• Introduction
• Supported Providers
• Example Configuration
• Generic DDNS Plugin
• Build & Install
• Origin & References

In-a-Dyn is a small and simple Dynamic DNS, DDNS, client with HTTPS support. It is commonly available in many GNU/Linux distributions, used in off the shelf routers and Internet gateways to automate the task of keeping your DNS record up to date with any IP address changes from your ISP. It can also be used in installations with redundant (backup) connections to the Internet.

Most people are unaware that they share a pool of Internet addresses with other users of the same Internet Service Provider (ISP). Protocols like DHCP, PPPoE, or PPPoA are used to give you an address and a way to connect to the Internet, but usually not a way for others to connect to you. If you want to run an Internet server on such a connection you risk losing your IP address every time you reconnect, or in DHCP even when the lease is renegotiated.

By using a DDNS client such as inadyn you can register an Internet name at certain providers that the DDNS client updates, periodically and/or on demand when your IP changes. In-A-Dyn can maintain multiple host names with the same IP address, and has a web based IP detection which runs well behind a NAT router.

Some of these services are free of charge for non-commercial use, some take a small fee, but also provide more domains to choose from.

DDNS providers not supported natively like http://twoDNS.de, can be enabled using the generic DDNS plugin. See below for configuration examples.

• http://www.dyndns.org
• http://freedns.afraid.org
• http://www.zoneedit.com
• http://www.no-ip.com
• http://www.easydns.com
• http://www.tzo.com
• http://www.3322.org
• http://www.dnsomatic.com
• http://www.tunnelbroker.net
• http://dns.he.net/
• http://www.dynsip.org
• http://www.sitelutions.com
• http://www.dnsexit.com
• http://www.changeip.com
• http://www.zerigo.com
• http://www.dhis.org
• https://nsupdate.info
• http://duckdns.org
• https://www.loopia.com
• https://www.namecheap.com
• https://domains.google.com
• https://www.ovh.com
• https://www.dtdns.com
• http://giradns.com
• https://www.duiadns.net
• https://ddnss.de
• http://dynv6.com
• http://ipv4.dynv6.com

In-A-Dyn supports HTTPS for DDNS providers that support this, which you must check yourself. So far DynDNS, FreeDNS, nsupdate.info, and Loopia have been verified to support HTTPS.

HTTPS is strongly recommended since it protects your credentials from being snooped and reduces the risk of someone hijacking your account.

Note: Currently no HTTPS certificate validation is performed, patches welcome!

In-A-Dyn supports updating several DDNS servers, several accounts even on different DDNS providers. The following /etc/inadyn.conf example show how this can be done:

# In-A-Dyn v2.0 configuration file format
period          = 300

provider [email protected] {
    ssl         = true
    username    = charlie
    password    = snoopy
    hostname    = { "peanuts", "woodstock" }
}

provider [email protected]:1 {
    username    = ian
    password    = secret
    hostname    = flemming.no-ip.com
}

provider [email protected]:2 {
    username       = james
    password       = bond
    hostname       = spectre.no-ip.com
    checkip-server = api.ipify.org
}

provider [email protected]:3 {
    username        = spaceman
    password        = bowie
    hostname        = spaceman.no-ip.com
    checkip-command = /sbin/ifconfig eth0 | grep 'inet6 addr'
}

provider [email protected] {
    ssl         = true
    username    = futurekid
    password    = dreoadsad/+dsad21321    # update-key-in-advanced-tab
    hostname    = 1234534245321           # tunnel-id
}

provider [email protected] {
    username = your_token
    password = n/a
    hostname = { host1.dynv6.net, host2.dynv6.net }
}

In this example only the DynDNS and Tunnelbroker accounts use SSL, the No-IP account will still use regular HTTP. See below for more on SSL. Notice how this configuration file has two different users of the No-IP provider -- this is achieved by appending a :ID to the provider name.

We also define a custom cache directory, default is to use /var/cache. In our case /mnt is a system specific persistent store for caching your IP as reported to each provider. In-A-Dyn use this to ensure you are not locked out of your account for excessive updates, which may happen if your device Internet gateway running inadyn gets stuck in a reboot loop, or similar.

However, for the caching mechanism to be 100% foolproof the system clock must be set correctly -- if you have issues with the system clock not being set properly at boot, e.g. pending receipt of an NTP message, use the command line option --startup-delay=SEC. To tell inadyn it is OK to proceed before the SEC timeout, use SIGUSR2.

The last system defined is the IPv6 https://tunnelbroker.net service provided by Hurricane Electric. Here hostname is set to the tunnel ID and password must be the Update key found in the Advanced configuration tab. Also, [email protected] requires SSL!

Sometimes the default checkip-server for a DDNS provider can be very slow to respond, to this end Inadyn now supports overriding this server with a custom one, like for custom DDNS provider, or even a custom command. See the man pages, or the below section, for more information.

NOTE: In a multi-user server setup, make sure to chmod your .conf to 600 (read-write only by you/root) to protect against other users reading your DDNS server credentials.

In addition to the default DDNS providers supported by Inadyn, custom DDNS providers can be defined in the config file.. Use custom {} in instead of the provider {} section used in examples above.

In-A-Dyn use HTTP basic authentication (base64 encoded) to communicate username and password to the server. If you do not have a username and/or password, you can leave these fields out. Basic authentication, will still be used in communication with the server, but with empty username and password.

A DDNS provider like http://twoDNS.de can be setup like this:

custom twoDNS {
    username       = myuser
    password       = mypass
    checkip-server = checkip.two-dns.de
    checkip-path   = /
    ssl            = true
    ddns-server    = update.twodns.de
    ddns-path      = "/update?hostname="
    hostname       = myhostname.dd-dns.de
}

For https://www.namecheap.com DDNS can look as follows. Notice how the hostname syntax differs between these two DDNS providers. You need to investigate details like this yourself when using the generic/custom DDNS plugin:

custom namecheap {
    username    = myuser
    password    = mypass
    ssl         = true
    ddns-server = dynamicdns.park-your-domain.com
    ddns-path   = "/update?domain=YOURDOMAIN.TLD&password=mypass&host="
    hostname    = { "alpha", "beta", "gamma" }
}

Here three subdomains are updated, one HTTP GET update request for every listed DDNS server and path is performed, for every listed hostname. Some providers, like FreeDNS, support setting up CNAME records to reduce the amount of records you need to update.

Your hostname is automatically appended to the end of the ddns-path, as is customary, before it is communicated to the server. Username is your Namecheap username, and password would be the one given to you in the Dynamic DNS panel from Namecheap. Here is an alternative config to illustrate how the hostname setting works:

custom kruskakli {
    username    = myuser
    password    = mypass
    ssl         = true
    ddns-server = dynamicdns.park-your-domain.com
    ddns-path   = "/update?password=mypass&domain="
    hostname    = YOURDOMAIN.TLD
}

The generic plugin can also be used with providers that require the client's new IP in the update request. Here is an example of how this can be done if we pretend that http://dyn.com is not supported by inadyn. The ddns-path differs between providers and is something you must figure out. The support pages sometimes list this under an API section, or similar.

# This emulates [email protected]
custom randomhandle {
    username    = DYNUSERNAME
    password    = DYNPASSWORD
    ssl         = true
    ddns-server = members.dyndns.org
    ddns-path   = "/nic/update?hostname=%h.dyndns.org&myip=%i"
    hostname    = { YOURHOST, alias }
}

Here a fully custom ddns-path with format specifiers are used, see the inadyn.conf(5) man page for details on this.

When using the generic plugin you should first inspect the response from the DDNS provider. By default In-A-Dyn looks for a 200 HTTP response OK code and the strings "good", "OK", "true", or "updated" in the HTTP response body. If the DDNS provider returns something else you can add a list of possible ddns-response = { Arrr, kilroy }, or just a single ddns-response = Cool -- if your provider does give any response then use ddns-response = "".

If your DDNS provider does not provide you with a checkip-server, you can use other free services, like http://ipify.com

checkip-server = api.ipify.com

or even use a script or command:

checkip-command = /sbin/ifconfig eth0 | grep 'inet addr'

These two settings can also be used in standard provider{} sections.

Note: hostname is required, even if everything is encoded in the ddns-path! The given hostname is appended to the ddns-path used for updates, unless you use append-myip in which case your IP address will be appended instead. When using append-myip you probably need to encode your DNS hostname in the ddns-path instead — as is done in the last example above.

By default inadyn tries to build with GnuTLS for HTTPS support. GnuTLS is the recommended SSL library to use on UNIX distributions which do not provide OpenSSL as a system library. However, when OpenSSL is available as a system library, for example in many embedded systems:

./configure --enable-openssl

To completely disable inadyn HTTPS support:

./configure --disable-ssl

For more details on the OpenSSL and GNU GPL license issue, see:

• https://lists.debian.org/debian-legal/2004/05/msg00595.html
• https://people.gnome.org/~markmc/openssl-and-the-gpl

In-A-Dyn v2.0 and later requires two additonal libraries, libite and libConfuse, the latter is available from most UNIX distributions as a pre-built package, the former is however currently only available as a source tarball. Make sure to install the -dev or -devel package of libConfuse when building Inadyn.

This is the continuation of Narcis Ilisei's original INADYN. Now maintained by Joachim Nilsson. Please file bug reports, or send pull requests for bug fixes and proposed extensions at GitHub.