how to configure SERVFAIL/weird answer caches

Unbound
1

Hello,

could someone share details of how SERVFAIL cache works and how it can be configured? Pointers to places in code where I can tweak constants are also welcome.

Background:
I'm trying to configure Unbound to cache everything for one day (`cache-min-ttl: 86400`). The intent is to create a "snapshot" in Unbound's cache, and then I plan to re-query that snapshot from another piece of software repeatedly.

I cannot find anything about SERVFAIL cache in unbound.conf or at https://unbound.docs.nlnetlabs.nl/en/latest/ .

My question can be generalized to "how do I make Unbound to cache everything including broken answers for a specified period of time"?

Thank you!

2

Hi Petr,

I believe you need to change the value of util/data/msgparse.h:NORR_TTL.
By default it caches the SERVFAILS that are generated from the iterator module because of upstream issues for 5 seconds.
Changing that to 86400 would have the effect you look after.

Best regards,
-- George