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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 (
"context"
)
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
)
// An addrList represents a list of network endpoint addresses.
type addrList []Addr
// isIPv4 returns true if the 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
}
// 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) (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, errNoSuitableAddress
}
return addrs, nil
}
// ipv4only reports whether the kernel supports IPv4 addressing mode
// and addr is an IPv4 address.
func ipv4only(addr IPAddr) bool {
return supportsIPv4 && addr.IP.To4() != nil
}
// ipv6only reports whether the kernel supports IPv6 addressing mode
// and addr is an IPv6 address except IPv4-mapped IPv6 address.
func ipv6only(addr IPAddr) bool {
return supportsIPv6 && len(addr.IP) == IPv6len && addr.IP.To4() == 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) {
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 := byteIndex(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 byteIndex(host, ':') >= 0 {
return addrErr(hostport, tooManyColons)
}
if byteIndex(host, '%') >= 0 {
return addrErr(hostport, "missing brackets in address")
}
}
if byteIndex(hostport[j:], '[') >= 0 {
return addrErr(hostport, "unexpected '[' in address")
}
if byteIndex(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" 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
}
// 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 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 = LookupPort(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.
var ip IP
if ip = parseIPv4(host); ip != nil {
return addrList{inetaddr(IPAddr{IP: ip})}, nil
}
var zone string
if ip, zone = parseIPv6(host, true); ip != nil {
return addrList{inetaddr(IPAddr{IP: ip, Zone: zone})}, nil
}
// Try as a DNS name.
ips, err := lookupIPContext(ctx, host)
if err != nil {
return nil, err
}
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)
}