libgo/go/net/ipsock_posix.go

   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.
   4
   5 // +build aix darwin dragonfly freebsd linux nacl netbsd openbsd solaris windows
   6
   7 package net
   8
   9 import (
  10         "context"
  11         "runtime"
  12         "syscall"
  13 )
  14
  15 func probeIPv4Stack() bool {
  16         s, err := socketFunc(syscall.AF_INET, syscall.SOCK_STREAM, syscall.IPPROTO_TCP)
  17         switch err {
  18         case syscall.EAFNOSUPPORT, syscall.EPROTONOSUPPORT:
  19                 return false
  20         case nil:
  21                 closeFunc(s)
  22         }
  23         return true
  24 }
  25
  26 // Should we try to use the IPv4 socket interface if we're
  27 // only dealing with IPv4 sockets?  As long as the host system
  28 // understands IPv6, it's okay to pass IPv4 addresses to the IPv6
  29 // interface. That simplifies our code and is most general.
  30 // Unfortunately, we need to run on kernels built without IPv6
  31 // support too. So probe the kernel to figure it out.
  32 //
  33 // probeIPv6Stack probes both basic IPv6 capability and IPv6 IPv4-
  34 // mapping capability which is controlled by IPV6_V6ONLY socket
  35 // option and/or kernel state "net.inet6.ip6.v6only".
  36 // It returns two boolean values. If the first boolean value is
  37 // true, kernel supports basic IPv6 functionality. If the second
  38 // boolean value is true, kernel supports IPv6 IPv4-mapping.
  39 func probeIPv6Stack() (supportsIPv6, supportsIPv4map bool) {
  40         var probes = []struct {
  41                 laddr TCPAddr
  42                 value int
  43         }{
  44                 // IPv6 communication capability
  45                 {laddr: TCPAddr{IP: ParseIP("::1")}, value: 1},
  46                 // IPv4-mapped IPv6 address communication capability
  47                 {laddr: TCPAddr{IP: IPv4(127, 0, 0, 1)}, value: 0},
  48         }
  49         var supps [2]bool
  50         switch runtime.GOOS {
  51         case "dragonfly", "openbsd":
  52                 // Some released versions of DragonFly BSD pretend to
  53                 // accept IPV6_V6ONLY=0 successfully, but the state
  54                 // still stays IPV6_V6ONLY=1. Eventually DragonFly BSD
  55                 // stops pretending, but the transition period would
  56                 // cause unpredictable behavior and we need to avoid
  57                 // it.
  58                 //
  59                 // OpenBSD also doesn't support IPV6_V6ONLY=0 but it
  60                 // never pretends to accept IPV6_V6OLY=0. It always
  61                 // returns an error and we don't need to probe the
  62                 // capability.
  63                 probes = probes[:1]
  64         }
  65
  66         for i := range probes {
  67                 s, err := socketFunc(syscall.AF_INET6, syscall.SOCK_STREAM, syscall.IPPROTO_TCP)
  68                 if err != nil {
  69                         continue
  70                 }
  71                 defer closeFunc(s)
  72                 syscall.SetsockoptInt(s, syscall.IPPROTO_IPV6, syscall.IPV6_V6ONLY, probes[i].value)
  73                 sa, err := probes[i].laddr.sockaddr(syscall.AF_INET6)
  74                 if err != nil {
  75                         continue
  76                 }
  77                 if err := syscall.Bind(s, sa); err != nil {
  78                         continue
  79                 }
  80                 supps[i] = true
  81         }
  82
  83         return supps[0], supps[1]
  84 }
  85
  86 // favoriteAddrFamily returns the appropriate address family to
  87 // the given net, laddr, raddr and mode. At first it figures
  88 // address family out from the net. If mode indicates "listen"
  89 // and laddr is a wildcard, it assumes that the user wants to
  90 // make a passive connection with a wildcard address family, both
  91 // AF_INET and AF_INET6, and a wildcard address like following:
  92 //
  93 //      1. A wild-wild listen, "tcp" + ""
  94 //      If the platform supports both IPv6 and IPv6 IPv4-mapping
  95 //      capabilities, or does not support IPv4, we assume that
  96 //      the user wants to listen on both IPv4 and IPv6 wildcard
  97 //      addresses over an AF_INET6 socket with IPV6_V6ONLY=0.
  98 //      Otherwise we prefer an IPv4 wildcard address listen over
  99 //      an AF_INET socket.
 100 //
 101 //      2. A wild-ipv4wild listen, "tcp" + "0.0.0.0"
 102 //      Same as 1.
 103 //
 104 //      3. A wild-ipv6wild listen, "tcp" + "[::]"
 105 //      Almost same as 1 but we prefer an IPv6 wildcard address
 106 //      listen over an AF_INET6 socket with IPV6_V6ONLY=0 when
 107 //      the platform supports IPv6 capability but not IPv6 IPv4-
 108 //      mapping capability.
 109 //
 110 //      4. A ipv4-ipv4wild listen, "tcp4" + "" or "0.0.0.0"
 111 //      We use an IPv4 (AF_INET) wildcard address listen.
 112 //
 113 //      5. A ipv6-ipv6wild listen, "tcp6" + "" or "[::]"
 114 //      We use an IPv6 (AF_INET6, IPV6_V6ONLY=1) wildcard address
 115 //      listen.
 116 //
 117 // Otherwise guess: if the addresses are IPv4 then returns AF_INET,
 118 // or else returns AF_INET6.  It also returns a boolean value what
 119 // designates IPV6_V6ONLY option.
 120 //
 121 // Note that OpenBSD allows neither "net.inet6.ip6.v6only=1" change
 122 // nor IPPROTO_IPV6 level IPV6_V6ONLY socket option setting.
 123 func favoriteAddrFamily(net string, laddr, raddr sockaddr, mode string) (family int, ipv6only bool) {
 124         switch net[len(net)-1] {
 125         case '4':
 126                 return syscall.AF_INET, false
 127         case '6':
 128                 return syscall.AF_INET6, true
 129         }
 130
 131         if mode == "listen" && (laddr == nil || laddr.isWildcard()) {
 132                 if supportsIPv4map || !supportsIPv4 {
 133                         return syscall.AF_INET6, false
 134                 }
 135                 if laddr == nil {
 136                         return syscall.AF_INET, false
 137                 }
 138                 return laddr.family(), false
 139         }
 140
 141         if (laddr == nil || laddr.family() == syscall.AF_INET) &&
 142                 (raddr == nil || raddr.family() == syscall.AF_INET) {
 143                 return syscall.AF_INET, false
 144         }
 145         return syscall.AF_INET6, false
 146 }
 147
 148 // Internet sockets (TCP, UDP, IP)
 149 func internetSocket(ctx context.Context, net string, laddr, raddr sockaddr, sotype, proto int, mode string) (fd *netFD, err error) {
 150         if (runtime.GOOS == "windows" || runtime.GOOS == "openbsd" || runtime.GOOS == "nacl") && mode == "dial" && raddr.isWildcard() {
 151                 raddr = raddr.toLocal(net)
 152         }
 153         family, ipv6only := favoriteAddrFamily(net, laddr, raddr, mode)
 154         return socket(ctx, net, family, sotype, proto, ipv6only, laddr, raddr)
 155 }
 156
 157 func ipToSockaddr(family int, ip IP, port int, zone string) (syscall.Sockaddr, error) {
 158         switch family {
 159         case syscall.AF_INET:
 160                 if len(ip) == 0 {
 161                         ip = IPv4zero
 162                 }
 163                 ip4 := ip.To4()
 164                 if ip4 == nil {
 165                         return nil, &AddrError{Err: "non-IPv4 address", Addr: ip.String()}
 166                 }
 167                 sa := &syscall.SockaddrInet4{Port: port}
 168                 copy(sa.Addr[:], ip4)
 169                 return sa, nil
 170         case syscall.AF_INET6:
 171                 // In general, an IP wildcard address, which is either
 172                 // "0.0.0.0" or "::", means the entire IP addressing
 173                 // space. For some historical reason, it is used to
 174                 // specify "any available address" on some operations
 175                 // of IP node.
 176                 //
 177                 // When the IP node supports IPv4-mapped IPv6 address,
 178                 // we allow an listener to listen to the wildcard
 179                 // address of both IP addressing spaces by specifying
 180                 // IPv6 wildcard address.
 181                 if len(ip) == 0 || ip.Equal(IPv4zero) {
 182                         ip = IPv6zero
 183                 }
 184                 // We accept any IPv6 address including IPv4-mapped
 185                 // IPv6 address.
 186                 ip6 := ip.To16()
 187                 if ip6 == nil {
 188                         return nil, &AddrError{Err: "non-IPv6 address", Addr: ip.String()}
 189                 }
 190                 sa := &syscall.SockaddrInet6{Port: port, ZoneId: uint32(zoneToInt(zone))}
 191                 copy(sa.Addr[:], ip6)
 192                 return sa, nil
 193         }
 194         return nil, &AddrError{Err: "invalid address family", Addr: ip.String()}
 195 }