[Dnsmasq-discuss] Query retried "out of nothing"

Dominik dl6er at dl6er.de
Sun Apr 4 15:54:15 UTC 2021


Hey Simon,

I'm currently testing the tip of dnsmasq master and noticed the following:
When running the test http://test-ipv6.com/ I do see some queries being
retried seemingly without any indication.

Example from the log:

Apr  4 17:43:58 dnsmasq[3054422]: 467 192.168.2.224/49166 query[AAAA]
ipv4.nop.hu from 192.168.2.224
Apr  4 17:43:58 dnsmasq[3054422]: 467 192.168.2.224/49166 forwarded
ipv4.nop.hu to 8.8.8.8
[... many unrelated lines ...]
Apr  4 17:43:58 dnsmasq[3054422]: 467 192.168.2.224/49166 forwarded
ipv4.nop.hu to 8.8.8.8
[... many unrelated lines ...]
Apr  4 17:43:58 dnsmasq[3054422]: 467 192.168.2.224/49166 reply error is
SERVFAIL

There was seemingly nothing triggering the second forwarding. A Wireshark
recording revealed that the re-forwarding was triggered because of
receiving a SERVFAIL but this was not logged.

Interestingly, when querying this domain alone, it works as expected and no
re-submission is tried:

Apr  4 17:45:55 dnsmasq[3054422]: 483 192.168.2.224/40200 query[AAAA]
ipv4.nop.hu from 192.168.2.224
Apr  4 17:45:55 dnsmasq[3054422]: 483 192.168.2.224/40200 forwarded
ipv4.nop.hu to 8.8.8.8
Apr  4 17:45:55 dnsmasq[3054422]: 483 192.168.2.224/40200 reply error is
SERVFAIL

So there seems to be an issue with the new retry mechanism behaving
differently when under load and when handling a single query. Should the
query be retried at all when upstream responsed with SERVFAIL (I have only
one server, 8.8.8.8, configured as upstream DNS resolver)?


I'm happy to run additional tests or provide additional information, if
required. I can also share the Wireshark recording and the full log if you cannot reproduce this. I prefer to share it off-list because the log may contain sensitive information.

Best,
Dominik




More information about the Dnsmasq-discuss mailing list