tun_device: add a getter for the underlying file descriptor

src/libstrongswan/networking/tun_device.c

@@ -192,6 +192,12 @@ METHOD(tun_device_t, get_name, char*,
 	return this->if_name;
 }
 
+METHOD(tun_device_t, get_fd, int,
+	private_tun_device_t *this)
+{
+	return this->tunfd;
+}
+
 METHOD(tun_device_t, write_packet, bool,
 	private_tun_device_t *this, chunk_t packet)
 {
@@ -398,6 +404,7 @@ tun_device_t *tun_device_create(const char *name_tmpl)
 			.get_mtu = _get_mtu,
 			.set_mtu = _set_mtu,
 			.get_name = _get_name,
+			.get_fd = _get_fd,
 			.set_address = _set_address,
 			.up = _up,
 			.destroy = _destroy,

src/libstrongswan/networking/tun_device.h

@@ -94,6 +94,13 @@ struct tun_device_t {
 	 */
 	char *(*get_name)(tun_device_t *this);
 
+	/**
+	 * Get the underlying tun file descriptor.
+	 *
+	 * @return				file descriptor of this tun device
+	 */
+	int (*get_fd)(tun_device_t *this);
+
 	/**
 	 * Destroy a tun_device_t
 	 */