├── README.md
└── SimpleDNSServer.py


/README.md:
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 1 | Introduction
 2 | =========================
 3 | 
 4 | SimpleDNSServer is a simple DNS server which redirects DNS query to hosting machine. It is an enhancement of [miniDNS](http://code.google.com/p/minidns/).
 5 | 
 6 | Additionally, you can specify a hosts file, in which ip address will be chosen instead. 
 7 | 
 8 | Python 3.x is being supported on master branch. Please use tag py2.7 for python 2.x。
 9 | 
10 | 


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/SimpleDNSServer.py:
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  1 | #!/usr/bin/env python
  2 | 
  3 | import sys
  4 | import socket
  5 | import _thread
  6 | import re
  7 | from datetime import datetime
  8 | 
  9 | # DNSQuery class from http://code.activestate.com/recipes/491264-mini-fake-dns-server/
 10 | class DNSQuery:
 11 |     def __init__(self, data):
 12 |         self.data=data
 13 |         self.domain=''
 14 |         
 15 |         tipo = (data[2] >> 3) & 15   # Opcode bits
 16 |         if tipo == 0:                     # Standard query
 17 |             ini=12
 18 |             lon=data[ini]
 19 |             while lon != 0:
 20 |                 self.domain+=data[ini+1:ini+lon+1].decode('ascii')+'.'
 21 |                 ini+=lon+1
 22 |                 lon=data[ini]
 23 |     
 24 |     def respuesta(self, ip):
 25 |         packet=b''
 26 |         if self.domain:
 27 |             packet+=self.data[:2] + b'\x81\x80'
 28 |             packet+=self.data[4:6] + self.data[4:6] + b'\x00\x00\x00\x00'   # Questions and Answers Counts
 29 |             packet+=self.data[12:]                                         # Original Domain Name Question
 30 |             packet+=b'\xc0\x0c'                                             # Pointer to domain name
 31 |             packet+=b'\x00\x01\x00\x01\x00\x00\x00\x3c\x00\x04'             # Response type, ttl and resource data length -> 4 bytes
 32 |             packet+=str.join('',map(lambda x: chr(int(x)), ip.split('.'))).encode('latin') # 4bytes of IP
 33 |         return packet
 34 | 
 35 | 
 36 | # get_ip_address by domain name
 37 | def get_ip_address_by_domain(domain):
 38 |     ip_address = '127.0.0.1'
 39 |     domain = domain.rstrip('.')
 40 |     if domain in host_ip_map:
 41 |         ip_address = host_ip_map[domain]
 42 |     else:
 43 |         list = socket.getaddrinfo(domain, 80)
 44 |         if len(list) > 0:
 45 |             ip_address = list[0][4][0]
 46 |             
 47 |     return ip_address
 48 | 
 49 | 
 50 | def usage():
 51 |     print("")
 52 |     print("Usage:")
 53 |     print("")
 54 |     print("\t# SimpleDNSServer [hosts file]")
 55 |     print("")
 56 |     print("Description:")
 57 |     print("")
 58 |     print("\tSimpleDNSServer will redirect DNS query to local machine.")
 59 |     print("")
 60 |     print("\tYou can optionally specify a hosts file to the command line:\n")
 61 |     print("\t\t# SimpleDNSServer hosts\n")
 62 |     print("\tThe ip address will be chosen prior to system hosts setting and remote dns query from local machine. \n")
 63 |     print("\tIf SimpleDNSServer and the DNS setting machine are same, you should set an optional DNS server in the DNS setting to avoid DNS query failure caused by redirecting recursively.\n")
 64 |     print("")
 65 |     
 66 |     sys.exit(1)
 67 | 
 68 | def query_and_send_back_ip(data, addr, reqtime):
 69 | 	try:
 70 | 		p=DNSQuery(data)
 71 | 		print('%s Request domain: %s from %s' % (reqtime.strftime("%H:%M:%S.%f"), p.domain, addr[0]))
 72 | 		ip = get_ip_address_by_domain(p.domain)
 73 | 		udps.sendto(p.respuesta(ip), addr)
 74 | 		dis = datetime.now() - reqtime
 75 | 
 76 | 		print('%s Request from %s cost %s : %s -> %s' % (reqtime.strftime("%H:%M:%S.%f"), addr[0], dis.seconds + dis.microseconds/1000000, p.domain, get_ip_address_by_domain(p.domain)))
 77 | 	except Exception as e:
 78 | 		print('query for:%s error:%s' % (p.domain, e))
 79 | 
 80 | def get_host_ip_map(hostsfile):
 81 | 	host_ip_map = {}
 82 | 	try:
 83 | 		f = open(hostsfile)
 84 | 		for l in f.readlines():
 85 | 			if not l.startswith('#'):
 86 | 				addrs = re.findall('[^\s]+', l)
 87 | 				if len(addrs) > 1:
 88 | 					for ad in addrs[1:]:
 89 | 						host_ip_map[ad] = addrs[0]
 90 |     
 91 | 	except:
 92 | 		pass
 93 | 	finally:
 94 | 		if not f:
 95 | 			f.close()
 96 |     
 97 | 	return host_ip_map
 98 | 
 99 | 
100 | if __name__ == '__main__':
101 |     hostsfile = None
102 |     host_ip_map = {}
103 |     
104 |     if len(sys.argv) > 1:
105 |         if len(sys.argv) > 2 or sys.argv[-1] == '-h' or sys.argv[-1] == '--help':
106 |             usage()
107 |         else:
108 |             hostsfile = sys.argv[-1]
109 |             host_ip_map = get_host_ip_map(hostsfile)
110 |     
111 |     try:
112 |         udps = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
113 |         udps.bind(('',53))
114 |     except Exception as e:
115 |         print("Failed to create socket on UDP port 53:", e)
116 |         sys.exit(1)
117 |     
118 |     print('SimpleDNSServer :: hosts file -> %s\n' % hostsfile)
119 |     
120 |     try:
121 |         while 1:
122 |             data, addr = udps.recvfrom(1024)
123 |             _thread.start_new_thread(query_and_send_back_ip, (data, addr, datetime.now()))
124 |     except KeyboardInterrupt:
125 |         print('\n^C, Exit!')
126 |     except Exception as e:
127 |         print('\nError: %s' % e)
128 |     finally:
129 |         udps.close()
130 | 
131 | 


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