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

[Peter Lieven <pl@kamp.de>]

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