get_random_once
get_random_once(test_key, sizeof(test_key));
get_random_once((buf), (nbytes))
get_random_once(&nf_conntrack_hash_rnd, sizeof(nf_conntrack_hash_rnd));
get_random_once(&nf_ct_expect_hashrnd, sizeof(nf_ct_expect_hashrnd));
get_random_once(&nf_nat_hash_rnd, sizeof(nf_nat_hash_rnd));