Several games have reported an issue where a misbehaving VPN client spawns a gazillion simultaneous connections to the game. While this does not appear to be intentional or malicious, this effectively operates similarly to a denial of service attack by swamping the game. It can cause lag and mysterious errors like “Too many open files”.
v2.8.0 incorporates a new setting to limit the max number of simultaneous connections from the same IP. While this will certainly help, it may not completely solve the lag if the client keeps hammering at the server.
If you’re using the 1-click image (or install a firewall manually), you can block an IP at the server level using the ufw firewall command:
sudo ufw insert 1 deny from BAD_IP_GOES_HERE
(the ‘insert 1’ puts this rule at the head of the list above any “allow” rules - thanks to Alice for figuring that out.)
You should be able to get the bad IP from the game debug log. You can also use the following command in the server shell to show connections to the game port. Be sure to check both the MU client port (e.g., 4201) and the websocket port (from server.yml - usually 4202).
ss -tapn | grep 4201
If you need further help, it’s best to ask on the discord.