vmware: Disable UDP offload for primary interface

[zmrow]

Issue number:
N/A
Depends on #2829

Description of changes:
We've had reports of Bottlerocket in VMware having networking issues that we've traced back to the combination of our 5.10 kernel and the vmxnet3 driver. This driver enables UDP offload which has caused conflicts with NSX-T in certain environments.

This PR adds a systemd unit to VMware variants only. The systemd unit disables UDP offload via ethtool commands for the default primary interface in VMware: eth0.

The unit does reference eth0. Given that eth0 is the default primary interface in VMware, and changing it isn't trivial (especially with EKS-A), this felt pretty safe and should cover the 98% use case.

If a user does opt to do their own networking shenanigans, and runs into an issue where UDP offload is a problem, they are able to use a bootstrap container to run this same set of commands for their preferred interface.

Testing done:

• Build an aws-k8s-1.24 image and ensure the unit does not exist and is not run

bash-5.1# systemctl --type=service | grep -i disable-udp
bash-5.1#

• Build a vmware-k8s-1.24 image and ensure the unit runs and the settings are applied for the interface.

bash-5.1# systemctl --type=service | grep -i disable-udp
  disable-udp-offload.service            loaded active     exited          Disables UDP offload

bash-5.1# ethtool -k eth0        
Features for eth0:
...
tx-udp_tnl-segmentation: off
tx-udp_tnl-csum-segmentation: off
...

Without the systemd unit - the settings show as "on":

bash-5.1# ethtool -k eth0 | grep -i tx-udp
tx-udp_tnl-segmentation: on
tx-udp_tnl-csum-segmentation: on

Terms of contribution:

By submitting this pull request, I agree that this contribution is dual-licensed under the terms of both the Apache License, version 2.0, and the MIT license.

[bcressey]

In VMware, Bottlerocket's 5.10 kernel and the vmxnet3 driver can conflict with NSX-T in certain environments. Disabling UDP offload works around the problem.

Couple notes:

• 5.15 kernel is also affected
• NSX / NSX-T reportedly is not involved

Please revise the PR description and commit message accordingly.

[zmrow]

^ Addresses @bcressey 's comments.