netdev - Re: [PATCH v3] netfilter: nf_conntrack_sip: Handle Cisco 7941/7945 IP phones

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Date:	Mon, 22 Nov 2010 08:52:14 +0100
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Kevin Cernekee <cernekee@...il.com>
Cc:	Patrick McHardy <kaber@...sh.net>,
	"David S. Miller" <davem@...emloft.net>,
	Alexey Kuznetsov <kuznet@....inr.ac.ru>,
	"Pekka Savola (ipv6)" <pekkas@...core.fi>,
	James Morris <jmorris@...ei.org>,
	Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
	netfilter-devel@...r.kernel.org, netfilter@...r.kernel.org,
	coreteam@...filter.org, linux-kernel@...r.kernel.org,
	netdev@...r.kernel.org
Subject: Re: [PATCH v3] netfilter: nf_conntrack_sip: Handle Cisco 7941/7945
 IP phones

Le dimanche 21 novembre 2010 à 18:40 -0800, Kevin Cernekee a écrit :
> [v3:
>   Only activate the new forced_dport logic if the IP matches, but the
>   port does not. ]
> 
> Most SIP devices use a source port of 5060/udp on SIP requests, so the
> response automatically comes back to port 5060:
> 
> phone_ip:5060 -> proxy_ip:5060   REGISTER
> proxy_ip:5060 -> phone_ip:5060   100 Trying
> 
> The newer Cisco IP phones, however, use a randomly chosen high source
> port for the SIP request but expect the response on port 5060:
> 
> phone_ip:49173 -> proxy_ip:5060  REGISTER
> proxy_ip:5060 -> phone_ip:5060   100 Trying
> 
> Standard Linux NAT, with or without nf_nat_sip, will send the reply back
> to port 49173, not 5060:
> 
> phone_ip:49173 -> proxy_ip:5060  REGISTER
> proxy_ip:5060 -> phone_ip:49173  100 Trying
> 
> But the phone is not listening on 49173, so it will never see the reply.
> 
> This patch modifies nf_*_sip to work around this quirk by extracting
> the SIP response port from the Via: header, iff the source IP in the
> packet header matches the source IP in the SIP request.
> 
> Signed-off-by: Kevin Cernekee <cernekee@...il.com>
> ---

Thanks for doing this work Keven !

Acked-by: Eric Dumazet <eric.dumazet@...il.com>



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