Add FreeBSD support

Signed-off-by: Brady OBrien <brady.obrien128@gmail.com>

tun_freebsd.go

@@ -0,0 +1,507 @@
+/* SPDX-License-Identifier: GPL-2.0
+ *
+ * Copyright (C) 2017-2018 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
+ */
+
+package main
+
+import (
+	"./rwcancel"
+	"bytes"
+	"errors"
+	"fmt"
+	"golang.org/x/net/ipv6"
+	"golang.org/x/sys/unix"
+	"io/ioutil"
+	"net"
+	"os"
+	"path/filepath"
+	"time"
+	"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
+
+// Structure for iface mtu get/set ioctls
+type ifreq_mtu struct {
+	Name [_IFNAMESIZ]byte
+	MTU  uint32
+	Pad0 [12]byte
+}
+
+// Structure for interface status request ioctl
+type ifstat struct {
+	IfsName [_IFNAMESIZ]byte
+	Ascii   [_IFSTATMAX]byte
+}
+
+// NativeTun is a hack to work around the first 4 bytes "packet
+// information" because there doesn't seem to be an IFF_NO_PI for darwin.
+type NativeTun struct {
+	name                    string
+	fd                      *os.File
+	rwcancel                *rwcancel.RWCancel
+	mtu                     int
+	events                  chan TUNEvent
+	errors                  chan error
+	statusListenersShutdown chan struct{}
+}
+
+// Figure out the interface name for an open tun device file descriptor
+func TunIfaceName(f *os.File) (string, error) {
+	//Terrible hack to make up for freebsd not having a TUNGIFNAME
+
+	fd := f.Fd()
+	//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,
+	)
+
+	defer unix.Close(confd)
+
+	if err != nil {
+		return "", err
+	}
+
+	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
+		ifname := iface.Name
+		copy(ifstatus.IfsName[:], ifname)
+
+		// 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
+		}
+		if i != -1 {
+			nullStr = nullStr[:i]
+		}
+		statStr := string(nullStr)
+		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 {
+			return "", err
+		}
+
+		if pidNum == procPid {
+			return ifname, nil
+		}
+
+	}
+
+	return "", nil
+}
+
+// Destroy a named system interface
+func DestroyIface(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) (TUNDevice, error) {
+	if len(name) > _IFNAMESIZ-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
+	}
+
+	nameif, err := TunIfaceName(tunfile)
+
+	if err != nil {
+		tunfile.Close()
+		return nil, err
+	}
+
+	tunfd := tunfile.Fd()
+
+	// 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
+	 * 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
+	ctfd, err := unix.Socket(
+		unix.AF_INET,
+		unix.SOCK_DGRAM,
+		0,
+	)
+
+	if err != nil {
+		return nil, err
+	}
+
+	defer unix.Close(ctfd)
+
+	// set up struct for iface rename
+	var newnp [_IFNAMESIZ]byte
+	copy(newnp[:], name)
+
+	var ifr ifreq_ptr
+	copy(ifr.Name[:], nameif)
+	ifr.Data = uintptr(unsafe.Pointer(&newnp[0]))
+
+	//do actual ioctl to rename iface
+	_, _, errno = unix.Syscall(
+		unix.SYS_IOCTL,
+		uintptr(ctfd),
+		uintptr(unix.SIOCSIFNAME),
+		uintptr(unsafe.Pointer(&ifr)),
+	)
+	if errno != 0 {
+		tunfile.Close()
+		DestroyIface(name)
+		return nil, fmt.Errorf("Failed to rename %s to %s: %s", nameif, name, errno.Error())
+	}
+
+	tun, err := CreateTUNFromFile(tunfile)
+
+	if err != nil {
+		return nil, err
+	}
+
+	if err == nil && name == "tun" {
+		fname := os.Getenv("WG_FREEBSD_TUN_NAME_FILE")
+		if fname != "" {
+			os.MkdirAll(filepath.Dir(fname), 0700)
+			ioutil.WriteFile(fname, []byte(tun.(*NativeTun).name+"\n"), 0400)
+		}
+	}
+
+	return tun, err
+}
+
+func CreateTUNFromFile(file *os.File) (TUNDevice, error) {
+
+	tun := &NativeTun{
+		fd:                      file,
+		mtu:                     1500,
+		events:                  make(chan TUNEvent, 10),
+		errors:                  make(chan error, 1),
+		statusListenersShutdown: make(chan struct{}),
+	}
+
+	_, err := tun.Name()
+
+	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
+	}
+
+	// TODO: Fix this very naive implementation
+	go func(tun *NativeTun) {
+		var (
+			statusUp  bool
+			statusMTU int
+		)
+
+		for {
+			intr, err := net.InterfaceByName(tun.name)
+			if err != nil {
+				tun.errors <- err
+				return
+			}
+
+			// Up / Down event
+			up := (intr.Flags & net.FlagUp) != 0
+			if up != statusUp && up {
+				tun.events <- TUNEventUp
+			}
+			if up != statusUp && !up {
+				tun.events <- TUNEventDown
+			}
+			statusUp = up
+
+			// MTU changes
+			if intr.MTU != statusMTU {
+				tun.events <- TUNEventMTUUpdate
+			}
+			statusMTU = intr.MTU
+
+			select {
+			case <-time.After(time.Second / 10):
+			case <-tun.statusListenersShutdown:
+				return
+			}
+		}
+	}(tun)
+
+	// set default MTU
+	err = tun.setMTU(DefaultMTU)
+	if err != nil {
+		tun.Close()
+		return nil, err
+	}
+
+	return tun, nil
+}
+
+func (tun *NativeTun) Name() (string, error) {
+	name, err := TunIfaceName(tun.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 {
+	close(tun.statusListenersShutdown)
+	err1 := tun.rwcancel.Cancel()
+	err2 := tun.fd.Close()
+	err3 := DestroyIface(tun.name)
+	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
+
+}