1 // Copyright 2009 The Go Authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style
3 // license that can be found in the LICENSE file.
5 // +build darwin freebsd linux netbsd openbsd windows
11 // Should we try to use the IPv4 socket interface if we're
12 // only dealing with IPv4 sockets? As long as the host system
13 // understands IPv6, it's okay to pass IPv4 addresses to the IPv6
14 // interface. That simplifies our code and is most general.
15 // Unfortunately, we need to run on kernels built without IPv6
16 // support too. So probe the kernel to figure it out.
18 // probeIPv6Stack probes both basic IPv6 capability and IPv6 IPv4-
19 // mapping capability which is controlled by IPV6_V6ONLY socket
20 // option and/or kernel state "net.inet6.ip6.v6only".
21 // It returns two boolean values. If the first boolean value is
22 // true, kernel supports basic IPv6 functionality. If the second
23 // boolean value is true, kernel supports IPv6 IPv4-mapping.
24 func probeIPv6Stack() (supportsIPv6, supportsIPv4map bool) {
25 var probes = []struct {
29 // IPv6 communication capability
30 {TCPAddr{IP: ParseIP("::1")}, false},
31 // IPv6 IPv4-mapped address communication capability
32 {TCPAddr{IP: IPv4(127, 0, 0, 1)}, false},
35 for i := range probes {
36 s, err := syscall.Socket(syscall.AF_INET6, syscall.SOCK_STREAM, syscall.IPPROTO_TCP)
41 syscall.SetsockoptInt(s, syscall.IPPROTO_IPV6, syscall.IPV6_V6ONLY, 0)
42 sa, err := probes[i].la.toAddr().sockaddr(syscall.AF_INET6)
46 err = syscall.Bind(s, sa)
53 return probes[0].ok, probes[1].ok
56 // favoriteAddrFamily returns the appropriate address family to
57 // the given net, laddr, raddr and mode. At first it figures
58 // address family out from the net. If mode indicates "listen"
59 // and laddr is a wildcard, it assumes that the user wants to
60 // make a passive connection with a wildcard address family, both
61 // AF_INET and AF_INET6, and a wildcard address like following:
63 // 1. A wild-wild listen, "tcp" + ""
64 // If the platform supports both IPv6 and IPv6 IPv4-mapping
65 // capabilities, we assume that the user want to listen on
66 // both IPv4 and IPv6 wildcard address over an AF_INET6
67 // socket with IPV6_V6ONLY=0. Otherwise we prefer an IPv4
68 // wildcard address listen over an AF_INET socket.
70 // 2. A wild-ipv4wild listen, "tcp" + "0.0.0.0"
73 // 3. A wild-ipv6wild listen, "tcp" + "[::]"
74 // Almost same as 1 but we prefer an IPv6 wildcard address
75 // listen over an AF_INET6 socket with IPV6_V6ONLY=0 when
76 // the platform supports IPv6 capability but not IPv6 IPv4-
77 // mapping capability.
79 // 4. A ipv4-ipv4wild listen, "tcp4" + "" or "0.0.0.0"
80 // We use an IPv4 (AF_INET) wildcard address listen.
82 // 5. A ipv6-ipv6wild listen, "tcp6" + "" or "[::]"
83 // We use an IPv6 (AF_INET6, IPV6_V6ONLY=1) wildcard address
86 // Otherwise guess: if the addresses are IPv4 then returns AF_INET,
87 // or else returns AF_INET6. It also returns a boolean value what
88 // designates IPV6_V6ONLY option.
90 // Note that OpenBSD allows neither "net.inet6.ip6.v6only=1" change
91 // nor IPPROTO_IPV6 level IPV6_V6ONLY socket option setting.
92 func favoriteAddrFamily(net string, laddr, raddr sockaddr, mode string) (family int, ipv6only bool) {
93 switch net[len(net)-1] {
95 return syscall.AF_INET, false
97 return syscall.AF_INET6, true
100 if mode == "listen" && laddr.isWildcard() {
102 return syscall.AF_INET6, false
104 return laddr.family(), false
107 if (laddr == nil || laddr.family() == syscall.AF_INET) &&
108 (raddr == nil || raddr.family() == syscall.AF_INET) {
109 return syscall.AF_INET, false
111 return syscall.AF_INET6, false
114 // Internet sockets (TCP, UDP, IP)
116 // A sockaddr represents a TCP, UDP or IP network address that can
117 // be converted into a syscall.Sockaddr.
118 type sockaddr interface {
122 sockaddr(family int) (syscall.Sockaddr, error)
125 func internetSocket(net string, laddr, raddr sockaddr, sotype, proto int, mode string, toAddr func(syscall.Sockaddr) Addr) (fd *netFD, err error) {
126 var la, ra syscall.Sockaddr
127 family, ipv6only := favoriteAddrFamily(net, laddr, raddr, mode)
129 if la, err = laddr.sockaddr(family); err != nil {
134 if ra, err = raddr.sockaddr(family); err != nil {
138 fd, err = socket(net, family, sotype, proto, ipv6only, la, ra, toAddr)
146 if mode == "listen" {
149 return nil, &OpError{mode, net, addr, err}
152 func ipToSockaddr(family int, ip IP, port int) (syscall.Sockaddr, error) {
154 case syscall.AF_INET:
158 if ip = ip.To4(); ip == nil {
159 return nil, InvalidAddrError("non-IPv4 address")
161 s := new(syscall.SockaddrInet4)
162 for i := 0; i < IPv4len; i++ {
167 case syscall.AF_INET6:
171 // IPv4 callers use 0.0.0.0 to mean "announce on any available address".
172 // In IPv6 mode, Linux treats that as meaning "announce on 0.0.0.0",
173 // which it refuses to do. Rewrite to the IPv6 unspecified address.
174 if ip.Equal(IPv4zero) {
177 if ip = ip.To16(); ip == nil {
178 return nil, InvalidAddrError("non-IPv6 address")
180 s := new(syscall.SockaddrInet6)
181 for i := 0; i < IPv6len; i++ {
187 return nil, InvalidAddrError("unexpected socket family")