seren/gandi-dyndns

A script to update a Gandi A record to point at a machine's external IP address.

gandi_dyndns

This implements a simple dynamic DNS updater for the Gandi registrar. It uses their XML-RPC API to update the zone file for a subdomain of a domain name to point at the external IPv4 address of the computer it has been run from.

It requires a server running a reasonably recent version of Python 2. It has been tested on Ubuntu/Arch Linux using Python 2.7.

Walkthrough

Last updated December 29th, 2015.

Say you'd like to be able to access your home server externally at dynamic.example.com.

API Key

First, you must apply for an API key with Gandi. Visit https://www.gandi.net/admin/api_key and apply for (at least) the production API key by following their directions. Once your request has been approved, you can return to this page to retrieve the production API key.

A Record Setup

Then, you'll need to create a DNS A record in the zone file for your example.com domain. This is how you'll access your server over the Internet at large!

1. Visit https://www.gandi.net/admin/domain and click on the example.com domain.
2. Click on "Edit the Zone" under "Zone files".
3. Click "Create a new version".
4. Click "Add".
5. Change the values to:

Field	Value
Type	A
TTL	5 minutes
Name	dynamic
Value	127.0.0.1

1. Click "Submit".
2. Click "Use this version".
3. Click "Submit".

Script Configuration

Then you'd need to configure the script.

1. Copy config-example.json to config.json, and put it in the same directory as the script.
2. Open it with a text editor, and change it to look like the following:

{
  "api_key": "yourtwentyfourcharapikey",
  "domains": { "example.com": ["dynamic"] }
}

You can apply for/retrieve your production API key at https://www.gandi.net/admin/api_key.

If you'd like to update more than one record with the external IP, simply add more values to the list in the domains dict:

  "domains": { "example.com": ["dynamic", "@", "mail", "xmpp"] }

If you'd like to update multiple domains, add more keys to the domains dict:

  "domains": {
    "example.com": ["dynamic"],
    "example.org": ["www"]
  }

If you would like to determine your external IP with a shell command instead of using external services, specify the command to run in the 'command' key:

  "command": "ipconfig getifaddr en0"

The command should return the external IP address on stdout.

1. Save and close the file.

Running the Script

You can run the script from the command line of an OSX/Unix system as described in the Use section. It will be useful to run this on a cron system of some kind so that as long as the server is running, it will update its own IP address (see: http://code.tutsplus.com/tutorials/scheduling-tasks-with-cron-jobs--net-8800). Running the script with the test parameter is also a good idea, so you can ensure that good results come back from most of the providers.

Logs are written to stdout/stderr and the default log level is INFO. You can change the log level by setting the LOG_LEVEL environment variable. Ex:

LOG_LEVEL=DEBUG ./gandi_dyndns.py

Notes

The first time your A record is configured, it may take several hours for the changes to propogate through the DNS system!

We set the A record's TTL to 5 minutes so that when the address is dynamically updated by the script, that's the (hopefully) longest amount of time that would pass before the DNS system caught up with the change. Setting this much lower wouldn't be of much use, and could even cause DNS errors (see http://www.zytrax.com/books/dns/info/minimum-ttl.html).

Configuration

config.json

Config values for your Gandi account and domain/subdomain must be located in a config.json file in the same directory as the script. config-example.json contains an example configuration including all configurable options, and should be used as a template for your personal config.json.

providers.json

The providers.json file contains a list of all providers that are queried for an external IP address. The providers are always queried in a random order, and several are queried each time the script is run in order to minimize the chance of obtaining an invalid IP address as returned by a single provider. When the results from several different providers concur, that address is used.

Use

Simply running the script will cause it to update the IP address immediately.

./gandi_dyndns.py

To test all the providers and see what kind of results they return, you can run the script with the test parameter:

./gandi_dyndns.py test

This will print out all the addressed received from each provider. Not every provider may return a single, or even uniform/correct, IP address! This is expected behavior, and the script waits for consensus around a given IP amongst several providers before selecting it to be used.