# DNS Updater

A small CLI that updates existing A records on supported DNS providers to match the current IP of your machine (either its public “WAN” IP or the IP of a local network interface).

Runs once and exits — ideal to schedule with cron or a systemd timer.

## Features
- Update existing A records on multiple providers in one run
- Providers: DigitalOcean, Vultr
- Public IP lookup via pluggable services (ipecho, jsonip, etc.)
- Resolve IP from a local interface (e.g., `eth0`)
- Skips updates when the record is already up-to-date
- Structured, human-readable logging

## How It Works
- Loads the YAML config and registers DNS providers.
- Selects the configured public IP lookup service.
- Iterates `updates` and, for each record:
  - Resolves the target IP from `wan` (public IP) or a local interface name.
  - Looks up the existing record by name on the provider.
  - Updates the record only if the IP changed.

Only A records are listed/updated; records must already exist.

## Install
- Requirements: Go 1.23+ (module toolchain sets `go1.24.1`).

Build with Makefile:

```
make build
```

Or directly with Go:

```
go build -v -o build/dnsupdater cmd/dnsupdater/main.go
```

## Configuration
See `config.example.yml` for a full example. Create your own `config.yml` alongside the binary (or pass `-config`):

```yaml
services:
  IPLookup: ipecho   # one of: ipecho, jsonip, ifconfig.me, ip.me, icanhazip

providers:
  digitalocean:
    token: <YOUR_DO_TOKEN>
  vultr:
    token: <YOUR_VULTR_TOKEN>

updates:
  digitalocean:
    domain1.com:
      www: wan        # use public IP
      app: eth0       # use IP from local interface
    domain2.com:
      www: wan
  vultr:
    example.com:
      www: wan
```

- `services.IPLookup`: public IP lookup backend. Supported values: `ipecho`, `jsonip`, `ifconfig.me`, `ip.me`, `icanhazip`.
- `providers`: map of provider name to credentials. Current providers: `digitalocean`, `vultr`.
- `updates`: which domains/records to update per provider.
  - Value must be either `wan` (public IP) or a local interface name (e.g., `eth0`).

Known limitation: literal IPv4 strings in `updates` (e.g., `84.24.254.21`) are not interpreted as IPs and will fail; use `wan` or an interface name instead.

## Usage

```
./build/dnsupdater -config ./config.yml     # run once
./build/dnsupdater -v                       # print version
```

Logs are written to stderr in a readable format.

### Scheduling
- Cron: `*/5 * * * * /path/to/dnsupdater -config /path/to/config.yml >/dev/null 2>&1`
- systemd (example): create a service and timer that invoke the binary every few minutes.

## Testing

```
make test
```

## Provider Notes
- DigitalOcean: updates existing A records via the Domains API.
- Vultr: updates existing A records via the DNS API.
- Records must already exist; creation is not implemented.

## Troubleshooting
- “Invalid DNS service”: the name under `updates:` doesn’t match a configured provider.
- “Failed to fetch ip”: `wan` lookup failed or the local interface name is wrong.
- No change: when the on-file IP matches the resolved IP, the tool logs success without making an API call.

## License
AGPL-3.0-only. See `LICENSE`.