Optimize Ping message

src/neo/Ledger/Blockchain.cs

@@ -349,8 +349,6 @@ private VerifyResult OnNewBlock(Block block)
                     return VerifyResult.Invalid;
                 block_cache.TryAdd(block.Hash, block);
                 block_cache_unverified.Remove(block.Index);
-                // We can store the new block in block_cache and tell the new height to other nodes before Persist().
-                system.LocalNode.Tell(Message.Create(MessageCommand.Ping, PingPayload.Create(Singleton.Height + 1)));
                 Persist(block);
                 SaveHeaderHashList();
                 if (block_cache_unverified.TryGetValue(Height + 1, out var unverifiedBlocks))
@@ -359,6 +357,8 @@ private VerifyResult OnNewBlock(Block block)
                         Self.Tell(unverifiedBlock, ActorRefs.NoSender);
                     block_cache_unverified.Remove(Height + 1);
                 }
+                // We can store the new block in block_cache and tell the new height to other nodes after Persist().
+                system.LocalNode.Tell(Message.Create(MessageCommand.Ping, PingPayload.Create(Singleton.Height)));
             }
             return VerifyResult.Succeed;
         }

src/neo/Network/P2P/RemoteNode.cs

@@ -29,6 +29,7 @@ internal class Relay { public IInventory Inventory; }
         public int ListenerTcpPort { get; private set; } = 0;
         public VersionPayload Version { get; private set; }
         public uint LastBlockIndex { get; private set; } = 0;
+        public uint LastHeightSent { get; private set; } = 0;
         public bool IsFullNode { get; private set; } = false;
 
         public RemoteNode(NeoSystem system, object connection, IPEndPoint remote, IPEndPoint local)
@@ -124,6 +125,11 @@ protected override void OnReceive(object message)
                     RefreshPendingKnownHashes();
                     break;
                 case Message msg:
+                    if (msg.Command == MessageCommand.Ping && msg.Payload is PingPayload ping)
+                    {
+                        if (LastHeightSent >= ping.LastBlockIndex) return;
+                        LastHeightSent = ping.LastBlockIndex;
+                    }
                     EnqueueMessage(msg);
                     break;
                 case IInventory inventory: