netdev - Re: [PATCH v7 net-next 4/4] netvsc: refactor notifier/event handling code to use the failover framework

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Date:   Mon, 23 Apr 2018 23:06:55 +0300
From:   "Michael S. Tsirkin" <mst@...hat.com>
To:     Siwei Liu <loseweigh@...il.com>
Cc:     Stephen Hemminger <stephen@...workplumber.org>,
        Jiri Pirko <jiri@...nulli.us>,
        Sridhar Samudrala <sridhar.samudrala@...el.com>,
        David Miller <davem@...emloft.net>,
        Netdev <netdev@...r.kernel.org>,
        virtualization@...ts.linux-foundation.org,
        virtio-dev@...ts.oasis-open.org,
        "Brandeburg, Jesse" <jesse.brandeburg@...el.com>,
        Alexander Duyck <alexander.h.duyck@...el.com>,
        Jakub Kicinski <kubakici@...pl>,
        Jason Wang <jasowang@...hat.com>
Subject: Re: [PATCH v7 net-next 4/4] netvsc: refactor notifier/event handling
 code to use the failover framework

On Mon, Apr 23, 2018 at 12:44:39PM -0700, Siwei Liu wrote:
> On Mon, Apr 23, 2018 at 10:56 AM, Michael S. Tsirkin <mst@...hat.com> wrote:
> > On Mon, Apr 23, 2018 at 10:44:40AM -0700, Stephen Hemminger wrote:
> >> On Mon, 23 Apr 2018 20:24:56 +0300
> >> "Michael S. Tsirkin" <mst@...hat.com> wrote:
> >>
> >> > On Mon, Apr 23, 2018 at 10:04:06AM -0700, Stephen Hemminger wrote:
> >> > > > >
> >> > > > >I will NAK patches to change to common code for netvsc especially the
> >> > > > >three device model.  MS worked hard with distro vendors to support transparent
> >> > > > >mode, ans we really can't have a new model; or do backport.
> >> > > > >
> >> > > > >Plus, DPDK is now dependent on existing model.
> >> > > >
> >> > > > Sorry, but nobody here cares about dpdk or other similar oddities.
> >> > >
> >> > > The network device model is a userspace API, and DPDK is a userspace application.
> >> >
> >> > It is userspace but are you sure dpdk is actually poking at netdevs?
> >> > AFAIK it's normally banging device registers directly.
> >> >
> >> > > You can't go breaking userspace even if you don't like the application.
> >> >
> >> > Could you please explain how is the proposed patchset breaking
> >> > userspace? Ignoring DPDK for now, I don't think it changes the userspace
> >> > API at all.
> >> >
> >>
> >> The DPDK has a device driver vdev_netvsc which scans the Linux network devices
> >> to look for Linux netvsc device and the paired VF device and setup the
> >> DPDK environment.  This setup creates a DPDK failsafe (bondingish) instance
> >> and sets up TAP support over the Linux netvsc device as well as the Mellanox
> >> VF device.
> >>
> >> So it depends on existing 2 device model. You can't go to a 3 device model
> >> or start hiding devices from userspace.
> >
> > Okay so how does the existing patch break that? IIUC does not go to
> > a 3 device model since netvsc calls failover_register directly.
> >
> >> Also, I am working on associating netvsc and VF device based on serial number
> >> rather than MAC address. The serial number is how Windows works now, and it makes
> >> sense for Linux and Windows to use the same mechanism if possible.
> >
> > Maybe we should support same for virtio ...
> > Which serial do you mean? From vpd?
> >
> > I guess you will want to keep supporting MAC for old hypervisors?
> >
> > It all seems like a reasonable thing to support in the generic core.
> 
> That's the reason why I chose explicit identifier rather than rely on
> MAC address to bind/pair a device. MAC address can change. Even if it
> can't, malicious guest user can fake MAC address to skip binding.
> 
> -Siwei

Address should be sampled at device creation to prevent this
kind of hack. Not that it buys the malicious user much:
if you can poke at MAC addresses you probably already can
break networking.




> 
> >
> > --
> > MST