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"
"os"
"sync"
"time"
"unsafe"
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"golang.org/x/sys/windows"
"golang.zx2c4.com/wireguard/tun/wintun"
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)
const (
packetExchangeMax uint32 = 256 // Number of packets that may be written at a time
packetExchangeAlignment uint32 = 16 // Number of bytes packets are aligned to in exchange buffers
packetSizeMax uint32 = 0xf000 - packetExchangeAlignment // Maximum packet size
packetExchangeSize uint32 = 0x100000 // Exchange buffer size (defaults to 1MiB)
retryRate = 4 // Number of retries per second to reopen device pipe
retryTimeout = 5 // Number of seconds to tolerate adapter unavailable
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)
type exchgBufRead struct {
data [packetExchangeSize]byte
offset uint32
avail uint32
}
type exchgBufWrite struct {
data [packetExchangeSize]byte
offset uint32
packetNum uint32
}
type NativeTun struct {
wt *wintun.Wintun
tunFileRead *os.File
tunFileWrite *os.File
tunLock sync.Mutex
close bool
rdBuff *exchgBufRead
wrBuff *exchgBufWrite
events chan TUNEvent
errors chan error
forcedMtu int
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}
func packetAlign(size uint32) uint32 {
return (size + (packetExchangeAlignment - 1)) &^ (packetExchangeAlignment - 1)
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}
//
// CreateTUN creates a Wintun adapter with the given name. Should a Wintun
// adapter with the same name exist, it is reused.
//
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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, errors.New("Creating Wintun adapter failed: " + err.Error())
}
} 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, errors.New("Setting interface name failed: " + err.Error())
}
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err = wt.FlushInterface()
if err != nil {
wt.DeleteInterface(0)
return nil, errors.New("Flushing interface failed: " + err.Error())
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}
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return &NativeTun{
wt: wt,
rdBuff: &exchgBufRead{},
wrBuff: &exchgBufWrite{},
events: make(chan TUNEvent, 10),
errors: make(chan error, 1),
forcedMtu: 1500,
}, nil
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}
func (tun *NativeTun) openTUN() error {
retries := retryTimeout * retryRate
if tun.close {
return os.ErrClosed
}
var err error
name := tun.wt.DataFileName()
for tun.tunFileRead == nil {
tun.tunFileRead, err = os.OpenFile(name, os.O_RDONLY, 0)
if err != nil {
if retries > 0 && !tun.close {
time.Sleep(time.Second / retryRate)
retries--
continue
}
return err
}
}
for tun.tunFileWrite == nil {
tun.tunFileWrite, err = os.OpenFile(name, os.O_WRONLY, 0)
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if err != nil {
if retries > 0 {
time.Sleep(time.Second / retryRate)
retries--
continue
}
return err
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}
}
return nil
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}
func (tun *NativeTun) closeTUN() (err error) {
for tun.tunFileRead != nil {
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tun.tunLock.Lock()
if tun.tunFileRead == nil {
tun.tunLock.Unlock()
break
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}
t := tun.tunFileRead
tun.tunFileRead = nil
err = t.Close()
tun.tunLock.Unlock()
break
}
for tun.tunFileWrite != nil {
tun.tunLock.Lock()
if tun.tunFileWrite == nil {
tun.tunLock.Unlock()
break
}
t := tun.tunFileWrite
tun.tunFileWrite = nil
err2 := t.Close()
tun.tunLock.Unlock()
if err == nil {
err = err2
}
break
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}
return
}
func (tun *NativeTun) getTUN() (read *os.File, write *os.File, err error) {
read, write = tun.tunFileRead, tun.tunFileWrite
if read == nil || write == nil {
read, write = nil, nil
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tun.tunLock.Lock()
if tun.tunFileRead != nil && tun.tunFileWrite != nil {
read, write = tun.tunFileRead, tun.tunFileWrite
tun.tunLock.Unlock()
return
}
err = tun.closeTUN()
if err != nil {
tun.tunLock.Unlock()
return
}
err = tun.openTUN()
if err == nil {
read, write = tun.tunFileRead, tun.tunFileWrite
}
tun.tunLock.Unlock()
return
}
return
}
func (tun *NativeTun) shouldReopenHandle(err error) bool {
if pe, ok := err.(*os.PathError); ok && pe.Err == windows.ERROR_OPERATION_ABORTED {
return !tun.close
}
return false
}
func (tun *NativeTun) Name() (string, error) {
return tun.wt.GetInterfaceName()
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}
func (tun *NativeTun) File() *os.File {
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return nil
}
func (tun *NativeTun) Events() chan TUNEvent {
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return tun.events
}
func (tun *NativeTun) Close() error {
tun.close = true
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err1 := tun.closeTUN()
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if tun.events != nil {
close(tun.events)
}
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_, _, err2 := tun.wt.DeleteInterface(0)
if err1 == nil {
err1 = err2
}
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return err1
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}
func (tun *NativeTun) MTU() (int, error) {
return tun.forcedMtu, nil
}
//TODO: This is a temporary hack. We really need to be monitoring the interface in real time and adapting to MTU changes.
func (tun *NativeTun) ForceMtu(mtu int) {
tun.forcedMtu = mtu
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}
func (tun *NativeTun) Read(buff []byte, offset int) (int, error) {
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select {
case err := <-tun.errors:
return 0, err
default:
}
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for {
if tun.rdBuff.offset+packetExchangeAlignment <= tun.rdBuff.avail {
// Get packet from the exchange buffer.
packet := tun.rdBuff.data[tun.rdBuff.offset:]
size := *(*uint32)(unsafe.Pointer(&packet[0]))
pSize := packetAlign(packetExchangeAlignment + size)
if packetSizeMax < size || tun.rdBuff.avail < tun.rdBuff.offset+pSize {
// Invalid packet size.
tun.rdBuff.avail = 0
continue
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}
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packet = packet[packetExchangeAlignment : packetExchangeAlignment+size]
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// Copy data.
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copy(buff[offset:], packet)
tun.rdBuff.offset += pSize
return int(size), nil
}
// Get TUN data pipe.
file, _, err := tun.getTUN()
if err != nil {
return 0, err
}
// Fill queue.
n, err := file.Read(tun.rdBuff.data[:])
if err != nil {
tun.rdBuff.avail = 0
if tun.shouldReopenHandle(err) {
tun.closeTUN()
continue
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}
return 0, err
}
tun.rdBuff.offset = 0
tun.rdBuff.avail = uint32(n)
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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 {
if tun.wrBuff.offset == 0 {
return nil
}
// Get TUN data pipe.
_, file, err := tun.getTUN()
if err != nil {
return err
}
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// Flush write buffer.
_, err = file.Write(tun.wrBuff.data[:tun.wrBuff.offset])
tun.wrBuff.packetNum = 0
tun.wrBuff.offset = 0
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if err != nil {
if tun.shouldReopenHandle(err) {
tun.closeTUN()
return nil
}
return err
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}
return nil
}
func (tun *NativeTun) putTunPacket(buff []byte) error {
size := uint32(len(buff))
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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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}
pSize := packetAlign(packetExchangeAlignment + size)
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if tun.wrBuff.packetNum >= packetExchangeMax || tun.wrBuff.offset+pSize >= packetExchangeSize {
// Exchange buffer is full -> flush first.
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err := tun.Flush()
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if err != nil {
return err
}
}
// Write packet to the exchange buffer.
packet := tun.wrBuff.data[tun.wrBuff.offset : tun.wrBuff.offset+pSize]
*(*uint32)(unsafe.Pointer(&packet[0])) = size
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packet = packet[packetExchangeAlignment : packetExchangeAlignment+size]
copy(packet, buff)
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tun.wrBuff.packetNum++
tun.wrBuff.offset += pSize
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return nil
}
func (tun *NativeTun) Write(buff []byte, offset int) (int, error) {
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err := tun.putTunPacket(buff[offset:])
if err != nil {
return 0, err
}
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return len(buff) - offset, nil
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}
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//
// GUID returns Windows adapter instance ID.
//
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func (tun *NativeTun) GUID() windows.GUID {
return *(*windows.GUID)(tun.wt)
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}