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, Balance, MonitorEvent, Persist, TransactionOutputs};
34 use chain::transaction::{OutPoint, TransactionData};
35 use chain::keysinterface::Sign;
36 use util::logger::Logger;
38 use util::events::EventHandler;
39 use ln::channelmanager::ChannelDetails;
45 /// An implementation of [`chain::Watch`] for monitoring channels.
47 /// Connected and disconnected blocks must be provided to `ChainMonitor` as documented by
48 /// [`chain::Watch`]. May be used in conjunction with [`ChannelManager`] to monitor channels locally
49 /// or used independently to monitor channels remotely. See the [module-level documentation] for
52 /// [`ChannelManager`]: crate::ln::channelmanager::ChannelManager
53 /// [module-level documentation]: crate::chain::chainmonitor
54 pub struct ChainMonitor<ChannelSigner: Sign, C: Deref, T: Deref, F: Deref, L: Deref, P: Deref>
55 where C::Target: chain::Filter,
56 T::Target: BroadcasterInterface,
57 F::Target: FeeEstimator,
59 P::Target: channelmonitor::Persist<ChannelSigner>,
62 pub monitors: RwLock<HashMap<OutPoint, ChannelMonitor<ChannelSigner>>>,
63 chain_source: Option<C>,
70 impl<ChannelSigner: Sign, C: Deref, T: Deref, F: Deref, L: Deref, P: Deref> ChainMonitor<ChannelSigner, C, T, F, L, P>
71 where C::Target: chain::Filter,
72 T::Target: BroadcasterInterface,
73 F::Target: FeeEstimator,
75 P::Target: channelmonitor::Persist<ChannelSigner>,
77 /// Dispatches to per-channel monitors, which are responsible for updating their on-chain view
78 /// of a channel and reacting accordingly based on transactions in the given chain data. See
79 /// [`ChannelMonitor::block_connected`] for details. Any HTLCs that were resolved on chain will
80 /// be returned by [`chain::Watch::release_pending_monitor_events`].
82 /// Calls back to [`chain::Filter`] if any monitor indicated new outputs to watch. Subsequent
83 /// calls must not exclude any transactions matching the new outputs nor any in-block
84 /// descendants of such transactions. It is not necessary to re-fetch the block to obtain
86 fn process_chain_data<FN>(&self, header: &BlockHeader, txdata: &TransactionData, process: FN)
88 FN: Fn(&ChannelMonitor<ChannelSigner>, &TransactionData) -> Vec<TransactionOutputs>
90 let mut dependent_txdata = Vec::new();
91 let monitors = self.monitors.read().unwrap();
92 for monitor in monitors.values() {
93 let mut txn_outputs = process(monitor, txdata);
95 // Register any new outputs with the chain source for filtering, storing any dependent
96 // transactions from within the block that previously had not been included in txdata.
97 if let Some(ref chain_source) = self.chain_source {
98 let block_hash = header.block_hash();
99 for (txid, mut outputs) in txn_outputs.drain(..) {
100 for (idx, output) in outputs.drain(..) {
101 // Register any new outputs with the chain source for filtering and recurse
102 // if it indicates that there are dependent transactions within the block
103 // that had not been previously included in txdata.
104 let output = WatchedOutput {
105 block_hash: Some(block_hash),
106 outpoint: OutPoint { txid, index: idx as u16 },
107 script_pubkey: output.script_pubkey,
109 if let Some(tx) = chain_source.register_output(output) {
110 dependent_txdata.push(tx);
117 // Recursively call for any dependent transactions that were identified by the chain source.
118 if !dependent_txdata.is_empty() {
119 dependent_txdata.sort_unstable_by_key(|(index, _tx)| *index);
120 dependent_txdata.dedup_by_key(|(index, _tx)| *index);
121 let txdata: Vec<_> = dependent_txdata.iter().map(|(index, tx)| (*index, tx)).collect();
122 self.process_chain_data(header, &txdata, process);
126 /// Creates a new `ChainMonitor` used to watch on-chain activity pertaining to channels.
128 /// When an optional chain source implementing [`chain::Filter`] is provided, the chain monitor
129 /// will call back to it indicating transactions and outputs of interest. This allows clients to
130 /// pre-filter blocks or only fetch blocks matching a compact filter. Otherwise, clients may
131 /// always need to fetch full blocks absent another means for determining which blocks contain
132 /// transactions relevant to the watched channels.
133 pub fn new(chain_source: Option<C>, broadcaster: T, logger: L, feeest: F, persister: P) -> Self {
135 monitors: RwLock::new(HashMap::new()),
139 fee_estimator: feeest,
144 /// Gets the balances in the contained [`ChannelMonitor`]s which are claimable on-chain or
145 /// claims which are awaiting confirmation.
147 /// Includes the balances from each [`ChannelMonitor`] *except* those included in
148 /// `ignored_channels`, allowing you to filter out balances from channels which are still open
149 /// (and whose balance should likely be pulled from the [`ChannelDetails`]).
151 /// See [`ChannelMonitor::get_claimable_balances`] for more details on the exact criteria for
152 /// inclusion in the return value.
153 pub fn get_claimable_balances(&self, ignored_channels: &[&ChannelDetails]) -> Vec<Balance> {
154 let mut ret = Vec::new();
155 let monitors = self.monitors.read().unwrap();
156 for (_, monitor) in monitors.iter().filter(|(funding_outpoint, _)| {
157 for chan in ignored_channels {
158 if chan.funding_txo.as_ref() == Some(funding_outpoint) {
164 ret.append(&mut monitor.get_claimable_balances());
169 #[cfg(any(test, feature = "fuzztarget", feature = "_test_utils"))]
170 pub fn get_and_clear_pending_events(&self) -> Vec<events::Event> {
171 use util::events::EventsProvider;
172 let events = core::cell::RefCell::new(Vec::new());
173 let event_handler = |event: &events::Event| events.borrow_mut().push(event.clone());
174 self.process_pending_events(&event_handler);
179 impl<ChannelSigner: Sign, C: Deref, T: Deref, F: Deref, L: Deref, P: Deref>
180 chain::Listen for ChainMonitor<ChannelSigner, C, T, F, L, P>
182 C::Target: chain::Filter,
183 T::Target: BroadcasterInterface,
184 F::Target: FeeEstimator,
186 P::Target: channelmonitor::Persist<ChannelSigner>,
188 fn block_connected(&self, block: &Block, height: u32) {
189 let header = &block.header;
190 let txdata: Vec<_> = block.txdata.iter().enumerate().collect();
191 log_debug!(self.logger, "New best block {} at height {} provided via block_connected", header.block_hash(), height);
192 self.process_chain_data(header, &txdata, |monitor, txdata| {
193 monitor.block_connected(
194 header, txdata, height, &*self.broadcaster, &*self.fee_estimator, &*self.logger)
198 fn block_disconnected(&self, header: &BlockHeader, height: u32) {
199 let monitors = self.monitors.read().unwrap();
200 log_debug!(self.logger, "Latest block {} at height {} removed via block_disconnected", header.block_hash(), height);
201 for monitor in monitors.values() {
202 monitor.block_disconnected(
203 header, height, &*self.broadcaster, &*self.fee_estimator, &*self.logger);
208 impl<ChannelSigner: Sign, C: Deref, T: Deref, F: Deref, L: Deref, P: Deref>
209 chain::Confirm for ChainMonitor<ChannelSigner, C, T, F, L, P>
211 C::Target: chain::Filter,
212 T::Target: BroadcasterInterface,
213 F::Target: FeeEstimator,
215 P::Target: channelmonitor::Persist<ChannelSigner>,
217 fn transactions_confirmed(&self, header: &BlockHeader, txdata: &TransactionData, height: u32) {
218 log_debug!(self.logger, "{} provided transactions confirmed at height {} in block {}", txdata.len(), height, header.block_hash());
219 self.process_chain_data(header, txdata, |monitor, txdata| {
220 monitor.transactions_confirmed(
221 header, txdata, height, &*self.broadcaster, &*self.fee_estimator, &*self.logger)
225 fn transaction_unconfirmed(&self, txid: &Txid) {
226 log_debug!(self.logger, "Transaction {} reorganized out of chain", txid);
227 let monitors = self.monitors.read().unwrap();
228 for monitor in monitors.values() {
229 monitor.transaction_unconfirmed(txid, &*self.broadcaster, &*self.fee_estimator, &*self.logger);
233 fn best_block_updated(&self, header: &BlockHeader, height: u32) {
234 log_debug!(self.logger, "New best block {} at height {} provided via best_block_updated", header.block_hash(), height);
235 self.process_chain_data(header, &[], |monitor, txdata| {
236 // While in practice there shouldn't be any recursive calls when given empty txdata,
237 // it's still possible if a chain::Filter implementation returns a transaction.
238 debug_assert!(txdata.is_empty());
239 monitor.best_block_updated(
240 header, height, &*self.broadcaster, &*self.fee_estimator, &*self.logger)
244 fn get_relevant_txids(&self) -> Vec<Txid> {
245 let mut txids = Vec::new();
246 let monitors = self.monitors.read().unwrap();
247 for monitor in monitors.values() {
248 txids.append(&mut monitor.get_relevant_txids());
251 txids.sort_unstable();
257 impl<ChannelSigner: Sign, C: Deref , T: Deref , F: Deref , L: Deref , P: Deref >
258 chain::Watch<ChannelSigner> for ChainMonitor<ChannelSigner, C, T, F, L, P>
259 where C::Target: chain::Filter,
260 T::Target: BroadcasterInterface,
261 F::Target: FeeEstimator,
263 P::Target: channelmonitor::Persist<ChannelSigner>,
265 /// Adds the monitor that watches the channel referred to by the given outpoint.
267 /// Calls back to [`chain::Filter`] with the funding transaction and outputs to watch.
269 /// Note that we persist the given `ChannelMonitor` while holding the `ChainMonitor`
271 fn watch_channel(&self, funding_outpoint: OutPoint, monitor: ChannelMonitor<ChannelSigner>) -> Result<(), ChannelMonitorUpdateErr> {
272 let mut monitors = self.monitors.write().unwrap();
273 let entry = match monitors.entry(funding_outpoint) {
274 hash_map::Entry::Occupied(_) => {
275 log_error!(self.logger, "Failed to add new channel data: channel monitor for given outpoint is already present");
276 return Err(ChannelMonitorUpdateErr::PermanentFailure)},
277 hash_map::Entry::Vacant(e) => e,
279 if let Err(e) = self.persister.persist_new_channel(funding_outpoint, &monitor) {
280 log_error!(self.logger, "Failed to persist new channel data");
284 let funding_txo = monitor.get_funding_txo();
285 log_trace!(self.logger, "Got new Channel Monitor for channel {}", log_bytes!(funding_txo.0.to_channel_id()[..]));
287 if let Some(ref chain_source) = self.chain_source {
288 monitor.load_outputs_to_watch(chain_source);
291 entry.insert(monitor);
295 /// Note that we persist the given `ChannelMonitor` update while holding the
296 /// `ChainMonitor` monitors lock.
297 fn update_channel(&self, funding_txo: OutPoint, update: ChannelMonitorUpdate) -> Result<(), ChannelMonitorUpdateErr> {
298 // Update the monitor that watches the channel referred to by the given outpoint.
299 let monitors = self.monitors.read().unwrap();
300 match monitors.get(&funding_txo) {
302 log_error!(self.logger, "Failed to update channel monitor: no such monitor registered");
304 // We should never ever trigger this from within ChannelManager. Technically a
305 // user could use this object with some proxying in between which makes this
306 // possible, but in tests and fuzzing, this should be a panic.
307 #[cfg(any(test, feature = "fuzztarget"))]
308 panic!("ChannelManager generated a channel update for a channel that was not yet registered!");
309 #[cfg(not(any(test, feature = "fuzztarget")))]
310 Err(ChannelMonitorUpdateErr::PermanentFailure)
313 log_trace!(self.logger, "Updating Channel Monitor for channel {}", log_funding_info!(monitor));
314 let update_res = monitor.update_monitor(&update, &self.broadcaster, &self.fee_estimator, &self.logger);
315 if let Err(e) = &update_res {
316 log_error!(self.logger, "Failed to update channel monitor: {:?}", e);
318 // Even if updating the monitor returns an error, the monitor's state will
319 // still be changed. So, persist the updated monitor despite the error.
320 let persist_res = self.persister.update_persisted_channel(funding_txo, &update, monitor);
321 if let Err(ref e) = persist_res {
322 log_error!(self.logger, "Failed to persist channel monitor update: {:?}", e);
324 if update_res.is_err() {
325 Err(ChannelMonitorUpdateErr::PermanentFailure)
333 fn release_pending_monitor_events(&self) -> Vec<MonitorEvent> {
334 let mut pending_monitor_events = Vec::new();
335 for monitor in self.monitors.read().unwrap().values() {
336 pending_monitor_events.append(&mut monitor.get_and_clear_pending_monitor_events());
338 pending_monitor_events
342 impl<ChannelSigner: Sign, C: Deref, T: Deref, F: Deref, L: Deref, P: Deref> events::EventsProvider for ChainMonitor<ChannelSigner, C, T, F, L, P>
343 where C::Target: chain::Filter,
344 T::Target: BroadcasterInterface,
345 F::Target: FeeEstimator,
347 P::Target: channelmonitor::Persist<ChannelSigner>,
349 /// Processes [`SpendableOutputs`] events produced from each [`ChannelMonitor`] upon maturity.
351 /// An [`EventHandler`] may safely call back to the provider, though this shouldn't be needed in
352 /// order to handle these events.
354 /// [`SpendableOutputs`]: events::Event::SpendableOutputs
355 fn process_pending_events<H: Deref>(&self, handler: H) where H::Target: EventHandler {
356 let mut pending_events = Vec::new();
357 for monitor in self.monitors.read().unwrap().values() {
358 pending_events.append(&mut monitor.get_and_clear_pending_events());
360 for event in pending_events.drain(..) {
361 handler.handle_event(&event);
368 use ::{check_added_monitors, get_local_commitment_txn};
369 use ln::features::InitFeatures;
370 use ln::functional_test_utils::*;
371 use util::events::MessageSendEventsProvider;
372 use util::test_utils::{OnRegisterOutput, TxOutReference};
374 /// Tests that in-block dependent transactions are processed by `block_connected` when not
375 /// included in `txdata` but returned by [`chain::Filter::register_output`]. For instance,
376 /// a (non-anchor) commitment transaction's HTLC output may be spent in the same block as the
377 /// commitment transaction itself. An Electrum client may filter the commitment transaction but
378 /// needs to return the HTLC transaction so it can be processed.
380 fn connect_block_checks_dependent_transactions() {
381 let chanmon_cfgs = create_chanmon_cfgs(2);
382 let node_cfgs = create_node_cfgs(2, &chanmon_cfgs);
383 let node_chanmgrs = create_node_chanmgrs(2, &node_cfgs, &[None, None]);
384 let nodes = create_network(2, &node_cfgs, &node_chanmgrs);
385 let channel = create_announced_chan_between_nodes(
386 &nodes, 0, 1, InitFeatures::known(), InitFeatures::known());
388 // Send a payment, saving nodes[0]'s revoked commitment and HTLC-Timeout transactions.
389 let (commitment_tx, htlc_tx) = {
390 let payment_preimage = route_payment(&nodes[0], &vec!(&nodes[1])[..], 5_000_000).0;
391 let mut txn = get_local_commitment_txn!(nodes[0], channel.2);
392 claim_payment(&nodes[0], &vec!(&nodes[1])[..], payment_preimage);
394 assert_eq!(txn.len(), 2);
395 (txn.remove(0), txn.remove(0))
398 // Set expectations on nodes[1]'s chain source to return dependent transactions.
399 let htlc_output = TxOutReference(commitment_tx.clone(), 0);
400 let to_local_output = TxOutReference(commitment_tx.clone(), 1);
401 let htlc_timeout_output = TxOutReference(htlc_tx.clone(), 0);
402 nodes[1].chain_source
403 .expect(OnRegisterOutput { with: htlc_output, returns: Some((1, htlc_tx)) })
404 .expect(OnRegisterOutput { with: to_local_output, returns: None })
405 .expect(OnRegisterOutput { with: htlc_timeout_output, returns: None });
407 // Notify nodes[1] that nodes[0]'s revoked commitment transaction was mined. The chain
408 // source should return the dependent HTLC transaction when the HTLC output is registered.
409 mine_transaction(&nodes[1], &commitment_tx);
411 // Clean up so uninteresting assertions don't fail.
412 check_added_monitors!(nodes[1], 1);
413 nodes[1].node.get_and_clear_pending_msg_events();
414 nodes[1].node.get_and_clear_pending_events();