• Emmanuel Grumbach's avatar
    cfg80211/mac80211: ignore signal if the frame was heard on wrong channel · 3afc2167
    Emmanuel Grumbach authored
    On 2.4Ghz band, the channels overlap since the delta
    between different channels is 5Mhz while the width of the
    receiver is 20Mhz (at least).
    This means that we can hear beacons or probe responses from
    adjacent channels. These frames will have a significant
    lower RSSI which will feed all kinds of logic with inaccurate
    data. An obvious example is the roaming algorithm that will
    think our AP is getting weak and will try to move to another
    In order to avoid this, update the signal only if the frame
    has been heard on the same channel as the one advertised by
    the AP in its DS / HT IEs.
    We refrain from updating the values only if the AP is
    already in the BSS list so that we will still have a valid
    (but inaccurate) value if the AP was heard on an adjacent
    channel only.
    To achieve this, stop taking the channel from DS / HT IEs
    in mac80211. The DS / HT IEs is taken into account to
    discard the frame if it was received on a disabled channel.
    This can happen due to the same phenomenon: the frame is
    sent on channel 12, but heard on channel 11 while channel
    12 can be disabled on certain devices. Since this check
    is done in cfg80211, stop even checking this in mac80211.
    Signed-off-by: default avatarEmmanuel Grumbach <emmanuel.grumbach@intel.com>
    [remove unused rx_freq variable]
    Signed-off-by: default avatarJohannes Berg <johannes.berg@intel.com>
cfg80211.h 165 KB