200 lines
6.6 KiB
Go
200 lines
6.6 KiB
Go
// 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 dragonfly freebsd linux nacl netbsd openbsd solaris windows
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package net
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import (
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"context"
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"runtime"
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"syscall"
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)
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// BUG(rsc,mikio): On DragonFly BSD and OpenBSD, listening on the
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// "tcp" and "udp" networks does not listen for both IPv4 and IPv6
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// connections. This is due to the fact that IPv4 traffic will not be
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// routed to an IPv6 socket - two separate sockets are required if
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// both address families are to be supported.
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// See inet6(4) for details.
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func probeIPv4Stack() bool {
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s, err := socketFunc(syscall.AF_INET, syscall.SOCK_STREAM, syscall.IPPROTO_TCP)
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switch err {
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case syscall.EAFNOSUPPORT, syscall.EPROTONOSUPPORT:
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return false
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case nil:
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closeFunc(s)
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}
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return true
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}
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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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laddr TCPAddr
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value int
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}{
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// IPv6 communication capability
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{laddr: TCPAddr{IP: ParseIP("::1")}, value: 1},
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// IPv4-mapped IPv6 address communication capability
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{laddr: TCPAddr{IP: IPv4(127, 0, 0, 1)}, value: 0},
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}
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var supps [2]bool
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switch runtime.GOOS {
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case "dragonfly", "openbsd":
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// Some released versions of DragonFly BSD pretend to
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// accept IPV6_V6ONLY=0 successfully, but the state
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// still stays IPV6_V6ONLY=1. Eventually DragonFly BSD
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// stops pretending, but the transition period would
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// cause unpredictable behavior and we need to avoid
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// it.
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//
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// OpenBSD also doesn't support IPV6_V6ONLY=0 but it
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// never pretends to accept IPV6_V6OLY=0. It always
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// returns an error and we don't need to probe the
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// capability.
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probes = probes[:1]
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}
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for i := range probes {
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s, err := socketFunc(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 closeFunc(s)
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syscall.SetsockoptInt(s, syscall.IPPROTO_IPV6, syscall.IPV6_V6ONLY, probes[i].value)
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sa, err := probes[i].laddr.sockaddr(syscall.AF_INET6)
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if err != nil {
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continue
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}
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if err := syscall.Bind(s, sa); err != nil {
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continue
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}
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supps[i] = true
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}
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return supps[0], supps[1]
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}
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// favoriteAddrFamily returns the appropriate address family to
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// the given net, laddr, raddr 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 is a wildcard, it assumes that the user wants to
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// make a passive connection with a wildcard address family, both
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// AF_INET and AF_INET6, and a wildcard address like following:
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//
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// 1. A wild-wild listen, "tcp" + ""
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// If the platform supports both IPv6 and IPv6 IPv4-mapping
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// capabilities, or does not support IPv4, we assume that
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// the user wants to listen on both IPv4 and IPv6 wildcard
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// addresses over an AF_INET6 socket with IPV6_V6ONLY=0.
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// Otherwise we prefer an IPv4 wildcard address listen over
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// an AF_INET socket.
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//
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// 2. A wild-ipv4wild listen, "tcp" + "0.0.0.0"
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// Same as 1.
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//
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// 3. A wild-ipv6wild listen, "tcp" + "[::]"
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// Almost same as 1 but we prefer an IPv6 wildcard address
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// listen over an AF_INET6 socket with IPV6_V6ONLY=0 when
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// the platform supports IPv6 capability but not IPv6 IPv4-
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// mapping capability.
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//
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// 4. A ipv4-ipv4wild listen, "tcp4" + "" or "0.0.0.0"
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// We use an IPv4 (AF_INET) wildcard address listen.
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//
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// 5. A ipv6-ipv6wild listen, "tcp6" + "" or "[::]"
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// We use an IPv6 (AF_INET6, IPV6_V6ONLY=1) wildcard address
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// listen.
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//
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// Otherwise guess: if the addresses are IPv4 then returns AF_INET,
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// or else returns AF_INET6. It also returns a boolean value what
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// designates IPV6_V6ONLY option.
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//
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// Note that OpenBSD allows neither "net.inet6.ip6.v6only=1" change
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// nor IPPROTO_IPV6 level IPV6_V6ONLY socket option setting.
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func favoriteAddrFamily(net string, laddr, raddr sockaddr, mode string) (family int, ipv6only bool) {
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switch net[len(net)-1] {
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case '4':
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return syscall.AF_INET, false
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case '6':
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return syscall.AF_INET6, true
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}
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if mode == "listen" && (laddr == nil || laddr.isWildcard()) {
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if supportsIPv4map || !supportsIPv4 {
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return syscall.AF_INET6, false
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}
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if laddr == nil {
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return syscall.AF_INET, false
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}
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return laddr.family(), false
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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, false
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}
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return syscall.AF_INET6, false
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}
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// Internet sockets (TCP, UDP, IP)
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func internetSocket(ctx context.Context, net string, laddr, raddr sockaddr, sotype, proto int, mode string) (fd *netFD, err error) {
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family, ipv6only := favoriteAddrFamily(net, laddr, raddr, mode)
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return socket(ctx, net, family, sotype, proto, ipv6only, laddr, raddr)
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}
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func ipToSockaddr(family int, ip IP, port int, zone string) (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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ip4 := ip.To4()
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if ip4 == nil {
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return nil, &AddrError{Err: "non-IPv4 address", Addr: ip.String()}
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}
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sa := &syscall.SockaddrInet4{Port: port}
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copy(sa.Addr[:], ip4)
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return sa, nil
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case syscall.AF_INET6:
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// In general, an IP wildcard address, which is either
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// "0.0.0.0" or "::", means the entire IP addressing
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// space. For some historical reason, it is used to
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// specify "any available address" on some operations
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// of IP node.
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//
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// When the IP node supports IPv4-mapped IPv6 address,
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// we allow an listener to listen to the wildcard
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// address of both IP addressing spaces by specifying
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// IPv6 wildcard address.
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if len(ip) == 0 || ip.Equal(IPv4zero) {
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ip = IPv6zero
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}
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// We accept any IPv6 address including IPv4-mapped
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// IPv6 address.
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ip6 := ip.To16()
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if ip6 == nil {
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return nil, &AddrError{Err: "non-IPv6 address", Addr: ip.String()}
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}
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sa := &syscall.SockaddrInet6{Port: port, ZoneId: uint32(zoneToInt(zone))}
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copy(sa.Addr[:], ip6)
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return sa, nil
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}
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return nil, &AddrError{Err: "invalid address family", Addr: ip.String()}
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}
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