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747 |
jeremybenn |
// Copyright 2009 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// +build darwin freebsd linux netbsd openbsd windows
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package net
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import "syscall"
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// Should we try to use the IPv4 socket interface if we're
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// only dealing with IPv4 sockets? As long as the host system
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// understands IPv6, it's okay to pass IPv4 addresses to the IPv6
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// interface. That simplifies our code and is most general.
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// Unfortunately, we need to run on kernels built without IPv6
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// support too. So probe the kernel to figure it out.
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//
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// probeIPv6Stack probes both basic IPv6 capability and IPv6 IPv4-
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// mapping capability which is controlled by IPV6_V6ONLY socket
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// option and/or kernel state "net.inet6.ip6.v6only".
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// It returns two boolean values. If the first boolean value is
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// true, kernel supports basic IPv6 functionality. If the second
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// boolean value is true, kernel supports IPv6 IPv4-mapping.
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func probeIPv6Stack() (supportsIPv6, supportsIPv4map bool) {
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var probes = []struct {
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la TCPAddr
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ok bool
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}{
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// IPv6 communication capability
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{TCPAddr{IP: ParseIP("::1")}, false},
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// IPv6 IPv4-mapped address communication capability
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{TCPAddr{IP: IPv4(127, 0, 0, 1)}, false},
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}
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for i := range probes {
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s, err := syscall.Socket(syscall.AF_INET6, syscall.SOCK_STREAM, syscall.IPPROTO_TCP)
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if err != nil {
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continue
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}
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defer closesocket(s)
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sa, err := probes[i].la.toAddr().sockaddr(syscall.AF_INET6)
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if err != nil {
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continue
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}
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err = syscall.Bind(s, sa)
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if err != nil {
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continue
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}
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probes[i].ok = true
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}
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return probes[0].ok, probes[1].ok
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}
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// favoriteAddrFamily returns the appropriate address family to
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// the given net, raddr, laddr and mode. At first it figures
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// address family out from the net. If mode indicates "listen"
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// and laddr.(type).IP is nil, it assumes that the user wants to
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// make a passive connection with wildcard address family, both
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// INET and INET6, and wildcard address. Otherwise guess: if the
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// addresses are IPv4 then returns INET, or else returns INET6.
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func favoriteAddrFamily(net string, raddr, laddr sockaddr, mode string) int {
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switch net[len(net)-1] {
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case '4':
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return syscall.AF_INET
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case '6':
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return syscall.AF_INET6
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}
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if mode == "listen" {
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switch a := laddr.(type) {
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case *TCPAddr:
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if a.IP == nil && supportsIPv6 {
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return syscall.AF_INET6
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}
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case *UDPAddr:
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if a.IP == nil && supportsIPv6 {
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return syscall.AF_INET6
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}
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case *IPAddr:
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if a.IP == nil && supportsIPv6 {
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return syscall.AF_INET6
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}
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}
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}
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if (laddr == nil || laddr.family() == syscall.AF_INET) &&
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(raddr == nil || raddr.family() == syscall.AF_INET) {
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return syscall.AF_INET
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}
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return syscall.AF_INET6
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}
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// Internet sockets (TCP, UDP)
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// A sockaddr represents a TCP or UDP network address that can
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// be converted into a syscall.Sockaddr.
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type sockaddr interface {
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Addr
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sockaddr(family int) (syscall.Sockaddr, error)
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family() int
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}
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func internetSocket(net string, laddr, raddr sockaddr, sotype, proto int, mode string, toAddr func(syscall.Sockaddr) Addr) (fd *netFD, err error) {
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var oserr error
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var la, ra syscall.Sockaddr
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family := favoriteAddrFamily(net, raddr, laddr, mode)
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if laddr != nil {
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if la, oserr = laddr.sockaddr(family); oserr != nil {
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goto Error
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}
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}
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if raddr != nil {
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if ra, oserr = raddr.sockaddr(family); oserr != nil {
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goto Error
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}
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}
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fd, oserr = socket(net, family, sotype, proto, la, ra, toAddr)
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if oserr != nil {
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goto Error
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}
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return fd, nil
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Error:
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addr := raddr
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if mode == "listen" {
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addr = laddr
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}
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return nil, &OpError{mode, net, addr, oserr}
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}
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func ipToSockaddr(family int, ip IP, port int) (syscall.Sockaddr, error) {
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switch family {
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case syscall.AF_INET:
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if len(ip) == 0 {
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ip = IPv4zero
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}
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if ip = ip.To4(); ip == nil {
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return nil, InvalidAddrError("non-IPv4 address")
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}
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s := new(syscall.SockaddrInet4)
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for i := 0; i < IPv4len; i++ {
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s.Addr[i] = ip[i]
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}
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s.Port = port
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return s, nil
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case syscall.AF_INET6:
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if len(ip) == 0 {
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ip = IPv6zero
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}
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// IPv4 callers use 0.0.0.0 to mean "announce on any available address".
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// In IPv6 mode, Linux treats that as meaning "announce on 0.0.0.0",
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// which it refuses to do. Rewrite to the IPv6 all zeros.
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if ip.Equal(IPv4zero) {
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ip = IPv6zero
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}
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if ip = ip.To16(); ip == nil {
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return nil, InvalidAddrError("non-IPv6 address")
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}
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s := new(syscall.SockaddrInet6)
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for i := 0; i < IPv6len; i++ {
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s.Addr[i] = ip[i]
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}
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s.Port = port
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return s, nil
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}
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return nil, InvalidAddrError("unexpected socket family")
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}
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