Investigate if we can switch back to iptables-legacy on WSL with older kernels

[jandubois]

in Rancher Desktop 1.13 we require a WSL kernel 5.15.0.0 or later because we use Alpine 3.19 which now uses nf_tables by default, which requires kernel support missing in earlier WSL kernels.

This can be an issue for users that don't have access to the Store, and also for users that intentionally want to run an older kernel because of unresolved hibernation issues with later kernels (see #6606).

Maybe it will be possible to adjust a couple of symlinks in a provisioning script during the boot phase (only when the kernel is too old), to switch back to iptables-legacy?

This would need to be verified with a full BATS test, and even then we should include a diagnostic that explains that this would be an unsupported configuration.

This fallback would also provide some safety in case the Rancher Desktop upgrade proceeds even though the kernel update failed for any reason. Right now this would result in a broken Rancher Desktop installation that could only be fixed by an Uninstall/Reinstall cycle, which would lose all existing local images and settings.

References:

• Alpine Linux should default to nf_tables backend (#14058) · Issues · alpine / aports · GitLab
• main/iptables: make default iptables* links to nft variant (!47102) · Merge requests · alpine / aports · GitLab
• main/iptables: split legacy tools and libraries (7f294b87) · Commits · alpine / aports · GitLab

[jandubois]

This has been addressed in the 1.13.1 release, which switches back to iptables-legacy when the kernel is too old.