ln/refactor: split up construct_pending_htlc_status to get error

To be able to obtain the underlying error reason for the pending HTLC,
break up the helper method into two parts. This also removes some
unnecessary wrapping/unwrapping of messages in PendingHTLCStatus types.

Author: carlaKC

lightning/src/ln/channelmanager.rs

@@ -4487,67 +4487,55 @@ where
 		})
 	}
 
-	fn construct_pending_htlc_status<'a>(
-		&self, msg: &msgs::UpdateAddHTLC, counterparty_node_id: &PublicKey, shared_secret: [u8; 32],
-		decoded_hop: onion_utils::Hop, allow_underpay: bool,
-		next_packet_pubkey_opt: Option<Result<PublicKey, secp256k1::Error>>,
-	) -> PendingHTLCStatus {
-		macro_rules! return_err {
-			($msg: expr, $reason: expr, $data: expr) => {
-				{
-					let logger = WithContext::from(&self.logger, Some(*counterparty_node_id), Some(msg.channel_id), Some(msg.payment_hash));
-					log_info!(logger, "Failed to accept/forward incoming HTLC: {}", $msg);
-					if msg.blinding_point.is_some() {
-						return PendingHTLCStatus::Fail(HTLCFailureMsg::Malformed(
-							msgs::UpdateFailMalformedHTLC {
-								channel_id: msg.channel_id,
-								htlc_id: msg.htlc_id,
-								sha256_of_onion: [0; 32],
-								failure_code: LocalHTLCFailureReason::InvalidOnionBlinding.failure_code(),
-							}
-						))
+	fn construct_pending_htlc_fail_msg<'a>(&self, msg: &msgs::UpdateAddHTLC,
+		counterparty_node_id: &PublicKey, shared_secret: [u8; 32], inbound_err: InboundHTLCErr) -> HTLCFailureMsg {
+		let logger = WithContext::from(&self.logger, Some(*counterparty_node_id), Some(msg.channel_id), Some(msg.payment_hash));
+		log_info!(logger, "Failed to accept/forward incoming HTLC: {}", inbound_err.msg);
+
+		if msg.blinding_point.is_some() {
+			return HTLCFailureMsg::Malformed(
+				msgs::UpdateFailMalformedHTLC {
+					channel_id: msg.channel_id,
+					htlc_id: msg.htlc_id,
+					sha256_of_onion: [0; 32],
+					failure_code: LocalHTLCFailureReason::InvalidOnionBlinding.failure_code(),
 					}
-					let failure = HTLCFailReason::reason($reason, $data.to_vec())
-						.get_encrypted_failure_packet(&shared_secret, &None);
-					return PendingHTLCStatus::Fail(HTLCFailureMsg::Relay(msgs::UpdateFailHTLC {
-						channel_id: msg.channel_id,
-						htlc_id: msg.htlc_id,
-						reason: failure.data,
-					}));
-				}
-			}
+			)
 		}
+
+		let failure = HTLCFailReason::reason(inbound_err.reason, inbound_err.err_data.to_vec())
+					.get_encrypted_failure_packet(&shared_secret, &None);
+		return HTLCFailureMsg::Relay(msgs::UpdateFailHTLC {
+			channel_id: msg.channel_id,
+			htlc_id: msg.htlc_id,
+			reason: failure.data,
+		});
+	}
+
+	fn get_pending_htlc_info<'a>(
+		&self, msg: &msgs::UpdateAddHTLC, shared_secret: [u8; 32],
+		decoded_hop: onion_utils::Hop, allow_underpay: bool,
+		next_packet_pubkey_opt: Option<Result<PublicKey, secp256k1::Error>>,
+	) -> Result<PendingHTLCInfo, InboundHTLCErr> {
 		match decoded_hop {
 			onion_utils::Hop::Receive { .. } | onion_utils::Hop::BlindedReceive { .. } |
 			onion_utils::Hop::TrampolineReceive { .. } | onion_utils::Hop::TrampolineBlindedReceive { .. } => {
 				// OUR PAYMENT!
+				// Note that we could obviously respond immediately with an update_fulfill_htlc
+				// message, however that would leak that we are the recipient of this payment, so
+				// instead we stay symmetric with the forwarding case, only responding (after a
+				// delay) once they've send us a commitment_signed!
 				let current_height: u32 = self.best_block.read().unwrap().height;
-				match create_recv_pending_htlc_info(decoded_hop, shared_secret, msg.payment_hash,
+				create_recv_pending_htlc_info(decoded_hop, shared_secret, msg.payment_hash,
 					msg.amount_msat, msg.cltv_expiry, None, allow_underpay, msg.skimmed_fee_msat,
 					current_height)
-				{
-					Ok(info) => {
-						// Note that we could obviously respond immediately with an update_fulfill_htlc
-						// message, however that would leak that we are the recipient of this payment, so
-						// instead we stay symmetric with the forwarding case, only responding (after a
-						// delay) once they've sent us a commitment_signed!
-						PendingHTLCStatus::Forward(info)
-					},
-					Err(InboundHTLCErr { reason, err_data, msg }) => return_err!(msg, reason , &err_data)
-				}
 			},
 			onion_utils::Hop::Forward { .. } | onion_utils::Hop::BlindedForward { .. } => {
-				match create_fwd_pending_htlc_info(msg, decoded_hop, shared_secret, next_packet_pubkey_opt) {
-					Ok(info) => PendingHTLCStatus::Forward(info),
-					Err(InboundHTLCErr { reason, err_data, msg }) => return_err!(msg, reason, &err_data)
-				}
+				create_fwd_pending_htlc_info(msg, decoded_hop, shared_secret, next_packet_pubkey_opt)
 			},
 			onion_utils::Hop::TrampolineForward { .. } | onion_utils::Hop::TrampolineBlindedForward { .. } => {
-				match create_fwd_pending_htlc_info(msg, decoded_hop, shared_secret, next_packet_pubkey_opt) {
-					Ok(info) => PendingHTLCStatus::Forward(info),
-					Err(InboundHTLCErr { reason, err_data, msg }) => return_err!(msg, reason, &err_data)
-				}
-			}
+				create_fwd_pending_htlc_info(msg, decoded_hop, shared_secret, next_packet_pubkey_opt)
+			},
 		}
 	}
 
@@ -5839,16 +5827,14 @@ where
 					}
 				}
 
-				match self.construct_pending_htlc_status(
-					&update_add_htlc, &incoming_counterparty_node_id, shared_secret, next_hop,
-					incoming_accept_underpaying_htlcs, next_packet_details_opt.map(|d| d.next_packet_pubkey),
+				match self.get_pending_htlc_info(
+					&update_add_htlc, shared_secret, next_hop, incoming_accept_underpaying_htlcs,
+					next_packet_details_opt.map(|d| d.next_packet_pubkey),
 				) {
-					PendingHTLCStatus::Forward(htlc_forward) => {
-						htlc_forwards.push((htlc_forward, update_add_htlc.htlc_id));
-					},
-					PendingHTLCStatus::Fail(htlc_fail) => {
+					Ok(info) => htlc_forwards.push((info, update_add_htlc.htlc_id)),
+					Err(inbound_err) => {
 						let htlc_destination = get_failed_htlc_destination(outgoing_scid_opt, update_add_htlc.payment_hash);
-						htlc_fails.push((htlc_fail, htlc_destination));
+						htlc_fails.push((self.construct_pending_htlc_fail_msg(&update_add_htlc, &incoming_counterparty_node_id, shared_secret, inbound_err), htlc_destination));
 					},
 				}
 			}
@@ -11784,7 +11770,6 @@ where
 				payment.htlcs.retain(|htlc| {
 					// If height is approaching the number of blocks we think it takes us to get
 					// our commitment transaction confirmed before the HTLC expires, plus the
-					// number of blocks we generally consider it to take to do a commitment update,
 					// just give up on it and fail the HTLC.
 					if height >= htlc.cltv_expiry - HTLC_FAIL_BACK_BUFFER {
 						let mut htlc_msat_height_data = htlc.value.to_be_bytes().to_vec();