[systemd-devel] About stable network interface names

[Andrei Borzenkov]

09.06.2017 23:42, Martin Wilck пишет:
> On Tue, 2017-06-06 at 21:40 +0300, Andrei Borzenkov wrote:
>>
>> Can device and function really change? My understanding is that
>> device
>> part is determined by bus physical wiring and function by PCI card
>> design; this leaves bus as volatile run-time enumeration value.
> 
> For PCIe, that's only true for the "function" part.
> https://superuser.com/questions/1060808/how-is-the-device-determined-in
> -pci-enumeration-bus-device-function
> 

I do not see anything there that would imply device designation is
random. You have PCIe switch port instead of IDSEL wiring but port is
most likely hardwired and does not change. Actually this article says
the same

--><--
Since each device has its own independent set of wires, the device IDs
are essentially all hard-coded
--><--


> The systemd docs are a bit misleading for PCIe, as they talk about
> "physical/geographical location" for the common enp$Xs$Yf$Z scheme,
> which is actually just the BDF. The interface on my laptop is called
> enp0s31f6 although the laptop doesn't have "slot 31". (1)
> 

The reason for this scheme is to generate unique names during boot. All
this buzz about "predictability" etc is just usual marketing stuff to
better sell it.