测试方法

import socketserverimport struct# DNS Queryclass SinDNSQuery:    def __init__(self, data):        i = 1        self.name = ''        while True:            d = data[i]            if d == 0:                break;            if d < 32:                self.name = self.name + '.'            else:                self.name = self.name + chr(d)            i = i + 1        self.querybytes = data[0:i + 1]        (self.type, self.classify) = struct.unpack('>HH', data[i + 1:i + 5])        self.len = i + 5    def getbytes(self):        return self.querybytes + struct.pack('>HH', self.type, self.classify)# DNS Answer RRS# this class is also can be use as Authority RRS or Additional RRSclass SinDNSAnswer:    def __init__(self, ip):        self.name = 49164        self.type = 1        self.classify = 1        self.timetolive = 190        self.datalength = 4        self.ip = ip    def getbytes(self):        res = struct.pack('>HHHLH', self.name, self.type, self.classify, self.timetolive, self.datalength)        s = self.ip.split('.')        res = res + struct.pack('BBBB', int(s[0]), int(s[1]), int(s[2]), int(s[3]))        return res# DNS frame# must initialized by a DNS query frameclass SinDNSFrame:    def __init__(self, data):        (self.id, self.flags, self.quests, self.answers, self.author, self.addition) = struct.unpack('>HHHHHH', data[0:12])        self.query = SinDNSQuery(data[12:])    def getname(self):        return self.query.name    def setip(self, ip):        self.answer = SinDNSAnswer(ip)        self.answers = 1        self.flags = 33152    def getbytes(self):        res = struct.pack('>HHHHHH', self.id, self.flags, self.quests, self.answers, self.author, self.addition)        res = res + self.query.getbytes()        if self.answers != 0:            res = res + self.answer.getbytes()        return res# A UDPHandler to handle DNS queryclass SinDNSUDPHandler(socketserver.BaseRequestHandler):    def handle(self):        data = self.request[0].strip()        dns = SinDNSFrame(data)        socket = self.request[1]        namemap = SinDNSServer.namemap        if(dns.query.type==1):            # If this is query a A record, then response it
            name = dns.getname();            if namemap.__contains__(name):                # If have record, response it                dns.setip(namemap[name])                socket.sendto(dns.getbytes(), self.client_address)            elif namemap.__contains__('*'):                # Response default address                dns.setip(namemap['*'])                socket.sendto(dns.getbytes(), self.client_address)            else:                # ignore it                socket.sendto(data, self.client_address)        else:            # If this is not query a A record, ignore it            socket.sendto(data, self.client_address)# DNS Server# It only support A record query# user it, U can create a simple DNS serverclass SinDNSServer:    def __init__(self, port=53):        SinDNSServer.namemap = {}        self.port = port    def addname(self, name, ip):        SinDNSServer.namemap[name] = ip    def start(self):        HOST, PORT = "0.0.0.0", self.port        server = socketserver.UDPServer((HOST, PORT), SinDNSUDPHandler)        server.serve_forever()# Now, test itif __name__ == "__main__":    sev = SinDNSServer()    sev.addname('www.aa.com', '192.168.0.1')    # add a A record    sev.addname('www.aa.com.www.bb.com', '192.168.0.2')    # add a A record    sev.addname('*', '192.168.0.5') # default address    sev.start() # start DNS server# Now, U can use "nslookup" command to test it# Such as "nslookup www.aa.com"