Re: [ovs-dev] [PATCH RFC] netdev-dpdk: Fix device obtain mac address when received first packet in vhost type

[Yuanhan Liu <yliu@fridaylinux.org>]

On Fri, Nov 24, 2017 at 05:59:09PM +0800, Chen Hailin wrote:
> Hi Aaron Conole && Jianfeng,
> 
> The stp could not work in ovs-dpdk vhostuser.
> Because the attached vhost device doesn't have MAC address.
> 
> Now we have two ways to solve this problem.
> 1. The vhost learns MAC address from packet like as my first patch.

I do agree with Aaron this is not the right way.

> 2. The virtio notifies MAC address actively to vhost user .

Unfortunately, AFAIK, there is no way to achieve that so far. we could
either let virtio/QEMU to expose the CQ to vhost or add a new VHOST_USER
message to carry the mac address. While vhost-user is a generic interface
adding a virtio-net specific message also doesn't seem quite right.
Exposing CQ is probably the best we can do.

Anyway, both need spec change.

	--yliu
> 
> In my opinions,  if we treat it as a device,  we should allocate 
> MAC address for the device when the VM started.
> 
> Which one do you think better?
> 
> 
> 
> Best Regards,
> Chen Hailin
> chenhl@arraynetworks.com.cn
>  
> From: Aaron Conole
> Date: 2017-11-18 10:00
> To: Hailin Chen
> CC: ovs-dev@openvswitch.org; Maxime Coquelin; cloud@arraynetworks.com.cn
> Subject: Re: [ovs-dev] [PATCH RFC] netdev-dpdk: Fix device obtain mac address when received first packet in vhost type
> Hi Hailin,
>  
> Hailin Chen <chenhl@arraynetworks.com.cn> writes:
>  
> > The stp could not work on netdev-dpdk if network is loop.
> > Because the stp protocol negotiates designate port by sending
> > BPDU packets which contains MAC address.
> > However the device doesn't have MAC address in vhostuser type.
> > Thus, function send_bpdu_cb would not send BPDU packets.
> >
> > This patch will set the MAC for device when received first packet.
> >
> > Signed-off-by: Hailin Chen <chenhl@arraynetworks.com.cn>
> > ---
>  
> Thanks for the patch.
>  
> In general, I don't think this is the right approach to deal with this
> type of issue.  I believe the problem statement is that OvS bridge is
> unaware of the guest MAC address - did I get it right?  In that case, I
> would think that a better way to solve this would be to have virtio tell
> the mac address of the guest.  I don't recall right now if that's
> allowed in the virtio spec, but I do remember some kind of negotiation
> features.
>  
> I've CC'd Maxime, who is one of the maintainers of the virtio code from
> DPDK side.  Perhaps there is an alternate way to solve this.
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