# \[PATCH net-next v4 20/33\] vhost\_net: also populate XDP frame size

- From: Jesper Dangaard Brouer \<hidden\>
- Date: 2020-05-14 10:50:52 
- List: netdev
- Page: https://ratatoskr.run/netdev/2020/05/7734148
- Thread: https://ratatoskr.run/netdev/2020/05/7734128/t.md

```text
In vhost_net_build_xdp() the 'buf' that gets queued via an xdp_buff
have embedded a struct tun_xdp_hdr (located at xdp->data_hard_start)
which contains the buffer length 'buflen' (with tailroom for
skb_shared_info). Also storing this buflen in xdp->frame_sz, does not
obsolete struct tun_xdp_hdr, as it also contains a struct
virtio_net_hdr with other information.

Cc: Jason Wang <redacted>
Signed-off-by: Jesper Dangaard Brouer <redacted>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Acked-by: Jason Wang <redacted>
---
 drivers/vhost/net.c |    1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
index 2927f02cc7e1..516519dcc8ff 100644
--- a/drivers/vhost/net.c
+++ b/drivers/vhost/net.c
@@ -747,6 +747,7 @@ static int vhost_net_build_xdp(struct vhost_net_virtqueue *nvq,
 	xdp->data = buf + pad;
 	xdp->data_end = xdp->data + len;
 	hdr->buflen = buflen;
+	xdp->frame_sz = buflen;
 
 	--net->refcnt_bias;
 	alloc_frag->offset += buflen;


```