Timeout when attempting NFS mount over IPv6

This document (000019618) is provided subject to the disclaimer at the end of this document.

Environment

SUSE Linux Enterprise Server 12 SP5
SUSE Linux Enterprise Server 15 SP1

Situation

On SUSE Linux Enterprise 12 SP5 or 15 SP1, when attempting an NFS mount over IPv6, the attempt may timeout.

There could be many causes for such a symptom. This document only covers one possible cause. This particular problem only occurs if the network interface has scatter-gather turned off, which is not common. This setting can be checked with:

ethtool -k eth0 | grep scatter

This did not occur on SLES 12 SP4.

Can't mount NFS over IPv6.

Resolution

For the full solution, update the linux kernel with public maintenance.

For SLES 12 SP5, depending on your kernel flavor:
kernel-default-4.12.14-122.20.1
kernel-rt-4.12.14-10.5.1
kernel-azure-4.12.14-16.10.1

For SLES 15 SP1, depending on your kernel flavor:
kernel-default-4.12.14-197.34.1
kernel-rt-4.12.14-14.20.1
kernel-azure-4.12.14-8.27.1

An alternative to updating the kernel is to insure scatter-gather is on, for the network interface used for the communication in question. This can be accomplished on-the-fly with the command:

ethtool -K eth0 sg on

(Where "eth0" may need to be replaced with the actual name of the interface in question.)

To create a "permanent" setting that comes into effect during boot, edit /etc/sysconfig/network/ifcfg-eth0
and set:
ETHTOOL_OPTIONS='-K eth0 sg on'

Where "eth0" (in both the file name and the setting) may need to be replaced with the actual name of the interface in question.

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.