_ Git - rust-lightning/blob - lightning/src/routing/scoring.rs

   1 // This file is Copyright its original authors, visible in version control
   2 // history.
   3 //
   4 // This file is licensed under the Apache License, Version 2.0 <LICENSE-APACHE
   5 // or http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   6 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your option.
   7 // You may not use this file except in accordance with one or both of these
   8 // licenses.
   9
  10 //! Utilities for scoring payment channels.
  11 //!
  12 //! [`Scorer`] may be given to [`find_route`] to score payment channels during path finding when a
  13 //! custom [`Score`] implementation is not needed.
  14 //!
  15 //! # Example
  16 //!
  17 //! ```
  18 //! # extern crate secp256k1;
  19 //! #
  20 //! # use lightning::routing::network_graph::NetworkGraph;
  21 //! # use lightning::routing::router::{RouteParameters, find_route};
  22 //! # use lightning::routing::scoring::{Scorer, ScoringParameters};
  23 //! # use lightning::util::logger::{Logger, Record};
  24 //! # use secp256k1::key::PublicKey;
  25 //! #
  26 //! # struct FakeLogger {};
  27 //! # impl Logger for FakeLogger {
  28 //! #     fn log(&self, record: &Record) { unimplemented!() }
  29 //! # }
  30 //! # fn find_scored_route(payer: PublicKey, params: RouteParameters, network_graph: NetworkGraph) {
  31 //! # let logger = FakeLogger {};
  32 //! #
  33 //! // Use the default channel penalties.
  34 //! let scorer = Scorer::default();
  35 //!
  36 //! // Or use custom channel penalties.
  37 //! let scorer = Scorer::new(ScoringParameters {
  38 //!     base_penalty_msat: 1000,
  39 //!     failure_penalty_msat: 2 * 1024 * 1000,
  40 //!     ..ScoringParameters::default()
  41 //! });
  42 //!
  43 //! let route = find_route(&payer, &params, &network_graph, None, &logger, &scorer);
  44 //! # }
  45 //! ```
  46 //!
  47 //! # Note
  48 //!
  49 //! Persisting when built with feature `no-std` and restoring without it, or vice versa, uses
  50 //! different types and thus is undefined.
  51 //!
  52 //! [`find_route`]: crate::routing::router::find_route
  53
  54 use ln::msgs::DecodeError;
  55 use routing::network_graph::NodeId;
  56 use routing::router::RouteHop;
  57 use util::ser::{Readable, Writeable, Writer};
  58
  59 use prelude::*;
  60 use core::cell::{RefCell, RefMut};
  61 use core::ops::DerefMut;
  62 use core::time::Duration;
  63 use io::{self, Read};
  64 use sync::{Mutex, MutexGuard};
  65
  66 /// We define Score ever-so-slightly differently based on whether we are being built for C bindings
  67 /// or not. For users, `LockableScore` must somehow be writeable to disk. For Rust users, this is
  68 /// no problem - you move a `Score` that implements `Writeable` into a `Mutex`, lock it, and now
  69 /// you have the original, concrete, `Score` type, which presumably implements `Writeable`.
  70 ///
  71 /// For C users, once you've moved the `Score` into a `LockableScore` all you have after locking it
  72 /// is an opaque trait object with an opaque pointer with no type info. Users could take the unsafe
  73 /// approach of blindly casting that opaque pointer to a concrete type and calling `Writeable` from
  74 /// there, but other languages downstream of the C bindings (e.g. Java) can't even do that.
  75 /// Instead, we really want `Score` and `LockableScore` to implement `Writeable` directly, which we
  76 /// do here by defining `Score` differently for `cfg(c_bindings)`.
  77 macro_rules! define_score { ($($supertrait: path)*) => {
  78 /// An interface used to score payment channels for path finding.
  79 ///
  80 ///     Scoring is in terms of fees willing to be paid in order to avoid routing through a channel.
  81 pub trait Score $(: $supertrait)* {
  82         /// Returns the fee in msats willing to be paid to avoid routing `send_amt_msat` through the
  83         /// given channel in the direction from `source` to `target`.
  84         ///
  85         /// The channel's capacity (less any other MPP parts which are also being considered for use in
  86         /// the same payment) is given by `channel_capacity_msat`. It may be guessed from various
  87         /// sources or assumed from no data at all.
  88         ///
  89         /// For hints provided in the invoice, we assume the channel has sufficient capacity to accept
  90         /// the invoice's full amount, and provide a `channel_capacity_msat` of `None`. In all other
  91         /// cases it is set to `Some`, even if we're guessing at the channel value.
  92         ///
  93         /// Your code should be overflow-safe through a `channel_capacity_msat` of 21 million BTC.
  94         fn channel_penalty_msat(&self, short_channel_id: u64, send_amt_msat: u64, capacity_msat: u64, source: &NodeId, target: &NodeId) -> u64;
  95
  96         /// Handles updating channel penalties after failing to route through a channel.
  97         fn payment_path_failed(&mut self, path: &[&RouteHop], short_channel_id: u64);
  98
  99         /// Handles updating channel penalties after successfully routing along a path.
 100         fn payment_path_successful(&mut self, path: &[&RouteHop]);
 101 }
 102
 103 impl<S: Score, T: DerefMut<Target=S> $(+ $supertrait)*> Score for T {
 104         fn channel_penalty_msat(&self, short_channel_id: u64, send_amt_msat: u64, capacity_msat: u64, source: &NodeId, target: &NodeId) -> u64 {
 105                 self.deref().channel_penalty_msat(short_channel_id, send_amt_msat, capacity_msat, source, target)
 106         }
 107
 108         fn payment_path_failed(&mut self, path: &[&RouteHop], short_channel_id: u64) {
 109                 self.deref_mut().payment_path_failed(path, short_channel_id)
 110         }
 111
 112         fn payment_path_successful(&mut self, path: &[&RouteHop]) {
 113                 self.deref_mut().payment_path_successful(path)
 114         }
 115 }
 116 } }
 117
 118 #[cfg(c_bindings)]
 119 define_score!(Writeable);
 120 #[cfg(not(c_bindings))]
 121 define_score!();
 122
 123 /// A scorer that is accessed under a lock.
 124 ///
 125 /// Needed so that calls to [`Score::channel_penalty_msat`] in [`find_route`] can be made while
 126 /// having shared ownership of a scorer but without requiring internal locking in [`Score`]
 127 /// implementations. Internal locking would be detrimental to route finding performance and could
 128 /// result in [`Score::channel_penalty_msat`] returning a different value for the same channel.
 129 ///
 130 /// [`find_route`]: crate::routing::router::find_route
 131 pub trait LockableScore<'a> {
 132         /// The locked [`Score`] type.
 133         type Locked: 'a + Score;
 134
 135         /// Returns the locked scorer.
 136         fn lock(&'a self) -> Self::Locked;
 137 }
 138
 139 /// (C-not exported)
 140 impl<'a, T: 'a + Score> LockableScore<'a> for Mutex<T> {
 141         type Locked = MutexGuard<'a, T>;
 142
 143         fn lock(&'a self) -> MutexGuard<'a, T> {
 144                 Mutex::lock(self).unwrap()
 145         }
 146 }
 147
 148 impl<'a, T: 'a + Score> LockableScore<'a> for RefCell<T> {
 149         type Locked = RefMut<'a, T>;
 150
 151         fn lock(&'a self) -> RefMut<'a, T> {
 152                 self.borrow_mut()
 153         }
 154 }
 155
 156 #[cfg(c_bindings)]
 157 /// A concrete implementation of [`LockableScore`] which supports multi-threading.
 158 pub struct MultiThreadedLockableScore<S: Score> {
 159         score: Mutex<S>,
 160 }
 161 #[cfg(c_bindings)]
 162 /// (C-not exported)
 163 impl<'a, T: Score + 'a> LockableScore<'a> for MultiThreadedLockableScore<T> {
 164         type Locked = MutexGuard<'a, T>;
 165
 166         fn lock(&'a self) -> MutexGuard<'a, T> {
 167                 Mutex::lock(&self.score).unwrap()
 168         }
 169 }
 170
 171 #[cfg(c_bindings)]
 172 impl<T: Score> MultiThreadedLockableScore<T> {
 173         /// Creates a new [`MultiThreadedLockableScore`] given an underlying [`Score`].
 174         pub fn new(score: T) -> Self {
 175                 MultiThreadedLockableScore { score: Mutex::new(score) }
 176         }
 177 }
 178
 179 #[cfg(c_bindings)]
 180 /// (C-not exported)
 181 impl<'a, T: Writeable> Writeable for RefMut<'a, T> {
 182         fn write<W: Writer>(&self, writer: &mut W) -> Result<(), io::Error> {
 183                 T::write(&**self, writer)
 184         }
 185 }
 186
 187 #[cfg(c_bindings)]
 188 /// (C-not exported)
 189 impl<'a, S: Writeable> Writeable for MutexGuard<'a, S> {
 190         fn write<W: Writer>(&self, writer: &mut W) -> Result<(), io::Error> {
 191                 S::write(&**self, writer)
 192         }
 193 }
 194
 195 /// [`Score`] implementation that provides reasonable default behavior.
 196 ///
 197 /// Used to apply a fixed penalty to each channel, thus avoiding long paths when shorter paths with
 198 /// slightly higher fees are available. Will further penalize channels that fail to relay payments.
 199 ///
 200 /// See [module-level documentation] for usage.
 201 ///
 202 /// [module-level documentation]: crate::routing::scoring
 203 #[cfg(not(feature = "no-std"))]
 204 pub type Scorer = ScorerUsingTime::<std::time::Instant>;
 205 /// [`Score`] implementation that provides reasonable default behavior.
 206 ///
 207 /// Used to apply a fixed penalty to each channel, thus avoiding long paths when shorter paths with
 208 /// slightly higher fees are available. Will further penalize channels that fail to relay payments.
 209 ///
 210 /// See [module-level documentation] for usage and [`ScoringParameters`] for customization.
 211 ///
 212 /// [module-level documentation]: crate::routing::scoring
 213 #[cfg(feature = "no-std")]
 214 pub type Scorer = ScorerUsingTime::<time::Eternity>;
 215
 216 // Note that ideally we'd hide ScorerUsingTime from public view by sealing it as well, but rustdoc
 217 // doesn't handle this well - instead exposing a `Scorer` which has no trait implementation(s) or
 218 // methods at all.
 219
 220 /// [`Score`] implementation.
 221 ///
 222 /// See [`Scorer`] for details.
 223 ///
 224 /// # Note
 225 ///
 226 /// Mixing the `no-std` feature between serialization and deserialization results in undefined
 227 /// behavior.
 228 ///
 229 /// (C-not exported) generally all users should use the [`Scorer`] type alias.
 230 pub struct ScorerUsingTime<T: Time> {
 231         params: ScoringParameters,
 232         // TODO: Remove entries of closed channels.
 233         channel_failures: HashMap<u64, ChannelFailure<T>>,
 234 }
 235
 236 /// Parameters for configuring [`Scorer`].
 237 pub struct ScoringParameters {
 238         /// A fixed penalty in msats to apply to each channel.
 239         ///
 240         /// Default value: 500 msat
 241         pub base_penalty_msat: u64,
 242
 243         /// A penalty in msats to apply to a channel upon failing to relay a payment.
 244         ///
 245         /// This accumulates for each failure but may be reduced over time based on
 246         /// [`failure_penalty_half_life`] or when successfully routing through a channel.
 247         ///
 248         /// Default value: 1,024,000 msat
 249         ///
 250         /// [`failure_penalty_half_life`]: Self::failure_penalty_half_life
 251         pub failure_penalty_msat: u64,
 252
 253         /// When the amount being sent over a channel is this many 1024ths of the total channel
 254         /// capacity, we begin applying [`overuse_penalty_msat_per_1024th`].
 255         ///
 256         /// Default value: 128 1024ths (i.e. begin penalizing when an HTLC uses 1/8th of a channel)
 257         ///
 258         /// [`overuse_penalty_msat_per_1024th`]: Self::overuse_penalty_msat_per_1024th
 259         pub overuse_penalty_start_1024th: u16,
 260
 261         /// A penalty applied, per whole 1024ths of the channel capacity which the amount being sent
 262         /// over the channel exceeds [`overuse_penalty_start_1024th`] by.
 263         ///
 264         /// Default value: 20 msat (i.e. 2560 msat penalty to use 1/4th of a channel, 7680 msat penalty
 265         ///                to use half a channel, and 12,560 msat penalty to use 3/4ths of a channel)
 266         ///
 267         /// [`overuse_penalty_start_1024th`]: Self::overuse_penalty_start_1024th
 268         pub overuse_penalty_msat_per_1024th: u64,
 269
 270         /// The time required to elapse before any accumulated [`failure_penalty_msat`] penalties are
 271         /// cut in half.
 272         ///
 273         /// Successfully routing through a channel will immediately cut the penalty in half as well.
 274         ///
 275         /// # Note
 276         ///
 277         /// When built with the `no-std` feature, time will never elapse. Therefore, this penalty will
 278         /// never decay.
 279         ///
 280         /// [`failure_penalty_msat`]: Self::failure_penalty_msat
 281         pub failure_penalty_half_life: Duration,
 282 }
 283
 284 impl_writeable_tlv_based!(ScoringParameters, {
 285         (0, base_penalty_msat, required),
 286         (1, overuse_penalty_start_1024th, (default_value, 128)),
 287         (2, failure_penalty_msat, required),
 288         (3, overuse_penalty_msat_per_1024th, (default_value, 20)),
 289         (4, failure_penalty_half_life, required),
 290 });
 291
 292 /// Accounting for penalties against a channel for failing to relay any payments.
 293 ///
 294 /// Penalties decay over time, though accumulate as more failures occur.
 295 struct ChannelFailure<T: Time> {
 296         /// Accumulated penalty in msats for the channel as of `last_updated`.
 297         undecayed_penalty_msat: u64,
 298
 299         /// Last time the channel either failed to route or successfully routed a payment. Used to decay
 300         /// `undecayed_penalty_msat`.
 301         last_updated: T,
 302 }
 303
 304 impl<T: Time> ScorerUsingTime<T> {
 305         /// Creates a new scorer using the given scoring parameters.
 306         pub fn new(params: ScoringParameters) -> Self {
 307                 Self {
 308                         params,
 309                         channel_failures: HashMap::new(),
 310                 }
 311         }
 312
 313         /// Creates a new scorer using `penalty_msat` as a fixed channel penalty.
 314         #[cfg(any(test, feature = "fuzztarget", feature = "_test_utils"))]
 315         pub fn with_fixed_penalty(penalty_msat: u64) -> Self {
 316                 Self::new(ScoringParameters {
 317                         base_penalty_msat: penalty_msat,
 318                         failure_penalty_msat: 0,
 319                         failure_penalty_half_life: Duration::from_secs(0),
 320                         overuse_penalty_start_1024th: 1024,
 321                         overuse_penalty_msat_per_1024th: 0,
 322                 })
 323         }
 324 }
 325
 326 impl<T: Time> ChannelFailure<T> {
 327         fn new(failure_penalty_msat: u64) -> Self {
 328                 Self {
 329                         undecayed_penalty_msat: failure_penalty_msat,
 330                         last_updated: T::now(),
 331                 }
 332         }
 333
 334         fn add_penalty(&mut self, failure_penalty_msat: u64, half_life: Duration) {
 335                 self.undecayed_penalty_msat = self.decayed_penalty_msat(half_life) + failure_penalty_msat;
 336                 self.last_updated = T::now();
 337         }
 338
 339         fn reduce_penalty(&mut self, half_life: Duration) {
 340                 self.undecayed_penalty_msat = self.decayed_penalty_msat(half_life) >> 1;
 341                 self.last_updated = T::now();
 342         }
 343
 344         fn decayed_penalty_msat(&self, half_life: Duration) -> u64 {
 345                 self.last_updated.elapsed().as_secs()
 346                         .checked_div(half_life.as_secs())
 347                         .and_then(|decays| self.undecayed_penalty_msat.checked_shr(decays as u32))
 348                         .unwrap_or(0)
 349         }
 350 }
 351
 352 impl<T: Time> Default for ScorerUsingTime<T> {
 353         fn default() -> Self {
 354                 Self::new(ScoringParameters::default())
 355         }
 356 }
 357
 358 impl Default for ScoringParameters {
 359         fn default() -> Self {
 360                 Self {
 361                         base_penalty_msat: 500,
 362                         failure_penalty_msat: 1024 * 1000,
 363                         failure_penalty_half_life: Duration::from_secs(3600),
 364                         overuse_penalty_start_1024th: 1024 / 8,
 365                         overuse_penalty_msat_per_1024th: 20,
 366                 }
 367         }
 368 }
 369
 370 impl<T: Time> Score for ScorerUsingTime<T> {
 371         fn channel_penalty_msat(
 372                 &self, short_channel_id: u64, send_amt_msat: u64, capacity_msat: u64, _source: &NodeId, _target: &NodeId
 373         ) -> u64 {
 374                 let failure_penalty_msat = self.channel_failures
 375                         .get(&short_channel_id)
 376                         .map_or(0, |value| value.decayed_penalty_msat(self.params.failure_penalty_half_life));
 377
 378                 let mut penalty_msat = self.params.base_penalty_msat + failure_penalty_msat;
 379                 let send_1024ths = send_amt_msat.checked_mul(1024).unwrap_or(u64::max_value()) / capacity_msat;
 380                 if send_1024ths > self.params.overuse_penalty_start_1024th as u64 {
 381                         penalty_msat = penalty_msat.checked_add(
 382                                         (send_1024ths - self.params.overuse_penalty_start_1024th as u64)
 383                                         .checked_mul(self.params.overuse_penalty_msat_per_1024th).unwrap_or(u64::max_value()))
 384                                 .unwrap_or(u64::max_value());
 385                 }
 386
 387                 penalty_msat
 388         }
 389
 390         fn payment_path_failed(&mut self, _path: &[&RouteHop], short_channel_id: u64) {
 391                 let failure_penalty_msat = self.params.failure_penalty_msat;
 392                 let half_life = self.params.failure_penalty_half_life;
 393                 self.channel_failures
 394                         .entry(short_channel_id)
 395                         .and_modify(|failure| failure.add_penalty(failure_penalty_msat, half_life))
 396                         .or_insert_with(|| ChannelFailure::new(failure_penalty_msat));
 397         }
 398
 399         fn payment_path_successful(&mut self, path: &[&RouteHop]) {
 400                 let half_life = self.params.failure_penalty_half_life;
 401                 for hop in path.iter() {
 402                         self.channel_failures
 403                                 .entry(hop.short_channel_id)
 404                                 .and_modify(|failure| failure.reduce_penalty(half_life));
 405                 }
 406         }
 407 }
 408
 409 impl<T: Time> Writeable for ScorerUsingTime<T> {
 410         #[inline]
 411         fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
 412                 self.params.write(w)?;
 413                 self.channel_failures.write(w)?;
 414                 write_tlv_fields!(w, {});
 415                 Ok(())
 416         }
 417 }
 418
 419 impl<T: Time> Readable for ScorerUsingTime<T> {
 420         #[inline]
 421         fn read<R: Read>(r: &mut R) -> Result<Self, DecodeError> {
 422                 let res = Ok(Self {
 423                         params: Readable::read(r)?,
 424                         channel_failures: Readable::read(r)?,
 425                 });
 426                 read_tlv_fields!(r, {});
 427                 res
 428         }
 429 }
 430
 431 impl<T: Time> Writeable for ChannelFailure<T> {
 432         #[inline]
 433         fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
 434                 let duration_since_epoch = T::duration_since_epoch() - self.last_updated.elapsed();
 435                 write_tlv_fields!(w, {
 436                         (0, self.undecayed_penalty_msat, required),
 437                         (2, duration_since_epoch, required),
 438                 });
 439                 Ok(())
 440         }
 441 }
 442
 443 impl<T: Time> Readable for ChannelFailure<T> {
 444         #[inline]
 445         fn read<R: Read>(r: &mut R) -> Result<Self, DecodeError> {
 446                 let mut undecayed_penalty_msat = 0;
 447                 let mut duration_since_epoch = Duration::from_secs(0);
 448                 read_tlv_fields!(r, {
 449                         (0, undecayed_penalty_msat, required),
 450                         (2, duration_since_epoch, required),
 451                 });
 452                 Ok(Self {
 453                         undecayed_penalty_msat,
 454                         last_updated: T::now() - (T::duration_since_epoch() - duration_since_epoch),
 455                 })
 456         }
 457 }
 458
 459 pub(crate) mod time {
 460         use core::ops::Sub;
 461         use core::time::Duration;
 462         /// A measurement of time.
 463         pub trait Time: Sub<Duration, Output = Self> where Self: Sized {
 464                 /// Returns an instance corresponding to the current moment.
 465                 fn now() -> Self;
 466
 467                 /// Returns the amount of time elapsed since `self` was created.
 468                 fn elapsed(&self) -> Duration;
 469
 470                 /// Returns the amount of time passed since the beginning of [`Time`].
 471                 ///
 472                 /// Used during (de-)serialization.
 473                 fn duration_since_epoch() -> Duration;
 474         }
 475
 476         /// A state in which time has no meaning.
 477         #[derive(Debug, PartialEq, Eq)]
 478         pub struct Eternity;
 479
 480         #[cfg(not(feature = "no-std"))]
 481         impl Time for std::time::Instant {
 482                 fn now() -> Self {
 483                         std::time::Instant::now()
 484                 }
 485
 486                 fn duration_since_epoch() -> Duration {
 487                         use std::time::SystemTime;
 488                         SystemTime::now().duration_since(SystemTime::UNIX_EPOCH).unwrap()
 489                 }
 490
 491                 fn elapsed(&self) -> Duration {
 492                         std::time::Instant::elapsed(self)
 493                 }
 494         }
 495
 496         impl Time for Eternity {
 497                 fn now() -> Self {
 498                         Self
 499                 }
 500
 501                 fn duration_since_epoch() -> Duration {
 502                         Duration::from_secs(0)
 503                 }
 504
 505                 fn elapsed(&self) -> Duration {
 506                         Duration::from_secs(0)
 507                 }
 508         }
 509
 510         impl Sub<Duration> for Eternity {
 511                 type Output = Self;
 512
 513                 fn sub(self, _other: Duration) -> Self {
 514                         self
 515                 }
 516         }
 517 }
 518
 519 pub(crate) use self::time::Time;
 520
 521 #[cfg(test)]
 522 mod tests {
 523         use super::{ScoringParameters, ScorerUsingTime, Time};
 524         use super::time::Eternity;
 525
 526         use ln::features::{ChannelFeatures, NodeFeatures};
 527         use routing::scoring::Score;
 528         use routing::network_graph::NodeId;
 529         use routing::router::RouteHop;
 530         use util::ser::{Readable, Writeable};
 531
 532         use bitcoin::secp256k1::PublicKey;
 533         use core::cell::Cell;
 534         use core::ops::Sub;
 535         use core::time::Duration;
 536         use io;
 537
 538         /// Time that can be advanced manually in tests.
 539         #[derive(Debug, PartialEq, Eq)]
 540         struct SinceEpoch(Duration);
 541
 542         impl SinceEpoch {
 543                 thread_local! {
 544                         static ELAPSED: Cell<Duration> = core::cell::Cell::new(Duration::from_secs(0));
 545                 }
 546
 547                 fn advance(duration: Duration) {
 548                         Self::ELAPSED.with(|elapsed| elapsed.set(elapsed.get() + duration))
 549                 }
 550         }
 551
 552         impl Time for SinceEpoch {
 553                 fn now() -> Self {
 554                         Self(Self::duration_since_epoch())
 555                 }
 556
 557                 fn duration_since_epoch() -> Duration {
 558                         Self::ELAPSED.with(|elapsed| elapsed.get())
 559                 }
 560
 561                 fn elapsed(&self) -> Duration {
 562                         Self::duration_since_epoch() - self.0
 563                 }
 564         }
 565
 566         impl Sub<Duration> for SinceEpoch {
 567                 type Output = Self;
 568
 569                 fn sub(self, other: Duration) -> Self {
 570                         Self(self.0 - other)
 571                 }
 572         }
 573
 574         #[test]
 575         fn time_passes_when_advanced() {
 576                 let now = SinceEpoch::now();
 577                 assert_eq!(now.elapsed(), Duration::from_secs(0));
 578
 579                 SinceEpoch::advance(Duration::from_secs(1));
 580                 SinceEpoch::advance(Duration::from_secs(1));
 581
 582                 let elapsed = now.elapsed();
 583                 let later = SinceEpoch::now();
 584
 585                 assert_eq!(elapsed, Duration::from_secs(2));
 586                 assert_eq!(later - elapsed, now);
 587         }
 588
 589         #[test]
 590         fn time_never_passes_in_an_eternity() {
 591                 let now = Eternity::now();
 592                 let elapsed = now.elapsed();
 593                 let later = Eternity::now();
 594
 595                 assert_eq!(now.elapsed(), Duration::from_secs(0));
 596                 assert_eq!(later - elapsed, now);
 597         }
 598
 599         /// A scorer for testing with time that can be manually advanced.
 600         type Scorer = ScorerUsingTime::<SinceEpoch>;
 601
 602         fn source_node_id() -> NodeId {
 603                 NodeId::from_pubkey(&PublicKey::from_slice(&hex::decode("02eec7245d6b7d2ccb30380bfbe2a3648cd7a942653f5aa340edcea1f283686619").unwrap()[..]).unwrap())
 604         }
 605
 606         fn target_node_id() -> NodeId {
 607                 NodeId::from_pubkey(&PublicKey::from_slice(&hex::decode("0324653eac434488002cc06bbfb7f10fe18991e35f9fe4302dbea6d2353dc0ab1c").unwrap()[..]).unwrap())
 608         }
 609
 610         #[test]
 611         fn penalizes_without_channel_failures() {
 612                 let scorer = Scorer::new(ScoringParameters {
 613                         base_penalty_msat: 1_000,
 614                         failure_penalty_msat: 512,
 615                         failure_penalty_half_life: Duration::from_secs(1),
 616                         overuse_penalty_start_1024th: 1024,
 617                         overuse_penalty_msat_per_1024th: 0,
 618                 });
 619                 let source = source_node_id();
 620                 let target = target_node_id();
 621                 assert_eq!(scorer.channel_penalty_msat(42, 1, 1, &source, &target), 1_000);
 622
 623                 SinceEpoch::advance(Duration::from_secs(1));
 624                 assert_eq!(scorer.channel_penalty_msat(42, 1, 1, &source, &target), 1_000);
 625         }
 626
 627         #[test]
 628         fn accumulates_channel_failure_penalties() {
 629                 let mut scorer = Scorer::new(ScoringParameters {
 630                         base_penalty_msat: 1_000,
 631                         failure_penalty_msat: 64,
 632                         failure_penalty_half_life: Duration::from_secs(10),
 633                         overuse_penalty_start_1024th: 1024,
 634                         overuse_penalty_msat_per_1024th: 0,
 635                 });
 636                 let source = source_node_id();
 637                 let target = target_node_id();
 638                 assert_eq!(scorer.channel_penalty_msat(42, 1, 1, &source, &target), 1_000);
 639
 640                 scorer.payment_path_failed(&[], 42);
 641                 assert_eq!(scorer.channel_penalty_msat(42, 1, 1, &source, &target), 1_064);
 642
 643                 scorer.payment_path_failed(&[], 42);
 644                 assert_eq!(scorer.channel_penalty_msat(42, 1, 1, &source, &target), 1_128);
 645
 646                 scorer.payment_path_failed(&[], 42);
 647                 assert_eq!(scorer.channel_penalty_msat(42, 1, 1, &source, &target), 1_192);
 648         }
 649
 650         #[test]
 651         fn decays_channel_failure_penalties_over_time() {
 652                 let mut scorer = Scorer::new(ScoringParameters {
 653                         base_penalty_msat: 1_000,
 654                         failure_penalty_msat: 512,
 655                         failure_penalty_half_life: Duration::from_secs(10),
 656                         overuse_penalty_start_1024th: 1024,
 657                         overuse_penalty_msat_per_1024th: 0,
 658                 });
 659                 let source = source_node_id();
 660                 let target = target_node_id();
 661                 assert_eq!(scorer.channel_penalty_msat(42, 1, 1, &source, &target), 1_000);
 662
 663                 scorer.payment_path_failed(&[], 42);
 664                 assert_eq!(scorer.channel_penalty_msat(42, 1, 1, &source, &target), 1_512);
 665
 666                 SinceEpoch::advance(Duration::from_secs(9));
 667                 assert_eq!(scorer.channel_penalty_msat(42, 1, 1, &source, &target), 1_512);
 668
 669                 SinceEpoch::advance(Duration::from_secs(1));
 670                 assert_eq!(scorer.channel_penalty_msat(42, 1, 1, &source, &target), 1_256);
 671
 672                 SinceEpoch::advance(Duration::from_secs(10 * 8));
 673                 assert_eq!(scorer.channel_penalty_msat(42, 1, 1, &source, &target), 1_001);
 674
 675                 SinceEpoch::advance(Duration::from_secs(10));
 676                 assert_eq!(scorer.channel_penalty_msat(42, 1, 1, &source, &target), 1_000);
 677
 678                 SinceEpoch::advance(Duration::from_secs(10));
 679                 assert_eq!(scorer.channel_penalty_msat(42, 1, 1, &source, &target), 1_000);
 680         }
 681
 682         #[test]
 683         fn decays_channel_failure_penalties_without_shift_overflow() {
 684                 let mut scorer = Scorer::new(ScoringParameters {
 685                         base_penalty_msat: 1_000,
 686                         failure_penalty_msat: 512,
 687                         failure_penalty_half_life: Duration::from_secs(10),
 688                         overuse_penalty_start_1024th: 1024,
 689                         overuse_penalty_msat_per_1024th: 0,
 690                 });
 691                 let source = source_node_id();
 692                 let target = target_node_id();
 693                 assert_eq!(scorer.channel_penalty_msat(42, 1, 1, &source, &target), 1_000);
 694
 695                 scorer.payment_path_failed(&[], 42);
 696                 assert_eq!(scorer.channel_penalty_msat(42, 1, 1, &source, &target), 1_512);
 697
 698                 // An unchecked right shift 64 bits or more in ChannelFailure::decayed_penalty_msat would
 699                 // cause an overflow.
 700                 SinceEpoch::advance(Duration::from_secs(10 * 64));
 701                 assert_eq!(scorer.channel_penalty_msat(42, 1, 1, &source, &target), 1_000);
 702
 703                 SinceEpoch::advance(Duration::from_secs(10));
 704                 assert_eq!(scorer.channel_penalty_msat(42, 1, 1, &source, &target), 1_000);
 705         }
 706
 707         #[test]
 708         fn accumulates_channel_failure_penalties_after_decay() {
 709                 let mut scorer = Scorer::new(ScoringParameters {
 710                         base_penalty_msat: 1_000,
 711                         failure_penalty_msat: 512,
 712                         failure_penalty_half_life: Duration::from_secs(10),
 713                         overuse_penalty_start_1024th: 1024,
 714                         overuse_penalty_msat_per_1024th: 0,
 715                 });
 716                 let source = source_node_id();
 717                 let target = target_node_id();
 718                 assert_eq!(scorer.channel_penalty_msat(42, 1, 1, &source, &target), 1_000);
 719
 720                 scorer.payment_path_failed(&[], 42);
 721                 assert_eq!(scorer.channel_penalty_msat(42, 1, 1, &source, &target), 1_512);
 722
 723                 SinceEpoch::advance(Duration::from_secs(10));
 724                 assert_eq!(scorer.channel_penalty_msat(42, 1, 1, &source, &target), 1_256);
 725
 726                 scorer.payment_path_failed(&[], 42);
 727                 assert_eq!(scorer.channel_penalty_msat(42, 1, 1, &source, &target), 1_768);
 728
 729                 SinceEpoch::advance(Duration::from_secs(10));
 730                 assert_eq!(scorer.channel_penalty_msat(42, 1, 1, &source, &target), 1_384);
 731         }
 732
 733         #[test]
 734         fn reduces_channel_failure_penalties_after_success() {
 735                 let mut scorer = Scorer::new(ScoringParameters {
 736                         base_penalty_msat: 1_000,
 737                         failure_penalty_msat: 512,
 738                         failure_penalty_half_life: Duration::from_secs(10),
 739                         overuse_penalty_start_1024th: 1024,
 740                         overuse_penalty_msat_per_1024th: 0,
 741                 });
 742                 let source = source_node_id();
 743                 let target = target_node_id();
 744                 assert_eq!(scorer.channel_penalty_msat(42, 1, 1, &source, &target), 1_000);
 745
 746                 scorer.payment_path_failed(&[], 42);
 747                 assert_eq!(scorer.channel_penalty_msat(42, 1, 1, &source, &target), 1_512);
 748
 749                 SinceEpoch::advance(Duration::from_secs(10));
 750                 assert_eq!(scorer.channel_penalty_msat(42, 1, 1, &source, &target), 1_256);
 751
 752                 let hop = RouteHop {
 753                         pubkey: PublicKey::from_slice(target.as_slice()).unwrap(),
 754                         node_features: NodeFeatures::known(),
 755                         short_channel_id: 42,
 756                         channel_features: ChannelFeatures::known(),
 757                         fee_msat: 1,
 758                         cltv_expiry_delta: 18,
 759                 };
 760                 scorer.payment_path_successful(&[&hop]);
 761                 assert_eq!(scorer.channel_penalty_msat(42, 1, 1, &source, &target), 1_128);
 762
 763                 SinceEpoch::advance(Duration::from_secs(10));
 764                 assert_eq!(scorer.channel_penalty_msat(42, 1, 1, &source, &target), 1_064);
 765         }
 766
 767         #[test]
 768         fn restores_persisted_channel_failure_penalties() {
 769                 let mut scorer = Scorer::new(ScoringParameters {
 770                         base_penalty_msat: 1_000,
 771                         failure_penalty_msat: 512,
 772                         failure_penalty_half_life: Duration::from_secs(10),
 773                         overuse_penalty_start_1024th: 1024,
 774                         overuse_penalty_msat_per_1024th: 0,
 775                 });
 776                 let source = source_node_id();
 777                 let target = target_node_id();
 778
 779                 scorer.payment_path_failed(&[], 42);
 780                 assert_eq!(scorer.channel_penalty_msat(42, 1, 1, &source, &target), 1_512);
 781
 782                 SinceEpoch::advance(Duration::from_secs(10));
 783                 assert_eq!(scorer.channel_penalty_msat(42, 1, 1, &source, &target), 1_256);
 784
 785                 scorer.payment_path_failed(&[], 43);
 786                 assert_eq!(scorer.channel_penalty_msat(43, 1, 1, &source, &target), 1_512);
 787
 788                 let mut serialized_scorer = Vec::new();
 789                 scorer.write(&mut serialized_scorer).unwrap();
 790
 791                 let deserialized_scorer = <Scorer>::read(&mut io::Cursor::new(&serialized_scorer)).unwrap();
 792                 assert_eq!(deserialized_scorer.channel_penalty_msat(42, 1, 1, &source, &target), 1_256);
 793                 assert_eq!(deserialized_scorer.channel_penalty_msat(43, 1, 1, &source, &target), 1_512);
 794         }
 795
 796         #[test]
 797         fn decays_persisted_channel_failure_penalties() {
 798                 let mut scorer = Scorer::new(ScoringParameters {
 799                         base_penalty_msat: 1_000,
 800                         failure_penalty_msat: 512,
 801                         failure_penalty_half_life: Duration::from_secs(10),
 802                         overuse_penalty_start_1024th: 1024,
 803                         overuse_penalty_msat_per_1024th: 0,
 804                 });
 805                 let source = source_node_id();
 806                 let target = target_node_id();
 807
 808                 scorer.payment_path_failed(&[], 42);
 809                 assert_eq!(scorer.channel_penalty_msat(42, 1, 1, &source, &target), 1_512);
 810
 811                 let mut serialized_scorer = Vec::new();
 812                 scorer.write(&mut serialized_scorer).unwrap();
 813
 814                 SinceEpoch::advance(Duration::from_secs(10));
 815
 816                 let deserialized_scorer = <Scorer>::read(&mut io::Cursor::new(&serialized_scorer)).unwrap();
 817                 assert_eq!(deserialized_scorer.channel_penalty_msat(42, 1, 1, &source, &target), 1_256);
 818
 819                 SinceEpoch::advance(Duration::from_secs(10));
 820                 assert_eq!(deserialized_scorer.channel_penalty_msat(42, 1, 1, &source, &target), 1_128);
 821         }
 822
 823         #[test]
 824         fn charges_per_1024th_penalty() {
 825                 let scorer = Scorer::new(ScoringParameters {
 826                         base_penalty_msat: 0,
 827                         failure_penalty_msat: 0,
 828                         failure_penalty_half_life: Duration::from_secs(0),
 829                         overuse_penalty_start_1024th: 256,
 830                         overuse_penalty_msat_per_1024th: 100,
 831                 });
 832                 let source = source_node_id();
 833                 let target = target_node_id();
 834
 835                 assert_eq!(scorer.channel_penalty_msat(42, 1_000, 1_024_000, &source, &target), 0);
 836                 assert_eq!(scorer.channel_penalty_msat(42, 256_999, 1_024_000, &source, &target), 0);
 837                 assert_eq!(scorer.channel_penalty_msat(42, 257_000, 1_024_000, &source, &target), 100);
 838                 assert_eq!(scorer.channel_penalty_msat(42, 258_000, 1_024_000, &source, &target), 200);
 839                 assert_eq!(scorer.channel_penalty_msat(42, 512_000, 1_024_000, &source, &target), 256 * 100);
 840         }
 841 }