Add bssid/freq hint for driver-based BSS selection

This uses the new nl80211 attributes to allow the connect command to
provide bssid and freq hints to the driver without limiting roaming to
the specific BSS/frequency. This can be used by drivers that perform
internal BSS selection (WPA_DRIVER_FLAGS_BSS_SELECTION) as a candidate
for initial association.

Signed-off-by: Dmitry Shmidt <dimitrysh@google.com>

src/drivers/driver.h

@@ -403,6 +403,16 @@ struct wpa_driver_associate_params {
 	 * responsible for selecting with which BSS to associate. */
 	const u8 *bssid;
 
+	/**
+	 * bssid_hint - BSSID of a proposed AP
+	 *
+	 * This indicates which BSS has been found a suitable candidate for
+	 * initial association for drivers that use driver/firmwate-based BSS
+	 * selection. Unlike the @bssid parameter, @bssid_hint does not limit
+	 * the driver from selecting other BSSes in the ESS.
+	 */
+	const u8 *bssid_hint;
+
 	/**
 	 * ssid - The selected SSID
 	 */
@@ -420,6 +430,16 @@ struct wpa_driver_associate_params {
 	 */
 	int freq;
 
+	/**
+	 * freq_hint - Frequency of the channel the proposed AP is using
+	 *
+	 * This provides a channel on which a suitable BSS has been found as a
+	 * hint for the driver. Unlike the @freq parameter, @freq_hint does not
+	 * limit the driver from selecting other channels for
+	 * driver/firmware-based BSS selection.
+	 */
+	int freq_hint;
+
 	/**
 	 * bg_scan_period - Background scan period in seconds, 0 to disable
 	 * background scan, or -1 to indicate no change to default driver

src/drivers/driver_nl80211.c

@@ -8391,6 +8391,13 @@ static int nl80211_connect_common(struct wpa_driver_nl80211_data *drv,
 		NLA_PUT(msg, NL80211_ATTR_MAC, ETH_ALEN, params->bssid);
 	}
 
+	if (params->bssid_hint) {
+		wpa_printf(MSG_DEBUG, "  * bssid_hint=" MACSTR,
+			   MAC2STR(params->bssid_hint));
+		NLA_PUT(msg, NL80211_ATTR_MAC_HINT, ETH_ALEN,
+			params->bssid_hint);
+	}
+
 	if (params->freq) {
 		wpa_printf(MSG_DEBUG, "  * freq=%d", params->freq);
 		NLA_PUT_U32(msg, NL80211_ATTR_WIPHY_FREQ, params->freq);
@@ -8398,6 +8405,12 @@ static int nl80211_connect_common(struct wpa_driver_nl80211_data *drv,
 	} else
 		drv->assoc_freq = 0;
 
+	if (params->freq_hint) {
+		wpa_printf(MSG_DEBUG, "  * freq_hint=%d", params->freq_hint);
+		NLA_PUT_U32(msg, NL80211_ATTR_WIPHY_FREQ_HINT,
+			    params->freq_hint);
+	}
+
 	if (params->bg_scan_period >= 0) {
 		wpa_printf(MSG_DEBUG, "  * bg scan period=%d",
 			   params->bg_scan_period);

wpa_supplicant/wpa_supplicant.c

@@ -1656,6 +1656,8 @@ static void wpas_start_assoc_cb(struct wpa_radio_work *work, int deinit)
 			params.bssid = bss->bssid;
 			params.freq = bss->freq;
 		}
+		params.bssid_hint = bss->bssid;
+		params.freq_hint = bss->freq;
 	} else {
 		params.ssid = ssid->ssid;
 		params.ssid_len = ssid->ssid_len;