1.1.1.1 - RFC 8509 root key trust anchor sentinel support

1.1.1.1 now supports RFC 8509 ↗ root key trust anchor sentinels. They let you check whether the responding resolver trusts a DNSSEC root key ahead of a key rollover.

To check for KSK-2024 (key tag 38696), query DNSSEC-signed names in dnstest.dev:

# On a sentinel-aware resolver that trusts KSK-2024:

# Returns NOERROR with an A answer.
dig @1.1.1.1 root-key-sentinel-is-ta-38696.dnstest.dev. A +noall +comments +answer

# Returns SERVFAIL without an answer.
dig @1.1.1.1 root-key-sentinel-not-ta-38696.dnstest.dev. A +noall +comments +answer

# CD bypasses sentinel processing and returns the original A answer.
dig @1.1.1.1 root-key-sentinel-not-ta-38696.dnstest.dev. A +cdflag +noall +comments +answer

For background on DNSSEC validation, refer to DNSKEY.