Improve server control and logging of the DOS blacklist (#10904)

* Log kicks related to DOS bans

* unBlacklistDos method

Added a method to remove an IP that was blacklisted for being a potential DOS attack.

* Added a command to add/remove/list DOS bans

* Switched from spaces to a tab in the subnet-ban command

Switched from spaces to a tab in the subnet-ban command's listing function. This is better for accessibility and customizability.

* Use info(String, Object...) instead of String.format

* Fixed formatting to fit style guidelines

core/src/mindustry/net/Administration.java

@@ -91,6 +91,10 @@ public class Administration{
         dosBlacklist.add(address);
     }
 
+    public synchronized void unBlacklistDos(String address){
+        dosBlacklist.remove(address);
+    }
+
     public synchronized boolean isDosBlacklisted(String address){
         return dosBlacklist.contains(address);
     }

core/src/mindustry/net/ArcNetProvider.java

@@ -113,6 +113,8 @@ public class ArcNetProvider implements NetProvider{
 
                 //kill connections above the limit to prevent spam
                 if((playerLimitCache > 0 && server.getConnections().length > playerLimitCache) || netServer.admins.isDosBlacklisted(ip)){
+                    Log.info("Closing connection @ - IP marked as a potential DOS attack.", ip);
+
                     connection.close(DcReason.closed);
                     return;
                 }

server/src/mindustry/server/ServerControl.java

@@ -666,7 +666,7 @@ public class ServerControl implements ApplicationListener{
             if(arg.length == 0){
                 info("Subnets banned: @", netServer.admins.getSubnetBans().isEmpty() ? "<none>" : "");
                 for(String subnet : netServer.admins.getSubnetBans()){
-                    info("&lw  " + subnet);
+                    info("&lw\t" + subnet);
                 }
             }else if(arg.length == 1){
                 err("You must provide a subnet to add or remove.");
@@ -1054,6 +1054,35 @@ public class ServerControl implements ApplicationListener{
             }
         });
 
+        handler.register("dos-ban", "[add/remove] [ip]", "Add or remove a DOS ban.", arg -> {
+            if(arg.length == 0){
+                info("DOS bans: @", netServer.admins.dosBlacklist.isEmpty() ? "<none>" : "");
+
+                netServer.admins.dosBlacklist.forEach(address -> {
+                    info("&lw\t" + address);
+                });
+                return;
+            }else if(arg.length == 1){
+                err("Expected either zero or two parameters, but only got one parameter.");
+                return;
+            }
+
+            String action = arg[0].toLowerCase();
+            String ip = arg[1];
+
+            if(action.equals("add")){
+                netServer.admins.blacklistDos(ip);
+                info("Dos banned: @", ip);
+                return;
+            }else if(action.equals("remove")){
+                netServer.admins.unBlacklistDos(ip);
+                info("Removed dos ban: @", ip);
+                return;
+            }
+
+            err("Unrecognized action: @", action);
+        });
+
         mods.eachClass(p -> p.registerServerCommands(handler));
     }