}
}
+ 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 {
let recommended_value_msat = final_value_msat * ROUTE_CAPACITY_PROVISION_FACTOR as u64;
let mut path_value_msat = final_value_msat;
- // We don't want multiple paths (as per MPP) share liquidity of the same channels.
- // This map allows paths to be aware of the channel use by other paths in the same call.
- // This would help to make a better path finding decisions and not "overbook" channels.
- // It is unaware of the directions (except for `next_outbound_htlc_limit_msat` in
- // `first_hops`).
- let mut bookkept_channels_liquidity_available_msat = HashMap::with_capacity(network_nodes.len());
+ // 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,
+ // liquidity used in one direction will not offset any used in the opposite direction.
+ let mut used_channel_liquidities: HashMap<(u64, bool), u64> =
+ HashMap::with_capacity(network_nodes.len());
// Keeping track of how much value we already collected across other paths. Helps to decide:
// - how much a new path should be transferring (upper bound);
// - 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 available_liquidity_msat = bookkept_channels_liquidity_available_msat
- .entry(short_channel_id)
- .or_insert_with(|| $candidate.effective_capacity().as_msat());
+ let htlc_maximum_msat = $candidate.htlc_maximum_msat();
// It is tricky to subtract $next_hops_fee_msat from available liquidity here.
// It may be misleading because we might later choose to reduce the value transferred
// fees caused by one expensive channel, but then this channel could have been used
// if the amount being transferred over this path is lower.
// We do this for now, but this is a subject for removal.
- if let Some(available_value_contribution_msat) = available_liquidity_msat.checked_sub($next_hops_fee_msat) {
+ if let Some(mut available_value_contribution_msat) = htlc_maximum_msat.checked_sub($next_hops_fee_msat) {
+ let used_liquidity_msat = used_channel_liquidities
+ .get(&(short_channel_id, $src_node_id < $dest_node_id))
+ .map_or(0, |used_liquidity_msat| {
+ available_value_contribution_msat = available_value_contribution_msat
+ .saturating_sub(*used_liquidity_msat);
+ *used_liquidity_msat
+ });
// Routing Fragmentation Mitigation heuristic:
//
}
}
+ let available_liquidity_msat = htlc_maximum_msat - used_liquidity_msat;
let path_penalty_msat = $next_hops_path_penalty_msat.saturating_add(
scorer.channel_penalty_msat(short_channel_id, amount_to_transfer_over_msat,
- *available_liquidity_msat, &$src_node_id, &$dest_node_id));
+ available_liquidity_msat, &$src_node_id, &$dest_node_id));
let new_graph_node = RouteGraphNode {
node_id: $src_node_id,
lowest_fee_to_peer_through_node: total_fee_msat,
// TODO: diversify by nodes (so that all paths aren't doomed if one node is offline).
'paths_collection: loop {
- // For every new path, start from scratch, except
- // bookkept_channels_liquidity_available_msat, which will improve
- // the further iterations of path finding. Also don't erase first_hop_targets.
+ // For every new path, start from scratch, except for used_channel_liquidities, which
+ // helps to avoid reusing previously selected paths in future iterations.
targets.clear();
dist.clear();
hit_minimum_limit = false;
// Remember that we used these channels so that we don't rely
// on the same liquidity in future paths.
let mut prevented_redundant_path_selection = false;
- for (payment_hop, _) in payment_path.hops.iter() {
- let channel_liquidity_available_msat = bookkept_channels_liquidity_available_msat.get_mut(&payment_hop.candidate.short_channel_id()).unwrap();
- let mut spent_on_hop_msat = value_contribution_msat;
- let next_hops_fee_msat = payment_hop.next_hops_fee_msat;
- spent_on_hop_msat += next_hops_fee_msat;
- if spent_on_hop_msat == *channel_liquidity_available_msat {
+ let prev_hop_iter = core::iter::once(&our_node_id)
+ .chain(payment_path.hops.iter().map(|(hop, _)| &hop.node_id));
+ for (prev_hop, (hop, _)) in prev_hop_iter.zip(payment_path.hops.iter()) {
+ let spent_on_hop_msat = value_contribution_msat + hop.next_hops_fee_msat;
+ let used_liquidity_msat = used_channel_liquidities
+ .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() {
// 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;
}
- *channel_liquidity_available_msat -= spent_on_hop_msat;
+ debug_assert!(*used_liquidity_msat <= hop.candidate.htlc_maximum_msat());
}
if !prevented_redundant_path_selection {
// If we weren't capped by hitting a liquidity limit on a channel in the path,
// we'll probably end up picking the same path again on the next iteration.
// Decrease the available liquidity of a hop in the middle of the path.
let victim_scid = payment_path.hops[(payment_path.hops.len()) / 2].0.candidate.short_channel_id();
+ let exhausted = u64::max_value();
log_trace!(logger, "Disabling channel {} for future path building iterations to avoid duplicates.", victim_scid);
- let victim_liquidity = bookkept_channels_liquidity_available_msat.get_mut(&victim_scid).unwrap();
- *victim_liquidity = 0;
+ *used_channel_liquidities.entry((victim_scid, false)).or_default() = exhausted;
+ *used_channel_liquidities.entry((victim_scid, true)).or_default() = exhausted;
}
// Track the total amount all our collected paths allow to send so that we:
projects / rust-lightning / blobdiff