122 lines
3.5 KiB
Go
122 lines
3.5 KiB
Go
// Copyright (c) 2020 Tailscale Inc & 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 netns
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import (
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"math/bits"
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"strings"
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"syscall"
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"golang.org/x/sys/windows"
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"golang.zx2c4.com/wireguard/windows/tunnel/winipcfg"
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"tailscale.com/net/interfaces"
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"tailscale.com/util/endian"
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)
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func interfaceIndex(iface *winipcfg.IPAdapterAddresses) uint32 {
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if iface == nil {
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// The zero ifidx means "unspecified". If we end up passing zero
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// to bindSocket*(), it unsets the binding and lets the socket
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// behave as normal again, which is what we want if there's no
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// default route we can use.
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return 0
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}
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return iface.IfIndex
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}
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// control binds c to the Windows interface that holds a default
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// route, and is not the Tailscale WinTun interface.
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func control(network, address string, c syscall.RawConn) error {
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if strings.HasPrefix(address, "127.") {
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// Don't bind to an interface for localhost connections,
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// otherwise we get:
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// connectex: The requested address is not valid in its context
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// (The derphttp tests were failing)
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return nil
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}
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canV4, canV6 := false, false
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switch network {
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case "tcp", "udp":
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canV4, canV6 = true, true
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case "tcp4", "udp4":
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canV4 = true
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case "tcp6", "udp6":
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canV6 = true
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}
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if canV4 {
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iface, err := interfaces.GetWindowsDefault(windows.AF_INET)
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if err != nil {
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return err
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}
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if err := bindSocket4(c, interfaceIndex(iface)); err != nil {
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return err
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}
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}
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if canV6 {
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iface, err := interfaces.GetWindowsDefault(windows.AF_INET6)
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if err != nil {
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return err
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}
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if err := bindSocket6(c, interfaceIndex(iface)); err != nil {
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return err
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}
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}
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return nil
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}
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// sockoptBoundInterface is the value of IP_UNICAST_IF and IPV6_UNICAST_IF.
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//
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// See https://docs.microsoft.com/en-us/windows/win32/winsock/ipproto-ip-socket-options
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// and https://docs.microsoft.com/en-us/windows/win32/winsock/ipproto-ipv6-socket-options
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const sockoptBoundInterface = 31
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// bindSocket4 binds the given RawConn to the network interface with
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// index ifidx, for IPv4 traffic only.
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func bindSocket4(c syscall.RawConn, ifidx uint32) error {
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// For IPv4 (but NOT IPv6) the interface index must be passed
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// as a big-endian integer (regardless of platform endianness)
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// because the underlying sockopt takes either an IPv4 address
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// or an index shoved into IPv4 address representation (an IP
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// in 0.0.0.0/8 means it's actually an index).
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//
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// See https://docs.microsoft.com/en-us/windows/win32/winsock/ipproto-ip-socket-options
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// and IP_UNICAST_IF.
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indexAsAddr := nativeToBigEndian(ifidx)
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var controlErr error
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err := c.Control(func(fd uintptr) {
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controlErr = windows.SetsockoptInt(windows.Handle(fd), windows.IPPROTO_IP, sockoptBoundInterface, int(indexAsAddr))
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})
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if err != nil {
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return err
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}
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return controlErr
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}
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// bindSocket6 binds the given RawConn to the network interface with
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// index ifidx, for IPv6 traffic only.
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func bindSocket6(c syscall.RawConn, ifidx uint32) error {
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var controlErr error
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err := c.Control(func(fd uintptr) {
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controlErr = windows.SetsockoptInt(windows.Handle(fd), windows.IPPROTO_IPV6, sockoptBoundInterface, int(ifidx))
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})
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if err != nil {
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return err
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}
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return controlErr
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}
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// nativeToBigEndian returns i converted into big-endian
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// representation, suitable for passing to Windows APIs that require a
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// mangled uint32.
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func nativeToBigEndian(i uint32) uint32 {
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if endian.Big {
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return i
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}
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return bits.ReverseBytes32(i)
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}
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