netdev - Re: DDoS attack causing bad effect on conntrack searches

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Message-Id: <20100423.011328.107238355.davem@davemloft.net>
Date:	Fri, 23 Apr 2010 01:13:28 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	eric.dumazet@...il.com
Cc:	hawk@...u.dk, paulmck@...ux.vnet.ibm.com, kaber@...sh.net,
	xiaosuo@...il.com, hawk@...x.dk, netdev@...r.kernel.org,
	netfilter-devel@...r.kernel.org
Subject: Re: DDoS attack causing bad effect on conntrack searches

From: Eric Dumazet <eric.dumazet@...il.com>
Date: Fri, 23 Apr 2010 07:44:38 +0200

> Le jeudi 22 avril 2010 à 16:44 -0700, David Miller a écrit :
>> Eric, I wonder if we run into some kind of issue on 32-bit systems
>> because we always lose a bit of the conntrack hash value when we store
>> it into the 'nulls' area?
>> 
>> Wouldn't that make the "get_nulls_value(n) != hash" fail?
>> --
> 
> 
> Well, 'hash' at this time is not the result of the jhash() transform [0
> - 0xFFFFFFFF], but a slot number in htable [0 - (300032-1)].

Aha, I see.

I really can't see what might cause this behavior then.
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