From 0c3a47c0162c80062005e8187c16ee624498fdfd Mon Sep 17 00:00:00 2001 From: Matt Corallo Date: Tue, 12 Jul 2022 20:30:00 +0000 Subject: [PATCH] Fix tracking of collected value across pathfinding iterations If we end up "paying" for an `htlc_minimum_msat` with fees, we increment `already_collected_value_msat` by more than the amount of the path that we collected (who's `value_contribution_msat` is higher than the total payment amount, despite having been reduced down to the payment amount). This throws off our total value collection target, though in the coming commit(s) it would also throw off our path selection calculations. --- lightning/src/routing/router.rs | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/lightning/src/routing/router.rs b/lightning/src/routing/router.rs index a97e1b6ff..88757e867 100644 --- a/lightning/src/routing/router.rs +++ b/lightning/src/routing/router.rs @@ -1476,7 +1476,7 @@ 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, lowest_fee_to_node, total_cltv_delta, value_contribution_msat, path_htlc_minimum_msat, path_penalty_msat, path_length_to_node, .. }) = targets.pop() { + 'path_construction: while let Some(RouteGraphNode { node_id, lowest_fee_to_node, total_cltv_delta, mut value_contribution_msat, path_htlc_minimum_msat, path_penalty_msat, path_length_to_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. @@ -1542,7 +1542,9 @@ where L::Target: Logger { // on some channels we already passed (assuming dest->source direction). Here, we // recompute the fees again, so that if that's the case, we match the currently // underpaid htlc_minimum_msat with fees. - payment_path.update_value_and_recompute_fees(cmp::min(value_contribution_msat, final_value_msat)); + debug_assert_eq!(payment_path.get_value_msat(), value_contribution_msat); + value_contribution_msat = cmp::min(value_contribution_msat, final_value_msat); + payment_path.update_value_and_recompute_fees(value_contribution_msat); // Since a path allows to transfer as much value as // the smallest channel it has ("bottleneck"), we should recompute -- 2.39.5