wireguard-go/tun/tun_windows.go

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/* SPDX-License-Identifier: MIT
*
* Copyright (C) 2018-2020 WireGuard LLC. All Rights Reserved.
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*/
package tun
import (
"errors"
"fmt"
"log"
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"os"
"sync/atomic"
"time"
_ "unsafe"
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"golang.org/x/sys/windows"
"golang.zx2c4.com/wireguard/tun/wintun"
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)
const (
rateMeasurementGranularity = uint64((time.Second / 2) / time.Nanosecond)
spinloopRateThreshold = 800000000 / 8 // 800mbps
spinloopDuration = uint64(time.Millisecond / 80 / time.Nanosecond) // ~1gbit/s
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)
type rateJuggler struct {
current uint64
nextByteCount uint64
nextStartTime int64
changing int32
}
type NativeTun struct {
wt *wintun.Adapter
handle windows.Handle
close bool
events chan Event
errors chan error
forcedMTU int
rate rateJuggler
session wintun.Session
readWait windows.Handle
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}
var WintunPool, _ = wintun.MakePool("WireGuard")
var WintunStaticRequestedGUID *windows.GUID
//go:linkname procyield runtime.procyield
func procyield(cycles uint32)
//go:linkname nanotime runtime.nanotime
func nanotime() int64
//
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// CreateTUN creates a Wintun interface with the given name. Should a Wintun
// interface with the same name exist, it is reused.
//
func CreateTUN(ifname string, mtu int) (Device, error) {
return CreateTUNWithRequestedGUID(ifname, WintunStaticRequestedGUID, mtu)
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}
//
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// CreateTUNWithRequestedGUID creates a Wintun interface with the given name and
// a requested GUID. Should a Wintun interface with the same name exist, it is reused.
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//
func CreateTUNWithRequestedGUID(ifname string, requestedGUID *windows.GUID, mtu int) (Device, error) {
var err error
var wt *wintun.Adapter
// Does an interface with this name already exist?
wt, err = WintunPool.OpenAdapter(ifname)
if err == nil {
// If so, we delete it, in case it has weird residual configuration.
_, err = wt.Delete(true)
if err != nil {
return nil, fmt.Errorf("Error deleting already existing interface: %w", err)
}
}
wt, rebootRequired, err := WintunPool.CreateAdapter(ifname, requestedGUID)
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if err != nil {
return nil, fmt.Errorf("Error creating interface: %w", err)
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}
if rebootRequired {
log.Println("Windows indicated a reboot is required.")
}
forcedMTU := 1420
if mtu > 0 {
forcedMTU = mtu
}
tun := &NativeTun{
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wt: wt,
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handle: windows.InvalidHandle,
events: make(chan Event, 10),
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errors: make(chan error, 1),
forcedMTU: forcedMTU,
}
tun.session, err = wt.StartSession(0x800000) // Ring capacity, 8 MiB
if err != nil {
tun.wt.Delete(false)
close(tun.events)
return nil, fmt.Errorf("Error starting session: %w", err)
}
tun.readWait = tun.session.ReadWaitEvent()
return tun, nil
}
func (tun *NativeTun) Name() (string, error) {
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return tun.wt.Name()
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}
func (tun *NativeTun) File() *os.File {
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return nil
}
func (tun *NativeTun) Events() chan Event {
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return tun.events
}
func (tun *NativeTun) Close() error {
tun.close = true
tun.session.End()
var err error
if tun.wt != nil {
_, err = tun.wt.Delete(false)
}
close(tun.events)
return err
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}
func (tun *NativeTun) MTU() (int, error) {
return tun.forcedMTU, nil
}
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// 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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}
// Note: Read() and Write() assume the caller comes only from a single thread; there's no locking.
func (tun *NativeTun) Read(buff []byte, offset int) (int, error) {
retry:
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select {
case err := <-tun.errors:
return 0, err
default:
}
start := nanotime()
shouldSpin := atomic.LoadUint64(&tun.rate.current) >= spinloopRateThreshold && uint64(start-atomic.LoadInt64(&tun.rate.nextStartTime)) <= rateMeasurementGranularity*2
for {
if tun.close {
return 0, os.ErrClosed
}
packet, err := tun.session.ReceivePacket()
switch err {
case nil:
packetSize := len(packet)
copy(buff[offset:], packet)
tun.session.ReleaseReceivePacket(packet)
tun.rate.update(uint64(packetSize))
return packetSize, nil
case windows.ERROR_NO_MORE_ITEMS:
if !shouldSpin || uint64(nanotime()-start) >= spinloopDuration {
windows.WaitForSingleObject(tun.readWait, windows.INFINITE)
goto retry
}
procyield(1)
continue
case windows.ERROR_HANDLE_EOF:
return 0, os.ErrClosed
case windows.ERROR_INVALID_DATA:
return 0, errors.New("Send ring corrupt")
}
return 0, fmt.Errorf("Read failed: %w", err)
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}
}
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func (tun *NativeTun) Flush() error {
return nil
}
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func (tun *NativeTun) Write(buff []byte, offset int) (int, error) {
if tun.close {
return 0, os.ErrClosed
}
packetSize := len(buff) - offset
tun.rate.update(uint64(packetSize))
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packet, err := tun.session.AllocateSendPacket(packetSize)
if err == nil {
copy(packet, buff[offset:])
tun.session.SendPacket(packet)
return packetSize, nil
}
switch err {
case windows.ERROR_HANDLE_EOF:
return 0, os.ErrClosed
case windows.ERROR_BUFFER_OVERFLOW:
return 0, nil // Dropping when ring is full.
}
return 0, fmt.Errorf("Write failed: %w", err)
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}
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// LUID returns Windows interface instance ID.
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func (tun *NativeTun) LUID() uint64 {
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return tun.wt.LUID()
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}
// RunningVersion returns the running version of the Wintun driver.
func (tun *NativeTun) RunningVersion() (version uint32, err error) {
return wintun.RunningVersion()
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}
func (rate *rateJuggler) update(packetLen uint64) {
now := nanotime()
total := atomic.AddUint64(&rate.nextByteCount, packetLen)
period := uint64(now - atomic.LoadInt64(&rate.nextStartTime))
if period >= rateMeasurementGranularity {
if !atomic.CompareAndSwapInt32(&rate.changing, 0, 1) {
return
}
atomic.StoreInt64(&rate.nextStartTime, now)
atomic.StoreUint64(&rate.current, total*uint64(time.Second/time.Nanosecond)/period)
atomic.StoreUint64(&rate.nextByteCount, 0)
atomic.StoreInt32(&rate.changing, 0)
}
}