1. 07 Mar, 2012 1 commit
    • Paul Stewart's avatar
      mac80211: Filter duplicate IE ids · fcff4f10
      Paul Stewart authored
      mac80211 is lenient with respect to reception of corrupted beacons.
      Even if the frame is corrupted as a whole, the available IE elements
      are still passed back and accepted, sometimes replacing legitimate
      data.  It is unknown to what extent this "feature" is made use of,
      but it is clear that in some cases, this is detrimental.  One such
      case is reported in http://crosbug.com/26832 where an AP corrupts
      its beacons but not its probe responses.
      
      One approach would be to completely reject frames with invaid data
      (for example, if the last tag extends beyond the end of the enclosing
      PDU).  The enclosed approach is much more conservative: we simply
      prevent later IEs from overwriting the state from previous ones.
      This approach hopes that there might be some salient data in the
      IE stream before the corruption, and seeks to at least prevent that
      data from being overwritten.  This approach will fix the case above.
      
      Further, we flag element structures that contain data we think might
      be corrupted, so that as we fill the mac80211 BSS structure, we try
      not to replace data from an un-corrupted probe response with that
      of a corrupted beacon, for example.
      
      Short of any statistics gathering in the various forms of AP breakage,
      it's not possible to ascertain the side effects of more stringent
      discarding of data.
      Signed-off-by: default avatarPaul Stewart <pstew@chromium.org>
      Cc: Sam Leffler <sleffler@chromium.org>
      Cc: Eliad Peller <eliad@wizery.com>
      Acked-by: default avatarJohannes Berg <johannes@sipsolutions.net>
      Signed-off-by: default avatarJohn W. Linville <linville@tuxdriver.com>
      fcff4f10
  2. 06 Mar, 2012 39 commits