fix(kad): preserve deadline in keep alive logic

protocols/kad/CHANGELOG.md

@@ -1,3 +1,10 @@
+## 0.43.3 - unreleased
+
+- Preserve existing `KeepAlive::Until` timeout instead of continuously setting new `KeepAlive::Until(Instant::now() + self.config.idle_timeout)`.
+  See [PR 3801].
+
+[PR 3801]: https://github.com/libp2p/rust-libp2p/pull/3801
+
 ## 0.43.2
 
 - Export pub enum `RoutingUpdate`. See [PR 3739].

protocols/kad/Cargo.toml

@@ -3,7 +3,7 @@ name = "libp2p-kad"
 edition = "2021"
 rust-version = "1.65.0"
 description = "Kademlia protocol for libp2p"
-version = "0.43.2"
+version = "0.43.3"
 authors = ["Parity Technologies <[email protected]>"]
 license = "MIT"
 repository = "https://github.com/libp2p/rust-libp2p"

protocols/kad/src/handler_priv.rs

@@ -757,12 +757,15 @@ where
             }
         }
 
-        if self.outbound_substreams.is_empty() && self.inbound_substreams.is_empty() {
-            // We destroyed all substreams in this function.
-            self.keep_alive = KeepAlive::Until(Instant::now() + self.config.idle_timeout);
-        } else {
-            self.keep_alive = KeepAlive::Yes;
-        }
+        let no_streams = self.outbound_substreams.is_empty() && self.inbound_substreams.is_empty();
+        self.keep_alive = match (no_streams, self.keep_alive) {
+            // No open streams. Preserve the existing idle timeout.
+            (true, k @ KeepAlive::Until(_)) => k,
+            // No open streams. Set idle timeout.
+            (true, _) => KeepAlive::Until(Instant::now() + self.config.idle_timeout),
+            // Keep alive for open streams.
+            (false, _) => KeepAlive::Yes,
+        };
 
         Poll::Pending
     }