hi, sorry if this hasn't been answered already - only the details in the last subframe are accurate. the rest aren't!
-a On 28 October 2015 at 08:34, Jinghao Shi <jingh...@buffalo.edu> wrote: > Hi, > > Recently I used an OpenWRT router (TP-LINK WDR3500, AR9340, ATH9K) to sniff > packets, and I found that the MCS information in the radiotap header is > possible corrupted. > > In theory, all A-MPDU subframes should be sent in the same bit rate > (MCS/BW/GI), since they have the same PPDU header. However, in the packet > trace, I found the MCS in each A-MPDU subframe's radiotap header is > different: they are in the same MCS index, but have different BW and GI > flag. I was able to confirm that only the last subframe has the correct MCS > information by looking at the logs at the transmitter side. > > Here is a trace snippet to illustrate the problem: > > https://www.cloudshark.org/captures/2dad885fee3e (the pcap file is also > attached). > > I was able to trace the function that set the MCS information in > ath_rx_status structure. It is in > ar9003_mac.c:ath9k_hw_process_rxdesc_edma() (or > mac.c:ath9k_hw_rxprocdesc()?) It seems the corrupted MCS information is > passed from the firmware. > > So my questions are: > > Is this a bug that MCS information is not accurate? > If so, is this caused by the firmware? > > I also attached the kmsg logs of the sniffer device. > > Thanks, > Jinghao > > _______________________________________________ > ath9k-devel mailing list > ath9k-devel@lists.ath9k.org > https://lists.ath9k.org/mailman/listinfo/ath9k-devel > _______________________________________________ ath9k-devel mailing list ath9k-devel@lists.ath9k.org https://lists.ath9k.org/mailman/listinfo/ath9k-devel
