Proposed F19 Feature: systemd/udev Predictable Network Interface Names

[Matt Domsch]

On Mon, Feb 25, 2013 at 11:02:55AM -0600, Andy Gospodarek wrote:
> On Sat, Feb 23, 2013 at 10:28:21AM +0100, Bill Nottingham wrote:
> > Matt Domsch (Matt_Domsch at dell.com) said: 
> > > On Wed, Feb 13, 2013 at 01:57:42PM -0600, Bill Nottingham wrote:
> > > > > If we can solve the installtime naming convention choice to not
> > > > > eliminate biosdevname, be able to disable systemd/udevd naming, and
> > > > > have the default be possible on a per-system-vendor basis, and solve
> > > > > the NPAR/SR-IOV/Mellanox naming problems, then I can support this
> > > > > proposal.  Without fixing these shortcomings though, my customers will
> > > > > have a fit at me.
> > > > 
> > > > If you're agreeing that biosdevname should be limited to type9/type41
> > > > (if I'm reading you right), and if the systemd/udev names still use those
> > > > fields, what parts of biosdevname are you still requiring? The actual
> > > > namespace used, or something else?
> > > 
> > > I'd prefer if we didn't force users through another namespace change.
> > > I took a lot of flack for changing the namespace once.  From their
> > > perspective, it's still udev doing the renaming, only now the code
> > > moved from a udev helper into udev itself.
> > 
> > True; the users likely don't care other than how they enable/disable it.
> > 
> > > I'd like to see the SR-IOV & NPAR devices handled.  Those aren't
> > > represented in type9/type41, and their commonplace on Dell systems.
> > > 
> > > I'd like to see the Dell-specific PCI VPD-R code from biosdevname
> > > included in udev, as that's used to map multi-port devices to port
> > > numbers.  Those aren't represented in type9/type41, and they're
> > > commonplace on Dell systems.
> > 
> > OK.
> > 
> > > I'd like to see kernel driver work to be sure every multi-port driver
> > > with the same PCI b/d/b/f sets dev_id.  That isn't necessarily true
> > > today, which makes it hard to trust.  biosdevname needs this too,
> > > until such a time as it's dead.
> > 
> > Do we have a list of these, or is it a matter of doing a driver audit?
> > CC'ing gospo.
> 
> (Thanks, Bill, though I've been following this thread as I am on the
> list).
> 
> Right now almost no drivers actually set dev_id.  In fact mlx4_en,
> cxgb4, and sfc seem to be the only ones right now.  If we feel like this
> a requirement there will be work on the kernel side to add this.

The challenge here is that because struct netdev is initialized to all
zeros, code that consumes dev_id can't tell the difference between a
driver _setting_ the value to 0 because it has 2 ports 0 and 1, and a
default (unset) value of 0.  I think the only solution here is to make
sure the kernel drivers, if they need to set it, always set this
non-zero, so udev, seeing a non-zero value, knows it's a valid value
to use.

-- 
Matt Domsch
Technology Strategist
Dell | Office of the CTO