npf_conndb_getnext
if ((con = npf_conndb_getnext(conn_db, con)) == head) {
npf_conn_t * npf_conndb_getnext(npf_conndb_t *, npf_conn_t *);
con = npf_conndb_getnext(cd, NULL);
npf_conn_t *next = npf_conndb_getnext(cd, con);
conn = npf_conndb_getnext(cd, conn);