npf_conn_getbackkey
bk = npf_conn_getbackkey(con, alen);
bk = npf_conn_getbackkey(con, con->c_alen);
bk = npf_conn_getbackkey(con, NPF_CONNKEY_ALEN(fw));
bk = npf_conn_getbackkey(con, alen);
bk = npf_conn_getbackkey(con, NPF_CONNKEY_ALEN(fw));
const npf_connkey_t *bk = npf_conn_getbackkey(con, NPF_CONNKEY_ALEN(fw));
npf_connkey_t * npf_conn_getbackkey(npf_conn_t *, unsigned);