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:
> > On Fri, Oct 09, 2009 at 07:12:07PM +0530, K, Narendra wrote:
> > > > 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
--
To unsubscribe from this list: send the line "unsubscribe linux-hotplug" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
