• Johannes Berg's avatar
    cfg80211: disallow bridging managed/adhoc interfaces · ad4bb6f8
    Johannes Berg authored
    A number of people have tried to add a wireless interface
    (in managed mode) to a bridge and then complained that it
    doesn't work. It cannot work, however, because in 802.11
    networks all packets need to be acknowledged and as such
    need to be sent to the right address. Promiscuous doesn't
    help here. The wireless address format used for these
    links has only space for three addresses, the
     * transmitter, which must be equal to the sender (origin)
     * receiver (on the wireless medium), which is the AP in
       the case of managed mode
     * the recipient (destination), which is on the APs local
       network segment
    
    In an IBSS, it is similar, but the receiver and recipient
    must match and the third address is used as the BSSID.
    
    To avoid such mistakes in the future, disallow adding a
    wireless interface to a bridge.
    
    Felix has recently added a four-address mode to the AP
    and client side that can be used (after negotiating that
    it is possible, which must happen out-of-band by setting
    up both sides) for bridging, so allow that case.
    Signed-off-by: default avatarJohannes Berg <johannes@sipsolutions.net>
    Acked-by: default avatarStephen Hemminger <shemminger@vyatta.com>
    Signed-off-by: default avatarJohn W. Linville <linville@tuxdriver.com>
    ad4bb6f8
br_if.c 9.72 KB