#!/usr/bin/python3
# Copyright (c) 2014, Ralf Jung <post@ralfj.de>
# All rights reserved.
# 
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# modification, are permitted provided that the following conditions are met:
# 
# 1. Redistributions of source code must retain the above copyright notice, this
#    list of conditions and the following disclaimer. 
# 2. Redistributions in binary form must reproduce the above copyright notice,
#    this list of conditions and the following disclaimer in the documentation
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# 
# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
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# DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR
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# ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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# either expressed or implied, of the FreeBSD Project.

import urllib.request, socket, sys, argparse

# configuration variables
server = 'ipv4.ns.ralfj.de'
domains = ['domain.dyn.ralfj.de'] # list of domains to update
password = 'yourpassword'
# END of configuration variables

# allow overwriting some values on the command-line
parser = argparse.ArgumentParser(description='Update a domain managed by a dyn-nsupdate server')
parser.add_argument("-s", "--server",
                    dest="server", default=server,
                    help="The dyn-nsupdate server")
parser.add_argument("-p", "--password",
                    dest="password", default=password,
                    help="The password used to update the domains")
parser.add_argument("-v", "--verbose",
                    action="store_true", dest="verbose",
                    help="Be more verbose")
parser.add_argument("domains",  metavar='DOMAIN', nargs='*', default=domains,
                    help="The domains to update")
args = parser.parse_args()

def urlopen(url):
    return urllib.request.urlopen(url).read().decode('utf-8').strip()

myip = urlopen('https://'+args.server+'/checkip')

def update_domain(domain):
    '''Update the given domain, using the global server, user, password. Returns True on success, False on failure.'''
    global myip, args
    # check if the domain is already mapped to our current IP
    try:
        domainip = socket.gethostbyname(domain)
        if myip == domainip:
            # nothing to do
            if args.verbose:
                print("Domain",domain,"already up-to-date, not doing anything")
            return True
    except socket.gaierror: # domain not found
        pass

    # we need to update the IP
    result = urlopen('https://'+args.server+'/update?password='+urllib.parse.quote(args.password)+'&domain='+urllib.parse.quote(domain)+'&ip='+urllib.parse.quote(myip))
    if 'good '+myip == result: 
        print("Successfully updated domain",domain,"to",myip)
        # all went all right
        return True
    else:
        # Something went wrong
        print("Unexpected answer from server",server,"while updating",domain,"to",myip)
        print(result)
        return False

exitcode = 0
for domain in args.domains:
    if not update_domain(domain):
        exitcode = 1
sys.exit(exitcode)