feat(discv4): neighbors packet logging (#12042)

Co-authored-by: Oliver Nordbjerg <hi@notbjerg.me>

Cargo.lock

@@ -6922,6 +6922,7 @@ dependencies = [
  "discv5",
  "enr",
  "generic-array",
+ "itertools 0.13.0",
  "parking_lot",
  "rand 0.8.5",
  "reth-ethereum-forks",

crates/net/discv4/Cargo.toml

@@ -42,6 +42,7 @@ parking_lot.workspace = true
 rand = { workspace = true, optional = true }
 generic-array.workspace = true
 serde = { workspace = true, optional = true }
+itertools.workspace = true
 
 [dev-dependencies]
 assert_matches.workspace = true

crates/net/discv4/src/lib.rs

@@ -38,6 +38,7 @@ use discv5::{
     ConnectionDirection, ConnectionState,
 };
 use enr::Enr;
+use itertools::Itertools;
 use parking_lot::Mutex;
 use proto::{EnrRequest, EnrResponse};
 use reth_ethereum_forks::ForkId;
@@ -861,7 +862,7 @@ impl Discv4Service {
         let Some(bucket) = self.kbuckets.get_bucket(&key) else { return false };
         if bucket.num_entries() < MAX_NODES_PER_BUCKET / 2 {
             // skip half empty bucket
-            return false;
+            return false
         }
         self.remove_key(node_id, key)
     }
@@ -1406,6 +1407,16 @@ impl Discv4Service {
             }
         };
 
+        // log the peers we discovered
+        trace!(target: "discv4",
+            target=format!("{:#?}", node_id),
+            peers_count=msg.nodes.len(),
+            peers=format!("[{:#}]", msg.nodes.iter()
+                .map(|node_rec| node_rec.id
+            ).format(", ")),
+            "Received peers from Neighbours packet"
+        );
+
         // This is the recursive lookup step where we initiate new FindNode requests for new nodes
         // that were discovered.
         for node in msg.nodes.into_iter().map(NodeRecord::into_ipv4_mapped) {