channeld: get told when announce depth already reached.

If channeld dies for some reason (eg, reconnect) and we didn't yet announce
the channel, we can miss doing so.  This is unusual, because if lightningd
restarts it rearms the callback which gives us funding_locked, so it only
happens if just channel dies before sending the announcement message.

This problem applies to both temporary announcement (for gossipd) and
the real one.  For the temporary one, simply re-send on startup, and
remote the error msg gossipd gives if it sees a second one.  For the
real one, we need a flag to tell us the depth is sufficient; the peer
will ignore re-sends anyway.

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

channeld/channel.c

@@ -1940,6 +1940,10 @@ static void handle_funding_locked(struct peer *peer, const u8 *msg)
 
 static void handle_funding_announce_depth(struct peer *peer)
 {
+	/* This can happen if we got told already at init time */
+	if (peer->announce_depth_reached)
+		return;
+
 	peer->announce_depth_reached = true;
 	send_announcement_signatures(peer);
 
@@ -2449,7 +2453,8 @@ static void init_channel(struct peer *peer)
 				   &peer->shutdown_sent[REMOTE],
 				   &peer->final_scriptpubkey,
 				   &peer->channel_flags,
-				   &funding_signed))
+				   &funding_signed,
+				   &peer->announce_depth_reached))
 		master_badmsg(WIRE_CHANNEL_INIT, msg);
 
 	status_trace("init %s: remote_per_commit = %s, old_remote_per_commit = %s"
@@ -2516,6 +2521,10 @@ static void init_channel(struct peer *peer)
 	if (funding_signed)
 		enqueue_peer_msg(peer, take(funding_signed));
 
+	/* It's possible that we died previously before doing these. */
+	send_temporary_announcement(peer);
+	send_announcement_signatures(peer);
+
 	billboard_update(peer);
 	tal_free(msg);
 }

channeld/channel_wire.csv

@@ -58,6 +58,7 @@ channel_init,,final_scriptpubkey,final_scriptpubkey_len*u8
 channel_init,,flags,u8
 channel_init,,init_peer_pkt_len,u16
 channel_init,,init_peer_pkt,init_peer_pkt_len*u8
+channel_init,,reached_announce_depth,bool
 
 # Tx is deep enough, go!
 channel_funding_locked,1002

gossipd/routing.c

@@ -1516,8 +1516,9 @@ void handle_local_add_channel(struct routing_state *rstate, u8 *msg)
 		return;
 	}
 
+	/* Can happen on channeld restart. */
 	if (get_channel(rstate, &scid)) {
-		status_broken("Attempted to local_add_channel a known channel");
+		status_trace("Attempted to local_add_channel a known channel");
 		return;
 	}
 

lightningd/channel_control.c

@@ -186,6 +186,7 @@ bool peer_start_channeld(struct channel *channel,
 	u64 num_revocations;
 	struct lightningd *ld = channel->peer->ld;
 	const struct config *cfg = &ld->config;
+	bool reached_announce_depth;
 
 	msg = towire_hsm_client_hsmfd(tmpctx, &channel->peer->id, HSM_CAP_SIGN_GOSSIP | HSM_CAP_ECDH);
 	if (!wire_sync_write(ld->hsm_fd, take(msg)))
@@ -223,10 +224,16 @@ bool peer_start_channeld(struct channel *channel,
 
 	if (channel->scid) {
 		funding_channel_id = *channel->scid;
-		log_debug(channel->log, "Already have funding locked in");
+		reached_announce_depth
+			= (short_channel_id_blocknum(&funding_channel_id)
+			   + ANNOUNCE_MIN_DEPTH <= get_block_height(ld->topology));
+		log_debug(channel->log, "Already have funding locked in%s",
+			  reached_announce_depth
+			  ? " (and ready to announce)" : "");
 	} else {
 		log_debug(channel->log, "Waiting for funding confirmations");
 		memset(&funding_channel_id, 0, sizeof(funding_channel_id));
+		reached_announce_depth = false;
 	}
 
 	num_revocations = revocations_received(&channel->their_shachain.chain);
@@ -281,7 +288,8 @@ bool peer_start_channeld(struct channel *channel,
 				      p2wpkh_for_keyidx(tmpctx, ld,
 							channel->final_key_idx),
 				      channel->channel_flags,
-				      funding_signed);
+				      funding_signed,
+				      reached_announce_depth);
 
 	/* We don't expect a response: we are triggered by funding_depth_cb. */
 	subd_send_msg(channel->owner, take(initmsg));