Preview: ipsock.go
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/proc/thread-self/root/opt/golang/1.22.0/src/net/ipsock.go
// 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 = bytealg.CountString(addr, ':') > 0
case "tcp", "udp":
// IPv6 literal. (addr contains a port, so look for '[')
want6 = bytealg.CountString(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 := bytealg.LastIndexByteString(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 := bytealg.LastIndexByteString(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}
}
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