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};
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 for (txid, outputs) in txn_outputs.drain(..) {
91 for (idx, output) in outputs.iter() {
92 chain_source.register_output(&OutPoint { txid, index: *idx as u16 }, &output.script_pubkey);
99 /// Dispatches to per-channel monitors, which are responsible for updating their on-chain view
100 /// of a channel based on the disconnected block. See [`ChannelMonitor::block_disconnected`] for
102 pub fn block_disconnected(&self, header: &BlockHeader, disconnected_height: u32) {
103 let monitors = self.monitors.read().unwrap();
104 for monitor in monitors.values() {
105 monitor.block_disconnected(header, disconnected_height, &*self.broadcaster, &*self.fee_estimator, &*self.logger);
109 /// Creates a new `ChainMonitor` used to watch on-chain activity pertaining to channels.
111 /// When an optional chain source implementing [`chain::Filter`] is provided, the chain monitor
112 /// will call back to it indicating transactions and outputs of interest. This allows clients to
113 /// pre-filter blocks or only fetch blocks matching a compact filter. Otherwise, clients may
114 /// always need to fetch full blocks absent another means for determining which blocks contain
115 /// transactions relevant to the watched channels.
116 pub fn new(chain_source: Option<C>, broadcaster: T, logger: L, feeest: F, persister: P) -> Self {
118 monitors: RwLock::new(HashMap::new()),
122 fee_estimator: feeest,
128 impl<ChannelSigner: Sign, C: Deref + Send + Sync, T: Deref + Send + Sync, F: Deref + Send + Sync, L: Deref + Send + Sync, P: Deref + Send + Sync>
129 chain::Listen for ChainMonitor<ChannelSigner, C, T, F, L, P>
132 C::Target: chain::Filter,
133 T::Target: BroadcasterInterface,
134 F::Target: FeeEstimator,
136 P::Target: channelmonitor::Persist<ChannelSigner>,
138 fn block_connected(&self, block: &Block, height: u32) {
139 let txdata: Vec<_> = block.txdata.iter().enumerate().collect();
140 ChainMonitor::block_connected(self, &block.header, &txdata, height);
143 fn block_disconnected(&self, header: &BlockHeader, height: u32) {
144 ChainMonitor::block_disconnected(self, header, height);
148 impl<ChannelSigner: Sign, C: Deref + Sync + Send, T: Deref + Sync + Send, F: Deref + Sync + Send, L: Deref + Sync + Send, P: Deref + Sync + Send>
149 chain::Watch<ChannelSigner> for ChainMonitor<ChannelSigner, C, T, F, L, P>
150 where C::Target: chain::Filter,
151 T::Target: BroadcasterInterface,
152 F::Target: FeeEstimator,
154 P::Target: channelmonitor::Persist<ChannelSigner>,
156 /// Adds the monitor that watches the channel referred to by the given outpoint.
158 /// Calls back to [`chain::Filter`] with the funding transaction and outputs to watch.
160 /// Note that we persist the given `ChannelMonitor` while holding the `ChainMonitor`
162 fn watch_channel(&self, funding_outpoint: OutPoint, monitor: ChannelMonitor<ChannelSigner>) -> Result<(), ChannelMonitorUpdateErr> {
163 let mut monitors = self.monitors.write().unwrap();
164 let entry = match monitors.entry(funding_outpoint) {
165 hash_map::Entry::Occupied(_) => {
166 log_error!(self.logger, "Failed to add new channel data: channel monitor for given outpoint is already present");
167 return Err(ChannelMonitorUpdateErr::PermanentFailure)},
168 hash_map::Entry::Vacant(e) => e,
170 if let Err(e) = self.persister.persist_new_channel(funding_outpoint, &monitor) {
171 log_error!(self.logger, "Failed to persist new channel data");
175 let funding_txo = monitor.get_funding_txo();
176 log_trace!(self.logger, "Got new Channel Monitor for channel {}", log_bytes!(funding_txo.0.to_channel_id()[..]));
178 if let Some(ref chain_source) = self.chain_source {
179 monitor.load_outputs_to_watch(chain_source);
182 entry.insert(monitor);
186 /// Note that we persist the given `ChannelMonitor` update while holding the
187 /// `ChainMonitor` monitors lock.
188 fn update_channel(&self, funding_txo: OutPoint, update: ChannelMonitorUpdate) -> Result<(), ChannelMonitorUpdateErr> {
189 // Update the monitor that watches the channel referred to by the given outpoint.
190 let monitors = self.monitors.read().unwrap();
191 match monitors.get(&funding_txo) {
193 log_error!(self.logger, "Failed to update channel monitor: no such monitor registered");
195 // We should never ever trigger this from within ChannelManager. Technically a
196 // user could use this object with some proxying in between which makes this
197 // possible, but in tests and fuzzing, this should be a panic.
198 #[cfg(any(test, feature = "fuzztarget"))]
199 panic!("ChannelManager generated a channel update for a channel that was not yet registered!");
200 #[cfg(not(any(test, feature = "fuzztarget")))]
201 Err(ChannelMonitorUpdateErr::PermanentFailure)
204 log_trace!(self.logger, "Updating Channel Monitor for channel {}", log_funding_info!(monitor));
205 let update_res = monitor.update_monitor(&update, &self.broadcaster, &self.fee_estimator, &self.logger);
206 if let Err(e) = &update_res {
207 log_error!(self.logger, "Failed to update channel monitor: {:?}", e);
209 // Even if updating the monitor returns an error, the monitor's state will
210 // still be changed. So, persist the updated monitor despite the error.
211 let persist_res = self.persister.update_persisted_channel(funding_txo, &update, monitor);
212 if let Err(ref e) = persist_res {
213 log_error!(self.logger, "Failed to persist channel monitor update: {:?}", e);
215 if update_res.is_err() {
216 Err(ChannelMonitorUpdateErr::PermanentFailure)
224 fn release_pending_monitor_events(&self) -> Vec<MonitorEvent> {
225 let mut pending_monitor_events = Vec::new();
226 for monitor in self.monitors.read().unwrap().values() {
227 pending_monitor_events.append(&mut monitor.get_and_clear_pending_monitor_events());
229 pending_monitor_events
233 impl<ChannelSigner: Sign, C: Deref, T: Deref, F: Deref, L: Deref, P: Deref> events::EventsProvider for ChainMonitor<ChannelSigner, C, T, F, L, P>
234 where C::Target: chain::Filter,
235 T::Target: BroadcasterInterface,
236 F::Target: FeeEstimator,
238 P::Target: channelmonitor::Persist<ChannelSigner>,
240 fn get_and_clear_pending_events(&self) -> Vec<Event> {
241 let mut pending_events = Vec::new();
242 for monitor in self.monitors.read().unwrap().values() {
243 pending_events.append(&mut monitor.get_and_clear_pending_events());