(sorry to send HTML the first time... oops)
Over the weekend I found a bug in minstrel-ht that might well be
implicated here.
The last retransmit rate is meant to be a 'get the packet there
reliably' rate; minstrel-ht doesn't do that right, and can pick a
fairly flaky rate instead.
Can't generate a proper patch right now, so this diff might not apply
cleanly, but the fix is simply to change 75 to 99 in the two places
below:
@@ -437,7 +448,7 @@ minstrel_ht_set_best_prob_rate(struct mi
(max_tp_group != MINSTREL_CCK_GROUP))
return;
- if (mrs->prob_ewma > MINSTREL_FRAC(75, 100)) {
+ if (mrs->prob_ewma > MINSTREL_FRAC(99, 100)) {
cur_tp_avg = minstrel_ht_get_tp_avg(mi, cur_group, cur_idx);
if (cur_tp_avg > tmp_tp_avg)
mi->max_prob_rate = index;
@@ -526,7 +537,7 @@ minstrel_ht_prob_rate_reduce_streams(str
* Rules for rate selection:
* - max_prob_rate must use only one stream, as a tradeoff between delivery
* probability and throughput during strong fluctuations
- * - as long as the max prob rate has a probability of more than 75%, pick
+ * - as long as the max prob rate has a probability of more than 99%, pick
* higher throughput rates, even if the probablity is a bit lower
*/
static void
On Tue, Feb 24, 2015 at 11:29 AM, Sujith Manoharan <sujith@xxxxxxxxxxx> wrote:
> Jouni Malinen wrote:
>
> > Even I think that this goes a bit too far especially on 2.4 GHz band,
>
> > but I would actually consider limiting EAPOL frames to using non-HT/VHT
>
> > (e.g., 6 Mbps OFDM at least for EAPOL-Key frames) to avoid some
>
> > interoperability issues. I would say that the current minstrel_ht
>
> > behavior is somewhat excessive for EAPOL-Key frames in the other
>
> > direction. Using MCS 14 with fallback to something like MCS 5 for the
>
> > second Data frame after an association can certainly fail.
>
> >
>
> > Number of Linux drivers do already limit EAPOL frame TX rate, so this
>
> > specific item is mainly applicable only to driver that use minstrel from
>
> > mac80211 (e.g., ath9k). Though, that IEEE80211_TX_CTL_USE_MINRATE would
>
> > likely affect most mac80211 drivers.
>
>
> We had this in the ath9k RC, where EAPOL frames were sent out at min-rate
>
> on the VO queue. I think instead of re-introducing it in the driver,
>
> having it in minstrel is cleaner.
>
>
> Sujith
>
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