I am wondering if it is possible to extract 802.11 frames on a router running OpenWrt operating as an access point. I tried using tcpdump and loading the dumped packets in Wireshark, but I could only see up to the 'Ethernet II' header.
Why not just use Wireshark? And from my experience you need to be in monitor mode. You will know it's working when you see probes, beacons and the like. Try a