netdev - Re: PATCH: Network Device Naming mechanism and policy

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Date:	Sun, 11 Oct 2009 16:10:03 -0500
From:	Rob Townley <rob.townley@...il.com>
To:	Greg KH <greg@...ah.com>
Cc:	Matt Domsch <Matt_Domsch@...l.com>,
	Stephen Hemminger <shemminger@...tta.com>,
	netdev@...r.kernel.org, linux-hotplug@...r.kernel.org,
	Narendra_K@...l.com, jordan_hargrave@...l.com
Subject: Re: PATCH: Network Device Naming mechanism and policy

On Sat, Oct 10, 2009 at 12:23 AM, Greg KH <greg@...ah.com> wrote:
> On Fri, Oct 09, 2009 at 11:40:57PM -0500, Matt Domsch wrote:
>> The fundamental roadblock to this is that enumeration != naming,
>> except that it is for network devices, and we keep changing the
>> enumeration order.
>
> No, the hardware changes the enumeration order, it places _no_
> guarantees on what order stuff will be found in.  So this is not the
> kernel changing, just to be clear.
>
> Again, I have a machine here that likes to reorder PCI devices every 4th
> or so boot times, and that's fine according to the PCI spec.  Yeah, it's
> a crappy BIOS, but the manufacturer rightly pointed out that it is not
> in violation of anything.
>
>> Today, port naming is completely nondeterministic.  If you have but
>> one NIC, there are few chances to get the name wrong (it'll be eth0).
>> If you have >1 NIC, chances increase to get it wrong.
>
> That is why all distros name network devices based on the only
> deterministic thing they have today, the MAC address.  I still fail to
> see why you do not like this solution, it is honestly the only way to
> properly name network devices in a sane manner.
>
> All distros also provide a way to easily rename the network devices, to
> place a specific name on a specific MAC address, so again, this should
> all be solved already.
>
> No matter how badly your BIOS teams mess up the PCI enumeration order :)
>
> thanks,
>
> greg k-h
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So when an add-in PCI NIC has a lower MAC than the motherboard NICs,
the add-in cards will come before the motherboard NICs.   i don't like it.

But please whatever is done, make sure ping and tracert still works when
telling it to use a ethX source interface:

eth0 = 4.3.2.8, the default gateway is thru eth1.
ping -I eth0 208.67.222.222              FAILS
ping -I 4.3.2.8 208.67.222.222          WORKS
tracert -i eth0 -I 208.67.222.222        FAILS
tracert -s 4.3.2.8 -I 208.67.222.222   WORKS
tracert -i eth0 208.67.222.222           FAILS
tracert -s 4.3.2.8 208.67.222.222      WORKS
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