asterisk users - Mar 2012 - How can I get SIP/SDP values to a variable?

Hello all!

I wonder if there's a way to read SDP values into a variable in Asterisk? I
have successfully used SIP_HEADER function to get all I want out of SIP part of
the message, no problem. But I would like to be able to read SDP part as well,
anyone?
Reason I want to to this is: testing the SIP_ALG condition in incoming invite
message. Majority of cases can be detected just by comparing src ip address and
"via", but some devices only rewrite SDP "c" value for
example and so on ...
I haven't found any information anywhere how to achieve reading SDP with
asterisk. I can use 1.8 and 10 versions.

Thanks in advance

Rennes Neps
Elion Ettev?tted AS
rennes.neps at elion.ee

?

On 03/13/2012 05:58 AM, Rennes Neps wrote:
> I wonder if there's a way to read SDP values into a variable in
Asterisk? I have successfully used SIP_HEADER function to get all I want out of
SIP part of the message, no problem. But I would like to be able to read SDP
part as well, anyone?
> Reason I want to to this is: testing the SIP_ALG condition in incoming
invite message. Majority of cases can be detected just by comparing src ip
address and "via", but some devices only rewrite SDP "c"
value for example and so on ...
> I haven't found any information anywhere how to achieve reading SDP
with asterisk. I can use 1.8 and 10 versions.
There is no mechanism in Asterisk to do this. The most practical 
approach would probably be to put a stateless SIP proxy in front of 
Asterisk and write whatever logic you like there, causing it to add one 
or more headers to the SIP messages that can be accessed from the 
dialplan in Asterisk.

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