netdev - Re: H.245v10+ support in nf_conntrack

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Message-ID: <20090901123240.GE18651@sirena.org.uk>
Date:	Tue, 1 Sep 2009 13:32:40 +0100
From:	Mark Brown <broonie@...nsource.wolfsonmicro.com>
To:	Andreas Jaggi <aj@...n.ch>
Cc:	Patrick McHardy <kaber@...sh.net>,
	Jing Min Zhao <zhaojingmin@...rs.sourceforge.net>,
	netdev@...r.kernel.org
Subject: Re: H.245v10+ support in nf_conntrack_h323?

On Tue, Sep 01, 2009 at 02:10:33PM +0200, Andreas Jaggi wrote:

> For me it looks like nf_conntrack_h323 is not only doing connection
> tracking, but also doing protocol enforcement (by dropping packets which
> do not correspond exactly to H.245v7).
> Perhaps there should be a config option to disable the protocol
> enforcement?

It's not going to be a deliberate attempt at enforcement that's the
issue here - doing any substantial enforcement would require a full
decode of the PER messages, involving having a full copy of the (rather
large) ASN.1 in the kernel.  It's much more likely that a shortcut taken
in decoding the message is getting confused by something that the
endpoint is choosing to send, a brief glance at the ASN.1 code certainly
suggests that to me.  Chances are it's not even a new v10 feature that's
causing the issue.
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