I think this is the wrong job for Kamailio. On Mon, May 21, 2018 at 10:16:20PM +0300, George Diamantopoulos wrote:
> Hello all, > > I've been hitting a wall in getting T.38 fallback to G.711 to work in a > specific case, and I was wondering if I could use kamailio to the rescue, > since all my other endeavours have failed miserably. > > In short, this is this the scenario where I need to have this manipulation > happen: > - During an established dialog between a SIP endpoint and asterisk (with > kamailio in the middle acting as proxy), the latter (asterisk) sends a > re-INVITE with a single offer for m=image with T.38 in the SDP. > - The other (eccentric) endpoint (yes, it's a Cisco) replies with 200 OK, > but will reject the T.38 offer in the SDP body instead by including a port > number of '0' > - Instead of falling back to G.711 as configured, asterisk in that case > will do nothing, and the dialog will eventually end with a BYE (don't > remember which of the two endpoints will send that, but it doesn't matter > much) > > The thing here is that asterisk *WILL* fallback to G711 with a second > re-INVITE, if the other endpoint replies to the first T.38 re-INVITE with a > negative response (488) instead of a positive one (200) declining the media > in the SDP body. I've looked at using freeswitch for a fax gateway instead, > but apparently FS doesn't support fallback at all even in the 488 reply > case, much less in the inactive media stream in 200 OK corner case I'm > investigating. > > So, I thought I'd do that in kamailio and convert those 200 OKs to 488s > with change_reply_status() from the textopsx module. Of course, the > universe hates me, and this will fail spectacularly: > > > ERROR: textopsx [textopsx.c:301]: ki_change_reply_status(): the class of > provisional or positive final replies cannot be changed > > So you can't change a reply's "class" with change_reply_status(), only the > response code within that class can be manipulated. > > I guess my question is now whether there is any way to do this sort of > transformation with kamailio, perhaps with some other function or method? > > If anyone else has had to deal with this problem and come up with a > different solution I'd be glad to hear it, as neither my head nor the > surrounding walls can take any more mutual banging at this point. Thanks! > > BR, > George. > > P.S. I hate fax > _______________________________________________ > Kamailio (SER) - Users Mailing List > [email protected] > https://lists.kamailio.org/cgi-bin/mailman/listinfo/sr-users -- Alex Balashov | Principal | Evariste Systems LLC Tel: +1-706-510-6800 / +1-800-250-5920 (toll-free) Web: http://www.evaristesys.com/, http://www.csrpswitch.com/ _______________________________________________ Kamailio (SER) - Users Mailing List [email protected] https://lists.kamailio.org/cgi-bin/mailman/listinfo/sr-users
