What is the simplest way to identify the branch (by branch index) to which a reply belongs in an ONREPLY-ROUTE?
I have parallel forking with my registrar and do passive call statekeeping. The problem is that it must be branch-aware; I need to know if, for example, I got a successful provisional reply on one branch of the call and a failure on the other, and deal with those separately.
Right now my statekeeping information is keyed by Call-ID, but since that persists across two branches, obviously some sort of branch-identifying information has to be present.
I've tried setting a persistent variable to the value of $T_branch_idx inside a BRANCH-ROUTE, but in ONREPLY-ROUTE that just shows up with the most recent branch index, regardless of which branch the reply actually came in on.
I'm probably missing something quite obvious here, so I ask - how do I incorporate some form of branch awareness into ONREPLY-ROUTEs? I really do not care what form that is - be it branch index, or some other built-in value, as long as it is consistent.