I understand that one reason why tun0 does not support IPv6 is that
it does not support multicast. I can live without neighbour discovery
messages and stuff, and I think I have the right code otherwise.

  Are there other downsides of setting IF_MULTICAST on the tun interface?

  I've sent a PR on this. 

] Train travel features AC outlets with no take-off restrictions|gigabit is no[
]   Michael Richardson, Solidum Systems   Oh where, oh where has|problem  with[
]     mcr@solidum.com   www.solidum.com   the little fishy gone?|PAX.port 1100[
] panic("Just another NetBSD/notebook using, kernel hacking, security guy");  [