handshake: hand in client fd on exec instead of gratuitous fd passing.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

lightningd/handshake/handshake.c

@@ -965,12 +965,12 @@ static void responder(int fd,
 }
 
 #ifndef TESTING
-/* We expect hsmfd as fd 3, then a request then the clientfd */
+/* We expect hsmfd as fd 3, clientfd as 4 */
 int main(int argc, char *argv[])
 {
 	u8 *msg;
 	struct pubkey my_id, their_id;
-	int hsmfd = 3, clientfd;
+	int hsmfd = 3, clientfd = 4;
 	struct secret ck, rk, sk;
 	struct crypto_state *cs;
 
@@ -989,7 +989,6 @@ int main(int argc, char *argv[])
 	msg = wire_sync_read(NULL, REQ_FD);
 	if (!msg)
 		status_failed(WIRE_BAD_COMMAND, "%s", strerror(errno));
-	clientfd = fdpass_recv(REQ_FD);
 	if (clientfd < 0)
 		status_failed(WIRE_BAD_FDPASS, "%s", strerror(errno));
 

lightningd/peer_control.c

@@ -147,7 +147,7 @@ static void peer_got_hsmfd(struct subdaemon *hsm, const u8 *msg,
 				    handshake_status_wire_type_name,
 				    handshake_control_wire_type_name,
 				    NULL, NULL,
-				    peer->hsmfd, -1);
+				    peer->hsmfd, peer->fd, -1);
 	if (!peer->owner) {
 		log_unusual(peer->ld->log, "Could not subdaemon handshake: %s",
 			    strerror(errno));
@@ -155,6 +155,9 @@ static void peer_got_hsmfd(struct subdaemon *hsm, const u8 *msg,
 		goto error;
 	}
 
+	/* Peer struct longer owns fd. */
+	peer->fd = -1;
+
 	/* Now handshake owns peer: until it succeeds, peer vanishes
 	 * when it does. */
 	tal_steal(peer->owner, peer);
@@ -168,13 +171,10 @@ static void peer_got_hsmfd(struct subdaemon *hsm, const u8 *msg,
 		peer_set_condition(peer, "Starting handshake as responder");
 	}
 
-	/* Now hand peer fd to the handshake daemon, it hand back on success */
-	subdaemon_req(peer->owner, take(req),
-		      peer->fd, &peer->fd,
+	/* Now hand peer request to the handshake daemon: hands it
+	 * back on success */
+	subdaemon_req(peer->owner, take(req), -1, &peer->fd,
 		      handshake_succeeded, peer);
-
-	/* Peer struct longer owns fd. */
-	peer->fd = -1;
 	return;
 
 error: