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Subjecttest SYN cookies (was Re: SYN cookies security bugfix?)
Alan Cox <> writes:

> > I received a forwarded message from SuSE regarding a security vulnerability
> > with respect to randomization of the ISN for SYN cookies - or something to
> > that effect. I have not been able to find the patch which addresses this
> > problem; if anyone can point me towards it, I would be appreciative.
> Its fixed in 2.2.20, you can grab the 2.2 patch from there

What is a good way to test SYN cookies? I can induce a three-second
delay (on victim host V) before new TCP connections are accepted by
sending a burst of 2000 SYN packets (from attacker A), where V is
running a 2.2.14 or 2.2.17 kernel. During the three seconds ICMP echo
requests from A to V are being answered.

Turning on SYN cookies after /proc is mounted does not affect the
three-second pause, though, so I figure that either the pause is not
on account of a full half-open connection queue or SYN cookies are not

--Ed Cashin PGP public key:

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