>On Sunday, October 21, 2012 09:58:18 PM David H. Lynch Jr. wrote: >> I am looking for an easy means to determine the characteristics of a >> transmitted packet. >> Particularly whether it is HT20/HT40-/HT40+ I have used a variety of >> sniffers, airodump, wireshark, ... and I can not seem to find anything >> that will tell me what I am after - or I do not know how to use them. >differentiating between HT40+ and HT40- will be difficult to do with >just one standard wifi device (should be possible with two though). >If you use mac80211, have you setup your monitor channel by adding >the HT20/HT40+/HT40- flag? ># iw dev wlanX set channel 1 HT40+ (or HT40-/HT20) This is setting up to send on channel 1 HT40+ correct ? I am already doing that I need to know if it is succeeding I am using Packettspammer to send with all the channel/frequency radiotap headers removed. an setting up using iw for what I want as above. >This might help. >As for retrieving the information: >If a HT20/HT40 frame was received, it should have a radiotap >IEEE80211_RADIOTAP_MCS header element (on the monitor interface dump). >In this element should provide the MCS and flags for > - BW40 (if false => HT20, if true => HT40+ or HT40- depending > on the channel configuration) > - Short GI > - Greenfield flag > - (LDPC) Wireshark appears to handle RadioTap - I am seeing lots of other flags etc. but not BW40. >But I don't know if any of this information is parsed by any of the >current tools (depends on the version I guess). At least for wireshark >you can always look at the raw hex dump of the package, so it should >be there! The definitions of what RADIOTAP_MCS bit means what are in: ><include/net/ieee80211_radiotap.h> Googling Radiotap produces lots of comments that suggest that Radiotap headers - send and receive are not necescarily complete or accurate from device to device - is that a reasonable conclusion ? >Regards, > Chr Thanks -- To unsubscribe from this list: send the line "unsubscribe linux-wireless" in the body of a message to majordomo@... More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe linux-wireless" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
