Add OpenBSD tun driver support

1 files changed, 366 insertions, 0 deletions

diff --git a/tun_openbsd.go b/tun_openbsd.go
new file mode 100644
index 0000000..97d8f38
--- /dev/null
+++ b/tun_openbsd.go
@@ -0,0 +1,366 @@
+/* SPDX-License-Identifier: GPL-2.0
+ *
+ * Copyright (C) 2017-2018 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
+ */
+
+package main
+
+import (
+	"./rwcancel"
+	"errors"
+	"fmt"
+	"golang.org/x/net/ipv6"
+	"golang.org/x/sys/unix"
+	"io/ioutil"
+	"net"
+	"os"
+	"syscall"
+	"unsafe"
+)
+
+// Structure for iface mtu get/set ioctls
+type ifreq_mtu struct {
+	Name [unix.IFNAMSIZ]byte
+	MTU  uint32
+	Pad0 [12]byte
+}
+
+const _TUNSIFMODE = 0x8004745d
+
+type NativeTun struct {
+	name        string
+	fd          *os.File
+	rwcancel    *rwcancel.RWCancel
+	events      chan TUNEvent
+	errors      chan error
+	routeSocket int
+}
+
+func (tun *NativeTun) RoutineRouteListener(tunIfindex int) {
+	var (
+		statusUp  bool
+		statusMTU int
+	)
+
+	defer close(tun.events)
+
+	data := make([]byte, os.Getpagesize())
+	for {
+		n, err := unix.Read(tun.routeSocket, data)
+		if err != nil {
+			tun.errors <- err
+			return
+		}
+
+		if n < 8 {
+			continue
+		}
+
+		if data[3 /* type */] != unix.RTM_IFINFO {
+			continue
+		}
+		ifindex := int(*(*uint16)(unsafe.Pointer(&data[6 /* ifindex */])))
+		if ifindex != tunIfindex {
+			continue
+		}
+
+		iface, err := net.InterfaceByIndex(ifindex)
+		if err != nil {
+			tun.errors <- err
+			return
+		}
+
+		// Up / Down event
+		up := (iface.Flags & net.FlagUp) != 0
+		if up != statusUp && up {
+			tun.events <- TUNEventUp
+		}
+		if up != statusUp && !up {
+			tun.events <- TUNEventDown
+		}
+		statusUp = up
+
+		// MTU changes
+		if iface.MTU != statusMTU {
+			tun.events <- TUNEventMTUUpdate
+		}
+		statusMTU = iface.MTU
+	}
+}
+
+func errorIsEBUSY(err error) bool {
+	if pe, ok := err.(*os.PathError); ok {
+		if errno, ok := pe.Err.(syscall.Errno); ok && errno == syscall.EBUSY {
+			return true
+		}
+	}
+	if errno, ok := err.(syscall.Errno); ok && errno == syscall.EBUSY {
+		return true
+	}
+	return false
+}
+
+func CreateTUN(name string) (TUNDevice, error) {
+	ifIndex := -1
+	if name != "tun" {
+		_, err := fmt.Sscanf(name, "tun%d", &ifIndex)
+		if err != nil || ifIndex < 0 {
+			return nil, fmt.Errorf("Interface name must be tun[0-9]*")
+		}
+	}
+
+	var tunfile *os.File
+	var err error
+
+	if ifIndex != -1 {
+		tunfile, err = os.OpenFile(fmt.Sprintf("/dev/tun%d", ifIndex), unix.O_RDWR, 0)
+	} else {
+		for ifIndex = 0; ifIndex < 256; ifIndex += 1 {
+			tunfile, err = os.OpenFile(fmt.Sprintf("/dev/tun%d", ifIndex), unix.O_RDWR, 0)
+			if err == nil || !errorIsEBUSY(err) {
+				break
+			}
+		}
+	}
+
+	if err != nil {
+		return nil, err
+	}
+
+	// Set TUN iface to broadcast mode
+	ifmodemode := unix.IFF_BROADCAST
+	_, _, errno := unix.Syscall(
+		unix.SYS_IOCTL,
+		uintptr(tunfile.Fd()),
+		uintptr(_TUNSIFMODE),
+		uintptr(unsafe.Pointer(&ifmodemode)),
+	)
+
+	if errno != 0 {
+		return nil, fmt.Errorf("error %s", errno.Error())
+	}
+
+	tun, err := CreateTUNFromFile(tunfile)
+
+	if err == nil && name == "tun" {
+		fname := os.Getenv("WG_TUN_NAME_FILE")
+		if fname != "" {
+			ioutil.WriteFile(fname, []byte(tun.(*NativeTun).name+"\n"), 0400)
+		}
+	}
+
+	return tun, err
+}
+
+func CreateTUNFromFile(file *os.File) (TUNDevice, error) {
+
+	tun := &NativeTun{
+		fd:     file,
+		events: make(chan TUNEvent, 10),
+		errors: make(chan error, 1),
+	}
+
+	name, err := tun.Name()
+	if err != nil {
+		tun.fd.Close()
+		return nil, err
+	}
+
+	tunIfindex, err := func() (int, error) {
+		iface, err := net.InterfaceByName(name)
+		if err != nil {
+			return -1, err
+		}
+		return iface.Index, nil
+	}()
+	if err != nil {
+		tun.fd.Close()
+		return nil, err
+	}
+
+	tun.rwcancel, err = rwcancel.NewRWCancel(int(file.Fd()))
+	if err != nil {
+		tun.fd.Close()
+		return nil, err
+	}
+
+	tun.routeSocket, err = unix.Socket(unix.AF_ROUTE, unix.SOCK_RAW, unix.AF_UNSPEC)
+	if err != nil {
+		tun.fd.Close()
+		return nil, err
+	}
+
+	go tun.RoutineRouteListener(tunIfindex)
+
+	// set default MTU
+	err = tun.setMTU(DefaultMTU)
+	if err != nil {
+		tun.Close()
+		return nil, err
+	}
+
+	return tun, nil
+}
+
+func (tun *NativeTun) Name() (string, error) {
+	gostat, err := tun.fd.Stat()
+	if err != nil {
+		tun.name = ""
+		return "", err
+	}
+	stat := gostat.Sys().(*syscall.Stat_t)
+	tun.name = fmt.Sprintf("tun%d", stat.Rdev%256)
+	return tun.name, nil
+}
+
+func (tun *NativeTun) File() *os.File {
+	return tun.fd
+}
+
+func (tun *NativeTun) Events() chan TUNEvent {
+	return tun.events
+}
+
+func (tun *NativeTun) doRead(buff []byte, offset int) (int, error) {
+	select {
+	case err := <-tun.errors:
+		return 0, err
+	default:
+		buff := buff[offset-4:]
+		n, err := tun.fd.Read(buff[:])
+		if n < 4 {
+			return 0, err
+		}
+		return n - 4, err
+	}
+}
+
+func (tun *NativeTun) Read(buff []byte, offset int) (int, error) {
+	for {
+		n, err := tun.doRead(buff, offset)
+		if err == nil || !rwcancel.ErrorIsEAGAIN(err) {
+			return n, err
+		}
+		if !tun.rwcancel.ReadyRead() {
+			return 0, errors.New("tun device closed")
+		}
+	}
+}
+
+func (tun *NativeTun) Write(buff []byte, offset int) (int, error) {
+
+	// reserve space for header
+
+	buff = buff[offset-4:]
+
+	// add packet information header
+
+	buff[0] = 0x00
+	buff[1] = 0x00
+	buff[2] = 0x00
+
+	if buff[4]>>4 == ipv6.Version {
+		buff[3] = unix.AF_INET6
+	} else {
+		buff[3] = unix.AF_INET
+	}
+
+	// write
+
+	return tun.fd.Write(buff)
+}
+
+func (tun *NativeTun) Close() error {
+	var err3 error
+	err1 := tun.rwcancel.Cancel()
+	err2 := tun.fd.Close()
+	if tun.routeSocket != -1 {
+		unix.Shutdown(tun.routeSocket, unix.SHUT_RDWR)
+		err3 = unix.Close(tun.routeSocket)
+		tun.routeSocket = -1
+	} else if tun.events != nil {
+		close(tun.events)
+	}
+	if err1 != nil {
+		return err1
+	}
+	if err2 != nil {
+		return err2
+	}
+	return err3
+}
+
+func (tun *NativeTun) setMTU(n int) error {
+	// open datagram socket
+
+	var fd int
+
+	fd, err := unix.Socket(
+		unix.AF_INET,
+		unix.SOCK_DGRAM,
+		0,
+	)
+
+	if err != nil {
+		return err
+	}
+
+	defer unix.Close(fd)
+
+	// do ioctl call
+
+	var ifr ifreq_mtu
+	copy(ifr.Name[:], tun.name)
+	ifr.MTU = uint32(n)
+
+	_, _, errno := unix.Syscall(
+		unix.SYS_IOCTL,
+		uintptr(fd),
+		uintptr(unix.SIOCSIFMTU),
+		uintptr(unsafe.Pointer(&ifr)),
+	)
+
+	if errno != 0 {
+		return fmt.Errorf("failed to set MTU on %s", tun.name)
+	}
+
+	return nil
+}
+
+func (tun *NativeTun) MTU() (int, error) {
+	// open datagram socket
+
+	fd, err := unix.Socket(
+		unix.AF_INET,
+		unix.SOCK_DGRAM,
+		0,
+	)
+
+	if err != nil {
+		return 0, err
+	}
+
+	defer unix.Close(fd)
+
+	// do ioctl call
+	var ifr ifreq_mtu
+	copy(ifr.Name[:], tun.name)
+
+	_, _, errno := unix.Syscall(
+		unix.SYS_IOCTL,
+		uintptr(fd),
+		uintptr(unix.SIOCGIFMTU),
+		uintptr(unsafe.Pointer(&ifr)),
+	)
+	if errno != 0 {
+		return 0, fmt.Errorf("failed to get MTU on %s", tun.name)
+	}
+
+	// convert result to signed 32-bit int
+	mtu := ifr.MTU
+	if mtu >= (1 << 31) {
+		return int(mtu-(1<<31)) - (1 << 31), nil
+	}
+	return int(mtu), nil
+
+}