nl80211: fix scheduled scan RSSI matchset attribute confusion

The scheduled scan matchsets were intended to be a list of filters,
with the found BSS having to pass at least one of them to be passed
to the host. When the RSSI attribute was added, however, this was
broken and currently wpa_supplicant adds that attribute in its own
matchset; however, it doesn't intend that to mean that anything
that passes the RSSI filter should be passed to the host, instead
it wants it to mean that everything needs to also have higher RSSI.

This is semantically problematic because we have a list of filters
like [ SSID1, SSID2, SSID3, RSSI ] with no real indication which
one should be OR'ed and which one AND'ed.

To fix this, move the RSSI filter attribute into each matchset. As
we need to stay backward compatible, treat a matchset with only the
RSSI attribute as a "default RSSI filter" for all other matchsets,
but only if there are other matchsets (an RSSI-only matchset by
itself is still desirable.)

To make driver implementation easier, keep a global min_rssi_thold
for the entire request as well. The only affected driver is ath6kl.

I found this when I looked into the code after Raja Mani submitted
a patch fixing the n_match_sets calculation to disregard the RSSI,
but that patch didn't address the semantic issue.

Reported-by: Raja Mani <rmani@qti.qualcomm.com>
Acked-by: Luciano Coelho <luciano.coelho@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

2 files changed, 17 insertions, 5 deletions

diff --git a/drivers/net/wireless/ath/ath6kl/cfg80211.c b/drivers/net/wireless/ath/ath6kl/cfg80211.c
index fd4c89df67e..eba32f56850 100644
--- a/drivers/net/wireless/ath/ath6kl/cfg80211.c
+++ b/drivers/net/wireless/ath/ath6kl/cfg80211.c
@@ -3256,6 +3256,15 @@ static int ath6kl_cfg80211_sscan_start(struct wiphy *wiphy,
 	struct ath6kl_vif *vif = netdev_priv(dev);
 	u16 interval;
 	int ret, rssi_thold;
+	int n_match_sets = request->n_match_sets;
+
+	/*
+	 * If there's a matchset w/o an SSID, then assume it's just for
+	 * the RSSI (nothing else is currently supported) and ignore it.
+	 * The device only supports a global RSSI filter that we set below.
+	 */
+	if (n_match_sets == 1 && !request->match_sets[0].ssid.ssid_len)
+		n_match_sets = 0;
 
 	if (ar->state != ATH6KL_STATE_ON)
 		return -EIO;
@@ -3268,11 +3277,11 @@ static int ath6kl_cfg80211_sscan_start(struct wiphy *wiphy,
 	ret = ath6kl_set_probed_ssids(ar, vif, request->ssids,
 				      request->n_ssids,
 				      request->match_sets,
-				      request->n_match_sets);
+				      n_match_sets);
 	if (ret < 0)
 		return ret;
 
-	if (!request->n_match_sets) {
+	if (!n_match_sets) {
 		ret = ath6kl_wmi_bssfilter_cmd(ar->wmi, vif->fw_vif_idx,
 					       ALL_BSS_FILTER, 0);
 		if (ret < 0)
@@ -3286,12 +3295,12 @@ static int ath6kl_cfg80211_sscan_start(struct wiphy *wiphy,
 
 	if (test_bit(ATH6KL_FW_CAPABILITY_RSSI_SCAN_THOLD,
 		     ar->fw_capabilities)) {
-		if (request->rssi_thold <= NL80211_SCAN_RSSI_THOLD_OFF)
+		if (request->min_rssi_thold <= NL80211_SCAN_RSSI_THOLD_OFF)
 			rssi_thold = 0;
-		else if (request->rssi_thold < -127)
+		else if (request->min_rssi_thold < -127)
 			rssi_thold = -127;
 		else
-			rssi_thold = request->rssi_thold;
+			rssi_thold = request->min_rssi_thold;
 
 		ret = ath6kl_wmi_set_rssi_filter_cmd(ar->wmi, vif->fw_vif_idx,
 						     rssi_thold);
diff --git a/drivers/net/wireless/iwlwifi/mvm/scan.c b/drivers/net/wireless/iwlwifi/mvm/scan.c
index 0e000796061..9674bfd978f 100644
--- a/drivers/net/wireless/iwlwifi/mvm/scan.c
+++ b/drivers/net/wireless/iwlwifi/mvm/scan.c
@@ -595,6 +595,9 @@ static void iwl_scan_offload_build_ssid(struct cfg80211_sched_scan_request *req,
 	 * config match list.
 	 */
 	for (i = 0; i < req->n_match_sets && i < PROBE_OPTION_MAX; i++) {
+		/* skip empty SSID matchsets */
+		if (!req->match_sets[i].ssid.ssid_len)
+			continue;
 		scan->direct_scan[i].id = WLAN_EID_SSID;
 		scan->direct_scan[i].len = req->match_sets[i].ssid.ssid_len;
 		memcpy(scan->direct_scan[i].ssid, req->match_sets[i].ssid.ssid,