Implement full support for IPv6 (#8742)

src/main/java/net/minecraftforge/client/IFluidTypeRenderProperties.java

@@ -1,3 +1,8 @@
+/*
+ * Copyright (c) Forge Development LLC and contributors
+ * SPDX-License-Identifier: LGPL-2.1-only
+ */
+
 package net.minecraftforge.client;
 
 import com.mojang.blaze3d.shaders.FogShape;

src/main/java/net/minecraftforge/common/ForgeConfig.java

@@ -103,6 +103,8 @@ public class ForgeConfig {
 
         public final BooleanValue useCombinedDepthStencilAttachment;
 
+        public final BooleanValue compressLanIPv6Addresses;
+
         Client(ForgeConfigSpec.Builder builder) {
             builder.comment("Client only settings, mostly things related to rendering")
                    .push("client");
@@ -129,6 +131,11 @@ public class ForgeConfig {
                     .translation("forge.configgui.useCombinedDepthStencilAttachment")
                     .define("useCombinedDepthStencilAttachment", false);
 
+            compressLanIPv6Addresses = builder
+                    .comment("When enabled, Forge will convert discovered 'Open to LAN' IPv6 addresses to their more compact, compressed representation")
+                    .translation("forge.configgui.compressLanIPv6Addresses")
+                    .define("compressLanIPv6Addresses", true);
+
             builder.pop();
         }
     }

src/main/java/net/minecraftforge/common/SoundAction.java

@@ -1,3 +1,8 @@
+/*
+ * Copyright (c) Forge Development LLC and contributors
+ * SPDX-License-Identifier: LGPL-2.1-only
+ */
+
 package net.minecraftforge.common;
 
 import java.util.Map;

src/main/java/net/minecraftforge/common/SoundActions.java

@@ -1,3 +1,8 @@
+/*
+ * Copyright (c) Forge Development LLC and contributors
+ * SPDX-License-Identifier: LGPL-2.1-only
+ */
+
 package net.minecraftforge.common;
 
 /**

src/main/java/net/minecraftforge/common/extensions/IForgeBoat.java

@@ -1,3 +1,8 @@
+/*
+ * Copyright (c) Forge Development LLC and contributors
+ * SPDX-License-Identifier: LGPL-2.1-only
+ */
+
 package net.minecraftforge.common.extensions;
 
 import net.minecraft.world.entity.vehicle.Boat;

src/main/java/net/minecraftforge/common/extensions/IForgeLivingEntity.java

@@ -1,3 +1,8 @@
+/*
+ * Copyright (c) Forge Development LLC and contributors
+ * SPDX-License-Identifier: LGPL-2.1-only
+ */
+
 package net.minecraftforge.common.extensions;
 
 import net.minecraft.world.entity.LivingEntity;

src/main/java/net/minecraftforge/fluids/FluidInteractionRegistry.java

@@ -1,3 +1,8 @@
+/*
+ * Copyright (c) Forge Development LLC and contributors
+ * SPDX-License-Identifier: LGPL-2.1-only
+ */
+
 package net.minecraftforge.fluids;
 
 import net.minecraft.core.BlockPos;

src/main/java/net/minecraftforge/fluids/FluidType.java

@@ -1,3 +1,8 @@
+/*
+ * Copyright (c) Forge Development LLC and contributors
+ * SPDX-License-Identifier: LGPL-2.1-only
+ */
+
 package net.minecraftforge.fluids;
 
 import com.google.common.collect.ImmutableMap;

src/main/java/net/minecraftforge/network/DualStackUtils.java

@@ -0,0 +1,88 @@
+/*
+ * Copyright (c) Forge Development LLC and contributors
+ * SPDX-License-Identifier: LGPL-2.1-only
+ */
+
+package net.minecraftforge.network;
+
+import net.minecraft.client.multiplayer.resolver.ResolvedServerAddress;
+import net.minecraft.client.multiplayer.resolver.ServerAddress;
+import net.minecraft.client.multiplayer.resolver.ServerNameResolver;
+import net.minecraft.util.HttpUtil;
+
+import javax.annotation.Nullable;
+import java.net.Inet6Address;
+import java.net.InetAddress;
+import java.net.InetSocketAddress;
+import java.net.UnknownHostException;
+import java.util.Optional;
+
+public class DualStackUtils
+{
+    /**
+     * Resolve the address and see if Java and the OS return an IPv6 or IPv4 one, then let Netty know
+     * accordingly (it doesn't understand the {@code java.net.preferIPv6Addresses=system} property).
+     *
+     * @param hostAddress The address you want to check
+     * @return true if IPv6, false if IPv4
+     */
+    public static boolean checkIPv6(final String hostAddress)
+    {
+        final Optional<InetSocketAddress> hostAddr =
+                ServerNameResolver.DEFAULT
+                        .resolveAddress(ServerAddress.parseString(hostAddress))
+                        .map(ResolvedServerAddress::asInetSocketAddress);
+
+        if (hostAddr.isPresent()) return checkIPv6(hostAddr.get().getAddress());
+        else return false;
+    }
+
+    /**
+     * Checks if an address is an IPv6 one or an IPv4 one, lets Netty know accordingly and returns the result.
+     *
+     * @param inetAddress The address you want to check
+     * @return true if IPv6, false if IPv4
+     */
+    public static boolean checkIPv6(final InetAddress inetAddress)
+    {
+        if (inetAddress instanceof Inet6Address)
+        {
+            System.setProperty("java.net.preferIPv4Stack", "false");
+            System.setProperty("java.net.preferIPv6Addresses", "true");
+            return true;
+        }
+        else
+        {
+            System.setProperty("java.net.preferIPv4Stack", "true");
+            System.setProperty("java.net.preferIPv6Addresses", "false");
+            return false;
+        }
+    }
+
+    /**
+     * Get the device's local IP address, taking into account scenarios where the client's network adapter
+     * supports IPv6 and has it enabled but the router's LAN does not.
+     *
+     * @return the client's local IP address or {@code null} if unable to determine it
+     */
+    @Nullable
+    public static InetAddress getLocalAddress()
+    {
+        final InetAddress localAddr = new InetSocketAddress(HttpUtil.getAvailablePort()).getAddress();
+        if (localAddr.isAnyLocalAddress()) return localAddr;
+
+        try
+        {
+            return InetAddress.getByName("localhost");
+        }
+        catch (final UnknownHostException e)
+        {
+            return null;
+        }
+    }
+
+    public static String getMulticastGroup() {
+        if (checkIPv6(getLocalAddress())) return "FF75:230::60";
+        else return "224.0.2.60";
+    }
+}