hostapd: Disable VHT caps for STAs when no valid VHT MCS found

Disable VHT caps for STAs for which there is not even a single
allowed MCS in any supported number of streams. i.e STA is
advertising 3 (not supported) as VHT MCS rates for all supported
streams.

Signed-off-by: Rajkumar Manoharan <rmanohar@qti.qualcomm.com>

diff --git a/src/ap/ieee802_11_vht.c b/src/ap/ieee802_11_vht.c
index 159693f..171538a 100644 (file)
--- a/src/ap/ieee802_11_vht.c
+++ b/src/ap/ieee802_11_vht.c
@@ -90,13 +90,55 @@ u8 * hostapd_eid_vht_operation(struct hostapd_data *hapd, u8 *eid)
 }
 
 
+static int check_valid_vht_mcs(struct hostapd_hw_modes *mode,
+                              const u8 *sta_vht_capab)
+{
+       const struct ieee80211_vht_capabilities *vht_cap;
+       struct ieee80211_vht_capabilities ap_vht_cap;
+       u16 sta_rx_mcs_set, ap_tx_mcs_set;
+       int i;
+
+       if (!mode)
+               return 1;
+
+       /*
+        * Disable VHT caps for STAs for which there is not even a single
+        * allowed MCS in any supported number of streams, i.e., STA is
+        * advertising 3 (not supported) as VHT MCS rates for all supported
+        * stream cases.
+        */
+       os_memcpy(&ap_vht_cap.vht_supported_mcs_set, mode->vht_mcs_set,
+                 sizeof(ap_vht_cap.vht_supported_mcs_set));
+       vht_cap = (const struct ieee80211_vht_capabilities *) sta_vht_capab;
+
+       /* AP Tx MCS map vs. STA Rx MCS map */
+       sta_rx_mcs_set = le_to_host16(vht_cap->vht_supported_mcs_set.rx_map);
+       ap_tx_mcs_set = le_to_host16(ap_vht_cap.vht_supported_mcs_set.tx_map);
+
+       for (i = 0; i < VHT_RX_NSS_MAX_STREAMS; i++) {
+               if ((ap_tx_mcs_set & (0x3 << (i * 2))) == 3)
+                       continue;
+
+               if ((sta_rx_mcs_set & (0x3 << (i * 2))) == 3)
+                       continue;
+
+               return 1;
+       }
+
+       wpa_printf(MSG_DEBUG,
+                  "No matching VHT MCS found between AP TX and STA RX");
+       return 0;
+}
+
+
 u16 copy_sta_vht_capab(struct hostapd_data *hapd, struct sta_info *sta,
                       const u8 *vht_capab, size_t vht_capab_len)
 {
        /* Disable VHT caps for STAs associated to no-VHT BSSes. */
        if (!vht_capab ||
            vht_capab_len < sizeof(struct ieee80211_vht_capabilities) ||
-           hapd->conf->disable_11ac) {
+           hapd->conf->disable_11ac ||
+           !check_valid_vht_mcs(hapd->iface->current_mode, vht_capab)) {
                sta->flags &= ~WLAN_STA_VHT;
                os_free(sta->vht_capabilities);
                sta->vht_capabilities = NULL;