On Fri, Oct 09, 2009 at 09:36:13AM -0700, Greg KH wrote:

On Fri, Oct 09, 2009 at 09:00:01AM -0500, Narendra K wrote:

quoted

On Fri, Oct 09, 2009 at 07:12:07PM +0530, K, Narendra wrote:

quoted

quoted

example udev config:
SUBSYSTEM=="net",

SYMLINK+="net/by-mac/$sysfs{ifindex}.$sysfs{address}"

work as well.  But coupling the ifindex to the MAC address like this
doesn't work.  (In general, coupling any two unrelated attributes when
trying to do persistent names doesn't work.)

Attaching the latest patch incorporating review comments.

By creating character devices for every network device, we can use
udev to maintain alternate naming policies for devices, including
additional names for the same device, without interfering with the
name that the kernel assigns a device.

This is conditionalized on CONFIG_NET_CDEV.  If enabled (the default),
device nodes will automatically be created in /dev/netdev/ for each
network device.  (/dev/net/ is already populated by the tun device.)

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.

How does this patch work with the network namespace functionality?

There is a monitonically increasing static ifindex kept in
net/core/dev.c:dev_new_index(), which is shared across all namespaces.
struct net_device ifindex field is assigned from this.  So two devices
in two different namespaces can't share an ifindex value.  However,
the device can be present (or not) in the per-namespace dev_name_hash
and dev_index_hashes.  This patch doesn't change this at all.

uevents aren't namespaced.  Presumably that means /dev can't be
polyinstantiated.  Therefore, all devnodes in /dev/netdev/* will be
visible to all processes, where 'ifconfig' and friends would only show
device names in the processes namespace.  This doesn't mean the app
can _do_ anything (it's the same as if it tried to act on a device
using an ifindex for a device not in its namespace), but yes, the fact
that such a device exists will be exposed.

-- 
Matt Domsch
Technology Strategist, Dell Office of the CTO
linux.dell.com & www.dell.com/linux