[arch-general] [arch-dev-public] network interface naming with systemd 197

[Dave Reisner]

On Mon, Jan 07, 2013 at 09:35:45AM -0600, Leonid Isaev wrote:
> On Mon, 07 Jan 2013 08:23:10 +0100
> Andrea Scarpino <andrea at archlinux.org> wrote:
> 
> > On Monday 07 January 2013 07:51:30 Allan McRae wrote:
> > > Upstream decision...  vanilla packages should follow it.
> > 
> > I agree with Allan. We don't use to change the default behavior. Ship it as 
> > default and add two lines on how to disable it.
> > 
> 
> If I may chime in... regarding switching from MAC-based iface naming to
> ID_NET_NAME_PATH-based naming. How exactly are these ID_NET_NAME_PATH
> variables assigned?
> 
> For instance, I have a box with 2 pci intel cards:
> 1. DEVPATH=/devices/pci0000:00/0000:00:05.0/0000:02:00.0/net/elan0
>    ID_NET_NAME_PATH=enp2s0f0
> 2. DEVPATH=/devices/pci0000:00/0000:00:06.0/0000:03:00.0/net/elan1
>    ID_NET_NAME_PATH=enp3s0f0
> 
> Do I correctly understand that "enp?s0f0" is chosen based on a particular pci
> slot the card is inserted in and will change if I choose to replug the cards?

Yes, it's derived from the PCI path of the card in this case, and yes
it'll change if you physically move the card. There's some examples of
composed paths in udev source:

http://cgit.freedesktop.org/systemd/systemd/tree/src/udev/udev-builtin-net_id.c#n21

If this is a concern to you, ID_NET_NAME_MAC is also available, which
will always be the MAC from the hardware and should never be any
possible faked address from the OS side.

$ macchanger -m 12:34:56:78:90:ab eth0
 Current MAC: de:ad:be:ef:00:01 (unknown)
 Faked MAC:   12:34:56:78:90:ab (unknown)

$ udevadm info -q property /sys/class/net/eth0 | grep ID_NET_NAME_MAC
 ID_NET_NAME_MAC=enxdeadbeef01

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