wpa_auth: Deplete group rekey eloop handler for strict rekeying

When strict group rekeying is in effect, every station that leaves will
cause a rekeying to happen 0.5 s after leaving. However, if a lot of
stations join/leave, the previous code could postpone this rekeying
forever, since it always re-registers the handling with a 0.5 s timeout.

Use eloop_deplete_timeout() to address that, only registering the
timeout from scratch if it wasn't pending.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>

src/ap/wpa_auth.c

@@ -698,9 +698,10 @@ void wpa_auth_sta_deinit(struct wpa_state_machine *sm)
 		wpa_auth_logger(sm->wpa_auth, sm->addr, LOGGER_DEBUG,
 				"strict rekeying - force GTK rekey since STA "
 				"is leaving");
-		eloop_cancel_timeout(wpa_rekey_gtk, sm->wpa_auth, NULL);
-		eloop_register_timeout(0, 500000, wpa_rekey_gtk, sm->wpa_auth,
-				       NULL);
+		if (eloop_deplete_timeout(0, 500000, wpa_rekey_gtk,
+					  sm->wpa_auth, NULL) == -1)
+			eloop_register_timeout(0, 500000, wpa_rekey_gtk, sm->wpa_auth,
+					       NULL);
 	}
 
 	eloop_cancel_timeout(wpa_send_eapol_timeout, sm->wpa_auth, sm);