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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	// Internet protocol family sockets for POSIX
     8	
     9	package net
    10	
    11	import (
    12		"runtime"
    13		"syscall"
    14		"time"
    15	)
    16	
    17	// BUG(rsc,mikio): On DragonFly BSD and OpenBSD, listening on the
    18	// "tcp" and "udp" networks does not listen for both IPv4 and IPv6
    19	// connections. This is due to the fact that IPv4 traffic will not be
    20	// routed to an IPv6 socket - two separate sockets are required if
    21	// both address families are to be supported.
    22	// See inet6(4) for details.
    23	
    24	func probeIPv4Stack() bool {
    25		s, err := socketFunc(syscall.AF_INET, syscall.SOCK_STREAM, syscall.IPPROTO_TCP)
    26		switch err {
    27		case syscall.EAFNOSUPPORT, syscall.EPROTONOSUPPORT:
    28			return false
    29		case nil:
    30			closeFunc(s)
    31		}
    32		return true
    33	}
    34	
    35	// Should we try to use the IPv4 socket interface if we're
    36	// only dealing with IPv4 sockets?  As long as the host system
    37	// understands IPv6, it's okay to pass IPv4 addresses to the IPv6
    38	// interface.  That simplifies our code and is most general.
    39	// Unfortunately, we need to run on kernels built without IPv6
    40	// support too.  So probe the kernel to figure it out.
    41	//
    42	// probeIPv6Stack probes both basic IPv6 capability and IPv6 IPv4-
    43	// mapping capability which is controlled by IPV6_V6ONLY socket
    44	// option and/or kernel state "net.inet6.ip6.v6only".
    45	// It returns two boolean values.  If the first boolean value is
    46	// true, kernel supports basic IPv6 functionality.  If the second
    47	// boolean value is true, kernel supports IPv6 IPv4-mapping.
    48	func probeIPv6Stack() (supportsIPv6, supportsIPv4map bool) {
    49		var probes = []struct {
    50			laddr TCPAddr
    51			value int
    52		}{
    53			// IPv6 communication capability
    54			{laddr: TCPAddr{IP: ParseIP("::1")}, value: 1},
    55			// IPv6 IPv4-mapped address communication capability
    56			{laddr: TCPAddr{IP: IPv4(127, 0, 0, 1)}, value: 0},
    57		}
    58		var supps [2]bool
    59		switch runtime.GOOS {
    60		case "dragonfly", "openbsd":
    61			// Some released versions of DragonFly BSD pretend to
    62			// accept IPV6_V6ONLY=0 successfully, but the state
    63			// still stays IPV6_V6ONLY=1. Eventually DragonFly BSD
    64			// stops preteding, but the transition period would
    65			// cause unpredictable behavior and we need to avoid
    66			// it.
    67			//
    68			// OpenBSD also doesn't support IPV6_V6ONLY=0 but it
    69			// never pretends to accept IPV6_V6OLY=0. It always
    70			// returns an error and we don't need to probe the
    71			// capability.
    72			probes = probes[:1]
    73		}
    74	
    75		for i := range probes {
    76			s, err := socketFunc(syscall.AF_INET6, syscall.SOCK_STREAM, syscall.IPPROTO_TCP)
    77			if err != nil {
    78				continue
    79			}
    80			defer closeFunc(s)
    81			syscall.SetsockoptInt(s, syscall.IPPROTO_IPV6, syscall.IPV6_V6ONLY, probes[i].value)
    82			sa, err := probes[i].laddr.sockaddr(syscall.AF_INET6)
    83			if err != nil {
    84				continue
    85			}
    86			if err := syscall.Bind(s, sa); err != nil {
    87				continue
    88			}
    89			supps[i] = true
    90		}
    91	
    92		return supps[0], supps[1]
    93	}
    94	
    95	// favoriteAddrFamily returns the appropriate address family to
    96	// the given net, laddr, raddr and mode.  At first it figures
    97	// address family out from the net.  If mode indicates "listen"
    98	// and laddr is a wildcard, it assumes that the user wants to
    99	// make a passive connection with a wildcard address family, both
   100	// AF_INET and AF_INET6, and a wildcard address like following:
   101	//
   102	//	1. A wild-wild listen, "tcp" + ""
   103	//	If the platform supports both IPv6 and IPv6 IPv4-mapping
   104	//	capabilities, we assume that the user want to listen on
   105	//	both IPv4 and IPv6 wildcard address over an AF_INET6
   106	//	socket with IPV6_V6ONLY=0.  Otherwise we prefer an IPv4
   107	//	wildcard address listen over an AF_INET socket.
   108	//
   109	//	2. A wild-ipv4wild listen, "tcp" + "0.0.0.0"
   110	//	Same as 1.
   111	//
   112	//	3. A wild-ipv6wild listen, "tcp" + "[::]"
   113	//	Almost same as 1 but we prefer an IPv6 wildcard address
   114	//	listen over an AF_INET6 socket with IPV6_V6ONLY=0 when
   115	//	the platform supports IPv6 capability but not IPv6 IPv4-
   116	//	mapping capability.
   117	//
   118	//	4. A ipv4-ipv4wild listen, "tcp4" + "" or "0.0.0.0"
   119	//	We use an IPv4 (AF_INET) wildcard address listen.
   120	//
   121	//	5. A ipv6-ipv6wild listen, "tcp6" + "" or "[::]"
   122	//	We use an IPv6 (AF_INET6, IPV6_V6ONLY=1) wildcard address
   123	//	listen.
   124	//
   125	// Otherwise guess: if the addresses are IPv4 then returns AF_INET,
   126	// or else returns AF_INET6.  It also returns a boolean value what
   127	// designates IPV6_V6ONLY option.
   128	//
   129	// Note that OpenBSD allows neither "net.inet6.ip6.v6only=1" change
   130	// nor IPPROTO_IPV6 level IPV6_V6ONLY socket option setting.
   131	func favoriteAddrFamily(net string, laddr, raddr sockaddr, mode string) (family int, ipv6only bool) {
   132		switch net[len(net)-1] {
   133		case '4':
   134			return syscall.AF_INET, false
   135		case '6':
   136			return syscall.AF_INET6, true
   137		}
   138	
   139		if mode == "listen" && (laddr == nil || laddr.isWildcard()) {
   140			if supportsIPv4map {
   141				return syscall.AF_INET6, false
   142			}
   143			if laddr == nil {
   144				return syscall.AF_INET, false
   145			}
   146			return laddr.family(), false
   147		}
   148	
   149		if (laddr == nil || laddr.family() == syscall.AF_INET) &&
   150			(raddr == nil || raddr.family() == syscall.AF_INET) {
   151			return syscall.AF_INET, false
   152		}
   153		return syscall.AF_INET6, false
   154	}
   155	
   156	// Internet sockets (TCP, UDP, IP)
   157	
   158	func internetSocket(net string, laddr, raddr sockaddr, deadline time.Time, sotype, proto int, mode string) (fd *netFD, err error) {
   159		family, ipv6only := favoriteAddrFamily(net, laddr, raddr, mode)
   160		return socket(net, family, sotype, proto, ipv6only, laddr, raddr, deadline)
   161	}
   162	
   163	func ipToSockaddr(family int, ip IP, port int, zone string) (syscall.Sockaddr, error) {
   164		switch family {
   165		case syscall.AF_INET:
   166			if len(ip) == 0 {
   167				ip = IPv4zero
   168			}
   169			if ip = ip.To4(); ip == nil {
   170				return nil, &AddrError{Err: "non-IPv4 address", Addr: ip.String()}
   171			}
   172			sa := new(syscall.SockaddrInet4)
   173			for i := 0; i < IPv4len; i++ {
   174				sa.Addr[i] = ip[i]
   175			}
   176			sa.Port = port
   177			return sa, nil
   178		case syscall.AF_INET6:
   179			if len(ip) == 0 {
   180				ip = IPv6zero
   181			}
   182			// IPv4 callers use 0.0.0.0 to mean "announce on any available address".
   183			// In IPv6 mode, Linux treats that as meaning "announce on 0.0.0.0",
   184			// which it refuses to do.  Rewrite to the IPv6 unspecified address.
   185			if ip.Equal(IPv4zero) {
   186				ip = IPv6zero
   187			}
   188			if ip = ip.To16(); ip == nil {
   189				return nil, &AddrError{Err: "non-IPv6 address", Addr: ip.String()}
   190			}
   191			sa := new(syscall.SockaddrInet6)
   192			for i := 0; i < IPv6len; i++ {
   193				sa.Addr[i] = ip[i]
   194			}
   195			sa.Port = port
   196			sa.ZoneId = uint32(zoneToInt(zone))
   197			return sa, nil
   198		}
   199		return nil, &AddrError{Err: "invalid address family", Addr: ip.String()}
   200	}
   201	

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