As on the tx path of vxlan over esp, skb->inner_network_header would be
set on vxlan_xmit() and xfrm4_tunnel_encap_add(), and the later one can
overwrite the former one. It causes skb_udp_tunnel_segment() to use a
wrong skb->inner_network_header, then the issue occurs.
This patch is to fix it by calling xfrm_output_gso() instead when the
inner_protocol is set, in which gso_segment of inner_protocol will be
done first.
While at it, also improve some code around.
Fixes: 7862b4058b9f ("esp: Add gso handlers for esp4 and esp6") Reported-by: Xiumei Mu <xmu@redhat.com> Signed-off-by: Xin Long <lucien.xin@gmail.com> Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>