[SR-Users] Branch variables in branch_failure_route

Daniel-Constantin Mierla miconda at gmail.com
Wed Sep 14 16:36:00 CEST 2016


there is no variable that is stored in the scope of the branch. What you
can use is a hash table and compose the key from callid and branch index
variables with expires that is same as transaction lifetime (max
retransmission timeout).

And indeed you need to 'touch' the r-uri in order to signal to kamailio
that you have a new destination and want to create a new branch. It may
work to just use append_branch(), otherwise reassigning $ru to itself
should do it.


On 14/09/16 16:11, Paul Smith wrote:
> Hi,
> I am struggling to figure out variable scope in branches and
> branch_failure_routes.  Is there a way to store a variable in a branch
> route so that I can then read it from the branch failure route if that
> branch fails?  Also does writing $ru in branch_failure_route append a
> branch?
> For example I have multiple SIP devices registered to Kamailio on the
> same account credentials.  The devices are behind same NAT, so same
> public IP.  Some devices have SRTP required and some cannot use SRTP
> at all, Kamailio does not know in advance of the call whether the call
> will use SRTP or RTP.
> When I send a call to that user Kamailio correctly parallel forks to
> all the registered devices.  I use rtpengine offer to send SDP with
> RTP/SAVP in the initial invites.
> If one of the devices sends a 488 due to not being able to handle the
> RTP/SAVP I then want to run rtpengine_offer with RTP/AVP and send
> another invite to the same  device.  
> In the branch failure route I seem to have to read the current $ru and
> then write it back into $ru before calling t_relay() or I get 
> Sep 14 14:56:06 registrar-secure /usr/sbin/kamailio[10168]: ERROR: tm
> [t_fwd.c:1771]: t_forward_nonack(): ERROR: t_forward_nonack: no
> branches for forwarding
> This code seems to work, but it feels like I’m doing something very
> wrong…. in particular $avp(triedrtpout) is set for the transaction, I
> should be setting it separately for each branch.  
>     event_route[tm:branch-failure:SRTP] { # Handle failure response
>             xlog("L_INFO", "Handling $T_reply_code response to $rm to
>     ru: <$ru> and du: $du\n");
>             if(t_check_status("488") && is_method("INVITE")) {
>                     if ($avp(triedsrtpout)==1) {
>                             # set $ru seems to create a new branch ...
>     even when we set it to its current value.
>                             # we want to generate a new SIP INVITE to
>     the same AOR but with different SDP
>                             $avp(buffer)=$ru;
>                             $ru=$avp(buffer);
>                             xlog("L_INFO","488 caught. Resending to $ru");
>                             # try with unencrypted RTP/AVP
>                             rtpengine_delete();
>                             rtpengine_offer("to-tag trust-address
>     replace-origin replace-session-connection ICE=force RTP/AVP");
>                             if (!t_relay()) {
>                                     sl_reply_error();
>                             }
>                     }
>             }
>     }
> I am using kamailio 4.2 debian package for this registrar.
> Sorry for the rambling question … I don’t understand enough to write
> the short version!
> Paul
> _______________________________________________
> SIP Express Router (SER) and Kamailio (OpenSER) - sr-users mailing list
> sr-users at lists.sip-router.org
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Daniel-Constantin Mierla
http://www.asipto.com - http://www.kamailio.org
http://twitter.com/#!/miconda - http://www.linkedin.com/in/miconda

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