Add opt-in, driver-based WAN failover/CGNAT guard#2
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When a connection fails over to a CGNAT'd path (e.g. a 4G USB modem as WAN backup), the public IP seen from the internet becomes a shared carrier address that can't route back home. Publishing it would point the domain at a dead address. This adds an optional guard that asks the router whether it's on such a path and, if so, skips the update and leaves records on the last good IP. - src/routers/: driver-based abstraction (registry + factory). Core stays agnostic; all router specifics live in a driver. No `router` config block -> feature is fully inert (opt-in). - AsuswrtMerlin driver: authenticates to the router web UI and reads nvram via appGet.cgi (no extra deps; built on Node http/https, handles self-signed + cookies). Pauses updates on secondary-WAN failover, private/CGNAT WAN IP (incl. 100.64.0.0/10), or WAN-IP vs router realip-probe mismatch. Fails open if the router can't be reached, so a transient glitch never freezes DDNS. - GuardState: de-dupes notifications so pause/resume emails fire only on a state transition, not every cron run. - Password is supplied via an env var named in config (passwordEnv); never stored in config.json. - Docs: README section + AGENTS.md; IPv6/AAAA noted as a TODO. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
- Logger: create the log directory if missing and swallow write failures (one-line stderr warning) instead of throwing. A missing log dir was crash-looping the cron job before it reached any update. - index.js: guard the IP-change notification behind !dryRun so a dry-run no longer sends real emails; logs "Would send" instead. - Rename the --dryRun flag to --dry-run in the docs (yargs camel-cases it, so both forms work). Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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What
Adds an opt-in, driver-based guard that refuses to publish the detected public IP while the connection is on a WAN failover path / behind CGNAT (e.g. a 4G USB modem used as WAN backup). In that state the public IP is a shared carrier address that can't route back home — publishing it would point the domain at a dead address. The guard skips the update and leaves records on the last known-good IP instead.
Design
src/routers/— registry + factory. Norouterblock in config → feature is fully inert (opt-in).AsuswrtMerlindriver — authenticates to the router web UI and reads nvram viaappGet.cgi(no new deps; built on Nodehttp/https, handles self-signed certs + cookies). Pauses on any of: secondary-WAN failover (wan1_primary), private/CGNAT WAN IP (incl.100.64.0.0/10), or WAN IP ≠ the router's ownrealipexternal-IP probe. Fails open if the router is unreachable, so a transient glitch never freezes DDNS.GuardState— de-dupes notifications so pause/resume emails fire only on a state transition.passwordEnv) — never stored inconfig.json.Testing
publishable: true.routerblock is present.Docs
README section +
AGENTS.md. IPv6 / AAAA support noted as a TODO/Roadmap item (separate feature).