Openvswitch IPv6 L2 GRE tunnel not working

Installing and Using OpenWrt
1

Has anyone been able to get this working on OpenWRT 22.03? I understand that it was patched on OVS in 2019, and added to the OVS FAQ:

https://docs.openvswitch.org/en/latest/faq/configuration/
Quote:
"Q: Does Open vSwitch support IPv6 GRE?
A: Yes. L2 tunnel interface GRE over IPv6 is supported. L3 GRE tunnel over IPv6 is not supported."

My setup is fairly simple:

opkg update
opkg install openvswitch 
opkg install kmod-openvswitch-gre 
export PATH=$PATH:/usr/share/openvswitch/scripts 
ovs-ctl start 

ovs-vsctl add-br br0
ovs-vsctl add-br br0-10 br0 10
ovs-vsctl add-port br0-10 wlan0
ovs-vsctl add-port br0 tun6 -- set interface tun6 type=ip6gre options:remote_ip=<my-IPv6-Dst> options:packet_type=legacy_l2

The error I get in the last command is:
"ovs-vsctl: Error detected while setting up 'tun6': could not add network device tun6 to ofproto (Address family not supported by protocol). See ovs-vswitchd log for details."

When I install kmod-gre6, I don't get that IPv6 error. But, I don't see any outbound GRE packets on a tcpdump.

• I notice that the interface ip6gre0 does not exist until I install Kmod-gre6.  
• The above configuration works fine with an IPv4 tunnel destination (slightly different ovs-vsctl command).
• Kmod-gre is a requirement for "kmod-openvswitch-gre", but not kmod-gre6??    
• I know that plain vanilla OpenWRT can do IPv6 GRE L2 tunnels, as I have a working setup for that.  
• I've tried installing all the Openvswitch packages available in Luci:  openvswitch-python3, openvswitch-ovn-host, etc.

Am I missing a command, or is OpenWRT, OVS, and IPv6 GRE tunnels just not compatible?

2

I got the IPv6 tunnel working with the same ovs-vsctl commands in my first post. I used a couple Ubuntu Server 22.04.1 VM's with OVS 2.17.3.

So, looks like there's some sort of incompatibility with OpenWRT, or there's an extra command I need.

3

It appears OVS IPv6 GRE tunnels don't like multiple default GW's from the IPv6 Router Advertisements. I set a static IPv6 address/GW, which eliminated the RA GW's, and it started working. Maybe the problem is that RA's use link local (fe80) addresses, just a hunch.

I've got another problem with the destination not liking the IPv6 Extended Headers from OVS, which vanilla OpenWRT does not use. But, that's a totally separate issue...