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 <[email protected]>
---
Sorry, resending, I mistakenly sent to lkml instead of linux-wireless.
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
On Thu, Feb 18, 2010 at 1:40 PM, Lukáš Turek <[email protected]> wrote:
> On 18.2.2010 03:13 Luis R. Rodriguez wrote:
>> coverage = (distance + 449) / 450;
>> coverage/450 = distance + 499
>> (coverage/450) - 499 = distance
>
> Inverting the formula like this doesn't make much sense...
>
> The addition of 449 is there to round the resulting number up, because the
> coverage class limits maximum distance and if it was rounded down as normal
> integer division does, the resulting ACK timeout would be too low.
>
> However, if you subtract 449 in the inverted formula, you get something like a
> minimum distance for the coverage class - which doesn't mean anything,
> because higher ACK timeout and slot time works for smaller distances too.
> Maximum distance is what's interesting to the user. So the correct
> calculation is just multiplying the coverage class by 450 as I'm doing in
> print_phy_handler():
>
> printf("\tCoverage class: %d (up to %dm)\n", coverage, 450 * coverage);
Thanks I'll fix and resend.
Luis
On 18.2.2010 03:13 Luis R. Rodriguez wrote:
> coverage = (distance + 449) / 450;
> coverage/450 = distance + 499
> (coverage/450) - 499 = distance
Inverting the formula like this doesn't make much sense...
The addition of 449 is there to round the resulting number up, because the
coverage class limits maximum distance and if it was rounded down as normal
integer division does, the resulting ACK timeout would be too low.
However, if you subtract 449 in the inverted formula, you get something like a
minimum distance for the coverage class - which doesn't mean anything,
because higher ACK timeout and slot time works for smaller distances too.
Maximum distance is what's interesting to the user. So the correct
calculation is just multiplying the coverage class by 450 as I'm doing in
print_phy_handler():
printf("\tCoverage class: %d (up to %dm)\n", coverage, 450 * coverage);
Lukas Turek