1 files changed, 307 insertions, 0 deletions
diff --git a/src/net/ipsock.go b/src/net/ipsock.go
new file mode 100644
index 0000000..7d0684d
--- /dev/null
+++ b/src/net/ipsock.go
@@ -0,0 +1,307 @@
+// 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}
+}