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SubjectRe: [PATCH 2.6.18-rc5] PCI: sort device lists breadth-first
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 <>
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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