_ 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, channel_capacity_msat: Option<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, channel_capacity_msat: Option<u64>, source: &NodeId, target: &NodeId) -> u64 {
 105                 self.deref().channel_penalty_msat(short_channel_id, send_amt_msat, channel_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 /// (C-not exported)
 173 impl<'a, T: Writeable> Writeable for RefMut<'a, T> {
 174         fn write<W: Writer>(&self, writer: &mut W) -> Result<(), io::Error> {
 175                 T::write(&**self, writer)
 176         }
 177 }
 178
 179 #[cfg(c_bindings)]
 180 /// (C-not exported)
 181 impl<'a, S: Writeable> Writeable for MutexGuard<'a, S> {
 182         fn write<W: Writer>(&self, writer: &mut W) -> Result<(), io::Error> {
 183                 S::write(&**self, writer)
 184         }
 185 }
 186
 187 /// [`Score`] implementation that provides reasonable default behavior.
 188 ///
 189 /// Used to apply a fixed penalty to each channel, thus avoiding long paths when shorter paths with
 190 /// slightly higher fees are available. Will further penalize channels that fail to relay payments.
 191 ///
 192 /// See [module-level documentation] for usage.
 193 ///
 194 /// [module-level documentation]: crate::routing::scoring
 195 #[cfg(not(feature = "no-std"))]
 196 pub type Scorer = ScorerUsingTime::<std::time::Instant>;
 197 /// [`Score`] implementation that provides reasonable default behavior.
 198 ///
 199 /// Used to apply a fixed penalty to each channel, thus avoiding long paths when shorter paths with
 200 /// slightly higher fees are available. Will further penalize channels that fail to relay payments.
 201 ///
 202 /// See [module-level documentation] for usage and [`ScoringParameters`] for customization.
 203 ///
 204 /// [module-level documentation]: crate::routing::scoring
 205 #[cfg(feature = "no-std")]
 206 pub type Scorer = ScorerUsingTime::<time::Eternity>;
 207
 208 // Note that ideally we'd hide ScorerUsingTime from public view by sealing it as well, but rustdoc
 209 // doesn't handle this well - instead exposing a `Scorer` which has no trait implementation(s) or
 210 // methods at all.
 211
 212 /// [`Score`] implementation.
 213 ///
 214 /// See [`Scorer`] for details.
 215 ///
 216 /// # Note
 217 ///
 218 /// Mixing the `no-std` feature between serialization and deserialization results in undefined
 219 /// behavior.
 220 ///
 221 /// (C-not exported) generally all users should use the [`Scorer`] type alias.
 222 pub struct ScorerUsingTime<T: Time> {
 223         params: ScoringParameters,
 224         // TODO: Remove entries of closed channels.
 225         channel_failures: HashMap<u64, ChannelFailure<T>>,
 226 }
 227
 228 /// Parameters for configuring [`Scorer`].
 229 pub struct ScoringParameters {
 230         /// A fixed penalty in msats to apply to each channel.
 231         ///
 232         /// Default value: 500 msat
 233         pub base_penalty_msat: u64,
 234
 235         /// A penalty in msats to apply to a channel upon failing to relay a payment.
 236         ///
 237         /// This accumulates for each failure but may be reduced over time based on
 238         /// [`failure_penalty_half_life`] or when successfully routing through a channel.
 239         ///
 240         /// Default value: 1,024,000 msat
 241         ///
 242         /// [`failure_penalty_half_life`]: Self::failure_penalty_half_life
 243         pub failure_penalty_msat: u64,
 244
 245         /// When the amount being sent over a channel is this many 1024ths of the total channel
 246         /// capacity, we begin applying [`overuse_penalty_msat_per_1024th`].
 247         ///
 248         /// Default value: 128 1024ths (i.e. begin penalizing when an HTLC uses 1/8th of a channel)
 249         ///
 250         /// [`overuse_penalty_msat_per_1024th`]: Self::overuse_penalty_msat_per_1024th
 251         pub overuse_penalty_start_1024th: u16,
 252
 253         /// A penalty applied, per whole 1024ths of the channel capacity which the amount being sent
 254         /// over the channel exceeds [`overuse_penalty_start_1024th`] by.
 255         ///
 256         /// Default value: 20 msat (i.e. 2560 msat penalty to use 1/4th of a channel, 7680 msat penalty
 257         ///                to use half a channel, and 12,560 msat penalty to use 3/4ths of a channel)
 258         ///
 259         /// [`overuse_penalty_start_1024th`]: Self::overuse_penalty_start_1024th
 260         pub overuse_penalty_msat_per_1024th: u64,
 261
 262         /// The time required to elapse before any accumulated [`failure_penalty_msat`] penalties are
 263         /// cut in half.
 264         ///
 265         /// Successfully routing through a channel will immediately cut the penalty in half as well.
 266         ///
 267         /// # Note
 268         ///
 269         /// When built with the `no-std` feature, time will never elapse. Therefore, this penalty will
 270         /// never decay.
 271         ///
 272         /// [`failure_penalty_msat`]: Self::failure_penalty_msat
 273         pub failure_penalty_half_life: Duration,
 274 }
 275
 276 impl_writeable_tlv_based!(ScoringParameters, {
 277         (0, base_penalty_msat, required),
 278         (1, overuse_penalty_start_1024th, (default_value, 128)),
 279         (2, failure_penalty_msat, required),
 280         (3, overuse_penalty_msat_per_1024th, (default_value, 20)),
 281         (4, failure_penalty_half_life, required),
 282 });
 283
 284 /// Accounting for penalties against a channel for failing to relay any payments.
 285 ///
 286 /// Penalties decay over time, though accumulate as more failures occur.
 287 struct ChannelFailure<T: Time> {
 288         /// Accumulated penalty in msats for the channel as of `last_updated`.
 289         undecayed_penalty_msat: u64,
 290
 291         /// Last time the channel either failed to route or successfully routed a payment. Used to decay
 292         /// `undecayed_penalty_msat`.
 293         last_updated: T,
 294 }
 295
 296 impl<T: Time> ScorerUsingTime<T> {
 297         /// Creates a new scorer using the given scoring parameters.
 298         pub fn new(params: ScoringParameters) -> Self {
 299                 Self {
 300                         params,
 301                         channel_failures: HashMap::new(),
 302                 }
 303         }
 304
 305         /// Creates a new scorer using `penalty_msat` as a fixed channel penalty.
 306         #[cfg(any(test, feature = "fuzztarget", feature = "_test_utils"))]
 307         pub fn with_fixed_penalty(penalty_msat: u64) -> Self {
 308                 Self::new(ScoringParameters {
 309                         base_penalty_msat: penalty_msat,
 310                         failure_penalty_msat: 0,
 311                         failure_penalty_half_life: Duration::from_secs(0),
 312                         overuse_penalty_start_1024th: 1024,
 313                         overuse_penalty_msat_per_1024th: 0,
 314                 })
 315         }
 316 }
 317
 318 impl<T: Time> ChannelFailure<T> {
 319         fn new(failure_penalty_msat: u64) -> Self {
 320                 Self {
 321                         undecayed_penalty_msat: failure_penalty_msat,
 322                         last_updated: T::now(),
 323                 }
 324         }
 325
 326         fn add_penalty(&mut self, failure_penalty_msat: u64, half_life: Duration) {
 327                 self.undecayed_penalty_msat = self.decayed_penalty_msat(half_life) + failure_penalty_msat;
 328                 self.last_updated = T::now();
 329         }
 330
 331         fn reduce_penalty(&mut self, half_life: Duration) {
 332                 self.undecayed_penalty_msat = self.decayed_penalty_msat(half_life) >> 1;
 333                 self.last_updated = T::now();
 334         }
 335
 336         fn decayed_penalty_msat(&self, half_life: Duration) -> u64 {
 337                 self.last_updated.elapsed().as_secs()
 338                         .checked_div(half_life.as_secs())
 339                         .and_then(|decays| self.undecayed_penalty_msat.checked_shr(decays as u32))
 340                         .unwrap_or(0)
 341         }
 342 }
 343
 344 impl<T: Time> Default for ScorerUsingTime<T> {
 345         fn default() -> Self {
 346                 Self::new(ScoringParameters::default())
 347         }
 348 }
 349
 350 impl Default for ScoringParameters {
 351         fn default() -> Self {
 352                 Self {
 353                         base_penalty_msat: 500,
 354                         failure_penalty_msat: 1024 * 1000,
 355                         failure_penalty_half_life: Duration::from_secs(3600),
 356                         overuse_penalty_start_1024th: 1024 / 8,
 357                         overuse_penalty_msat_per_1024th: 20,
 358                 }
 359         }
 360 }
 361
 362 impl<T: Time> Score for ScorerUsingTime<T> {
 363         fn channel_penalty_msat(
 364                 &self, short_channel_id: u64, send_amt_msat: u64, chan_capacity_opt: Option<u64>, _source: &NodeId, _target: &NodeId
 365         ) -> u64 {
 366                 let failure_penalty_msat = self.channel_failures
 367                         .get(&short_channel_id)
 368                         .map_or(0, |value| value.decayed_penalty_msat(self.params.failure_penalty_half_life));
 369
 370                 let mut penalty_msat = self.params.base_penalty_msat + failure_penalty_msat;
 371
 372                 if let Some(chan_capacity_msat) = chan_capacity_opt {
 373                         let send_1024ths = send_amt_msat.checked_mul(1024).unwrap_or(u64::max_value()) / chan_capacity_msat;
 374
 375                         if send_1024ths > self.params.overuse_penalty_start_1024th as u64 {
 376                                 penalty_msat = penalty_msat.checked_add(
 377                                                 (send_1024ths - self.params.overuse_penalty_start_1024th as u64)
 378                                                 .checked_mul(self.params.overuse_penalty_msat_per_1024th).unwrap_or(u64::max_value()))
 379                                         .unwrap_or(u64::max_value());
 380                         }
 381                 }
 382
 383                 penalty_msat
 384         }
 385
 386         fn payment_path_failed(&mut self, _path: &[&RouteHop], short_channel_id: u64) {
 387                 let failure_penalty_msat = self.params.failure_penalty_msat;
 388                 let half_life = self.params.failure_penalty_half_life;
 389                 self.channel_failures
 390                         .entry(short_channel_id)
 391                         .and_modify(|failure| failure.add_penalty(failure_penalty_msat, half_life))
 392                         .or_insert_with(|| ChannelFailure::new(failure_penalty_msat));
 393         }
 394
 395         fn payment_path_successful(&mut self, path: &[&RouteHop]) {
 396                 let half_life = self.params.failure_penalty_half_life;
 397                 for hop in path.iter() {
 398                         self.channel_failures
 399                                 .entry(hop.short_channel_id)
 400                                 .and_modify(|failure| failure.reduce_penalty(half_life));
 401                 }
 402         }
 403 }
 404
 405 impl<T: Time> Writeable for ScorerUsingTime<T> {
 406         #[inline]
 407         fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
 408                 self.params.write(w)?;
 409                 self.channel_failures.write(w)?;
 410                 write_tlv_fields!(w, {});
 411                 Ok(())
 412         }
 413 }
 414
 415 impl<T: Time> Readable for ScorerUsingTime<T> {
 416         #[inline]
 417         fn read<R: Read>(r: &mut R) -> Result<Self, DecodeError> {
 418                 let res = Ok(Self {
 419                         params: Readable::read(r)?,
 420                         channel_failures: Readable::read(r)?,
 421                 });
 422                 read_tlv_fields!(r, {});
 423                 res
 424         }
 425 }
 426
 427 impl<T: Time> Writeable for ChannelFailure<T> {
 428         #[inline]
 429         fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
 430                 let duration_since_epoch = T::duration_since_epoch() - self.last_updated.elapsed();
 431                 write_tlv_fields!(w, {
 432                         (0, self.undecayed_penalty_msat, required),
 433                         (2, duration_since_epoch, required),
 434                 });
 435                 Ok(())
 436         }
 437 }
 438
 439 impl<T: Time> Readable for ChannelFailure<T> {
 440         #[inline]
 441         fn read<R: Read>(r: &mut R) -> Result<Self, DecodeError> {
 442                 let mut undecayed_penalty_msat = 0;
 443                 let mut duration_since_epoch = Duration::from_secs(0);
 444                 read_tlv_fields!(r, {
 445                         (0, undecayed_penalty_msat, required),
 446                         (2, duration_since_epoch, required),
 447                 });
 448                 Ok(Self {
 449                         undecayed_penalty_msat,
 450                         last_updated: T::now() - (T::duration_since_epoch() - duration_since_epoch),
 451                 })
 452         }
 453 }
 454
 455 pub(crate) mod time {
 456         use core::ops::Sub;
 457         use core::time::Duration;
 458         /// A measurement of time.
 459         pub trait Time: Sub<Duration, Output = Self> where Self: Sized {
 460                 /// Returns an instance corresponding to the current moment.
 461                 fn now() -> Self;
 462
 463                 /// Returns the amount of time elapsed since `self` was created.
 464                 fn elapsed(&self) -> Duration;
 465
 466                 /// Returns the amount of time passed since the beginning of [`Time`].
 467                 ///
 468                 /// Used during (de-)serialization.
 469                 fn duration_since_epoch() -> Duration;
 470         }
 471
 472         /// A state in which time has no meaning.
 473         #[derive(Debug, PartialEq, Eq)]
 474         pub struct Eternity;
 475
 476         #[cfg(not(feature = "no-std"))]
 477         impl Time for std::time::Instant {
 478                 fn now() -> Self {
 479                         std::time::Instant::now()
 480                 }
 481
 482                 fn duration_since_epoch() -> Duration {
 483                         use std::time::SystemTime;
 484                         SystemTime::now().duration_since(SystemTime::UNIX_EPOCH).unwrap()
 485                 }
 486
 487                 fn elapsed(&self) -> Duration {
 488                         std::time::Instant::elapsed(self)
 489                 }
 490         }
 491
 492         impl Time for Eternity {
 493                 fn now() -> Self {
 494                         Self
 495                 }
 496
 497                 fn duration_since_epoch() -> Duration {
 498                         Duration::from_secs(0)
 499                 }
 500
 501                 fn elapsed(&self) -> Duration {
 502                         Duration::from_secs(0)
 503                 }
 504         }
 505
 506         impl Sub<Duration> for Eternity {
 507                 type Output = Self;
 508
 509                 fn sub(self, _other: Duration) -> Self {
 510                         self
 511                 }
 512         }
 513 }
 514
 515 pub(crate) use self::time::Time;
 516
 517 #[cfg(test)]
 518 mod tests {
 519         use super::{ScoringParameters, ScorerUsingTime, Time};
 520         use super::time::Eternity;
 521
 522         use ln::features::{ChannelFeatures, NodeFeatures};
 523         use routing::scoring::Score;
 524         use routing::network_graph::NodeId;
 525         use routing::router::RouteHop;
 526         use util::ser::{Readable, Writeable};
 527
 528         use bitcoin::secp256k1::PublicKey;
 529         use core::cell::Cell;
 530         use core::ops::Sub;
 531         use core::time::Duration;
 532         use io;
 533
 534         /// Time that can be advanced manually in tests.
 535         #[derive(Debug, PartialEq, Eq)]
 536         struct SinceEpoch(Duration);
 537
 538         impl SinceEpoch {
 539                 thread_local! {
 540                         static ELAPSED: Cell<Duration> = core::cell::Cell::new(Duration::from_secs(0));
 541                 }
 542
 543                 fn advance(duration: Duration) {
 544                         Self::ELAPSED.with(|elapsed| elapsed.set(elapsed.get() + duration))
 545                 }
 546         }
 547
 548         impl Time for SinceEpoch {
 549                 fn now() -> Self {
 550                         Self(Self::duration_since_epoch())
 551                 }
 552
 553                 fn duration_since_epoch() -> Duration {
 554                         Self::ELAPSED.with(|elapsed| elapsed.get())
 555                 }
 556
 557                 fn elapsed(&self) -> Duration {
 558                         Self::duration_since_epoch() - self.0
 559                 }
 560         }
 561
 562         impl Sub<Duration> for SinceEpoch {
 563                 type Output = Self;
 564
 565                 fn sub(self, other: Duration) -> Self {
 566                         Self(self.0 - other)
 567                 }
 568         }
 569
 570         #[test]
 571         fn time_passes_when_advanced() {
 572                 let now = SinceEpoch::now();
 573                 assert_eq!(now.elapsed(), Duration::from_secs(0));
 574
 575                 SinceEpoch::advance(Duration::from_secs(1));
 576                 SinceEpoch::advance(Duration::from_secs(1));
 577
 578                 let elapsed = now.elapsed();
 579                 let later = SinceEpoch::now();
 580
 581                 assert_eq!(elapsed, Duration::from_secs(2));
 582                 assert_eq!(later - elapsed, now);
 583         }
 584
 585         #[test]
 586         fn time_never_passes_in_an_eternity() {
 587                 let now = Eternity::now();
 588                 let elapsed = now.elapsed();
 589                 let later = Eternity::now();
 590
 591                 assert_eq!(now.elapsed(), Duration::from_secs(0));
 592                 assert_eq!(later - elapsed, now);
 593         }
 594
 595         /// A scorer for testing with time that can be manually advanced.
 596         type Scorer = ScorerUsingTime::<SinceEpoch>;
 597
 598         fn source_node_id() -> NodeId {
 599                 NodeId::from_pubkey(&PublicKey::from_slice(&hex::decode("02eec7245d6b7d2ccb30380bfbe2a3648cd7a942653f5aa340edcea1f283686619").unwrap()[..]).unwrap())
 600         }
 601
 602         fn target_node_id() -> NodeId {
 603                 NodeId::from_pubkey(&PublicKey::from_slice(&hex::decode("0324653eac434488002cc06bbfb7f10fe18991e35f9fe4302dbea6d2353dc0ab1c").unwrap()[..]).unwrap())
 604         }
 605
 606         #[test]
 607         fn penalizes_without_channel_failures() {
 608                 let scorer = Scorer::new(ScoringParameters {
 609                         base_penalty_msat: 1_000,
 610                         failure_penalty_msat: 512,
 611                         failure_penalty_half_life: Duration::from_secs(1),
 612                         overuse_penalty_start_1024th: 1024,
 613                         overuse_penalty_msat_per_1024th: 0,
 614                 });
 615                 let source = source_node_id();
 616                 let target = target_node_id();
 617                 assert_eq!(scorer.channel_penalty_msat(42, 1, Some(1), &source, &target), 1_000);
 618
 619                 SinceEpoch::advance(Duration::from_secs(1));
 620                 assert_eq!(scorer.channel_penalty_msat(42, 1, Some(1), &source, &target), 1_000);
 621         }
 622
 623         #[test]
 624         fn accumulates_channel_failure_penalties() {
 625                 let mut scorer = Scorer::new(ScoringParameters {
 626                         base_penalty_msat: 1_000,
 627                         failure_penalty_msat: 64,
 628                         failure_penalty_half_life: Duration::from_secs(10),
 629                         overuse_penalty_start_1024th: 1024,
 630                         overuse_penalty_msat_per_1024th: 0,
 631                 });
 632                 let source = source_node_id();
 633                 let target = target_node_id();
 634                 assert_eq!(scorer.channel_penalty_msat(42, 1, Some(1), &source, &target), 1_000);
 635
 636                 scorer.payment_path_failed(&[], 42);
 637                 assert_eq!(scorer.channel_penalty_msat(42, 1, Some(1), &source, &target), 1_064);
 638
 639                 scorer.payment_path_failed(&[], 42);
 640                 assert_eq!(scorer.channel_penalty_msat(42, 1, Some(1), &source, &target), 1_128);
 641
 642                 scorer.payment_path_failed(&[], 42);
 643                 assert_eq!(scorer.channel_penalty_msat(42, 1, Some(1), &source, &target), 1_192);
 644         }
 645
 646         #[test]
 647         fn decays_channel_failure_penalties_over_time() {
 648                 let mut scorer = Scorer::new(ScoringParameters {
 649                         base_penalty_msat: 1_000,
 650                         failure_penalty_msat: 512,
 651                         failure_penalty_half_life: Duration::from_secs(10),
 652                         overuse_penalty_start_1024th: 1024,
 653                         overuse_penalty_msat_per_1024th: 0,
 654                 });
 655                 let source = source_node_id();
 656                 let target = target_node_id();
 657                 assert_eq!(scorer.channel_penalty_msat(42, 1, Some(1), &source, &target), 1_000);
 658
 659                 scorer.payment_path_failed(&[], 42);
 660                 assert_eq!(scorer.channel_penalty_msat(42, 1, Some(1), &source, &target), 1_512);
 661
 662                 SinceEpoch::advance(Duration::from_secs(9));
 663                 assert_eq!(scorer.channel_penalty_msat(42, 1, Some(1), &source, &target), 1_512);
 664
 665                 SinceEpoch::advance(Duration::from_secs(1));
 666                 assert_eq!(scorer.channel_penalty_msat(42, 1, Some(1), &source, &target), 1_256);
 667
 668                 SinceEpoch::advance(Duration::from_secs(10 * 8));
 669                 assert_eq!(scorer.channel_penalty_msat(42, 1, Some(1), &source, &target), 1_001);
 670
 671                 SinceEpoch::advance(Duration::from_secs(10));
 672                 assert_eq!(scorer.channel_penalty_msat(42, 1, Some(1), &source, &target), 1_000);
 673
 674                 SinceEpoch::advance(Duration::from_secs(10));
 675                 assert_eq!(scorer.channel_penalty_msat(42, 1, Some(1), &source, &target), 1_000);
 676         }
 677
 678         #[test]
 679         fn decays_channel_failure_penalties_without_shift_overflow() {
 680                 let mut scorer = Scorer::new(ScoringParameters {
 681                         base_penalty_msat: 1_000,
 682                         failure_penalty_msat: 512,
 683                         failure_penalty_half_life: Duration::from_secs(10),
 684                         overuse_penalty_start_1024th: 1024,
 685                         overuse_penalty_msat_per_1024th: 0,
 686                 });
 687                 let source = source_node_id();
 688                 let target = target_node_id();
 689                 assert_eq!(scorer.channel_penalty_msat(42, 1, Some(1), &source, &target), 1_000);
 690
 691                 scorer.payment_path_failed(&[], 42);
 692                 assert_eq!(scorer.channel_penalty_msat(42, 1, Some(1), &source, &target), 1_512);
 693
 694                 // An unchecked right shift 64 bits or more in ChannelFailure::decayed_penalty_msat would
 695                 // cause an overflow.
 696                 SinceEpoch::advance(Duration::from_secs(10 * 64));
 697                 assert_eq!(scorer.channel_penalty_msat(42, 1, Some(1), &source, &target), 1_000);
 698
 699                 SinceEpoch::advance(Duration::from_secs(10));
 700                 assert_eq!(scorer.channel_penalty_msat(42, 1, Some(1), &source, &target), 1_000);
 701         }
 702
 703         #[test]
 704         fn accumulates_channel_failure_penalties_after_decay() {
 705                 let mut scorer = Scorer::new(ScoringParameters {
 706                         base_penalty_msat: 1_000,
 707                         failure_penalty_msat: 512,
 708                         failure_penalty_half_life: Duration::from_secs(10),
 709                         overuse_penalty_start_1024th: 1024,
 710                         overuse_penalty_msat_per_1024th: 0,
 711                 });
 712                 let source = source_node_id();
 713                 let target = target_node_id();
 714                 assert_eq!(scorer.channel_penalty_msat(42, 1, Some(1), &source, &target), 1_000);
 715
 716                 scorer.payment_path_failed(&[], 42);
 717                 assert_eq!(scorer.channel_penalty_msat(42, 1, Some(1), &source, &target), 1_512);
 718
 719                 SinceEpoch::advance(Duration::from_secs(10));
 720                 assert_eq!(scorer.channel_penalty_msat(42, 1, Some(1), &source, &target), 1_256);
 721
 722                 scorer.payment_path_failed(&[], 42);
 723                 assert_eq!(scorer.channel_penalty_msat(42, 1, Some(1), &source, &target), 1_768);
 724
 725                 SinceEpoch::advance(Duration::from_secs(10));
 726                 assert_eq!(scorer.channel_penalty_msat(42, 1, Some(1), &source, &target), 1_384);
 727         }
 728
 729         #[test]
 730         fn reduces_channel_failure_penalties_after_success() {
 731                 let mut scorer = Scorer::new(ScoringParameters {
 732                         base_penalty_msat: 1_000,
 733                         failure_penalty_msat: 512,
 734                         failure_penalty_half_life: Duration::from_secs(10),
 735                         overuse_penalty_start_1024th: 1024,
 736                         overuse_penalty_msat_per_1024th: 0,
 737                 });
 738                 let source = source_node_id();
 739                 let target = target_node_id();
 740                 assert_eq!(scorer.channel_penalty_msat(42, 1, Some(1), &source, &target), 1_000);
 741
 742                 scorer.payment_path_failed(&[], 42);
 743                 assert_eq!(scorer.channel_penalty_msat(42, 1, Some(1), &source, &target), 1_512);
 744
 745                 SinceEpoch::advance(Duration::from_secs(10));
 746                 assert_eq!(scorer.channel_penalty_msat(42, 1, Some(1), &source, &target), 1_256);
 747
 748                 let hop = RouteHop {
 749                         pubkey: PublicKey::from_slice(target.as_slice()).unwrap(),
 750                         node_features: NodeFeatures::known(),
 751                         short_channel_id: 42,
 752                         channel_features: ChannelFeatures::known(),
 753                         fee_msat: 1,
 754                         cltv_expiry_delta: 18,
 755                 };
 756                 scorer.payment_path_successful(&[&hop]);
 757                 assert_eq!(scorer.channel_penalty_msat(42, 1, Some(1), &source, &target), 1_128);
 758
 759                 SinceEpoch::advance(Duration::from_secs(10));
 760                 assert_eq!(scorer.channel_penalty_msat(42, 1, Some(1), &source, &target), 1_064);
 761         }
 762
 763         #[test]
 764         fn restores_persisted_channel_failure_penalties() {
 765                 let mut scorer = Scorer::new(ScoringParameters {
 766                         base_penalty_msat: 1_000,
 767                         failure_penalty_msat: 512,
 768                         failure_penalty_half_life: Duration::from_secs(10),
 769                         overuse_penalty_start_1024th: 1024,
 770                         overuse_penalty_msat_per_1024th: 0,
 771                 });
 772                 let source = source_node_id();
 773                 let target = target_node_id();
 774
 775                 scorer.payment_path_failed(&[], 42);
 776                 assert_eq!(scorer.channel_penalty_msat(42, 1, Some(1), &source, &target), 1_512);
 777
 778                 SinceEpoch::advance(Duration::from_secs(10));
 779                 assert_eq!(scorer.channel_penalty_msat(42, 1, Some(1), &source, &target), 1_256);
 780
 781                 scorer.payment_path_failed(&[], 43);
 782                 assert_eq!(scorer.channel_penalty_msat(43, 1, Some(1), &source, &target), 1_512);
 783
 784                 let mut serialized_scorer = Vec::new();
 785                 scorer.write(&mut serialized_scorer).unwrap();
 786
 787                 let deserialized_scorer = <Scorer>::read(&mut io::Cursor::new(&serialized_scorer)).unwrap();
 788                 assert_eq!(deserialized_scorer.channel_penalty_msat(42, 1, Some(1), &source, &target), 1_256);
 789                 assert_eq!(deserialized_scorer.channel_penalty_msat(43, 1, Some(1), &source, &target), 1_512);
 790         }
 791
 792         #[test]
 793         fn decays_persisted_channel_failure_penalties() {
 794                 let mut scorer = Scorer::new(ScoringParameters {
 795                         base_penalty_msat: 1_000,
 796                         failure_penalty_msat: 512,
 797                         failure_penalty_half_life: Duration::from_secs(10),
 798                         overuse_penalty_start_1024th: 1024,
 799                         overuse_penalty_msat_per_1024th: 0,
 800                 });
 801                 let source = source_node_id();
 802                 let target = target_node_id();
 803
 804                 scorer.payment_path_failed(&[], 42);
 805                 assert_eq!(scorer.channel_penalty_msat(42, 1, Some(1), &source, &target), 1_512);
 806
 807                 let mut serialized_scorer = Vec::new();
 808                 scorer.write(&mut serialized_scorer).unwrap();
 809
 810                 SinceEpoch::advance(Duration::from_secs(10));
 811
 812                 let deserialized_scorer = <Scorer>::read(&mut io::Cursor::new(&serialized_scorer)).unwrap();
 813                 assert_eq!(deserialized_scorer.channel_penalty_msat(42, 1, Some(1), &source, &target), 1_256);
 814
 815                 SinceEpoch::advance(Duration::from_secs(10));
 816                 assert_eq!(deserialized_scorer.channel_penalty_msat(42, 1, Some(1), &source, &target), 1_128);
 817         }
 818
 819         #[test]
 820         fn charges_per_1024th_penalty() {
 821                 let scorer = Scorer::new(ScoringParameters {
 822                         base_penalty_msat: 0,
 823                         failure_penalty_msat: 0,
 824                         failure_penalty_half_life: Duration::from_secs(0),
 825                         overuse_penalty_start_1024th: 256,
 826                         overuse_penalty_msat_per_1024th: 100,
 827                 });
 828                 let source = source_node_id();
 829                 let target = target_node_id();
 830
 831                 assert_eq!(scorer.channel_penalty_msat(42, 1_000, None, &source, &target), 0);
 832                 assert_eq!(scorer.channel_penalty_msat(42, 1_000, Some(1_024_000), &source, &target), 0);
 833                 assert_eq!(scorer.channel_penalty_msat(42, 256_999, Some(1_024_000), &source, &target), 0);
 834                 assert_eq!(scorer.channel_penalty_msat(42, 257_000, Some(1_024_000), &source, &target), 100);
 835                 assert_eq!(scorer.channel_penalty_msat(42, 258_000, Some(1_024_000), &source, &target), 200);
 836                 assert_eq!(scorer.channel_penalty_msat(42, 512_000, Some(1_024_000), &source, &target), 256 * 100);
 837         }
 838 }