Messages in this thread | | | Subject | Re: test SYN cookies (was Re: SYN cookies security bugfix?) | From | Ed L Cashin <> | Date | 11 Nov 2001 00:17:30 -0500 |
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Thank you much for the reply.
Alan Cox <alan@lxorguk.ukuu.org.uk> writes:
> > Is there anyone who has any evidence that SYN cookies do anything in > > kernel 2.2.x? If so, how did you get that evidence, because I would > > like to reproduce it. > > They work fine for me in 2.2.19/2.2.20.
That was reassuring enough that I persisted and found that the problem was this: my home-spun SYN-flooder wasn't changing the TCP sequence number, and so the "victim" was discarding the packets.
The three-second pause I observed previously was a red herring that went away when I started using separate hosts for flooding and connection-testing.
Now I see a night-and-day difference between with and without SYN cookies (although when tcp_max_syn_backlog is set to more than a five it takes a long time to fill the queue).
Thanks again.
-- --Ed Cashin PGP public key: ecashin@terry.uga.edu http://www.terry.uga.edu/~ecashin/pgp/
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