X-Git-Url: http://git.bitcoin.ninja/index.cgi?a=blobdiff_plain;f=lightning%2Fsrc%2Fchain%2Fmod.rs;h=43add75950d6a50c3c07c5a07e525fd7154bf216;hb=4bd9b05465c5517e454842ec46016d0a96c0ea9e;hp=ffa5ed968be4d62e391f613a337f464b37d31b27;hpb=88fef649b15fa030cb91de76d58346a0bc408834;p=rust-lightning diff --git a/lightning/src/chain/mod.rs b/lightning/src/chain/mod.rs index ffa5ed96..43add759 100644 --- a/lightning/src/chain/mod.rs +++ b/lightning/src/chain/mod.rs @@ -1,5 +1,410 @@ +// This file is Copyright its original authors, visible in version control +// history. +// +// This file is licensed under the Apache License, Version 2.0 or the MIT license +// , 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::TxOut; +use bitcoin::hash_types::{BlockHash, Txid}; +use bitcoin::network::constants::Network; +use bitcoin::secp256k1::PublicKey; + +use crate::chain::channelmonitor::{ChannelMonitor, ChannelMonitorUpdate, MonitorEvent}; +use crate::chain::keysinterface::Sign; +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 best known block as identified by its hash and height. +#[derive(Clone, Copy, PartialEq, Eq)] +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, Debug)] +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/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; +} + +/// 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: &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) { + 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 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 +/// +/// 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: &BlockHeader, 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: &BlockHeader, height: u32); + /// 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. + /// + /// 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, 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, Option)>; +} + +/// 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) 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 [`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. + /// + /// 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). + /// + /// 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`]. + /// + /// 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 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, +} + +/// 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 [`ChannelMonitorUpdateStatus`] for more details about how to handle +/// multiple instances. +/// +/// [`PermanentFailure`]: ChannelMonitorUpdateStatus::PermanentFailure +pub trait Watch { + /// 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 [`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) -> ChannelMonitorUpdateStatus; + + /// Updates a channel identified by `funding_txo` by applying `update` to its monitor. + /// + /// Implementations must call [`update_monitor`] with the given update. See + /// [`ChannelMonitorUpdateStatus`] for invariants around returning an error. + /// + /// [`update_monitor`]: channelmonitor::ChannelMonitor::update_monitor + 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. + /// + /// 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, Option)>; +} + +/// 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 [`InProgress`]. +/// +/// [`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 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. + /// + /// 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, + + /// Outpoint identifying the transaction output. + pub outpoint: OutPoint, + + /// Spending condition of the transaction output. + pub script_pubkey: Script, +} + +impl Listen for core::ops::Deref { + 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) { + (**self).block_disconnected(header, height); + } +} + +impl Listen for (T, U) +where + T::Target: Listen, + U::Target: Listen, +{ + 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) { + self.0.block_disconnected(header, height); + self.1.block_disconnected(header, height); + } +}