Move tun to subpackage

tun/tun.go

@@ -0,0 +1,27 @@
+/* SPDX-License-Identifier: GPL-2.0
+ *
+ * Copyright (C) 2017-2018 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
+ * Copyright (C) 2017-2018 Mathias N. Hall-Andersen <mathias@hall-andersen.dk>.
+ */
+
+package tun
+
+import "os"
+
+type TUNEvent int
+
+const (
+	TUNEventUp = 1 << iota
+	TUNEventDown
+	TUNEventMTUUpdate
+)
+
+type TUNDevice interface {
+	File() *os.File                 // returns the file descriptor of the device
+	Read([]byte, int) (int, error)  // read a packet from the device (without any additional headers)
+	Write([]byte, int) (int, error) // writes a packet to the device (without any additional headers)
+	MTU() (int, error)              // returns the MTU of the device
+	Name() (string, error)          // fetches and returns the current name
+	Events() chan TUNEvent          // returns a constant channel of events related to the device
+	Close() error                   // stops the device and closes the event channel
+}

tun/tun_darwin.go

@@ -0,0 +1,382 @@
+/* SPDX-License-Identifier: GPL-2.0
+ *
+ * Copyright (C) 2017-2018 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
+ * Copyright (C) 2017-2018 Mathias N. Hall-Andersen <mathias@hall-andersen.dk>.
+ */
+
+package tun
+
+import (
+	"../rwcancel"
+	"errors"
+	"fmt"
+	"golang.org/x/net/ipv6"
+	"golang.org/x/sys/unix"
+	"io/ioutil"
+	"net"
+	"os"
+	"unsafe"
+)
+
+const utunControlName = "com.apple.net.utun_control"
+
+// _CTLIOCGINFO value derived from /usr/include/sys/{kern_control,ioccom}.h
+const _CTLIOCGINFO = (0x40000000 | 0x80000000) | ((100 & 0x1fff) << 16) | uint32(byte('N'))<<8 | 3
+
+// sockaddr_ctl specifeid in /usr/include/sys/kern_control.h
+type sockaddrCtl struct {
+	scLen      uint8
+	scFamily   uint8
+	ssSysaddr  uint16
+	scID       uint32
+	scUnit     uint32
+	scReserved [5]uint32
+}
+
+type nativeTun struct {
+	name        string
+	fd          *os.File
+	rwcancel    *rwcancel.RWCancel
+	events      chan TUNEvent
+	errors      chan error
+	routeSocket int
+}
+
+var sockaddrCtlSize uintptr = 32
+
+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 < 14 {
+			continue
+		}
+
+		if data[3 /* type */] != unix.RTM_IFINFO {
+			continue
+		}
+		ifindex := int(*(*uint16)(unsafe.Pointer(&data[12 /* 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 CreateTUN(name string, mtu int) (TUNDevice, error) {
+	ifIndex := -1
+	if name != "utun" {
+		_, err := fmt.Sscanf(name, "utun%d", &ifIndex)
+		if err != nil || ifIndex < 0 {
+			return nil, fmt.Errorf("Interface name must be utun[0-9]*")
+		}
+	}
+
+	fd, err := unix.Socket(unix.AF_SYSTEM, unix.SOCK_DGRAM, 2)
+
+	if err != nil {
+		return nil, err
+	}
+
+	var ctlInfo = &struct {
+		ctlID   uint32
+		ctlName [96]byte
+	}{}
+
+	copy(ctlInfo.ctlName[:], []byte(utunControlName))
+
+	_, _, errno := unix.Syscall(
+		unix.SYS_IOCTL,
+		uintptr(fd),
+		uintptr(_CTLIOCGINFO),
+		uintptr(unsafe.Pointer(ctlInfo)),
+	)
+
+	if errno != 0 {
+		return nil, fmt.Errorf("_CTLIOCGINFO: %v", errno)
+	}
+
+	sc := sockaddrCtl{
+		scLen:     uint8(sockaddrCtlSize),
+		scFamily:  unix.AF_SYSTEM,
+		ssSysaddr: 2,
+		scID:      ctlInfo.ctlID,
+		scUnit:    uint32(ifIndex) + 1,
+	}
+
+	scPointer := unsafe.Pointer(&sc)
+
+	_, _, errno = unix.RawSyscall(
+		unix.SYS_CONNECT,
+		uintptr(fd),
+		uintptr(scPointer),
+		uintptr(sockaddrCtlSize),
+	)
+
+	if errno != 0 {
+		return nil, fmt.Errorf("SYS_CONNECT: %v", errno)
+	}
+
+	tun, err := CreateTUNFromFile(os.NewFile(uintptr(fd), ""), mtu)
+
+	if err == nil && name == "utun" {
+		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) (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)
+
+	err = tun.setMTU(mtu)
+	if err != nil {
+		tun.Close()
+		return nil, err
+	}
+
+	return tun, nil
+}
+
+func (tun *nativeTun) Name() (string, error) {
+
+	var ifName struct {
+		name [16]byte
+	}
+	ifNameSize := uintptr(16)
+
+	_, _, errno := unix.Syscall6(
+		unix.SYS_GETSOCKOPT,
+		uintptr(tun.fd.Fd()),
+		2, /* #define SYSPROTO_CONTROL 2 */
+		2, /* #define UTUN_OPT_IFNAME 2 */
+		uintptr(unsafe.Pointer(&ifName)),
+		uintptr(unsafe.Pointer(&ifNameSize)), 0)
+
+	if errno != 0 {
+		return "", fmt.Errorf("SYS_GETSOCKOPT: %v", errno)
+	}
+
+	tun.name = string(ifName.name[:ifNameSize-1])
+	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 [32]byte
+	copy(ifr[:], tun.name)
+	*(*uint32)(unsafe.Pointer(&ifr[unix.IFNAMSIZ])) = uint32(n)
+	_, _, errno := unix.Syscall(
+		unix.SYS_IOCTL,
+		uintptr(fd),
+		uintptr(unix.SIOCSIFMTU),
+		uintptr(unsafe.Pointer(&ifr[0])),
+	)
+
+	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 [64]byte
+	copy(ifr[:], tun.name)
+	_, _, errno := unix.Syscall(
+		unix.SYS_IOCTL,
+		uintptr(fd),
+		uintptr(unix.SIOCGIFMTU),
+		uintptr(unsafe.Pointer(&ifr[0])),
+	)
+	if errno != 0 {
+		return 0, fmt.Errorf("failed to get MTU on %s", tun.name)
+	}
+
+	return int(*(*int32)(unsafe.Pointer(&ifr[16]))), nil
+}

tun/tun_freebsd.go

@@ -0,0 +1,518 @@
+/* SPDX-License-Identifier: GPL-2.0
+ *
+ * Copyright (C) 2017-2018 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
+ */
+
+package tun
+
+import (
+	"../rwcancel"
+	"bytes"
+	"errors"
+	"fmt"
+	"golang.org/x/net/ipv6"
+	"golang.org/x/sys/unix"
+	"net"
+	"os"
+	"unsafe"
+)
+
+// _TUNSIFHEAD, value derived from sys/net/{if_tun,ioccom}.h
+// const _TUNSIFHEAD = ((0x80000000) | (((4) & ((1 << 13) - 1) ) << 16) | (uint32(byte('t')) << 8) | (96))
+const _TUNSIFHEAD = 0x80047460
+const _TUNSIFMODE = 0x8004745e
+const _TUNSIFPID = 0x2000745f
+
+// Iface status string max len
+const _IFSTATMAX = 800
+
+const SIZEOF_UINTPTR = 4 << (^uintptr(0) >> 32 & 1)
+
+// structure for iface requests with a pointer
+type ifreq_ptr struct {
+	Name [unix.IFNAMSIZ]byte
+	Data uintptr
+	Pad0 [24 - SIZEOF_UINTPTR]byte
+}
+
+// Structure for iface mtu get/set ioctls
+type ifreq_mtu struct {
+	Name [unix.IFNAMSIZ]byte
+	MTU  uint32
+	Pad0 [12]byte
+}
+
+// Structure for interface status request ioctl
+type ifstat struct {
+	IfsName [unix.IFNAMSIZ]byte
+	Ascii   [_IFSTATMAX]byte
+}
+
+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 < 14 {
+			continue
+		}
+
+		if data[3 /* type */] != unix.RTM_IFINFO {
+			continue
+		}
+		ifindex := int(*(*uint16)(unsafe.Pointer(&data[12 /* 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 tunName(fd uintptr) (string, error) {
+	//Terrible hack to make up for freebsd not having a TUNGIFNAME
+
+	//First, make sure the tun pid matches this proc's pid
+	_, _, errno := unix.Syscall(
+		unix.SYS_IOCTL,
+		uintptr(fd),
+		uintptr(_TUNSIFPID),
+		uintptr(0),
+	)
+
+	if errno != 0 {
+		return "", fmt.Errorf("failed to set tun device PID: %s", errno.Error())
+	}
+
+	// Open iface control socket
+
+	confd, err := unix.Socket(
+		unix.AF_INET,
+		unix.SOCK_DGRAM,
+		0,
+	)
+
+	if err != nil {
+		return "", err
+	}
+
+	defer unix.Close(confd)
+
+	procPid := os.Getpid()
+
+	//Try to find interface with matching PID
+	for i := 1; ; i++ {
+		iface, _ := net.InterfaceByIndex(i)
+		if err != nil || iface == nil {
+			break
+		}
+
+		// Structs for getting data in and out of SIOCGIFSTATUS ioctl
+		var ifstatus ifstat
+		copy(ifstatus.IfsName[:], iface.Name)
+
+		// Make the syscall to get the status string
+		_, _, errno := unix.Syscall(
+			unix.SYS_IOCTL,
+			uintptr(confd),
+			uintptr(unix.SIOCGIFSTATUS),
+			uintptr(unsafe.Pointer(&ifstatus)),
+		)
+
+		if errno != 0 {
+			continue
+		}
+
+		nullStr := ifstatus.Ascii[:]
+		i := bytes.IndexByte(nullStr, 0)
+		if i < 1 {
+			continue
+		}
+		statStr := string(nullStr[:i])
+		var pidNum int = 0
+
+		// Finally get the owning PID
+		// Format string taken from sys/net/if_tun.c
+		_, err := fmt.Sscanf(statStr, "\tOpened by PID %d\n", &pidNum)
+		if err != nil {
+			continue
+		}
+
+		if pidNum == procPid {
+			return iface.Name, nil
+		}
+	}
+
+	return "", nil
+}
+
+// Destroy a named system interface
+func tunDestroy(name string) error {
+	// open control 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 [32]byte
+	copy(ifr[:], name)
+	_, _, errno := unix.Syscall(
+		unix.SYS_IOCTL,
+		uintptr(fd),
+		uintptr(unix.SIOCIFDESTROY),
+		uintptr(unsafe.Pointer(&ifr[0])),
+	)
+
+	if errno != 0 {
+		return fmt.Errorf("failed to destroy interface %s: %s", name, errno.Error())
+	}
+
+	return nil
+}
+
+func CreateTUN(name string, mtu int) (TUNDevice, error) {
+	if len(name) > unix.IFNAMSIZ-1 {
+		return nil, errors.New("interface name too long")
+	}
+
+	// See if interface already exists
+	iface, _ := net.InterfaceByName(name)
+	if iface != nil {
+		return nil, fmt.Errorf("interface %s already exists", name)
+	}
+
+	tunfile, err := os.OpenFile("/dev/tun", unix.O_RDWR, 0)
+
+	if err != nil {
+		return nil, err
+	}
+	tunfd := tunfile.Fd()
+	assignedName, err := tunName(tunfd)
+	if err != nil {
+		tunfile.Close()
+		return nil, err
+	}
+
+	// Enable ifhead mode, otherwise tun will complain if it gets a non-AF_INET packet
+	ifheadmode := 1
+	_, _, errno := unix.Syscall(
+		unix.SYS_IOCTL,
+		uintptr(tunfd),
+		uintptr(_TUNSIFHEAD),
+		uintptr(unsafe.Pointer(&ifheadmode)),
+	)
+
+	if errno != 0 {
+		return nil, fmt.Errorf("error %s", errno.Error())
+	}
+
+	// Set TUN iface to broadcast mode. TUN inferfaces on freebsd come up in point to point by default
+	ifmodemode := unix.IFF_BROADCAST
+	_, _, errno = unix.Syscall(
+		unix.SYS_IOCTL,
+		uintptr(tunfd),
+		uintptr(_TUNSIFMODE),
+		uintptr(unsafe.Pointer(&ifmodemode)),
+	)
+
+	if errno != 0 {
+		return nil, fmt.Errorf("error %s", errno.Error())
+	}
+
+	// Rename tun interface
+
+	// Open control socket
+	confd, err := unix.Socket(
+		unix.AF_INET,
+		unix.SOCK_DGRAM,
+		0,
+	)
+
+	if err != nil {
+		return nil, err
+	}
+
+	defer unix.Close(confd)
+
+	// set up struct for iface rename
+	var newnp [unix.IFNAMSIZ]byte
+	copy(newnp[:], name)
+
+	var ifr ifreq_ptr
+	copy(ifr.Name[:], assignedName)
+	ifr.Data = uintptr(unsafe.Pointer(&newnp[0]))
+
+	//do actual ioctl to rename iface
+	_, _, errno = unix.Syscall(
+		unix.SYS_IOCTL,
+		uintptr(confd),
+		uintptr(unix.SIOCSIFNAME),
+		uintptr(unsafe.Pointer(&ifr)),
+	)
+	if errno != 0 {
+		tunfile.Close()
+		tunDestroy(name)
+		return nil, fmt.Errorf("failed to rename %s to %s: %s", assignedName, name, errno.Error())
+	}
+
+	return CreateTUNFromFile(tunfile, mtu)
+}
+
+func CreateTUNFromFile(file *os.File, mtu int) (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)
+
+	err = tun.setMTU(mtu)
+	if err != nil {
+		tun.Close()
+		return nil, err
+	}
+
+	return tun, nil
+}
+
+func (tun *nativeTun) Name() (string, error) {
+	name, err := tunName(tun.fd.Fd())
+	if err != nil {
+		return "", err
+	}
+	tun.name = name
+	return 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 err4 error
+	err1 := tun.rwcancel.Cancel()
+	err2 := tun.fd.Close()
+	err3 := tunDestroy(tun.name)
+	if tun.routeSocket != -1 {
+		unix.Shutdown(tun.routeSocket, unix.SHUT_RDWR)
+		err4 = 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
+	}
+	if err3 != nil {
+		return err3
+	}
+	return err4
+}
+
+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
+}

tun/tun_linux.go

@@ -0,0 +1,468 @@
+/* SPDX-License-Identifier: GPL-2.0
+ *
+ * Copyright (C) 2017-2018 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
+ * Copyright (C) 2017-2018 Mathias N. Hall-Andersen <mathias@hall-andersen.dk>.
+ */
+
+/* Copyright 2018 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved. */
+
+package tun
+
+/* Implementation of the TUN device interface for linux
+ */
+
+import (
+	"../rwcancel"
+	"bytes"
+	"errors"
+	"fmt"
+	"golang.org/x/net/ipv6"
+	"golang.org/x/sys/unix"
+	"net"
+	"os"
+	"strconv"
+	"sync"
+	"time"
+	"unsafe"
+)
+
+const (
+	cloneDevicePath = "/dev/net/tun"
+	ifReqSize       = unix.IFNAMSIZ + 64
+)
+
+type nativeTun struct {
+	fd                      *os.File
+	fdCancel                *rwcancel.RWCancel
+	index                   int32         // if index
+	name                    string        // name of interface
+	errors                  chan error    // async error handling
+	events                  chan TUNEvent // device related events
+	nopi                    bool          // the device was pased IFF_NO_PI
+	netlinkSock             int
+	netlinkCancel           *rwcancel.RWCancel
+	hackListenerClosed      sync.Mutex
+	statusListenersShutdown chan struct{}
+}
+
+func (tun *nativeTun) File() *os.File {
+	return tun.fd
+}
+
+func (tun *nativeTun) routineHackListener() {
+	defer tun.hackListenerClosed.Unlock()
+	/* This is needed for the detection to work across network namespaces
+	 * If you are reading this and know a better method, please get in touch.
+	 */
+	fd := int(tun.fd.Fd())
+	for {
+		_, err := unix.Write(fd, nil)
+		switch err {
+		case unix.EINVAL:
+			tun.events <- TUNEventUp
+		case unix.EIO:
+			tun.events <- TUNEventDown
+		default:
+			return
+		}
+		select {
+		case <-time.After(time.Second):
+		case <-tun.statusListenersShutdown:
+			return
+		}
+	}
+}
+
+func createNetlinkSocket() (int, error) {
+	sock, err := unix.Socket(unix.AF_NETLINK, unix.SOCK_RAW, unix.NETLINK_ROUTE)
+	if err != nil {
+		return -1, err
+	}
+	saddr := &unix.SockaddrNetlink{
+		Family: unix.AF_NETLINK,
+		Groups: uint32((1 << (unix.RTNLGRP_LINK - 1)) | (1 << (unix.RTNLGRP_IPV4_IFADDR - 1)) | (1 << (unix.RTNLGRP_IPV6_IFADDR - 1))),
+	}
+	err = unix.Bind(sock, saddr)
+	if err != nil {
+		return -1, err
+	}
+	return sock, nil
+}
+
+func (tun *nativeTun) routineNetlinkListener() {
+	defer func() {
+		unix.Close(tun.netlinkSock)
+		tun.hackListenerClosed.Lock()
+		close(tun.events)
+	}()
+
+	for msg := make([]byte, 1<<16); ; {
+
+		var err error
+		var msgn int
+		for {
+			msgn, _, _, _, err = unix.Recvmsg(tun.netlinkSock, msg[:], nil, 0)
+			if err == nil || !rwcancel.ErrorIsEAGAIN(err) {
+				break
+			}
+			if !tun.netlinkCancel.ReadyRead() {
+				tun.errors <- fmt.Errorf("netlink socket closed: %s", err.Error())
+				return
+			}
+		}
+		if err != nil {
+			tun.errors <- fmt.Errorf("failed to receive netlink message: %s", err.Error())
+			return
+		}
+
+		select {
+		case <-tun.statusListenersShutdown:
+			return
+		default:
+		}
+
+		for remain := msg[:msgn]; len(remain) >= unix.SizeofNlMsghdr; {
+
+			hdr := *(*unix.NlMsghdr)(unsafe.Pointer(&remain[0]))
+
+			if int(hdr.Len) > len(remain) {
+				break
+			}
+
+			switch hdr.Type {
+			case unix.NLMSG_DONE:
+				remain = []byte{}
+
+			case unix.RTM_NEWLINK:
+				info := *(*unix.IfInfomsg)(unsafe.Pointer(&remain[unix.SizeofNlMsghdr]))
+				remain = remain[hdr.Len:]
+
+				if info.Index != tun.index {
+					// not our interface
+					continue
+				}
+
+				if info.Flags&unix.IFF_RUNNING != 0 {
+					tun.events <- TUNEventUp
+				}
+
+				if info.Flags&unix.IFF_RUNNING == 0 {
+					tun.events <- TUNEventDown
+				}
+
+				tun.events <- TUNEventMTUUpdate
+
+			default:
+				remain = remain[hdr.Len:]
+			}
+		}
+	}
+}
+
+func (tun *nativeTun) isUp() (bool, error) {
+	inter, err := net.InterfaceByName(tun.name)
+	return inter.Flags&net.FlagUp != 0, err
+}
+
+func getDummySock() (int, error) {
+	return unix.Socket(
+		unix.AF_INET,
+		unix.SOCK_DGRAM,
+		0,
+	)
+}
+
+func getIFIndex(name string) (int32, error) {
+	fd, err := getDummySock()
+	if err != nil {
+		return 0, err
+	}
+
+	defer unix.Close(fd)
+
+	var ifr [ifReqSize]byte
+	copy(ifr[:], name)
+	_, _, errno := unix.Syscall(
+		unix.SYS_IOCTL,
+		uintptr(fd),
+		uintptr(unix.SIOCGIFINDEX),
+		uintptr(unsafe.Pointer(&ifr[0])),
+	)
+
+	if errno != 0 {
+		return 0, errno
+	}
+
+	return *(*int32)(unsafe.Pointer(&ifr[unix.IFNAMSIZ])), nil
+}
+
+func (tun *nativeTun) setMTU(n int) error {
+
+	// open datagram socket
+
+	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 [ifReqSize]byte
+	copy(ifr[:], tun.name)
+	*(*uint32)(unsafe.Pointer(&ifr[unix.IFNAMSIZ])) = uint32(n)
+	_, _, errno := unix.Syscall(
+		unix.SYS_IOCTL,
+		uintptr(fd),
+		uintptr(unix.SIOCSIFMTU),
+		uintptr(unsafe.Pointer(&ifr[0])),
+	)
+
+	if errno != 0 {
+		return errors.New("failed to set MTU of TUN device")
+	}
+
+	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 [ifReqSize]byte
+	copy(ifr[:], tun.name)
+	_, _, errno := unix.Syscall(
+		unix.SYS_IOCTL,
+		uintptr(fd),
+		uintptr(unix.SIOCGIFMTU),
+		uintptr(unsafe.Pointer(&ifr[0])),
+	)
+	if errno != 0 {
+		return 0, errors.New("failed to get MTU of TUN device: " + strconv.FormatInt(int64(errno), 10))
+	}
+
+	return int(*(*int32)(unsafe.Pointer(&ifr[unix.IFNAMSIZ]))), nil
+}
+
+func (tun *nativeTun) Name() (string, error) {
+
+	var ifr [ifReqSize]byte
+	_, _, errno := unix.Syscall(
+		unix.SYS_IOCTL,
+		tun.fd.Fd(),
+		uintptr(unix.TUNGETIFF),
+		uintptr(unsafe.Pointer(&ifr[0])),
+	)
+	if errno != 0 {
+		return "", errors.New("failed to get name of TUN device: " + strconv.FormatInt(int64(errno), 10))
+	}
+	nullStr := ifr[:]
+	i := bytes.IndexByte(nullStr, 0)
+	if i != -1 {
+		nullStr = nullStr[:i]
+	}
+	tun.name = string(nullStr)
+	return tun.name, nil
+}
+
+func (tun *nativeTun) Write(buff []byte, offset int) (int, error) {
+
+	if tun.nopi {
+		buff = buff[offset:]
+	} else {
+		// reserve space for header
+
+		buff = buff[offset-4:]
+
+		// add packet information header
+
+		buff[0] = 0x00
+		buff[1] = 0x00
+
+		if buff[4]>>4 == ipv6.Version {
+			buff[2] = 0x86
+			buff[3] = 0xdd
+		} else {
+			buff[2] = 0x08
+			buff[3] = 0x00
+		}
+	}
+
+	// write
+
+	return tun.fd.Write(buff)
+}
+
+func (tun *nativeTun) doRead(buff []byte, offset int) (int, error) {
+	select {
+	case err := <-tun.errors:
+		return 0, err
+	default:
+		if tun.nopi {
+			return tun.fd.Read(buff[offset:])
+		} else {
+			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.fdCancel.ReadyRead() {
+			return 0, errors.New("tun device closed")
+		}
+	}
+}
+
+func (tun *nativeTun) Events() chan TUNEvent {
+	return tun.events
+}
+
+func (tun *nativeTun) Close() error {
+	var err1 error
+	if tun.statusListenersShutdown != nil {
+		close(tun.statusListenersShutdown)
+		if tun.netlinkCancel != nil {
+			err1 = tun.netlinkCancel.Cancel()
+		}
+	} else if tun.events != nil {
+		close(tun.events)
+	}
+	err2 := tun.fd.Close()
+	err3 := tun.fdCancel.Cancel()
+
+	if err1 != nil {
+		return err1
+	}
+	if err2 != nil {
+		return err2
+	}
+	return err3
+}
+
+func CreateTUN(name string, mtu int) (TUNDevice, error) {
+
+	// open clone device
+
+	// HACK: we open it as a raw Fd first, so that f.nonblock=false
+	// when we make it into a file object.
+	nfd, err := unix.Open(cloneDevicePath, os.O_RDWR, 0)
+	if err != nil {
+		return nil, err
+	}
+
+	err = unix.SetNonblock(nfd, true)
+	if err != nil {
+		return nil, err
+	}
+
+	fd := os.NewFile(uintptr(nfd), cloneDevicePath)
+	if err != nil {
+		return nil, err
+	}
+
+	// create new device
+
+	var ifr [ifReqSize]byte
+	var flags uint16 = unix.IFF_TUN // | unix.IFF_NO_PI (disabled for TUN status hack)
+	nameBytes := []byte(name)
+	if len(nameBytes) >= unix.IFNAMSIZ {
+		return nil, errors.New("interface name too long")
+	}
+	copy(ifr[:], nameBytes)
+	*(*uint16)(unsafe.Pointer(&ifr[unix.IFNAMSIZ])) = flags
+
+	_, _, errno := unix.Syscall(
+		unix.SYS_IOCTL,
+		fd.Fd(),
+		uintptr(unix.TUNSETIFF),
+		uintptr(unsafe.Pointer(&ifr[0])),
+	)
+	if errno != 0 {
+		return nil, errno
+	}
+
+	return CreateTUNFromFile(fd, mtu)
+}
+
+func CreateTUNFromFile(file *os.File, mtu int) (TUNDevice, error) {
+	tun := &nativeTun{
+		fd:                      file,
+		events:                  make(chan TUNEvent, 5),
+		errors:                  make(chan error, 5),
+		statusListenersShutdown: make(chan struct{}),
+		nopi: false,
+	}
+	var err error
+
+	tun.fdCancel, err = rwcancel.NewRWCancel(int(file.Fd()))
+	if err != nil {
+		tun.fd.Close()
+		return nil, err
+	}
+
+	_, err = tun.Name()
+	if err != nil {
+		tun.fd.Close()
+		return nil, err
+	}
+
+	// start event listener
+
+	tun.index, err = getIFIndex(tun.name)
+	if err != nil {
+		return nil, err
+	}
+
+	tun.netlinkSock, err = createNetlinkSocket()
+	if err != nil {
+		tun.fd.Close()
+		return nil, err
+	}
+	tun.netlinkCancel, err = rwcancel.NewRWCancel(tun.netlinkSock)
+	if err != nil {
+		tun.fd.Close()
+		return nil, err
+	}
+
+	tun.hackListenerClosed.Lock()
+	go tun.routineNetlinkListener()
+	go tun.routineHackListener() // cross namespace
+
+	err = tun.setMTU(mtu)
+	if err != nil {
+		tun.Close()
+		return nil, err
+	}
+
+	return tun, nil
+}

tun/tun_openbsd.go

@@ -0,0 +1,359 @@
+/* SPDX-License-Identifier: GPL-2.0
+ *
+ * Copyright (C) 2017-2018 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
+ */
+
+package tun
+
+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, mtu int) (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, mtu)
+
+	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) (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)
+
+	err = tun.setMTU(mtu)
+	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)
+	}
+
+	return int(*(*int32)(unsafe.Pointer(&ifr.MTU))), nil
+}