Mode Validation Checks Between Client and Server

src/main/java/com/nomiceu/nomilabs/config/LabsConfig.java

@@ -717,6 +717,11 @@ public static class Advanced {
         @Config.LangKey("config.nomilabs.advanced.server_welcome_name")
         public String serverWelcomeName = "Minecraft";
 
+        @Config.Comment({ "Whether mode check fail message should link to the Nomi-CEu GitHub page.",
+                "[default: false]" })
+        @Config.LangKey("config.nomilabs.advanced.mode_check_nomi_ceu")
+        public boolean modeCheckNomiCeuLink = false;
+
         public static class WindowOverrides {
 
             @Config.Comment({ "Override for the Minecraft Window Title.",

src/main/java/com/nomiceu/nomilabs/mixin/vanilla/FMLHandshakeMessageModListMixin.java

@@ -0,0 +1,60 @@
+package com.nomiceu.nomilabs.mixin.vanilla;
+
+import java.util.List;
+import java.util.Map;
+
+import net.minecraftforge.fml.common.ModContainer;
+import net.minecraftforge.fml.common.network.handshake.FMLHandshakeMessage;
+
+import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.Shadow;
+import org.spongepowered.asm.mixin.Unique;
+import org.spongepowered.asm.mixin.injection.At;
+import org.spongepowered.asm.mixin.injection.Inject;
+import org.spongepowered.asm.mixin.injection.callback.CallbackInfo;
+
+import com.nomiceu.nomilabs.NomiLabs;
+import com.nomiceu.nomilabs.mixinhelper.AccessibleModListMessage;
+import com.nomiceu.nomilabs.util.LabsModeHelper;
+
+import io.netty.buffer.ByteBuf;
+
+/**
+ * Sends Labs Mode Data in Mod List Handshake.
+ */
+@Mixin(value = FMLHandshakeMessage.ModList.class, remap = false)
+public class FMLHandshakeMessageModListMixin implements AccessibleModListMessage {
+
+    @Shadow
+    private Map<String, String> modTags;
+    @Unique
+    private static final String labs$modeId = "\0LABS_MODE_DATA\0";
+
+    @Unique
+    private String labs$mode = "";
+
+    @Inject(method = "<init>(Ljava/util/List;)V", at = @At("TAIL"))
+    private void initModeData(List<ModContainer> modList, CallbackInfo ci) {
+        NomiLabs.LOGGER.info("[Labs Mode Validation] Injecting Mode Data into Mod List Handshake...");
+        labs$mode = LabsModeHelper.getMode();
+
+        modTags.put(labs$modeId, labs$mode);
+    }
+
+    @Inject(method = "fromBytes", at = @At("TAIL"))
+    private void initModeFromBytes(ByteBuf buffer, CallbackInfo ci) {
+        NomiLabs.LOGGER.info("[Labs Mode Validation] Reading Mode Data from Mod List Handshake...");
+        labs$mode = modTags.get(labs$modeId);
+
+        if (labs$mode == null) {
+            NomiLabs.LOGGER.error("[Labs Mode Validation] No Mode Data in Mod List Handshake!");
+            labs$mode = "";
+        }
+    }
+
+    @Unique
+    @Override
+    public String labs$getMode() {
+        return labs$mode;
+    }
+}

src/main/java/com/nomiceu/nomilabs/mixin/vanilla/FMLNetworkHandlerMixin.java

@@ -0,0 +1,65 @@
+package com.nomiceu.nomilabs.mixin.vanilla;
+
+import net.minecraftforge.fml.common.network.handshake.FMLHandshakeMessage;
+import net.minecraftforge.fml.common.network.internal.FMLNetworkHandler;
+import net.minecraftforge.fml.relauncher.Side;
+
+import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.injection.At;
+import org.spongepowered.asm.mixin.injection.Inject;
+import org.spongepowered.asm.mixin.injection.callback.CallbackInfoReturnable;
+
+import com.nomiceu.nomilabs.NomiLabs;
+import com.nomiceu.nomilabs.config.LabsConfig;
+import com.nomiceu.nomilabs.mixinhelper.AccessibleModListMessage;
+import com.nomiceu.nomilabs.util.LabsModeHelper;
+
+/**
+ * Checks Mode Data in Mod List Handshake.
+ */
+@Mixin(value = FMLNetworkHandler.class, remap = false)
+public class FMLNetworkHandlerMixin {
+
+    @Inject(method = "checkModList(Lnet/minecraftforge/fml/common/network/handshake/FMLHandshakeMessage$ModList;Lnet/minecraftforge/fml/relauncher/Side;)Ljava/lang/String;",
+            at = @At("RETURN"),
+            cancellable = true)
+    private static void checkModeInfo(FMLHandshakeMessage.ModList modListPacket, Side side,
+                                      CallbackInfoReturnable<String> cir) {
+        if (cir.getReturnValue() != null) {
+            NomiLabs.LOGGER.error("[Labs Mode Validation] Ignoring Mode Checks due to Invalid Mod List!");
+            return;
+        }
+
+        String mode = ((AccessibleModListMessage) modListPacket).labs$getMode();
+        if (mode.isEmpty()) {
+            NomiLabs.LOGGER.error("[Labs Mode Validation] No Mode Data!");
+            cir.setReturnValue(
+                    "§cMode Validation Failed!§r\n\nCheck your client and server, and make sure they are on the same version!");
+            return;
+        }
+
+        if (mode.equals(LabsModeHelper.getMode())) {
+            NomiLabs.LOGGER.info("[Labs Mode Validation] Mode Match.");
+            return;
+        }
+
+        NomiLabs.LOGGER.error("[Labs Mode Validation] Mode Mismatch! Received: {}, Expected: {}", mode,
+                LabsModeHelper.getMode());
+
+        String modeMismatchText;
+        // Data coming from server
+        if (side.isServer())
+            modeMismatchText = String.format("Server expects mode §a%s§r, but you are on mode §e%s§r!",
+                    LabsModeHelper.formatMode(mode),
+                    LabsModeHelper.getFormattedMode());
+        else
+            modeMismatchText = String.format("Server expects mode §a%s§r, but you are on mode §e%s§r!",
+                    LabsModeHelper.getFormattedMode(), LabsModeHelper.formatMode(mode));
+
+        String linkText = "";
+        if (LabsConfig.advanced.modeCheckNomiCeuLink)
+            linkText = "\n\nSee §bhttps://github.com/Nomi-CEu/Nomi-CEu/blob/main/overrides/README.md§r for information on switching modes!";
+
+        cir.setReturnValue("§cServer Mode Rejection:§r" + "\n\n" + modeMismatchText + linkText);
+    }
+}

src/main/java/com/nomiceu/nomilabs/mixinhelper/AccessibleModListMessage.java

@@ -0,0 +1,6 @@
+package com.nomiceu.nomilabs.mixinhelper;
+
+public interface AccessibleModListMessage {
+
+    String labs$getMode();
+}

src/main/java/com/nomiceu/nomilabs/util/LabsModeHelper.java

@@ -28,7 +28,11 @@ public static boolean isExpert() {
     }
 
     public static String getFormattedMode() {
-        return StringUtils.capitalize(getMode());
+        return formatMode(getMode());
+    }
+
+    public static String formatMode(String mode) {
+        return StringUtils.capitalize(mode);
     }
 
     /**

src/main/resources/assets/nomilabs/lang/en_us.lang

@@ -121,6 +121,7 @@ config.nomilabs.advanced.client_side_methods=Client Side ONLY Methods
 config.nomilabs.advanced.server_side_fields=Server Side ONLY Fields
 config.nomilabs.advanced.server_side_methods=Server Side ONLY Methods
 config.nomilabs.advanced.server_welcome_name=Server Welcome Name
+config.nomilabs.advanced.mode_check_nomi_ceu=Mode Check Nomi-CEu Link
 
 config.nomilabs.advanced.tiers=Quest Tier Detector Settings
 config.nomilabs.advanced.tiers.normal_qb_ids=Normal Mode Quest IDs

src/main/resources/mixins.nomilabs.json

@@ -8,6 +8,8 @@
     "AccessibleFluidRegistry",
     "CommandDifficultyMixin",
     "FluidRegistryMixin",
+    "FMLHandshakeMessageModListMixin",
+    "FMLNetworkHandlerMixin",
     "ForgeRegistryMixin",
     "GameDataMixin",
     "ItemStackMixin",