[OpenSIPS-Users] different ip in from as initial invite

[Liviu Chircu]

On 28.01.2020 14:43, Miha via Users wrote:
> Costumer is saying that he expects from like it was send in 200ok (not 
> in inital invite, tag and CALLERID stays always the same) and we 
> should confirm with ACK that has from same as in 200 ok from them.

Hi miha,

That is complete nonsense, RFC 3261 is on your side, section § 8.2.6.2:

    The From field of the response MUST equal the From header field of
    the request.  The Call-ID header field of the response MUST equal the
    Call-ID header field of the request.  The CSeq header field of the
    response MUST equal the CSeq field of the request. The Via header
    field values in the response MUST equal the Via header field values
    in the request and MUST maintain the same ordering.

However, if you are really keen to help them out... maybe you could 
store their
200 OK From header in a $dlg_val, then fix the ACK's From header to use 
this val.

But how will you handle the From header for other sequential requests?  
And if these
requests are initiated by the downstream side, you will have to change 
the To instead
of the From, as the UAC must swap them!  We are basically opening 
Pandora's Box by
doing down this route.  It's not impossible to get right, but it will 
take some work.

Regards,

-- 
Liviu Chircu
www.twitter.com/liviuchircu | www.opensips-solutions.com

OpenSIPS Summit, Amsterdam, May 2020
   www.opensips.org/events
OpenSIPS Bootcamp, Miami, March 2020
   www.opensips.org/training

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