Re: [PATCH v12 6/8] net/tap: support local migration with virtio-net

[Markus Armbruster <armbru@redhat.com>]

Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru> writes:

> On 10.03.26 16:46, Markus Armbruster wrote:
>> Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru> writes:
>> 
>>> Support transferring of TAP state (including open fd) through
>>> migration stream as part of viritio-net "local-migration".
>>>
>>> Add new option, incoming-fds, which should be set to true to
>>> trigger new logic.
>>>
>>> For new option require explicitly unset script and downscript,
>>> to keep possibility of implementing support for them in future.
>>>
>>> Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>
>> [...]
>> 
>>> diff --git a/qapi/net.json b/qapi/net.json
>>> index 118bd349651..79f5ce9f431 100644
>>> --- a/qapi/net.json
>>> +++ b/qapi/net.json
>>> @@ -355,6 +355,9 @@
>>>   # @poll-us: maximum number of microseconds that could be spent on busy
>>>   #     polling for tap (since 2.7)
>>>   #
>>> +# @incoming-fds: do not open/connnect any resources, instead wait for
>>> +#     TAP state from incoming migration stream.  (Since 11.0)
>> "resources"?  The name @incoming-fds suggests this is about file
>> descriptors...
>
> Hmm. But, I can't say "open any file descriptors"..
>
>
>> "wait for TAP state from" does not make sense.  Do you mean "retrieve
>> TAP state from"?
>
> Retrieve means actively do something, but I mean, that FDs will come in
> future from incoming migration stream, and we just wait for it and "do nothing"
> at the moment of net-tap initialization.
>
>
> Let me try to reword:
>
> Do not open or create any TAP devices. Prepare for getting opened
> TAP file descriptors from incoming migration stream.

Better, thanks!

>> Is any part of NetdevTapOptions ignored when @incoming-fds is true?
>
> Hmm yes. sndbuf, vnet_hdr and ifname. I should add this information here.

I dislike ignoring the user's instructions silently.  Can we make it an
error?

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