More flexible fee rate estimates

Author: benthecarman

lightning/src/chain/chaininterface.rs

@@ -48,21 +48,23 @@ pub trait BroadcasterInterface {
 /// estimation.
 #[derive(Clone, Copy, Debug, Hash, PartialEq, Eq)]
 pub enum ConfirmationTarget {
-	/// We'd like a transaction to confirm in the future, but don't want to commit most of the fees
-	/// required to do so yet. The remaining fees will come via a Child-Pays-For-Parent (CPFP) fee
-	/// bump of the transaction.
-	///
-	/// The feerate returned should be the absolute minimum feerate required to enter most node
-	/// mempools across the network. Note that if you are not able to obtain this feerate estimate,
-	/// you should likely use the furthest-out estimate allowed by your fee estimator.
-	MempoolMinimum,
-	/// We are happy with a transaction confirming slowly, at least within a day or so worth of
-	/// blocks.
-	Background,
-	/// We'd like a transaction to confirm without major delayed, i.e., within the next 12-24 blocks.
-	Normal,
-	/// We'd like a transaction to confirm in the next few blocks.
-	HighPriority,
+	/// We need to sweep an HTLC after a force close transaction. This should be a high priority
+	/// transaction.
+	HtlcSweep,
+	/// The highest fee rate we will allow our channel counterparty to have in a non-anchor channel.
+	/// Having this be a low value can cause force closures. Using 10x your HighPriority fee rate can
+	/// be a good default.
+	MaxAllowedNonAnchorChannelRemoteFee,
+	/// The lowest fee rate we will allow our channel counterparty to have in a channel. This should
+	/// be at least the mempool minimum.
+	MinAllowedChannelRemoteFee,
+	/// Fee rate to use for anchor channels. This is safe to just be the mempool minimum.
+	AnchorChannelFee,
+	/// Fee rate to use for non-anchor channels. A good estimate is within the next 12-24 blocks.
+	NonAnchorChannelFee,
+	/// When cooperative closing channel, the minimum fee rate we will accept. Recommended at least
+	/// within a day or so worth of blocks.
+	ChannelCloseMinimum,
 }
 
 /// A trait which should be implemented to provide feerate information on a number of time
@@ -135,7 +137,7 @@ mod tests {
 		let test_fee_estimator = &TestFeeEstimator { sat_per_kw };
 		let fee_estimator = LowerBoundedFeeEstimator::new(test_fee_estimator);
 
-		assert_eq!(fee_estimator.bounded_sat_per_1000_weight(ConfirmationTarget::Background), FEERATE_FLOOR_SATS_PER_KW);
+		assert_eq!(fee_estimator.bounded_sat_per_1000_weight(ConfirmationTarget::AnchorChannelFee), FEERATE_FLOOR_SATS_PER_KW);
 	}
 
 	#[test]
@@ -144,6 +146,6 @@ mod tests {
 		let test_fee_estimator = &TestFeeEstimator { sat_per_kw };
 		let fee_estimator = LowerBoundedFeeEstimator::new(test_fee_estimator);
 
-		assert_eq!(fee_estimator.bounded_sat_per_1000_weight(ConfirmationTarget::Background), sat_per_kw);
+		assert_eq!(fee_estimator.bounded_sat_per_1000_weight(ConfirmationTarget::AnchorChannelFee), sat_per_kw);
 	}
 }

lightning/src/chain/onchaintx.rs

@@ -580,7 +580,7 @@ impl<ChannelSigner: WriteableEcdsaChannelSigner> OnchainTxHandler<ChannelSigner>
 		if cached_request.is_malleable() {
 			if cached_request.requires_external_funding() {
 				let target_feerate_sat_per_1000_weight = cached_request.compute_package_feerate(
-					fee_estimator, ConfirmationTarget::HighPriority, force_feerate_bump
+					fee_estimator, ConfirmationTarget::HtlcSweep, force_feerate_bump
 				);
 				if let Some(htlcs) = cached_request.construct_malleable_package_with_external_funding(self) {
 					return Some((
@@ -631,7 +631,7 @@ impl<ChannelSigner: WriteableEcdsaChannelSigner> OnchainTxHandler<ChannelSigner>
 					debug_assert_eq!(tx.txid(), self.holder_commitment.trust().txid(),
 						"Holder commitment transaction mismatch");
 
-					let conf_target = ConfirmationTarget::HighPriority;
+					let conf_target = ConfirmationTarget::HtlcSweep;
 					let package_target_feerate_sat_per_1000_weight = cached_request
 						.compute_package_feerate(fee_estimator, conf_target, force_feerate_bump);
 					if let Some(input_amount_sat) = output.funding_amount {

lightning/src/chain/package.rs

@@ -1111,13 +1111,14 @@ fn compute_fee_from_spent_amounts<F: Deref, L: Deref>(input_amounts: u64, predic
 	where F::Target: FeeEstimator,
 	      L::Target: Logger,
 {
-	let mut updated_feerate = fee_estimator.bounded_sat_per_1000_weight(ConfirmationTarget::HighPriority) as u64;
+	let mut updated_feerate = fee_estimator.bounded_sat_per_1000_weight(ConfirmationTarget::HtlcSweep) as u64;
+	let min_feerate = fee_estimator.bounded_sat_per_1000_weight(ConfirmationTarget::ChannelCloseMinimum) as u64;
 	let mut fee = updated_feerate * (predicted_weight as u64) / 1000;
 	if input_amounts <= fee {
-		updated_feerate = fee_estimator.bounded_sat_per_1000_weight(ConfirmationTarget::Normal) as u64;
+		updated_feerate = cmp::max(min_feerate, updated_feerate / 2);
 		fee = updated_feerate * (predicted_weight as u64) / 1000;
 		if input_amounts <= fee {
-			updated_feerate = fee_estimator.bounded_sat_per_1000_weight(ConfirmationTarget::Background) as u64;
+			updated_feerate = cmp::max(min_feerate, updated_feerate / 2);
 			fee = updated_feerate * (predicted_weight as u64) / 1000;
 			if input_amounts <= fee {
 				log_error!(logger, "Failed to generate an on-chain punishment tx as even low priority fee ({} sat) was more than the entire claim balance ({} sat)",

lightning/src/ln/channel.rs

@@ -1168,7 +1168,7 @@ impl<SP: Deref> ChannelContext<SP> where SP::Target: SignerProvider  {
 		match self.config.options.max_dust_htlc_exposure {
 			MaxDustHTLCExposure::FeeRateMultiplier(multiplier) => {
 				let feerate_per_kw = fee_estimator.bounded_sat_per_1000_weight(
-					ConfirmationTarget::HighPriority);
+					ConfirmationTarget::HtlcSweep);
 				feerate_per_kw as u64 * multiplier
 			},
 			MaxDustHTLCExposure::FixedLimitMsat(limit) => limit,
@@ -2155,23 +2155,14 @@ impl<SP: Deref> Channel<SP> where
 		// apply to channels supporting anchor outputs since HTLC transactions are pre-signed with a
 		// zero fee, so their fee is no longer considered to determine dust limits.
 		if !channel_type.supports_anchors_zero_fee_htlc_tx() {
-			let upper_limit = cmp::max(250 * 25,
-				fee_estimator.bounded_sat_per_1000_weight(ConfirmationTarget::HighPriority) as u64 * 10);
+			let upper_limit =
+				fee_estimator.bounded_sat_per_1000_weight(ConfirmationTarget::MaxAllowedNonAnchorChannelRemoteFee) as u64;
 			if feerate_per_kw as u64 > upper_limit {
 				return Err(ChannelError::Close(format!("Peer's feerate much too high. Actual: {}. Our expected upper limit: {}", feerate_per_kw, upper_limit)));
 			}
 		}
 
-		// We can afford to use a lower bound with anchors than previously since we can now bump
-		// fees when broadcasting our commitment. However, we must still make sure we meet the
-		// minimum mempool feerate, until package relay is deployed, such that we can ensure the
-		// commitment transaction propagates throughout node mempools on its own.
-		let lower_limit_conf_target = if channel_type.supports_anchors_zero_fee_htlc_tx() {
-			ConfirmationTarget::MempoolMinimum
-		} else {
-			ConfirmationTarget::Background
-		};
-		let lower_limit = fee_estimator.bounded_sat_per_1000_weight(lower_limit_conf_target);
+		let lower_limit = fee_estimator.bounded_sat_per_1000_weight(ConfirmationTarget::MinAllowedChannelRemoteFee);
 		// Some fee estimators round up to the next full sat/vbyte (ie 250 sats per kw), causing
 		// occasional issues with feerate disagreements between an initiator that wants a feerate
 		// of 1.1 sat/vbyte and a receiver that wants 1.1 rounded up to 2. Thus, we always add 250
@@ -4155,8 +4146,10 @@ impl<SP: Deref> Channel<SP> where
 		// Propose a range from our current Background feerate to our Normal feerate plus our
 		// force_close_avoidance_max_fee_satoshis.
 		// If we fail to come to consensus, we'll have to force-close.
-		let mut proposed_feerate = fee_estimator.bounded_sat_per_1000_weight(ConfirmationTarget::Background);
-		let normal_feerate = fee_estimator.bounded_sat_per_1000_weight(ConfirmationTarget::Normal);
+		let mut proposed_feerate = fee_estimator.bounded_sat_per_1000_weight(ConfirmationTarget::ChannelCloseMinimum);
+		// Use NonAnchorChannelFee because this should be an estimate for a channel close
+		// that we don't expect to be need fee bumping
+		let normal_feerate = fee_estimator.bounded_sat_per_1000_weight(ConfirmationTarget::NonAnchorChannelFee);
 		let mut proposed_max_feerate = if self.context.is_outbound() { normal_feerate } else { u32::max_value() };
 
 		// The spec requires that (when the channel does not have anchors) we only send absolute
@@ -5727,9 +5720,9 @@ impl<SP: Deref> OutboundV1Channel<SP> where SP::Target: SignerProvider {
 		debug_assert!(channel_type.is_subset(&channelmanager::provided_channel_type_features(&config)));
 
 		let commitment_conf_target = if channel_type.supports_anchors_zero_fee_htlc_tx() {
-			ConfirmationTarget::MempoolMinimum
+			ConfirmationTarget::AnchorChannelFee
 		} else {
-			ConfirmationTarget::Normal
+			ConfirmationTarget::NonAnchorChannelFee
 		};
 		let commitment_feerate = fee_estimator.bounded_sat_per_1000_weight(commitment_conf_target);
 
@@ -6019,7 +6012,7 @@ impl<SP: Deref> OutboundV1Channel<SP> where SP::Target: SignerProvider {
 		// whatever reason.
 		if self.context.channel_type.supports_anchors_zero_fee_htlc_tx() {
 			self.context.channel_type.clear_anchors_zero_fee_htlc_tx();
-			self.context.feerate_per_kw = fee_estimator.bounded_sat_per_1000_weight(ConfirmationTarget::Normal);
+			self.context.feerate_per_kw = fee_estimator.bounded_sat_per_1000_weight(ConfirmationTarget::NonAnchorChannelFee);
 			assert!(!self.context.channel_transaction_parameters.channel_type_features.supports_anchors_nonzero_fee_htlc_tx());
 		} else if self.context.channel_type.supports_scid_privacy() {
 			self.context.channel_type.clear_scid_privacy();

lightning/src/ln/channelmanager.rs

@@ -2638,9 +2638,9 @@ where
 	/// will be accepted on the given channel, and after additional timeout/the closing of all
 	/// pending HTLCs, the channel will be closed on chain.
 	///
-	///  * If we are the channel initiator, we will pay between our [`Background`] and
-	///    [`ChannelConfig::force_close_avoidance_max_fee_satoshis`] plus our [`Normal`] fee
-	///    estimate.
+	///  * If we are the channel initiator, we will pay between our [`ChannelCloseMinimum`] and
+	///    [`ChannelConfig::force_close_avoidance_max_fee_satoshis`] plus our [`NonAnchorChannelFee`]
+	///    fee estimate.
 	///  * If our counterparty is the channel initiator, we will require a channel closing
 	///    transaction feerate of at least our [`Background`] feerate or the feerate which
 	///    would appear on a force-closure transaction, whichever is lower. We will allow our
@@ -2654,8 +2654,8 @@ where
 	/// channel.
 	///
 	/// [`ChannelConfig::force_close_avoidance_max_fee_satoshis`]: crate::util::config::ChannelConfig::force_close_avoidance_max_fee_satoshis
-	/// [`Background`]: crate::chain::chaininterface::ConfirmationTarget::Background
-	/// [`Normal`]: crate::chain::chaininterface::ConfirmationTarget::Normal
+	/// [`ChannelCloseMinimum`]: crate::chain::chaininterface::ConfirmationTarget::ChannelCloseMinimum
+	/// [`NonAnchorChannelFee`]: crate::chain::chaininterface::ConfirmationTarget::NonAnchorChannelFee
 	/// [`SendShutdown`]: crate::events::MessageSendEvent::SendShutdown
 	pub fn close_channel(&self, channel_id: &ChannelId, counterparty_node_id: &PublicKey) -> Result<(), APIError> {
 		self.close_channel_internal(channel_id, counterparty_node_id, None, None)
@@ -2669,8 +2669,8 @@ where
 	/// the channel being closed or not:
 	///  * If we are the channel initiator, we will pay at least this feerate on the closing
 	///    transaction. The upper-bound is set by
-	///    [`ChannelConfig::force_close_avoidance_max_fee_satoshis`] plus our [`Normal`] fee
-	///    estimate (or `target_feerate_sat_per_1000_weight`, if it is greater).
+	///    [`ChannelConfig::force_close_avoidance_max_fee_satoshis`] plus our [`NonAnchorChannelFee`]
+	///    fee estimate (or `target_feerate_sat_per_1000_weight`, if it is greater).
 	///  * If our counterparty is the channel initiator, we will refuse to accept a channel closure
 	///    transaction feerate below `target_feerate_sat_per_1000_weight` (or the feerate which
 	///    will appear on a force-closure transaction, whichever is lower).
@@ -2688,8 +2688,7 @@ where
 	/// channel.
 	///
 	/// [`ChannelConfig::force_close_avoidance_max_fee_satoshis`]: crate::util::config::ChannelConfig::force_close_avoidance_max_fee_satoshis
-	/// [`Background`]: crate::chain::chaininterface::ConfirmationTarget::Background
-	/// [`Normal`]: crate::chain::chaininterface::ConfirmationTarget::Normal
+	/// [`NonAnchorChannelFee`]: crate::chain::chaininterface::ConfirmationTarget::NonAnchorChannelFee
 	/// [`SendShutdown`]: crate::events::MessageSendEvent::SendShutdown
 	pub fn close_channel_with_feerate_and_script(&self, channel_id: &ChannelId, counterparty_node_id: &PublicKey, target_feerate_sats_per_1000_weight: Option<u32>, shutdown_script: Option<ShutdownScript>) -> Result<(), APIError> {
 		self.close_channel_internal(channel_id, counterparty_node_id, target_feerate_sats_per_1000_weight, shutdown_script)
@@ -4752,8 +4751,8 @@ where
 		PersistenceNotifierGuard::optionally_notify(self, || {
 			let mut should_persist = NotifyOption::SkipPersistNoEvents;
 
-			let normal_feerate = self.fee_estimator.bounded_sat_per_1000_weight(ConfirmationTarget::Normal);
-			let min_mempool_feerate = self.fee_estimator.bounded_sat_per_1000_weight(ConfirmationTarget::MempoolMinimum);
+			let non_anchor_feerate = self.fee_estimator.bounded_sat_per_1000_weight(ConfirmationTarget::NonAnchorChannelFee);
+			let anchor_feerate = self.fee_estimator.bounded_sat_per_1000_weight(ConfirmationTarget::AnchorChannelFee);
 
 			let per_peer_state = self.per_peer_state.read().unwrap();
 			for (_cp_id, peer_state_mutex) in per_peer_state.iter() {
@@ -4763,9 +4762,9 @@ where
 					|(chan_id, phase)| if let ChannelPhase::Funded(chan) = phase { Some((chan_id, chan)) } else { None }
 				) {
 					let new_feerate = if chan.context.get_channel_type().supports_anchors_zero_fee_htlc_tx() {
-						min_mempool_feerate
+						anchor_feerate
 					} else {
-						normal_feerate
+						non_anchor_feerate
 					};
 					let chan_needs_persist = self.update_channel_fee(chan_id, chan, new_feerate);
 					if chan_needs_persist == NotifyOption::DoPersist { should_persist = NotifyOption::DoPersist; }
@@ -4797,8 +4796,8 @@ where
 		PersistenceNotifierGuard::optionally_notify(self, || {
 			let mut should_persist = NotifyOption::SkipPersistNoEvents;
 
-			let normal_feerate = self.fee_estimator.bounded_sat_per_1000_weight(ConfirmationTarget::Normal);
-			let min_mempool_feerate = self.fee_estimator.bounded_sat_per_1000_weight(ConfirmationTarget::MempoolMinimum);
+			let non_anchor_feerate = self.fee_estimator.bounded_sat_per_1000_weight(ConfirmationTarget::NonAnchorChannelFee);
+			let anchor_feerate = self.fee_estimator.bounded_sat_per_1000_weight(ConfirmationTarget::AnchorChannelFee);
 
 			let mut handle_errors: Vec<(Result<(), _>, _)> = Vec::new();
 			let mut timed_out_mpp_htlcs = Vec::new();
@@ -4845,9 +4844,9 @@ where
 						match phase {
 							ChannelPhase::Funded(chan) => {
 								let new_feerate = if chan.context.get_channel_type().supports_anchors_zero_fee_htlc_tx() {
-									min_mempool_feerate
+									anchor_feerate
 								} else {
-									normal_feerate
+									non_anchor_feerate
 								};
 								let chan_needs_persist = self.update_channel_fee(chan_id, chan, new_feerate);
 								if chan_needs_persist == NotifyOption::DoPersist { should_persist = NotifyOption::DoPersist; }

lightning/src/util/config.rs

@@ -438,20 +438,20 @@ pub struct ChannelConfig {
 	/// funder/initiator.
 	///
 	/// When we are the funder, because we have to pay the channel closing fee, we bound the
-	/// acceptable fee by our [`Background`] and [`Normal`] fees, with the upper bound increased by
+	/// 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
-	/// [`Normal`] feerate during normal operation, this value represents the additional fee we're
+	/// [`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
-	/// [`Background`] fee estimate, but allow our counterparty to pay as much fee as they like.
+	/// [`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.
 	///
-	/// [`Normal`]: crate::chain::chaininterface::ConfirmationTarget::Normal
-	/// [`Background`]: crate::chain::chaininterface::ConfirmationTarget::Background
+	/// [`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.