+// 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.
+
//! Traits and utility impls which allow other parts of rust-lightning to interact with the
//! blockchain.
//!
//! Includes traits for monitoring and receiving notifications of new blocks and block
//! disconnections, transaction broadcasting, and feerate information requests.
-use bitcoin::blockdata::block::{Block, BlockHeader};
-use bitcoin::blockdata::transaction::Transaction;
-use bitcoin::blockdata::script::Script;
-use bitcoin::blockdata::constants::genesis_block;
-use bitcoin::util::hash::BitcoinHash;
-use bitcoin_hashes::sha256d::Hash as Sha256dHash;
-use bitcoin::network::constants::Network;
-
-use util::logger::Logger;
+use core::{cmp, ops::Deref};
+use core::convert::TryInto;
-use std::sync::{Mutex,Weak,MutexGuard,Arc};
-use std::sync::atomic::{AtomicUsize, Ordering};
-use std::collections::HashSet;
+use bitcoin::blockdata::transaction::Transaction;
-/// Used to give chain error details upstream
-pub enum ChainError {
- /// Client doesn't support UTXO lookup (but the chain hash matches our genesis block hash)
- NotSupported,
- /// Chain isn't the one watched
- NotWatched,
- /// Tx doesn't exist or is unconfirmed
- UnknownTx,
+// TODO: Define typed abstraction over feerates to handle their conversions.
+pub(crate) fn compute_feerate_sat_per_1000_weight(fee_sat: u64, weight: u64) -> u32 {
+ (fee_sat * 1000 / weight).try_into().unwrap_or(u32::max_value())
}
-
-/// An interface to request notification of certain scripts as they appear the
-/// chain.
-///
-/// Note that all of the functions implemented here *must* be reentrant-safe (obviously - they're
-/// called from inside the library in response to ChainListener events, P2P events, or timer
-/// events).
-pub trait ChainWatchInterface: Sync + Send {
- /// Provides a txid/random-scriptPubKey-in-the-tx which much be watched for.
- fn install_watch_tx(&self, txid: &Sha256dHash, script_pub_key: &Script);
-
- /// Provides an outpoint which must be watched for, providing any transactions which spend the
- /// given outpoint.
- fn install_watch_outpoint(&self, outpoint: (Sha256dHash, u32), out_script: &Script);
-
- /// Indicates that a listener needs to see all transactions.
- fn watch_all_txn(&self);
-
- /// Gets the script and value in satoshis for a given unspent transaction output given a
- /// short_channel_id (aka unspent_tx_output_identier). For BTC/tBTC channels the top three
- /// bytes are the block height, the next 3 the transaction index within the block, and the
- /// final two the output within the transaction.
- fn get_chain_utxo(&self, genesis_hash: Sha256dHash, unspent_tx_output_identifier: u64) -> Result<(Script, u64), ChainError>;
-
- /// Gets the list of transactions and transaction indices that the ChainWatchInterface is
- /// watching for.
- fn filter_block<'a>(&self, block: &'a Block) -> (Vec<&'a Transaction>, Vec<u32>);
-
- /// Returns a usize that changes when the ChainWatchInterface's watched data is modified.
- /// Users of `filter_block` should pre-save a copy of `reentered`'s return value and use it to
- /// determine whether they need to re-filter a given block.
- fn reentered(&self) -> usize;
+pub(crate) const fn fee_for_weight(feerate_sat_per_1000_weight: u32, weight: u64) -> u64 {
+ ((feerate_sat_per_1000_weight as u64 * weight) + 1000 - 1) / 1000
}
/// An interface to send a transaction to the Bitcoin network.
-pub trait BroadcasterInterface: Sync + Send {
- /// Sends a transaction out to (hopefully) be mined.
- fn broadcast_transaction(&self, tx: &Transaction);
-}
-
-/// A trait indicating a desire to listen for events from the chain
-pub trait ChainListener: Sync + Send {
- /// Notifies a listener that a block was connected.
- /// Note that if a new transaction/outpoint is watched during a block_connected call, the block
- /// *must* be re-scanned with the new transaction/outpoints and block_connected should be
- /// called again with the same header and (at least) the new transactions.
+pub trait BroadcasterInterface {
+ /// Sends a list of transactions out to (hopefully) be mined.
+ /// This only needs to handle the actual broadcasting of transactions, LDK will automatically
+ /// rebroadcast transactions that haven't made it into a block.
///
- /// Note that if non-new transaction/outpoints may be registered during a call, a second call
- /// *must not* happen.
+ /// In some cases LDK may attempt to broadcast a transaction which double-spends another
+ /// and this isn't a bug and can be safely ignored.
///
- /// This also means those counting confirmations using block_connected callbacks should watch
- /// for duplicate headers and not count them towards confirmations!
- fn block_connected(&self, header: &BlockHeader, height: u32, txn_matched: &[&Transaction], indexes_of_txn_matched: &[u32]);
- /// Notifies a listener that a block was disconnected.
- /// Unlike block_connected, this *must* never be called twice for the same disconnect event.
- /// Height must be the one of the block which was disconnected (not new height of the best chain)
- fn block_disconnected(&self, header: &BlockHeader, disconnected_height: u32);
+ /// If more than one transaction is given, these transactions should be considered to be a
+ /// package and broadcast together. Some of the transactions may or may not depend on each other,
+ /// be sure to manage both cases correctly.
+ ///
+ /// Bitcoin transaction packages are defined in BIP 331 and here:
+ /// <https://github.com/bitcoin/bitcoin/blob/master/doc/policy/packages.md>
+ fn broadcast_transactions(&self, txs: &[&Transaction]);
}
-/// An enum that represents the speed at which we want a transaction to confirm used for feerate
+/// An enum that represents the priority at which we want a transaction to confirm used for feerate
/// estimation.
+#[derive(Clone, Copy, Debug, Hash, PartialEq, Eq)]
pub enum ConfirmationTarget {
- /// We are happy with this transaction confirming slowly when feerate drops some.
- Background,
- /// We'd like this transaction to confirm without major delay, but 12-18 blocks is fine.
- Normal,
- /// We'd like this transaction to confirm in the next few blocks.
- HighPriority,
+ /// We have some funds available on chain which we need to spend prior to some expiry time at
+ /// which point our counterparty may be able to steal them. Generally we have in the high tens
+ /// to low hundreds of blocks to get our transaction on-chain, but we shouldn't risk too low a
+ /// fee - this should be a relatively high priority feerate.
+ OnChainSweep,
+ /// This is the lowest feerate we will allow our channel counterparty to have in an anchor
+ /// channel in order to close the channel if a channel party goes away.
+ ///
+ /// This needs to be sufficient to get into the mempool when the channel needs to
+ /// be force-closed. Setting too high may result in force-closures if our counterparty attempts
+ /// to use a lower feerate. Because this is for anchor channels, we can always bump the feerate
+ /// later; the feerate here only needs to be sufficient to enter the mempool.
+ ///
+ /// A good estimate is the expected mempool minimum at the time of force-closure. Obviously this
+ /// is not an estimate which is very easy to calculate because we do not know the future. Using
+ /// a simple long-term fee estimate or tracking of the mempool minimum is a good approach to
+ /// ensure you can always close the channel. A future change to Bitcoin's P2P network
+ /// (package relay) may obviate the need for this entirely.
+ MinAllowedAnchorChannelRemoteFee,
+ /// The lowest feerate we will allow our channel counterparty to have in a non-anchor channel.
+ ///
+ /// This is the feerate on the transaction which we (or our counterparty) will broadcast in
+ /// order to close the channel if a channel party goes away. Setting this value too high will
+ /// cause immediate force-closures in order to avoid having an unbroadcastable state.
+ ///
+ /// This feerate represents the fee we pick now, which must be sufficient to enter a block at an
+ /// arbitrary time in the future. Obviously this is not an estimate which is very easy to
+ /// calculate. This can leave channels subject to being unable to close if feerates rise, and in
+ /// general you should prefer anchor channels to ensure you can increase the feerate when the
+ /// transactions need broadcasting.
+ ///
+ /// Do note some fee estimators round up to the next full sat/vbyte (ie 250 sats per kw),
+ /// causing occasional issues with feerate disagreements between an initiator that wants a
+ /// feerate of 1.1 sat/vbyte and a receiver that wants 1.1 rounded up to 2. If your fee
+ /// estimator rounds subtracting 250 to your desired feerate here can help avoid this issue.
+ ///
+ /// [`ChannelConfig::max_dust_htlc_exposure`]: crate::util::config::ChannelConfig::max_dust_htlc_exposure
+ MinAllowedNonAnchorChannelRemoteFee,
+ /// This is the feerate on the transaction which we (or our counterparty) will broadcast in
+ /// order to close the channel if a channel party goes away.
+ ///
+ /// This needs to be sufficient to get into the mempool when the channel needs to
+ /// be force-closed. Setting too low may result in force-closures. Because this is for anchor
+ /// channels, it can be a low value as we can always bump the feerate later.
+ ///
+ /// A good estimate is the expected mempool minimum at the time of force-closure. Obviously this
+ /// is not an estimate which is very easy to calculate because we do not know the future. Using
+ /// a simple long-term fee estimate or tracking of the mempool minimum is a good approach to
+ /// ensure you can always close the channel. A future change to Bitcoin's P2P network
+ /// (package relay) may obviate the need for this entirely.
+ AnchorChannelFee,
+ /// Lightning is built around the ability to broadcast a transaction in the future to close our
+ /// channel and claim all pending funds. In order to do so, non-anchor channels are built with
+ /// transactions which we need to be able to broadcast at some point in the future.
+ ///
+ /// This feerate represents the fee we pick now, which must be sufficient to enter a block at an
+ /// arbitrary time in the future. Obviously this is not an estimate which is very easy to
+ /// calculate, so most lightning nodes use some relatively high-priority feerate using the
+ /// current mempool. This leaves channels subject to being unable to close if feerates rise, and
+ /// in general you should prefer anchor channels to ensure you can increase the feerate when the
+ /// transactions need broadcasting.
+ ///
+ /// Since this should represent the feerate of a channel close that does not need fee
+ /// bumping, this is also used as an upper bound for our attempted feerate when doing cooperative
+ /// closure of any channel.
+ NonAnchorChannelFee,
+ /// When cooperatively closing a channel, this is the minimum feerate we will accept.
+ /// Recommended at least within a day or so worth of blocks.
+ ///
+ /// This will also be used when initiating a cooperative close of a channel. When closing a
+ /// channel you can override this fee by using
+ /// [`ChannelManager::close_channel_with_feerate_and_script`].
+ ///
+ /// [`ChannelManager::close_channel_with_feerate_and_script`]: crate::ln::channelmanager::ChannelManager::close_channel_with_feerate_and_script
+ ChannelCloseMinimum,
}
/// A trait which should be implemented to provide feerate information on a number of time
/// horizons.
///
+/// If access to a local mempool is not feasible, feerate estimates should be fetched from a set of
+/// third-parties hosting them. Note that this enables them to affect the propagation of your
+/// pre-signed transactions at any time and therefore endangers the safety of channels funds. It
+/// should be considered carefully as a deployment.
+///
/// Note that all of the functions implemented here *must* be reentrant-safe (obviously - they're
-/// called from inside the library in response to ChainListener events, P2P events, or timer
-/// events).
-pub trait FeeEstimator: Sync + Send {
+/// called from inside the library in response to chain events, P2P events, or timer events).
+pub trait FeeEstimator {
/// Gets estimated satoshis of fee required per 1000 Weight-Units.
///
- /// Must be no smaller than 253 (ie 1 satoshi-per-byte rounded up to ensure later round-downs
- /// don't put us below 1 satoshi-per-byte).
+ /// LDK will wrap this method and ensure that the value returned is no smaller than 253
+ /// (ie 1 satoshi-per-byte rounded up to ensure later round-downs don't put us below 1 satoshi-per-byte).
///
- /// This translates to:
+ /// The following unit conversions can be used to convert to sats/KW:
/// * satoshis-per-byte * 250
- /// * ceil(satoshis-per-kbyte / 4)
- fn get_est_sat_per_1000_weight(&self, confirmation_target: ConfirmationTarget) -> u64;
+ /// * satoshis-per-kbyte / 4
+ fn get_est_sat_per_1000_weight(&self, confirmation_target: ConfirmationTarget) -> u32;
}
/// Minimum relay fee as required by bitcoin network mempool policy.
pub const MIN_RELAY_FEE_SAT_PER_1000_WEIGHT: u64 = 4000;
+/// Minimum feerate that takes a sane approach to bitcoind weight-to-vbytes rounding.
+/// See the following Core Lightning commit for an explanation:
+/// <https://github.com/ElementsProject/lightning/commit/2e687b9b352c9092b5e8bd4a688916ac50b44af0>
+pub const FEERATE_FLOOR_SATS_PER_KW: u32 = 253;
-/// Utility for tracking registered txn/outpoints and checking for matches
-pub struct ChainWatchedUtil {
- watch_all: bool,
-
- // We are more conservative in matching during testing to ensure everything matches *exactly*,
- // even though during normal runtime we take more optimized match approaches...
- #[cfg(test)]
- watched_txn: HashSet<(Sha256dHash, Script)>,
- #[cfg(not(test))]
- watched_txn: HashSet<Script>,
-
- watched_outpoints: HashSet<(Sha256dHash, u32)>,
-}
-
-impl ChainWatchedUtil {
- /// Constructs an empty (watches nothing) ChainWatchedUtil
- pub fn new() -> Self {
- Self {
- watch_all: false,
- watched_txn: HashSet::new(),
- watched_outpoints: HashSet::new(),
- }
- }
-
- /// Registers a tx for monitoring, returning true if it was a new tx and false if we'd already
- /// been watching for it.
- pub fn register_tx(&mut self, txid: &Sha256dHash, script_pub_key: &Script) -> bool {
- if self.watch_all { return false; }
- #[cfg(test)]
- {
- self.watched_txn.insert((txid.clone(), script_pub_key.clone()))
- }
- #[cfg(not(test))]
- {
- let _tx_unused = txid; // It's used in cfg(test), though
- self.watched_txn.insert(script_pub_key.clone())
- }
- }
-
- /// Registers an outpoint for monitoring, returning true if it was a new outpoint and false if
- /// we'd already been watching for it
- pub fn register_outpoint(&mut self, outpoint: (Sha256dHash, u32), _script_pub_key: &Script) -> bool {
- if self.watch_all { return false; }
- self.watched_outpoints.insert(outpoint)
- }
-
- /// Sets us to match all transactions, returning true if this is a new setting and false if
- /// we'd already been set to match everything.
- pub fn watch_all(&mut self) -> bool {
- if self.watch_all { return false; }
- self.watch_all = true;
- true
- }
-
- /// Checks if a given transaction matches the current filter.
- pub fn does_match_tx(&self, tx: &Transaction) -> bool {
- if self.watch_all {
- return true;
- }
- for out in tx.output.iter() {
- #[cfg(test)]
- for &(ref txid, ref script) in self.watched_txn.iter() {
- if *script == out.script_pubkey {
- if tx.txid() == *txid {
- return true;
- }
- }
- }
- #[cfg(not(test))]
- for script in self.watched_txn.iter() {
- if *script == out.script_pubkey {
- return true;
- }
- }
- }
- for input in tx.input.iter() {
- for outpoint in self.watched_outpoints.iter() {
- let &(outpoint_hash, outpoint_index) = outpoint;
- if outpoint_hash == input.previous_output.txid && outpoint_index == input.previous_output.vout {
- return true;
- }
- }
- }
- false
- }
-}
-
-/// Utility for notifying listeners about new blocks, and handling block rescans if new watch
-/// data is registered.
-pub struct BlockNotifier<'a> {
- listeners: Mutex<Vec<Weak<ChainListener + 'a>>>, //TODO(vmw): try removing Weak
- chain_monitor: Arc<ChainWatchInterface>,
-}
-
-impl<'a> BlockNotifier<'a> {
- /// Constructs a new BlockNotifier without any listeners.
- pub fn new(chain_monitor: Arc<ChainWatchInterface>) -> BlockNotifier<'a> {
- BlockNotifier {
- listeners: Mutex::new(Vec::new()),
- chain_monitor,
- }
- }
-
- /// Register the given listener to receive events. Only a weak pointer is provided and
- /// the registration should be freed once that pointer expires.
- // TODO: unregister
- pub fn register_listener(&self, listener: Weak<ChainListener + 'a>) {
- let mut vec = self.listeners.lock().unwrap();
- vec.push(listener);
- }
-
- /// Notify listeners that a block was connected given a full, unfiltered block.
- ///
- /// Handles re-scanning the block and calling block_connected again if listeners register new
- /// watch data during the callbacks for you (see ChainListener::block_connected for more info).
- pub fn block_connected<'b>(&self, block: &'b Block, height: u32) {
- let mut reentered = true;
- while reentered {
- let (matched, matched_index) = self.chain_monitor.filter_block(block);
- reentered = self.block_connected_checked(&block.header, height, matched.as_slice(), matched_index.as_slice());
- }
- }
-
- /// Notify listeners that a block was connected, given pre-filtered list of transactions in the
- /// block which matched the filter (probably using does_match_tx).
- ///
- /// Returns true if notified listeners registered additional watch data (implying that the
- /// block must be re-scanned and this function called again prior to further block_connected
- /// calls, see ChainListener::block_connected for more info).
- pub fn block_connected_checked(&self, header: &BlockHeader, height: u32, txn_matched: &[&Transaction], indexes_of_txn_matched: &[u32]) -> bool {
- let last_seen = self.chain_monitor.reentered();
-
- let listeners = self.listeners.lock().unwrap().clone();
- for listener in listeners.iter() {
- match listener.upgrade() {
- Some(arc) => arc.block_connected(header, height, txn_matched, indexes_of_txn_matched),
- None => ()
- }
- }
- return last_seen != self.chain_monitor.reentered();
- }
-
-
- /// Notify listeners that a block was disconnected.
- pub fn block_disconnected(&self, header: &BlockHeader, disconnected_height: u32) {
- let listeners = self.listeners.lock().unwrap().clone();
- for listener in listeners.iter() {
- match listener.upgrade() {
- Some(arc) => arc.block_disconnected(&header, disconnected_height),
- None => ()
- }
- }
- }
-
-}
-
-/// Utility to capture some common parts of ChainWatchInterface implementors.
+/// Wraps a `Deref` to a `FeeEstimator` so that any fee estimations provided by it
+/// are bounded below by `FEERATE_FLOOR_SATS_PER_KW` (253 sats/KW).
///
-/// Keeping a local copy of this in a ChainWatchInterface implementor is likely useful.
-pub struct ChainWatchInterfaceUtil {
- network: Network,
- watched: Mutex<ChainWatchedUtil>,
- reentered: AtomicUsize,
- logger: Arc<Logger>,
-}
+/// Note that this does *not* implement [`FeeEstimator`] to make it harder to accidentally mix the
+/// two.
+pub(crate) struct LowerBoundedFeeEstimator<F: Deref>(pub F) where F::Target: FeeEstimator;
-/// Register listener
-impl ChainWatchInterface for ChainWatchInterfaceUtil {
- fn install_watch_tx(&self, txid: &Sha256dHash, script_pub_key: &Script) {
- let mut watched = self.watched.lock().unwrap();
- if watched.register_tx(txid, script_pub_key) {
- self.reentered.fetch_add(1, Ordering::Relaxed);
- }
+impl<F: Deref> LowerBoundedFeeEstimator<F> where F::Target: FeeEstimator {
+ /// Creates a new `LowerBoundedFeeEstimator` which wraps the provided fee_estimator
+ pub fn new(fee_estimator: F) -> Self {
+ LowerBoundedFeeEstimator(fee_estimator)
}
- fn install_watch_outpoint(&self, outpoint: (Sha256dHash, u32), out_script: &Script) {
- let mut watched = self.watched.lock().unwrap();
- if watched.register_outpoint(outpoint, out_script) {
- self.reentered.fetch_add(1, Ordering::Relaxed);
- }
+ pub fn bounded_sat_per_1000_weight(&self, confirmation_target: ConfirmationTarget) -> u32 {
+ cmp::max(
+ self.0.get_est_sat_per_1000_weight(confirmation_target),
+ FEERATE_FLOOR_SATS_PER_KW,
+ )
}
+}
- fn watch_all_txn(&self) {
- let mut watched = self.watched.lock().unwrap();
- if watched.watch_all() {
- self.reentered.fetch_add(1, Ordering::Relaxed);
- }
- }
+#[cfg(test)]
+mod tests {
+ use super::{FEERATE_FLOOR_SATS_PER_KW, LowerBoundedFeeEstimator, ConfirmationTarget, FeeEstimator};
- fn get_chain_utxo(&self, genesis_hash: Sha256dHash, _unspent_tx_output_identifier: u64) -> Result<(Script, u64), ChainError> {
- if genesis_hash != genesis_block(self.network).header.bitcoin_hash() {
- return Err(ChainError::NotWatched);
- }
- Err(ChainError::NotSupported)
+ struct TestFeeEstimator {
+ sat_per_kw: u32,
}
- fn filter_block<'a>(&self, block: &'a Block) -> (Vec<&'a Transaction>, Vec<u32>) {
- let mut matched = Vec::new();
- let mut matched_index = Vec::new();
- {
- let watched = self.watched.lock().unwrap();
- for (index, transaction) in block.txdata.iter().enumerate() {
- if self.does_match_tx_unguarded(transaction, &watched) {
- matched.push(transaction);
- matched_index.push(index as u32);
- }
- }
+ impl FeeEstimator for TestFeeEstimator {
+ fn get_est_sat_per_1000_weight(&self, _: ConfirmationTarget) -> u32 {
+ self.sat_per_kw
}
- (matched, matched_index)
}
- fn reentered(&self) -> usize {
- self.reentered.load(Ordering::Relaxed)
- }
-}
+ #[test]
+ fn test_fee_estimator_less_than_floor() {
+ let sat_per_kw = FEERATE_FLOOR_SATS_PER_KW - 1;
+ let test_fee_estimator = &TestFeeEstimator { sat_per_kw };
+ let fee_estimator = LowerBoundedFeeEstimator::new(test_fee_estimator);
-impl ChainWatchInterfaceUtil {
- /// Creates a new ChainWatchInterfaceUtil for the given network
- pub fn new(network: Network, logger: Arc<Logger>) -> ChainWatchInterfaceUtil {
- ChainWatchInterfaceUtil {
- network: network,
- watched: Mutex::new(ChainWatchedUtil::new()),
- reentered: AtomicUsize::new(1),
- logger: logger,
- }
+ assert_eq!(fee_estimator.bounded_sat_per_1000_weight(ConfirmationTarget::AnchorChannelFee), FEERATE_FLOOR_SATS_PER_KW);
}
+ #[test]
+ fn test_fee_estimator_greater_than_floor() {
+ let sat_per_kw = FEERATE_FLOOR_SATS_PER_KW + 1;
+ let test_fee_estimator = &TestFeeEstimator { sat_per_kw };
+ let fee_estimator = LowerBoundedFeeEstimator::new(test_fee_estimator);
- /// Checks if a given transaction matches the current filter.
- pub fn does_match_tx(&self, tx: &Transaction) -> bool {
- let watched = self.watched.lock().unwrap();
- self.does_match_tx_unguarded (tx, &watched)
- }
-
- fn does_match_tx_unguarded(&self, tx: &Transaction, watched: &MutexGuard<ChainWatchedUtil>) -> bool {
- watched.does_match_tx(tx)
+ assert_eq!(fee_estimator.bounded_sat_per_1000_weight(ConfirmationTarget::AnchorChannelFee), sat_per_kw);
}
}
projects / rust-lightning / blobdiff