1# Copyright (C) Dnspython Contributors, see LICENSE for text of ISC license 2 3# Copyright (C) 2001-2017 Nominum, Inc. 4# 5# Permission to use, copy, modify, and distribute this software and its 6# documentation for any purpose with or without fee is hereby granted, 7# provided that the above copyright notice and this permission notice 8# appear in all copies. 9# 10# THE SOFTWARE IS PROVIDED "AS IS" AND NOMINUM DISCLAIMS ALL WARRANTIES 11# WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF 12# MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL NOMINUM BE LIABLE FOR 13# ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES 14# WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN 15# ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT 16# OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. 17 18"""DNS Opcodes.""" 19 20import dns.exception 21 22#: Query 23QUERY = 0 24#: Inverse Query (historical) 25IQUERY = 1 26#: Server Status (unspecified and unimplemented anywhere) 27STATUS = 2 28#: Notify 29NOTIFY = 4 30#: Dynamic Update 31UPDATE = 5 32 33_by_text = { 34 'QUERY': QUERY, 35 'IQUERY': IQUERY, 36 'STATUS': STATUS, 37 'NOTIFY': NOTIFY, 38 'UPDATE': UPDATE 39} 40 41# We construct the inverse mapping programmatically to ensure that we 42# cannot make any mistakes (e.g. omissions, cut-and-paste errors) that 43# would cause the mapping not to be true inverse. 44 45_by_value = {y: x for x, y in _by_text.items()} 46 47 48class UnknownOpcode(dns.exception.DNSException): 49 """An DNS opcode is unknown.""" 50 51 52def from_text(text): 53 """Convert text into an opcode. 54 55 *text*, a ``text``, the textual opcode 56 57 Raises ``dns.opcode.UnknownOpcode`` if the opcode is unknown. 58 59 Returns an ``int``. 60 """ 61 62 if text.isdigit(): 63 value = int(text) 64 if value >= 0 and value <= 15: 65 return value 66 value = _by_text.get(text.upper()) 67 if value is None: 68 raise UnknownOpcode 69 return value 70 71 72def from_flags(flags): 73 """Extract an opcode from DNS message flags. 74 75 *flags*, an ``int``, the DNS flags. 76 77 Returns an ``int``. 78 """ 79 80 return (flags & 0x7800) >> 11 81 82 83def to_flags(value): 84 """Convert an opcode to a value suitable for ORing into DNS message 85 flags. 86 87 *value*, an ``int``, the DNS opcode value. 88 89 Returns an ``int``. 90 """ 91 92 return (value << 11) & 0x7800 93 94 95def to_text(value): 96 """Convert an opcode to text. 97 98 *value*, an ``int`` the opcode value, 99 100 Raises ``dns.opcode.UnknownOpcode`` if the opcode is unknown. 101 102 Returns a ``text``. 103 """ 104 105 text = _by_value.get(value) 106 if text is None: 107 text = str(value) 108 return text 109 110 111def is_update(flags): 112 """Is the opcode in flags UPDATE? 113 114 *flags*, an ``int``, the DNS message flags. 115 116 Returns a ``bool``. 117 """ 118 119 return from_flags(flags) == UPDATE 120