[tahoe-dev] [tahoe-lafs] #867: use ipv6

[Randall Mason]

On Fri, Feb 15, 2013 at 9:06 PM, Greg Troxel <gdt at ir.bbn.com> wrote:

> Also, fe80:: addresses should probably be ignored, as they are meant to
> be used only on a single link.
>
Would you be able to elaborate about this?  Specifically about my use case
of two hosts on tunnel brokers, but link-local.  I feel it's important, and
nobody's going to be typing in the furls manually, so who does it benefit
to have less capability than more?

Other advantages are that they are not routed, so that they can be more
"secret" than other addresses.  If you didn't want the world to know that
you were using Tahoe, preferring more local over more remote addresses
could be better.

If you bring up a host, or set of hosts, in an environment without a DHCP
server, and no IPv6 router, and don't run Avahi/Bonjour the only address
that you'll come up with is the fe80 address.  With them included, your
tahoe cluster can be brought up and connected to without any configuration,
without any infrastructure, it would even work with only a crossover cable.

If everything is totally mis-configured, and you end up on different
subnets, with static IPs and a bunch of different network partitions, your
Tahoe cluster would still work, and surely not route there and back again
like a Hobbit.  You can have two different radvd instances advertising
different routers and address spaces on the same network.  Same with DHCP.
You can easily send your data to Germany, the CIA, and China and be on the
same link-local network because one DHCP server had your MAC set up to be
ignored, and the other DHCP server has your friend's MAC set up to be
ignored.

There is still the little voice in the back of my head that says "those are
weired and you hate it when you only have a 169.254.x.x address in v4, why
would you use the same thing in v6"?  And the idea about them leaking MAC
addresses doesn't speak well for them being required, but I don't know if I
want them off by default.  I don't care a whole bunch if the world knows my
MAC address because I can randomize it when I want and not end up with
giving up my identity or a paper trail to my house.  If you really want
privacy then you should already be randomizing all your MAC addresses on
boot and every day or so.  But I still want people to be able to disable
this if they really want.  I used Microsoft Word for years after knowing
that they save my MAC address in EVERY document.
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