cfg80211: average ack rssi support for data frames

Average ack rssi will be given to userspace via NL80211 interface
if firmware is capable. Userspace tool ‘iw’ can process this
information and give the output as one of the fields in
‘iw dev wlanX station dump’.

Example output :

localhost ~ #iw dev wlan-5000mhz station dump Station
34:f3:9a:aa:3b:29 (on wlan-5000mhz)
        inactive time:  5370 ms
        rx bytes:       85321
        rx packets:     576
        tx bytes:       14225
        tx packets:     71
        tx retries:     0
        tx failed:      2
        beacon loss:    0
        rx drop misc:   0
        signal:         -54 dBm
        signal avg:     -53 dBm
        tx bitrate:     866.7 MBit/s VHT-MCS 9 80MHz short GI VHT-NSS 2
        rx bitrate:     866.7 MBit/s VHT-MCS 9 80MHz short GI VHT-NSS 2
        avg ack signal: -56 dBm
        authorized:     yes
        authenticated:  yes
        associated:     yes
        preamble:       short
        WMM/WME:        yes
        MFP:            no
        TDLS peer:      no
        DTIM period:    2
        beacon interval:100
       short preamble: yes
       short slot time:yes
       connected time: 203 seconds

Main use case is to measure the signal strength of a connected station
to AP. Data packet transmit rates and bandwidth used by station can vary
a lot even if the station is at fixed location, especially if the rates
used are multi stream(2stream, 3stream) rates with different bandwidth(20/40/80 Mhz).
These multi stream rates are sensitive and station can use different transmit power
for each of the rate and bandwidth combinations. RSSI measured from these RX packets
on AP will be not stable and can vary a lot with in a short time.
Whereas 802.11 ack frames from station are sent relatively at a constant
rate (6/12/24 Mbps) with constant bandwidth(20 Mhz).
So average rssi of the ack packets is good and more accurate.

Signed-off-by: Balaji Pothunoori <bpothuno@codeaurora.org>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

include/net/cfg80211.h

@@ -1152,6 +1152,8 @@ struct cfg80211_tid_stats {
  * @pertid: per-TID statistics, see &struct cfg80211_tid_stats, using the last
  *	(IEEE80211_NUM_TIDS) index for MSDUs not encapsulated in QoS-MPDUs.
  * @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.
  */
 struct station_info {
 	u64 filled;
@@ -1197,6 +1199,7 @@ struct station_info {
 	u8 rx_beacon_signal_avg;
 	struct cfg80211_tid_stats pertid[IEEE80211_NUM_TIDS + 1];
 	s8 ack_signal;
+	s8 avg_ack_signal;
 };
 
 #if IS_ENABLED(CONFIG_CFG80211)

include/uapi/linux/nl80211.h

@@ -2981,6 +2981,8 @@ enum nl80211_sta_bss_param {
  *	received from the station (u64, usec)
  * @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_DATA_ACK_SIGNAL_AVG: avg signal strength of (data)
+ *	ACK frame (s8, dBm)
  * @__NL80211_STA_INFO_AFTER_LAST: internal
  * @NL80211_STA_INFO_MAX: highest possible station info attribute
  */
@@ -3020,6 +3022,7 @@ enum nl80211_sta_info {
 	NL80211_STA_INFO_RX_DURATION,
 	NL80211_STA_INFO_PAD,
 	NL80211_STA_INFO_ACK_SIGNAL,
+	NL80211_STA_INFO_DATA_ACK_SIGNAL_AVG,
 
 	/* keep last */
 	__NL80211_STA_INFO_AFTER_LAST,
@@ -5066,6 +5069,9 @@ enum nl80211_feature_flags {
  *	"radar detected" event.
  * @NL80211_EXT_FEATURE_CONTROL_PORT_OVER_NL80211: Driver supports sending and
  *	receiving control port frames over nl80211 instead of the netdevice.
+ * @NL80211_EXT_FEATURE_DATA_ACK_SIGNAL_SUPPORT: This Driver support data ack
+ *	rssi if firmware support, this flag is to intimate about ack rssi
+ *	support to nl80211.
  *
  * @NUM_NL80211_EXT_FEATURES: number of extended features.
  * @MAX_NL80211_EXT_FEATURES: highest extended feature index.
@@ -5098,6 +5104,7 @@ enum nl80211_ext_feature_index {
 	NL80211_EXT_FEATURE_HIGH_ACCURACY_SCAN,
 	NL80211_EXT_FEATURE_DFS_OFFLOAD,
 	NL80211_EXT_FEATURE_CONTROL_PORT_OVER_NL80211,
+	NL80211_EXT_FEATURE_DATA_ACK_SIGNAL_SUPPORT,
 
 	/* add new features before the definition below */
 	NUM_NL80211_EXT_FEATURES,

net/wireless/nl80211.c

@@ -4541,6 +4541,9 @@ static int nl80211_send_station(struct sk_buff *msg, u32 cmd, u32 portid,
 	PUT_SINFO_U64(BEACON_RX, rx_beacon);
 	PUT_SINFO(BEACON_SIGNAL_AVG, rx_beacon_signal_avg, u8);
 	PUT_SINFO(ACK_SIGNAL, ack_signal, u8);
+	if (wiphy_ext_feature_isset(&rdev->wiphy,
+				    NL80211_EXT_FEATURE_DATA_ACK_SIGNAL_SUPPORT))
+		PUT_SINFO(DATA_ACK_SIGNAL_AVG, avg_ack_signal, s8);
 
 #undef PUT_SINFO
 #undef PUT_SINFO_U64