[Kamailio-Users] append_hf

[Iñaki Baz Castillo]

El Lunes, 24 de Noviembre de 2008, Daniel-Constantin Mierla escribió:
> Hello,
>
> On 11/24/08 04:01, Matteo D'Amato wrote:
> > Hello,
> > 	 I'm trying to append trunk group information to my Contact header
> > so I'm, using append_hf as follows
> >
> >
> >     append_hf("tgrp=30001 \r\n", "Contact");
>
> this appends a new header. For what you need try subst() or
> search_append() functions.
>
> Alternative:
>
> remove_hf("Contact");
>
> append_hf("Contact: $hdr(contact);tgrp=30001\r\n", "Contact");

Anyway I consider operations like this on SIP URI very dangerous due to 
complex SIP URI syntax:


a) Contact: sip:user at domain.org;param=AAA
Here "param=AAA" is a *header* param since SIP URI uses addr_spec form (there 
is no < > enclosing the SIP URI).

b) Contact: <sip:user at domain.org>;param=AAA
Here "param=AAA" is a *header* param since SIP URI uses name_addr form (there 
are < >) and the param is out of the < >.

c) Contact: <sip:user at domain.org;param=AAA>
Here "param=AAA" is a *SIP URI* param since SIP URI uses name_addr form (there 
are < >) and the param is INTO the < >.

If Matteo want to adds a header param then the above solution will work, but 
if he wants to add a SIP URI param then it won't work.
Note that when creating an in-dialog request, the Request URI must be the 
Contact previously received in the initial INVITE (or 200 OK), and the RURI 
must include Contact *SIP URI* params (case c), but *NOT* the Contact header 
params (cases a and b).


There are URI Transformations to get URI params:
  
http://kamailio.org/dokuwiki/doku.php/transformations:devel#uri_transformations
but they don't allow adding/modifying/deleting a param, just reading it.


PD: I consider SIP URI BNF grammar a pain.


-- 
Iñaki Baz Castillo