Ryan Malloy 1ab88a25f7 coredns: hidden-primary architecture with AXFR for HE secondaries
Goal: serve the public DNS face via Hurricane Electric's free
secondary-DNS service (dns.he.net), with CoreDNS on dell01 acting as
the hidden primary. We edit zones here; HE pulls them via AXFR.

Changes:
- scripts/prepare-zones.sh:
  * SOA mname: ns1.vultr.com -> ns1.he.net (so the apex SOA reflects
    HE as the primary in published RDATA)
  * Strip ns?.vultr.com NS records from each zone and inject the five
    HE nameservers (ns1..ns5.he.net) as the authoritative NS set
- Corefile (shared `common` snippet):
  * Add `transfer { to * }` to authorize AXFR. Tried specific IPs +
    `*` mixed on the same line but CoreDNS silently fails to bind
    server blocks with that syntax; bare `to *` is the only form that
    actually starts the listeners. Trade-off: NOTIFY targeting is lost
    (HE polls per SOA refresh=3600s instead of being pushed). For DNS
    data this is fine since each record is publicly queryable anyway.

Verified AXFR end-to-end: `dig @dell01 -p 5353 acrazy.org AXFR +tcp`
returns 41 records with the new HE NS set and HE-rooted SOA.

Still needed (operator action):
- Firewall NAT for TCP/53 -> 172.16.1.15:5353 (so HE can connect in)
- Add each of the 91 zones at dns.he.net as Secondary DNS pointing
  at 154.27.180.210
- Update each domain's registrar NS records from Vultr -> HE
2026-05-16 15:49:42 -06:00
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