[OpenSIPS-Users] serialize_branches() and timeouts

[Alexander Kogan]

Agreed, it's really ugly. But on practice it means that the caller has 
two confirmed dialogs with the same did, but opensips has only one. And 
when caller sends BYE for one of its dialogs it ruins the dialog on 
OpenSIPS.... So it seems much better to make an ugly solution...

Best regards,
Alexander Kogan,
Director of R&D
5g Future
http://5gfuture.com


On 28.06.2023 11:52, Bogdan-Andrei Iancu wrote:
> Hi Alexander.
>
> The problem here is not related to the ability or inability of 
> OpenSIPS to drop the late 200 OK - the problem is you MUST not drop 
> it, as you will break the signaling. Again, a callee party sending a 
> 200 OK expects an ACK and nothing else.
> If you drop (on OpenSIPS level) the late 200 OK, the vendor 1 will 
> remain inconsistent - it will keep retransmitting the 200 OK as it 
> expected the ACK for it.
>
> Of course, there is the ugly approach of "playing dead", dropping 
> every single late 200 OK from Vendor 1, forcing it to generate a BYE 
> (eventually) and close the call. But this is something really ugly.
>
> Regards,
>
> Bogdan-Andrei Iancu
>
> OpenSIPS Founder and Developer
>   https://www.opensips-solutions.com
>   https://www.siphub.com
>
> On 6/28/23 10:13 AM, Alexander Kogan wrote:
>> Hi,
>>
>> I got the point. Nevertheless, isn't it a good idea to have a way to 
>> discard messages of branches that have already been timed out instead 
>> of reanimating them? E.g. t_check() could return -2 in 
>> reply_received(), or drop() action could be allowed for 200...
>>
>> Best regards,
>> Alexander Kogan,
>> Director of R&D
>> 5g Future
>> http://5gfuture.com
>>
>>
>> On 28.06.2023 10:37, Bogdan-Andrei Iancu wrote:
>>> Hi Alexander,
>>>
>>> According to RFC3261, there is noting a proxy should/must do about a 
>>> received 200 OK rather than sending further to the caller (even if 
>>> the 200 OK is received on an old branch). Basically, if for whatever 
>>> reasons you end up getting 200 OK from several branches of the same 
>>> transaction, you need to forward them all to caller - why? as in 
>>> SIP, once a 200 OK was fired by a callee device, there is no 
>>> signaling /mechanism available to "cancel"/"reject"/"discard" that 
>>> it. The only way to handle "unwanted" 200 OK is to accept it, ack 
>>> it  and then send a BYE for it.
>>> Now, as a proxy does not have the necessary "logic" to decide which 
>>> 200 OK to keep and which to BYE, there is nothing to be done than 
>>> "moving" this decision to the caller - so pass all the 200 OK to 
>>> caller and let it decide which to keep or not.
>>>
>>> Regards,
>>>
>>> Bogdan-Andrei Iancu
>>>
>>> OpenSIPS Founder and Developer
>>>   https://www.opensips-solutions.com
>>>   https://www.siphub.com
>>>
>>> On 6/27/23 5:59 PM, Alexander Kogan wrote:
>>>> Hello,
>>>>
>>>> I've got such a call flow:
>>>>
>>>> Client      OpenSIPS
>>>> |--INVITE-->|
>>>> |<--100-----| Vendor1
>>>> |           |--INVITE-->|
>>>> |           |--INVITE-->|
>>>> |           |--INVITE-->|
>>>> |           |           |           Vendor2
>>>> | |--INVITE------------- >|
>>>> | |<--100-----------------|
>>>> | |<--180-----------------|
>>>> |<--180-----|                       |
>>>> |           |<--200-----------------|
>>>> |<--200-----|                       |
>>>> |           |                       |
>>>> |           |<--200-----|           |
>>>> |<--200-----|        |
>>>> |           |           |           |
>>>>
>>>> The first branch was timed out and we switched up to the next one. 
>>>> A bit later we received 200 OK from the first one. The question is 
>>>> - how to avoid passing 200 to the first leg? drop() doesn't work 
>>>> for final responses. I also can't use t_cancel_branches() because 
>>>> it works in onreply_route only which is not called in case of 
>>>> timeout....
>>>>
>>>
>