Stale cache feature problems

Borja Marcos borjam at
Thu Nov 11 09:27:08 UTC 2021


I’ve been trying the stale answers feature out of curiosity (seems to be a useful idea) but I have ran into problems.

I tried at home, so nobody was actually hurt!

I am running BIND 9.16.22 built from ports on FreeBSD 13-STABLE and I didn’t attempt any tuning,  I just enabled
stale-answer-enable yes;

First problem: I experienced random SERVFAILS with no apparent reason while i had the feature turned on. I think it 
especially affected CDNs with multiple chained CNAMES and complex DNS server infrastructures. 

As far as I know I have good connectivity, both IPv4 and IPv6.

The queries that failed a lot were: A and AAAA A and AAAA A and AAAA A and AAAA

The errors started when I enabled the feature, and they completely went away when I disabled it days later (I feed the
querylog and errors into Graylog)

Second problem: There is a bug. If I comment out the stale-answer-enable line on named.conf and I issue a “rndc
reconfig” the feature does not get turned off. It stays on until I restart the daemon.



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