Score without uncertainty for exact liquidity

For direct channels, the channel liquidity is known with certainty. Use
this knowledge in ProbabilisticScorer by either penalizing with the
per-hop penalty or u64::max_value depending on the amount.

diff --git a/lightning/src/routing/scoring.rs b/lightning/src/routing/scoring.rs
index 2c62e6465041254e815bcbf9f372189e10830fb3..38e3c838425f5957fddb0a525dc15ca8cbc24eca 100644 (file)
--- a/lightning/src/routing/scoring.rs
+++ b/lightning/src/routing/scoring.rs
@@ -903,6 +903,14 @@ impl<G: Deref<Target = NetworkGraph>, L: Deref, T: Time> Score for Probabilistic
        fn channel_penalty_msat(
                &self, short_channel_id: u64, source: &NodeId, target: &NodeId, usage: ChannelUsage
        ) -> u64 {
+               if let EffectiveCapacity::ExactLiquidity { liquidity_msat } = usage.effective_capacity {
+                       if usage.amount_msat > liquidity_msat {
+                               return u64::max_value();
+                       } else {
+                               return self.params.base_penalty_msat;
+                       };
+               }
+
                let liquidity_offset_half_life = self.params.liquidity_offset_half_life;
                let amount_msat = usage.amount_msat;
                let capacity_msat = usage.effective_capacity.as_msat()
@@ -2574,4 +2582,28 @@ mod tests {
                let usage = ChannelUsage { inflight_htlc_msat: 251, ..usage };
                assert_eq!(scorer.channel_penalty_msat(42, &source, &target, usage), u64::max_value());
        }
+
+       #[test]
+       fn removes_uncertainity_when_exact_liquidity_known() {
+               let network_graph = network_graph();
+               let logger = TestLogger::new();
+               let params = ProbabilisticScoringParameters::default();
+               let scorer = ProbabilisticScorer::new(params, &network_graph, &logger);
+               let source = source_node_id();
+               let target = target_node_id();
+
+               let base_penalty_msat = params.base_penalty_msat;
+               let usage = ChannelUsage {
+                       amount_msat: 750,
+                       inflight_htlc_msat: 0,
+                       effective_capacity: EffectiveCapacity::ExactLiquidity { liquidity_msat: 1_000 },
+               };
+               assert_eq!(scorer.channel_penalty_msat(42, &source, &target, usage), base_penalty_msat);
+
+               let usage = ChannelUsage { amount_msat: 1_000, ..usage };
+               assert_eq!(scorer.channel_penalty_msat(42, &source, &target, usage), base_penalty_msat);
+
+               let usage = ChannelUsage { amount_msat: 1_001, ..usage };
+               assert_eq!(scorer.channel_penalty_msat(42, &source, &target, usage), u64::max_value());
+       }
 }