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108 lines
2.5 KiB
108 lines
2.5 KiB
6 years ago
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# Copyright (C) 2001-2007, 2009-2011 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 Opcodes."""
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import dns.exception
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QUERY = 0
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IQUERY = 1
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STATUS = 2
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NOTIFY = 4
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UPDATE = 5
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_by_text = {
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'QUERY': QUERY,
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'IQUERY': IQUERY,
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'STATUS': STATUS,
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'NOTIFY': NOTIFY,
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'UPDATE': UPDATE
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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 = dict((y, x) for x, y in _by_text.items())
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class UnknownOpcode(dns.exception.DNSException):
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"""An DNS opcode is unknown."""
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def from_text(text):
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"""Convert text into an opcode.
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@param text: the textual opcode
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@type text: string
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@raises UnknownOpcode: the opcode is unknown
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@rtype: int
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"""
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if text.isdigit():
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value = int(text)
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if value >= 0 and value <= 15:
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return value
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value = _by_text.get(text.upper())
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if value is None:
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raise UnknownOpcode
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return value
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def from_flags(flags):
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"""Extract an opcode from DNS message flags.
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@param flags: int
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@rtype: int
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"""
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return (flags & 0x7800) >> 11
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def to_flags(value):
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"""Convert an opcode to a value suitable for ORing into DNS message
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flags.
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@rtype: int
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"""
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return (value << 11) & 0x7800
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def to_text(value):
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"""Convert an opcode to text.
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@param value: the opcdoe
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@type value: int
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@raises UnknownOpcode: the opcode is unknown
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@rtype: string
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"""
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text = _by_value.get(value)
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if text is None:
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text = str(value)
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return text
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def is_update(flags):
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"""True if the opcode in flags is UPDATE.
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@param flags: DNS flags
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@type flags: int
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@rtype: bool
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"""
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return from_flags(flags) == UPDATE
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