//! Structs and traits which allow other parts of rust-lightning to interact with the blockchain.
-use bitcoin::blockdata::script::Script;
-use bitcoin::blockdata::transaction::TxOut;
+use bitcoin::blockdata::block::{Block, Header};
+use bitcoin::blockdata::constants::genesis_block;
+use bitcoin::blockdata::script::{Script, ScriptBuf};
use bitcoin::hash_types::{BlockHash, Txid};
+use bitcoin::network::constants::Network;
+use bitcoin::secp256k1::PublicKey;
-use chain::keysinterface::ChannelKeys;
-use chain::transaction::OutPoint;
-use ln::channelmonitor::{ChannelMonitor, ChannelMonitorUpdate, ChannelMonitorUpdateErr, MonitorEvent};
+use crate::chain::channelmonitor::{ChannelMonitor, ChannelMonitorUpdate, MonitorEvent};
+use crate::sign::ecdsa::WriteableEcdsaChannelSigner;
+use crate::chain::transaction::{OutPoint, TransactionData};
+
+use crate::prelude::*;
pub mod chaininterface;
+pub mod chainmonitor;
+pub mod channelmonitor;
pub mod transaction;
-pub mod keysinterface;
+pub(crate) mod onchaintx;
+pub(crate) mod package;
-/// The `Access` trait defines behavior for accessing chain data and state, such as blocks and
-/// UTXOs.
-pub trait Access: Send + Sync {
- /// Returns the transaction output of a funding transaction encoded by [`short_channel_id`].
- /// Returns an error if `genesis_hash` is for a different chain or if such a transaction output
- /// is unknown.
- ///
- /// [`short_channel_id`]: https://github.com/lightningnetwork/lightning-rfc/blob/master/07-routing-gossip.md#definition-of-short_channel_id
- fn get_utxo(&self, genesis_hash: &BlockHash, short_channel_id: u64) -> Result<TxOut, AccessError>;
+/// The best known block as identified by its hash and height.
+#[derive(Clone, Copy, PartialEq, Eq)]
+pub struct BestBlock {
+ block_hash: BlockHash,
+ height: u32,
}
-/// An error when accessing the chain via [`Access`].
+impl BestBlock {
+ /// Constructs a `BestBlock` that represents the genesis block at height 0 of the given
+ /// network.
+ pub fn from_network(network: Network) -> Self {
+ BestBlock {
+ block_hash: genesis_block(network).header.block_hash(),
+ height: 0,
+ }
+ }
+
+ /// Returns a `BestBlock` as identified by the given block hash and height.
+ pub fn new(block_hash: BlockHash, height: u32) -> Self {
+ BestBlock { block_hash, height }
+ }
+
+ /// Returns the best block hash.
+ pub fn block_hash(&self) -> BlockHash { self.block_hash }
+
+ /// Returns the best block height.
+ pub fn height(&self) -> u32 { self.height }
+}
+
+
+/// The `Listen` trait is used to notify when blocks have been connected or disconnected from the
+/// chain.
+///
+/// Useful when needing to replay chain data upon startup or as new chain events occur. Clients
+/// sourcing chain data using a block-oriented API should prefer this interface over [`Confirm`].
+/// Such clients fetch the entire header chain whereas clients using [`Confirm`] only fetch headers
+/// when needed.
+///
+/// By using [`Listen::filtered_block_connected`] this interface supports clients fetching the
+/// entire header chain and only blocks with matching transaction data using BIP 157 filters or
+/// other similar filtering.
+pub trait Listen {
+ /// Notifies the listener that a block was added at the given height, with the transaction data
+ /// possibly filtered.
+ fn filtered_block_connected(&self, header: &Header, txdata: &TransactionData, height: u32);
+
+ /// Notifies the listener that a block was added at the given height.
+ fn block_connected(&self, block: &Block, height: u32) {
+ let txdata: Vec<_> = block.txdata.iter().enumerate().collect();
+ self.filtered_block_connected(&block.header, &txdata, height);
+ }
+
+ /// Notifies the listener that a block was removed at the given height.
+ fn block_disconnected(&self, header: &Header, height: u32);
+}
+
+/// The `Confirm` trait is used to notify LDK when relevant transactions have been confirmed on
+/// chain or unconfirmed during a chain reorganization.
+///
+/// Clients sourcing chain data using a transaction-oriented API should prefer this interface over
+/// [`Listen`]. For instance, an Electrum-based transaction sync implementation may implement
+/// [`Filter`] to subscribe to relevant transactions and unspent outputs it should monitor for
+/// on-chain activity. Then, it needs to notify LDK via this interface upon observing any changes
+/// with reference to the confirmation status of the monitored objects.
+///
+/// # Use
+/// The intended use is as follows:
+/// - Call [`transactions_confirmed`] to notify LDK whenever any of the registered transactions or
+/// outputs are, respectively, confirmed or spent on chain.
+/// - Call [`transaction_unconfirmed`] to notify LDK whenever any transaction returned by
+/// [`get_relevant_txids`] is no longer confirmed in the block with the given block hash.
+/// - Call [`best_block_updated`] to notify LDK whenever a new chain tip becomes available.
+///
+/// # Order
///
-/// [`Access`]: trait.Access.html
-#[derive(Clone)]
-pub enum AccessError {
- /// The requested chain is unknown.
- UnknownChain,
+/// Clients must call these methods in chain order. Specifically:
+/// - Transactions which are confirmed in a particular block must be given before transactions
+/// confirmed in a later block.
+/// - Dependent transactions within the same block must be given in topological order, possibly in
+/// separate calls.
+/// - All unconfirmed transactions must be given after the original confirmations and before *any*
+/// reconfirmations, i.e., [`transactions_confirmed`] and [`transaction_unconfirmed`] calls should
+/// never be interleaved, but always conduced *en bloc*.
+/// - Any reconfirmed transactions need to be explicitly unconfirmed before they are reconfirmed
+/// in regard to the new block.
+///
+/// See individual method documentation for further details.
+///
+/// [`transactions_confirmed`]: Self::transactions_confirmed
+/// [`transaction_unconfirmed`]: Self::transaction_unconfirmed
+/// [`best_block_updated`]: Self::best_block_updated
+/// [`get_relevant_txids`]: Self::get_relevant_txids
+pub trait Confirm {
+ /// Notifies LDK of transactions confirmed in a block with a given header and height.
+ ///
+ /// Must be called for any transactions registered by [`Filter::register_tx`] or any
+ /// transactions spending an output registered by [`Filter::register_output`]. Such transactions
+ /// appearing in the same block do not need to be included in the same call; instead, multiple
+ /// calls with additional transactions may be made so long as they are made in [chain order].
+ ///
+ /// May be called before or after [`best_block_updated`] for the corresponding block. However,
+ /// in the event of a chain reorganization, it must not be called with a `header` that is no
+ /// longer in the chain as of the last call to [`best_block_updated`].
+ ///
+ /// [chain order]: Confirm#order
+ /// [`best_block_updated`]: Self::best_block_updated
+ fn transactions_confirmed(&self, header: &Header, txdata: &TransactionData, height: u32);
+ /// Notifies LDK of a transaction that is no longer confirmed as result of a chain reorganization.
+ ///
+ /// Must be called for any transaction returned by [`get_relevant_txids`] if it has been
+ /// reorganized out of the best chain or if it is no longer confirmed in the block with the
+ /// given block hash. Once called, the given transaction will not be returned
+ /// by [`get_relevant_txids`], unless it has been reconfirmed via [`transactions_confirmed`].
+ ///
+ /// [`get_relevant_txids`]: Self::get_relevant_txids
+ /// [`transactions_confirmed`]: Self::transactions_confirmed
+ fn transaction_unconfirmed(&self, txid: &Txid);
+ /// Notifies LDK of an update to the best header connected at the given height.
+ ///
+ /// Must be called whenever a new chain tip becomes available. May be skipped for intermediary
+ /// blocks.
+ fn best_block_updated(&self, header: &Header, height: u32);
+ /// Returns transactions that must be monitored for reorganization out of the chain along
+ /// with the height and the hash of the block as part of which it had been previously confirmed.
+ ///
+ /// Note that the returned `Option<BlockHash>` might be `None` for channels created with LDK
+ /// 0.0.112 and prior, in which case you need to manually track previous confirmations.
+ ///
+ /// Will include any transactions passed to [`transactions_confirmed`] that have insufficient
+ /// confirmations to be safe from a chain reorganization. Will not include any transactions
+ /// passed to [`transaction_unconfirmed`], unless later reconfirmed.
+ ///
+ /// Must be called to determine the subset of transactions that must be monitored for
+ /// reorganization. Will be idempotent between calls but may change as a result of calls to the
+ /// other interface methods. Thus, this is useful to determine which transactions must be
+ /// given to [`transaction_unconfirmed`].
+ ///
+ /// If any of the returned transactions are confirmed in a block other than the one with the
+ /// given hash at the given height, they need to be unconfirmed and reconfirmed via
+ /// [`transaction_unconfirmed`] and [`transactions_confirmed`], respectively.
+ ///
+ /// [`transactions_confirmed`]: Self::transactions_confirmed
+ /// [`transaction_unconfirmed`]: Self::transaction_unconfirmed
+ fn get_relevant_txids(&self) -> Vec<(Txid, u32, Option<BlockHash>)>;
+}
- /// The requested transaction doesn't exist or hasn't confirmed.
- UnknownTx,
+/// An enum representing the status of a channel monitor update persistence.
+///
+/// These are generally used as the return value for an implementation of [`Persist`] which is used
+/// as the storage layer for a [`ChainMonitor`]. See the docs on [`Persist`] for a high-level
+/// explanation of how to handle different cases.
+///
+/// While `UnrecoverableError` is provided as a failure variant, it is not truly "handled" on the
+/// calling side, and generally results in an immediate panic. For those who prefer to avoid
+/// panics, `InProgress` can be used and you can retry the update operation in the background or
+/// shut down cleanly.
+///
+/// Note that channels should generally *not* be force-closed after a persistence failure.
+/// Force-closing with the latest [`ChannelMonitorUpdate`] applied may result in a transaction
+/// being broadcast which can only be spent by the latest [`ChannelMonitor`]! Thus, if the
+/// latest [`ChannelMonitor`] is not durably persisted anywhere and exists only in memory, naively
+/// calling [`ChannelManager::force_close_broadcasting_latest_txn`] *may result in loss of funds*!
+///
+/// [`Persist`]: chainmonitor::Persist
+/// [`ChainMonitor`]: chainmonitor::ChainMonitor
+/// [`ChannelManager::force_close_broadcasting_latest_txn`]: crate::ln::channelmanager::ChannelManager::force_close_broadcasting_latest_txn
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub enum ChannelMonitorUpdateStatus {
+ /// The update has been durably persisted and all copies of the relevant [`ChannelMonitor`]
+ /// have been updated.
+ ///
+ /// This includes performing any `fsync()` calls required to ensure the update is guaranteed to
+ /// be available on restart even if the application crashes.
+ Completed,
+ /// Indicates that the update will happen asynchronously in the background or that a transient
+ /// failure occurred which is being retried in the background and will eventually complete.
+ ///
+ /// This will "freeze" a channel, preventing us from revoking old states or submitting a new
+ /// commitment transaction to the counterparty. Once the update(s) which are `InProgress` have
+ /// been completed, a [`MonitorEvent::Completed`] can be used to restore the channel to an
+ /// operational state.
+ ///
+ /// Even when a channel has been "frozen", updates to the [`ChannelMonitor`] can continue to
+ /// occur (e.g. if an inbound HTLC which we forwarded was claimed upstream, resulting in us
+ /// attempting to claim it on this channel) and those updates must still be persisted.
+ ///
+ /// No updates to the channel will be made which could invalidate other [`ChannelMonitor`]s
+ /// until a [`MonitorEvent::Completed`] is provided, even if you return no error on a later
+ /// monitor update for the same channel.
+ ///
+ /// For deployments where a copy of [`ChannelMonitor`]s and other local state are backed up in
+ /// a remote location (with local copies persisted immediately), it is anticipated that all
+ /// updates will return [`InProgress`] until the remote copies could be updated.
+ ///
+ /// Note that while fully asynchronous persistence of [`ChannelMonitor`] data is generally
+ /// reliable, this feature is considered beta, and a handful of edge-cases remain. Until the
+ /// remaining cases are fixed, in rare cases, *using this feature may lead to funds loss*.
+ ///
+ /// [`InProgress`]: ChannelMonitorUpdateStatus::InProgress
+ InProgress,
+ /// Indicates that an update has failed and will not complete at any point in the future.
+ ///
+ /// Currently returning this variant will cause LDK to immediately panic to encourage immediate
+ /// shutdown. In the future this may be updated to disconnect peers and refuse to continue
+ /// normal operation without a panic.
+ ///
+ /// Applications which wish to perform an orderly shutdown after failure should consider
+ /// returning [`InProgress`] instead and simply shut down without ever marking the update
+ /// complete.
+ ///
+ /// [`InProgress`]: ChannelMonitorUpdateStatus::InProgress
+ UnrecoverableError,
}
/// The `Watch` trait defines behavior for watching on-chain activity pertaining to channels as
/// blocks are connected and disconnected.
///
/// Each channel is associated with a [`ChannelMonitor`]. Implementations of this trait are
-/// responsible for maintaining a set of monitors such that they can be updated accordingly as
-/// channel state changes and HTLCs are resolved. See method documentation for specific
-/// requirements.
-///
-/// Implementations **must** ensure that updates are successfully applied and persisted upon method
-/// completion. If an update fails with a [`PermanentFailure`], then it must immediately shut down
-/// without taking any further action such as persisting the current state.
-///
-/// If an implementation maintains multiple instances of a channel's monitor (e.g., by storing
-/// backup copies), then it must ensure that updates are applied across all instances. Otherwise, it
-/// could result in a revoked transaction being broadcast, allowing the counterparty to claim all
-/// funds in the channel. See [`ChannelMonitorUpdateErr`] for more details about how to handle
-/// multiple instances.
-///
-/// [`ChannelMonitor`]: ../ln/channelmonitor/struct.ChannelMonitor.html
-/// [`ChannelMonitorUpdateErr`]: ../ln/channelmonitor/enum.ChannelMonitorUpdateErr.html
-/// [`PermanentFailure`]: ../ln/channelmonitor/enum.ChannelMonitorUpdateErr.html#variant.PermanentFailure
-pub trait Watch: Send + Sync {
- /// Keys needed by monitors for creating and signing transactions.
- type Keys: ChannelKeys;
-
+/// responsible for maintaining a set of monitors such that they can be updated as channel state
+/// changes. On each update, *all copies* of a [`ChannelMonitor`] must be updated and the update
+/// persisted to disk to ensure that the latest [`ChannelMonitor`] state can be reloaded if the
+/// application crashes.
+///
+/// See method documentation and [`ChannelMonitorUpdateStatus`] for specific requirements.
+pub trait Watch<ChannelSigner: WriteableEcdsaChannelSigner> {
/// Watches a channel identified by `funding_txo` using `monitor`.
///
/// Implementations are responsible for watching the chain for the funding transaction along
- /// with spends of its output and any outputs returned by [`get_outputs_to_watch`]. In practice,
- /// this means calling [`block_connected`] and [`block_disconnected`] on the monitor and
- /// including all such transactions that meet this criteria.
+ /// with any spends of outputs returned by [`get_outputs_to_watch`]. In practice, this means
+ /// calling [`block_connected`] and [`block_disconnected`] on the monitor.
///
- /// [`get_outputs_to_watch`]: ../ln/channelmonitor/struct.ChannelMonitor.html#method.get_outputs_to_watch
- /// [`block_connected`]: ../ln/channelmonitor/struct.ChannelMonitor.html#method.block_connected
- /// [`block_disconnected`]: ../ln/channelmonitor/struct.ChannelMonitor.html#method.block_disconnected
- fn watch_channel(&self, funding_txo: OutPoint, monitor: ChannelMonitor<Self::Keys>) -> Result<(), ChannelMonitorUpdateErr>;
+ /// A return of `Err(())` indicates that the channel should immediately be force-closed without
+ /// broadcasting the funding transaction.
+ ///
+ /// If the given `funding_txo` has previously been registered via `watch_channel`, `Err(())`
+ /// must be returned.
+ ///
+ /// [`get_outputs_to_watch`]: channelmonitor::ChannelMonitor::get_outputs_to_watch
+ /// [`block_connected`]: channelmonitor::ChannelMonitor::block_connected
+ /// [`block_disconnected`]: channelmonitor::ChannelMonitor::block_disconnected
+ fn watch_channel(&self, funding_txo: OutPoint, monitor: ChannelMonitor<ChannelSigner>) -> Result<ChannelMonitorUpdateStatus, ()>;
/// Updates a channel identified by `funding_txo` by applying `update` to its monitor.
///
- /// Implementations must call [`update_monitor`] with the given update. See
- /// [`ChannelMonitorUpdateErr`] for invariants around returning an error.
+ /// Implementations must call [`ChannelMonitor::update_monitor`] with the given update. This
+ /// may fail (returning an `Err(())`), in which case this should return
+ /// [`ChannelMonitorUpdateStatus::InProgress`] (and the update should never complete). This
+ /// generally implies the channel has been closed (either by the funding outpoint being spent
+ /// on-chain or the [`ChannelMonitor`] having decided to do so and broadcasted a transaction),
+ /// and the [`ChannelManager`] state will be updated once it sees the funding spend on-chain.
///
- /// [`update_monitor`]: ../ln/channelmonitor/struct.ChannelMonitor.html#method.update_monitor
- /// [`ChannelMonitorUpdateErr`]: ../ln/channelmonitor/enum.ChannelMonitorUpdateErr.html
- fn update_channel(&self, funding_txo: OutPoint, update: ChannelMonitorUpdate) -> Result<(), ChannelMonitorUpdateErr>;
+ /// In general, persistence failures should be retried after returning
+ /// [`ChannelMonitorUpdateStatus::InProgress`] and eventually complete. If a failure truly
+ /// cannot be retried, the node should shut down immediately after returning
+ /// [`ChannelMonitorUpdateStatus::UnrecoverableError`], see its documentation for more info.
+ ///
+ /// [`ChannelManager`]: crate::ln::channelmanager::ChannelManager
+ fn update_channel(&self, funding_txo: OutPoint, update: &ChannelMonitorUpdate) -> ChannelMonitorUpdateStatus;
/// Returns any monitor events since the last call. Subsequent calls must only return new
/// events.
- fn release_pending_monitor_events(&self) -> Vec<MonitorEvent>;
+ ///
+ /// Note that after any block- or transaction-connection calls to a [`ChannelMonitor`], no
+ /// further events may be returned here until the [`ChannelMonitor`] has been fully persisted
+ /// to disk.
+ ///
+ /// For details on asynchronous [`ChannelMonitor`] updating and returning
+ /// [`MonitorEvent::Completed`] here, see [`ChannelMonitorUpdateStatus::InProgress`].
+ fn release_pending_monitor_events(&self) -> Vec<(OutPoint, Vec<MonitorEvent>, Option<PublicKey>)>;
}
/// The `Filter` trait defines behavior for indicating chain activity of interest pertaining to
///
/// Note that use as part of a [`Watch`] implementation involves reentrancy. Therefore, the `Filter`
/// should not block on I/O. Implementations should instead queue the newly monitored data to be
-/// processed later. Then, in order to block until the data has been processed, any `Watch`
-/// invocation that has called the `Filter` must return [`TemporaryFailure`].
+/// processed later. Then, in order to block until the data has been processed, any [`Watch`]
+/// invocation that has called the `Filter` must return [`InProgress`].
///
-/// [`Watch`]: trait.Watch.html
-/// [`TemporaryFailure`]: ../ln/channelmonitor/enum.ChannelMonitorUpdateErr.html#variant.TemporaryFailure
+/// [`InProgress`]: ChannelMonitorUpdateStatus::InProgress
/// [BIP 157]: https://github.com/bitcoin/bips/blob/master/bip-0157.mediawiki
/// [BIP 158]: https://github.com/bitcoin/bips/blob/master/bip-0158.mediawiki
-pub trait Filter: Send + Sync {
+pub trait Filter {
/// Registers interest in a transaction with `txid` and having an output with `script_pubkey` as
/// a spending condition.
- fn register_tx(&self, txid: Txid, script_pubkey: Script);
+ fn register_tx(&self, txid: &Txid, script_pubkey: &Script);
+
+ /// Registers interest in spends of a transaction output.
+ ///
+ /// Note that this method might be called during processing of a new block. You therefore need
+ /// to ensure that also dependent output spents within an already connected block are correctly
+ /// handled, e.g., by re-scanning the block in question whenever new outputs have been
+ /// registered mid-processing.
+ fn register_output(&self, output: WatchedOutput);
+}
+
+/// A transaction output watched by a [`ChannelMonitor`] for spends on-chain.
+///
+/// Used to convey to a [`Filter`] such an output with a given spending condition. Any transaction
+/// spending the output must be given to [`ChannelMonitor::block_connected`] either directly or via
+/// [`Confirm::transactions_confirmed`].
+///
+/// If `block_hash` is `Some`, this indicates the output was created in the corresponding block and
+/// may have been spent there. See [`Filter::register_output`] for details.
+///
+/// [`ChannelMonitor`]: channelmonitor::ChannelMonitor
+/// [`ChannelMonitor::block_connected`]: channelmonitor::ChannelMonitor::block_connected
+#[derive(Clone, PartialEq, Eq, Hash)]
+pub struct WatchedOutput {
+ /// First block where the transaction output may have been spent.
+ pub block_hash: Option<BlockHash>,
+
+ /// Outpoint identifying the transaction output.
+ pub outpoint: OutPoint,
- /// Registers interest in spends of a transaction output identified by `outpoint` having
- /// `script_pubkey` as the spending condition.
- fn register_output(&self, outpoint: OutPoint, script_pubkey: Script);
+ /// Spending condition of the transaction output.
+ pub script_pubkey: ScriptBuf,
}
+
+impl<T: Listen> Listen for core::ops::Deref<Target = T> {
+ fn filtered_block_connected(&self, header: &Header, txdata: &TransactionData, height: u32) {
+ (**self).filtered_block_connected(header, txdata, height);
+ }
+
+ fn block_disconnected(&self, header: &Header, height: u32) {
+ (**self).block_disconnected(header, height);
+ }
+}
+
+impl<T: core::ops::Deref, U: core::ops::Deref> Listen for (T, U)
+where
+ T::Target: Listen,
+ U::Target: Listen,
+{
+ fn filtered_block_connected(&self, header: &Header, txdata: &TransactionData, height: u32) {
+ self.0.filtered_block_connected(header, txdata, height);
+ self.1.filtered_block_connected(header, txdata, height);
+ }
+
+ fn block_disconnected(&self, header: &Header, height: u32) {
+ self.0.block_disconnected(header, height);
+ self.1.block_disconnected(header, height);
+ }
+}
+
+/// A unique identifier to track each pending output claim within a [`ChannelMonitor`].
+///
+/// This is not exported to bindings users as we just use [u8; 32] directly.
+#[derive(Copy, Clone, Debug, Hash, PartialEq, Eq)]
+pub struct ClaimId(pub [u8; 32]);