[Kamailio-Users] force_rtp_proxy() usage with IP that is not natively homed

[Daniel-Constantin Mierla]

Hello,

On 02.11.2009 8:09 Uhr, Klaus Darilion wrote:
> Hi Alex!
>
> This sounds like you need fix_nated_sdp("2","4.4.4.4") after 
> force_rtp_proxy(). With K1.5 this is not possible (probably a crash 
> will happen as both functions mangle the SDP).
>
> I 3.0 you could use msg_apply_changes() between the two function calls:
> http://sip-router.org/docbook/sip-router/branch/master/modules_k/textops/textops.html#id2996272 
>
in 1.5 can be looped back or use another instance on a different ip or 
port just for updating the sdp.

Cheers,
Daniel


>
>
> regards
> klaus
>
> Alex Balashov schrieb:
>> 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!
>>
>
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-- 
Daniel-Constantin Mierla
* http://www.asipto.com/