Re: New Denial of Service Attack ...

[Christopher Blizzard]

In message <199609250552.AA19213@zen.isi.edu>, postel@ISI.EDU writes:
:----- Begin Included Message -----
:
:Subject: Re: FW: Latest attacks....
:Date: Thu, 19 Sep 1996 08:39:02 +0100
:From: Jon Crowcroft <J.Crowcroft@cs.ucl.ac.uk>
:
:
:Date: Wed, 18 Sep 1996 14:32:14 -0600
:From: vjs@mica.denver.sgi.com (Vernon Schryver)
:Subject: SYN bombing defense
:
:As reported here, in article <vxjiv9hkmcb.fsf_-_@dominator.eecs.harvard.edu>
:in comp.protocols.tcp-ip, Robert Morris  <rtm@dominator.eecs.harvard.edu> wrot
:e:
:
:>Perhaps TCP's listen queue should use random early drop (RED), a
:>technique used by routers to prevent any one source from monopolizing
:>a queue. See http://www-nrg.ee.lbl.gov/floyd/abstracts.html#FJ93 or
:>rfc1254.
:> ...
:
:I've just hacked IRIX 6.3 to do random-drop when sonewconn() in
:tcp_input.c fails.  It works great!  An IP22 receiving 1200 bogus
:SYN's per second directed to port 23 continues to answer requests
:for new telnet as if nothing is happening.
:

Alan Cox just released a patch vs Linux 2.0.21 that does this.  It works 
quite well.  As best I can tell from the patch and the mail that preceded 
it it attempts to maintain about 30% free in the receive queue.  I've 
been running it for a couple of days and it does quite well defending 
against these attacks.  I've stuck it on my web page.

http://odin.nyser.net/~blizzard/linux/

--Chris

:
:Vernon Schryver,  vjs@sgi.com
:
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Christopher Blizzard   | "The truth knocks on the door and you say
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