Re: [PATCH 2.6.18-rc5] PCI: sort device lists breadth-first

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Arjan van de Ven wrote:

On Fri, 2006-09-08 at 11:18 -0500, Matt Domsch wrote:

On Fri, Sep 08, 2006 at 11:56:39AM -0400, Dave Jones wrote:

On Thu, Sep 07, 2006 at 10:14:22PM -0500, Matt Domsch wrote:
 > Problem:
 > New Dell PowerEdge servers have 2 embedded ethernet ports, which are
 > labeled NIC1 and NIC2 on the chassis, in the BIOS setup screens, and
 > in the printed documentation.  Assuming no other add-in ethernet ports
 > in the system, Linux 2.4 kernels name these eth0 and eth1
 > respectively.  Many people have come to expect this naming.  Linux 2.6
 > kernels name these eth1 and eth0 respectively (backwards from
 > expectations).  I also have reports that various Sun and HP servers
 > have similar behavior.
This came up years back when 2.6 was something new, and the answer 
then was 'bind the interface to the MAC address'.

Both Red Hat-based distros and openSuSE-based distros do something
like this with configuration files automatically.  Red Hat's
anaconda/kudzu puts the HWADDR lines in the generated
/etc/sysconfig/network-scripts/ifcfg-* files.  openSuSE's udev rules
puts lines in /etc/udev/rules.d/30-net_persistent_names.rules the
first time it discovers a new interface.  Both methods are intended to
maintain a persistent name for each NIC, after being set up the first
time.  Neither deals well with replacing one NIC with another - you
must edit the config files.

This works pretty well post-install.  It doesn't work well at install
time, all the installers use the kernel's original names, and then
those names become the persistent names in the config files.



Whilst your patch will fix the case that's currently broken (2.4->2.6),
doesn't it offer equal possibility to break existing setups when people move
from <=2.6.18 -> 2.6.19 ?

If they're using config files / udev rules as suggested, it shouldn't
break them.

If they're not, then yes, this could.  Debian's
/etc/network/interfaces file allows use of hwaddr fields, though by
default it doesn't appear anything sets it up.

I'm open to suggestions on how *not* to break setups that don't use
the MAC addresses.


to be honest I really don't like the PCI ordering change thing for this.
It's just too fragile altogether to cause a fixed ordering as you want.

Maybe the kernel's initial ordering should do a numeric sort by mac
address or something.. (or userspace should)
That wouldn't match any existing setup, and would be subject to mid-list insertions if a NIC were added/replaced. And that is fragile.
I was looking for an easy way to do PCI slot to MAC, and from there MAC to IP, so any NIC plugged into a given slot could be called eth0 (for instance) and given the "right" IP address, but that's not easy. Can be done with some searching in /sys, but it's non-trivial. 

--
Bill Davidsen <[email protected]>
  Obscure bug of 2004: BASH BUFFER OVERFLOW - if bash is being run by a
normal user and is setuid root, with the "vi" line edit mode selected,
and the character set is "big5," an off-by-one errors occurs during
wildcard (glob) expansion.

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