Method to log duration connexion with OpenVPN

[droumanet]

Hi everybody,

I like OPNsense and I use it at my school, for my students. OPNsense protect the classroom and permit them to connect to their classroom computer (servers farm).
However, I can't figure how to use OpenVPN log's to manage how much time a user still connected.
I've got the start of authentication through AD, but never the end of communication.
I've read a post on OpenVPN (seems to be old) on disconnect event missing (https://serverfault.com/questions/681249/openvpn-doesnt-log-user-disconnect-event).

Any idea if it's possible and how to do this?

Thanks,