Why is ddclient giving me an "Invalid IP" error when trying to update dynamic DNS?

I am having a really hard time getting ddclient (which updates OpenDNS with my current IP address) to work. I have it running as a daemon, but it never succeeds in updating my IP address at openDNS.

To troubleshoot, I am running ddclient from the command line as follows.

(In these examples, values in square brackets [] are stand-ins for the real values for security reasons)

My /etc/ddclient.conf contains:

use=web, web=checkip.dyndns.org/, web-skip='IP Address'
server=updates.opendns.com
protocol=dyndns2
login=[my login]
password=[my password]
Home

When I run:

sudo ddclient -daemon=0 -debug -verbose -noquiet

I get:

WARNING:  file /var/cache/ddclient/ddclient.cache, line 3: Invalid Value for keyword 'ip' = ''
...
WARNING:  skipping update of Home from <nothing> to [my real ip].
WARNING:   last updated <never> but last attempt on Tue Oct  4 08:38:32 2011 failed.

If I rm the cache file, ddclient does work once, but then it fails on subsequent times.

Known bug - fixed upstream - get the latest version from a PPA

This is/was from a known "bug" -- it's caused by the dynamic DNS provider using the dyndns2 protocol incorrectly and sending malformed responses to ddclient.

• ddclient sourceforge trac ticket
• Debian bug report

The problem has long since been fixed in ddclient (based on one of the patches linked in the trac), but Ubuntu's ddclient is so ancient (inherited from upstream) that it can't even be patched manually. (Ubuntu is on rev. 106/Jan-2009, while the latest is r130/Nov-2011).

Solution:

1. Add this PPA with sudo apt-add-repository ppa:nathan-renniewaldock/ppa
2. sudo apt-get update && sudo apt-get install ddclient (will upgrade if necessary)

The PPA has the latest versions for 10.04, 11.10 and 12.04.

For the curious, here's the patch/buggy bit:

        # bug #10: some dyndns providers does not return the IP so
        # we can't use the returned IP
        my ($status, $returnedip) = split / /, lc $line;
        $ip = $returnedip if (not $ip);

You want the newer ddclient package from ppa:nathan-renniewaldock/ppa but beware that this PPA contains many other packages that you might not want if all you want to do is get ddclient working. Use these steps to only upgrade ddclient.

sudo apt-get install python-software-properties
sudo apt-add-repository ppa:nathan-renniewaldock/ppa

Now, as root, create the file /etc/apt/preferences.d/nathan-prefs and edit it to look like this (including the blank line which is important):

Package: *
Pin: release o=LP-PPA-nathan-renniewaldock
Pin-Priority: 400

Package: ddclient
Pin: release o=LP-PPA-nathan-renniewaldock
Pin-Priority: 500

This tells apt-get to ignore packages from the PPA other than ddclient. So now it should be safe to do this to install it:

sudo apt-get update && sudo apt-get install ddclient

Or if you have already installed it, do this:

sudo apt-get upgrade

Just check that only ddclient is going to be upgraded.