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, Header};
13 use bitcoin::blockdata::constants::genesis_block;
14 use bitcoin::blockdata::script::{Script, ScriptBuf};
15 use bitcoin::hash_types::{BlockHash, Txid};
16 use bitcoin::network::constants::Network;
17 use bitcoin::secp256k1::PublicKey;
19 use crate::chain::channelmonitor::{ChannelMonitor, ChannelMonitorUpdate, MonitorEvent};
20 use crate::ln::ChannelId;
21 use crate::sign::ecdsa::WriteableEcdsaChannelSigner;
22 use crate::chain::transaction::{OutPoint, TransactionData};
24 use crate::prelude::*;
26 pub mod chaininterface;
28 pub mod channelmonitor;
30 pub(crate) mod onchaintx;
31 pub(crate) mod package;
33 /// The best known block as identified by its hash and height.
34 #[derive(Clone, Copy, PartialEq, Eq)]
35 pub struct BestBlock {
36 block_hash: BlockHash,
41 /// Constructs a `BestBlock` that represents the genesis block at height 0 of the given
43 pub fn from_network(network: Network) -> Self {
45 block_hash: genesis_block(network).header.block_hash(),
50 /// Returns a `BestBlock` as identified by the given block hash and height.
51 pub fn new(block_hash: BlockHash, height: u32) -> Self {
52 BestBlock { block_hash, height }
55 /// Returns the best block hash.
56 pub fn block_hash(&self) -> BlockHash { self.block_hash }
58 /// Returns the best block height.
59 pub fn height(&self) -> u32 { self.height }
63 /// The `Listen` trait is used to notify when blocks have been connected or disconnected from the
66 /// Useful when needing to replay chain data upon startup or as new chain events occur. Clients
67 /// sourcing chain data using a block-oriented API should prefer this interface over [`Confirm`].
68 /// Such clients fetch the entire header chain whereas clients using [`Confirm`] only fetch headers
71 /// By using [`Listen::filtered_block_connected`] this interface supports clients fetching the
72 /// entire header chain and only blocks with matching transaction data using BIP 157 filters or
73 /// other similar filtering.
75 /// Notifies the listener that a block was added at the given height, with the transaction data
76 /// possibly filtered.
77 fn filtered_block_connected(&self, header: &Header, txdata: &TransactionData, height: u32);
79 /// Notifies the listener that a block was added at the given height.
80 fn block_connected(&self, block: &Block, height: u32) {
81 let txdata: Vec<_> = block.txdata.iter().enumerate().collect();
82 self.filtered_block_connected(&block.header, &txdata, height);
85 /// Notifies the listener that a block was removed at the given height.
86 fn block_disconnected(&self, header: &Header, height: u32);
89 /// The `Confirm` trait is used to notify LDK when relevant transactions have been confirmed on
90 /// chain or unconfirmed during a chain reorganization.
92 /// Clients sourcing chain data using a transaction-oriented API should prefer this interface over
93 /// [`Listen`]. For instance, an Electrum-based transaction sync implementation may implement
94 /// [`Filter`] to subscribe to relevant transactions and unspent outputs it should monitor for
95 /// on-chain activity. Then, it needs to notify LDK via this interface upon observing any changes
96 /// with reference to the confirmation status of the monitored objects.
99 /// The intended use is as follows:
100 /// - Call [`transactions_confirmed`] to notify LDK whenever any of the registered transactions or
101 /// outputs are, respectively, confirmed or spent on chain.
102 /// - Call [`transaction_unconfirmed`] to notify LDK whenever any transaction returned by
103 /// [`get_relevant_txids`] is no longer confirmed in the block with the given block hash.
104 /// - Call [`best_block_updated`] to notify LDK whenever a new chain tip becomes available.
108 /// Clients must call these methods in chain order. Specifically:
109 /// - Transactions which are confirmed in a particular block must be given before transactions
110 /// confirmed in a later block.
111 /// - Dependent transactions within the same block must be given in topological order, possibly in
113 /// - All unconfirmed transactions must be given after the original confirmations and before *any*
114 /// reconfirmations, i.e., [`transactions_confirmed`] and [`transaction_unconfirmed`] calls should
115 /// never be interleaved, but always conduced *en bloc*.
116 /// - Any reconfirmed transactions need to be explicitly unconfirmed before they are reconfirmed
117 /// in regard to the new block.
119 /// See individual method documentation for further details.
121 /// [`transactions_confirmed`]: Self::transactions_confirmed
122 /// [`transaction_unconfirmed`]: Self::transaction_unconfirmed
123 /// [`best_block_updated`]: Self::best_block_updated
124 /// [`get_relevant_txids`]: Self::get_relevant_txids
126 /// Notifies LDK of transactions confirmed in a block with a given header and height.
128 /// Must be called for any transactions registered by [`Filter::register_tx`] or any
129 /// transactions spending an output registered by [`Filter::register_output`]. Such transactions
130 /// appearing in the same block do not need to be included in the same call; instead, multiple
131 /// calls with additional transactions may be made so long as they are made in [chain order].
133 /// May be called before or after [`best_block_updated`] for the corresponding block. However,
134 /// in the event of a chain reorganization, it must not be called with a `header` that is no
135 /// longer in the chain as of the last call to [`best_block_updated`].
137 /// [chain order]: Confirm#order
138 /// [`best_block_updated`]: Self::best_block_updated
139 fn transactions_confirmed(&self, header: &Header, txdata: &TransactionData, height: u32);
140 /// Notifies LDK of a transaction that is no longer confirmed as result of a chain reorganization.
142 /// Must be called for any transaction returned by [`get_relevant_txids`] if it has been
143 /// reorganized out of the best chain or if it is no longer confirmed in the block with the
144 /// given block hash. Once called, the given transaction will not be returned
145 /// by [`get_relevant_txids`], unless it has been reconfirmed via [`transactions_confirmed`].
147 /// [`get_relevant_txids`]: Self::get_relevant_txids
148 /// [`transactions_confirmed`]: Self::transactions_confirmed
149 fn transaction_unconfirmed(&self, txid: &Txid);
150 /// Notifies LDK of an update to the best header connected at the given height.
152 /// Must be called whenever a new chain tip becomes available. May be skipped for intermediary
154 fn best_block_updated(&self, header: &Header, height: u32);
155 /// Returns transactions that must be monitored for reorganization out of the chain along
156 /// with the height and the hash of the block as part of which it had been previously confirmed.
158 /// Note that the returned `Option<BlockHash>` might be `None` for channels created with LDK
159 /// 0.0.112 and prior, in which case you need to manually track previous confirmations.
161 /// Will include any transactions passed to [`transactions_confirmed`] that have insufficient
162 /// confirmations to be safe from a chain reorganization. Will not include any transactions
163 /// passed to [`transaction_unconfirmed`], unless later reconfirmed.
165 /// Must be called to determine the subset of transactions that must be monitored for
166 /// reorganization. Will be idempotent between calls but may change as a result of calls to the
167 /// other interface methods. Thus, this is useful to determine which transactions must be
168 /// given to [`transaction_unconfirmed`].
170 /// If any of the returned transactions are confirmed in a block other than the one with the
171 /// given hash at the given height, they need to be unconfirmed and reconfirmed via
172 /// [`transaction_unconfirmed`] and [`transactions_confirmed`], respectively.
174 /// [`transactions_confirmed`]: Self::transactions_confirmed
175 /// [`transaction_unconfirmed`]: Self::transaction_unconfirmed
176 fn get_relevant_txids(&self) -> Vec<(Txid, u32, Option<BlockHash>)>;
179 /// An enum representing the status of a channel monitor update persistence.
181 /// These are generally used as the return value for an implementation of [`Persist`] which is used
182 /// as the storage layer for a [`ChainMonitor`]. See the docs on [`Persist`] for a high-level
183 /// explanation of how to handle different cases.
185 /// While `UnrecoverableError` is provided as a failure variant, it is not truly "handled" on the
186 /// calling side, and generally results in an immediate panic. For those who prefer to avoid
187 /// panics, `InProgress` can be used and you can retry the update operation in the background or
188 /// shut down cleanly.
190 /// Note that channels should generally *not* be force-closed after a persistence failure.
191 /// Force-closing with the latest [`ChannelMonitorUpdate`] applied may result in a transaction
192 /// being broadcast which can only be spent by the latest [`ChannelMonitor`]! Thus, if the
193 /// latest [`ChannelMonitor`] is not durably persisted anywhere and exists only in memory, naively
194 /// calling [`ChannelManager::force_close_broadcasting_latest_txn`] *may result in loss of funds*!
196 /// [`Persist`]: chainmonitor::Persist
197 /// [`ChainMonitor`]: chainmonitor::ChainMonitor
198 /// [`ChannelManager::force_close_broadcasting_latest_txn`]: crate::ln::channelmanager::ChannelManager::force_close_broadcasting_latest_txn
199 #[derive(Clone, Copy, Debug, PartialEq, Eq)]
200 pub enum ChannelMonitorUpdateStatus {
201 /// The update has been durably persisted and all copies of the relevant [`ChannelMonitor`]
202 /// have been updated.
204 /// This includes performing any `fsync()` calls required to ensure the update is guaranteed to
205 /// be available on restart even if the application crashes.
207 /// Indicates that the update will happen asynchronously in the background or that a transient
208 /// failure occurred which is being retried in the background and will eventually complete.
210 /// This will "freeze" a channel, preventing us from revoking old states or submitting a new
211 /// commitment transaction to the counterparty. Once the update(s) which are `InProgress` have
212 /// been completed, a [`MonitorEvent::Completed`] can be used to restore the channel to an
213 /// operational state.
215 /// Even when a channel has been "frozen", updates to the [`ChannelMonitor`] can continue to
216 /// occur (e.g. if an inbound HTLC which we forwarded was claimed upstream, resulting in us
217 /// attempting to claim it on this channel) and those updates must still be persisted.
219 /// No updates to the channel will be made which could invalidate other [`ChannelMonitor`]s
220 /// until a [`MonitorEvent::Completed`] is provided, even if you return no error on a later
221 /// monitor update for the same channel.
223 /// For deployments where a copy of [`ChannelMonitor`]s and other local state are backed up in
224 /// a remote location (with local copies persisted immediately), it is anticipated that all
225 /// updates will return [`InProgress`] until the remote copies could be updated.
227 /// Note that while fully asynchronous persistence of [`ChannelMonitor`] data is generally
228 /// reliable, this feature is considered beta, and a handful of edge-cases remain. Until the
229 /// remaining cases are fixed, in rare cases, *using this feature may lead to funds loss*.
231 /// [`InProgress`]: ChannelMonitorUpdateStatus::InProgress
233 /// Indicates that an update has failed and will not complete at any point in the future.
235 /// Currently returning this variant will cause LDK to immediately panic to encourage immediate
236 /// shutdown. In the future this may be updated to disconnect peers and refuse to continue
237 /// normal operation without a panic.
239 /// Applications which wish to perform an orderly shutdown after failure should consider
240 /// returning [`InProgress`] instead and simply shut down without ever marking the update
243 /// [`InProgress`]: ChannelMonitorUpdateStatus::InProgress
247 /// The `Watch` trait defines behavior for watching on-chain activity pertaining to channels as
248 /// blocks are connected and disconnected.
250 /// Each channel is associated with a [`ChannelMonitor`]. Implementations of this trait are
251 /// responsible for maintaining a set of monitors such that they can be updated as channel state
252 /// changes. On each update, *all copies* of a [`ChannelMonitor`] must be updated and the update
253 /// persisted to disk to ensure that the latest [`ChannelMonitor`] state can be reloaded if the
254 /// application crashes.
256 /// See method documentation and [`ChannelMonitorUpdateStatus`] for specific requirements.
257 pub trait Watch<ChannelSigner: WriteableEcdsaChannelSigner> {
258 /// Watches a channel identified by `funding_txo` using `monitor`.
260 /// Implementations are responsible for watching the chain for the funding transaction along
261 /// with any spends of outputs returned by [`get_outputs_to_watch`]. In practice, this means
262 /// calling [`block_connected`] and [`block_disconnected`] on the monitor.
264 /// A return of `Err(())` indicates that the channel should immediately be force-closed without
265 /// broadcasting the funding transaction.
267 /// If the given `funding_txo` has previously been registered via `watch_channel`, `Err(())`
268 /// must be returned.
270 /// [`get_outputs_to_watch`]: channelmonitor::ChannelMonitor::get_outputs_to_watch
271 /// [`block_connected`]: channelmonitor::ChannelMonitor::block_connected
272 /// [`block_disconnected`]: channelmonitor::ChannelMonitor::block_disconnected
273 fn watch_channel(&self, funding_txo: OutPoint, monitor: ChannelMonitor<ChannelSigner>) -> Result<ChannelMonitorUpdateStatus, ()>;
275 /// Updates a channel identified by `funding_txo` by applying `update` to its monitor.
277 /// Implementations must call [`ChannelMonitor::update_monitor`] with the given update. This
278 /// may fail (returning an `Err(())`), in which case this should return
279 /// [`ChannelMonitorUpdateStatus::InProgress`] (and the update should never complete). This
280 /// generally implies the channel has been closed (either by the funding outpoint being spent
281 /// on-chain or the [`ChannelMonitor`] having decided to do so and broadcasted a transaction),
282 /// and the [`ChannelManager`] state will be updated once it sees the funding spend on-chain.
284 /// In general, persistence failures should be retried after returning
285 /// [`ChannelMonitorUpdateStatus::InProgress`] and eventually complete. If a failure truly
286 /// cannot be retried, the node should shut down immediately after returning
287 /// [`ChannelMonitorUpdateStatus::UnrecoverableError`], see its documentation for more info.
289 /// [`ChannelManager`]: crate::ln::channelmanager::ChannelManager
290 fn update_channel(&self, funding_txo: OutPoint, update: &ChannelMonitorUpdate) -> ChannelMonitorUpdateStatus;
292 /// Returns any monitor events since the last call. Subsequent calls must only return new
295 /// Note that after any block- or transaction-connection calls to a [`ChannelMonitor`], no
296 /// further events may be returned here until the [`ChannelMonitor`] has been fully persisted
299 /// For details on asynchronous [`ChannelMonitor`] updating and returning
300 /// [`MonitorEvent::Completed`] here, see [`ChannelMonitorUpdateStatus::InProgress`].
301 fn release_pending_monitor_events(&self) -> Vec<(OutPoint, ChannelId, Vec<MonitorEvent>, Option<PublicKey>)>;
304 /// The `Filter` trait defines behavior for indicating chain activity of interest pertaining to
307 /// This is useful in order to have a [`Watch`] implementation convey to a chain source which
308 /// transactions to be notified of. Notification may take the form of pre-filtering blocks or, in
309 /// the case of [BIP 157]/[BIP 158], only fetching a block if the compact filter matches. If
310 /// receiving full blocks from a chain source, any further filtering is unnecessary.
312 /// After an output has been registered, subsequent block retrievals from the chain source must not
313 /// exclude any transactions matching the new criteria nor any in-block descendants of such
316 /// Note that use as part of a [`Watch`] implementation involves reentrancy. Therefore, the `Filter`
317 /// should not block on I/O. Implementations should instead queue the newly monitored data to be
318 /// processed later. Then, in order to block until the data has been processed, any [`Watch`]
319 /// invocation that has called the `Filter` must return [`InProgress`].
321 /// [`InProgress`]: ChannelMonitorUpdateStatus::InProgress
322 /// [BIP 157]: https://github.com/bitcoin/bips/blob/master/bip-0157.mediawiki
323 /// [BIP 158]: https://github.com/bitcoin/bips/blob/master/bip-0158.mediawiki
325 /// Registers interest in a transaction with `txid` and having an output with `script_pubkey` as
326 /// a spending condition.
327 fn register_tx(&self, txid: &Txid, script_pubkey: &Script);
329 /// Registers interest in spends of a transaction output.
331 /// Note that this method might be called during processing of a new block. You therefore need
332 /// to ensure that also dependent output spents within an already connected block are correctly
333 /// handled, e.g., by re-scanning the block in question whenever new outputs have been
334 /// registered mid-processing.
335 fn register_output(&self, output: WatchedOutput);
338 /// A transaction output watched by a [`ChannelMonitor`] for spends on-chain.
340 /// Used to convey to a [`Filter`] such an output with a given spending condition. Any transaction
341 /// spending the output must be given to [`ChannelMonitor::block_connected`] either directly or via
342 /// [`Confirm::transactions_confirmed`].
344 /// If `block_hash` is `Some`, this indicates the output was created in the corresponding block and
345 /// may have been spent there. See [`Filter::register_output`] for details.
347 /// [`ChannelMonitor`]: channelmonitor::ChannelMonitor
348 /// [`ChannelMonitor::block_connected`]: channelmonitor::ChannelMonitor::block_connected
349 #[derive(Clone, PartialEq, Eq, Hash)]
350 pub struct WatchedOutput {
351 /// First block where the transaction output may have been spent.
352 pub block_hash: Option<BlockHash>,
354 /// Outpoint identifying the transaction output.
355 pub outpoint: OutPoint,
357 /// Spending condition of the transaction output.
358 pub script_pubkey: ScriptBuf,
361 impl<T: Listen> Listen for dyn core::ops::Deref<Target = T> {
362 fn filtered_block_connected(&self, header: &Header, txdata: &TransactionData, height: u32) {
363 (**self).filtered_block_connected(header, txdata, height);
366 fn block_disconnected(&self, header: &Header, height: u32) {
367 (**self).block_disconnected(header, height);
371 impl<T: core::ops::Deref, U: core::ops::Deref> Listen for (T, U)
376 fn filtered_block_connected(&self, header: &Header, txdata: &TransactionData, height: u32) {
377 self.0.filtered_block_connected(header, txdata, height);
378 self.1.filtered_block_connected(header, txdata, height);
381 fn block_disconnected(&self, header: &Header, height: u32) {
382 self.0.block_disconnected(header, height);
383 self.1.block_disconnected(header, height);
387 /// A unique identifier to track each pending output claim within a [`ChannelMonitor`].
389 /// This is not exported to bindings users as we just use [u8; 32] directly.
390 #[derive(Copy, Clone, Debug, Hash, PartialEq, Eq)]
391 pub struct ClaimId(pub [u8; 32]);