netdev - Re: [PATCH 1/1] netfilter: Add possibility to turn off netfilters defrag per netns

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Date:	Wed, 4 Jan 2012 19:05:10 +0100 (CET)
From:	Jozsef Kadlecsik <kadlec@...ckhole.kfki.hu>
To:	Pablo Neira Ayuso <pablo@...filter.org>
cc:	Hans Schillstrom <hans.schillstrom@...csson.com>,
	Jan Engelhardt <jengelh@...ozas.de>,
	Patrick McHardy <kaber@...sh.net>,
	"netfilter-devel@...r.kernel.org" <netfilter-devel@...r.kernel.org>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"hans@...illstrom.com" <hans@...illstrom.com>
Subject: Re: [PATCH 1/1] netfilter: Add possibility to turn off netfilters
 defrag per netns

On Wed, 4 Jan 2012, Pablo Neira Ayuso wrote:

> On Wed, Jan 04, 2012 at 12:48:35PM +0100, Hans Schillstrom wrote:
> > I like that idea, an "early" table at prio -500 with PREROUTING.
> > There is also a need for a new flag "--allfrags"
> > i.e. all fragments needs to be sorted out and sent to same dest for defrag.
> > 
> > ex.
> > iptables -t early -A PREROUTING -i eth0 --allfrags -j NOTRACK
> 
> New tables add too much overhead. We have discussed this before with
> Patrick.
> 
> Since this still remains specific to your needs, I think you can
> remove nf_conntrack module in your setup.
> 
> I don't come with one sane setup that may want selectively defragment
> some traffic yes and other not.
> 
> Am I missing anything else?

I agree. If you don't want defragmentation at all, then make sure you 
don't load the nf_conntrack module directly/indirectly. Conntrack doesn't 
work without defragmentation anyway.

The only thing what such a really-early table could buy at the moment is 
to specify which flows not to defragment at layer 3 level.

If we had dynamic hooks registration and hook priorities at table level, 
that'd come handy now.

Best regards,
Jozsef
-
E-mail  : kadlec@...ckhole.kfki.hu, kadlecsik.jozsef@...ner.mta.hu
PGP key : http://www.kfki.hu/~kadlec/pgp_public_key.txt
Address : Wigner Research Centre for Physics, Hungarian Academy of Sciences
          H-1525 Budapest 114, POB. 49, Hungary
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