1 // This file is Copyright its original authors, visible in version control
4 // This file is licensed under the Apache License, Version 2.0 <LICENSE-APACHE
5 // or http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
6 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your option.
7 // You may not use this file except in accordance with one or both of these
10 //! Logic to connect off-chain channel management with on-chain transaction monitoring.
12 //! [`ChainMonitor`] is an implementation of [`chain::Watch`] used both to process blocks and to
13 //! update [`ChannelMonitor`]s accordingly. If any on-chain events need further processing, it will
14 //! make those available as [`MonitorEvent`]s to be consumed.
16 //! [`ChainMonitor`] is parameterized by an optional chain source, which must implement the
17 //! [`chain::Filter`] trait. This provides a mechanism to signal new relevant outputs back to light
18 //! clients, such that transactions spending those outputs are included in block data.
20 //! [`ChainMonitor`] may be used directly to monitor channels locally or as a part of a distributed
21 //! setup to monitor channels remotely. In the latter case, a custom [`chain::Watch`] implementation
22 //! would be responsible for routing each update to a remote server and for retrieving monitor
23 //! events. The remote server would make use of [`ChainMonitor`] for block processing and for
24 //! servicing [`ChannelMonitor`] updates from the client.
26 use bitcoin::blockdata::block::{Block, BlockHeader};
27 use bitcoin::hash_types::Txid;
30 use chain::{Filter, WatchedOutput};
31 use chain::chaininterface::{BroadcasterInterface, FeeEstimator};
32 use chain::channelmonitor;
33 use chain::channelmonitor::{ChannelMonitor, ChannelMonitorUpdate, ChannelMonitorUpdateErr, MonitorEvent, Persist, TransactionOutputs};
34 use chain::transaction::{OutPoint, TransactionData};
35 use chain::keysinterface::Sign;
36 use util::logger::Logger;
38 use util::events::EventHandler;
44 /// An implementation of [`chain::Watch`] for monitoring channels.
46 /// Connected and disconnected blocks must be provided to `ChainMonitor` as documented by
47 /// [`chain::Watch`]. May be used in conjunction with [`ChannelManager`] to monitor channels locally
48 /// or used independently to monitor channels remotely. See the [module-level documentation] for
51 /// [`ChannelManager`]: crate::ln::channelmanager::ChannelManager
52 /// [module-level documentation]: crate::chain::chainmonitor
53 pub struct ChainMonitor<ChannelSigner: Sign, C: Deref, T: Deref, F: Deref, L: Deref, P: Deref>
54 where C::Target: chain::Filter,
55 T::Target: BroadcasterInterface,
56 F::Target: FeeEstimator,
58 P::Target: channelmonitor::Persist<ChannelSigner>,
61 pub monitors: RwLock<HashMap<OutPoint, ChannelMonitor<ChannelSigner>>>,
62 chain_source: Option<C>,
69 impl<ChannelSigner: Sign, C: Deref, T: Deref, F: Deref, L: Deref, P: Deref> ChainMonitor<ChannelSigner, C, T, F, L, P>
70 where C::Target: chain::Filter,
71 T::Target: BroadcasterInterface,
72 F::Target: FeeEstimator,
74 P::Target: channelmonitor::Persist<ChannelSigner>,
76 /// Dispatches to per-channel monitors, which are responsible for updating their on-chain view
77 /// of a channel and reacting accordingly based on transactions in the given chain data. See
78 /// [`ChannelMonitor::block_connected`] for details. Any HTLCs that were resolved on chain will
79 /// be returned by [`chain::Watch::release_pending_monitor_events`].
81 /// Calls back to [`chain::Filter`] if any monitor indicated new outputs to watch. Subsequent
82 /// calls must not exclude any transactions matching the new outputs nor any in-block
83 /// descendants of such transactions. It is not necessary to re-fetch the block to obtain
85 fn process_chain_data<FN>(&self, header: &BlockHeader, txdata: &TransactionData, process: FN)
87 FN: Fn(&ChannelMonitor<ChannelSigner>, &TransactionData) -> Vec<TransactionOutputs>
89 let mut dependent_txdata = Vec::new();
90 let monitors = self.monitors.read().unwrap();
91 for monitor in monitors.values() {
92 let mut txn_outputs = process(monitor, txdata);
94 // Register any new outputs with the chain source for filtering, storing any dependent
95 // transactions from within the block that previously had not been included in txdata.
96 if let Some(ref chain_source) = self.chain_source {
97 let block_hash = header.block_hash();
98 for (txid, mut outputs) in txn_outputs.drain(..) {
99 for (idx, output) in outputs.drain(..) {
100 // Register any new outputs with the chain source for filtering and recurse
101 // if it indicates that there are dependent transactions within the block
102 // that had not been previously included in txdata.
103 let output = WatchedOutput {
104 block_hash: Some(block_hash),
105 outpoint: OutPoint { txid, index: idx as u16 },
106 script_pubkey: output.script_pubkey,
108 if let Some(tx) = chain_source.register_output(output) {
109 dependent_txdata.push(tx);
116 // Recursively call for any dependent transactions that were identified by the chain source.
117 if !dependent_txdata.is_empty() {
118 dependent_txdata.sort_unstable_by_key(|(index, _tx)| *index);
119 dependent_txdata.dedup_by_key(|(index, _tx)| *index);
120 let txdata: Vec<_> = dependent_txdata.iter().map(|(index, tx)| (*index, tx)).collect();
121 self.process_chain_data(header, &txdata, process);
125 /// Creates a new `ChainMonitor` used to watch on-chain activity pertaining to channels.
127 /// When an optional chain source implementing [`chain::Filter`] is provided, the chain monitor
128 /// will call back to it indicating transactions and outputs of interest. This allows clients to
129 /// pre-filter blocks or only fetch blocks matching a compact filter. Otherwise, clients may
130 /// always need to fetch full blocks absent another means for determining which blocks contain
131 /// transactions relevant to the watched channels.
132 pub fn new(chain_source: Option<C>, broadcaster: T, logger: L, feeest: F, persister: P) -> Self {
134 monitors: RwLock::new(HashMap::new()),
138 fee_estimator: feeest,
143 #[cfg(any(test, feature = "fuzztarget", feature = "_test_utils"))]
144 pub fn get_and_clear_pending_events(&self) -> Vec<events::Event> {
145 use util::events::EventsProvider;
146 let events = core::cell::RefCell::new(Vec::new());
147 let event_handler = |event| events.borrow_mut().push(event);
148 self.process_pending_events(&event_handler);
153 impl<ChannelSigner: Sign, C: Deref, T: Deref, F: Deref, L: Deref, P: Deref>
154 chain::Listen for ChainMonitor<ChannelSigner, C, T, F, L, P>
156 C::Target: chain::Filter,
157 T::Target: BroadcasterInterface,
158 F::Target: FeeEstimator,
160 P::Target: channelmonitor::Persist<ChannelSigner>,
162 fn block_connected(&self, block: &Block, height: u32) {
163 let header = &block.header;
164 let txdata: Vec<_> = block.txdata.iter().enumerate().collect();
165 log_debug!(self.logger, "New best block {} at height {} provided via block_connected", header.block_hash(), height);
166 self.process_chain_data(header, &txdata, |monitor, txdata| {
167 monitor.block_connected(
168 header, txdata, height, &*self.broadcaster, &*self.fee_estimator, &*self.logger)
172 fn block_disconnected(&self, header: &BlockHeader, height: u32) {
173 let monitors = self.monitors.read().unwrap();
174 log_debug!(self.logger, "Latest block {} at height {} removed via block_disconnected", header.block_hash(), height);
175 for monitor in monitors.values() {
176 monitor.block_disconnected(
177 header, height, &*self.broadcaster, &*self.fee_estimator, &*self.logger);
182 impl<ChannelSigner: Sign, C: Deref, T: Deref, F: Deref, L: Deref, P: Deref>
183 chain::Confirm for ChainMonitor<ChannelSigner, C, T, F, L, P>
185 C::Target: chain::Filter,
186 T::Target: BroadcasterInterface,
187 F::Target: FeeEstimator,
189 P::Target: channelmonitor::Persist<ChannelSigner>,
191 fn transactions_confirmed(&self, header: &BlockHeader, txdata: &TransactionData, height: u32) {
192 log_debug!(self.logger, "{} provided transactions confirmed at height {} in block {}", txdata.len(), height, header.block_hash());
193 self.process_chain_data(header, txdata, |monitor, txdata| {
194 monitor.transactions_confirmed(
195 header, txdata, height, &*self.broadcaster, &*self.fee_estimator, &*self.logger)
199 fn transaction_unconfirmed(&self, txid: &Txid) {
200 log_debug!(self.logger, "Transaction {} reorganized out of chain", txid);
201 let monitors = self.monitors.read().unwrap();
202 for monitor in monitors.values() {
203 monitor.transaction_unconfirmed(txid, &*self.broadcaster, &*self.fee_estimator, &*self.logger);
207 fn best_block_updated(&self, header: &BlockHeader, height: u32) {
208 log_debug!(self.logger, "New best block {} at height {} provided via best_block_updated", header.block_hash(), height);
209 self.process_chain_data(header, &[], |monitor, txdata| {
210 // While in practice there shouldn't be any recursive calls when given empty txdata,
211 // it's still possible if a chain::Filter implementation returns a transaction.
212 debug_assert!(txdata.is_empty());
213 monitor.best_block_updated(
214 header, height, &*self.broadcaster, &*self.fee_estimator, &*self.logger)
218 fn get_relevant_txids(&self) -> Vec<Txid> {
219 let mut txids = Vec::new();
220 let monitors = self.monitors.read().unwrap();
221 for monitor in monitors.values() {
222 txids.append(&mut monitor.get_relevant_txids());
225 txids.sort_unstable();
231 impl<ChannelSigner: Sign, C: Deref , T: Deref , F: Deref , L: Deref , P: Deref >
232 chain::Watch<ChannelSigner> for ChainMonitor<ChannelSigner, C, T, F, L, P>
233 where C::Target: chain::Filter,
234 T::Target: BroadcasterInterface,
235 F::Target: FeeEstimator,
237 P::Target: channelmonitor::Persist<ChannelSigner>,
239 /// Adds the monitor that watches the channel referred to by the given outpoint.
241 /// Calls back to [`chain::Filter`] with the funding transaction and outputs to watch.
243 /// Note that we persist the given `ChannelMonitor` while holding the `ChainMonitor`
245 fn watch_channel(&self, funding_outpoint: OutPoint, monitor: ChannelMonitor<ChannelSigner>) -> Result<(), ChannelMonitorUpdateErr> {
246 let mut monitors = self.monitors.write().unwrap();
247 let entry = match monitors.entry(funding_outpoint) {
248 hash_map::Entry::Occupied(_) => {
249 log_error!(self.logger, "Failed to add new channel data: channel monitor for given outpoint is already present");
250 return Err(ChannelMonitorUpdateErr::PermanentFailure)},
251 hash_map::Entry::Vacant(e) => e,
253 if let Err(e) = self.persister.persist_new_channel(funding_outpoint, &monitor) {
254 log_error!(self.logger, "Failed to persist new channel data");
258 let funding_txo = monitor.get_funding_txo();
259 log_trace!(self.logger, "Got new Channel Monitor for channel {}", log_bytes!(funding_txo.0.to_channel_id()[..]));
261 if let Some(ref chain_source) = self.chain_source {
262 monitor.load_outputs_to_watch(chain_source);
265 entry.insert(monitor);
269 /// Note that we persist the given `ChannelMonitor` update while holding the
270 /// `ChainMonitor` monitors lock.
271 fn update_channel(&self, funding_txo: OutPoint, update: ChannelMonitorUpdate) -> Result<(), ChannelMonitorUpdateErr> {
272 // Update the monitor that watches the channel referred to by the given outpoint.
273 let monitors = self.monitors.read().unwrap();
274 match monitors.get(&funding_txo) {
276 log_error!(self.logger, "Failed to update channel monitor: no such monitor registered");
278 // We should never ever trigger this from within ChannelManager. Technically a
279 // user could use this object with some proxying in between which makes this
280 // possible, but in tests and fuzzing, this should be a panic.
281 #[cfg(any(test, feature = "fuzztarget"))]
282 panic!("ChannelManager generated a channel update for a channel that was not yet registered!");
283 #[cfg(not(any(test, feature = "fuzztarget")))]
284 Err(ChannelMonitorUpdateErr::PermanentFailure)
287 log_trace!(self.logger, "Updating Channel Monitor for channel {}", log_funding_info!(monitor));
288 let update_res = monitor.update_monitor(&update, &self.broadcaster, &self.fee_estimator, &self.logger);
289 if let Err(e) = &update_res {
290 log_error!(self.logger, "Failed to update channel monitor: {:?}", e);
292 // Even if updating the monitor returns an error, the monitor's state will
293 // still be changed. So, persist the updated monitor despite the error.
294 let persist_res = self.persister.update_persisted_channel(funding_txo, &update, monitor);
295 if let Err(ref e) = persist_res {
296 log_error!(self.logger, "Failed to persist channel monitor update: {:?}", e);
298 if update_res.is_err() {
299 Err(ChannelMonitorUpdateErr::PermanentFailure)
307 fn release_pending_monitor_events(&self) -> Vec<MonitorEvent> {
308 let mut pending_monitor_events = Vec::new();
309 for monitor in self.monitors.read().unwrap().values() {
310 pending_monitor_events.append(&mut monitor.get_and_clear_pending_monitor_events());
312 pending_monitor_events
316 impl<ChannelSigner: Sign, C: Deref, T: Deref, F: Deref, L: Deref, P: Deref> events::EventsProvider for ChainMonitor<ChannelSigner, C, T, F, L, P>
317 where C::Target: chain::Filter,
318 T::Target: BroadcasterInterface,
319 F::Target: FeeEstimator,
321 P::Target: channelmonitor::Persist<ChannelSigner>,
323 /// Processes [`SpendableOutputs`] events produced from each [`ChannelMonitor`] upon maturity.
325 /// An [`EventHandler`] may safely call back to the provider, though this shouldn't be needed in
326 /// order to handle these events.
328 /// [`SpendableOutputs`]: events::Event::SpendableOutputs
329 fn process_pending_events<H: Deref>(&self, handler: H) where H::Target: EventHandler {
330 let mut pending_events = Vec::new();
331 for monitor in self.monitors.read().unwrap().values() {
332 pending_events.append(&mut monitor.get_and_clear_pending_events());
334 for event in pending_events.drain(..) {
335 handler.handle_event(event);
342 use ::{check_added_monitors, get_local_commitment_txn};
343 use ln::features::InitFeatures;
344 use ln::functional_test_utils::*;
345 use util::events::MessageSendEventsProvider;
346 use util::test_utils::{OnRegisterOutput, TxOutReference};
348 /// Tests that in-block dependent transactions are processed by `block_connected` when not
349 /// included in `txdata` but returned by [`chain::Filter::register_output`]. For instance,
350 /// a (non-anchor) commitment transaction's HTLC output may be spent in the same block as the
351 /// commitment transaction itself. An Electrum client may filter the commitment transaction but
352 /// needs to return the HTLC transaction so it can be processed.
354 fn connect_block_checks_dependent_transactions() {
355 let chanmon_cfgs = create_chanmon_cfgs(2);
356 let node_cfgs = create_node_cfgs(2, &chanmon_cfgs);
357 let node_chanmgrs = create_node_chanmgrs(2, &node_cfgs, &[None, None]);
358 let nodes = create_network(2, &node_cfgs, &node_chanmgrs);
359 let channel = create_announced_chan_between_nodes(
360 &nodes, 0, 1, InitFeatures::known(), InitFeatures::known());
362 // Send a payment, saving nodes[0]'s revoked commitment and HTLC-Timeout transactions.
363 let (commitment_tx, htlc_tx) = {
364 let payment_preimage = route_payment(&nodes[0], &vec!(&nodes[1])[..], 5_000_000).0;
365 let mut txn = get_local_commitment_txn!(nodes[0], channel.2);
366 claim_payment(&nodes[0], &vec!(&nodes[1])[..], payment_preimage);
368 assert_eq!(txn.len(), 2);
369 (txn.remove(0), txn.remove(0))
372 // Set expectations on nodes[1]'s chain source to return dependent transactions.
373 let htlc_output = TxOutReference(commitment_tx.clone(), 0);
374 let to_local_output = TxOutReference(commitment_tx.clone(), 1);
375 let htlc_timeout_output = TxOutReference(htlc_tx.clone(), 0);
376 nodes[1].chain_source
377 .expect(OnRegisterOutput { with: htlc_output, returns: Some((1, htlc_tx)) })
378 .expect(OnRegisterOutput { with: to_local_output, returns: None })
379 .expect(OnRegisterOutput { with: htlc_timeout_output, returns: None });
381 // Notify nodes[1] that nodes[0]'s revoked commitment transaction was mined. The chain
382 // source should return the dependent HTLC transaction when the HTLC output is registered.
383 mine_transaction(&nodes[1], &commitment_tx);
385 // Clean up so uninteresting assertions don't fail.
386 check_added_monitors!(nodes[1], 1);
387 nodes[1].node.get_and_clear_pending_msg_events();
388 nodes[1].node.get_and_clear_pending_events();