libgo: update to Go 1.11

[official-gcc.git] / libgo / go / 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"
        "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 {
        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 = count(addr, ':') > 0
        case "tcp", "udp":
                // IPv6 literal. (addr contains a port, so look for '[')
                want6 = count(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 := 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(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". 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 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 (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, 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}
}