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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.
// Internet protocol family sockets
package net
import (
"errors"
"time"
)
var (
// supportsIPv4 reports whether the platform supports IPv4
// networking functionality.
supportsIPv4 bool
// supportsIPv6 reports whether the platform supports IPv6
// networking functionality.
supportsIPv6 bool
// 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.
supportsIPv4map bool
)
func init() {
sysInit()
supportsIPv4 = probeIPv4Stack()
supportsIPv6, supportsIPv4map = probeIPv6Stack()
}
// A netaddr represents a network endpoint address or a list of
// network endpoint addresses.
type netaddr interface {
// toAddr returns the address represented in Addr interface.
// It returns a nil interface when the address is nil.
toAddr() Addr
}
// An addrList represents a list of network endpoint addresses.
type addrList []netaddr
func (al addrList) toAddr() Addr {
switch len(al) {
case 0:
return nil
case 1:
return al[0].toAddr()
default:
// For now, we'll roughly pick first one without
// considering dealing with any preferences such as
// DNS TTL, transport path quality, network routing
// information.
return al[0].toAddr()
}
}
var errNoSuitableAddress = errors.New("no suitable address found")
// firstFavoriteAddr returns an address or a list of addresses that
// implement the netaddr interface. Known filters are nil, ipv4only
// and ipv6only. It returns any address when filter is nil. The result
// contains at least one address when error is nil.
func firstFavoriteAddr(filter func(IP) IP, ips []IP, inetaddr func(IP) netaddr) (netaddr, error) {
if filter != nil {
return firstSupportedAddr(filter, ips, inetaddr)
}
var (
ipv4, ipv6, swap bool
list addrList
)
for _, ip := range ips {
// We'll take any IP address, but since the dialing
// code does not yet try multiple addresses
// effectively, prefer to use an IPv4 address if
// possible. This is especially relevant if localhost
// resolves to [ipv6-localhost, ipv4-localhost]. Too
// much code assumes localhost == ipv4-localhost.
if ip4 := ipv4only(ip); ip4 != nil && !ipv4 {
list = append(list, inetaddr(ip4))
ipv4 = true
if ipv6 {
swap = true
}
} else if ip6 := ipv6only(ip); ip6 != nil && !ipv6 {
list = append(list, inetaddr(ip6))
ipv6 = true
}
if ipv4 && ipv6 {
if swap {
list[0], list[1] = list[1], list[0]
}
break
}
}
switch len(list) {
case 0:
return nil, errNoSuitableAddress
case 1:
return list[0], nil
default:
return list, nil
}
}
func firstSupportedAddr(filter func(IP) IP, ips []IP, inetaddr func(IP) netaddr) (netaddr, error) {
for _, ip := range ips {
if ip := filter(ip); ip != nil {
return inetaddr(ip), nil
}
}
return nil, errNoSuitableAddress
}
// ipv4only returns IPv4 addresses that we can use with the kernel's
// IPv4 addressing modes. If ip is an IPv4 address, ipv4only returns ip.
// Otherwise it returns nil.
func ipv4only(ip IP) IP {
if supportsIPv4 && ip.To4() != nil {
return ip
}
return nil
}
// ipv6only returns IPv6 addresses that we can use with the kernel's
// IPv6 addressing modes. It returns IPv4-mapped IPv6 addresses as
// nils and returns other IPv6 address types as IPv6 addresses.
func ipv6only(ip IP) IP {
if supportsIPv6 && len(ip) == IPv6len && ip.To4() == nil {
return ip
}
return nil
}
// SplitHostPort splits a network address of the form "host:port",
// "[host]:port" or "[ipv6-host%zone]:port" into host or
// ipv6-host%zone and port. A literal address or host name for IPv6
// must be enclosed in square brackets, as in "[::1]:80",
// "[ipv6-host]:http" or "[ipv6-host%zone]:80".
func SplitHostPort(hostport string) (host, port string, err error) {
j, k := 0, 0
// The port starts after the last colon.
i := last(hostport, ':')
if i < 0 {
goto missingPort
}
if hostport[0] == '[' {
// Expect the first ']' just before the last ':'.
end := byteIndex(hostport, ']')
if end < 0 {
err = &AddrError{"missing ']' in address", hostport}
return
}
switch end + 1 {
case len(hostport):
// There can't be a ':' behind the ']' now.
goto 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] == ':' {
goto tooManyColons
}
goto missingPort
}
host = hostport[1:end]
j, k = 1, end+1 // there can't be a '[' resp. ']' before these positions
} else {
host = hostport[:i]
if byteIndex(host, ':') >= 0 {
goto tooManyColons
}
if byteIndex(host, '%') >= 0 {
goto missingBrackets
}
}
if byteIndex(hostport[j:], '[') >= 0 {
err = &AddrError{"unexpected '[' in address", hostport}
return
}
if byteIndex(hostport[k:], ']') >= 0 {
err = &AddrError{"unexpected ']' in address", hostport}
return
}
port = hostport[i+1:]
return
missingPort:
err = &AddrError{"missing port in address", hostport}
return
tooManyColons:
err = &AddrError{"too many colons in address", hostport}
return
missingBrackets:
err = &AddrError{"missing brackets in address", hostport}
return
}
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" or, if host contains a colon or a percent sign,
// "[host]:port".
func JoinHostPort(host, port string) string {
// If host has colons or a percent sign, have to bracket it.
if byteIndex(host, ':') >= 0 || byteIndex(host, '%') >= 0 {
return "[" + host + "]:" + port
}
return host + ":" + port
}
// resolveInternetAddr resolves addr that is either a literal IP
// address or a DNS name and returns an internet protocol family
// address. It returns a list that contains a pair of different
// address family addresses when addr is a DNS name and the name has
// multiple address family records. The result contains at least one
// address when error is nil.
func resolveInternetAddr(net, addr string, deadline time.Time) (netaddr, error) {
var (
err error
host, port, zone 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 = parsePort(net, port); err != nil {
return nil, err
}
}
case "ip", "ip4", "ip6":
if addr != "" {
host = addr
}
default:
return nil, UnknownNetworkError(net)
}
inetaddr := func(ip IP) netaddr {
switch net {
case "tcp", "tcp4", "tcp6":
return &TCPAddr{IP: ip, Port: portnum, Zone: zone}
case "udp", "udp4", "udp6":
return &UDPAddr{IP: ip, Port: portnum, Zone: zone}
case "ip", "ip4", "ip6":
return &IPAddr{IP: ip, Zone: zone}
default:
panic("unexpected network: " + net)
}
}
if host == "" {
return inetaddr(nil), nil
}
// Try as a literal IP address.
var ip IP
if ip = parseIPv4(host); ip != nil {
return inetaddr(ip), nil
}
if ip, zone = parseIPv6(host, true); ip != nil {
return inetaddr(ip), nil
}
// Try as a DNS name.
host, zone = splitHostZone(host)
ips, err := lookupIPDeadline(host, deadline)
if err != nil {
return nil, err
}
var filter func(IP) IP
if net != "" && net[len(net)-1] == '4' {
filter = ipv4only
}
if net != "" && net[len(net)-1] == '6' || zone != "" {
filter = ipv6only
}
return firstFavoriteAddr(filter, ips, inetaddr)
}
func zoneToString(zone int) string {
if zone == 0 {
return ""
}
if ifi, err := InterfaceByIndex(zone); err == nil {
return ifi.Name
}
return uitoa(uint(zone))
}
func zoneToInt(zone string) int {
if zone == "" {
return 0
}
if ifi, err := InterfaceByName(zone); err == nil {
return ifi.Index
}
n, _, _ := dtoi(zone, 0)
return n
}