[Pdns-users] MSG SIZE exceeds 512 bytes

abang abang at t-ipnet.net
Wed Dec 5 14:40:09 UTC 2012

Hello Peter,

that explains a lot. Does the Recursor full support EDNS0? I ask because 
there is no "OPT PSEUDOSECTION" in the dig output. Is this pesudosection 
not mandatory?


dig +noanswer +nostats +edns=0 @nameserver

; <<>> DiG 9.8.1-P1 <<>> +noanswer +nostats +edns=0 @nameserver
; (1 server found)
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 55200
;; flags: qr rd ra; QUERY: 1, ANSWER: 13, AUTHORITY: 0, ADDITIONAL: 1

; EDNS: version: 0, flags:; udp: 512
;.                              IN      NS

Am 05.12.2012 14:16, schrieb Peter van Dijk:
> Hello Winfried,
> On Dec 5, 2012, at 10:07 , abang wrote:
>> I wonder how can a answer packet from our PowerDNS Recursor (3.4-pre) exceeds 512 bytes. I thought this is the limit and it should be truncated. The MSG SIZE in the example below is 701. Has someone a explanation for this?
> dig, by default, sends an EDNS bufsize with a request (4096 bytes in the version I tested), allowing the server to go beyond 512 bytes. If you add +noedns or +bufsize=512, you should see a truncated answer (although, if additionals are the reason, the TC-flag will not be set).
> HOWEVER, if the packet cache is enabled, and the query that caused a packet cache entry happened to have EDNS, non-EDNS clients coming in after that will also get the big answer. I will write a ticket about this.
> Kind regards,

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