1 files changed, 232 insertions, 83 deletions

diff --git a/libgo/go/net/lookup.go b/libgo/go/net/lookup.go
index 7aa111ba92..cc2013e432 100644
--- a/libgo/go/net/lookup.go
+++ b/libgo/go/net/lookup.go
@@ -1,12 +1,13 @@
-// Copyright 2012 The Go Authors.  All rights reserved.
+// 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 (
+	"context"
+	"internal/nettrace"
 	"internal/singleflight"
-	"time"
 )
 
 // protocols contains minimal mappings between internet protocol
@@ -14,17 +15,101 @@ import (
 // protocol numbers.
 //
 // See http://www.iana.org/assignments/protocol-numbers
+//
+// On Unix, this map is augmented by readProtocols via lookupProtocol.
 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,
+	"icmp":      1,
+	"igmp":      2,
+	"tcp":       6,
+	"udp":       17,
+	"ipv6-icmp": 58,
+}
+
+// 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, nacl, etc).
+// On Unix, this map is augmented by readServices via goLookupPort.
+var services = map[string]map[string]int{
+	"udp": {
+		"domain": 53,
+	},
+	"tcp": {
+		"ftp":    21,
+		"ftps":   990,
+		"gopher": 70, // ʕ◔ϖ◔ʔ
+		"http":   80,
+		"https":  443,
+		"imap2":  143,
+		"imap3":  220,
+		"imaps":  993,
+		"pop3":   110,
+		"pop3s":  995,
+		"smtp":   25,
+		"ssh":    22,
+		"telnet": 23,
+	},
+}
+
+const maxProtoLength = len("RSVP-E2E-IGNORE") + 10 // with room to grow
+
+func lookupProtocolMap(name string) (int, error) {
+	var lowerProtocol [maxProtoLength]byte
+	n := copy(lowerProtocol[:], name)
+	lowerASCIIBytes(lowerProtocol[:n])
+	proto, found := protocols[string(lowerProtocol[:n])]
+	if !found || n != len(name) {
+		return 0, &AddrError{Err: "unknown IP protocol specified", Addr: name}
+	}
+	return proto, nil
+}
+
+const maxServiceLength = len("mobility-header") + 10 // with room to grow
+
+func lookupPortMap(network, service string) (port int, error error) {
+	switch network {
+	case "tcp4", "tcp6":
+		network = "tcp"
+	case "udp4", "udp6":
+		network = "udp"
+	}
+
+	if m, ok := services[network]; ok {
+		var lowerService [maxServiceLength]byte
+		n := copy(lowerService[:], service)
+		lowerASCIIBytes(lowerService[:n])
+		if port, ok := m[string(lowerService[:n])]; ok && n == len(service) {
+			return port, nil
+		}
+	}
+	return 0, &AddrError{Err: "unknown port", Addr: network + "/" + service}
+}
+
+// DefaultResolver is the resolver used by the package-level Lookup
+// functions and by Dialers without a specified Resolver.
+var DefaultResolver = &Resolver{}
+
+// A Resolver looks up names and numbers.
+//
+// A nil *Resolver is equivalent to a zero Resolver.
+type Resolver struct {
+	// PreferGo controls whether Go's built-in DNS resolver is preferred
+	// on platforms where it's available. It is equivalent to setting
+	// GODEBUG=netdns=go, but scoped to just this resolver.
+	PreferGo bool
+
+	// TODO(bradfitz): optional interface impl override hook
+	// TODO(bradfitz): Timeout time.Duration?
 }
 
 // LookupHost looks up the given host using the local resolver.
-// It returns an array of that host's addresses.
+// It returns a slice of that host's addresses.
 func LookupHost(host string) (addrs []string, err error) {
+	return DefaultResolver.LookupHost(context.Background(), host)
+}
+
+// LookupHost looks up the given host using the local resolver.
+// It returns a slice of that host's addresses.
+func (r *Resolver) LookupHost(ctx context.Context, host string) (addrs []string, err error) {
 	// Make sure that no matter what we do later, host=="" is rejected.
 	// ParseIP, for example, does accept empty strings.
 	if host == "" {
@@ -33,43 +118,77 @@ func LookupHost(host string) (addrs []string, err error) {
 	if ip := ParseIP(host); ip != nil {
 		return []string{host}, nil
 	}
-	return lookupHost(host)
+	return r.lookupHost(ctx, 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) (ips []IP, err error) {
+// It returns a slice of that host's IPv4 and IPv6 addresses.
+func LookupIP(host string) ([]IP, error) {
+	addrs, err := DefaultResolver.LookupIPAddr(context.Background(), host)
+	if err != nil {
+		return nil, err
+	}
+	ips := make([]IP, len(addrs))
+	for i, ia := range addrs {
+		ips[i] = ia.IP
+	}
+	return ips, nil
+}
+
+// LookupIPAddr looks up host using the local resolver.
+// It returns a slice of that host's IPv4 and IPv6 addresses.
+func (r *Resolver) LookupIPAddr(ctx context.Context, host string) ([]IPAddr, error) {
 	// Make sure that no matter what we do later, host=="" is rejected.
 	// ParseIP, for example, does accept empty strings.
 	if host == "" {
 		return nil, &DNSError{Err: errNoSuchHost.Error(), Name: host}
 	}
 	if ip := ParseIP(host); ip != nil {
-		return []IP{ip}, nil
+		return []IPAddr{{IP: ip}}, nil
 	}
-	addrs, err := lookupIPMerge(host)
-	if err != nil {
-		return
+	trace, _ := ctx.Value(nettrace.TraceKey{}).(*nettrace.Trace)
+	if trace != nil && trace.DNSStart != nil {
+		trace.DNSStart(host)
 	}
-	ips = make([]IP, len(addrs))
-	for i, addr := range addrs {
-		ips[i] = addr.IP
+	// The underlying resolver func is lookupIP by default but it
+	// can be overridden by tests. This is needed by net/http, so it
+	// uses a context key instead of unexported variables.
+	resolverFunc := r.lookupIP
+	if alt, _ := ctx.Value(nettrace.LookupIPAltResolverKey{}).(func(context.Context, string) ([]IPAddr, error)); alt != nil {
+		resolverFunc = alt
 	}
-	return
-}
 
-var lookupGroup singleflight.Group
-
-// 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 []IPAddr, err error) {
-	addrsi, err, shared := lookupGroup.Do(host, func() (interface{}, error) {
-		return testHookLookupIP(lookupIP, host)
+	ch := lookupGroup.DoChan(host, func() (interface{}, error) {
+		return testHookLookupIP(ctx, resolverFunc, host)
 	})
-	return lookupIPReturn(addrsi, err, shared)
+
+	select {
+	case <-ctx.Done():
+		// The DNS lookup timed out for some reason. Force
+		// future requests to start the DNS lookup again
+		// rather than waiting for the current lookup to
+		// complete. See issue 8602.
+		err := mapErr(ctx.Err())
+		lookupGroup.Forget(host)
+		if trace != nil && trace.DNSDone != nil {
+			trace.DNSDone(nil, false, err)
+		}
+		return nil, err
+	case r := <-ch:
+		if trace != nil && trace.DNSDone != nil {
+			addrs, _ := r.Val.([]IPAddr)
+			trace.DNSDone(ipAddrsEface(addrs), r.Shared, r.Err)
+		}
+		return lookupIPReturn(r.Val, r.Err, r.Shared)
+	}
 }
 
+// lookupGroup merges LookupIPAddr calls together for lookups
+// for the same host. The lookupGroup key is is the LookupIPAddr.host
+// argument.
+// The return values are ([]IPAddr, error).
+var lookupGroup singleflight.Group
+
 // lookupIPReturn turns the return values from singleflight.Do into
 // the return values from LookupIP.
 func lookupIPReturn(addrsi interface{}, err error, shared bool) ([]IPAddr, error) {
@@ -85,52 +204,25 @@ func lookupIPReturn(addrsi interface{}, err error, shared bool) ([]IPAddr, error
 	return addrs, nil
 }
 
-// lookupIPDeadline looks up a hostname with a deadline.
-func lookupIPDeadline(host string, deadline time.Time) (addrs []IPAddr, err error) {
-	if deadline.IsZero() {
-		return lookupIPMerge(host)
-	}
-
-	// We could push the deadline down into the name resolution
-	// functions.  However, the most commonly used implementation
-	// calls getaddrinfo, which has no timeout.
-
-	timeout := deadline.Sub(time.Now())
-	if timeout <= 0 {
-		return nil, errTimeout
-	}
-	t := time.NewTimer(timeout)
-	defer t.Stop()
-
-	ch := lookupGroup.DoChan(host, func() (interface{}, error) {
-		return testHookLookupIP(lookupIP, host)
-	})
-
-	select {
-	case <-t.C:
-		// The DNS lookup timed out for some reason.  Force
-		// future requests to start the DNS lookup again
-		// rather than waiting for the current lookup to
-		// complete.  See issue 8602.
-		lookupGroup.Forget(host)
-
-		return nil, errTimeout
-
-	case r := <-ch:
-		return lookupIPReturn(r.Val, r.Err, r.Shared)
+// ipAddrsEface returns an empty interface slice of addrs.
+func ipAddrsEface(addrs []IPAddr) []interface{} {
+	s := make([]interface{}, len(addrs))
+	for i, v := range addrs {
+		s[i] = v
 	}
+	return s
 }
 
 // LookupPort looks up the port for the given network and service.
 func LookupPort(network, service string) (port int, err error) {
-	if service == "" {
-		// Lock in the legacy behavior that an empty string
-		// means port 0. See Issue 13610.
-		return 0, nil
-	}
-	port, _, ok := dtoi(service, 0)
-	if !ok && port != big && port != -big {
-		port, err = lookupPort(network, service)
+	return DefaultResolver.LookupPort(context.Background(), network, service)
+}
+
+// LookupPort looks up the port for the given network and service.
+func (r *Resolver) LookupPort(ctx context.Context, network, service string) (port int, err error) {
+	port, needsLookup := parsePort(service)
+	if needsLookup {
+		port, err = r.lookupPort(ctx, network, service)
 		if err != nil {
 			return 0, err
 		}
@@ -141,44 +233,101 @@ func LookupPort(network, service string) (port int, err error) {
 	return port, nil
 }
 
-// LookupCNAME returns the canonical DNS host for the given name.
+// LookupCNAME returns the canonical name for the given host.
+// 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.
+//
+// A canonical name is the final name after following zero
+// or more CNAME records.
+// LookupCNAME does not return an error if host does not
+// contain DNS "CNAME" records, as long as host resolves to
+// address records.
+func LookupCNAME(host string) (cname string, err error) {
+	return DefaultResolver.lookupCNAME(context.Background(), host)
+}
+
+// LookupCNAME returns the canonical name for the given host.
 // 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)
+//
+// A canonical name is the final name after following zero
+// or more CNAME records.
+// LookupCNAME does not return an error if host does not
+// contain DNS "CNAME" records, as long as host resolves to
+// address records.
+func (r *Resolver) LookupCNAME(ctx context.Context, host string) (cname string, err error) {
+	return r.lookupCNAME(ctx, host)
 }
 
 // LookupSRV tries to resolve an SRV query of the given service,
-// protocol, and domain name.  The proto is "tcp" or "udp".
+// 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
+// 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)
+	return DefaultResolver.lookupSRV(context.Background(), service, proto, 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 (r *Resolver) LookupSRV(ctx context.Context, service, proto, name string) (cname string, addrs []*SRV, err error) {
+	return r.lookupSRV(ctx, service, proto, name)
+}
+
+// LookupMX returns the DNS MX records for the given domain name sorted by preference.
+func LookupMX(name string) ([]*MX, error) {
+	return DefaultResolver.lookupMX(context.Background(), name)
 }
 
 // LookupMX returns the DNS MX records for the given domain name sorted by preference.
-func LookupMX(name string) (mxs []*MX, err error) {
-	return lookupMX(name)
+func (r *Resolver) LookupMX(ctx context.Context, name string) ([]*MX, error) {
+	return r.lookupMX(ctx, name)
 }
 
 // LookupNS returns the DNS NS records for the given domain name.
-func LookupNS(name string) (nss []*NS, err error) {
-	return lookupNS(name)
+func LookupNS(name string) ([]*NS, error) {
+	return DefaultResolver.lookupNS(context.Background(), name)
+}
+
+// LookupNS returns the DNS NS records for the given domain name.
+func (r *Resolver) LookupNS(ctx context.Context, name string) ([]*NS, error) {
+	return r.lookupNS(ctx, name)
+}
+
+// LookupTXT returns the DNS TXT records for the given domain name.
+func LookupTXT(name string) ([]string, error) {
+	return DefaultResolver.lookupTXT(context.Background(), name)
 }
 
 // LookupTXT returns the DNS TXT records for the given domain name.
-func LookupTXT(name string) (txts []string, err error) {
-	return lookupTXT(name)
+func (r *Resolver) LookupTXT(ctx context.Context, name string) ([]string, error) {
+	return r.lookupTXT(ctx, name)
 }
 
 // LookupAddr performs a reverse lookup for the given address, returning a list
 // of names mapping to that address.
+//
+// When using the host C library resolver, at most one result will be
+// returned. To bypass the host resolver, use a custom Resolver.
 func LookupAddr(addr string) (names []string, err error) {
-	return lookupAddr(addr)
+	return DefaultResolver.lookupAddr(context.Background(), addr)
+}
+
+// LookupAddr performs a reverse lookup for the given address, returning a list
+// of names mapping to that address.
+func (r *Resolver) LookupAddr(ctx context.Context, addr string) (names []string, err error) {
+	return r.lookupAddr(ctx, addr)
 }