Dynamic DNS client for Cloudflare

A small tool for updating IPv6 address at Cloudflare DNS with the currently detected address of the specified network interface.

It is provided with systemd service and timer files for automation.

Updates AAAA records at Cloudflare according to the current IPv6 address.

Requires a network interface name for a IPv6 address lookup, domain name[s]
and Cloudflare API token with edit access rights to corresponding DNS zone.

Usage:
  cloudflare-dynamic-dns [flags]

Flags:
      --config string              config file (default is $HOME/.cloudflare-dynamic-dns.yaml)
      --domains strings            Domain names to assign the IPv6 address to.
  -h, --help                       help for cloudflare-dynamic-dns
      --iface string               Network interface to look up for a IPv6 address.
      --log-level string           Sets logging level: trace, debug, info, warning, error, fatal, panic. (default "info")
      --priority-subnets strings   IPv6 subnets to prefer over others.
                                   If multiple IPv6 addresses are found on the interface, the one from the subnet with the highest priority is used.
      --systemd                    Switch operation mode for running in systemd.
                                   In this mode previously used ipv6 address is preserved between runs to avoid unnecessary calls to CloudFlare API.
      --token string               Cloudflare API token with DNS edit access rights.
      --ttl int                    Time to live, in seconds, of the DNS record. Must be between 60 and 86400, or 1 for 'automatic'. (default 1)

Installation

AUR

There is a package in AUR, which can be used on Arch-based distros.

yay -S cloudflare-dynamic-dns

Manual

Download the archive for your OS from the releases page.

Or get the source code and build the binary:

git clone https://github.com/Zebradil/cloudflare-dynamic-dns.git
# OR
curl -sL https://github.com/Zebradil/cloudflare-dynamic-dns/archive/refs/heads/master.tar.gz | tar xz

cd cloudflare-dynamic-dns-master
go build -o cloudflare-dynamic-dns main.go

Now you can run cloudflare-dynamic-dns manually (see Usage section).

If you want to do some automation with systemd, cloudflare-dynamic-dns has to be installed system-wide (it is possible to run systemd timer and service without root privileges, but I do not provide ready-to-use configuration for this yet):

sudo install -Dm755 cloudflare-dynamic-dns -t /usr/bin
sudo install -Dm644 systemd/* -t /usr/lib/systemd/system
sudo install -m700 -d /etc/cloudflare-dynamic-dns/config.d

Usage

Run manually

0. Follow the steps from the Installation section.
1. Run ./cloudflare-dynamic-dns --domains 'example.com,*.example.com' --iface eth0 --token cloudflare-api-token
   • NOTE: instead of compiling cloudflare-dynamic-dns binary, it can be replaced with go run main.go in the command above.

Instead of specifying command line arguments, it is possible to create ~/.cloudflare-dynamic-dns.yaml with the following structure:

iface: eth0
token: cloudflare-api-token
domains:
  - example.com
  - "*.example.com"
# Optional
#prioritySubnets:
#  - 2001:db8::/32
#  - 2001:db8:1::/48

And then run ./cloudflare-dynamic-dns (or go run main.go) without arguments. Or put the configuration in any place and specify it with --config flag:

./cloudflare-dynamic-dns --config /any/place/config.yaml

Priority subnets

If multiple IPv6 addresses are found on the interface, the one from the subnet with the highest priority is used. If no priority subnets are specified, the first address is used. Priority subnets are specified in the configuration file:

prioritySubnets:
  - 2001:db8::/32
  - 2001:db8:1::/48

Or via --priority-subnets flag:

./cloudflare-dynamic-dns --priority-subnets '2001:db8::/32,2001:db8:1::/48'

Systemd service and timer

It is possible to run cloudflare-dynamic-dns periodically via systemd. This requires privileged access to the system. Make sure that required systemd files are installed (see Installation section for details).

# 1. Create configuration file `/etc/cloudflare-dynamic-dns/config.d/<name>.yaml`
#    For example (I use "example.com" as <name>, replace the values according to your needs):
sudo tee -a /etc/cloudflare-dynamic-dns/config.d/example.com.yaml <<EOF
iface: eth0
token: cloudflare-api-token
domains:
  - example.com
  - "*.example.com"
EOF

# 3. Enable systemd timer
sudo systemctl enable --now [email protected]

This way (via running multiple timers) you can use multiple configurations at the same time.

By default, a timer is triggered one minute after boot and then every 5 minutes. It is not configurable currently.

To avoid unnecessary requests to Cloudflare API state files are used. They're created in /var/lib/cloudflare-dynamic-dns/ and named using configuration variables in corresponding config files (iface and md5 hash of domains). A state file contains IPv6 address which was set in a Cloudflare DNS AAAA record during the last successful run. If the current IPv6 address is the same as the one in the state file, no additional API requests are done.

Development

Builds and releases are done with goreleaser.

Use the following Taskfile tasks to build the application:

# Build with go for the current platform
task build

# Build with GoReleaser for all configured platforms
task goreleaser:build

License

MIT