Re: [Qemu-devel] [PATCH] net: fix qemu_announce_self not emitting packets

[Paolo Bonzini <pbonzini@redhat.com>]

On 07/06/2016 10:02, Peter Lieven wrote:
> Am 07.06.2016 um 09:55 schrieb Paolo Bonzini:
>>
>> On 07/06/2016 09:37, Peter Lieven wrote:
>>> commit fefe2a78 accidently dropped the code path for injecting
>>> raw packets. This feature is needed for sending gratuitous ARPs
>>> after an incoming migration has completed. The result is increased
>>> network downtime for vservers where the network card is not virtio-net
>>> with the VIRTIO_NET_F_GUEST_ANNOUNCE feature.
>>>
>>> Fixes: fefe2a78abde932e0f340b21bded2c86def1d242
>>> Cc: qemu-stable@nongnu.org
>>> Cc: yanghy@cn.fujitsu.com
>>> Signed-off-by: Peter Lieven <pl@kamp.de>
>>> ---
>>>   net/net.c | 6 +++++-
>>>   1 file changed, 5 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/net/net.c b/net/net.c
>>> index 5f3e5a9..d5834ea 100644
>>> --- a/net/net.c
>>> +++ b/net/net.c
>>> @@ -722,7 +722,11 @@ ssize_t qemu_deliver_packet_iov(NetClientState
>>> *sender,
>>>           return 0;
>>>       }
>>>   -    if (nc->info->receive_iov) {
>>> +    if (flags & QEMU_NET_PACKET_FLAG_RAW && iovcnt == 1 &&
>>> +        nc->info->receive_raw) {
>>> +        /* this is required for qemu_announce_self() */
>>> +        ret = nc->info->receive_raw(nc, iov[0].iov_base,
>>> iov[0].iov_len);
>> Possibly move "iovcnt == 1" from the if condition to an assertion
>> inside it?
> 
> I do not know if there is any other user that emits raw packets than
> qemu_announce_self.

Currently all senders of raw packets go through qemu_send_packet_raw,
which has iovcnt == 1.

> The question is do you want to abort or just return -1 (which is the
> case without this patch).

I want to abort, since it's currently impossible to get into that
situation.  If someone wants to introduce
qemu_sendv_packet_async_with_flags, they must also introduce
nc->info->receive_raw_iov or something like that.

Thanks,

Paolo