lightningd/subd: msgcb return -1 to close channel.

They can't free it while we're using it, but they can return a value
to close it.

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

lightningd/gossip_control.c

@@ -128,7 +128,7 @@ static void peer_ready(struct subd *gossip, const u8 *msg)
 	peer_set_condition(peer, "Exchanging gossip");
 }
 
-static size_t gossip_msg(struct subd *gossip, const u8 *msg, const int *fds)
+static int gossip_msg(struct subd *gossip, const u8 *msg, const int *fds)
 {
 	enum gossip_wire_type t = fromwire_peektype(msg);
 

lightningd/hsm_control.c

@@ -38,7 +38,7 @@ static void hsm_finished(struct subd *hsm, int status)
 	errx(1, "HSM failed (signal %u), exiting.", WTERMSIG(status));
 }
 
-static size_t hsm_msg(struct subd *hsm, const u8 *msg, const int *fds)
+static int hsm_msg(struct subd *hsm, const u8 *msg, const int *fds)
 {
 	enum hsm_wire_type t = fromwire_peektype(msg);
 	u8 *badmsg;

lightningd/peer_control.c

@@ -616,9 +616,7 @@ static bool opening_got_hsm_funding_sig(struct subd *hsm, const u8 *resp,
 	return true;
 }
 
-static size_t update_channel_status(struct subd *sd,
-				    const u8 *msg,
-				    const int *unused)
+static int channel_msg(struct subd *sd, const u8 *msg, const int *unused)
 {
 	enum channel_wire_type t = fromwire_peektype(msg);
 
@@ -674,7 +672,7 @@ static void peer_start_channeld(struct peer *peer, bool am_funder,
 	peer->owner = new_subd(peer->ld, peer->ld,
 			       "lightningd_channel", peer,
 			       channel_wire_type_name,
-			       update_channel_status, NULL,
+			       channel_msg, NULL,
 			       peer->fd, peer->gossip_client_fd, -1);
 	if (!peer->owner) {
 		log_unusual(peer->log, "Could not subdaemon channel: %s",

lightningd/subd.c

@@ -262,7 +262,9 @@ static struct io_plan *sd_msg_read(struct io_conn *conn, struct subd *sd)
 		log_info(sd->log, "UPDATE %s", sd->msgname(type));
 
 		if (sd->msgcb) {
-			size_t i = sd->msgcb(sd, sd->msg_in, sd->fds_in);
+			int i = sd->msgcb(sd, sd->msg_in, sd->fds_in);
+			if (i < 0)
+				return io_close(conn);
 			if (i != 0) {
 				/* Don't ask for fds twice! */
 				assert(!sd->fds_in);
@@ -328,8 +330,8 @@ struct subd *new_subd(const tal_t *ctx,
 				const char *name,
 				struct peer *peer,
 				const char *(*msgname)(int msgtype),
-				size_t (*msgcb)(struct subd *, const u8 *,
-						const int *fds),
+				int (*msgcb)(struct subd *, const u8 *,
+					     const int *fds),
 				void (*finished)(struct subd *, int),
 				...)
 {

lightningd/subd.h

@@ -30,7 +30,7 @@ struct subd {
 	struct log *log;
 
 	/* Callback when non-reply message comes in. */
-	size_t (*msgcb)(struct subd *, const u8 *, const int *);
+	int (*msgcb)(struct subd *, const u8 *, const int *);
 	const char *(*msgname)(int msgtype);
 	void (*finished)(struct subd *sd, int status);
 
@@ -60,7 +60,8 @@ struct subd {
  * @...: the fds to hand as fd 3, 4... terminated with -1.
  *
  * @msgcb gets called with @fds set to NULL: if it returns a positive number,
- * that many @fds are received before calling again.
+ * that many @fds are received before calling again.  If it returns -1, the
+ * subdaemon is shutdown.
  *
  * If this succeeds subd owns @peer.
  */
@@ -69,7 +70,7 @@ struct subd *new_subd(const tal_t *ctx,
 		      const char *name,
 		      struct peer *peer,
 		      const char *(*msgname)(int msgtype),
-		      size_t (*msgcb)(struct subd *, const u8 *, const int *fds),
+		      int (*msgcb)(struct subd *, const u8 *, const int *fds),
 		      void (*finished)(struct subd *, int), ...);
 
 /**