mac80211: Do not generate CQM events based on first Beacon frames

The signal strength value in a single RX frame is not that reliable,
so it is better to delay start of CQM events until there is a real
average signal strength from more than a single Beacon frame
available.

Signed-off-by: Jouni Malinen <j@w1.fi>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

2 files changed, 16 insertions, 0 deletions

diff --git a/net/mac80211/ieee80211_i.h b/net/mac80211/ieee80211_i.h
index 9af50fbcd48b..16f7fb164c2d 100644
--- a/net/mac80211/ieee80211_i.h
+++ b/net/mac80211/ieee80211_i.h
@@ -369,6 +369,13 @@ struct ieee80211_if_managed {
         int ave_beacon_signal;
 
         /*
+         * Number of Beacon frames used in ave_beacon_signal. This can be used
+         * to avoid generating less reliable cqm events that would be based
+         * only on couple of received frames.
+         */
+        unsigned int count_beacon_signal;
+
+        /*
          * Last Beacon frame signal strength average (ave_beacon_signal / 16)
          * that triggered a cqm event. 0 indicates that no event has been
          * generated for the current association.
diff --git a/net/mac80211/mlme.c b/net/mac80211/mlme.c
index 7915726d791e..0cb822cc12e9 100644
--- a/net/mac80211/mlme.c
+++ b/net/mac80211/mlme.c
@@ -54,6 +54,12 @@
  */
 #define IEEE80211_SIGNAL_AVE_WEIGHT     3
 
+/*
+ * How many Beacon frames need to have been used in average signal strength
+ * before starting to indicate signal change events.
+ */
+#define IEEE80211_SIGNAL_AVE_MIN_COUNT  4
+
 #define TMR_RUNNING_TIMER       0
 #define TMR_RUNNING_CHANSW      1
 
@@ -1555,13 +1561,16 @@ static void ieee80211_rx_mgmt_beacon(struct ieee80211_sub_if_data *sdata,
                 ifmgd->flags &= ~IEEE80211_STA_RESET_SIGNAL_AVE;
                 ifmgd->ave_beacon_signal = rx_status->signal * 16;
                 ifmgd->last_cqm_event_signal = 0;
+                ifmgd->count_beacon_signal = 1;
         } else {
                 ifmgd->ave_beacon_signal =
                         (IEEE80211_SIGNAL_AVE_WEIGHT * rx_status->signal * 16 +
                          (16 - IEEE80211_SIGNAL_AVE_WEIGHT) *
                          ifmgd->ave_beacon_signal) / 16;
+                ifmgd->count_beacon_signal++;
         }
         if (bss_conf->cqm_rssi_thold &&
+            ifmgd->count_beacon_signal >= IEEE80211_SIGNAL_AVE_MIN_COUNT &&
             !(local->hw.flags & IEEE80211_HW_SUPPORTS_CQM_RSSI)) {
                 int sig = ifmgd->ave_beacon_signal / 16;
                 int last_event = ifmgd->last_cqm_event_signal;