Re: net device renaming 2-step, IFNAMSIZ limit

[Matt Domsch <Matt_Domsch@dell.com>]

> On Tue, Feb 8, 2011 at 6:42 AM, Kay Sievers <kay.sievers@vrfy.org> wrote:
> > If biosdevname ever needs a two-step renaming, there is something
> > wrong. Two-step renaming happens only for conflicting names. We do not
> > want to support renaming in conflicting namespaces anymore.

biosdevname by default uses --policy=physical, which uses the emN and
pci<slot>p<port>_<vf> convention.  I believed (incorrectly)
that all renames were 2-step, thus going from eth100 -> pci4p1_63
could overflow.  Since only renames in the same space use the 2-step
process, then this isn't as much of a concern.

biosdevname does have --policy=all_ethN, for those who really love
their ethN convention.  It's not default, and it's not in the udev
rules file to use it, but it would be an option.  As long
as we don't have >10k devices, we're ok.  


> > Also, we can not use hashes without checking for conflicts, it's
> > unlikely to happen, but we just don't do such hacks. Just use the
> > ifindex or whatever fits to be correct.

I do like the idea of using ifindex here instead of a hash, just
because we allow any arbitrary-length name to be used in a rename
rule.  biosdevname itself won't exceed the length, but if someone had
a rule that would move from eth12345 to eth67890, it would trigger.

Thanks,
Matt

-- 
Matt Domsch
Technology Strategist
Dell | Office of the CTO