Add missing kernel config checks

[st3iny]

Add additional kernel config checks for NETFILTER_XT_MATCH_COMMENT and NETFILTER_XT_MATCH_MULTIPORT as they are both required to run k3s.

Proposed Changes

I was experimenting with minimal linux kernels and k3s the other day. I used your excellent check-config.sh script to check my configuration. However, k3s didn't run and required extra config options that were missing from the script.

Types of Changes

I added 2 missing config checks to the script. I categorized them as required as the server failed to start without them. Furthermore, I bootstrapped vanilla servers without any extra configuration (e.g. env variables) during my testing.

Verification

Here are some error messages taken from journalctl -u k3s.service.

Regarding NETFILTER_XT_MATCH_COMMENT:
Feb 11 22:57:15 virtoo k3s[6375]: panic: F0211 22:57:15.908590 6375 network_policy_controller.go:341] Failed to run iptables command to insert in INPUT chain running [/usr/bin/iptables -t filter -I INPUT 1 -m comment --comment kube-router netpol - 4IA2OSFRMVNDXBVV -j KUBE-ROUTER-INPUT --wait]: exit status 1: Warning: Extension comment revision 0 not supported, missing kernel module?

Regarding NETFILTER_XT_MATCH_MULTIPORT:
Feb 11 23:02:34 virtoo k3s[2678]: panic: F0211 23:02:34.075017 2678 network_policy_controller.go:336] Failed to verify rule exists in KUBE-ROUTER-INPUT chain due to running [/usr/bin/iptables -t filter -C KUBE-ROUTER-INPUT -p tcp -m comment --comment allow LOCAL TCP traffic to node ports - LR7XO7NXDBGQJD2M -m addrtype --dst-type LOCAL -m multiport --dports 30000:32767 -j RETURN --wait]: exit status 2: Warning: Extension multiport revision 0 not supported, missing kernel module?

Those error messages vanish and the server starts when both match extensions are compiled into the kernel (or as modules).

Testing

I don't think this is subject to unit testing. Please let me know otherwise.

Linked Issues

User-Facing Change

NONE

Further Comments

[cwayne18]

Thanks a lot for the PR and especially for signing your commit! Just as a heads up we're currently under code freeze as we enter release week, but we can review and merge for you once freeze is lifted (assuming review passes). Thanks again!

[cwayne18]

Thanks again for the contribution!