Update DNS-O-Matic with a Python Script


DNS-O-Matic is a service from OpenDNS that updates several dynamic DNS services. This is handy if your router will only update one dynamic DNS provider but you need to update more than one (e.g. I update OpenDNS to make use of their excellent parental controls and DynDNS to register a name on the internet for my home server).

I’ve yet to find a router that can update DNS-O-Matic. It’s possible to install an updater client on each computer on your network but I’d rather have something requiring less maintenance.

Here’s a Python script I wrote that runs on a home server. It’s on a cron job to check every 10 minutes.

Disclaimer This code is hacked together and is not well tested. Please let me know if you can improve it.

````python #!/usr/bin/env python

# Adapted from: http://ubuntuforums.org/archive/index.php/t-247563.html
# Need to make sure Python is installed with SSL support on OpenWRT

from base64 import encodestring
from socket import gethostbyname
from urllib import urlencode
from urllib2 import Request, urlopen

#Put your username, password and hostname here.
username='YOURUSERNAME'
password='YOURPASSWORD'
# I added the dynname line below and also changed hostname so that it
# updates all accounts but checks for something with my IP
hostname='all.dnsomatic.com'
dynname='YOURDYNNAME'
#See https://www.dnsomatic.com/wiki/api for explanation of the
# following parameter values and options
wildcard='NOCHG'
mx='NOCHG'
backmx='NOCHG'

############################################
## DO NOT EDIT ANYTHING BEYOND THIS POINT ##
############################################

print '\nDNS-O-Matic.com updater is running!!!\n'

#Get your current dynamic IP
lookup=gethostbyname(dynname)
print 'DNS-O-Matic is set to', lookup

#Get actual external IP.
ip_external = urlopen('http://myip.dnsomatic.com')
myip = ip_external.read()
ip_external.close()
print 'Your actual IP is' , myip

#Compare those IPs
if lookup == myip :
    print 'No change in DNS entry.'
else:
    #change the DNS entry

    data = {}
    data['hostname'] = hostname
    data['myip'] = myip
    data['wildcard'] = wildcard
    data['mx'] = mx
    data['backmx'] = backmx

    url_values = urlencode(data)

    url = 'https://updates.dnsomatic.com:443/nic/update?' + url_values
    request = Request(url)

    base64string = encodestring(username + ':' + password)[:-1]
    request.add_header("Authorization", "Basic %s" % base64string)
    request.add_header('User-Agent',username + ' - Home User - 1.0')

    htmlFile = urlopen(request)
    htmlData = htmlFile.read()
    htmlFile.close()

    results = htmlData.split()
    if results[0] == 'good':
        print "DNS updated to " + results[1]
    else:
        print 'DNS update failed with error: ' + results[0]

`````

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