linux-kernel - Re: [PATCH 2.6.21-rc6] [netfilter] early

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Message-Id: <20070406102433.d3a670a5.dada1@cosmosbay.com>
Date:	Fri, 6 Apr 2007 10:24:33 +0200
From:	Eric Dumazet <dada1@...mosbay.com>
To:	Vasily Averin <vvs@...ru>
Cc:	"David S. Miller" <davem@...emloft.net>,
	Patrick McHardy <kaber@...sh.net>,
	Andrew Morton <akpm@...ux-foundation.org>,
	netfilter-devel@...ts.netfilter.org, rusty@...tcorp.com.au,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	devel@...nvz.org
Subject: Re: [PATCH 2.6.21-rc6] [netfilter] early_drop imrovement

On Fri, 06 Apr 2007 12:00:29 +0400
Vasily Averin <vvs@...ru> wrote:

> When the number of conntracks is reached ip_conntrack_max limit, early_drop() is
> called and tries to free one of already used conntracks in one of the hash
> buckets. If it does not find any conntracks that may be freed, it
> leads to transmission errors.
> However it is not fair because of current hash bucket may be empty but the
> neighbour ones can have the number of conntracks that can be freed. With the
> following patch early_drop() will search conntracks in all hash buckets.

Have you tested your patch in a DOS situation ?
Some machines have a huge ip_conntrack_max.
A single scan of the whole table might take 1000 ms or even more.


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