Cloudflare DDNS

Simple C application wrapped into a container for updating Cloudflare DNS records.
It allows you to use Cloudflare as a Dynamic DNS.

The container is built from scratch and only contains the statically-linked executable and SSL certficates in order to minimize its footprint.

The goal was minimize resource usage for use on routers/Aps, like the Mikrotik hAp ax, that can run containers.

The compressed image size is 2.4MB.

A special thanks to @gmasini97 for the contributions.

How It Works

Waits for your public IP to change, it checks for changes with a set time interval (UPDATE_INTERVAL, see Environment Variables).
The IP is checked using Cloudflare APIs (https://cloudflare.com/cdn-cgi/trace).

Then deletes all DNS records, except for CNAME records if SKIP_CNAME is set to 1 (see Environment Variables).

Generate new DNS records from the specified templates (BIND_TEMPLATE and BIND_TEMPLATE_NOPROXY, see Environment Variables).

Set UPDATE_INTERVAL to a negative number (i.e.: -1) for updating the DNS records once and exiting.

When the container is started it will always udpate the records at least once.

Resource Usage

The UNcompressed image size is 5.6MB.

RAM usage is roughly 1MB.

Network usage depends on how frequent you want to check for IP changes. Setting UPDATE_INTERVAL to 30 gives these consumptions:

• Data received: 720KB/h
• Data sent: 260KB/h

Prerequisites

This documentation assumes you already have a Cloudflare account set up with a domain registered.

Generate an API Token

1. Visit https://dash.cloudflare.com/profile/api-tokens.
2. Click the "Create Token" button.
3. Use the template "Edit zone DNS".
4. In the "Zone Resources" section choose: "Include", "Specific Zone" and the zone.
5. Scroll to the bottom and click the "Continue to summary" button.
6. Click the "Create Token" button.
7. Copy your newly generate token.

List your ZoneIDs

Open a terminal and type:

curl -X GET "https://api.cloudflare.com/client/v4/zones" \
     -H "Authorization: Bearer YOUR_TOKEN" \
     -H "Content-Type: application/json"

Replace YOUR_TOKEN with the previously generated token.

Environment Variables

Variable	Description	Example
TOKEN	Cloudflare API Token
ZONEID	Cloudflare Zone ID
UPDATE_INTERVAL	Time to wait between IP checks in seconds. -1 for updating DNS records once.	30
SKIP_CNAME	Wheter to skip CNAME records. Set to 1 for skipping, 0 for deleting them.	1
DOMAIN	Your domain name	example.com
BIND_TEMPLATE		%domain%. 1 IN A %ip%
BIND_TEMPLATE_NOPROXY
HEALTHCHECK_URL	Http address to send a heartbeat signal. A GET request to this address is made everytime an IP check is made.	https://hc-ping.com/<uuid>

BIND_TEMPLATE and BIND_TEMPLATE_NOPROXY are used to generate Zone files (see: https://en.wikipedia.org/wiki/Zone_file).
The DNS records generated from BIND_TEMPLATE are proxied from Cloudflare.
The DNS records generated from BIND_TEMPLATE_NOPROXY are NOT proxied from Cloudflare.
Template variables:

• %domain% is replaced with the content of the environment variable DOMAIN.
• %ip% is replaced with your public IP.
• ; is replaced with a new line.

Docker

Build the image yourself

Pull the repository:

$ git clone https://github.com/mircopergreffi/cloudflare-ddns
$ cd cloudflare-ddns

Create .env file from example.env and edit it:

$ cp example.env .env
$ vi .env

Build the image:

$ docker build -t cloudflare-ddns .

Run the image:

$ docker run -d --env-file .env cloudflare-ddns

Prebuilt image

Create a .env file from the template (example.env).
Pull and run the image:

$ docker run -d --env-file .env \
    mircopergreffi/cloudflare-ddns