[Pdns-users] CNAME NXDOMAIN problem
Peter van Dijk
peter.van.dijk at netherlabs.nl
Fri Nov 22 11:05:54 UTC 2013
On Nov 22, 2013, at 9:45 , Francois Claire wrote:
>> Appears that you receive nxdomain from nameserver, see at the end of trace.
> Indeed the g2.ebay.com. DNS server (18.104.22.168) answers thumbs.g.ebay.com. with an NXDomain:
> 14:13:38.023503 IP W.X.Y.Z.4994 > 22.214.171.124.53: 26515 [1au] A? thumbs.g.ebay.com. (54)
> 14:13:38.196462 IP 126.96.36.199.53 > W.X.Y.Z.4994: 26515 NXDomain*- 0/1/1 (96)
> But when using dig, the g2.ebay.com. DNS server answers a CNAME record:
> $ dig @188.8.131.52 thumbs.g.ebay.com
> ; <<>> DiG 9.8.4-P2 <<>> @184.108.40.206 thumbs.g.ebay.com
> ; (1 server found)
> ;; global options: +cmd
> ;; Got answer:
> ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 58678
> ;; flags: qr aa rd; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 0
> ;; WARNING: recursion requested but not available
> ;; QUESTION SECTION:
> ;thumbs.g.ebay.com. IN A
> ;; ANSWER SECTION:
> thumbs.g.ebay.com. 60 IN CNAME c.ebay.georedirector.akadns.net.
> ;; Query time: 177 msec
> ;; SERVER: 220.127.116.11#53(18.104.22.168)
> ;; WHEN: Thu Nov 21 14:41:08 2013
> ;; MSG SIZE rcvd: 80
> So why is the powerDNS recursor receiving an NXDomain ? Is its query malformed ?
I don't know why your recursor is receiving NXDomain (mine does not, for example) - but this does not appear to be a PowerDNS Recursor issue.
However, the g*.ebay.com servers are definitely broken. While the relevant query (dig +norec +noedns @22.214.171.124 thumbs.g.ebay.com A) returns the right CNAME for me, various other queries (replace A in the query with MX, ANY or even CNAME) yield NXDOMAIN. A recursor that receives NXDOMAIN when asking for a specific type is allowed to assume the NXDOMAIN applies to all other types.
Given that they are broken like this, I'm not surprised they manage to reply NXDOMAIN to A-queries as well, in specific situations.
If you have a contact at eBay, please let them know that their name servers are broken. I will also look into finding a contact.
Peter van Dijk
Netherlabs Computer Consulting BV - http://www.netherlabs.nl/
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