vxlan_headroom
vxlan_headroom(0)))
err = skb_tunnel_check_pmtu(skb, ndst, vxlan_headroom(flags & VXLAN_F_GPE),
vxlan_headroom((flags & VXLAN_F_GPE) | VXLAN_F_IPV6),
int max_mtu = lowerdev->mtu - vxlan_headroom(vxlan->cfg.flags);
max_mtu = lowerdev->mtu - vxlan_headroom(flags);
needed_headroom += vxlan_headroom(flags);