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122 lines
3.1 KiB
122 lines
3.1 KiB
# Copyright (C) Dnspython Contributors, see LICENSE for text of ISC license
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# Copyright (C) 2001-2017 Nominum, Inc.
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#
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# Permission to use, copy, modify, and distribute this software and its
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# documentation for any purpose with or without fee is hereby granted,
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# provided that the above copyright notice and this permission notice
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# appear in all copies.
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#
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# THE SOFTWARE IS PROVIDED "AS IS" AND NOMINUM DISCLAIMS ALL WARRANTIES
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# WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
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# MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL NOMINUM BE LIABLE FOR
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# ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
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# WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
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# ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT
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# OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
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"""DNS Rdata Classes."""
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import re
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import dns.exception
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RESERVED0 = 0
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IN = 1
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CH = 3
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HS = 4
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NONE = 254
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ANY = 255
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_by_text = {
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'RESERVED0': RESERVED0,
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'IN': IN,
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'CH': CH,
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'HS': HS,
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'NONE': NONE,
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'ANY': ANY
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}
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# We construct the inverse mapping programmatically to ensure that we
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# cannot make any mistakes (e.g. omissions, cut-and-paste errors) that
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# would cause the mapping not to be true inverse.
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_by_value = {y: x for x, y in _by_text.items()}
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# Now that we've built the inverse map, we can add class aliases to
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# the _by_text mapping.
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_by_text.update({
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'INTERNET': IN,
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'CHAOS': CH,
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'HESIOD': HS
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})
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_metaclasses = {
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NONE: True,
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ANY: True
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}
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_unknown_class_pattern = re.compile('CLASS([0-9]+)$', re.I)
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class UnknownRdataclass(dns.exception.DNSException):
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"""A DNS class is unknown."""
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def from_text(text):
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"""Convert text into a DNS rdata class value.
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The input text can be a defined DNS RR class mnemonic or
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instance of the DNS generic class syntax.
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For example, "IN" and "CLASS1" will both result in a value of 1.
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Raises ``dns.rdatatype.UnknownRdataclass`` if the class is unknown.
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Raises ``ValueError`` if the rdata class value is not >= 0 and <= 65535.
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Returns an ``int``.
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"""
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value = _by_text.get(text.upper())
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if value is None:
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match = _unknown_class_pattern.match(text)
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if match is None:
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raise UnknownRdataclass
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value = int(match.group(1))
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if value < 0 or value > 65535:
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raise ValueError("class must be between >= 0 and <= 65535")
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return value
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def to_text(value):
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"""Convert a DNS rdata type value to text.
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If the value has a known mnemonic, it will be used, otherwise the
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DNS generic class syntax will be used.
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Raises ``ValueError`` if the rdata class value is not >= 0 and <= 65535.
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Returns a ``str``.
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"""
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if value < 0 or value > 65535:
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raise ValueError("class must be between >= 0 and <= 65535")
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text = _by_value.get(value)
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if text is None:
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text = 'CLASS' + repr(value)
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return text
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def is_metaclass(rdclass):
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"""True if the specified class is a metaclass.
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The currently defined metaclasses are ANY and NONE.
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*rdclass* is an ``int``.
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"""
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if rdclass in _metaclasses:
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return True
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return False
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