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;
41 use std::collections::{HashMap, hash_map};
42 use std::sync::RwLock;
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 #[cfg(any(test, feature = "fuzztarget", feature = "_test_utils"))]
145 pub fn get_and_clear_pending_events(&self) -> Vec<events::Event> {
146 use util::events::EventsProvider;
147 let events = core::cell::RefCell::new(Vec::new());
148 let event_handler = |event| events.borrow_mut().push(event);
149 self.process_pending_events(&event_handler);
154 impl<ChannelSigner: Sign, C: Deref, T: Deref, F: Deref, L: Deref, P: Deref>
155 chain::Listen for ChainMonitor<ChannelSigner, C, T, F, L, P>
157 C::Target: chain::Filter,
158 T::Target: BroadcasterInterface,
159 F::Target: FeeEstimator,
161 P::Target: channelmonitor::Persist<ChannelSigner>,
163 fn block_connected(&self, block: &Block, height: u32) {
164 let header = &block.header;
165 let txdata: Vec<_> = block.txdata.iter().enumerate().collect();
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 for monitor in monitors.values() {
175 monitor.block_disconnected(
176 header, height, &*self.broadcaster, &*self.fee_estimator, &*self.logger);
181 impl<ChannelSigner: Sign, C: Deref, T: Deref, F: Deref, L: Deref, P: Deref>
182 chain::Confirm for ChainMonitor<ChannelSigner, C, T, F, L, P>
184 C::Target: chain::Filter,
185 T::Target: BroadcasterInterface,
186 F::Target: FeeEstimator,
188 P::Target: channelmonitor::Persist<ChannelSigner>,
190 fn transactions_confirmed(&self, header: &BlockHeader, txdata: &TransactionData, height: u32) {
191 self.process_chain_data(header, txdata, |monitor, txdata| {
192 monitor.transactions_confirmed(
193 header, txdata, height, &*self.broadcaster, &*self.fee_estimator, &*self.logger)
197 fn transaction_unconfirmed(&self, txid: &Txid) {
198 let monitors = self.monitors.read().unwrap();
199 for monitor in monitors.values() {
200 monitor.transaction_unconfirmed(txid, &*self.broadcaster, &*self.fee_estimator, &*self.logger);
204 fn best_block_updated(&self, header: &BlockHeader, height: u32) {
205 self.process_chain_data(header, &[], |monitor, txdata| {
206 // While in practice there shouldn't be any recursive calls when given empty txdata,
207 // it's still possible if a chain::Filter implementation returns a transaction.
208 debug_assert!(txdata.is_empty());
209 monitor.best_block_updated(
210 header, height, &*self.broadcaster, &*self.fee_estimator, &*self.logger)
214 fn get_relevant_txids(&self) -> Vec<Txid> {
215 let mut txids = Vec::new();
216 let monitors = self.monitors.read().unwrap();
217 for monitor in monitors.values() {
218 txids.append(&mut monitor.get_relevant_txids());
221 txids.sort_unstable();
227 impl<ChannelSigner: Sign, C: Deref , T: Deref , F: Deref , L: Deref , P: Deref >
228 chain::Watch<ChannelSigner> for ChainMonitor<ChannelSigner, C, T, F, L, P>
229 where C::Target: chain::Filter,
230 T::Target: BroadcasterInterface,
231 F::Target: FeeEstimator,
233 P::Target: channelmonitor::Persist<ChannelSigner>,
235 /// Adds the monitor that watches the channel referred to by the given outpoint.
237 /// Calls back to [`chain::Filter`] with the funding transaction and outputs to watch.
239 /// Note that we persist the given `ChannelMonitor` while holding the `ChainMonitor`
241 fn watch_channel(&self, funding_outpoint: OutPoint, monitor: ChannelMonitor<ChannelSigner>) -> Result<(), ChannelMonitorUpdateErr> {
242 let mut monitors = self.monitors.write().unwrap();
243 let entry = match monitors.entry(funding_outpoint) {
244 hash_map::Entry::Occupied(_) => {
245 log_error!(self.logger, "Failed to add new channel data: channel monitor for given outpoint is already present");
246 return Err(ChannelMonitorUpdateErr::PermanentFailure)},
247 hash_map::Entry::Vacant(e) => e,
249 if let Err(e) = self.persister.persist_new_channel(funding_outpoint, &monitor) {
250 log_error!(self.logger, "Failed to persist new channel data");
254 let funding_txo = monitor.get_funding_txo();
255 log_trace!(self.logger, "Got new Channel Monitor for channel {}", log_bytes!(funding_txo.0.to_channel_id()[..]));
257 if let Some(ref chain_source) = self.chain_source {
258 monitor.load_outputs_to_watch(chain_source);
261 entry.insert(monitor);
265 /// Note that we persist the given `ChannelMonitor` update while holding the
266 /// `ChainMonitor` monitors lock.
267 fn update_channel(&self, funding_txo: OutPoint, update: ChannelMonitorUpdate) -> Result<(), ChannelMonitorUpdateErr> {
268 // Update the monitor that watches the channel referred to by the given outpoint.
269 let monitors = self.monitors.read().unwrap();
270 match monitors.get(&funding_txo) {
272 log_error!(self.logger, "Failed to update channel monitor: no such monitor registered");
274 // We should never ever trigger this from within ChannelManager. Technically a
275 // user could use this object with some proxying in between which makes this
276 // possible, but in tests and fuzzing, this should be a panic.
277 #[cfg(any(test, feature = "fuzztarget"))]
278 panic!("ChannelManager generated a channel update for a channel that was not yet registered!");
279 #[cfg(not(any(test, feature = "fuzztarget")))]
280 Err(ChannelMonitorUpdateErr::PermanentFailure)
283 log_trace!(self.logger, "Updating Channel Monitor for channel {}", log_funding_info!(monitor));
284 let update_res = monitor.update_monitor(&update, &self.broadcaster, &self.fee_estimator, &self.logger);
285 if let Err(e) = &update_res {
286 log_error!(self.logger, "Failed to update channel monitor: {:?}", e);
288 // Even if updating the monitor returns an error, the monitor's state will
289 // still be changed. So, persist the updated monitor despite the error.
290 let persist_res = self.persister.update_persisted_channel(funding_txo, &update, monitor);
291 if let Err(ref e) = persist_res {
292 log_error!(self.logger, "Failed to persist channel monitor update: {:?}", e);
294 if update_res.is_err() {
295 Err(ChannelMonitorUpdateErr::PermanentFailure)
303 fn release_pending_monitor_events(&self) -> Vec<MonitorEvent> {
304 let mut pending_monitor_events = Vec::new();
305 for monitor in self.monitors.read().unwrap().values() {
306 pending_monitor_events.append(&mut monitor.get_and_clear_pending_monitor_events());
308 pending_monitor_events
312 impl<ChannelSigner: Sign, C: Deref, T: Deref, F: Deref, L: Deref, P: Deref> events::EventsProvider for ChainMonitor<ChannelSigner, C, T, F, L, P>
313 where C::Target: chain::Filter,
314 T::Target: BroadcasterInterface,
315 F::Target: FeeEstimator,
317 P::Target: channelmonitor::Persist<ChannelSigner>,
319 /// Processes [`SpendableOutputs`] events produced from each [`ChannelMonitor`] upon maturity.
321 /// An [`EventHandler`] may safely call back to the provider, though this shouldn't be needed in
322 /// order to handle these events.
324 /// [`SpendableOutputs`]: events::Event::SpendableOutputs
325 fn process_pending_events<H: Deref>(&self, handler: H) where H::Target: EventHandler {
326 let mut pending_events = Vec::new();
327 for monitor in self.monitors.read().unwrap().values() {
328 pending_events.append(&mut monitor.get_and_clear_pending_events());
330 for event in pending_events.drain(..) {
331 handler.handle_event(event);
338 use ::{check_added_monitors, get_local_commitment_txn};
339 use ln::features::InitFeatures;
340 use ln::functional_test_utils::*;
341 use util::events::MessageSendEventsProvider;
342 use util::test_utils::{OnRegisterOutput, TxOutReference};
344 /// Tests that in-block dependent transactions are processed by `block_connected` when not
345 /// included in `txdata` but returned by [`chain::Filter::register_output`]. For instance,
346 /// a (non-anchor) commitment transaction's HTLC output may be spent in the same block as the
347 /// commitment transaction itself. An Electrum client may filter the commitment transaction but
348 /// needs to return the HTLC transaction so it can be processed.
350 fn connect_block_checks_dependent_transactions() {
351 let chanmon_cfgs = create_chanmon_cfgs(2);
352 let node_cfgs = create_node_cfgs(2, &chanmon_cfgs);
353 let node_chanmgrs = create_node_chanmgrs(2, &node_cfgs, &[None, None]);
354 let nodes = create_network(2, &node_cfgs, &node_chanmgrs);
355 let channel = create_announced_chan_between_nodes(
356 &nodes, 0, 1, InitFeatures::known(), InitFeatures::known());
358 // Send a payment, saving nodes[0]'s revoked commitment and HTLC-Timeout transactions.
359 let (commitment_tx, htlc_tx) = {
360 let payment_preimage = route_payment(&nodes[0], &vec!(&nodes[1])[..], 5_000_000).0;
361 let mut txn = get_local_commitment_txn!(nodes[0], channel.2);
362 claim_payment(&nodes[0], &vec!(&nodes[1])[..], payment_preimage);
364 assert_eq!(txn.len(), 2);
365 (txn.remove(0), txn.remove(0))
368 // Set expectations on nodes[1]'s chain source to return dependent transactions.
369 let htlc_output = TxOutReference(commitment_tx.clone(), 0);
370 let to_local_output = TxOutReference(commitment_tx.clone(), 1);
371 let htlc_timeout_output = TxOutReference(htlc_tx.clone(), 0);
372 nodes[1].chain_source
373 .expect(OnRegisterOutput { with: htlc_output, returns: Some((1, htlc_tx)) })
374 .expect(OnRegisterOutput { with: to_local_output, returns: None })
375 .expect(OnRegisterOutput { with: htlc_timeout_output, returns: None });
377 // Notify nodes[1] that nodes[0]'s revoked commitment transaction was mined. The chain
378 // source should return the dependent HTLC transaction when the HTLC output is registered.
379 mine_transaction(&nodes[1], &commitment_tx);
381 // Clean up so uninteresting assertions don't fail.
382 check_added_monitors!(nodes[1], 1);
383 nodes[1].node.get_and_clear_pending_msg_events();
384 nodes[1].node.get_and_clear_pending_events();