【Python Network】分解DNS查询结果

针对DNS查询records，通过NS、PTR、CNAME和MX类别不同，返回数据将包含另外主机名。为了解最终的IP地址，通过将返回信息分解。继续使用PyDNS获取详细信息。

#! /usr/bin/env python

# DNS query program - Example 4 - DNSquery.py

import sys, DNS, re, DNSany

def getreverse(query):

    """ Given the query, returns an approciate reverse lookup string

        under IN-ADDR.ARPA if query is an IP address; otherwire, return

        None. This function is not IPv6-compatiable. """

    if re.search("^\d+.\d+.\d+.\d+$", query):

        octets = query.split('.')

        octets.reverse()

        return '.'.join(octets) + '.IN-ADDR.ADDR'

    return None

def formatline(index, typename, descr, data):

    retval = "%-2s %-5s" % (index, typename)

    data = data.replace("\n", "\n ")

    if descr != None and len(descr):

        retval += " %-12s" % (descr + ":")

    return retval + " " + data

DNS.DiscoverNameServers()

queries = [(sys.argv[1], DNS.Type.ANY)]

donequeries = []

descriptions = {'A': 'IP address',

                'TXT': 'Data',

                'PTR': 'Host name',

                'CNAME': 'Alias for',

                'NS': 'Name server'}

while len(queries):

    (query, qtype) = queries.pop(0)

    if query in donequeries:

        # Don't look up the same thing twice

        continue

    donequeries.append(query)

    print "-" * 77

    print "Results for %s (lookup type %s)" % (query, DNS.Type.typestr(qtype))

    print

    rev = getreverse(query)

    if rev is not None:

        print "IP address given; doing reverse lookup using", rev

        query = rev

    answers = DNSany.nslookup(query, qtype, verbose = 0)

    if not len(answers):

        print "Not found"

    count = 0

    for answer in answers:

        count += 1

        if answer['typename'] == 'MX':

            print formatline(count, 'MX', 'Mail Server',

                             "%s, priority %d" % (answer['data'][1], answer['data'][0]))

            queries.append((answer['data'][1], DNS.Type.A))

        elif answer['typename'] == 'SOA':

            data = "\n" + "\n".join(str(x) for x in answer['data'])

            print formatline(count, 'SOA', 'Start of authority', data)

        elif answer['typename'] in descriptions:

            print formatline(count, answer['typename'], descriptions[answer['typename']], str(answer['data']))

        else:

            print formatline(count, answer['typename'], None, str(answer['data']))

        if answer['typename'] in ['CNAME', 'PTR']:

            queries.append((answer['data'], DNS.Type.ANY))

        if answer['typename'] == 'NS':

            queries.append((answer['data'], DNS.Type.A))

以baidu.com为例，运行截图如下。