contradicting clock samples replace stored ones

1 files changed, 15 insertions, 3 deletions

diff --git a/src/transport/paths.rs b/src/transport/paths.rs
index 6512759..2ef3a12 100644
--- a/src/transport/paths.rs
+++ b/src/transport/paths.rs
@@ -107,7 +107,7 @@ const SWITCH_MIN: Duration = Duration::from_millis(5);
 /// Paths kept at most: they are of peers this node chose among, but bounded anyway.
 const MAX_PATHS: usize = 4096;
 /// A path's clock sample with the narrowest bound is kept this long at most; then the
-/// next one takes its place, so a clock that was set anew shows within this time.
+/// next one takes its place. (A clock set anew shows at once: `Table::clock`.)
 const CLOCK_KEPT: Duration = Duration::from_secs(300);
 
 /// How far a peer's clock is ahead of ours (behind if negative), from a PING and its
@@ -395,14 +395,18 @@ impl Table {
     }
 
     /// A clock sample from a PONG over `address`: kept if its bound is as narrow as the
-    /// one kept, or that one is older than `CLOCK_KEPT`. The narrowest bound is the
+    /// one kept, or that one is older than `CLOCK_KEPT`, or the two can't both be right
+    /// (their bounds don't overlap: a clock was set anew). The narrowest bound is the
     /// round trip least delayed by queues and relays.
     fn clock(&mut self, address: &str, offset: ClockOffset, now: Instant) {
         let Some(path) = self.paths.get_mut(address) else {
             return;
         };
         let replaces = path.clock.is_none_or(|(kept, at)| {
-            offset.within_ms <= kept.within_ms || now.saturating_duration_since(at) >= CLOCK_KEPT
+            offset.within_ms <= kept.within_ms
+                || now.saturating_duration_since(at) >= CLOCK_KEPT
+                || offset.offset_ms.abs_diff(kept.offset_ms)
+                    > offset.within_ms.saturating_add(kept.within_ms)
         });
         if replaces {
             path.clock = Some((offset, now));
@@ -1224,6 +1228,14 @@ mod tests {
             table.paths["libp2p:z"].clock.map(|(kept, _)| kept),
             Some(wider)
         );
+        // A clock set anew: a sample the kept one contradicts takes its place at once,
+        // its bound wider or not.
+        let set_anew = ClockOffset::of(UnixMillis(25_000), heard, rtt * 8);
+        table.clock("libp2p:z", set_anew, now + CLOCK_KEPT);
+        assert_eq!(
+            table.paths["libp2p:z"].clock.map(|(kept, _)| kept),
+            Some(set_anew)
+        );
     }
 
     /// A peer's only path is measured too once messages go over it, unless its