wpa_supplicant: Allow global scan frequencies configuration

This allows one to limit the channels that wpa_supplicant will
scan. This is a useful addition to the freq_list configurable
in the network {} section.

Signed-hostap: Ben Greear <greearb@candelatech.com>

wpa_supplicant/config.c

@@ -1826,6 +1826,7 @@ void wpa_config_free(struct wpa_config *config)
 	os_free(config->pssid);
 	os_free(config->p2p_pref_chan);
 	os_free(config->autoscan);
+	os_free(config->freq_list);
 	wpabuf_free(config->wps_nfc_dh_pubkey);
 	wpabuf_free(config->wps_nfc_dh_privkey);
 	wpabuf_free(config->wps_nfc_dev_pw);
@@ -2733,6 +2734,21 @@ static int wpa_global_config_parse_bin(const struct global_parse_data *data,
 }
 
 
+static int wpa_config_process_freq_list(const struct global_parse_data *data,
+					struct wpa_config *config, int line,
+					const char *value)
+{
+	int *freqs;
+
+	freqs = wpa_config_parse_int_array(value);
+	if (freqs == NULL)
+		return -1;
+	os_free(config->freq_list);
+	config->freq_list = freqs;
+	return 0;
+}
+
+
 static int wpa_config_process_country(const struct global_parse_data *data,
 				      struct wpa_config *config, int line,
 				      const char *pos)
@@ -3088,6 +3104,7 @@ static const struct global_parse_data global_fields[] = {
 	{ INT(beacon_int), 0 },
 	{ FUNC(ap_vendor_elements), 0 },
 	{ INT_RANGE(ignore_old_scan_res, 0, 1), 0 },
+	{ FUNC(freq_list), 0 },
 };
 
 #undef FUNC

wpa_supplicant/config.h

@@ -644,6 +644,14 @@ struct wpa_config {
 	 */
 	unsigned int max_num_sta;
 
+	/**
+	 * freq_list - Array of allowed scan frequencies or %NULL for all
+	 *
+	 * This is an optional zero-terminated array of frequencies in
+	 * megahertz (MHz) to allow for narrowing scanning range.
+	 */
+	int *freq_list;
+
 	/**
 	 * changed_parameters - Bitmap of changed parameters since last update
 	 */

wpa_supplicant/config_file.c

@@ -1015,6 +1015,16 @@ static void wpa_config_write_global(FILE *f, struct wpa_config *config)
 	if (config->ignore_old_scan_res)
 		fprintf(f, "ignore_old_scan_res=%d\n",
 			config->ignore_old_scan_res);
+
+	if (config->freq_list && config->freq_list[0]) {
+		int i;
+		fprintf(f, "freq_list=");
+		for (i = 0; config->freq_list[i]; i++) {
+			fprintf(f, "%s%u", i > 0 ? " " : "",
+				config->freq_list[i]);
+		}
+		fprintf(f, "\n");
+	}
 }
 
 #endif /* CONFIG_NO_CONFIG_WRITE */

wpa_supplicant/scan.c

@@ -749,6 +749,13 @@ ssid_list_set:
 		os_free(wpa_s->next_scan_freqs);
 	wpa_s->next_scan_freqs = NULL;
 
+	/* See if user specified frequencies. If so, scan only those. */
+	if (wpa_s->conf->freq_list && !params.freqs) {
+		wpa_dbg(wpa_s, MSG_DEBUG,
+			"Optimize scan based on conf->freq_list");
+		int_array_concat(&params.freqs, wpa_s->conf->freq_list);
+	}
+
 	params.filter_ssids = wpa_supplicant_build_filter_ssids(
 		wpa_s->conf, &params.num_filter_ssids);
 	if (extra_ie) {

wpa_supplicant/wpa_supplicant.conf

@@ -524,6 +524,9 @@ fast_reauth=1
 # set, scan results that do not match any of the specified frequencies are not
 # considered when selecting a BSS.
 #
+# This can also be set on the outside of the network block. In this case,
+# it limits the frequencies that will be scanned.
+#
 # bgscan: Background scanning
 # wpa_supplicant behavior for background scanning can be specified by
 # configuring a bgscan module. These modules are responsible for requesting
@@ -1231,3 +1234,10 @@ SGVsbG8gV29ybGQhCg==
 network={
 	key_mgmt=NONE
 }
+
+
+# Example config file that will only scan on channel 36.
+freq_list=5180
+network={
+	key_mgmt=NONE
+}