Add ModernForgeConnectionType to supports Forge-1.20.2+ (#1176)

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

@@ -36,6 +36,7 @@ import com.velocitypowered.proxy.connection.MinecraftConnection;
 import com.velocitypowered.proxy.connection.MinecraftConnectionAssociation;
 import com.velocitypowered.proxy.connection.MinecraftSessionHandler;
 import com.velocitypowered.proxy.connection.client.ConnectedPlayer;
+import com.velocitypowered.proxy.connection.forge.modern.ModernForgeConnectionType;
 import com.velocitypowered.proxy.connection.util.ConnectionRequestResults.Impl;
 import com.velocitypowered.proxy.protocol.StateRegistry;
 import com.velocitypowered.proxy.protocol.packet.Handshake;
@@ -188,6 +189,9 @@ public class VelocityServerConnection implements MinecraftConnectionAssociation,
       handshake.setServerAddress(createBungeeGuardForwardingAddress(secret));
     } else if (proxyPlayer.getConnection().getType() == ConnectionTypes.LEGACY_FORGE) {
       handshake.setServerAddress(playerVhost + HANDSHAKE_HOSTNAME_TOKEN);
+    } else if (proxyPlayer.getConnection().getType() instanceof ModernForgeConnectionType) {
+      handshake.setServerAddress(playerVhost + ((ModernForgeConnectionType) proxyPlayer
+              .getConnection().getType()).getModernToken());
     } else {
       handshake.setServerAddress(playerVhost);
     }

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

@@ -28,6 +28,8 @@ import com.velocitypowered.proxy.connection.ConnectionTypes;
 import com.velocitypowered.proxy.connection.MinecraftConnection;
 import com.velocitypowered.proxy.connection.MinecraftSessionHandler;
 import com.velocitypowered.proxy.connection.forge.legacy.LegacyForgeConstants;
+import com.velocitypowered.proxy.connection.forge.modern.ModernForgeConnectionType;
+import com.velocitypowered.proxy.connection.forge.modern.ModernForgeConstants;
 import com.velocitypowered.proxy.connection.util.VelocityInboundConnection;
 import com.velocitypowered.proxy.protocol.MinecraftPacket;
 import com.velocitypowered.proxy.protocol.StateRegistry;
@@ -152,6 +154,10 @@ public class HandshakeSessionHandler implements MinecraftSessionHandler {
   }
 
   private ConnectionType getHandshakeConnectionType(Handshake handshake) {
+    if (handshake.getServerAddress().contains(ModernForgeConstants.MODERN_FORGE_TOKEN)
+            && handshake.getProtocolVersion().compareTo(ProtocolVersion.MINECRAFT_1_20_2) >= 0) {
+      return new ModernForgeConnectionType(handshake.getServerAddress());
+    }
     // Determine if we're using Forge (1.8 to 1.12, may not be the case in 1.13).
     if (handshake.getServerAddress().endsWith(LegacyForgeConstants.HANDSHAKE_HOSTNAME_TOKEN)
         && handshake.getProtocolVersion().compareTo(ProtocolVersion.MINECRAFT_1_13) < 0) {

proxy/src/main/java/com/velocitypowered/proxy/connection/forge/modern/ModernForgeConnectionType.java

@@ -0,0 +1,65 @@
+/*
+ * Copyright (C) 2018-2023 Velocity Contributors
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+package com.velocitypowered.proxy.connection.forge.modern;
+
+import static com.velocitypowered.proxy.connection.forge.modern.ModernForgeConstants.MODERN_FORGE_TOKEN;
+
+import com.velocitypowered.proxy.connection.backend.BackendConnectionPhases;
+import com.velocitypowered.proxy.connection.client.ClientConnectionPhases;
+import com.velocitypowered.proxy.connection.util.ConnectionTypeImpl;
+
+/**
+ * Contains extra logic.
+ */
+public class ModernForgeConnectionType extends ConnectionTypeImpl {
+
+  public final String hostName;
+
+  /**
+   * initialize the host name into an internal variable.
+   *
+   * @param hostName address from the client
+   */
+  public ModernForgeConnectionType(String hostName) {
+    super(ClientConnectionPhases.VANILLA,
+        BackendConnectionPhases.VANILLA);
+    this.hostName = hostName;
+  }
+
+  /**
+   * Align the acquisition logic with the internal code of Forge.
+   *
+   * @return returns the final correct hostname
+   */
+  public String getModernToken() {
+    int natVersion = 0;
+    int idx = hostName.indexOf('\0');
+    if (idx != -1) {
+      for (var pt : hostName.split("\0")) {
+        if (pt.startsWith(MODERN_FORGE_TOKEN)) {
+          if (pt.length() > MODERN_FORGE_TOKEN.length()) {
+            natVersion = Integer.parseInt(
+                    pt.substring(MODERN_FORGE_TOKEN.length()));
+          }
+        }
+      }
+    }
+    return natVersion == 0 ? "\0" + MODERN_FORGE_TOKEN : "\0"
+            + MODERN_FORGE_TOKEN + natVersion;
+  }
+}

proxy/src/main/java/com/velocitypowered/proxy/connection/forge/modern/ModernForgeConstants.java

@@ -0,0 +1,25 @@
+/*
+ * Copyright (C) 2018-2023 Velocity Contributors
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+package com.velocitypowered.proxy.connection.forge.modern;
+
+/**
+ * Constants for use with Modern Forge systems.
+ */
+public class ModernForgeConstants {
+  public static final String MODERN_FORGE_TOKEN = "FORGE";
+}