[Asrg] For DNSBLs, embedded IPv4 in IPv6

[Frank Ellermann]

John Levine wrote:

> Someone pointed out that in some popular dual stack systems,
> connections from IPv4 addresses appear as IPv6 addresses
> in :FFFF:0000:0000/96

Yes, that is what I meant when I mentioned RFC 4408, (ab)using
::FFFF:127.0.0.2 as an "obvious" test entry.  Another proposal
in the meeting was to use one of the IPv6 example addresses
for this purpose.  But I can't remember the example addresses
without my 4408 cheat sheet, an obvious entry would be better.

> The immediate question is whether to add a sentence or two
> to the DNSBL spec saying that if you have a DNSBL listing
> both v4 and v6 addresses, and you list a v4 address, you
> SHOULD or MUST also list the corresponding embedded v6

No.  It is the job of the clients to get this right, they are
supposed to ask for the IPv4 form of these addresses.  With
::FFFF:127.0.0.2 as a possible *exception* for test purposes.

 Frank