Router: track whether candidate hops target blinded paths.

Will be useful to determine whether these hops should count towards our
intermediate hop count.

Author: valentinewallace

lightning/src/routing/router.rs

@@ -1121,6 +1121,7 @@ struct RouteGraphNode {
 	total_cltv_delta: u32,
 	/// The number of hops walked up to this node.
 	path_length_to_node: u8,
+	is_intro_node: bool,
 }
 
 impl cmp::Ord for RouteGraphNode {
@@ -1161,6 +1162,9 @@ pub struct FirstHopCandidate<'a> {
 	///
 	/// This is not exported to bindings users as lifetimes are not expressible in most languages.
 	pub payer_node_id: &'a NodeId,
+
+	/// Whether the target of this hop is the introduction node of a payee-supplied blinded path.
+	pub(crate) targets_blinded_path: bool,
 }
 
 /// A [`CandidateRouteHop::PublicHop`] entry.
@@ -1174,12 +1178,14 @@ pub struct PublicHopCandidate<'a> {
 	/// The short channel ID of the channel, i.e. the identifier by which we refer to this
 	/// channel.
 	pub short_channel_id: u64,
+	/// Whether the target of this hop is the introduction node of a payee-supplied blinded path.
+	pub(crate) targets_blinded_path: bool,
 }
 
 impl<'a> PublicHopCandidate<'a> {
 	#[cfg(test)]
 	pub(super) fn new(info: DirectedChannelInfo<'a>, short_channel_id: u64) -> Self {
-		Self { info, short_channel_id }
+		Self { info, short_channel_id, targets_blinded_path: false }
 	}
 }
 
@@ -2375,6 +2381,7 @@ where L::Target: Logger {
 										total_cltv_delta: hop_total_cltv_delta,
 										value_contribution_msat,
 										path_length_to_node,
+										is_intro_node: $candidate.blinded_hint_idx().is_some(),
 									};
 									targets.push(new_graph_node);
 									old_entry.next_hops_fee_msat = $next_hops_fee_msat;
@@ -2450,7 +2457,7 @@ where L::Target: Logger {
 	// This data can later be helpful to optimize routing (pay lower fees).
 	macro_rules! add_entries_to_cheapest_to_target_node {
 		( $node: expr, $node_id: expr, $next_hops_value_contribution: expr,
-		  $next_hops_cltv_delta: expr, $next_hops_path_length: expr ) => {
+		  $next_hops_cltv_delta: expr, $next_hops_path_length: expr, $is_intro_node: expr ) => {
 			let fee_to_target_msat;
 			let next_hops_path_htlc_minimum_msat;
 			let next_hops_path_penalty_msat;
@@ -2476,7 +2483,7 @@ where L::Target: Logger {
 				if let Some(first_channels) = first_hop_targets.get(&$node_id) {
 					for details in first_channels {
 						let candidate = CandidateRouteHop::FirstHop(FirstHopCandidate {
-							details, payer_node_id: &our_node_id,
+							details, payer_node_id: &our_node_id, targets_blinded_path: false,
 						});
 						add_entry!(&candidate, fee_to_target_msat,
 							$next_hops_value_contribution,
@@ -2501,6 +2508,7 @@ where L::Target: Logger {
 										let candidate = CandidateRouteHop::PublicHop(PublicHopCandidate {
 											info: directed_channel,
 											short_channel_id: *chan_id,
+											targets_blinded_path: $is_intro_node,
 										});
 										add_entry!(&candidate,
 											fee_to_target_msat,
@@ -2533,7 +2541,7 @@ where L::Target: Logger {
 		payee_node_id_opt.map(|payee| first_hop_targets.get(&payee).map(|first_channels| {
 			for details in first_channels {
 				let candidate = CandidateRouteHop::FirstHop(FirstHopCandidate {
-					details, payer_node_id: &our_node_id,
+					details, payer_node_id: &our_node_id, targets_blinded_path: false,
 				});
 				let added = add_entry!(&candidate, 0, path_value_msat,
 									0, 0u64, 0, 0).is_some();
@@ -2551,7 +2559,7 @@ where L::Target: Logger {
 			// If not, targets.pop() will not even let us enter the loop in step 2.
 			None => {},
 			Some(node) => {
-				add_entries_to_cheapest_to_target_node!(node, payee, path_value_msat, 0, 0);
+				add_entries_to_cheapest_to_target_node!(node, payee, path_value_msat, 0, 0, false);
 			},
 		});
 
@@ -2609,7 +2617,7 @@ where L::Target: Logger {
 				);
 				for details in first_channels {
 					let first_hop_candidate = CandidateRouteHop::FirstHop(FirstHopCandidate {
-						details, payer_node_id: &our_node_id,
+						details, payer_node_id: &our_node_id, targets_blinded_path: true,
 					});
 					let blinded_path_fee = match compute_fees(path_contribution_msat, candidate.fees()) {
 						Some(fee) => fee,
@@ -2665,6 +2673,7 @@ where L::Target: Logger {
 						.map(|(info, _)| CandidateRouteHop::PublicHop(PublicHopCandidate {
 							info,
 							short_channel_id: hop.short_channel_id,
+							targets_blinded_path: false
 						}))
 						.unwrap_or_else(|| CandidateRouteHop::PrivateHop(PrivateHopCandidate { hint: hop, target_node_id: target }));
 
@@ -2709,7 +2718,7 @@ where L::Target: Logger {
 						);
 						for details in first_channels {
 							let first_hop_candidate = CandidateRouteHop::FirstHop(FirstHopCandidate {
-								details, payer_node_id: &our_node_id,
+								details, payer_node_id: &our_node_id, targets_blinded_path: false
 							});
 							add_entry!(&first_hop_candidate,
 								aggregate_next_hops_fee_msat, aggregate_path_contribution_msat,
@@ -2758,7 +2767,7 @@ where L::Target: Logger {
 							);
 							for details in first_channels {
 								let first_hop_candidate = CandidateRouteHop::FirstHop(FirstHopCandidate {
-									details, payer_node_id: &our_node_id,
+									details, payer_node_id: &our_node_id, targets_blinded_path: false
 								});
 								add_entry!(&first_hop_candidate,
 									aggregate_next_hops_fee_msat,
@@ -2789,7 +2798,9 @@ where L::Target: Logger {
 		// Both these cases (and other cases except reaching recommended_value_msat) mean that
 		// paths_collection will be stopped because found_new_path==false.
 		// This is not necessarily a routing failure.
-		'path_construction: while let Some(RouteGraphNode { node_id, total_cltv_delta, mut value_contribution_msat, path_length_to_node, .. }) = targets.pop() {
+		'path_construction: while let Some(RouteGraphNode {
+			node_id, total_cltv_delta, mut value_contribution_msat, path_length_to_node, is_intro_node, ..
+		}) = targets.pop() {
 
 			// Since we're going payee-to-payer, hitting our node as a target means we should stop
 			// traversing the graph and arrange the path out of what we found.
@@ -2926,7 +2937,7 @@ where L::Target: Logger {
 				Some(node) => {
 					add_entries_to_cheapest_to_target_node!(node, node_id,
 						value_contribution_msat,
-						total_cltv_delta, path_length_to_node);
+						total_cltv_delta, path_length_to_node, is_intro_node);
 				},
 			}
 		}

lightning/src/routing/scoring.rs

@@ -1323,7 +1323,7 @@ impl<G: Deref<Target = NetworkGraph<L>>, L: Deref> ScoreLookUp for Probabilistic
 		&self, candidate: &CandidateRouteHop, usage: ChannelUsage, score_params: &ProbabilisticScoringFeeParameters
 	) -> u64 {
 		let (scid, target) = match candidate {
-			CandidateRouteHop::PublicHop(PublicHopCandidate { info, short_channel_id }) => {
+			CandidateRouteHop::PublicHop(PublicHopCandidate { info, short_channel_id, .. }) => {
 				(short_channel_id, info.target())
 			},
 			_ => return 0,

lightning/src/util/test_utils.rs

@@ -174,6 +174,7 @@ impl<'a> Router for TestRouter<'a> {
 										let candidate = CandidateRouteHop::FirstHop(FirstHopCandidate {
 											details: first_hops[idx],
 											payer_node_id: &node_id,
+											targets_blinded_path: false,
 										});
 										scorer.channel_penalty_msat(&candidate, usage, &Default::default());
 										continue;
@@ -186,6 +187,7 @@ impl<'a> Router for TestRouter<'a> {
 								let candidate = CandidateRouteHop::PublicHop(PublicHopCandidate {
 									info: directed,
 									short_channel_id: hop.short_channel_id,
+									targets_blinded_path: false,
 								});
 								scorer.channel_penalty_msat(&candidate, usage, &Default::default());
 							} else {