nl80211: Add per peer statistics to compute FCS error rate

Add support for drivers to report the total number of MPDUs received
and the number of MPDUs received with an FCS error from a specific
peer. These counters will be incremented only when the TA of the
frame matches the MAC address of the peer irrespective of FCS
error.

It should be noted that the TA field in the frame might be corrupted
when there is an FCS error and TA matching logic would fail in such
cases. Hence, FCS error counter might not be fully accurate, but it can
provide help in detecting bad RX links in significant number of cases.
This FCS error counter without full accuracy can be used, e.g., to
trigger a kick-out of a connected client with a bad link in AP mode to
force such a client to roam to another AP.

Signed-off-by: Ankita Bajaj <[e-mail]>
Signed-off-by: Jouni Malinen <[e-mail]>
Signed-off-by: Johannes Berg <[e-mail]>

include/net/cfg80211.h

···
  * @ack_signal: signal strength (in dBm) of the last ACK frame.
  * @avg_ack_signal: average rssi value of ack packet for the no of msdu's has
  *	been sent.
+ * @rx_mpdu_count: number of MPDUs received from this station
+ * @fcs_err_count: number of packets (MPDUs) received from this station with
+ *	an FCS error. This counter should be incremented only when TA of the
+ *	received packet with an FCS error matches the peer MAC address.
  */
 struct station_info {
 	u64 filled;
···
 	struct cfg80211_tid_stats *pertid;
 	s8 ack_signal;
 	s8 avg_ack_signal;
+
+	u32 rx_mpdu_count;
+	u32 fcs_err_count;
 };
 
 #if IS_ENABLED(CONFIG_CFG80211)

include/uapi/linux/nl80211.h

···
  * @NL80211_STA_INFO_PAD: attribute used for padding for 64-bit alignment
  * @NL80211_STA_INFO_ACK_SIGNAL: signal strength of the last ACK frame(u8, dBm)
  * @NL80211_STA_INFO_ACK_SIGNAL_AVG: avg signal strength of ACK frames (s8, dBm)
+ * @NL80211_STA_INFO_RX_MPDUS: total number of received packets (MPDUs)
+ *	(u32, from this station)
+ * @NL80211_STA_INFO_FCS_ERROR_COUNT: total number of packets (MPDUs) received
+ *	with an FCS error (u32, from this station). This count may not include
+ *	some packets with an FCS error due to TA corruption. Hence this counter
+ *	might not be fully accurate.
  * @__NL80211_STA_INFO_AFTER_LAST: internal
  * @NL80211_STA_INFO_MAX: highest possible station info attribute
  */
···
 	NL80211_STA_INFO_PAD,
 	NL80211_STA_INFO_ACK_SIGNAL,
 	NL80211_STA_INFO_ACK_SIGNAL_AVG,
+	NL80211_STA_INFO_RX_MPDUS,
+	NL80211_STA_INFO_FCS_ERROR_COUNT,
 
 	/* keep last */
 	__NL80211_STA_INFO_AFTER_LAST,

net/wireless/nl80211.c

···
 	PUT_SINFO_U64(RX_DROP_MISC, rx_dropped_misc);
 	PUT_SINFO_U64(BEACON_RX, rx_beacon);
 	PUT_SINFO(BEACON_SIGNAL_AVG, rx_beacon_signal_avg, u8);
+	PUT_SINFO(RX_MPDUS, rx_mpdu_count, u32);
+	PUT_SINFO(FCS_ERROR_COUNT, fcs_err_count, u32);
 	if (wiphy_ext_feature_isset(&rdev->wiphy,
 				    NL80211_EXT_FEATURE_ACK_SIGNAL_SUPPORT)) {
 		PUT_SINFO(ACK_SIGNAL, ack_signal, u8);