Predictable network interface naming changed in SLES 15 SP3 for certain devices

This document (000020541) is provided subject to the disclaimer at the end of this document.

Environment

SUSE Linux Enterprise Server 15 Service Pack 3 (SLES 15 SP3)
SUSE Linux Enterprise Server 15 Service Pack 4 (SLES 15 SP4)

Situation

On SLES servers booted with net.ifnames=1 to activate predictable network interface naming with systemd/udev NamePolicy, the interfaces of certain network devices get named differently after upgrading from SLES 15 SP2 (or earlier) to SLES 15 SP3 or later.

Resolution

Swap the order of slot and path in NamePolicy in /etc/systemd/network/99-default.link to
NamePolicy=keep kernel database onboard path slot

Rebuild the initrd with
# /usr/bin/dracut --logfile /var/log/YaST2/mkinitrd.log --force
and reboot the system.

Relevant output of udevadm info -e for the device mentioned in the cause section should now look like this :
P: /devices/pci0000:85/0000:85:02.0/0000:86:00.0/net/enp134s0f0
E: DEVPATH=/devices/pci0000:85/0000:85:02.0/0000:86:00.0/net/enp134s0f0
E: INTERFACE=enp134s0f0
E: ID_NET_NAME_PATH=enp134s0f0
E: ID_NET_NAME_SLOT=ens7f0
E: ID_NET_DRIVER=i40e
E: ID_NET_LINK_FILE=/etc/systemd/network/99-default.link


The policies are outlined in:  man systemd.link.

For some systems the additional step of removing the 70-persistent-net.rules found at /etc/udev/rules.d/70-persistent-net.rules is needed to unlock predictable network interface names.

Cause

In the observed case on SLES 15 SP3, the cause is that some Intel SR-IOV physical and virtual function interfaces exposed the ID_NET_NAME_SLOT property, which had not been exposed previously.

Considering the default policy in /usr/lib/systemd/network/99-default.link :
[Link]
NamePolicy=keep kernel database onboard slot path

interfaces that were earlier named based on ID_NET_NAME_PATH now get named based on ID_NET_NAME_SLOT if this property has not been exposed in earlier SLES versions.

The command "udevadm info -e" will expose the available properties for the devices.
Relevant lines from the output for an example device :
P: /devices/pci0000:85/0000:85:02.0/0000:86:00.0/net/ens7f0
E: DEVPATH=/devices/pci0000:85/0000:85:02.0/0000:86:00.0/net/ens7f0
E: SUBSYSTEM=net
E: INTERFACE=ens7f0
E: ID_NET_NAME_PATH=enp134s0f0
E: ID_NET_NAME_SLOT=ens7f0
E: ID_VENDOR_FROM_DATABASE=Intel Corporation
E: ID_MODEL_FROM_DATABASE=Ethernet Controller XXV710 for 25GbE SFP28 (Ethernet 25G 2P XXV710 Adapter)
E: ID_PATH=pci-0000:86:00.0
E: ID_NET_DRIVER=i40e
E: ID_NET_LINK_FILE=/etc/systemd/network/99-default.link


 

Status

Reported to Engineering

Disclaimer

This Support Knowledgebase provides a valuable tool for SUSE customers and parties interested in our products and solutions to acquire information, ideas and learn from one another. Materials are provided for informational, personal or non-commercial use within your organization and are presented "AS IS" WITHOUT WARRANTY OF ANY KIND.

  • Document ID:000020541
  • Creation Date: 07-Jul-2022
  • Modified Date:07-Jul-2022
    • SUSE Linux Enterprise Server

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