cloudflare-ddns

Introduction

A script for dynamically updating a CloudFlare DNS record. I use CloudFlare to host DNS for a domain and I wanted to point an A record in that domain to a host who's IP address changes occasionally. CloudFlare has an API to do this, so this happened.

Dependencies

You'll need a python interpreter and the following libraries:

• PyYAML (pip install pyyaml)
• Requests (pip install requests)

Usage

First you'll want to fill out the configuration file. Make a copy of config.yaml.template named config.yaml, then fill out the options in config.yaml. The comments in the file make it fairly self explanatory.

Now to do a one-off update of your DNS record, simply run cloudflare_ddns.py from your terminal. It'll get your public IP address, then update the CloudFlare DNS record with it. Easy! (In fact, you should probably do this once to test that your config file is correct.) You should see something like this:

jpk@truth:~/code/cloudflare-ddns$ ./cloudflare_ddns.py 
Tue Oct  8 22:09:00 2013, success, 123.45.67.89
jpk@truth:~/code/cloudflare-ddns$ 

If it fails, it'll print the failure response CloudFlare returns. Check your config.yaml and try again.

If you're like me, though, you probably want it to run periodically in the background to keep the record up-to-date as your public IP address changes. Just add a line to your crontab and let cron run it for you. My crontab has a line in it like this:

# Every 15 minutes, check public ip, and update a record on cloudflare.
*/15 * * * * ~/code/cloudflare-ddns/cloudflare-ddns.py >> ~/code/cloudflare-ddns/logs/log.txt

That will update the record every 15 minutes. You'll want the paths there to match up with wherever you checked this repo out. The redirection to append to a log file is optional, but handy for debugging if you notice the DNS record isn't staying up-to-date or something.

Getting the CloudFlare Record ID

The only tricky thing about the configuration is cf_record_id. This is CloudFlare's id for the DNS record you want to update. You'll need to make a call to their API to find out what this is. You can use this command to make that call:

curl https://www.cloudflare.com/api_json.html   
    -d 'a=rec_load_all'   
    -d 'tkn=368812311fb987a376a39e58bc0793ae18708'   
    -d 'email=_@jpk.is'   
    -d 'z=jpk.is' | python -mjson.tool

This should pretty-print a bunch of JSON, part of which will be a list of objects representing DNS records in your zone. They look like this:

...
{
    "auto_ttl": 0, 
    "content": "123.45.67.89", 
    "display_content": "123.45.67.89", 
    "display_name": "ddns", 
    "name": "ddns.domain.com", 
    "prio": null, 
    "props": {
        "cf_open": 1, 
        "cloud_on": 0, 
        "expired_ssl": 0, 
        "expiring_ssl": 0, 
        "pending_ssl": 0, 
        "proxiable": 1, 
        "ssl": 0, 
        "vanity_lock": 0
    }, 
    "rec_id": "12345678", 
    "rec_tag": "[some long hex value]", 
    "service_mode": "0", 
    "ssl_expires_on": null, 
    "ssl_id": null, 
    "ssl_status": null, 
    "ttl": "120", 
    "ttl_ceil": 86400, 
    "type": "A", 
    "zone_name": "domain.com"
},
...

Find the one with a name field that matches the host you're wanting to update, and the rec_id field is the record id you want to put in your config. (In this case "ddns.domain.com" is the one we're looking for, and it has a record id of "12345678".)

If you want to learn more about the CloudFlare API, you can read on here.

Credits and Thanks

• CloudFlare for having an API and otherwise generally being cool.
• jsonip.com for making grabbing your public IP from a script super easy. Put together by @geuis. Go to his twitter and shower him with praise.