netdev - Re: [PATCH net-next] tcp: avoid tx starvation by SYNACK packets

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Message-ID: <201206010939.22620.hans.schillstrom@ericsson.com>
Date:	Fri, 1 Jun 2012 09:36:12 +0200
From:	Hans Schillstrom <hans.schillstrom@...csson.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
CC:	netdev <netdev@...r.kernel.org>,
	Neal Cardwell <ncardwell@...gle.com>,
	Tom Herbert <therbert@...gle.com>,
	Jesper Dangaard Brouer <brouer@...hat.com>
Subject: Re: [PATCH net-next] tcp: avoid tx starvation by SYNACK packets

On Thursday 31 May 2012 23:56:37 Eric Dumazet wrote:
> From: Eric Dumazet <edumazet@...gle.com>
> 
> pfifo_fast being the default Qdisc, its pretty easy to fill it with
> SYNACK (small) packets while host is under SYNFLOOD attack.
> 
> Packets of established TCP sessions are dropped and host appears almost
> dead.
> 
> Avoid this problem assigning TC_PRIO_FILLER priority to SYNACK
> generated in SYNCOOKIE mode, so that these packets are enqueued into
> pfifo_fast band 2.
> 
> Other packets, queued to band 0 or 1 are dequeued before any SYNACK
> packets waiting in band 2.
> 
Thanks Eric,
the patch is in under test now.

-- 
Regards
Hans Schillstrom
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