mac80211: Track Beacon signal strength and implement cqm events

Calculate a running average of the signal strength reported for Beacon
frames and indicate cqm events if the average value moves below or
above the configured threshold value (and filter out repetitive events
with by using the configured hysteresis).

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

1 files changed, 45 insertions, 0 deletions

diff --git a/net/mac80211/mlme.c b/net/mac80211/mlme.c
index c686d1b90f9f..de7519eb2b5d 100644
--- a/net/mac80211/mlme.c
+++ b/net/mac80211/mlme.c
@@ -46,6 +46,13 @@
  */
 #define IEEE80211_PROBE_WAIT            (HZ / 2)
 
+/*
+ * Weight given to the latest Beacon frame when calculating average signal
+ * strength for Beacon frames received in the current BSS. This must be
+ * between 1 and 15.
+ */
+#define IEEE80211_SIGNAL_AVE_WEIGHT     3
+
 #define TMR_RUNNING_TIMER       0
 #define TMR_RUNNING_CHANSW      1
 
@@ -732,6 +739,8 @@ static void ieee80211_set_associated(struct ieee80211_sub_if_data *sdata,
         sdata->u.mgd.associated = cbss;
         memcpy(sdata->u.mgd.bssid, cbss->bssid, ETH_ALEN);
 
+        sdata->u.mgd.flags |= IEEE80211_STA_RESET_SIGNAL_AVE;
+
         /* just to be sure */
         sdata->u.mgd.flags &= ~(IEEE80211_STA_CONNECTION_POLL |
                                 IEEE80211_STA_BEACON_POLL);
@@ -1347,6 +1356,7 @@ static void ieee80211_rx_mgmt_beacon(struct ieee80211_sub_if_data *sdata,
                                      struct ieee80211_rx_status *rx_status)
 {
         struct ieee80211_if_managed *ifmgd = &sdata->u.mgd;
+        struct ieee80211_bss_conf *bss_conf = &sdata->vif.bss_conf;
         size_t baselen;
         struct ieee802_11_elems elems;
         struct ieee80211_local *local = sdata->local;
@@ -1382,6 +1392,41 @@ static void ieee80211_rx_mgmt_beacon(struct ieee80211_sub_if_data *sdata,
         if (memcmp(bssid, mgmt->bssid, ETH_ALEN) != 0)
                 return;
 
+        /* Track average RSSI from the Beacon frames of the current AP */
+        ifmgd->last_beacon_signal = rx_status->signal;
+        if (ifmgd->flags & IEEE80211_STA_RESET_SIGNAL_AVE) {
+                ifmgd->flags &= ~IEEE80211_STA_RESET_SIGNAL_AVE;
+                ifmgd->ave_beacon_signal = rx_status->signal;
+                ifmgd->last_cqm_event_signal = 0;
+        } else {
+                ifmgd->ave_beacon_signal =
+                        (IEEE80211_SIGNAL_AVE_WEIGHT * rx_status->signal * 16 +
+                         (16 - IEEE80211_SIGNAL_AVE_WEIGHT) *
+                         ifmgd->ave_beacon_signal) / 16;
+        }
+        if (bss_conf->cqm_rssi_thold &&
+            !(local->hw.flags & IEEE80211_HW_SUPPORTS_CQM_RSSI)) {
+                int sig = ifmgd->ave_beacon_signal / 16;
+                int last_event = ifmgd->last_cqm_event_signal;
+                int thold = bss_conf->cqm_rssi_thold;
+                int hyst = bss_conf->cqm_rssi_hyst;
+                if (sig < thold &&
+                    (last_event == 0 || sig < last_event - hyst)) {
+                        ifmgd->last_cqm_event_signal = sig;
+                        ieee80211_cqm_rssi_notify(
+                                &sdata->vif,
+                                NL80211_CQM_RSSI_THRESHOLD_EVENT_LOW,
+                                GFP_KERNEL);
+                } else if (sig > thold &&
+                           (last_event == 0 || sig > last_event + hyst)) {
+                        ifmgd->last_cqm_event_signal = sig;
+                        ieee80211_cqm_rssi_notify(
+                                &sdata->vif,
+                                NL80211_CQM_RSSI_THRESHOLD_EVENT_HIGH,
+                                GFP_KERNEL);
+                }
+        }
+
         if (ifmgd->flags & IEEE80211_STA_BEACON_POLL) {
 #ifdef CONFIG_MAC80211_VERBOSE_DEBUG
                 if (net_ratelimit()) {