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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.
//go:build unix || (js && wasm) || windows
package net
import (
"context"
"internal/poll"
"net/netip"
"runtime"
"syscall"
)
// probe probes IPv4, IPv6 and IPv4-mapped IPv6 communication
// capabilities which are controlled by the IPV6_V6ONLY socket option
// and kernel configuration.
//
// Should we try to use the IPv4 socket interface if we're only
// dealing with IPv4 sockets? As long as the host system understands
// IPv4-mapped IPv6, it's okay to pass IPv4-mapped IPv6 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.
func (p *ipStackCapabilities) probe() {
s, err := sysSocket(syscall.AF_INET, syscall.SOCK_STREAM, syscall.IPPROTO_TCP)
switch err {
case syscall.EAFNOSUPPORT, syscall.EPROTONOSUPPORT:
case nil:
poll.CloseFunc(s)
p.ipv4Enabled = true
}
var probes = []struct {
laddr TCPAddr
value int
}{
// IPv6 communication capability
{laddr: TCPAddr{IP: ParseIP("::1")}, value: 1},
// IPv4-mapped IPv6 address communication capability
{laddr: TCPAddr{IP: IPv4(127, 0, 0, 1)}, value: 0},
}
switch runtime.GOOS {
case "dragonfly", "openbsd":
// The latest DragonFly BSD and OpenBSD kernels don't
// support IPV6_V6ONLY=0. They always return an error
// and we don't need to probe the capability.
probes = probes[:1]
}
for i := range probes {
s, err := sysSocket(syscall.AF_INET6, syscall.SOCK_STREAM, syscall.IPPROTO_TCP)
if err != nil {
continue
}
defer poll.CloseFunc(s)
syscall.SetsockoptInt(s, syscall.IPPROTO_IPV6, syscall.IPV6_V6ONLY, probes[i].value)
sa, err := probes[i].laddr.sockaddr(syscall.AF_INET6)
if err != nil {
continue
}
if err := syscall.Bind(s, sa); err != nil {
continue
}
if i == 0 {
p.ipv6Enabled = true
} else {
p.ipv4MappedIPv6Enabled = true
}
}
}
// favoriteAddrFamily returns the appropriate address family for the
// given network, laddr, raddr and mode.
//
// If mode indicates "listen" and laddr is a wildcard, we assume that
// the user wants to make a passive-open connection with a wildcard
// address family, both AF_INET and AF_INET6, and a wildcard address
// like the following:
//
// - A listen for a wildcard communication domain, "tcp" or
// "udp", with a wildcard address: If the platform supports
// both IPv6 and IPv4-mapped IPv6 communication capabilities,
// or does not support IPv4, we use a dual stack, AF_INET6 and
// IPV6_V6ONLY=0, wildcard address listen. The dual stack
// wildcard address listen may fall back to an IPv6-only,
// AF_INET6 and IPV6_V6ONLY=1, wildcard address listen.
// Otherwise we prefer an IPv4-only, AF_INET, wildcard address
// listen.
//
// - A listen for a wildcard communication domain, "tcp" or
// "udp", with an IPv4 wildcard address: same as above.
//
// - A listen for a wildcard communication domain, "tcp" or
// "udp", with an IPv6 wildcard address: same as above.
//
// - A listen for an IPv4 communication domain, "tcp4" or "udp4",
// with an IPv4 wildcard address: We use an IPv4-only, AF_INET,
// wildcard address listen.
//
// - A listen for an IPv6 communication domain, "tcp6" or "udp6",
// with an IPv6 wildcard address: We use an IPv6-only, AF_INET6
// and IPV6_V6ONLY=1, wildcard address listen.
//
// Otherwise guess: If the addresses are IPv4 then returns AF_INET,
// or else returns AF_INET6. It also returns a boolean value what
// designates IPV6_V6ONLY option.
//
// Note that the latest DragonFly BSD and OpenBSD kernels allow
// neither "net.inet6.ip6.v6only=1" change nor IPPROTO_IPV6 level
// IPV6_V6ONLY socket option setting.
func favoriteAddrFamily(network string, laddr, raddr sockaddr, mode string) (family int, ipv6only bool) {
switch network[len(network)-1] {
case '4':
return syscall.AF_INET, false
case '6':
return syscall.AF_INET6, true
}
if mode == "listen" && (laddr == nil || laddr.isWildcard()) {
if supportsIPv4map() || !supportsIPv4() {
return syscall.AF_INET6, false
}
if laddr == nil {
return syscall.AF_INET, false
}
return laddr.family(), false
}
if (laddr == nil || laddr.family() == syscall.AF_INET) &&
(raddr == nil || raddr.family() == syscall.AF_INET) {
return syscall.AF_INET, false
}
return syscall.AF_INET6, false
}
func internetSocket(ctx context.Context, net string, laddr, raddr sockaddr, sotype, proto int, mode string, ctrlCtxFn func(context.Context, string, string, syscall.RawConn) error) (fd *netFD, err error) {
if (runtime.GOOS == "aix" || runtime.GOOS == "windows" || runtime.GOOS == "openbsd") && mode == "dial" && raddr.isWildcard() {
raddr = raddr.toLocal(net)
}
family, ipv6only := favoriteAddrFamily(net, laddr, raddr, mode)
return socket(ctx, net, family, sotype, proto, ipv6only, laddr, raddr, ctrlCtxFn)
}
func ipToSockaddrInet4(ip IP, port int) (syscall.SockaddrInet4, error) {
if len(ip) == 0 {
ip = IPv4zero
}
ip4 := ip.To4()
if ip4 == nil {
return syscall.SockaddrInet4{}, &AddrError{Err: "non-IPv4 address", Addr: ip.String()}
}
sa := syscall.SockaddrInet4{Port: port}
copy(sa.Addr[:], ip4)
return sa, nil
}
func ipToSockaddrInet6(ip IP, port int, zone string) (syscall.SockaddrInet6, error) {
// In general, an IP wildcard address, which is either
// "0.0.0.0" or "::", means the entire IP addressing
// space. For some historical reason, it is used to
// specify "any available address" on some operations
// of IP node.
//
// When the IP node supports IPv4-mapped IPv6 address,
// we allow a listener to listen to the wildcard
// address of both IP addressing spaces by specifying
// IPv6 wildcard address.
if len(ip) == 0 || ip.Equal(IPv4zero) {
ip = IPv6zero
}
// We accept any IPv6 address including IPv4-mapped
// IPv6 address.
ip6 := ip.To16()
if ip6 == nil {
return syscall.SockaddrInet6{}, &AddrError{Err: "non-IPv6 address", Addr: ip.String()}
}
sa := syscall.SockaddrInet6{Port: port, ZoneId: uint32(zoneCache.index(zone))}
copy(sa.Addr[:], ip6)
return sa, nil
}
func ipToSockaddr(family int, ip IP, port int, zone string) (syscall.Sockaddr, error) {
switch family {
case syscall.AF_INET:
sa, err := ipToSockaddrInet4(ip, port)
if err != nil {
return nil, err
}
return &sa, nil
case syscall.AF_INET6:
sa, err := ipToSockaddrInet6(ip, port, zone)
if err != nil {
return nil, err
}
return &sa, nil
}
return nil, &AddrError{Err: "invalid address family", Addr: ip.String()}
}
func addrPortToSockaddrInet4(ap netip.AddrPort) (syscall.SockaddrInet4, error) {
// ipToSockaddrInet4 has special handling here for zero length slices.
// We do not, because netip has no concept of a generic zero IP address.
addr := ap.Addr()
if !addr.Is4() {
return syscall.SockaddrInet4{}, &AddrError{Err: "non-IPv4 address", Addr: addr.String()}
}
sa := syscall.SockaddrInet4{
Addr: addr.As4(),
Port: int(ap.Port()),
}
return sa, nil
}
func addrPortToSockaddrInet6(ap netip.AddrPort) (syscall.SockaddrInet6, error) {
// ipToSockaddrInet6 has special handling here for zero length slices.
// We do not, because netip has no concept of a generic zero IP address.
//
// addr is allowed to be an IPv4 address, because As16 will convert it
// to an IPv4-mapped IPv6 address.
// The error message is kept consistent with ipToSockaddrInet6.
addr := ap.Addr()
if !addr.IsValid() {
return syscall.SockaddrInet6{}, &AddrError{Err: "non-IPv6 address", Addr: addr.String()}
}
sa := syscall.SockaddrInet6{
Addr: addr.As16(),
Port: int(ap.Port()),
ZoneId: uint32(zoneCache.index(addr.Zone())),
}
return sa, nil
}
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