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// 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 freebsd linux openbsd windows
package net
import "syscall"
// 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 {
la TCPAddr
ok bool
}{
// IPv6 communication capability
{TCPAddr{IP: ParseIP("::1")}, false},
// IPv6 IPv4-mapped address communication capability
{TCPAddr{IP: IPv4(127, 0, 0, 1)}, false},
}
for i := range probes {
s, errno := syscall.Socket(syscall.AF_INET6, syscall.SOCK_STREAM, syscall.IPPROTO_TCP)
if errno != 0 {
continue
}
defer closesocket(s)
sa, err := probes[i].la.toAddr().sockaddr(syscall.AF_INET6)
if err != nil {
continue
}
errno = syscall.Bind(s, sa)
if errno != 0 {
continue
}
probes[i].ok = true
}
return probes[0].ok, probes[1].ok
}
// favoriteAddrFamily returns the appropriate address family to
// the given net, raddr, laddr and mode. At first it figures
// address family out from the net. If mode indicates "listen"
// and laddr.(type).IP is nil, it assumes that the user wants to
// make a passive connection with wildcard address family, both
// INET and INET6, and wildcard address. Otherwise guess: if the
// addresses are IPv4 then returns INET, or else returns INET6.
func favoriteAddrFamily(net string, raddr, laddr sockaddr, mode string) int {
switch net[len(net)-1] {
case '4':
return syscall.AF_INET
case '6':
return syscall.AF_INET6
}
if mode == "listen" {
switch a := laddr.(type) {
case *TCPAddr:
if a.IP == nil && supportsIPv6 {
return syscall.AF_INET6
}
case *UDPAddr:
if a.IP == nil && supportsIPv6 {
return syscall.AF_INET6
}
case *IPAddr:
if a.IP == nil && supportsIPv6 {
return syscall.AF_INET6
}
}
}
if (laddr == nil || laddr.family() == syscall.AF_INET) &&
(raddr == nil || raddr.family() == syscall.AF_INET) {
return syscall.AF_INET
}
return syscall.AF_INET6
}
// TODO(rsc): if syscall.OS == "linux", we're supposed to read
// /proc/sys/net/core/somaxconn,
// to take advantage of kernels that have raised the limit.
func listenBacklog() int { return syscall.SOMAXCONN }
// Internet sockets (TCP, UDP)
// A sockaddr represents a TCP or UDP network address that can
// be converted into a syscall.Sockaddr.
type sockaddr interface {
Addr
sockaddr(family int) (syscall.Sockaddr, error)
family() int
}
func internetSocket(net string, laddr, raddr sockaddr, socktype, proto int, mode string, toAddr func(syscall.Sockaddr) Addr) (fd *netFD, err error) {
var oserr error
var la, ra syscall.Sockaddr
family := favoriteAddrFamily(net, raddr, laddr, mode)
if laddr != nil {
if la, oserr = laddr.sockaddr(family); oserr != nil {
goto Error
}
}
if raddr != nil {
if ra, oserr = raddr.sockaddr(family); oserr != nil {
goto Error
}
}
fd, oserr = socket(net, family, socktype, proto, la, ra, toAddr)
if oserr != nil {
goto Error
}
return fd, nil
Error:
addr := raddr
if mode == "listen" {
addr = laddr
}
return nil, &OpError{mode, net, addr, oserr}
}
func ipToSockaddr(family int, ip IP, port int) (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")
}
s := new(syscall.SockaddrInet4)
for i := 0; i < IPv4len; i++ {
s.Addr[i] = ip[i]
}
s.Port = port
return s, 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 all zeros.
if ip.Equal(IPv4zero) {
ip = IPv6zero
}
if ip = ip.To16(); ip == nil {
return nil, InvalidAddrError("non-IPv6 address")
}
s := new(syscall.SockaddrInet6)
for i := 0; i < IPv6len; i++ {
s.Addr[i] = ip[i]
}
s.Port = port
return s, nil
}
return nil, InvalidAddrError("unexpected socket family")
}
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