# 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 Message Flags."""
# Standard DNS flags
QR = 0x8000
AA = 0x0400
TC = 0x0200
RD = 0x0100
RA = 0x0080
AD = 0x0020
CD = 0x0010
# EDNS flags
DO = 0x8000
_by_text = {
'QR': QR,
'AA': AA,
'TC': TC,
'RD': RD,
'RA': RA,
'AD': AD,
'CD': CD
}
_edns_by_text = {
'DO': DO
}
# We construct the inverse mappings programmatically to ensure that we
# cannot make any mistakes (e.g. omissions, cut-and-paste errors) that
# would cause the mappings not to be true inverses.
_by_value = dict((y, x) for x, y in _by_text.items())
_edns_by_value = dict((y, x) for x, y in _edns_by_text.items())
def _order_flags(table):
order = list(table.items())
order.sort()
order.reverse()
return order
_flags_order = _order_flags(_by_value)
_edns_flags_order = _order_flags(_edns_by_value)
def _from_text(text, table):
flags = 0
tokens = text.split()
for t in tokens:
flags = flags | table[t.upper()]
return flags
def _to_text(flags, table, order):
text_flags = []
for k, v in order:
if flags & k != 0:
text_flags.append(v)
return ' '.join(text_flags)
def from_text(text):
"""Convert a space-separated list of flag text values into a flags
value.
@rtype: int"""
return _from_text(text, _by_text)
def to_text(flags):
"""Convert a flags value into a space-separated list of flag text
values.
@rtype: string"""
return _to_text(flags, _by_value, _flags_order)
def edns_from_text(text):
"""Convert a space-separated list of EDNS flag text values into a EDNS
flags value.
@rtype: int"""
return _from_text(text, _edns_by_text)
def edns_to_text(flags):
"""Convert an EDNS flags value into a space-separated list of EDNS flag
text values.
@rtype: string"""
return _to_text(flags, _edns_by_value, _edns_flags_order)
|