mirror of
https://github.com/autc04/Retro68.git
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316 lines
9.0 KiB
Go
316 lines
9.0 KiB
Go
// Copyright 2009 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package net
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import (
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"context"
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"internal/bytealg"
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"runtime"
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"sync"
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)
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// BUG(rsc,mikio): On DragonFly BSD and OpenBSD, listening on the
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// "tcp" and "udp" networks does not listen for both IPv4 and IPv6
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// connections. This is due to the fact that IPv4 traffic will not be
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// routed to an IPv6 socket - two separate sockets are required if
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// both address families are to be supported.
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// See inet6(4) for details.
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type ipStackCapabilities struct {
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sync.Once // guards following
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ipv4Enabled bool
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ipv6Enabled bool
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ipv4MappedIPv6Enabled bool
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}
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var ipStackCaps ipStackCapabilities
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// supportsIPv4 reports whether the platform supports IPv4 networking
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// functionality.
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func supportsIPv4() bool {
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ipStackCaps.Once.Do(ipStackCaps.probe)
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return ipStackCaps.ipv4Enabled
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}
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// supportsIPv6 reports whether the platform supports IPv6 networking
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// functionality.
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func supportsIPv6() bool {
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ipStackCaps.Once.Do(ipStackCaps.probe)
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return ipStackCaps.ipv6Enabled
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}
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// supportsIPv4map reports whether the platform supports mapping an
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// IPv4 address inside an IPv6 address at transport layer
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// protocols. See RFC 4291, RFC 4038 and RFC 3493.
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func supportsIPv4map() bool {
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// Some operating systems provide no support for mapping IPv4
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// addresses to IPv6, and a runtime check is unnecessary.
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switch runtime.GOOS {
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case "dragonfly", "openbsd":
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return false
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}
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ipStackCaps.Once.Do(ipStackCaps.probe)
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return ipStackCaps.ipv4MappedIPv6Enabled
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}
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// An addrList represents a list of network endpoint addresses.
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type addrList []Addr
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// isIPv4 reports whether addr contains an IPv4 address.
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func isIPv4(addr Addr) bool {
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switch addr := addr.(type) {
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case *TCPAddr:
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return addr.IP.To4() != nil
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case *UDPAddr:
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return addr.IP.To4() != nil
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case *IPAddr:
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return addr.IP.To4() != nil
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}
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return false
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}
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// isNotIPv4 reports whether addr does not contain an IPv4 address.
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func isNotIPv4(addr Addr) bool { return !isIPv4(addr) }
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// forResolve returns the most appropriate address in address for
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// a call to ResolveTCPAddr, ResolveUDPAddr, or ResolveIPAddr.
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// IPv4 is preferred, unless addr contains an IPv6 literal.
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func (addrs addrList) forResolve(network, addr string) Addr {
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var want6 bool
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switch network {
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case "ip":
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// IPv6 literal (addr does NOT contain a port)
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want6 = count(addr, ':') > 0
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case "tcp", "udp":
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// IPv6 literal. (addr contains a port, so look for '[')
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want6 = count(addr, '[') > 0
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}
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if want6 {
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return addrs.first(isNotIPv4)
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}
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return addrs.first(isIPv4)
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}
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// first returns the first address which satisfies strategy, or if
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// none do, then the first address of any kind.
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func (addrs addrList) first(strategy func(Addr) bool) Addr {
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for _, addr := range addrs {
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if strategy(addr) {
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return addr
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}
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}
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return addrs[0]
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}
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// partition divides an address list into two categories, using a
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// strategy function to assign a boolean label to each address.
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// The first address, and any with a matching label, are returned as
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// primaries, while addresses with the opposite label are returned
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// as fallbacks. For non-empty inputs, primaries is guaranteed to be
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// non-empty.
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func (addrs addrList) partition(strategy func(Addr) bool) (primaries, fallbacks addrList) {
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var primaryLabel bool
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for i, addr := range addrs {
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label := strategy(addr)
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if i == 0 || label == primaryLabel {
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primaryLabel = label
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primaries = append(primaries, addr)
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} else {
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fallbacks = append(fallbacks, addr)
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}
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}
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return
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}
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// filterAddrList applies a filter to a list of IP addresses,
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// yielding a list of Addr objects. Known filters are nil, ipv4only,
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// and ipv6only. It returns every address when the filter is nil.
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// The result contains at least one address when error is nil.
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func filterAddrList(filter func(IPAddr) bool, ips []IPAddr, inetaddr func(IPAddr) Addr, originalAddr string) (addrList, error) {
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var addrs addrList
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for _, ip := range ips {
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if filter == nil || filter(ip) {
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addrs = append(addrs, inetaddr(ip))
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}
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}
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if len(addrs) == 0 {
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return nil, &AddrError{Err: errNoSuitableAddress.Error(), Addr: originalAddr}
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}
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return addrs, nil
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}
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// ipv4only reports whether addr is an IPv4 address.
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func ipv4only(addr IPAddr) bool {
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return addr.IP.To4() != nil
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}
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// ipv6only reports whether addr is an IPv6 address except IPv4-mapped IPv6 address.
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func ipv6only(addr IPAddr) bool {
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return len(addr.IP) == IPv6len && addr.IP.To4() == nil
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}
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// SplitHostPort splits a network address of the form "host:port",
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// "host%zone:port", "[host]:port" or "[host%zone]:port" into host or
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// host%zone and port.
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//
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// A literal IPv6 address in hostport must be enclosed in square
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// brackets, as in "[::1]:80", "[::1%lo0]:80".
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//
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// See func Dial for a description of the hostport parameter, and host
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// and port results.
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func SplitHostPort(hostport string) (host, port string, err error) {
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const (
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missingPort = "missing port in address"
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tooManyColons = "too many colons in address"
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)
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addrErr := func(addr, why string) (host, port string, err error) {
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return "", "", &AddrError{Err: why, Addr: addr}
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}
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j, k := 0, 0
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// The port starts after the last colon.
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i := last(hostport, ':')
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if i < 0 {
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return addrErr(hostport, missingPort)
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}
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if hostport[0] == '[' {
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// Expect the first ']' just before the last ':'.
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end := bytealg.IndexByteString(hostport, ']')
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if end < 0 {
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return addrErr(hostport, "missing ']' in address")
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}
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switch end + 1 {
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case len(hostport):
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// There can't be a ':' behind the ']' now.
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return addrErr(hostport, missingPort)
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case i:
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// The expected result.
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default:
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// Either ']' isn't followed by a colon, or it is
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// followed by a colon that is not the last one.
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if hostport[end+1] == ':' {
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return addrErr(hostport, tooManyColons)
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}
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return addrErr(hostport, missingPort)
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}
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host = hostport[1:end]
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j, k = 1, end+1 // there can't be a '[' resp. ']' before these positions
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} else {
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host = hostport[:i]
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if bytealg.IndexByteString(host, ':') >= 0 {
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return addrErr(hostport, tooManyColons)
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}
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}
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if bytealg.IndexByteString(hostport[j:], '[') >= 0 {
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return addrErr(hostport, "unexpected '[' in address")
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}
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if bytealg.IndexByteString(hostport[k:], ']') >= 0 {
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return addrErr(hostport, "unexpected ']' in address")
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}
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port = hostport[i+1:]
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return host, port, nil
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}
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func splitHostZone(s string) (host, zone string) {
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// The IPv6 scoped addressing zone identifier starts after the
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// last percent sign.
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if i := last(s, '%'); i > 0 {
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host, zone = s[:i], s[i+1:]
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} else {
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host = s
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}
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return
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}
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// JoinHostPort combines host and port into a network address of the
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// form "host:port". If host contains a colon, as found in literal
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// IPv6 addresses, then JoinHostPort returns "[host]:port".
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//
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// See func Dial for a description of the host and port parameters.
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func JoinHostPort(host, port string) string {
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// We assume that host is a literal IPv6 address if host has
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// colons.
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if bytealg.IndexByteString(host, ':') >= 0 {
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return "[" + host + "]:" + port
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}
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return host + ":" + port
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}
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// internetAddrList resolves addr, which may be a literal IP
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// address or a DNS name, and returns a list of internet protocol
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// family addresses. The result contains at least one address when
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// error is nil.
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func (r *Resolver) internetAddrList(ctx context.Context, net, addr string) (addrList, error) {
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var (
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err error
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host, port string
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portnum int
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)
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switch net {
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case "tcp", "tcp4", "tcp6", "udp", "udp4", "udp6":
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if addr != "" {
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if host, port, err = SplitHostPort(addr); err != nil {
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return nil, err
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}
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if portnum, err = r.LookupPort(ctx, net, port); err != nil {
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return nil, err
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}
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}
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case "ip", "ip4", "ip6":
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if addr != "" {
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host = addr
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}
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default:
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return nil, UnknownNetworkError(net)
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}
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inetaddr := func(ip IPAddr) Addr {
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switch net {
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case "tcp", "tcp4", "tcp6":
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return &TCPAddr{IP: ip.IP, Port: portnum, Zone: ip.Zone}
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case "udp", "udp4", "udp6":
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return &UDPAddr{IP: ip.IP, Port: portnum, Zone: ip.Zone}
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case "ip", "ip4", "ip6":
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return &IPAddr{IP: ip.IP, Zone: ip.Zone}
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default:
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panic("unexpected network: " + net)
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}
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}
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if host == "" {
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return addrList{inetaddr(IPAddr{})}, nil
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}
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// Try as a literal IP address, then as a DNS name.
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ips, err := r.lookupIPAddr(ctx, net, host)
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if err != nil {
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return nil, err
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}
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// Issue 18806: if the machine has halfway configured
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// IPv6 such that it can bind on "::" (IPv6unspecified)
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// but not connect back to that same address, fall
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// back to dialing 0.0.0.0.
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if len(ips) == 1 && ips[0].IP.Equal(IPv6unspecified) {
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ips = append(ips, IPAddr{IP: IPv4zero})
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}
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var filter func(IPAddr) bool
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if net != "" && net[len(net)-1] == '4' {
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filter = ipv4only
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}
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if net != "" && net[len(net)-1] == '6' {
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filter = ipv6only
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}
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return filterAddrList(filter, ips, inetaddr, host)
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}
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func loopbackIP(net string) IP {
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if net != "" && net[len(net)-1] == '6' {
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return IPv6loopback
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}
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return IP{127, 0, 0, 1}
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}
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