ansible dynamic inventory script for local network

dynamic-inv-local-network.py

#!/usr/bin/env python

""" 
    dynamic-inv-local-network.py - dynamic ansible inventory file for use a local network
    
    usage: ansible --ask-vault-password -i dynamic-inv-local-network.py all -m ping
"""

from __future__ import (print_function, absolute_import, division, unicode_literals)

import socket
import subprocess

# json is not alway default installed, if json is not installed simplejson is installed
# for this reason python will check is json is installed or it will fallback to simplejson
try:
    import json
except ImportError:
    import simplejson as json

def inventory():
    """ function: create a dynamicly generated inventory for ansible """
    ipaddrs = find_nodes()
    
    return {
            'all': {
                'hosts': [ipaddrs],
                'vars': {},
                },
            '_meta': {
                'hostvars': {
                    ipaddrs: {
                        'ansible_ssh_user': 'ansible',
                        }
                    },
                },
            'nodes': [ipaddrs]
        }

def find_nodes():
    """ function: return ipaddress in you local network where port 22 is open """
    for ip in all_local_ipaddrs():
        if port_22_is_open(ip):
            return ip

def all_local_ipaddrs():
    """ function: find all active ipaddress in your local network """
    lines = subprocess.check_output(['arp', '-a']).split('\n')
    for line in lines:
        if '(' not in line:
            continue
        
        afterbracketopen = line.split('(')[1]
        ipaddr = afterbracketopen.split(')')[0]
        
        yield ipaddr

def port_22_is_open(ipaddr):
    """ function: check if port 22 is open """
    sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    sock.settimeout(1)
    result = sock.connect_ex((ipaddr, 22))
    sock.close()
    
    return result == 0

def main():
    """ function: main function for returning the dynamic inventory """
    print('{}' .format(json.dumps(inventory(), sort_keys=True, indent=2)))

if __name__ == "__main__":
    main()