src/net/ipsock.go - go - Git at Google

 // 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}
 }
	// 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}
	}