[1.21] Implement common networking with config tasks

patches/net/minecraft/client/multiplayer/ClientCommonPacketListenerImpl.java.patch

@@ -36,12 +36,12 @@
 +        }
 +
 +        if (p_295727_.payload() instanceof net.neoforged.neoforge.network.payload.CommonVersionPayload commonVersionPayload) {
-+            net.neoforged.neoforge.network.registration.NetworkRegistry.checkCommonVersion(this.getConnection(), commonVersionPayload);
++            net.neoforged.neoforge.network.registration.NetworkRegistry.checkCommonVersion(this, commonVersionPayload);
 +            return;
 +        }
 +
 +        if (p_295727_.payload() instanceof net.neoforged.neoforge.network.payload.CommonRegisterPayload commonRegisterPayload) {
-+            net.neoforged.neoforge.network.registration.NetworkRegistry.onCommonRegister(this.getConnection(), commonRegisterPayload);
++            net.neoforged.neoforge.network.registration.NetworkRegistry.onCommonRegister(this, commonRegisterPayload);
 +            return;
 +        }
 +

patches/net/minecraft/server/network/ServerCommonPacketListenerImpl.java.patch

@@ -36,12 +36,12 @@
 +        }
 +
 +        if (p_294276_.payload() instanceof net.neoforged.neoforge.network.payload.CommonVersionPayload commonVersionPayload) {
-+            net.neoforged.neoforge.network.registration.NetworkRegistry.checkCommonVersion(this.getConnection(), commonVersionPayload);
++            net.neoforged.neoforge.network.registration.NetworkRegistry.checkCommonVersion(this, commonVersionPayload);
 +            return;
 +        }
 +
 +        if (p_294276_.payload() instanceof net.neoforged.neoforge.network.payload.CommonRegisterPayload commonRegisterPayload) {
-+            net.neoforged.neoforge.network.registration.NetworkRegistry.onCommonRegister(this.getConnection(), commonRegisterPayload);
++            net.neoforged.neoforge.network.registration.NetworkRegistry.onCommonRegister(this, commonRegisterPayload);
 +            return;
 +        }
 +

src/main/java/net/neoforged/neoforge/network/ConfigurationInitialization.java

@@ -12,10 +12,14 @@
 import net.neoforged.bus.api.SubscribeEvent;
 import net.neoforged.fml.common.EventBusSubscriber;
 import net.neoforged.neoforge.network.configuration.CheckExtensibleEnums;
+import net.neoforged.neoforge.network.configuration.CommonRegisterTask;
+import net.neoforged.neoforge.network.configuration.CommonVersionTask;
 import net.neoforged.neoforge.network.configuration.RegistryDataMapNegotiation;
 import net.neoforged.neoforge.network.configuration.SyncConfig;
 import net.neoforged.neoforge.network.configuration.SyncRegistries;
 import net.neoforged.neoforge.network.event.RegisterConfigurationTasksEvent;
+import net.neoforged.neoforge.network.payload.CommonRegisterPayload;
+import net.neoforged.neoforge.network.payload.CommonVersionPayload;
 import net.neoforged.neoforge.network.payload.ConfigFilePayload;
 import net.neoforged.neoforge.network.payload.FrozenRegistryPayload;
 import net.neoforged.neoforge.network.payload.FrozenRegistrySyncCompletedPayload;
@@ -39,12 +43,18 @@ public static void configureEarlyTasks(ServerConfigurationPacketListener listene
 
     @SubscribeEvent
     private static void configureModdedClient(RegisterConfigurationTasksEvent event) {
-        if (event.getListener().hasChannel(ConfigFilePayload.TYPE)) {
-            event.register(new SyncConfig(event.getListener()));
+        ServerConfigurationPacketListener listener = event.getListener();
+        if (listener.hasChannel(CommonVersionPayload.TYPE) && listener.hasChannel(CommonRegisterPayload.TYPE)) {
+            event.register(new CommonVersionTask());
+            event.register(new CommonRegisterTask());
+        }
+
+        if (listener.hasChannel(ConfigFilePayload.TYPE)) {
+            event.register(new SyncConfig(listener));
         }
 
         //These two can always be registered they detect the listener connection type internally and will skip themselves.
-        event.register(new RegistryDataMapNegotiation(event.getListener()));
-        event.register(new CheckExtensibleEnums(event.getListener()));
+        event.register(new RegistryDataMapNegotiation(listener));
+        event.register(new CheckExtensibleEnums(listener));
     }
 }

src/main/java/net/neoforged/neoforge/network/configuration/CommonRegisterTask.java

@@ -0,0 +1,37 @@
+/*
+ * Copyright (c) NeoForged and contributors
+ * SPDX-License-Identifier: LGPL-2.1-only
+ */
+
+package net.neoforged.neoforge.network.configuration;
+
+import java.util.function.Consumer;
+import net.minecraft.network.ConnectionProtocol;
+import net.minecraft.network.protocol.PacketFlow;
+import net.minecraft.network.protocol.common.custom.CustomPacketPayload;
+import net.minecraft.resources.ResourceLocation;
+import net.neoforged.neoforge.internal.versions.neoforge.NeoForgeVersion;
+import net.neoforged.neoforge.network.payload.CommonRegisterPayload;
+import net.neoforged.neoforge.network.registration.NetworkRegistry;
+import org.jetbrains.annotations.ApiStatus;
+
+/**
+ * Common Register configuration task. After completion of {@link CommonVersionTask}, sends a {@link CommonRegisterPayload} to the client
+ * containing all known serverbound channels, and awaits a response containing the client's known clientbound channels.
+ */
+@ApiStatus.Internal
+public record CommonRegisterTask() implements ICustomConfigurationTask {
+    public static final Type TYPE = new Type(ResourceLocation.fromNamespaceAndPath(NeoForgeVersion.MOD_ID, "common_register"));
+
+    @Override
+    public Type type() {
+        return TYPE;
+    }
+
+    @Override
+    public void run(Consumer<CustomPacketPayload> sender) {
+        // There is currently no implementation for a version handshake, and the only existing version is 1, so we only send 1.
+        // Version negotiation will have to be implemented properly if a version 2 is ever added.
+        sender.accept(new CommonRegisterPayload(1, ConnectionProtocol.PLAY, NetworkRegistry.getCommonPlayChannels(PacketFlow.SERVERBOUND)));
+    }
+}

src/main/java/net/neoforged/neoforge/network/configuration/CommonVersionTask.java

@@ -0,0 +1,32 @@
+/*
+ * Copyright (c) NeoForged and contributors
+ * SPDX-License-Identifier: LGPL-2.1-only
+ */
+
+package net.neoforged.neoforge.network.configuration;
+
+import java.util.function.Consumer;
+import net.minecraft.network.protocol.common.custom.CustomPacketPayload;
+import net.minecraft.resources.ResourceLocation;
+import net.neoforged.neoforge.internal.versions.neoforge.NeoForgeVersion;
+import net.neoforged.neoforge.network.payload.CommonVersionPayload;
+import org.jetbrains.annotations.ApiStatus;
+
+/**
+ * Common Version configuration task. Initiated after registry sync to begin the c:register handshake.
+ * The server will start the task, send c:version to the client, and await a reply. Upon reply, we transition to {@link CommonRegisterTask}.
+ */
+@ApiStatus.Internal
+public record CommonVersionTask() implements ICustomConfigurationTask {
+    public static final Type TYPE = new Type(ResourceLocation.fromNamespaceAndPath(NeoForgeVersion.MOD_ID, "common_version"));
+
+    @Override
+    public Type type() {
+        return TYPE;
+    }
+
+    @Override
+    public void run(Consumer<CustomPacketPayload> sender) {
+        sender.accept(new CommonVersionPayload());
+    }
+}

src/main/java/net/neoforged/neoforge/network/registration/NetworkRegistry.java

@@ -48,6 +48,8 @@
 import net.neoforged.neoforge.common.extensions.ICommonPacketListener;
 import net.neoforged.neoforge.internal.versions.neoforge.NeoForgeVersion;
 import net.neoforged.neoforge.network.configuration.CheckExtensibleEnums;
+import net.neoforged.neoforge.network.configuration.CommonRegisterTask;
+import net.neoforged.neoforge.network.configuration.CommonVersionTask;
 import net.neoforged.neoforge.network.connection.ConnectionType;
 import net.neoforged.neoforge.network.event.RegisterPayloadHandlersEvent;
 import net.neoforged.neoforge.network.filters.NetworkFilters;
@@ -379,7 +381,6 @@ public static void initializeNeoForgeConnection(ServerConfigurationPacketListene
         nowListeningOn.addAll(getInitialListeningChannels(listener.flow()));
         nowListeningOn.addAll(setup.getChannels(ConnectionProtocol.CONFIGURATION).keySet());
         listener.send(new MinecraftRegisterPayload(nowListeningOn.build()));
-        sendCommonPayloads(listener);
     }
 
     /**
@@ -419,7 +420,6 @@ public static boolean initializeOtherConnection(ServerConfigurationPacketListene
                 .filter(registration -> registration.getValue().optional())
                 .forEach(registration -> nowListeningOn.add(registration.getKey()));
         listener.send(new MinecraftRegisterPayload(nowListeningOn.build()));
-        sendCommonPayloads(listener);
 
         return true;
     }
@@ -516,7 +516,6 @@ public static void initializeNeoForgeConnection(ClientConfigurationPacketListene
         nowListeningOn.addAll(getInitialListeningChannels(listener.flow()));
         nowListeningOn.addAll(setup.getChannels(ConnectionProtocol.CONFIGURATION).keySet());
         listener.send(new MinecraftRegisterPayload(nowListeningOn.build()));
-        sendCommonPayloads(listener);
     }
 
     /**
@@ -569,7 +568,6 @@ public static void initializeOtherConnection(ClientConfigurationPacketListener l
                 .filter(registration -> registration.getValue().optional())
                 .forEach(registration -> nowListeningOn.add(registration.getKey()));
         listener.send(new MinecraftRegisterPayload(nowListeningOn.build()));
-        sendCommonPayloads(listener);
     }
 
     /**
@@ -724,14 +722,22 @@ public static Set<ResourceLocation> getInitialServerUnregisterChannels() {
      * <p>
      * Invoked on the network thread.
      * 
-     * @param connection The current connection.
-     * @param payload    The incoming version payload.
+     * @param listener The receiving listener.
+     * @param payload  The incoming version payload.
      */
-    public static void checkCommonVersion(Connection connection, CommonVersionPayload payload) {
+    public static void checkCommonVersion(ICommonPacketListener listener, CommonVersionPayload payload) {
         List<Integer> otherVersions = payload.versions();
         if (otherVersions.stream().noneMatch(SUPPORTED_COMMON_NETWORKING_VERSIONS::contains)) {
             String versions = String.join(", ", SUPPORTED_COMMON_NETWORKING_VERSIONS.stream().map(i -> i.toString()).toList());
-            connection.disconnect(Component.literal("Unsupported common network version. This installation of NeoForge only supports: " + versions));
+            listener.disconnect(Component.literal("Unsupported common network version. This installation of NeoForge only supports: " + versions));
+        }
+
+        if (listener.protocol() == ConnectionProtocol.CONFIGURATION) {
+            if (listener.flow() == PacketFlow.SERVERBOUND) {
+                ((ServerConfigurationPacketListener) listener).finishCurrentTask(CommonVersionTask.TYPE);
+            } else {
+                listener.send(new CommonVersionPayload());
+            }
         }
     }
 
@@ -740,13 +746,21 @@ public static void checkCommonVersion(Connection connection, CommonVersionPayloa
      * <p>
      * Invoked on the network thread.
      *
-     * @param connection The connection to add the channels to.
-     * @param payload    The incoming register payload.
+     * @param listener The receiving listener.
+     * @param payload  The incoming register payload.
      */
-    public static void onCommonRegister(Connection connection, CommonRegisterPayload payload) {
-        Set<ResourceLocation> channels = ChannelAttributes.getOrCreateCommonChannels(connection, payload.protocol());
+    public static void onCommonRegister(ICommonPacketListener listener, CommonRegisterPayload payload) {
+        Set<ResourceLocation> channels = ChannelAttributes.getOrCreateCommonChannels(listener.getConnection(), payload.protocol());
         channels.clear();
         channels.addAll(payload.channels());
+
+        if (listener.protocol() == ConnectionProtocol.CONFIGURATION) {
+            if (listener.flow() == PacketFlow.SERVERBOUND) {
+                ((ServerConfigurationPacketListener) listener).finishCurrentTask(CommonRegisterTask.TYPE);
+            } else {
+                listener.send(new CommonRegisterPayload(1, ConnectionProtocol.PLAY, getCommonPlayChannels(PacketFlow.CLIENTBOUND)));
+            }
+        }
     }
 
     public static Set<ResourceLocation> getCommonPlayChannels(PacketFlow flow) {
@@ -758,16 +772,6 @@ public static Set<ResourceLocation> getCommonPlayChannels(PacketFlow flow) {
                 .collect(Collectors.toSet());
     }
 
-    public static void sendCommonPayloads(ICommonPacketListener listener) {
-        if (listener.hasChannel(CommonVersionPayload.ID)) {
-            listener.send(new CommonVersionPayload());
-        }
-
-        if (listener.hasChannel(CommonRegisterPayload.ID)) {
-            listener.send(new CommonRegisterPayload(1, ConnectionProtocol.PLAY, getCommonPlayChannels(listener.flow())));
-        }
-    }
-
     /**
      * Invoked when the configuration phase of a connection is completed.
      * <p>