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 //! Structs and traits which allow other parts of rust-lightning to interact with the blockchain.
12 use bitcoin::blockdata::block::{Block, BlockHeader};
13 use bitcoin::blockdata::constants::genesis_block;
14 use bitcoin::blockdata::script::Script;
15 use bitcoin::blockdata::transaction::TxOut;
16 use bitcoin::hash_types::{BlockHash, Txid};
17 use bitcoin::network::constants::Network;
18 use bitcoin::secp256k1::PublicKey;
20 use chain::channelmonitor::{ChannelMonitor, ChannelMonitorUpdate, MonitorEvent};
21 use chain::keysinterface::Sign;
22 use chain::transaction::{OutPoint, TransactionData};
26 pub mod chaininterface;
28 pub mod channelmonitor;
30 pub mod keysinterface;
31 pub(crate) mod onchaintx;
32 pub(crate) mod package;
34 /// The best known block as identified by its hash and height.
35 #[derive(Clone, Copy, PartialEq)]
36 pub struct BestBlock {
37 block_hash: BlockHash,
42 /// Constructs a `BestBlock` that represents the genesis block at height 0 of the given
44 pub fn from_genesis(network: Network) -> Self {
46 block_hash: genesis_block(network).header.block_hash(),
51 /// Returns a `BestBlock` as identified by the given block hash and height.
52 pub fn new(block_hash: BlockHash, height: u32) -> Self {
53 BestBlock { block_hash, height }
56 /// Returns the best block hash.
57 pub fn block_hash(&self) -> BlockHash { self.block_hash }
59 /// Returns the best block height.
60 pub fn height(&self) -> u32 { self.height }
63 /// An error when accessing the chain via [`Access`].
64 #[derive(Clone, Debug)]
65 pub enum AccessError {
66 /// The requested chain is unknown.
69 /// The requested transaction doesn't exist or hasn't confirmed.
73 /// The `Access` trait defines behavior for accessing chain data and state, such as blocks and
76 /// Returns the transaction output of a funding transaction encoded by [`short_channel_id`].
77 /// Returns an error if `genesis_hash` is for a different chain or if such a transaction output
80 /// [`short_channel_id`]: https://github.com/lightning/bolts/blob/master/07-routing-gossip.md#definition-of-short_channel_id
81 fn get_utxo(&self, genesis_hash: &BlockHash, short_channel_id: u64) -> Result<TxOut, AccessError>;
84 /// The `Listen` trait is used to notify when blocks have been connected or disconnected from the
87 /// Useful when needing to replay chain data upon startup or as new chain events occur. Clients
88 /// sourcing chain data using a block-oriented API should prefer this interface over [`Confirm`].
89 /// Such clients fetch the entire header chain whereas clients using [`Confirm`] only fetch headers
92 /// By using [`Listen::filtered_block_connected`] this interface supports clients fetching the
93 /// entire header chain and only blocks with matching transaction data using BIP 157 filters or
94 /// other similar filtering.
96 /// Notifies the listener that a block was added at the given height, with the transaction data
97 /// possibly filtered.
98 fn filtered_block_connected(&self, header: &BlockHeader, txdata: &TransactionData, height: u32);
100 /// Notifies the listener that a block was added at the given height.
101 fn block_connected(&self, block: &Block, height: u32) {
102 let txdata: Vec<_> = block.txdata.iter().enumerate().collect();
103 self.filtered_block_connected(&block.header, &txdata, height);
106 /// Notifies the listener that a block was removed at the given height.
107 fn block_disconnected(&self, header: &BlockHeader, height: u32);
110 /// The `Confirm` trait is used to notify when transactions have been confirmed on chain or
111 /// unconfirmed during a chain reorganization.
113 /// Clients sourcing chain data using a transaction-oriented API should prefer this interface over
114 /// [`Listen`]. For instance, an Electrum client may implement [`Filter`] by subscribing to activity
115 /// related to registered transactions and outputs. Upon notification, it would pass along the
116 /// matching transactions using this interface.
120 /// The intended use is as follows:
121 /// - Call [`transactions_confirmed`] to process any on-chain activity of interest.
122 /// - Call [`transaction_unconfirmed`] to process any transaction returned by [`get_relevant_txids`]
123 /// that has been reorganized out of the chain.
124 /// - Call [`best_block_updated`] whenever a new chain tip becomes available.
128 /// Clients must call these methods in chain order. Specifically:
129 /// - Transactions confirmed in a block must be given before transactions confirmed in a later
131 /// - Dependent transactions within the same block must be given in topological order, possibly in
133 /// - Unconfirmed transactions must be given after the original confirmations and before any
136 /// See individual method documentation for further details.
138 /// [`transactions_confirmed`]: Self::transactions_confirmed
139 /// [`transaction_unconfirmed`]: Self::transaction_unconfirmed
140 /// [`best_block_updated`]: Self::best_block_updated
141 /// [`get_relevant_txids`]: Self::get_relevant_txids
143 /// Processes transactions confirmed in a block with a given header and height.
145 /// Should be called for any transactions registered by [`Filter::register_tx`] or any
146 /// transactions spending an output registered by [`Filter::register_output`]. Such transactions
147 /// appearing in the same block do not need to be included in the same call; instead, multiple
148 /// calls with additional transactions may be made so long as they are made in [chain order].
150 /// May be called before or after [`best_block_updated`] for the corresponding block. However,
151 /// in the event of a chain reorganization, it must not be called with a `header` that is no
152 /// longer in the chain as of the last call to [`best_block_updated`].
154 /// [chain order]: Confirm#order
155 /// [`best_block_updated`]: Self::best_block_updated
156 fn transactions_confirmed(&self, header: &BlockHeader, txdata: &TransactionData, height: u32);
158 /// Processes a transaction that is no longer confirmed as result of a chain reorganization.
160 /// Should be called for any transaction returned by [`get_relevant_txids`] if it has been
161 /// reorganized out of the best chain. Once called, the given transaction will not be returned
162 /// by [`get_relevant_txids`], unless it has been reconfirmed via [`transactions_confirmed`].
164 /// [`get_relevant_txids`]: Self::get_relevant_txids
165 /// [`transactions_confirmed`]: Self::transactions_confirmed
166 fn transaction_unconfirmed(&self, txid: &Txid);
168 /// Processes an update to the best header connected at the given height.
170 /// Should be called when a new header is available but may be skipped for intermediary blocks
171 /// if they become available at the same time.
172 fn best_block_updated(&self, header: &BlockHeader, height: u32);
174 /// Returns transactions that should be monitored for reorganization out of the chain.
176 /// Will include any transactions passed to [`transactions_confirmed`] that have insufficient
177 /// confirmations to be safe from a chain reorganization. Will not include any transactions
178 /// passed to [`transaction_unconfirmed`], unless later reconfirmed.
180 /// May be called to determine the subset of transactions that must still be monitored for
181 /// reorganization. Will be idempotent between calls but may change as a result of calls to the
182 /// other interface methods. Thus, this is useful to determine which transactions may need to be
183 /// given to [`transaction_unconfirmed`].
185 /// [`transactions_confirmed`]: Self::transactions_confirmed
186 /// [`transaction_unconfirmed`]: Self::transaction_unconfirmed
187 fn get_relevant_txids(&self) -> Vec<Txid>;
190 /// An enum representing the status of a channel monitor update persistence.
191 #[derive(Clone, Copy, Debug, PartialEq)]
192 pub enum ChannelMonitorUpdateStatus {
193 /// The update has been durably persisted and all copies of the relevant [`ChannelMonitor`]
194 /// have been updated.
196 /// This includes performing any `fsync()` calls required to ensure the update is guaranteed to
197 /// be available on restart even if the application crashes.
199 /// Used to indicate a temporary failure (eg connection to a watchtower or remote backup of
200 /// our state failed, but is expected to succeed at some point in the future).
202 /// Such a failure will "freeze" a channel, preventing us from revoking old states or
203 /// submitting new commitment transactions to the counterparty. Once the update(s) which failed
204 /// have been successfully applied, a [`MonitorEvent::Completed`] can be used to restore the
205 /// channel to an operational state.
207 /// Note that a given [`ChannelManager`] will *never* re-generate a [`ChannelMonitorUpdate`].
208 /// If you return this error you must ensure that it is written to disk safely before writing
209 /// the latest [`ChannelManager`] state, or you should return [`PermanentFailure`] instead.
211 /// Even when a channel has been "frozen", updates to the [`ChannelMonitor`] can continue to
212 /// occur (e.g. if an inbound HTLC which we forwarded was claimed upstream, resulting in us
213 /// attempting to claim it on this channel) and those updates must still be persisted.
215 /// No updates to the channel will be made which could invalidate other [`ChannelMonitor`]s
216 /// until a [`MonitorEvent::Completed`] is provided, even if you return no error on a later
217 /// monitor update for the same channel.
219 /// For deployments where a copy of ChannelMonitors and other local state are backed up in a
220 /// remote location (with local copies persisted immediately), it is anticipated that all
221 /// updates will return [`InProgress`] until the remote copies could be updated.
223 /// [`PermanentFailure`]: ChannelMonitorUpdateStatus::PermanentFailure
224 /// [`InProgress`]: ChannelMonitorUpdateStatus::InProgress
225 /// [`ChannelManager`]: crate::ln::channelmanager::ChannelManager
227 /// Used to indicate no further channel monitor updates will be allowed (likely a disk failure
228 /// or a remote copy of this [`ChannelMonitor`] is no longer reachable and thus not updatable).
230 /// When this is returned, [`ChannelManager`] will force-close the channel but *not* broadcast
231 /// our current commitment transaction. This avoids a dangerous case where a local disk failure
232 /// (e.g. the Linux-default remounting of the disk as read-only) causes [`PermanentFailure`]s
233 /// for all monitor updates. If we were to broadcast our latest commitment transaction and then
234 /// restart, we could end up reading a previous [`ChannelMonitor`] and [`ChannelManager`],
235 /// revoking our now-broadcasted state before seeing it confirm and losing all our funds.
237 /// Note that this is somewhat of a tradeoff - if the disk is really gone and we may have lost
238 /// the data permanently, we really should broadcast immediately. If the data can be recovered
239 /// with manual intervention, we'd rather close the channel, rejecting future updates to it,
240 /// and broadcast the latest state only if we have HTLCs to claim which are timing out (which
241 /// we do as long as blocks are connected).
243 /// In order to broadcast the latest local commitment transaction, you'll need to call
244 /// [`ChannelMonitor::get_latest_holder_commitment_txn`] and broadcast the resulting
245 /// transactions once you've safely ensured no further channel updates can be generated by your
246 /// [`ChannelManager`].
248 /// Note that at least one final [`ChannelMonitorUpdate`] may still be provided, which must
249 /// still be processed by a running [`ChannelMonitor`]. This final update will mark the
250 /// [`ChannelMonitor`] as finalized, ensuring no further updates (e.g. revocation of the latest
251 /// commitment transaction) are allowed.
253 /// Note that even if you return a [`PermanentFailure`] due to unavailability of secondary
254 /// [`ChannelMonitor`] copies, you should still make an attempt to store the update where
255 /// possible to ensure you can claim HTLC outputs on the latest commitment transaction
256 /// broadcasted later.
258 /// In case of distributed watchtowers deployment, the new version must be written to disk, as
259 /// state may have been stored but rejected due to a block forcing a commitment broadcast. This
260 /// storage is used to claim outputs of rejected state confirmed onchain by another watchtower,
261 /// lagging behind on block processing.
263 /// [`PermanentFailure`]: ChannelMonitorUpdateStatus::PermanentFailure
264 /// [`ChannelManager`]: crate::ln::channelmanager::ChannelManager
268 /// The `Watch` trait defines behavior for watching on-chain activity pertaining to channels as
269 /// blocks are connected and disconnected.
271 /// Each channel is associated with a [`ChannelMonitor`]. Implementations of this trait are
272 /// responsible for maintaining a set of monitors such that they can be updated accordingly as
273 /// channel state changes and HTLCs are resolved. See method documentation for specific
276 /// Implementations **must** ensure that updates are successfully applied and persisted upon method
277 /// completion. If an update fails with a [`PermanentFailure`], then it must immediately shut down
278 /// without taking any further action such as persisting the current state.
280 /// If an implementation maintains multiple instances of a channel's monitor (e.g., by storing
281 /// backup copies), then it must ensure that updates are applied across all instances. Otherwise, it
282 /// could result in a revoked transaction being broadcast, allowing the counterparty to claim all
283 /// funds in the channel. See [`ChannelMonitorUpdateStatus`] for more details about how to handle
284 /// multiple instances.
286 /// [`PermanentFailure`]: ChannelMonitorUpdateStatus::PermanentFailure
287 pub trait Watch<ChannelSigner: Sign> {
288 /// Watches a channel identified by `funding_txo` using `monitor`.
290 /// Implementations are responsible for watching the chain for the funding transaction along
291 /// with any spends of outputs returned by [`get_outputs_to_watch`]. In practice, this means
292 /// calling [`block_connected`] and [`block_disconnected`] on the monitor.
294 /// Note: this interface MUST error with [`ChannelMonitorUpdateStatus::PermanentFailure`] if
295 /// the given `funding_txo` has previously been registered via `watch_channel`.
297 /// [`get_outputs_to_watch`]: channelmonitor::ChannelMonitor::get_outputs_to_watch
298 /// [`block_connected`]: channelmonitor::ChannelMonitor::block_connected
299 /// [`block_disconnected`]: channelmonitor::ChannelMonitor::block_disconnected
300 fn watch_channel(&self, funding_txo: OutPoint, monitor: ChannelMonitor<ChannelSigner>) -> ChannelMonitorUpdateStatus;
302 /// Updates a channel identified by `funding_txo` by applying `update` to its monitor.
304 /// Implementations must call [`update_monitor`] with the given update. See
305 /// [`ChannelMonitorUpdateStatus`] for invariants around returning an error.
307 /// [`update_monitor`]: channelmonitor::ChannelMonitor::update_monitor
308 fn update_channel(&self, funding_txo: OutPoint, update: ChannelMonitorUpdate) -> ChannelMonitorUpdateStatus;
310 /// Returns any monitor events since the last call. Subsequent calls must only return new
313 /// Note that after any block- or transaction-connection calls to a [`ChannelMonitor`], no
314 /// further events may be returned here until the [`ChannelMonitor`] has been fully persisted
317 /// For details on asynchronous [`ChannelMonitor`] updating and returning
318 /// [`MonitorEvent::Completed`] here, see [`ChannelMonitorUpdateStatus::InProgress`].
319 fn release_pending_monitor_events(&self) -> Vec<(OutPoint, Vec<MonitorEvent>, Option<PublicKey>)>;
322 /// The `Filter` trait defines behavior for indicating chain activity of interest pertaining to
325 /// This is useful in order to have a [`Watch`] implementation convey to a chain source which
326 /// transactions to be notified of. Notification may take the form of pre-filtering blocks or, in
327 /// the case of [BIP 157]/[BIP 158], only fetching a block if the compact filter matches. If
328 /// receiving full blocks from a chain source, any further filtering is unnecessary.
330 /// After an output has been registered, subsequent block retrievals from the chain source must not
331 /// exclude any transactions matching the new criteria nor any in-block descendants of such
334 /// Note that use as part of a [`Watch`] implementation involves reentrancy. Therefore, the `Filter`
335 /// should not block on I/O. Implementations should instead queue the newly monitored data to be
336 /// processed later. Then, in order to block until the data has been processed, any [`Watch`]
337 /// invocation that has called the `Filter` must return [`InProgress`].
339 /// [`InProgress`]: ChannelMonitorUpdateStatus::InProgress
340 /// [BIP 157]: https://github.com/bitcoin/bips/blob/master/bip-0157.mediawiki
341 /// [BIP 158]: https://github.com/bitcoin/bips/blob/master/bip-0158.mediawiki
343 /// Registers interest in a transaction with `txid` and having an output with `script_pubkey` as
344 /// a spending condition.
345 fn register_tx(&self, txid: &Txid, script_pubkey: &Script);
347 /// Registers interest in spends of a transaction output.
349 /// Note that this method might be called during processing of a new block. You therefore need
350 /// to ensure that also dependent output spents within an already connected block are correctly
351 /// handled, e.g., by re-scanning the block in question whenever new outputs have been
352 /// registered mid-processing.
353 fn register_output(&self, output: WatchedOutput);
356 /// A transaction output watched by a [`ChannelMonitor`] for spends on-chain.
358 /// Used to convey to a [`Filter`] such an output with a given spending condition. Any transaction
359 /// spending the output must be given to [`ChannelMonitor::block_connected`] either directly or via
360 /// [`Confirm::transactions_confirmed`].
362 /// If `block_hash` is `Some`, this indicates the output was created in the corresponding block and
363 /// may have been spent there. See [`Filter::register_output`] for details.
365 /// [`ChannelMonitor`]: channelmonitor::ChannelMonitor
366 /// [`ChannelMonitor::block_connected`]: channelmonitor::ChannelMonitor::block_connected
367 #[derive(Clone, PartialEq, Hash)]
368 pub struct WatchedOutput {
369 /// First block where the transaction output may have been spent.
370 pub block_hash: Option<BlockHash>,
372 /// Outpoint identifying the transaction output.
373 pub outpoint: OutPoint,
375 /// Spending condition of the transaction output.
376 pub script_pubkey: Script,
379 impl<T: Listen> Listen for core::ops::Deref<Target = T> {
380 fn filtered_block_connected(&self, header: &BlockHeader, txdata: &TransactionData, height: u32) {
381 (**self).filtered_block_connected(header, txdata, height);
384 fn block_disconnected(&self, header: &BlockHeader, height: u32) {
385 (**self).block_disconnected(header, height);
389 impl<T: core::ops::Deref, U: core::ops::Deref> Listen for (T, U)
394 fn filtered_block_connected(&self, header: &BlockHeader, txdata: &TransactionData, height: u32) {
395 self.0.filtered_block_connected(header, txdata, height);
396 self.1.filtered_block_connected(header, txdata, height);
399 fn block_disconnected(&self, header: &BlockHeader, height: u32) {
400 self.0.block_disconnected(header, height);
401 self.1.block_disconnected(header, height);