Get max HTLC from CandidateRouteHop instead of EffectiveCapacity

With the addition of blinded route hints, we can't assume that any provided
route hint has enough capacity for the entire payment anymore. Blinded route
hints provided a max_htlc_msat, so use that in routing.

Author: valentinewallace

lightning/src/routing/router.rs

@@ -957,16 +957,23 @@ impl<'a> CandidateRouteHop<'a> {
 }
 
 #[inline]
-fn max_htlc_from_capacity(capacity: EffectiveCapacity, max_channel_saturation_power_of_half: u8) -> u64 {
+fn max_htlc_from_route_candidate(candidate: &CandidateRouteHop, max_channel_saturation_power_of_half: u8) -> u64 {
 	let saturation_shift: u32 = max_channel_saturation_power_of_half as u32;
-	match capacity {
-		EffectiveCapacity::ExactLiquidity { liquidity_msat } => liquidity_msat,
-		EffectiveCapacity::Infinite => u64::max_value(),
-		EffectiveCapacity::Unknown => EffectiveCapacity::Unknown.as_msat(),
-		EffectiveCapacity::MaximumHTLC { amount_msat } =>
-			amount_msat.checked_shr(saturation_shift).unwrap_or(0),
-		EffectiveCapacity::Total { capacity_msat, htlc_maximum_msat } =>
-			cmp::min(capacity_msat.checked_shr(saturation_shift).unwrap_or(0), htlc_maximum_msat),
+	match candidate {
+		CandidateRouteHop::FirstHop { details } => details.next_outbound_htlc_limit_msat,
+		CandidateRouteHop::PublicHop { info, .. } => {
+			match info.effective_capacity() {
+				EffectiveCapacity::MaximumHTLC { amount_msat } =>
+					amount_msat.checked_shr(saturation_shift).unwrap_or(0),
+				EffectiveCapacity::Total { capacity_msat, htlc_maximum_msat } =>
+					cmp::min(capacity_msat.checked_shr(saturation_shift).unwrap_or(0), htlc_maximum_msat),
+				_ => {
+					debug_assert!(false);
+					EffectiveCapacity::Unknown.as_msat()
+				}
+			}
+		},
+		CandidateRouteHop::PrivateHop { hint } => hint.htlc_maximum_msat.unwrap_or(u64::max_value()),
 	}
 }
 
@@ -1479,7 +1486,7 @@ where L::Target: Logger {
 			if $src_node_id != $dest_node_id {
 				let short_channel_id = $candidate.short_channel_id();
 				let effective_capacity = $candidate.effective_capacity();
-				let htlc_maximum_msat = max_htlc_from_capacity(effective_capacity, channel_saturation_pow_half);
+				let htlc_maximum_msat = max_htlc_from_route_candidate(&$candidate, channel_saturation_pow_half);
 
 				// It is tricky to subtract $next_hops_fee_msat from available liquidity here.
 				// It may be misleading because we might later choose to reduce the value transferred
@@ -2023,8 +2030,7 @@ where L::Target: Logger {
 						.entry((hop.candidate.short_channel_id(), *prev_hop < hop.node_id))
 						.and_modify(|used_liquidity_msat| *used_liquidity_msat += spent_on_hop_msat)
 						.or_insert(spent_on_hop_msat);
-					let hop_capacity = hop.candidate.effective_capacity();
-					let hop_max_msat = max_htlc_from_capacity(hop_capacity, channel_saturation_pow_half);
+					let hop_max_msat = max_htlc_from_route_candidate(&hop.candidate, channel_saturation_pow_half);
 					if *used_liquidity_msat == hop_max_msat {
 						// If this path used all of this channel's available liquidity, we know
 						// this path will not be selected again in the next loop iteration.