AP: Set STA assoc flag in the driver before sending Assoc Resp frame

Previously, stations were added to the driver only after the
(Re)Association Response frame was acked. In the time period between the
station has acked the (Re)Association Response frame and the time the
station was added to the kernel, the station can already start sending
Data frames, which will be dropped by the hardware/driver. In addition
to the data loss, the driver may ignore NDPs with PM bit set from this
STA.

Fix this by setting/adding the STA with associated flag set to the
driver before the AP sends the (Re)Association Response frame with
status success. If the (Re)Association Response frame wasn't acked,
remove the station from the driver.

Note that setting a station to associated state before the non-AP
station acknowledges the (Re)Association Response frame is not compliant
with the IEEE 802.11 standard that specifically states that a non-AP
station should transition to authenticated/associated state only after
it acknowledged the (Re)Association Response frame. However, this is a
justifiable simplification to work around the issue described above since

1. The station will be removed in case it does not acknowledge the
   (Re)Association Response frame.
2. All Data frames would be dropped until the station is set to
   authorized state and there are no known issues with processing the
   other Class 3 frames during the short window before the
   acknowledgement is seen.

Signed-off-by: Andrei Otcheretianski <andrei.otcheretianski@intel.com>

src/ap/ieee802_11.c

@@ -1739,6 +1739,62 @@ static void send_deauth(struct hostapd_data *hapd, const u8 *addr,
 }
 
 
+static int add_associated_sta(struct hostapd_data *hapd,
+			      struct sta_info *sta)
+{
+	struct ieee80211_ht_capabilities ht_cap;
+	struct ieee80211_vht_capabilities vht_cap;
+
+	/*
+	 * Remove the STA entry to ensure the STA PS state gets cleared and
+	 * configuration gets updated. This is relevant for cases, such as
+	 * FT-over-the-DS, where a station re-associates back to the same AP but
+	 * skips the authentication flow, or if working with a driver that
+	 * does not support full AP client state.
+	 */
+	if (!sta->added_unassoc)
+		hostapd_drv_sta_remove(hapd, sta->addr);
+
+#ifdef CONFIG_IEEE80211N
+	if (sta->flags & WLAN_STA_HT)
+		hostapd_get_ht_capab(hapd, sta->ht_capabilities, &ht_cap);
+#endif /* CONFIG_IEEE80211N */
+#ifdef CONFIG_IEEE80211AC
+	if (sta->flags & WLAN_STA_VHT)
+		hostapd_get_vht_capab(hapd, sta->vht_capabilities, &vht_cap);
+#endif /* CONFIG_IEEE80211AC */
+
+	/*
+	 * Add the station with forced WLAN_STA_ASSOC flag. The sta->flags
+	 * will be set when the ACK frame for the (Re)Association Response frame
+	 * is processed (TX status driver event).
+	 */
+	if (hostapd_sta_add(hapd, sta->addr, sta->aid, sta->capability,
+			    sta->supported_rates, sta->supported_rates_len,
+			    sta->listen_interval,
+			    sta->flags & WLAN_STA_HT ? &ht_cap : NULL,
+			    sta->flags & WLAN_STA_VHT ? &vht_cap : NULL,
+			    sta->flags | WLAN_STA_ASSOC, sta->qosinfo,
+			    sta->vht_opmode, sta->added_unassoc)) {
+		hostapd_logger(hapd, sta->addr,
+			       HOSTAPD_MODULE_IEEE80211, HOSTAPD_LEVEL_NOTICE,
+			       "Could not %s STA to kernel driver",
+			       sta->added_unassoc ? "set" : "add");
+
+		if (sta->added_unassoc) {
+			hostapd_drv_sta_remove(hapd, sta->addr);
+			sta->added_unassoc = 0;
+		}
+
+		return -1;
+	}
+
+	sta->added_unassoc = 0;
+
+	return 0;
+}
+
+
 static u16 send_assoc_resp(struct hostapd_data *hapd, struct sta_info *sta,
 			   u16 status_code, int reassoc, const u8 *ies,
 			   size_t ies_len)
@@ -2076,9 +2132,36 @@ static void handle_assoc(struct hostapd_data *hapd,
 	sta->timeout_next = STA_NULLFUNC;
 
  fail:
+	/*
+	 * In case of a successful response, add the station to the driver.
+	 * Otherwise, the kernel may ignore Data frames before we process the
+	 * ACK frame (TX status). In case of a failure, this station will be
+	 * removed.
+	 *
+	 * Note that this is not compliant with the IEEE 802.11 standard that
+	 * states that a non-AP station should transition into the
+	 * authenticated/associated state only after the station acknowledges
+	 * the (Re)Association Response frame. However, still do this as:
+	 *
+	 * 1. In case the station does not acknowledge the (Re)Association
+	 *    Response frame, it will be removed.
+	 * 2. Data frames will be dropped in the kernel until the station is
+	 *    set into authorized state, and there are no significant known
+	 *    issues with processing other non-Data Class 3 frames during this
+	 *    window.
+	 */
+	if (resp == WLAN_STATUS_SUCCESS && add_associated_sta(hapd, sta))
+		resp = WLAN_STATUS_AP_UNABLE_TO_HANDLE_NEW_STA;
+
 	reply_res = send_assoc_resp(hapd, sta, resp, reassoc, pos, left);
-	if (sta->added_unassoc && (resp != WLAN_STATUS_SUCCESS ||
-				   reply_res != WLAN_STATUS_SUCCESS)) {
+
+	/*
+	 * Remove the station in case tranmission of a success response fails
+	 * (the STA was added associated to the driver) or if the station was
+	 * previously added unassociated.
+	 */
+	if ((reply_res != WLAN_STATUS_SUCCESS &&
+	     resp == WLAN_STATUS_SUCCESS) || sta->added_unassoc) {
 		hostapd_drv_sta_remove(hapd, sta->addr);
 		sta->added_unassoc = 0;
 	}
@@ -2574,8 +2657,6 @@ static void handle_assoc_cb(struct hostapd_data *hapd,
 	u16 status;
 	struct sta_info *sta;
 	int new_assoc = 1;
-	struct ieee80211_ht_capabilities ht_cap;
-	struct ieee80211_vht_capabilities vht_cap;
 
 	sta = ap_get_sta(hapd, mgmt->da);
 	if (!sta) {
@@ -2589,21 +2670,26 @@ static void handle_assoc_cb(struct hostapd_data *hapd,
 		wpa_printf(MSG_INFO,
 			   "handle_assoc_cb(reassoc=%d) - too short payload (len=%lu)",
 			   reassoc, (unsigned long) len);
-		goto remove_sta;
+		hostapd_drv_sta_remove(hapd, sta->addr);
+		return;
 	}
 
+	if (reassoc)
+		status = le_to_host16(mgmt->u.reassoc_resp.status_code);
+	else
+		status = le_to_host16(mgmt->u.assoc_resp.status_code);
+
 	if (!ok) {
 		hostapd_logger(hapd, mgmt->da, HOSTAPD_MODULE_IEEE80211,
 			       HOSTAPD_LEVEL_DEBUG,
 			       "did not acknowledge association response");
 		sta->flags &= ~WLAN_STA_ASSOC_REQ_OK;
-		goto remove_sta;
-	}
+		/* The STA is added only in case of SUCCESS */
+		if (status == WLAN_STATUS_SUCCESS)
+			hostapd_drv_sta_remove(hapd, sta->addr);
 
-	if (reassoc)
-		status = le_to_host16(mgmt->u.reassoc_resp.status_code);
-	else
-		status = le_to_host16(mgmt->u.assoc_resp.status_code);
+		return;
+	}
 
 	if (status != WLAN_STATUS_SUCCESS)
 		return;
@@ -2639,54 +2725,6 @@ static void handle_assoc_cb(struct hostapd_data *hapd,
 	sta->sa_query_timed_out = 0;
 #endif /* CONFIG_IEEE80211W */
 
-	/*
-	 * Remove the STA entry in order to make sure the STA PS state gets
-	 * cleared and configuration gets updated in case of reassociation back
-	 * to the same AP.
-	 *
-	 * This is relevant for cases, such as FT over the DS, where a station
-	 * reassociates back to the same AP but skips the authentication flow
-	 * and if working with a driver that doesn't support full AP client
-	 * state.
-	 */
-	if (!sta->added_unassoc)
-		hostapd_drv_sta_remove(hapd, sta->addr);
-
-#ifdef CONFIG_IEEE80211N
-	if (sta->flags & WLAN_STA_HT)
-		hostapd_get_ht_capab(hapd, sta->ht_capabilities, &ht_cap);
-#endif /* CONFIG_IEEE80211N */
-#ifdef CONFIG_IEEE80211AC
-	if (sta->flags & WLAN_STA_VHT)
-		hostapd_get_vht_capab(hapd, sta->vht_capabilities, &vht_cap);
-#endif /* CONFIG_IEEE80211AC */
-
-	if (hostapd_sta_add(hapd, sta->addr, sta->aid, sta->capability,
-			    sta->supported_rates, sta->supported_rates_len,
-			    sta->listen_interval,
-			    sta->flags & WLAN_STA_HT ? &ht_cap : NULL,
-			    sta->flags & WLAN_STA_VHT ? &vht_cap : NULL,
-			    sta->flags, sta->qosinfo, sta->vht_opmode,
-			    sta->added_unassoc)) {
-		hostapd_logger(hapd, sta->addr, HOSTAPD_MODULE_IEEE80211,
-			       HOSTAPD_LEVEL_NOTICE,
-			       "Could not %s STA to kernel driver",
-			       sta->added_unassoc ? "set" : "add");
-		ap_sta_disconnect(hapd, sta, sta->addr,
-				  WLAN_REASON_DISASSOC_AP_BUSY);
-		if (sta->added_unassoc)
-			goto remove_sta;
-		return;
-	}
-
-	/*
-	 * added_unassoc flag is set for a station that was added to the driver
-	 * in unassociated state. Clear this flag once the station has completed
-	 * association, to make sure the STA entry will be cleared from the
-	 * driver in case of reassociation back to the same AP.
-	 */
-	sta->added_unassoc = 0;
-
 	if (sta->flags & WLAN_STA_WDS) {
 		int ret;
 		char ifname_wds[IFNAMSIZ + 1];
@@ -2718,14 +2756,7 @@ static void handle_assoc_cb(struct hostapd_data *hapd,
 	else
 		wpa_auth_sm_event(sta->wpa_sm, WPA_ASSOC);
 	hapd->new_assoc_sta_cb(hapd, sta, !new_assoc);
-
 	ieee802_1x_notify_port_enabled(sta->eapol_sm, 1);
-
-remove_sta:
-	if (sta->added_unassoc) {
-		hostapd_drv_sta_remove(hapd, sta->addr);
-		sta->added_unassoc = 0;
-	}
 }