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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 dragonfly freebsd linux netbsd openbsd 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
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, 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, 0)
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, toAddr func(syscall.Sockaddr) Addr) (fd *netFD, err error) {
family, ipv6only := favoriteAddrFamily(net, laddr, raddr, mode)
return socket(net, family, sotype, proto, ipv6only, laddr, raddr, deadline, toAddr)
}
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")
}
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