ack message pb

res = osip_find_transaction_and_add_event(os, sipevent);	if (res != 0) {		/* this event has no transaction, */		if (MSG_IS_REQUEST(sipevent->sip)){			reqtrans = osip_create_transaction(osip, sipevent);			osip_transaction_add_event(reqtrans, sipevent);		}	}//I set up my ack callback functionosip_set_message_callback(osip ,OSIP_IST_ACK_RECEIVED,  &cb_rcvack);