ifchange-ddns

ifchange-ddns - Monitor network interface and update DDNS

What is it?

This is a small program to monitor a given network interface and update DDNS when the IPv4 address changes.

I wrote this because OpenBSD dhclient removed the dhclient-script functionality and I needed a way to update DDNS when my ISP assigns a new IPv4 address.

The current implementation only has support for namecheap DNS. Other providers can be easily added.

How do I use it?

Assuming you also use namecheap:

1. Build the client for your platform:

       $ make
       $ # or make for openbsd
       $ make openbsd
   

2. If you want to run this as a daemon on OpenBSD: Assuming the interface you want to monitor is em0 and the entry to update is host.mydomain.com, as root, do:

      # cp bin/openbsd-amd64/ifchange-ddns /usr/local/bin/
      # mkdir /etc/ifchanged
      # cp dist/keyfile.conf /etc/ifchanged/ddns.conf
      # cp dist/openbsd/ifchanged /etc/rc.d
      # cat <<EOF >> /etc/rc.conf.local
      # ifchanged_flags="em0 host.mydomain.com /etc/ifchanged/ddns.conf"
      # ifchanged_user=nobody
      # EOF
      # chmod -R og-rw /etc/ifchanged
      # chown nobody /etc/ifchanged
   

   Next, edit /etc/ifchanged/ddns.conf with the correct DDNS update key from the control panel. The example in dist/keyfile.conf is for reference only.

   Finally, start the daemon:

      # /etc/rc.d/ifchanged start
   

   If you want the daemon to start at every boot, add "ifchanged" to pkg_scripts in /etc/rc.conf.local

Where do I see logs?

By default, the daemon sends logs to syslog

Can I use this on a different platform?

Yes, on platforms that have a hook for dhclient-script, you can use this as a "oneshot" update program:

    $ ifchange-ddns --oneshot em0 host.mydomain.com /etc/ifchanged/ddns.conf

You may have to write a small shell script to parse the input provided by dhclient-script and invoke ifchange-ddns.