docs Add ufw to k3s known issues

Addresses rancher/k3s#2059 by adding information on the modifications needed to run k3s with ufw enabled.

Oct 04 '20 15:10 t0xicCode

Thank you! @erikwilson @Oats87 can you review this?

Oct 04 '20 15:10 cjellick

I can run some tests and push the resulting iptables changes here. I was under the impression that the original issue had delved into the details, but it doesn’t hurt to check it again.

Nov 25 '20 22:11 t0xicCode

I can run some tests and push the resulting iptables changes here. I was under the impression that the original issue had delved into the details, but it doesn’t hurt to check it again.

That'd be great if you could do that -- the original issue seemed to be more of a "It happens to work with these rules" but I've had to fight these system-level firewalls a few times on issues like this, where certain things work but others don't.

Nov 25 '20 22:11 Oats87

@SheilaghM @davidnuzik Should we close this PR, then open an issue in the K3s repo for further investigation?

Dec 23 '20 22:12 catherineluse