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Filename : reversename.py
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# Copyright (C) 2006, 2007, 2009-2011 Nominum, Inc.
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# provided that the above copyright notice and this permission notice
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# WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
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"""DNS Reverse Map Names.

@var ipv4_reverse_domain: The DNS IPv4 reverse-map domain, in-addr.arpa.
@type ipv4_reverse_domain: dns.name.Name object
@var ipv6_reverse_domain: The DNS IPv6 reverse-map domain, ip6.arpa.
@type ipv6_reverse_domain: dns.name.Name object
"""

import binascii
import sys

import dns.name
import dns.ipv6
import dns.ipv4

ipv4_reverse_domain = dns.name.from_text('in-addr.arpa.')
ipv6_reverse_domain = dns.name.from_text('ip6.arpa.')


def from_address(text):
    """Convert an IPv4 or IPv6 address in textual form into a Name object whose
    value is the reverse-map domain name of the address.
    @param text: an IPv4 or IPv6 address in textual form (e.g. '127.0.0.1',
    '::1')
    @type text: str
    @rtype: dns.name.Name object
    """
    try:
        v6 = dns.ipv6.inet_aton(text)
        if dns.ipv6.is_mapped(v6):
            if sys.version_info >= (3,):
                parts = ['%d' % byte for byte in v6[12:]]
            else:
                parts = ['%d' % ord(byte) for byte in v6[12:]]
            origin = ipv4_reverse_domain
        else:
            parts = [x for x in str(binascii.hexlify(v6).decode())]
            origin = ipv6_reverse_domain
    except Exception:
        parts = ['%d' %
                 byte for byte in bytearray(dns.ipv4.inet_aton(text))]
        origin = ipv4_reverse_domain
    parts.reverse()
    return dns.name.from_text('.'.join(parts), origin=origin)


def to_address(name):
    """Convert a reverse map domain name into textual address form.
    @param name: an IPv4 or IPv6 address in reverse-map form.
    @type name: dns.name.Name object
    @rtype: str
    """
    if name.is_subdomain(ipv4_reverse_domain):
        name = name.relativize(ipv4_reverse_domain)
        labels = list(name.labels)
        labels.reverse()
        text = b'.'.join(labels)
        # run through inet_aton() to check syntax and make pretty.
        return dns.ipv4.inet_ntoa(dns.ipv4.inet_aton(text))
    elif name.is_subdomain(ipv6_reverse_domain):
        name = name.relativize(ipv6_reverse_domain)
        labels = list(name.labels)
        labels.reverse()
        parts = []
        i = 0
        l = len(labels)
        while i < l:
            parts.append(b''.join(labels[i:i + 4]))
            i += 4
        text = b':'.join(parts)
        # run through inet_aton() to check syntax and make pretty.
        return dns.ipv6.inet_ntoa(dns.ipv6.inet_aton(text))
    else:
        raise dns.exception.SyntaxError('unknown reverse-map address family')