mirror of
https://git.zx2c4.com/wireguard-go
synced 2024-11-15 01:05:15 +01:00
364 lines
8.7 KiB
Go
364 lines
8.7 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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"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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)
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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 string
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signalName *uint16
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tunFile *os.File
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tunLock sync.Mutex
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rdBuff *exchgBufRead
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wrBuff *exchgBufWrite
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tunDataAvail windows.Handle
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userClose windows.Handle
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events chan TUNEvent
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errors chan error
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}
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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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signalNameUTF16, err := windows.UTF16PtrFromString(wt.SignalEventName())
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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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// Create instance.
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tun := &NativeTun{
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wt: wt,
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tunName: wt.DataFileName(),
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signalName: signalNameUTF16,
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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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}
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// Create close event.
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tun.userClose, err = windows.CreateEvent(nil, 1 /*TRUE*/, 0 /*FALSE*/, nil)
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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 tun, nil
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}
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func (tun *NativeTun) openTUN() error {
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for {
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// Open interface data pipe.
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// Data pipe must be opened first, as the interface data available event is created when somebody actually connects to the data pipe.
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file, err := os.OpenFile(tun.tunName, os.O_RDWR|os.O_SYNC, 0600)
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if err != nil {
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// After examining possible error conditions, many arose that were only temporary: windows.ERROR_FILE_NOT_FOUND, "read <filename> closed", etc.
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// To simplify, we will enter a retry-loop on _any_ error until session is closed by user.
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switch evt, e := windows.WaitForSingleObject(tun.userClose, 1000); evt {
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case windows.WAIT_OBJECT_0, windows.WAIT_ABANDONED:
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return errors.New("TUN closed")
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case windows.WAIT_TIMEOUT:
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continue
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default:
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return errors.New("Unexpected result from WaitForSingleObject: " + e.Error())
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}
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}
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// Open interface data available event.
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event, err := windows.OpenEvent(windows.SYNCHRONIZE, false, tun.signalName)
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if err != nil {
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file.Close()
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return errors.New("Opening interface data ready event failed: " + err.Error())
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}
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tun.tunFile = file
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tun.tunDataAvail = event
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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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tun.tunLock.Lock()
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defer tun.tunLock.Unlock()
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if tun.tunDataAvail != 0 {
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// Close interface data ready event.
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e := windows.CloseHandle(tun.tunDataAvail)
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if err != nil {
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err = e
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}
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tun.tunDataAvail = 0
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}
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if tun.tunFile != nil {
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// Close interface data pipe.
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e := tun.tunFile.Close()
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if err != nil {
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err = e
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}
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tun.tunFile = nil
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}
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return
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}
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func (tun *NativeTun) getTUN() (*os.File, windows.Handle, error) {
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tun.tunLock.Lock()
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defer tun.tunLock.Unlock()
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if tun.tunFile == nil || tun.tunDataAvail == 0 {
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// TUN device is not open (yet).
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err := tun.openTUN()
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if err != nil {
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return nil, 0, err
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}
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}
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return tun.tunFile, tun.tunDataAvail, nil
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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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windows.SetEvent(tun.userClose)
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err := windows.CloseHandle(tun.userClose)
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e := tun.closeTUN()
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if err == nil {
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err = e
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}
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if tun.events != nil {
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close(tun.events)
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}
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_, _, e = tun.wt.DeleteInterface(0)
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if err == nil {
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err = e
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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 1500, nil
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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[:pSize]
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// Copy data.
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copy(buff[offset:], packet[packetExchangeAlignment:packetExchangeAlignment+size])
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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 ready event.
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_, tunDataAvail, 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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// Wait for user close or interface data.
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r, err := windows.WaitForMultipleObjects([]windows.Handle{tun.userClose, tunDataAvail}, false, windows.INFINITE)
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if err != nil {
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return 0, errors.New("Waiting for data failed: " + err.Error())
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}
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switch r {
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case windows.WAIT_OBJECT_0 + 0, windows.WAIT_ABANDONED + 0:
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return 0, errors.New("TUN closed")
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case windows.WAIT_OBJECT_0 + 1:
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// Data is available.
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case windows.WAIT_ABANDONED + 1:
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// TUN stopped.
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tun.closeTUN()
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case windows.WAIT_TIMEOUT:
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// Congratulations, we reached infinity. Let's do it again! :)
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continue
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default:
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return 0, errors.New("unexpected result from WaitForMultipleObjects")
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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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n, err := file.Read(tun.rdBuff.data[:])
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if err != nil {
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// TUN interface stopped, failed, etc. Retry.
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tun.rdBuff.avail = 0
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tun.closeTUN()
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continue
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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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_, err = file.Write(tun.wrBuff.data[:tun.wrBuff.offset])
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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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// TUN interface stopped, failed, etc. Drop.
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tun.closeTUN()
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return err
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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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copy(packet[packetExchangeAlignment:packetExchangeAlignment+size], 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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