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Source file src/net/ipsock_posix.go

Documentation: net

     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 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 == "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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