Henning,

Thanks for the explanation.  This does clear it up for me.

Do you happen to know if there is a list of pseudo vars that fall under the non special case?   (a list for those psedo vars where msg_apply_changes needs to be called for the update to be reflected while in routing file processing that is.)

Thanks,

Karthik

On Wed, Jun 13, 2018 at 1:39 PM, Henning Westerholt <hw@kamailio.org> wrote:

Am Mittwoch, 13. Juni 2018, 20:28:13 CEST schrieb Alex Balashov:
> On Wed, Jun 13, 2018 at 01:26:07PM -0500, Karthik Srinivasan wrote:
> > Could you explain why we need to call this function when manipulating $fU
> > ?
>
> Some PV manipulations work that way, others don't. :-) "Because
> Kamailio".

Don't want to dig into to much technical details here..

But to give a bit more context, the Kamailio architecture related to SIP
message processing is optimized to avoid re-parsing of the message during
configuration processing. This works with so called "lumps" which are more or
less like a programming patch file (e.g. change, delete parts). This lumps are
applied shortly before sending the message out or if you call
msg_apply_changes().

Some parts of the SIP message are accessed directly, because they are "more
important" (like the request URI) are handled specially, some like the From
user are done like a normal SIP header part as described above.

For a bit more details and to look into the details, have a look to the
dbg_sip_msg([log_level], [facility]) function in the debugger module.

Best regards,

Henning