[SR-Users] Can't work around double SDP rewrite issue with rtpengine and config script SDP manipulation

[George Diamantopoulos]

Daniel, that worked instantly, thank you!

Care to elaborate on how msg_apply_changes() interferes with loose_route? I
also remember msg_apply_changes() complaining if called after
record_route(), is it related?

On Mon, 1 Jun 2020 at 21:24, Daniel-Constantin Mierla <miconda at gmail.com>
wrote:

> Hello,
>
> use msg_apply_changes just after replace_body_str(), eventually before
> loose routing processing for requests within dialog.
>
> Cheers,
> Daniel
> On 01.06.20 13:34, George Diamantopoulos wrote:
>
> Hello all,
>
> I'm facing one of those cases where I need to edit the body of a SIP
> message, which is then to be fed to rtpengine for processing. Although I've
> taken every precaution I've read about on this list and elsewhere, I can't
> prevent the edited line from appearing twice in the outgoing message.
>
> The configuration file used is huge, so I'm going to try to provide a
> high-level overview here. But first, the things (I think) I know to be
> requirements, and which I have striven to meet:
>
>    - If SDP is to be edited, then all such processing is to be carried
>    out in such a way in the script, so that msg_apply_changes() is run as many
>    times as needed before rtpengine offer/answer/manage is called.
>    - rtpengine offer/answer/manage is to be called only once per script
>    iteration
>    - msg_apply_changes can only be called in a request route, or in the
>    core reply_route (i.e. *not* in tm-managed on_reply_route[XXX] blocks)
>
> In my case, additionally the following are true:
>
>    - SDP processing (other than the one performed by rtpengine) takes
>    place in one common route for all cases where it needs to happen. These are
>    two at the moment in my scenario:
>    - Early in the WITHINDLG route (of the example config file)
>       - After the sanity checks in the reply_route (of the example config
>       file)
>    - msg_apply changes() is called once, for each script iteration:
>       - right before rtpengine_manage() is called, provided that
>       t_is_request_route() returns true (so that I don't accidentally call it
>       from a branch route or anything)
>          - rtpengine_manage() is called in its own route, which is very
>          similar to the example config file's "NATMANAGE" route. Since NATMANAGE is
>          called in all branch and on_reply_routes, I employ t_is_request_route()
>          here to make sure it won't execute in those cases.
>       - at the end of the "core" reply_route
>
> Now regarding the actual config-file-controlled SDP manipulation, it only
> consists of a single call to replace_body_str(). The purpose is to edit a
> line in the message body from something like:
>
>    - a=fmtp:101 0-16
>
> to something along the lines of:
>
>    - a=fmtp:101 0-15
>
> For replies, this works as expected.
>
> For in-dialog requests, however, I end up with both the original and the
> edited lines:
> a=fmtp:101 0-16 (the original line)
> ... other SDP stuff ...
> a=fmtp:101 0-15 (the edited line)
>
> If anyone could point out any misconceptions I have about
> msg_apply_changes, SDP rewriting from the script and rtp_engine_X()
> interoperability, I would be more than grateful.
>
> Thank you in advance and I apologize for the long read.
>
> Best regards,
> George Diamantopoulos
>
> _______________________________________________
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>
> --
> Daniel-Constantin Mierla -- www.asipto.comwww.twitter.com/miconda -- www.linkedin.com/in/miconda
> Funding: https://www.paypal.me/dcmierla
>
>
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