After deciding to simplify my linode VM, I gave my LXC setup, however so incredibly cool, the end-of-life notice. The routing was a pain, and I decided to save some memory^1 and go with the stock linode kernel to benefit from their support. Using pv_grub was cool, but linode won't support it.
After switching kernels, I ran into a few glitches:
Interesting error message, eh? Almost as good as treason uncloaked! Searches turned up some recommendations to ensure matching tuns or taps on the client and server, as well as ensuring matching lzo compression settings - all that is standard requirements for OpenVPN, and they weren't my issue.
Ack! I was just about to elaborate on the changes I took to render that error begone when it reared its ugly head once more. The horror!
I avoid rebooting if I can, but I've thrown in the towel and decided to do it. I've changed so much with sticky bits like netfilter rules that I've decided to just do it.
...5 minutes go by, elevator music playing...
Its still occurring; and although I found a rougue client setup that I forgot about that was trying to connect without lzo, I disabled it, and the error continues.
Tcpdump reveals this funny bit:
21:08:56.542726 f2:3c:91:ae:13:53 > ff:ff:ff:ff:ff:ff, ethertype Unknown (0x88a2), length 32: 0x0000: 1000 ffff ff01 0000 0000 0000 0000 0000 ................ 0x0010: 0000
Turning on ipv6 clears that up:
21:26:49.553612 IP6 fe80::1 > ff02::1: ICMP6, router advertisement, length 64
but still doesn't explain why I'm still getting that IP packet with unknown IP version=15 seen message.
Hmm. No, still getting that error about the ethertype Unknown.
Here's something; the ICMP6 broadcast is legit, but the 0x88a2 broadcast is fishy. Check out this thread from gentoo. They suggest its a some device announcing itself to the world. Wonderful! Since its a broadcast, the nature of the tun device receives it too, so I'm trying out the solution they suggest to use ebtables.
-A FORWARD -p 0x88a2 -j DROP
didn't do it, so I'm trying:
-A INPUT -p 0x88a2 -j DROP
Not there yet, now trying:
ebtables -A INPUT -s f2:3c:91:ae:13:53/ff:ff:ff:ff:ff:ff -j DROP ebtables -A FORWARD -s f2:3c:91:ae:13:53/ff:ff:ff:ff:ff:ff -j DROP
Hey what do you know - f2:3c:91:ae:13:53 is my MAC addr. Its probably something to do with the hardware platform that linode is using, that may use AoE.
I'm just going to dial down the verbosity of OpenVPN until it becomes an issue. Argh, that didn't work either, and I couldn't give it up; so decided to switch back to the Ubuntu stock kernel. That seems to have fixed all sorts of annoyances. I'm pretty certain that unknown ethertype was AoE, the module being compiled into the linode kernel.
aoe: AoE v50 initialised.
I suspect that was the culprit of the unknown ethertype, but I'm still not sure about the original oddity; the IP packet with unknown IP version=15 seen log. That's thankfully gone away, it could have been something missing from the linode kernel, or it could have been one of the new rules I've setup with ufw.
Ufw rocks; I dig it.
^1 - I am not sure if using the stock linode kernel or the stock ubuntu kernel will be more memory efficient, could be the latter, as only the necessary modules will get loaded in. Its a theory.