gossipd: when we refresh channel, don't override pending updates.

We can have an update pending because it's too fast, but
refresh_local_channel is supposed to make sure we're up-to-date, so
force immediate application in that case.

Otherwise, we call update_local_channel at the bottom which frees the
pending update.  This can mean that we miss a change in fees, for example.

Changelog-Fixed: errors: Errors returning a `channel_update` no longer return an outdated one.

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

gossipd/gossip_generation.c

@@ -314,6 +314,7 @@ struct local_cupdate {
 
 	bool disable;
 	bool even_if_identical;
+	bool even_if_too_soon;
 
 	u16 cltv_expiry_delta;
 	struct amount_msat htlc_minimum, htlc_maximum;
@@ -409,7 +410,7 @@ static void update_local_channel(struct local_cupdate *lc /* frees! */)
 		next = hc->bcast.timestamp
 			+ GOSSIP_MIN_INTERVAL(daemon->rstate->dev_fast_gossip);
 
-		if (timestamp < next) {
+		if (timestamp < next && !lc->even_if_too_soon) {
 			status_debug("channel_update %s/%u: delaying %u secs",
 				     type_to_string(tmpctx,
 						    struct short_channel_id,
@@ -503,10 +504,21 @@ void refresh_local_channel(struct daemon *daemon,
 	if (!is_halfchan_defined(hc))
 		return;
 
+	/* If there's an update pending already, force it to apply now. */
+	if (local_chan->channel_update_timer) {
+		lc = reltimer_arg(local_chan->channel_update_timer);
+		lc->even_if_too_soon = true;
+		update_local_channel(lc);
+		/* Free timer */
+		local_chan->channel_update_timer
+			= tal_free(local_chan->channel_update_timer);
+	}
+
 	lc = tal(NULL, struct local_cupdate);
 	lc->daemon = daemon;
 	lc->local_chan = local_chan;
 	lc->even_if_identical = even_if_identical;
+	lc->even_if_too_soon = false;
 
 	prev = cast_const(u8 *,
 			  gossip_store_get(tmpctx, daemon->rstate->gs,
@@ -546,6 +558,7 @@ bool handle_local_channel_update(struct daemon *daemon,
 
 	lc->daemon = daemon;
 	lc->even_if_identical = false;
+	lc->even_if_too_soon = false;
 
 	/* FIXME: We should get scid from lightningd when setting up the
 	 * connection, so no per-peer daemon can mess with channels other than

gossipd/test/run-check_node_announcement.c

@@ -68,6 +68,9 @@ void *notleak_(const void *ptr UNNEEDED, bool plus_children UNNEEDED)
 /* Generated stub for queue_peer_msg */
 void queue_peer_msg(struct peer *peer UNNEEDED, const u8 *msg TAKES UNNEEDED)
 { fprintf(stderr, "queue_peer_msg called!\n"); abort(); }
+/* Generated stub for reltimer_arg */
+void *reltimer_arg(struct oneshot *t UNNEEDED)
+{ fprintf(stderr, "reltimer_arg called!\n"); abort(); }
 /* Generated stub for status_failed */
 void status_failed(enum status_failreason code UNNEEDED,
 		   const char *fmt UNNEEDED, ...)

gossipd/test/run-crc32_of_update.c

@@ -107,6 +107,9 @@ void queue_peer_from_store(struct peer *peer UNNEEDED,
 /* Generated stub for queue_peer_msg */
 void queue_peer_msg(struct peer *peer UNNEEDED, const u8 *msg TAKES UNNEEDED)
 { fprintf(stderr, "queue_peer_msg called!\n"); abort(); }
+/* Generated stub for reltimer_arg */
+void *reltimer_arg(struct oneshot *t UNNEEDED)
+{ fprintf(stderr, "reltimer_arg called!\n"); abort(); }
 /* Generated stub for status_failed */
 void status_failed(enum status_failreason code UNNEEDED,
 		   const char *fmt UNNEEDED, ...)