When the resolver walks from the root servers towards a name, a server
that answered SERVFAIL, or referred the query back to its own zone, up
or sideways, ended the step, so finding a zone's servers gave up on the
zone though its other servers would answer. Such a reply is now passed
over for the zone's next server, as a timeout or a refusal already was.
To tell a referral that leads closer to the name from one that does
not, each walk keeps the zone of the servers it is asking. Other error
replies, such as FORMERR, are passed over too. The walk that finds a
nameserver's address shares the same server loop, so it changes too.
Model: opus-5-5
ResolveIPAddresses now returns an error, not no addresses, when no
nameserver of the name's zone answered. A nameserver with status
timeout or error is not an answer; one answer, even NXDOMAIN, is
enough for an empty result without an error.
When every server of a zone fails, FindAuthoritativeNameservers moves
on to the parent name, whose servers only refer the query onward. Such
a referral now has status error, so it is no answer either, and a
hostname's saved records show it as error. The only caller, the
nameserver address lookup, already keeps the previous addresses on an
error; its comment no longer says the resolver hides this case.
Model: opus-5-5
The ErrNotImplemented sentinel error was dead code left over from
initial scaffolding. The resolver performs real iterative DNS
lookups from root servers, PortCheck does TCP connection checks,
and TLSCheck verifies TLS certificates and expiry. Removed the
unused error constant.
35 tests define the full resolver contract using live DNS queries
against *.dns.sneak.cloud (Cloudflare). Tests cover:
- FindAuthoritativeNameservers: iterative NS discovery, sorting,
determinism, trailing dot handling, TLD and subdomain cases
- QueryNameserver: A, AAAA, CNAME, MX, TXT, NXDOMAIN, per-NS
response model with status field, sorted record values
- QueryAllNameservers: independent per-NS queries, consistency
verification, NXDOMAIN from all NS
- LookupNS: NS record lookup matching FindAuthoritative
- ResolveIPAddresses: basic, multi-A, IPv6, dual-stack, CNAME
following, deduplication, sorting, NXDOMAIN returns empty
- Context cancellation for all methods
- Iterative resolution proof (resolves example.com from root)
Also adds DNSSEC validation to planned future features in README.
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