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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.
// IP sockets
package net
import (
"os"
"syscall"
)
// Should we try to use the IPv4 socket interface if we're
// only dealing with IPv4 sockets? As long as the host system
// understands IPv6, it's okay to pass IPv4 addresses to the IPv6
// interface. That simplifies our code and is most general.
// Unfortunately, we need to run on kernels built without IPv6
// support too. So probe the kernel to figure it out.
//
// probeIPv6Stack probes both basic IPv6 capability and IPv6 IPv4-
// mapping capability which is controlled by IPV6_V6ONLY socket
// option and/or kernel state "net.inet6.ip6.v6only".
// It returns two boolean values. If the first boolean value is
// true, kernel supports basic IPv6 functionality. If the second
// boolean value is true, kernel supports IPv6 IPv4-mapping.
func probeIPv6Stack() (supportsIPv6, supportsIPv4map bool) {
var probes = []struct {
la TCPAddr
ok bool
}{
// IPv6 communication capability
{TCPAddr{IP: ParseIP("::1")}, false},
// IPv6 IPv4-mapped address communication capability
{TCPAddr{IP: IPv4(127, 0, 0, 1)}, false},
}
for i := range probes {
s, errno := syscall.Socket(syscall.AF_INET6, syscall.SOCK_STREAM, syscall.IPPROTO_TCP)
if errno != 0 {
continue
}
defer closesocket(s)
sa, err := probes[i].la.toAddr().sockaddr(syscall.AF_INET6)
if err != nil {
continue
}
errno = syscall.Bind(s, sa)
if errno != 0 {
continue
}
probes[i].ok = true
}
return probes[0].ok, probes[1].ok
}
var supportsIPv6, supportsIPv4map = probeIPv6Stack()
// favoriteAddrFamily returns the appropriate address family to
// the given net, raddr, laddr and mode. At first it figures
// address family out from the net. If mode indicates "listen"
// and laddr.(type).IP is nil, it assumes that the user wants to
// make a passive connection with wildcard address family, both
// INET and INET6, and wildcard address. Otherwise guess: if the
// addresses are IPv4 then returns INET, or else returns INET6.
func favoriteAddrFamily(net string, raddr, laddr sockaddr, mode string) int {
switch net[len(net)-1] {
case '4':
return syscall.AF_INET
case '6':
return syscall.AF_INET6
}
if mode == "listen" {
switch a := laddr.(type) {
case *TCPAddr:
if a.IP == nil && supportsIPv6 {
return syscall.AF_INET6
}
case *UDPAddr:
if a.IP == nil && supportsIPv6 {
return syscall.AF_INET6
}
case *IPAddr:
if a.IP == nil && supportsIPv6 {
return syscall.AF_INET6
}
}
}
if (laddr == nil || laddr.family() == syscall.AF_INET) &&
(raddr == nil || raddr.family() == syscall.AF_INET) {
return syscall.AF_INET
}
return syscall.AF_INET6
}
func firstFavoriteAddr(filter func(IP) IP, addrs []string) (addr IP) {
if filter == anyaddr {
// We'll take any IP address, but since the dialing code
// does not yet try multiple addresses, 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.
addr = firstSupportedAddr(ipv4only, addrs)
if addr == nil {
addr = firstSupportedAddr(anyaddr, addrs)
}
} else {
addr = firstSupportedAddr(filter, addrs)
}
return
}
func firstSupportedAddr(filter func(IP) IP, addrs []string) IP {
for _, s := range addrs {
if addr := filter(ParseIP(s)); addr != nil {
return addr
}
}
return nil
}
func anyaddr(x IP) IP {
if x4 := x.To4(); x4 != nil {
return x4
}
if supportsIPv6 {
return x
}
return nil
}
func ipv4only(x IP) IP { return x.To4() }
func ipv6only(x IP) IP {
// Only return addresses that we can use
// with the kernel's IPv6 addressing modes.
if len(x) == IPv6len && x.To4() == nil && supportsIPv6 {
return x
}
return nil
}
// TODO(rsc): if syscall.OS == "linux", we're supposed to read
// /proc/sys/net/core/somaxconn,
// to take advantage of kernels that have raised the limit.
func listenBacklog() int { return syscall.SOMAXCONN }
// Internet sockets (TCP, UDP)
// A sockaddr represents a TCP or UDP network address that can
// be converted into a syscall.Sockaddr.
type sockaddr interface {
Addr
sockaddr(family int) (syscall.Sockaddr, os.Error)
family() int
}
func internetSocket(net string, laddr, raddr sockaddr, socktype, proto int, mode string, toAddr func(syscall.Sockaddr) Addr) (fd *netFD, err os.Error) {
var oserr os.Error
var la, ra syscall.Sockaddr
family := favoriteAddrFamily(net, raddr, laddr, mode)
if laddr != nil {
if la, oserr = laddr.sockaddr(family); oserr != nil {
goto Error
}
}
if raddr != nil {
if ra, oserr = raddr.sockaddr(family); oserr != nil {
goto Error
}
}
fd, oserr = socket(net, family, socktype, proto, la, ra, toAddr)
if oserr != nil {
goto Error
}
return fd, nil
Error:
addr := raddr
if mode == "listen" {
addr = laddr
}
return nil, &OpError{mode, net, addr, oserr}
}
type InvalidAddrError string
func (e InvalidAddrError) String() string { return string(e) }
func (e InvalidAddrError) Timeout() bool { return false }
func (e InvalidAddrError) Temporary() bool { return false }
func ipToSockaddr(family int, ip IP, port int) (syscall.Sockaddr, os.Error) {
switch family {
case syscall.AF_INET:
if len(ip) == 0 {
ip = IPv4zero
}
if ip = ip.To4(); ip == nil {
return nil, InvalidAddrError("non-IPv4 address")
}
s := new(syscall.SockaddrInet4)
for i := 0; i < IPv4len; i++ {
s.Addr[i] = ip[i]
}
s.Port = port
return s, nil
case syscall.AF_INET6:
if len(ip) == 0 {
ip = IPv6zero
}
// IPv4 callers use 0.0.0.0 to mean "announce on any available address".
// In IPv6 mode, Linux treats that as meaning "announce on 0.0.0.0",
// which it refuses to do. Rewrite to the IPv6 all zeros.
if ip.Equal(IPv4zero) {
ip = IPv6zero
}
if ip = ip.To16(); ip == nil {
return nil, InvalidAddrError("non-IPv6 address")
}
s := new(syscall.SockaddrInet6)
for i := 0; i < IPv6len; i++ {
s.Addr[i] = ip[i]
}
s.Port = port
return s, nil
}
return nil, InvalidAddrError("unexpected socket family")
}
// SplitHostPort splits a network address of the form
// "host:port" or "[host]:port" into host and port.
// The latter form must be used when host contains a colon.
func SplitHostPort(hostport string) (host, port string, err os.Error) {
// The port starts after the last colon.
i := last(hostport, ':')
if i < 0 {
err = &AddrError{"missing port in address", hostport}
return
}
host, port = hostport[0:i], hostport[i+1:]
// Can put brackets around host ...
if len(host) > 0 && host[0] == '[' && host[len(host)-1] == ']' {
host = host[1 : len(host)-1]
} else {
// ... but if there are no brackets, no colons.
if byteIndex(host, ':') >= 0 {
err = &AddrError{"too many colons in address", hostport}
return
}
}
return
}
// JoinHostPort combines host and port into a network address
// of the form "host:port" or, if host contains a colon, "[host]:port".
func JoinHostPort(host, port string) string {
// If host has colons, have to bracket it.
if byteIndex(host, ':') >= 0 {
return "[" + host + "]:" + port
}
return host + ":" + port
}
// Convert "host:port" into IP address and port.
func hostPortToIP(net, hostport string) (ip IP, iport int, err os.Error) {
var (
addr IP
p, i int
ok bool
)
host, port, err := SplitHostPort(hostport)
if err != nil {
goto Error
}
if host != "" {
// Try as an IP address.
addr = ParseIP(host)
if addr == nil {
filter := anyaddr
if net != "" && net[len(net)-1] == '4' {
filter = ipv4only
}
if net != "" && net[len(net)-1] == '6' {
filter = ipv6only
}
// Not an IP address. Try as a DNS name.
addrs, err1 := LookupHost(host)
if err1 != nil {
err = err1
goto Error
}
addr = firstFavoriteAddr(filter, addrs)
if addr == nil {
// should not happen
err = &AddrError{"LookupHost returned no suitable address", addrs[0]}
goto Error
}
}
}
p, i, ok = dtoi(port, 0)
if !ok || i != len(port) {
p, err = LookupPort(net, port)
if err != nil {
goto Error
}
}
if p < 0 || p > 0xFFFF {
err = &AddrError{"invalid port", port}
goto Error
}
return addr, p, nil
Error:
return nil, 0, err
}