rc80211_minstrel: fix contention window calculation

The contention window is supposed to be a power of two minus one, i.e.
15, 31, 63, 127...  minstrel_rate_init() forgets to subtract 1, so the
sequence becomes 15, 32, 66, 134...

Bug reported by Dan Halperin <dhalperi@cs.washington.edu>

Signed-off-by: Pavel Roskin <proski@gnu.org>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

diff --git a/net/mac80211/rc80211_minstrel.c b/net/mac80211/rc80211_minstrel.c
index 7c5142988bbb77f140d373e26414f9bd0dec31b7..6e5d68b4e427a232dfeebcfe98f666bb2618bb1c 100644 (file)
--- a/net/mac80211/rc80211_minstrel.c
+++ b/net/mac80211/rc80211_minstrel.c
@@ -418,7 +418,7 @@ minstrel_rate_init(void *priv, struct ieee80211_supported_band *sband,
 
                        /* contention window */
                        tx_time_single += t_slot + min(cw, mp->cw_max);
-                       cw = (cw + 1) << 1;
+                       cw = (cw << 1) | 1;
 
                        tx_time += tx_time_single;
                        tx_time_cts += tx_time_single + mi->sp_ack_dur;