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-rw-r--r--src/net/ipsock.go315
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diff --git a/src/net/ipsock.go b/src/net/ipsock.go
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+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package net
+
+import (
+ "context"
+ "internal/bytealg"
+ "runtime"
+ "sync"
+)
+
+// BUG(rsc,mikio): On DragonFly BSD and OpenBSD, listening on the
+// "tcp" and "udp" networks does not listen for both IPv4 and IPv6
+// connections. This is due to the fact that IPv4 traffic will not be
+// routed to an IPv6 socket - two separate sockets are required if
+// both address families are to be supported.
+// See inet6(4) for details.
+
+type ipStackCapabilities struct {
+ sync.Once // guards following
+ ipv4Enabled bool
+ ipv6Enabled bool
+ ipv4MappedIPv6Enabled bool
+}
+
+var ipStackCaps ipStackCapabilities
+
+// supportsIPv4 reports whether the platform supports IPv4 networking
+// functionality.
+func supportsIPv4() bool {
+ ipStackCaps.Once.Do(ipStackCaps.probe)
+ return ipStackCaps.ipv4Enabled
+}
+
+// supportsIPv6 reports whether the platform supports IPv6 networking
+// functionality.
+func supportsIPv6() bool {
+ ipStackCaps.Once.Do(ipStackCaps.probe)
+ return ipStackCaps.ipv6Enabled
+}
+
+// supportsIPv4map reports whether the platform supports mapping an
+// IPv4 address inside an IPv6 address at transport layer
+// protocols. See RFC 4291, RFC 4038 and RFC 3493.
+func supportsIPv4map() bool {
+ // Some operating systems provide no support for mapping IPv4
+ // addresses to IPv6, and a runtime check is unnecessary.
+ switch runtime.GOOS {
+ case "dragonfly", "openbsd":
+ return false
+ }
+
+ ipStackCaps.Once.Do(ipStackCaps.probe)
+ return ipStackCaps.ipv4MappedIPv6Enabled
+}
+
+// An addrList represents a list of network endpoint addresses.
+type addrList []Addr
+
+// isIPv4 reports whether addr contains an IPv4 address.
+func isIPv4(addr Addr) bool {
+ switch addr := addr.(type) {
+ case *TCPAddr:
+ return addr.IP.To4() != nil
+ case *UDPAddr:
+ return addr.IP.To4() != nil
+ case *IPAddr:
+ return addr.IP.To4() != nil
+ }
+ return false
+}
+
+// isNotIPv4 reports whether addr does not contain an IPv4 address.
+func isNotIPv4(addr Addr) bool { return !isIPv4(addr) }
+
+// forResolve returns the most appropriate address in address for
+// a call to ResolveTCPAddr, ResolveUDPAddr, or ResolveIPAddr.
+// IPv4 is preferred, unless addr contains an IPv6 literal.
+func (addrs addrList) forResolve(network, addr string) Addr {
+ var want6 bool
+ switch network {
+ case "ip":
+ // IPv6 literal (addr does NOT contain a port)
+ want6 = count(addr, ':') > 0
+ case "tcp", "udp":
+ // IPv6 literal. (addr contains a port, so look for '[')
+ want6 = count(addr, '[') > 0
+ }
+ if want6 {
+ return addrs.first(isNotIPv4)
+ }
+ return addrs.first(isIPv4)
+}
+
+// first returns the first address which satisfies strategy, or if
+// none do, then the first address of any kind.
+func (addrs addrList) first(strategy func(Addr) bool) Addr {
+ for _, addr := range addrs {
+ if strategy(addr) {
+ return addr
+ }
+ }
+ return addrs[0]
+}
+
+// partition divides an address list into two categories, using a
+// strategy function to assign a boolean label to each address.
+// The first address, and any with a matching label, are returned as
+// primaries, while addresses with the opposite label are returned
+// as fallbacks. For non-empty inputs, primaries is guaranteed to be
+// non-empty.
+func (addrs addrList) partition(strategy func(Addr) bool) (primaries, fallbacks addrList) {
+ var primaryLabel bool
+ for i, addr := range addrs {
+ label := strategy(addr)
+ if i == 0 || label == primaryLabel {
+ primaryLabel = label
+ primaries = append(primaries, addr)
+ } else {
+ fallbacks = append(fallbacks, addr)
+ }
+ }
+ return
+}
+
+// filterAddrList applies a filter to a list of IP addresses,
+// yielding a list of Addr objects. Known filters are nil, ipv4only,
+// and ipv6only. It returns every address when the filter is nil.
+// The result contains at least one address when error is nil.
+func filterAddrList(filter func(IPAddr) bool, ips []IPAddr, inetaddr func(IPAddr) Addr, originalAddr string) (addrList, error) {
+ var addrs addrList
+ for _, ip := range ips {
+ if filter == nil || filter(ip) {
+ addrs = append(addrs, inetaddr(ip))
+ }
+ }
+ if len(addrs) == 0 {
+ return nil, &AddrError{Err: errNoSuitableAddress.Error(), Addr: originalAddr}
+ }
+ return addrs, nil
+}
+
+// ipv4only reports whether addr is an IPv4 address.
+func ipv4only(addr IPAddr) bool {
+ return addr.IP.To4() != nil
+}
+
+// ipv6only reports whether addr is an IPv6 address except IPv4-mapped IPv6 address.
+func ipv6only(addr IPAddr) bool {
+ return len(addr.IP) == IPv6len && addr.IP.To4() == nil
+}
+
+// SplitHostPort splits a network address of the form "host:port",
+// "host%zone:port", "[host]:port" or "[host%zone]:port" into host or
+// host%zone and port.
+//
+// A literal IPv6 address in hostport must be enclosed in square
+// brackets, as in "[::1]:80", "[::1%lo0]:80".
+//
+// See func Dial for a description of the hostport parameter, and host
+// and port results.
+func SplitHostPort(hostport string) (host, port string, err error) {
+ const (
+ missingPort = "missing port in address"
+ tooManyColons = "too many colons in address"
+ )
+ addrErr := func(addr, why string) (host, port string, err error) {
+ return "", "", &AddrError{Err: why, Addr: addr}
+ }
+ j, k := 0, 0
+
+ // The port starts after the last colon.
+ i := last(hostport, ':')
+ if i < 0 {
+ return addrErr(hostport, missingPort)
+ }
+
+ if hostport[0] == '[' {
+ // Expect the first ']' just before the last ':'.
+ end := bytealg.IndexByteString(hostport, ']')
+ if end < 0 {
+ return addrErr(hostport, "missing ']' in address")
+ }
+ switch end + 1 {
+ case len(hostport):
+ // There can't be a ':' behind the ']' now.
+ return addrErr(hostport, missingPort)
+ case i:
+ // The expected result.
+ default:
+ // Either ']' isn't followed by a colon, or it is
+ // followed by a colon that is not the last one.
+ if hostport[end+1] == ':' {
+ return addrErr(hostport, tooManyColons)
+ }
+ return addrErr(hostport, missingPort)
+ }
+ host = hostport[1:end]
+ j, k = 1, end+1 // there can't be a '[' resp. ']' before these positions
+ } else {
+ host = hostport[:i]
+ if bytealg.IndexByteString(host, ':') >= 0 {
+ return addrErr(hostport, tooManyColons)
+ }
+ }
+ if bytealg.IndexByteString(hostport[j:], '[') >= 0 {
+ return addrErr(hostport, "unexpected '[' in address")
+ }
+ if bytealg.IndexByteString(hostport[k:], ']') >= 0 {
+ return addrErr(hostport, "unexpected ']' in address")
+ }
+
+ port = hostport[i+1:]
+ return host, port, nil
+}
+
+func splitHostZone(s string) (host, zone string) {
+ // The IPv6 scoped addressing zone identifier starts after the
+ // last percent sign.
+ if i := last(s, '%'); i > 0 {
+ host, zone = s[:i], s[i+1:]
+ } else {
+ host = s
+ }
+ return
+}
+
+// JoinHostPort combines host and port into a network address of the
+// form "host:port". If host contains a colon, as found in literal
+// IPv6 addresses, then JoinHostPort returns "[host]:port".
+//
+// See func Dial for a description of the host and port parameters.
+func JoinHostPort(host, port string) string {
+ // We assume that host is a literal IPv6 address if host has
+ // colons.
+ if bytealg.IndexByteString(host, ':') >= 0 {
+ return "[" + host + "]:" + port
+ }
+ return host + ":" + port
+}
+
+// internetAddrList resolves addr, which may be a literal IP
+// address or a DNS name, and returns a list of internet protocol
+// family addresses. The result contains at least one address when
+// error is nil.
+func (r *Resolver) internetAddrList(ctx context.Context, net, addr string) (addrList, error) {
+ var (
+ err error
+ host, port string
+ portnum int
+ )
+ switch net {
+ case "tcp", "tcp4", "tcp6", "udp", "udp4", "udp6":
+ if addr != "" {
+ if host, port, err = SplitHostPort(addr); err != nil {
+ return nil, err
+ }
+ if portnum, err = r.LookupPort(ctx, net, port); err != nil {
+ return nil, err
+ }
+ }
+ case "ip", "ip4", "ip6":
+ if addr != "" {
+ host = addr
+ }
+ default:
+ return nil, UnknownNetworkError(net)
+ }
+ inetaddr := func(ip IPAddr) Addr {
+ switch net {
+ case "tcp", "tcp4", "tcp6":
+ return &TCPAddr{IP: ip.IP, Port: portnum, Zone: ip.Zone}
+ case "udp", "udp4", "udp6":
+ return &UDPAddr{IP: ip.IP, Port: portnum, Zone: ip.Zone}
+ case "ip", "ip4", "ip6":
+ return &IPAddr{IP: ip.IP, Zone: ip.Zone}
+ default:
+ panic("unexpected network: " + net)
+ }
+ }
+ if host == "" {
+ return addrList{inetaddr(IPAddr{})}, nil
+ }
+
+ // Try as a literal IP address, then as a DNS name.
+ ips, err := r.lookupIPAddr(ctx, net, host)
+ if err != nil {
+ return nil, err
+ }
+ // Issue 18806: if the machine has halfway configured
+ // IPv6 such that it can bind on "::" (IPv6unspecified)
+ // but not connect back to that same address, fall
+ // back to dialing 0.0.0.0.
+ if len(ips) == 1 && ips[0].IP.Equal(IPv6unspecified) {
+ ips = append(ips, IPAddr{IP: IPv4zero})
+ }
+
+ var filter func(IPAddr) bool
+ if net != "" && net[len(net)-1] == '4' {
+ filter = ipv4only
+ }
+ if net != "" && net[len(net)-1] == '6' {
+ filter = ipv6only
+ }
+ return filterAddrList(filter, ips, inetaddr, host)
+}
+
+func loopbackIP(net string) IP {
+ if net != "" && net[len(net)-1] == '6' {
+ return IPv6loopback
+ }
+ return IP{127, 0, 0, 1}
+}