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"
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"os"
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"sync"
"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 {
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wt *wintun.Interface
handle windows.Handle
close bool
events chan Event
errors chan error
forcedMTU int
rate rateJuggler
rings *wintun.RingDescriptor
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writeLock sync.Mutex
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}
const WintunPool = wintun.Pool("WireGuard")
//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, nil, 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
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var wt *wintun.Interface
// Does an interface with this name already exist?
wt, err = WintunPool.GetInterface(ifname)
if err == nil {
// If so, we delete it, in case it has weird residual configuration.
_, err = wt.DeleteInterface()
if err != nil {
return nil, fmt.Errorf("Error deleting already existing interface: %v", err)
}
}
wt, _, err = WintunPool.CreateInterface(ifname, requestedGUID)
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if err != nil {
return nil, fmt.Errorf("Error creating interface: %v", err)
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}
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.rings, err = wintun.NewRingDescriptor()
if err != nil {
tun.Close()
return nil, fmt.Errorf("Error creating events: %v", err)
}
tun.handle, err = tun.wt.Register(tun.rings)
if err != nil {
tun.Close()
return nil, fmt.Errorf("Error registering rings: %v", err)
}
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
if tun.rings.Send.TailMoved != 0 {
windows.SetEvent(tun.rings.Send.TailMoved) // wake the reader if it's sleeping
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}
if tun.handle != windows.InvalidHandle {
windows.CloseHandle(tun.handle)
}
tun.rings.Close()
var err error
if tun.wt != nil {
_, err = tun.wt.DeleteInterface()
}
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:
}
if tun.close {
return 0, os.ErrClosed
}
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buffHead := atomic.LoadUint32(&tun.rings.Send.Ring.Head)
if buffHead >= wintun.PacketCapacity {
return 0, os.ErrClosed
}
start := nanotime()
shouldSpin := atomic.LoadUint64(&tun.rate.current) >= spinloopRateThreshold && uint64(start-atomic.LoadInt64(&tun.rate.nextStartTime)) <= rateMeasurementGranularity*2
var buffTail uint32
for {
buffTail = atomic.LoadUint32(&tun.rings.Send.Ring.Tail)
if buffHead != buffTail {
break
}
if tun.close {
return 0, os.ErrClosed
}
if !shouldSpin || uint64(nanotime()-start) >= spinloopDuration {
windows.WaitForSingleObject(tun.rings.Send.TailMoved, windows.INFINITE)
goto retry
}
procyield(1)
}
if buffTail >= wintun.PacketCapacity {
return 0, os.ErrClosed
}
buffContent := tun.rings.Send.Ring.Wrap(buffTail - buffHead)
if buffContent < uint32(unsafe.Sizeof(wintun.PacketHeader{})) {
return 0, errors.New("incomplete packet header in send ring")
}
packet := (*wintun.Packet)(unsafe.Pointer(&tun.rings.Send.Ring.Data[buffHead]))
if packet.Size > wintun.PacketSizeMax {
return 0, errors.New("packet too big in send ring")
}
alignedPacketSize := wintun.PacketAlign(uint32(unsafe.Sizeof(wintun.PacketHeader{})) + packet.Size)
if alignedPacketSize > buffContent {
return 0, errors.New("incomplete packet in send ring")
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}
copy(buff[offset:], packet.Data[:packet.Size])
buffHead = tun.rings.Send.Ring.Wrap(buffHead + alignedPacketSize)
atomic.StoreUint32(&tun.rings.Send.Ring.Head, buffHead)
tun.rate.update(uint64(packet.Size))
return int(packet.Size), nil
}
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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 := uint32(len(buff) - offset)
tun.rate.update(uint64(packetSize))
alignedPacketSize := wintun.PacketAlign(uint32(unsafe.Sizeof(wintun.PacketHeader{})) + packetSize)
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tun.writeLock.Lock()
defer tun.writeLock.Unlock()
buffHead := atomic.LoadUint32(&tun.rings.Receive.Ring.Head)
if buffHead >= wintun.PacketCapacity {
return 0, os.ErrClosed
}
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buffTail := atomic.LoadUint32(&tun.rings.Receive.Ring.Tail)
if buffTail >= wintun.PacketCapacity {
return 0, os.ErrClosed
}
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buffSpace := tun.rings.Receive.Ring.Wrap(buffHead - buffTail - wintun.PacketAlignment)
if alignedPacketSize > buffSpace {
return 0, nil // Dropping when ring is full.
}
packet := (*wintun.Packet)(unsafe.Pointer(&tun.rings.Receive.Ring.Data[buffTail]))
packet.Size = packetSize
copy(packet.Data[:packetSize], buff[offset:])
atomic.StoreUint32(&tun.rings.Receive.Ring.Tail, tun.rings.Receive.Ring.Wrap(buffTail+alignedPacketSize))
if atomic.LoadInt32(&tun.rings.Receive.Ring.Alertable) != 0 {
windows.SetEvent(tun.rings.Receive.TailMoved)
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}
return int(packetSize), nil
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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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}
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// Version returns the version of the Wintun driver and NDIS system currently loaded.
func (tun *NativeTun) Version() (driverVersion string, ndisVersion string, err error) {
return tun.wt.Version()
}
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)
}
}