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// This file is Copyright its original authors, visible in version control
// history.
//
// This file is licensed under the Apache License, Version 2.0 <LICENSE-APACHE
// or http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your option.
// You may not use this file except in accordance with one or both of these
// licenses.
//! Structs and traits which allow other parts of rust-lightning to interact with the blockchain.
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::hash_types::{BlockHash, Txid};
use bitcoin::network::constants::Network;
use chain::channelmonitor::{ChannelMonitor, ChannelMonitorUpdate, MonitorEvent};
use chain::keysinterface::Sign;
use chain::transaction::{OutPoint, TransactionData};
use 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 best known block as identified by its hash and height.
#[derive(Clone, Copy, PartialEq)]
pub struct BestBlock {
block_hash: BlockHash,
height: u32,
}
impl BestBlock {
/// Constructs a `BestBlock` that represents the genesis block at height 0 of the given
/// network.
pub fn from_genesis(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 }
}
/// An error when accessing the chain via [`Access`].
#[derive(Clone)]
pub enum AccessError {
/// The requested chain is unknown.
UnknownChain,
/// The requested transaction doesn't exist or hasn't confirmed.
UnknownTx,
}
/// The `Access` trait defines behavior for accessing chain data and state, such as blocks and
/// UTXOs.
pub trait Access {
/// 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 `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.
pub trait Listen {
/// Notifies the listener that a block was added at the given height.
fn block_connected(&self, block: &Block, height: u32);
/// 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.
///
/// 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.
///
/// # 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.
///
/// # 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.
/// - 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.
///
/// 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 {
/// Processes transactions confirmed in a block with a given header and height.
///
/// Should 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: &BlockHeader, txdata: &TransactionData, height: u32);
/// Processes 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`].
///
/// [`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.
///
/// Should be called when a new header is available but may be skipped for intermediary blocks
/// if they become available at the same time.
fn best_block_updated(&self, header: &BlockHeader, height: u32);
/// Returns transactions that should be monitored for reorganization out of the chain.
///
/// 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.
///
/// May be called to determine the subset of transactions that must still 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
/// given to [`transaction_unconfirmed`].
///
/// [`transactions_confirmed`]: Self::transactions_confirmed
/// [`transaction_unconfirmed`]: Self::transaction_unconfirmed
fn get_relevant_txids(&self) -> Vec<Txid>;
}
/// An error enum representing a failure to persist a channel monitor update.
#[derive(Clone, Copy, Debug, PartialEq)]
pub enum ChannelMonitorUpdateErr {
/// 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.
///
/// 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.
///
/// [`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).
///
/// 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.
///
/// This failure may also signal a failure to update the local persisted copy of one of
/// the channel monitor instance.
///
/// 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)
///
/// 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,
}
/// 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.
///
/// [`PermanentFailure`]: ChannelMonitorUpdateErr::PermanentFailure
pub trait Watch<ChannelSigner: Sign> {
/// 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
/// 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>;
/// 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.
///
/// [`update_monitor`]: channelmonitor::ChannelMonitor::update_monitor
fn update_channel(&self, funding_txo: OutPoint, update: ChannelMonitorUpdate) -> Result<(), ChannelMonitorUpdateErr>;
/// Returns any monitor events since the last call. Subsequent calls must only return new
/// events.
///
/// 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::UpdateCompleted`] here, see [`ChannelMonitorUpdateErr::TemporaryFailure`].
fn release_pending_monitor_events(&self) -> Vec<MonitorEvent>;
}
/// The `Filter` trait defines behavior for indicating chain activity of interest pertaining to
/// channels.
///
/// This is useful in order to have a [`Watch`] implementation convey to a chain source which
/// transactions to be notified of. Notification may take the form of pre-filtering blocks or, in
/// the case of [BIP 157]/[BIP 158], only fetching a block if the compact filter matches. If
/// receiving full blocks from a chain source, any further filtering is unnecessary.
///
/// After an output has been registered, subsequent block retrievals from the chain source must not
/// exclude any transactions matching the new criteria nor any in-block descendants of such
/// transactions.
///
/// 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`].
///
/// [`TemporaryFailure`]: ChannelMonitorUpdateErr::TemporaryFailure
/// [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 a transaction with `txid` and having an output with `script_pubkey` as
/// a spending condition.
fn register_tx(&self, txid: &Txid, script_pubkey: &Script);
/// 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)>;
}
/// 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`].
///
/// 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)]
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,
/// Spending condition of the transaction output.
pub script_pubkey: Script,
}
impl<T: Listen> Listen for core::ops::Deref<Target = T> {
fn block_connected(&self, block: &Block, height: u32) {
(**self).block_connected(block, height);
}
fn block_disconnected(&self, header: &BlockHeader, 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 block_connected(&self, block: &Block, height: u32) {
self.0.block_connected(block, height);
self.1.block_connected(block, height);
}
fn block_disconnected(&self, header: &BlockHeader, height: u32) {
self.0.block_disconnected(header, height);
self.1.block_disconnected(header, height);
}
}