ddupdate 0.0.4

Update dns data for dynamic ip addresses

General

ddupdate is a tool for automatically updating dns data for a system using e. g., DHCP. The goal is it should be possible to access a system with a fixed dns name such as myhost.somewhere.net even if the IP address is changed.

From another perspective, ddupdate is a tool replicating part of the existing ddclient functionality, but with a better overall design and user interaction. In particular, it has better help, logging and documentation. Thanks to the plugin design, it’s also much easier to provide support for new services and address detection strategies.

Status

Like… well, alpha. Fresh code, here is probably bugs lurking around. That said, it supports more than 10 services including duckdns, afraid.org, no-ip.com and dynu.com. Ip addresses to register can be retrieved in a multitude of ways from none at all (trusting the service provider) to the generic ‘cmd’ plugin which can use the output from a command.

Dependencies

Just a few:

• python3

• python3-straight-plugin

• python3-setuptools

• The /usr/bin/ip command is used in some plugins.

Installation

ddupdate can be run as a regular user straight off the cloned git directory. To make a test version possible to run from anywhere make a symlink:

$ ln -s $PWD/src/ddupdate§i/ddupdate $HOME/bin/ddupdate

User installations are not supported at this point. To make a local site installation in /usr/local run something like:

$ sudo python3 setup.py --prefix=/usr/local

Configuration

Configuration is basically about selecting a plugin for a specific ddns service and possibly another plugin which provides the ip address to be registered. Some plugins needs specific options.

First question is what kind of ip address which should be registered. The most common case is to use the address as seen from the internet. This makes it possible for users on internet to access the machine.

On the other hand, it might be necessary to register another type of address for example when using DHCP addresses on an internal network behind a router and the machine should be reached by users on this network. In this case the machine’s real address should be registered.

First, list all plugins:

$ ddupdate --list-plugins ip-plugins
ip-disabled          Force update service to provide ip address
ip-from-command      Obtain address from a command
default-if           Get ip address from default interface (linux)
default-web-ip       Obtain external address as seen from the net
hardcoded-if         Get address from a configuration option
$ ddupdate --list-plugins services
changeip             Updates DNS data on changeip.com
dnsexit              Updates DNS data on www.dnsexit.com
dry-run              Debug dummy update plugin
dtdns                Updates DNS data on dtdns.com
duckdns              Updates DNS data on duckdns.org
duiadns              Updates DNS data on duiadns.com
dynu                 Updates DNS data on dynu.com
freedns.afraid       Updates DNS data on freedns.afraid.org
freedns.io           Updates DNS data on freedns.io
no-ip                Updates DNS data on no-ip.com
now-dns              Updates DNS data on now-dns.com
system-ns            Updates DNS data on system-ns.com

Next, pick an update plugin and check the help info, here dynu:

$ ddupdate --help dynu
Name: dynu
Source: /home/al/src/ddupdate/src/ddupdate/plugins/plugins_base.py

Update a dns entry on dynu.com

Supports ip address discovery and can thus work with the ip-disabled
plugin.

.netrc: Use a line like:
    machine api.dynu.com login <username> password <password>

Options:
    none

If all looks good, register on dynu.com. This will end up in a hostname, username and password. Create an entry in the ~/.netrc file like:

machine api.dynu.com login <username> password <secret>

Note that this file must be protected for other users (otherwise no tools will accept it). Do:

$ chmod 600 ~/.netrc

Now, let’s select the plugin which provides the ip address to register. For the default case, the default-web-ip plugin generates the address as seen from the network. This can be tested using:

$ ./ddupdate --ip-plugin default-web-ip --service-plugin dry-run
dry-run: Using address 90.224.208.212 and hostname host.nowhere.net

All looks good. Now, let’s try to actually update that hostname on dynu.com:

$ ./ddupdate --ip-plugin default-web-ip --service-plugin dynu \
  --hostname myhost.dynu.net -L info
INFO - Loglevel: INFO
INFO - Using hostname: myhost.dynu.net
INFO - Using ip address plugin: default-web-ip
INFO - Using service plugin: dynu
INFO - Plugin options:
INFO - Using ip address: 90.224.208.212
INFO - Update OK

Again fine. Update /etc/ddupdate.conf to something like:

[update]
address-plugin = web-default-ip
service-plugin = dynu
hostname = myhost.dynu.net
loglevel = info

After which it should be possible to just invoke ddupdate without any options.

Configuring systemd

systemd is used to invoke ddupdate periodically. The safest bet is not to use the upstream systemd files. Do:

$ sudo cp /lib/systemd/system/ddupdate* /etc/systemd/system

Check the two /etc/ files, in particular for paths. Test the service and the logged info:

$ sudo systemctl daemon-reload $ sudo systemcl start ddupdate.service $ sudo journalctl -u ddupdate.service

When all is fine make sure ddupdate is run hourly using:

$ sudo systemctl start ddupdate.timer $ sudo systemctl enable ddupdate.timer

Configuring NetworkManager

NetworkManager can be configured to start/stop ddupdate when interfaces goes up or down. An example script to drop in /etc/NetworkManager/dispatcher.d is distributed in the package.

Packaging

ddupdate has a multitude of packaging:

• ddupdate is available as a pypi package from the master branch. It can be installed using pip:

  $ pip install --user ddupdate

• fedora is packaged in the fedora branch. Building requires the fedora toolchain in the rpmdevtools and rpm-build packages. To build:

  $ git clone -b fedora git clone https://github.com/leamas/ddupdate.git
  $ cd ddupdate
  $ spectool -g ddupdate.spec
  $ rpmbuild -D "_sourcedir $PWD" -ba ddupdate.spec

  This creates both a source and a binary rpm package underneath rpmbuild.

• The debian packaging is based on gbp and lives in the debian and pristine-tar branches. The packages git-buildpackage, devscripts and git are required to build. To build current version 0.0.2 do:

  $ git clone -b debian https://github.com/leamas/ddupdate.git
  $ cd ddupdate
  $ gbp buildpackage --git-upstream-tag=0.0.2.
  $ git clean -fd    # To be able to rebuild

Writing plugins

Writing plugins is not hard. Most plugins are about 10-20 lines of code + docs, most of which is boilerplate stuff. The best way is to look at the existing plugins and pick solutions from them. Some hints:

• Before writing the plugin, make tests with wget or curl to make sure how the api works. Essential step, this one.

• Each plugin must contain a main class derived from IpPlugin or ServicePlugin. The class docstring is the help <plugin> documentation.

• The class _name property is the official name of the plugin, must be unique. _oneliner is indeed the short summary displayed by –list-plugins.

• Authentication:

  • Some sites uses standard basic authentication. This is handled by http_basic_auth_setup e. g., no_ip.py

  • Others uses username + password in the url e. g., dnsexit.py

  • Other uses hashed passwords, e. g., dynu.py

  • API tokens are handled in e. g., duckdns.py

  • Some have broken basic authentication, see now_dns.py

• Reply decoding:

  • Most sites just returns some text, simple enough

  • json: example in system_ns.py

  • html: example in duiadns.py