import dns.query
import dns.tsigkeyring
import dns.update
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=="


def update():
  # Get command line args
  if len(sys.argv) != 3:
    print "Usage: dnsupdate.py hostname 192.168.0.1"
    return 

  hostname = sys.argv[1]
  ipaddress = sys.argv[2]
  
  # Sanity check incoming data
  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, 60, '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__":
  update()