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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, ChannelMonitorUpdateErr, 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>; } /// 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`]: channelmonitor::ChannelMonitor /// [`ChannelMonitorUpdateErr`]: channelmonitor::ChannelMonitorUpdateErr /// [`PermanentFailure`]: channelmonitor::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. /// /// [`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 /// [`ChannelMonitorUpdateErr`]: channelmonitor::ChannelMonitorUpdateErr 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. 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`]: channelmonitor::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); } }