Re: [PATCH net-next 8/8] virtio_net: introduce receive_small_xdp()

On Thu, 30 Mar 2023 12:48:22 +0200, Paolo Abeni [off-list ref] wrote:

On Tue, 2023-03-28 at 20:04 +0800, Xuan Zhuo wrote:

quoted

@@ -949,15 +1042,11 @@ static struct sk_buff *receive_small(struct net_device *dev,
 {
 	struct sk_buff *skb;
 	struct bpf_prog *xdp_prog;
-	unsigned int xdp_headroom = (unsigned long)ctx;
-	unsigned int header_offset = VIRTNET_RX_PAD + xdp_headroom;
+	unsigned int header_offset = VIRTNET_RX_PAD;
 	unsigned int headroom = vi->hdr_len + header_offset;

This changes (reduces) the headroom for non-xpd-pass skbs.

[...]

quoted

+	buf += header_offset;
+	memcpy(skb_vnet_hdr(skb), buf, vi->hdr_len);

AFAICS, that also means that receive_small(), for such packets, will
look for the virtio header in a different location. Is that expected?

That is a mistake.

Will fix.

Thanks.

Thanks.

Paolo