netdev - Re: [RFC PATCH 2/3] netdev: kernel-only IFF

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Date:   Wed, 4 Apr 2018 11:02:44 -0700
From:   Siwei Liu <loseweigh@...il.com>
To:     David Ahern <dsahern@...il.com>
Cc:     Jiri Pirko <jiri@...nulli.us>, Si-Wei Liu <si-wei.liu@...cle.com>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Stephen Hemminger <stephen@...workplumber.org>,
        Alexander Duyck <alexander.h.duyck@...el.com>,
        David Miller <davem@...emloft.net>,
        "Brandeburg, Jesse" <jesse.brandeburg@...el.com>,
        Jakub Kicinski <kubakici@...pl>,
        Jason Wang <jasowang@...hat.com>,
        "Samudrala, Sridhar" <sridhar.samudrala@...el.com>,
        Netdev <netdev@...r.kernel.org>,
        virtualization@...ts.linux-foundation.org
Subject: Re: [RFC PATCH 2/3] netdev: kernel-only IFF_HIDDEN netdevice

On Wed, Apr 4, 2018 at 10:21 AM, David Ahern <dsahern@...il.com> wrote:
> On 4/4/18 1:36 AM, Siwei Liu wrote:
>> On Tue, Apr 3, 2018 at 6:04 PM, David Ahern <dsahern@...il.com> wrote:
>>> On 4/3/18 9:42 AM, Jiri Pirko wrote:
>>>>>
>>>>> There are other use cases that want to hide a device from userspace. I
>>>>
>>>> What usecases do you have in mind?
>>>
>>> As mentioned in a previous response some kernel drivers create control
>>> netdevs. Just as in this case users should not be mucking with it, and
>>> S/W like lldpd should ignore it.
>>>
>>>>
>>>>> would prefer a better solution than playing games with name prefixes and
>>>>> one that includes an API for users to list all devices -- even ones
>>>>> hidden by default.
>>>>
>>>> Netdevice hiding feels a bit scarry for me. This smells like a workaround
>>>> for userspace issues. Why can't the netdevice be visible always and
>>>> userspace would know what is it and what should it do with it?
>>>>
>>>> Once we start with hiding, there are other things related to that which
>>>> appear. Like who can see what, levels of visibility etc...
>>>>
>>>
>>> I would not advocate for any API that does not allow users to have full
>>> introspection. The intent is to hide the netdev by default but have an
>>> option to see it.
>>
>> I'm fine with having a link dump API to inspect the hidden netdev. As
>> said, the name for hidden netdevs should be in a separate device
>> namespace, and we did not even get closer to what it should look like
>> as I don't want to make it just an option for ip link. Perhaps a new
>> set of sub-commands of, say, 'ip device'.
>
> It is a netdev so there is no reason to have a separate ip command to
> inspect it. 'ip link' is the right place.

If you're still thinking the visibility is part of link attribute
rather than a separate namespace, I'd say we are trying to solve
essentially different problems, and I really don't understand your
proposal in solving that problem to be honest.

So, let's step back on studying your case if that's the right thing
and let's talk about concrete examples.

-Siwei