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# Copyright (C) 2001-2017 Nominum, Inc.
#
# Permission to use, copy, modify, and distribute this software and its
# documentation for any purpose with or without fee is hereby granted,
# provided that the above copyright notice and this permission notice
# appear in all copies.
#
# THE SOFTWARE IS PROVIDED "AS IS" AND NOMINUM DISCLAIMS ALL WARRANTIES
# WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
# MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL NOMINUM BE LIABLE FOR
# ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
# WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
# ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT
# OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
"""DNS Opcodes."""
import dns.exception
#: Query
QUERY = 0
#: Inverse Query (historical)
IQUERY = 1
#: Server Status (unspecified and unimplemented anywhere)
STATUS = 2
#: Notify
NOTIFY = 4
#: Dynamic Update
UPDATE = 5
_by_text = {
'QUERY': QUERY,
'IQUERY': IQUERY,
'STATUS': STATUS,
'NOTIFY': NOTIFY,
'UPDATE': UPDATE
}
# We construct the inverse mapping programmatically to ensure that we
# cannot make any mistakes (e.g. omissions, cut-and-paste errors) that
# would cause the mapping not to be true inverse.
_by_value = dict((y, x) for x, y in _by_text.items())
class UnknownOpcode(dns.exception.DNSException):
"""An DNS opcode is unknown."""
def from_text(text):
"""Convert text into an opcode.
*text*, a ``text``, the textual opcode
Raises ``dns.opcode.UnknownOpcode`` if the opcode is unknown.
Returns an ``int``.
"""
if text.isdigit():
value = int(text)
if value >= 0 and value <= 15:
return value
value = _by_text.get(text.upper())
if value is None:
raise UnknownOpcode
return value
def from_flags(flags):
"""Extract an opcode from DNS message flags.
*flags*, an ``int``, the DNS flags.
Returns an ``int``.
"""
return (flags & 0x7800) >> 11
def to_flags(value):
"""Convert an opcode to a value suitable for ORing into DNS message
flags.
*value*, an ``int``, the DNS opcode value.
Returns an ``int``.
"""
return (value << 11) & 0x7800
def to_text(value):
"""Convert an opcode to text.
*value*, an ``int`` the opcode value,
Raises ``dns.opcode.UnknownOpcode`` if the opcode is unknown.
Returns a ``text``.
"""
text = _by_value.get(value)
if text is None:
text = str(value)
return text
def is_update(flags):
"""Is the opcode in flags UPDATE?
*flags*, an ``int``, the DNS message flags.
Returns a ``bool``.
"""
return from_flags(flags) == UPDATE
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