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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	// BUG(rsc,mikio): On DragonFly BSD and OpenBSD, listening on the
    16	// "tcp" and "udp" networks does not listen for both IPv4 and IPv6
    17	// connections. This is due to the fact that IPv4 traffic will not be
    18	// routed to an IPv6 socket - two separate sockets are required if
    19	// both address families are to be supported.
    20	// See inet6(4) for details.
    21	
    22	func probeIPv4Stack() bool {
    23		s, err := socketFunc(syscall.AF_INET, syscall.SOCK_STREAM, syscall.IPPROTO_TCP)
    24		switch err {
    25		case syscall.EAFNOSUPPORT, syscall.EPROTONOSUPPORT:
    26			return false
    27		case nil:
    28			closeFunc(s)
    29		}
    30		return true
    31	}
    32	
    33	// Should we try to use the IPv4 socket interface if we're
    34	// only dealing with IPv4 sockets?  As long as the host system
    35	// understands IPv6, it's okay to pass IPv4 addresses to the IPv6
    36	// interface. That simplifies our code and is most general.
    37	// Unfortunately, we need to run on kernels built without IPv6
    38	// support too. So probe the kernel to figure it out.
    39	//
    40	// probeIPv6Stack probes both basic IPv6 capability and IPv6 IPv4-
    41	// mapping capability which is controlled by IPV6_V6ONLY socket
    42	// option and/or kernel state "net.inet6.ip6.v6only".
    43	// It returns two boolean values. If the first boolean value is
    44	// true, kernel supports basic IPv6 functionality. If the second
    45	// boolean value is true, kernel supports IPv6 IPv4-mapping.
    46	func probeIPv6Stack() (supportsIPv6, supportsIPv4map bool) {
    47		var probes = []struct {
    48			laddr TCPAddr
    49			value int
    50		}{
    51			// IPv6 communication capability
    52			{laddr: TCPAddr{IP: ParseIP("::1")}, value: 1},
    53			// IPv4-mapped IPv6 address communication capability
    54			{laddr: TCPAddr{IP: IPv4(127, 0, 0, 1)}, value: 0},
    55		}
    56		var supps [2]bool
    57		switch runtime.GOOS {
    58		case "dragonfly", "openbsd":
    59			// Some released versions of DragonFly BSD pretend to
    60			// accept IPV6_V6ONLY=0 successfully, but the state
    61			// still stays IPV6_V6ONLY=1. Eventually DragonFly BSD
    62			// stops pretending, but the transition period would
    63			// cause unpredictable behavior and we need to avoid
    64			// it.
    65			//
    66			// OpenBSD also doesn't support IPV6_V6ONLY=0 but it
    67			// never pretends to accept IPV6_V6OLY=0. It always
    68			// returns an error and we don't need to probe the
    69			// capability.
    70			probes = probes[:1]
    71		}
    72	
    73		for i := range probes {
    74			s, err := socketFunc(syscall.AF_INET6, syscall.SOCK_STREAM, syscall.IPPROTO_TCP)
    75			if err != nil {
    76				continue
    77			}
    78			defer closeFunc(s)
    79			syscall.SetsockoptInt(s, syscall.IPPROTO_IPV6, syscall.IPV6_V6ONLY, probes[i].value)
    80			sa, err := probes[i].laddr.sockaddr(syscall.AF_INET6)
    81			if err != nil {
    82				continue
    83			}
    84			if err := syscall.Bind(s, sa); err != nil {
    85				continue
    86			}
    87			supps[i] = true
    88		}
    89	
    90		return supps[0], supps[1]
    91	}
    92	
    93	// favoriteAddrFamily returns the appropriate address family to
    94	// the given net, laddr, raddr and mode. At first it figures
    95	// address family out from the net. If mode indicates "listen"
    96	// and laddr is a wildcard, it assumes that the user wants to
    97	// make a passive connection with a wildcard address family, both
    98	// AF_INET and AF_INET6, and a wildcard address like following:
    99	//
   100	//	1. A wild-wild listen, "tcp" + ""
   101	//	If the platform supports both IPv6 and IPv6 IPv4-mapping
   102	//	capabilities, or does not support IPv4, we assume that
   103	//	the user wants to listen on both IPv4 and IPv6 wildcard
   104	//	addresses over an AF_INET6 socket with IPV6_V6ONLY=0.
   105	//	Otherwise we prefer an IPv4 wildcard address listen over
   106	//	an AF_INET socket.
   107	//
   108	//	2. A wild-ipv4wild listen, "tcp" + "0.0.0.0"
   109	//	Same as 1.
   110	//
   111	//	3. A wild-ipv6wild listen, "tcp" + "[::]"
   112	//	Almost same as 1 but we prefer an IPv6 wildcard address
   113	//	listen over an AF_INET6 socket with IPV6_V6ONLY=0 when
   114	//	the platform supports IPv6 capability but not IPv6 IPv4-
   115	//	mapping capability.
   116	//
   117	//	4. A ipv4-ipv4wild listen, "tcp4" + "" or "0.0.0.0"
   118	//	We use an IPv4 (AF_INET) wildcard address listen.
   119	//
   120	//	5. A ipv6-ipv6wild listen, "tcp6" + "" or "[::]"
   121	//	We use an IPv6 (AF_INET6, IPV6_V6ONLY=1) wildcard address
   122	//	listen.
   123	//
   124	// Otherwise guess: if the addresses are IPv4 then returns AF_INET,
   125	// or else returns AF_INET6.  It also returns a boolean value what
   126	// designates IPV6_V6ONLY option.
   127	//
   128	// Note that OpenBSD allows neither "net.inet6.ip6.v6only=1" change
   129	// nor IPPROTO_IPV6 level IPV6_V6ONLY socket option setting.
   130	func favoriteAddrFamily(net string, laddr, raddr sockaddr, mode string) (family int, ipv6only bool) {
   131		switch net[len(net)-1] {
   132		case '4':
   133			return syscall.AF_INET, false
   134		case '6':
   135			return syscall.AF_INET6, true
   136		}
   137	
   138		if mode == "listen" && (laddr == nil || laddr.isWildcard()) {
   139			if supportsIPv4map || !supportsIPv4 {
   140				return syscall.AF_INET6, false
   141			}
   142			if laddr == nil {
   143				return syscall.AF_INET, false
   144			}
   145			return laddr.family(), false
   146		}
   147	
   148		if (laddr == nil || laddr.family() == syscall.AF_INET) &&
   149			(raddr == nil || raddr.family() == syscall.AF_INET) {
   150			return syscall.AF_INET, false
   151		}
   152		return syscall.AF_INET6, false
   153	}
   154	
   155	// Internet sockets (TCP, UDP, IP)
   156	func internetSocket(ctx context.Context, net string, laddr, raddr sockaddr, sotype, proto int, mode string) (fd *netFD, err error) {
   157		family, ipv6only := favoriteAddrFamily(net, laddr, raddr, mode)
   158		return socket(ctx, net, family, sotype, proto, ipv6only, laddr, raddr)
   159	}
   160	
   161	func ipToSockaddr(family int, ip IP, port int, zone string) (syscall.Sockaddr, error) {
   162		switch family {
   163		case syscall.AF_INET:
   164			if len(ip) == 0 {
   165				ip = IPv4zero
   166			}
   167			ip4 := ip.To4()
   168			if ip4 == nil {
   169				return nil, &AddrError{Err: "non-IPv4 address", Addr: ip.String()}
   170			}
   171			sa := &syscall.SockaddrInet4{Port: port}
   172			copy(sa.Addr[:], ip4)
   173			return sa, nil
   174		case syscall.AF_INET6:
   175			// In general, an IP wildcard address, which is either
   176			// "0.0.0.0" or "::", means the entire IP addressing
   177			// space. For some historical reason, it is used to
   178			// specify "any available address" on some operations
   179			// of IP node.
   180			//
   181			// When the IP node supports IPv4-mapped IPv6 address,
   182			// we allow an listener to listen to the wildcard
   183			// address of both IP addressing spaces by specifying
   184			// IPv6 wildcard address.
   185			if len(ip) == 0 || ip.Equal(IPv4zero) {
   186				ip = IPv6zero
   187			}
   188			// We accept any IPv6 address including IPv4-mapped
   189			// IPv6 address.
   190			ip6 := ip.To16()
   191			if ip6 == nil {
   192				return nil, &AddrError{Err: "non-IPv6 address", Addr: ip.String()}
   193			}
   194			sa := &syscall.SockaddrInet6{Port: port, ZoneId: uint32(zoneToInt(zone))}
   195			copy(sa.Addr[:], ip6)
   196			return sa, nil
   197		}
   198		return nil, &AddrError{Err: "invalid address family", Addr: ip.String()}
   199	}
   200	

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