...
Run Format

Source file src/net/ipsock_posix.go

  // 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 nacl netbsd openbsd solaris windows
  
  package net
  
  import (
  	"context"
  	"runtime"
  	"syscall"
  )
  
  func probeIPv4Stack() bool {
  	s, err := socketFunc(syscall.AF_INET, syscall.SOCK_STREAM, syscall.IPPROTO_TCP)
  	switch err {
  	case syscall.EAFNOSUPPORT, syscall.EPROTONOSUPPORT:
  		return false
  	case nil:
  		closeFunc(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
  		value int
  	}{
  		// IPv6 communication capability
  		{laddr: TCPAddr{IP: ParseIP("::1")}, value: 1},
  		// IPv4-mapped IPv6 address communication capability
  		{laddr: TCPAddr{IP: IPv4(127, 0, 0, 1)}, value: 0},
  	}
  	var supps [2]bool
  	switch runtime.GOOS {
  	case "dragonfly", "openbsd":
  		// Some released versions of DragonFly BSD pretend to
  		// accept IPV6_V6ONLY=0 successfully, but the state
  		// still stays IPV6_V6ONLY=1. Eventually DragonFly BSD
  		// stops pretending, but the transition period would
  		// cause unpredictable behavior and we need to avoid
  		// it.
  		//
  		// OpenBSD also doesn't support IPV6_V6ONLY=0 but it
  		// never pretends to accept IPV6_V6OLY=0. It always
  		// returns an error and we don't need to probe the
  		// capability.
  		probes = probes[:1]
  	}
  
  	for i := range probes {
  		s, err := socketFunc(syscall.AF_INET6, syscall.SOCK_STREAM, syscall.IPPROTO_TCP)
  		if err != nil {
  			continue
  		}
  		defer closeFunc(s)
  		syscall.SetsockoptInt(s, syscall.IPPROTO_IPV6, syscall.IPV6_V6ONLY, probes[i].value)
  		sa, err := probes[i].laddr.sockaddr(syscall.AF_INET6)
  		if err != nil {
  			continue
  		}
  		if err := syscall.Bind(s, sa); err != nil {
  			continue
  		}
  		supps[i] = true
  	}
  
  	return supps[0], supps[1]
  }
  
  // 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, or does not support IPv4, we assume that
  //	the user wants to listen on both IPv4 and IPv6 wildcard
  //	addresses 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 || !supportsIPv4 {
  			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(ctx context.Context, net string, laddr, raddr sockaddr, sotype, proto int, mode string) (fd *netFD, err error) {
  	if (runtime.GOOS == "windows" || runtime.GOOS == "openbsd" || runtime.GOOS == "nacl") && mode == "dial" && raddr.isWildcard() {
  		raddr = raddr.toLocal(net)
  	}
  	family, ipv6only := favoriteAddrFamily(net, laddr, raddr, mode)
  	return socket(ctx, net, family, sotype, proto, ipv6only, laddr, raddr)
  }
  
  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
  		}
  		ip4 := ip.To4()
  		if ip4 == nil {
  			return nil, &AddrError{Err: "non-IPv4 address", Addr: ip.String()}
  		}
  		sa := &syscall.SockaddrInet4{Port: port}
  		copy(sa.Addr[:], ip4)
  		return sa, nil
  	case syscall.AF_INET6:
  		// In general, an IP wildcard address, which is either
  		// "0.0.0.0" or "::", means the entire IP addressing
  		// space. For some historical reason, it is used to
  		// specify "any available address" on some operations
  		// of IP node.
  		//
  		// When the IP node supports IPv4-mapped IPv6 address,
  		// we allow an listener to listen to the wildcard
  		// address of both IP addressing spaces by specifying
  		// IPv6 wildcard address.
  		if len(ip) == 0 || ip.Equal(IPv4zero) {
  			ip = IPv6zero
  		}
  		// We accept any IPv6 address including IPv4-mapped
  		// IPv6 address.
  		ip6 := ip.To16()
  		if ip6 == nil {
  			return nil, &AddrError{Err: "non-IPv6 address", Addr: ip.String()}
  		}
  		sa := &syscall.SockaddrInet6{Port: port, ZoneId: uint32(zoneToInt(zone))}
  		copy(sa.Addr[:], ip6)
  		return sa, nil
  	}
  	return nil, &AddrError{Err: "invalid address family", Addr: ip.String()}
  }
  

View as plain text