gossipd: add an internal flag to force a channel update

This overcomes the internal spam filter on updates, which can be useful
if we're actually trying to send through such a node.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Changelog-Fixed: Protocol: always accept channel_updates from errors, even they'd otherwise be rejected as spam.
Fixes: #4300

gossipd/gossip_generation.c

@@ -392,7 +392,7 @@ static void update_local_channel(struct local_cupdate *lc /* frees! */)
 	msg = handle_channel_update(daemon->rstate, update,
 				    find_peer(daemon,
 					      &chan->nodes[!direction]->id),
-				    NULL);
+				    NULL, true);
 	if (msg)
 		status_failed(STATUS_FAIL_INTERNAL_ERROR,
 			      "%s: rejected local channel update %s: %s",

gossipd/gossip_store.c

@@ -829,7 +829,7 @@ u32 gossip_store_load(struct routing_state *rstate, struct gossip_store *gs)
 		case WIRE_CHANNEL_UPDATE:
 			if (!routing_add_channel_update(rstate,
 							take(msg), gs->len,
-							NULL)) {
+							NULL, false)) {
 				bad = "Bad channel_update";
 				goto badmsg;
 			}

gossipd/gossipd.c

@@ -268,7 +268,7 @@ static u8 *handle_channel_update_msg(struct peer *peer, const u8 *msg)
 
 	unknown_scid.u64 = 0;
 	err = handle_channel_update(peer->daemon->rstate, msg, peer,
-				    &unknown_scid);
+				    &unknown_scid, false);
 	if (err) {
 		if (unknown_scid.u64 != 0)
 			query_unknown_channel(peer->daemon, peer, &unknown_scid);
@@ -1797,7 +1797,7 @@ static struct io_plan *handle_payment_failure(struct io_conn *conn,
 			     tal_hex(tmpctx, channel_update),
 			     tal_hex(tmpctx, error));
 		u8 *err = handle_channel_update(daemon->rstate, channel_update,
-						NULL, NULL);
+						NULL, NULL, true);
 		if (err) {
 			status_info("extracted bad channel_update %s from onionreply %s",
 				    sanitize_error(err, err, NULL),

gossipd/routing.c

@@ -1674,10 +1674,10 @@ bool routing_add_channel_announcement(struct routing_state *rstate,
 	/* If we had private updates, they'll immediately create the channel. */
 	if (private_updates[0])
 		routing_add_channel_update(rstate, take(private_updates[0]), 0,
-					   peer);
+					   peer, false);
 	if (private_updates[1])
 		routing_add_channel_update(rstate, take(private_updates[1]), 0,
-					   peer);
+					   peer, false);
 
 	return true;
 }
@@ -1872,7 +1872,7 @@ static void process_pending_channel_update(struct daemon *daemon,
 	if (!cupdate)
 		return;
 
-	err = handle_channel_update(rstate, cupdate, peer, NULL);
+	err = handle_channel_update(rstate, cupdate, peer, NULL, false);
 	if (err) {
 		/* FIXME: We could send this error back to peer if != NULL */
 		status_peer_debug(peer ? &peer->id : NULL,
@@ -2021,7 +2021,8 @@ static void set_connection_values(struct chan *chan,
 bool routing_add_channel_update(struct routing_state *rstate,
 				const u8 *update TAKES,
 				u32 index,
-				struct peer *peer)
+				struct peer *peer,
+				bool ignore_timestamp)
 {
 	secp256k1_ecdsa_signature signature;
 	struct short_channel_id short_channel_id;
@@ -2111,7 +2112,7 @@ bool routing_add_channel_update(struct routing_state *rstate,
 	/* Discard older updates */
 	hc = &chan->half[direction];
 
-	if (is_halfchan_defined(hc)) {
+	if (is_halfchan_defined(hc) && !ignore_timestamp) {
 		/* If we're loading from store, duplicate entries are a bug. */
 		if (index != 0) {
 			status_broken("gossip_store channel_update %u replaces %u!",
@@ -2222,7 +2223,8 @@ bool routing_add_channel_update(struct routing_state *rstate,
 	}
 
 	status_peer_debug(peer ? &peer->id : NULL,
-			  "Received channel_update for channel %s/%d now %s",
+			  "Received %schannel_update for channel %s/%d now %s",
+			  ignore_timestamp ? "(forced) " : "",
 			  type_to_string(tmpctx, struct short_channel_id,
 					 &short_channel_id),
 			  channel_flags & 0x01,
@@ -2281,7 +2283,8 @@ void remove_channel_from_store(struct routing_state *rstate,
 
 u8 *handle_channel_update(struct routing_state *rstate, const u8 *update TAKES,
 			  struct peer *peer,
-			  struct short_channel_id *unknown_scid)
+			  struct short_channel_id *unknown_scid,
+			  bool force)
 {
 	u8 *serialized;
 	const struct node_id *owner;
@@ -2376,7 +2379,7 @@ u8 *handle_channel_update(struct routing_state *rstate, const u8 *update TAKES,
 		return err;
 	}
 
-	routing_add_channel_update(rstate, take(serialized), 0, peer);
+	routing_add_channel_update(rstate, take(serialized), 0, peer, force);
 	return NULL;
 }
 

gossipd/routing.h

@@ -402,7 +402,8 @@ struct chan *next_chan(const struct node *node, struct chan_map_iter *i);
  * (if not NULL). */
 u8 *handle_channel_update(struct routing_state *rstate, const u8 *update TAKES,
 			  struct peer *peer,
-			  struct short_channel_id *unknown_scid);
+			  struct short_channel_id *unknown_scid,
+			  bool force);
 
 /* Returns NULL if all OK, otherwise an error for the peer which sent.
  * If was_unknown is not NULL, sets it to true if that was the reason for
@@ -456,7 +457,8 @@ bool routing_add_channel_announcement(struct routing_state *rstate,
 bool routing_add_channel_update(struct routing_state *rstate,
 				const u8 *update TAKES,
 				u32 index,
-				struct peer *peer);
+				struct peer *peer,
+				bool ignore_timestamp);
 /**
  * Add a node_announcement to the network view without checking it
  *

gossipd/test/run-crc32_of_update.c

@@ -58,7 +58,8 @@ struct timeabs gossip_time_now(const struct routing_state *rstate UNNEEDED)
 /* Generated stub for handle_channel_update */
 u8 *handle_channel_update(struct routing_state *rstate UNNEEDED, const u8 *update TAKES UNNEEDED,
 			  struct peer *peer UNNEEDED,
-			  struct short_channel_id *unknown_scid UNNEEDED)
+			  struct short_channel_id *unknown_scid UNNEEDED,
+			  bool force UNNEEDED)
 { fprintf(stderr, "handle_channel_update called!\n"); abort(); }
 /* Generated stub for handle_node_announcement */
 u8 *handle_node_announcement(struct routing_state *rstate UNNEEDED, const u8 *node UNNEEDED,