ClientKeepAlivePacket is processed incorrectly

[GreenpixDev]

Description

The Minestom server isn't processing ClientKeepAlivePacket correctly.

This happens because all packets with CONFIGURATION and PLAY states are added to the player's packet queue and processed in the minestom tick thread (see method PacketProcessor#process(PlayerConnection, int, ByteBuffer)).

As a result, the player's latency is overestimated. For example, if you run a local minestom server, the latency will be about 50ms instead of the expected 0ms.

Report

The problem is relevant for the commit: e8e22a2

Steps to reproduce:

1. Start the demo server locally
2. Connect at localhost address
3. Measure ping. To measure it you can add latency console output to the method KeepAliveListener#listener(ClientKeepAlivePacket, Player)

public static void listener(ClientKeepAlivePacket packet, Player player) {
    final long packetId = packet.id();
    if (packetId != player.getLastKeepAlive()) {
        player.kick(KICK_MESSAGE);
        return;
    }
    player.refreshAnswerKeepAlive(true);
    // Update latency
    final int latency = (int) (System.currentTimeMillis() - packetId);
    player.refreshLatency(latency);
+    System.out.println(latency)
}

Result

Expected result: latency close to 0ms
Actual result: latency close to 50ms

Potential solution

Potential solution: process the packet ClientKeepAlivePacket bypassing the player's packet queue (similar to packets with HANDSHAKE, STATUS and LOGIN states)