Add builtin server transfer support for ViaProxy (#4723)

bootstrap/viaproxy/src/main/java/org/geysermc/geyser/platform/viaproxy/GeyserViaProxyPlugin.java

@@ -37,6 +37,7 @@ import org.apache.logging.log4j.LogManager;
 import org.geysermc.geyser.GeyserBootstrap;
 import org.geysermc.geyser.GeyserImpl;
 import org.geysermc.geyser.GeyserLogger;
+import org.geysermc.geyser.api.event.EventRegistrar;
 import org.geysermc.geyser.api.network.AuthType;
 import org.geysermc.geyser.api.util.PlatformType;
 import org.geysermc.geyser.command.GeyserCommandManager;
@@ -44,6 +45,7 @@ import org.geysermc.geyser.configuration.GeyserConfiguration;
 import org.geysermc.geyser.dump.BootstrapDumpInfo;
 import org.geysermc.geyser.ping.GeyserLegacyPingPassthrough;
 import org.geysermc.geyser.ping.IGeyserPingPassthrough;
+import org.geysermc.geyser.platform.viaproxy.listener.GeyserServerTransferListener;
 import org.geysermc.geyser.session.GeyserSession;
 import org.geysermc.geyser.text.GeyserLocale;
 import org.geysermc.geyser.util.FileUtils;
@@ -57,7 +59,7 @@ import java.nio.file.Files;
 import java.nio.file.Path;
 import java.util.UUID;
 
-public class GeyserViaProxyPlugin extends ViaProxyPlugin implements GeyserBootstrap {
+public class GeyserViaProxyPlugin extends ViaProxyPlugin implements GeyserBootstrap, EventRegistrar {
 
     public static final File ROOT_FOLDER = new File(PluginManager.PLUGINS_DIR, "Geyser");
 
@@ -120,6 +122,7 @@ public class GeyserViaProxyPlugin extends ViaProxyPlugin implements GeyserBootst
         }
 
         this.geyser = GeyserImpl.load(PlatformType.VIAPROXY, this);
+        this.geyser.eventBus().register(this, new GeyserServerTransferListener());
         LoopbackUtil.checkAndApplyLoopback(this.logger);
     }
 

bootstrap/viaproxy/src/main/java/org/geysermc/geyser/platform/viaproxy/listener/GeyserServerTransferListener.java

@@ -0,0 +1,62 @@
+/*
+ * Copyright (c) 2024 GeyserMC. http://geysermc.org
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ *
+ * @author GeyserMC
+ * @link https://github.com/GeyserMC/Geyser
+ */
+
+package org.geysermc.geyser.platform.viaproxy.listener;
+
+import com.google.common.cache.Cache;
+import com.google.common.cache.CacheBuilder;
+import com.google.common.net.HostAndPort;
+import org.geysermc.event.PostOrder;
+import org.geysermc.event.subscribe.Subscribe;
+import org.geysermc.geyser.api.event.bedrock.SessionLoginEvent;
+import org.geysermc.geyser.api.event.java.ServerTransferEvent;
+import org.geysermc.geyser.session.GeyserSession;
+
+import java.util.Map;
+import java.util.concurrent.TimeUnit;
+
+public class GeyserServerTransferListener {
+
+    private final Cache<String, Map<String, byte[]>> cookieStorages = CacheBuilder.newBuilder().expireAfterWrite(1, TimeUnit.MINUTES).build();
+
+    @Subscribe(postOrder = PostOrder.FIRST)
+    private void onServerTransfer(final ServerTransferEvent event) {
+        this.cookieStorages.put(event.connection().xuid(), event.cookies());
+        final GeyserSession geyserSession = (GeyserSession) event.connection();
+        final HostAndPort hostAndPort = HostAndPort.fromString(geyserSession.getClientData().getServerAddress()).withDefaultPort(19132);
+        event.bedrockHost(hostAndPort.getHost());
+        event.bedrockPort(hostAndPort.getPort());
+    }
+
+    @Subscribe(postOrder = PostOrder.FIRST)
+    private void onSessionLogin(final SessionLoginEvent event) {
+        final Map<String, byte[]> cookies = this.cookieStorages.asMap().remove(event.connection().xuid());
+        if (cookies != null) {
+            event.cookies(cookies);
+            event.transferring(true);
+        }
+    }
+
+}