Adding DynDNS to Gandi.net

Gandi.net doesn't support DynDNS but does have a DNS API. Surely there must be a way to create a dyndns-like capability to my Gandi.net domain using the API?!? This also inluded an opportunity to learn a bit more about Python.

= Old solution(s) =

Having friends is a good thing. This allowed me to use a dynamic DNS service that operated very simply using a http GET call to update a sub-domain. It simply responds No update needed if the IP-address you're calling from hasn't changed. This is not a good solution if you want to host your own mail-server!

When I was doing my IPv6 certification with Huricane Electric I ran into the dynamic DNS service that they have. To get access to their DNS service, you have to do the IPv6 certification but the service is pretty good! You can enable dynamic updates for specific DNS entries, each entry having its own DDNS key for authentication.

== Shell Scripts ==

To update your DNS records, you need to know the IP-address your ISP has allocated to you. For this I had created a shell script. Prety self-explanatory I hope...

getMyWANIP () {
local currentIP persistfile oldIP
persistfile=/etc/currentWanIp
oldIP=$(cat $persistfile)

# Retrieve the page containing the IP-address from the router
result=`fetch -q -o- http://username:password@192.0.2.1/cgi-bin/status-interfaces.sh`
RC=$?

if [ $RC -eq 0 ] ; then
   # Extract the IP-address from the web-page (crude!)
   currentIP=$(echo "${result}" | grep -A 1 -m 1 "IP Address" | tail -n 1 | tr -dc '[0-9.]')
   if [ ! "${currentIP}" = "${oldIP}" ] ; then
      echo -n ${currentIP} > ${persistfile}
   fi
else
   currentIP=${oldIP}
fi

echo -n $currentIP
}

In my DynDNS script I would use kind of a voting system to check if the IP-address updated or if the ISP link was down.

#!/bin/sh
. /home/root/bin/myWanIP.inc

hostname=brnrd.eu
DDNSKey=<myHEnetDDNSkey>
HEnetAccount=<myHEnetAccount>
CACert="--ca-cert=/etc/ssl/certs/cacert3.pem"
HEurl="https://dyn.dns.he.net/nic/update"

sendMail() {
   [ $# -gt 0 ] && mailSubject="$*"
   mail -s "$mailSubject" root@brnrd.eu <<- MAIL-BODY
   dyndns.myfriend.net result: $myfriendResult
   dyndns.myfriend.net     RC: $myfriendRC
   dyndns.myfriend.net  error: $myfriendError

   dyn.dns.he.net     result: $HEnetResult
   dyn.dns.he.net         RC: $HEnetRC
   dyn.dns.he.net      error: $henetError
   MAIL-BODY
}

updateHEnet () {
   local hostname errFile url fetchResult fetchRC
   hostname=$1
   errFile=$2
   url="${HEurl}?password=${DDNSKey}&hostname=${hostname}"
   fetchResult=`fetch -4qo- ${CACert} "${url}" 2>>${errFile}`
   fetchRC=$?
   [ $# -ge 3 ] && eval $3="${fetchResult%% *}"
   [ $# -ge 4 ] && eval $4="${fetchResult##* }"
   return ${fetchRC}
}

# Initialize Integer variables
IPAddressChanged=0
fetchRC=0

rm -f /tmp/henetResult.err

myfriendResult=`fetch -4qo- http://dyndns.myfriend.net:37/0.0.0.0/spil.myfriend.net/<DDNSkey>/ 2>/tmp/myfriendResult.err`
myfriendRC=$?
# RC !=0 -> fetch error # Result != "No update needed" -> IP address changed
[ "X${myfriendResult}" != "XUpdate not needed" ] && IPAddressChanged=$((IPAddressChanged+1))
[ "${myfriendRC}" -gt 0 ] && {
   fetchRC=$((fetchRC+1)) # set 1st bit
   myfriendError=`cat /tmp/myfriendResult.err`
}

updateHEnet brnrd.eu /tmp/henetResult.err HEnetResult HEnetIP
HEnetRC=$?
[ "${HEnetResult}" = "good" ] && {
   IPAddressChanged=$((IPAddressChanged+1))
   updateHEnet ${hostname} /tmp/henetResult.err
}
[ ${HEnetRC} -gt 0  ] && {
   fetchRC=$((fetchRC+2)) # set 2nd bit
   henetError=`cat /tmp/henetResult.err`
}

# No changes to IP-address so move on
[ ${IPAddressChanged} -eq 0 ] && exit 0

# Both fetches failed, no internet connection?
[ ${fetchRC} -eq 3 ] && {
   sendMail "Updating Dynamic DNS Failed: No internet connection?"
   exit 2
}

# IP address seems to have changed
# Single vote...
[ ${IPAddressChanged}  -eq 1 ] && {
   # Inconclusive result
   [ ${HEnetRC} -eq 0 ] && {
   getIPaddress modemIP
   [ "X${HEnetIP}" = "X${modemIP}" ] && sendMail "IP Address changed"
      exit 1
   }
   [ ${HEnetRC} -ge 1 ] && sendMail "IP Address likely changed"
   exit 1
}

= Python =

Since the examples of Gandi.net use Python, I thought this was a good opportunity to learn a bit more python-scripting. To replace the earlier shell script to retrieve the IP-address from the router

import httplib
import re

# Retrieve status page from CPE
conn = httplib.HTTPConnection('192.0.2.1')

# Create your Basic-auth string with \
# echo -n "username:password" | b64encode -r auth
req = conn.request("GET","/cgi-bin/status-interfaces.sh","",{"Authorization": "Basic dXNlcm5hbWU6cGFzc3dvcmQ="})
body = conn.getresponse().read()

# Extract current IP-address from html body
p1 = re.compile(r'<tr id="wan_ip_addr">.*?(\d*\.\d*\.\d*\.\d*).*?</tr>\n',re.DOTALL)
s1 = p1.search(body)
inetIP = s1.group(1)