Daemon to create a wifi hotspot on linux (Python recipe) by Prahlad Yeri

ActiveState Code (http://code.activestate.com/recipes/578904/)

#!/usr/bin/env python
#@author: Prahlad Yeri
#@description: Small daemon to create a wifi hotspot on linux
#@license: MIT
import sys
import os
import argparse
import cli
import json
import socket

class Proto:
	pass
	
const = Proto()

#global const = Proto() #struct to hold startup parameters
#const.debug = False
#const.verbose = False
#const.command = 'start'
#const.argv = None

stores = Proto() #struct to dump misc variables
stores.running  = False

def validate_ip(addr):
	try:
		socket.inet_aton(addr)
		return True # legal
	except socket.error:
		return False # Not legal	

def configure():
	global wlan, ppp, IP, Netmask
	#CHECK WHETHER WIFI IS SUPPORTED OR NOT
	print 'Verifying connections'
	wlan=''
	ppp=''
	s=cli.execute_shell('iwconfig')
	if s!=None:
		lines = s.splitlines()
		#print 'and it is:'  + s
		for line in lines:
			if not line.startswith(' ') and not line.startswith('mon.') and 'IEEE 802.11' in line:
				wlan=line.split(' ')[0]
				print 'Wifi interface found: ' + wlan
			
	if wlan=='':
		print 'Wireless interface could not be found on your device.'
		return
			
	#print 'Verifying Internet connections'
	s=cli.execute_shell('ifconfig')
	lines = s.splitlines()
	iface=[]
	for line in lines:
		if not line.startswith(' ') and not line.startswith(wlan) and not line.startswith('lo') and not line.startswith('mon.') and len(line)>0:
			iface.append(line.split(' ')[0])
			#print 'f::' + line
			
	if len(iface)==0:
		print 'No network nic could be found on your deivce to interface with the LAN'
	elif len(iface)==1:
		ppp=iface[0]
		print 'Network interface found: ' + ppp
	else:
		rniface=range(len(iface))
		s=''
		while True:
			for i in rniface:
				print i, iface[i]
			try: s = int(input("Enter number for internet supplying NIC :"))
			except: continue
			if s not in rniface:
				continue
			ppp=iface[s]
			break
	
	while True:
		IP= raw_input('Enter an IP address for your ap [192.168.45.1] :')
		#except: continue
		#print type(IP)
		#sys.exit(0)
		if IP==None or IP=='':
			IP='192.168.45.1'
		if not validate_ip(IP): continue
		break
		
	Netmask='255.255.255.0'
	
	#CONFIGURE SSID, PASSWORD, ETC.
	SSID=raw_input('Enter SSID [joe_ssid] :')
	if SSID=='': SSID='joe_ssid'
	password=raw_input('Enter 10 digit password [1234567890] :')
	if password=='': password='1234567890'
	
	f = open('run.dat','r')
	lout=[]
	for line in f.readlines():
		lout.append(line.replace('<SSID>',SSID).replace('<PASS>',password))
		
	f.close()
	f = open('run.conf','w')
	f.writelines(lout)
	f.close()
	
	print 'created hostapd configuration: run.conf'
	
	dc = {'wlan': wlan, 'inet':ppp, 'ip':IP, 'netmask':Netmask, 'SSID':SSID, 'password':password}
	json.dump(dc, open('hotspotd.json','wb'))
	print dc
	print 'Configuration saved'
	
	#CHECK WIFI DRIVERS AND ISSUE WARNINGS
	

def check_dependencies():
	#CHECK FOR DEPENDENCIES
	if len(cli.check_sysfile('hostapd'))==0:
		print 'hostapd executable not found. Make sure you have installed hostapd.'
		return False
	elif len(cli.check_sysfile('dnsmasq'))==0:
		print 'dnsmasq executable not found. Make sure you have installed dnsmasq.'
		return False
	else:
		return True

def check_interfaces():
	global wlan, ppp
	print 'Verifying interfaces'
	s=cli.execute_shell('ifconfig')
	lines = s.splitlines()
	bwlan = False
	bppp  = False
	
	for line in lines:
		if not line.startswith(' ') and len(line)>0:
			text=line.split(' ')[0]
			if text.startswith(wlan):
				bwlan = True
			elif text.startswith('ppp0'):
				bppp = True
				
	if not bwlan:
		print wlan + ' interface was not found. Make sure your wifi is on.'
		return False
	elif not bppp:
		print ppp + ' interface was not found. Make sure you are connected to the internet.'
		return False
	else:
		print 'done.'
		return True
		
def pre_start():
	try:
		oper = platform.linux_distribution()
		if oper[0].lower()=='ubuntu' and oper[2].lower()=='trusty':
			#trusty patch
			print 'applying hostapd workaround for ubuntu trusty.'
			cli.execute_shell('nmcli nm wifi off')
			cli.execute_shell('rfkill unblock wlan')
			cli.execute_shell('sleep 1')
			print 'done.'
	except:
		pass

def start_router():
	if not check_dependencies():
		return
	elif not check_interfaces():
		return
	pre_start()
	s = 'ifconfig ' + wlan + ' up ' + IP + ' netmask ' + Netmask
	print 'created interface: mon.' + wlan + ' on IP: ' + IP
	r = cli.execute_shell(s)
	cli.writelog(r)
	#cli.writelog('sleeping for 2 seconds.')
	print 'wait..'
	cli.execute_shell('sleep 2')
	i = IP.rindex('.')
	ipparts=IP[0:i]
	
	#stop dnsmasq if already running.
	if cli.is_process_running('dnsmasq')>0:
		print 'stopping dnsmasq'
		cli.execute_shell('killall dnsmasq')
	
	
	#stop hostapd if already running.
	if cli.is_process_running('hostapd')>0:
		print 'stopping hostapd'
		cli.execute_shell('killall hostapd')
	
	#enable forwarding in sysctl.
	print 'enabling forward in sysctl.'
	r=cli.set_sysctl('net.ipv4.ip_forward','1')
	print r.strip()
	
	#enable forwarding in iptables.
	print 'creating NAT using iptables: ' + wlan + '<->' + ppp
	cli.execute_shell('iptables -P FORWARD ACCEPT')
	
	#add iptables rules to create the NAT.
	cli.execute_shell('iptables --table nat --delete-chain')
	cli.execute_shell('iptables --table nat -F')
	r=cli.execute_shell('iptables --table nat -X')
	if len(r.strip())>0: print r.strip()
	cli.execute_shell('iptables -t nat -A POSTROUTING -o ' + ppp +  ' -j MASQUERADE')
	cli.execute_shell('iptables -A FORWARD -i ' + ppp + ' -o ' + wlan + ' -j ACCEPT -m state --state RELATED,ESTABLISHED')
	cli.execute_shell('iptables -A FORWARD -i ' + wlan + ' -o ' + ppp + ' -j ACCEPT')
	
	#allow traffic to/from wlan
	cli.execute_shell('iptables -A OUTPUT --out-interface ' + wlan + ' -j ACCEPT')
	cli.execute_shell('iptables -A INPUT --in-interface ' + wlan +  ' -j ACCEPT')

	
	#start dnsmasq
	s = 'dnsmasq --dhcp-authoritative --interface=' + wlan + ' --dhcp-range=' + ipparts + '.20,' + ipparts +'.100,' + Netmask + ',4h'
	print 'running dnsmasq'
	r = cli.execute_shell(s)
	cli.writelog(r)
	
	#~ f = open(os.getcwd() + '/hostapd.tem','r')
	#~ lout=[]
	#~ for line in f.readlines():
		#~ lout.append(line.replace('<SSID>',SSID).replace('<PASS>',password))
		#~ 
	#~ f.close()
	#~ f = open(os.getcwd() + '/hostapd.conf','w')
	#~ f.writelines(lout)
	#~ f.close()
	
	#writelog('created: ' + os.getcwd() + '/hostapd.conf')
	#start hostapd
	#s = 'hostapd -B ' + os.path.abspath('run.conf')
	s = 'hostapd -B ' + os.getcwd() + '/run.conf'
	cli.writelog('running hostapd')
	#cli.writelog('sleeping for 2 seconds.')
	cli.writelog('wait..')	
	cli.execute_shell('sleep 2')
	r = cli.execute_shell(s)
	cli.writelog(r)
	print 'hotspot is running.'
	return	
	
def stop_router():
	#bring down the interface
	cli.execute_shell('ifconfig mon.' + wlan + ' down')

	#TODO: Find some workaround. killing hostapd brings down the wlan0 interface in ifconfig.
	#~ #stop hostapd
	#~ if cli.is_process_running('hostapd')>0:
		#~ cli.writelog('stopping hostapd')
		#~ cli.execute_shell('pkill hostapd')

	#stop dnsmasq
	if cli.is_process_running('dnsmasq')>0:
		cli.writelog('stopping dnsmasq')
		cli.execute_shell('killall dnsmasq')

	#disable forwarding in iptables.
	cli.writelog('disabling forward rules in iptables.')
	cli.execute_shell('iptables -P FORWARD DROP')
	
	#delete iptables rules that were added for wlan traffic.
	if wlan != None:
		cli.execute_shell('iptables -D OUTPUT --out-interface ' + wlan + ' -j ACCEPT')
		cli.execute_shell('iptables -D INPUT --in-interface ' + wlan +  ' -j ACCEPT')
	cli.execute_shell('iptables --table nat --delete-chain')
	cli.execute_shell('iptables --table nat -F')
	cli.execute_shell('iptables --table nat -X')
	#disable forwarding in sysctl.
	cli.writelog('disabling forward in sysctl.')
	r = cli.set_sysctl('net.ipv4.ip_forward','0')
	print r.strip()
	#cli.execute_shell('ifconfig ' + wlan + ' down'  + IP + ' netmask ' + Netmask)
	#cli.execute_shell('ip addr flush ' + wlan)
	print 'hotspot has stopped.'
	return

if __name__ == "__main__":
	global wlan, ppp, IP, Netmask

	#check root or not
	if os.getenv('USER') != 'root':
		print "You need root permissions to do this, sloth!"
		sys.exit(1)
		
	scpath = os.path.realpath(__file__)
	realdir = os.path.dirname(scpath)
	os.chdir(realdir)
	#print 'changed directory to ' + os.path.dirname(scpath)
	#if an instance is already running, then quit
	parser = argparse.ArgumentParser(description='A small daemon to create a wifi hotspot on linux')
	parser.add_argument('-v', '--verbose', required=False, action='store_true')
	parser.add_argument('command', choices=['start', 'stop', 'configure'])
	args = parser.parse_args()
	#const.verbose = args.verbose
	#const.command = args.command
	#const.blocking = args.blocking
	#const.argv = [os.getcwd() + '/server.py'] + sys.argv[1:]
	cli.arguments = args #initialize

	newconfig = False
	if not os.path.exists('hotspotd.json'):
		configure()
		newconfig=True

	dc =json.load(open('hotspotd.json'))
	wlan = dc['wlan']
	ppp = dc['inet']
	IP=dc['ip']
	Netmask=dc['netmask']
	SSID = dc['SSID']
	password = dc['password']
	
	if args.command == 'configure':
		if not newconfig: configure()
	elif args.command == 'stop':
		stop_router()
	elif args.command == 'start':
		if (cli.is_process_running('hostapd') != 0 and cli.is_process_running('dnsmasq') != 0):
			print 'hotspot is already running.'
		else:
			start_router()