Re: IPv6: what is required of lower layers?

[Mouse <mouse%Rodents-Montreal.ORG@localhost>]

I wrote, about a day and a half ago, of some issues I was having with
sending v6 over (what I later said was) a VPN setup built atop tun
interfaces.

I have now managed to make it work, or at least ping6 works.

What did I do?

- Give tun interfaces a non-zero-length link-layer address (which is
   constant - data = "\0" len = 1 - not that I think that is relevant).

- Make tun capable (via TUNSIFMODE) if being IFF_MULTICAST interfaces
   (combined with either IFF_BROADCAST or IFF_POINTOPOINT).

- Make nd6_ifptomac() return non-nil for IFT_TUNNEL as well as the
   types it previously did so for.

I don't know which of these are actually needed, but I suspect they all
are.  The last two definitely are.  (Before these changes, ndp -na kept
reporting (incomplete) despite having exchanged the relevant packets
with the peer.  I'm not sure whether that's actually relevant, but the
two changes occurred at the same time.)

The other changes were in my tun control program; it now handles v6
multicast packets specially.

Thank you, all of you.  I probably could have figured this out by
myself, but at the very least it would have taken substantially longer.

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