use bitcoin::blockdata::block::{Block, BlockHeader};
use bitcoin::blockdata::constants::genesis_block;
use bitcoin::blockdata::script::Script;
-use bitcoin::blockdata::transaction::{Transaction, TxOut};
+use bitcoin::blockdata::transaction::TxOut;
use bitcoin::hash_types::{BlockHash, Txid};
use bitcoin::network::constants::Network;
+use bitcoin::secp256k1::PublicKey;
-use chain::channelmonitor::{ChannelMonitor, ChannelMonitorUpdate, MonitorEvent};
-use chain::keysinterface::Sign;
-use chain::transaction::{OutPoint, TransactionData};
+use crate::chain::channelmonitor::{ChannelMonitor, ChannelMonitorUpdate, MonitorEvent};
+use crate::chain::keysinterface::WriteableEcdsaChannelSigner;
+use crate::chain::transaction::{OutPoint, TransactionData};
-use prelude::*;
+use crate::prelude::*;
pub mod chaininterface;
pub mod chainmonitor;
pub(crate) mod package;
/// The best known block as identified by its hash and height.
-#[derive(Clone, Copy, PartialEq)]
+#[derive(Clone, Copy, PartialEq, Eq)]
pub struct BestBlock {
block_hash: BlockHash,
height: u32,
}
/// An error when accessing the chain via [`Access`].
-#[derive(Clone)]
+#[derive(Clone, Debug)]
pub enum AccessError {
/// The requested chain is unknown.
UnknownChain,
/// 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
+ /// [`short_channel_id`]: https://github.com/lightning/bolts/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>;
}
/// 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: &BlockHeader, txdata: &TransactionData, height: u32);
+
/// Notifies the listener that a block was added at the given height.
- fn block_connected(&self, block: &Block, height: u32);
+ 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: &BlockHeader, height: u32);
}
-/// The `Confirm` trait is used to notify when transactions have been confirmed on chain or
-/// unconfirmed during a chain reorganization.
+/// 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 client may implement [`Filter`] by subscribing to activity
-/// related to registered transactions and outputs. Upon notification, it would pass along the
-/// matching transactions using this interface.
+/// [`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 process any on-chain activity of interest.
-/// - Call [`transaction_unconfirmed`] to process any transaction returned by [`get_relevant_txids`]
-/// that has been reorganized out of the chain.
-/// - Call [`best_block_updated`] whenever a new chain tip becomes available.
+/// - 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
///
/// Clients must call these methods in chain order. Specifically:
-/// - Transactions confirmed in a block must be given before transactions confirmed in a later
-/// block.
+/// - 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.
-/// - Unconfirmed transactions must be given after the original confirmations and before any
-/// reconfirmation.
+/// - 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.
///
/// [`best_block_updated`]: Self::best_block_updated
/// [`get_relevant_txids`]: Self::get_relevant_txids
pub trait Confirm {
- /// Processes transactions confirmed in a block with a given header and height.
+ /// Notifies LDK of transactions confirmed in a block with a given header and height.
///
- /// Should be called for any transactions registered by [`Filter::register_tx`] or any
+ /// 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].
/// 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
+ /// [chain order]: Confirm#order
/// [`best_block_updated`]: Self::best_block_updated
fn transactions_confirmed(&self, header: &BlockHeader, txdata: &TransactionData, height: u32);
-
- /// Processes a transaction that is no longer confirmed as result of a chain reorganization.
+ /// Notifies LDK of a transaction that is no longer confirmed as result of a chain reorganization.
///
- /// Should be called for any transaction returned by [`get_relevant_txids`] if it has been
- /// reorganized out of the best chain. Once called, the given transaction should not be returned
- /// by [`get_relevant_txids`] unless it has been reconfirmed via [`transactions_confirmed`].
+ /// 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);
-
- /// Processes an update to the best header connected at the given height.
+ /// Notifies LDK of an update to the best header connected at the given height.
///
- /// Should be called when a new header is available but may be skipped for intermediary blocks
- /// if they become available at the same time.
+ /// Must be called whenever a new chain tip becomes available. May be skipped for intermediary
+ /// blocks.
fn best_block_updated(&self, header: &BlockHeader, height: u32);
-
- /// Returns transactions that should be monitored for reorganization out of the chain.
+ /// Returns transactions that must be monitored for reorganization out of the chain along
+ /// with the hash of the block as part of which it had been previously confirmed.
///
- /// Should include any transactions passed to [`transactions_confirmed`] that have insufficient
- /// confirmations to be safe from a chain reorganization. Should not include any transactions
- /// passed to [`transaction_unconfirmed`] unless later reconfirmed.
+ /// 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.
///
- /// May be called to determine the subset of transactions that must still be monitored for
+ /// 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 may need to be
+ /// 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, 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>;
+ fn get_relevant_txids(&self) -> Vec<(Txid, Option<BlockHash>)>;
}
-/// An error enum representing a failure to persist a channel monitor update.
-#[derive(Clone, Copy, Debug, PartialEq)]
-pub enum ChannelMonitorUpdateErr {
+/// An enum representing the status of a channel monitor update persistence.
+#[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,
/// Used to indicate a temporary failure (eg connection to a watchtower or remote backup of
/// our state failed, but is expected to succeed at some point in the future).
///
/// Such a failure will "freeze" a channel, preventing us from revoking old states or
- /// submitting new commitment transactions to the counterparty. Once the update(s) that failed
- /// have been successfully applied, a [`MonitorEvent::UpdateCompleted`] event should be returned
- /// via [`Watch::release_pending_monitor_events`] which will then restore the channel to an
- /// operational state.
- ///
- /// Note that a given ChannelManager will *never* re-generate a given ChannelMonitorUpdate. If
- /// you return a TemporaryFailure you must ensure that it is written to disk safely before
- /// writing out the latest ChannelManager state.
- ///
- /// Even when a channel has been "frozen" updates to the ChannelMonitor can continue to occur
- /// (eg if an inbound HTLC which we forwarded was claimed upstream resulting in us attempting
- /// to claim it on this channel) and those updates must be applied wherever they can be. At
- /// least one such updated ChannelMonitor must be persisted otherwise PermanentFailure should
- /// be returned to get things on-chain ASAP using only the in-memory copy. Obviously updates to
- /// the channel which would invalidate previous ChannelMonitors are not made when a channel has
- /// been "frozen".
- ///
- /// Note that even if updates made after TemporaryFailure succeed you must still provide a
- /// [`MonitorEvent::UpdateCompleted`] to ensure you have the latest monitor and re-enable
- /// normal channel operation. Note that this is normally generated through a call to
- /// [`ChainMonitor::channel_monitor_updated`].
- ///
- /// Note that the update being processed here will not be replayed for you when you return a
- /// [`MonitorEvent::UpdateCompleted`] event via [`Watch::release_pending_monitor_events`], so
- /// you must store the update itself on your own local disk prior to returning a
- /// TemporaryFailure. You may, of course, employ a journaling approach, storing only the
- /// ChannelMonitorUpdate on disk without updating the monitor itself, replaying the journal at
- /// reload-time.
+ /// submitting new commitment transactions to the counterparty. Once the update(s) which failed
+ /// have been successfully applied, a [`MonitorEvent::Completed`] can be used to restore the
+ /// channel to an operational state.
+ ///
+ /// Note that a given [`ChannelManager`] will *never* re-generate a [`ChannelMonitorUpdate`].
+ /// If you return this error you must ensure that it is written to disk safely before writing
+ /// the latest [`ChannelManager`] state, or you should return [`PermanentFailure`] instead.
+ ///
+ /// 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 ChannelMonitors and other local state are backed up in a
/// remote location (with local copies persisted immediately), it is anticipated that all
- /// updates will return TemporaryFailure until the remote copies could be updated.
+ /// updates will return [`InProgress`] until the remote copies could be updated.
+ ///
+ /// [`PermanentFailure`]: ChannelMonitorUpdateStatus::PermanentFailure
+ /// [`InProgress`]: ChannelMonitorUpdateStatus::InProgress
+ /// [`ChannelManager`]: crate::ln::channelmanager::ChannelManager
+ InProgress,
+ /// Used to indicate no further channel monitor updates will be allowed (likely a disk failure
+ /// or a remote copy of this [`ChannelMonitor`] is no longer reachable and thus not updatable).
+ ///
+ /// When this is returned, [`ChannelManager`] will force-close the channel but *not* broadcast
+ /// our current commitment transaction. This avoids a dangerous case where a local disk failure
+ /// (e.g. the Linux-default remounting of the disk as read-only) causes [`PermanentFailure`]s
+ /// for all monitor updates. If we were to broadcast our latest commitment transaction and then
+ /// restart, we could end up reading a previous [`ChannelMonitor`] and [`ChannelManager`],
+ /// revoking our now-broadcasted state before seeing it confirm and losing all our funds.
///
- /// [`ChainMonitor::channel_monitor_updated`]: chainmonitor::ChainMonitor::channel_monitor_updated
- TemporaryFailure,
- /// Used to indicate no further channel monitor updates will be allowed (eg we've moved on to a
- /// different watchtower and cannot update with all watchtowers that were previously informed
- /// of this channel).
+ /// Note that this is somewhat of a tradeoff - if the disk is really gone and we may have lost
+ /// the data permanently, we really should broadcast immediately. If the data can be recovered
+ /// with manual intervention, we'd rather close the channel, rejecting future updates to it,
+ /// and broadcast the latest state only if we have HTLCs to claim which are timing out (which
+ /// we do as long as blocks are connected).
///
- /// At reception of this error, ChannelManager will force-close the channel and return at
- /// least a final ChannelMonitorUpdate::ChannelForceClosed which must be delivered to at
- /// least one ChannelMonitor copy. Revocation secret MUST NOT be released and offchain channel
- /// update must be rejected.
+ /// In order to broadcast the latest local commitment transaction, you'll need to call
+ /// [`ChannelMonitor::get_latest_holder_commitment_txn`] and broadcast the resulting
+ /// transactions once you've safely ensured no further channel updates can be generated by your
+ /// [`ChannelManager`].
///
- /// This failure may also signal a failure to update the local persisted copy of one of
- /// the channel monitor instance.
+ /// Note that at least one final [`ChannelMonitorUpdate`] may still be provided, which must
+ /// still be processed by a running [`ChannelMonitor`]. This final update will mark the
+ /// [`ChannelMonitor`] as finalized, ensuring no further updates (e.g. revocation of the latest
+ /// commitment transaction) are allowed.
///
- /// Note that even when you fail a holder commitment transaction update, you must store the
- /// update to ensure you can claim from it in case of a duplicate copy of this ChannelMonitor
- /// broadcasts it (e.g distributed channel-monitor deployment)
+ /// Note that even if you return a [`PermanentFailure`] due to unavailability of secondary
+ /// [`ChannelMonitor`] copies, you should still make an attempt to store the update where
+ /// possible to ensure you can claim HTLC outputs on the latest commitment transaction
+ /// broadcasted later.
///
/// In case of distributed watchtowers deployment, the new version must be written to disk, as
/// state may have been stored but rejected due to a block forcing a commitment broadcast. This
/// storage is used to claim outputs of rejected state confirmed onchain by another watchtower,
/// lagging behind on block processing.
+ ///
+ /// [`PermanentFailure`]: ChannelMonitorUpdateStatus::PermanentFailure
+ /// [`ChannelManager`]: crate::ln::channelmanager::ChannelManager
PermanentFailure,
}
/// 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
+/// funds in the channel. See [`ChannelMonitorUpdateStatus`] for more details about how to handle
/// multiple instances.
///
-/// [`PermanentFailure`]: ChannelMonitorUpdateErr::PermanentFailure
-pub trait Watch<ChannelSigner: Sign> {
+/// [`PermanentFailure`]: ChannelMonitorUpdateStatus::PermanentFailure
+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 any spends of outputs returned by [`get_outputs_to_watch`]. In practice, this means
/// calling [`block_connected`] and [`block_disconnected`] on the monitor.
///
- /// Note: this interface MUST error with `ChannelMonitorUpdateErr::PermanentFailure` if
+ /// Note: this interface MUST error with [`ChannelMonitorUpdateStatus::PermanentFailure`] if
/// the given `funding_txo` has previously been registered via `watch_channel`.
///
/// [`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<(), ChannelMonitorUpdateErr>;
+ fn watch_channel(&self, funding_txo: OutPoint, monitor: ChannelMonitor<ChannelSigner>) -> 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.
+ /// [`ChannelMonitorUpdateStatus`] for invariants around returning an error.
///
/// [`update_monitor`]: channelmonitor::ChannelMonitor::update_monitor
- fn update_channel(&self, funding_txo: OutPoint, update: ChannelMonitorUpdate) -> Result<(), ChannelMonitorUpdateErr>;
+ 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.
/// to disk.
///
/// For details on asynchronous [`ChannelMonitor`] updating and returning
- /// [`MonitorEvent::UpdateCompleted`] here, see [`ChannelMonitorUpdateErr::TemporaryFailure`].
- fn release_pending_monitor_events(&self) -> Vec<MonitorEvent>;
+ /// [`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`].
+/// invocation that has called the `Filter` must return [`InProgress`].
///
-/// [`TemporaryFailure`]: ChannelMonitorUpdateErr::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 {
/// Registers interest in spends of a transaction output.
///
- /// Optionally, when `output.block_hash` is set, should return any transaction spending the
- /// output that is found in the corresponding block along with its index.
- ///
- /// This return value is useful for Electrum clients in order to supply in-block descendant
- /// transactions which otherwise were not included. This is not necessary for other clients if
- /// such descendant transactions were already included (e.g., when a BIP 157 client provides the
- /// full block).
- fn register_output(&self, output: WatchedOutput) -> Option<(usize, Transaction)>;
+ /// 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
-/// the return value of [`Filter::register_output`].
+/// [`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, Hash)]
+#[derive(Clone, PartialEq, Eq, Hash)]
pub struct WatchedOutput {
/// First block where the transaction output may have been spent.
pub block_hash: Option<BlockHash>,
}
impl<T: Listen> Listen for core::ops::Deref<Target = T> {
- fn block_connected(&self, block: &Block, height: u32) {
- (**self).block_connected(block, height);
+ fn filtered_block_connected(&self, header: &BlockHeader, txdata: &TransactionData, height: u32) {
+ (**self).filtered_block_connected(header, txdata, height);
}
fn block_disconnected(&self, header: &BlockHeader, height: u32) {
T::Target: Listen,
U::Target: Listen,
{
- fn block_connected(&self, block: &Block, height: u32) {
- self.0.block_connected(block, height);
- self.1.block_connected(block, height);
+ fn filtered_block_connected(&self, header: &BlockHeader, 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: &BlockHeader, height: u32) {
projects / rust-lightning / blobdiff