Import windows scafolding

1 files changed, 286 insertions, 0 deletions

diff --git a/tun/tun_windows.go b/tun/tun_windows.go
new file mode 100644
index 0000000..19a9d2d
--- /dev/null
+++ b/tun/tun_windows.go
@@ -0,0 +1,286 @@
+/* SPDX-License-Identifier: MIT
+ *
+ * Copyright (C) 2018-2019 WireGuard LLC. All Rights Reserved.
+ */
+
+package tun
+
+import (
+	"errors"
+	"fmt"
+	"os"
+	"unsafe"
+
+	"golang.org/x/sys/windows"
+)
+
+const (
+	TUN_MIN_PACKET_SIZE      = 20
+	TUN_MAX_PACKET_SIZE      = 1600
+	TUN_MAX_PACKET_EXCHANGE  = 256 // Number of packets that can be exchanged at a time
+	TUN_EXCHANGE_BUFFER_SIZE = 410632
+)
+
+const (
+	TUN_SIGNAL_DATA_AVAIL = 0
+	TUN_SIGNAL_CLOSE      = 1
+
+	TUN_SIGNAL_MAX = 2
+)
+
+type TunPacket struct {
+	size uint32
+	data [TUN_MAX_PACKET_SIZE]byte
+}
+
+type TunRWQueue struct {
+	numPackets uint32
+	packets    [TUN_MAX_PACKET_EXCHANGE]TunPacket
+	left       uint32
+}
+
+type nativeTun struct {
+	ifname       string
+	tunName      string
+	signalName   *uint16
+	tunFile      *os.File
+	wrBuff       TunRWQueue
+	rdBuff       TunRWQueue
+	signals      [TUN_SIGNAL_MAX]windows.Handle
+	rdNextPacket uint32
+	events       chan TUNEvent
+	errors       chan error
+}
+
+func CreateTUN(ifname string) (TUNDevice, error) {
+	signalNameUTF16, err := windows.UTF16PtrFromString(fmt.Sprintf("Global\\TUN_EVENT_%s", ifname))
+	if err != nil {
+		return nil, err
+	}
+
+	// Create instance.
+	tun := &nativeTun{
+		ifname:     ifname,
+		tunName:    fmt.Sprintf("\\\\.\\Global\\TUN_%s_DEVICE", ifname),
+		signalName: signalNameUTF16,
+		events:     make(chan TUNEvent, 10),
+		errors:     make(chan error, 1),
+	}
+
+	// Create close event.
+	tun.signals[TUN_SIGNAL_CLOSE], err = windows.CreateEvent(nil, 1 /*TRUE*/, 0 /*FALSE*/, nil)
+	if err != nil {
+		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.signals[TUN_SIGNAL_CLOSE], 1000); evt {
+			case windows.WAIT_OBJECT_0, windows.WAIT_ABANDONED:
+				return errors.New("TUN closed")
+			case windows.WAIT_TIMEOUT:
+				continue
+			default:
+				return fmt.Errorf("unexpected result from WaitForSingleObject:", e)
+			}
+		}
+
+		// Open interface data available event.
+		event, err := windows.OpenEvent(windows.SYNCHRONIZE, false, tun.signalName)
+		if err != nil {
+			file.Close()
+			return fmt.Errorf("opening interface data ready event failed:", err)
+		}
+
+		tun.tunFile = file
+		tun.signals[TUN_SIGNAL_DATA_AVAIL] = event
+
+		return nil
+	}
+}
+
+func (tun *nativeTun) closeTUN() (err error) {
+	if tun.signals[TUN_SIGNAL_DATA_AVAIL] != 0 {
+		// Close interface data ready event.
+		e := windows.CloseHandle(tun.signals[TUN_SIGNAL_DATA_AVAIL])
+		if err != nil {
+			err = e
+		}
+
+		tun.signals[TUN_SIGNAL_DATA_AVAIL] = 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) Name() (string, error) {
+	return tun.ifname, nil
+}
+
+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.signals[TUN_SIGNAL_CLOSE])
+	err := windows.CloseHandle(tun.signals[TUN_SIGNAL_CLOSE])
+
+	e := tun.closeTUN()
+	if err == nil {
+		err = e
+	}
+
+	if tun.events != nil {
+		close(tun.events)
+	}
+
+	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.rdNextPacket < tun.rdBuff.numPackets {
+				// Get packet from the queue.
+				tunPacket := &tun.rdBuff.packets[tun.rdNextPacket]
+				tun.rdNextPacket++
+
+				if tunPacket.size < TUN_MIN_PACKET_SIZE || TUN_MAX_PACKET_SIZE < tunPacket.size {
+					// Invalid packet size.
+					continue
+				}
+
+				// Copy data.
+				copy(buff[offset:], tunPacket.data[:tunPacket.size])
+				return int(tunPacket.size), nil
+			}
+
+			if tun.signals[TUN_SIGNAL_DATA_AVAIL] == 0 {
+				// Data pipe and interface data available event are not open (yet).
+				err := tun.openTUN()
+				if err != nil {
+					return 0, err
+				}
+			}
+
+			if tun.rdBuff.numPackets < TUN_MAX_PACKET_EXCHANGE || tun.rdBuff.left == 0 {
+				// Buffer was not full. Wait for the interface data or user close.
+				r, err := windows.WaitForMultipleObjects(tun.signals[:], false, windows.INFINITE)
+				if err != nil {
+					return 0, fmt.Errorf("waiting for data failed:", err)
+				}
+				switch r {
+				case windows.WAIT_OBJECT_0 + TUN_SIGNAL_DATA_AVAIL:
+					// Data is available.
+				case windows.WAIT_ABANDONED + TUN_SIGNAL_DATA_AVAIL:
+					// TUN stopped. Reopen it.
+					tun.closeTUN()
+					continue
+				case windows.WAIT_OBJECT_0 + TUN_SIGNAL_CLOSE, windows.WAIT_ABANDONED + TUN_SIGNAL_CLOSE:
+					return 0, errors.New("TUN closed")
+				case windows.WAIT_TIMEOUT:
+					// Congratulations, we reached infinity. Let's do it again! :)
+					continue
+				default:
+					return 0, errors.New("unexpected result from WaitForMultipleObjects")
+				}
+			}
+
+			// Fill queue.
+			data := (*[TUN_EXCHANGE_BUFFER_SIZE]byte)(unsafe.Pointer(&tun.rdBuff))
+			n, err := tun.tunFile.Read(data[:])
+			tun.rdNextPacket = 0
+			if n != TUN_EXCHANGE_BUFFER_SIZE || err != nil {
+				// TUN interface stopped, returned incomplete data, etc.
+				// Retry.
+				tun.rdBuff.numPackets = 0
+				tun.closeTUN()
+				continue
+			}
+		}
+	}
+}
+
+func (tun *nativeTun) flush() error {
+	// Flush write buffer.
+	data := (*[TUN_EXCHANGE_BUFFER_SIZE]byte)(unsafe.Pointer(&tun.wrBuff))
+	n, err := tun.tunFile.Write(data[:])
+	tun.wrBuff.numPackets = 0
+	if err != nil {
+		return err
+	}
+	if n != TUN_EXCHANGE_BUFFER_SIZE {
+		return fmt.Errorf("%d byte(s) written, %d byte(s) expected", n, TUN_EXCHANGE_BUFFER_SIZE)
+	}
+
+	return nil
+}
+
+func (tun *nativeTun) putTunPacket(buff []byte) error {
+	size := len(buff)
+	if size == 0 {
+		return errors.New("empty packet")
+	}
+	if size > TUN_MAX_PACKET_SIZE {
+		return errors.New("packet too big")
+	}
+
+	if tun.wrBuff.numPackets >= TUN_MAX_PACKET_EXCHANGE {
+		// Queue is full -> flush first.
+		err := tun.flush()
+		if err != nil {
+			return err
+		}
+	}
+
+	// Push packet to the buffer.
+	tunPacket := &tun.wrBuff.packets[tun.wrBuff.numPackets]
+	tunPacket.size = uint32(size)
+	copy(tunPacket.data[:size], buff)
+
+	tun.wrBuff.numPackets++
+
+	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()
+}