TCA_GACT_PARMS
if (nla_put(skb, TCA_GACT_PARMS, sizeof(opt), &opt))
[TCA_GACT_PARMS] = { .len = sizeof(struct tc_gact) },
if (tb[TCA_GACT_PARMS] == NULL)
parm = nla_data(tb[TCA_GACT_PARMS]);