[sr-dev] recursive calls to failure_route strange behavior

[Miklos Tirpak]

Hi Daniel,

On 11/20/2009 04:38 PM, 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?

yes.

> 
> 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. If I do no drop replies, then it is hard to implement the proper 
> logic for different kinds of redirects:
> - no answer
> - busy

Yes, the above case is quite complicated, by default I think the 408 
will be sent back because it is the lowest response code.

The priority list is: 6xx > 3xx > 4xx > 5xx.
The lowest response wins within the class but 401, 407, 415, 420, 484 
are preferred over other 4xx responses.

If this is an issue then we can implement more sophisticated drop 
commands that drop only selected branches, for example a single branch 
that is being processed in failure route.

Miklos

> 
> 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.
>