Proposed F19 Feature: systemd/udev Predictable Network Interface Names

[Kay Sievers]

On Thu, Jan 24, 2013 at 8:57 PM, Bill Nottingham <notting at redhat.com> wrote:
> Matthew Miller (mattdm at fedoraproject.org) said:
>> > But I guess we simply have a different definition of a user here. Your
>> > definition is probably closer to what the page calls "admins", which is
>> > covered by the next lines in the feature page, which you didn't paste:
>>
>> Right. For Fedora, developers and admins are an important subset of users.
>>
>> > "As biosdevname is installed by default ...  most administrators won't
>> > see this either. "
>>
>> If the new scheme really is better, we should suck it up and make the whole
>> change. It'd be better to do what we can to make that transition easier --
>> like using similar names were possible -- than to have a weird mixed state.
>
> So, thinking - if we were to go this route, I think we'd want a clean
> break, where we don't use biosdevname at all if we're using this.

It's maybe a bit painful but might be the least confusing option.
Ugh, that thing really seems to accelerate itself quite a bit. :)

> The simplest way to do that would be:
> - change biosdevname to not be installed by default
> - enable these rules only on install, not on upgrade
> both of which are pretty easily doable.
>
> To quote the documentation, of the device name formats:
>
>  * Two character prefixes based on the type of interface:
>  *   en -- ethernet
>  *   wl -- wlan
>  *   ww -- wwan
>  *
>  * Type of names:
>  *   o<index>                              -- on-board device index number
>  *   s<slot>[f<function>][d<dev_id>]       -- hotplug slot index number
>  *   x<MAC>                                -- MAC address
>  *   p<bus>s<slot>[f<function>][d<dev_id>] -- PCI geographical location
>  *   p<bus>s<slot>[f<function>][u<port>][..][c<config>][i<interface>]
>  *                                         -- USB port number chain
>
> What concerns would people have with this naming? Off the top of my head:
>
> - wwan devices aren't always discoverable (they can show up as ethernet)

Yeah, it's not about discovery from userspace, we will not try that.
It is directly exported by the kernel, the original name of that
device was already wwan0. The kernel has netdev type names it exports
like "wlan", "vlan", "wwan". They are visible in sysfs, there is no
logic really in userspace.

> - devices that biosdevname considers emX via enumeration/guessing would
>   now have enpXsY, which could be considered 'uglier'

Yeah, it's based on PCI IRQ table heurisitcs biosdevname does, with
looking at bus == 0, and it starts counting at 1 all the devices
there. We don't want to do that, and reserve the "onboard" names to
actual real firmware records, and not base it on guesses. It's
probably reasobably safe what biosdevname does in most cases, but we
better do not get into that business and keep the safe, but granted,
ugly name.

Kay