Re: [RFC PATCH 0/2] Faster/parallel SYN handling to mitigate SYN floods

Eric Dumazet
2012-05-31T12:58:27Z

On Thu, 2012-05-31 at 14:51 +0200, Jesper Dangaard Brouer wrote:
> On Thu, 2012-05-31 at 00:40 +0200, Jesper Dangaard Brouer wrote:
> > That seems like a very unlikely situation, which we perhaps should
> > neglect as we are under SYN attack.
> >
> > I will test the attack vector, if we instead of dropping the reqsk,
> > fall back into the slow locked path.
>
> I can provoke this attack vector, and performance is worse, if not
> dropping the reqsk early.
>
> Generator SYN flood at 750Kpps, sending false retransmits mixture.
>
> - With early drop: 406 Kpps
> - With return to locked processing: 251 Kpps
>
> Its still better than the approx 150Kpps, without any patches.
>

How many different IP addresses are used by your generator ?

Or maybe you disabled IP route cache ?