[OpenSIPS-Users] reply_to_via and topmost Via addressing

Bogdan-Andrei Iancu bogdan at opensips.org
Tue Mar 5 10:38:34 EST 2019

Hi John,

Thanks for pointing out the outdated param, I just removed it from the 
online docs.

In terms of reply routing, everything is encapsulated in the TM module - 
the replies inside a transaction are all the time routed back 
automatically to the source IP and port of the request - this applies 
for both types of replies sent out by opensips - internally generated or 

Now, about the "received" / "port" - indeed, these params are added to 
the top received VIA hdr if rport is needed (forced or received as empty 
param) or if there are differences between the adv VIA IP and the src IP 
form network level.
The only control you have is to force it, indirectly by doing force_rport().


Bogdan-Andrei Iancu

OpenSIPS Founder and Developer
OpenSIPS Summit 2019

On 03/05/2019 12:47 PM, John Quick wrote:
> Update to my earlier post: I found a change log for v1.5 or 1.6 that says
> "reply_to_via" option has been withdrawn.
> So the documentation needs to be corrected because it is still shown right
> through to v2.4
> I still have some questions about how much control we have over the routing
> of replies:
> Is it possible to change the destination where replies are sent or will they
> always be routed to the source address of the corresponding SIP request,
> even when the topmost Via has a different address in its URI?
> The answer to that question may be in 2 parts because some responses are
> generated internally - e.g. "100 Giving a try", some 200 OK's - while others
> are received from a downstream server and can be caught in onreply_route.
> [It is also possible to explicitly generate responses using t_reply() or
> sl_send_reply(), but these offer no routing options].
> Supplementary to this, is the addition of ";received=w.x.y.z" to the topmost
> Via something that is always done when the source of a request doesn't match
> the Via's URI? Does this happen inside t_relay()? Do we have any control of
> this from within the script?
> Thanks.
> John Quick
> Smartvox Limited
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