Consider channels with one direction useless for routing

This is actually only useful when we just restarted and received
an outdated channel update, which we keep for
STALE_CHANNEL_UPDATE_AGE_LIMIT_SECS to give
it a chance to send a channel update. During that time, we
still should not be used it for routing.

Author: naumenkogs

lightning/src/routing/router.rs

@@ -1274,19 +1274,23 @@ where L::Target: Logger {
 					for chan_id in $node.channels.iter() {
 						let chan = network_channels.get(chan_id).unwrap();
 						if !chan.features.requires_unknown_bits() {
-							if let Some((directed_channel, source)) = chan.as_directed_to(&$node_id) {
-								if first_hops.is_none() || *source != our_node_id {
-									if directed_channel.direction().enabled {
-										let candidate = CandidateRouteHop::PublicHop {
-											info: directed_channel,
-											short_channel_id: *chan_id,
-										};
-										add_entry!(candidate, *source, $node_id,
-											$fee_to_target_msat,
-											$next_hops_value_contribution,
-											$next_hops_path_htlc_minimum_msat,
-											$next_hops_path_penalty_msat,
-											$next_hops_cltv_delta, $next_hops_path_length);
+							// We consider channels with only one direction filled useless,
+							// so we should check that both directions are present.
+							if chan.as_directed_from(&$node_id).is_some() {
+								if let Some((directed_channel, source)) = chan.as_directed_to(&$node_id) {
+									if first_hops.is_none() || *source != our_node_id {
+										if directed_channel.direction().enabled {
+											let candidate = CandidateRouteHop::PublicHop {
+												info: directed_channel,
+												short_channel_id: *chan_id,
+											};
+											add_entry!(candidate, *source, $node_id,
+												$fee_to_target_msat,
+												$next_hops_value_contribution,
+												$next_hops_path_htlc_minimum_msat,
+												$next_hops_path_penalty_msat,
+												$next_hops_cltv_delta, $next_hops_path_length);
+										}
 									}
 								}
 							}