Tracking the origin of forwarded requests

I have a firewall rule in OpenWRT to forward all DNS requests to my pihole. This works fine and is great!
My question involves being able to track down the original source of the request. As of now, it seems all forwarded queries come from my router (192.168.1.2).
Is is possible to log or track where the forwards are coming from so I can find what client is sending the DNS that needs forwarding?