1 files changed, 28 insertions, 1 deletions
diff --git a/src/tun_linux.go b/src/tun_linux.go
index accc6c6..a728a48 100644
--- a/src/tun_linux.go
+++ b/src/tun_linux.go
@@ -56,6 +56,10 @@ type NativeTun struct {
 	events chan TUNEvent // device related events
 }
 
+func (tun *NativeTun) File() *os.File {
+	return tun.fd
+}
+
 func (tun *NativeTun) RoutineNetlinkListener() {
 	sock := int(C.bind_rtmgrp())
 	if sock < 0 {
@@ -222,7 +226,7 @@ func (tun *NativeTun) MTU() (int, error) {
 
 	val := binary.LittleEndian.Uint32(ifr[16:20])
 	if val >= (1 << 31) {
-		return int(val-(1<<31)) - (1 << 31), nil
+		return int(toInt32(val)), nil
 	}
 	return int(val), nil
 }
@@ -248,6 +252,29 @@ func (tun *NativeTun) Close() error {
 	return nil
 }
 
+func CreateTUNFromFile(name string, fd *os.File) (TUNDevice, error) {
+	device := &NativeTun{
+		fd:     fd,
+		name:   name,
+		events: make(chan TUNEvent, 5),
+		errors: make(chan error, 5),
+	}
+
+	// start event listener
+
+	var err error
+	device.index, err = getIFIndex(device.name)
+	if err != nil {
+		return nil, err
+	}
+
+	go device.RoutineNetlinkListener()
+
+	// set default MTU
+
+	return device, device.setMTU(DefaultMTU)
+}
+
 func CreateTUN(name string) (TUNDevice, error) {
 
 	// open clone device