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
Read the original article Hit count: 722

Filed under:

ubuntu

|

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

© Server Fault or respective owner

Related posts about ubuntu

Cannot update, apt-get cannot fetch index files

as seen on Ask Ubuntu - Search for 'Ask Ubuntu'
I have a fresh install of Ubuntu 11.10 from the iso 'ubuntu-11.10-desktop-amd64.iso'. I installed this in VMWare Fusion 4.1.1 running on OSX 10.7.3. When setting up the VM, I allowed easy install to take care of creating my user and installing VMWare tools. No problems during installation, everything… >>> More
'sudo apt-get update' error on Ubuntu 12.04

as seen on Ask Ubuntu - Search for 'Ask Ubuntu'
When I type in 'sudo apt-get update' I get this mohd-arafat-hossain@TUD:~$ sudo apt-get update [sudo] password for mohd-arafat-hossain: Ign http://bd.archive.ubuntu.com precise InRelease Ign http://bd.archive.ubuntu.com precise-updates InRelease Ign http://bd.archive.ubuntu… >>> More
Opening Skype, Opera, OpenOffice logs me off

as seen on Ask Ubuntu - Search for 'Ask Ubuntu'
Whats common among Skype, Opera, OpenOffice in Ubuntu ? Whenever I open these applications I get logged off and shows back me the login screen. This started happening since the 10.10 upgrade. Forgot to mention : Yes, its x64.Each time I open these applications, the UI shows and then crashes. I… >>> More
Update information outdated

as seen on Ask Ubuntu - Search for 'Ask Ubuntu'
I have a warning triangle that my update information is outdated, the last update was 12 days ago. I use Ubuntu 11.10. A run of sudo apt-get update produces the following output: Ign http://ppa.launchpad.net oneiric InRelease Ign http://de.archive.ubuntu.com oneiric InRelease … >>> More
ubuntu/apt-get update said "Failed to Fetch http:// .... 404 not found"

as seen on Server Fault - Search for 'Server Fault'
Hi all, I'm trying to run apt-get update on ubuntu 9.10 I've configured my proxy server and I can access the internet without any problem: /etc/apt# wget "http://www.google.com" Resolving (...) Proxy request sent, awaiting response... 200 OK Length: 292 [text/html] Saving to: `index.html' 100%[=================================================================================================================================>]… >>> More

Related posts about kernel

Can't install kernel-uek-headers for currently running kernel

as seen on Server Fault - Search for 'Server Fault'
I have just created a VM in VMWare and installed a minimal install of Oracle Enterprise Linux 6.3. # cat /etc/oracle-release Oracle Linux Server release 6.3 It is running with the UEK kernel. # uname -r 2.6.39-200.24.1.el6uek.x86_64 When I try and install VMWare Tools, I get the following error… >>> More
Why does my laptop resume immediately after suspend?

as seen on Ask Ubuntu - Search for 'Ask Ubuntu'
I seem to be having some problem with suspend mode. Every time I try to suspend my laptop, it just locks the screen. Or maybe it successfully suspends just to resume only an instant after. What could cause such a behaviour? I'm running 32-bit Ubuntu 12.04 with the 3.2.0-25 kernel on a HP dv5-1178er… >>> More
Fedora error log file

as seen on Server Fault - Search for 'Server Fault'
I am running a java application using this wrapper service yajsw. The problem it just stopped without any error in its logs file. So I was wondering will there be any system log file which will indicate the cause of it going down? Partial of the log file. Apr 6 00:12:20 localhost kernel: imklog… >>> More
External USB drive is failing

as seen on Super User - Search for 'Super User'
I have an external USB 2.0 drive WD My Book Mirror Edition, running in RAID 1 (mirroring) mode. A while ago the hard drive started to fail: it stops responding (directories are not listed returning an error after a big timeout). Sometimes it works for weeks before a failure, sometimes – few hours… >>> More
Problem with RAID5 (mdadm) - disk detached

as seen on Server Fault - Search for 'Server Fault'
Having these lines in /var/log/syslog Apr 18 16:53:05 Server kernel: [4487878.816036] ata4: EH in SWNCQ mode,QC:qc_active 0x1 sactive 0x1 Apr 18 16:53:05 Server kernel: [4487878.816058] ata4: SWNCQ:qc_active 0x1 defer_bits 0x0 last_issue_tag 0x0 Apr 18 16:53:05 Server kernel: [4487878… >>> More