[Pdns-users] serveral ALIAS questions

Klaus Darilion klaus.mailinglists at pernau.at
Mon Jun 11 14:23:44 UTC 2018

Am 11.06.2018 um 12:53 schrieb Klaus Darilion:
> Hi!
> We soon put ALIAS into production. Hence, I have some questions to
> better understand what's going on internally in PDNS.
> a) What happens if the backend query (from PDNS-auth to resolver) is
> unanswered? Will PDNS timeout the outstanding query or will it be kept
> on the list for ever? If it times out - will PDNS send any responses?
> I stopped the resolver and sent a query to an ALIAS RR. My obervation
> is, that PDNS did send an upstream query, but it:
>  - does not resend to the resolver
>  - does not send any response (eg SERVFAIL) upstream
> Hence I supsect that such unanswered backend queries will resist in some
> queue forever.
> Can you please comment an what really happens if the resolver is not
> available?
> b) AFAIS the backend query supports only UDP without EDNS0. Hence, only
> resposnes up to 512 bytes. Correct?
> c) AFAIS queries to ALIAS RRs are not cached in the packet cache. Why not?

d) It seems that the ALIAS handling is not not recursive and hence does
not have loop detection. Ie. foobar.com ALIAS www.foobar.com could be
handled without asking the resolver. But every query is sent to the
resolver. That could be optimized resolving local (in zone, or if target
is another authoritative zone). But then loop-detection must be added
too. Currently there is no loop detection/prevention, only a throtteling
by the resolver (if implemented in the resolver).

Was this just not optimized or was it by design to handling recursion
via the resolver?


More information about the Pdns-users mailing list