+ /// [`MIN_CLTV_EXPIRY_DELTA`]: crate::ln::channelmanager::MIN_CLTV_EXPIRY_DELTA
+ pub cltv_expiry_delta: u16,
+ /// Limit our total exposure to potential loss to on-chain fees on close, including in-flight
+ /// HTLCs which are burned to fees as they are too small to claim on-chain and fees on
+ /// commitment transaction(s) broadcasted by our counterparty in excess of our own fee estimate.
+ ///
+ /// # HTLC-based Dust Exposure
+ ///
+ /// When an HTLC present in one of our channels is below a "dust" threshold, the HTLC will
+ /// not be claimable on-chain, instead being turned into additional miner fees if either
+ /// party force-closes the channel. Because the threshold is per-HTLC, our total exposure
+ /// to such payments may be substantial if there are many dust HTLCs present when the
+ /// channel is force-closed.
+ ///
+ /// The dust threshold for each HTLC is based on the `dust_limit_satoshis` for each party in a
+ /// channel negotiated throughout the channel open process, along with the fees required to have
+ /// a broadcastable HTLC spending transaction. When a channel supports anchor outputs
+ /// (specifically the zero fee HTLC transaction variant), this threshold no longer takes into
+ /// account the HTLC transaction fee as it is zero. Because of this, you may want to set this
+ /// value to a fixed limit for channels using anchor outputs, while the fee rate multiplier
+ /// variant is primarily intended for use with pre-anchor channels.
+ ///
+ /// The selected limit is applied for sent, forwarded, and received HTLCs and limits the total
+ /// exposure across all three types per-channel.
+ ///
+ /// # Transaction Fee Dust Exposure
+ ///
+ /// Further, counterparties broadcasting a commitment transaction in a force-close may result
+ /// in other balance being burned to fees, and thus all fees on commitment and HTLC
+ /// transactions in excess of our local fee estimates are included in the dust calculation.
+ ///
+ /// Because of this, another way to look at this limit is to divide it by 43,000 (or 218,750
+ /// for non-anchor channels) and see it as the maximum feerate disagreement (in sats/vB) per
+ /// non-dust HTLC we're allowed to have with our peers before risking a force-closure for
+ /// inbound channels.
+ // This works because, for anchor channels the on-chain cost is 172 weight (172+703 for
+ // non-anchors with an HTLC-Success transaction), i.e.
+ // dust_exposure_limit_msat / 1000 = 172 * feerate_in_sat_per_vb / 4 * HTLC count
+ // dust_exposure_limit_msat = 43,000 * feerate_in_sat_per_vb * HTLC count
+ // dust_exposure_limit_msat / HTLC count / 43,000 = feerate_in_sat_per_vb
+ ///
+ /// Thus, for the default value of 10_000 * a current feerate estimate of 10 sat/vB (or 2,500
+ /// sat/KW), we risk force-closure if we disagree with our peer by:
+ /// * `10_000 * 2_500 / 43_000 / (483*2)` = 0.6 sat/vB for anchor channels with 483 HTLCs in
+ /// both directions (the maximum),
+ /// * `10_000 * 2_500 / 43_000 / (50*2)` = 5.8 sat/vB for anchor channels with 50 HTLCs in both
+ /// directions (the LDK default max from [`ChannelHandshakeConfig::our_max_accepted_htlcs`])
+ /// * `10_000 * 2_500 / 218_750 / (483*2)` = 0.1 sat/vB for non-anchor channels with 483 HTLCs
+ /// in both directions (the maximum),
+ /// * `10_000 * 2_500 / 218_750 / (50*2)` = 1.1 sat/vB for non-anchor channels with 50 HTLCs
+ /// in both (the LDK default maximum from [`ChannelHandshakeConfig::our_max_accepted_htlcs`])
+ ///
+ /// Note that when using [`MaxDustHTLCExposure::FeeRateMultiplier`] this maximum disagreement
+ /// will scale linearly with increases (or decreases) in the our feerate estimates. Further,
+ /// for anchor channels we expect our counterparty to use a relatively low feerate estimate
+ /// while we use [`ConfirmationTarget::OnChainSweep`] (which should be relatively high) and
+ /// feerate disagreement force-closures should only occur when theirs is higher than ours.
+ ///
+ /// Default value: [`MaxDustHTLCExposure::FeeRateMultiplier`] with a multiplier of 10_000.
+ ///
+ /// [`ConfirmationTarget::OnChainSweep`]: crate::chain::chaininterface::ConfirmationTarget::OnChainSweep
+ pub max_dust_htlc_exposure: MaxDustHTLCExposure,
+ /// The additional fee we're willing to pay to avoid waiting for the counterparty's
+ /// `to_self_delay` to reclaim funds.
+ ///
+ /// When we close a channel cooperatively with our counterparty, we negotiate a fee for the
+ /// closing transaction which both sides find acceptable, ultimately paid by the channel
+ /// funder/initiator.
+ ///
+ /// When we are the funder, because we have to pay the channel closing fee, we bound the
+ /// acceptable fee by our [`ChannelCloseMinimum`] and [`NonAnchorChannelFee`] fees, with the upper bound increased by
+ /// this value. Because the on-chain fee we'd pay to force-close the channel is kept near our
+ /// [`NonAnchorChannelFee`] feerate during normal operation, this value represents the additional fee we're
+ /// willing to pay in order to avoid waiting for our counterparty's to_self_delay to reclaim our
+ /// funds.
+ ///
+ /// When we are not the funder, we require the closing transaction fee pay at least our
+ /// [`ChannelCloseMinimum`] fee estimate, but allow our counterparty to pay as much fee as they like.
+ /// Thus, this value is ignored when we are not the funder.
+ ///
+ /// Default value: 1000 satoshis.
+ ///
+ /// [`NonAnchorChannelFee`]: crate::chain::chaininterface::ConfirmationTarget::NonAnchorChannelFee
+ /// [`ChannelCloseMinimum`]: crate::chain::chaininterface::ConfirmationTarget::ChannelCloseMinimum
+ pub force_close_avoidance_max_fee_satoshis: u64,
+ /// If set, allows this channel's counterparty to skim an additional fee off this node's inbound
+ /// HTLCs. Useful for liquidity providers to offload on-chain channel costs to end users.
+ ///
+ /// Usage:
+ /// - The payee will set this option and set its invoice route hints to use [intercept scids]
+ /// generated by this channel's counterparty.
+ /// - The counterparty will get an [`HTLCIntercepted`] event upon payment forward, and call
+ /// [`forward_intercepted_htlc`] with less than the amount provided in
+ /// [`HTLCIntercepted::expected_outbound_amount_msat`]. The difference between the expected and
+ /// actual forward amounts is their fee. See
+ /// <https://github.com/BitcoinAndLightningLayerSpecs/lsp/tree/main/LSPS2#flow-lsp-trusts-client-model>
+ /// for how this feature may be used in the LSP use case.
+ ///
+ /// # Note
+ /// It's important for payee wallet software to verify that [`PaymentClaimable::amount_msat`] is
+ /// as-expected if this feature is activated, otherwise they may lose money!
+ /// [`PaymentClaimable::counterparty_skimmed_fee_msat`] provides the fee taken by the
+ /// counterparty.
+ ///
+ /// # Note
+ /// Switching this config flag on may break compatibility with versions of LDK prior to 0.0.116.
+ /// Unsetting this flag between restarts may lead to payment receive failures.
+ ///
+ /// Default value: false.
+ ///
+ /// [intercept scids]: crate::ln::channelmanager::ChannelManager::get_intercept_scid
+ /// [`forward_intercepted_htlc`]: crate::ln::channelmanager::ChannelManager::forward_intercepted_htlc
+ /// [`HTLCIntercepted`]: crate::events::Event::HTLCIntercepted
+ /// [`HTLCIntercepted::expected_outbound_amount_msat`]: crate::events::Event::HTLCIntercepted::expected_outbound_amount_msat
+ /// [`PaymentClaimable::amount_msat`]: crate::events::Event::PaymentClaimable::amount_msat
+ /// [`PaymentClaimable::counterparty_skimmed_fee_msat`]: crate::events::Event::PaymentClaimable::counterparty_skimmed_fee_msat
+ // TODO: link to bLIP when it's merged
+ pub accept_underpaying_htlcs: bool,
+}
+
+impl ChannelConfig {
+ /// Applies the given [`ChannelConfigUpdate`] as a partial update to the [`ChannelConfig`].
+ pub fn apply(&mut self, update: &ChannelConfigUpdate) {
+ if let Some(forwarding_fee_proportional_millionths) = update.forwarding_fee_proportional_millionths {
+ self.forwarding_fee_proportional_millionths = forwarding_fee_proportional_millionths;
+ }
+ if let Some(forwarding_fee_base_msat) = update.forwarding_fee_base_msat {
+ self.forwarding_fee_base_msat = forwarding_fee_base_msat;
+ }
+ if let Some(cltv_expiry_delta) = update.cltv_expiry_delta {
+ self.cltv_expiry_delta = cltv_expiry_delta;
+ }
+ if let Some(max_dust_htlc_exposure_msat) = update.max_dust_htlc_exposure_msat {
+ self.max_dust_htlc_exposure = max_dust_htlc_exposure_msat;
+ }
+ if let Some(force_close_avoidance_max_fee_satoshis) = update.force_close_avoidance_max_fee_satoshis {
+ self.force_close_avoidance_max_fee_satoshis = force_close_avoidance_max_fee_satoshis;
+ }
+ }