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

[Iñaki Baz Castillo]

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.


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?





-- 
Iñaki Baz Castillo <ibc at aliax.net>