340 lines
8.3 KiB
Go
340 lines
8.3 KiB
Go
/* SPDX-License-Identifier: MIT
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*
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* Copyright (C) 2018-2019 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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"os"
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"sync"
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"syscall"
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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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packetExchangeMax uint32 = 256 // Number of packets that may be written at a time
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packetExchangeAlignment uint32 = 16 // Number of bytes packets are aligned to in exchange buffers
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packetSizeMax uint32 = 0xf000 - packetExchangeAlignment // Maximum packet size
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packetExchangeSize uint32 = 0x100000 // Exchange buffer size (defaults to 1MiB)
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retryRate = 4 // Number of retries per second to reopen device pipe
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retryTimeout = 5 // Number of seconds to tolerate adapter unavailable
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)
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type exchgBufRead struct {
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data [packetExchangeSize]byte
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offset uint32
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avail uint32
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}
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type exchgBufWrite struct {
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data [packetExchangeSize]byte
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offset uint32
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packetNum uint32
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}
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type NativeTun struct {
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wt *wintun.Wintun
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tunName *uint16
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tunFile windows.Handle
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tunLock sync.Mutex
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close bool
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rdBuff *exchgBufRead
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wrBuff *exchgBufWrite
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events chan TUNEvent
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errors chan error
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forcedMtu int
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}
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//sys getOverlappedResult(handle windows.Handle, overlapped *windows.Overlapped, done *uint32, wait bool) (err error) = kernel32.GetOverlappedResult
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func packetAlign(size uint32) uint32 {
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return (size + (packetExchangeAlignment - 1)) &^ (packetExchangeAlignment - 1)
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}
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//
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// CreateTUN creates a Wintun adapter with the given name. Should a Wintun
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// adapter with the same name exist, it is reused.
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//
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func CreateTUN(ifname string) (TUNDevice, error) {
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// Does an interface with this name already exist?
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wt, err := wintun.GetInterface(ifname, 0)
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if wt == nil {
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// Interface does not exist or an error occured. Create one.
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wt, _, err = wintun.CreateInterface("WireGuard Tunnel Adapter", 0)
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if err != nil {
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return nil, errors.New("Creating Wintun adapter failed: " + err.Error())
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}
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} else if err != nil {
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// Foreign interface with the same name found.
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// We could create a Wintun interface under a temporary name. But, should our
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// proces die without deleting this interface first, the interface would remain
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// orphaned.
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return nil, err
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}
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err = wt.SetInterfaceName(ifname)
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if err != nil {
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wt.DeleteInterface(0)
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return nil, errors.New("Setting interface name failed: " + err.Error())
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}
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err = wt.FlushInterface()
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if err != nil {
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wt.DeleteInterface(0)
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return nil, errors.New("Flushing interface failed: " + err.Error())
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}
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tunNameUTF16, err := windows.UTF16PtrFromString(wt.DataFileName())
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if err != nil {
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wt.DeleteInterface(0)
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return nil, err
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}
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return &NativeTun{
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wt: wt,
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tunName: tunNameUTF16,
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tunFile: windows.InvalidHandle,
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rdBuff: &exchgBufRead{},
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wrBuff: &exchgBufWrite{},
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events: make(chan TUNEvent, 10),
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errors: make(chan error, 1),
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forcedMtu: 1500,
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}, nil
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}
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func (tun *NativeTun) openTUN() error {
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retries := retryTimeout * retryRate
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for {
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if tun.close {
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return errors.New("Cancelled")
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}
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file, err := windows.CreateFile(tun.tunName, windows.GENERIC_READ|windows.GENERIC_WRITE, 0, nil, windows.OPEN_EXISTING, windows.FILE_ATTRIBUTE_NORMAL|windows.FILE_FLAG_OVERLAPPED|windows.FILE_FLAG_NO_BUFFERING, 0)
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if err != nil {
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if retries > 0 {
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time.Sleep(time.Second / retryRate)
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retries--
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continue
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}
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return err
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}
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tun.tunFile = file
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return nil
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}
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}
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func (tun *NativeTun) closeTUN() (err error) {
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if tun.tunFile != windows.InvalidHandle {
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tun.tunLock.Lock()
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defer tun.tunLock.Unlock()
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if tun.tunFile == windows.InvalidHandle {
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return
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}
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t := tun.tunFile
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tun.tunFile = windows.InvalidHandle
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err = windows.CloseHandle(t)
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}
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return
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}
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func (tun *NativeTun) getTUN() (windows.Handle, error) {
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if tun.tunFile == windows.InvalidHandle {
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tun.tunLock.Lock()
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defer tun.tunLock.Unlock()
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if tun.tunFile != windows.InvalidHandle {
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return tun.tunFile, nil
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}
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err := tun.openTUN()
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if err != nil {
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return windows.InvalidHandle, err
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}
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}
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return tun.tunFile, nil
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}
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func (tun *NativeTun) isIOCancelled(err error) bool {
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// Read&WriteFile() return the same ERROR_OPERATION_ABORTED if we close the handle
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// or the TUN device is put down. We need a "close" flag to distinguish.
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en, ok := err.(syscall.Errno)
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if tun.close && ok && en == windows.ERROR_OPERATION_ABORTED {
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return true
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}
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return false
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}
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func (tun *NativeTun) Name() (string, error) {
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return tun.wt.GetInterfaceName()
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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 TUNEvent {
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return tun.events
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}
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func (tun *NativeTun) Close() error {
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tun.close = true
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err1 := tun.closeTUN()
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if tun.events != nil {
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close(tun.events)
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}
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_, _, err2 := tun.wt.DeleteInterface(0)
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if err1 == nil {
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err1 = err2
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}
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return err1
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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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func (tun *NativeTun) Read(buff []byte, offset int) (int, error) {
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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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for {
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if tun.rdBuff.offset+packetExchangeAlignment <= tun.rdBuff.avail {
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// Get packet from the exchange buffer.
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packet := tun.rdBuff.data[tun.rdBuff.offset:]
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size := *(*uint32)(unsafe.Pointer(&packet[0]))
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pSize := packetAlign(packetExchangeAlignment + size)
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if packetSizeMax < size || tun.rdBuff.avail < tun.rdBuff.offset+pSize {
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// Invalid packet size.
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tun.rdBuff.avail = 0
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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)
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tun.rdBuff.offset += pSize
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return int(size), nil
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}
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// Get TUN data pipe.
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file, err := tun.getTUN()
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if err != nil {
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return 0, err
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}
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// Fill queue.
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var n uint32
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overlapped := &windows.Overlapped{}
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err = windows.ReadFile(file, tun.rdBuff.data[:], &n, overlapped)
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if err != nil {
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if en, ok := err.(syscall.Errno); ok && en == windows.ERROR_IO_PENDING {
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err = getOverlappedResult(file, overlapped, &n, true)
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}
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if err != nil {
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tun.rdBuff.avail = 0
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if tun.isIOCancelled(err) {
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return 0, err
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}
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tun.closeTUN()
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continue
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}
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}
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tun.rdBuff.offset = 0
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tun.rdBuff.avail = uint32(n)
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}
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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 {
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// Get TUN data pipe.
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file, err := tun.getTUN()
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if err != nil {
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return err
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}
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// Flush write buffer.
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var n uint32
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overlapped := &windows.Overlapped{}
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err = windows.WriteFile(file, tun.wrBuff.data[:tun.wrBuff.offset], &n, overlapped)
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tun.wrBuff.packetNum = 0
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tun.wrBuff.offset = 0
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if err != nil {
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if en, ok := err.(syscall.Errno); ok && en == windows.ERROR_IO_PENDING {
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err = getOverlappedResult(file, overlapped, &n, true)
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}
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if err != nil {
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if tun.isIOCancelled(err) {
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return err
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}
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tun.closeTUN()
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return nil
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}
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}
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return nil
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}
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func (tun *NativeTun) putTunPacket(buff []byte) error {
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size := uint32(len(buff))
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if size == 0 {
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return errors.New("Empty packet")
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}
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if size > packetSizeMax {
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return errors.New("Packet too big")
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}
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pSize := packetAlign(packetExchangeAlignment + size)
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if tun.wrBuff.packetNum >= packetExchangeMax || tun.wrBuff.offset+pSize >= packetExchangeSize {
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// Exchange buffer is full -> flush first.
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err := tun.flush()
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if err != nil {
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return err
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}
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}
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// Write packet to the exchange buffer.
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packet := tun.wrBuff.data[tun.wrBuff.offset : tun.wrBuff.offset+pSize]
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*(*uint32)(unsafe.Pointer(&packet[0])) = size
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packet = packet[packetExchangeAlignment : packetExchangeAlignment+size]
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copy(packet, buff)
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tun.wrBuff.packetNum++
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tun.wrBuff.offset += pSize
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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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err := tun.putTunPacket(buff[offset:])
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if err != nil {
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return 0, err
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}
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// Flush write buffer.
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return len(buff) - offset, tun.flush()
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}
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//
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// GUID returns Windows adapter instance ID.
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//
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func (tun *NativeTun) GUID() windows.GUID {
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return *(*windows.GUID)(tun.wt)
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}
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