164 lines
4.5 KiB
Python
164 lines
4.5 KiB
Python
""" Multicast DNS Service Discovery for Python, v0.14-wmcbrine
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Copyright 2003 Paul Scott-Murphy, 2014 William McBrine
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This module provides a framework for the use of DNS Service Discovery
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using IP multicast.
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This library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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This library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with this library; if not, write to the Free Software
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Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301
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USA
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"""
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import re
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import socket
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# Some timing constants
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_UNREGISTER_TIME = 125 # ms
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_CHECK_TIME = 175 # ms
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_REGISTER_TIME = 225 # ms
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_LISTENER_TIME = 200 # ms
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_BROWSER_TIME = 10000 # ms
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_DUPLICATE_PACKET_SUPPRESSION_INTERVAL = 1000 # ms
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_DUPLICATE_QUESTION_INTERVAL = 999 # ms # Must be 1ms less than _DUPLICATE_PACKET_SUPPRESSION_INTERVAL
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_CACHE_CLEANUP_INTERVAL = 10 # s
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_LOADED_SYSTEM_TIMEOUT = 10 # s
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_STARTUP_TIMEOUT = 9 # s must be lower than _LOADED_SYSTEM_TIMEOUT
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_ONE_SECOND = 1000 # ms
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# If the system is loaded or the event
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# loop was blocked by another task that was doing I/O in the loop
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# (shouldn't happen but it does in practice) we need to give
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# a buffer timeout to ensure a coroutine can finish before
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# the future times out
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# Some DNS constants
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_MDNS_ADDR = '224.0.0.251'
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_MDNS_ADDR6 = 'ff02::fb'
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_MDNS_PORT = 5353
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_DNS_PORT = 53
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_DNS_HOST_TTL = 120 # two minute for host records (A, SRV etc) as-per RFC6762
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_DNS_OTHER_TTL = 4500 # 75 minutes for non-host records (PTR, TXT etc) as-per RFC6762
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# Currently we enforce a minimum TTL for PTR records to avoid
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# ServiceBrowsers generating excessive queries refresh queries.
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# Apple uses a 15s minimum TTL, however we do not have the same
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# level of rate limit and safe guards so we use 1/4 of the recommended value
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_DNS_PTR_MIN_TTL = _DNS_OTHER_TTL / 4
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_DNS_PACKET_HEADER_LEN = 12
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_MAX_MSG_TYPICAL = 1460 # unused
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_MAX_MSG_ABSOLUTE = 8966
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_FLAGS_QR_MASK = 0x8000 # query response mask
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_FLAGS_QR_QUERY = 0x0000 # query
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_FLAGS_QR_RESPONSE = 0x8000 # response
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_FLAGS_AA = 0x0400 # Authoritative answer
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_FLAGS_TC = 0x0200 # Truncated
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_FLAGS_RD = 0x0100 # Recursion desired
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_FLAGS_RA = 0x8000 # Recursion available
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_FLAGS_Z = 0x0040 # Zero
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_FLAGS_AD = 0x0020 # Authentic data
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_FLAGS_CD = 0x0010 # Checking disabled
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_CLASS_IN = 1
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_CLASS_CS = 2
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_CLASS_CH = 3
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_CLASS_HS = 4
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_CLASS_NONE = 254
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_CLASS_ANY = 255
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_CLASS_MASK = 0x7FFF
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_CLASS_UNIQUE = 0x8000
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_CLASS_IN_UNIQUE = _CLASS_IN | _CLASS_UNIQUE
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_TYPE_A = 1
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_TYPE_NS = 2
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_TYPE_MD = 3
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_TYPE_MF = 4
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_TYPE_CNAME = 5
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_TYPE_SOA = 6
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_TYPE_MB = 7
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_TYPE_MG = 8
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_TYPE_MR = 9
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_TYPE_NULL = 10
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_TYPE_WKS = 11
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_TYPE_PTR = 12
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_TYPE_HINFO = 13
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_TYPE_MINFO = 14
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_TYPE_MX = 15
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_TYPE_TXT = 16
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_TYPE_AAAA = 28
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_TYPE_SRV = 33
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_TYPE_NSEC = 47
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_TYPE_ANY = 255
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# Mapping constants to names
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_CLASSES = {
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_CLASS_IN: "in",
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_CLASS_CS: "cs",
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_CLASS_CH: "ch",
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_CLASS_HS: "hs",
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_CLASS_NONE: "none",
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_CLASS_ANY: "any",
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}
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_TYPES = {
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_TYPE_A: "a",
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_TYPE_NS: "ns",
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_TYPE_MD: "md",
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_TYPE_MF: "mf",
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_TYPE_CNAME: "cname",
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_TYPE_SOA: "soa",
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_TYPE_MB: "mb",
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_TYPE_MG: "mg",
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_TYPE_MR: "mr",
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_TYPE_NULL: "null",
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_TYPE_WKS: "wks",
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_TYPE_PTR: "ptr",
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_TYPE_HINFO: "hinfo",
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_TYPE_MINFO: "minfo",
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_TYPE_MX: "mx",
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_TYPE_TXT: "txt",
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_TYPE_AAAA: "quada",
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_TYPE_SRV: "srv",
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_TYPE_ANY: "any",
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_TYPE_NSEC: "nsec",
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}
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_ADDRESS_RECORD_TYPES = {_TYPE_A, _TYPE_AAAA}
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_HAS_A_TO_Z = re.compile(r'[A-Za-z]')
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_HAS_ONLY_A_TO_Z_NUM_HYPHEN = re.compile(r'^[A-Za-z0-9\-]+$')
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_HAS_ONLY_A_TO_Z_NUM_HYPHEN_UNDERSCORE = re.compile(r'^[A-Za-z0-9\-\_]+$')
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_HAS_ASCII_CONTROL_CHARS = re.compile(r'[\x00-\x1f\x7f]')
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_EXPIRE_REFRESH_TIME_PERCENT = 75
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_LOCAL_TRAILER = '.local.'
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_TCP_PROTOCOL_LOCAL_TRAILER = '._tcp.local.'
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_NONTCP_PROTOCOL_LOCAL_TRAILER = '._udp.local.'
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# https://datatracker.ietf.org/doc/html/rfc6763#section-9
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_SERVICE_TYPE_ENUMERATION_NAME = "_services._dns-sd._udp.local."
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try:
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_IPPROTO_IPV6 = socket.IPPROTO_IPV6
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except AttributeError:
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# Sigh: https://bugs.python.org/issue29515
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_IPPROTO_IPV6 = 41
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