station: fallback to periodic scan if regdom unset

The kernel handles setting the regulatory domain by receiving beacons
which set the country IE. Presumably since most regulatory domains
disallow 6GHz the default (world) domain also disables it. This means
until the country is set, 6GHz is disabled.

This poses a problem for IWD's quick scanning since it only scans a few
frequencies and this likely isn't enough beacons for the firmware to
update the country, leaving 6Ghz inaccessable to the user without manual
intervention (e.g. iw scan passive, or periodic scans by IWD).

To try and work around this limitation the quick scan logic has been
updated to check if a 6GHz AP has been connected to before and if that
frequency is disabled (but supported). If this is the case IWD will opt
for a full passive scan rather than scanning a limited set of
frequencies.

src/station.c

@@ -112,6 +112,8 @@ struct station {
 	struct scan_freq_set *scan_freqs_order[3];
 	unsigned int dbus_scan_subset_idx;
 
+	uint32_t wiphy_watch;
+
 	bool preparing_roam : 1;
 	bool roam_scan_full : 1;
 	bool signal_low : 1;
@@ -1353,11 +1355,35 @@ static void station_quick_scan_destroy(void *userdata)
 static int station_quick_scan_trigger(struct station *station)
 {
 	struct scan_freq_set *known_freq_set;
+	bool known_6ghz;
+	const struct scan_freq_set *disabled = wiphy_get_disabled_freqs(
+								station->wiphy);
+
+	if (wiphy_regdom_is_updating(station->wiphy)) {
+		l_debug("regdom is updating, delaying quick scan");
+		return -EAGAIN;
+	}
 
 	known_freq_set = known_networks_get_recent_frequencies(5);
 	if (!known_freq_set)
 		return -ENODATA;
 
+	known_6ghz = scan_freq_set_get_bands(known_freq_set) & BAND_FREQ_6_GHZ;
+
+	/*
+	 * This means IWD has previously connected to a 6GHz AP before, but now
+	 * the regulatory domain disallows 6GHz likely caused by a reboot, the
+	 * firmware going down, or a regulatory update. The only way to
+	 * re-enable 6GHz is to get enough beacons via scanning for the firmware
+	 * to set the regulatory domain. A quick scan is very unlikely to do
+	 * this since its so limited, so return an error which will fall back to
+	 * full autoconnect.
+	 */
+	if ((scan_freq_set_get_bands(disabled) & BAND_FREQ_6_GHZ) &&
+				wiphy_country_is_unknown(station->wiphy) &&
+				known_6ghz)
+		return -ENOTSUP;
+
 	if (!wiphy_constrain_freq_set(station->wiphy, known_freq_set)) {
 		scan_freq_set_free(known_freq_set);
 		return -ENOTSUP;
@@ -1446,6 +1472,7 @@ static void station_enter_state(struct station *station,
 	uint64_t id = netdev_get_wdev_id(station->netdev);
 	struct l_dbus *dbus = dbus_get_bus();
 	bool disconnected;
+	int ret;
 
 	l_debug("Old State: %s, new state: %s",
 			station_state_to_string(station->state),
@@ -1462,7 +1489,8 @@ static void station_enter_state(struct station *station,
 
 	switch (state) {
 	case STATION_STATE_AUTOCONNECT_QUICK:
-		if (!station_quick_scan_trigger(station))
+		ret = station_quick_scan_trigger(station);
+		if (ret == 0 || ret == -EAGAIN)
 			break;
 
 		station->state = STATION_STATE_AUTOCONNECT_FULL;
@@ -3988,6 +4016,35 @@ static void station_fill_scan_freq_subsets(struct station *station)
 	}
 }
 
+static void station_wiphy_watch(struct wiphy *wiphy,
+				enum wiphy_state_watch_event event,
+				void *user_data)
+{
+	struct station *station = user_data;
+	int ret;
+
+	if (event != WIPHY_STATE_WATCH_EVENT_REGDOM_DONE)
+		return;
+
+	/*
+	 * The only state that requires special handling is for
+	 * quick scans since the previous quick scan was delayed until
+	 * the regulatory domain updated. Try again in case 6Ghz is now
+	 * unlocked (unlikely), or advance to full autoconnect. Just in
+	 * case this update came during a quick scan, ignore it.
+	 */
+	if (station->state != STATION_STATE_AUTOCONNECT_QUICK ||
+			station->quick_scan_id)
+		return;
+
+	ret = station_quick_scan_trigger(station);
+	if (!ret)
+		return;
+
+	L_WARN_ON(ret == -EAGAIN);
+	station_enter_state(station, STATION_STATE_AUTOCONNECT_FULL);
+}
+
 static struct station *station_create(struct netdev *netdev)
 {
 	struct station *station;
@@ -4008,6 +4065,10 @@ static struct station *station_create(struct netdev *netdev)
 	station->wiphy = netdev_get_wiphy(netdev);
 	station->netdev = netdev;
 
+	station->wiphy_watch = wiphy_state_watch_add(station->wiphy,
+							station_wiphy_watch,
+							station, NULL);
+
 	l_queue_push_head(station_list, station);
 
 	l_dbus_object_add_interface(dbus, netdev_get_path(netdev),
@@ -4117,6 +4178,8 @@ static void station_free(struct station *station)
 	if (station->scan_freqs_order[2])
 		scan_freq_set_free(station->scan_freqs_order[2]);
 
+	wiphy_state_watch_remove(station->wiphy, station->wiphy_watch);
+
 	l_free(station);
 }