Re: [PATCH] net: tun: fix tun_xdp_one() for IFF_TUN mode

On Tue, 2021-06-22 at 15:51 +0800, Jason Wang wrote:

quoted

@@ -2388,14 +2406,18 @@ static int tun_xdp_one(struct tun_struct *tun,
          skb_reserve(skb, xdp->data - xdp->data_hard_start);
          skb_put(skb, xdp->data_end - xdp->data);
   
-       if (virtio_net_hdr_to_skb(skb, gso, tun_is_little_endian(tun))) {
+       if (!gso)
+               skb_reset_mac_header(skb);
+       else if (virtio_net_hdr_to_skb(skb, gso, tun_is_little_endian(tun))) {
                  atomic_long_inc(&tun->rx_frame_errors);
                  kfree_skb(skb);

This should work as well.

Actually there's no need for the skb_reset_mac_header() as that's going
to happen anyway just a few lines down — either from eth_type_trans()
or explicitly in the IFF_TUN code path that I added in my first patch.

I also stripped out a lot more code from vhost_net_build_xdp() in the
!sock_hlen case where it was pointless.

https://git.infradead.org/users/dwmw2/linux.git/shortlog/vhost-net

I'll repost the whole series after I take look at whether I can get it
to work without *either* side doing the vnet header, and add a test
case based on my userspace code in 
https://gitlab.com/openconnect/openconnect/-/blob/vhost/vhost.c