Simple DynDNS Service using (apache) webserver and DNSMasq

dyn_dns_app.py

#!/usr/bin/env python 
# Simple Dynamic DNS update script for use with DNSMasq
#
# Install this WSGI script on a (apache) webserver. Make sure
# DNSMasq runs as the same user as this script does on the webserver
# E.g: /etc/default/dnsmasq add: (Debian and deriatives)
# DNSMASQ_USER='wsgiuser'
#
# ### DNSMASQ.CONF ###
# domain-needed
# bogus-priv
# filterwin2k
# no-resolv
# no-dhcp-interface=eth0
# bind-interfaces
# no-hosts
# addn-hosts=/tmp/dynhosts
# domain=dyn.z25.org
# expand-hosts
# ### END DNSMASQ.CONF ###
#
# ### APACHE EXAMPLE CONF ###
# # This file defines the apache configuration for the dyndns.example.com domain
# # (change example.com to your own domain name, of course)
# <VirtualHost *:80>
#         ServerName dyndns.example.com
#         # dyndns interface
#         ServerAdmin support@example.com
#
#         DocumentRoot /var/www/dyndns/
#         WSGIScriptAlias /nic/update /var/www/dyndns/dyn_dns.py
#         <Directory /var/www/dyndns/>
#                 Options FollowSymLinks MultiViews +ExecCGI
#                 AllowOverride FileInfo
#                 AddHandler wsgi-script .py
#                 Order allow,deny
#                 allow from all
#         </Directory>
#
#         LogLevel warn
#         ErrorLog /var/log/apache2/dyndns.error.log
#         CustomLog /var/log/apache2/dyndns.access.log combined
#         ServerSignature On
#  </VirtualHost>
# ### END APACHE EXAMPLE CONF ###

from cgi import parse_qs, escape

import psutil  
import os  
import signal  

def signal_dnsmasq():
    pids = psutil.get_pid_list()
    for pid in pids:  
        if psutil.Process(pid).name == "dnsmasq":  
            os.kill(pid,signal.SIGHUP)  
            break  

def update_host(hostname, ip):
    line_to_update = "%s\t%s\n" %(ip, hostname)
    with open('/tmp/dynhosts', 'r') as f:
        data = f.readlines()

    updated = False
    # need to enumerate list iter to update data
    for idx, line in enumerate(data):
        # split tab delimiter
        hn = line.split('\t')[1]
        # remove end of line char
        hn = hn.split('\n')[0]
        if line == line_to_update:
            return
        elif hn == hostname:
            data[idx] = line_to_update
            updated = True
    if not updated:
        data.append(line_to_update)
    with open('/tmp/dynhosts', 'w') as f:
        f.writelines(data)
    signal_dnsmasq()

def dyn_dns_app(environ, start_response):
    status = '404 Not Found' # HTTP Status
    headers = [('Content-type', 'text/plain')] # HTTP Headers
    
    # The returned object is going to be printed
    ip = environ['REMOTE_ADDR']
    d = parse_qs(environ['QUERY_STRING'])
    hostname = d.get('hostname')
    if hostname:
        status = '200 OK'
        update_host(hostname[0], ip)
        start_response(status, headers)
        return ["good"]
    else:
        start_response(status, headers) 
        return [""]

application = dyn_dns_app
 
if __name__ == '__main__':
    from wsgiref.simple_server import make_server
    
    httpd = make_server('', 8000, dyn_dns_app)
    print "Serving on port 8000..."

    # Serve until process is killed
    httpd.serve_forever()