11n DFS Channel selection Implementation

[Himali]

Hi,

      We have implemented the 11n DFS Channel selection ( making channel 
scan list according to HT mode) in FreeBSD. Please find the attached 
patch for the same.

        In this, we are making scan list for 11NA/NG mode also. So, 
channel marked with HT flags will also be included in scan list.
        Another things that we have done is putting Extension channel 
also in NOL list after radar detected on channel (required when we 
configured 11n mode).

       Test Procedure:
       (1) Creation and configuration of interface for 11n mode
            ifconfig -v wlan0 create wlandev ath0 wlanmode ap
            ifconfig -v wlan0 regdomain FCC3
            ifconfig -v wlan0 country US
            ifconfig wlan0 ht
            ifconfig wlan0 htcompat
            ifconfig wlan0 mode 11na
            ifconfig wlan0 up

       (2) By using command "sysctl net.wlan.0.radar=1" , we can 
generate radar interrupt and put the channel in NOL list. For 11n mode, 
this will put extension channel also in NOL list.
            For example, if radar detected on channel 153 (5765 MHz) 
then its extension channel 149 (5745 MHz) will also goes in NOL list and 
AP will not consider these two channel for next channel selection criteria.

Let us know in case of any queries regarding this.

Thanks and Regards,
Himali


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