[sr-dev] recursive calls to failure_route strange behavior

[Miklos Tirpak]

Hi,

On 11/20/2009 04:57 PM, Michal Matyska wrote:
> Daniel-Constantin Mierla píše v Pá 20. 11. 2009 v 16:53 +0100:
>> On 20.11.2009 16:38 Uhr, Daniel-Constantin Mierla wrote:
>>>
>>> On 20.11.2009 9:53 Uhr, Miklos Tirpak wrote:
>>>> On 11/20/2009 12:58 AM, Andres Moya wrote:
>>>>> Dear all!
>>>>>
>>>>> Please help. I have problem dealing with recursive call in failure 
>>>>> route.
>>>>>
>>>>> this route happen first time for authentication to external SIP 
>>>>> provider (react on code 401), then it have response 480 i want to 
>>>>> direct traffic to another operator via cr_route.
>>>>>
>>>>> First i relay INVITE and getting 401, then sending authentication, 
>>>>> but provider gives 480. I can see it in a dump of SIP session. But 
>>>>> my failure_route still thinking that reply code is 401 on second 
>>>>> reply. Maybe because i dont understand well how branches concept 
>>>>> work here? Or using kamailio 3.0? ;) Looks like it give me status 
>>>>> code of first reply and ignoring actual code in reply. :( I don't 
>>>>> know if it something with development version or my own 
>>>>> misunderstanding. sorry
>>>> This is correct, the proxy must choose one of the two responses to 
>>>> forward and 401 has higher precedence than 480 (RFC3261, 16.7: 
>>>> "Choosing the best response"). The failure route always works on the 
>>>> selected response as opposed to the last response received.
>>> I think this is wrong imo, if I got it right from your email, because 
>>> the failure route should work on a selected reply from the last set of 
>>> branches in serial forking.
>>>
>>> Do you say that if I get 301 with couple of contacts, then in failure 
>>> route I create new branches, relay, all failed because of timeout 
>>> and/or busy, I get back in failure route with the 301?
>>>
>>> I cannot drop all replies because maybe the reply I want to be sent 
>>> back to caller is from a previous branch. Think at:
>>>
>>> A calls B
>>> B phone gives busy
>>> B has redirect to C in such case
>>> C phone gives timeout
>>> C has now redirect to voice mail
>>> Voice mail returns server failure
>>>
>>> If I need to drop the replies then I will send the 500 reply which is 
>>> wrong.
>> ... actually, while it might be questionable whether to select the reply 
>> to be sent back to caller from last serial forking set of branches or 
>> from entire set of branches, triggering failure route should be with a 
>> reply from last set of branches, otherwise you cannot take the right 
>> decision for new branches.
> 
> If I understand correctly, then whenever you start above mentioned "new
> set of branches" just call t_drop_replies() and you are done.

yes, you can solve it this way.

Back to Daniel's example, if I was the caller then I would like to 
receive the 486 back so that I know that the callee is busy and I should 
retry the call later. This means that the 408 should be dropped, but 
only if there was already a branch replied with 486. Or the 408 should 
be given some preference from failure route. Neither of them is 
implemented as far as I know.
On the other hand, the script can get really complicated because of 
these checks and drops.

Miklos

> 
> Michal
> 
>> Cheers,
>> Daniel
>>
>>
>>> If I do no drop replies, then it is hard to implement the proper logic 
>>> for different kinds of redirects:
>>> - no answer
>>> - busy
>>>
>>> Cheers,
>>> Daniel
>>>
>>>> Try to add t_drop_replies() to the failure route block when the 401 
>>>> is processed. This function drops all the existing replies, 401 in 
>>>> your case, hence 401 will not be selected again when 480 is received.