untested control handler

proxy/src/main/java/com/velocitypowered/proxy/connection/backend/VelocityServerConnection.java

@@ -2,6 +2,7 @@ package com.velocitypowered.proxy.connection.backend;
 
 import static com.velocitypowered.proxy.VelocityServer.GSON;
 import static com.velocitypowered.proxy.connection.forge.legacy.LegacyForgeConstants.HANDSHAKE_HOSTNAME_TOKEN;
+import static com.velocitypowered.proxy.network.Connections.FLOW_HANDLER;
 import static com.velocitypowered.proxy.network.Connections.FRAME_DECODER;
 import static com.velocitypowered.proxy.network.Connections.FRAME_ENCODER;
 import static com.velocitypowered.proxy.network.Connections.HANDLER;
@@ -34,6 +35,7 @@ import com.velocitypowered.proxy.server.VelocityRegisteredServer;
 import io.netty.channel.Channel;
 import io.netty.channel.ChannelFutureListener;
 import io.netty.channel.ChannelInitializer;
+import io.netty.handler.flow.FlowControlHandler;
 import io.netty.handler.timeout.ReadTimeoutHandler;
 import java.util.concurrent.CompletableFuture;
 import java.util.concurrent.TimeUnit;
@@ -83,6 +85,7 @@ public class VelocityServerConnection implements MinecraftConnectionAssociation,
                         TimeUnit.MILLISECONDS))
                 .addLast(FRAME_DECODER, new MinecraftVarintFrameDecoder())
                 .addLast(FRAME_ENCODER, MinecraftVarintLengthEncoder.INSTANCE)
+                .addLast(FLOW_HANDLER, new FlowControlHandler())
                 .addLast(MINECRAFT_DECODER,
                     new MinecraftDecoder(ProtocolUtils.Direction.CLIENTBOUND))
                 .addLast(MINECRAFT_ENCODER,

proxy/src/main/java/com/velocitypowered/proxy/network/Connections.java

@@ -6,6 +6,7 @@ public class Connections {
   public static final String CIPHER_ENCODER = "cipher-encoder";
   public static final String COMPRESSION_DECODER = "compression-decoder";
   public static final String COMPRESSION_ENCODER = "compression-encoder";
+  public static final String FLOW_HANDLER = "flow-handler";
   public static final String FRAME_DECODER = "frame-decoder";
   public static final String FRAME_ENCODER = "frame-encoder";
   public static final String HANDLER = "handler";