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::Event;
40 use std::collections::{HashMap, hash_map};
41 use std::sync::RwLock;
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 connected block. 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 pub fn block_connected(&self, header: &BlockHeader, txdata: &TransactionData, height: u32) {
86 self.process_chain_data(header, txdata, |monitor, txdata| {
87 monitor.block_connected(
88 header, txdata, height, &*self.broadcaster, &*self.fee_estimator, &*self.logger)
92 /// Dispatches to per-channel monitors, which are responsible for updating their on-chain view
93 /// of a channel and reacting accordingly to newly confirmed transactions. For details, see
94 /// [`ChannelMonitor::transactions_confirmed`].
96 /// Used instead of [`block_connected`] by clients that are notified of transactions rather than
97 /// blocks. May be called before or after [`best_block_updated`] for transactions in the
98 /// corresponding block. See [`best_block_updated`] for further calling expectations.
100 /// [`block_connected`]: Self::block_connected
101 /// [`best_block_updated`]: Self::best_block_updated
102 pub fn transactions_confirmed(&self, header: &BlockHeader, txdata: &TransactionData, height: u32) {
103 self.process_chain_data(header, txdata, |monitor, txdata| {
104 monitor.transactions_confirmed(
105 header, txdata, height, &*self.broadcaster, &*self.fee_estimator, &*self.logger)
109 /// Dispatches to per-channel monitors, which are responsible for updating their on-chain view
110 /// of a channel and reacting accordingly based on the new chain tip. For details, see
111 /// [`ChannelMonitor::best_block_updated`].
113 /// Used instead of [`block_connected`] by clients that are notified of transactions rather than
114 /// blocks. May be called before or after [`transactions_confirmed`] for the corresponding
117 /// Must be called after new blocks become available for the most recent block. Intermediary
118 /// blocks, however, may be safely skipped. In the event of a chain re-organization, this only
119 /// needs to be called for the most recent block assuming `transaction_unconfirmed` is called
120 /// for any affected transactions.
122 /// [`block_connected`]: Self::block_connected
123 /// [`transactions_confirmed`]: Self::transactions_confirmed
124 /// [`transaction_unconfirmed`]: Self::transaction_unconfirmed
125 pub fn best_block_updated(&self, header: &BlockHeader, height: u32) {
126 self.process_chain_data(header, &[], |monitor, txdata| {
127 // While in practice there shouldn't be any recursive calls when given empty txdata,
128 // it's still possible if a chain::Filter implementation returns a transaction.
129 debug_assert!(txdata.is_empty());
130 monitor.best_block_updated(
131 header, height, &*self.broadcaster, &*self.fee_estimator, &*self.logger)
135 fn process_chain_data<FN>(&self, header: &BlockHeader, txdata: &TransactionData, process: FN)
137 FN: Fn(&ChannelMonitor<ChannelSigner>, &TransactionData) -> Vec<TransactionOutputs>
139 let mut dependent_txdata = Vec::new();
140 let monitors = self.monitors.read().unwrap();
141 for monitor in monitors.values() {
142 let mut txn_outputs = process(monitor, txdata);
144 // Register any new outputs with the chain source for filtering, storing any dependent
145 // transactions from within the block that previously had not been included in txdata.
146 if let Some(ref chain_source) = self.chain_source {
147 let block_hash = header.block_hash();
148 for (txid, mut outputs) in txn_outputs.drain(..) {
149 for (idx, output) in outputs.drain(..) {
150 // Register any new outputs with the chain source for filtering and recurse
151 // if it indicates that there are dependent transactions within the block
152 // that had not been previously included in txdata.
153 let output = WatchedOutput {
154 block_hash: Some(block_hash),
155 outpoint: OutPoint { txid, index: idx as u16 },
156 script_pubkey: output.script_pubkey,
158 if let Some(tx) = chain_source.register_output(output) {
159 dependent_txdata.push(tx);
166 // Recursively call for any dependent transactions that were identified by the chain source.
167 if !dependent_txdata.is_empty() {
168 dependent_txdata.sort_unstable_by_key(|(index, _tx)| *index);
169 dependent_txdata.dedup_by_key(|(index, _tx)| *index);
170 let txdata: Vec<_> = dependent_txdata.iter().map(|(index, tx)| (*index, tx)).collect();
171 self.process_chain_data(header, &txdata, process);
175 /// Dispatches to per-channel monitors, which are responsible for updating their on-chain view
176 /// of a channel based on the disconnected block. See [`ChannelMonitor::block_disconnected`] for
178 pub fn block_disconnected(&self, header: &BlockHeader, disconnected_height: u32) {
179 let monitors = self.monitors.read().unwrap();
180 for monitor in monitors.values() {
181 monitor.block_disconnected(header, disconnected_height, &*self.broadcaster, &*self.fee_estimator, &*self.logger);
185 /// Dispatches to per-channel monitors, which are responsible for updating their on-chain view
186 /// of a channel based on transactions unconfirmed as a result of a chain reorganization. See
187 /// [`ChannelMonitor::transaction_unconfirmed`] for details.
189 /// Used instead of [`block_disconnected`] by clients that are notified of transactions rather
190 /// than blocks. May be called before or after [`best_block_updated`] for transactions in the
191 /// corresponding block. See [`best_block_updated`] for further calling expectations.
193 /// [`block_disconnected`]: Self::block_disconnected
194 /// [`best_block_updated`]: Self::best_block_updated
195 pub fn transaction_unconfirmed(&self, txid: &Txid) {
196 let monitors = self.monitors.read().unwrap();
197 for monitor in monitors.values() {
198 monitor.transaction_unconfirmed(txid, &*self.broadcaster, &*self.fee_estimator, &*self.logger);
202 /// Returns the set of txids that should be monitored for re-organization out of the chain.
203 pub fn get_relevant_txids(&self) -> Vec<Txid> {
204 let mut txids = Vec::new();
205 let monitors = self.monitors.read().unwrap();
206 for monitor in monitors.values() {
207 txids.append(&mut monitor.get_relevant_txids());
210 txids.sort_unstable();
215 /// Creates a new `ChainMonitor` used to watch on-chain activity pertaining to channels.
217 /// When an optional chain source implementing [`chain::Filter`] is provided, the chain monitor
218 /// will call back to it indicating transactions and outputs of interest. This allows clients to
219 /// pre-filter blocks or only fetch blocks matching a compact filter. Otherwise, clients may
220 /// always need to fetch full blocks absent another means for determining which blocks contain
221 /// transactions relevant to the watched channels.
222 pub fn new(chain_source: Option<C>, broadcaster: T, logger: L, feeest: F, persister: P) -> Self {
224 monitors: RwLock::new(HashMap::new()),
228 fee_estimator: feeest,
234 impl<ChannelSigner: Sign, C: Deref + Send + Sync, T: Deref + Send + Sync, F: Deref + Send + Sync, L: Deref + Send + Sync, P: Deref + Send + Sync>
235 chain::Listen for ChainMonitor<ChannelSigner, C, T, F, L, P>
238 C::Target: chain::Filter,
239 T::Target: BroadcasterInterface,
240 F::Target: FeeEstimator,
242 P::Target: channelmonitor::Persist<ChannelSigner>,
244 fn block_connected(&self, block: &Block, height: u32) {
245 let txdata: Vec<_> = block.txdata.iter().enumerate().collect();
246 ChainMonitor::block_connected(self, &block.header, &txdata, height);
249 fn block_disconnected(&self, header: &BlockHeader, height: u32) {
250 ChainMonitor::block_disconnected(self, header, height);
254 impl<ChannelSigner: Sign, C: Deref + Sync + Send, T: Deref + Sync + Send, F: Deref + Sync + Send, L: Deref + Sync + Send, P: Deref + Sync + Send>
255 chain::Watch<ChannelSigner> for ChainMonitor<ChannelSigner, C, T, F, L, P>
256 where C::Target: chain::Filter,
257 T::Target: BroadcasterInterface,
258 F::Target: FeeEstimator,
260 P::Target: channelmonitor::Persist<ChannelSigner>,
262 /// Adds the monitor that watches the channel referred to by the given outpoint.
264 /// Calls back to [`chain::Filter`] with the funding transaction and outputs to watch.
266 /// Note that we persist the given `ChannelMonitor` while holding the `ChainMonitor`
268 fn watch_channel(&self, funding_outpoint: OutPoint, monitor: ChannelMonitor<ChannelSigner>) -> Result<(), ChannelMonitorUpdateErr> {
269 let mut monitors = self.monitors.write().unwrap();
270 let entry = match monitors.entry(funding_outpoint) {
271 hash_map::Entry::Occupied(_) => {
272 log_error!(self.logger, "Failed to add new channel data: channel monitor for given outpoint is already present");
273 return Err(ChannelMonitorUpdateErr::PermanentFailure)},
274 hash_map::Entry::Vacant(e) => e,
276 if let Err(e) = self.persister.persist_new_channel(funding_outpoint, &monitor) {
277 log_error!(self.logger, "Failed to persist new channel data");
281 let funding_txo = monitor.get_funding_txo();
282 log_trace!(self.logger, "Got new Channel Monitor for channel {}", log_bytes!(funding_txo.0.to_channel_id()[..]));
284 if let Some(ref chain_source) = self.chain_source {
285 monitor.load_outputs_to_watch(chain_source);
288 entry.insert(monitor);
292 /// Note that we persist the given `ChannelMonitor` update while holding the
293 /// `ChainMonitor` monitors lock.
294 fn update_channel(&self, funding_txo: OutPoint, update: ChannelMonitorUpdate) -> Result<(), ChannelMonitorUpdateErr> {
295 // Update the monitor that watches the channel referred to by the given outpoint.
296 let monitors = self.monitors.read().unwrap();
297 match monitors.get(&funding_txo) {
299 log_error!(self.logger, "Failed to update channel monitor: no such monitor registered");
301 // We should never ever trigger this from within ChannelManager. Technically a
302 // user could use this object with some proxying in between which makes this
303 // possible, but in tests and fuzzing, this should be a panic.
304 #[cfg(any(test, feature = "fuzztarget"))]
305 panic!("ChannelManager generated a channel update for a channel that was not yet registered!");
306 #[cfg(not(any(test, feature = "fuzztarget")))]
307 Err(ChannelMonitorUpdateErr::PermanentFailure)
310 log_trace!(self.logger, "Updating Channel Monitor for channel {}", log_funding_info!(monitor));
311 let update_res = monitor.update_monitor(&update, &self.broadcaster, &self.fee_estimator, &self.logger);
312 if let Err(e) = &update_res {
313 log_error!(self.logger, "Failed to update channel monitor: {:?}", e);
315 // Even if updating the monitor returns an error, the monitor's state will
316 // still be changed. So, persist the updated monitor despite the error.
317 let persist_res = self.persister.update_persisted_channel(funding_txo, &update, monitor);
318 if let Err(ref e) = persist_res {
319 log_error!(self.logger, "Failed to persist channel monitor update: {:?}", e);
321 if update_res.is_err() {
322 Err(ChannelMonitorUpdateErr::PermanentFailure)
330 fn release_pending_monitor_events(&self) -> Vec<MonitorEvent> {
331 let mut pending_monitor_events = Vec::new();
332 for monitor in self.monitors.read().unwrap().values() {
333 pending_monitor_events.append(&mut monitor.get_and_clear_pending_monitor_events());
335 pending_monitor_events
339 impl<ChannelSigner: Sign, C: Deref, T: Deref, F: Deref, L: Deref, P: Deref> events::EventsProvider for ChainMonitor<ChannelSigner, C, T, F, L, P>
340 where C::Target: chain::Filter,
341 T::Target: BroadcasterInterface,
342 F::Target: FeeEstimator,
344 P::Target: channelmonitor::Persist<ChannelSigner>,
346 fn get_and_clear_pending_events(&self) -> Vec<Event> {
347 let mut pending_events = Vec::new();
348 for monitor in self.monitors.read().unwrap().values() {
349 pending_events.append(&mut monitor.get_and_clear_pending_events());
357 use ::{check_added_monitors, get_local_commitment_txn};
358 use ln::features::InitFeatures;
359 use ln::functional_test_utils::*;
360 use util::events::EventsProvider;
361 use util::events::MessageSendEventsProvider;
362 use util::test_utils::{OnRegisterOutput, TxOutReference};
364 /// Tests that in-block dependent transactions are processed by `block_connected` when not
365 /// included in `txdata` but returned by [`chain::Filter::register_output`]. For instance,
366 /// a (non-anchor) commitment transaction's HTLC output may be spent in the same block as the
367 /// commitment transaction itself. An Electrum client may filter the commitment transaction but
368 /// needs to return the HTLC transaction so it can be processed.
370 fn connect_block_checks_dependent_transactions() {
371 let chanmon_cfgs = create_chanmon_cfgs(2);
372 let node_cfgs = create_node_cfgs(2, &chanmon_cfgs);
373 let node_chanmgrs = create_node_chanmgrs(2, &node_cfgs, &[None, None]);
374 let nodes = create_network(2, &node_cfgs, &node_chanmgrs);
375 let channel = create_announced_chan_between_nodes(
376 &nodes, 0, 1, InitFeatures::known(), InitFeatures::known());
378 // Send a payment, saving nodes[0]'s revoked commitment and HTLC-Timeout transactions.
379 let (commitment_tx, htlc_tx) = {
380 let payment_preimage = route_payment(&nodes[0], &vec!(&nodes[1])[..], 5_000_000).0;
381 let mut txn = get_local_commitment_txn!(nodes[0], channel.2);
382 claim_payment(&nodes[0], &vec!(&nodes[1])[..], payment_preimage, 5_000_000);
384 assert_eq!(txn.len(), 2);
385 (txn.remove(0), txn.remove(0))
388 // Set expectations on nodes[1]'s chain source to return dependent transactions.
389 let htlc_output = TxOutReference(commitment_tx.clone(), 0);
390 let to_local_output = TxOutReference(commitment_tx.clone(), 1);
391 let htlc_timeout_output = TxOutReference(htlc_tx.clone(), 0);
392 nodes[1].chain_source
393 .expect(OnRegisterOutput { with: htlc_output, returns: Some((1, htlc_tx)) })
394 .expect(OnRegisterOutput { with: to_local_output, returns: None })
395 .expect(OnRegisterOutput { with: htlc_timeout_output, returns: None });
397 // Notify nodes[1] that nodes[0]'s revoked commitment transaction was mined. The chain
398 // source should return the dependent HTLC transaction when the HTLC output is registered.
399 mine_transaction(&nodes[1], &commitment_tx);
401 // Clean up so uninteresting assertions don't fail.
402 check_added_monitors!(nodes[1], 1);
403 nodes[1].node.get_and_clear_pending_msg_events();
404 nodes[1].node.get_and_clear_pending_events();