Viewing file:  opcode.py (2.48 KB) -rw-r--r--
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# Copyright (C) 2001-2007, 2009-2011 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 = 0
IQUERY = 1
STATUS = 2
NOTIFY = 4
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.
@param text: the textual opcode
@type text: string
@raises UnknownOpcode: the opcode is unknown
@rtype: 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.
@param flags: int
@rtype: int
"""
return (flags & 0x7800) >> 11
def to_flags(value):
"""Convert an opcode to a value suitable for ORing into DNS message
flags.
@rtype: int
"""
return (value << 11) & 0x7800
def to_text(value):
"""Convert an opcode to text.
@param value: the opcdoe
@type value: int
@raises UnknownOpcode: the opcode is unknown
@rtype: string
"""
text = _by_value.get(value)
if text is None:
text = str(value)
return text
def is_update(flags):
"""True if the opcode in flags is UPDATE.
@param flags: DNS flags
@type flags: int
@rtype: bool
"""
return from_flags(flags) == UPDATE
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