/// 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, {
(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),
});
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,
}
}
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.
}
}
- 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 {
}
}
+#[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<I1: Iterator, I2: Iterator>(mut iter_a: I1, mut iter_b: I2)
+-> bool where I1::Item: PartialEq<I2::Item> {
+ 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.
// 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;
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,
// - 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
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
.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,
}
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;
}
// 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;
// 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::<u64>());
+ 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::<Vec<Result<RouteHop, LightningError>>>::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)})?,
// 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);
}
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).
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);
}
}
}
+ #[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.
projects / rust-lightning / commitdiff