Maintained by: NLnet Labs

[Unbound-users] reddit.com issue

W.C.A. Wijngaards
Mon Aug 25 09:16:38 CEST 2014


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Hi,

On 08/25/2014 06:58 AM, Thomas Guthmann wrote:
> Hi,
> 
> Like this ?
> 
> 15    A IN http???www.reddit.com. 221.211696 iterator wait for
> 173.245.58.24 22 AAAA IN http???www.reddit.com. 0.097014 iterator
> wait for 198.41.222.24

Yes.  The reddit servers (or likely, their load-balancers) are not
following the DNS specifications.  They are dropping the query and
they should be replying.  There was a draft at the IETF even to mark
this as harmful, but it did not progress through the standards track,
I believe.  If they want to refuse the query for unclear reasons (what
is wrong with responding NXDOMAIN?) they could choose from nice error
codes like SERVFAIL and FORMERR and REFUSED.

Unbound notices the domain does not respond to A queries.  And marks
the domain as timeouted, down, for A queries.  Unbound stops sending A
queries there to attempt to trottle down traffic towards that stricken
server.  If A queries get replies (there is an exponential backoff to
the queries sent out) then unbound marks the server as responsive
again (the server is considered back up) and queries are resumed.

Best regards,
   Wouter

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