UrlBlogGrey

I use Dynamic DNS Service's free service to access my home computer network when I'm away. The Domain Name Service (DNS) protocol performs the translation from a domain (i.e. www.yahoo.com) to an Internet Protocol (IP) address. This is like using the yellow pages to look-up the address for a person using their first & last name. Normally, you have to pay to register a domain name. Fortunately, there are services like those provided by Dynamic DNS Services which are free and easy to use.

I have a Linksys WRT54GS wireless access point at the center of my home network. I've installed the OpenWRT firmware on the access point to take advantage of some capabilities not present in the off-the-shelf firmware (see my post "OpenWRT on our Linksys WRT54GS"). Since the access point is powered "on" all the time and it has direct access to the WAN (Internet) interface of the network, it seems like an ideal place to run a program capable of maintaining my dynamic DNS entry.

There is a program called 'inadyn' that can publish an IP address to the Dynamic DNS Service. I needed to install 'inadyn' on my OpenWRT access point. This was done by editing the /etc/ipkg.conf file on the OpenWRT system to contain an entry for the URL of the package list that includes inadyn (http://www.syslinx.org/wrt54g/openwrt). Here's some output from my secure shell session:

root@OpenWrt:/etc# more ipkg.conf
src whiterussian http://downloads.openwrt.org/whiterussian/packages
src non-free http://downloads.openwrt.org/whiterussian/packages/non-free
src phil http://www.syslinx.org/wrt54g/openwrt
dest root /
dest ram /tmp

Then, I installed the inadyn program using the web interface provided with OpenWRT. Next, I created a configuration file that is used by inadyn to determine how it should connect to the Dynamic DNS Service and update your entry. Again, here's some shell output indicating the contents of my configuration file (located in /etc/inadyn.conf):

root@OpenWrt:~# more /etc/inadyn.conf
--username foo --password bar --update_period 60000 --alias foo.dyn-o-saur.com

Lastly, I created an initialization script that will be run when the router restarts. Since the inadyn program will run continuously, this initialization script should keep us in business indefinitely. I named my script S50inadyn, which indicates the order (once the network facilities are active) in which the script should be run during start-up. Here's some shell output indicating the contents of the file:

root@OpenWrt:/etc# cd /etc/init.d/
root@OpenWrt:/etc/init.d# ls
S05nvram     S41wpa       S50dropbear  S50telnet    rcS
S10boot      S45firewall  S50httpd     S60cron
S40network   S50dnsmasq   S50inadyn    S99done
root@OpenWrt:/etc/init.d# more S50inadyn
#!/bin/sh
/usr/bin/inadyn --input_file /etc/inadyn.conf &

You should be able to restart the router and see that the inadyn program is running. Simply login to the router and get a list of processes:

root@OpenWrt:/etc/init.d# ps -ea | grep inadyn
  513 root        332 S   /usr/bin/inadyn --input_file /etc/inadyn.conf

Now you can access the WAN port of your access point using a convenient DNS name. You'll probably want to configure some port-forwarding rules in order to access computers within your network. However, I recommend using port-mapping in order to lessen the obviousness of your open ports.