This adds HT capability IE parsing for scanning. You will now
be able to easily review what HT capabilities your AP supports
with a simple iw scan.
Sreenshot of a scan result of a 1-stream AP:
BSS 00:03:7f:12:34:56 (on wlan6)
TSF: 1817911860 usec (0d, 00:30:17)
freq: 2427
beacon interval: 100
capability: ESS ShortPreamble SpectrumMgmt ShortSlotTime (0x0521)
signal: -60.00 dBm
last seen: 11390 ms ago
SSID: sucia-perra
Supported rates: 1.0* 2.0* 5.5* 11.0* 6.0 9.0 12.0 18.0
DS Parameter set: channel 4
Power constraint: 0 dB
ERP: <no flags>
Extended supported rates: 24.0 36.0 48.0 54.0
HT capabilities:
Capabilities: 0x010c
HT20
SM Power Save disabled
RX STBC 1-stream
Max AMSDU length: 7935 bytes
No DSSS/CCK HT40
Maximum RX AMPDU length 65535 bytes (exponent: 0x003)
Minimum RX AMPDU time spacing: 1/2 usec (0x02)
MCS set: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ff
Supported RX MCS Indexes:
MCS Index 0
MCS Index 1
MCS Index 2
MCS Index 3
MCS Index 4
MCS Index 5
MCS Index 6
MCS Index 7
No TX MCS set defined
Extended capabilities: HT Information Exchange Supported
WMM: * Parameter version 1
* u-APSD
* BE: CW 15-1023, AIFSN 3
* BK: CW 15-1023, AIFSN 7
* VI: CW 7-15, AIFSN 2, TXOP 3008 usec
* VO: acm CW 3-7, AIFSN 2, TXOP 1504 usec
Signed-off-by: Luis R. Rodriguez <lrodriguez@xxxxxxxxxxx>
---
scan.c | 175 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
1 files changed, 175 insertions(+), 0 deletions(-)
diff --git a/scan.c b/scan.c
index 99df462..1889bd0 100644
--- a/scan.c
+++ b/scan.c
@@ -421,6 +421,180 @@ static void print_rsn(const uint8_t type, uint8_t len, const uint8_t *data)
print_rsn_ie("CCMP", "IEEE 802.1X", len, data);
}
+/*
+ * There are only 4 possible values, we just use a case instead of computing it,
+ * but technically this can also be computed through the formula:
+ *
+ * Max AMPDU length = (2 ^ (13 + exponent)) - 1 bytes
+ */
+__u32 compute_ampdu_length(__u8 exponent)
+{
+ switch (exponent) {
+ case 0: return 8191; /* (2 ^(13 + 0)) -1 */
+ case 1: return 16383; /* (2 ^(13 + 1)) -1 */
+ case 2: return 32767; /* (2 ^(13 + 2)) -1 */
+ case 3: return 65535; /* (2 ^(13 + 3)) -1 */
+ default: return 0;
+ }
+}
+
+const char *print_ampdu_space(__u8 space)
+{
+ switch (space) {
+ case 0: return "No restriction";
+ case 1: return "1/4 usec";
+ case 2: return "1/2 usec";
+ case 3: return "1 usec";
+ case 4: return "2 usec";
+ case 5: return "4 usec";
+ case 6: return "8 usec";
+ case 7: return "16 usec";
+ default:
+ return "Uknown";
+ }
+}
+
+static void print_ht_capa(const uint8_t type, uint8_t len, const uint8_t *data)
+{
+#define PRINT_HT_CAP(_cond, _str) \
+ do { \
+ if (_cond) \
+ printf("\t\t\t" _str "\n"); \
+ } while (0)
+ struct ht_cap_data {
+ __u16 cap;
+ __u8 ampdu_params;
+ struct {
+ __u8 rx_mcs_bitmask[10]; /* last 3 bits reserved */
+ __u16 max_rx_rate_1mbps: 10,
+ reserved_0: 6;
+ __u8 tx_rx_mcs_defined:1,
+ tx_rx_mcs_not_equal:1,
+ tx_max_streams:2,
+ tx_unequal_modulation:1,
+ reserved_1:3; /* 3 reserved bits here */
+ __u8 reserved_2[3]; /* 24 reserved bits here = 27 */
+ } mcs_set;
+ __u16 ht_extend_cap;
+ __u32 tx_beamform_cap;
+ __u8 asel_cap;
+ } __attribute__((packed)) ht_cap;
+ struct ht_cap_data *htc = &ht_cap;
+ __u8 ampdu_exponent, ampdu_spacing, bit;
+ __u32 max_ampdu_length, i;
+ bool tx_rx_mcs_equal = false;
+
+ if (len != 26) {
+ printf("\n\t\tHT Capability IE len != expected 26 bytes, skipping parse\n");
+ return;
+ }
+
+ memcpy(&ht_cap, data, 26);
+
+ printf("\n\t\tCapabilities: %#.4x\n", htc->cap);
+
+ PRINT_HT_CAP((htc->cap & BIT(0)), "RX LDCP");
+ PRINT_HT_CAP((htc->cap & BIT(1)), "HT20/HT40");
+ PRINT_HT_CAP(!(htc->cap & BIT(1)), "HT20");
+
+ PRINT_HT_CAP(((htc->cap >> 2) & 0x3) == 0, "Static SM Power Save");
+ PRINT_HT_CAP(((htc->cap >> 2) & 0x3) == 1, "Dynamic SM Power Save");
+ PRINT_HT_CAP(((htc->cap >> 2) & 0x3) == 3, "SM Power Save disabled");
+
+ PRINT_HT_CAP((htc->cap & BIT(4)), "RX Greenfield");
+ PRINT_HT_CAP((htc->cap & BIT(5)), "RX HT20 SGI");
+ PRINT_HT_CAP((htc->cap & BIT(6)), "RX HT40 SGI");
+ PRINT_HT_CAP((htc->cap & BIT(7)), "TX STBC");
+
+ PRINT_HT_CAP(((htc->cap >> 8) & 0x3) == 0, "No RX STBC");
+ PRINT_HT_CAP(((htc->cap >> 8) & 0x3) == 1, "RX STBC 1-stream");
+ PRINT_HT_CAP(((htc->cap >> 8) & 0x3) == 2, "RX STBC 2-streams");
+ PRINT_HT_CAP(((htc->cap >> 8) & 0x3) == 3, "RX STBC 3-streams");
+
+ PRINT_HT_CAP((htc->cap & BIT(10)), "HT Delayed Block Ack");
+
+ PRINT_HT_CAP((htc->cap & BIT(11)), "Max AMSDU length: 3839 bytes");
+ PRINT_HT_CAP(!(htc->cap & BIT(11)), "Max AMSDU length: 7935 bytes");
+
+ /*
+ * For beacons and probe response this would mean the BSS
+ * does or does not allow the usage of DSSS/CCK HT40.
+ * Otherwise it means the STA does or does not use
+ * DSSS/CCK HT40.
+ */
+ PRINT_HT_CAP((htc->cap & BIT(12)), "DSSS/CCK HT40");
+ PRINT_HT_CAP(!(htc->cap & BIT(12)), "No DSSS/CCK HT40");
+
+ /* BIT(13) is reserved */
+
+ PRINT_HT_CAP((htc->cap & BIT(14)), "40 MHz Intolerant");
+
+ PRINT_HT_CAP((htc->cap & BIT(15)), "L-SIG TXOP protection");
+
+ ampdu_exponent = htc->ampdu_params & 0x3;
+ max_ampdu_length = compute_ampdu_length(ampdu_exponent);
+ if (max_ampdu_length) {
+ printf("\t\tMaximum RX AMPDU length %d bytes (exponent: 0x0%02x)\n",
+ compute_ampdu_length(ampdu_exponent), ampdu_exponent);
+ }
+ else
+ printf("\t\tMaximum RX AMPDU length: unrecognized bytes "
+ "(exponent: %d)\n", ampdu_exponent);
+
+
+ ampdu_spacing = (htc->ampdu_params >> 2) & 0x3 ;
+ printf("\t\tMinimum RX AMPDU time spacing: %s (0x%02x)\n",
+ print_ampdu_space(ampdu_spacing), ampdu_spacing);
+
+ /* This is the whole MCS set, which is 16 bytes */
+ printf("\t\tMCS set: ");
+ data+=2;
+ for (i = 15; i != 0; i--) {
+ printf(" %.2x", data[i]);
+ }
+ printf("\n");
+
+ if (htc->mcs_set.tx_rx_mcs_defined && htc->mcs_set.tx_rx_mcs_not_equal)
+ tx_rx_mcs_equal = true;
+ if (tx_rx_mcs_equal)
+ printf("\t\tSupported TX/RX MCS Indexes:\n");
+ else
+ printf("\t\tSupported RX MCS Indexes:\n");
+ /*
+ * Parses the RX MCS rates. Only 10 bits correspond to actual MCS rates
+ * MCS [0-76]
+ */
+ for (i = 0; i < 10; i++) {
+ for (bit = 0; bit < 8; bit++) {
+ /* Only bits 0-76 are valid, bits 76-79 are reserved */
+ if (((i * 8) + bit) > 76)
+ break;
+ if (htc->mcs_set.rx_mcs_bitmask[i] & BIT(bit))
+ printf("\t\t\tMCS Index %d\n",
+ (i * 8) + bit);
+ }
+ }
+
+ if (!htc->mcs_set.tx_rx_mcs_defined) {
+ /* This is actually quite common */
+ printf("\t\tNo TX MCS set defined\n");
+ goto out;
+ }
+
+ if (htc->mcs_set.tx_rx_mcs_not_equal) {
+ printf("\t\tMaximum supported TX spatial streams: %d\n",
+ htc->mcs_set.tx_max_streams);
+ printf("\t\tTX unequal modulation ");
+ if (htc->mcs_set.tx_unequal_modulation)
+ printf("supported\n");
+ else
+ printf("unsupported\n");
+ }
+
+out:
+ return;
+}
+
static void print_capabilities(const uint8_t type, uint8_t len, const uint8_t *data)
{
int i, base, bit;
@@ -518,6 +692,7 @@ static const struct ie_print ieprinters[] = {
[7] = { "Country", print_country, 3, 255, BIT(PRINT_SCAN), },
[32] = { "Power constraint", print_powerconstraint, 1, 1, BIT(PRINT_SCAN), },
[42] = { "ERP", print_erp, 1, 255, BIT(PRINT_SCAN), },
+ [45] = { "HT capabilities", print_ht_capa, 1, 255, BIT(PRINT_SCAN), },
[48] = { "RSN", print_rsn, 2, 255, BIT(PRINT_SCAN), },
[50] = { "Extended supported rates", print_supprates, 0, 255, BIT(PRINT_SCAN), },
[127] = { "Extended capabilities", print_capabilities, 0, 255, BIT(PRINT_SCAN), },
--
1.6.3.3
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