Add support for NetBSD tun(4) interface

ipc/uapi_bsd.go

@@ -1,4 +1,4 @@
-//go:build darwin || freebsd || openbsd
+//go:build darwin || freebsd || openbsd || netbsd
 
 /* SPDX-License-Identifier: MIT
  *

ipc/uapi_unix.go

@@ -1,4 +1,4 @@
-//go:build linux || darwin || freebsd || openbsd
+//go:build linux || darwin || freebsd || openbsd || netbsd
 
 /* SPDX-License-Identifier: MIT
  *

tun/tun_netbsd.go

@@ -0,0 +1,374 @@
+/* SPDX-License-Identifier: MIT
+ *
+ * Copyright (C) 2017-2020 WireGuard LLC. All Rights Reserved.
+ */
+
+package tun
+
+import (
+	"fmt"
+	"io/ioutil"
+	"net"
+	"os"
+	"syscall"
+	"unsafe"
+
+	"golang.org/x/net/ipv6"
+	"golang.org/x/sys/unix"
+)
+
+// Structure for iface mtu get/set ioctls
+type ifreq_mtu struct {
+	Name [unix.IFNAMSIZ]byte
+	MTU  uint32
+	Pad0 [12]byte
+}
+
+const (
+    _TUNGIFHEAD = 0x40047441
+    _TUNSIFMODE = 0x80047458
+    _TUNSIFHEAD = 0x80047442
+)
+
+type NativeTun struct {
+	name        string
+	tunFile     *os.File
+	events      chan Event
+	errors      chan error
+	routeSocket int
+}
+
+func (tun *NativeTun) routineRouteListener(tunIfindex int) {
+	var (
+		statusUp  bool
+		statusMTU int
+	)
+
+	defer close(tun.events)
+
+	check := func() bool {
+		iface, err := net.InterfaceByIndex(tunIfindex)
+		if err != nil {
+			tun.errors <- err
+			return true
+		}
+
+		// Up / Down event
+		up := (iface.Flags & net.FlagUp) != 0
+		if up != statusUp && up {
+			tun.events <- EventUp
+		}
+		if up != statusUp && !up {
+			tun.events <- EventDown
+		}
+		statusUp = up
+
+		// MTU changes
+		if iface.MTU != statusMTU {
+			tun.events <- EventMTUUpdate
+		}
+		statusMTU = iface.MTU
+		return false
+	}
+
+	if check() {
+		return
+	}
+
+	data := make([]byte, os.Getpagesize())
+	for {
+		n, err := unix.Read(tun.routeSocket, data)
+		if err != nil {
+			if errno, ok := err.(syscall.Errno); ok && errno == syscall.EINTR {
+				continue
+			}
+			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
+		}
+		if check() {
+			return
+		}
+	}
+}
+
+func errorIsEBUSY(err error) bool {
+	if pe, ok := err.(*os.PathError); ok {
+		err = pe.Err
+	}
+	if errno, ok := err.(syscall.Errno); ok && errno == syscall.EBUSY {
+		return true
+	}
+	return false
+}
+
+func CreateTUN(name string, mtu int) (Device, 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
+	}
+
+	tun, err := CreateTUNFromFile(tunfile, mtu)
+
+	// Enable ifhead mode, otherwise tun will complain if it gets a non-AF_INET packet
+	ifheadmode := 1
+	var errno syscall.Errno
+    _, _, errno = unix.Syscall(
+        unix.SYS_IOCTL,
+        tunfile.Fd(),
+        uintptr(_TUNSIFHEAD),
+        uintptr(unsafe.Pointer(&ifheadmode)),
+    )
+
+    if errno != 0 {
+        tunfile.Close()
+        return nil, fmt.Errorf("Unable to put into IFHEAD mode: %v", errno)
+    }
+
+    _, _, errno = unix.Syscall(
+        unix.SYS_IOCTL,
+        tunfile.Fd(),
+        uintptr(_TUNGIFHEAD),
+        uintptr(unsafe.Pointer(&ifheadmode)),
+    )
+
+    if errno != 0 || ifheadmode != 1 {
+        tunfile.Close()
+        return nil, fmt.Errorf("Unable to validate IFHEAD mode: %v (ifheadmode = %d)", errno, ifheadmode)
+    }
+
+	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, mtu int) (Device, error) {
+	tun := &NativeTun{
+		tunFile: file,
+		events:  make(chan Event, 10),
+		errors:  make(chan error, 1),
+	}
+
+	name, err := tun.Name()
+	if err != nil {
+		tun.tunFile.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.tunFile.Close()
+		return nil, err
+	}
+
+	tun.routeSocket, err = unix.Socket(unix.AF_ROUTE, unix.SOCK_RAW, unix.AF_UNSPEC)
+	if err != nil {
+		tun.tunFile.Close()
+		return nil, err
+	}
+
+	go tun.routineRouteListener(tunIfindex)
+
+	currentMTU, err := tun.MTU()
+	if err != nil || currentMTU != mtu {
+		err = tun.setMTU(mtu)
+		if err != nil {
+			tun.Close()
+			return nil, err
+		}
+	}
+
+	return tun, nil
+}
+
+func (tun *NativeTun) Name() (string, error) {
+	gostat, err := tun.tunFile.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.tunFile
+}
+
+func (tun *NativeTun) Events() chan Event {
+	return tun.events
+}
+
+func (tun *NativeTun) Read(buff []byte, offset int) (int, error) {
+	select {
+	case err := <-tun.errors:
+		return 0, err
+	default:
+		buff := buff[offset-4:]
+        // buff := buff[offset:]
+		n, err := tun.tunFile.Read(buff[:])
+		if n < 4 {
+			return 0, err
+		}
+		return n - 4, err
+        // return n, err
+	}
+}
+
+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.tunFile.Write(buff)
+}
+
+func (tun *NativeTun) Flush() error {
+	// TODO: can flushing be implemented by buffering and using sendmmsg?
+	return nil
+}
+
+func (tun *NativeTun) Close() error {
+	var err2 error
+	err1 := tun.tunFile.Close()
+	if tun.routeSocket != -1 {
+		unix.Shutdown(tun.routeSocket, unix.SHUT_RDWR)
+		err2 = unix.Close(tun.routeSocket)
+		tun.routeSocket = -1
+	} else if tun.events != nil {
+		close(tun.events)
+	}
+	if err1 != nil {
+		return err1
+	}
+	return err2
+}
+
+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)
+	}
+
+	return int(*(*int32)(unsafe.Pointer(&ifr.MTU))), nil
+}