Paper/patches/server/0721-Add-packet-limiter-config.patch

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 9c0c181013d419d1a74f86b5d8cecf83b28925c6..335d9e5f11ad3469f3a0310782e41283973f5a5f 100644
--- a/src/main/java/net/minecraft/network/Connection.java
+++ b/src/main/java/net/minecraft/network/Connection.java
@@ -153,6 +153,22 @@ public class Connection extends SimpleChannelInboundHandler<Packet<?>> {
         }
     }
     // Paper end - allow controlled flushing
+    // 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));
+        }));
+        this.setReadOnly();
+        this.stopReadingPackets = true;
+    }
+    // Paper end - packet limiter
 
     public Connection(PacketFlow side) {
         this.receiving = side;
@@ -233,6 +249,45 @@ public class Connection extends SimpleChannelInboundHandler<Packet<?>> {
 
     protected void channelRead0(ChannelHandlerContext channelhandlercontext, Packet<?> packet) {
         if (this.channel.isOpen()) {
+            // 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:
+                                    this.killForPacketSpam();
+                                    return;
+                            }
+                        }
+                    }
+                }
+            }
+            // Paper end - packet limiter
             try {
                 Connection.genericsFtw(packet, this.packetListener);
             } catch (RunningOnDifferentThreadException cancelledpackethandleexception) {