Help: kernel: TCP: Possible SYN flooding on port 60543. Sending cookies.

[amorak]

Getting the below error constantly. Would love some advice on how to diagnose it as a concern or not...

 

[ColinTaylor]

The quickest way to identify the source of the problem is probably to systematically turn off each of your clients until the messages top. I'd start with IoT and "smart" devices.

 

[amorak]

Thanks for the reply! Is there a log I can look at to figure out which MAC is causing these syn floodings? I have 60 devices connected, so it's a PITA to disconnect and determine what's causing it....

 

[ColinTaylor]

The only information is what's shown.

You could SSH into the router and issue the following command to try and determine what service is being hammered.

netstat -ntap | grep 60543

Change 60543 to the port number currently shown in the syslog.

My guess is that it's probably the router's Media Server. If it is and you don't actually use that you can turn it off.

 

[amorak]

Thanks Colin, that worked great! It's all my 4-5 Belkin Wemo's... Which has been having connection troubles as of late! Any thoughts there on what to do?

 

[ColinTaylor]

Sorry what "worked great"? I don't know anything about Wemo's. What was the output of the netstat command?

 

[amorak]

Sorry what "worked great"? I don't know anything about Wemo's. What was the output of the netstat command?

Sorry - I meant that it worked great in helping me determine the IPs that were causing the flooding. It was 4 or 5 iPs, all belonging to my WEMO smart plugs. I then googled it and came across this thread below here on SMB, that others came in and fixed it by disabling uPnP. I've done the same and the flooding in the syslog is gone.

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