[PATCH] iw: add country IE parsing

[Luis R. Rodriguez]

Spits out the channels as seen on the IE, useful when debugging
issues with APs. When found the equivalent distance of the
coverage class is printed out in meters.

Signed-off-by: Luis R. Rodriguez <lrodriguez@xxxxxxxxxxx>
---

OK so I removed the line that says we're printing IEs and also
added a distance compuation based on Lukáš Turek's forumal.

coverage = (distance + 449) / 450;
coverage/450 = distance + 499
(coverage/450) - 499 = distance 

So in meters:

distance = (coverage/450) - 499

 scan.c |   96 ++++++++++++++++++++++++++++++++++++++++++++++++++++-----------
 1 files changed, 79 insertions(+), 17 deletions(-)

diff --git a/scan.c b/scan.c
index ec63e61..2d7f15e 100644
--- a/scan.c
+++ b/scan.c
@@ -36,6 +36,23 @@ struct scan_params {
 	bool show_both_ie_sets;
 };
 
+#define IEEE80211_COUNTRY_EXTENSION_ID 201
+
+struct ieee80211_country_ie_triplet {
+	union {
+		struct {
+			__u8 first_channel;
+			__u8 num_channels;
+			__s8 max_power;
+		} __attribute__ ((packed)) chans;
+		struct {
+			__u8 reg_extension_id;
+			__u8 reg_class;
+			__u8 coverage_class;
+		} __attribute__ ((packed)) ext;
+	};
+} __attribute__ ((packed));
+
 static int handle_scan(struct nl80211_state *state,
 		       struct nl_cb *cb,
 		       struct nl_msg *msg,
@@ -143,29 +160,74 @@ static void print_ds(const uint8_t type, uint8_t len, const uint8_t *data)
 	printf(" channel %d\n", data[0]);
 }
 
-static void print_country(const uint8_t type, uint8_t len, const uint8_t *data)
+static const char *country_env_str(char environment)
 {
-	int i;
-
-	printf(" %.*s", 2, data);
-	switch (data[2]) {
+	switch (environment) {
 	case 'I':
-		printf(" (indoor)");
-		break;
+		return "Indoor only";
 	case 'O':
-		printf(" (outdoor)");
-		break;
+		return "Outdoor only";
 	case ' ':
-		printf(" (in/outdoor)");
-		break;
+		return "Indoor/Outdoor";
 	default:
-		printf(" (invalid environment)");
-		break;
+		return "bogus";
 	}
-	printf(", data:");
-	for(i=0; i<len-3; i++)
-		printf(" %.02x", data[i + 3]);
-	printf("\n");
+}
+
+/*
+ * Using the inverse of the distance to coverage class
+ * formula we get that in meters
+ * distance = (coverage/450) - 499
+ */
+static int coverage_class_to_distance(__u8 coverage_class)
+{
+	return (coverage_class / 450) - 499;
+}
+
+static void print_country(const uint8_t type, uint8_t len, const uint8_t *data)
+{
+	printf(" %.*s", 2, data);
+
+	printf("\tEnvironment: %s\n", country_env_str(data[2]));
+
+	data += 3;
+	len -= 3;
+
+	if (len < 3) {
+		printf("\t\tNo country IE triplets present\n");
+		return;
+	}
+
+	while (len >= 3) {
+		int end_channel;
+		struct ieee80211_country_ie_triplet *triplet =
+			(struct ieee80211_country_ie_triplet *) data;
+
+		if (triplet->ext.reg_extension_id >= IEEE80211_COUNTRY_EXTENSION_ID) {
+			printf("\t\tExtension ID: %d Regulatory Class: %d Coverage class: %d (Approx %d meters)\n",
+			       triplet->ext.reg_extension_id,
+			       triplet->ext.reg_class,
+			       triplet->ext.coverage_class,
+			       coverage_class_to_distance(triplet->ext.coverage_class));
+
+			data += 3;
+			len -= 3;
+			continue;
+		}
+
+		/* 2 GHz */
+		if (triplet->chans.first_channel <= 14)
+			end_channel = triplet->chans.first_channel + (triplet->chans.num_channels - 1);
+		else
+			end_channel =  triplet->chans.first_channel + (4 * (triplet->chans.num_channels - 1));
+
+		printf("\t\tChannels [%d - %d]\n", triplet->chans.first_channel, end_channel);
+
+		data += 3;
+		len -= 3;
+	}
+
+	return;
 }
 
 static void print_powerconstraint(const uint8_t type, uint8_t len, const uint8_t *data)
-- 
1.6.3.3

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