Mellanox hardware detection issues a warning because loopback device has no vendor

[Doug Szumski]

The Mellanox hardware manager attempts to find Mellanox devices by iterating through the contents of /sys/class/net and checking the vendor field in /sys/class/net/$NIC/device/vendor. However, the vendor file may not exist for the loopback device. This can cause the following warning during Mellanox hardware detection:

Dec 14 19:34:32 localhost ironic-python-agent: 2017-12-14 19:34:32.453 2515 WARNING root [-] Can't find field vendor for device lo in device class net: IOError: [Errno 2] No such file or directory: '/sys/class/net/lo/device/vendor'

IPA ramdisk info:
-----------------

[devuser@localhost ~]$ cat /etc/centos-release
CentOS Linux release 7.4.1708 (Core)

[devuser@localhost ~]$ uname -a
Linux localhost.localdomain 3.10.0-693.11.1.el7.x86_64 #1 SMP Mon Dec 4 23:52:40 UTC 2017 x86_64 x86_64 x86_64 GNU/Linux

[devuser@localhost ~]$ stat /sys/class/net/lo/device/vendor
stat: cannot stat '/sys/class/net/lo/device/vendor': No such file or directory

Relevant code:
--------------

Hardware detection:

https://github.com/openstack/ironic-python-agent/blame/stable/pike/ironic_python_agent/hardware_managers/mlnx.py#L62

The above method then calls this:

https://github.com/openstack/ironic-python-agent/blame/master/ironic_python_agent/hardware.py#L56

[Dmitry Tantsur (divius)]

Is this bug only about the warning or is something actual broken? From the code I assume the former, so setting priority to low.

[Doug Szumski (dszumski)]

Thanks - it's only about the warning which could cause confusion. Nothing is broken.

[Jay Faulkner (jason-oldos)]

We'd happily merge a small patch to fix this kind of issue; but due to the nature of hardware detection in IPA we cannot track down and eliminate all warning/error cases across all varied hardwares. Sorry :(.