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

[Zhang Chen]

On 06/15/2017 12:31 PM, Jason Wang wrote:
> 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.

But we use filter-redirector send packet to colo-compare that get the 
packet with the vnet header.

That is colo-compare see:

address@hidden:colo_compare_pkt_info_src src/dst: 192.168.4.144 
s: seq/ack=2181260317/2075177759 res=0 flags=18 spkt_size: 95

address@hidden:colo_compare_pkt_info_dst src/dst: 192.168.4.88 
d: seq/ack=2181260317/2075177759 res=0 flags=18 dpkt_size: 95

colo-compare ppkt: 0000:  01 00 00 00  00 00 22 00  10 00 00 00  12 14 
fc 1d ......".........
colo-compare ppkt: 0010:  1a 6b 52 54  00 12 34 56  08 00 45 00  00 45 
12 61 .kRT..4V..E..E.a
colo-compare ppkt: 0020:  40 00 40 06  9e 19 c0 a8  04 90 c0 a8  04 58 
04 d2 @address@hidden
colo-compare ppkt: 0030:  ca 98 82 03  64 1d 7b b0  b3 1f 80 18  00 e3 
8a 70 ....d.{........p
colo-compare ppkt: 0040:  00 00 01 01  08 0a 00 00  5b fa 00 4d  f1 aa 
73 65 ........[..M..se
colo-compare ppkt: 0050:  72 76 65 72  20 67 65 74  20 69 74 20  34 36 
38    rver get it 468
colo-compare spkt: 0000:  01 00 00 00  00 00 22 00  10 00 00 00  12 14 
fc 1d ......".........
colo-compare spkt: 0010:  1a 6b 52 54  00 12 34 56  08 00 45 00  00 45 
12 61 .kRT..4V..E..E.a
colo-compare spkt: 0020:  40 00 40 06  9e 19 c0 a8  04 90 c0 a8  04 58 
04 d2 @address@hidden
colo-compare spkt: 0030:  ca 98 82 03  64 1d 7b b0  b3 1f 80 18  00 e3 
8a 70 ....d.{........p
colo-compare spkt: 0040:  00 00 01 01  08 0a 00 00  5c 02 00 4d  f1 aa 
73 65 ........\..M..se
colo-compare spkt: 0050:  72 76 65 72  20 67 65 74  20 69 74 20  34 36 
38    rver get it 468

So, colo-compare need to know the vnet_hdr_len for skip this field, then 
colo-compare
can parse the net packet correctly.
Back to this patch, how should I fix it?

Thanks
Zhang Chen


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

--
Thanks
Zhang Chen