how does udev rename an interface?

[martin f krafft <madduck@madduck.net>]

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udev has the ability to rename network interfaces. At least on my
system, udevsend is called from /etc/hotplug.d/default. A network
device usually triggers two hotplug events, the first for the
device, and the second for the network interface. Therefore, udev
runs twice, but network interface renaming only makes sense during
the second invocation, since it only applies to network interfaces.

I have two questions about how udev handles this:

  - /etc/hotplug.d/net/*.hotplug are run before udevsend is called
    from /etc/hotplug.d/default. Thus, if a tool such as ifplugd
    already configures the network interface with
    /etc/hotplug.d/net, udev effectively cannot change the
    interface name because the interface is in use.

  - even if udev changes the interface name, how does it communicate
    the new name to net.agent and all the other hook scripts? The
    interface name is stored in $INTERFACE in the environment of the
    hotplug process, and udev cannot change that environment (or can
    it?).

How does udev deal with this?

Thanks,

-- 
martin;              (greetings from the heart of the sun.)
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