[sr-dev] force_rtp_proxy() usage with IP that is not natively homed

[vallimamod abdullah]

Hi Alex,

I had the same exact issue some time ago with a nated server and I
solved it with a hacked mediaproxy. I have made it send the public sdp
IP for outgoing sessions (for the clients to send rtp to the public
IP) and local IP for incoming session so that the gateway can send the
rtp to the lan IP.

It was a quick and dirty hack that worked well for my needs. If you
are interested, I can send it to you.

Cheers,
- vma
.


On Mon, Nov 2, 2009 at 7:38 AM, Alex Balashov <abalashov at evaristesys.com> wrote:
> Sorry for cross-posting from k-users; was hoping maybe someone here has some
> insights, as rtpproxy is a sparsely documented topic.
>
> -------- Original Message --------
> Subject: force_rtp_proxy() usage with IP that is not natively homed
> Date: Mon, 02 Nov 2009 01:23:40 -0500
> From: Alex Balashov <abalashov at evaristesys.com>
> To: kamailio <users at lists.kamailio.org>
>
> Greetings,
>
> Please excuse the apparent silliness of this request, but I am curious
>  if there is a combination of flags passed to force_rtp_proxy()
> and/or rtpproxy invocation options that can allow force_rtp_proxy() to
> substitute an SDP endpoint IP that is not a physical device/interface
> on the host on which rtpproxy is running?
>
> Let me explain further:
>
> 1. I have a host with a single network interface that has private IP
> 192.168.1.254.
>
> 2. I am receiving an inbound call from outside the network, coming in
> on a public IP address 4.4.4.4 that is a 1-to-1 DNAT/SNAT to
> 192.168.1.254.
>
> 3. The call is forwarded to a PBX on the same LAN as the native
> interface, e.g. 192.168.1.250.
>
> 4. I would like to set up SDP in such a way that 192.168.1.250
> sendsmedia to the 192.168.1.254 interface while the outside host
> initiating the call sends its media to 4.4.4.4.
>
>
> Under normal circumstances in which both the public and private
> interface were physically present on the machine, this would call for
> the use of "bridging" mode (rtpproxy invoked with -l
> 4.4.4.4/192.168.1.254 and use of "ie" and "ei" flags with
> force_rtp_proxy() - we have previously established that
> rtpproxy_offer/answer do not actually seem to work as advertised).
>
> But is it possible to "bridge" to an IP that is not routed to the box?
>
> I expected that force_rtp_proxy()'s second parameter - ip_address -
> would do this.  However, this does not appear to let me override the
> SDP endpoint with any IP address I want;  it seems that I am still
> limited to choosing from those IPs physically available on the
> rtpproxy host.  I would guess that this is because ip_address is
> passed as a parameter through rtpproxy's control API socket and is
> validated by rtpproxy itself, and if it is not a local existing
> address, is overridden with one that is.
>
> Is there a clever combination of flags that can be used to accomplish
> this, or is it a lost cause?
>
> Thanks!
>
> --
> Alex Balashov - Principal
> Evariste Systems
> Web     : http://www.evaristesys.com/
> Tel     : (+1) (678) 954-0670
> Direct  : (+1) (678) 954-0671
>
>
> --
> Alex Balashov - Principal
> Evariste Systems
> Web     : http://www.evaristesys.com/
> Tel     : (+1) (678) 954-0670
> Direct  : (+1) (678) 954-0671
>
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