How to disable NIC offloading on RHCOS

Solution Verified - Updated

Environment

  • RHOCP 4.x
  • OpenShift SDN

Issue

  • We would like to disable permanently network interfaces offloading on RHCOS nodes like LRO / GRO
  • RHCOS doesn't have ethtool installed

Resolution

IMPORTANT: Do not run this solution in clusters that use OVN-Kubernetes

RHCOS has NetworkManager 1.14+ so it recognizes ethtool.* properties.
The changes can be run easily using a proper NIC name and a specific offloading technique, for example, to disable Large receive offload (LRO) on NIC ens1:

sudo  nmcli conn modify ens3  ethtool.feature-lro off

If there is no MachineConfig redefining /etc/sysconfig/network-scripts/ifcfg-$NIC file, then the change will be persistent according to Content from github.com is not included.openshift-machine-config-operator Q&A
If there were applied some changes for /etc/sysconfig/network-scripts/ifcfg-$NIC included in a MachineConfig, then the same MachineConfig should be updated to include ETHTOOL_OPTS

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