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Fix overflow in ProbabilisticScorer

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When a routing hint is given in an invoice, the effective capacity of
the channel is assumed to be infinite (i.e., u64::max_value) if the hop
is private. Adding 1 to this in the success probability calculation will
cause an overflow and ultimately an `index out of bounds panic` in
log10_times_1024. This was not an issue with using log10 because the use
of f64 would give infinite which casts to 0 for u64.
This commit is contained in:
Jeffrey Czyz 2022-03-24 18:21:29 -05:00
parent 5b36449c59
commit 4ea18e3232
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GPG key ID: 3A4E08275D5E96D2
1 changed files with 18 additions and 2 deletions
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20
lightning/src/routing/scoring.rs
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@ -673,8 +673,8 @@ impl<L: Deref<Target = u64>, T: Time, U: Deref<Target = T>> DirectedChannelLiqui
} else if amount_msat <= min_liquidity_msat {
0
} else {
let numerator = max_liquidity_msat + 1 - amount_msat;
let denominator = max_liquidity_msat + 1 - min_liquidity_msat;
let numerator = (max_liquidity_msat - amount_msat).saturating_add(1);
let denominator = (max_liquidity_msat - min_liquidity_msat).saturating_add(1);
approx::negative_log10_times_1024(numerator, denominator)
.saturating_mul(liquidity_penalty_multiplier_msat) / 1024
}
@ -2061,4 +2061,20 @@ mod tests {
let scorer = ProbabilisticScorer::new(params, &network_graph);
assert_eq!(scorer.channel_penalty_msat(42, 128, 1_024, &source, &target), 1085);
}
#[test]
fn calculates_log10_without_overflowing_u64_max_value() {
let network_graph = network_graph();
let source = source_node_id();
let target = target_node_id();
let params = ProbabilisticScoringParameters {
base_penalty_msat: 0, ..Default::default()
};
let scorer = ProbabilisticScorer::new(params, &network_graph);
assert_eq!(
scorer.channel_penalty_msat(42, u64::max_value(), u64::max_value(), &source, &target),
20_000,
);
}
}