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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, or does not support IPv4, we assume that
   105	//	the user wants to listen on both IPv4 and IPv6 wildcard
   106	//	addresses over an AF_INET6 socket with IPV6_V6ONLY=0.
   107	//	Otherwise we prefer an IPv4 wildcard address listen over
   108	//	an AF_INET socket.
   109	//
   110	//	2. A wild-ipv4wild listen, "tcp" + "0.0.0.0"
   111	//	Same as 1.
   112	//
   113	//	3. A wild-ipv6wild listen, "tcp" + "[::]"
   114	//	Almost same as 1 but we prefer an IPv6 wildcard address
   115	//	listen over an AF_INET6 socket with IPV6_V6ONLY=0 when
   116	//	the platform supports IPv6 capability but not IPv6 IPv4-
   117	//	mapping capability.
   118	//
   119	//	4. A ipv4-ipv4wild listen, "tcp4" + "" or "0.0.0.0"
   120	//	We use an IPv4 (AF_INET) wildcard address listen.
   121	//
   122	//	5. A ipv6-ipv6wild listen, "tcp6" + "" or "[::]"
   123	//	We use an IPv6 (AF_INET6, IPV6_V6ONLY=1) wildcard address
   124	//	listen.
   125	//
   126	// Otherwise guess: if the addresses are IPv4 then returns AF_INET,
   127	// or else returns AF_INET6.  It also returns a boolean value what
   128	// designates IPV6_V6ONLY option.
   129	//
   130	// Note that OpenBSD allows neither "net.inet6.ip6.v6only=1" change
   131	// nor IPPROTO_IPV6 level IPV6_V6ONLY socket option setting.
   132	func favoriteAddrFamily(net string, laddr, raddr sockaddr, mode string) (family int, ipv6only bool) {
   133		switch net[len(net)-1] {
   134		case '4':
   135			return syscall.AF_INET, false
   136		case '6':
   137			return syscall.AF_INET6, true
   138		}
   139	
   140		if mode == "listen" && (laddr == nil || laddr.isWildcard()) {
   141			if supportsIPv4map || !supportsIPv4 {
   142				return syscall.AF_INET6, false
   143			}
   144			if laddr == nil {
   145				return syscall.AF_INET, false
   146			}
   147			return laddr.family(), false
   148		}
   149	
   150		if (laddr == nil || laddr.family() == syscall.AF_INET) &&
   151			(raddr == nil || raddr.family() == syscall.AF_INET) {
   152			return syscall.AF_INET, false
   153		}
   154		return syscall.AF_INET6, false
   155	}
   156	
   157	// Internet sockets (TCP, UDP, IP)
   158	
   159	func internetSocket(net string, laddr, raddr sockaddr, deadline time.Time, sotype, proto int, mode string, cancel <-chan struct{}) (fd *netFD, err error) {
   160		family, ipv6only := favoriteAddrFamily(net, laddr, raddr, mode)
   161		return socket(net, family, sotype, proto, ipv6only, laddr, raddr, deadline, cancel)
   162	}
   163	
   164	func ipToSockaddr(family int, ip IP, port int, zone string) (syscall.Sockaddr, error) {
   165		switch family {
   166		case syscall.AF_INET:
   167			if len(ip) == 0 {
   168				ip = IPv4zero
   169			}
   170			if ip = ip.To4(); ip == nil {
   171				return nil, &AddrError{Err: "non-IPv4 address", Addr: ip.String()}
   172			}
   173			sa := new(syscall.SockaddrInet4)
   174			for i := 0; i < IPv4len; i++ {
   175				sa.Addr[i] = ip[i]
   176			}
   177			sa.Port = port
   178			return sa, nil
   179		case syscall.AF_INET6:
   180			if len(ip) == 0 {
   181				ip = IPv6zero
   182			}
   183			// IPv4 callers use 0.0.0.0 to mean "announce on any available address".
   184			// In IPv6 mode, Linux treats that as meaning "announce on 0.0.0.0",
   185			// which it refuses to do.  Rewrite to the IPv6 unspecified address.
   186			if ip.Equal(IPv4zero) {
   187				ip = IPv6zero
   188			}
   189			if ip = ip.To16(); ip == nil {
   190				return nil, &AddrError{Err: "non-IPv6 address", Addr: ip.String()}
   191			}
   192			sa := new(syscall.SockaddrInet6)
   193			for i := 0; i < IPv6len; i++ {
   194				sa.Addr[i] = ip[i]
   195			}
   196			sa.Port = port
   197			sa.ZoneId = uint32(zoneToInt(zone))
   198			return sa, nil
   199		}
   200		return nil, &AddrError{Err: "invalid address family", Addr: ip.String()}
   201	}
   202	

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