[OpenSIPS-Users] [OpenSIPS-Devel] [RFC] OpenSIPS 2.0 - changes on the SIP messages

[Emmanuel BUU]

Hello,

First of all, I want to stress that the whole concept of message 
scripting is a fabulous asset. It enables us
to adapt to so many situations without recompling C code. I have the 
feeling that the whole concept has emerged from a rather practical
and performance oriented approach (which is good). We should maybe look 
at what we idealy would like:

We want to be able to modify the message and see the modification "in 
real time". For some values,
we also want either to undo some changes (mainly the module developpers) 
or access the original values
the scripts writers.

So IMHO there should be some place where the original message stand, 
preparsed by the core. The modifications should be applied on a 
preparsed copy
and the module developper should be able to access both but modify only 
the one that is intented to handle the modification. At the end of the 
processing
the modified message should be translated from a parsed form to a text 
buffer.

This process might be slower than the original lump model that is highly 
optimized but it may lead to a more sold ground.

I agree with the remark about branch isolation.

Emmauel

Bogdan-Andrei Iancu a écrit :
> Hi,
>
> sorry for crossposting, but I thing this topic is interesting both for 
> users (as experience) and for developers (as solution).
>
> So, right now the code for 2.0 got to a stage were we need to "apply" 
> changes on the received messages (like adding VIA headers, changing 
> headers, etc). And before starting the work on this area, I would like 
> to get some opinions on the available options:
>
>     1) keep the current mechanism for changing the SIP messages by using 
> lumps that are applied only when the message is sent out :
>        Advantages: code is there and works; the mechanism is very fast ; 
> no need to re-parse the message after the parsing
>        Disadvantages : from script or code, you are not able to see the 
> previous changes you did on the message, like:
>                  if you remove a hdr, it will be marked to be removed, 
> but you will still see it there after the removed
>                  if you add a new hdr, you will not be able to see it 
> (it will be actually added only when the message will be sent out)
>                  if you replace the contact hdr (like after 
> fix_nated_contact() ) will not see the new contact, but the old one
>                  trying to apply 2 changes in the same area (like 
> changing twice the contact) will result in bogus result.
>
>     2) find a new approach that will allow to push in realtime the 
> changes on messages
>        Advantages: the change will take affect instantly, so all the 
> disadvantages from 1) (as user experience in operating opensips) will 
> disappear .
>        Disadvantages : the code will probably be slower (the changes 
> part), but will speed up other parts of the code (where you need to 
> manually identify the prev changes);
>              changed parts of the SIP message will require re-parsing 
> (so the code will have to check the state of a header (if parsed or not) 
> before each usage)
>              you will not be able to undo changes on the SIP messages in 
> an easy way (for example during the parallel and serial forking on 
> per-branch changes)
>
> So this is the dilemma: if the current mechanism (with applying changes 
> at the end) such a bad user experience (scripting) in order to try for 
> 2.0 a different approach ?
>
> I would like to hear some opinions from both people writing scripts and 
> people writing code.
>
> Thanks and regards,
> Bogdan
>
>