On Thu, 2009-10-29 at 07:25 -0700, Greg KH wrote:

On Thu, Oct 29, 2009 at 08:11:25AM -0500, Matt Domsch wrote:

quoted

Netdev team - are you in agreement that having multiple names to
address the same netdevice is a worthwhile thing to add, to allow a
variety of naming schemes to exist simultaneously?  If not, this whole
discussion will be moot, and my basic problem, that the ethX naming
convention is nondeterministic, but we need determinism, remains
unresolved.

I'm still totally confused as to why you think this.  What is wrong with
what we do today, which is name network devices in a deterministic
manner by their MAC in userspace?  That name goes into the kernel, and
everyone uses the same name and is happy.

If you don't like naming by MAC, then pick some other deterministic
naming scheme that works for your hardware and write udev rules for it.

You could easily name them in a way that could keep the lowest number
(eth0) for the lowest PCI id if you so desired and your BIOS guaranteed
it.

This way the kernel has only one name, and so does userspace, and
everyone is happy.

I thought there was a general trend in udev development to provide
default rules that work for almost everyone, so few users/administrators
need to override or add to them.  Compare disks and net devices:

1. Stable kernel device id
Disks: block device number
Net devices: ifindex

2. Unique identifier (across reboot)
Disks: label or UUID (each with limitations)
Net devices: (MAC address, subtype)

3. Name assignment mechanism
Disks: kernel suggests a name; udev can assign any number
Net devices: kernel assigns a single name; udev can override it

4. Default name assignment policy
Disks: names disk by device path (id), label and UUID
Net devices: assigns arbitrary stable names per (MAC address, subtype)

5. Naming by users
Disks: user can identify by any method without having to choose on a
system-wide basis
Net devices: user must identify by single name; policy can be overridden
on a system-wide basis

I fully understand the technical reasons for differences 3-5, but why
should users have to put up with it?

Ben.

-- 
Ben Hutchings, Senior Software Engineer, Solarflare Communications
Not speaking for my employer; that's the marketing department's job.
They asked us to note that Solarflare product names are trademarked.

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