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