//!
//! [`find_route`]: crate::routing::router::find_route
-use ln::msgs::DecodeError;
-use routing::gossip::{EffectiveCapacity, NetworkGraph, NodeId};
-use routing::router::RouteHop;
-use util::ser::{Readable, ReadableArgs, Writeable, Writer};
-use util::logger::Logger;
-use util::time::Time;
-
-use prelude::*;
-use core::fmt;
+use crate::ln::msgs::DecodeError;
+use crate::routing::gossip::{EffectiveCapacity, NetworkGraph, NodeId};
+use crate::routing::router::RouteHop;
+use crate::util::ser::{Readable, ReadableArgs, Writeable, Writer};
+use crate::util::logger::Logger;
+use crate::util::time::Time;
+
+use crate::prelude::*;
+use core::{cmp, fmt};
use core::cell::{RefCell, RefMut};
use core::convert::TryInto;
use core::ops::{Deref, DerefMut};
use core::time::Duration;
-use io::{self, Read};
-use sync::{Mutex, MutexGuard};
+use crate::io::{self, Read};
+use crate::sync::{Mutex, MutexGuard};
/// We define Score ever-so-slightly differently based on whether we are being built for C bindings
/// or not. For users, `LockableScore` must somehow be writeable to disk. For Rust users, this is
/// use the Persister to persist it.
pub trait WriteableScore<'a>: LockableScore<'a> + Writeable {}
+#[cfg(not(c_bindings))]
impl<'a, T> WriteableScore<'a> for T where T: LockableScore<'a> + Writeable {}
/// (C-not exported)
score: Mutex<S>,
}
#[cfg(c_bindings)]
-/// (C-not exported)
+/// A locked `MultiThreadedLockableScore`.
+pub struct MultiThreadedScoreLock<'a, S: Score>(MutexGuard<'a, S>);
+#[cfg(c_bindings)]
+impl<'a, T: Score + 'a> Score for MultiThreadedScoreLock<'a, T> {
+ fn channel_penalty_msat(&self, scid: u64, source: &NodeId, target: &NodeId, usage: ChannelUsage) -> u64 {
+ self.0.channel_penalty_msat(scid, source, target, usage)
+ }
+ fn payment_path_failed(&mut self, path: &[&RouteHop], short_channel_id: u64) {
+ self.0.payment_path_failed(path, short_channel_id)
+ }
+ fn payment_path_successful(&mut self, path: &[&RouteHop]) {
+ self.0.payment_path_successful(path)
+ }
+ fn probe_failed(&mut self, path: &[&RouteHop], short_channel_id: u64) {
+ self.0.probe_failed(path, short_channel_id)
+ }
+ fn probe_successful(&mut self, path: &[&RouteHop]) {
+ self.0.probe_successful(path)
+ }
+}
+#[cfg(c_bindings)]
+impl<'a, T: Score + 'a> Writeable for MultiThreadedScoreLock<'a, T> {
+ fn write<W: Writer>(&self, writer: &mut W) -> Result<(), io::Error> {
+ self.0.write(writer)
+ }
+}
+
+#[cfg(c_bindings)]
impl<'a, T: Score + 'a> LockableScore<'a> for MultiThreadedLockableScore<T> {
- type Locked = MutexGuard<'a, T>;
+ type Locked = MultiThreadedScoreLock<'a, T>;
- fn lock(&'a self) -> MutexGuard<'a, T> {
- Mutex::lock(&self.score).unwrap()
+ fn lock(&'a self) -> MultiThreadedScoreLock<'a, T> {
+ MultiThreadedScoreLock(Mutex::lock(&self.score).unwrap())
}
}
+#[cfg(c_bindings)]
+impl<T: Score> Writeable for MultiThreadedLockableScore<T> {
+ fn write<W: Writer>(&self, writer: &mut W) -> Result<(), io::Error> {
+ self.lock().write(writer)
+ }
+}
+
+#[cfg(c_bindings)]
+impl<'a, T: Score + 'a> WriteableScore<'a> for MultiThreadedLockableScore<T> {}
+
#[cfg(c_bindings)]
impl<T: Score> MultiThreadedLockableScore<T> {
/// Creates a new [`MultiThreadedLockableScore`] given an underlying [`Score`].
}
/// Proposed use of a channel passed as a parameter to [`Score::channel_penalty_msat`].
-#[derive(Clone, Copy)]
+#[derive(Clone, Copy, Debug)]
pub struct ChannelUsage {
/// The amount to send through the channel, denominated in millisatoshis.
pub amount_msat: u64,
#[cfg(not(feature = "no-std"))]
type ConfiguredTime = std::time::Instant;
#[cfg(feature = "no-std")]
-use util::time::Eternity;
+use crate::util::time::Eternity;
#[cfg(feature = "no-std")]
type ConfiguredTime = Eternity;
/// [`Score`] implementation using channel success probability distributions.
///
-/// Based on *Optimally Reliable & Cheap Payment Flows on the Lightning Network* by Rene Pickhardt
-/// and Stefan Richter [[1]]. Given the uncertainty of channel liquidity balances, probability
-/// distributions are defined based on knowledge learned from successful and unsuccessful attempts.
-/// Then the negative `log10` of the success probability is used to determine the cost of routing a
-/// specific HTLC amount through a channel.
+/// Channels are tracked with upper and lower liquidity bounds - when an HTLC fails at a channel,
+/// we learn that the upper-bound on the available liquidity is lower than the amount of the HTLC.
+/// When a payment is forwarded through a channel (but fails later in the route), we learn the
+/// lower-bound on the channel's available liquidity must be at least the value of the HTLC.
+///
+/// These bounds are then used to determine a success probability using the formula from
+/// *Optimally Reliable & Cheap Payment Flows on the Lightning Network* by Rene Pickhardt
+/// and Stefan Richter [[1]] (i.e. `(upper_bound - payment_amount) / (upper_bound - lower_bound)`).
///
-/// Knowledge about channel liquidity balances takes the form of upper and lower bounds on the
-/// possible liquidity. Certainty of the bounds is decreased over time using a decay function. See
-/// [`ProbabilisticScoringParameters`] for details.
+/// This probability is combined with the [`liquidity_penalty_multiplier_msat`] and
+/// [`liquidity_penalty_amount_multiplier_msat`] parameters to calculate a concrete penalty in
+/// milli-satoshis. The penalties, when added across all hops, have the property of being linear in
+/// terms of the entire path's success probability. This allows the router to directly compare
+/// penalties for different paths. See the documentation of those parameters for the exact formulas.
///
-/// Since the scorer aims to learn the current channel liquidity balances, it works best for nodes
-/// with high payment volume or that actively probe the [`NetworkGraph`]. Nodes with low payment
-/// volume are more likely to experience failed payment paths, which would need to be retried.
+/// The liquidity bounds are decayed by halving them every [`liquidity_offset_half_life`].
+///
+/// Further, we track the history of our upper and lower liquidity bounds for each channel,
+/// allowing us to assign a second penalty (using [`historical_liquidity_penalty_multiplier_msat`]
+/// and [`historical_liquidity_penalty_amount_multiplier_msat`]) based on the same probability
+/// formula, but using the history of a channel rather than our latest estimates for the liquidity
+/// bounds.
///
/// # Note
///
/// behavior.
///
/// [1]: https://arxiv.org/abs/2107.05322
+/// [`liquidity_penalty_multiplier_msat`]: ProbabilisticScoringParameters::liquidity_penalty_multiplier_msat
+/// [`liquidity_penalty_amount_multiplier_msat`]: ProbabilisticScoringParameters::liquidity_penalty_amount_multiplier_msat
+/// [`liquidity_offset_half_life`]: ProbabilisticScoringParameters::liquidity_offset_half_life
+/// [`historical_liquidity_penalty_multiplier_msat`]: ProbabilisticScoringParameters::historical_liquidity_penalty_multiplier_msat
+/// [`historical_liquidity_penalty_amount_multiplier_msat`]: ProbabilisticScoringParameters::historical_liquidity_penalty_amount_multiplier_msat
pub type ProbabilisticScorer<G, L> = ProbabilisticScorerUsingTime::<G, L, ConfiguredTime>;
/// Probabilistic [`Score`] implementation.
/// uncertainty bounds of the channel liquidity balance. Amounts above the upper bound will
/// result in a `u64::max_value` penalty, however.
///
+ /// `-log10(success_probability) * liquidity_penalty_multiplier_msat`
+ ///
/// Default value: 30,000 msat
///
/// [`liquidity_offset_half_life`]: Self::liquidity_offset_half_life
pub liquidity_penalty_multiplier_msat: u64,
- /// The time required to elapse before any knowledge learned about channel liquidity balances is
- /// cut in half.
+ /// Whenever this amount of time elapses since the last update to a channel's liquidity bounds,
+ /// the distance from the bounds to "zero" is cut in half. In other words, the lower-bound on
+ /// the available liquidity is halved and the upper-bound moves half-way to the channel's total
+ /// capacity.
///
- /// The bounds are defined in terms of offsets and are initially zero. Increasing the offsets
- /// gives tighter bounds on the channel liquidity balance. Thus, halving the offsets decreases
- /// the certainty of the channel liquidity balance.
+ /// Because halving the liquidity bounds grows the uncertainty on the channel's liquidity,
+ /// the penalty for an amount within the new bounds may change. See the [`ProbabilisticScorer`]
+ /// struct documentation for more info on the way the liquidity bounds are used.
///
- /// Default value: 1 hour
+ /// For example, if the channel's capacity is 1 million sats, and the current upper and lower
+ /// liquidity bounds are 200,000 sats and 600,000 sats, after this amount of time the upper
+ /// and lower liquidity bounds will be decayed to 100,000 and 800,000 sats.
+ ///
+ /// Default value: 6 hours
///
/// # Note
///
/// [`liquidity_penalty_amount_multiplier_msat`]: Self::liquidity_penalty_amount_multiplier_msat
pub historical_liquidity_penalty_amount_multiplier_msat: u64,
+ /// If we aren't learning any new datapoints for a channel, the historical liquidity bounds
+ /// tracking can simply live on with increasingly stale data. Instead, when a channel has not
+ /// seen a liquidity estimate update for this amount of time, the historical datapoints are
+ /// decayed by half.
+ ///
+ /// Note that after 16 or more half lives all historical data will be completely gone.
+ ///
+ /// Default value: 14 days
+ pub historical_no_updates_half_life: Duration,
+
/// Manual penalties used for the given nodes. Allows to set a particular penalty for a given
/// node. Note that a manual penalty of `u64::max_value()` means the node would not ever be
/// considered during path finding.
self.buckets[bucket_idx as usize] = self.buckets[bucket_idx as usize].saturating_add(32);
}
}
+ /// Decay all buckets by the given number of half-lives. Used to more aggressively remove old
+ /// datapoints as we receive newer information.
+ fn time_decay_data(&mut self, half_lives: u32) {
+ for e in self.buckets.iter_mut() {
+ *e = e.checked_shr(half_lives).unwrap_or(0);
+ }
+ }
}
impl_writeable_tlv_based!(HistoricalBucketRangeTracker, { (0, buckets, required) });
+struct HistoricalMinMaxBuckets<'a> {
+ min_liquidity_offset_history: &'a HistoricalBucketRangeTracker,
+ max_liquidity_offset_history: &'a HistoricalBucketRangeTracker,
+}
+
+impl HistoricalMinMaxBuckets<'_> {
+ #[inline]
+ fn calculate_success_probability_times_billion(&self, required_decays: u32, payment_amt_64th_bucket: u8) -> Option<u64> {
+ // If historical penalties are enabled, calculate the penalty by walking the set of
+ // historical liquidity bucket (min, max) combinations (where min_idx < max_idx) and, for
+ // each, calculate the probability of success given our payment amount, then total the
+ // weighted average probability of success.
+ //
+ // We use a sliding scale to decide which point within a given bucket will be compared to
+ // the amount being sent - for lower-bounds, the amount being sent is compared to the lower
+ // edge of the first bucket (i.e. zero), but compared to the upper 7/8ths of the last
+ // bucket (i.e. 9 times the index, or 63), with each bucket in between increasing the
+ // comparison point by 1/64th. For upper-bounds, the same applies, however with an offset
+ // of 1/64th (i.e. starting at one and ending at 64). This avoids failing to assign
+ // penalties to channels at the edges.
+ //
+ // If we used the bottom edge of buckets, we'd end up never assigning any penalty at all to
+ // such a channel when sending less than ~0.19% of the channel's capacity (e.g. ~200k sats
+ // for a 1 BTC channel!).
+ //
+ // If we used the middle of each bucket we'd never assign any penalty at all when sending
+ // less than 1/16th of a channel's capacity, or 1/8th if we used the top of the bucket.
+ let mut total_valid_points_tracked = 0;
+
+ // Rather than actually decaying the individual buckets, which would lose precision, we
+ // simply track whether all buckets would be decayed to zero, in which case we treat it as
+ // if we had no data.
+ let mut is_fully_decayed = true;
+ let mut check_track_bucket_contains_undecayed_points =
+ |bucket_val: u16| if bucket_val.checked_shr(required_decays).unwrap_or(0) > 0 { is_fully_decayed = false; };
+
+ for (min_idx, min_bucket) in self.min_liquidity_offset_history.buckets.iter().enumerate() {
+ check_track_bucket_contains_undecayed_points(*min_bucket);
+ for max_bucket in self.max_liquidity_offset_history.buckets.iter().take(8 - min_idx) {
+ total_valid_points_tracked += (*min_bucket as u64) * (*max_bucket as u64);
+ check_track_bucket_contains_undecayed_points(*max_bucket);
+ }
+ }
+ // If the total valid points is smaller than 1.0 (i.e. 32 in our fixed-point scheme), treat
+ // it as if we were fully decayed.
+ if total_valid_points_tracked.checked_shr(required_decays).unwrap_or(0) < 32*32 || is_fully_decayed {
+ return None;
+ }
+
+ let mut cumulative_success_prob_times_billion = 0;
+ for (min_idx, min_bucket) in self.min_liquidity_offset_history.buckets.iter().enumerate() {
+ for (max_idx, max_bucket) in self.max_liquidity_offset_history.buckets.iter().enumerate().take(8 - min_idx) {
+ let bucket_prob_times_million = (*min_bucket as u64) * (*max_bucket as u64)
+ * 1024 * 1024 / total_valid_points_tracked;
+ let min_64th_bucket = min_idx as u8 * 9;
+ let max_64th_bucket = (7 - max_idx as u8) * 9 + 1;
+ if payment_amt_64th_bucket > max_64th_bucket {
+ // Success probability 0, the payment amount is above the max liquidity
+ } else if payment_amt_64th_bucket <= min_64th_bucket {
+ cumulative_success_prob_times_billion += bucket_prob_times_million * 1024;
+ } else {
+ cumulative_success_prob_times_billion += bucket_prob_times_million *
+ ((max_64th_bucket - payment_amt_64th_bucket) as u64) * 1024 /
+ ((max_64th_bucket - min_64th_bucket) as u64);
+ }
+ }
+ }
+
+ Some(cumulative_success_prob_times_billion)
+ }
+}
+
/// Accounting for channel liquidity balance uncertainty.
///
/// Direction is defined in terms of [`NodeId`] partial ordering, where the source node is the
base_penalty_msat: 0,
base_penalty_amount_multiplier_msat: 0,
liquidity_penalty_multiplier_msat: 0,
- liquidity_offset_half_life: Duration::from_secs(3600),
+ liquidity_offset_half_life: Duration::from_secs(6 * 60 * 60),
liquidity_penalty_amount_multiplier_msat: 0,
historical_liquidity_penalty_multiplier_msat: 0,
historical_liquidity_penalty_amount_multiplier_msat: 0,
+ historical_no_updates_half_life: Duration::from_secs(60 * 60 * 24 * 14),
manual_node_penalties: HashMap::new(),
anti_probing_penalty_msat: 0,
considered_impossible_penalty_msat: 0,
base_penalty_msat: 500,
base_penalty_amount_multiplier_msat: 8192,
liquidity_penalty_multiplier_msat: 30_000,
- liquidity_offset_half_life: Duration::from_secs(3600),
+ liquidity_offset_half_life: Duration::from_secs(6 * 60 * 60),
liquidity_penalty_amount_multiplier_msat: 192,
historical_liquidity_penalty_multiplier_msat: 10_000,
historical_liquidity_penalty_amount_multiplier_msat: 64,
+ historical_no_updates_half_life: Duration::from_secs(60 * 60 * 24 * 14),
manual_node_penalties: HashMap::new(),
anti_probing_penalty_msat: 250,
considered_impossible_penalty_msat: 1_0000_0000_000,
if params.historical_liquidity_penalty_multiplier_msat != 0 ||
params.historical_liquidity_penalty_amount_multiplier_msat != 0 {
- // If historical penalties are enabled, calculate the penalty by walking the set of
- // historical liquidity bucket (min, max) combinations (where min_idx < max_idx)
- // and, for each, calculate the probability of success given our payment amount, then
- // total the weighted average probability of success.
- //
- // We use a sliding scale to decide which point within a given bucket will be compared
- // to the amount being sent - for lower-bounds, the amount being sent is compared to
- // the lower edge of the first bucket (i.e. zero), but compared to the upper 7/8ths of
- // the last bucket (i.e. 9 times the index, or 63), with each bucket in between
- // increasing the comparison point by 1/64th. For upper-bounds, the same applies,
- // however with an offset of 1/64th (i.e. starting at one and ending at 64). This
- // avoids failing to assign penalties to channels at the edges.
- //
- // If we used the bottom edge of buckets, we'd end up never assigning any penalty at
- // all to such a channel when sending less than ~0.19% of the channel's capacity (e.g.
- // ~200k sats for a 1 BTC channel!).
- //
- // If we used the middle of each bucket we'd never assign any penalty at all when
- // sending less than 1/16th of a channel's capacity, or 1/8th if we used the top of the
- // bucket.
- let mut total_valid_points_tracked = 0;
- for (min_idx, min_bucket) in self.min_liquidity_offset_history.buckets.iter().enumerate() {
- for max_bucket in self.max_liquidity_offset_history.buckets.iter().take(8 - min_idx) {
- total_valid_points_tracked += (*min_bucket as u64) * (*max_bucket as u64);
- }
- }
- if total_valid_points_tracked == 0 {
- // If we don't have any valid points, redo the non-historical calculation with no
- // liquidity bounds tracked and the historical penalty multipliers.
+ let required_decays = self.now.duration_since(*self.last_updated).as_secs()
+ .checked_div(params.historical_no_updates_half_life.as_secs())
+ .map_or(u32::max_value(), |decays| cmp::min(decays, u32::max_value() as u64) as u32);
+ let payment_amt_64th_bucket = amount_msat * 64 / self.capacity_msat;
+ debug_assert!(payment_amt_64th_bucket <= 64);
+ if payment_amt_64th_bucket > 64 { return res; }
+
+ let buckets = HistoricalMinMaxBuckets {
+ min_liquidity_offset_history: &self.min_liquidity_offset_history,
+ max_liquidity_offset_history: &self.max_liquidity_offset_history,
+ };
+ if let Some(cumulative_success_prob_times_billion) = buckets
+ .calculate_success_probability_times_billion(required_decays, payment_amt_64th_bucket as u8) {
+ let historical_negative_log10_times_2048 = approx::negative_log10_times_2048(cumulative_success_prob_times_billion + 1, 1024 * 1024 * 1024);
+ res = res.saturating_add(Self::combined_penalty_msat(amount_msat,
+ historical_negative_log10_times_2048, params.historical_liquidity_penalty_multiplier_msat,
+ params.historical_liquidity_penalty_amount_multiplier_msat));
+ } else {
+ // If we don't have any valid points (or, once decayed, we have less than a full
+ // point), redo the non-historical calculation with no liquidity bounds tracked and
+ // the historical penalty multipliers.
let max_capacity = self.capacity_msat.saturating_sub(amount_msat).saturating_add(1);
let negative_log10_times_2048 =
approx::negative_log10_times_2048(max_capacity, self.capacity_msat.saturating_add(1));
params.historical_liquidity_penalty_amount_multiplier_msat));
return res;
}
-
- let payment_amt_64th_bucket = amount_msat * 64 / self.capacity_msat;
- debug_assert!(payment_amt_64th_bucket <= 64);
- if payment_amt_64th_bucket > 64 { return res; }
-
- let mut cumulative_success_prob_times_billion = 0;
- for (min_idx, min_bucket) in self.min_liquidity_offset_history.buckets.iter().enumerate() {
- for (max_idx, max_bucket) in self.max_liquidity_offset_history.buckets.iter().enumerate().take(8 - min_idx) {
- let bucket_prob_times_million = (*min_bucket as u64) * (*max_bucket as u64)
- * 1024 * 1024 / total_valid_points_tracked;
- let min_64th_bucket = min_idx as u64 * 9;
- let max_64th_bucket = (7 - max_idx as u64) * 9 + 1;
- if payment_amt_64th_bucket > max_64th_bucket {
- // Success probability 0, the payment amount is above the max liquidity
- } else if payment_amt_64th_bucket <= min_64th_bucket {
- cumulative_success_prob_times_billion += bucket_prob_times_million * 1024;
- } else {
- cumulative_success_prob_times_billion += bucket_prob_times_million *
- (max_64th_bucket - payment_amt_64th_bucket) * 1024 /
- (max_64th_bucket - min_64th_bucket);
- }
- }
- }
- let historical_negative_log10_times_2048 = approx::negative_log10_times_2048(cumulative_success_prob_times_billion + 1, 1024 * 1024 * 1024);
- res = res.saturating_add(Self::combined_penalty_msat(amount_msat,
- historical_negative_log10_times_2048, params.historical_liquidity_penalty_multiplier_msat,
- params.historical_liquidity_penalty_amount_multiplier_msat));
}
res
impl<L: DerefMut<Target = u64>, BRT: DerefMut<Target = HistoricalBucketRangeTracker>, T: Time, U: DerefMut<Target = T>> DirectedChannelLiquidity<'_, L, BRT, T, U> {
/// Adjusts the channel liquidity balance bounds when failing to route `amount_msat`.
fn failed_at_channel<Log: Deref>(&mut self, amount_msat: u64, chan_descr: fmt::Arguments, logger: &Log) where Log::Target: Logger {
- if amount_msat < self.max_liquidity_msat() {
- log_debug!(logger, "Setting max liquidity of {} to {}", chan_descr, amount_msat);
+ let existing_max_msat = self.max_liquidity_msat();
+ if amount_msat < existing_max_msat {
+ log_debug!(logger, "Setting max liquidity of {} from {} to {}", chan_descr, existing_max_msat, amount_msat);
self.set_max_liquidity_msat(amount_msat);
} else {
- log_trace!(logger, "Max liquidity of {} already more than {}", chan_descr, amount_msat);
+ log_trace!(logger, "Max liquidity of {} is {} (already less than or equal to {})",
+ chan_descr, existing_max_msat, amount_msat);
}
}
/// Adjusts the channel liquidity balance bounds when failing to route `amount_msat` downstream.
fn failed_downstream<Log: Deref>(&mut self, amount_msat: u64, chan_descr: fmt::Arguments, logger: &Log) where Log::Target: Logger {
- if amount_msat > self.min_liquidity_msat() {
- log_debug!(logger, "Setting min liquidity of {} to {}", chan_descr, amount_msat);
+ let existing_min_msat = self.min_liquidity_msat();
+ if amount_msat > existing_min_msat {
+ log_debug!(logger, "Setting min liquidity of {} from {} to {}", existing_min_msat, chan_descr, amount_msat);
self.set_min_liquidity_msat(amount_msat);
} else {
- log_trace!(logger, "Min liquidity of {} already less than {}", chan_descr, amount_msat);
+ log_trace!(logger, "Min liquidity of {} is {} (already greater than or equal to {})",
+ chan_descr, existing_min_msat, amount_msat);
}
}
}
fn update_history_buckets(&mut self) {
+ let half_lives = self.now.duration_since(*self.last_updated).as_secs()
+ .checked_div(self.params.historical_no_updates_half_life.as_secs())
+ .map(|v| v.try_into().unwrap_or(u32::max_value())).unwrap_or(u32::max_value());
+ self.min_liquidity_offset_history.time_decay_data(half_lives);
+ self.max_liquidity_offset_history.time_decay_data(half_lives);
+
debug_assert!(*self.min_liquidity_offset_msat <= self.capacity_msat);
self.min_liquidity_offset_history.track_datapoint(
// Ensure the bucket index we pass is in the range [0, 7], even if the liquidity offset
} else {
self.decayed_offset_msat(*self.max_liquidity_offset_msat)
};
- *self.last_updated = self.now;
self.update_history_buckets();
+ *self.last_updated = self.now;
}
/// Adjusts the upper bound of the channel liquidity balance in this direction.
} else {
self.decayed_offset_msat(*self.min_liquidity_offset_msat)
};
- *self.last_updated = self.now;
self.update_history_buckets();
+ *self.last_updated = self.now;
}
}
return base_penalty_msat;
}
},
- EffectiveCapacity::Total { capacity_msat, htlc_maximum_msat: Some(htlc_maximum_msat) } => {
+ EffectiveCapacity::Total { capacity_msat, htlc_maximum_msat } => {
if htlc_maximum_msat >= capacity_msat/2 {
anti_probing_penalty_msat = self.params.anti_probing_penalty_msat;
}
.get(&hop.short_channel_id)
.and_then(|channel| channel.as_directed_to(&target));
- if hop.short_channel_id == short_channel_id && hop_idx == 0 {
+ let at_failed_channel = hop.short_channel_id == short_channel_id;
+ if at_failed_channel && hop_idx == 0 {
log_warn!(self.logger, "Payment failed at the first hop - we do not attempt to learn channel info in such cases as we can directly observe local state.\n\tBecause we know the local state, we should generally not see failures here - this may be an indication that your channel peer on channel {} is broken and you may wish to close the channel.", hop.short_channel_id);
}
// Only score announced channels.
if let Some((channel, source)) = channel_directed_from_source {
let capacity_msat = channel.effective_capacity().as_msat();
- if hop.short_channel_id == short_channel_id {
+ if at_failed_channel {
self.channel_liquidities
.entry(hop.short_channel_id)
.or_insert_with(ChannelLiquidity::new)
.as_directed_mut(source, &target, capacity_msat, &self.params)
.failed_at_channel(amount_msat, format_args!("SCID {}, towards {:?}", hop.short_channel_id, target), &self.logger);
- break;
+ } else {
+ self.channel_liquidities
+ .entry(hop.short_channel_id)
+ .or_insert_with(ChannelLiquidity::new)
+ .as_directed_mut(source, &target, capacity_msat, &self.params)
+ .failed_downstream(amount_msat, format_args!("SCID {}, towards {:?}", hop.short_channel_id, target), &self.logger);
}
-
- self.channel_liquidities
- .entry(hop.short_channel_id)
- .or_insert_with(ChannelLiquidity::new)
- .as_directed_mut(source, &target, capacity_msat, &self.params)
- .failed_downstream(amount_msat, format_args!("SCID {}, towards {:?}", hop.short_channel_id, target), &self.logger);
} else {
log_debug!(self.logger, "Not able to penalize channel with SCID {} as we do not have graph info for it (likely a route-hint last-hop).",
hop.short_channel_id);
}
+ if at_failed_channel { break; }
}
}
#[cfg(test)]
mod tests {
use super::{ChannelLiquidity, HistoricalBucketRangeTracker, ProbabilisticScoringParameters, ProbabilisticScorerUsingTime};
- use util::time::Time;
- use util::time::tests::SinceEpoch;
+ use crate::util::time::Time;
+ use crate::util::time::tests::SinceEpoch;
- use ln::features::{ChannelFeatures, NodeFeatures};
- use ln::msgs::{ChannelAnnouncement, ChannelUpdate, UnsignedChannelAnnouncement, UnsignedChannelUpdate};
- use routing::gossip::{EffectiveCapacity, NetworkGraph, NodeId};
- use routing::router::RouteHop;
- use routing::scoring::{ChannelUsage, Score};
- use util::ser::{ReadableArgs, Writeable};
- use util::test_utils::TestLogger;
+ use crate::ln::channelmanager;
+ use crate::ln::msgs::{ChannelAnnouncement, ChannelUpdate, UnsignedChannelAnnouncement, UnsignedChannelUpdate};
+ use crate::routing::gossip::{EffectiveCapacity, NetworkGraph, NodeId};
+ use crate::routing::router::RouteHop;
+ use crate::routing::scoring::{ChannelUsage, Score};
+ use crate::util::ser::{ReadableArgs, Writeable};
+ use crate::util::test_utils::TestLogger;
use bitcoin::blockdata::constants::genesis_block;
use bitcoin::hashes::Hash;
use bitcoin::network::constants::Network;
use bitcoin::secp256k1::{PublicKey, Secp256k1, SecretKey};
use core::time::Duration;
- use io;
+ use crate::io;
fn source_privkey() -> SecretKey {
SecretKey::from_slice(&[42; 32]).unwrap()
let node_2_secret = &SecretKey::from_slice(&[40; 32]).unwrap();
let secp_ctx = Secp256k1::new();
let unsigned_announcement = UnsignedChannelAnnouncement {
- features: ChannelFeatures::known(),
+ features: channelmanager::provided_channel_features(),
chain_hash: genesis_hash,
short_channel_id,
node_id_1: PublicKey::from_secret_key(&secp_ctx, &node_1_key),
bitcoin_signature_2: secp_ctx.sign_ecdsa(&msghash, &node_2_secret),
contents: unsigned_announcement,
};
- let chain_source: Option<&::util::test_utils::TestChainSource> = None;
+ let chain_source: Option<&crate::util::test_utils::TestChainSource> = None;
network_graph.update_channel_from_announcement(
&signed_announcement, &chain_source).unwrap();
update_channel(network_graph, short_channel_id, node_1_key, 0);
network_graph.update_channel(&signed_update).unwrap();
}
+ fn path_hop(pubkey: PublicKey, short_channel_id: u64, fee_msat: u64) -> RouteHop {
+ RouteHop {
+ pubkey,
+ node_features: channelmanager::provided_node_features(),
+ short_channel_id,
+ channel_features: channelmanager::provided_channel_features(),
+ fee_msat,
+ cltv_expiry_delta: 18,
+ }
+ }
+
fn payment_path_for_amount(amount_msat: u64) -> Vec<RouteHop> {
vec![
- RouteHop {
- pubkey: source_pubkey(),
- node_features: NodeFeatures::known(),
- short_channel_id: 41,
- channel_features: ChannelFeatures::known(),
- fee_msat: 1,
- cltv_expiry_delta: 18,
- },
- RouteHop {
- pubkey: target_pubkey(),
- node_features: NodeFeatures::known(),
- short_channel_id: 42,
- channel_features: ChannelFeatures::known(),
- fee_msat: 2,
- cltv_expiry_delta: 18,
- },
- RouteHop {
- pubkey: recipient_pubkey(),
- node_features: NodeFeatures::known(),
- short_channel_id: 43,
- channel_features: ChannelFeatures::known(),
- fee_msat: amount_msat,
- cltv_expiry_delta: 18,
- },
+ path_hop(source_pubkey(), 41, 1),
+ path_hop(target_pubkey(), 42, 2),
+ path_hop(recipient_pubkey(), 43, amount_msat),
]
}
let usage = ChannelUsage {
amount_msat: 1_024,
inflight_htlc_msat: 0,
- effective_capacity: EffectiveCapacity::Total { capacity_msat: 1_024_000, htlc_maximum_msat: Some(1_000) },
+ effective_capacity: EffectiveCapacity::Total { capacity_msat: 1_024_000, htlc_maximum_msat: 1_000 },
};
assert_eq!(scorer.channel_penalty_msat(42, &source, &target, usage), 0);
let usage = ChannelUsage { amount_msat: 10_240, ..usage };
let usage = ChannelUsage {
amount_msat: 128,
inflight_htlc_msat: 0,
- effective_capacity: EffectiveCapacity::Total { capacity_msat: 1_024, htlc_maximum_msat: Some(1_000) },
+ effective_capacity: EffectiveCapacity::Total { capacity_msat: 1_024, htlc_maximum_msat: 1_000 },
};
assert_eq!(scorer.channel_penalty_msat(42, &source, &target, usage), 58);
let usage = ChannelUsage { amount_msat: 256, ..usage };
let usage = ChannelUsage {
amount_msat: 39,
inflight_htlc_msat: 0,
- effective_capacity: EffectiveCapacity::Total { capacity_msat: 100, htlc_maximum_msat: Some(1_000) },
+ effective_capacity: EffectiveCapacity::Total { capacity_msat: 100, htlc_maximum_msat: 1_000 },
};
assert_eq!(scorer.channel_penalty_msat(42, &source, &target, usage), 0);
let usage = ChannelUsage { amount_msat: 50, ..usage };
let usage = ChannelUsage {
amount_msat: 500,
inflight_htlc_msat: 0,
- effective_capacity: EffectiveCapacity::Total { capacity_msat: 1_000, htlc_maximum_msat: Some(1_000) },
+ effective_capacity: EffectiveCapacity::Total { capacity_msat: 1_000, htlc_maximum_msat: 1_000 },
};
let failed_path = payment_path_for_amount(500);
let successful_path = payment_path_for_amount(200);
let usage = ChannelUsage {
amount_msat: 250,
inflight_htlc_msat: 0,
- effective_capacity: EffectiveCapacity::Total { capacity_msat: 1_000, htlc_maximum_msat: Some(1_000) },
+ effective_capacity: EffectiveCapacity::Total { capacity_msat: 1_000, htlc_maximum_msat: 1_000 },
};
assert_eq!(scorer.channel_penalty_msat(42, &source, &target, usage), 128);
let usage = ChannelUsage { amount_msat: 500, ..usage };
let usage = ChannelUsage {
amount_msat: 250,
inflight_htlc_msat: 0,
- effective_capacity: EffectiveCapacity::Total { capacity_msat: 1_000, htlc_maximum_msat: Some(1_000) },
+ effective_capacity: EffectiveCapacity::Total { capacity_msat: 1_000, htlc_maximum_msat: 1_000 },
};
assert_eq!(scorer.channel_penalty_msat(42, &source, &target, usage), 128);
let usage = ChannelUsage { amount_msat: 500, ..usage };
assert_eq!(scorer.channel_penalty_msat(42, &source, &target, usage), u64::max_value());
}
+ #[test]
+ fn ignores_channels_after_removed_failed_channel() {
+ // Previously, if we'd tried to send over a channel which was removed from the network
+ // graph before we call `payment_path_failed` (which is the default if the we get a "no
+ // such channel" error in the `InvoicePayer`), we would call `failed_downstream` on all
+ // channels in the route, even ones which they payment never reached. This tests to ensure
+ // we do not score such channels.
+ let secp_ctx = Secp256k1::new();
+ let logger = TestLogger::new();
+ let genesis_hash = genesis_block(Network::Testnet).header.block_hash();
+ let mut network_graph = NetworkGraph::new(genesis_hash, &logger);
+ let secret_a = SecretKey::from_slice(&[42; 32]).unwrap();
+ let secret_b = SecretKey::from_slice(&[43; 32]).unwrap();
+ let secret_c = SecretKey::from_slice(&[44; 32]).unwrap();
+ let secret_d = SecretKey::from_slice(&[45; 32]).unwrap();
+ add_channel(&mut network_graph, 42, secret_a, secret_b);
+ // Don't add the channel from B -> C.
+ add_channel(&mut network_graph, 44, secret_c, secret_d);
+
+ let pub_a = PublicKey::from_secret_key(&secp_ctx, &secret_a);
+ let pub_b = PublicKey::from_secret_key(&secp_ctx, &secret_b);
+ let pub_c = PublicKey::from_secret_key(&secp_ctx, &secret_c);
+ let pub_d = PublicKey::from_secret_key(&secp_ctx, &secret_d);
+
+ let path = vec![
+ path_hop(pub_b, 42, 1),
+ path_hop(pub_c, 43, 2),
+ path_hop(pub_d, 44, 100),
+ ];
+
+ let node_a = NodeId::from_pubkey(&pub_a);
+ let node_b = NodeId::from_pubkey(&pub_b);
+ let node_c = NodeId::from_pubkey(&pub_c);
+ let node_d = NodeId::from_pubkey(&pub_d);
+
+ let params = ProbabilisticScoringParameters {
+ liquidity_penalty_multiplier_msat: 1_000,
+ ..ProbabilisticScoringParameters::zero_penalty()
+ };
+ let mut scorer = ProbabilisticScorer::new(params, &network_graph, &logger);
+
+ let usage = ChannelUsage {
+ amount_msat: 250,
+ inflight_htlc_msat: 0,
+ effective_capacity: EffectiveCapacity::Total { capacity_msat: 1_000, htlc_maximum_msat: 1_000 },
+ };
+ assert_eq!(scorer.channel_penalty_msat(42, &node_a, &node_b, usage), 128);
+ // Note that a default liquidity bound is used for B -> C as no channel exists
+ assert_eq!(scorer.channel_penalty_msat(43, &node_b, &node_c, usage), 128);
+ assert_eq!(scorer.channel_penalty_msat(44, &node_c, &node_d, usage), 128);
+
+ scorer.payment_path_failed(&path.iter().collect::<Vec<_>>(), 43);
+
+ assert_eq!(scorer.channel_penalty_msat(42, &node_a, &node_b, usage), 80);
+ // Note that a default liquidity bound is used for B -> C as no channel exists
+ assert_eq!(scorer.channel_penalty_msat(43, &node_b, &node_c, usage), 128);
+ assert_eq!(scorer.channel_penalty_msat(44, &node_c, &node_d, usage), 128);
+ }
+
#[test]
fn reduces_liquidity_upper_bound_along_path_on_success() {
let logger = TestLogger::new();
let usage = ChannelUsage {
amount_msat: 250,
inflight_htlc_msat: 0,
- effective_capacity: EffectiveCapacity::Total { capacity_msat: 1_000, htlc_maximum_msat: Some(1_000) },
+ effective_capacity: EffectiveCapacity::Total { capacity_msat: 1_000, htlc_maximum_msat: 1_000 },
};
let path = payment_path_for_amount(500);
let usage = ChannelUsage {
amount_msat: 0,
inflight_htlc_msat: 0,
- effective_capacity: EffectiveCapacity::Total { capacity_msat: 1_024, htlc_maximum_msat: Some(1_024) },
+ effective_capacity: EffectiveCapacity::Total { capacity_msat: 1_024, htlc_maximum_msat: 1_024 },
};
assert_eq!(scorer.channel_penalty_msat(42, &source, &target, usage), 0);
let usage = ChannelUsage { amount_msat: 1_023, ..usage };
let usage = ChannelUsage {
amount_msat: 256,
inflight_htlc_msat: 0,
- effective_capacity: EffectiveCapacity::Total { capacity_msat: 1_024, htlc_maximum_msat: Some(1_000) },
+ effective_capacity: EffectiveCapacity::Total { capacity_msat: 1_024, htlc_maximum_msat: 1_000 },
};
assert_eq!(scorer.channel_penalty_msat(42, &source, &target, usage), 125);
let usage = ChannelUsage {
amount_msat: 512,
inflight_htlc_msat: 0,
- effective_capacity: EffectiveCapacity::Total { capacity_msat: 1_024, htlc_maximum_msat: Some(1_000) },
+ effective_capacity: EffectiveCapacity::Total { capacity_msat: 1_024, htlc_maximum_msat: 1_000 },
};
assert_eq!(scorer.channel_penalty_msat(42, &source, &target, usage), 300);
let usage = ChannelUsage {
amount_msat: 500,
inflight_htlc_msat: 0,
- effective_capacity: EffectiveCapacity::Total { capacity_msat: 1_000, htlc_maximum_msat: Some(1_000) },
+ effective_capacity: EffectiveCapacity::Total { capacity_msat: 1_000, htlc_maximum_msat: 1_000 },
};
scorer.payment_path_failed(&payment_path_for_amount(500).iter().collect::<Vec<_>>(), 42);
let usage = ChannelUsage {
amount_msat: 500,
inflight_htlc_msat: 0,
- effective_capacity: EffectiveCapacity::Total { capacity_msat: 1_000, htlc_maximum_msat: Some(1_000) },
+ effective_capacity: EffectiveCapacity::Total { capacity_msat: 1_000, htlc_maximum_msat: 1_000 },
};
scorer.payment_path_failed(&payment_path_for_amount(500).iter().collect::<Vec<_>>(), 42);
let usage = ChannelUsage {
amount_msat: 100_000_000,
inflight_htlc_msat: 0,
- effective_capacity: EffectiveCapacity::Total { capacity_msat: 950_000_000, htlc_maximum_msat: Some(1_000) },
+ effective_capacity: EffectiveCapacity::Total { capacity_msat: 950_000_000, htlc_maximum_msat: 1_000 },
};
assert_eq!(scorer.channel_penalty_msat(42, &source, &target, usage), 4375);
let usage = ChannelUsage {
- effective_capacity: EffectiveCapacity::Total { capacity_msat: 1_950_000_000, htlc_maximum_msat: Some(1_000) }, ..usage
+ effective_capacity: EffectiveCapacity::Total { capacity_msat: 1_950_000_000, htlc_maximum_msat: 1_000 }, ..usage
};
assert_eq!(scorer.channel_penalty_msat(42, &source, &target, usage), 2739);
let usage = ChannelUsage {
- effective_capacity: EffectiveCapacity::Total { capacity_msat: 2_950_000_000, htlc_maximum_msat: Some(1_000) }, ..usage
+ effective_capacity: EffectiveCapacity::Total { capacity_msat: 2_950_000_000, htlc_maximum_msat: 1_000 }, ..usage
};
assert_eq!(scorer.channel_penalty_msat(42, &source, &target, usage), 2236);
let usage = ChannelUsage {
- effective_capacity: EffectiveCapacity::Total { capacity_msat: 3_950_000_000, htlc_maximum_msat: Some(1_000) }, ..usage
+ effective_capacity: EffectiveCapacity::Total { capacity_msat: 3_950_000_000, htlc_maximum_msat: 1_000 }, ..usage
};
assert_eq!(scorer.channel_penalty_msat(42, &source, &target, usage), 1983);
let usage = ChannelUsage {
- effective_capacity: EffectiveCapacity::Total { capacity_msat: 4_950_000_000, htlc_maximum_msat: Some(1_000) }, ..usage
+ effective_capacity: EffectiveCapacity::Total { capacity_msat: 4_950_000_000, htlc_maximum_msat: 1_000 }, ..usage
};
assert_eq!(scorer.channel_penalty_msat(42, &source, &target, usage), 1637);
let usage = ChannelUsage {
- effective_capacity: EffectiveCapacity::Total { capacity_msat: 5_950_000_000, htlc_maximum_msat: Some(1_000) }, ..usage
+ effective_capacity: EffectiveCapacity::Total { capacity_msat: 5_950_000_000, htlc_maximum_msat: 1_000 }, ..usage
};
assert_eq!(scorer.channel_penalty_msat(42, &source, &target, usage), 1606);
let usage = ChannelUsage {
- effective_capacity: EffectiveCapacity::Total { capacity_msat: 6_950_000_000, htlc_maximum_msat: Some(1_000) }, ..usage
+ effective_capacity: EffectiveCapacity::Total { capacity_msat: 6_950_000_000, htlc_maximum_msat: 1_000 }, ..usage
};
assert_eq!(scorer.channel_penalty_msat(42, &source, &target, usage), 1331);
let usage = ChannelUsage {
- effective_capacity: EffectiveCapacity::Total { capacity_msat: 7_450_000_000, htlc_maximum_msat: Some(1_000) }, ..usage
+ effective_capacity: EffectiveCapacity::Total { capacity_msat: 7_450_000_000, htlc_maximum_msat: 1_000 }, ..usage
};
assert_eq!(scorer.channel_penalty_msat(42, &source, &target, usage), 1387);
let usage = ChannelUsage {
- effective_capacity: EffectiveCapacity::Total { capacity_msat: 7_950_000_000, htlc_maximum_msat: Some(1_000) }, ..usage
+ effective_capacity: EffectiveCapacity::Total { capacity_msat: 7_950_000_000, htlc_maximum_msat: 1_000 }, ..usage
};
assert_eq!(scorer.channel_penalty_msat(42, &source, &target, usage), 1379);
let usage = ChannelUsage {
- effective_capacity: EffectiveCapacity::Total { capacity_msat: 8_950_000_000, htlc_maximum_msat: Some(1_000) }, ..usage
+ effective_capacity: EffectiveCapacity::Total { capacity_msat: 8_950_000_000, htlc_maximum_msat: 1_000 }, ..usage
};
assert_eq!(scorer.channel_penalty_msat(42, &source, &target, usage), 1363);
let usage = ChannelUsage {
- effective_capacity: EffectiveCapacity::Total { capacity_msat: 9_950_000_000, htlc_maximum_msat: Some(1_000) }, ..usage
+ effective_capacity: EffectiveCapacity::Total { capacity_msat: 9_950_000_000, htlc_maximum_msat: 1_000 }, ..usage
};
assert_eq!(scorer.channel_penalty_msat(42, &source, &target, usage), 1355);
}
let usage = ChannelUsage {
amount_msat: 128,
inflight_htlc_msat: 0,
- effective_capacity: EffectiveCapacity::Total { capacity_msat: 1_024, htlc_maximum_msat: Some(1_000) },
+ effective_capacity: EffectiveCapacity::Total { capacity_msat: 1_024, htlc_maximum_msat: 1_000 },
};
let params = ProbabilisticScoringParameters {
let usage = ChannelUsage {
amount_msat: 512_000,
inflight_htlc_msat: 0,
- effective_capacity: EffectiveCapacity::Total { capacity_msat: 1_024_000, htlc_maximum_msat: Some(1_000) },
+ effective_capacity: EffectiveCapacity::Total { capacity_msat: 1_024_000, htlc_maximum_msat: 1_000 },
};
let params = ProbabilisticScoringParameters {
let usage = ChannelUsage {
amount_msat: 750,
inflight_htlc_msat: 0,
- effective_capacity: EffectiveCapacity::Total { capacity_msat: 1_000, htlc_maximum_msat: Some(1_000) },
+ effective_capacity: EffectiveCapacity::Total { capacity_msat: 1_000, htlc_maximum_msat: 1_000 },
};
assert_ne!(scorer.channel_penalty_msat(42, &source, &target, usage), u64::max_value());
let params = ProbabilisticScoringParameters {
historical_liquidity_penalty_multiplier_msat: 1024,
historical_liquidity_penalty_amount_multiplier_msat: 1024,
+ historical_no_updates_half_life: Duration::from_secs(10),
..ProbabilisticScoringParameters::zero_penalty()
};
let mut scorer = ProbabilisticScorer::new(params, &network_graph, &logger);
let usage = ChannelUsage {
amount_msat: 100,
inflight_htlc_msat: 0,
- effective_capacity: EffectiveCapacity::Total { capacity_msat: 1_024, htlc_maximum_msat: Some(1_024) },
+ effective_capacity: EffectiveCapacity::Total { capacity_msat: 1_024, htlc_maximum_msat: 1_024 },
};
// With no historical data the normal liquidity penalty calculation is used.
assert_eq!(scorer.channel_penalty_msat(42, &source, &target, usage), 47);
// still remember that there was some failure in the past, and assign a non-0 penalty.
scorer.payment_path_failed(&payment_path_for_amount(1000).iter().collect::<Vec<_>>(), 43);
assert_eq!(scorer.channel_penalty_msat(42, &source, &target, usage), 198);
+
+ // Advance the time forward 16 half-lives (which the docs claim will ensure all data is
+ // gone), and check that we're back to where we started.
+ SinceEpoch::advance(Duration::from_secs(10 * 16));
+ assert_eq!(scorer.channel_penalty_msat(42, &source, &target, usage), 47);
}
#[test]
let usage = ChannelUsage {
amount_msat: 512_000,
inflight_htlc_msat: 0,
- effective_capacity: EffectiveCapacity::Total { capacity_msat: 1_024_000, htlc_maximum_msat: Some(1_000) },
+ effective_capacity: EffectiveCapacity::Total { capacity_msat: 1_024_000, htlc_maximum_msat: 1_000 },
};
assert_eq!(scorer.channel_penalty_msat(42, &source, &target, usage), 0);
let usage = ChannelUsage {
amount_msat: 512_000,
inflight_htlc_msat: 0,
- effective_capacity: EffectiveCapacity::Total { capacity_msat: 1_024_000, htlc_maximum_msat: Some(1_024_000) },
+ effective_capacity: EffectiveCapacity::Total { capacity_msat: 1_024_000, htlc_maximum_msat: 1_024_000 },
};
assert_eq!(scorer.channel_penalty_msat(42, &source, &target, usage), 500);
let usage = ChannelUsage {
amount_msat: 512_000,
inflight_htlc_msat: 0,
- effective_capacity: EffectiveCapacity::Total { capacity_msat: 1_024_000, htlc_maximum_msat: Some(512_000) },
+ effective_capacity: EffectiveCapacity::Total { capacity_msat: 1_024_000, htlc_maximum_msat: 512_000 },
};
assert_eq!(scorer.channel_penalty_msat(42, &source, &target, usage), 500);
let usage = ChannelUsage {
amount_msat: 512_000,
inflight_htlc_msat: 0,
- effective_capacity: EffectiveCapacity::Total { capacity_msat: 1_024_000, htlc_maximum_msat: Some(511_999) },
+ effective_capacity: EffectiveCapacity::Total { capacity_msat: 1_024_000, htlc_maximum_msat: 511_999 },
};
assert_eq!(scorer.channel_penalty_msat(42, &source, &target, usage), 0);
}
projects / rust-lightning / blobdiff