mac80211: notify the driver upon BAR Rx

When we receive a BAR, this typically means that our peer
doesn't hear our Block-Acks or that we can't hear its
frames. Either way, it is a good indication that the link
is in a bad condition. This is why it can serve as a probe
to the driver.
Use the event_callback callback for this.
Since more events with the same data will be added in the
feature, the structure that describes the data attached to
the event is called in a generic name: ieee80211_ba_event.

This also means that from now on, the event_callback can't
sleep.
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

include/net/mac80211.h

@@ -337,10 +337,12 @@ enum ieee80211_bss_change {
  * enum ieee80211_event_type - event to be notified to the low level driver
  * @RSSI_EVENT: AP's rssi crossed the a threshold set by the driver.
  * @MLME_EVENT: event related to MLME
+ * @BAR_RX_EVENT: a BAR was received
  */
 enum ieee80211_event_type {
 	RSSI_EVENT,
 	MLME_EVENT,
+	BAR_RX_EVENT,
 };
 
 /**
@@ -399,18 +401,32 @@ struct ieee80211_mlme_event {
 	u16 reason;
 };
 
+/**
+ * struct ieee80211_ba_event - data attached for BlockAck related events
+ * @sta: pointer to the &ieee80211_sta to which this event relates
+ * @tid: the tid
+ * @ssn: the starting sequence number
+ */
+struct ieee80211_ba_event {
+	struct ieee80211_sta *sta;
+	u16 tid;
+	u16 ssn;
+};
+
 /**
  * struct ieee80211_event - event to be sent to the driver
  * @type: The event itself. See &enum ieee80211_event_type.
  * @rssi: relevant if &type is %RSSI_EVENT
  * @mlme: relevant if &type is %AUTH_EVENT
- * @u:    union holding the above two fields
+ * @ba: relevant if &type is %BAR_RX_EVENT
+ * @u:union holding the fields above
  */
 struct ieee80211_event {
 	enum ieee80211_event_type type;
 	union {
 		struct ieee80211_rssi_event rssi;
 		struct ieee80211_mlme_event mlme;
+		struct ieee80211_ba_event ba;
 	} u;
 };
 
@@ -3001,7 +3017,7 @@ enum ieee80211_reconfig_type {
  *	The callback can sleep.
  * @event_callback: Notify driver about any event in mac80211. See
  *	&enum ieee80211_event_type for the different types.
- *	The callback can sleep.
+ *	The callback must be atomic.
  *
  * @release_buffered_frames: Release buffered frames according to the given
  *	parameters. In the case where the driver buffers some frames for

net/mac80211/rx.c

@@ -2427,6 +2427,9 @@ ieee80211_rx_h_ctrl(struct ieee80211_rx_data *rx, struct sk_buff_head *frames)
 		struct {
 			__le16 control, start_seq_num;
 		} __packed bar_data;
+		struct ieee80211_event event = {
+			.type = BAR_RX_EVENT,
+		};
 
 		if (!rx->sta)
 			return RX_DROP_MONITOR;
@@ -2442,6 +2445,9 @@ ieee80211_rx_h_ctrl(struct ieee80211_rx_data *rx, struct sk_buff_head *frames)
 			return RX_DROP_MONITOR;
 
 		start_seq_num = le16_to_cpu(bar_data.start_seq_num) >> 4;
+		event.u.ba.tid = tid;
+		event.u.ba.ssn = start_seq_num;
+		event.u.ba.sta = &rx->sta->sta;
 
 		/* reset session timer */
 		if (tid_agg_rx->timeout)
@@ -2454,6 +2460,8 @@ ieee80211_rx_h_ctrl(struct ieee80211_rx_data *rx, struct sk_buff_head *frames)
 						 start_seq_num, frames);
 		spin_unlock(&tid_agg_rx->reorder_lock);
 
+		drv_event_callback(rx->local, rx->sdata, &event);
+
 		kfree_skb(skb);
 		return RX_QUEUED;
 	}