possible SYN flooding on port 80. Sending cookies

Posted by Sparsh Gupta on Server Fault See other posts from Server Fault or by Sparsh Gupta
Published on 2011-02-17T20:28:18Z Indexed on 2012/06/07 4:42 UTC
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ubuntu

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kernel

I recently had a server downtime. I looked everywhere and the only thing I found in my log files is:

Feb 17 18:58:04 localhost kernel: possible SYN flooding on port 80. Sending cookies.
Feb 17 18:59:33 localhost kernel: possible SYN flooding on port 80. Sending cookies.

Can someone give me more information about it. WHat is it, How can I debug the cause and how can I fix the same. I also posted ipconntrack suddenly became toooo large which has another data point I found unusual, wondering if the two things is connected as they occured exactly at the same time but at different servers. One at reverse proxy and other at actual backend Varnish server)

Thanks

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