The networking code within OpenVPN uses separate functions for IPv4 and IPv6
code paths. A couple of years ago, there was a major overhaul of how IPv4 was han-
dled, but the work was never done for the IPv6 functions. OpenVPN 2.3 does sup-
port a completely native IPv6 transport as well as encapsulated traffic. Using IPv6
DNS servers and garnering that information from DHCP isn't supported, but is on
the roadmap for v2.4.
push "redirect-gateway ipv6" is also on the list. You can still imitate a default route
with IPv6 by pushing the special routes manually:
push "route-ipv6 ::/0 2600:dead:beef::1"