Detect onchain timeout of a HTLC in ChannelManager block_connected

Pass failure backward

Author: Antoine Riard

src/ln/channelmanager.rs

@@ -1558,7 +1558,7 @@ impl ChannelManager {
 						rejected_by_dest: !payment_retryable,
 					});
 				} else {
-					panic!("should have onion error packet here");
+					//TODO: Pass this back (see GH #243)
 				}
 			},
 			HTLCSource::PreviousHopData(HTLCPreviousHopData { short_channel_id, htlc_id, incoming_packet_shared_secret }) => {
@@ -2715,6 +2715,8 @@ impl ChainListener for ChannelManager {
 			for htlc_update in self.monitor.fetch_pending_htlc_updated() {
 				if let Some(preimage) = htlc_update.payment_preimage {
 					self.claim_funds_internal(self.channel_state.lock().unwrap(), htlc_update.source, preimage);
+				} else {
+					self.fail_htlc_backwards_internal(self.channel_state.lock().unwrap(), htlc_update.source, &htlc_update.payment_hash, HTLCFailReason::Reason { failure_code: 0x4000 | 10, data: Vec::new() });
 				}
 			}
 		}

src/ln/channelmonitor.rs

@@ -1287,6 +1287,31 @@ impl ChannelMonitor {
 								txn_to_broadcast.push(single_htlc_tx);
 							}
 						}
+						if !htlc.offered {
+							// TODO: If the HTLC has already expired, potentially merge it with the
+							// rest of the claim transaction, as above.
+							let input = TxIn {
+								previous_output: BitcoinOutPoint {
+									txid: commitment_txid,
+									vout: htlc.transaction_output_index,
+								},
+								script_sig: Script::new(),
+								sequence: idx as u32,
+								witness: Vec::new(),
+							};
+							let mut timeout_tx = Transaction {
+								version: 2,
+								lock_time: htlc.cltv_expiry,
+								input: vec![input],
+								output: vec!(TxOut {
+									script_pubkey: self.destination_script.clone(),
+									value: htlc.amount_msat / 1000,
+								}),
+							};
+							let sighash_parts = bip143::SighashComponents::new(&timeout_tx);
+							sign_input!(sighash_parts, timeout_tx.input[0], htlc.amount_msat / 1000, vec![0]);
+							txn_to_broadcast.push(timeout_tx);
+						}
 					}
 
 					if inputs.is_empty() { return (txn_to_broadcast, (commitment_txid, watch_outputs), spendable_outputs, htlc_updated); } // Nothing to be done...probably a false positive/local tx