RFC: interface description

[Brooks Davis]

On Fri, Aug 14, 2009 at 10:49:24AM -0700, Li, Qing wrote:
> > 
> > My point has always been - if I have to add/do an ioctl I can always
> > also use a library call that will read it from a .txt, .xml, .db file
> > or whatever and I don't have to go to the kernel, handle all the
> > string length problems there, ... especially as the kernel cannot do
> > anything with that string.
> 
> The interface description feature is a useful feature. Quite a few
> products out there actually put a label on the physical box so it's
> reasonable to have the ability to label the ports in the kernel.
> 
> There are quite a few embedded systems and not-so-standalone boxes
> out there that are derivatives of FreeBSD. These systems might not
> have the luxury of a file system. And getting coredumps from the
> field with such information embedded in the ifnet{} just makes
> debugging field issues a little bit easier.

I think this is a decently compelling argument for in-kernel
descriptions.  They do solve some synchronization issues and one pointer
is probably an acceptable price to pay given all the edge cases related
to keeping a file in sync if you went the totally user land route.

I general, I don't think we should try too hard to solve every problem
here.  Adding a pointer to ifnet, a quick get/set ioctl, ifconfig
support, and support for ifdesc_<ifp> or similar variables in rc.conf
is probably as much as makes sense to do.  This is mostly a feature for
appliance builders.  If I were working on adding the ability to slim down
ifnet to the base system, I'd certainly make this an optional feature,
but there are much fatter targets at the moment.

-- Brooks
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