// 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" "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 { 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} }