Merge pull request #1691 from TheBlueMatt/2022-08-dust-retry

Correct payment resolution after on chain failure of dust HTLCs

Author: valentinewallace

lightning/src/chain/channelmonitor.rs

@@ -619,7 +619,7 @@ pub enum Balance {
 /// An HTLC which has been irrevocably resolved on-chain, and has reached ANTI_REORG_DELAY.
 #[derive(PartialEq)]
 struct IrrevocablyResolvedHTLC {
-	commitment_tx_output_idx: u32,
+	commitment_tx_output_idx: Option<u32>,
 	/// The txid of the transaction which resolved the HTLC, this may be a commitment (if the HTLC
 	/// was not present in the confirmed commitment transaction), HTLC-Success, or HTLC-Timeout
 	/// transaction.
@@ -628,11 +628,39 @@ struct IrrevocablyResolvedHTLC {
 	payment_preimage: Option<PaymentPreimage>,
 }
 
-impl_writeable_tlv_based!(IrrevocablyResolvedHTLC, {
-	(0, commitment_tx_output_idx, required),
-	(1, resolving_txid, option),
-	(2, payment_preimage, option),
-});
+// In LDK versions prior to 0.0.111 commitment_tx_output_idx was not Option-al and
+// IrrevocablyResolvedHTLC objects only existed for non-dust HTLCs. This was a bug, but to maintain
+// backwards compatibility we must ensure we always write out a commitment_tx_output_idx field,
+// using `u32::max_value()` as a sentinal to indicate the HTLC was dust.
+impl Writeable for IrrevocablyResolvedHTLC {
+	fn write<W: Writer>(&self, writer: &mut W) -> Result<(), io::Error> {
+		let mapped_commitment_tx_output_idx = self.commitment_tx_output_idx.unwrap_or(u32::max_value());
+		write_tlv_fields!(writer, {
+			(0, mapped_commitment_tx_output_idx, required),
+			(1, self.resolving_txid, option),
+			(2, self.payment_preimage, option),
+		});
+		Ok(())
+	}
+}
+
+impl Readable for IrrevocablyResolvedHTLC {
+	fn read<R: io::Read>(reader: &mut R) -> Result<Self, DecodeError> {
+		let mut mapped_commitment_tx_output_idx = 0;
+		let mut resolving_txid = None;
+		let mut payment_preimage = None;
+		read_tlv_fields!(reader, {
+			(0, mapped_commitment_tx_output_idx, required),
+			(1, resolving_txid, option),
+			(2, payment_preimage, option),
+		});
+		Ok(Self {
+			commitment_tx_output_idx: if mapped_commitment_tx_output_idx == u32::max_value() { None } else { Some(mapped_commitment_tx_output_idx) },
+			resolving_txid,
+			payment_preimage,
+		})
+	}
+}
 
 /// A ChannelMonitor handles chain events (blocks connected and disconnected) and generates
 /// on-chain transactions to ensure no loss of funds occurs.
@@ -1485,7 +1513,7 @@ impl<Signer: Sign> ChannelMonitorImpl<Signer> {
 			}
 		}
 		let htlc_resolved = self.htlcs_resolved_on_chain.iter()
-			.find(|v| if v.commitment_tx_output_idx == htlc_commitment_tx_output_idx {
+			.find(|v| if v.commitment_tx_output_idx == Some(htlc_commitment_tx_output_idx) {
 				debug_assert!(htlc_spend_txid_opt.is_none());
 				htlc_spend_txid_opt = v.resolving_txid;
 				true
@@ -1775,7 +1803,7 @@ impl<Signer: Sign> ChannelMonitor<Signer> {
 		macro_rules! walk_htlcs {
 			($holder_commitment: expr, $htlc_iter: expr) => {
 				for (htlc, source) in $htlc_iter {
-					if us.htlcs_resolved_on_chain.iter().any(|v| Some(v.commitment_tx_output_idx) == htlc.transaction_output_index) {
+					if us.htlcs_resolved_on_chain.iter().any(|v| v.commitment_tx_output_idx == htlc.transaction_output_index) {
 						// We should assert that funding_spend_confirmed is_some() here, but we
 						// have some unit tests which violate HTLC transaction CSVs entirely and
 						// would fail.
@@ -2902,12 +2930,10 @@ impl<Signer: Sign> ChannelMonitorImpl<Signer> {
 						source: source.clone(),
 						htlc_value_satoshis,
 					}));
-					if let Some(idx) = commitment_tx_output_idx {
-						self.htlcs_resolved_on_chain.push(IrrevocablyResolvedHTLC {
-							commitment_tx_output_idx: idx, resolving_txid: Some(entry.txid),
-							payment_preimage: None,
-						});
-					}
+					self.htlcs_resolved_on_chain.push(IrrevocablyResolvedHTLC {
+						commitment_tx_output_idx, resolving_txid: Some(entry.txid),
+						payment_preimage: None,
+					});
 				},
 				OnchainEvent::MaturingOutput { descriptor } => {
 					log_debug!(logger, "Descriptor {} has got enough confirmations to be passed upstream", log_spendable!(descriptor));
@@ -2917,7 +2943,7 @@ impl<Signer: Sign> ChannelMonitorImpl<Signer> {
 				},
 				OnchainEvent::HTLCSpendConfirmation { commitment_tx_output_idx, preimage, .. } => {
 					self.htlcs_resolved_on_chain.push(IrrevocablyResolvedHTLC {
-						commitment_tx_output_idx, resolving_txid: Some(entry.txid),
+						commitment_tx_output_idx: Some(commitment_tx_output_idx), resolving_txid: Some(entry.txid),
 						payment_preimage: preimage,
 					});
 				},

lightning/src/ln/functional_test_utils.rs

@@ -669,6 +669,72 @@ pub fn sign_funding_transaction<'a, 'b, 'c>(node_a: &Node<'a, 'b, 'c>, node_b: &
 	tx
 }
 
+// Receiver must have been initialized with manually_accept_inbound_channels set to true.
+pub fn open_zero_conf_channel<'a, 'b, 'c, 'd>(initiator: &'a Node<'b, 'c, 'd>, receiver: &'a Node<'b, 'c, 'd>, initiator_config: Option<UserConfig>) -> (bitcoin::Transaction, [u8; 32]) {
+	let initiator_channels = initiator.node.list_usable_channels().len();
+	let receiver_channels = receiver.node.list_usable_channels().len();
+
+	initiator.node.create_channel(receiver.node.get_our_node_id(), 100_000, 10_001, 42, initiator_config).unwrap();
+	let open_channel = get_event_msg!(initiator, MessageSendEvent::SendOpenChannel, receiver.node.get_our_node_id());
+
+	receiver.node.handle_open_channel(&initiator.node.get_our_node_id(), InitFeatures::known(), &open_channel);
+	let events = receiver.node.get_and_clear_pending_events();
+	assert_eq!(events.len(), 1);
+	match events[0] {
+		Event::OpenChannelRequest { temporary_channel_id, .. } => {
+			receiver.node.accept_inbound_channel_from_trusted_peer_0conf(&temporary_channel_id, &initiator.node.get_our_node_id(), 0).unwrap();
+		},
+		_ => panic!("Unexpected event"),
+	};
+
+	let accept_channel = get_event_msg!(receiver, MessageSendEvent::SendAcceptChannel, initiator.node.get_our_node_id());
+	assert_eq!(accept_channel.minimum_depth, 0);
+	initiator.node.handle_accept_channel(&receiver.node.get_our_node_id(), InitFeatures::known(), &accept_channel);
+
+	let (temporary_channel_id, tx, _) = create_funding_transaction(&initiator, &receiver.node.get_our_node_id(), 100_000, 42);
+	initiator.node.funding_transaction_generated(&temporary_channel_id, &receiver.node.get_our_node_id(), tx.clone()).unwrap();
+	let funding_created = get_event_msg!(initiator, MessageSendEvent::SendFundingCreated, receiver.node.get_our_node_id());
+
+	receiver.node.handle_funding_created(&initiator.node.get_our_node_id(), &funding_created);
+	check_added_monitors!(receiver, 1);
+	let bs_signed_locked = receiver.node.get_and_clear_pending_msg_events();
+	assert_eq!(bs_signed_locked.len(), 2);
+	let as_channel_ready;
+	match &bs_signed_locked[0] {
+		MessageSendEvent::SendFundingSigned { node_id, msg } => {
+			assert_eq!(*node_id, initiator.node.get_our_node_id());
+			initiator.node.handle_funding_signed(&receiver.node.get_our_node_id(), &msg);
+			check_added_monitors!(initiator, 1);
+
+			assert_eq!(initiator.tx_broadcaster.txn_broadcasted.lock().unwrap().len(), 1);
+			assert_eq!(initiator.tx_broadcaster.txn_broadcasted.lock().unwrap().split_off(0)[0], tx);
+
+			as_channel_ready = get_event_msg!(initiator, MessageSendEvent::SendChannelReady, receiver.node.get_our_node_id());
+		}
+		_ => panic!("Unexpected event"),
+	}
+	match &bs_signed_locked[1] {
+		MessageSendEvent::SendChannelReady { node_id, msg } => {
+			assert_eq!(*node_id, initiator.node.get_our_node_id());
+			initiator.node.handle_channel_ready(&receiver.node.get_our_node_id(), &msg);
+		}
+		_ => panic!("Unexpected event"),
+	}
+
+	receiver.node.handle_channel_ready(&initiator.node.get_our_node_id(), &as_channel_ready);
+
+	let as_channel_update = get_event_msg!(initiator, MessageSendEvent::SendChannelUpdate, receiver.node.get_our_node_id());
+	let bs_channel_update = get_event_msg!(receiver, MessageSendEvent::SendChannelUpdate, initiator.node.get_our_node_id());
+
+	initiator.node.handle_channel_update(&receiver.node.get_our_node_id(), &bs_channel_update);
+	receiver.node.handle_channel_update(&initiator.node.get_our_node_id(), &as_channel_update);
+
+	assert_eq!(initiator.node.list_usable_channels().len(), initiator_channels + 1);
+	assert_eq!(receiver.node.list_usable_channels().len(), receiver_channels + 1);
+
+	(tx, as_channel_ready.channel_id)
+}
+
 pub fn create_chan_between_nodes_with_value_init<'a, 'b, 'c>(node_a: &Node<'a, 'b, 'c>, node_b: &Node<'a, 'b, 'c>, channel_value: u64, push_msat: u64, a_flags: InitFeatures, b_flags: InitFeatures) -> Transaction {
 	let create_chan_id = node_a.node.create_channel(node_b.node.get_our_node_id(), channel_value, push_msat, 42, None).unwrap();
 	let open_channel_msg = get_event_msg!(node_a, MessageSendEvent::SendOpenChannel, node_b.node.get_our_node_id());