remove mesh fix for subsequent commit

Author: jxs

protocols/gossipsub/CHANGELOG.md

@@ -1,4 +1,9 @@
 ## 0.50.0
+- Fix underflow when shuffling peers after prunning.
+  See [PR 6183](https://github.com/libp2p/rust-libp2p/pull/6183)
+
+  See [PR 6112](https://github.com/libp2p/rust-libp2p/pull/6112)
+
 - Remove peer penalty for duplicate messages.
   See [PR 6112](https://github.com/libp2p/rust-libp2p/pull/6112)
 
@@ -13,7 +18,7 @@
 
 - Fix incorrect default values in ConfigBuilder
   See [PR 6113](https://github.com/libp2p/rust-libp2p/pull/6113)
-  
+
 - Remove duplicated config `set_topic_max_transmit_size` method, prefer `max_transmit_size_for_topic`.
   See [PR 6173](https://github.com/libp2p/rust-libp2p/pull/6173).
 

protocols/gossipsub/src/behaviour.rs

@@ -1366,6 +1366,8 @@ where
             tracing::error!(peer_id = %peer_id, "Peer non-existent when handling graft");
             return;
         };
+        // Needs to be here to comply with the borrow checker.
+        let is_outbound = connected_peer.outbound;
 
         // For each topic, if a peer has grafted us, then we necessarily must be in their mesh
         // and they must be subscribed to the topic. Ensure we have recorded the mapping.
@@ -1453,9 +1455,10 @@ where
                     }
 
                     // check mesh upper bound and only allow graft if the upper bound is not reached
+                    // or if it is an outbound peer
                     let mesh_n_high = self.config.mesh_n_high_for_topic(&topic_hash);
 
-                    if peers.len() >= mesh_n_high {
+                    if peers.len() >= mesh_n_high && !is_outbound {
                         to_prune_topics.insert(topic_hash.clone());
                         continue;
                     }
@@ -2225,9 +2228,7 @@ where
                     score_p1.partial_cmp(&score_p2).unwrap_or(Ordering::Equal)
                 });
                 // shuffle everything except the last retain_scores many peers (the best ones)
-                if peers.len() > self.config.retain_scores() {
-                    shuffled[..peers.len() - self.config.retain_scores()].shuffle(&mut rng);
-                }
+                shuffled[..peers.len() - self.config.retain_scores()].shuffle(&mut rng);
 
                 // count total number of outbound peers
                 let mut outbound = shuffled