Patch "mac80211: minstrel: Change expected throughput unit back to Kbps" has been added to the 4.4-stable tree

This is a note to let you know that I've just added the patch titled

mac80211: minstrel: Change expected throughput unit back to Kbps

to the 4.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
mac80211-minstrel-change-expected-throughput-unit-back-to-kbps.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Sven Eckelmann <[email protected]>
Date: Tue, 2 Feb 2016 08:12:26 +0100
Subject: mac80211: minstrel: Change expected throughput unit back to Kbps

From: Sven Eckelmann <[email protected]>

commit 212c5a5e6ba61678be6b5fee576e38bccb50b613 upstream.

The change from cur_tp to the function minstrel_get_tp_avg/minstrel_ht_get_tp_avg changed the unit used for the current throughput. For example in minstrel_ht the correct conversion between them would be:

    mrs->cur_tp / 10 == minstrel_ht_get_tp_avg(..).

This factor 10 must also be included in the calculation of minstrel_get_expected_throughput and minstrel_ht_get_expected_throughput to return values with the unit [Kbps] instead of [10Kbps]. Otherwise routing algorithms like B.A.T.M.A.N. V will make incorrect decision based on these values. Its kernel based implementation expects expected_throughput always to have the unit [Kbps] and not sometimes [10Kbps] and sometimes [Kbps].

The same requirement has iw or olsrdv2's nl80211 based statistics module which retrieve the same data via NL80211_STA_INFO_TX_BITRATE.

---
 net/mac80211/rc80211_minstrel.c    |    2 +-
 net/mac80211/rc80211_minstrel_ht.c |    3 ++-
 2 files changed, 3 insertions(+), 2 deletions(-)

@@ -711,7 +711,7 @@ static u32 minstrel_get_expected_through
 	 * computing cur_tp
 	 */
 	tmp_mrs = &mi->r[idx].stats;
-	tmp_cur_tp = minstrel_get_tp_avg(&mi->r[idx], tmp_mrs->prob_ewma);
+	tmp_cur_tp = minstrel_get_tp_avg(&mi->r[idx], tmp_mrs->prob_ewma) * 10;
 	tmp_cur_tp = tmp_cur_tp * 1200 * 8 / 1024;
 
 	return tmp_cur_tp;

@@ -1334,7 +1334,8 @@ static u32 minstrel_ht_get_expected_thro
 	prob = mi->groups[i].rates[j].prob_ewma;
 
 	/* convert tp_avg from pkt per second in kbps */
-	tp_avg = minstrel_ht_get_tp_avg(mi, i, j, prob) * AVG_PKT_SIZE * 8 / 1024;
+	tp_avg = minstrel_ht_get_tp_avg(mi, i, j, prob) * 10;
+	tp_avg = tp_avg * AVG_PKT_SIZE * 8 / 1024;
 
 	return tp_avg;
 }

Patches currently in stable-queue which might be from [email protected] are

queue-4.4/mac80211-minstrel-change-expected-throughput-unit-back-to-kbps.patch