From: Florian Westphal <fw@strlen.de>
To: Ulrich Weber <ulrich.weber@gmail.com>
Cc: netfilter-devel@vger.kernel.org, Patrick McHardy <kaber@trash.net>
Subject: Re: [RFC] SIP conntrack handler and TCP fragmentation
Date: Wed, 12 Oct 2016 09:52:12 +0200 [thread overview]
Message-ID: <20161012075212.GA26177@breakpoint.cc> (raw)
In-Reply-To: <c92b64f3-9f69-eb7c-402c-3e489f73a527@gmail.com>
Ulrich Weber <ulrich.weber@gmail.com> wrote:
> we had a customer with a Cisco Phone using SIP over TCP
> which subscribed to 15 Phone numbers.
>
> Since 15 subscribe calls dont fit in one packet, these
> requests were fragmented in multiple TCP packets.
>
> One of these fragments gets rejected then by nf_conntrack_sip with:
> nf_ct_sip: dropping packet: cannot parse cseq
>
> The Cisco phone will send retransmits, which got dropped too,
> times out after some time, reconnects and same games
> starts again...
>
> I know the proper solution would be TCP defragmentation
> in the nf_conntrack_sip kernel module. However I'm not
> sure if this is worth the effort.
I think an even better solution would be a SIP proxy that can
inject expectations to keep datapath in kernel and only deals with
the signalling traffic.
> What about just accepting unparsable TCP SIP packets?
I wonder why this patch did not fix your problem:
3a7b21eaf4fb3c971bdb47a98f570550ddfe4471
Author: Patrick McHardy <kaber@trash.net>
netfilter: nf_ct_sip: don't drop packets with offsets pointing outside the packet
It specifically deals with this problem (l7 size larger than packet
size).
next prev parent reply other threads:[~2016-10-12 8:17 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-10-12 7:38 [RFC] SIP conntrack handler and TCP fragmentation Ulrich Weber
2016-10-12 7:52 ` Florian Westphal [this message]
2016-10-12 8:52 ` Ulrich Weber
2016-10-12 11:41 ` Florian Westphal
2016-10-12 12:27 ` Ulrich Weber
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