• Johannes Berg's avatar
    cfg80211: validate channel settings across interfaces · 59bbb6f7
    Johannes Berg authored
    Currently, there's a problem that affects regulatory
    enforcement and connection stability, in that it is
    possible to switch the channel while connected to a
    network or joined to an IBSS.
    The problem comes from the fact that we only validate
    the channel against the current interface's type, not
    against any other interface. Thus, you have any type
    of interface up, additionally bring up a monitor mode
    interface and switch the channel on the monitor. This
    will obviously also switch the channel on the other
    The problem now is that if you do that while sending
    beacons for IBSS mode, you can switch to a disabled
    channel or a channel that doesn't allow beaconing.
    Combined with a managed mode interface connected to
    an AP instead of an IBSS interface, you can easily
    break the connection that way.
    To fix this, this patch validates any channel change
    with all available interfaces, and disallows such
    changes on secondary interfaces if another interface
    is connected to an AP or joined to an IBSS.
    Signed-off-by: default avatarJohannes Berg <johannes@sipsolutions.net>
    Signed-off-by: default avatarJohn W. Linville <linville@tuxdriver.com>