Question about dynamic IPv6-PTR-Generation

John Levine johnl at
Sat Aug 27 21:01:26 UTC 2016

>Though, if you want to participate in the cargo cult of generic PTRs,
>you don't need the complexity of draft-woodworth-bulk-rr's regex-driven
>templates in your nameserver. Knot DNS's "minimal viable product"
>implementation is ~300 SLOC and uses a hardcoded template.

Having looked at the draft, I agree that its complexity and the multiple
changes it makes to exisitng DNS semantics make it dead on arrival.

My suggestion if you really want to do this is to use a specialized
server.  People who serve DNSBLs use a specialized server called
rbldnsd.  You give it CIDR ranges of addresses and it synthesizes
DNSBL records, including patching the addresses into TXT records so
they can return stuff like this: TXT "Blocked -- see http://www.bad.example?ip="

where the was plugged in on the fly.

rDNS and DNSBLs are quite similar in DNS function, so you could
probably modify rbldnsd to generate PTR records with patterns in the
same way.  Then just delegate your rDNS zones to it. Since v6 rDNS
breaks names on 4-bit boundaries, even if your delegations are rather
irregular, it's not all that many delegations.


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