Implement fail backward in case of detection of revoked tx

Refactor block_connected to ease output resolution

Add test_commitment_revoked_fail_backward

Close lightningdevkit#137

Author: Antoine Riard

src/ln/channelmanager.rs

@@ -2517,7 +2517,6 @@ impl ChainListener for ChannelManager {
 	fn block_connected(&self, header: &BlockHeader, height: u32, txn_matched: &[&Transaction], indexes_of_txn_matched: &[u32]) {
 		let _ = self.total_consistency_lock.read().unwrap();
 		let mut failed_channels = Vec::new();
-		let mut hash_to_remove = Vec::new();
 		{
 			let mut channel_lock = self.channel_state.lock().unwrap();
 			let channel_state = channel_lock.borrow_parts();
@@ -2586,32 +2585,24 @@ impl ChainListener for ChannelManager {
 				true
 			});
 
-			for tx in txn_matched {
-				if let Some(payments_data) = self.monitor.is_resolving_output(&tx) {
-					for payment_data in payments_data {
-						hash_to_remove.push((payment_data.0, payment_data.1));
-					}
-				}
-			}
 		}
 		for failure in failed_channels.drain(..) {
 			self.finish_force_close_channel(failure);
 		}
 		{
 			let mut channel_state = Some(self.channel_state.lock().unwrap());
-			for (payment_preimage, payment_hash) in hash_to_remove {
-				if let Some(preimage) = payment_preimage {
-					if channel_state.is_none() { channel_state = Some(self.channel_state.lock().unwrap());}
-					if let Some(mut entry) = channel_state.as_mut().unwrap().claimable_htlcs.remove(&payment_hash) {
-						for source in entry.drain(..) {
-							self.claim_funds_internal(channel_state.take().unwrap(), HTLCSource::PreviousHopData(source), preimage);
-						}
-					}
-				} else {
-					if channel_state.is_none() { channel_state = Some(self.channel_state.lock().unwrap());}
-					if let Some(mut entry) = channel_state.as_mut().unwrap().claimable_htlcs.remove(&payment_hash) {
-						for source in entry.drain(..) {
-							self.fail_htlc_backwards_internal(channel_state.take().unwrap(), HTLCSource::PreviousHopData(source), &payment_hash, HTLCFailReason::Reason { failure_code: 0x1000 | 14, data: Vec::new() });
+			for tx in txn_matched {
+				if let Some(payments_data) = self.monitor.is_resolving_output(&tx) {
+					for payment_data in payments_data {
+						if channel_state.is_none() { channel_state = Some(self.channel_state.lock().unwrap()); }
+						if let Some(mut entry) = channel_state.as_mut().unwrap().claimable_htlcs.remove(&payment_data.1) {
+							for source in entry.drain(..) {
+								if let Some(preimage) = payment_data.0 {
+									self.claim_funds_internal(channel_state.take().unwrap(), HTLCSource::PreviousHopData(source), preimage);
+								} else {
+									self.fail_htlc_backwards_internal(channel_state.take().unwrap(), HTLCSource::PreviousHopData(source), &payment_data.1, HTLCFailReason::Reason { failure_code: 0x1000 | 14, data: Vec::new() });
+								}
+							}
 						}
 					}
 				}
@@ -6276,6 +6267,54 @@ mod tests {
 		assert_eq!(node_txn[2].clone().input[0].witness.last().unwrap().len(), 133);
 	}
 
+	#[test]
+	fn test_commitment_revoked_fail_backward() {
+		// Test that in case of a revoked commitment tx, we detect the resolution of output by justice tx
+		// and fail backward accordingly.
+
+		let nodes = create_network(3);
+
+		// Create some initial channels
+		create_announced_chan_between_nodes(&nodes, 0, 1);
+		let chan_2 = create_announced_chan_between_nodes(&nodes, 1, 2);
+
+		// Rebalance the network a bit by relaying one payment through all the channels...
+		send_payment(&nodes[0], &vec!(&nodes[1], &nodes[2])[..], 8000000);
+		send_payment(&nodes[0], &vec!(&nodes[1], &nodes[2])[..], 8000000);
+
+		let (payment_preimage, _payment_hash) = route_payment(&nodes[0], &vec!(&nodes[1], &nodes[2])[..], 3000000);
+		// Get the will-be-revoked local txn from nodes[2]
+		let revoked_local_txn = nodes[2].node.channel_state.lock().unwrap().by_id.get(&chan_2.2).unwrap().last_local_commitment_txn.clone();
+		// Revoke the old state
+		claim_payment(&nodes[0], &vec!(&nodes[1], &nodes[2])[..], payment_preimage);
+
+		route_payment(&nodes[0], &vec!(&nodes[1], &nodes[2])[..], 3000000);
+
+		let header = BlockHeader { version: 0x20000000, prev_blockhash: Default::default(), merkle_root: Default::default(), time: 42, bits: 42, nonce: 42};
+		nodes[1].chain_monitor.block_connected_with_filtering(&Block { header, txdata: vec![revoked_local_txn[0].clone()] }, 1);
+		{
+			let mut added_monitors = nodes[1].chan_monitor.added_monitors.lock().unwrap();
+			assert_eq!(added_monitors.len(), 1);
+			added_monitors.clear();
+		}
+		let events = nodes[1].node.get_and_clear_pending_msg_events();
+		assert_eq!(events.len(), 2);
+		match events[0] {
+			MessageSendEvent::BroadcastChannelUpdate { msg: msgs::ChannelUpdate { .. } } => {},
+			_ => panic!("Unexpected event"),
+		}
+		match events[1] {
+			MessageSendEvent::UpdateHTLCs { ref node_id, updates: msgs::CommitmentUpdate { ref update_add_htlcs, ref update_fail_htlcs, ref update_fulfill_htlcs, ref update_fail_malformed_htlcs, .. } } => {
+				assert!(update_add_htlcs.is_empty());
+				assert!(!update_fail_htlcs.is_empty());
+				assert!(update_fulfill_htlcs.is_empty());
+				assert!(update_fail_malformed_htlcs.is_empty());
+				assert_eq!(nodes[0].node.get_our_node_id(), *node_id);
+			},
+			_ => panic!("Unexpected event"),
+		}
+	}
+
 	#[test]
 	fn test_htlc_ignore_latest_remote_commitment() {
 		// Test that HTLC transactions spending the latest remote commitment transaction are simply

src/ln/channelmonitor.rs

@@ -89,8 +89,8 @@ pub trait ManyChannelMonitor: Send + Sync {
 	/// ChainWatchInterfaces such that the provided monitor receives block_connected callbacks with
 	/// any spends of it.
 	fn add_update_monitor(&self, funding_txo: OutPoint, monitor: ChannelMonitor) -> Result<(), ChannelMonitorUpdateErr>;
-	/// In case of commitment tx broadcasted onchain, we need to detect resolution of its outputs by a success tx
-	/// (HTLC-Success or preimage tx) and extract preimages from them to claim backward inbound htlcs in others channels 
+	/// In case of commitment tx broadcasted onchain, we need to detect resolution of its outputs by a success tx, a timeout tx
+	/// or if it's a revoked one and pass state backward to advance inbound htlcs in others channels 
 	/// belonging to same payment route
 	fn is_resolving_output(&self, tx: &Transaction) -> Option<Vec<(Option<[u8;32]>, [u8;32])>>;
 }
@@ -184,6 +184,7 @@ impl<Key : Send + cmp::Eq + hash::Hash + 'static> SimpleManyChannelMonitor<Key>
 		monitors.insert(key, monitor);
 		Ok(())
 	}
+
 }
 
 impl ManyChannelMonitor for SimpleManyChannelMonitor<OutPoint> {
@@ -1502,6 +1503,16 @@ impl ChannelMonitor {
 	pub(crate) fn is_resolving_output(&self, tx: &Transaction) -> Option<Vec<(Option<[u8;32]>, [u8;32])>> {
 		let mut hash_to_remove = Vec::new();
 		if tx.input.len() > 0 {
+			let commitment_number = 0xffffffffffff - ((((tx.input[0].sequence as u64 & 0xffffff) << 3*8) | (tx.lock_time as u64 & 0xffffff)) ^ self.commitment_transaction_number_obscure_factor);
+			if commitment_number >= self.get_min_seen_secret() {
+				if let Some(ref local_commitment_tx) = self.current_local_signed_commitment_tx {
+					for &(ref htlc_output, _, _) in &local_commitment_tx.htlc_outputs {
+						if htlc_output.offered {
+							hash_to_remove.push((None, htlc_output.payment_hash.clone()));
+						}
+					}
+				}
+			}
 			for input in &tx.input {
 				let mut payment_data = (None, None);
 				if let Some(ref current_local_signed_commitment_tx) = self.current_local_signed_commitment_tx {
@@ -1552,6 +1563,7 @@ impl ChannelMonitor {
 		}
 		None
 	}
+
 }
 
 const MAX_ALLOC_SIZE: usize = 64*1024;