flowi_oif
fl->flowi_oif == oifindex;
if (fl->flowi_oif) {
dev = dev_get_by_index_rcu(net, fl->flowi_oif);
fl->flowi_oif = 0;
fl->flowi_oif = md_info->link;
fl.flowi_oif = xi->p.link;
params.oif = fl->flowi_oif;
oif = fl->flowi_oif ? : fl->flowi_l3mdev;
fl->flowi_oif = skb->skb_iif;
fl->flowi_oif = oif;
fl1->flowi_oif = fl->flowi_oif;