OpenVPN IPv6 between pfSense endpoints with IPv4 traffic inbetween
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So when I switch my OpenVPN tunnels between two pfSense+ servers over to IPv6 they seem to connect ok. The only traffic over the tunnels is RFC 1918 IPv4 addresses, so IPv6 is only used to talk back and forth over the internet with the pfSense servers.
Ok so here is where the weird starts. I can ping all the addresses fine internally with no packet loss or anything, but HTTP/HTTPS and SSH traffic is just... wonky. It seems to connect, but I get no reliable data transfer.
Switch back to IPv4 on the OpenVPN client to force an IPv4 instead of an IPv6 tunnel, everything works fine.
OpenVPN DCO is enabled on both sides. If I disable it, IPv6 tunnels work fine. If I do IPv4 with DCO, it works like a champ because that was my initial setup.
Is this an OpenVPN DCO bug?