PPP dual wan interface

Hi Guys

My MT has dual wan. Public IPs are assigned to 1 DNS. So when people connect with VPN (SSTP, L2tp etc) it is load balanced.

Everything works fine with the mangle rules. Only thing is where can I find the interface they are connected to. Of course I can scan the logs but is there an easy way to find the wan interface where they connected to ?

Kind regards