Check pending funding in can_accept_incoming_htlc

If there are any pending splices when an accepting an incoming HTLC, the
HTLC needs to be validated against each pending FundingScope. Otherwise,
once the splice is locked, the HTLC could have been failed when it
should have been forwarded / claimed, or vice versa, under the promoted
FundingScope.

Author: jkczyz

lightning/src/ln/channel.rs

@@ -8134,7 +8134,21 @@ impl<SP: Deref> FundedChannel<SP> where
 		}
 
 		let dust_exposure_limiting_feerate = self.context.get_dust_exposure_limiting_feerate(&fee_estimator);
-		let htlc_stats = self.context.get_pending_htlc_stats(&self.funding, None, dust_exposure_limiting_feerate);
+
+		core::iter::once(&self.funding)
+			.chain(self.pending_funding.iter())
+			.map(|funding| self.can_accept_incoming_htlc_for_funding(funding, msg, dust_exposure_limiting_feerate, &logger))
+			.collect::<Result<(), LocalHTLCFailureReason>>()
+	}
+
+	fn can_accept_incoming_htlc_for_funding<L: Deref>(
+		&self, funding: &FundingScope, msg: &msgs::UpdateAddHTLC,
+		dust_exposure_limiting_feerate: u32, logger: &L,
+	) -> Result<(), LocalHTLCFailureReason>
+	where
+		L::Target: Logger,
+	{
+		let htlc_stats = self.context.get_pending_htlc_stats(funding, None, dust_exposure_limiting_feerate);
 		let max_dust_htlc_exposure_msat = self.context.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 {
@@ -8143,11 +8157,11 @@ impl<SP: Deref> FundedChannel<SP> where
 				on_counterparty_tx_dust_htlc_exposure_msat, max_dust_htlc_exposure_msat);
 			return Err(LocalHTLCFailureReason::DustLimitCounterparty)
 		}
-		let htlc_success_dust_limit = if self.funding.get_channel_type().supports_anchors_zero_fee_htlc_tx() {
+		let htlc_success_dust_limit = if funding.get_channel_type().supports_anchors_zero_fee_htlc_tx() {
 			0
 		} else {
 			let dust_buffer_feerate = self.context.get_dust_buffer_feerate(None) as u64;
-			dust_buffer_feerate * htlc_success_tx_weight(self.funding.get_channel_type()) / 1000
+			dust_buffer_feerate * htlc_success_tx_weight(funding.get_channel_type()) / 1000
 		};
 		let exposure_dust_limit_success_sats = htlc_success_dust_limit + self.context.holder_dust_limit_satoshis;
 		if msg.amount_msat / 1000 < exposure_dust_limit_success_sats {
@@ -8159,7 +8173,7 @@ impl<SP: Deref> FundedChannel<SP> where
 			}
 		}
 
-		let anchor_outputs_value_msat = if self.funding.get_channel_type().supports_anchors_zero_fee_htlc_tx() {
+		let anchor_outputs_value_msat = if funding.get_channel_type().supports_anchors_zero_fee_htlc_tx() {
 			ANCHOR_OUTPUT_VALUE_SATOSHI * 2 * 1000
 		} else {
 			0
@@ -8175,23 +8189,23 @@ impl<SP: Deref> FundedChannel<SP> where
 		}
 
 		let pending_value_to_self_msat =
-			self.funding.value_to_self_msat + htlc_stats.pending_inbound_htlcs_value_msat - removed_outbound_total_msat;
+			funding.value_to_self_msat + htlc_stats.pending_inbound_htlcs_value_msat - removed_outbound_total_msat;
 		let pending_remote_value_msat =
-			self.funding.get_value_satoshis() * 1000 - pending_value_to_self_msat;
+			funding.get_value_satoshis() * 1000 - pending_value_to_self_msat;
 
-		if !self.funding.is_outbound() {
+		if !funding.is_outbound() {
 			// `Some(())` is for the fee spike buffer we keep for the remote. 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 mut remote_fee_cost_incl_stuck_buffer_msat = self.context.next_remote_commit_tx_fee_msat(&self.funding, None, Some(()));
-			if !self.funding.get_channel_type().supports_anchors_zero_fee_htlc_tx() {
+			let mut remote_fee_cost_incl_stuck_buffer_msat = self.context.next_remote_commit_tx_fee_msat(funding, None, Some(()));
+			if !funding.get_channel_type().supports_anchors_zero_fee_htlc_tx() {
 				remote_fee_cost_incl_stuck_buffer_msat *= FEE_SPIKE_BUFFER_FEE_INCREASE_MULTIPLE;
 			}
-			if pending_remote_value_msat.saturating_sub(self.funding.holder_selected_channel_reserve_satoshis * 1000).saturating_sub(anchor_outputs_value_msat) < remote_fee_cost_incl_stuck_buffer_msat {
+			if pending_remote_value_msat.saturating_sub(funding.holder_selected_channel_reserve_satoshis * 1000).saturating_sub(anchor_outputs_value_msat) < 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.context.channel_id());
 				return Err(LocalHTLCFailureReason::FeeSpikeBuffer);
 			}