X-Git-Url: http://git.bitcoin.ninja/index.cgi?a=blobdiff_plain;f=lightning%2Fsrc%2Fchain%2Fchaininterface.rs;h=913fa007d378e91ba5666e3d34ae11c15010ce13;hb=543674f1dac007586be8c94ae73af1ca82b5e095;hp=83fee4d674d1611e82dccee1e1c674e8fb94f9aa;hpb=ec35fe62a12e392ebf2aed90f8f4124ec9c6f7d7;p=rust-lightning diff --git a/lightning/src/chain/chaininterface.rs b/lightning/src/chain/chaininterface.rs index 83fee4d6..913fa007 100644 --- a/lightning/src/chain/chaininterface.rs +++ b/lightning/src/chain/chaininterface.rs @@ -13,41 +13,137 @@ //! Includes traits for monitoring and receiving notifications of new blocks and block //! disconnections, transaction broadcasting, and feerate information requests. +use core::{cmp, ops::Deref}; +use core::convert::TryInto; + use bitcoin::blockdata::transaction::Transaction; +// 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()) +} +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 { - /// Sends a transaction out to (hopefully) be mined. - fn broadcast_transaction(&self, tx: &Transaction); + /// 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. + /// + /// 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. + /// + /// 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. + /// We'd like a transaction to confirm in the future, but don't want to commit most of the fees + /// required to do so yet. The remaining fees will come via a Child-Pays-For-Parent (CPFP) fee + /// bump of the transaction. + /// + /// The feerate returned should be the absolute minimum feerate required to enter most node + /// mempools across the network. Note that if you are not able to obtain this feerate estimate, + /// you should likely use the furthest-out estimate allowed by your fee estimator. + MempoolMinimum, + /// We are happy with a transaction confirming slowly, at least within a day or so worth of + /// blocks. Background, - /// We'd like this transaction to confirm without major delay, but 12-18 blocks is fine. + /// We'd like a transaction to confirm without major delayed, i.e., within the next 12-24 blocks. Normal, - /// We'd like this transaction to confirm in the next few blocks. + /// We'd like a transaction to confirm in the next few blocks. HighPriority, } /// 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 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) + /// * 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: +/// +pub const FEERATE_FLOOR_SATS_PER_KW: u32 = 253; + +/// 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). +/// +/// Note that this does *not* implement [`FeeEstimator`] to make it harder to accidentally mix the +/// two. +pub(crate) struct LowerBoundedFeeEstimator(pub F) where F::Target: FeeEstimator; + +impl LowerBoundedFeeEstimator where F::Target: FeeEstimator { + /// Creates a new `LowerBoundedFeeEstimator` which wraps the provided fee_estimator + pub fn new(fee_estimator: F) -> Self { + LowerBoundedFeeEstimator(fee_estimator) + } + + 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, + ) + } +} + +#[cfg(test)] +mod tests { + use super::{FEERATE_FLOOR_SATS_PER_KW, LowerBoundedFeeEstimator, ConfirmationTarget, FeeEstimator}; + + struct TestFeeEstimator { + sat_per_kw: u32, + } + + impl FeeEstimator for TestFeeEstimator { + fn get_est_sat_per_1000_weight(&self, _: ConfirmationTarget) -> u32 { + self.sat_per_kw + } + } + + #[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); + + assert_eq!(fee_estimator.bounded_sat_per_1000_weight(ConfirmationTarget::Background), 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); + + assert_eq!(fee_estimator.bounded_sat_per_1000_weight(ConfirmationTarget::Background), sat_per_kw); + } +}