[sr-dev] recursive calls to failure_route strange behavior

[Daniel-Constantin Mierla]

On 20.11.2009 17:32 Uhr, Daniel-Constantin Mierla wrote:
> Hello,
>
> On 20.11.2009 17:04 Uhr, Miklos Tirpak wrote:
>> 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.
> also 487 (request canceled) has the highest priority.
>
>
>>
>> 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.
>
> It just looks a bit unpredictable right now, mainly with what happens 
> in failure route because the reply code presented there is not what is 
> expected. So I would add a parameter:
>
> t_drop_replies("all");
> t_drop_replies("last");
>
> It is not hard to implement at all. In SR is a flag to mark the start 
> of last set of branches -- so getting the first branch in the last 
> step would be:
>
>    for(first_branch=t->nr_of_outgoings-1; first_branch>=0; 
> first_branch--)
>        if(t->uac[first_branch].flags&TM_UAC_FLAG_FB)
>            break;
>
> But I would do it opposite, to have script simpler (and be K 
> compatible and have uac_redirect and other k modules work as expected 
> :-) ), instead of drop function, have drop by default the replies from 
> last set of branches, and then t_keep_replies() so one ca decide to 
> keep the replies. Probably can be switched one way or another (K or S)

> but config compatibility mode.

errata: by config compatibility mode (e.g., #!KAMAILIO and #!SER)


>
>
> Cheers,
> Daniel
>
>>
>> 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.
>>>
>

-- 
Daniel-Constantin Mierla
* http://www.asipto.com/