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  //go:build unix || js || wasip1 || windows
     6  
     7  package net
     8  
     9  import (
    10  	"context"
    11  	"internal/poll"
    12  	"net/netip"
    13  	"runtime"
    14  	"syscall"
    15  )
    16  
    17  // probe probes IPv4, IPv6 and IPv4-mapped IPv6 communication
    18  // capabilities which are controlled by the IPV6_V6ONLY socket option
    19  // and kernel configuration.
    20  //
    21  // Should we try to use the IPv4 socket interface if we're only
    22  // dealing with IPv4 sockets? As long as the host system understands
    23  // IPv4-mapped IPv6, it's okay to pass IPv4-mapped IPv6 addresses to
    24  // the IPv6 interface. That simplifies our code and is most
    25  // general. Unfortunately, we need to run on kernels built without
    26  // IPv6 support too. So probe the kernel to figure it out.
    27  func (p *ipStackCapabilities) probe() {
    28  	switch runtime.GOOS {
    29  	case "js", "wasip1":
    30  		// Both ipv4 and ipv6 are faked; see net_fake.go.
    31  		p.ipv4Enabled = true
    32  		p.ipv6Enabled = true
    33  		p.ipv4MappedIPv6Enabled = true
    34  		return
    35  	}
    36  
    37  	s, err := sysSocket(syscall.AF_INET, syscall.SOCK_STREAM, syscall.IPPROTO_TCP)
    38  	switch err {
    39  	case syscall.EAFNOSUPPORT, syscall.EPROTONOSUPPORT:
    40  	case nil:
    41  		poll.CloseFunc(s)
    42  		p.ipv4Enabled = true
    43  	}
    44  	var probes = []struct {
    45  		laddr TCPAddr
    46  		value int
    47  	}{
    48  		// IPv6 communication capability
    49  		{laddr: TCPAddr{IP: ParseIP("::1")}, value: 1},
    50  		// IPv4-mapped IPv6 address communication capability
    51  		{laddr: TCPAddr{IP: IPv4(127, 0, 0, 1)}, value: 0},
    52  	}
    53  	switch runtime.GOOS {
    54  	case "dragonfly", "openbsd":
    55  		// The latest DragonFly BSD and OpenBSD kernels don't
    56  		// support IPV6_V6ONLY=0. They always return an error
    57  		// and we don't need to probe the capability.
    58  		probes = probes[:1]
    59  	}
    60  	for i := range probes {
    61  		s, err := sysSocket(syscall.AF_INET6, syscall.SOCK_STREAM, syscall.IPPROTO_TCP)
    62  		if err != nil {
    63  			continue
    64  		}
    65  		defer poll.CloseFunc(s)
    66  		syscall.SetsockoptInt(s, syscall.IPPROTO_IPV6, syscall.IPV6_V6ONLY, probes[i].value)
    67  		sa, err := probes[i].laddr.sockaddr(syscall.AF_INET6)
    68  		if err != nil {
    69  			continue
    70  		}
    71  		if err := syscall.Bind(s, sa); err != nil {
    72  			continue
    73  		}
    74  		if i == 0 {
    75  			p.ipv6Enabled = true
    76  		} else {
    77  			p.ipv4MappedIPv6Enabled = true
    78  		}
    79  	}
    80  }
    81  
    82  // favoriteAddrFamily returns the appropriate address family for the
    83  // given network, laddr, raddr and mode.
    84  //
    85  // If mode indicates "listen" and laddr is a wildcard, we assume that
    86  // the user wants to make a passive-open connection with a wildcard
    87  // address family, both AF_INET and AF_INET6, and a wildcard address
    88  // like the following:
    89  //
    90  //   - A listen for a wildcard communication domain, "tcp" or
    91  //     "udp", with a wildcard address: If the platform supports
    92  //     both IPv6 and IPv4-mapped IPv6 communication capabilities,
    93  //     or does not support IPv4, we use a dual stack, AF_INET6 and
    94  //     IPV6_V6ONLY=0, wildcard address listen. The dual stack
    95  //     wildcard address listen may fall back to an IPv6-only,
    96  //     AF_INET6 and IPV6_V6ONLY=1, wildcard address listen.
    97  //     Otherwise we prefer an IPv4-only, AF_INET, wildcard address
    98  //     listen.
    99  //
   100  //   - A listen for a wildcard communication domain, "tcp" or
   101  //     "udp", with an IPv4 wildcard address: same as above.
   102  //
   103  //   - A listen for a wildcard communication domain, "tcp" or
   104  //     "udp", with an IPv6 wildcard address: same as above.
   105  //
   106  //   - A listen for an IPv4 communication domain, "tcp4" or "udp4",
   107  //     with an IPv4 wildcard address: We use an IPv4-only, AF_INET,
   108  //     wildcard address listen.
   109  //
   110  //   - A listen for an IPv6 communication domain, "tcp6" or "udp6",
   111  //     with an IPv6 wildcard address: We use an IPv6-only, AF_INET6
   112  //     and IPV6_V6ONLY=1, wildcard address listen.
   113  //
   114  // Otherwise guess: If the addresses are IPv4 then returns AF_INET,
   115  // or else returns AF_INET6. It also returns a boolean value what
   116  // designates IPV6_V6ONLY option.
   117  //
   118  // Note that the latest DragonFly BSD and OpenBSD kernels allow
   119  // neither "net.inet6.ip6.v6only=1" change nor IPPROTO_IPV6 level
   120  // IPV6_V6ONLY socket option setting.
   121  func favoriteAddrFamily(network string, laddr, raddr sockaddr, mode string) (family int, ipv6only bool) {
   122  	switch network[len(network)-1] {
   123  	case '4':
   124  		return syscall.AF_INET, false
   125  	case '6':
   126  		return syscall.AF_INET6, true
   127  	}
   128  
   129  	if mode == "listen" && (laddr == nil || laddr.isWildcard()) {
   130  		if supportsIPv4map() || !supportsIPv4() {
   131  			return syscall.AF_INET6, false
   132  		}
   133  		if laddr == nil {
   134  			return syscall.AF_INET, false
   135  		}
   136  		return laddr.family(), false
   137  	}
   138  
   139  	if (laddr == nil || laddr.family() == syscall.AF_INET) &&
   140  		(raddr == nil || raddr.family() == syscall.AF_INET) {
   141  		return syscall.AF_INET, false
   142  	}
   143  	return syscall.AF_INET6, false
   144  }
   145  
   146  func internetSocket(ctx context.Context, net string, laddr, raddr sockaddr, sotype, proto int, mode string, ctrlCtxFn func(context.Context, string, string, syscall.RawConn) error) (fd *netFD, err error) {
   147  	switch runtime.GOOS {
   148  	case "aix", "windows", "openbsd", "js", "wasip1":
   149  		if mode == "dial" && raddr.isWildcard() {
   150  			raddr = raddr.toLocal(net)
   151  		}
   152  	}
   153  	family, ipv6only := favoriteAddrFamily(net, laddr, raddr, mode)
   154  	return socket(ctx, net, family, sotype, proto, ipv6only, laddr, raddr, ctrlCtxFn)
   155  }
   156  
   157  func ipToSockaddrInet4(ip IP, port int) (syscall.SockaddrInet4, error) {
   158  	if len(ip) == 0 {
   159  		ip = IPv4zero
   160  	}
   161  	ip4 := ip.To4()
   162  	if ip4 == nil {
   163  		return syscall.SockaddrInet4{}, &AddrError{Err: "non-IPv4 address", Addr: ip.String()}
   164  	}
   165  	sa := syscall.SockaddrInet4{Port: port}
   166  	copy(sa.Addr[:], ip4)
   167  	return sa, nil
   168  }
   169  
   170  func ipToSockaddrInet6(ip IP, port int, zone string) (syscall.SockaddrInet6, error) {
   171  	// In general, an IP wildcard address, which is either
   172  	// "0.0.0.0" or "::", means the entire IP addressing
   173  	// space. For some historical reason, it is used to
   174  	// specify "any available address" on some operations
   175  	// of IP node.
   176  	//
   177  	// When the IP node supports IPv4-mapped IPv6 address,
   178  	// we allow a listener to listen to the wildcard
   179  	// address of both IP addressing spaces by specifying
   180  	// IPv6 wildcard address.
   181  	if len(ip) == 0 || ip.Equal(IPv4zero) {
   182  		ip = IPv6zero
   183  	}
   184  	// We accept any IPv6 address including IPv4-mapped
   185  	// IPv6 address.
   186  	ip6 := ip.To16()
   187  	if ip6 == nil {
   188  		return syscall.SockaddrInet6{}, &AddrError{Err: "non-IPv6 address", Addr: ip.String()}
   189  	}
   190  	sa := syscall.SockaddrInet6{Port: port, ZoneId: uint32(zoneCache.index(zone))}
   191  	copy(sa.Addr[:], ip6)
   192  	return sa, nil
   193  }
   194  
   195  func ipToSockaddr(family int, ip IP, port int, zone string) (syscall.Sockaddr, error) {
   196  	switch family {
   197  	case syscall.AF_INET:
   198  		sa, err := ipToSockaddrInet4(ip, port)
   199  		if err != nil {
   200  			return nil, err
   201  		}
   202  		return &sa, nil
   203  	case syscall.AF_INET6:
   204  		sa, err := ipToSockaddrInet6(ip, port, zone)
   205  		if err != nil {
   206  			return nil, err
   207  		}
   208  		return &sa, nil
   209  	}
   210  	return nil, &AddrError{Err: "invalid address family", Addr: ip.String()}
   211  }
   212  
   213  func addrPortToSockaddrInet4(ap netip.AddrPort) (syscall.SockaddrInet4, error) {
   214  	// ipToSockaddrInet4 has special handling here for zero length slices.
   215  	// We do not, because netip has no concept of a generic zero IP address.
   216  	addr := ap.Addr()
   217  	if !addr.Is4() {
   218  		return syscall.SockaddrInet4{}, &AddrError{Err: "non-IPv4 address", Addr: addr.String()}
   219  	}
   220  	sa := syscall.SockaddrInet4{
   221  		Addr: addr.As4(),
   222  		Port: int(ap.Port()),
   223  	}
   224  	return sa, nil
   225  }
   226  
   227  func addrPortToSockaddrInet6(ap netip.AddrPort) (syscall.SockaddrInet6, error) {
   228  	// ipToSockaddrInet6 has special handling here for zero length slices.
   229  	// We do not, because netip has no concept of a generic zero IP address.
   230  	//
   231  	// addr is allowed to be an IPv4 address, because As16 will convert it
   232  	// to an IPv4-mapped IPv6 address.
   233  	// The error message is kept consistent with ipToSockaddrInet6.
   234  	addr := ap.Addr()
   235  	if !addr.IsValid() {
   236  		return syscall.SockaddrInet6{}, &AddrError{Err: "non-IPv6 address", Addr: addr.String()}
   237  	}
   238  	sa := syscall.SockaddrInet6{
   239  		Addr:   addr.As16(),
   240  		Port:   int(ap.Port()),
   241  		ZoneId: uint32(zoneCache.index(addr.Zone())),
   242  	}
   243  	return sa, nil
   244  }
   245
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