linux-kernel - [PATCH bpf-next v6 1/2] virtio_net: keep vnet header zeroed if XDP is loaded for small buffer

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Date:   Tue, 25 Feb 2020 12:32:11 +0900
From:   Yuya Kusakabe <yuya.kusakabe@...il.com>
To:     jasowang@...hat.com
Cc:     andriin@...com, ast@...nel.org, bpf@...r.kernel.org,
        daniel@...earbox.net, davem@...emloft.net, hawk@...nel.org,
        john.fastabend@...il.com, kafai@...com, kuba@...nel.org,
        linux-kernel@...r.kernel.org, mst@...hat.com,
        netdev@...r.kernel.org, songliubraving@...com, yhs@...com,
        yuya.kusakabe@...il.com
Subject: [PATCH bpf-next v6 1/2] virtio_net: keep vnet header zeroed if XDP is loaded for small buffer

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@...il.com>
---
 drivers/net/virtio_net.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 2fe7a3188282..f39d0218bdaa 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -735,10 +735,10 @@ static struct sk_buff *receive_small(struct net_device *dev,
 	}
 	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;
-- 
2.24.1