How to make a branch trigger persistent (still being active after failure route is triggered)? - sr-users

16 Dec 2022

Hi List

Some time ago, during my learning curve with kamailio, I learned that a
branch route is where you make modifications to callerId's.

So I extensively re-engineered the config to move as much as possible
of callerid modification into branch routes.

But now I discovered, when a call is dispatched via dispatch group with
multiple destinations and one destination fails, therefore the failure
route is triggered, the branch route is not being called on the second
attempt, thus callerid being in the wrong format.

Example:

dispatcher.lst

As an example, consider having dispatcher group 2001 for national traffic over two
dedicated links and Dispatcher group 2002 for international traffic.

2001 sip:192.168.1.1:5060 0 0 name="Carrier1"
2001 sip:192.168.2.1:5060 0 0 name="Carrier1"

2002 sip:192.168.1.3:5060 0 0 name="Carrier2"

request_route
{
	# We determine where we want to send the call
	# and choose dispatch group 2001, the 'national' one.
	# But there are are other dispatch groups and branch triggers
	# set this way and routed to DISPATCHCALL
	$avp(dispgroup) = 2001;
	t_on_branch("BR_TO_NATIONAL");
	route(DISPATCHCALL);
}

route[DISPATCHCALL]
{
	t_set_fr(120000,1500); # Fast Failover
	t_set_max_lifetime(300000,0);
	t_set_retr(200,800);
	if (ds_select_dst("$avp(dispgroup)", "6")) {
		if (ds_is_from_list(-1,0,"$du")) {
			t_on_failure("DISPATCH_FAILURE");
			route(RELAY);
		}
	}
}

branch_route[BR_TO_NATIONAL]
{
	# Here I make sure, all CallerId and Header are correct for the
	# national Carrier
}

failure_route[DISPATCH_FAILURE]
{
	if (t_check_status("(5[0-9][0-9])") or (t_branch_timeout() and
!t_branch_replied())) {
		# Try next DS.
		if (ds_next_dst()) {
			xlog("L_INFO", "     --> retargeting request\n");
			t_on_failure("DISPATCH_FAILURE");
			route(RELAY); #### RIGHT HERE!
			exit;
		}
	}
	# We fail
	xlog("L_ERROR", "Call Failed\n");
}

My issue is not, that if the call is routed after the first path failed
(marked with #### RIGHT HERE!) then the appropriate branch route is not
triggered again and the headers are wrong. But I can not set t_on_branch
within route[DISPATCHCALL] or route[DISPATCH_FAILURE] because this is
called with a different pre-set branch trigger, depending on the target
dispatch group.

Is there a way to make a branch trigger more persistent?

-- 
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