wireguard-go/tun/tun_windows.go
Simon Rozman a1aabb21ae Elaborate the failing step when forwarding errors on return
Signed-off-by: Simon Rozman <simon@rozman.si>
2019-03-04 16:37:11 +01:00

357 lines
8.6 KiB
Go

/* SPDX-License-Identifier: MIT
*
* Copyright (C) 2018-2019 WireGuard LLC. All Rights Reserved.
*/
package tun
import (
"errors"
"os"
"sync"
"unsafe"
"golang.org/x/sys/windows"
"golang.zx2c4.com/wireguard/tun/wintun"
)
const (
packetExchangeMax uint32 = 256 // Number of packets that may be written at a time
packetExchangeAlignment uint32 = 16 // Number of bytes packets are aligned to in exchange buffers
packetSizeMax uint32 = 0xf000 - packetExchangeAlignment // Maximum packet size
packetExchangeSize uint32 = 0x100000 // Exchange buffer size (defaults to 1MiB)
)
type exchgBufRead struct {
data [packetExchangeSize]byte
offset uint32
avail uint32
}
type exchgBufWrite struct {
data [packetExchangeSize]byte
offset uint32
packetNum uint32
}
type NativeTun struct {
wt *wintun.Wintun
tunName string
signalName *uint16
tunFile *os.File
tunLock sync.Mutex
rdBuff *exchgBufRead
wrBuff *exchgBufWrite
tunDataAvail windows.Handle
userClose windows.Handle
events chan TUNEvent
errors chan error
}
func packetAlign(size uint32) uint32 {
return (size + (packetExchangeAlignment - 1)) &^ (packetExchangeAlignment - 1)
}
func CreateTUN(ifname string) (TUNDevice, error) {
// Does an interface with this name already exist?
wt, err := wintun.GetInterface(ifname, 0)
if wt == nil {
// Interface does not exist or an error occured. Create one.
wt, _, err = wintun.CreateInterface("WireGuard Tunnel Adapter", 0)
if err != nil {
return nil, errors.New("Creating Wintun adapter failed: " + err.Error())
}
} else if err != nil {
// Foreign interface with the same name found.
// We could create a Wintun interface under a temporary name. But, should our
// proces die without deleting this interface first, the interface would remain
// orphaned.
return nil, err
}
err = wt.SetInterfaceName(ifname)
if err != nil {
wt.DeleteInterface(0)
return nil, errors.New("Setting interface name failed: " + err.Error())
}
err = wt.FlushInterface()
if err != nil {
wt.DeleteInterface(0)
return nil, errors.New("Flushing interface failed: " + err.Error())
}
signalNameUTF16, err := windows.UTF16PtrFromString(wt.SignalEventName())
if err != nil {
wt.DeleteInterface(0)
return nil, err
}
// Create instance.
tun := &NativeTun{
wt: wt,
tunName: wt.DataFileName(),
signalName: signalNameUTF16,
rdBuff: &exchgBufRead{},
wrBuff: &exchgBufWrite{},
events: make(chan TUNEvent, 10),
errors: make(chan error, 1),
}
// Create close event.
tun.userClose, err = windows.CreateEvent(nil, 1 /*TRUE*/, 0 /*FALSE*/, nil)
if err != nil {
wt.DeleteInterface(0)
return nil, err
}
return tun, nil
}
func (tun *NativeTun) openTUN() error {
for {
// Open interface data pipe.
// Data pipe must be opened first, as the interface data available event is created when somebody actually connects to the data pipe.
file, err := os.OpenFile(tun.tunName, os.O_RDWR|os.O_SYNC, 0600)
if err != nil {
// After examining possible error conditions, many arose that were only temporary: windows.ERROR_FILE_NOT_FOUND, "read <filename> closed", etc.
// To simplify, we will enter a retry-loop on _any_ error until session is closed by user.
switch evt, e := windows.WaitForSingleObject(tun.userClose, 1000); evt {
case windows.WAIT_OBJECT_0, windows.WAIT_ABANDONED:
return errors.New("TUN closed")
case windows.WAIT_TIMEOUT:
continue
default:
return errors.New("Unexpected result from WaitForSingleObject: " + e.Error())
}
}
// Open interface data available event.
event, err := windows.OpenEvent(windows.SYNCHRONIZE, false, tun.signalName)
if err != nil {
file.Close()
return errors.New("Opening interface data ready event failed: " + err.Error())
}
tun.tunFile = file
tun.tunDataAvail = event
return nil
}
}
func (tun *NativeTun) closeTUN() (err error) {
tun.tunLock.Lock()
defer tun.tunLock.Unlock()
if tun.tunDataAvail != 0 {
// Close interface data ready event.
e := windows.CloseHandle(tun.tunDataAvail)
if err != nil {
err = e
}
tun.tunDataAvail = 0
}
if tun.tunFile != nil {
// Close interface data pipe.
e := tun.tunFile.Close()
if err != nil {
err = e
}
tun.tunFile = nil
}
return
}
func (tun *NativeTun) getTUN() (*os.File, windows.Handle, error) {
tun.tunLock.Lock()
defer tun.tunLock.Unlock()
if tun.tunFile == nil || tun.tunDataAvail == 0 {
// TUN device is not open (yet).
err := tun.openTUN()
if err != nil {
return nil, 0, err
}
}
return tun.tunFile, tun.tunDataAvail, nil
}
func (tun *NativeTun) Name() (string, error) {
return tun.wt.GetInterfaceName()
}
func (tun *NativeTun) File() *os.File {
return nil
}
func (tun *NativeTun) Events() chan TUNEvent {
return tun.events
}
func (tun *NativeTun) Close() error {
windows.SetEvent(tun.userClose)
err := windows.CloseHandle(tun.userClose)
e := tun.closeTUN()
if err == nil {
err = e
}
if tun.events != nil {
close(tun.events)
}
_, _, e = tun.wt.DeleteInterface(0)
if err == nil {
err = e
}
return err
}
func (tun *NativeTun) MTU() (int, error) {
return 1500, nil
}
func (tun *NativeTun) Read(buff []byte, offset int) (int, error) {
select {
case err := <-tun.errors:
return 0, err
default:
}
for {
if tun.rdBuff.offset+packetExchangeAlignment <= tun.rdBuff.avail {
// Get packet from the exchange buffer.
packet := tun.rdBuff.data[tun.rdBuff.offset:]
size := *(*uint32)(unsafe.Pointer(&packet[0]))
pSize := packetAlign(packetExchangeAlignment + size)
if packetSizeMax < size || tun.rdBuff.avail < tun.rdBuff.offset+pSize {
// Invalid packet size.
tun.rdBuff.avail = 0
continue
}
packet = packet[:pSize]
// Copy data.
copy(buff[offset:], packet[packetExchangeAlignment:packetExchangeAlignment+size])
tun.rdBuff.offset += pSize
return int(size), nil
}
// Get TUN data ready event.
_, tunDataAvail, err := tun.getTUN()
if err != nil {
return 0, err
}
// Wait for user close or interface data.
r, err := windows.WaitForMultipleObjects([]windows.Handle{tun.userClose, tunDataAvail}, false, windows.INFINITE)
if err != nil {
return 0, errors.New("Waiting for data failed: " + err.Error())
}
switch r {
case windows.WAIT_OBJECT_0 + 0, windows.WAIT_ABANDONED + 0:
return 0, errors.New("TUN closed")
case windows.WAIT_OBJECT_0 + 1:
// Data is available.
case windows.WAIT_ABANDONED + 1:
// TUN stopped.
tun.closeTUN()
case windows.WAIT_TIMEOUT:
// Congratulations, we reached infinity. Let's do it again! :)
continue
default:
return 0, errors.New("unexpected result from WaitForMultipleObjects")
}
// Get TUN data pipe.
file, _, err := tun.getTUN()
if err != nil {
return 0, err
}
// Fill queue.
n, err := file.Read(tun.rdBuff.data[:])
if err != nil {
// TUN interface stopped, failed, etc. Retry.
tun.rdBuff.avail = 0
tun.closeTUN()
continue
}
tun.rdBuff.offset = 0
tun.rdBuff.avail = uint32(n)
}
}
// Note: flush() and putTunPacket() assume the caller comes only from a single thread; there's no locking.
func (tun *NativeTun) flush() error {
// Get TUN data pipe.
file, _, err := tun.getTUN()
if err != nil {
return err
}
// Flush write buffer.
_, err = file.Write(tun.wrBuff.data[:tun.wrBuff.offset])
tun.wrBuff.packetNum = 0
tun.wrBuff.offset = 0
if err != nil {
// TUN interface stopped, failed, etc. Drop.
tun.closeTUN()
return err
}
return nil
}
func (tun *NativeTun) putTunPacket(buff []byte) error {
size := uint32(len(buff))
if size == 0 {
return errors.New("Empty packet")
}
if size > packetSizeMax {
return errors.New("Packet too big")
}
pSize := packetAlign(packetExchangeAlignment + size)
if tun.wrBuff.packetNum >= packetExchangeMax || tun.wrBuff.offset+pSize >= packetExchangeSize {
// Exchange buffer is full -> flush first.
err := tun.flush()
if err != nil {
return err
}
}
// Write packet to the exchange buffer.
packet := tun.wrBuff.data[tun.wrBuff.offset : tun.wrBuff.offset+pSize]
*(*uint32)(unsafe.Pointer(&packet[0])) = size
copy(packet[packetExchangeAlignment:packetExchangeAlignment+size], buff)
tun.wrBuff.packetNum++
tun.wrBuff.offset += pSize
return nil
}
func (tun *NativeTun) Write(buff []byte, offset int) (int, error) {
err := tun.putTunPacket(buff[offset:])
if err != nil {
return 0, err
}
// Flush write buffer.
return len(buff) - offset, tun.flush()
}
func (tun *NativeTun) GUID() windows.GUID {
return *(*windows.GUID)(tun.wt)
}