can_accept_incoming_htlc

Author: tankyleo

lightning/src/ln/channel.rs

@@ -4411,84 +4411,70 @@ where
 
 	#[rustfmt::skip]
 	fn can_accept_incoming_htlc<L: Deref>(
-		&self, funding: &FundingScope, msg: &msgs::UpdateAddHTLC,
+		&self, funding: &FundingScope,
 		dust_exposure_limiting_feerate: Option<u32>, logger: &L,
 	) -> Result<(), LocalHTLCFailureReason>
 	where
 		L::Target: Logger,
 	{
-		let htlc_stats = self.get_pending_htlc_stats(funding, None, dust_exposure_limiting_feerate);
+		// `Some(())` is for the fee spike buffer we keep for the remote if the channel is not zero fee. This deviates from the spec because the fee spike buffer requirement
+		// doesn't exist on the receiver's side, only on the sender's. Note that with anchor
+		// outputs we are no longer as sensitive to fee spikes, so we need to account for them.
+		//
+		// A `None` `HTLCCandidate` is used as in this case because we're already accounting for
+		// the incoming HTLC as it has been fully committed by both sides.
+		let fee_spike_buffer_htlc = if funding.get_channel_type().supports_anchor_zero_fee_commitments() {
+			0
+		} else {
+			1
+		};
+		let next_commitment_htlcs = self.next_commitment_htlcs(None);
+		let value_to_self_msat = self.get_next_commitment_value_to_self_msat(funding);
+		let next_commitment_stats = SpecTxBuilder {}.get_builder_stats(funding.is_outbound(), funding.get_value_satoshis(), value_to_self_msat, &next_commitment_htlcs, fee_spike_buffer_htlc, self.feerate_per_kw, dust_exposure_limiting_feerate, funding.get_channel_type(), self.holder_dust_limit_satoshis, self.counterparty_dust_limit_satoshis);
+
 		let max_dust_htlc_exposure_msat = self.get_max_dust_htlc_exposure_msat(dust_exposure_limiting_feerate);
-		let on_counterparty_tx_dust_htlc_exposure_msat = htlc_stats.on_counterparty_tx_dust_exposure_msat;
-		if on_counterparty_tx_dust_htlc_exposure_msat > max_dust_htlc_exposure_msat {
+		if next_commitment_stats.on_counterparty_tx_dust_exposure_msat > max_dust_htlc_exposure_msat {
 			// Note that the total dust exposure includes both the dust HTLCs and the excess mining fees of the counterparty commitment transaction
 			log_info!(logger, "Cannot accept value that would put our total dust exposure at {} over the limit {} on counterparty commitment tx",
-				on_counterparty_tx_dust_htlc_exposure_msat, max_dust_htlc_exposure_msat);
+			        next_commitment_stats.on_counterparty_tx_dust_exposure_msat, max_dust_htlc_exposure_msat);
 			return Err(LocalHTLCFailureReason::DustLimitCounterparty)
 		}
-		let dust_buffer_feerate = self.get_dust_buffer_feerate(None);
-		let (htlc_success_tx_fee_sat, _) = second_stage_tx_fees_sat(
-			&funding.get_channel_type(), dust_buffer_feerate,
-		);
-		let exposure_dust_limit_success_sats = htlc_success_tx_fee_sat + self.holder_dust_limit_satoshis;
-		if msg.amount_msat / 1000 < exposure_dust_limit_success_sats {
-			let on_holder_tx_dust_htlc_exposure_msat = htlc_stats.on_holder_tx_dust_exposure_msat;
-			if on_holder_tx_dust_htlc_exposure_msat > max_dust_htlc_exposure_msat {
-				log_info!(logger, "Cannot accept value that would put our exposure to dust HTLCs at {} over the limit {} on holder commitment tx",
-					on_holder_tx_dust_htlc_exposure_msat, max_dust_htlc_exposure_msat);
-				return Err(LocalHTLCFailureReason::DustLimitHolder)
-			}
+		if next_commitment_stats.on_holder_tx_dust_exposure_msat > max_dust_htlc_exposure_msat {
+			// Note: We now always check holder dust exposure, whereas we previously would only
+			// do it if the incoming HTLC was dust on our own commitment transaction
+			log_info!(logger, "Cannot accept value that would put our exposure to dust HTLCs at {} over the limit {} on holder commitment tx",
+				next_commitment_stats.on_holder_tx_dust_exposure_msat, max_dust_htlc_exposure_msat);
+			return Err(LocalHTLCFailureReason::DustLimitHolder)
 		}
 
 		if !funding.is_outbound() {
-			let removed_outbound_total_msat: u64 = self.pending_outbound_htlcs
-				.iter()
-				.filter_map(|htlc| {
-					matches!(
-						htlc.state,
-						OutboundHTLCState::AwaitingRemoteRevokeToRemove(OutboundHTLCOutcome::Success(_, _))
-						| OutboundHTLCState::AwaitingRemovedRemoteRevoke(OutboundHTLCOutcome::Success(_, _))
-					)
-					.then_some(htlc.amount_msat)
-				})
-				.sum();
-			let pending_value_to_self_msat =
-				funding.value_to_self_msat + htlc_stats.pending_inbound_htlcs_value_msat - removed_outbound_total_msat;
-			let pending_remote_value_msat =
-				funding.get_value_satoshis() * 1000 - pending_value_to_self_msat;
-			// Subtract any non-HTLC outputs from the local and remote balances
-			let (_, remote_balance_before_fee_msat) = SpecTxBuilder {}.subtract_non_htlc_outputs(
-				funding.is_outbound(),
-				pending_value_to_self_msat,
-				pending_remote_value_msat,
-				funding.get_channel_type()
-			);
-
-			// `Some(())` is for the fee spike buffer we keep for the remote if the channel is
-			// not zero fee. This deviates from the spec because the fee spike buffer requirement
-			// doesn't exist on the receiver's side, only on the sender's. Note that with anchor
-			// outputs we are no longer as sensitive to fee spikes, so we need to account for them.
-			//
-			// A `None` `HTLCCandidate` is used as in this case because we're already accounting for
-			// the incoming HTLC as it has been fully committed by both sides.
-			let fee_spike_buffer_htlc = if funding.get_channel_type().supports_anchor_zero_fee_commitments() {
-				None
-			} else {
-				Some(())
-			};
-
-			let mut remote_fee_cost_incl_stuck_buffer_msat = self.next_remote_commit_tx_fee_msat(
-				funding, None, fee_spike_buffer_htlc,
-			);
+			let mut remote_fee_cost_incl_stuck_buffer_msat = next_commitment_stats.counterparty_commit_tx_fee_sat * 1000;
 			if !funding.get_channel_type().supports_anchors_zero_fee_htlc_tx() {
 				remote_fee_cost_incl_stuck_buffer_msat *= FEE_SPIKE_BUFFER_FEE_INCREASE_MULTIPLE;
 			}
+			let remote_balance_before_fee_msat = next_commitment_stats.counterparty_balance_msat.unwrap_or(0);
 			if remote_balance_before_fee_msat.saturating_sub(funding.holder_selected_channel_reserve_satoshis * 1000) < remote_fee_cost_incl_stuck_buffer_msat {
 				log_info!(logger, "Attempting to fail HTLC due to fee spike buffer violation in channel {}. Rebalancing is required.", &self.channel_id());
 				return Err(LocalHTLCFailureReason::FeeSpikeBuffer);
 			}
 		}
 
+		#[cfg(any(test, fuzzing))]
+		{
+			let next_commitment_stats = if fee_spike_buffer_htlc == 1 {
+				SpecTxBuilder {}.get_builder_stats(funding.is_outbound(), funding.get_value_satoshis(), value_to_self_msat, &next_commitment_htlcs, 0, self.feerate_per_kw, dust_exposure_limiting_feerate, funding.get_channel_type(), self.holder_dust_limit_satoshis, self.counterparty_dust_limit_satoshis)
+			} else {
+				next_commitment_stats
+			};
+			let mut predicted_htlcs = next_commitment_htlcs;
+			predicted_htlcs.sort_unstable();
+			*funding.next_remote_fee.lock().unwrap() = PredictedNextFee {
+				predicted_feerate: self.feerate_per_kw,
+				predicted_htlcs,
+				predicted_fee_sat: next_commitment_stats.counterparty_commit_tx_fee_sat,
+			};
+		}
+
 		Ok(())
 	}
 
@@ -9451,7 +9437,7 @@ where
 	/// this function determines whether to fail the HTLC, or forward / claim it.
 	#[rustfmt::skip]
 	pub fn can_accept_incoming_htlc<F: Deref, L: Deref>(
-		&self, msg: &msgs::UpdateAddHTLC, fee_estimator: &LowerBoundedFeeEstimator<F>, logger: L
+		&self, fee_estimator: &LowerBoundedFeeEstimator<F>, logger: L
 	) -> Result<(), LocalHTLCFailureReason>
 	where
 		F::Target: FeeEstimator,
@@ -9467,7 +9453,7 @@ where
 
 		core::iter::once(&self.funding)
 			.chain(self.pending_funding.iter())
-			.try_for_each(|funding| self.context.can_accept_incoming_htlc(funding, msg, dust_exposure_limiting_feerate, &logger))
+			.try_for_each(|funding| self.context.can_accept_incoming_htlc(funding, dust_exposure_limiting_feerate, &logger))
 	}
 
 	pub fn get_cur_holder_commitment_transaction_number(&self) -> u64 {

lightning/src/ln/channelmanager.rs

@@ -6262,7 +6262,7 @@ where
 							&chan.context,
 							Some(update_add_htlc.payment_hash),
 						);
-						chan.can_accept_incoming_htlc(update_add_htlc, &self.fee_estimator, &logger)
+						chan.can_accept_incoming_htlc(&self.fee_estimator, &logger)
 					},
 				) {
 					Some(Ok(_)) => {},