LKML Archive on lore.kernel.org
help / color / mirror / Atom feed
From: Ross Vandegrift <ross@kallisti.us>
To: Andi Kleen <andi@firstfloor.org>
Cc: Glenn Griffin <ggriffin.kernel@gmail.com>,
	netdev@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] Add IPv6 support to TCP SYN cookies
Date: Tue, 5 Feb 2008 16:23:35 -0500	[thread overview]
Message-ID: <20080205212335.GA11287@kallisti.us> (raw)
In-Reply-To: <20080205201106.GB26150@one.firstfloor.org>

On Tue, Feb 05, 2008 at 09:11:06PM +0100, Andi Kleen wrote:
> > The problem is that any reasonably recent PC can generate enough
> > forged SYN packets to overwhelm reasonable SYN queues on a much more
> > powerful server.
> 
> Have you actually seen this with a recent kernel in the wild or are
> you just talking theoretically?
> 
> Linux uses some heuristics to manage the syn queue that should
> still ensure reasonable service even without cookies under attack.
> Also SYN-RECV sockets are stored in a special data structure optimized
> to use minimal resources.
> 
> It is far from the classical head drop method that was so vunerable
> to syn flooding.

I work at a hosting company and we see these kinds of issues in the
real world fairly frequently.  I would guess maybe a monthly basis.
The servers where we have seen this are typically running RHEL 4 or 5
kernels, so I can't really speak to how recent the kernel is in this
specific term.

If I can find a box that we could temporary get a kernel.org kernel
on, I'll see if I can get a real comparison together.  We have
collected a few of the more effective attack tools that have been left
on compromised systems, so it wouldn't be too difficult to get some
numbers.

-- 
Ross Vandegrift
ross@kallisti.us

"The good Christian should beware of mathematicians, and all those who
make empty prophecies. The danger already exists that the mathematicians
have made a covenant with the devil to darken the spirit and to confine
man in the bonds of Hell."
	--St. Augustine, De Genesi ad Litteram, Book II, xviii, 37

  reply	other threads:[~2008-02-05 21:23 UTC|newest]

Thread overview: 41+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-02-04 23:01 Glenn Griffin
2008-02-05 15:55 ` Andi Kleen
2008-02-05 15:42   ` Alan Cox
2008-02-05 16:39     ` Andi Kleen
2008-02-05 16:03       ` Alan Cox
2008-02-05 16:48         ` Andi Kleen
2008-02-05 16:14           ` Alan Cox
2008-02-05 20:50       ` Willy Tarreau
2008-02-05 18:29   ` Glenn Griffin
2008-02-05 19:25     ` Ross Vandegrift
2008-02-05 20:11       ` Andi Kleen
2008-02-05 21:23         ` Ross Vandegrift [this message]
2008-02-06  8:53           ` Andi Kleen
2008-02-07 19:44             ` Ross Vandegrift
2008-02-08 12:07               ` Andi Kleen
2008-02-12 20:38                 ` Ross Vandegrift
2008-02-05 20:02     ` Andi Kleen
2008-02-05 20:39       ` Evgeniy Polyakov
2008-02-05 20:53         ` Andi Kleen
2008-02-05 21:50           ` Evgeniy Polyakov
2008-02-05 21:20         ` Alan Cox
2008-02-05 21:52           ` Evgeniy Polyakov
2008-02-05 21:20             ` Willy Tarreau
2008-02-05 22:05             ` Alan Cox
2008-02-06  1:52               ` Glenn Griffin
2008-02-06  7:50                 ` Andi Kleen
2008-02-06 17:36                   ` Glenn Griffin
2008-02-06 18:45                     ` Andi Kleen
2008-02-06 23:03                       ` Glenn Griffin
2008-02-06  9:13                 ` Evgeniy Polyakov
2008-02-06 18:30                   ` Glenn Griffin
2008-02-07  7:24                     ` Evgeniy Polyakov
2008-02-07  9:40                       ` Eric Dumazet
2008-02-08  5:32                         ` Glenn Griffin
2008-02-08  5:49                           ` Glenn Griffin
2008-02-11 16:07                             ` YOSHIFUJI Hideaki / 吉藤英明
2008-02-18 23:45                               ` Glenn Griffin
2008-02-13  7:31                         ` YOSHIFUJI Hideaki / 吉藤英明
2008-02-05 19:57   ` Jan Engelhardt
2008-02-05 21:25     ` Alan Cox
2008-02-04 23:01 Glenn Griffin

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20080205212335.GA11287@kallisti.us \
    --to=ross@kallisti.us \
    --cc=andi@firstfloor.org \
    --cc=ggriffin.kernel@gmail.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=netdev@vger.kernel.org \
    --subject='Re: [PATCH] Add IPv6 support to TCP SYN cookies' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).