From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Spottedleaf <Spottedleaf@users.noreply.github.com>
Date: Fri, 30 Oct 2020 22:37:16 -0700
Subject: [PATCH] Add packet limiter config

Example config:
packet-limiter:
  kick-message: '&cSent too many packets'
  limits:
    all:
      interval: 7.0
      max-packet-rate: 500.0
    ServerboundPlaceRecipePacket:
      interval: 4.0
      max-packet-rate: 5.0
      action: DROP

all section refers to all incoming packets, the action for all is
hard coded to KICK.

For specific limits, the section name is the class's name,
and an action can be defined: DROP or KICK

If interval or rate are less-than 0, the limit is ignored

diff --git a/src/main/java/net/minecraft/network/Connection.java b/src/main/java/net/minecraft/network/Connection.java
index 6e75a5e7eb51a5bbb7b73436bbd37df1519cb0fc..a0434b92615c10a319eb4528808a83d01df2c516 100644
--- a/src/main/java/net/minecraft/network/Connection.java
+++ b/src/main/java/net/minecraft/network/Connection.java
@@ -132,6 +132,22 @@ public class Connection extends SimpleChannelInboundHandler<Packet<?>> {
         return null;
     }
     // Paper end - add utility methods
+    // Paper start - packet limiter
+    protected final Object PACKET_LIMIT_LOCK = new Object();
+    protected final @Nullable io.papermc.paper.util.IntervalledCounter allPacketCounts = io.papermc.paper.configuration.GlobalConfiguration.get().packetLimiter.allPackets.isEnabled() ? new io.papermc.paper.util.IntervalledCounter(
+        (long)(io.papermc.paper.configuration.GlobalConfiguration.get().packetLimiter.allPackets.interval() * 1.0e9)
+    ) : null;
+    protected final java.util.Map<Class<? extends net.minecraft.network.protocol.Packet<?>>, io.papermc.paper.util.IntervalledCounter> packetSpecificLimits = new java.util.HashMap<>();
+
+    private boolean stopReadingPackets;
+    private void killForPacketSpam() {
+        this.sendPacket(new ClientboundDisconnectPacket(io.papermc.paper.adventure.PaperAdventure.asVanilla(io.papermc.paper.configuration.GlobalConfiguration.get().packetLimiter.kickMessage)), PacketSendListener.thenRun(() -> {
+            this.disconnect(io.papermc.paper.adventure.PaperAdventure.asVanilla(io.papermc.paper.configuration.GlobalConfiguration.get().packetLimiter.kickMessage));
+        }), true);
+        this.setReadOnly();
+        this.stopReadingPackets = true;
+    }
+    // Paper end - packet limiter
 
     public Connection(PacketFlow side) {
         this.receiving = side;
@@ -224,6 +240,55 @@ public class Connection extends SimpleChannelInboundHandler<Packet<?>> {
             if (packetlistener == null) {
                 throw new IllegalStateException("Received a packet before the packet listener was initialized");
             } else {
+                // Paper start - packet limiter
+                if (this.stopReadingPackets) {
+                    return;
+                }
+                if (this.allPacketCounts != null ||
+                    io.papermc.paper.configuration.GlobalConfiguration.get().packetLimiter.overrides.containsKey(packet.getClass())) {
+                    long time = System.nanoTime();
+                    synchronized (PACKET_LIMIT_LOCK) {
+                        if (this.allPacketCounts != null) {
+                            this.allPacketCounts.updateAndAdd(1, time);
+                            if (this.allPacketCounts.getRate() >= io.papermc.paper.configuration.GlobalConfiguration.get().packetLimiter.allPackets.maxPacketRate()) {
+                                this.killForPacketSpam();
+                                return;
+                            }
+                        }
+
+                        for (Class<?> check = packet.getClass(); check != Object.class; check = check.getSuperclass()) {
+                            io.papermc.paper.configuration.GlobalConfiguration.PacketLimiter.PacketLimit packetSpecificLimit =
+                                io.papermc.paper.configuration.GlobalConfiguration.get().packetLimiter.overrides.get(check);
+                            if (packetSpecificLimit == null || !packetSpecificLimit.isEnabled()) {
+                                continue;
+                            }
+                            io.papermc.paper.util.IntervalledCounter counter = this.packetSpecificLimits.computeIfAbsent((Class)check, (clazz) -> {
+                                return new io.papermc.paper.util.IntervalledCounter((long)(packetSpecificLimit.interval() * 1.0e9));
+                            });
+                            counter.updateAndAdd(1, time);
+                            if (counter.getRate() >= packetSpecificLimit.maxPacketRate()) {
+                                switch (packetSpecificLimit.action()) {
+                                    case DROP:
+                                        return;
+                                    case KICK:
+                                        String deobfedPacketName = io.papermc.paper.util.ObfHelper.INSTANCE.deobfClassName(check.getName());
+
+                                        String playerName;
+                                        if (this.packetListener instanceof net.minecraft.server.network.ServerCommonPacketListenerImpl impl) {
+                                            playerName = impl.getOwner().getName();
+                                        } else {
+                                            playerName = this.getLoggableAddress(net.minecraft.server.MinecraftServer.getServer().logIPs());
+                                        }
+
+                                        Connection.LOGGER.warn("{} kicked for packet spamming: {}", playerName, deobfedPacketName.substring(deobfedPacketName.lastIndexOf(".") + 1));
+                                        this.killForPacketSpam();
+                                        return;
+                                }
+                            }
+                        }
+                    }
+                }
+                // Paper end - packet limiter
                 if (packetlistener.shouldHandleMessage(packet)) {
                     try {
                         Connection.genericsFtw(packet, packetlistener);