Three of the four failures in the week to 2026-09-23 (09-19, 09-21, 09-23)
had one signature. The Cloudflare zone lookup returned an empty body at its
15s cap, a bare json.load crashed with tracebacks instead of a cause, and the
script carried empty IDs on to a PATCH against zones//dns_records/.
Cloudflare rejected it, so there was no DNS impact, but only by accident.
- Cloudflare calls go through cf(): 3 announced tries, and a call counts
only when the body says success:true.
- success:true is not trusted as shape. pick() validates every body and
prints only the fields asked for, or one line saying why not. It requires
exactly one zone named phasefinal.com and exactly one A record named
headscale.phasefinal.com, each with a non-empty id and content. Two A
records are refused rather than half-updated, and an empty id can no
longer shift the content into the id slot.
- No write without both IDs. The run ends on a confirmation that the record
now reads the new address. The previous final line was an echo whose exit
status was always 0, even when the parse inside it failed.
- Only a global unicast IPv4 is published (python ipaddress is_global).
Loopback, RFC1918, link-local, CGNAT and documentation ranges are retried
and then refused.
- curl -q as the first argument ignores ~/.curlrc, so a verbose config can
never log the bearer token. The vault CLI path is quoted. The empty
data-array expansion is safe under set -u on bash < 4.4.
Tests: services/headscale-ddns/test_headscale_ddns.py, 12 cases with curl,
the vault CLI and sleep stubbed. Each failure case asserts the FATAL line's
stated reason, so a run that died earlier for an unrelated cause cannot pass
it. The documentation-range fixtures (203.0.113.x) were themselves rejected
by the new public-IP guard: a free positive control.
Live: a manual run and a unit run both printed "unchanged 70.230.226.88",
Result=success. Cross-model bug-hunt (heid "Talus", Gróa + seat): all 8
findings folded.
The failed-START notifier built earlier today had its first REAL firing at
15:28: headscale-ddns.service exited 1 after succeeding all afternoon. The
detection worked. The alarm was also useless, and that is the finding.
Both failure paths exited 1 IN SILENCE, so the message said "exit status 1" and
nothing else. An alarm you cannot act on costs the same triage as no alarm at
all -- the notifier did its job and the subject script had no diagnostics for it
to carry.
Cause was transient and harmless: icanhazip.com did not answer inside its 10s
cap, so the IP came back empty and the regex guard refused it. No DNS impact --
the record already held the right address, verified against 1.1.1.1 before
touching anything, and the next timer run succeeded. Arithmetic confirms it:
~17s vault read + 10s curl timeout = 27s against the 28s the failing run took.
Fixed, both verified by making them fail:
- every exit path names its cause; a missing vault key names the key, an
EMPTY token is distinguished from a failed read, and a dead WAN lookup adds
"DNS left unchanged" because that is the fact the reader needs
- the WAN lookup retries 3x with ANNOUNCED attempts -- one third-party blip
should not page a human, and a silent retry would hide a degrading
dependency
⚠ ALSO: this script was not tracked anywhere. A fix to the thing every mesh
client resolves through lived on exactly one disk. Script, unit and timer are
in the repo now.
Measured and recorded: the vault read is 17 of the script's 18 seconds, every
10 minutes. Not a fault, but it bounds any retry budget and it is fleet-wide --
svos-dev's alarm unit carries the same 17-second note.
vh