Comment 7 for bug 1676363

Looking at how the subnet type is being parsed by cloud-init here[1] it seems that "ipv6_slaac" and "ipv6_dhcpv6-stateful" will both work fine - at least in that regard -, but "ipv6_dhcpv6-stateless" will be interpreted as dhcpv6 instead of slaac.

They also seem to completely ignore any netmask and routes information.

[1] https://git.launchpad.net/cloud-init/tree/cloudinit/sources/helpers/openstack.py#n571