DNS rules referencing rule-sets that contain only ip_cidr predicates
silently stopped matching when legacy DNS mode was disabled, because the
IP-CIDR branch cannot match against an in-flight DNS query. The existing
validation intentionally let every rule_set through on the premise that
mixed sets still work via their non-IP branches, which is only true when
such a branch exists. Track whether a rule-set carries any non-IP-CIDR
predicate and reject pure-IP references the same way bare ip_cidr fields
are already rejected.
Return SUCCESS with empty answers instead of an error when the
queried address family has no range configured. Reject configurations
where neither inet4_range nor inet6_range is set.
The TTL computation and assignment loops treat OPT record's Hdr.Ttl
as a regular TTL, but per RFC 6891 it encodes EDNS0 metadata
(ExtRCode|Version|Flags). This corrupts cached responses causing
systemd-resolved to reject them with EDNS version 255.
Also fix pointer aliasing: storeCache() stored raw *dns.Msg pointer
so subsequent mutations by Exchange() corrupted cached data.
- Skip OPT records in all TTL loops (Exchange + loadResponse)
- Use message.Copy() in storeCache() to isolate cache from mutations
The cache deduplication in Client.Exchange uses a channel-based lock
per DNS question. Waiting goroutines blocked on <-cond without context
awareness, causing them to accumulate indefinitely when the owning
goroutine's transport call stalls. Add select on ctx.Done() so waiters
respect context cancellation and timeouts.
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