0f4809f366
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
238 lines
5.8 KiB
Go
238 lines
5.8 KiB
Go
/* SPDX-License-Identifier: MIT
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*
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* Copyright (C) 2018-2021 WireGuard LLC. All Rights Reserved.
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*/
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package tun
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import (
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"errors"
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"fmt"
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"log"
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"os"
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"sync"
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"sync/atomic"
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"time"
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_ "unsafe"
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"golang.org/x/sys/windows"
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"golang.zx2c4.com/wireguard/tun/wintun"
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)
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const (
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rateMeasurementGranularity = uint64((time.Second / 2) / time.Nanosecond)
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spinloopRateThreshold = 800000000 / 8 // 800mbps
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spinloopDuration = uint64(time.Millisecond / 80 / time.Nanosecond) // ~1gbit/s
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)
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type rateJuggler struct {
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current uint64
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nextByteCount uint64
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nextStartTime int64
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changing int32
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}
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type NativeTun struct {
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wt *wintun.Adapter
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handle windows.Handle
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close bool
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events chan Event
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errors chan error
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forcedMTU int
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rate rateJuggler
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session wintun.Session
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readWait windows.Handle
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closeOnce sync.Once
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}
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var WintunPool, _ = wintun.MakePool("WireGuard")
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var WintunStaticRequestedGUID *windows.GUID
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//go:linkname procyield runtime.procyield
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func procyield(cycles uint32)
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//go:linkname nanotime runtime.nanotime
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func nanotime() int64
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//
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// CreateTUN creates a Wintun interface with the given name. Should a Wintun
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// interface with the same name exist, it is reused.
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//
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func CreateTUN(ifname string, mtu int) (Device, error) {
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return CreateTUNWithRequestedGUID(ifname, WintunStaticRequestedGUID, mtu)
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}
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//
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// CreateTUNWithRequestedGUID creates a Wintun interface with the given name and
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// a requested GUID. Should a Wintun interface with the same name exist, it is reused.
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//
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func CreateTUNWithRequestedGUID(ifname string, requestedGUID *windows.GUID, mtu int) (Device, error) {
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var err error
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var wt *wintun.Adapter
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// Does an interface with this name already exist?
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wt, err = WintunPool.OpenAdapter(ifname)
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if err == nil {
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// If so, we delete it, in case it has weird residual configuration.
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_, err = wt.Delete(true)
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if err != nil {
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return nil, fmt.Errorf("Error deleting already existing interface: %w", err)
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}
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}
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wt, rebootRequired, err := WintunPool.CreateAdapter(ifname, requestedGUID)
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if err != nil {
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return nil, fmt.Errorf("Error creating interface: %w", err)
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}
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if rebootRequired {
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log.Println("Windows indicated a reboot is required.")
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}
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forcedMTU := 1420
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if mtu > 0 {
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forcedMTU = mtu
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}
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tun := &NativeTun{
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wt: wt,
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handle: windows.InvalidHandle,
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events: make(chan Event, 10),
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errors: make(chan error, 1),
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forcedMTU: forcedMTU,
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}
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tun.session, err = wt.StartSession(0x800000) // Ring capacity, 8 MiB
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if err != nil {
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tun.wt.Delete(false)
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close(tun.events)
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return nil, fmt.Errorf("Error starting session: %w", err)
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}
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tun.readWait = tun.session.ReadWaitEvent()
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return tun, nil
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}
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func (tun *NativeTun) Name() (string, error) {
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return tun.wt.Name()
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}
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func (tun *NativeTun) File() *os.File {
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return nil
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}
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func (tun *NativeTun) Events() chan Event {
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return tun.events
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}
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func (tun *NativeTun) Close() error {
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var err error
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tun.closeOnce.Do(func() {
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tun.close = true
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tun.session.End()
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if tun.wt != nil {
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_, err = tun.wt.Delete(false)
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}
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close(tun.events)
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})
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return err
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}
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func (tun *NativeTun) MTU() (int, error) {
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return tun.forcedMTU, nil
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}
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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.
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func (tun *NativeTun) ForceMTU(mtu int) {
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tun.forcedMTU = mtu
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}
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// Note: Read() and Write() assume the caller comes only from a single thread; there's no locking.
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func (tun *NativeTun) Read(buff []byte, offset int) (int, error) {
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retry:
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select {
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case err := <-tun.errors:
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return 0, err
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default:
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}
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start := nanotime()
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shouldSpin := atomic.LoadUint64(&tun.rate.current) >= spinloopRateThreshold && uint64(start-atomic.LoadInt64(&tun.rate.nextStartTime)) <= rateMeasurementGranularity*2
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for {
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if tun.close {
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return 0, os.ErrClosed
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}
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packet, err := tun.session.ReceivePacket()
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switch err {
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case nil:
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packetSize := len(packet)
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copy(buff[offset:], packet)
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tun.session.ReleaseReceivePacket(packet)
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tun.rate.update(uint64(packetSize))
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return packetSize, nil
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case windows.ERROR_NO_MORE_ITEMS:
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if !shouldSpin || uint64(nanotime()-start) >= spinloopDuration {
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windows.WaitForSingleObject(tun.readWait, windows.INFINITE)
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goto retry
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}
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procyield(1)
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continue
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case windows.ERROR_HANDLE_EOF:
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return 0, os.ErrClosed
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case windows.ERROR_INVALID_DATA:
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return 0, errors.New("Send ring corrupt")
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}
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return 0, fmt.Errorf("Read failed: %w", err)
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}
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}
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func (tun *NativeTun) Flush() error {
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return nil
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}
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func (tun *NativeTun) Write(buff []byte, offset int) (int, error) {
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if tun.close {
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return 0, os.ErrClosed
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}
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packetSize := len(buff) - offset
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tun.rate.update(uint64(packetSize))
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packet, err := tun.session.AllocateSendPacket(packetSize)
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if err == nil {
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copy(packet, buff[offset:])
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tun.session.SendPacket(packet)
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return packetSize, nil
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}
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switch err {
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case windows.ERROR_HANDLE_EOF:
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return 0, os.ErrClosed
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case windows.ERROR_BUFFER_OVERFLOW:
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return 0, nil // Dropping when ring is full.
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}
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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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}
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// RunningVersion returns the running version of the Wintun driver.
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func (tun *NativeTun) RunningVersion() (version uint32, err error) {
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return wintun.RunningVersion()
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}
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func (rate *rateJuggler) update(packetLen uint64) {
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now := nanotime()
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total := atomic.AddUint64(&rate.nextByteCount, packetLen)
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period := uint64(now - atomic.LoadInt64(&rate.nextStartTime))
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if period >= rateMeasurementGranularity {
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if !atomic.CompareAndSwapInt32(&rate.changing, 0, 1) {
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return
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}
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atomic.StoreInt64(&rate.nextStartTime, now)
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atomic.StoreUint64(&rate.current, total*uint64(time.Second/time.Nanosecond)/period)
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atomic.StoreUint64(&rate.nextByteCount, 0)
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atomic.StoreInt32(&rate.changing, 0)
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}
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}
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