3 Mar
2022
3 Mar
'22
3:02 p.m.
On 03.03.22 12:07, Rhys Hanrahan wrote:
Any advice appreciated, as this is my first time dealing with SRTP
(and rtpengine). Feeling very stuck. Thanks!
Yeah, me too. ;-)
Basically you need to call "rtpengine_manage" with the correct
parameter, i.e. either RTP/AVP or RTP/SAVP, based on whether audio to
the destination of the message is to be encrypted or not. This applies
to basically any message with "application/sdp" content, i.e. both the
INVITE *and* the 183 or 200 reply.
Thus if you relay from encrypted to plaintext, the INVITE's handler
needs to call rtpengine_manage("… RTP/AVP") and the response handler
needs to call rtpengine_manage("… RTP/SAVP").
In my code I discover these settings (for both call source and
destination) during the INVITE, then I save them in a couple of XAVU
variables. All the other handlers just select source / destination based
on whether the message's source IP address is the same as the INVITE's.
IMHO it's way easier to program the whole thing in Python instead of
Kamailio's language. This in turn would be much simpler if Kamailio used
threads instead of separate processes and shared memory, but apparently
you can't have everything. :-P
--
-- Matthias Urlichs