cfg80211: Address some corner cases in scan result channel updating
cfg80211_get_bss_channel() is used to update the RX channel based on the available frame payload information (channel number from DSSS Parameter Set element or HT Operation element). This is needed on 2.4 GHz channels where frames may be received on neighboring channels due to overlapping frequency range. This might of some use on the 5 GHz band in some corner cases, but things are more complex there since there is no n:1 or 1:n mapping between channel numbers and frequencies due to multiple different starting frequencies in different operating classes. This could result in ieee80211_channel_to_frequency() returning incorrect frequency and ieee80211_get_channel() returning incorrect channel information (or indication of no match). In the previous implementation, this could result in some scan results being dropped completely, e.g., for the 4.9 GHz channels. That prevented connection to such BSSs. Fix this by using the driver-provided channel pointer if ieee80211_get_channel() does not find matching channel data for the channel number in the frame payload and if the scan is done with 5 MHz or 10 MHz channel bandwidth. While doing this, also add comments describing what the function is trying to achieve to make it easier to understand what happens here and why. Signed-off-by: NJouni Malinen <jouni@codeaurora.org> Signed-off-by: NJohannes Berg <johannes.berg@intel.com>
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