mac80211: add beacon filtering support

Add IEEE80211_HW_BEACON_FILTERING flag so that driver inform that it supports
beacon filtering. Drivers need to call the new function
ieee80211_beacon_loss() to notify about beacon loss.

Signed-off-by: Kalle Valo <kalle.valo@nokia.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

5 files changed, 92 insertions, 1 deletions

diff --git a/Documentation/DocBook/mac80211.tmpl b/Documentation/DocBook/mac80211.tmpl
index 8af6d9626878..fbeaffc1dcc3 100644
--- a/Documentation/DocBook/mac80211.tmpl
+++ b/Documentation/DocBook/mac80211.tmpl
@@ -227,6 +227,12 @@ usage should require reading the full document.
 !Pinclude/net/mac80211.h Powersave support
     </chapter>
 
+    <chapter id="beacon-filter">
+      <title>Beacon filter support</title>
+!Pinclude/net/mac80211.h Beacon filter support
+!Finclude/net/mac80211.h ieee80211_beacon_loss
+    </chapter>
+
     <chapter id="qos">
       <title>Multiple queues and QoS support</title>
       <para>TBD</para>
diff --git a/include/net/mac80211.h b/include/net/mac80211.h
index 174dc1d7526b..d881ed8ad2c1 100644
--- a/include/net/mac80211.h
+++ b/include/net/mac80211.h
@@ -882,6 +882,10 @@ enum ieee80211_tkip_key_type {
  *
  * @IEEE80211_HW_MFP_CAPABLE:
  *      Hardware supports management frame protection (MFP, IEEE 802.11w).
+ *
+ * @IEEE80211_HW_BEACON_FILTER:
+ *      Hardware supports dropping of irrelevant beacon frames to
+ *      avoid waking up cpu.
  */
 enum ieee80211_hw_flags {
         IEEE80211_HW_RX_INCLUDES_FCS                    = 1<<1,
@@ -897,6 +901,7 @@ enum ieee80211_hw_flags {
         IEEE80211_HW_PS_NULLFUNC_STACK                  = 1<<11,
         IEEE80211_HW_SUPPORTS_DYNAMIC_PS                = 1<<12,
         IEEE80211_HW_MFP_CAPABLE                        = 1<<13,
+        IEEE80211_HW_BEACON_FILTER                      = 1<<14,
 };
 
 /**
@@ -1121,6 +1126,24 @@ ieee80211_get_alt_retry_rate(const struct ieee80211_hw *hw,
  */
 
 /**
+ * DOC: Beacon filter support
+ *
+ * Some hardware have beacon filter support to reduce host cpu wakeups
+ * which will reduce system power consumption. It usuallly works so that
+ * the firmware creates a checksum of the beacon but omits all constantly
+ * changing elements (TSF, TIM etc). Whenever the checksum changes the
+ * beacon is forwarded to the host, otherwise it will be just dropped. That
+ * way the host will only receive beacons where some relevant information
+ * (for example ERP protection or WMM settings) have changed.
+ *
+ * Beacon filter support is informed with %IEEE80211_HW_BEACON_FILTER flag.
+ * The driver needs to enable beacon filter support whenever power save is
+ * enabled, that is %IEEE80211_CONF_PS is set. When power save is enabled,
+ * the stack will not check for beacon miss at all and the driver needs to
+ * notify about complete loss of beacons with ieee80211_beacon_loss().
+ */
+
+/**
  * DOC: Frame filtering
  *
  * mac80211 requires to see many management frames for proper
@@ -1970,6 +1993,16 @@ void ieee80211_stop_tx_ba_cb_irqsafe(struct ieee80211_hw *hw, const u8 *ra,
 struct ieee80211_sta *ieee80211_find_sta(struct ieee80211_hw *hw,
                                          const u8 *addr);
 
+/**
+ * ieee80211_beacon_loss - inform hardware does not receive beacons
+ *
+ * @vif: &struct ieee80211_vif pointer from &struct ieee80211_if_init_conf.
+ *
+ * When beacon filtering is enabled with IEEE80211_HW_BEACON_FILTERING and
+ * IEEE80211_CONF_PS is set, the driver needs to inform whenever the
+ * hardware is not receiving beacons with this function.
+ */
+void ieee80211_beacon_loss(struct ieee80211_vif *vif);
 
 /* Rate control API */
 
diff --git a/net/mac80211/ieee80211_i.h b/net/mac80211/ieee80211_i.h
index 8a617a7fc090..acba78e1a5ca 100644
--- a/net/mac80211/ieee80211_i.h
+++ b/net/mac80211/ieee80211_i.h
@@ -275,6 +275,7 @@ struct ieee80211_if_managed {
         struct timer_list chswitch_timer;
         struct work_struct work;
         struct work_struct chswitch_work;
+        struct work_struct beacon_loss_work;
 
         u8 bssid[ETH_ALEN], prev_bssid[ETH_ALEN];
 
@@ -1086,6 +1087,7 @@ void ieee80211_send_nullfunc(struct ieee80211_local *local,
                              int powersave);
 void ieee80211_sta_rx_notify(struct ieee80211_sub_if_data *sdata,
                              struct ieee80211_hdr *hdr);
+void ieee80211_beacon_loss_work(struct work_struct *work);
 
 void ieee80211_wake_queues_by_reason(struct ieee80211_hw *hw,
                                      enum queue_stop_reason reason);
diff --git a/net/mac80211/iface.c b/net/mac80211/iface.c
index dd2a276fa8ca..91e8e1bacaaa 100644
--- a/net/mac80211/iface.c
+++ b/net/mac80211/iface.c
@@ -477,6 +477,9 @@ static int ieee80211_stop(struct net_device *dev)
                  */
                 cancel_work_sync(&sdata->u.mgd.work);
                 cancel_work_sync(&sdata->u.mgd.chswitch_work);
+
+                cancel_work_sync(&sdata->u.mgd.beacon_loss_work);
+
                 /*
                  * When we get here, the interface is marked down.
                  * Call synchronize_rcu() to wait for the RX path
diff --git a/net/mac80211/mlme.c b/net/mac80211/mlme.c
index 8f30f4d19da0..7ecda9d59d8a 100644
--- a/net/mac80211/mlme.c
+++ b/net/mac80211/mlme.c
@@ -610,6 +610,8 @@ static void ieee80211_set_associated(struct ieee80211_sub_if_data *sdata,
                 bss_info_changed |= ieee80211_handle_bss_capability(sdata,
                         bss->cbss.capability, bss->has_erp_value, bss->erp_value);
 
+                cfg80211_hold_bss(&bss->cbss);
+
                 ieee80211_rx_bss_put(local, bss);
         }
 
@@ -751,6 +753,8 @@ static void ieee80211_set_disassoc(struct ieee80211_sub_if_data *sdata,
 {
         struct ieee80211_if_managed *ifmgd = &sdata->u.mgd;
         struct ieee80211_local *local = sdata->local;
+        struct ieee80211_conf *conf = &local_to_hw(local)->conf;
+        struct ieee80211_bss *bss;
         struct sta_info *sta;
         u32 changed = 0, config_changed = 0;
 
@@ -774,6 +778,15 @@ static void ieee80211_set_disassoc(struct ieee80211_sub_if_data *sdata,
 
         ieee80211_sta_tear_down_BA_sessions(sta);
 
+        bss = ieee80211_rx_bss_get(local, ifmgd->bssid,
+                                   conf->channel->center_freq,
+                                   ifmgd->ssid, ifmgd->ssid_len);
+
+        if (bss) {
+                cfg80211_unhold_bss(&bss->cbss);
+                ieee80211_rx_bss_put(local, bss);
+        }
+
         if (self_disconnected) {
                 if (deauth)
                         ieee80211_send_deauth_disassoc(sdata,
@@ -925,6 +938,33 @@ void ieee80211_sta_rx_notify(struct ieee80211_sub_if_data *sdata,
                           jiffies + IEEE80211_MONITORING_INTERVAL);
 }
 
+void ieee80211_beacon_loss_work(struct work_struct *work)
+{
+        struct ieee80211_sub_if_data *sdata =
+                container_of(work, struct ieee80211_sub_if_data,
+                             u.mgd.beacon_loss_work);
+        struct ieee80211_if_managed *ifmgd = &sdata->u.mgd;
+
+        printk(KERN_DEBUG "%s: driver reports beacon loss from AP %pM "
+               "- sending probe request\n", sdata->dev->name,
+               sdata->u.mgd.bssid);
+
+        ifmgd->flags |= IEEE80211_STA_PROBEREQ_POLL;
+        ieee80211_send_probe_req(sdata, ifmgd->bssid, ifmgd->ssid,
+                                 ifmgd->ssid_len, NULL, 0);
+
+        mod_timer(&ifmgd->timer, jiffies + IEEE80211_MONITORING_INTERVAL);
+}
+
+void ieee80211_beacon_loss(struct ieee80211_vif *vif)
+{
+        struct ieee80211_sub_if_data *sdata = vif_to_sdata(vif);
+
+        queue_work(sdata->local->hw.workqueue,
+                   &sdata->u.mgd.beacon_loss_work);
+}
+EXPORT_SYMBOL(ieee80211_beacon_loss);
+
 static void ieee80211_associated(struct ieee80211_sub_if_data *sdata)
 {
         struct ieee80211_if_managed *ifmgd = &sdata->u.mgd;
@@ -959,7 +999,13 @@ static void ieee80211_associated(struct ieee80211_sub_if_data *sdata)
                 goto unlock;
         }
 
-        if (time_after(jiffies,
+        /*
+         * Beacon filtering is only enabled with power save and then the
+         * stack should not check for beacon loss.
+         */
+        if (!((local->hw.flags & IEEE80211_HW_BEACON_FILTER) &&
+              (local->hw.conf.flags & IEEE80211_CONF_PS)) &&
+            time_after(jiffies,
                        ifmgd->last_beacon + IEEE80211_MONITORING_INTERVAL)) {
                 printk(KERN_DEBUG "%s: beacon loss from AP %pM "
                        "- sending probe request\n",
@@ -1869,6 +1915,7 @@ void ieee80211_sta_setup_sdata(struct ieee80211_sub_if_data *sdata)
         ifmgd = &sdata->u.mgd;
         INIT_WORK(&ifmgd->work, ieee80211_sta_work);
         INIT_WORK(&ifmgd->chswitch_work, ieee80211_chswitch_work);
+        INIT_WORK(&ifmgd->beacon_loss_work, ieee80211_beacon_loss_work);
         setup_timer(&ifmgd->timer, ieee80211_sta_timer,
                     (unsigned long) sdata);
         setup_timer(&ifmgd->chswitch_timer, ieee80211_chswitch_timer,