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Re: [osip-dev] implicit subscription

From: Aymeric Moizard
Subject: Re: [osip-dev] implicit subscription
Date: Thu, 8 Jun 2017 14:34:00 +0200

2017-06-07 16:33 GMT+02:00 FEICHTER Christoph <address@hidden>:

hi aymeric,

Hi Christoph
Tks for the patch! Here are my comments:

First, I think it's important to make sure current application
won't get affected by the new behavior.

1/ EXOSIP_CALL_CLOSED should remain as it should fire
"at the same time" as before. (when receving BYE).

sidenote: even if dialog is still alive, the "call" can be
considered CLOSED. CLOSED is something related
to audio/video/media being active or not.

2/ the same is true for EXOSIP_CALL_RELEASED

sidenote: RELEASED is an event that allow to verify
that resource are RELEASED internally. If you remove
it for some use-case, it will break this idea. And currently
it would introduce leaks into all my apps ;)

3/ If I'm correct, an implicit subscription has a timeout
and I was expecting this "expires" to be the exact reason
for delaying the "dialog deletion" and the RELEASED event.

In your proposed change, there is no "delay" idea. It's just ON
and OFF.

Thus, it would introduce some leak risk: if the APP don't call
"eXosip_call_remove", the context would remain. (existing app
would suffer much from this)


According to me, the new variable "implicitSubscriptionActive" 
should be something like implicitSubscriptionExpireTime and should
contains the time subscription will expire. Once expires, the
dialog would be internally deleted and EXOSIP_CALL_RELEASED
would fire.

What do you think?

see the attached git-diffs

for a try to keep calls in terminated state

to be able to send an receive NOTIFY requests for implicit subscriptions.


I set the flag ‘implicitSubscriptionActive’

in case of REFER requests as well as NOTIFY requests.


please have a look and give me some feedback.






From: Aymeric Moizard [mailto:address@hidden]
Sent: Samstag, 06. Mai 2017 11:29
To: FEICHTER Christoph
Cc: address@hidden
Subject: RE: implicit subscription




Le 6 mai 2017 9:38 AM, "FEICHTER Christoph" <Christoph.FEICHTER@frequentis.com> a écrit :

hi aymeric,


thanks for your information and assessment.


I think the logic for keeping a dialog alive must be even more intelligent;

it should be:

-          there was a REFER transaction

-          there was a NOTIFY transaction

-          the subscription state of the last NOTIFY was NOT “terminated”


That was exactly what I meant by: "to be complete" ;)


because in case the call to the transfer target has been completed

before the BYE between transferor and transferee, the dialog can be release as it works now.


I will give this a try and see, how we could add this to eXosip.

… and send you a patch for review ;-)









From: Aymeric Moizard [mailto:address@hidden]
Sent: Freitag, 05. Mai 2017 16:08
To: FEICHTER Christoph
Cc: address@hidden
Subject: Re: implicit subscription


Hi Christoph,


Unfortunatly, there is no support for sending a NOTIFY

after a BYE has been received or sent.


I have the feeling that it would require a minor modification

to "_eXosip_release_finished_calls". 


If a REFER transaction exist, we could decide to maintain

the dialog for a period. Even a static period could be useful

and enough simple to make it possible. To be complete,

it would require to analyse NOTIFY, if any....


In pseudo-code, if REFER exists, then returns 0 (and do

not delete the dialog.)






2017-05-03 15:22 GMT+02:00 FEICHTER Christoph <Christoph.FEICHTER@frequentis.com>:

hi aymeric,


how is it intended to generate a NOTIFY request of an

implicit subscription, which is sent after the original call is already terminated ?


the scenario which I address is shown here:


the NOTIFY request that I mean is message #15.


such a NOTIFY request after the BYE,

shall it be built as out-of-dialog request ? (using eXosip_message_build_request)

or is there a mechanism in eXosip to keep the call alive,

when there is an implicit subscription active ?









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