+	switch sa := sa.(type) {
+	case *syscall.SockaddrInet4:
+		addr = &UDPAddr{IP: sa.Addr[0:], Port: sa.Port}
+	case *syscall.SockaddrInet6:
+		addr = &UDPAddr{IP: sa.Addr[0:], Port: sa.Port, Zone: zoneToString(int(sa.ZoneId))}
+	}
+	return
+}
+
+// ReadFrom implements the PacketConn ReadFrom method.
+func (c *UDPConn) ReadFrom(b []byte) (int, Addr, error) {
+	if !c.ok() {
+		return 0, nil, syscall.EINVAL
+	}
+	n, addr, err := c.ReadFromUDP(b)
+	return n, addr.toAddr(), err
+}
+
+// ReadMsgUDP reads a packet from c, copying the payload into b and
+// the associated out-of-band data into oob.  It returns the number
+// of bytes copied into b, the number of bytes copied into oob, the
+// flags that were set on the packet and the source address of the
+// packet.
+func (c *UDPConn) ReadMsgUDP(b, oob []byte) (n, oobn, flags int, addr *UDPAddr, err error) {
+	if !c.ok() {
+		return 0, 0, 0, nil, syscall.EINVAL
+	}
+	var sa syscall.Sockaddr
+	n, oobn, flags, sa, err = c.fd.readMsg(b, oob)
+	switch sa := sa.(type) {
+	case *syscall.SockaddrInet4:
+		addr = &UDPAddr{IP: sa.Addr[0:], Port: sa.Port}
+	case *syscall.SockaddrInet6:
+		addr = &UDPAddr{IP: sa.Addr[0:], Port: sa.Port, Zone: zoneToString(int(sa.ZoneId))}
+	}
+	return
+}
+
+// WriteToUDP writes a UDP packet to addr via c, copying the payload
+// from b.
+//
+// WriteToUDP can be made to time out and return an error with
+// Timeout() == true after a fixed time limit; see SetDeadline and
+// SetWriteDeadline.  On packet-oriented connections, write timeouts
+// are rare.
+func (c *UDPConn) WriteToUDP(b []byte, addr *UDPAddr) (int, error) {
+	if !c.ok() {
+		return 0, syscall.EINVAL
+	}
+	if c.fd.isConnected {
+		return 0, &OpError{"write", c.fd.net, addr, ErrWriteToConnected}
+	}
+	if addr == nil {
+		return 0, &OpError{Op: "write", Net: c.fd.net, Addr: nil, Err: errMissingAddress}
+	}
+	sa, err := addr.sockaddr(c.fd.family)
+	if err != nil {
+		return 0, &OpError{"write", c.fd.net, addr, err}
+	}
+	return c.fd.writeTo(b, sa)
+}
+
+// WriteTo implements the PacketConn WriteTo method.
+func (c *UDPConn) WriteTo(b []byte, addr Addr) (int, error) {
+	if !c.ok() {
+		return 0, syscall.EINVAL
+	}
+	a, ok := addr.(*UDPAddr)
+	if !ok {
+		return 0, &OpError{"write", c.fd.net, addr, syscall.EINVAL}
+	}
+	return c.WriteToUDP(b, a)
+}
+
+// WriteMsgUDP writes a packet to addr via c, copying the payload from
+// b and the associated out-of-band data from oob.  It returns the
+// number of payload and out-of-band bytes written.
+func (c *UDPConn) WriteMsgUDP(b, oob []byte, addr *UDPAddr) (n, oobn int, err error) {
+	if !c.ok() {
+		return 0, 0, syscall.EINVAL
+	}
+	if c.fd.isConnected {
+		return 0, 0, &OpError{"write", c.fd.net, addr, ErrWriteToConnected}
+	}
+	if addr == nil {
+		return 0, 0, &OpError{Op: "write", Net: c.fd.net, Addr: nil, Err: errMissingAddress}
+	}
+	sa, err := addr.sockaddr(c.fd.family)
+	if err != nil {
+		return 0, 0, &OpError{"write", c.fd.net, addr, err}
+	}
+	return c.fd.writeMsg(b, oob, sa)
+}
+
+// DialUDP connects to the remote address raddr on the network net,
+// which must be "udp", "udp4", or "udp6".  If laddr is not nil, it is
+// used as the local address for the connection.
+func DialUDP(net string, laddr, raddr *UDPAddr) (*UDPConn, error) {
+	switch net {
+	case "udp", "udp4", "udp6":
+	default:
+		return nil, &OpError{Op: "dial", Net: net, Addr: raddr, Err: UnknownNetworkError(net)}
+	}
+	if raddr == nil {
+		return nil, &OpError{Op: "dial", Net: net, Addr: nil, Err: errMissingAddress}
+	}
+	return dialUDP(net, laddr, raddr, noDeadline)
+}
+
+func dialUDP(net string, laddr, raddr *UDPAddr, deadline time.Time) (*UDPConn, error) {
+	fd, err := internetSocket(net, laddr, raddr, deadline, syscall.SOCK_DGRAM, 0, "dial")
+	if err != nil {
+		return nil, &OpError{Op: "dial", Net: net, Addr: raddr, Err: err}
+	}
+	return newUDPConn(fd), nil
+}
+
+// ListenUDP listens for incoming UDP packets addressed to the local
+// address laddr.  Net must be "udp", "udp4", or "udp6".  If laddr has
+// a port of 0, ListenUDP will choose an available port.
+// The LocalAddr method of the returned UDPConn can be used to
+// discover the port.  The returned connection's ReadFrom and WriteTo
+// methods can be used to receive and send UDP packets with per-packet
+// addressing.
+func ListenUDP(net string, laddr *UDPAddr) (*UDPConn, error) {
+	switch net {
+	case "udp", "udp4", "udp6":
+	default:
+		return nil, &OpError{Op: "listen", Net: net, Addr: laddr, Err: UnknownNetworkError(net)}
+	}
+	if laddr == nil {
+		laddr = &UDPAddr{}
+	}
+	fd, err := internetSocket(net, laddr, nil, noDeadline, syscall.SOCK_DGRAM, 0, "listen")
+	if err != nil {
+		return nil, &OpError{Op: "listen", Net: net, Addr: laddr, Err: err}
+	}
+	return newUDPConn(fd), nil
+}
+
+// ListenMulticastUDP listens for incoming multicast UDP packets
+// addressed to the group address gaddr on ifi, which specifies the
+// interface to join.  ListenMulticastUDP uses default multicast
+// interface if ifi is nil.
+func ListenMulticastUDP(net string, ifi *Interface, gaddr *UDPAddr) (*UDPConn, error) {
+	switch net {
+	case "udp", "udp4", "udp6":
+	default:
+		return nil, &OpError{Op: "listen", Net: net, Addr: gaddr, Err: UnknownNetworkError(net)}
+	}
+	if gaddr == nil || gaddr.IP == nil {
+		return nil, &OpError{Op: "listen", Net: net, Addr: nil, Err: errMissingAddress}
+	}
+	fd, err := internetSocket(net, gaddr, nil, noDeadline, syscall.SOCK_DGRAM, 0, "listen")
+	if err != nil {
+		return nil, &OpError{Op: "listen", Net: net, Addr: gaddr, Err: err}
+	}
+	c := newUDPConn(fd)
+	if ip4 := gaddr.IP.To4(); ip4 != nil {
+		if err := listenIPv4MulticastUDP(c, ifi, ip4); err != nil {
+			c.Close()
+			return nil, &OpError{Op: "listen", Net: net, Addr: &IPAddr{IP: ip4}, Err: err}
+		}
+	} else {
+		if err := listenIPv6MulticastUDP(c, ifi, gaddr.IP); err != nil {
+			c.Close()
+			return nil, &OpError{Op: "listen", Net: net, Addr: &IPAddr{IP: gaddr.IP}, Err: err}
+		}
+	}
+	return c, nil
+}
+
+func listenIPv4MulticastUDP(c *UDPConn, ifi *Interface, ip IP) error {
+	if ifi != nil {
+		if err := setIPv4MulticastInterface(c.fd, ifi); err != nil {
+			return err
+		}
+	}
+	if err := setIPv4MulticastLoopback(c.fd, false); err != nil {
+		return err
+	}
+	if err := joinIPv4Group(c.fd, ifi, ip); err != nil {
+		return err
+	}
+	return nil
+}
+
+func listenIPv6MulticastUDP(c *UDPConn, ifi *Interface, ip IP) error {
+	if ifi != nil {
+		if err := setIPv6MulticastInterface(c.fd, ifi); err != nil {
+			return err
+		}
+	}
+	if err := setIPv6MulticastLoopback(c.fd, false); err != nil {
+		return err
+	}
+	if err := joinIPv6Group(c.fd, ifi, ip); err != nil {
+		return err
+	}
+	return nil
+}
diff --git a/src/net/unicast_posix_test.go b/src/net/unicast_posix_test.go
new file mode 100644
index 000000000..452ac9254
--- /dev/null
+++ b/src/net/unicast_posix_test.go
@@ -0,0 +1,466 @@
+// Copyright 2011 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build !plan9
+
+package net
+
+import (
+	"runtime"
+	"syscall"
+	"testing"
+)
+
+var listenerTests = []struct {
+	net      string
+	laddr    string
+	ipv6     bool // test with underlying AF_INET6 socket
+	wildcard bool // test with wildcard address
+}{
+	{net: "tcp", laddr: "", wildcard: true},
+	{net: "tcp", laddr: "0.0.0.0", wildcard: true},
+	{net: "tcp", laddr: "[::ffff:0.0.0.0]", wildcard: true},
+	{net: "tcp", laddr: "[::]", ipv6: true, wildcard: true},
+
+	{net: "tcp", laddr: "127.0.0.1"},
+	{net: "tcp", laddr: "[::ffff:127.0.0.1]"},
+	{net: "tcp", laddr: "[::1]", ipv6: true},
+
+	{net: "tcp4", laddr: "", wildcard: true},
+	{net: "tcp4", laddr: "0.0.0.0", wildcard: true},
+	{net: "tcp4", laddr: "[::ffff:0.0.0.0]", wildcard: true},
+
+	{net: "tcp4", laddr: "127.0.0.1"},
+	{net: "tcp4", laddr: "[::ffff:127.0.0.1]"},
+
+	{net: "tcp6", laddr: "", ipv6: true, wildcard: true},
+	{net: "tcp6", laddr: "[::]", ipv6: true, wildcard: true},
+
+	{net: "tcp6", laddr: "[::1]", ipv6: true},
+}
+
+// TestTCPListener tests both single and double listen to a test
+// listener with same address family, same listening address and
+// same port.
+func TestTCPListener(t *testing.T) {
+	switch runtime.GOOS {
+	case "plan9":
+		t.Skipf("skipping test on %q", runtime.GOOS)
+	}
+
+	for _, tt := range listenerTests {
+		if tt.wildcard && (testing.Short() || !*testExternal) {
+			continue
+		}
+		if tt.ipv6 && !supportsIPv6 {
+			continue
+		}
+		l1, port := usableListenPort(t, tt.net, tt.laddr)
+		checkFirstListener(t, tt.net, tt.laddr+":"+port, l1)
+		l2, err := Listen(tt.net, tt.laddr+":"+port)
+		checkSecondListener(t, tt.net, tt.laddr+":"+port, err, l2)
+		l1.Close()
+	}
+}
+
+// TestUDPListener tests both single and double listen to a test
+// listener with same address family, same listening address and
+// same port.
+func TestUDPListener(t *testing.T) {
+	switch runtime.GOOS {
+	case "plan9":
+		t.Skipf("skipping test on %q", runtime.GOOS)
+	}
+
+	toudpnet := func(net string) string {
+		switch net {
+		case "tcp":
+			return "udp"
+		case "tcp4":
+			return "udp4"
+		case "tcp6":
+			return "udp6"
+		}
+		return "<nil>"
+	}
+
+	for _, tt := range listenerTests {
+		if tt.wildcard && (testing.Short() || !*testExternal) {
+			continue
+		}
+		if tt.ipv6 && !supportsIPv6 {
+			continue
+		}
+		tt.net = toudpnet(tt.net)
+		l1, port := usableListenPacketPort(t, tt.net, tt.laddr)
+		checkFirstListener(t, tt.net, tt.laddr+":"+port, l1)
+		l2, err := ListenPacket(tt.net, tt.laddr+":"+port)
+		checkSecondListener(t, tt.net, tt.laddr+":"+port, err, l2)
+		l1.Close()
+	}
+}
+
+var dualStackListenerTests = []struct {
+	net1     string // first listener
+	laddr1   string
+	net2     string // second listener
+	laddr2   string
+	wildcard bool  // test with wildcard address
+	xerr     error // expected error value, nil or other
+}{
+	// Test cases and expected results for the attemping 2nd listen on the same port
+	// 1st listen                2nd listen                 darwin  freebsd  linux  openbsd
+	// ------------------------------------------------------------------------------------
+	// "tcp"  ""                 "tcp"  ""                    -        -       -       -
+	// "tcp"  ""                 "tcp"  "0.0.0.0"             -        -       -       -
+	// "tcp"  "0.0.0.0"          "tcp"  ""                    -        -       -       -
+	// ------------------------------------------------------------------------------------
+	// "tcp"  ""                 "tcp"  "[::]"                -        -       -       ok
+	// "tcp"  "[::]"             "tcp"  ""                    -        -       -       ok
+	// "tcp"  "0.0.0.0"          "tcp"  "[::]"                -        -       -       ok
+	// "tcp"  "[::]"             "tcp"  "0.0.0.0"             -        -       -       ok
+	// "tcp"  "[::ffff:0.0.0.0]" "tcp"  "[::]"                -        -       -       ok
+	// "tcp"  "[::]"             "tcp"  "[::ffff:0.0.0.0]"    -        -       -       ok
+	// ------------------------------------------------------------------------------------
+	// "tcp4" ""                 "tcp6" ""                    ok       ok      ok      ok
+	// "tcp6" ""                 "tcp4" ""                    ok       ok      ok      ok
+	// "tcp4" "0.0.0.0"          "tcp6" "[::]"                ok       ok      ok      ok
+	// "tcp6" "[::]"             "tcp4" "0.0.0.0"             ok       ok      ok      ok
+	// ------------------------------------------------------------------------------------
+	// "tcp"  "127.0.0.1"        "tcp"  "[::1]"               ok       ok      ok      ok
+	// "tcp"  "[::1]"            "tcp"  "127.0.0.1"           ok       ok      ok      ok
+	// "tcp4" "127.0.0.1"        "tcp6" "[::1]"               ok       ok      ok      ok
+	// "tcp6" "[::1]"            "tcp4" "127.0.0.1"           ok       ok      ok      ok
+	//
+	// Platform default configurations:
+	// darwin, kernel version 11.3.0
+	//	net.inet6.ip6.v6only=0 (overridable by sysctl or IPV6_V6ONLY option)
+	// freebsd, kernel version 8.2
+	//	net.inet6.ip6.v6only=1 (overridable by sysctl or IPV6_V6ONLY option)
+	// linux, kernel version 3.0.0
+	//	net.ipv6.bindv6only=0 (overridable by sysctl or IPV6_V6ONLY option)
+	// openbsd, kernel version 5.0
+	//	net.inet6.ip6.v6only=1 (overriding is prohibited)
+
+	{net1: "tcp", laddr1: "", net2: "tcp", laddr2: "", wildcard: true, xerr: syscall.EADDRINUSE},
+	{net1: "tcp", laddr1: "", net2: "tcp", laddr2: "0.0.0.0", wildcard: true, xerr: syscall.EADDRINUSE},
+	{net1: "tcp", laddr1: "0.0.0.0", net2: "tcp", laddr2: "", wildcard: true, xerr: syscall.EADDRINUSE},
+
+	{net1: "tcp", laddr1: "", net2: "tcp", laddr2: "[::]", wildcard: true, xerr: syscall.EADDRINUSE},
+	{net1: "tcp", laddr1: "[::]", net2: "tcp", laddr2: "", wildcard: true, xerr: syscall.EADDRINUSE},
+	{net1: "tcp", laddr1: "0.0.0.0", net2: "tcp", laddr2: "[::]", wildcard: true, xerr: syscall.EADDRINUSE},
+	{net1: "tcp", laddr1: "[::]", net2: "tcp", laddr2: "0.0.0.0", wildcard: true, xerr: syscall.EADDRINUSE},
+	{net1: "tcp", laddr1: "[::ffff:0.0.0.0]", net2: "tcp", laddr2: "[::]", wildcard: true, xerr: syscall.EADDRINUSE},
+	{net1: "tcp", laddr1: "[::]", net2: "tcp", laddr2: "[::ffff:0.0.0.0]", wildcard: true, xerr: syscall.EADDRINUSE},
+
+	{net1: "tcp4", laddr1: "", net2: "tcp6", laddr2: "", wildcard: true},
+	{net1: "tcp6", laddr1: "", net2: "tcp4", laddr2: "", wildcard: true},
+	{net1: "tcp4", laddr1: "0.0.0.0", net2: "tcp6", laddr2: "[::]", wildcard: true},
+	{net1: "tcp6", laddr1: "[::]", net2: "tcp4", laddr2: "0.0.0.0", wildcard: true},
+
+	{net1: "tcp", laddr1: "127.0.0.1", net2: "tcp", laddr2: "[::1]"},
+	{net1: "tcp", laddr1: "[::1]", net2: "tcp", laddr2: "127.0.0.1"},
+	{net1: "tcp4", laddr1: "127.0.0.1", net2: "tcp6", laddr2: "[::1]"},
+	{net1: "tcp6", laddr1: "[::1]", net2: "tcp4", laddr2: "127.0.0.1"},
+}
+
+// TestDualStackTCPListener tests both single and double listen
+// to a test listener with various address families, different
+// listening address and same port.
+func TestDualStackTCPListener(t *testing.T) {
+	if testing.Short() {
+		t.Skip("skipping in -short mode, see issue 5001")
+	}
+	switch runtime.GOOS {
+	case "plan9":
+		t.Skipf("skipping test on %q", runtime.GOOS)
+	}
+	if !supportsIPv6 {
+		t.Skip("ipv6 is not supported")
+	}
+
+	for _, tt := range dualStackListenerTests {
+		if tt.wildcard && !*testExternal {
+			continue
+		}
+		switch runtime.GOOS {
+		case "openbsd":
+			if tt.wildcard && differentWildcardAddr(tt.laddr1, tt.laddr2) {
+				tt.xerr = nil
+			}
+		}
+		l1, port := usableListenPort(t, tt.net1, tt.laddr1)
+		laddr := tt.laddr1 + ":" + port
+		checkFirstListener(t, tt.net1, laddr, l1)
+		laddr = tt.laddr2 + ":" + port
+		l2, err := Listen(tt.net2, laddr)
+		checkDualStackSecondListener(t, tt.net2, laddr, tt.xerr, err, l2)
+		l1.Close()
+	}
+}
+
+// TestDualStackUDPListener tests both single and double listen
+// to a test listener with various address families, differnet
+// listening address and same port.
+func TestDualStackUDPListener(t *testing.T) {
+	switch runtime.GOOS {
+	case "plan9":
+		t.Skipf("skipping test on %q", runtime.GOOS)
+	}
+	if !supportsIPv6 {
+		t.Skip("ipv6 is not supported")
+	}
+
+	toudpnet := func(net string) string {
+		switch net {
+		case "tcp":
+			return "udp"
+		case "tcp4":
+			return "udp4"
+		case "tcp6":
+			return "udp6"
+		}
+		return "<nil>"
+	}
+
+	for _, tt := range dualStackListenerTests {
+		if tt.wildcard && (testing.Short() || !*testExternal) {
+			continue
+		}
+		tt.net1 = toudpnet(tt.net1)
+		tt.net2 = toudpnet(tt.net2)
+		switch runtime.GOOS {
+		case "openbsd":
+			if tt.wildcard && differentWildcardAddr(tt.laddr1, tt.laddr2) {
+				tt.xerr = nil
+			}
+		}
+		l1, port := usableListenPacketPort(t, tt.net1, tt.laddr1)
+		laddr := tt.laddr1 + ":" + port
+		checkFirstListener(t, tt.net1, laddr, l1)
+		laddr = tt.laddr2 + ":" + port
+		l2, err := ListenPacket(tt.net2, laddr)
+		checkDualStackSecondListener(t, tt.net2, laddr, tt.xerr, err, l2)
+		l1.Close()
+	}
+}
+
+func usableListenPort(t *testing.T, net, laddr string) (l Listener, port string) {
+	var nladdr string
+	var err error
+	switch net {
+	default:
+		panic("usableListenPort net=" + net)
+	case "tcp", "tcp4", "tcp6":
+		l, err = Listen(net, laddr+":0")
+		if err != nil {
+			t.Fatalf("Probe Listen(%q, %q) failed: %v", net, laddr, err)
+		}
+		nladdr = l.(*TCPListener).Addr().String()
+	}
+	_, port, err = SplitHostPort(nladdr)
+	if err != nil {
+		t.Fatalf("SplitHostPort failed: %v", err)
+	}
+	return l, port
+}
+
+func usableListenPacketPort(t *testing.T, net, laddr string) (l PacketConn, port string) {
+	var nladdr string
+	var err error
+	switch net {
+	default:
+		panic("usableListenPacketPort net=" + net)
+	case "udp", "udp4", "udp6":
+		l, err = ListenPacket(net, laddr+":0")
+		if err != nil {
+			t.Fatalf("Probe ListenPacket(%q, %q) failed: %v", net, laddr, err)
+		}
+		nladdr = l.(*UDPConn).LocalAddr().String()
+	}
+	_, port, err = SplitHostPort(nladdr)
+	if err != nil {
+		t.Fatalf("SplitHostPort failed: %v", err)
+	}
+	return l, port
+}
+
+func differentWildcardAddr(i, j string) bool {
+	if (i == "" || i == "0.0.0.0" || i == "::ffff:0.0.0.0") && (j == "" || j == "0.0.0.0" || j == "::ffff:0.0.0.0") {
+		return false
+	}
+	if i == "[::]" && j == "[::]" {
+		return false
+	}
+	return true
+}
+
+func checkFirstListener(t *testing.T, net, laddr string, l interface{}) {
+	switch net {
+	case "tcp":
+		fd := l.(*TCPListener).fd
+		checkDualStackAddrFamily(t, net, laddr, fd)
+	case "tcp4":
+		fd := l.(*TCPListener).fd
+		if fd.family != syscall.AF_INET {
+			t.Fatalf("First Listen(%q, %q) returns address family %v, expected %v", net, laddr, fd.family, syscall.AF_INET)
+		}
+	case "tcp6":
+		fd := l.(*TCPListener).fd
+		if fd.family != syscall.AF_INET6 {
+			t.Fatalf("First Listen(%q, %q) returns address family %v, expected %v", net, laddr, fd.family, syscall.AF_INET6)
+		}
+	case "udp":
+		fd := l.(*UDPConn).fd
+		checkDualStackAddrFamily(t, net, laddr, fd)
+	case "udp4":
+		fd := l.(*UDPConn).fd
+		if fd.family != syscall.AF_INET {
+			t.Fatalf("First ListenPacket(%q, %q) returns address family %v, expected %v", net, laddr, fd.family, syscall.AF_INET)
+		}
+	case "udp6":
+		fd := l.(*UDPConn).fd
+		if fd.family != syscall.AF_INET6 {
+			t.Fatalf("First ListenPacket(%q, %q) returns address family %v, expected %v", net, laddr, fd.family, syscall.AF_INET6)
+		}
+	default:
+		t.Fatalf("Unexpected network: %q", net)
+	}
+}
+
+func checkSecondListener(t *testing.T, net, laddr string, err error, l interface{}) {
+	switch net {
+	case "tcp", "tcp4", "tcp6":
+		if err == nil {
+			l.(*TCPListener).Close()
+			t.Fatalf("Second Listen(%q, %q) should fail", net, laddr)
+		}
+	case "udp", "udp4", "udp6":
+		if err == nil {
+			l.(*UDPConn).Close()
+			t.Fatalf("Second ListenPacket(%q, %q) should fail", net, laddr)
+		}
+	default:
+		t.Fatalf("Unexpected network: %q", net)
+	}
+}
+
+func checkDualStackSecondListener(t *testing.T, net, laddr string, xerr, err error, l interface{}) {
+	switch net {
+	case "tcp", "tcp4", "tcp6":
+		if xerr == nil && err != nil || xerr != nil && err == nil {
+			t.Fatalf("Second Listen(%q, %q) returns %v, expected %v", net, laddr, err, xerr)
+		}
+		if err == nil {
+			l.(*TCPListener).Close()
+		}
+	case "udp", "udp4", "udp6":
+		if xerr == nil && err != nil || xerr != nil && err == nil {
+			t.Fatalf("Second ListenPacket(%q, %q) returns %v, expected %v", net, laddr, err, xerr)
+		}
+		if err == nil {
+			l.(*UDPConn).Close()
+		}
+	default:
+		t.Fatalf("Unexpected network: %q", net)
+	}
+}
+
+func checkDualStackAddrFamily(t *testing.T, net, laddr string, fd *netFD) {
+	switch a := fd.laddr.(type) {
+	case *TCPAddr:
+		// If a node under test supports both IPv6 capability
+		// and IPv6 IPv4-mapping capability, we can assume
+		// that the node listens on a wildcard address with an
+		// AF_INET6 socket.
+		if supportsIPv4map && fd.laddr.(*TCPAddr).isWildcard() {
+			if fd.family != syscall.AF_INET6 {
+				t.Fatalf("Listen(%q, %q) returns address family %v, expected %v", net, laddr, fd.family, syscall.AF_INET6)
+			}
+		} else {
+			if fd.family != a.family() {
+				t.Fatalf("Listen(%q, %q) returns address family %v, expected %v", net, laddr, fd.family, a.family())
+			}
+		}
+	case *UDPAddr:
+		// If a node under test supports both IPv6 capability
+		// and IPv6 IPv4-mapping capability, we can assume
+		// that the node listens on a wildcard address with an
+		// AF_INET6 socket.
+		if supportsIPv4map && fd.laddr.(*UDPAddr).isWildcard() {
+			if fd.family != syscall.AF_INET6 {
+				t.Fatalf("ListenPacket(%q, %q) returns address family %v, expected %v", net, laddr, fd.family, syscall.AF_INET6)
+			}
+		} else {
+			if fd.family != a.family() {
+				t.Fatalf("ListenPacket(%q, %q) returns address family %v, expected %v", net, laddr, fd.family, a.family())
+			}
+		}
+	default:
+		t.Fatalf("Unexpected protocol address type: %T", a)
+	}
+}
+
+var prohibitionaryDialArgTests = []struct {
+	net  string
+	addr string
+}{
+	{"tcp6", "127.0.0.1"},
+	{"tcp6", "[::ffff:127.0.0.1]"},
+}
+
+func TestProhibitionaryDialArgs(t *testing.T) {
+	switch runtime.GOOS {
+	case "plan9":
+		t.Skipf("skipping test on %q", runtime.GOOS)
+	}
+	// This test requires both IPv6 and IPv6 IPv4-mapping functionality.
+	if !supportsIPv4map || testing.Short() || !*testExternal {
+		return
+	}
+
+	l, port := usableListenPort(t, "tcp", "[::]")
+	defer l.Close()
+
+	for _, tt := range prohibitionaryDialArgTests {
+		c, err := Dial(tt.net, tt.addr+":"+port)
+		if err == nil {
+			c.Close()
+			t.Fatalf("Dial(%q, %q) should fail", tt.net, tt.addr)
+		}
+	}
+}
+
+func TestWildWildcardListener(t *testing.T) {
+	switch runtime.GOOS {
+	case "plan9":
+		t.Skipf("skipping test on %q", runtime.GOOS)
+	}
+
+	if testing.Short() || !*testExternal {
+		t.Skip("skipping test to avoid external network")
+	}
+
+	defer func() {
+		if p := recover(); p != nil {
+			t.Fatalf("Listen, ListenPacket or protocol-specific Listen panicked: %v", p)
+		}
+	}()
+
+	if ln, err := Listen("tcp", ""); err == nil {
+		ln.Close()
+	}
+	if ln, err := ListenPacket("udp", ""); err == nil {
+		ln.Close()
+	}
+	if ln, err := ListenTCP("tcp", nil); err == nil {
+		ln.Close()
+	}
+	if ln, err := ListenUDP("udp", nil); err == nil {
+		ln.Close()
+	}
+	if ln, err := ListenIP("ip:icmp", nil); err == nil {
+		ln.Close()
+	}
+}
diff --git a/src/net/unix_test.go b/src/net/unix_test.go
new file mode 100644
index 000000000..1cdff3908
--- /dev/null
+++ b/src/net/unix_test.go
@@ -0,0 +1,333 @@
+// Copyright 2013 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build !nacl,!plan9,!windows
+
+package net
+
+import (
+	"bytes"
+	"os"
+	"reflect"
+	"runtime"
+	"syscall"
+	"testing"
+	"time"
+)
+
+func TestReadUnixgramWithUnnamedSocket(t *testing.T) {
+	addr := testUnixAddr()
+	la, err := ResolveUnixAddr("unixgram", addr)
+	if err != nil {
+		t.Fatalf("ResolveUnixAddr failed: %v", err)
+	}
+	c, err := ListenUnixgram("unixgram", la)
+	if err != nil {
+		t.Fatalf("ListenUnixgram failed: %v", err)
+	}
+	defer func() {
+		c.Close()
+		os.Remove(addr)
+	}()
+
+	off := make(chan bool)
+	data := [5]byte{1, 2, 3, 4, 5}
+	go func() {
+		defer func() { off <- true }()
+		s, err := syscall.Socket(syscall.AF_UNIX, syscall.SOCK_DGRAM, 0)
+		if err != nil {
+			t.Errorf("syscall.Socket failed: %v", err)
+			return
+		}
+		defer syscall.Close(s)
+		rsa := &syscall.SockaddrUnix{Name: addr}
+		if err := syscall.Sendto(s, data[:], 0, rsa); err != nil {
+			t.Errorf("syscall.Sendto failed: %v", err)
+			return
+		}
+	}()
+
+	<-off
+	b := make([]byte, 64)
+	c.SetReadDeadline(time.Now().Add(100 * time.Millisecond))
+	n, from, err := c.ReadFrom(b)
+	if err != nil {
+		t.Fatalf("UnixConn.ReadFrom failed: %v", err)
+	}
+	if from != nil {
+		t.Fatalf("neighbor address is %v", from)
+	}
+	if !bytes.Equal(b[:n], data[:]) {
+		t.Fatalf("got %v, want %v", b[:n], data[:])
+	}
+}
+
+func TestReadUnixgramWithZeroBytesBuffer(t *testing.T) {
+	// issue 4352: Recvfrom failed with "address family not
+	// supported by protocol family" if zero-length buffer provided
+
+	addr := testUnixAddr()
+	la, err := ResolveUnixAddr("unixgram", addr)
+	if err != nil {
+		t.Fatalf("ResolveUnixAddr failed: %v", err)
+	}
+	c, err := ListenUnixgram("unixgram", la)
+	if err != nil {
+		t.Fatalf("ListenUnixgram failed: %v", err)
+	}
+	defer func() {
+		c.Close()
+		os.Remove(addr)
+	}()
+
+	off := make(chan bool)
+	go func() {
+		defer func() { off <- true }()
+		c, err := DialUnix("unixgram", nil, la)
+		if err != nil {
+			t.Errorf("DialUnix failed: %v", err)
+			return
+		}
+		defer c.Close()
+		if _, err := c.Write([]byte{1, 2, 3, 4, 5}); err != nil {
+			t.Errorf("UnixConn.Write failed: %v", err)
+			return
+		}
+	}()
+
+	<-off
+	c.SetReadDeadline(time.Now().Add(100 * time.Millisecond))
+	_, from, err := c.ReadFrom(nil)
+	if err != nil {
+		t.Fatalf("UnixConn.ReadFrom failed: %v", err)
+	}
+	if from != nil {
+		t.Fatalf("neighbor address is %v", from)
+	}
+}
+
+func TestUnixgramAutobind(t *testing.T) {
+	if runtime.GOOS != "linux" {
+		t.Skip("skipping: autobind is linux only")
+	}
+
+	laddr := &UnixAddr{Name: "", Net: "unixgram"}
+	c1, err := ListenUnixgram("unixgram", laddr)
+	if err != nil {
+		t.Fatalf("ListenUnixgram failed: %v", err)
+	}
+	defer c1.Close()
+
+	// retrieve the autobind address
+	autoAddr := c1.LocalAddr().(*UnixAddr)
+	if len(autoAddr.Name) <= 1 {
+		t.Fatalf("invalid autobind address: %v", autoAddr)
+	}
+	if autoAddr.Name[0] != '@' {
+		t.Fatalf("invalid autobind address: %v", autoAddr)
+	}
+
+	c2, err := DialUnix("unixgram", nil, autoAddr)
+	if err != nil {
+		t.Fatalf("DialUnix failed: %v", err)
+	}
+	defer c2.Close()
+
+	if !reflect.DeepEqual(c1.LocalAddr(), c2.RemoteAddr()) {
+		t.Fatalf("expected autobind address %v, got %v", c1.LocalAddr(), c2.RemoteAddr())
+	}
+}
+
+func TestUnixAutobindClose(t *testing.T) {
+	if runtime.GOOS != "linux" {
+		t.Skip("skipping: autobind is linux only")
+	}
+	laddr := &UnixAddr{Name: "", Net: "unix"}
+	ln, err := ListenUnix("unix", laddr)
+	if err != nil {
+		t.Fatalf("ListenUnix failed: %v", err)
+	}
+	ln.Close()
+}
+
+func TestUnixgramWrite(t *testing.T) {
+	addr := testUnixAddr()
+	laddr, err := ResolveUnixAddr("unixgram", addr)
+	if err != nil {
+		t.Fatalf("ResolveUnixAddr failed: %v", err)
+	}
+	c, err := ListenPacket("unixgram", addr)
+	if err != nil {
+		t.Fatalf("ListenPacket failed: %v", err)
+	}
+	defer os.Remove(addr)
+	defer c.Close()
+
+	testUnixgramWriteConn(t, laddr)
+	testUnixgramWritePacketConn(t, laddr)
+}
+
+func testUnixgramWriteConn(t *testing.T, raddr *UnixAddr) {
+	c, err := Dial("unixgram", raddr.String())
+	if err != nil {
+		t.Fatalf("Dial failed: %v", err)
+	}
+	defer c.Close()
+
+	if _, err := c.(*UnixConn).WriteToUnix([]byte("Connection-oriented mode socket"), raddr); err == nil {
+		t.Fatal("WriteToUnix should fail")
+	} else if err.(*OpError).Err != ErrWriteToConnected {
+		t.Fatalf("WriteToUnix should fail as ErrWriteToConnected: %v", err)
+	}
+	if _, err = c.(*UnixConn).WriteTo([]byte("Connection-oriented mode socket"), raddr); err == nil {
+		t.Fatal("WriteTo should fail")
+	} else if err.(*OpError).Err != ErrWriteToConnected {
+		t.Fatalf("WriteTo should fail as ErrWriteToConnected: %v", err)
+	}
+	if _, _, err = c.(*UnixConn).WriteMsgUnix([]byte("Connection-oriented mode socket"), nil, raddr); err == nil {
+		t.Fatal("WriteTo should fail")
+	} else if err.(*OpError).Err != ErrWriteToConnected {
+		t.Fatalf("WriteMsgUnix should fail as ErrWriteToConnected: %v", err)
+	}
+	if _, err := c.Write([]byte("Connection-oriented mode socket")); err != nil {
+		t.Fatalf("Write failed: %v", err)
+	}
+}
+
+func testUnixgramWritePacketConn(t *testing.T, raddr *UnixAddr) {
+	addr := testUnixAddr()
+	c, err := ListenPacket("unixgram", addr)
+	if err != nil {
+		t.Fatalf("ListenPacket failed: %v", err)
+	}
+	defer os.Remove(addr)
+	defer c.Close()
+
+	if _, err := c.(*UnixConn).WriteToUnix([]byte("Connectionless mode socket"), raddr); err != nil {
+		t.Fatalf("WriteToUnix failed: %v", err)
+	}
+	if _, err := c.WriteTo([]byte("Connectionless mode socket"), raddr); err != nil {
+		t.Fatalf("WriteTo failed: %v", err)
+	}
+	if _, _, err := c.(*UnixConn).WriteMsgUnix([]byte("Connectionless mode socket"), nil, raddr); err != nil {
+		t.Fatalf("WriteMsgUnix failed: %v", err)
+	}
+	if _, err := c.(*UnixConn).Write([]byte("Connectionless mode socket")); err == nil {
+		t.Fatal("Write should fail")
+	}
+}
+
+func TestUnixConnLocalAndRemoteNames(t *testing.T) {
+	for _, laddr := range []string{"", testUnixAddr()} {
+		laddr := laddr
+		taddr := testUnixAddr()
+		ta, err := ResolveUnixAddr("unix", taddr)
+		if err != nil {
+			t.Fatalf("ResolveUnixAddr failed: %v", err)
+		}
+		ln, err := ListenUnix("unix", ta)
+		if err != nil {
+			t.Fatalf("ListenUnix failed: %v", err)
+		}
+		defer func() {
+			ln.Close()
+			os.Remove(taddr)
+		}()
+
+		done := make(chan int)
+		go transponder(t, ln, done)
+
+		la, err := ResolveUnixAddr("unix", laddr)
+		if err != nil {
+			t.Fatalf("ResolveUnixAddr failed: %v", err)
+		}
+		c, err := DialUnix("unix", la, ta)
+		if err != nil {
+			t.Fatalf("DialUnix failed: %v", err)
+		}
+		defer func() {
+			c.Close()
+			if la != nil {
+				defer os.Remove(laddr)
+			}
+		}()
+		if _, err := c.Write([]byte("UNIXCONN LOCAL AND REMOTE NAME TEST")); err != nil {
+			t.Fatalf("UnixConn.Write failed: %v", err)
+		}
+
+		switch runtime.GOOS {
+		case "android", "linux":
+			if laddr == "" {
+				laddr = "@" // autobind feature
+			}
+		}
+		var connAddrs = [3]struct{ got, want Addr }{
+			{ln.Addr(), ta},
+			{c.LocalAddr(), &UnixAddr{Name: laddr, Net: "unix"}},
+			{c.RemoteAddr(), ta},
+		}
+		for _, ca := range connAddrs {
+			if !reflect.DeepEqual(ca.got, ca.want) {
+				t.Fatalf("got %#v, expected %#v", ca.got, ca.want)
+			}
+		}
+
+		<-done
+	}
+}
+
+func TestUnixgramConnLocalAndRemoteNames(t *testing.T) {
+	for _, laddr := range []string{"", testUnixAddr()} {
+		laddr := laddr
+		taddr := testUnixAddr()
+		ta, err := ResolveUnixAddr("unixgram", taddr)
+		if err != nil {
+			t.Fatalf("ResolveUnixAddr failed: %v", err)
+		}
+		c1, err := ListenUnixgram("unixgram", ta)
+		if err != nil {
+			t.Fatalf("ListenUnixgram failed: %v", err)
+		}
+		defer func() {
+			c1.Close()
+			os.Remove(taddr)
+		}()
+
+		var la *UnixAddr
+		if laddr != "" {
+			if la, err = ResolveUnixAddr("unixgram", laddr); err != nil {
+				t.Fatalf("ResolveUnixAddr failed: %v", err)
+			}
+		}
+		c2, err := DialUnix("unixgram", la, ta)
+		if err != nil {
+			t.Fatalf("DialUnix failed: %v", err)
+		}
+		defer func() {
+			c2.Close()
+			if la != nil {
+				defer os.Remove(laddr)
+			}
+		}()
+
+		switch runtime.GOOS {
+		case "android", "linux":
+			if laddr == "" {
+				laddr = "@" // autobind feature
+			}
+		}
+
+		var connAddrs = [4]struct{ got, want Addr }{
+			{c1.LocalAddr(), ta},
+			{c1.RemoteAddr(), nil},
+			{c2.LocalAddr(), &UnixAddr{Name: laddr, Net: "unixgram"}},
+			{c2.RemoteAddr(), ta},
+		}
+		for _, ca := range connAddrs {
+			if !reflect.DeepEqual(ca.got, ca.want) {
+				t.Fatalf("got %#v, expected %#v", ca.got, ca.want)
+			}
+		}
+	}
+}
diff --git a/src/net/unixsock.go b/src/net/unixsock.go
new file mode 100644
index 000000000..85955845b
--- /dev/null
+++ b/src/net/unixsock.go
@@ -0,0 +1,43 @@
+// Copyright 2009 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package net
+
+// UnixAddr represents the address of a Unix domain socket end point.
+type UnixAddr struct {
+	Name string
+	Net  string
+}
+
+// Network returns the address's network name, "unix", "unixgram" or
+// "unixpacket".
+func (a *UnixAddr) Network() string {
+	return a.Net
+}
+
+func (a *UnixAddr) String() string {
+	if a == nil {
+		return "<nil>"
+	}
+	return a.Name
+}
+
+func (a *UnixAddr) toAddr() Addr {
+	if a == nil {
+		return nil
+	}
+	return a
+}
+
+// ResolveUnixAddr parses addr as a Unix domain socket address.
+// The string net gives the network name, "unix", "unixgram" or
+// "unixpacket".
+func ResolveUnixAddr(net, addr string) (*UnixAddr, error) {
+	switch net {
+	case "unix", "unixgram", "unixpacket":
+		return &UnixAddr{Name: addr, Net: net}, nil
+	default:
+		return nil, UnknownNetworkError(net)
+	}
+}
diff --git a/src/net/unixsock_plan9.go b/src/net/unixsock_plan9.go
new file mode 100644
index 000000000..c60c1d83b
--- /dev/null
+++ b/src/net/unixsock_plan9.go
@@ -0,0 +1,143 @@
+// Copyright 2009 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package net
+
+import (
+	"os"
+	"syscall"
+	"time"
+)
+
+// UnixConn is an implementation of the Conn interface for connections
+// to Unix domain sockets.
+type UnixConn struct {
+	conn
+}
+
+// ReadFromUnix reads a packet from c, copying the payload into b.  It
+// returns the number of bytes copied into b and the source address of
+// the packet.
+//
+// ReadFromUnix can be made to time out and return an error with
+// Timeout() == true after a fixed time limit; see SetDeadline and
+// SetReadDeadline.
+func (c *UnixConn) ReadFromUnix(b []byte) (int, *UnixAddr, error) {
+	return 0, nil, syscall.EPLAN9
+}
+
+// ReadFrom implements the PacketConn ReadFrom method.
+func (c *UnixConn) ReadFrom(b []byte) (int, Addr, error) {
+	return 0, nil, syscall.EPLAN9
+}
+
+// ReadMsgUnix reads a packet from c, copying the payload into b and
+// the associated out-of-band data into oob.  It returns the number of
+// bytes copied into b, the number of bytes copied into oob, the flags
+// that were set on the packet, and the source address of the packet.
+func (c *UnixConn) ReadMsgUnix(b, oob []byte) (n, oobn, flags int, addr *UnixAddr, err error) {
+	return 0, 0, 0, nil, syscall.EPLAN9
+}
+
+// WriteToUnix writes a packet to addr via c, copying the payload from b.
+//
+// WriteToUnix can be made to time out and return an error with
+// Timeout() == true after a fixed time limit; see SetDeadline and
+// SetWriteDeadline.  On packet-oriented connections, write timeouts
+// are rare.
+func (c *UnixConn) WriteToUnix(b []byte, addr *UnixAddr) (int, error) {
+	return 0, syscall.EPLAN9
+}
+
+// WriteTo implements the PacketConn WriteTo method.
+func (c *UnixConn) WriteTo(b []byte, addr Addr) (int, error) {
+	return 0, syscall.EPLAN9
+}
+
+// WriteMsgUnix writes a packet to addr via c, copying the payload
+// from b and the associated out-of-band data from oob.  It returns
+// the number of payload and out-of-band bytes written.
+func (c *UnixConn) WriteMsgUnix(b, oob []byte, addr *UnixAddr) (n, oobn int, err error) {
+	return 0, 0, syscall.EPLAN9
+}
+
+// CloseRead shuts down the reading side of the Unix domain connection.
+// Most callers should just use Close.
+func (c *UnixConn) CloseRead() error {
+	return syscall.EPLAN9
+}
+
+// CloseWrite shuts down the writing side of the Unix domain connection.
+// Most callers should just use Close.
+func (c *UnixConn) CloseWrite() error {
+	return syscall.EPLAN9
+}
+
+// DialUnix connects to the remote address raddr on the network net,
+// which must be "unix", "unixgram" or "unixpacket".  If laddr is not
+// nil, it is used as the local address for the connection.
+func DialUnix(net string, laddr, raddr *UnixAddr) (*UnixConn, error) {
+	return dialUnix(net, laddr, raddr, noDeadline)
+}
+
+func dialUnix(net string, laddr, raddr *UnixAddr, deadline time.Time) (*UnixConn, error) {
+	return nil, syscall.EPLAN9
+}
+
+// UnixListener is a Unix domain socket listener.  Clients should
+// typically use variables of type Listener instead of assuming Unix
+// domain sockets.
+type UnixListener struct{}
+
+// ListenUnix announces on the Unix domain socket laddr and returns a
+// Unix listener.  The network net must be "unix" or "unixpacket".
+func ListenUnix(net string, laddr *UnixAddr) (*UnixListener, error) {
+	return nil, syscall.EPLAN9
+}
+
+// AcceptUnix accepts the next incoming call and returns the new
+// connection.
+func (l *UnixListener) AcceptUnix() (*UnixConn, error) {
+	return nil, syscall.EPLAN9
+}
+
+// Accept implements the Accept method in the Listener interface; it
+// waits for the next call and returns a generic Conn.
+func (l *UnixListener) Accept() (Conn, error) {
+	return nil, syscall.EPLAN9
+}
+
+// Close stops listening on the Unix address.  Already accepted
+// connections are not closed.
+func (l *UnixListener) Close() error {
+	return syscall.EPLAN9
+}
+
+// Addr returns the listener's network address.
+func (l *UnixListener) Addr() Addr { return nil }
+
+// SetDeadline sets the deadline associated with the listener.
+// A zero time value disables the deadline.
+func (l *UnixListener) SetDeadline(t time.Time) error {
+	return syscall.EPLAN9
+}
+
+// File returns a copy of the underlying os.File, set to blocking
+// mode.  It is the caller's responsibility to close f when finished.
+// Closing l does not affect f, and closing f does not affect l.
+//
+// The returned os.File's file descriptor is different from the
+// connection's.  Attempting to change properties of the original
+// using this duplicate may or may not have the desired effect.
+func (l *UnixListener) File() (*os.File, error) {
+	return nil, syscall.EPLAN9
+}
+
+// ListenUnixgram listens for incoming Unix datagram packets addressed
+// to the local address laddr.  The network net must be "unixgram".
+// The returned connection's ReadFrom and WriteTo methods can be used
+// to receive and send packets with per-packet addressing.
+func ListenUnixgram(net string, laddr *UnixAddr) (*UnixConn, error) {
+	return nil, syscall.EPLAN9
+}
diff --git a/src/net/unixsock_posix.go b/src/net/unixsock_posix.go
new file mode 100644
index 000000000..3c2e78bdc
--- /dev/null
+++ b/src/net/unixsock_posix.go
@@ -0,0 +1,362 @@
+// Copyright 2009 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build darwin dragonfly freebsd linux nacl netbsd openbsd solaris windows
+
+package net
+
+import (
+	"errors"
+	"os"
+	"syscall"
+	"time"
+)
+
+func unixSocket(net string, laddr, raddr sockaddr, mode string, deadline time.Time) (*netFD, error) {
+	var sotype int
+	switch net {
+	case "unix":
+		sotype = syscall.SOCK_STREAM
+	case "unixgram":
+		sotype = syscall.SOCK_DGRAM
+	case "unixpacket":
+		sotype = syscall.SOCK_SEQPACKET
+	default:
+		return nil, UnknownNetworkError(net)
+	}
+
+	switch mode {
+	case "dial":
+		if laddr != nil && laddr.isWildcard() {
+			laddr = nil
+		}
+		if raddr != nil && raddr.isWildcard() {
+			raddr = nil
+		}
+		if raddr == nil && (sotype != syscall.SOCK_DGRAM || laddr == nil) {
+			return nil, errMissingAddress
+		}
+	case "listen":
+	default:
+		return nil, errors.New("unknown mode: " + mode)
+	}
+
+	fd, err := socket(net, syscall.AF_UNIX, sotype, 0, false, laddr, raddr, deadline)
+	if err != nil {
+		return nil, err
+	}
+	return fd, nil
+}
+
+func sockaddrToUnix(sa syscall.Sockaddr) Addr {
+	if s, ok := sa.(*syscall.SockaddrUnix); ok {
+		return &UnixAddr{Name: s.Name, Net: "unix"}
+	}
+	return nil
+}
+
+func sockaddrToUnixgram(sa syscall.Sockaddr) Addr {
+	if s, ok := sa.(*syscall.SockaddrUnix); ok {
+		return &UnixAddr{Name: s.Name, Net: "unixgram"}
+	}
+	return nil
+}
+
+func sockaddrToUnixpacket(sa syscall.Sockaddr) Addr {
+	if s, ok := sa.(*syscall.SockaddrUnix); ok {
+		return &UnixAddr{Name: s.Name, Net: "unixpacket"}
+	}
+	return nil
+}
+
+func sotypeToNet(sotype int) string {
+	switch sotype {
+	case syscall.SOCK_STREAM:
+		return "unix"
+	case syscall.SOCK_DGRAM:
+		return "unixgram"
+	case syscall.SOCK_SEQPACKET:
+		return "unixpacket"
+	default:
+		panic("sotypeToNet unknown socket type")
+	}
+}
+
+func (a *UnixAddr) family() int {
+	return syscall.AF_UNIX
+}
+
+func (a *UnixAddr) isWildcard() bool {
+	return a == nil || a.Name == ""
+}
+
+func (a *UnixAddr) sockaddr(family int) (syscall.Sockaddr, error) {
+	if a == nil {
+		return nil, nil
+	}
+	return &syscall.SockaddrUnix{Name: a.Name}, nil
+}
+
+// UnixConn is an implementation of the Conn interface for connections
+// to Unix domain sockets.
+type UnixConn struct {
+	conn
+}
+
+func newUnixConn(fd *netFD) *UnixConn { return &UnixConn{conn{fd}} }
+
+// ReadFromUnix reads a packet from c, copying the payload into b.  It
+// returns the number of bytes copied into b and the source address of
+// the packet.
+//
+// ReadFromUnix can be made to time out and return an error with
+// Timeout() == true after a fixed time limit; see SetDeadline and
+// SetReadDeadline.
+func (c *UnixConn) ReadFromUnix(b []byte) (n int, addr *UnixAddr, err error) {
+	if !c.ok() {
+		return 0, nil, syscall.EINVAL
+	}
+	n, sa, err := c.fd.readFrom(b)
+	switch sa := sa.(type) {
+	case *syscall.SockaddrUnix:
+		if sa.Name != "" {
+			addr = &UnixAddr{Name: sa.Name, Net: sotypeToNet(c.fd.sotype)}
+		}
+	}
+	return
+}
+
+// ReadFrom implements the PacketConn ReadFrom method.
+func (c *UnixConn) ReadFrom(b []byte) (int, Addr, error) {
+	if !c.ok() {
+		return 0, nil, syscall.EINVAL
+	}
+	n, addr, err := c.ReadFromUnix(b)
+	return n, addr.toAddr(), err
+}
+
+// ReadMsgUnix reads a packet from c, copying the payload into b and
+// the associated out-of-band data into oob.  It returns the number of
+// bytes copied into b, the number of bytes copied into oob, the flags
+// that were set on the packet, and the source address of the packet.
+func (c *UnixConn) ReadMsgUnix(b, oob []byte) (n, oobn, flags int, addr *UnixAddr, err error) {
+	if !c.ok() {
+		return 0, 0, 0, nil, syscall.EINVAL
+	}
+	n, oobn, flags, sa, err := c.fd.readMsg(b, oob)
+	switch sa := sa.(type) {
+	case *syscall.SockaddrUnix:
+		if sa.Name != "" {
+			addr = &UnixAddr{Name: sa.Name, Net: sotypeToNet(c.fd.sotype)}
+		}
+	}
+	return
+}
+
+// WriteToUnix writes a packet to addr via c, copying the payload from b.
+//
+// WriteToUnix can be made to time out and return an error with
+// Timeout() == true after a fixed time limit; see SetDeadline and
+// SetWriteDeadline.  On packet-oriented connections, write timeouts
+// are rare.
+func (c *UnixConn) WriteToUnix(b []byte, addr *UnixAddr) (n int, err error) {
+	if !c.ok() {
+		return 0, syscall.EINVAL
+	}
+	if c.fd.isConnected {
+		return 0, &OpError{Op: "write", Net: c.fd.net, Addr: addr, Err: ErrWriteToConnected}
+	}
+	if addr == nil {
+		return 0, &OpError{Op: "write", Net: c.fd.net, Addr: nil, Err: errMissingAddress}
+	}
+	if addr.Net != sotypeToNet(c.fd.sotype) {
+		return 0, syscall.EAFNOSUPPORT
+	}
+	sa := &syscall.SockaddrUnix{Name: addr.Name}
+	return c.fd.writeTo(b, sa)
+}
+
+// WriteTo implements the PacketConn WriteTo method.
+func (c *UnixConn) WriteTo(b []byte, addr Addr) (n int, err error) {
+	if !c.ok() {
+		return 0, syscall.EINVAL
+	}
+	a, ok := addr.(*UnixAddr)
+	if !ok {
+		return 0, &OpError{"write", c.fd.net, addr, syscall.EINVAL}
+	}
+	return c.WriteToUnix(b, a)
+}
+
+// WriteMsgUnix writes a packet to addr via c, copying the payload
+// from b and the associated out-of-band data from oob.  It returns
+// the number of payload and out-of-band bytes written.
+func (c *UnixConn) WriteMsgUnix(b, oob []byte, addr *UnixAddr) (n, oobn int, err error) {
+	if !c.ok() {
+		return 0, 0, syscall.EINVAL
+	}
+	if c.fd.sotype == syscall.SOCK_DGRAM && c.fd.isConnected {
+		return 0, 0, &OpError{Op: "write", Net: c.fd.net, Addr: addr, Err: ErrWriteToConnected}
+	}
+	if addr != nil {
+		if addr.Net != sotypeToNet(c.fd.sotype) {
+			return 0, 0, syscall.EAFNOSUPPORT
+		}
+		sa := &syscall.SockaddrUnix{Name: addr.Name}
+		return c.fd.writeMsg(b, oob, sa)
+	}
+	return c.fd.writeMsg(b, oob, nil)
+}
+
+// CloseRead shuts down the reading side of the Unix domain connection.
+// Most callers should just use Close.
+func (c *UnixConn) CloseRead() error {
+	if !c.ok() {
+		return syscall.EINVAL
+	}
+	return c.fd.closeRead()
+}
+
+// CloseWrite shuts down the writing side of the Unix domain connection.
+// Most callers should just use Close.
+func (c *UnixConn) CloseWrite() error {
+	if !c.ok() {
+		return syscall.EINVAL
+	}
+	return c.fd.closeWrite()
+}
+
+// DialUnix connects to the remote address raddr on the network net,
+// which must be "unix", "unixgram" or "unixpacket".  If laddr is not
+// nil, it is used as the local address for the connection.
+func DialUnix(net string, laddr, raddr *UnixAddr) (*UnixConn, error) {
+	switch net {
+	case "unix", "unixgram", "unixpacket":
+	default:
+		return nil, &OpError{Op: "dial", Net: net, Addr: raddr, Err: UnknownNetworkError(net)}
+	}
+	return dialUnix(net, laddr, raddr, noDeadline)
+}
+
+func dialUnix(net string, laddr, raddr *UnixAddr, deadline time.Time) (*UnixConn, error) {
+	fd, err := unixSocket(net, laddr, raddr, "dial", deadline)
+	if err != nil {
+		return nil, &OpError{Op: "dial", Net: net, Addr: raddr, Err: err}
+	}
+	return newUnixConn(fd), nil
+}
+
+// UnixListener is a Unix domain socket listener.  Clients should
+// typically use variables of type Listener instead of assuming Unix
+// domain sockets.
+type UnixListener struct {
+	fd   *netFD
+	path string
+}
+
+// ListenUnix announces on the Unix domain socket laddr and returns a
+// Unix listener.  The network net must be "unix" or "unixpacket".
+func ListenUnix(net string, laddr *UnixAddr) (*UnixListener, error) {
+	switch net {
+	case "unix", "unixpacket":
+	default:
+		return nil, &OpError{Op: "listen", Net: net, Addr: laddr, Err: UnknownNetworkError(net)}
+	}
+	if laddr == nil {
+		return nil, &OpError{Op: "listen", Net: net, Addr: nil, Err: errMissingAddress}
+	}
+	fd, err := unixSocket(net, laddr, nil, "listen", noDeadline)
+	if err != nil {
+		return nil, &OpError{Op: "listen", Net: net, Addr: laddr, Err: err}
+	}
+	return &UnixListener{fd, fd.laddr.String()}, nil
+}
+
+// AcceptUnix accepts the next incoming call and returns the new
+// connection.
+func (l *UnixListener) AcceptUnix() (*UnixConn, error) {
+	if l == nil || l.fd == nil {
+		return nil, syscall.EINVAL
+	}
+	fd, err := l.fd.accept()
+	if err != nil {
+		return nil, err
+	}
+	c := newUnixConn(fd)
+	return c, nil
+}
+
+// Accept implements the Accept method in the Listener interface; it
+// waits for the next call and returns a generic Conn.
+func (l *UnixListener) Accept() (c Conn, err error) {
+	c1, err := l.AcceptUnix()
+	if err != nil {
+		return nil, err
+	}
+	return c1, nil
+}
+
+// Close stops listening on the Unix address.  Already accepted
+// connections are not closed.
+func (l *UnixListener) Close() error {
+	if l == nil || l.fd == nil {
+		return syscall.EINVAL
+	}
+
+	// The operating system doesn't clean up
+	// the file that announcing created, so
+	// we have to clean it up ourselves.
+	// There's a race here--we can't know for
+	// sure whether someone else has come along
+	// and replaced our socket name already--
+	// but this sequence (remove then close)
+	// is at least compatible with the auto-remove
+	// sequence in ListenUnix.  It's only non-Go
+	// programs that can mess us up.
+	if l.path[0] != '@' {
+		syscall.Unlink(l.path)
+	}
+	return l.fd.Close()
+}
+
+// Addr returns the listener's network address.
+func (l *UnixListener) Addr() Addr { return l.fd.laddr }
+
+// SetDeadline sets the deadline associated with the listener.
+// A zero time value disables the deadline.
+func (l *UnixListener) SetDeadline(t time.Time) (err error) {
+	if l == nil || l.fd == nil {
+		return syscall.EINVAL
+	}
+	return l.fd.setDeadline(t)
+}
+
+// File returns a copy of the underlying os.File, set to blocking
+// mode.  It is the caller's responsibility to close f when finished.
+// Closing l does not affect f, and closing f does not affect l.
+//
+// The returned os.File's file descriptor is different from the
+// connection's.  Attempting to change properties of the original
+// using this duplicate may or may not have the desired effect.
+func (l *UnixListener) File() (f *os.File, err error) { return l.fd.dup() }
+
+// ListenUnixgram listens for incoming Unix datagram packets addressed
+// to the local address laddr.  The network net must be "unixgram".
+// The returned connection's ReadFrom and WriteTo methods can be used
+// to receive and send packets with per-packet addressing.
+func ListenUnixgram(net string, laddr *UnixAddr) (*UnixConn, error) {
+	switch net {
+	case "unixgram":
+	default:
+		return nil, &OpError{Op: "listen", Net: net, Addr: laddr, Err: UnknownNetworkError(net)}
+	}
+	if laddr == nil {
+		return nil, &OpError{Op: "listen", Net: net, Addr: nil, Err: errMissingAddress}
+	}
+	fd, err := unixSocket(net, laddr, nil, "listen", noDeadline)
+	if err != nil {
+		return nil, &OpError{Op: "listen", Net: net, Addr: laddr, Err: err}
+	}
+	return newUnixConn(fd), nil
+}
diff --git a/src/net/url/example_test.go b/src/net/url/example_test.go
new file mode 100644
index 000000000..56c5dc696
--- /dev/null
+++ b/src/net/url/example_test.go
@@ -0,0 +1,41 @@
+// Copyright 2012 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package url_test
+
+import (
+	"fmt"
+	"log"
+	"net/url"
+)
+
+func ExampleValues() {
+	v := url.Values{}
+	v.Set("name", "Ava")
+	v.Add("friend", "Jess")
+	v.Add("friend", "Sarah")
+	v.Add("friend", "Zoe")
+	// v.Encode() == "name=Ava&friend=Jess&friend=Sarah&friend=Zoe"
+	fmt.Println(v.Get("name"))
+	fmt.Println(v.Get("friend"))
+	fmt.Println(v["friend"])
+	// Output:
+	// Ava
+	// Jess
+	// [Jess Sarah Zoe]
+}
+
+func ExampleURL() {
+	u, err := url.Parse("http://bing.com/search?q=dotnet")
+	if err != nil {
+		log.Fatal(err)
+	}
+	u.Scheme = "https"
+	u.Host = "google.com"
+	q := u.Query()
+	q.Set("q", "golang")
+	u.RawQuery = q.Encode()
+	fmt.Println(u)
+	// Output: https://google.com/search?q=golang
+}
diff --git a/src/net/url/url.go b/src/net/url/url.go
new file mode 100644
index 000000000..0b32cd7c8
--- /dev/null
+++ b/src/net/url/url.go
@@ -0,0 +1,701 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package url parses URLs and implements query escaping.
+// See RFC 3986.
+package url
+
+import (
+	"bytes"
+	"errors"
+	"sort"
+	"strconv"
+	"strings"
+)
+
+// Error reports an error and the operation and URL that caused it.
+type Error struct {
+	Op  string
+	URL string
+	Err error
+}
+
+func (e *Error) Error() string { return e.Op + " " + e.URL + ": " + e.Err.Error() }
+
+func ishex(c byte) bool {
+	switch {
+	case '0' <= c && c <= '9':
+		return true
+	case 'a' <= c && c <= 'f':
+		return true
+	case 'A' <= c && c <= 'F':
+		return true
+	}
+	return false
+}
+
+func unhex(c byte) byte {
+	switch {
+	case '0' <= c && c <= '9':
+		return c - '0'
+	case 'a' <= c && c <= 'f':
+		return c - 'a' + 10
+	case 'A' <= c && c <= 'F':
+		return c - 'A' + 10
+	}
+	return 0
+}
+
+type encoding int
+
+const (
+	encodePath encoding = 1 + iota
+	encodeUserPassword
+	encodeQueryComponent
+	encodeFragment
+)
+
+type EscapeError string
+
+func (e EscapeError) Error() string {
+	return "invalid URL escape " + strconv.Quote(string(e))
+}
+
+// Return true if the specified character should be escaped when
+// appearing in a URL string, according to RFC 3986.
+func shouldEscape(c byte, mode encoding) bool {
+	// §2.3 Unreserved characters (alphanum)
+	if 'A' <= c && c <= 'Z' || 'a' <= c && c <= 'z' || '0' <= c && c <= '9' {
+		return false
+	}
+
+	switch c {
+	case '-', '_', '.', '~': // §2.3 Unreserved characters (mark)
+		return false
+
+	case '$', '&', '+', ',', '/', ':', ';', '=', '?', '@': // §2.2 Reserved characters (reserved)
+		// Different sections of the URL allow a few of
+		// the reserved characters to appear unescaped.
+		switch mode {
+		case encodePath: // §3.3
+			// The RFC allows : @ & = + $ but saves / ; , for assigning
+			// meaning to individual path segments. This package
+			// only manipulates the path as a whole, so we allow those
+			// last two as well. That leaves only ? to escape.
+			return c == '?'
+
+		case encodeUserPassword: // §3.2.1
+			// The RFC allows ';', ':', '&', '=', '+', '$', and ',' in
+			// userinfo, so we must escape only '@', '/', and '?'.
+			// The parsing of userinfo treats ':' as special so we must escape
+			// that too.
+			return c == '@' || c == '/' || c == '?' || c == ':'
+
+		case encodeQueryComponent: // §3.4
+			// The RFC reserves (so we must escape) everything.
+			return true
+
+		case encodeFragment: // §4.1
+			// The RFC text is silent but the grammar allows
+			// everything, so escape nothing.
+			return false
+		}
+	}
+
+	// Everything else must be escaped.
+	return true
+}
+
+// QueryUnescape does the inverse transformation of QueryEscape, converting
+// %AB into the byte 0xAB and '+' into ' ' (space). It returns an error if
+// any % is not followed by two hexadecimal digits.
+func QueryUnescape(s string) (string, error) {
+	return unescape(s, encodeQueryComponent)
+}
+
+// unescape unescapes a string; the mode specifies
+// which section of the URL string is being unescaped.
+func unescape(s string, mode encoding) (string, error) {
+	// Count %, check that they're well-formed.
+	n := 0
+	hasPlus := false
+	for i := 0; i < len(s); {
+		switch s[i] {
+		case '%':
+			n++
+			if i+2 >= len(s) || !ishex(s[i+1]) || !ishex(s[i+2]) {
+				s = s[i:]
+				if len(s) > 3 {
+					s = s[0:3]
+				}
+				return "", EscapeError(s)
+			}
+			i += 3
+		case '+':
+			hasPlus = mode == encodeQueryComponent
+			i++
+		default:
+			i++
+		}
+	}
+
+	if n == 0 && !hasPlus {
+		return s, nil
+	}
+
+	t := make([]byte, len(s)-2*n)
+	j := 0
+	for i := 0; i < len(s); {
+		switch s[i] {
+		case '%':
+			t[j] = unhex(s[i+1])<<4 | unhex(s[i+2])
+			j++
+			i += 3
+		case '+':
+			if mode == encodeQueryComponent {
+				t[j] = ' '
+			} else {
+				t[j] = '+'
+			}
+			j++
+			i++
+		default:
+			t[j] = s[i]
+			j++
+			i++
+		}
+	}
+	return string(t), nil
+}
+
+// QueryEscape escapes the string so it can be safely placed
+// inside a URL query.
+func QueryEscape(s string) string {
+	return escape(s, encodeQueryComponent)
+}
+
+func escape(s string, mode encoding) string {
+	spaceCount, hexCount := 0, 0
+	for i := 0; i < len(s); i++ {
+		c := s[i]
+		if shouldEscape(c, mode) {
+			if c == ' ' && mode == encodeQueryComponent {
+				spaceCount++
+			} else {
+				hexCount++
+			}
+		}
+	}
+
+	if spaceCount == 0 && hexCount == 0 {
+		return s
+	}
+
+	t := make([]byte, len(s)+2*hexCount)
+	j := 0
+	for i := 0; i < len(s); i++ {
+		switch c := s[i]; {
+		case c == ' ' && mode == encodeQueryComponent:
+			t[j] = '+'
+			j++
+		case shouldEscape(c, mode):
+			t[j] = '%'
+			t[j+1] = "0123456789ABCDEF"[c>>4]
+			t[j+2] = "0123456789ABCDEF"[c&15]
+			j += 3
+		default:
+			t[j] = s[i]
+			j++
+		}
+	}
+	return string(t)
+}
+
+// A URL represents a parsed URL (technically, a URI reference).
+// The general form represented is:
+//
+//	scheme://[userinfo@]host/path[?query][#fragment]
+//
+// URLs that do not start with a slash after the scheme are interpreted as:
+//
+//	scheme:opaque[?query][#fragment]
+//
+// Note that the Path field is stored in decoded form: /%47%6f%2f becomes /Go/.
+// A consequence is that it is impossible to tell which slashes in the Path were
+// slashes in the raw URL and which were %2f. This distinction is rarely important,
+// but when it is a client must use other routines to parse the raw URL or construct
+// the parsed URL. For example, an HTTP server can consult req.RequestURI, and
+// an HTTP client can use URL{Host: "example.com", Opaque: "//example.com/Go%2f"}
+// instead of URL{Host: "example.com", Path: "/Go/"}.
+type URL struct {
+	Scheme   string
+	Opaque   string    // encoded opaque data
+	User     *Userinfo // username and password information
+	Host     string    // host or host:port
+	Path     string
+	RawQuery string // encoded query values, without '?'
+	Fragment string // fragment for references, without '#'
+}
+
+// User returns a Userinfo containing the provided username
+// and no password set.
+func User(username string) *Userinfo {
+	return &Userinfo{username, "", false}
+}
+
+// UserPassword returns a Userinfo containing the provided username
+// and password.
+// This functionality should only be used with legacy web sites.
+// RFC 2396 warns that interpreting Userinfo this way
+// ``is NOT RECOMMENDED, because the passing of authentication
+// information in clear text (such as URI) has proven to be a
+// security risk in almost every case where it has been used.''
+func UserPassword(username, password string) *Userinfo {
+	return &Userinfo{username, password, true}
+}
+
+// The Userinfo type is an immutable encapsulation of username and
+// password details for a URL. An existing Userinfo value is guaranteed
+// to have a username set (potentially empty, as allowed by RFC 2396),
+// and optionally a password.
+type Userinfo struct {
+	username    string
+	password    string
+	passwordSet bool
+}
+
+// Username returns the username.
+func (u *Userinfo) Username() string {
+	return u.username
+}
+
+// Password returns the password in case it is set, and whether it is set.
+func (u *Userinfo) Password() (string, bool) {
+	if u.passwordSet {
+		return u.password, true
+	}
+	return "", false
+}
+
+// String returns the encoded userinfo information in the standard form
+// of "username[:password]".
+func (u *Userinfo) String() string {
+	s := escape(u.username, encodeUserPassword)
+	if u.passwordSet {
+		s += ":" + escape(u.password, encodeUserPassword)
+	}
+	return s
+}
+
+// Maybe rawurl is of the form scheme:path.
+// (Scheme must be [a-zA-Z][a-zA-Z0-9+-.]*)
+// If so, return scheme, path; else return "", rawurl.
+func getscheme(rawurl string) (scheme, path string, err error) {
+	for i := 0; i < len(rawurl); i++ {
+		c := rawurl[i]
+		switch {
+		case 'a' <= c && c <= 'z' || 'A' <= c && c <= 'Z':
+		// do nothing
+		case '0' <= c && c <= '9' || c == '+' || c == '-' || c == '.':
+			if i == 0 {
+				return "", rawurl, nil
+			}
+		case c == ':':
+			if i == 0 {
+				return "", "", errors.New("missing protocol scheme")
+			}
+			return rawurl[0:i], rawurl[i+1:], nil
+		default:
+			// we have encountered an invalid character,
+			// so there is no valid scheme
+			return "", rawurl, nil
+		}
+	}
+	return "", rawurl, nil
+}
+
+// Maybe s is of the form t c u.
+// If so, return t, c u (or t, u if cutc == true).
+// If not, return s, "".
+func split(s string, c string, cutc bool) (string, string) {
+	i := strings.Index(s, c)
+	if i < 0 {
+		return s, ""
+	}
+	if cutc {
+		return s[0:i], s[i+len(c):]
+	}
+	return s[0:i], s[i:]
+}
+
+// Parse parses rawurl into a URL structure.
+// The rawurl may be relative or absolute.
+func Parse(rawurl string) (url *URL, err error) {
+	// Cut off #frag
+	u, frag := split(rawurl, "#", true)
+	if url, err = parse(u, false); err != nil {
+		return nil, err
+	}
+	if frag == "" {
+		return url, nil
+	}
+	if url.Fragment, err = unescape(frag, encodeFragment); err != nil {
+		return nil, &Error{"parse", rawurl, err}
+	}
+	return url, nil
+}
+
+// ParseRequestURI parses rawurl into a URL structure.  It assumes that
+// rawurl was received in an HTTP request, so the rawurl is interpreted
+// only as an absolute URI or an absolute path.
+// The string rawurl is assumed not to have a #fragment suffix.
+// (Web browsers strip #fragment before sending the URL to a web server.)
+func ParseRequestURI(rawurl string) (url *URL, err error) {
+	return parse(rawurl, true)
+}
+
+// parse parses a URL from a string in one of two contexts.  If
+// viaRequest is true, the URL is assumed to have arrived via an HTTP request,
+// in which case only absolute URLs or path-absolute relative URLs are allowed.
+// If viaRequest is false, all forms of relative URLs are allowed.
+func parse(rawurl string, viaRequest bool) (url *URL, err error) {
+	var rest string
+
+	if rawurl == "" && viaRequest {
+		err = errors.New("empty url")
+		goto Error
+	}
+	url = new(URL)
+
+	if rawurl == "*" {
+		url.Path = "*"
+		return
+	}
+
+	// Split off possible leading "http:", "mailto:", etc.
+	// Cannot contain escaped characters.
+	if url.Scheme, rest, err = getscheme(rawurl); err != nil {
+		goto Error
+	}
+	url.Scheme = strings.ToLower(url.Scheme)
+
+	rest, url.RawQuery = split(rest, "?", true)
+
+	if !strings.HasPrefix(rest, "/") {
+		if url.Scheme != "" {
+			// We consider rootless paths per RFC 3986 as opaque.
+			url.Opaque = rest
+			return url, nil
+		}
+		if viaRequest {
+			err = errors.New("invalid URI for request")
+			goto Error
+		}
+	}
+
+	if (url.Scheme != "" || !viaRequest && !strings.HasPrefix(rest, "///")) && strings.HasPrefix(rest, "//") {
+		var authority string
+		authority, rest = split(rest[2:], "/", false)
+		url.User, url.Host, err = parseAuthority(authority)
+		if err != nil {
+			goto Error
+		}
+		if strings.Contains(url.Host, "%") {
+			err = errors.New("hexadecimal escape in host")
+			goto Error
+		}
+	}
+	if url.Path, err = unescape(rest, encodePath); err != nil {
+		goto Error
+	}
+	return url, nil
+
+Error:
+	return nil, &Error{"parse", rawurl, err}
+}
+
+func parseAuthority(authority string) (user *Userinfo, host string, err error) {
+	i := strings.LastIndex(authority, "@")
+	if i < 0 {
+		host = authority
+		return
+	}
+	userinfo, host := authority[:i], authority[i+1:]
+	if strings.Index(userinfo, ":") < 0 {
+		if userinfo, err = unescape(userinfo, encodeUserPassword); err != nil {
+			return
+		}
+		user = User(userinfo)
+	} else {
+		username, password := split(userinfo, ":", true)
+		if username, err = unescape(username, encodeUserPassword); err != nil {
+			return
+		}
+		if password, err = unescape(password, encodeUserPassword); err != nil {
+			return
+		}
+		user = UserPassword(username, password)
+	}
+	return
+}
+
+// String reassembles the URL into a valid URL string.
+func (u *URL) String() string {
+	var buf bytes.Buffer
+	if u.Scheme != "" {
+		buf.WriteString(u.Scheme)
+		buf.WriteByte(':')
+	}
+	if u.Opaque != "" {
+		buf.WriteString(u.Opaque)
+	} else {
+		if u.Scheme != "" || u.Host != "" || u.User != nil {
+			buf.WriteString("//")
+			if ui := u.User; ui != nil {
+				buf.WriteString(ui.String())
+				buf.WriteByte('@')
+			}
+			if h := u.Host; h != "" {
+				buf.WriteString(h)
+			}
+		}
+		if u.Path != "" && u.Path[0] != '/' && u.Host != "" {
+			buf.WriteByte('/')
+		}
+		buf.WriteString(escape(u.Path, encodePath))
+	}
+	if u.RawQuery != "" {
+		buf.WriteByte('?')
+		buf.WriteString(u.RawQuery)
+	}
+	if u.Fragment != "" {
+		buf.WriteByte('#')
+		buf.WriteString(escape(u.Fragment, encodeFragment))
+	}
+	return buf.String()
+}
+
+// Values maps a string key to a list of values.
+// It is typically used for query parameters and form values.
+// Unlike in the http.Header map, the keys in a Values map
+// are case-sensitive.
+type Values map[string][]string
+
+// Get gets the first value associated with the given key.
+// If there are no values associated with the key, Get returns
+// the empty string. To access multiple values, use the map
+// directly.
+func (v Values) Get(key string) string {
+	if v == nil {
+		return ""
+	}
+	vs, ok := v[key]
+	if !ok || len(vs) == 0 {
+		return ""
+	}
+	return vs[0]
+}
+
+// Set sets the key to value. It replaces any existing
+// values.
+func (v Values) Set(key, value string) {
+	v[key] = []string{value}
+}
+
+// Add adds the value to key. It appends to any existing
+// values associated with key.
+func (v Values) Add(key, value string) {
+	v[key] = append(v[key], value)
+}
+
+// Del deletes the values associated with key.
+func (v Values) Del(key string) {
+	delete(v, key)
+}
+
+// ParseQuery parses the URL-encoded query string and returns
+// a map listing the values specified for each key.
+// ParseQuery always returns a non-nil map containing all the
+// valid query parameters found; err describes the first decoding error
+// encountered, if any.
+func ParseQuery(query string) (m Values, err error) {
+	m = make(Values)
+	err = parseQuery(m, query)
+	return
+}
+
+func parseQuery(m Values, query string) (err error) {
+	for query != "" {
+		key := query
+		if i := strings.IndexAny(key, "&;"); i >= 0 {
+			key, query = key[:i], key[i+1:]
+		} else {
+			query = ""
+		}
+		if key == "" {
+			continue
+		}
+		value := ""
+		if i := strings.Index(key, "="); i >= 0 {
+			key, value = key[:i], key[i+1:]
+		}
+		key, err1 := QueryUnescape(key)
+		if err1 != nil {
+			if err == nil {
+				err = err1
+			}
+			continue
+		}
+		value, err1 = QueryUnescape(value)
+		if err1 != nil {
+			if err == nil {
+				err = err1
+			}
+			continue
+		}
+		m[key] = append(m[key], value)
+	}
+	return err
+}
+
+// Encode encodes the values into ``URL encoded'' form
+// ("bar=baz&foo=quux") sorted by key.
+func (v Values) Encode() string {
+	if v == nil {
+		return ""
+	}
+	var buf bytes.Buffer
+	keys := make([]string, 0, len(v))
+	for k := range v {
+		keys = append(keys, k)
+	}
+	sort.Strings(keys)
+	for _, k := range keys {
+		vs := v[k]
+		prefix := QueryEscape(k) + "="
+		for _, v := range vs {
+			if buf.Len() > 0 {
+				buf.WriteByte('&')
+			}
+			buf.WriteString(prefix)
+			buf.WriteString(QueryEscape(v))
+		}
+	}
+	return buf.String()
+}
+
+// resolvePath applies special path segments from refs and applies
+// them to base, per RFC 3986.
+func resolvePath(base, ref string) string {
+	var full string
+	if ref == "" {
+		full = base
+	} else if ref[0] != '/' {
+		i := strings.LastIndex(base, "/")
+		full = base[:i+1] + ref
+	} else {
+		full = ref
+	}
+	if full == "" {
+		return ""
+	}
+	var dst []string
+	src := strings.Split(full, "/")
+	for _, elem := range src {
+		switch elem {
+		case ".":
+			// drop
+		case "..":
+			if len(dst) > 0 {
+				dst = dst[:len(dst)-1]
+			}
+		default:
+			dst = append(dst, elem)
+		}
+	}
+	if last := src[len(src)-1]; last == "." || last == ".." {
+		// Add final slash to the joined path.
+		dst = append(dst, "")
+	}
+	return "/" + strings.TrimLeft(strings.Join(dst, "/"), "/")
+}
+
+// IsAbs returns true if the URL is absolute.
+func (u *URL) IsAbs() bool {
+	return u.Scheme != ""
+}
+
+// Parse parses a URL in the context of the receiver.  The provided URL
+// may be relative or absolute.  Parse returns nil, err on parse
+// failure, otherwise its return value is the same as ResolveReference.
+func (u *URL) Parse(ref string) (*URL, error) {
+	refurl, err := Parse(ref)
+	if err != nil {
+		return nil, err
+	}
+	return u.ResolveReference(refurl), nil
+}
+
+// ResolveReference resolves a URI reference to an absolute URI from
+// an absolute base URI, per RFC 3986 Section 5.2.  The URI reference
+// may be relative or absolute.  ResolveReference always returns a new
+// URL instance, even if the returned URL is identical to either the
+// base or reference. If ref is an absolute URL, then ResolveReference
+// ignores base and returns a copy of ref.
+func (u *URL) ResolveReference(ref *URL) *URL {
+	url := *ref
+	if ref.Scheme == "" {
+		url.Scheme = u.Scheme
+	}
+	if ref.Scheme != "" || ref.Host != "" || ref.User != nil {
+		// The "absoluteURI" or "net_path" cases.
+		url.Path = resolvePath(ref.Path, "")
+		return &url
+	}
+	if ref.Opaque != "" {
+		url.User = nil
+		url.Host = ""
+		url.Path = ""
+		return &url
+	}
+	if ref.Path == "" {
+		if ref.RawQuery == "" {
+			url.RawQuery = u.RawQuery
+			if ref.Fragment == "" {
+				url.Fragment = u.Fragment
+			}
+		}
+	}
+	// The "abs_path" or "rel_path" cases.
+	url.Host = u.Host
+	url.User = u.User
+	url.Path = resolvePath(u.Path, ref.Path)
+	return &url
+}
+
+// Query parses RawQuery and returns the corresponding values.
+func (u *URL) Query() Values {
+	v, _ := ParseQuery(u.RawQuery)
+	return v
+}
+
+// RequestURI returns the encoded path?query or opaque?query
+// string that would be used in an HTTP request for u.
+func (u *URL) RequestURI() string {
+	result := u.Opaque
+	if result == "" {
+		result = escape(u.Path, encodePath)
+		if result == "" {
+			result = "/"
+		}
+	} else {
+		if strings.HasPrefix(result, "//") {
+			result = u.Scheme + ":" + result
+		}
+	}
+	if u.RawQuery != "" {
+		result += "?" + u.RawQuery
+	}
+	return result
+}
diff --git a/src/net/url/url_test.go b/src/net/url/url_test.go
new file mode 100644
index 000000000..d8b19d805
--- /dev/null
+++ b/src/net/url/url_test.go
@@ -0,0 +1,961 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package url
+
+import (
+	"fmt"
+	"reflect"
+	"strings"
+	"testing"
+)
+
+type URLTest struct {
+	in        string
+	out       *URL
+	roundtrip string // expected result of reserializing the URL; empty means same as "in".
+}
+
+var urltests = []URLTest{
+	// no path
+	{
+		"http://www.google.com",
+		&URL{
+			Scheme: "http",
+			Host:   "www.google.com",
+		},
+		"",
+	},
+	// path
+	{
+		"http://www.google.com/",
+		&URL{
+			Scheme: "http",
+			Host:   "www.google.com",
+			Path:   "/",
+		},
+		"",
+	},
+	// path with hex escaping
+	{
+		"http://www.google.com/file%20one%26two",
+		&URL{
+			Scheme: "http",
+			Host:   "www.google.com",
+			Path:   "/file one&two",
+		},
+		"http://www.google.com/file%20one&two",
+	},
+	// user
+	{
+		"ftp://webmaster@www.google.com/",
+		&URL{
+			Scheme: "ftp",
+			User:   User("webmaster"),
+			Host:   "www.google.com",
+			Path:   "/",
+		},
+		"",
+	},
+	// escape sequence in username
+	{
+		"ftp://john%20doe@www.google.com/",
+		&URL{
+			Scheme: "ftp",
+			User:   User("john doe"),
+			Host:   "www.google.com",
+			Path:   "/",
+		},
+		"ftp://john%20doe@www.google.com/",
+	},
+	// query
+	{
+		"http://www.google.com/?q=go+language",
+		&URL{
+			Scheme:   "http",
+			Host:     "www.google.com",
+			Path:     "/",
+			RawQuery: "q=go+language",
+		},
+		"",
+	},
+	// query with hex escaping: NOT parsed
+	{
+		"http://www.google.com/?q=go%20language",
+		&URL{
+			Scheme:   "http",
+			Host:     "www.google.com",
+			Path:     "/",
+			RawQuery: "q=go%20language",
+		},
+		"",
+	},
+	// %20 outside query
+	{
+		"http://www.google.com/a%20b?q=c+d",
+		&URL{
+			Scheme:   "http",
+			Host:     "www.google.com",
+			Path:     "/a b",
+			RawQuery: "q=c+d",
+		},
+		"",
+	},
+	// path without leading /, so no parsing
+	{
+		"http:www.google.com/?q=go+language",
+		&URL{
+			Scheme:   "http",
+			Opaque:   "www.google.com/",
+			RawQuery: "q=go+language",
+		},
+		"http:www.google.com/?q=go+language",
+	},
+	// path without leading /, so no parsing
+	{
+		"http:%2f%2fwww.google.com/?q=go+language",
+		&URL{
+			Scheme:   "http",
+			Opaque:   "%2f%2fwww.google.com/",
+			RawQuery: "q=go+language",
+		},
+		"http:%2f%2fwww.google.com/?q=go+language",
+	},
+	// non-authority with path
+	{
+		"mailto:/webmaster@golang.org",
+		&URL{
+			Scheme: "mailto",
+			Path:   "/webmaster@golang.org",
+		},
+		"mailto:///webmaster@golang.org", // unfortunate compromise
+	},
+	// non-authority
+	{
+		"mailto:webmaster@golang.org",
+		&URL{
+			Scheme: "mailto",
+			Opaque: "webmaster@golang.org",
+		},
+		"",
+	},
+	// unescaped :// in query should not create a scheme
+	{
+		"/foo?query=http://bad",
+		&URL{
+			Path:     "/foo",
+			RawQuery: "query=http://bad",
+		},
+		"",
+	},
+	// leading // without scheme should create an authority
+	{
+		"//foo",
+		&URL{
+			Host: "foo",
+		},
+		"",
+	},
+	// leading // without scheme, with userinfo, path, and query
+	{
+		"//user@foo/path?a=b",
+		&URL{
+			User:     User("user"),
+			Host:     "foo",
+			Path:     "/path",
+			RawQuery: "a=b",
+		},
+		"",
+	},
+	// Three leading slashes isn't an authority, but doesn't return an error.
+	// (We can't return an error, as this code is also used via
+	// ServeHTTP -> ReadRequest -> Parse, which is arguably a
+	// different URL parsing context, but currently shares the
+	// same codepath)
+	{
+		"///threeslashes",
+		&URL{
+			Path: "///threeslashes",
+		},
+		"",
+	},
+	{
+		"http://user:password@google.com",
+		&URL{
+			Scheme: "http",
+			User:   UserPassword("user", "password"),
+			Host:   "google.com",
+		},
+		"http://user:password@google.com",
+	},
+	// unescaped @ in username should not confuse host
+	{
+		"http://j@ne:password@google.com",
+		&URL{
+			Scheme: "http",
+			User:   UserPassword("j@ne", "password"),
+			Host:   "google.com",
+		},
+		"http://j%40ne:password@google.com",
+	},
+	// unescaped @ in password should not confuse host
+	{
+		"http://jane:p@ssword@google.com",
+		&URL{
+			Scheme: "http",
+			User:   UserPassword("jane", "p@ssword"),
+			Host:   "google.com",
+		},
+		"http://jane:p%40ssword@google.com",
+	},
+	{
+		"http://j@ne:password@google.com/p@th?q=@go",
+		&URL{
+			Scheme:   "http",
+			User:     UserPassword("j@ne", "password"),
+			Host:     "google.com",
+			Path:     "/p@th",
+			RawQuery: "q=@go",
+		},
+		"http://j%40ne:password@google.com/p@th?q=@go",
+	},
+	{
+		"http://www.google.com/?q=go+language#foo",
+		&URL{
+			Scheme:   "http",
+			Host:     "www.google.com",
+			Path:     "/",
+			RawQuery: "q=go+language",
+			Fragment: "foo",
+		},
+		"",
+	},
+	{
+		"http://www.google.com/?q=go+language#foo%26bar",
+		&URL{
+			Scheme:   "http",
+			Host:     "www.google.com",
+			Path:     "/",
+			RawQuery: "q=go+language",
+			Fragment: "foo&bar",
+		},
+		"http://www.google.com/?q=go+language#foo&bar",
+	},
+	{
+		"file:///home/adg/rabbits",
+		&URL{
+			Scheme: "file",
+			Host:   "",
+			Path:   "/home/adg/rabbits",
+		},
+		"file:///home/adg/rabbits",
+	},
+	// "Windows" paths are no exception to the rule.
+	// See golang.org/issue/6027, especially comment #9.
+	{
+		"file:///C:/FooBar/Baz.txt",
+		&URL{
+			Scheme: "file",
+			Host:   "",
+			Path:   "/C:/FooBar/Baz.txt",
+		},
+		"file:///C:/FooBar/Baz.txt",
+	},
+	// case-insensitive scheme
+	{
+		"MaIlTo:webmaster@golang.org",
+		&URL{
+			Scheme: "mailto",
+			Opaque: "webmaster@golang.org",
+		},
+		"mailto:webmaster@golang.org",
+	},
+	// Relative path
+	{
+		"a/b/c",
+		&URL{
+			Path: "a/b/c",
+		},
+		"a/b/c",
+	},
+	// escaped '?' in username and password
+	{
+		"http://%3Fam:pa%3Fsword@google.com",
+		&URL{
+			Scheme: "http",
+			User:   UserPassword("?am", "pa?sword"),
+			Host:   "google.com",
+		},
+		"",
+	},
+}
+
+// more useful string for debugging than fmt's struct printer
+func ufmt(u *URL) string {
+	var user, pass interface{}
+	if u.User != nil {
+		user = u.User.Username()
+		if p, ok := u.User.Password(); ok {
+			pass = p
+		}
+	}
+	return fmt.Sprintf("opaque=%q, scheme=%q, user=%#v, pass=%#v, host=%q, path=%q, rawq=%q, frag=%q",
+		u.Opaque, u.Scheme, user, pass, u.Host, u.Path, u.RawQuery, u.Fragment)
+}
+
+func DoTest(t *testing.T, parse func(string) (*URL, error), name string, tests []URLTest) {
+	for _, tt := range tests {
+		u, err := parse(tt.in)
+		if err != nil {
+			t.Errorf("%s(%q) returned error %s", name, tt.in, err)
+			continue
+		}
+		if !reflect.DeepEqual(u, tt.out) {
+			t.Errorf("%s(%q):\n\thave %v\n\twant %v\n",
+				name, tt.in, ufmt(u), ufmt(tt.out))
+		}
+	}
+}
+
+func BenchmarkString(b *testing.B) {
+	b.StopTimer()
+	b.ReportAllocs()
+	for _, tt := range urltests {
+		u, err := Parse(tt.in)
+		if err != nil {
+			b.Errorf("Parse(%q) returned error %s", tt.in, err)
+			continue
+		}
+		if tt.roundtrip == "" {
+			continue
+		}
+		b.StartTimer()
+		var g string
+		for i := 0; i < b.N; i++ {
+			g = u.String()
+		}
+		b.StopTimer()
+		if w := tt.roundtrip; g != w {
+			b.Errorf("Parse(%q).String() == %q, want %q", tt.in, g, w)
+		}
+	}
+}
+
+func TestParse(t *testing.T) {
+	DoTest(t, Parse, "Parse", urltests)
+}
+
+const pathThatLooksSchemeRelative = "//not.a.user@not.a.host/just/a/path"
+
+var parseRequestURLTests = []struct {
+	url           string
+	expectedValid bool
+}{
+	{"http://foo.com", true},
+	{"http://foo.com/", true},
+	{"http://foo.com/path", true},
+	{"/", true},
+	{pathThatLooksSchemeRelative, true},
+	{"//not.a.user@%66%6f%6f.com/just/a/path/also", true},
+	{"foo.html", false},
+	{"../dir/", false},
+	{"*", true},
+}
+
+func TestParseRequestURI(t *testing.T) {
+	for _, test := range parseRequestURLTests {
+		_, err := ParseRequestURI(test.url)
+		valid := err == nil
+		if valid != test.expectedValid {
+			t.Errorf("Expected valid=%v for %q; got %v", test.expectedValid, test.url, valid)
+		}
+	}
+
+	url, err := ParseRequestURI(pathThatLooksSchemeRelative)
+	if err != nil {
+		t.Fatalf("Unexpected error %v", err)
+	}
+	if url.Path != pathThatLooksSchemeRelative {
+		t.Errorf("Expected path %q; got %q", pathThatLooksSchemeRelative, url.Path)
+	}
+}
+
+func DoTestString(t *testing.T, parse func(string) (*URL, error), name string, tests []URLTest) {
+	for _, tt := range tests {
+		u, err := parse(tt.in)
+		if err != nil {
+			t.Errorf("%s(%q) returned error %s", name, tt.in, err)
+			continue
+		}
+		expected := tt.in
+		if len(tt.roundtrip) > 0 {
+			expected = tt.roundtrip
+		}
+		s := u.String()
+		if s != expected {
+			t.Errorf("%s(%q).String() == %q (expected %q)", name, tt.in, s, expected)
+		}
+	}
+}
+
+func TestURLString(t *testing.T) {
+	DoTestString(t, Parse, "Parse", urltests)
+
+	// no leading slash on path should prepend
+	// slash on String() call
+	noslash := URLTest{
+		"http://www.google.com/search",
+		&URL{
+			Scheme: "http",
+			Host:   "www.google.com",
+			Path:   "search",
+		},
+		"",
+	}
+	s := noslash.out.String()
+	if s != noslash.in {
+		t.Errorf("Expected %s; go %s", noslash.in, s)
+	}
+}
+
+type EscapeTest struct {
+	in  string
+	out string
+	err error
+}
+
+var unescapeTests = []EscapeTest{
+	{
+		"",
+		"",
+		nil,
+	},
+	{
+		"abc",
+		"abc",
+		nil,
+	},
+	{
+		"1%41",
+		"1A",
+		nil,
+	},
+	{
+		"1%41%42%43",
+		"1ABC",
+		nil,
+	},
+	{
+		"%4a",
+		"J",
+		nil,
+	},
+	{
+		"%6F",
+		"o",
+		nil,
+	},
+	{
+		"%", // not enough characters after %
+		"",
+		EscapeError("%"),
+	},
+	{
+		"%a", // not enough characters after %
+		"",
+		EscapeError("%a"),
+	},
+	{
+		"%1", // not enough characters after %
+		"",
+		EscapeError("%1"),
+	},
+	{
+		"123%45%6", // not enough characters after %
+		"",
+		EscapeError("%6"),
+	},
+	{
+		"%zzzzz", // invalid hex digits
+		"",
+		EscapeError("%zz"),
+	},
+}
+
+func TestUnescape(t *testing.T) {
+	for _, tt := range unescapeTests {
+		actual, err := QueryUnescape(tt.in)
+		if actual != tt.out || (err != nil) != (tt.err != nil) {
+			t.Errorf("QueryUnescape(%q) = %q, %s; want %q, %s", tt.in, actual, err, tt.out, tt.err)
+		}
+	}
+}
+
+var escapeTests = []EscapeTest{
+	{
+		"",
+		"",
+		nil,
+	},
+	{
+		"abc",
+		"abc",
+		nil,
+	},
+	{
+		"one two",
+		"one+two",
+		nil,
+	},
+	{
+		"10%",
+		"10%25",
+		nil,
+	},
+	{
+		" ?&=#+%!<>#\"{}|\\^[]`☺\t:/@$'()*,;",
+		"+%3F%26%3D%23%2B%25%21%3C%3E%23%22%7B%7D%7C%5C%5E%5B%5D%60%E2%98%BA%09%3A%2F%40%24%27%28%29%2A%2C%3B",
+		nil,
+	},
+}
+
+func TestEscape(t *testing.T) {
+	for _, tt := range escapeTests {
+		actual := QueryEscape(tt.in)
+		if tt.out != actual {
+			t.Errorf("QueryEscape(%q) = %q, want %q", tt.in, actual, tt.out)
+		}
+
+		// for bonus points, verify that escape:unescape is an identity.
+		roundtrip, err := QueryUnescape(actual)
+		if roundtrip != tt.in || err != nil {
+			t.Errorf("QueryUnescape(%q) = %q, %s; want %q, %s", actual, roundtrip, err, tt.in, "[no error]")
+		}
+	}
+}
+
+//var userinfoTests = []UserinfoTest{
+//	{"user", "password", "user:password"},
+//	{"foo:bar", "~!@#$%^&*()_+{}|[]\\-=`:;'\"<>?,./",
+//		"foo%3Abar:~!%40%23$%25%5E&*()_+%7B%7D%7C%5B%5D%5C-=%60%3A;'%22%3C%3E?,.%2F"},
+//}
+
+type EncodeQueryTest struct {
+	m        Values
+	expected string
+}
+
+var encodeQueryTests = []EncodeQueryTest{
+	{nil, ""},
+	{Values{"q": {"puppies"}, "oe": {"utf8"}}, "oe=utf8&q=puppies"},
+	{Values{"q": {"dogs", "&", "7"}}, "q=dogs&q=%26&q=7"},
+	{Values{
+		"a": {"a1", "a2", "a3"},
+		"b": {"b1", "b2", "b3"},
+		"c": {"c1", "c2", "c3"},
+	}, "a=a1&a=a2&a=a3&b=b1&b=b2&b=b3&c=c1&c=c2&c=c3"},
+}
+
+func TestEncodeQuery(t *testing.T) {
+	for _, tt := range encodeQueryTests {
+		if q := tt.m.Encode(); q != tt.expected {
+			t.Errorf(`EncodeQuery(%+v) = %q, want %q`, tt.m, q, tt.expected)
+		}
+	}
+}
+
+var resolvePathTests = []struct {
+	base, ref, expected string
+}{
+	{"a/b", ".", "/a/"},
+	{"a/b", "c", "/a/c"},
+	{"a/b", "..", "/"},
+	{"a/", "..", "/"},
+	{"a/", "../..", "/"},
+	{"a/b/c", "..", "/a/"},
+	{"a/b/c", "../d", "/a/d"},
+	{"a/b/c", ".././d", "/a/d"},
+	{"a/b", "./..", "/"},
+	{"a/./b", ".", "/a/"},
+	{"a/../", ".", "/"},
+	{"a/.././b", "c", "/c"},
+}
+
+func TestResolvePath(t *testing.T) {
+	for _, test := range resolvePathTests {
+		got := resolvePath(test.base, test.ref)
+		if got != test.expected {
+			t.Errorf("For %q + %q got %q; expected %q", test.base, test.ref, got, test.expected)
+		}
+	}
+}
+
+var resolveReferenceTests = []struct {
+	base, rel, expected string
+}{
+	// Absolute URL references
+	{"http://foo.com?a=b", "https://bar.com/", "https://bar.com/"},
+	{"http://foo.com/", "https://bar.com/?a=b", "https://bar.com/?a=b"},
+	{"http://foo.com/bar", "mailto:foo@example.com", "mailto:foo@example.com"},
+
+	// Path-absolute references
+	{"http://foo.com/bar", "/baz", "http://foo.com/baz"},
+	{"http://foo.com/bar?a=b#f", "/baz", "http://foo.com/baz"},
+	{"http://foo.com/bar?a=b", "/baz?c=d", "http://foo.com/baz?c=d"},
+
+	// Scheme-relative
+	{"https://foo.com/bar?a=b", "//bar.com/quux", "https://bar.com/quux"},
+
+	// Path-relative references:
+
+	// ... current directory
+	{"http://foo.com", ".", "http://foo.com/"},
+	{"http://foo.com/bar", ".", "http://foo.com/"},
+	{"http://foo.com/bar/", ".", "http://foo.com/bar/"},
+
+	// ... going down
+	{"http://foo.com", "bar", "http://foo.com/bar"},
+	{"http://foo.com/", "bar", "http://foo.com/bar"},
+	{"http://foo.com/bar/baz", "quux", "http://foo.com/bar/quux"},
+
+	// ... going up
+	{"http://foo.com/bar/baz", "../quux", "http://foo.com/quux"},
+	{"http://foo.com/bar/baz", "../../../../../quux", "http://foo.com/quux"},
+	{"http://foo.com/bar", "..", "http://foo.com/"},
+	{"http://foo.com/bar/baz", "./..", "http://foo.com/"},
+	// ".." in the middle (issue 3560)
+	{"http://foo.com/bar/baz", "quux/dotdot/../tail", "http://foo.com/bar/quux/tail"},
+	{"http://foo.com/bar/baz", "quux/./dotdot/../tail", "http://foo.com/bar/quux/tail"},
+	{"http://foo.com/bar/baz", "quux/./dotdot/.././tail", "http://foo.com/bar/quux/tail"},
+	{"http://foo.com/bar/baz", "quux/./dotdot/./../tail", "http://foo.com/bar/quux/tail"},
+	{"http://foo.com/bar/baz", "quux/./dotdot/dotdot/././../../tail", "http://foo.com/bar/quux/tail"},
+	{"http://foo.com/bar/baz", "quux/./dotdot/dotdot/./.././../tail", "http://foo.com/bar/quux/tail"},
+	{"http://foo.com/bar/baz", "quux/./dotdot/dotdot/dotdot/./../../.././././tail", "http://foo.com/bar/quux/tail"},
+	{"http://foo.com/bar/baz", "quux/./dotdot/../dotdot/../dot/./tail/..", "http://foo.com/bar/quux/dot/"},
+
+	// Remove any dot-segments prior to forming the target URI.
+	// http://tools.ietf.org/html/rfc3986#section-5.2.4
+	{"http://foo.com/dot/./dotdot/../foo/bar", "../baz", "http://foo.com/dot/baz"},
+
+	// Triple dot isn't special
+	{"http://foo.com/bar", "...", "http://foo.com/..."},
+
+	// Fragment
+	{"http://foo.com/bar", ".#frag", "http://foo.com/#frag"},
+
+	// RFC 3986: Normal Examples
+	// http://tools.ietf.org/html/rfc3986#section-5.4.1
+	{"http://a/b/c/d;p?q", "g:h", "g:h"},
+	{"http://a/b/c/d;p?q", "g", "http://a/b/c/g"},
+	{"http://a/b/c/d;p?q", "./g", "http://a/b/c/g"},
+	{"http://a/b/c/d;p?q", "g/", "http://a/b/c/g/"},
+	{"http://a/b/c/d;p?q", "/g", "http://a/g"},
+	{"http://a/b/c/d;p?q", "//g", "http://g"},
+	{"http://a/b/c/d;p?q", "?y", "http://a/b/c/d;p?y"},
+	{"http://a/b/c/d;p?q", "g?y", "http://a/b/c/g?y"},
+	{"http://a/b/c/d;p?q", "#s", "http://a/b/c/d;p?q#s"},
+	{"http://a/b/c/d;p?q", "g#s", "http://a/b/c/g#s"},
+	{"http://a/b/c/d;p?q", "g?y#s", "http://a/b/c/g?y#s"},
+	{"http://a/b/c/d;p?q", ";x", "http://a/b/c/;x"},
+	{"http://a/b/c/d;p?q", "g;x", "http://a/b/c/g;x"},
+	{"http://a/b/c/d;p?q", "g;x?y#s", "http://a/b/c/g;x?y#s"},
+	{"http://a/b/c/d;p?q", "", "http://a/b/c/d;p?q"},
+	{"http://a/b/c/d;p?q", ".", "http://a/b/c/"},
+	{"http://a/b/c/d;p?q", "./", "http://a/b/c/"},
+	{"http://a/b/c/d;p?q", "..", "http://a/b/"},
+	{"http://a/b/c/d;p?q", "../", "http://a/b/"},
+	{"http://a/b/c/d;p?q", "../g", "http://a/b/g"},
+	{"http://a/b/c/d;p?q", "../..", "http://a/"},
+	{"http://a/b/c/d;p?q", "../../", "http://a/"},
+	{"http://a/b/c/d;p?q", "../../g", "http://a/g"},
+
+	// RFC 3986: Abnormal Examples
+	// http://tools.ietf.org/html/rfc3986#section-5.4.2
+	{"http://a/b/c/d;p?q", "../../../g", "http://a/g"},
+	{"http://a/b/c/d;p?q", "../../../../g", "http://a/g"},
+	{"http://a/b/c/d;p?q", "/./g", "http://a/g"},
+	{"http://a/b/c/d;p?q", "/../g", "http://a/g"},
+	{"http://a/b/c/d;p?q", "g.", "http://a/b/c/g."},
+	{"http://a/b/c/d;p?q", ".g", "http://a/b/c/.g"},
+	{"http://a/b/c/d;p?q", "g..", "http://a/b/c/g.."},
+	{"http://a/b/c/d;p?q", "..g", "http://a/b/c/..g"},
+	{"http://a/b/c/d;p?q", "./../g", "http://a/b/g"},
+	{"http://a/b/c/d;p?q", "./g/.", "http://a/b/c/g/"},
+	{"http://a/b/c/d;p?q", "g/./h", "http://a/b/c/g/h"},
+	{"http://a/b/c/d;p?q", "g/../h", "http://a/b/c/h"},
+	{"http://a/b/c/d;p?q", "g;x=1/./y", "http://a/b/c/g;x=1/y"},
+	{"http://a/b/c/d;p?q", "g;x=1/../y", "http://a/b/c/y"},
+	{"http://a/b/c/d;p?q", "g?y/./x", "http://a/b/c/g?y/./x"},
+	{"http://a/b/c/d;p?q", "g?y/../x", "http://a/b/c/g?y/../x"},
+	{"http://a/b/c/d;p?q", "g#s/./x", "http://a/b/c/g#s/./x"},
+	{"http://a/b/c/d;p?q", "g#s/../x", "http://a/b/c/g#s/../x"},
+
+	// Extras.
+	{"https://a/b/c/d;p?q", "//g?q", "https://g?q"},
+	{"https://a/b/c/d;p?q", "//g#s", "https://g#s"},
+	{"https://a/b/c/d;p?q", "//g/d/e/f?y#s", "https://g/d/e/f?y#s"},
+	{"https://a/b/c/d;p#s", "?y", "https://a/b/c/d;p?y"},
+	{"https://a/b/c/d;p?q#s", "?y", "https://a/b/c/d;p?y"},
+}
+
+func TestResolveReference(t *testing.T) {
+	mustParse := func(url string) *URL {
+		u, err := Parse(url)
+		if err != nil {
+			t.Fatalf("Expected URL to parse: %q, got error: %v", url, err)
+		}
+		return u
+	}
+	opaque := &URL{Scheme: "scheme", Opaque: "opaque"}
+	for _, test := range resolveReferenceTests {
+		base := mustParse(test.base)
+		rel := mustParse(test.rel)
+		url := base.ResolveReference(rel)
+		if url.String() != test.expected {
+			t.Errorf("URL(%q).ResolveReference(%q) == %q, got %q", test.base, test.rel, test.expected, url.String())
+		}
+		// Ensure that new instances are returned.
+		if base == url {
+			t.Errorf("Expected URL.ResolveReference to return new URL instance.")
+		}
+		// Test the convenience wrapper too.
+		url, err := base.Parse(test.rel)
+		if err != nil {
+			t.Errorf("URL(%q).Parse(%q) failed: %v", test.base, test.rel, err)
+		} else if url.String() != test.expected {
+			t.Errorf("URL(%q).Parse(%q) == %q, got %q", test.base, test.rel, test.expected, url.String())
+		} else if base == url {
+			// Ensure that new instances are returned for the wrapper too.
+			t.Errorf("Expected URL.Parse to return new URL instance.")
+		}
+		// Ensure Opaque resets the URL.
+		url = base.ResolveReference(opaque)
+		if *url != *opaque {
+			t.Errorf("ResolveReference failed to resolve opaque URL: want %#v, got %#v", url, opaque)
+		}
+		// Test the convenience wrapper with an opaque URL too.
+		url, err = base.Parse("scheme:opaque")
+		if err != nil {
+			t.Errorf(`URL(%q).Parse("scheme:opaque") failed: %v`, test.base, err)
+		} else if *url != *opaque {
+			t.Errorf("Parse failed to resolve opaque URL: want %#v, got %#v", url, opaque)
+		} else if base == url {
+			// Ensure that new instances are returned, again.
+			t.Errorf("Expected URL.Parse to return new URL instance.")
+		}
+	}
+}
+
+func TestQueryValues(t *testing.T) {
+	u, _ := Parse("http://x.com?foo=bar&bar=1&bar=2")
+	v := u.Query()
+	if len(v) != 2 {
+		t.Errorf("got %d keys in Query values, want 2", len(v))
+	}
+	if g, e := v.Get("foo"), "bar"; g != e {
+		t.Errorf("Get(foo) = %q, want %q", g, e)
+	}
+	// Case sensitive:
+	if g, e := v.Get("Foo"), ""; g != e {
+		t.Errorf("Get(Foo) = %q, want %q", g, e)
+	}
+	if g, e := v.Get("bar"), "1"; g != e {
+		t.Errorf("Get(bar) = %q, want %q", g, e)
+	}
+	if g, e := v.Get("baz"), ""; g != e {
+		t.Errorf("Get(baz) = %q, want %q", g, e)
+	}
+	v.Del("bar")
+	if g, e := v.Get("bar"), ""; g != e {
+		t.Errorf("second Get(bar) = %q, want %q", g, e)
+	}
+}
+
+type parseTest struct {
+	query string
+	out   Values
+}
+
+var parseTests = []parseTest{
+	{
+		query: "a=1&b=2",
+		out:   Values{"a": []string{"1"}, "b": []string{"2"}},
+	},
+	{
+		query: "a=1&a=2&a=banana",
+		out:   Values{"a": []string{"1", "2", "banana"}},
+	},
+	{
+		query: "ascii=%3Ckey%3A+0x90%3E",
+		out:   Values{"ascii": []string{"<key: 0x90>"}},
+	},
+	{
+		query: "a=1;b=2",
+		out:   Values{"a": []string{"1"}, "b": []string{"2"}},
+	},
+	{
+		query: "a=1&a=2;a=banana",
+		out:   Values{"a": []string{"1", "2", "banana"}},
+	},
+}
+
+func TestParseQuery(t *testing.T) {
+	for i, test := range parseTests {
+		form, err := ParseQuery(test.query)
+		if err != nil {
+			t.Errorf("test %d: Unexpected error: %v", i, err)
+			continue
+		}
+		if len(form) != len(test.out) {
+			t.Errorf("test %d: len(form) = %d, want %d", i, len(form), len(test.out))
+		}
+		for k, evs := range test.out {
+			vs, ok := form[k]
+			if !ok {
+				t.Errorf("test %d: Missing key %q", i, k)
+				continue
+			}
+			if len(vs) != len(evs) {
+				t.Errorf("test %d: len(form[%q]) = %d, want %d", i, k, len(vs), len(evs))
+				continue
+			}
+			for j, ev := range evs {
+				if v := vs[j]; v != ev {
+					t.Errorf("test %d: form[%q][%d] = %q, want %q", i, k, j, v, ev)
+				}
+			}
+		}
+	}
+}
+
+type RequestURITest struct {
+	url *URL
+	out string
+}
+
+var requritests = []RequestURITest{
+	{
+		&URL{
+			Scheme: "http",
+			Host:   "example.com",
+			Path:   "",
+		},
+		"/",
+	},
+	{
+		&URL{
+			Scheme: "http",
+			Host:   "example.com",
+			Path:   "/a b",
+		},
+		"/a%20b",
+	},
+	// golang.org/issue/4860 variant 1
+	{
+		&URL{
+			Scheme: "http",
+			Host:   "example.com",
+			Opaque: "/%2F/%2F/",
+		},
+		"/%2F/%2F/",
+	},
+	// golang.org/issue/4860 variant 2
+	{
+		&URL{
+			Scheme: "http",
+			Host:   "example.com",
+			Opaque: "//other.example.com/%2F/%2F/",
+		},
+		"http://other.example.com/%2F/%2F/",
+	},
+	{
+		&URL{
+			Scheme:   "http",
+			Host:     "example.com",
+			Path:     "/a b",
+			RawQuery: "q=go+language",
+		},
+		"/a%20b?q=go+language",
+	},
+	{
+		&URL{
+			Scheme: "myschema",
+			Opaque: "opaque",
+		},
+		"opaque",
+	},
+	{
+		&URL{
+			Scheme:   "myschema",
+			Opaque:   "opaque",
+			RawQuery: "q=go+language",
+		},
+		"opaque?q=go+language",
+	},
+}
+
+func TestRequestURI(t *testing.T) {
+	for _, tt := range requritests {
+		s := tt.url.RequestURI()
+		if s != tt.out {
+			t.Errorf("%#v.RequestURI() == %q (expected %q)", tt.url, s, tt.out)
+		}
+	}
+}
+
+func TestParseFailure(t *testing.T) {
+	// Test that the first parse error is returned.
+	const url = "%gh&%ij"
+	_, err := ParseQuery(url)
+	errStr := fmt.Sprint(err)
+	if !strings.Contains(errStr, "%gh") {
+		t.Errorf(`ParseQuery(%q) returned error %q, want something containing %q"`, url, errStr, "%gh")
+	}
+}
+
+type shouldEscapeTest struct {
+	in     byte
+	mode   encoding
+	escape bool
+}
+
+var shouldEscapeTests = []shouldEscapeTest{
+	// Unreserved characters (§2.3)
+	{'a', encodePath, false},
+	{'a', encodeUserPassword, false},
+	{'a', encodeQueryComponent, false},
+	{'a', encodeFragment, false},
+	{'z', encodePath, false},
+	{'A', encodePath, false},
+	{'Z', encodePath, false},
+	{'0', encodePath, false},
+	{'9', encodePath, false},
+	{'-', encodePath, false},
+	{'-', encodeUserPassword, false},
+	{'-', encodeQueryComponent, false},
+	{'-', encodeFragment, false},
+	{'.', encodePath, false},
+	{'_', encodePath, false},
+	{'~', encodePath, false},
+
+	// User information (§3.2.1)
+	{':', encodeUserPassword, true},
+	{'/', encodeUserPassword, true},
+	{'?', encodeUserPassword, true},
+	{'@', encodeUserPassword, true},
+	{'$', encodeUserPassword, false},
+	{'&', encodeUserPassword, false},
+	{'+', encodeUserPassword, false},
+	{',', encodeUserPassword, false},
+	{';', encodeUserPassword, false},
+	{'=', encodeUserPassword, false},
+}
+
+func TestShouldEscape(t *testing.T) {
+	for _, tt := range shouldEscapeTests {
+		if shouldEscape(tt.in, tt.mode) != tt.escape {
+			t.Errorf("shouldEscape(%q, %v) returned %v; expected %v", tt.in, tt.mode, !tt.escape, tt.escape)
+		}
+	}
+}
diff --git a/src/net/z_last_test.go b/src/net/z_last_test.go
new file mode 100644
index 000000000..4f6a54a56
--- /dev/null
+++ b/src/net/z_last_test.go
@@ -0,0 +1,37 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package net
+
+import (
+	"flag"
+	"fmt"
+	"testing"
+)
+
+var testDNSFlood = flag.Bool("dnsflood", false, "whether to test dns query flooding")
+
+func TestDNSThreadLimit(t *testing.T) {
+	if !*testDNSFlood {
+		t.Skip("test disabled; use -dnsflood to enable")
+	}
+
+	const N = 10000
+	c := make(chan int, N)
+	for i := 0; i < N; i++ {
+		go func(i int) {
+			LookupIP(fmt.Sprintf("%d.net-test.golang.org", i))
+			c <- 1
+		}(i)
+	}
+	// Don't bother waiting for the stragglers; stop at 0.9 N.
+	for i := 0; i < N*9/10; i++ {
+		if i%100 == 0 {
+			//println("TestDNSThreadLimit:", i)
+		}
+		<-c
+	}
+
+	// If we're still here, it worked.
+}