hostapd: Allow coexistance of HT BSSes with WEP/TKIP BSSes

In multi BSS setups it wasn't possible to set up an HT BSS in
conjunction with a WEP/TKIP BSS. HT needed to be turned off entirely
to allow WEP/TKIP BSSes to be used.

In order to allow HT BSSes to coexist with non-HT WEP/TKIP BSSes add a
new BSS conf attribute "disable_11n" which disables HT capabilities on a
single BSS by suppressing HT IEs in the beacon and probe response
frames. Furthermore, mark all STAs associated to a WEP/TKIP BSS as
non-HT STAs. The disable_11n parameter is used internally; no new entry
is parsed from hostapd.conf.

This allows a non-HT WEP/TKIP BSS to coexist with a HT BSS without
having to disable HT mode entirely. Nevertheless, all STAs associated to
the WEP/TKIP BSS will only be served as if they were non-HT STAs.

Signed-off-by: Helmut Schaa <helmut.schaa@googlemail.com>

hostapd/config_file.c

@@ -1090,17 +1090,18 @@ static int hostapd_config_check_bss(struct hostapd_bss_config *bss,
 #ifdef CONFIG_IEEE80211N
 	if (conf->ieee80211n &&
 	    bss->ssid.security_policy == SECURITY_STATIC_WEP) {
+		bss->disable_11n = 1;
 		wpa_printf(MSG_ERROR, "HT (IEEE 802.11n) with WEP is not "
-			   "allowed");
-		return -1;
+			   "allowed, disabling HT capabilities");
 	}
 
 	if (conf->ieee80211n && bss->wpa &&
 	    !(bss->wpa_pairwise & WPA_CIPHER_CCMP) &&
 	    !(bss->rsn_pairwise & WPA_CIPHER_CCMP)) {
+		bss->disable_11n = 1;
 		wpa_printf(MSG_ERROR, "HT (IEEE 802.11n) with WPA/WPA2 "
-			   "requires CCMP to be enabled");
-		return -1;
+			   "requires CCMP to be enabled, disabling HT "
+			   "capabilities");
 	}
 #endif /* CONFIG_IEEE80211N */
 

src/ap/ap_config.h

@@ -328,6 +328,7 @@ struct hostapd_bss_config {
 #define TDLS_PROHIBIT BIT(0)
 #define TDLS_PROHIBIT_CHAN_SWITCH BIT(1)
 	int tdls;
+	int disable_11n;
 };
 
 

src/ap/ieee802_11.c

@@ -675,7 +675,7 @@ static u16 check_assoc_ies(struct hostapd_data *hapd, struct sta_info *sta,
 	if (resp != WLAN_STATUS_SUCCESS)
 		return resp;
 #ifdef CONFIG_IEEE80211N
-	resp = copy_sta_ht_capab(sta, elems.ht_capabilities,
+	resp = copy_sta_ht_capab(hapd, sta, elems.ht_capabilities,
 				 elems.ht_capabilities_len);
 	if (resp != WLAN_STATUS_SUCCESS)
 		return resp;

src/ap/ieee802_11.h

@@ -57,8 +57,8 @@ void ieee802_11_send_sa_query_req(struct hostapd_data *hapd,
 void hostapd_get_ht_capab(struct hostapd_data *hapd,
 			  struct ieee80211_ht_capabilities *ht_cap,
 			  struct ieee80211_ht_capabilities *neg_ht_cap);
-u16 copy_sta_ht_capab(struct sta_info *sta, const u8 *ht_capab,
-		      size_t ht_capab_len);
+u16 copy_sta_ht_capab(struct hostapd_data *hapd, struct sta_info *sta,
+		      const u8 *ht_capab, size_t ht_capab_len);
 void update_ht_state(struct hostapd_data *hapd, struct sta_info *sta);
 void hostapd_tx_status(struct hostapd_data *hapd, const u8 *addr,
 		       const u8 *buf, size_t len, int ack);

src/ap/ieee802_11_ht.c

@@ -30,7 +30,8 @@ u8 * hostapd_eid_ht_capabilities(struct hostapd_data *hapd, u8 *eid)
 	struct ieee80211_ht_capabilities *cap;
 	u8 *pos = eid;
 
-	if (!hapd->iconf->ieee80211n || !hapd->iface->current_mode)
+	if (!hapd->iconf->ieee80211n || !hapd->iface->current_mode ||
+	    hapd->conf->disable_11n)
 		return eid;
 
 	*pos++ = WLAN_EID_HT_CAP;
@@ -58,7 +59,7 @@ u8 * hostapd_eid_ht_operation(struct hostapd_data *hapd, u8 *eid)
 	struct ieee80211_ht_operation *oper;
 	u8 *pos = eid;
 
-	if (!hapd->iconf->ieee80211n)
+	if (!hapd->iconf->ieee80211n || hapd->conf->disable_11n)
 		return eid;
 
 	*pos++ = WLAN_EID_HT_OPERATION;
@@ -160,11 +161,13 @@ int hostapd_ht_operation_update(struct hostapd_iface *iface)
 }
 
 
-u16 copy_sta_ht_capab(struct sta_info *sta, const u8 *ht_capab,
-		      size_t ht_capab_len)
+u16 copy_sta_ht_capab(struct hostapd_data *hapd, struct sta_info *sta,
+		      const u8 *ht_capab, size_t ht_capab_len)
 {
+	/* Disable HT caps for STAs associated to no-HT BSSes. */
 	if (!ht_capab ||
-	    ht_capab_len < sizeof(struct ieee80211_ht_capabilities)) {
+	    ht_capab_len < sizeof(struct ieee80211_ht_capabilities) ||
+	    hapd->conf->disable_11n) {
 		sta->flags &= ~WLAN_STA_HT;
 		os_free(sta->ht_capabilities);
 		sta->ht_capabilities = NULL;