1. 16 Mar, 2015 1 commit
  2. 03 Mar, 2015 2 commits
  3. 26 Feb, 2015 1 commit
    • Jouni Malinen's avatar
      mac80211: Send EAPOL frames at lowest rate · 9c1c98a3
      Jouni Malinen authored
      The current minstrel_ht rate control behavior is somewhat optimistic in
      trying to find optimum TX rate. While this is usually fine for normal
      Data frames, there are cases where a more conservative set of retry
      parameters would be beneficial to make the connection more robust.
      
      EAPOL frames are critical to the authentication and especially the
      EAPOL-Key message 4/4 (the last message in the 4-way handshake) is
      important to get through to the AP. If that message is lost, the only
      recovery mechanism in many cases is to reassociate with the AP and start
      from scratch. This can often be avoided by trying to send the frame with
      more conservative rate and/or with more link layer retries.
      
      In most cases, minstrel_ht is currently using the initial EAPOL-Key
      frames for probing higher rates and this results in only five link layer
      transmission attempts (one at high(ish) MCS and four at MCS0). While
      this works with most APs, it looks like there are some deployed APs that
      may have issues with the EAPOL frames using HT MCS immediately after
      association. Similarly, there may be issues in cases where the signal
      strength or radio environment is not good enough to be able to get
      frames through even at couple of MCS 0 tries.
      
      The best approach for this would likely to be to reduce the TX rate for
      the last rate (3rd rate parameter in the set) to a low basic rate (say,
      6 Mbps on 5 GHz and 2 or 5.5 Mbps on 2.4 GHz), but doing that cleanly
      requires some more effort. For now, we can start with a simple one-liner
      that forces the minimum rate to be used for EAPOL frames similarly how
      the TX rate is selected for the IEEE 802.11 Management frames. This does
      result in a small extra latency added to the cases where the AP would be
      able to receive the higher rate, but taken into account how small number
      of EAPOL frames are used, this is likely to be insignificant. A future
      optimization in the minstrel_ht design can also allow this patch to be
      reverted to get back to the more optimized initial TX rate.
      
      It should also be noted that many drivers that do not use minstrel as
      the rate control algorithm are already doing similar workarounds by
      forcing the lowest TX rate to be used for EAPOL frames.
      
      Cc: stable@vger.kernel.org
      Reported-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      Tested-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      Signed-off-by: default avatarJouni Malinen <jouni@qca.qualcomm.com>
      Signed-off-by: default avatarJohannes Berg <johannes.berg@intel.com>
      9c1c98a3
  4. 24 Feb, 2015 7 commits
  5. 23 Feb, 2015 2 commits
  6. 22 Feb, 2015 7 commits
  7. 20 Feb, 2015 20 commits