[Kamailio-Users] DNS lookup for requests within dialog

[Daniel-Constantin Mierla]

Hello,

On 25.09.2009 17:16 Uhr, Olle E. Johansson wrote:
>
> [...]
>>>
>>>
>>> In my scenario kamailio is not a registrar, it's just a proxy
>>> forwarding requests from asterisk to the provider.
>>>
>> I see.
>>
>> As Juha said, REGISTER does not create a real dialog, since the 
>> contact in 200OK is the address of publisher not of destination. So a 
>> proxy does not have within-dialog like routing information.
>>
>> So here is a hack you can try:
>> - add record route on your proxy
>> - the provider should add its own record route to REGISTER reply -- 
>> if it is kamailio, that is simple via append_to_reply() from textops, 
>> just before save() call.
>> - hope/pray that asterisk is using these dialog info for building 
>> re-registration messages
>> - on your kamailio route based on Route header
>>
> RFC 3261, section 10.3:
> Registrars MUST ignore the Record-Route header field if it is included 
> in a REGISTER request. Registrars
> MUST NOT include a Record-Route header field in any response to a 
> REGISTER request.
> A registrar might receive a request that traversed a proxy which 
> treats REGISTER as an unknown request and
> which added a Record-Route header field value.
>
> Oops.
in the words of sipwarriors on this list, IETF specs s...ks most of the 
time and some implementations even more, so from the other side of the road:

IMWY RFH 3261, section '10.3' says:

Hazard plays an important role in getting SIP rolling, if you can tweak 
SIP messages and pray enough, things may work as you need even they 
shouldn't happen that way at all.

Glossary:
IMWI - It Must Work Yesterday - the international alliance and 
standardization group of management and sales people
RFH - request for hack

:-) Daniel

-- 
Daniel-Constantin Mierla
* Kamailio SIP Masterclass, Nov 9-13, 2009, Berlin
* http://www.asipto.com/index.php/sip-router-masterclass/