subd: use array of fd pointers, not fds, and use take().

This lets us specify that we want to keep some fds.

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

lightningd/gossip_control.c

@@ -152,7 +152,7 @@ void gossip_init(struct lightningd *ld)
 	u8 *init;
 	ld->gossip = new_subd(ld, ld, "lightningd_gossip", NULL,
 			      gossip_wire_type_name,
-			      gossip_msg, gossip_finished, -1);
+			      gossip_msg, gossip_finished, NULL);
 	if (!ld->gossip)
 		err(1, "Could not subdaemon gossip");
 

lightningd/hsm_control.c

@@ -92,7 +92,7 @@ void hsm_init(struct lightningd *ld, bool newdir)
 
 	ld->hsm = new_subd(ld, ld, "lightningd_hsm", NULL,
 			   hsm_wire_type_name,
-			   hsm_msg, hsm_finished, -1);
+			   hsm_msg, hsm_finished, NULL);
 	if (!ld->hsm)
 		err(1, "Could not subd hsm");
 

lightningd/new_connection.c

@@ -181,7 +181,7 @@ static bool got_handshake_hsmfd(struct subd *hsm, const u8 *msg,
 			      "lightningd_handshake", NULL,
 			      handshake_wire_type_name,
 			      NULL, NULL,
-			      fds[0], c->fd, -1);
+			      take(&fds[0]), take(&c->fd), NULL);
 	if (!handshaked) {
 		log_unusual(ld->log, "Could not subdaemon handshake: %s",
 			    strerror(errno));
@@ -191,8 +191,6 @@ static bool got_handshake_hsmfd(struct subd *hsm, const u8 *msg,
 	/* If handshake daemon fails, we just drop connection. */
 	tal_steal(handshaked, c);
 
-	/* We no longer own fd (closed; handshaked has copy). */
-	c->fd = -1;
 	if (c->known_id) {
 		req = towire_handshake_initiator(c, &ld->dstate.id,
 						 c->known_id);

lightningd/peer_control.c

@@ -1502,8 +1502,9 @@ static bool peer_start_channeld_hsmfd(struct subd *hsm, const u8 *resp,
 			       channel_wire_type_name,
 			       channel_msg,
 			       peer_owner_finished,
-			       peer->fd,
-			       peer->gossip_client_fd, fds[0], -1);
+			       take(&peer->fd),
+			       take(&peer->gossip_client_fd),
+			       take(&fds[0]), NULL);
 	if (!peer->owner) {
 		log_unusual(peer->log, "Could not subdaemon channel: %s",
 			    strerror(errno));
@@ -1777,15 +1778,13 @@ void peer_fundee_open(struct peer *peer, const u8 *from_peer)
 	peer->owner = new_subd(ld, ld, "lightningd_opening", peer,
 			       opening_wire_type_name,
 			       NULL, peer_owner_finished,
-			       peer->fd, peer->gossip_client_fd, -1);
+			       take(&peer->fd), take(&peer->gossip_client_fd),
+			       NULL);
 	if (!peer->owner) {
 		peer_fail(peer, "Failed to subdaemon opening: %s",
 			  strerror(errno));
 		return;
 	}
-	/* We handed off peer fd and gossip fd */
-	peer->fd = -1;
-	peer->gossip_client_fd = -1;
 
 	/* They will open channel. */
 	peer->funder = REMOTE;
@@ -1861,7 +1860,8 @@ static bool gossip_peer_released(struct subd *gossip,
 			   "lightningd_opening", fc->peer,
 			   opening_wire_type_name,
 			   NULL, peer_owner_finished,
-			   fc->peer->fd, fc->peer->gossip_client_fd, -1);
+			   take(&fc->peer->fd),
+			   take(&fc->peer->gossip_client_fd), NULL);
 	if (!opening) {
 		peer_fail(fc->peer, "Failed to subdaemon opening: %s",
 			  strerror(errno));
@@ -1869,10 +1869,6 @@ static bool gossip_peer_released(struct subd *gossip,
 	}
 	fc->peer->owner = opening;
 
-	/* They took our fds. */
-	fc->peer->fd = -1;
-	fc->peer->gossip_client_fd = -1;
-
 	/* We will fund channel */
 	fc->peer->funder = LOCAL;
 	channel_config(ld, &fc->peer->our_config,

lightningd/subd.c

@@ -124,7 +124,7 @@ static int subd(const char *dir, const char *name, bool debug,
 {
 	int childmsg[2], execfail[2];
 	pid_t childpid;
-	int err, fd;
+	int err, *fd;
 
 	if (socketpair(AF_LOCAL, SOCK_STREAM, 0, childmsg) != 0)
 		goto fail;
@@ -141,7 +141,7 @@ static int subd(const char *dir, const char *name, bool debug,
 		goto close_execfail_fail;
 
 	if (childpid == 0) {
-		int fdnum = 3;
+		int fdnum = 3, i;
 		long max;
 		const char *debug_arg = NULL;
 
@@ -155,18 +155,18 @@ static int subd(const char *dir, const char *name, bool debug,
 		}
 
 		/* Dup any extra fds up first. */
-		while ((fd = va_arg(ap, int)) != -1) {
+		while ((fd = va_arg(ap, int *)) != NULL) {
 			/* If this were stdin, dup2 closed! */
-			assert(fd != STDIN_FILENO);
-			if (!move_fd(fd, fdnum))
+			assert(*fd != STDIN_FILENO);
+			if (!move_fd(*fd, fdnum))
 				goto child_errno_fail;
 			fdnum++;
 		}
 
 		/* Make (fairly!) sure all other fds are closed. */
 		max = sysconf(_SC_OPEN_MAX);
-		for (fd = fdnum; fd < max; fd++)
-			close(fd);
+		for (i = fdnum; i < max; i++)
+			close(i);
 
 		if (debug)
 			debug_arg = "--debugger";
@@ -184,8 +184,12 @@ static int subd(const char *dir, const char *name, bool debug,
 	close(childmsg[1]);
 	close(execfail[1]);
 
-	while ((fd = va_arg(ap, int)) != -1)
-		close(fd);
+	while ((fd = va_arg(ap, int *)) != NULL) {
+		if (taken(fd)) {
+			close(*fd);
+			*fd = -1;
+		}
+	}
 
 	/* Child will close this without writing on successful exec. */
 	if (read(execfail[0], &err, sizeof(err)) == sizeof(err)) {

lightningd/subd.h

@@ -57,7 +57,7 @@ struct subd {
  * @msgname: function to get name from messages
  * @msgcb: function to call when non-fatal message received (or NULL)
  * @finished: function to call when it's finished (with exit status).
- * @...: the fds to hand as fd 3, 4... terminated with -1.
+ * @...: NULL-terminated list of pointers to  fds to hand as fd 3, 4... (can be take, if so, set to -1)
  *
  * @msgcb gets called with @fds set to NULL: if it returns a positive number,
  * that many @fds are received before calling again.  If it returns -1, the