On Tue, Oct 13, 2009 at 11:36:38AM -0600, dann frazier wrote:

1;2202;0cOn Tue, Oct 13, 2009 at 10:43:49PM +0530, Narendra_K@Dell.com wrote:

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These device nodes are not functional at the moment - open() returns 
-ENOSYS.  Their only purpose is to provide userspace with a kernel 
name to ifindex mapping, in a form that udev can easily manage.

If the idea is just to provide a userspace-visible mapping 
(and presumably take advantage of udev's infrastructure for 
naming) does this need kernel changes? Could this be a 
hierarchy under e.g. /etc/udev instead, using plain text 
files? It still means we need something like libnetdevname for 
apps to do the translation, but I'm not seeing why it matters 
how this map is stored. Is there some special property of the 
character devices (e.g. uevents) that we're not already 
getting with the existing interfaces?

Yes. The char device by itself doesn't help in any way. But it provides
a flexible mechanism to provide multiple names for the same device, just
the way it is for disks.

Right - so any reason this couldn't be implemented completely in
userspace by having udev manipulate plain text files under say
/etc/udev/net/?

I do agree that it would be nice for admins/installers to tweak/use
nic names in a similar way to storage names (udev rules), and it might
let us take advantage of a lot of the existing udev code.

Is there interest in this approach?

 - modify udev to manage network devices names as regular (non-device)
   files (stored in /etc/udev, /dev/netdev, or wherever)
 - use the existing udev rules to manage symlinks to these files
 - point libnetdevname at these text files for its name resolution

I've started prototyping this, and it certainly looks possible w/o any
kernel changes. However, I could probably use some advice from a udev
person to do a proper implementation.

-- 
dann frazier