Handle differing network versions for FML gracefully?

Signed-off-by: cpw <cpw+github@weeksfamily.ca>

src/main/java/net/minecraftforge/fml/network/ConnectionType.java

@@ -19,23 +19,23 @@
 
 package net.minecraftforge.fml.network;
 
-import java.util.Arrays;
-import java.util.Objects;
+import java.util.function.Function;
 
 public enum ConnectionType
 {
-    MODDED(NetworkHooks.NETVERSION), VANILLA(NetworkHooks.NOVERSION);
+    MODDED(s->Integer.valueOf(s.substring(FMLNetworkConstants.FMLNETMARKER.length()))), VANILLA(s->0);
 
-    private final String versionString;
+    private final Function<String, Integer> versionExtractor;
 
-    ConnectionType(String versionString)
-    {
-        this.versionString = versionString;
+    ConnectionType(Function<String, Integer> versionExtractor) {
+        this.versionExtractor = versionExtractor;
     }
-
     public static ConnectionType forVersionFlag(String vers)
     {
-        return Arrays.stream(values()).filter(ct->Objects.equals(ct.versionString, vers)).
-                findFirst().orElse(ConnectionType.VANILLA);
+        return vers.startsWith(FMLNetworkConstants.FMLNETMARKER) ? MODDED : VANILLA;
+    }
+
+    public int getFMLVersionNumber(final String fmlVersion) {
+        return versionExtractor.apply(fmlVersion);
     }
 }

src/main/java/net/minecraftforge/fml/network/FMLHandshakeHandler.java

@@ -72,7 +72,7 @@ import static net.minecraftforge.registries.ForgeRegistry.REGISTRIES;
  * final login phase will commence.
  */
 public class FMLHandshakeHandler {
-    static final Marker FMLHSMARKER = MarkerManager.getMarker("FMLHANDSHAKE").setParents(FMLNetworking.NETWORK);
+    static final Marker FMLHSMARKER = MarkerManager.getMarker("FMLHANDSHAKE").setParents(FMLNetworkConstants.NETWORK);
     private static final Logger LOGGER = LogManager.getLogger();
     static final ResourceLocation FML_HANDSHAKE_RESOURCE = new ResourceLocation("fml:handshake");
     private static final AttributeKey<FMLHandshakeHandler> FML_HANDSHAKE_HANDLER_ATTRIBUTE_KEY = AttributeKey.newInstance("fml:handshake");
@@ -83,7 +83,7 @@ public class FMLHandshakeHandler {
         channel = NetworkRegistry.ChannelBuilder.named(FML_HANDSHAKE_RESOURCE).
                 clientAcceptedVersions(a -> true).
                 serverAcceptedVersions(a -> true).
-                networkProtocolVersion(() -> NetworkHooks.NETVERSION).
+                networkProtocolVersion(() -> FMLNetworkConstants.NETVERSION).
                 simpleChannel();
         channel.messageBuilder(FMLHandshakeMessages.C2SAcknowledge.class, 99).
                 loginIndex(FMLHandshakeMessages.LoginIndexedMessage::getLoginIndex, FMLHandshakeMessages.LoginIndexedMessage::setLoginIndex).
@@ -208,7 +208,7 @@ public class FMLHandshakeHandler {
         channel.reply(reply, c.get());
         LOGGER.debug(FMLHSMARKER, "Accepted server connection");
         // Set the modded marker on the channel so we know we got packets
-        c.get().getNetworkManager().channel().attr(FMLNetworking.FML_MARKER).set(NetworkHooks.NETVERSION);
+        c.get().getNetworkManager().channel().attr(FMLNetworkConstants.FML_MARKER).set(FMLNetworkConstants.NETVERSION);
         this.registriesToReceive = new HashSet<>(serverModList.getRegistries());
         LOGGER.debug(REGISTRIES, "Expecting {} registries: {}", ()->this.registriesToReceive.size(), ()->this.registriesToReceive);
     }

src/main/java/net/minecraftforge/fml/network/FMLLoginWrapper.java

@@ -41,7 +41,7 @@ public class FMLLoginWrapper {
         wrapperChannel = NetworkRegistry.ChannelBuilder.named(FMLLoginWrapper.WRAPPER).
                 clientAcceptedVersions(a->true).
                 serverAcceptedVersions(a->true).
-                networkProtocolVersion(()->NetworkHooks.NETVERSION)
+                networkProtocolVersion(()-> FMLNetworkConstants.NETVERSION)
                 .eventNetworkChannel();
         wrapperChannel.addListener(this::wrapperReceived);
     }

src/main/java/net/minecraftforge/fml/network/FMLNetworkConstants.java

@@ -23,8 +23,15 @@ import io.netty.util.AttributeKey;
 import org.apache.logging.log4j.Marker;
 import org.apache.logging.log4j.MarkerManager;
 
-public class FMLNetworking
+/**
+ * Constants related to networking
+ */
+public class FMLNetworkConstants
 {
+    public static final String FMLNETMARKER = "FML";
+    public static final int FMLNETVERSION = 1;
+    public static final String NETVERSION = FMLNETMARKER + FMLNETVERSION;
+    public static final String NOVERSION = "NONE";
     static final Marker NETWORK = MarkerManager.getMarker("FMLNETWORK");
     static final AttributeKey<String> FML_MARKER = AttributeKey.valueOf("fml:marker");
 }

src/main/java/net/minecraftforge/fml/network/FMLPlayHandler.java

@@ -28,7 +28,7 @@ public class FMLPlayHandler
             .named(new ResourceLocation("fml", "play"))
             .clientAcceptedVersions(a -> true)
             .serverAcceptedVersions(a -> true)
-            .networkProtocolVersion(() -> NetworkHooks.NETVERSION)
+            .networkProtocolVersion(() -> FMLNetworkConstants.NETVERSION)
             .simpleChannel();
     static
     {

src/main/java/net/minecraftforge/fml/network/NetworkHooks.java

@@ -44,22 +44,15 @@ import java.util.function.Supplier;
 public class NetworkHooks
 {
     private static final Logger LOGGER = LogManager.getLogger();
-    public static final String NETVERSION = "FML1";
-    public static final String NOVERSION = "NONE";
 
     public static String getFMLVersion(final String ip)
     {
-        return ip.contains("\0") ? Objects.equals(ip.split("\0")[1], NETVERSION) ? NETVERSION : ip.split("\0")[1] : NOVERSION;
-    }
-
-    public static boolean accepts(final CPacketHandshake packet)
-    {
-        return Objects.equals(packet.getFMLVersion(), NETVERSION) || NetworkRegistry.acceptsVanillaClientConnections();
+        return ip.contains("\0") ? Objects.equals(ip.split("\0")[1], FMLNetworkConstants.NETVERSION) ? FMLNetworkConstants.NETVERSION : ip.split("\0")[1] : FMLNetworkConstants.NOVERSION;
     }
 
     public static ConnectionType getConnectionType(final Supplier<NetworkManager> connection)
     {
-        return ConnectionType.forVersionFlag(connection.get().channel().attr(FMLNetworking.FML_MARKER).get());
+        return ConnectionType.forVersionFlag(connection.get().channel().attr(FMLNetworkConstants.FML_MARKER).get());
     }
 
     public static Packet<?> getEntitySpawningPacket(Entity entity)
@@ -78,14 +71,14 @@ public class NetworkHooks
 
     public static void registerServerLoginChannel(NetworkManager manager, CPacketHandshake packet)
     {
-        manager.channel().attr(FMLNetworking.FML_MARKER).set(packet.getFMLVersion());
+        manager.channel().attr(FMLNetworkConstants.FML_MARKER).set(packet.getFMLVersion());
         FMLHandshakeHandler.registerHandshake(manager, NetworkDirection.LOGIN_TO_CLIENT);
     }
 
     public static void registerClientLoginChannel(NetworkManager manager)
     {
         if (manager == null || manager.channel() == null) return;
-        manager.channel().attr(FMLNetworking.FML_MARKER).set(NOVERSION);
+        manager.channel().attr(FMLNetworkConstants.FML_MARKER).set(FMLNetworkConstants.NOVERSION);
         FMLHandshakeHandler.registerHandshake(manager, NetworkDirection.LOGIN_TO_SERVER);
     }
 

src/main/java/net/minecraftforge/fml/network/NetworkRegistry.java

@@ -68,7 +68,7 @@ public class NetworkRegistry
         return listRejectedVanillaMods(NetworkInstance::tryClientVersionOnServer);
     }
 
-    static boolean acceptsVanillaClientConnections() {
+    public static boolean acceptsVanillaClientConnections() {
         return instances.isEmpty() || getNonVanillaNetworkMods().isEmpty();
     }
 

src/main/java/net/minecraftforge/fml/server/ServerLifecycleHooks.java

@@ -37,7 +37,10 @@ import net.minecraftforge.fml.event.server.FMLServerStartedEvent;
 import net.minecraftforge.fml.event.server.FMLServerStoppedEvent;
 import net.minecraftforge.fml.event.server.FMLServerStoppingEvent;
 import net.minecraftforge.fml.loading.FileUtils;
+import net.minecraftforge.fml.network.ConnectionType;
+import net.minecraftforge.fml.network.FMLNetworkConstants;
 import net.minecraftforge.fml.network.NetworkHooks;
+import net.minecraftforge.fml.network.NetworkRegistry;
 import net.minecraftforge.fml.packs.ResourcePackLoader;
 import org.apache.logging.log4j.LogManager;
 import org.apache.logging.log4j.Logger;
@@ -120,15 +123,19 @@ public class ServerLifecycleHooks
             return false;
         }
 
-        if (packet.getRequestedState() == EnumConnectionState.LOGIN && !NetworkHooks.accepts(packet))
-        {
-            manager.setConnectionState(EnumConnectionState.LOGIN);
-            TextComponentString text = new TextComponentString("This server has mods that require Forge to be installed on the client. Contact your server admin for more details.");
-            List<String> modNames = net.minecraftforge.fml.network.NetworkRegistry.getNonVanillaNetworkMods();
-            LOGGER.info(SERVERHOOKS,"Disconnecting vanilla connection attempt. Required mods {}", modNames);
-            manager.sendPacket(new SPacketDisconnectLogin(text));
-            manager.closeChannel(text);
-            return false;
+        if (packet.getRequestedState() == EnumConnectionState.LOGIN) {
+            final ConnectionType connectionType = ConnectionType.forVersionFlag(packet.getFMLVersion());
+            final int versionNumber = connectionType.getFMLVersionNumber(packet.getFMLVersion());
+
+            if (connectionType == ConnectionType.MODDED && versionNumber != FMLNetworkConstants.FMLNETVERSION) {
+                rejectConnection(manager, connectionType, "This modded server is not network compatible with your modded client. Please verify your Forge version closely matches the server. Got net version "+ versionNumber + " this server is net version "+FMLNetworkConstants.FMLNETVERSION);
+                return false;
+            }
+
+            if (connectionType == ConnectionType.VANILLA && !NetworkRegistry.acceptsVanillaClientConnections()) {
+                rejectConnection(manager, connectionType, "This server has mods that require Forge to be installed on the client. Contact your server admin for more details.");
+                return false;
+            }
         }
 
         if (packet.getRequestedState() == EnumConnectionState.STATUS) return true;
@@ -138,6 +145,14 @@ public class ServerLifecycleHooks
 
     }
 
+    private static void rejectConnection(final NetworkManager manager, ConnectionType type, String message) {
+        manager.setConnectionState(EnumConnectionState.LOGIN);
+        LOGGER.info(SERVERHOOKS, "Disconnecting {} connection attempt: ", type, message);
+        TextComponentString text = new TextComponentString(message);
+        manager.sendPacket(new SPacketDisconnectLogin(text));
+        manager.closeChannel(text);
+    }
+
     public static void handleExit(int retVal)
     {
 /*