Stale cache feature problems

[Borja Marcos]

Hi,

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:

doh.xfinity.com A and AAAA
ping.ui.com A and AAAA
gs.loc.apple.com A and AAAA
nv2-namain-deco.netatmo.net 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.



Cheers,





Borja.