Make GKeyDoneStations counting able to recover from mismatches

Previously, a bug in GKeyDoneStations count would remain in effect
until the authenticator is restarted. Make this more robust by
clearing the station count before each rekeying setup. While this
is not really supposed to be needed, there has been bugs in this
area in the past and it is safer to make the implementation recover
from such an issue automatically.

src/ap/wpa_auth.c

@@ -2265,20 +2265,23 @@ static int wpa_group_update_sta(struct wpa_state_machine *sm, void *ctx)
 	if (sm->wpa_ptk_state != WPA_PTK_PTKINITDONE) {
 		wpa_auth_logger(sm->wpa_auth, sm->addr, LOGGER_DEBUG,
 				"Not in PTKINITDONE; skip Group Key update");
+		sm->GUpdateStationKeys = FALSE;
 		return 0;
 	}
 	if (sm->GUpdateStationKeys) {
 		/*
-		 * This should not really happen, but just in case, make sure
-		 * we do not count the same STA twice in GKeyDoneStations.
+		 * This should not really happen, so add a debug log entry.
+		 * Since we clear the GKeyDoneStations before the loop, the
+		 * station needs to be counted here anyway.
 		 */
 		wpa_auth_logger(sm->wpa_auth, sm->addr, LOGGER_DEBUG,
-				"GUpdateStationKeys already set - do not "
-				"increment GKeyDoneStations");
-	} else {
-		sm->group->GKeyDoneStations++;
-		sm->GUpdateStationKeys = TRUE;
+				"GUpdateStationKeys was already set when "
+				"marking station for GTK rekeying");
 	}
+
+	sm->group->GKeyDoneStations++;
+	sm->GUpdateStationKeys = TRUE;
+
 	wpa_sm_step(sm);
 	return 0;
 }
@@ -2307,6 +2310,12 @@ static void wpa_group_setkeys(struct wpa_authenticator *wpa_auth,
 	 * including all STAs that could be in not-yet-completed state. */
 	wpa_gtk_update(wpa_auth, group);
 
+	if (group->GKeyDoneStations) {
+		wpa_printf(MSG_DEBUG, "wpa_group_setkeys: Unexpected "
+			   "GKeyDoneStations=%d when starting new GTK rekey",
+			   group->GKeyDoneStations);
+		group->GKeyDoneStations = 0;
+	}
 	wpa_auth_for_each_sta(wpa_auth, wpa_group_update_sta, NULL);
 	wpa_printf(MSG_DEBUG, "wpa_group_setkeys: GKeyDoneStations=%d",
 		   group->GKeyDoneStations);