loopia-dns-updater

This is a small utility for updating the Loopia DNS records through the Loopia API. It is capable of updating IPv4 A records and IPv6 AAAA records.

I'm using the tool myself and I have tested it, but please, make a backup of your domain before running this utility. Also run a dry run first to check that it behaves as expected.

Design decisions

1. Must work with lots of hosts/records behind SLAAC
2. Rely on the IP of the interface rather than use an external service to find the IP
3. Auto discover of records in need to be updated (idea from one of my brothers)
4. Should work with both IPv4 and IPv6
5. The use case is home use and small office use with a single FW/Router
6. No config or Loopia credicals on every host with IPv6 services
7. Should be a small stand-alone binary

Supported operating systems

The build script builds for Linux, FreeBSD and OpenBSD, but it should be possible to compile for other operating systems and CPU architectures.

Execution

The software runs as a single execution. Place it in cron or something similar to run periodically

The util will store the relevant IPs of the interfaces. If they are not updated, the util will not call Loopia to check whether update is needed. To force execution, delete the data directory.

Execution flags

Flag	Description
-c {file}	Config file location. If not set, /etc/loopia-dns-updater.yaml is used
-d	Debug output
-h	Show help
-n	Dry run
-q	Quiet. Minimal logging
-s	Data directory. A directory where the utility store it's data. If not set, /var/lib/loopia-dns-updater is used.

Logging

Logging is performed to stdout.

IPv4 handling

The IPv4 addresses are always treated as with netmask /32, i.e. the complete IP of the interface is updated in the DNS.

IPv6 handling

The IPv6 handling supports SLAAC. This is done by reading the netmask of the interface. The prefix (most often the upper 64 bits) is replaced in the AAAA record. The lower part (most often the lower 64 bits) is kept as is. This method also works for /128 addresses where the full address is replaced as with IPv4.

Configuration file

A sample file is provided below

domains:
  - name: example.com
    interfaces:
      - ifName: vio1
        matchUnknown4: true
        match4:
          - ssh.example.com
        match6:
          - ssh.example.com
      - ifName: vio5
        matchUnknown6: true

loopia:
  username: username-from-loopia-api
  password: password-of-loopia-api-user

Configuration items:

Item	Description
domains	List of domains to update
domains.name	FQDN of the domain
domains.interfaces	List of interfaces where to find IP for the domain
domains.interfaces.ifName	The interface name
domains.interfaces.match4	List of FQDN that should be assigned the IPv4 of the interface
domains.interfaces.match6	List of FQDN that should be assigned the IPv6 of the interface
domains.interfaces.matchUnknown4	Update A records that are not listed in any {this}.interfaces.match4 with the IPv4 of this interface
domains.interfaces.matchUnknown6	Update AAAA records that are not listed in any {this}.interfaces.match6 with the IPv6 of this interface
domains.ignore	List of FQDN that should not be modified by the matchUnknown{4|6} above
loopia.username	Loopia API user. The user will call GetSubdomains, GetZoneRecords and UpdateZoneRecord
loopia.password	Loopia API password
executeOnChange	Command to execute if the relevant IPs are changed