[SR-Users] can't assign values to $fU

[Daniel-Constantin Mierla]

Hello,

you have to put this from the perspective of: changes to the SIP message
(headers and body) are not immediately reflected. So even if you do a
replace or subst operation, changes are not visible. If you do
remove_hf() or append_hf(), it happens the same.

The FAQ has an entry for it:

  -
https://www.kamailio.org/wiki/tutorials/faq/main#why_changes_made_to_headers_or

$fu/U/d used to be read only, we made them r/w for convenience, as a
variable based operation instead of uac_replace_from().

The r-uri variables ($ru, $rU, $rd, ...) are not pointing to the SIP
message buffer, there is a special field (and buffer) inside the
internal structure of Kamailio, that's why changes to it are visible.
The corresponding variables pointing to the SIP message buffer are $ou,
$oU, ...

Cheers,
Daniel

On 13.06.18 23:05, Karthik Srinivasan wrote:
> 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 at kamailio.org
> <mailto:hw at 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
>
>
>
>
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-- 
Daniel-Constantin Mierla -- www.asipto.com
www.twitter.com/miconda -- www.linkedin.com/in/miconda
Kamailio World Conference -- www.kamailioworld.com

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