Expose windows Fd

.gitignore

@@ -1 +1,2 @@
 water.test
+.idea

syscalls_windows.go

@@ -88,19 +88,19 @@ func newOverlapped() (*syscall.Overlapped, error) {
 	return &overlapped, nil
 }
 
-type wfile struct {
+type File struct {
 	fd syscall.Handle
 	rl sync.Mutex
 	wl sync.Mutex
 	ro *syscall.Overlapped
 	wo *syscall.Overlapped
 }
 
-func (f *wfile) Close() error {
+func (f *File) Close() error {
 	return syscall.Close(f.fd)
 }
 
-func (f *wfile) Write(b []byte) (int, error) {
+func (f *File) Write(b []byte) (int, error) {
 	f.wl.Lock()
 	defer f.wl.Unlock()
 
@@ -115,7 +115,7 @@ func (f *wfile) Write(b []byte) (int, error) {
 	return getOverlappedResult(f.fd, f.wo)
 }
 
-func (f *wfile) Read(b []byte) (int, error) {
+func (f *File) Read(b []byte) (int, error) {
 	f.rl.Lock()
 	defer f.rl.Unlock()
 
@@ -130,6 +130,10 @@ func (f *wfile) Read(b []byte) (int, error) {
 	return getOverlappedResult(f.fd, f.ro)
 }
 
+func (f *File) Fd()syscall.Handle{
+	return f.fd
+}
+
 func ctl_code(device_type, function, method, access uint32) uint32 {
 	return (device_type << 16) | (access << 14) | (function << 2) | method
 }
@@ -257,7 +261,7 @@ func openDev(config Config) (ifce *Interface, err error) {
 	if err != nil {
 		return
 	}
-	fd := &wfile{fd: file, ro: ro, wo: wo}
+	fd := &File{fd: file, ro: ro, wo: wo}
 	ifce = &Interface{isTAP: (config.DeviceType == TAP), ReadWriteCloser: fd}
 
 	// bring up device.