Authoritative server returns spurious SOA.

[Habbie]

pdns_server = 2.9.21-svn.20061029.908

mysql> select name,type,content from records where name = 'wraith.sf.ca.us'; +-----------------+------+------------------------+ | name | type | content | +-----------------+------+------------------------+ | wraith.sf.ca.us | A | 192.58.220.5 | | wraith.sf.ca.us | NS | wraith.sf.ca.us | | wraith.sf.ca.us | NS | smidge.wraith.sf.ca.us | +-----------------+------+------------------------+

In this situation with a delegated domain with glue pointing at itself and on an authoritative server without recursion available PowerDNS will return an SOA record even when not queried for:

[augie@augnix ~]$ dig mx wraith.sf.ca.us @pdns-lab.sr.sonic.net

; <<>> DiG 9.3.1 <<>> mx wraith.sf.ca.us @pdns-lab.sr.sonic.net
; (1 server found)
;; global options:  printcmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 49090
;; flags: qr rd; QUERY: 1, ANSWER: 0, AUTHORITY: 3, ADDITIONAL: 2

;; QUESTION SECTION:
;wraith.sf.ca.us.               IN      MX

;; AUTHORITY SECTION:
sf.ca.us.               259200  IN      SOA     ns1.sonic.net. hostmaster.sonic.net. 2006120502 3600 300 1209600 3600
wraith.sf.ca.us.        3600    IN      NS      wraith.sf.ca.us.
wraith.sf.ca.us.        3600    IN      NS      smidge.wraith.sf.ca.us.

;; ADDITIONAL SECTION:
wraith.sf.ca.us.        3600    IN      A       192.58.220.5
smidge.wraith.sf.ca.us. 3600    IN      A       192.58.220.65

;; Query time: 3 msec
;; SERVER: 64.142.100.91#53(64.142.100.91)
;; WHEN: Thu Dec 28 12:24:22 2006
;; MSG SIZE  rcvd: 169

However with recursion available, the spurious SOA does not appear:

[augie@augnix ~]$ dig mx wraith.sf.ca.us @pdns-lab.sr.sonic.net

; <<>> DiG 9.3.1 <<>> mx wraith.sf.ca.us @pdns-lab.sr.sonic.net
; (1 server found)
;; global options:  printcmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 62080
;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 1

;; QUESTION SECTION:
;wraith.sf.ca.us.               IN      MX

;; ANSWER SECTION:
wraith.sf.ca.us.        85022   IN      MX      512 smidge.wraith.sf.ca.us.

;; ADDITIONAL SECTION:
smidge.wraith.sf.ca.us. 85022   IN      A       192.58.220.65

;; Query time: 0 msec
;; SERVER: 64.142.100.91#53(64.142.100.91)
;; WHEN: Thu Dec 28 12:25:36 2006
;; MSG SIZE  rcvd: 72

The spurious SOA stops some resolvers in their tracks and will cause them to stop recursing the tree, and thus in this case the correct MX record is never found.

[Habbie]

Attachment 'MySQL dump with single zone showing defect.' (powerdnslab.sql) https://gist.github.com/5466603

[Habbie]

Attachment 'The patch removes the conditionals that add the spurious SOA.' (pdns-packethandler.cc.patch) https://gist.github.com/5466604

[Habbie]

Author: anon You can see the defect after loading the MySQL dump by querying the kgctest zones.

Spurious SOA with glue that points to self:

[augie@augnix tmp]$ dig mx kgctest.sf.ca.us @pdns-lab.sr.sonic.net

; <<>> DiG 9.3.1 <<>> mx kgctest.sf.ca.us @pdns-lab.sr.sonic.net
; (1 server found)
;; global options:  printcmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 48736
;; flags: qr rd; QUERY: 1, ANSWER: 0, AUTHORITY: 3, ADDITIONAL: 2

;; QUESTION SECTION:
;kgctest.sf.ca.us.              IN      MX

;; AUTHORITY SECTION:
sf.ca.us.               259200  IN      SOA     ns1.sonic.net. hostmaster.sonic.net. 2006122202 3600 300 1209600 3600
kgctest.sf.ca.us.       259200  IN      NS      kgctest.sf.ca.us.
kgctest.sf.ca.us.       259200  IN      NS      ns2.kgctest.sf.ca.us.

;; ADDITIONAL SECTION:
kgctest.sf.ca.us.       259200  IN      A       64.142.122.13
ns2.kgctest.sf.ca.us.   259200  IN      A       64.142.122.14

;; Query time: 3 msec
;; SERVER: 64.142.100.91#53(64.142.100.91)
;; WHEN: Fri Dec 29 11:47:14 2006
;; MSG SIZE  rcvd: 167

No spurious SOA when glue points elsewhere:

[augie@augnix tmp]$ dig mx kgctest2.sf.ca.us @pdns-lab.sr.sonic.net

; <<>> DiG 9.3.1 <<>> mx kgctest2.sf.ca.us @pdns-lab.sr.sonic.net
; (1 server found)
;; global options:  printcmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 44482
;; flags: qr rd; QUERY: 1, ANSWER: 0, AUTHORITY: 2, ADDITIONAL: 0

;; QUESTION SECTION:
;kgctest2.sf.ca.us.             IN      MX

;; AUTHORITY SECTION:
kgctest2.sf.ca.us.      259200  IN      NS      ns1.kgctest2.inavlid.
kgctest2.sf.ca.us.      259200  IN      NS      ns2.kgctest2.inavlid.

;; Query time: 4 msec
;; SERVER: 64.142.100.91#53(64.142.100.91)
;; WHEN: Fri Dec 29 11:47:12 2006
;; MSG SIZE  rcvd: 87

[Habbie]

Author: ahu Strangely enough, this problem does not appear in the trunk of my code! Could you try with the latest snapshot from http://svn.powerdns.com/snapshots ?

[Habbie]

Author: anon http://wiki.powerdns.com/cgi-bin/trac.fcgi/changeset/947 fixed this.