>>  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. 
>	what did you do about TUN_PREPADDR (TUNSLMODE)?

	I've checked the PR.  i'm not sure if it is right to peep
	L3 header...

itojun