Buffer joins to world

This patch buffers the number of logins which will attempt to join
the world per tick, this attempts to reduce the impact that join floods
has on the server

paper-server/patches/sources/net/minecraft/network/Connection.java.patch

@@ -82,7 +82,34 @@
      }
  
      private void validateListener(ProtocolInfo<?> state, PacketListener listener) {
-@@ -431,7 +458,7 @@
+@@ -418,12 +445,26 @@
+         }
+     }
+ 
++    private static final int MAX_PER_TICK = io.papermc.paper.configuration.GlobalConfiguration.get().misc.maxJoinsPerTick; // Paper - Buffer joins to world
++    private static int joinAttemptsThisTick; // Paper - Buffer joins to world
++    private static int currTick; // Paper - Buffer joins to world
+     public void tick() {
+         this.flushQueue();
++        // Paper start - Buffer joins to world
++        if (Connection.currTick != net.minecraft.server.MinecraftServer.currentTick) {
++            Connection.currTick = net.minecraft.server.MinecraftServer.currentTick;
++            Connection.joinAttemptsThisTick = 0;
++        }
++        // Paper end - Buffer joins to world
+         PacketListener packetlistener = this.packetListener;
+ 
+         if (packetlistener instanceof TickablePacketListener tickablepacketlistener) {
++            // Paper start - Buffer joins to world
++            if (!(this.packetListener instanceof net.minecraft.server.network.ServerLoginPacketListenerImpl loginPacketListener)
++                || loginPacketListener.state != net.minecraft.server.network.ServerLoginPacketListenerImpl.State.VERIFYING
++                || Connection.joinAttemptsThisTick++ < MAX_PER_TICK) {
+             tickablepacketlistener.tick();
++            } // Paper end - Buffer joins to world
+         }
+ 
+         if (!this.isConnected() && !this.disconnectionHandled) {
+@@ -431,7 +472,7 @@
          }
  
          if (this.channel != null) {
@@ -91,7 +118,7 @@
          }
  
          if (this.tickCount++ % 20 == 0) {
-@@ -464,12 +491,15 @@
+@@ -464,12 +505,15 @@
      }
  
      public void disconnect(DisconnectionDetails disconnectionInfo) {
@@ -108,7 +135,7 @@
              this.disconnectionDetails = disconnectionInfo;
          }
  
-@@ -537,7 +567,7 @@
+@@ -537,7 +581,7 @@
      }
  
      public void configurePacketHandler(ChannelPipeline pipeline) {
@@ -117,11 +144,10 @@
              public void write(ChannelHandlerContext channelhandlercontext, Object object, ChannelPromise channelpromise) throws Exception {
                  super.write(channelhandlercontext, object, channelpromise);
              }
-@@ -660,7 +690,28 @@
+@@ -661,6 +705,27 @@
-                     });
  
                      packetlistener1.onDisconnect(disconnectiondetails);
-+                }
+                 }
 +                this.pendingActions.clear(); // Free up packet queue.
 +                // Paper start - Add PlayerConnectionCloseEvent
 +                final PacketListener packetListener = this.getPacketListener();
@@ -141,7 +167,7 @@
 +                            new com.destroystokyo.paper.event.player.PlayerConnectionCloseEvent(profile.getId(), profile.getName(),
 +                                ((InetSocketAddress) this.address).getAddress(), false).callEvent();
 +                    }
-                 }
++                }
 +                // Paper end - Add PlayerConnectionCloseEvent
  
              }