[Kamailio-Users] off-topic :: empty user part of Contact header

[kokoska rokoska]

Iñaki Baz Castillo napsal(a):
> El Domingo, 11 de Octubre de 2009, kokoska rokoska escribió:
>> Hello,
>>
>> I have a little bit off-topic question, but - may be - someone could
>> give me an advice :-)
>>
>> One of our users, when replying to INVITE, sends in 200 OK Contact
>> header without user part:
>>
>> SIP/2.0 200 OK
>> CSeq: 102 INVITE
>> Contact: <sip:1.2.3.4:1234>
>> ...
>>
>> instead of:
>>
>> SIP/2.0 200 OK
>> CSeq: 102 INVITE
>> Contact: <sip:user at 1.2.3.4:1234>
>> ...
>>
>> and it fools our SIP<->ISUP GW and it generates completely strange R-URI
>> in ACK :-(
>>
>>
>> My questions are:
>>
>> 1. Is it valid Contact (without user part)?
> 
> Yes, 100% valid.
> 
> 
>> 2. What SIP<->ISUP GW should do (mirror Contact without user part to
>> R-URI in ACK, reject/drop 200 OK etc.)? May be I can ask them to change
>> behaviour...
> 
> It's a correct behavior.
> 
> 
>> 3. What should do our proxy (drop 200 OK, using htable try to repair
>> R-URI in ACK or Contact in 200 OK etc.)?
> 
> Nothing.
> 
> 
>> Any suggestion is very appreciated :-)
> 
> Your UAC is broken as it should accept a Contact without username.
> 

Thank you very much, Inaki, for your valuable help!

I really appericiate your explanation - my thoughts were very similar,
but I have to be sure what is correct :-)

> 
> PS: Note that "Contact" must be understood by the UA which generated it. This 
> is, the gateway created that Contact without username so when it receives an 
> in-dialog request (i.e. ACK for 200, BYE, REFER, re-INVITE...) it must 
> recognize it, and for sure it does it (as it has stored the information about 
> dialog (from useri, to uri, request uri, remote contact, local contact, 
> From/To tags, Call-ID...).
> 
> 
> What kind of malformed Contact header is your UA generating upon receipt of a 
> Contact with no username?
> 

The worst thing is it is not "my" UA - I'm just using it like SIP<->ISUP
GW. So I have to ask manufacturer to "repair" it :-)

Back to your question: when this UA receives Contact without user-part
it genereates ACK (using some kind of internal magic :-) with R-URI like:

called_number at ip.of.my.proxy

so ACK loops infinitely (well, just 69 times :-) through the proxy...


Thanks once more, Inaki, for your explanation!


Best regards,

kokoska.rokoska