[SR-Users] Sending in-dialog requests from custom module's C code

[Ivan Ribakov]

Anyone with module dev experience here who had to do something similar or used tm_load.h interface for other purposes?

> On 7 May 2019, at 16:39, Ivan Ribakov <i.ribakov at zaleos.net> wrote:
> 
> I’m working on a custom Kamailio module where I need to send new-dialog and in-dialog requests on timer (hence I’m being forced to generate new messages from C code).
> 
> So far I’ve been using modules/tm/tm_load.h defined interface to generate messages and handle callbacks. New dialog messages are sent and processed normally. To do that I’m:
> 
> 1. Calling set_uac_request() to define request parameters
> 2. Calling tmb.t_request_outside() to send it outside any existing dialog
> 
> 
> I was able to send in-dialog requests (or so I thought) in a similar fashion, but I soon realised that responses to those requests were dropped because they couldn’t be matched against any known existing transaction. I’m attaching log messages that I believe support this theory and I’ve also observed UDP retransmissions.
> 
> tm [t_lookup.c:897]: t_reply_matching(): t_reply_matching: hash 50576 label 0 branch 0
> tm [t_lookup.c:990]: t_reply_matching(): no matching transaction exists
> tm [t_lookup.c:993]: t_reply_matching(): failure to match a transaction
> tm [t_lookup.c:1088]: t_check_msg(): msg (0x5abcb50) id=1 global id=1 T end=(nil)
> tm [t_reply.c:2195]: reply_received(): transaction not found - (branch -1)
> 
> 
> The way I’m currently generating in-dialog requests is very similar to what tmb.t_request_outside() does, the main difference being that I do the dialog setup manually, based on the call-ID, cseq and from/to tags (I’m tracking transaction identifiers separately) and then pass resulting uac_req_t to tmb.t_request_within() - https://gist.github.com/IvanRibakov/3302cb286b1f4b786d109b406f2435a2 <https://gist.github.com/IvanRibakov/3302cb286b1f4b786d109b406f2435a2>
> 
> 
> Now, the question part - does anyone know what I’m doing wrong/missing? As I mentioned, when looking at the generated message bodies, they look ok to me (left - initial request that started the dialog, right - first in-dialog request), so I’m guessing I’m missing some Kamailio internal steps needed to register new transaction.
> <kamailio_indialog_req.png>
> 
> SIP flow (up to the point when first UDP retransmission happens)
> <PastedGraphic-1.png>
> 
> I apologise in advance for the bulky question and will be extremely thankful for any guidance.
> 
> Regards,
> Ivan

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