Hi. I'm writing my own code to extract WLAN duration of each WLAN packet over the air. For efficiency, I want to capture only the mac header of the packet with tcpdump and calculate the wlan duration. When I inspect the pcap file containing only the mac header via wireshark, the frame length is calculated correctly, but I cannot find any clue to extract the frame length. As far as I know the L-SIG from radiotap header is supposed to contain length information, but I cannot see the relationship to the frame length. How does wireshark extract frame length from radiotap header and 802.11 MAC header?
Thanks in advance.
