""" Multicast DNS Service Discovery for Python, v0.14-wmcbrine

Copyright 2003 Paul Scott-Murphy, 2014 William McBrine

This module provides a framework for the use of DNS Service Discovery

using IP multicast.

This library is free software; you can redistribute it and/or

modify it under the terms of the GNU Lesser General Public

License as published by the Free Software Foundation; either

version 2.1 of the License, or (at your option) any later version.

This library is distributed in the hope that it will be useful,

but WITHOUT ANY WARRANTY; without even the implied warranty of

MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU

Lesser General Public License for more details.

You should have received a copy of the GNU Lesser General Public

License along with this library; if not, write to the Free Software

Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301

USA

"""

import re

import socket

# Some timing constants

_UNREGISTER_TIME = 125 # ms

_CHECK_TIME = 175 # ms

_REGISTER_TIME = 225 # ms

_LISTENER_TIME = 200 # ms

_BROWSER_TIME = 1000 # ms

_DUPLICATE_QUESTION_INTERVAL = _BROWSER_TIME - 1 # ms

_BROWSER_BACKOFF_LIMIT = 3600 # s

_CACHE_CLEANUP_INTERVAL = 10000 # ms

_LOADED_SYSTEM_TIMEOUT = 10 # s

_STARTUP_TIMEOUT = 9 # s must be lower than _LOADED_SYSTEM_TIMEOUT

_ONE_SECOND = 1000 # ms

# If the system is loaded or the event

# loop was blocked by another task that was doing I/O in the loop

# (shouldn't happen but it does in practice) we need to give

# a buffer timeout to ensure a coroutine can finish before

# the future times out

# Some DNS constants

_MDNS_ADDR = '224.0.0.251'

_MDNS_ADDR6 = 'ff02::fb'

_MDNS_PORT = 5353

_DNS_PORT = 53

_DNS_HOST_TTL = 120 # two minute for host records (A, SRV etc) as-per RFC6762

_DNS_OTHER_TTL = 4500 # 75 minutes for non-host records (PTR, TXT etc) as-per RFC6762

# Currently we enforce a minimum TTL for PTR records to avoid

# ServiceBrowsers generating excessive queries refresh queries.

# Apple uses a 15s minimum TTL, however we do not have the same

# level of rate limit and safe guards so we use 1/4 of the recommended value

_DNS_PTR_MIN_TTL = _DNS_OTHER_TTL / 4

_DNS_PACKET_HEADER_LEN = 12

_MAX_MSG_TYPICAL = 1460 # unused

_MAX_MSG_ABSOLUTE = 8966

_FLAGS_QR_MASK = 0x8000 # query response mask

_FLAGS_QR_QUERY = 0x0000 # query

_FLAGS_QR_RESPONSE = 0x8000 # response

_FLAGS_AA = 0x0400 # Authoritative answer

_FLAGS_TC = 0x0200 # Truncated

_FLAGS_RD = 0x0100 # Recursion desired

_FLAGS_RA = 0x8000 # Recursion available

_FLAGS_Z = 0x0040 # Zero

_FLAGS_AD = 0x0020 # Authentic data

_FLAGS_CD = 0x0010 # Checking disabled

_CLASS_IN = 1

_CLASS_CS = 2

_CLASS_CH = 3

_CLASS_HS = 4

_CLASS_NONE = 254

_CLASS_ANY = 255

_CLASS_MASK = 0x7FFF

_CLASS_UNIQUE = 0x8000

_TYPE_A = 1

_TYPE_NS = 2

_TYPE_MD = 3

_TYPE_MF = 4

_TYPE_CNAME = 5

_TYPE_SOA = 6

_TYPE_MB = 7

_TYPE_MG = 8

_TYPE_MR = 9

_TYPE_NULL = 10

_TYPE_WKS = 11

_TYPE_PTR = 12

_TYPE_HINFO = 13

_TYPE_MINFO = 14

_TYPE_MX = 15

_TYPE_TXT = 16

_TYPE_AAAA = 28

_TYPE_SRV = 33

_TYPE_NSEC = 47

_TYPE_ANY = 255

# Mapping constants to names

_CLASSES = {

_CLASS_IN: "in",

_CLASS_CS: "cs",

_CLASS_CH: "ch",

_CLASS_HS: "hs",

_CLASS_NONE: "none",

_CLASS_ANY: "any",

}

_TYPES = {

_TYPE_A: "a",

_TYPE_NS: "ns",

_TYPE_MD: "md",

_TYPE_MF: "mf",

_TYPE_CNAME: "cname",

_TYPE_SOA: "soa",

_TYPE_MB: "mb",

_TYPE_MG: "mg",

_TYPE_MR: "mr",

_TYPE_NULL: "null",

_TYPE_WKS: "wks",

_TYPE_PTR: "ptr",

_TYPE_HINFO: "hinfo",

_TYPE_MINFO: "minfo",

_TYPE_MX: "mx",

_TYPE_TXT: "txt",

_TYPE_AAAA: "quada",

_TYPE_SRV: "srv",

_TYPE_ANY: "any",

_TYPE_NSEC: "nsec",

}

_HAS_A_TO_Z = re.compile(r'[A-Za-z]')

_HAS_ONLY_A_TO_Z_NUM_HYPHEN = re.compile(r'^[A-Za-z0-9\-]+$')

_HAS_ONLY_A_TO_Z_NUM_HYPHEN_UNDERSCORE = re.compile(r'^[A-Za-z0-9\-\_]+$')

_HAS_ASCII_CONTROL_CHARS = re.compile(r'[\x00-\x1f\x7f]')

_EXPIRE_REFRESH_TIME_PERCENT = 75

_LOCAL_TRAILER = '.local.'

_TCP_PROTOCOL_LOCAL_TRAILER = '._tcp.local.'

_NONTCP_PROTOCOL_LOCAL_TRAILER = '._udp.local.'

# https://datatracker.ietf.org/doc/html/rfc6763#section-9

_SERVICE_TYPE_ENUMERATION_NAME = "_services._dns-sd._udp.local."

try:

_IPPROTO_IPV6 = socket.IPPROTO_IPV6

except AttributeError:

# Sigh: https://bugs.python.org/issue29515

_IPPROTO_IPV6 = 41