在上一篇中，的最后我们提到因为hosts文件不支持正则，会导致我们的随机域名DNS查询失败。
使用DNS代理服务器能够解决问题，
以下是我用gevent写的小工具。非常easy。我们仅仅拦截匹配的A记录。然后发送DNS Response，假设不匹配，那么我们服务器就是一个DNS代理，转发请求。
# -*- coding=utf-8 -*-import structfrom cStringIO import StringIOfrom collections import namedtuplefrom gevent import socketfrom gevent.server import DatagramServerHex = lambda x : '0x{0:04x}'.format(x) # Hex(256) => "0x0100"QueryResult = namedtuple("DnsQuery", "transactionID,flags,questions,answerRrs \ authorityRrs,additionalRrs,qname,qtype,qclass")LOCALDNS = ("114.114.114.114",53)Hosts = { "*.ttt.com":"173.194.127.144", # google ip}def preg_match(preg,real): """ only support '*' >>>preg_match("www.*.test*.com","www.python.test.com") True >>>preg_match("www.*.test*.com","www.python.tes.com") False """ pre = 0 for s in preg.split('*'): now = real.find(s) if now < pre: return False pre = now +len(s) return Truedef udp_send(address,data): sock = socket.socket(type=socket.SOCK_DGRAM) sock.connect(address) sock.send(data) response, address = sock.recvfrom(8192*4) return response,addressclass DnsParser: @classmethod def parseQuery(self,query): """ 6a 02 01 00 00 01 j..... 00 00 00 00 00 00 03 77 77 77 03 61 61 61 03 63 .......www.aaa.c 6f 6d 00 00 01 00 01 om..... dns query package like above 03 77 77 77 : three www """ transactionID,flags,questions,answerRrs,authorityRrs,additionalRrs = map(Hex,struct.unpack("!6H",query[:12])) quries = StringIO(query[12:]) c = struct.unpack("!c",quries.read(1))[0] domain = [] while c != '\x00': n = ord(c) domain.append(''.join(struct.unpack("!%sc" % n,quries.read(ord(c))))) c = struct.unpack("!c",quries.read(1))[0] domain = '.'.join(domain) qtype,qclass = map(Hex,struct.unpack("!2H",quries.read())) return QueryResult(transactionID,flags,questions,answerRrs, authorityRrs,additionalRrs,domain,qtype,qclass) @classmethod def generateReqponse(self,queryData,ip): """ only support ipv4 """ return ''.join([queryData[:2],"\x81\x80\x00\x01\x00\x02\x00\x00\x00\x00", queryData[12:],"\xc0\x0c","\x00\x01","\x00\x01","\x00\x00\x00\x1e","\x00\x04", struct.pack('BBBB',*map(int,ip.split('.'))) ])class DnsServer(DatagramServer): def handle(self,data,address): query = DnsParser.parseQuery(data) print "get dns query from %s,query:%s" %(str(address),str(query)) find = False for preg,ip in Hosts.iteritems(): if preg_match(preg,query.qname): find = True break if find and query.qtype == "0x0001": #only handle A record print 'domain:%s in hosts' % query.qname response = DnsParser.generateReqponse(data,ip) self.socket.sendto(response,address) else: print 'transfer for %s' % query.qname response,serveraddress = udp_send(LOCALDNS,data) self.socket.sendto(response,address)if __name__ == "__main__": DnsServer("192.168.9.178:53").serve_forever() 哈哈，刚好100行，不得不说python的强大。
来个截图：
功能有限。各位童鞋能够扩展，代码已经放到github，，有兴趣的童鞋一起完好。