[Pdns-users] TCP transport prefers recursion over local database

[Rafał Kupka]

Hello,

I've spot something strange in Powerdns behavior. It looks like query
over TCP uses recursion even if record is in local database (ldap
backend).

Configuration (incomplete):
cache-ttl=60
disable-axfr=yes
fancy-records=no
lazy-recursion=yes
negquery-cache-ttl=60
query-cache-ttl=20
queue-limit=1500
recursive-cache-ttl=10
recursor=172.30.0.2

Query results (TCP):
$ host -vv -u -t ns dominikanieruchomosci.com ns1.pronet.com.pl
Server: ns1.pronet.com.pl
Address: 193.108.35.15

...

dominikanieruchomosci.com       86813   IN      NS
ns1.pronet.com.pl
dominikanieruchomosci.com       86813   IN      NS
ns2.pronet.com.pl
Additional information:
ns2.pronet.com.pl       68551   IN      A       193.108.35.16
ns1.pronet.com.pl       68551   IN      A       193.108.35.15

Those records come from *.gtld-servers.net (NS) and [a-g]-dns.pl (A).
They had long TTL of upstream DNS servers.

Query results (UDP):
$ host -v -t ns dominikanieruchomosci.com ns1.pronet.com.pl
Server: ns1.pronet.com.pl
Address: 193.108.35.15

...

dominikanieruchomosci.com       3600    IN      NS ns1.pronet.com.pl
dominikanieruchomosci.com       3600    IN      NS ns2.pronet.com.pl
dominikanieruchomosci.com       3600    IN      NS ns3.pronet.com.pl
Additional information:
ns2.pronet.com.pl       3600    IN      A       193.108.35.16
ns3.pronet.com.pl       3600    IN      A       195.117.154.102
ns1.pronet.com.pl       3600    IN      A       193.108.35.15

That's data from local ldap server.

When I comment out resolver= line from config, TCP and UDP results
matches data from local database.

Server version 2.9.20. There are some TCP changes in 2.6.21 changelog
but unfortunately I cannot test it now. Maybe someone can test/confirm
that this is fixed in 2.6.21?

Kupson