import dns.query
import dns.tsigkeyring
import dns.update
from optparse import OptionParser
import re
import string
import sys

# dnsupdate.py
# Updates a dynamic dns-record using a TSIG key.

domain = "lubcke.se"
keyname = "lubcke.se."
keysecret = "ZGhNJ05b8ThmHOXhJvkvMw=="
ttl = 60

def get_ipaddress():
  # Connects to the dns server to determine which ip address
  # this host connects from
  import urllib
  remote = opener = urllib.FancyURLopener({})
  f = opener.open("http://www.wahlberg.se/~fredrik/ip.php")
  ip = f.read().strip()
  return ip

def main():
  # Define option parameters
  usage = "usage: %prog [-n] hostname [-i] ip adress [OPTIONS]"
  parser = OptionParser(usage)
  parser.add_option("-d", "--domain", 
                    type="string",
                    help="Name of the domain to update")
  parser.add_option("-i", "--ipaddress", 
                    type="string",
                    help="IP-address of the host")
  parser.add_option("-k", "--keyname", 
                    type="string",
                    help="Name of the TSIG key")
  parser.add_option("-n", "--name", 
                    type="string",
                    help="Name of the host to update")
  parser.add_option("-p", "--password", 
                    type="string",
                    help="The TSIG key")
  parser.add_option("-t", "--ttl", 
                    type="int",
                    help="TTL in seconds")
  (options, args) = parser.parse_args()
  

  global domain, ipaddress, keyname, keysecret, ttl

  if options.domain:
    domain = options.domain
  if options.ipaddress:
    ipaddress = options.ipaddress
  else:
    ipaddress = get_ipaddress()
  if options.keyname:
    keyname = options.keyname
  if options.password:
    keysecret = options.password
  if options.ttl:
    ttl = options.ttl
  
  if not options.name:
    print "A hostname is required for operation.\nEnter '%s -h' for usage information" % sys.argv[0]
    return 
  else:
    global hostname
    hostname = options.name

  update()


def update():
  # The update function connects to the dns server
  
  # Sanity check incoming data
  global hostname, ipaddress, ttl
  hostname = string.replace(hostname, "."+domain, '')
  if not re.search('^[12]?[0-9]?[0-9](\.[12]?[0-9]?[0-9]){3}$', ipaddress):
    print "Invalid ip address '%s'" % ipaddress
    return
  

  # The name of the key and the secret
  keyring = dns.tsigkeyring.from_text({
      keyname: keysecret
  })

  # dns.update.Update(name of domain, keyring, keyname)
  update = dns.update.Update(domain, keyring=keyring, keyname=keyname)

  # update.replace(hostname, ttl, record-type, new ip)
  update.replace(hostname, ttl, 'a', ipaddress)

  # doit, servername
  response = dns.query.tcp(update, 'nic.wahlberg.se')
  
  # Verify response
  if response.rcode() == 0:
    print "Host '%s.%s' has been added with ip address %s" % (hostname, domain, ipaddress)
  else:
    print "An error has occurred, the server returned:\n%s" % response

if __name__=="__main__":
  main()