Re: [Qemu-devel] [PATCH V6 02/10] net/filter-mirror.c: Make filter mirror support vnet support.

[Jason Wang]

On 2017年06月14日 16:04, Zhang Chen wrote:


On 06/13/2017 05:14 PM, Jason Wang wrote:


On 2017年06月12日 17:27, Zhang Chen wrote:

+        if (nf->direction == NET_FILTER_DIRECTION_RX ||
+            nf->direction == NET_FILTER_DIRECTION_ALL) {
+            vnet_hdr_len = nf->netdev->vnet_hdr_len;

This can only work if e.g virtio-net set its own vnet_hdr_len. But 
looks like it use guest_hdr_len instead.

I see in hw/net/virtio-net.c use the 
"qemu_set_vnet_hdr_len(nc->peer, n->guest_hdr_len);" to
set the nf->netdev->vnet_hdr_len, any case not include here? 

You mean:

        if (peer_has_vnet_hdr(n) &&
            qemu_has_vnet_hdr_len(nc->peer, n->guest_hdr_len)) {
            qemu_set_vnet_hdr_len(nc->peer, n->guest_hdr_len);
            n->host_hdr_len = n->guest_hdr_len;
        }

?

From the code, it only set peer's vnet header when peer supports 
vnet_hdr up to n->guest_hdr_len. If peer can't, virtio-net will strip 
the header.

So, We should get the n->guest_hdr_len in another way? like set a new 
parameter in NetClientState?
Any suggestion about it?

Thanks
Zhang Chen

Rethink about this, a question is do we really care guest vnet header 
len? During guest transmission, when packet reaches netfilter. The 
vnet_header should have been stripped to netdev->vnet_hdr_len.

I still think use nf->netdev->vnet_hdr_len is sufficient.

Thanks



Thanks