Added a tls_socket_t.splice method to wrap a file descriptor into TLS

src/libtls/tls_socket.h

@@ -54,6 +54,18 @@ struct tls_socket_t {
 	 */
 	bool (*write)(tls_socket_t *this, chunk_t data);
 
+	/**
+	 * Read/write plain data from file descriptor.
+	 *
+	 * This call is blocking, but a thread cancellation point. Data is
+	 * exchanged until one of the sockets gets closed or an error occurs.
+	 *
+	 * @param rfd		file descriptor to read plain data from
+	 * @param wfd		file descriptor to write plain data to
+	 * @return			TRUE if data exchanged successfully
+	 */
+	bool (*splice)(tls_socket_t *this, int rfd, int wfd);
+
 	/**
 	 * Get the underlying file descriptor passed to the constructor.
 	 *