mac80211: provide per-TID RX/TX MSDU counters

Implement the new counters cfg80211 can now advertise to userspace.
The TX code is in the sequence number handler, which is a bit odd,
but that place already knows the TID and frame type, so it was
easiest and least impact there.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>

net/mac80211/rx.c

@@ -2314,6 +2314,15 @@ ieee80211_rx_h_data(struct ieee80211_rx_data *rx)
 	if (unlikely(!ieee80211_is_data_present(hdr->frame_control)))
 		return RX_DROP_MONITOR;
 
+	if (rx->sta) {
+		/* The security index has the same property as needed
+		 * for the rx_msdu field, i.e. it is IEEE80211_NUM_TIDS
+		 * for non-QoS-data frames. Here we know it's a data
+		 * frame, so count MSDUs.
+		 */
+		rx->sta->rx_msdu[rx->security_idx]++;
+	}
+
 	/*
 	 * Send unexpected-4addr-frame event to hostapd. For older versions,
 	 * also drop the frame to cooked monitor interfaces.