nl80211: Support setting sched scan RSSI threshold

Allow the user to configure an RSSI threshold in dBm below which the
nl80211 driver won't report scan results. Currently only supported
during scheduled (PNO) scans.

Signed-off-by: Thomas Pedersen <c_tpeder@qca.qualcomm.com>
Signed-hostap: Jouni Malinen <jouni@qca.qualcomm.com>

src/drivers/driver.h

@@ -273,6 +273,15 @@ struct wpa_driver_scan_params {
 	 */
 	size_t num_filter_ssids;
 
+	/**
+	 * filter_rssi - Filter by RSSI
+	 *
+	 * The driver may filter scan results in firmware to reduce host
+	 * wakeups and thereby save power. Specify the RSSI threshold in s32
+	 * dBm.
+	 */
+	s32 filter_rssi;
+
 	/**
 	 * p2p_probe - Used to disable CCK (802.11b) rates for P2P probes
 	 *

src/drivers/driver_nl80211.c

@@ -3612,6 +3612,7 @@ static int wpa_driver_nl80211_sched_scan(void *priv,
 	struct wpa_driver_nl80211_data *drv = bss->drv;
 	int ret = 0;
 	struct nl_msg *msg, *ssids, *freqs, *match_set_ssid, *match_sets;
+	struct nl_msg *match_set_rssi;
 	size_t i;
 
 #ifdef ANDROID
@@ -3640,8 +3641,9 @@ static int wpa_driver_nl80211_sched_scan(void *priv,
 
 	NLA_PUT_U32(msg, NL80211_ATTR_SCHED_SCAN_INTERVAL, interval);
 
-	if (drv->num_filter_ssids &&
-	    (int) drv->num_filter_ssids <= drv->capa.max_match_sets) {
+	if ((drv->num_filter_ssids &&
+	    (int) drv->num_filter_ssids <= drv->capa.max_match_sets) ||
+	    params->filter_rssi) {
 		match_sets = nlmsg_alloc();
 
 		for (i = 0; i < drv->num_filter_ssids; i++) {
@@ -3661,6 +3663,18 @@ static int wpa_driver_nl80211_sched_scan(void *priv,
 			nlmsg_free(match_set_ssid);
 		}
 
+		if (params->filter_rssi) {
+			match_set_rssi = nlmsg_alloc();
+			NLA_PUT_U32(match_set_rssi,
+				    NL80211_SCHED_SCAN_MATCH_ATTR_RSSI,
+				    params->filter_rssi);
+			wpa_printf(MSG_MSGDUMP,
+				   "nl80211: Sched scan RSSI filter %d dBm",
+				   params->filter_rssi);
+			nla_put_nested(match_sets, 0, match_set_rssi);
+			nlmsg_free(match_set_rssi);
+		}
+
 		nla_put_nested(msg, NL80211_ATTR_SCHED_SCAN_MATCH,
 			       match_sets);
 		nlmsg_free(match_sets);

wpa_supplicant/config.c

@@ -2908,6 +2908,7 @@ static const struct global_parse_data global_fields[] = {
 	{ INT(bss_expiration_age), 0 },
 	{ INT(bss_expiration_scan_count), 0 },
 	{ INT_RANGE(filter_ssids, 0, 1), 0 },
+	{ INT_RANGE(filter_rssi, -100, 0), 0 },
 	{ INT(max_num_sta), 0 },
 	{ INT_RANGE(disassoc_low_ack, 0, 1), 0 },
 #ifdef CONFIG_HS20

wpa_supplicant/config.h

@@ -574,6 +574,14 @@ struct wpa_config {
 	 */
 	int filter_ssids;
 
+	/**
+	 * filter_rssi - RSSI-based scan result filtering
+	 *
+	 * 0 = do not filter scan results
+	 * -n = filter scan results below -n dBm
+	 */
+	int filter_rssi;
+
 	/**
 	 * max_num_sta - Maximum number of STAs in an AP/P2P GO
 	 */

wpa_supplicant/ctrl_iface.c

@@ -98,6 +98,9 @@ static int pno_start(struct wpa_supplicant *wpa_s)
 		ssid = ssid->next;
 	}
 
+	if (wpa_s->conf->filter_rssi)
+		params.filter_rssi = wpa_s->conf->filter_rssi;
+
 	ret = wpa_drv_sched_scan(wpa_s, &params, 10 * 1000);
 	os_free(params.filter_ssids);
 	if (ret == 0)