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};
29 use chain::{Filter, WatchedOutput};
30 use chain::chaininterface::{BroadcasterInterface, FeeEstimator};
31 use chain::channelmonitor;
32 use chain::channelmonitor::{ChannelMonitor, ChannelMonitorUpdate, ChannelMonitorUpdateErr, MonitorEvent, Persist};
33 use chain::transaction::{OutPoint, TransactionData};
34 use chain::keysinterface::Sign;
35 use util::logger::Logger;
37 use util::events::Event;
39 use std::collections::{HashMap, hash_map};
40 use std::sync::RwLock;
43 /// An implementation of [`chain::Watch`] for monitoring channels.
45 /// Connected and disconnected blocks must be provided to `ChainMonitor` as documented by
46 /// [`chain::Watch`]. May be used in conjunction with [`ChannelManager`] to monitor channels locally
47 /// or used independently to monitor channels remotely. See the [module-level documentation] for
50 /// [`ChannelManager`]: crate::ln::channelmanager::ChannelManager
51 /// [module-level documentation]: crate::chain::chainmonitor
52 pub struct ChainMonitor<ChannelSigner: Sign, C: Deref, T: Deref, F: Deref, L: Deref, P: Deref>
53 where C::Target: chain::Filter,
54 T::Target: BroadcasterInterface,
55 F::Target: FeeEstimator,
57 P::Target: channelmonitor::Persist<ChannelSigner>,
60 pub monitors: RwLock<HashMap<OutPoint, ChannelMonitor<ChannelSigner>>>,
61 chain_source: Option<C>,
68 impl<ChannelSigner: Sign, C: Deref, T: Deref, F: Deref, L: Deref, P: Deref> ChainMonitor<ChannelSigner, C, T, F, L, P>
69 where C::Target: chain::Filter,
70 T::Target: BroadcasterInterface,
71 F::Target: FeeEstimator,
73 P::Target: channelmonitor::Persist<ChannelSigner>,
75 /// Dispatches to per-channel monitors, which are responsible for updating their on-chain view
76 /// of a channel and reacting accordingly based on transactions in the connected block. See
77 /// [`ChannelMonitor::block_connected`] for details. Any HTLCs that were resolved on chain will
78 /// be returned by [`chain::Watch::release_pending_monitor_events`].
80 /// Calls back to [`chain::Filter`] if any monitor indicated new outputs to watch. Subsequent
81 /// calls must not exclude any transactions matching the new outputs nor any in-block
82 /// descendants of such transactions. It is not necessary to re-fetch the block to obtain
84 pub fn block_connected(&self, header: &BlockHeader, txdata: &TransactionData, height: u32) {
85 let monitors = self.monitors.read().unwrap();
86 for monitor in monitors.values() {
87 let mut txn_outputs = monitor.block_connected(header, txdata, height, &*self.broadcaster, &*self.fee_estimator, &*self.logger);
89 if let Some(ref chain_source) = self.chain_source {
90 let block_hash = header.block_hash();
91 for (txid, outputs) in txn_outputs.drain(..) {
92 for (idx, output) in outputs.iter() {
93 chain_source.register_output(WatchedOutput {
94 block_hash: Some(block_hash),
95 outpoint: OutPoint { txid, index: *idx as u16 },
96 script_pubkey: output.script_pubkey.clone(),
104 /// Dispatches to per-channel monitors, which are responsible for updating their on-chain view
105 /// of a channel based on the disconnected block. See [`ChannelMonitor::block_disconnected`] for
107 pub fn block_disconnected(&self, header: &BlockHeader, disconnected_height: u32) {
108 let monitors = self.monitors.read().unwrap();
109 for monitor in monitors.values() {
110 monitor.block_disconnected(header, disconnected_height, &*self.broadcaster, &*self.fee_estimator, &*self.logger);
114 /// Creates a new `ChainMonitor` used to watch on-chain activity pertaining to channels.
116 /// When an optional chain source implementing [`chain::Filter`] is provided, the chain monitor
117 /// will call back to it indicating transactions and outputs of interest. This allows clients to
118 /// pre-filter blocks or only fetch blocks matching a compact filter. Otherwise, clients may
119 /// always need to fetch full blocks absent another means for determining which blocks contain
120 /// transactions relevant to the watched channels.
121 pub fn new(chain_source: Option<C>, broadcaster: T, logger: L, feeest: F, persister: P) -> Self {
123 monitors: RwLock::new(HashMap::new()),
127 fee_estimator: feeest,
133 impl<ChannelSigner: Sign, C: Deref + Send + Sync, T: Deref + Send + Sync, F: Deref + Send + Sync, L: Deref + Send + Sync, P: Deref + Send + Sync>
134 chain::Listen for ChainMonitor<ChannelSigner, C, T, F, L, P>
137 C::Target: chain::Filter,
138 T::Target: BroadcasterInterface,
139 F::Target: FeeEstimator,
141 P::Target: channelmonitor::Persist<ChannelSigner>,
143 fn block_connected(&self, block: &Block, height: u32) {
144 let txdata: Vec<_> = block.txdata.iter().enumerate().collect();
145 ChainMonitor::block_connected(self, &block.header, &txdata, height);
148 fn block_disconnected(&self, header: &BlockHeader, height: u32) {
149 ChainMonitor::block_disconnected(self, header, height);
153 impl<ChannelSigner: Sign, C: Deref + Sync + Send, T: Deref + Sync + Send, F: Deref + Sync + Send, L: Deref + Sync + Send, P: Deref + Sync + Send>
154 chain::Watch<ChannelSigner> for ChainMonitor<ChannelSigner, C, T, F, L, P>
155 where C::Target: chain::Filter,
156 T::Target: BroadcasterInterface,
157 F::Target: FeeEstimator,
159 P::Target: channelmonitor::Persist<ChannelSigner>,
161 /// Adds the monitor that watches the channel referred to by the given outpoint.
163 /// Calls back to [`chain::Filter`] with the funding transaction and outputs to watch.
165 /// Note that we persist the given `ChannelMonitor` while holding the `ChainMonitor`
167 fn watch_channel(&self, funding_outpoint: OutPoint, monitor: ChannelMonitor<ChannelSigner>) -> Result<(), ChannelMonitorUpdateErr> {
168 let mut monitors = self.monitors.write().unwrap();
169 let entry = match monitors.entry(funding_outpoint) {
170 hash_map::Entry::Occupied(_) => {
171 log_error!(self.logger, "Failed to add new channel data: channel monitor for given outpoint is already present");
172 return Err(ChannelMonitorUpdateErr::PermanentFailure)},
173 hash_map::Entry::Vacant(e) => e,
175 if let Err(e) = self.persister.persist_new_channel(funding_outpoint, &monitor) {
176 log_error!(self.logger, "Failed to persist new channel data");
180 let funding_txo = monitor.get_funding_txo();
181 log_trace!(self.logger, "Got new Channel Monitor for channel {}", log_bytes!(funding_txo.0.to_channel_id()[..]));
183 if let Some(ref chain_source) = self.chain_source {
184 monitor.load_outputs_to_watch(chain_source);
187 entry.insert(monitor);
191 /// Note that we persist the given `ChannelMonitor` update while holding the
192 /// `ChainMonitor` monitors lock.
193 fn update_channel(&self, funding_txo: OutPoint, update: ChannelMonitorUpdate) -> Result<(), ChannelMonitorUpdateErr> {
194 // Update the monitor that watches the channel referred to by the given outpoint.
195 let monitors = self.monitors.read().unwrap();
196 match monitors.get(&funding_txo) {
198 log_error!(self.logger, "Failed to update channel monitor: no such monitor registered");
200 // We should never ever trigger this from within ChannelManager. Technically a
201 // user could use this object with some proxying in between which makes this
202 // possible, but in tests and fuzzing, this should be a panic.
203 #[cfg(any(test, feature = "fuzztarget"))]
204 panic!("ChannelManager generated a channel update for a channel that was not yet registered!");
205 #[cfg(not(any(test, feature = "fuzztarget")))]
206 Err(ChannelMonitorUpdateErr::PermanentFailure)
209 log_trace!(self.logger, "Updating Channel Monitor for channel {}", log_funding_info!(monitor));
210 let update_res = monitor.update_monitor(&update, &self.broadcaster, &self.fee_estimator, &self.logger);
211 if let Err(e) = &update_res {
212 log_error!(self.logger, "Failed to update channel monitor: {:?}", e);
214 // Even if updating the monitor returns an error, the monitor's state will
215 // still be changed. So, persist the updated monitor despite the error.
216 let persist_res = self.persister.update_persisted_channel(funding_txo, &update, monitor);
217 if let Err(ref e) = persist_res {
218 log_error!(self.logger, "Failed to persist channel monitor update: {:?}", e);
220 if update_res.is_err() {
221 Err(ChannelMonitorUpdateErr::PermanentFailure)
229 fn release_pending_monitor_events(&self) -> Vec<MonitorEvent> {
230 let mut pending_monitor_events = Vec::new();
231 for monitor in self.monitors.read().unwrap().values() {
232 pending_monitor_events.append(&mut monitor.get_and_clear_pending_monitor_events());
234 pending_monitor_events
238 impl<ChannelSigner: Sign, C: Deref, T: Deref, F: Deref, L: Deref, P: Deref> events::EventsProvider for ChainMonitor<ChannelSigner, C, T, F, L, P>
239 where C::Target: chain::Filter,
240 T::Target: BroadcasterInterface,
241 F::Target: FeeEstimator,
243 P::Target: channelmonitor::Persist<ChannelSigner>,
245 fn get_and_clear_pending_events(&self) -> Vec<Event> {
246 let mut pending_events = Vec::new();
247 for monitor in self.monitors.read().unwrap().values() {
248 pending_events.append(&mut monitor.get_and_clear_pending_events());