Linux Pinging the Linx server caused extremely high latency for all players on the server

[Blue mame]

Version

V2.6

Platform

Linux

Method to reproduce the content: Start a 7dtd server on a Linux system and continuously accept tcping packets. Connect to the network through the TCP server port, limit the total matching traffic and close the port, causing all players to be disconnected from that port for seven days.

 

[zztong]

What an interesting denial of service attack. I had to look up a few things to fully understand it as tcping is different than just a typical ICMP ping. This looks like a nasty problem to try and solve in the server software other than trying to find some kind of timer value maybe. Have you considered a firewall that limits connection attempts from a single IP?

 

[Blue mame]

What an interesting denial of service attack. I had to look up a few things to fully understand it as tcping is different than just a typical ICMP ping. This looks like a nasty problem to try and solve in the server software other than trying to find some kind of timer value maybe. Have you considered a firewall that limits connection attempts from a single IP?

Might need some kind of firewall policy? But this problem only exists on Linux systems, whereas there is no issue on Windows systems. I have tested Linux servers from multiple providers and found that this only happens on Linux.

 

[Blue mame]

Video demonstration

 

[zztong]

Might need some kind of firewall policy? But this problem only exists on Linux systems, whereas there is no issue on Windows systems. I have tested Linux servers from multiple providers and found that this only happens on Linux.

That's what I was thinking. Perhaps the Windows firewall already has such a rule by default. I mean, the game must accept connections. It's a matter of how quickly it should shed a connection that isn't doing anything. Shed it too quickly and you start dropping players with bad connections. Shed it too slowly and you get what you're seeing. Or at least that how I understand the issue.

 

[Blue mame]

That's what I was thinking. Perhaps the Windows firewall already has such a rule by default. I mean, the game must accept connections. It's a matter of how quickly it should shed a connection that isn't doing anything. Shed it too quickly and you start dropping players with bad connections. Shed it too slowly and you get what you're seeing. Or at least that how I understand the issue.

This can directly cause the server to enter a dead loop. As you can see in the video, I still maintained such a high latency for the next 3 minutes. If I don't restart the server, I won't be able to get rid of it. However, this situation won't occur in Windows. The server has already crashed, and even attacking Linux servers like this is completely cost-effective. Let me see if TFP has a solution to this problem

 

[WretchedDollie]

Hey All,

Thank you for taking the time to report this.

I added a ticket to our bug-tracking software for this so that the networking developers can investigate what is happening and determine the best course of action.

Thanks,
Dollie