Ipv6 / DNS questions

[Karl Denninger]

Perusing through the various documentation I've not yet found an answer
to this, and figure someone might know where to point me before I start
banging code beyond a shell script or three.

Assuming we have a "dual stack" system on the Internet; the provider is
willing to allocate us anywhere from a /56 to a /64 off stateless Ipv6
which our gateway (running FreeBSD), and that is working using dhcp6c. 
Said gateway then (typically) gets said /56 and allocates a /64 on the
internal interface, and runs rtadvd.  The clients run rtsold and are
getting addresses just fine.  Windows clients, Android phones and
similar are also having no problems.

Now posit a host "inside" the gateway that I wish to have an exposed
service on the Internet.  In the IPv4 world I run NAT, the DMZ'd host is
on a private address, and I port-twist at the gateway (e.g. a connection
to TCP port 5050 on the gateway goes to x.x.x.x:5050 on the internal
host.)  The external client is none the wiser; he only sees the single
outside IP.  For IPv6 of course the internal address is routable, but
this leads to a problem -- how does the outside guy know where it is?

Is there a dynamic DNS update method associated with Ipv6's address
assignment system?  Since the assignment is "stateless" it obviously
(and does, in my experience!) move.  I can deal with it via a couple of
shell scripts, and there are only a couple of hosts where it matters,
but this would dramatically simplify the IPv4 gameplaying that's
necessary to have something behind a gateway router while on a "globally
visible", but possibly changing "at whim", IpV6 address.

I assume someone has gone after this issue by now so if there's "prior
art" a pointer would be appreciated.

Thanks in advance!

-- 
Karl Denninger
karl at denninger.net <mailto:karl at denninger.net>
/The Market Ticker/
/[S/MIME encrypted email preferred]/
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