gossipd: add txout_failure when a close is seen.

This prevents a gratuitous lookup of we get a late channel_announce,
but even better, it suppresses the "bad gossip" messages in case of
a late channel_update, which have plagued Travis (especially since we
got aggressive in pushing our own updates).

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

gossipd/gossipd.c

@@ -1517,6 +1517,8 @@ static struct io_plan *handle_outpoint_spent(struct io_conn *conn,
 		    "Deleting channel %s due to the funding outpoint being "
 		    "spent",
 		    type_to_string(msg, struct short_channel_id, &scid));
+		/* Suppress any now-obsolete updates/announcements */
+		add_to_txout_failures(rstate, &scid);
 		remove_channel_from_store(rstate, chan);
 		/* Freeing is sufficient since everything else is allocated off
 		 * of the channel and this takes care of unregistering

gossipd/routing.c

@@ -258,8 +258,8 @@ static void txout_failure_age(struct routing_state *rstate)
 						   txout_failure_age, rstate);
 }
 
-static void add_to_txout_failures(struct routing_state *rstate,
-				  const struct short_channel_id *scid)
+void add_to_txout_failures(struct routing_state *rstate,
+			   const struct short_channel_id *scid)
 {
 	if (uintmap_add(&rstate->txout_failures, scid->u64, true)
 	    && ++rstate->num_txout_failures == 10000) {

gossipd/routing.h

@@ -529,4 +529,8 @@ void remove_channel_from_store(struct routing_state *rstate,
 const char *unfinalized_entries(const tal_t *ctx, struct routing_state *rstate);
 
 void remove_all_gossip(struct routing_state *rstate);
+
+/* This scid is dead to us. */
+void add_to_txout_failures(struct routing_state *rstate,
+			   const struct short_channel_id *scid);
 #endif /* LIGHTNING_GOSSIPD_ROUTING_H */