scan: Implement scan_oper_class_to_band

This function takes an Operating Channel and a Country String to convert
it into a band.  Using scan_oper_class_to_band and scan_channel_to_freq,
an Operating Channel, a Country String and a Channel Number together can
be converted into an actual frequency.  EU and US country codes based on
wpa_supplicant's tables.

src/scan.c

@@ -1113,6 +1113,110 @@ uint32_t scan_channel_to_freq(uint8_t channel, enum scan_band band)
 	return 0;
 }
 
+static const char *const oper_class_us_codes[] = {
+	"US", "CA"
+};
+
+static const char *const oper_class_eu_codes[] = {
+	"AL", "AM", "AT", "AZ", "BA", "BE", "BG", "BY", "CH", "CY", "CZ", "DE",
+	"DK", "EE", "EL", "ES", "FI", "FR", "GE", "HR", "HU", "IE", "IS", "IT",
+	"LI", "LT", "LU", "LV", "MD", "ME", "MK", "MT", "NL", "NO", "PL", "PT",
+	"RO", "RS", "RU", "SE", "SI", "SK", "TR", "UA", "UK"
+};
+
+/* Annex E, table E-1 */
+static const uint8_t oper_class_us_to_global[] = {
+	[1]  = 115, [2]  = 118, [3]  = 124, [4]  = 121,
+	[5]  = 125, [6]  = 103, [7]  = 103, [8]  = 102,
+	[9]  = 102, [10] = 101, [11] = 101, [12] = 81,
+	[13] = 94,  [14] = 95,  [15] = 96,  [22] = 116,
+	[23] = 119, [24] = 122, [25] = 126, [26] = 126,
+	[27] = 117, [28] = 120, [29] = 123, [30] = 127,
+	[31] = 127, [32] = 83,  [33] = 84
+};
+
+/* Annex E, table E-2 */
+static const uint8_t oper_class_eu_to_global[] = {
+	[1]  = 115, [2]  = 118, [3]  = 121, [4]  = 81,
+	[5]  = 116, [6]  = 119, [7]  = 122, [8]  = 117,
+	[9]  = 120, [10] = 123, [11] = 83,  [12] = 84,
+	[17] = 125
+};
+
+/* Annex E, table E-3 */
+static const uint8_t oper_class_jp_to_global[] = {
+	[1]  = 115, [2]  = 112, [3]  = 112, [4]  = 112,
+	[5]  = 112, [6]  = 112, [7]  = 109, [8]  = 109,
+	[9]  = 109, [10] = 109, [11] = 109, [12] = 113,
+	[13] = 113, [14] = 113, [15] = 113, [16] = 110,
+	[17] = 110, [18] = 110, [19] = 110, [20] = 110,
+	[21] = 114, [22] = 114, [23] = 114, [24] = 114,
+	[25] = 111, [26] = 111, [27] = 111, [28] = 111,
+	[29] = 111, [30] = 81,  [31] = 82,  [32] = 118,
+	[33] = 118, [34] = 121, [35] = 121, [36] = 116,
+	[37] = 119, [38] = 119, [39] = 122, [40] = 122,
+	[41] = 117, [42] = 120, [43] = 120, [44] = 123,
+	[45] = 123, [46] = 104, [47] = 104, [48] = 104,
+	[49] = 104, [50] = 104, [51] = 105, [52] = 105,
+	[53] = 105, [54] = 105, [55] = 105, [56] = 83,
+	[57] = 84,  [58] = 121
+};
+
+/* Annex E, table E-4 (only 2.4GHz and 4.9 / 5GHz bands) */
+static const enum scan_band oper_class_to_band_global[] = {
+	[81 ... 84]   = SCAN_BAND_2_4_GHZ,
+	[104 ... 127] = SCAN_BAND_5_GHZ,
+};
+
+enum scan_band scan_oper_class_to_band(const uint8_t *country,
+					uint8_t oper_class)
+{
+	unsigned int i;
+	int table = 0;
+
+	if (country && country[2] >= 1 && country[2] <= 4)
+		table = country[2];
+	else if (country) {
+		for (i = 0; i < L_ARRAY_SIZE(oper_class_us_codes); i++)
+			if (!memcmp(oper_class_us_codes[i], country, 2)) {
+				/* Use table E-1 */
+				table = 1;
+				break;
+			}
+
+		for (i = 0; i < L_ARRAY_SIZE(oper_class_eu_codes); i++)
+			if (!memcmp(oper_class_eu_codes[i], country, 2)) {
+				/* Use table E-2 */
+				table = 2;
+				break;
+			}
+
+		if (!memcmp("JP", country, 2))
+			/* Use table E-3 */
+			table = 3;
+	}
+
+	switch (table) {
+	case 1:
+		if (oper_class < L_ARRAY_SIZE(oper_class_us_to_global))
+			oper_class = oper_class_us_to_global[oper_class];
+		break;
+	case 2:
+		if (oper_class < L_ARRAY_SIZE(oper_class_eu_to_global))
+			oper_class = oper_class_eu_to_global[oper_class];
+		break;
+	case 3:
+		if (oper_class < L_ARRAY_SIZE(oper_class_jp_to_global))
+			oper_class = oper_class_jp_to_global[oper_class];
+		break;
+	}
+
+	if (oper_class < L_ARRAY_SIZE(oper_class_to_band_global))
+		return oper_class_to_band_global[oper_class];
+	else
+		return 0;
+}
+
 struct scan_freq_set {
 	uint16_t channels_2ghz;
 	struct l_uintset *channels_5ghz;

src/scan.h

@@ -88,6 +88,8 @@ void bss_get_supported_ciphers(struct scan_bss *bss,
 
 uint8_t scan_freq_to_channel(uint32_t freq, enum scan_band *out_band);
 uint32_t scan_channel_to_freq(uint8_t channel, enum scan_band band);
+enum scan_band scan_oper_class_to_band(const uint8_t *country,
+					uint8_t oper_class);
 
 struct scan_freq_set *scan_freq_set_new(void);
 void scan_freq_set_free(struct scan_freq_set *freqs);