Dynamic DNS Update Script for dynDNS behind NAT

Grateful thanks goes to "webasdf" on the forums (http://forum.mikrotik.com/viewtopic.php?p=171805#p171805) for this. I just edited it so that we can use the same identical script at every single one of our hotspots that are behind a Dynamic IP. The great ability of the original script by webasdf is that it uses DynDNS's html access method which means it will work behind a NAT'ed connection.

# Set needed variables
:local username "DYNDNSUSER"
:local password "DYNDNSPASSWORD"
:local hostname "DYNDNSHOSTNAME"
:local previousIP [:put [:resolve $hostname]];
:delay 1
:global dyndnsForce
:global previousIP 

# print some debug info
:log info ("UpdateDynDNS: username = $username")
:log info ("UpdateDynDNS: password = $password")
:log info ("UpdateDynDNS: hostname = $hostname")
:log info ("UpdateDynDNS: previousIP = $previousIP")

# get the current IP address from the internet (in case of double-nat)
/tool fetch mode=http address="checkip.dyndns.org" src-path="/" dst-path="/dyndns.checkip.html"
:delay 1
:local result [/file get dyndns.checkip.html contents]

# parse the current IP result
:local resultLen [:len $result]
:local startLoc [:find $result ": " -1]
:set startLoc ($startLoc + 2)
:local endLoc [:find $result "</body>" -1]
:local currentIP [:pick $result $startLoc $endLoc]
:log info "UpdateDynDNS: currentIP = $currentIP"

# Remove the # on next line to force an update every single time - useful for debugging,
# but you could end up getting blacklisted by DynDNS! 

#:set dyndnsForce true

# Determine if dyndns update is needed
# more dyndns updater request details http://www.dyndns.com/developers/specs/syntax.html

:if (($currentIP != $previousIP) || ($dyndnsForce = true)) do={
:set dyndnsForce false
:set previousIP $currentIP
:log info "$currentIP or $previousIP"
/tool fetch user=$username password=$password mode=http address="members.dyndns.org" \
src-path="nic/update?system=dyndns&hostname=$hostname&myip=$currentIP&wildcard=no" \
dst-path="/dyndns.txt"
:delay 1
:local result [/file get dyndns.txt contents]
:log info ("UpdateDynDNS: Dyndns update needed")
:log info ("UpdateDynDNS: Dyndns Update Result: ".$result)
:put ("Dyndns Update Result: ".$result)
} else={
:log info ("UpdateDynDNS: No dyndns update needed")
}