Re: [Qemu-devel] [Qemu-stable] [PATCH V2] net: fix qemu_announce_self not emitting packets

[Jason Wang <jasowang@redhat.com>]

On 2016年06月08日 15:13, Peter Lieven wrote:
> Am 08.06.2016 um 08:39 schrieb Jason Wang:
>>
>> On 2016年06月07日 21:00, 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: hongyang.yang@easystack.cn
>>> Signed-off-by: Peter Lieven <pl@kamp.de>
>>> ---
>>> v1->v2: assert that only raw packets with a plain buffer come in. [Paolo]
>>>
>>>    net/net.c | 10 +++++++++-
>>>    1 file changed, 9 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/net/net.c b/net/net.c
>>> index 5f3e5a9..5e1b5fa 100644
>>> --- a/net/net.c
>>> +++ b/net/net.c
>>> @@ -714,6 +714,11 @@ ssize_t qemu_deliver_packet_iov(NetClientState *sender,
>>>        NetClientState *nc = opaque;
>>>        int ret;
>>>    +    /* we currently only support sending raw packets via qemu_send_packet_raw.
>>> +     * If we want generic raw iov support we need to implement something like
>>> +     * .receive_raw_iov in NetClientInfo first. */
>>> +    assert(!(flags & QEMU_NET_PACKET_FLAG_RAW) || iovcnt == 1);
>>> +
>>>        if (nc->link_down) {
>>>            return iov_size(iov, iovcnt);
>>>        }
>>> @@ -722,7 +727,10 @@ ssize_t qemu_deliver_packet_iov(NetClientState *sender,
>>>            return 0;
>>>        }
>>>    -    if (nc->info->receive_iov) {
>>> +    if (flags & QEMU_NET_PACKET_FLAG_RAW && 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);
>>> +    } else  if (nc->info->receive_iov) {
>>>            ret = nc->info->receive_iov(nc, iov, iovcnt);
>>>        } else {
>>>            ret = nc_sendv_compat(nc, iov, iovcnt, flags);
>> We still have raw packet support in nv_sendv_compat, can we use it? (and then there's no need for the assert above).
> Okay, so Version 1 of the patch is more appropiate. I would either use V1 or revert fefe2a78. The issue is quite serious
> for live migration.
>
> Peter
>
>

V1 checks iovcnt and call receive_raw with hard coded first iov. Since 
we have raw packet support in nc_sendv_compat(), I mean when we detect 
QEMU_NET_PACKET_FLAG_RAW, call nc_sendv_compat() here.