Hi,

every couple of days I get the same problem. I suspend the system for
some hours, and when I come back, the DNS resolution fails. I.e. doing a
ping on a hostname returns "Not found".

The system recovers from this condition after some time, sometimes
after a few seconds but sometimes not even after a minute (that is when
I restart the pdns-recursor service manually and everything suddenly
works like nothing has happened).

NOTE: I have a vague feeling that the down-state of the NIC right after
suspend might be a contributor here. Sometimes it takes almost 5 second
to recover and set the IP address.

Checking the journalctl (after the resuming timestamp), it reveals only:

Jun 12 15:12:13 anon pdns-recursor[2190]: msg="Periodic statistics report" subsystem="stats" level="0" prio="Info" tid="0" ts="1718209993.347" cache-entries="4466" negcache-entries="6" packetcache-acquired="7154799" packetcache-contended>
Jun 12 15:12:13 anon pdns-recursor[2190]: msg="Periodic statistics report" subsystem="stats" level="0" prio="Info" tid="0" ts="1718209993.347" edns-entries="0" failed-host-entries="0" non-resolving-nameserver-entries="0" nsspeed-entries=>
Jun 12 15:12:13 anon pdns-recursor[2190]: msg="Periodic statistics report" subsystem="stats" level="0" prio="Info" tid="0" ts="1718209993.348" concurrent-queries="0" dot-outqueries="0" idle-tcpout-connections="0" outgoing-timeouts="51" t>
Jun 12 15:12:13 anon pdns-recursor[2190]: msg="Periodic statistics report" subsystem="stats" level="0" prio="Info" tid="0" ts="1718209993.348" packetcache-entries="447" packetcache-hitratio-perc="44" taskqueue-expired="0" taskqueue-pushe>
Jun 12 15:12:13 anon pdns-recursor[2190]: msg="Queries handled by thread" subsystem="stats" level="0" prio="Info" tid="0" ts="1718209993.348" count="8940" thread="0" tname="worker"
Jun 12 15:12:13 anon pdns-recursor[2190]: msg="Queries handled by thread" subsystem="stats" level="0" prio="Info" tid="0" ts="1718209993.348" count="2976" thread="1" tname="worker"
Jun 12 15:12:13 anon pdns-recursor[2190]: msg="Queries handled by thread" subsystem="stats" level="0" prio="Info" tid="0" ts="1718209993.348" count="2" thread="2" tname="tcpworker"
Jun 12 15:12:13 anon pdns-recursor[2190]: msg="Periodic QPS report" subsystem="stats" level="0" prio="Info" tid="0" ts="1718209993.348" averagedOver="37663" qps="0"

Best regards,
Eduard.

Hi,

it appears this bug never made it into my mailbox. Sorry for having
missed it.

ping is not super useful for debugging here. Could you try dig
instead?
[..]

I think you'll need to enable debug/trace logging to see something
useful. And yeah, if the NIC is down, I expect sending packets will
fail and you'll end up with negative cache entries. But dig will
tell us more.

Also it'd be good if you could talk directly to upstream, either on
IRC or in a github discussion. They'll have more ideas on how to
debug this.

Thanks,
Chris