kick sessions that stop responding to keep alives

src/main/java/com/zenith/network/SKeepAliveTask.java

@@ -5,7 +5,10 @@
 import org.geysermc.mcprotocollib.protocol.data.ProtocolState;
 import org.geysermc.mcprotocollib.protocol.packet.common.clientbound.ClientboundKeepAlivePacket;
 
+import java.util.concurrent.TimeUnit;
+
 import static com.zenith.Globals.CONFIG;
+import static com.zenith.Globals.SERVER_LOG;
 
 public class SKeepAliveTask implements Runnable {
     private final ServerSession session;
@@ -16,9 +19,24 @@ public SKeepAliveTask(ServerSession session) {
 
     @Override
     public void run() {
-        if (!session.isSpectator() && CONFIG.client.keepAliveHandling.keepAliveMode != KeepAliveMode.INDEPENDENT) return;
         var state = session.getPacketProtocol().getOutboundState();
         if (state != ProtocolState.CONFIGURATION && state != ProtocolState.GAME) return;
+        // detect half-open connections that are no longer responding to keep alives
+        // e.g. a controlling player whose internet connection has silently dropped
+        // disconnecting them lets the bot take over and resync teleports before the destination server kicks us
+        if (isKeepAliveTimedOut()) {
+            SERVER_LOG.info("[{}] Disconnecting session that has not responded to keep alives", session.getName());
+            session.disconnect("Timed out");
+            return;
+        }
+        if (!session.isSpectator() && CONFIG.client.keepAliveHandling.keepAliveMode != KeepAliveMode.INDEPENDENT) return;
         this.session.send(new ClientboundKeepAlivePacket(System.currentTimeMillis()));
     }
+
+    private boolean isKeepAliveTimedOut() {
+        if (!CONFIG.server.extra.timeout.enable) return false;
+        if (!session.isLoggedIn()) return false;
+        var elapsed = System.currentTimeMillis() - session.getLastKeepAliveResponseTime();
+        return elapsed > TimeUnit.SECONDS.toMillis(CONFIG.server.extra.timeout.seconds);
+    }
 }

src/main/java/com/zenith/network/server/ServerSession.java

@@ -86,6 +86,9 @@ public class ServerSession extends TcpServerSession {
     protected long ping = 0L;
     protected long lastKeepAliveId = 0L;
     protected long lastKeepAliveTime = 0L;
+    // last time we received a keep alive response from this session
+    // used to detect and disconnect half-open connections, e.g. after a controller's internet outage
+    protected volatile long lastKeepAliveResponseTime = System.currentTimeMillis();
 
     protected boolean whitelistChecked = false;
     protected boolean isPlayer = false;
@@ -290,6 +293,7 @@ public void disconnect(@Nullable final Component reason, final Throwable cause)
 
     public void setLoggedIn() {
         this.isLoggedIn = true;
+        this.lastKeepAliveResponseTime = System.currentTimeMillis();
         if (!Proxy.getInstance().getActiveConnections().contains(this))
             Proxy.getInstance().getActiveConnections().add(this);
     }

src/main/java/com/zenith/network/server/handler/player/incoming/SPlayerKeepAliveHandler.java

@@ -10,6 +10,7 @@ public class SPlayerKeepAliveHandler implements PacketHandler<ServerboundKeepAli
     public static final SPlayerKeepAliveHandler INSTANCE = new SPlayerKeepAliveHandler();
     @Override
     public ServerboundKeepAlivePacket apply(final ServerboundKeepAlivePacket packet, final ServerSession session) {
+        session.setLastKeepAliveResponseTime(System.currentTimeMillis());
         if (packet.getPingId() == session.getLastKeepAliveId()) {
             session.setPing(System.currentTimeMillis() - session.getLastKeepAliveTime());
         }

src/main/java/com/zenith/network/server/handler/spectator/incoming/KeepAliveSpectatorHandler.java

@@ -8,6 +8,7 @@ public class KeepAliveSpectatorHandler implements PacketHandler<ServerboundKeepA
     public static final KeepAliveSpectatorHandler INSTANCE = new KeepAliveSpectatorHandler();
     @Override
     public ServerboundKeepAlivePacket apply(final ServerboundKeepAlivePacket packet, final ServerSession session) {
+        session.setLastKeepAliveResponseTime(System.currentTimeMillis());
         if (packet.getPingId() == session.getLastKeepAliveId()) {
             session.setPing(System.currentTimeMillis() - session.getLastKeepAliveTime());
         }