Do not track plugin channels registered per-player on the proxy (#591)

We don't need to track this information since Velocity uses the JoinGame packet, which is about as good of a server rejoin mechanism we're likely to get in vanilla Minecraft.

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

@@ -198,13 +198,8 @@ public boolean handle(PluginMessage packet) {
       return true;
     }
 
-    // We need to specially handle REGISTER and UNREGISTER packets. Later on, we'll write them to
-    // the client.
-    if (PluginMessageUtil.isRegister(packet)) {
-      serverConn.getPlayer().getKnownChannels().addAll(PluginMessageUtil.getChannels(packet));
-      return false;
-    } else if (PluginMessageUtil.isUnregister(packet)) {
-      serverConn.getPlayer().getKnownChannels().removeAll(PluginMessageUtil.getChannels(packet));
+    // Register and unregister packets are simply forwarded to the server as-is.
+    if (PluginMessageUtil.isRegister(packet) || PluginMessageUtil.isUnregister(packet)) {
       return false;
     }
 

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

@@ -36,7 +36,6 @@
 import com.velocitypowered.proxy.protocol.packet.JoinGame;
 import com.velocitypowered.proxy.protocol.packet.KeepAlive;
 import com.velocitypowered.proxy.protocol.packet.PluginMessage;
-import com.velocitypowered.proxy.protocol.util.PluginMessageUtil;
 import java.io.IOException;
 import java.util.concurrent.CompletableFuture;
 import org.apache.logging.log4j.LogManager;
@@ -180,12 +179,6 @@ public boolean handle(PluginMessage packet) {
       return true;
     }
 
-    if (PluginMessageUtil.isRegister(packet)) {
-      serverConn.getPlayer().getKnownChannels().addAll(PluginMessageUtil.getChannels(packet));
-    } else if (PluginMessageUtil.isUnregister(packet)) {
-      serverConn.getPlayer().getKnownChannels().removeAll(PluginMessageUtil.getChannels(packet));
-    }
-
     // We always need to handle plugin messages, for Forge compatibility.
     if (serverConn.getPhase().handle(serverConn, serverConn.getPlayer(), packet)) {
       // Handled, but check the server connection phase.

proxy/src/main/java/com/velocitypowered/proxy/connection/client/ClientPlaySessionHandler.java

@@ -156,7 +156,6 @@ public void activated() {
     if (!channels.isEmpty()) {
       PluginMessage register = constructChannelsPacket(player.getProtocolVersion(), channels);
       player.getConnection().write(register);
-      player.getKnownChannels().addAll(channels);
     }
   }
 
@@ -295,7 +294,6 @@ public boolean handle(PluginMessage packet) {
             packet.getChannel());
       } else if (PluginMessageUtil.isRegister(packet)) {
         List<String> channels = PluginMessageUtil.getChannels(packet);
-        player.getKnownChannels().addAll(channels);
         List<ChannelIdentifier> channelIdentifiers = new ArrayList<>();
         for (String channel : channels) {
           try {
@@ -309,7 +307,6 @@ public boolean handle(PluginMessage packet) {
                 new PlayerChannelRegisterEvent(player, ImmutableList.copyOf(channelIdentifiers)));
         backendConn.write(packet.retain());
       } else if (PluginMessageUtil.isUnregister(packet)) {
-        player.getKnownChannels().removeAll(PluginMessageUtil.getChannels(packet));
         backendConn.write(packet.retain());
       } else if (PluginMessageUtil.isMcBrand(packet)) {
         String brand = PluginMessageUtil.readBrandMessage(packet.content());
@@ -485,12 +482,6 @@ public void handleBackendJoinGame(JoinGame joinGame, VelocityServerConnection de
     }
     serverBossBars.clear();
 
-    // Tell the server about this client's plugin message channels.
-    ProtocolVersion serverVersion = serverMc.getProtocolVersion();
-    if (!player.getKnownChannels().isEmpty()) {
-      serverMc.delayedWrite(constructChannelsPacket(serverVersion, player.getKnownChannels()));
-    }
-
     // If we had plugin messages queued during login/FML handshake, send them now.
     PluginMessage pm;
     while ((pm = loginPluginMessages.poll()) != null) {

proxy/src/main/java/com/velocitypowered/proxy/connection/client/ConnectedPlayer.java

@@ -77,12 +77,10 @@
 import com.velocitypowered.proxy.tablist.VelocityTabListLegacy;
 import com.velocitypowered.proxy.util.ClosestLocaleMatcher;
 import com.velocitypowered.proxy.util.DurationUtils;
-import com.velocitypowered.proxy.util.collect.CappedSet;
 import io.netty.buffer.ByteBufUtil;
 import io.netty.buffer.Unpooled;
 import java.net.InetSocketAddress;
 import java.util.ArrayDeque;
-import java.util.Collection;
 import java.util.Collections;
 import java.util.List;
 import java.util.Locale;
@@ -155,7 +153,6 @@ public class ConnectedPlayer implements MinecraftConnectionAssociation, Player,
   private final InternalTabList tabList;
   private final VelocityServer server;
   private ClientConnectionPhase connectionPhase;
-  private final Collection<String> knownChannels;
   private final CompletableFuture<Void> teardownFuture = new CompletableFuture<>();
   private @MonotonicNonNull List<String> serversToTry = null;
   private @MonotonicNonNull Boolean previousResourceResponse;
@@ -185,7 +182,6 @@ public class ConnectedPlayer implements MinecraftConnectionAssociation, Player,
     this.virtualHost = virtualHost;
     this.permissionFunction = PermissionFunction.ALWAYS_UNDEFINED;
     this.connectionPhase = connection.getType().getInitialClientPhase();
-    this.knownChannels = CappedSet.create(MAX_PLUGIN_CHANNELS);
     this.onlineMode = onlineMode;
 
     if (connection.getProtocolVersion().compareTo(ProtocolVersion.MINECRAFT_1_19_3) >= 0) {
@@ -1103,15 +1099,6 @@ public void setPhase(ClientConnectionPhase connectionPhase) {
     this.connectionPhase = connectionPhase;
   }
 
-  /**
-   * Return all the plugin message channels "known" to the client.
-   *
-   * @return the channels
-   */
-  public Collection<String> getKnownChannels() {
-    return knownChannels;
-  }
-
   @Override
   public @Nullable IdentifiedKey getIdentifiedKey() {
     return playerKey;

proxy/src/main/java/com/velocitypowered/proxy/connection/client/InitialConnectSessionHandler.java

@@ -24,7 +24,6 @@
 import com.velocitypowered.proxy.connection.backend.BungeeCordMessageResponder;
 import com.velocitypowered.proxy.connection.backend.VelocityServerConnection;
 import com.velocitypowered.proxy.protocol.packet.PluginMessage;
-import com.velocitypowered.proxy.protocol.util.PluginMessageUtil;
 import io.netty.buffer.ByteBufUtil;
 import io.netty.buffer.Unpooled;
 import org.apache.logging.log4j.LogManager;
@@ -55,15 +54,7 @@ public boolean handle(PluginMessage packet) {
         return true;
       }
 
-      if (PluginMessageUtil.isRegister(packet)) {
-        player.getKnownChannels().addAll(PluginMessageUtil.getChannels(packet));
-        serverConn.ensureConnected().write(packet.retain());
-        return true;
-      } else if (PluginMessageUtil.isUnregister(packet)) {
-        player.getKnownChannels().removeAll(PluginMessageUtil.getChannels(packet));
-        serverConn.ensureConnected().write(packet.retain());
-        return true;
-      } else if (BungeeCordMessageResponder.isBungeeCordMessage(packet)) {
+      if (BungeeCordMessageResponder.isBungeeCordMessage(packet)) {
         return true;
       }