Source file src/pkg/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 aix darwin dragonfly freebsd js,wasm linux nacl netbsd openbsd solaris windows
     6	
     7	package net
     8	
     9	import (
    10		"context"
    11		"internal/poll"
    12		"runtime"
    13		"syscall"
    14	)
    15	
    16	// Probe probes IPv4, IPv6 and IPv4-mapped IPv6 communication
    17	// capabilities which are controlled by the IPV6_V6ONLY socket option
    18	// and kernel configuration.
    19	//
    20	// Should we try to use the IPv4 socket interface if we're only
    21	// dealing with IPv4 sockets? As long as the host system understands
    22	// IPv4-mapped IPv6, it's okay to pass IPv4-mapeed IPv6 addresses to
    23	// the IPv6 interface. That simplifies our code and is most
    24	// general. Unfortunately, we need to run on kernels built without
    25	// IPv6 support too. So probe the kernel to figure it out.
    26	func (p *ipStackCapabilities) probe() {
    27		s, err := sysSocket(syscall.AF_INET, syscall.SOCK_STREAM, syscall.IPPROTO_TCP)
    28		switch err {
    29		case syscall.EAFNOSUPPORT, syscall.EPROTONOSUPPORT:
    30		case nil:
    31			poll.CloseFunc(s)
    32			p.ipv4Enabled = true
    33		}
    34		var probes = []struct {
    35			laddr TCPAddr
    36			value int
    37		}{
    38			// IPv6 communication capability
    39			{laddr: TCPAddr{IP: ParseIP("::1")}, value: 1},
    40			// IPv4-mapped IPv6 address communication capability
    41			{laddr: TCPAddr{IP: IPv4(127, 0, 0, 1)}, value: 0},
    42		}
    43		switch runtime.GOOS {
    44		case "dragonfly", "openbsd":
    45			// The latest DragonFly BSD and OpenBSD kernels don't
    46			// support IPV6_V6ONLY=0. They always return an error
    47			// and we don't need to probe the capability.
    48			probes = probes[:1]
    49		}
    50		for i := range probes {
    51			s, err := sysSocket(syscall.AF_INET6, syscall.SOCK_STREAM, syscall.IPPROTO_TCP)
    52			if err != nil {
    53				continue
    54			}
    55			defer poll.CloseFunc(s)
    56			syscall.SetsockoptInt(s, syscall.IPPROTO_IPV6, syscall.IPV6_V6ONLY, probes[i].value)
    57			sa, err := probes[i].laddr.sockaddr(syscall.AF_INET6)
    58			if err != nil {
    59				continue
    60			}
    61			if err := syscall.Bind(s, sa); err != nil {
    62				continue
    63			}
    64			if i == 0 {
    65				p.ipv6Enabled = true
    66			} else {
    67				p.ipv4MappedIPv6Enabled = true
    68			}
    69		}
    70	}
    71	
    72	// favoriteAddrFamily returns the appropriate address family for the
    73	// given network, laddr, raddr and mode.
    74	//
    75	// If mode indicates "listen" and laddr is a wildcard, we assume that
    76	// the user wants to make a passive-open connection with a wildcard
    77	// address family, both AF_INET and AF_INET6, and a wildcard address
    78	// like the following:
    79	//
    80	//	- A listen for a wildcard communication domain, "tcp" or
    81	//	  "udp", with a wildcard address: If the platform supports
    82	//	  both IPv6 and IPv4-mapped IPv6 communication capabilities,
    83	//	  or does not support IPv4, we use a dual stack, AF_INET6 and
    84	//	  IPV6_V6ONLY=0, wildcard address listen. The dual stack
    85	//	  wildcard address listen may fall back to an IPv6-only,
    86	//	  AF_INET6 and IPV6_V6ONLY=1, wildcard address listen.
    87	//	  Otherwise we prefer an IPv4-only, AF_INET, wildcard address
    88	//	  listen.
    89	//
    90	//	- A listen for a wildcard communication domain, "tcp" or
    91	//	  "udp", with an IPv4 wildcard address: same as above.
    92	//
    93	//	- A listen for a wildcard communication domain, "tcp" or
    94	//	  "udp", with an IPv6 wildcard address: same as above.
    95	//
    96	//	- A listen for an IPv4 communication domain, "tcp4" or "udp4",
    97	//	  with an IPv4 wildcard address: We use an IPv4-only, AF_INET,
    98	//	  wildcard address listen.
    99	//
   100	//	- A listen for an IPv6 communication domain, "tcp6" or "udp6",
   101	//	  with an IPv6 wildcard address: We use an IPv6-only, AF_INET6
   102	//	  and IPV6_V6ONLY=1, wildcard address listen.
   103	//
   104	// Otherwise guess: If the addresses are IPv4 then returns AF_INET,
   105	// or else returns AF_INET6. It also returns a boolean value what
   106	// designates IPV6_V6ONLY option.
   107	//
   108	// Note that the latest DragonFly BSD and OpenBSD kernels allow
   109	// neither "net.inet6.ip6.v6only=1" change nor IPPROTO_IPV6 level
   110	// IPV6_V6ONLY socket option setting.
   111	func favoriteAddrFamily(network string, laddr, raddr sockaddr, mode string) (family int, ipv6only bool) {
   112		switch network[len(network)-1] {
   113		case '4':
   114			return syscall.AF_INET, false
   115		case '6':
   116			return syscall.AF_INET6, true
   117		}
   118	
   119		if mode == "listen" && (laddr == nil || laddr.isWildcard()) {
   120			if supportsIPv4map() || !supportsIPv4() {
   121				return syscall.AF_INET6, false
   122			}
   123			if laddr == nil {
   124				return syscall.AF_INET, false
   125			}
   126			return laddr.family(), false
   127		}
   128	
   129		if (laddr == nil || laddr.family() == syscall.AF_INET) &&
   130			(raddr == nil || raddr.family() == syscall.AF_INET) {
   131			return syscall.AF_INET, false
   132		}
   133		return syscall.AF_INET6, false
   134	}
   135	
   136	func internetSocket(ctx context.Context, net string, laddr, raddr sockaddr, sotype, proto int, mode string, ctrlFn func(string, string, syscall.RawConn) error) (fd *netFD, err error) {
   137		if (runtime.GOOS == "aix" || runtime.GOOS == "windows" || runtime.GOOS == "openbsd" || runtime.GOOS == "nacl") && mode == "dial" && raddr.isWildcard() {
   138			raddr = raddr.toLocal(net)
   139		}
   140		family, ipv6only := favoriteAddrFamily(net, laddr, raddr, mode)
   141		return socket(ctx, net, family, sotype, proto, ipv6only, laddr, raddr, ctrlFn)
   142	}
   143	
   144	func ipToSockaddr(family int, ip IP, port int, zone string) (syscall.Sockaddr, error) {
   145		switch family {
   146		case syscall.AF_INET:
   147			if len(ip) == 0 {
   148				ip = IPv4zero
   149			}
   150			ip4 := ip.To4()
   151			if ip4 == nil {
   152				return nil, &AddrError{Err: "non-IPv4 address", Addr: ip.String()}
   153			}
   154			sa := &syscall.SockaddrInet4{Port: port}
   155			copy(sa.Addr[:], ip4)
   156			return sa, nil
   157		case syscall.AF_INET6:
   158			// In general, an IP wildcard address, which is either
   159			// "0.0.0.0" or "::", means the entire IP addressing
   160			// space. For some historical reason, it is used to
   161			// specify "any available address" on some operations
   162			// of IP node.
   163			//
   164			// When the IP node supports IPv4-mapped IPv6 address,
   165			// we allow an listener to listen to the wildcard
   166			// address of both IP addressing spaces by specifying
   167			// IPv6 wildcard address.
   168			if len(ip) == 0 || ip.Equal(IPv4zero) {
   169				ip = IPv6zero
   170			}
   171			// We accept any IPv6 address including IPv4-mapped
   172			// IPv6 address.
   173			ip6 := ip.To16()
   174			if ip6 == nil {
   175				return nil, &AddrError{Err: "non-IPv6 address", Addr: ip.String()}
   176			}
   177			sa := &syscall.SockaddrInet6{Port: port, ZoneId: uint32(zoneCache.index(zone))}
   178			copy(sa.Addr[:], ip6)
   179			return sa, nil
   180		}
   181		return nil, &AddrError{Err: "invalid address family", Addr: ip.String()}
   182	}
   183	

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