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::types::ChannelId;
21 use crate::sign::ecdsa::WriteableEcdsaChannelSigner;
22 use crate::chain::transaction::{OutPoint, TransactionData};
23 use crate::impl_writeable_tlv_based;
25 #[allow(unused_imports)]
26 use crate::prelude::*;
28 pub mod chaininterface;
30 pub mod channelmonitor;
32 pub(crate) mod onchaintx;
33 pub(crate) mod package;
35 /// The best known block as identified by its hash and height.
36 #[derive(Clone, Copy, Debug, Hash, PartialEq, Eq)]
37 pub struct BestBlock {
39 pub block_hash: BlockHash,
40 /// The height at which the block was confirmed.
45 /// Constructs a `BestBlock` that represents the genesis block at height 0 of the given
47 pub fn from_network(network: Network) -> Self {
49 block_hash: genesis_block(network).header.block_hash(),
54 /// Returns a `BestBlock` as identified by the given block hash and height.
55 pub fn new(block_hash: BlockHash, height: u32) -> Self {
56 BestBlock { block_hash, height }
60 impl_writeable_tlv_based!(BestBlock, {
61 (0, block_hash, required),
62 (2, height, required),
66 /// The `Listen` trait is used to notify when blocks have been connected or disconnected from the
69 /// Useful when needing to replay chain data upon startup or as new chain events occur. Clients
70 /// sourcing chain data using a block-oriented API should prefer this interface over [`Confirm`].
71 /// Such clients fetch the entire header chain whereas clients using [`Confirm`] only fetch headers
74 /// By using [`Listen::filtered_block_connected`] this interface supports clients fetching the
75 /// entire header chain and only blocks with matching transaction data using BIP 157 filters or
76 /// other similar filtering.
78 /// Notifies the listener that a block was added at the given height, with the transaction data
79 /// possibly filtered.
80 fn filtered_block_connected(&self, header: &Header, txdata: &TransactionData, height: u32);
82 /// Notifies the listener that a block was added at the given height.
83 fn block_connected(&self, block: &Block, height: u32) {
84 let txdata: Vec<_> = block.txdata.iter().enumerate().collect();
85 self.filtered_block_connected(&block.header, &txdata, height);
88 /// Notifies the listener that a block was removed at the given height.
89 fn block_disconnected(&self, header: &Header, height: u32);
92 /// The `Confirm` trait is used to notify LDK when relevant transactions have been confirmed on
93 /// chain or unconfirmed during a chain reorganization.
95 /// Clients sourcing chain data using a transaction-oriented API should prefer this interface over
96 /// [`Listen`]. For instance, an Electrum-based transaction sync implementation may implement
97 /// [`Filter`] to subscribe to relevant transactions and unspent outputs it should monitor for
98 /// on-chain activity. Then, it needs to notify LDK via this interface upon observing any changes
99 /// with reference to the confirmation status of the monitored objects.
102 /// The intended use is as follows:
103 /// - Call [`transactions_confirmed`] to notify LDK whenever any of the registered transactions or
104 /// outputs are, respectively, confirmed or spent on chain.
105 /// - Call [`transaction_unconfirmed`] to notify LDK whenever any transaction returned by
106 /// [`get_relevant_txids`] is no longer confirmed in the block with the given block hash.
107 /// - Call [`best_block_updated`] to notify LDK whenever a new chain tip becomes available.
111 /// Clients must call these methods in chain order. Specifically:
112 /// - Transactions which are confirmed in a particular block must be given before transactions
113 /// confirmed in a later block.
114 /// - Dependent transactions within the same block must be given in topological order, possibly in
116 /// - All unconfirmed transactions must be given after the original confirmations and before *any*
117 /// reconfirmations, i.e., [`transactions_confirmed`] and [`transaction_unconfirmed`] calls should
118 /// never be interleaved, but always conduced *en bloc*.
119 /// - Any reconfirmed transactions need to be explicitly unconfirmed before they are reconfirmed
120 /// in regard to the new block.
122 /// See individual method documentation for further details.
124 /// [`transactions_confirmed`]: Self::transactions_confirmed
125 /// [`transaction_unconfirmed`]: Self::transaction_unconfirmed
126 /// [`best_block_updated`]: Self::best_block_updated
127 /// [`get_relevant_txids`]: Self::get_relevant_txids
129 /// Notifies LDK of transactions confirmed in a block with a given header and height.
131 /// Must be called for any transactions registered by [`Filter::register_tx`] or any
132 /// transactions spending an output registered by [`Filter::register_output`]. Such transactions
133 /// appearing in the same block do not need to be included in the same call; instead, multiple
134 /// calls with additional transactions may be made so long as they are made in [chain order].
136 /// May be called before or after [`best_block_updated`] for the corresponding block. However,
137 /// in the event of a chain reorganization, it must not be called with a `header` that is no
138 /// longer in the chain as of the last call to [`best_block_updated`].
140 /// [chain order]: Confirm#order
141 /// [`best_block_updated`]: Self::best_block_updated
142 fn transactions_confirmed(&self, header: &Header, txdata: &TransactionData, height: u32);
143 /// Notifies LDK of a transaction that is no longer confirmed as result of a chain reorganization.
145 /// Must be called for any transaction returned by [`get_relevant_txids`] if it has been
146 /// reorganized out of the best chain or if it is no longer confirmed in the block with the
147 /// given block hash. Once called, the given transaction will not be returned
148 /// by [`get_relevant_txids`], unless it has been reconfirmed via [`transactions_confirmed`].
150 /// [`get_relevant_txids`]: Self::get_relevant_txids
151 /// [`transactions_confirmed`]: Self::transactions_confirmed
152 fn transaction_unconfirmed(&self, txid: &Txid);
153 /// Notifies LDK of an update to the best header connected at the given height.
155 /// Must be called whenever a new chain tip becomes available. May be skipped for intermediary
157 fn best_block_updated(&self, header: &Header, height: u32);
158 /// Returns transactions that must be monitored for reorganization out of the chain along
159 /// with the height and the hash of the block as part of which it had been previously confirmed.
161 /// Note that the returned `Option<BlockHash>` might be `None` for channels created with LDK
162 /// 0.0.112 and prior, in which case you need to manually track previous confirmations.
164 /// Will include any transactions passed to [`transactions_confirmed`] that have insufficient
165 /// confirmations to be safe from a chain reorganization. Will not include any transactions
166 /// passed to [`transaction_unconfirmed`], unless later reconfirmed.
168 /// Must be called to determine the subset of transactions that must be monitored for
169 /// reorganization. Will be idempotent between calls but may change as a result of calls to the
170 /// other interface methods. Thus, this is useful to determine which transactions must be
171 /// given to [`transaction_unconfirmed`].
173 /// If any of the returned transactions are confirmed in a block other than the one with the
174 /// given hash at the given height, they need to be unconfirmed and reconfirmed via
175 /// [`transaction_unconfirmed`] and [`transactions_confirmed`], respectively.
177 /// [`transactions_confirmed`]: Self::transactions_confirmed
178 /// [`transaction_unconfirmed`]: Self::transaction_unconfirmed
179 fn get_relevant_txids(&self) -> Vec<(Txid, u32, Option<BlockHash>)>;
182 /// An enum representing the status of a channel monitor update persistence.
184 /// These are generally used as the return value for an implementation of [`Persist`] which is used
185 /// as the storage layer for a [`ChainMonitor`]. See the docs on [`Persist`] for a high-level
186 /// explanation of how to handle different cases.
188 /// While `UnrecoverableError` is provided as a failure variant, it is not truly "handled" on the
189 /// calling side, and generally results in an immediate panic. For those who prefer to avoid
190 /// panics, `InProgress` can be used and you can retry the update operation in the background or
191 /// shut down cleanly.
193 /// Note that channels should generally *not* be force-closed after a persistence failure.
194 /// Force-closing with the latest [`ChannelMonitorUpdate`] applied may result in a transaction
195 /// being broadcast which can only be spent by the latest [`ChannelMonitor`]! Thus, if the
196 /// latest [`ChannelMonitor`] is not durably persisted anywhere and exists only in memory, naively
197 /// calling [`ChannelManager::force_close_broadcasting_latest_txn`] *may result in loss of funds*!
199 /// [`Persist`]: chainmonitor::Persist
200 /// [`ChainMonitor`]: chainmonitor::ChainMonitor
201 /// [`ChannelManager::force_close_broadcasting_latest_txn`]: crate::ln::channelmanager::ChannelManager::force_close_broadcasting_latest_txn
202 #[derive(Clone, Copy, Debug, PartialEq, Eq)]
203 pub enum ChannelMonitorUpdateStatus {
204 /// The update has been durably persisted and all copies of the relevant [`ChannelMonitor`]
205 /// have been updated.
207 /// This includes performing any `fsync()` calls required to ensure the update is guaranteed to
208 /// be available on restart even if the application crashes.
210 /// Indicates that the update will happen asynchronously in the background or that a transient
211 /// failure occurred which is being retried in the background and will eventually complete.
213 /// This will "freeze" a channel, preventing us from revoking old states or submitting a new
214 /// commitment transaction to the counterparty. Once the update(s) which are `InProgress` have
215 /// been completed, a [`MonitorEvent::Completed`] can be used to restore the channel to an
216 /// operational state.
218 /// Even when a channel has been "frozen", updates to the [`ChannelMonitor`] can continue to
219 /// occur (e.g. if an inbound HTLC which we forwarded was claimed upstream, resulting in us
220 /// attempting to claim it on this channel) and those updates must still be persisted.
222 /// No updates to the channel will be made which could invalidate other [`ChannelMonitor`]s
223 /// until a [`MonitorEvent::Completed`] is provided, even if you return no error on a later
224 /// monitor update for the same channel.
226 /// For deployments where a copy of [`ChannelMonitor`]s and other local state are backed up in
227 /// a remote location (with local copies persisted immediately), it is anticipated that all
228 /// updates will return [`InProgress`] until the remote copies could be updated.
230 /// Note that while fully asynchronous persistence of [`ChannelMonitor`] data is generally
231 /// reliable, this feature is considered beta, and a handful of edge-cases remain. Until the
232 /// remaining cases are fixed, in rare cases, *using this feature may lead to funds loss*.
234 /// [`InProgress`]: ChannelMonitorUpdateStatus::InProgress
236 /// Indicates that an update has failed and will not complete at any point in the future.
238 /// Currently returning this variant will cause LDK to immediately panic to encourage immediate
239 /// shutdown. In the future this may be updated to disconnect peers and refuse to continue
240 /// normal operation without a panic.
242 /// Applications which wish to perform an orderly shutdown after failure should consider
243 /// returning [`InProgress`] instead and simply shut down without ever marking the update
246 /// [`InProgress`]: ChannelMonitorUpdateStatus::InProgress
250 /// The `Watch` trait defines behavior for watching on-chain activity pertaining to channels as
251 /// blocks are connected and disconnected.
253 /// Each channel is associated with a [`ChannelMonitor`]. Implementations of this trait are
254 /// responsible for maintaining a set of monitors such that they can be updated as channel state
255 /// changes. On each update, *all copies* of a [`ChannelMonitor`] must be updated and the update
256 /// persisted to disk to ensure that the latest [`ChannelMonitor`] state can be reloaded if the
257 /// application crashes.
259 /// See method documentation and [`ChannelMonitorUpdateStatus`] for specific requirements.
260 pub trait Watch<ChannelSigner: WriteableEcdsaChannelSigner> {
261 /// Watches a channel identified by `funding_txo` using `monitor`.
263 /// Implementations are responsible for watching the chain for the funding transaction along
264 /// with any spends of outputs returned by [`get_outputs_to_watch`]. In practice, this means
265 /// calling [`block_connected`] and [`block_disconnected`] on the monitor.
267 /// A return of `Err(())` indicates that the channel should immediately be force-closed without
268 /// broadcasting the funding transaction.
270 /// If the given `funding_txo` has previously been registered via `watch_channel`, `Err(())`
271 /// must be returned.
273 /// [`get_outputs_to_watch`]: channelmonitor::ChannelMonitor::get_outputs_to_watch
274 /// [`block_connected`]: channelmonitor::ChannelMonitor::block_connected
275 /// [`block_disconnected`]: channelmonitor::ChannelMonitor::block_disconnected
276 fn watch_channel(&self, funding_txo: OutPoint, monitor: ChannelMonitor<ChannelSigner>) -> Result<ChannelMonitorUpdateStatus, ()>;
278 /// Updates a channel identified by `funding_txo` by applying `update` to its monitor.
280 /// Implementations must call [`ChannelMonitor::update_monitor`] with the given update. This
281 /// may fail (returning an `Err(())`), in which case this should return
282 /// [`ChannelMonitorUpdateStatus::InProgress`] (and the update should never complete). This
283 /// generally implies the channel has been closed (either by the funding outpoint being spent
284 /// on-chain or the [`ChannelMonitor`] having decided to do so and broadcasted a transaction),
285 /// and the [`ChannelManager`] state will be updated once it sees the funding spend on-chain.
287 /// In general, persistence failures should be retried after returning
288 /// [`ChannelMonitorUpdateStatus::InProgress`] and eventually complete. If a failure truly
289 /// cannot be retried, the node should shut down immediately after returning
290 /// [`ChannelMonitorUpdateStatus::UnrecoverableError`], see its documentation for more info.
292 /// [`ChannelManager`]: crate::ln::channelmanager::ChannelManager
293 fn update_channel(&self, funding_txo: OutPoint, update: &ChannelMonitorUpdate) -> ChannelMonitorUpdateStatus;
295 /// Returns any monitor events since the last call. Subsequent calls must only return new
298 /// Note that after any block- or transaction-connection calls to a [`ChannelMonitor`], no
299 /// further events may be returned here until the [`ChannelMonitor`] has been fully persisted
302 /// For details on asynchronous [`ChannelMonitor`] updating and returning
303 /// [`MonitorEvent::Completed`] here, see [`ChannelMonitorUpdateStatus::InProgress`].
304 fn release_pending_monitor_events(&self) -> Vec<(OutPoint, ChannelId, Vec<MonitorEvent>, Option<PublicKey>)>;
307 /// The `Filter` trait defines behavior for indicating chain activity of interest pertaining to
310 /// This is useful in order to have a [`Watch`] implementation convey to a chain source which
311 /// transactions to be notified of. Notification may take the form of pre-filtering blocks or, in
312 /// the case of [BIP 157]/[BIP 158], only fetching a block if the compact filter matches. If
313 /// receiving full blocks from a chain source, any further filtering is unnecessary.
315 /// After an output has been registered, subsequent block retrievals from the chain source must not
316 /// exclude any transactions matching the new criteria nor any in-block descendants of such
319 /// Note that use as part of a [`Watch`] implementation involves reentrancy. Therefore, the `Filter`
320 /// should not block on I/O. Implementations should instead queue the newly monitored data to be
321 /// processed later. Then, in order to block until the data has been processed, any [`Watch`]
322 /// invocation that has called the `Filter` must return [`InProgress`].
324 /// [`InProgress`]: ChannelMonitorUpdateStatus::InProgress
325 /// [BIP 157]: https://github.com/bitcoin/bips/blob/master/bip-0157.mediawiki
326 /// [BIP 158]: https://github.com/bitcoin/bips/blob/master/bip-0158.mediawiki
328 /// Registers interest in a transaction with `txid` and having an output with `script_pubkey` as
329 /// a spending condition.
330 fn register_tx(&self, txid: &Txid, script_pubkey: &Script);
332 /// Registers interest in spends of a transaction output.
334 /// Note that this method might be called during processing of a new block. You therefore need
335 /// to ensure that also dependent output spents within an already connected block are correctly
336 /// handled, e.g., by re-scanning the block in question whenever new outputs have been
337 /// registered mid-processing.
338 fn register_output(&self, output: WatchedOutput);
341 /// A transaction output watched by a [`ChannelMonitor`] for spends on-chain.
343 /// Used to convey to a [`Filter`] such an output with a given spending condition. Any transaction
344 /// spending the output must be given to [`ChannelMonitor::block_connected`] either directly or via
345 /// [`Confirm::transactions_confirmed`].
347 /// If `block_hash` is `Some`, this indicates the output was created in the corresponding block and
348 /// may have been spent there. See [`Filter::register_output`] for details.
350 /// [`ChannelMonitor`]: channelmonitor::ChannelMonitor
351 /// [`ChannelMonitor::block_connected`]: channelmonitor::ChannelMonitor::block_connected
352 #[derive(Clone, PartialEq, Eq, Hash)]
353 pub struct WatchedOutput {
354 /// First block where the transaction output may have been spent.
355 pub block_hash: Option<BlockHash>,
357 /// Outpoint identifying the transaction output.
358 pub outpoint: OutPoint,
360 /// Spending condition of the transaction output.
361 pub script_pubkey: ScriptBuf,
364 impl<T: Listen> Listen for dyn core::ops::Deref<Target = T> {
365 fn filtered_block_connected(&self, header: &Header, txdata: &TransactionData, height: u32) {
366 (**self).filtered_block_connected(header, txdata, height);
369 fn block_disconnected(&self, header: &Header, height: u32) {
370 (**self).block_disconnected(header, height);
374 impl<T: core::ops::Deref, U: core::ops::Deref> Listen for (T, U)
379 fn filtered_block_connected(&self, header: &Header, txdata: &TransactionData, height: u32) {
380 self.0.filtered_block_connected(header, txdata, height);
381 self.1.filtered_block_connected(header, txdata, height);
384 fn block_disconnected(&self, header: &Header, height: u32) {
385 self.0.block_disconnected(header, height);
386 self.1.block_disconnected(header, height);
390 /// A unique identifier to track each pending output claim within a [`ChannelMonitor`].
392 /// This is not exported to bindings users as we just use [u8; 32] directly.
393 #[derive(Copy, Clone, Debug, Hash, PartialEq, Eq)]
394 pub struct ClaimId(pub [u8; 32]);