Re: [Qemu-devel] [virtio-spec: RFC PATCH] virtio-spec: introduce VIRTIO_NET_F_GUEST_ANNOUNCE

[Jason Wang]

On 10/27/2011 09:32 AM, Rusty Russell wrote:
> On Wed, 26 Oct 2011 16:49:12 +0800, Jason Wang <address@hidden> wrote:
>> Network connections in guest need to be kept after migration. This is done by
>> sending gratuitous packet and let switch learn new port of the mac
>> address. As hypervisor does not have the knowledge of guest network
>> configurations such as tagged vlan or ipv6, it may require guest to send
>> gratuitous packet.
>>
>> This patch introduces a new feature bit of virtio network adapter -
>> VIRTIO_NET_F_GUEST_ANNOUNCE which is used to indicate the ability to send
>> gratuitous packets by guest. A new status bit - VIRTIO_NET_S_ANNOUNCE is also
>> introduced to notify the guest the need for sending gratuitous packet. When
>> guest notice this, it should clear it and send the gratuitous packet.
>>
>> Signed-off-by: Jason Wang <address@hidden>
> 
> Thanks!  I applied it manually, since you didn't enable change tracking
> in LyX (I like to produce a PDF showing changes between versions).
> 

Ok, I would enable it next time.

> Some minor cleanups, here's the main text below.
> 
> Cheers,
> Rusty.
> 
> Gratuitous Packet Sending
> 
> If the driver negotiates the VIRTIO_NET_F_GUEST_ANNOUNCE, it can ask the 
> guest to send gratuitous packets; this is usually done after the guest has 
> been physically migrated, and needs to announce its presence on the new 
> network links. (As hypervisor does not have the knowledge of guest network 
> configuration (eg. tagged vlan) it is simplest to prod the guest in this way).
> 
> The Guest needs to check VIRTIO_NET_S_ANNOUNCE bit in status field when it 
> notices the changes of device configuration.
> 
> Processing this notification involves:
> 
> Clearing VIRTIO_NET_S_ANNOUNCE bit in the status field.
> 
> Sending the gratuitous packets. 

Thanks for the cleanup.

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