Re: [Qemu-devel] [PATCH v2] net: Add support of VIRTIO_NET_F_GUEST_ANNOUNCE for vhost-net/vhost-user

[Stefan Hajnoczi]

On Mon, Jun 8, 2015 at 3:05 PM, Thibaut Collet <address@hidden> wrote:
>> I think Jason is pointing out that your patch lacks support for guests
>> that do not negotiate VIRTIO_NET_F_GUEST_ANNOUNCE.
>
> I have understood the issue with old guest pointed by Jason.
> I have thinking about the best way to do solve it and any advices are
> welcome.

1. Add vhost-user virtio-net command to inject packets

Add a new VhostUserRequest VHOST_USER_NET_INJECT_PACKET allowing QEMU
to hand a packet to the vhost-user process for injection.  This
command is virtio-net specific and fails if called on a different
device type.

2. Fail negotiation when VIRTIO_NET_F_GUEST_ANNOUNCE is not accepted

This is only really possible in VIRTIO 1.0 and later.  Pre-1.0 does
not allow the device to reject due to disabled features.

file:///home/stefanha/virtio/trunk/virtio-v1.0-cs02.html#x1-450001

Therefore this is not a great solution.

3. The easiest solution - nop .receive()

Just implement a nop .receive() which drops the packet and prints a
warning message to stderr.  This way VIRTIO_NET_F_GUEST_ANNOUNCE
guests work while legacy guests don't send a gratuitous ARP packet.

Stefan