- Cached messages that reach 0 TTL are considered expired. This prevents
Unbound itself from issuing replies with TTL 0 and possibly causing a
thundering herd at the last second. Upstream replies of TTL 0 still
get the usual pass-through but they are not considered for caching
from Unbound or any of its caching modules.
- 'serve-expired-reply-ttl' is changed and is now capped by the original
TTL value of the record to try and make some sense when replying
with expired records.
- TTL decoding was updated to adhere to RFC8767 section 4 where a set
high-order bit means the value is positive instead of 0.
- Added serve-stale functionality as described in
draft-ietf-dnsop-serve-stale-10. `serve-expired-*` options can be used
to configure the behavior.
- Updated cachedb to honor `serve-expired-ttl`; Fixes#107.
- Renamed statistic `num.zero_ttl` to `num.expired` as expired replies
come with a configurable TTL value (`serve-expired-reply-ttl`).
- Fixed stats when replying with cached, cname-aliased records.
- Added missing default values for redis cachedb backend.
