fix(swarm): prevent overflow in keep-alive computation

swarm/CHANGELOG.md

@@ -1,3 +1,8 @@
+## 0.43.7 - unreleased
+
+- Fix overflow in `KeepAlive` computation that could occur panic at `Delay::reset` if `SwarmBuilder::idle_connection_timeout` is configured too large.
+  See [PR 4644](https://github.com/libp2p/rust-libp2p/pull/4644).
+
 ## 0.43.6 - unreleased
 
 - Deprecate `libp2p::swarm::SwarmBuilder`.

swarm/src/connection.rs

@@ -351,13 +351,13 @@ where
                 (Shutdown::Later(timer, deadline), KeepAlive::Until(t)) => {
                     if *deadline != t {
                         *deadline = t;
+                        let now = Instant::now();
                         if let Some(new_duration) = deadline.checked_duration_since(Instant::now())
                         {
                             let effective_keep_alive = max(new_duration, *idle_timeout);
 
-                            let now = Instant::now();
-                            let safe_effective_keep_alive = checked_add_fraction(now, effective_keep_alive);
-
+                            // `Delay::reset` panics if `now + effective_keep_alive` is `> u64::MAX`.
+                            let safe_effective_keep_alive = checked_add_fraction(now, effective_keep_alive);                            
                             timer.reset(safe_effective_keep_alive)
                         }
                     }