Re: OT(?) -- Should the net.agent script cause "ifup lo" to be run?

[Bill Nottingham <notting@redhat.com>]

David Brownell (david-b@pacbell.net) said: 
> I guess I don't see what you mean by "actual hotplug device".
> What PCI or USB device wouldn't be a hotplug device, why?

Any PCI device in an non-hotplug slot is not really hot-pluggable
(at least without risk to the card and motherboard. ;) )

> What "drastic change"?

In all our previous OS releases, interfaces are not necessarily
brought up just because the module is loaded; this changes that.
For example, we have documented behavior on how to mark interfaces
not to be brought up at boot time; hotplug now breaks these assumptions.

Also, to maintain stable network interface ordering (with the current
kernel semantics), we load all the network modules once at boot so
all the device -> ethX mappings remain consistent; now hotplug tries
to activate all these interfaces. We've also noticed that (presumably
because of the PCI hotplug stuff), if you bring down an interface and
try and unload a module, it comes back. (This last one may be currently
fixed; it was reported against our last beta.)

> That patch to not make the ppp/isdn/... interfaces go "ifup" is
> in CVS, by the way.

Cool. You probably want to add plip to the list if it's not
already on it. :)

> Am I correct that the issue is that those
> devices get brought "up" differently than eth* interfaces?

Very differently. In fact, for PPP, by the time the device
exists in the kernel, you pretty much have to have already
run 'ifup' in some manner, unless you're not using any
networking scripts as all.

> And "lo" has yet a third kind of init model magic?

Not really, it's just brought up automatically here
when the network is started. It's certainly something
the hotplug scripts could do in the future; it's just
that it's not really a pluggable interface.

I was probably overly harsh in my assessment; it's not that
the scripts are buggy (aside from the ppp thing); it's that
in the current state what they do conflicts with how the
distribution used to work before. It would be good to be
able to configure it so that it can mesh better (for example,
handle USB and cardbus, but ignore other PCI stuff.)

One other minor note; it currently didn't seem to handle
multiple modules that support the same device as well, in
that I couldn't tell it to load tulip instead of xircom_tulip_cb,
without editing the modules.pcimap directly. Not sure where
you'd put 'preferences' like this though. (Please, correct
me if I'm wrong.)

Bill

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