wireguard-go/tun/tun_windows.go

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/* SPDX-License-Identifier: MIT
*
* Copyright (C) 2018-2019 WireGuard LLC. All Rights Reserved.
*/
package tun
import (
"errors"
"fmt"
"os"
"unsafe"
"git.zx2c4.com/wireguard-go/tun/wintun"
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"golang.org/x/sys/windows"
)
const (
packetSizeMax = 1600
packetExchangeMax = 256 // Number of packets that can be exchanged at a time
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)
const (
signalClose = iota
signalDataAvail
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signalMax
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)
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type tunPacket struct {
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size uint32
data [packetSizeMax]byte
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}
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type tunRWQueue struct {
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numPackets uint32
packets [packetExchangeMax]tunPacket
left bool
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}
type nativeTun struct {
wt *wintun.Wintun
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tunName string
signalName *uint16
tunFile *os.File
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wrBuff tunRWQueue
rdBuff tunRWQueue
signals [signalMax]windows.Handle
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rdNextPacket uint32
events chan TUNEvent
errors chan error
}
func CreateTUN(ifname string) (TUNDevice, error) {
// Does an interface with this name already exist?
wt, err := wintun.GetInterface(ifname, 0)
if wt == nil {
// Interface does not exist or an error occured. Create one.
wt, _, err = wintun.CreateInterface("WireGuard Tunnel Adapter", 0)
if err != nil {
return nil, err
}
} else if err != nil {
// Foreign interface with the same name found.
// We could create a Wintun interface under a temporary name. But, should our
// proces die without deleting this interface first, the interface would remain
// orphaned.
return nil, err
}
err = wt.SetInterfaceName(ifname)
if err != nil {
wt.DeleteInterface(0)
return nil, err
}
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err = wt.FlushInterface()
if err != nil {
wt.DeleteInterface(0)
return nil, err
}
signalNameUTF16, err := windows.UTF16PtrFromString(wt.SignalEventName())
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if err != nil {
wt.DeleteInterface(0)
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return nil, err
}
// Create instance.
tun := &nativeTun{
wt: wt,
tunName: wt.DataFileName(),
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signalName: signalNameUTF16,
events: make(chan TUNEvent, 10),
errors: make(chan error, 1),
}
// Create close event.
tun.signals[signalClose], err = windows.CreateEvent(nil, 1 /*TRUE*/, 0 /*FALSE*/, nil)
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if err != nil {
wt.DeleteInterface(0)
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return nil, err
}
return tun, nil
}
func (tun *nativeTun) openTUN() error {
for {
// Open interface data pipe.
// Data pipe must be opened first, as the interface data available event is created when somebody actually connects to the data pipe.
file, err := os.OpenFile(tun.tunName, os.O_RDWR|os.O_SYNC, 0600)
if err != nil {
// After examining possible error conditions, many arose that were only temporary: windows.ERROR_FILE_NOT_FOUND, "read <filename> closed", etc.
// To simplify, we will enter a retry-loop on _any_ error until session is closed by user.
switch evt, e := windows.WaitForSingleObject(tun.signals[signalClose], 1000); evt {
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case windows.WAIT_OBJECT_0, windows.WAIT_ABANDONED:
return errors.New("TUN closed")
case windows.WAIT_TIMEOUT:
continue
default:
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return errors.New("Unexpected result from WaitForSingleObject: " + e.Error())
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}
}
// Open interface data available event.
event, err := windows.OpenEvent(windows.SYNCHRONIZE, false, tun.signalName)
if err != nil {
file.Close()
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return errors.New("Opening interface data ready event failed: " + err.Error())
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}
tun.tunFile = file
tun.signals[signalDataAvail] = event
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return nil
}
}
func (tun *nativeTun) closeTUN() (err error) {
if tun.signals[signalDataAvail] != 0 {
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// Close interface data ready event.
e := windows.CloseHandle(tun.signals[signalDataAvail])
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if err != nil {
err = e
}
tun.signals[signalDataAvail] = 0
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}
if tun.tunFile != nil {
// Close interface data pipe.
e := tun.tunFile.Close()
if err != nil {
err = e
}
tun.tunFile = nil
}
return
}
func (tun *nativeTun) Name() (string, error) {
return tun.wt.GetInterfaceName()
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}
func (tun *nativeTun) File() *os.File {
return nil
}
func (tun *nativeTun) Events() chan TUNEvent {
return tun.events
}
func (tun *nativeTun) Close() error {
windows.SetEvent(tun.signals[signalClose])
err := windows.CloseHandle(tun.signals[signalClose])
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e := tun.closeTUN()
if err == nil {
err = e
}
if tun.events != nil {
close(tun.events)
}
_, _, e = tun.wt.DeleteInterface(0)
if err == nil {
err = e
}
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return err
}
func (tun *nativeTun) MTU() (int, error) {
return 1500, nil
}
func (tun *nativeTun) Read(buff []byte, offset int) (int, error) {
select {
case err := <-tun.errors:
return 0, err
default:
}
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for {
if tun.rdNextPacket < tun.rdBuff.numPackets {
// Get packet from the queue.
tunPacket := &tun.rdBuff.packets[tun.rdNextPacket]
tun.rdNextPacket++
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if packetSizeMax < tunPacket.size {
// Invalid packet size.
continue
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}
// Copy data.
copy(buff[offset:], tunPacket.data[:tunPacket.size])
return int(tunPacket.size), nil
}
if tun.signals[signalDataAvail] == 0 {
// Data pipe and interface data available event are not open (yet).
err := tun.openTUN()
if err != nil {
return 0, err
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}
}
// Wait for user close or interface data.
r, err := windows.WaitForMultipleObjects(tun.signals[:], false, windows.INFINITE)
if err != nil {
return 0, errors.New("Waiting for data failed: " + err.Error())
}
switch r {
case windows.WAIT_OBJECT_0 + signalClose, windows.WAIT_ABANDONED + signalClose:
return 0, errors.New("TUN closed")
case windows.WAIT_OBJECT_0 + signalDataAvail:
// Data is available.
case windows.WAIT_ABANDONED + signalDataAvail:
// TUN stopped. Reopen it.
tun.closeTUN()
continue
case windows.WAIT_TIMEOUT:
// Congratulations, we reached infinity. Let's do it again! :)
continue
default:
return 0, errors.New("unexpected result from WaitForMultipleObjects")
}
// Fill queue.
const bufSize = int(unsafe.Sizeof(tun.rdBuff))
n, err := tun.tunFile.Read((*[bufSize]byte)(unsafe.Pointer(&tun.rdBuff))[:])
tun.rdNextPacket = 0
if n != bufSize || err != nil {
// TUN interface stopped, returned incomplete data, etc.
// Retry.
tun.rdBuff.numPackets = 0
tun.closeTUN()
continue
}
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}
}
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// Note: flush() and putTunPacket() assume the caller comes only from a single thread; there's no locking.
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func (tun *nativeTun) flush() error {
// Flush write buffer.
const bufSize = int(unsafe.Sizeof(tun.wrBuff))
n, err := tun.tunFile.Write((*[bufSize]byte)(unsafe.Pointer(&tun.wrBuff))[:])
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tun.wrBuff.numPackets = 0
if err != nil {
return err
}
if n != bufSize {
return fmt.Errorf("%d byte(s) written, %d byte(s) expected", n, bufSize)
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}
return nil
}
func (tun *nativeTun) putTunPacket(buff []byte) error {
size := len(buff)
if size == 0 {
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return errors.New("Empty packet")
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}
if size > packetSizeMax {
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return errors.New("Packet too big")
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}
if tun.wrBuff.numPackets >= packetExchangeMax {
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// Queue is full -> flush first.
err := tun.flush()
if err != nil {
return err
}
}
// Push packet to the buffer.
tunPacket := &tun.wrBuff.packets[tun.wrBuff.numPackets]
tunPacket.size = uint32(size)
copy(tunPacket.data[:size], buff)
tun.wrBuff.numPackets++
return nil
}
func (tun *nativeTun) Write(buff []byte, offset int) (int, error) {
err := tun.putTunPacket(buff[offset:])
if err != nil {
return 0, err
}
// Flush write buffer.
return len(buff) - offset, tun.flush()
}