th_trace_ref
extern boolean_t th_trace_ref(const void *, ip_stack_t *);
if (!th_trace_ref(ipif, ipif->ipif_ill->ill_ipst)) {
if (!th_trace_ref(ill, ill->ill_ipst)) {
if (th_trace_ref(ire, ire->ire_ipst)) {
if (!th_trace_ref(ncec, ncec->ncec_ipst)) {