Ifconfig limitations

Hi folks!

I've been working on getting better FreeBSD support into cloud-init.
My working thesis has been that all I really need to replicate
what cloud-init on Linux is doing with ip addr/ip link and its
reading of `/sys/class/net/<device>/*` files is BSD's ifconfig(8)

This ifconfig parser is the implementation of that thesis:
https://github.com/canonical/cloud-init/blob/main/cloudinit/distros/parsers/ifconfig.py

However, trying to port cloud-init's Infiniband code seems to have
falsified my hypothesis.

In some cases, it's easily possible to tell if an interface is an
Infiniband interface: For example, it'll start with `ib`, or have
a GUID as `lladdr`:

https://github.com/canonical/cloud-init/pull/2003/files#diff-f143a014d8daaa1671a7feef90cc2b3f5c5759e234e5cd3382e438dde3703fd3

but in other cases, such as when the device is in Ethernet mode,
it's impossible to tell.

It means i would have to parse the highly verbose ibstat(8),
then map the Infiniband device name to the ifconfig names and
only then can I decide if the devices in ifconfig contain
infiniband devices, which ones they are, and what state / mode
they are in.

(if they even show up in ifconfig to begin with! tho this might
be a skill / knowledge issue, see: https://lists.freebsd.org/archives/freebsd-infiniband/2023-April/000011.html )

On Linux, cloud-init checks `/sys/net/mce0/type`.
If that type is 32, it's infiniband, if it's 1, it's ethernet.

We don't seem to have such a thing.
Sometimes we have useful groups, but not as many useful groups
as OpenBSD does, for instance. So I have determined that on
FreeBSD, the absence of groups marks a physical device.

But beyond that, there's not much overlap between Infiniband
and ifconfig, and that's a real shame.

Let's compare that to wlan!
the actual wifi devices don't show up in ifconfig, but they can
be easily found via `sysctl net.wlan.devices`.
Once plumbed in, a wlanX device shows a parent device and
belonging to the wlan group.

How hard would it be to emulate that behaviour for Infiniband?
What tooling do we have right now, that I may have missed?

Kind regards,

Mina Galić
Don't Try *my* PkgBase Repository: https://alpha.pkgbase.live/ — until i have a new hardware sponsor…