# Update check

How the console learns that a newer release exists. The DNS server serves the console with
`default-src 'self'` and no `connect-src`, so the browser cannot ask GitHub. It can ask its own
server to resolve a name with DNS Client, and DNS Client takes a DNS-over-HTTPS URL as the server.

This folder is that DNS-over-HTTPS server, a Cloudflare Pages Function at
`https://technitium-console.pages.dev/dns-query`. It knows one name,
`latest.technitium-console.pages.dev`, and answers its TXT with:

```
v=1 latest=1.4.0 server=15.5
```

`latest` is the latest release on GitHub, the one `install.sh` installs. `server` is the oldest
Technitium DNS Server it is made for: `technitiumServerMinimum` in that tag's `package.json`. A
release is announced only once the Docker image `latest` is that release, so that pulling gets it. The format is frozen: consoles already
installed read only this one, and ignore keys they do not know.

It reads GitHub at most once an hour and keeps the last good answer for up to a month, in case
GitHub is down. That copy lives in Cloudflare's cache, one per Cloudflare location, and can be
evicted sooner. It needs no secrets.

## Deploying

A Cloudflare Pages project connected to this repository:

- Production branch: `main`
- Root directory: `update-check`
- Build command: none
- Build output directory: `public`

## Running it locally

```sh
node --experimental-strip-types dev/update-check-serve.mjs
```

It listens on port 8853. To have it answer a fixed record instead of reading GitHub, set
`UPDATE_CHECK_FAKE='v=1 latest=9.9.9 server=15.5'`. The harness's DNS server reaches it at the
Docker network's gateway, as `http://<gateway>:8853/dns-query`.