[SR-Users] Kamailio PCSCF route logic

Weiqi Yao wyao at omniprophis.com
Wed Mar 30 17:16:55 CEST 2022

Thank you Henning for this information:

I found in our cfg there is no set_contact_alias() but a add_contact_alias() function called for INVITE|SUBSCRIBE|UPDATE|REGISTER messages. According to:
https://kamailio.org/docs/modules/5.5.x/modules/nathelper.html#nathelper.f.add_contact_alias, it is for add alias src ip/port/transport to the end of Contact URI line
I tried comment it out and I don't see the bad ;alias be fore TO: any more. However, it caused some other issue I'm now have an incomplete Contact URI line. And caused some further issue.

So I guess my original issue was after I add ;transport=tcp at the end of the Contac URI line the add_contact_alias() function can't find the correct line to append the alias parameter, and simply added to before the To: line. Do you know where does this add_contact_alias function actually been defined? Maybe I take a look at it and see if I can find some hint there.



From: Henning Westerholt <hw at gilawa.com>
Sent: Wednesday, March 30, 2022 2:48 AM
To: Kamailio (SER) - Users Mailing List <sr-users at lists.kamailio.org>
Cc: Weiqi Yao <wyao at omniprophis.com>
Subject: RE: Kamailio PCSCF route logic

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check out the different functions in this module: https://kamailio.org/docs/modules/5.5.x/modules/nathelper.html#nathelper.set_contact_alias



Henning Westerholt - https://skalatan.de/blog/
Kamailio services - https://gilawa.com<https://gilawa.com/>

From: sr-users <sr-users-bounces at lists.kamailio.org<mailto:sr-users-bounces at lists.kamailio.org>> On Behalf Of Weiqi Yao
Sent: Tuesday, March 29, 2022 8:10 PM
To: Kamailio (SER) - Users Mailing List <sr-users at lists.kamailio.org<mailto:sr-users at lists.kamailio.org>>
Subject: [SR-Users] Kamailio PCSCF route logic

Hello community,

We made some modifications to Kamailio PCSCF sample cfg file, so when PCSCF receiving an tcp SUBSCRIBE message it add ;transport=tcp to the end of Contact URI. Below is what we added the route block right after if (is_method("INVITE|SUBSCRIBE")) logic

         if (is_method("SUBSCRIBE") && proto=='tcp') {
            $var(original_contact_header) = $ct;
            $var(new_contact_header) = $(var(original_contact_header){re.subst,/(.*:.*)(>);/\1;transport=tcp>/g});
            append_hf("Contact: $var(new_contact_header)\r\n");

We did see the ;transport=tcp been added but we also seeing a bad line ;alias=[...] is added before the To: line
[cid:image001.png at 01D84420.B175CFC0]

Does anyone know what function might cause this ;alias been added before To: line?



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