More tweaks to Karst / Default player limit of 30

core/src/mindustry/core/NetClient.java

@@ -224,6 +224,13 @@ public class NetClient implements ApplicationListener{
         //do not receive chat messages from clients that are too young or not registered
         if(net.server() && player != null && player.con != null && (Time.timeSinceMillis(player.con.connectTime) < 500 || !player.con.hasConnected || !player.isAdded())) return;
 
+        //detect and kick for foul play
+        if(player != null && player.con != null && !player.con.chatRate.allow(2000, 20)){
+            player.con.kick(KickReason.kick);
+            netServer.admins.blacklistDos(player.con.address);
+            return;
+        }
+
         if(message.length() > maxTextLength){
             throw new ValidateException(player, "Player has sent a message above the text limit.");
         }

core/src/mindustry/net/Administration.java

@@ -21,6 +21,7 @@ public class Administration{
     public Seq<ChatFilter> chatFilters = new Seq<>();
     public Seq<ActionFilter> actionFilters = new Seq<>();
     public Seq<String> subnetBans = new Seq<>();
+    public ObjectSet<String> dosBlacklist = new ObjectSet<>();
     public ObjectMap<String, Long> kickedIPs = new ObjectMap<>();
 
     /** All player info. Maps UUIDs to info. This persists throughout restarts. Do not access directly. */
@@ -83,6 +84,14 @@ public class Administration{
         });
     }
 
+    public synchronized void blacklistDos(String address){
+        dosBlacklist.add(address);
+    }
+
+    public synchronized boolean isDosBlacklisted(String address){
+        return dosBlacklist.contains(address);
+    }
+
     /** @return time at which a player would be pardoned for a kick (0 means they were never kicked) */
     public long getKickTime(String uuid, String ip){
         return Math.max(getInfo(uuid).lastKicked, kickedIPs.get(ip, 0L));
@@ -162,7 +171,7 @@ public class Administration{
     }
 
     public int getPlayerLimit(){
-        return Core.settings.getInt("playerlimit", 0);
+        return Core.settings.getInt("playerlimit", headless ? 30 : 0);
     }
 
     public void setPlayerLimit(int limit){

core/src/mindustry/net/ArcNetProvider.java

@@ -11,6 +11,7 @@ import arc.util.*;
 import arc.util.Log.*;
 import arc.util.io.*;
 import mindustry.*;
+import mindustry.game.EventType.*;
 import mindustry.net.Net.*;
 import mindustry.net.Packets.*;
 import net.jpountz.lz4.*;
@@ -19,7 +20,6 @@ import java.io.*;
 import java.net.*;
 import java.nio.*;
 import java.nio.channels.*;
-import java.util.*;
 import java.util.concurrent.*;
 
 import static mindustry.Vars.*;
@@ -35,6 +35,8 @@ public class ArcNetProvider implements NetProvider{
     private static final LZ4FastDecompressor decompressor = LZ4Factory.fastestInstance().fastDecompressor();
     private static final LZ4Compressor compressor = LZ4Factory.fastestInstance().fastCompressor();
 
+    private volatile int playerLimitCache;
+
     public ArcNetProvider(){
         ArcNet.errorHandler = e -> {
             if(Log.level == LogLevel.debug){
@@ -42,6 +44,11 @@ public class ArcNetProvider implements NetProvider{
             }
         };
 
+        //fetch this in the main thread to prevent threading issues
+        Events.run(Trigger.update, () -> {
+            playerLimitCache = netServer.admins.getPlayerLimit();
+        });
+
         client = new Client(8192, 8192, new PacketSerializer());
         client.setDiscoveryPacket(packetSupplier);
         client.addListener(new NetListener(){
@@ -94,6 +101,12 @@ public class ArcNetProvider implements NetProvider{
             public void connected(Connection connection){
                 String ip = connection.getRemoteAddressTCP().getAddress().getHostAddress();
 
+                //kill connections above the limit to prevent spam
+                if((playerLimitCache > 0 && server.getConnections().length > playerLimitCache) || netServer.admins.isDosBlacklisted(ip)){
+                    connection.close(DcReason.closed);
+                    return;
+                }
+
                 ArcConnection kn = new ArcConnection(ip, connection);
 
                 Connect c = new Connect();

core/src/mindustry/net/NetConnection.java

@@ -28,6 +28,8 @@ public abstract class NetConnection{
     public long lastReceivedClientTime;
     /** Build requests that have been recently rejected. This is cleared every snapshot. */
     public Seq<BuildPlan> rejectedRequests = new Seq<>();
+    /** Handles chat spam rate limits. */
+    public Ratekeeper chatRate = new Ratekeeper();
 
     public boolean hasConnected, hasBegunConnecting, hasDisconnected;
     public float viewWidth, viewHeight, viewX, viewY;