Make docker listen on lan

docker_listen_lan.py

"""
Makes docker listen on lan
tcp://192.168.1.32:2375
http://192.168.1.32:2375
"""
import json
import copy
import fcntl
import socket
import string
import random
import struct
import argparse
import StringIO
import collections
import ConfigParser

__description__ = """Modifies docker config to listen on another address \
or port"""

def interface_ip(ifname):
    try:
        s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
        return socket.inet_ntoa(fcntl.ioctl(
            s.fileno(),
            0x8915,  # SIOCGIFADDR
            struct.pack('256s', ifname[:15])
        )[20:24])
    except:
        return False

DEFUALT_FILE = "/etc/default/docker"
DEFUALT_PORT = 2375
DEFUALT_ADDR = interface_ip("eth0") or \
    interface_ip("wlan0") or \
    socket.gethostbyname(socket.gethostname())

def arg_setup():
    arg_parser = argparse.ArgumentParser(description=__description__)
    arg_parser.add_argument("--address", "-a", type=str, \
        help="Address to host on", default=DEFUALT_ADDR)
    arg_parser.add_argument("--port", "-p", type=int, \
        help="Port to host on", default=DEFUALT_PORT)
    arg_parser.add_argument("--modfile", "-f", type=str, \
        help="File to change", default=DEFUALT_FILE)
    initial = vars(arg_parser.parse_args())
    args = {}
    for arg in initial:
        if initial[arg] is not None:
            args[arg] = initial[arg]
    return args

def run(port, address, modfile):
    listen_args = "-H tcp://{address}:{port}".format(port=port, address=address)
    settings_file = open(modfile, "ab")
    option = "DOCKER_OPTS=\"{listen_args} -H unix:///var/run/docker.sock\"\n".format(listen_args=listen_args)
    settings_file.write(option)
    settings_file.close()
    settings_file = open(modfile, "rb")
    for line in settings_file:
        print line[:-1]
    settings_file.close()
    return

def main():
    args = arg_setup()
    run(**args)
    return 0

if __name__ == "__main__":
    main()