diff --git a/lightning/src/ln/functional_tests.rs b/lightning/src/ln/functional_tests.rs index 9ecbee739f1..f39cb15fa94 100644 --- a/lightning/src/ln/functional_tests.rs +++ b/lightning/src/ln/functional_tests.rs @@ -1823,9 +1823,12 @@ fn test_channel_reserve_holding_cell_htlcs() { // attempt to send amt_msat > their_max_htlc_value_in_flight_msat { - let (mut route, our_payment_hash, _, our_payment_secret) = get_route_and_payment_hash!(nodes[0], nodes[2], recv_value_0); + let payment_params = PaymentParameters::from_node_id(nodes[2].node.get_our_node_id()) + .with_features(InvoiceFeatures::known()).with_max_channel_saturation_power_of_half(0); + let (mut route, our_payment_hash, _, our_payment_secret) = get_route_and_payment_hash!(nodes[0], nodes[2], payment_params, recv_value_0, TEST_FINAL_CLTV); route.paths[0].last_mut().unwrap().fee_msat += 1; assert!(route.paths[0].iter().rev().skip(1).all(|h| h.fee_msat == feemsat)); + unwrap_send_err!(nodes[0].node.send_payment(&route, our_payment_hash, &Some(our_payment_secret)), true, APIError::ChannelUnavailable { ref err }, assert!(regex::Regex::new(r"Cannot send value that would put us over the max HTLC value in flight our peer will accept \(\d+\)").unwrap().is_match(err))); assert!(nodes[0].node.get_and_clear_pending_msg_events().is_empty()); @@ -1844,7 +1847,12 @@ fn test_channel_reserve_holding_cell_htlcs() { if stat01.value_to_self_msat < stat01.channel_reserve_msat + commit_tx_fee_all_htlcs + ensure_htlc_amounts_above_dust_buffer + amt_msat { break; } - send_payment(&nodes[0], &vec![&nodes[1], &nodes[2]][..], recv_value_0); + + let payment_params = PaymentParameters::from_node_id(nodes[2].node.get_our_node_id()) + .with_features(InvoiceFeatures::known()).with_max_channel_saturation_power_of_half(0); + let route = get_route!(nodes[0], payment_params, recv_value_0, TEST_FINAL_CLTV).unwrap(); + let (payment_preimage, ..) = send_along_route(&nodes[0], route, &[&nodes[1], &nodes[2]], recv_value_0); + claim_payment(&nodes[0], &[&nodes[1], &nodes[2]], payment_preimage); let (stat01_, stat11_, stat12_, stat22_) = ( get_channel_value_stat!(nodes[0], chan_1.2), diff --git a/lightning/src/ln/payment_tests.rs b/lightning/src/ln/payment_tests.rs index 99c8682738d..d3feb96df11 100644 --- a/lightning/src/ln/payment_tests.rs +++ b/lightning/src/ln/payment_tests.rs @@ -942,7 +942,7 @@ fn failed_probe_yields_event() { let payment_params = PaymentParameters::from_node_id(nodes[2].node.get_our_node_id()); - let (route, _, _, _) = get_route_and_payment_hash!(&nodes[0], nodes[2], &payment_params, 9_999_000, 42); + let (route, _, _, _) = get_route_and_payment_hash!(&nodes[0], nodes[2], &payment_params, 9_998_000, 42); let (payment_hash, payment_id) = nodes[0].node.send_probe(route.paths[0].clone()).unwrap(); diff --git a/lightning/src/routing/gossip.rs b/lightning/src/routing/gossip.rs index 716ca2b305f..55887623c40 100644 --- a/lightning/src/routing/gossip.rs +++ b/lightning/src/routing/gossip.rs @@ -816,10 +816,6 @@ impl<'a> DirectedChannelInfoWithUpdate<'a> { /// Returns the [`EffectiveCapacity`] of the channel in the direction. #[inline] pub(super) fn effective_capacity(&self) -> EffectiveCapacity { self.inner.effective_capacity() } - - /// Returns the maximum HTLC amount allowed over the channel in the direction. - #[inline] - pub(super) fn htlc_maximum_msat(&self) -> u64 { self.inner.htlc_maximum_msat() } } impl<'a> fmt::Debug for DirectedChannelInfoWithUpdate<'a> { diff --git a/lightning/src/routing/router.rs b/lightning/src/routing/router.rs index 92a78829e2e..40cd439b1df 100644 --- a/lightning/src/routing/router.rs +++ b/lightning/src/routing/router.rs @@ -225,6 +225,21 @@ pub struct PaymentParameters { /// The maximum number of paths that may be used by (MPP) payments. /// Defaults to [`DEFAULT_MAX_PATH_COUNT`]. pub max_path_count: u8, + + /// Selects the maximum share of a channel's total capacity which will be sent over a channel, + /// as a power of 1/2. A higher value prefers to send the payment using more MPP parts whereas + /// a lower value prefers to send larger MPP parts, potentially saturating channels and + /// increasing failure probability for those paths. + /// + /// Note that this restriction will be relaxed during pathfinding after paths which meet this + /// restriction have been found. While paths which meet this criteria will be searched for, it + /// is ultimately up to the scorer to select them over other paths. + /// + /// A value of 0 will allow payments up to and including a channel's total announced usable + /// capacity, a value of one will only use up to half its capacity, two 1/4, etc. + /// + /// Default value: 1 + pub max_channel_saturation_power_of_half: u8, } impl_writeable_tlv_based!(PaymentParameters, { @@ -233,6 +248,7 @@ impl_writeable_tlv_based!(PaymentParameters, { (2, features, option), (3, max_path_count, (default_value, DEFAULT_MAX_PATH_COUNT)), (4, route_hints, vec_type), + (5, max_channel_saturation_power_of_half, (default_value, 1)), (6, expiry_time, option), }); @@ -246,6 +262,7 @@ impl PaymentParameters { expiry_time: None, max_total_cltv_expiry_delta: DEFAULT_MAX_TOTAL_CLTV_EXPIRY_DELTA, max_path_count: DEFAULT_MAX_PATH_COUNT, + max_channel_saturation_power_of_half: 1, } } @@ -288,6 +305,13 @@ impl PaymentParameters { pub fn with_max_path_count(self, max_path_count: u8) -> Self { Self { max_path_count, ..self } } + + /// Includes a limit for the maximum number of payment paths that may be used. + /// + /// (C-not exported) since bindings don't support move semantics + pub fn with_max_channel_saturation_power_of_half(self, max_channel_saturation_power_of_half: u8) -> Self { + Self { max_channel_saturation_power_of_half, ..self } + } } /// A list of hops along a payment path terminating with a channel to the recipient. @@ -433,16 +457,6 @@ impl<'a> CandidateRouteHop<'a> { } } - fn htlc_maximum_msat(&self) -> u64 { - match self { - CandidateRouteHop::FirstHop { details } => details.next_outbound_htlc_limit_msat, - CandidateRouteHop::PublicHop { info, .. } => info.htlc_maximum_msat(), - CandidateRouteHop::PrivateHop { hint } => { - hint.htlc_maximum_msat.unwrap_or(u64::max_value()) - }, - } - } - fn fees(&self) -> RoutingFees { match self { CandidateRouteHop::FirstHop { .. } => RoutingFees { @@ -464,6 +478,33 @@ impl<'a> CandidateRouteHop<'a> { } } +#[inline] +fn max_htlc_from_capacity(capacity: EffectiveCapacity, 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: None } => + capacity_msat.checked_shr(saturation_shift).unwrap_or(0), + EffectiveCapacity::Total { capacity_msat, htlc_maximum_msat: Some(htlc_max) } => + cmp::min(capacity_msat.checked_shr(saturation_shift).unwrap_or(0), htlc_max), + } +} + +fn iter_equal(mut iter_a: I1, mut iter_b: I2) +-> bool where I1::Item: PartialEq { + loop { + let a = iter_a.next(); + let b = iter_b.next(); + if a.is_none() && b.is_none() { return true; } + if a.is_none() || b.is_none() { return false; } + if a.unwrap().ne(&b.unwrap()) { return false; } + } +} + /// It's useful to keep track of the hops associated with the fees required to use them, /// so that we can choose cheaper paths (as per Dijkstra's algorithm). /// Fee values should be updated only in the context of the whole path, see update_value_and_recompute_fees. @@ -571,10 +612,9 @@ impl<'a> PaymentPath<'a> { // to the fees being paid not lining up with the actual limits. // // Note that this function is not aware of the available_liquidity limit, and thus does not - // support increasing the value being transferred. + // support increasing the value being transferred beyond what was selected during the initial + // routing passes. fn update_value_and_recompute_fees(&mut self, value_msat: u64) { - assert!(value_msat <= self.hops.last().unwrap().0.fee_msat); - let mut total_fee_paid_msat = 0 as u64; for i in (0..self.hops.len()).rev() { let last_hop = i == self.hops.len() - 1; @@ -882,6 +922,11 @@ where L::Target: Logger { final_value_msat }; + // When we start collecting routes we enforce the max_channel_saturation_power_of_half + // requirement strictly. After we've collected enough (or if we fail to find new routes) we + // drop the requirement by setting this to 0. + let mut channel_saturation_pow_half = payment_params.max_channel_saturation_power_of_half; + // Keep track of how much liquidity has been used in selected channels. Used to determine // if the channel can be used by additional MPP paths or to inform path finding decisions. It is // aware of direction *only* to ensure that the correct htlc_maximum_msat value is used. Hence, @@ -934,7 +979,8 @@ where L::Target: Logger { // - for first and last hops early in get_route if $src_node_id != $dest_node_id { let short_channel_id = $candidate.short_channel_id(); - let htlc_maximum_msat = $candidate.htlc_maximum_msat(); + let effective_capacity = $candidate.effective_capacity(); + let htlc_maximum_msat = max_htlc_from_capacity(effective_capacity, 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 @@ -1084,7 +1130,7 @@ where L::Target: Logger { let channel_usage = ChannelUsage { amount_msat: amount_to_transfer_over_msat, inflight_htlc_msat: used_liquidity_msat, - effective_capacity: $candidate.effective_capacity(), + effective_capacity, }; let channel_penalty_msat = scorer.channel_penalty_msat( short_channel_id, &$src_node_id, &$dest_node_id, channel_usage @@ -1505,12 +1551,14 @@ 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); - if *used_liquidity_msat == hop.candidate.htlc_maximum_msat() { + let hop_capacity = hop.candidate.effective_capacity(); + let hop_max_msat = max_htlc_from_capacity(hop_capacity, 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. prevented_redundant_path_selection = true; } - debug_assert!(*used_liquidity_msat <= hop.candidate.htlc_maximum_msat()); + debug_assert!(*used_liquidity_msat <= hop_max_msat); } if !prevented_redundant_path_selection { // If we weren't capped by hitting a liquidity limit on a channel in the path, @@ -1551,6 +1599,10 @@ where L::Target: Logger { } if !allow_mpp { + if !found_new_path && channel_saturation_pow_half != 0 { + channel_saturation_pow_half = 0; + continue 'paths_collection; + } // If we don't support MPP, no use trying to gather more value ever. break 'paths_collection; } @@ -1560,7 +1612,9 @@ where L::Target: Logger { // iteration. // In the latter case, making another path finding attempt won't help, // because we deterministically terminated the search due to low liquidity. - if already_collected_value_msat >= recommended_value_msat || !found_new_path { + if !found_new_path && channel_saturation_pow_half != 0 { + channel_saturation_pow_half = 0; + } else if already_collected_value_msat >= recommended_value_msat || !found_new_path { log_trace!(logger, "Have now collected {} msat (seeking {} msat) in paths. Last path loop {} a new path.", already_collected_value_msat, recommended_value_msat, if found_new_path { "found" } else { "did not find" }); break 'paths_collection; @@ -1676,8 +1730,32 @@ where L::Target: Logger { // Step (9). // Select the best route by lowest total cost. drawn_routes.sort_unstable_by_key(|paths| paths.iter().map(|path| path.get_cost_msat()).sum::()); + let selected_route = drawn_routes.first_mut().unwrap(); + + // Sort by the path itself and combine redundant paths. + // Note that we sort by SCIDs alone as its simpler but when combining we have to ensure we + // compare both SCIDs and NodeIds as individual nodes may use random aliases causing collisions + // across nodes. + selected_route.sort_unstable_by_key(|path| { + let mut key = [0u64; MAX_PATH_LENGTH_ESTIMATE as usize]; + debug_assert!(path.hops.len() <= key.len()); + for (scid, key) in path.hops.iter().map(|h| h.0.candidate.short_channel_id()).zip(key.iter_mut()) { + *key = scid; + } + key + }); + for idx in 0..(selected_route.len() - 1) { + if idx + 1 >= selected_route.len() { break; } + if iter_equal(selected_route[idx ].hops.iter().map(|h| (h.0.candidate.short_channel_id(), h.0.node_id)), + selected_route[idx + 1].hops.iter().map(|h| (h.0.candidate.short_channel_id(), h.0.node_id))) { + let new_value = selected_route[idx].get_value_msat() + selected_route[idx + 1].get_value_msat(); + selected_route[idx].update_value_and_recompute_fees(new_value); + selected_route.remove(idx + 1); + } + } + let mut selected_paths = Vec::>>::new(); - for payment_path in drawn_routes.first().unwrap() { + for payment_path in selected_route { let mut path = payment_path.hops.iter().map(|(payment_hop, node_features)| { Ok(RouteHop { pubkey: PublicKey::from_slice(payment_hop.node_id.as_slice()).map_err(|_| LightningError{err: format!("Public key {:?} is invalid", &payment_hop.node_id), action: ErrorAction::IgnoreAndLog(Level::Trace)})?, @@ -4763,17 +4841,18 @@ mod tests { // Get a route for 100 sats and check that we found the MPP route no problem and didn't // overpay at all. - let route = get_route(&our_id, &payment_params, &network_graph.read_only(), None, 100_000, 42, Arc::clone(&logger), &scorer, &random_seed_bytes).unwrap(); + let mut route = get_route(&our_id, &payment_params, &network_graph.read_only(), None, 100_000, 42, Arc::clone(&logger), &scorer, &random_seed_bytes).unwrap(); assert_eq!(route.paths.len(), 2); - // Paths are somewhat randomly ordered, but: - // * the first is channel 2 (1 msat fee) -> channel 4 -> channel 42 - // * the second is channel 1 (0 fee, but 99 sat maximum) -> channel 3 -> channel 42 - assert_eq!(route.paths[0][0].short_channel_id, 2); - assert_eq!(route.paths[0][0].fee_msat, 1); - assert_eq!(route.paths[0][2].fee_msat, 1_000); - assert_eq!(route.paths[1][0].short_channel_id, 1); - assert_eq!(route.paths[1][0].fee_msat, 0); - assert_eq!(route.paths[1][2].fee_msat, 99_000); + route.paths.sort_by_key(|path| path[0].short_channel_id); + // Paths are manually ordered ordered by SCID, so: + // * the first is channel 1 (0 fee, but 99 sat maximum) -> channel 3 -> channel 42 + // * the second is channel 2 (1 msat fee) -> channel 4 -> channel 42 + assert_eq!(route.paths[0][0].short_channel_id, 1); + assert_eq!(route.paths[0][0].fee_msat, 0); + assert_eq!(route.paths[0][2].fee_msat, 99_000); + assert_eq!(route.paths[1][0].short_channel_id, 2); + assert_eq!(route.paths[1][0].fee_msat, 1); + assert_eq!(route.paths[1][2].fee_msat, 1_000); assert_eq!(route.get_total_fees(), 1); assert_eq!(route.get_total_amount(), 100_000); } @@ -4787,7 +4866,8 @@ mod tests { let scorer = test_utils::TestScorer::with_penalty(0); let keys_manager = test_utils::TestKeysInterface::new(&[0u8; 32], Network::Testnet); let random_seed_bytes = keys_manager.get_secure_random_bytes(); - let payment_params = PaymentParameters::from_node_id(nodes[2]).with_features(InvoiceFeatures::known()); + let payment_params = PaymentParameters::from_node_id(nodes[2]).with_features(InvoiceFeatures::known()) + .with_max_channel_saturation_power_of_half(0); // We need a route consisting of 3 paths: // From our node to node2 via node0, node7, node1 (three paths one hop each). @@ -5235,12 +5315,13 @@ mod tests { assert_eq!(route.paths[0].len(), 1); assert_eq!(route.paths[1].len(), 1); + assert!((route.paths[0][0].short_channel_id == 3 && route.paths[1][0].short_channel_id == 2) || + (route.paths[0][0].short_channel_id == 2 && route.paths[1][0].short_channel_id == 3)); + assert_eq!(route.paths[0][0].pubkey, nodes[0]); - assert_eq!(route.paths[0][0].short_channel_id, 3); assert_eq!(route.paths[0][0].fee_msat, 50_000); assert_eq!(route.paths[1][0].pubkey, nodes[0]); - assert_eq!(route.paths[1][0].short_channel_id, 2); assert_eq!(route.paths[1][0].fee_msat, 50_000); } @@ -5641,6 +5722,50 @@ mod tests { } } + #[test] + fn avoids_saturating_channels() { + let (secp_ctx, network_graph, gossip_sync, _, logger) = build_graph(); + let (_, our_id, privkeys, nodes) = get_nodes(&secp_ctx); + + let scorer = ProbabilisticScorer::new(Default::default(), &*network_graph, Arc::clone(&logger)); + + // Set the fee on channel 13 to 100% to match channel 4 giving us two equivalent paths (us + // -> node 7 -> node2 and us -> node 1 -> node 2) which we should balance over. + update_channel(&gossip_sync, &secp_ctx, &privkeys[1], UnsignedChannelUpdate { + chain_hash: genesis_block(Network::Testnet).header.block_hash(), + short_channel_id: 4, + timestamp: 2, + flags: 0, + cltv_expiry_delta: (4 << 4) | 1, + htlc_minimum_msat: 0, + htlc_maximum_msat: OptionalField::Present(200_000_000), + fee_base_msat: 0, + fee_proportional_millionths: 0, + excess_data: Vec::new() + }); + update_channel(&gossip_sync, &secp_ctx, &privkeys[7], UnsignedChannelUpdate { + chain_hash: genesis_block(Network::Testnet).header.block_hash(), + short_channel_id: 13, + timestamp: 2, + flags: 0, + cltv_expiry_delta: (13 << 4) | 1, + htlc_minimum_msat: 0, + htlc_maximum_msat: OptionalField::Present(200_000_000), + fee_base_msat: 0, + fee_proportional_millionths: 0, + excess_data: Vec::new() + }); + + let payment_params = PaymentParameters::from_node_id(nodes[2]).with_features(InvoiceFeatures::known()); + let keys_manager = test_utils::TestKeysInterface::new(&[0u8; 32], Network::Testnet); + let random_seed_bytes = keys_manager.get_secure_random_bytes(); + // 150,000 sat is less than the available liquidity on each channel, set above. + let route = get_route(&our_id, &payment_params, &network_graph.read_only(), None, 150_000_000, 42, Arc::clone(&logger), &scorer, &random_seed_bytes).unwrap(); + assert_eq!(route.paths.len(), 2); + assert!((route.paths[0][1].short_channel_id == 4 && route.paths[1][1].short_channel_id == 13) || + (route.paths[1][1].short_channel_id == 4 && route.paths[0][1].short_channel_id == 13)); + } + #[cfg(not(feature = "no-std"))] pub(super) fn random_init_seed() -> u64 { // Because the default HashMap in std pulls OS randomness, we can use it as a (bad) RNG.