Importance of creating dialog in Kamailio right

 I know, the things described here might be obvious and considered "for beginners", but everyone can make stupid errors. Even the best of us :)
So, what I'm using Kamailio dialog module for?

• Keepalives with ka_timer parameter, mainly cause of the nature of mobile clients that are unstable due to the mobile network nature
• Presence PUBLISH'es via pua/pua_dialoginfo modules to separate presence server

 

With the second one actually, I've issued some "problems" due to configuration.

Most examples (at least what I've seen) on Kamailio configs, that are operating with the dialogs, have more-or-less this structure:

request_route {
   route(REQINIT);

   if (is_method("INVITE")) {
       dlg_manage();
   }

   route(WITHINDLG);

   ...

   route(AUTH);

   ...

}

There is a problem with this code. And it is, that this code creates dialogs for EVERY INVITE, even if not authed. 

So, the usual flow INVITE - 401 - INVITE (w/auth) - 200 will create 2 dialogs in this case. The first one will be not terminated correctly with connection with pua module. It will generate PUBLISH with the Trying state,  but on 401 - ACK, there would be no corresponding PUBLISH for the terminated state. And as usual, Expire here is 3600, and you will have a lot of "ringing" devices on your presence server.

The answer would be: create dialogs only for authed (and valid) INVITEs. This will also save some CPU not to create dialogs for spammers.

request_route {
   route(REQINIT);

   route(WITHINDLG);

   ...

   route(AUTH);

   if (is_method("INVITE")) {
       dlg_manage();
   }

   ...

}