From: Yuya Kusakabe <yuya.kusakabe@gmail.com>
Date: Tue, 25 Feb 2020 12:32:11 +0900
Subject: virtio_net: Keep vnet header zeroed if XDP is loaded for small buffer
Patch-mainline: v5.7-rc1
Git-commit: f1d4884d6871ded0592604b0e72e4a7bd292eab9
References: git-fixes

We do not want to care about the vnet header in receive_small() if XDP
is loaded, since we can not know whether or not the packet is modified
by XDP.

Fixes: f6b10209b90d ("virtio-net: switch to use build_skb() for small buffer")
Signed-off-by: Yuya Kusakabe <yuya.kusakabe@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Jason Wang <jasowang@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Link: https://lore.kernel.org/bpf/20200225033212.437563-1-yuya.kusakabe@gmail.com
Acked-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
---
 drivers/net/virtio_net.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -747,10 +747,10 @@ static struct sk_buff *receive_small(str
 	}
 	skb_reserve(skb, headroom - delta);
 	skb_put(skb, len);
-	if (!delta) {
+	if (!xdp_prog) {
 		buf += header_offset;
 		memcpy(skb_vnet_hdr(skb), buf, vi->hdr_len);
-	} /* keep zeroed vnet hdr since packet was changed by bpf */
+	} /* keep zeroed vnet hdr since XDP is loaded */
 
 err:
 	return skb;