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Source file src/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 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	}
   196	

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