1679 lines
56 KiB
Python
1679 lines
56 KiB
Python
from __future__ import absolute_import, division, print_function, unicode_literals
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""" 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 enum
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import errno
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import logging
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import select
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import socket
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import struct
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import threading
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import time
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from functools import reduce
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import netifaces
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from six import binary_type, indexbytes, int2byte, iteritems, text_type
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from six.moves import xrange
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__author__ = 'Paul Scott-Murphy, William McBrine'
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__maintainer__ = 'Jakub Stasiak <jakub@stasiak.at>'
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__version__ = '0.17.4'
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__license__ = 'LGPL'
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try:
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NullHandler = logging.NullHandler
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except AttributeError:
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# Python 2.6 fallback
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class NullHandler(logging.Handler):
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def emit(self, record):
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pass
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__all__ = [
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"__version__",
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"Zeroconf", "ServiceInfo", "ServiceBrowser",
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"Error", "InterfaceChoice", "ServiceStateChange",
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]
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log = logging.getLogger(__name__)
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log.addHandler(NullHandler())
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if log.level == logging.NOTSET:
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log.setLevel(logging.WARN)
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# hook for threads
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_GLOBAL_DONE = False
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# Some timing constants
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_UNREGISTER_TIME = 125
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_CHECK_TIME = 175
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_REGISTER_TIME = 225
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_LISTENER_TIME = 200
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_BROWSER_TIME = 500
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# Some DNS constants
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_MDNS_ADDR = '224.0.0.251'
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_MDNS_PORT = 5353
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_DNS_PORT = 53
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_DNS_TTL = 60 * 60 # one hour default TTL
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_MAX_MSG_TYPICAL = 1460 # unused
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_MAX_MSG_ABSOLUTE = 8972
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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 # Authorative 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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_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_ANY = 255
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# Mapping constants to names
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_CLASSES = {_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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_TYPES = {_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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# utility functions
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def current_time_millis():
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"""Current system time in milliseconds"""
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return time.time() * 1000
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# Exceptions
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class Error(Exception):
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pass
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class NonLocalNameException(Exception):
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pass
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class NonUniqueNameException(Exception):
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pass
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class NamePartTooLongException(Exception):
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pass
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class AbstractMethodException(Exception):
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pass
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class BadTypeInNameException(Exception):
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pass
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# implementation classes
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class DNSEntry(object):
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"""A DNS entry"""
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def __init__(self, name, type, class_):
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self.key = name.lower()
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self.name = name
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self.type = type
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self.class_ = class_ & _CLASS_MASK
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self.unique = (class_ & _CLASS_UNIQUE) != 0
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def __eq__(self, other):
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"""Equality test on name, type, and class"""
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return (isinstance(other, DNSEntry) and
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self.name == other.name and
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self.type == other.type and
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self.class_ == other.class_)
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def __ne__(self, other):
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"""Non-equality test"""
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return not self.__eq__(other)
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def get_class_(self, class_):
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"""Class accessor"""
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return _CLASSES.get(class_, "?(%s)" % class_)
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def get_type(self, t):
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"""Type accessor"""
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return _TYPES.get(t, "?(%s)" % t)
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def to_string(self, hdr, other):
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"""String representation with additional information"""
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result = "%s[%s,%s" % (hdr, self.get_type(self.type),
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self.get_class_(self.class_))
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if self.unique:
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result += "-unique,"
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else:
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result += ","
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result += self.name
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if other is not None:
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result += ",%s]" % (other)
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else:
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result += "]"
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return result
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class DNSQuestion(DNSEntry):
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"""A DNS question entry"""
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def __init__(self, name, type, class_):
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# if not name.endswith(".local."):
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# raise NonLocalNameException
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DNSEntry.__init__(self, name, type, class_)
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def answered_by(self, rec):
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"""Returns true if the question is answered by the record"""
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return (self.class_ == rec.class_ and
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(self.type == rec.type or self.type == _TYPE_ANY) and
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self.name == rec.name)
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def __repr__(self):
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"""String representation"""
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return DNSEntry.to_string(self, "question", None)
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class DNSRecord(DNSEntry):
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"""A DNS record - like a DNS entry, but has a TTL"""
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def __init__(self, name, type, class_, ttl):
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DNSEntry.__init__(self, name, type, class_)
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self.ttl = ttl
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self.created = current_time_millis()
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def __eq__(self, other):
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"""Tests equality as per DNSRecord"""
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return isinstance(other, DNSRecord) and DNSEntry.__eq__(self, other)
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def suppressed_by(self, msg):
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"""Returns true if any answer in a message can suffice for the
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information held in this record."""
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for record in msg.answers:
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if self.suppressed_by_answer(record):
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return True
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return False
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def suppressed_by_answer(self, other):
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"""Returns true if another record has same name, type and class,
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and if its TTL is at least half of this record's."""
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return self == other and other.ttl > (self.ttl / 2)
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def get_expiration_time(self, percent):
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"""Returns the time at which this record will have expired
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by a certain percentage."""
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return self.created + (percent * self.ttl * 10)
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def get_remaining_ttl(self, now):
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"""Returns the remaining TTL in seconds."""
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return max(0, (self.get_expiration_time(100) - now) / 1000)
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def is_expired(self, now):
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"""Returns true if this record has expired."""
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return self.get_expiration_time(100) <= now
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def is_stale(self, now):
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"""Returns true if this record is at least half way expired."""
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return self.get_expiration_time(50) <= now
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def reset_ttl(self, other):
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"""Sets this record's TTL and created time to that of
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another record."""
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self.created = other.created
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self.ttl = other.ttl
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def write(self, out):
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"""Abstract method"""
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raise AbstractMethodException
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def to_string(self, other):
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"""String representation with addtional information"""
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arg = "%s/%s,%s" % (self.ttl,
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self.get_remaining_ttl(current_time_millis()), other)
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return DNSEntry.to_string(self, "record", arg)
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class DNSAddress(DNSRecord):
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"""A DNS address record"""
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def __init__(self, name, type, class_, ttl, address):
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DNSRecord.__init__(self, name, type, class_, ttl)
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self.address = address
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def write(self, out):
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"""Used in constructing an outgoing packet"""
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out.write_string(self.address)
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def __eq__(self, other):
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"""Tests equality on address"""
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return isinstance(other, DNSAddress) and self.address == other.address
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def __repr__(self):
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"""String representation"""
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try:
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return socket.inet_ntoa(self.address)
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except Exception as e: # TODO stop catching all Exceptions
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log.exception('Unknown error, possibly benign: %r', e)
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return self.address
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class DNSHinfo(DNSRecord):
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"""A DNS host information record"""
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def __init__(self, name, type, class_, ttl, cpu, os):
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DNSRecord.__init__(self, name, type, class_, ttl)
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self.cpu = cpu
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self.os = os
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def write(self, out):
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"""Used in constructing an outgoing packet"""
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out.write_string(self.cpu)
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out.write_string(self.oso)
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def __eq__(self, other):
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"""Tests equality on cpu and os"""
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return (isinstance(other, DNSHinfo) and
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self.cpu == other.cpu and self.os == other.os)
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def __repr__(self):
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"""String representation"""
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return self.cpu + " " + self.os
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class DNSPointer(DNSRecord):
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"""A DNS pointer record"""
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def __init__(self, name, type, class_, ttl, alias):
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DNSRecord.__init__(self, name, type, class_, ttl)
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self.alias = alias
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def write(self, out):
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"""Used in constructing an outgoing packet"""
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out.write_name(self.alias)
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def __eq__(self, other):
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"""Tests equality on alias"""
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return isinstance(other, DNSPointer) and self.alias == other.alias
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def __repr__(self):
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"""String representation"""
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return self.to_string(self.alias)
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class DNSText(DNSRecord):
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"""A DNS text record"""
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def __init__(self, name, type_, class_, ttl, text):
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assert isinstance(text, (bytes, type(None)))
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DNSRecord.__init__(self, name, type_, class_, ttl)
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self.text = text
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def write(self, out):
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"""Used in constructing an outgoing packet"""
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out.write_string(self.text)
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def __eq__(self, other):
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"""Tests equality on text"""
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return isinstance(other, DNSText) and self.text == other.text
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def __repr__(self):
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"""String representation"""
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if len(self.text) > 10:
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return self.to_string(self.text[:7]) + "..."
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else:
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return self.to_string(self.text)
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class DNSService(DNSRecord):
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"""A DNS service record"""
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def __init__(self, name, type, class_, ttl, priority, weight, port, server):
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DNSRecord.__init__(self, name, type, class_, ttl)
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self.priority = priority
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self.weight = weight
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self.port = port
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self.server = server
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def write(self, out):
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"""Used in constructing an outgoing packet"""
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out.write_short(self.priority)
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out.write_short(self.weight)
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out.write_short(self.port)
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out.write_name(self.server)
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def __eq__(self, other):
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"""Tests equality on priority, weight, port and server"""
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return (isinstance(other, DNSService) and
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self.priority == other.priority and
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self.weight == other.weight and
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self.port == other.port and
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self.server == other.server)
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def __repr__(self):
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"""String representation"""
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return self.to_string("%s:%s" % (self.server, self.port))
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class DNSIncoming(object):
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"""Object representation of an incoming DNS packet"""
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def __init__(self, data):
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"""Constructor from string holding bytes of packet"""
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self.offset = 0
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self.data = data
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self.questions = []
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self.answers = []
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self.num_questions = 0
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self.num_answers = 0
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self.num_authorities = 0
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self.num_additionals = 0
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self.read_header()
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self.read_questions()
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self.read_others()
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def unpack(self, format):
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length = struct.calcsize(format)
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info = struct.unpack(format, self.data[self.offset:self.offset + length])
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self.offset += length
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return info
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def read_header(self):
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"""Reads header portion of packet"""
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(self.id, self.flags, self.num_questions, self.num_answers,
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self.num_quthorities, self.num_additionals) = self.unpack(b'!6H')
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def read_questions(self):
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"""Reads questions section of packet"""
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for i in xrange(self.num_questions):
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name = self.read_name()
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type, class_ = self.unpack(b'!HH')
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question = DNSQuestion(name, type, class_)
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self.questions.append(question)
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def read_int(self):
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"""Reads an integer from the packet"""
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return self.unpack(b'!I')[0]
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def read_character_string(self):
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"""Reads a character string from the packet"""
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length = indexbytes(self.data, self.offset)
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self.offset += 1
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return self.read_string(length)
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def read_string(self, length):
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"""Reads a string of a given length from the packet"""
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info = self.data[self.offset:self.offset + length]
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self.offset += length
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return info
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def read_unsigned_short(self):
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"""Reads an unsigned short from the packet"""
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return self.unpack(b'!H')[0]
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def read_others(self):
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"""Reads the answers, authorities and additionals section of the
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packet"""
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n = self.num_answers + self.num_authorities + self.num_additionals
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for i in xrange(n):
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domain = self.read_name()
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type, class_, ttl, length = self.unpack(b'!HHiH')
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rec = None
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if type == _TYPE_A:
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rec = DNSAddress(domain, type, class_, ttl, self.read_string(4))
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elif type == _TYPE_CNAME or type == _TYPE_PTR:
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rec = DNSPointer(domain, type, class_, ttl, self.read_name())
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elif type == _TYPE_TXT:
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rec = DNSText(domain, type, class_, ttl, self.read_string(length))
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elif type == _TYPE_SRV:
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rec = DNSService(domain, type, class_, ttl,
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self.read_unsigned_short(), self.read_unsigned_short(),
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self.read_unsigned_short(), self.read_name())
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elif type == _TYPE_HINFO:
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rec = DNSHinfo(domain, type, class_, ttl,
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self.read_character_string(), self.read_character_string())
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elif type == _TYPE_AAAA:
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rec = DNSAddress(domain, type, class_, ttl, self.read_string(16))
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else:
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# Try to ignore types we don't know about
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# Skip the payload for the resource record so the next
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# records can be parsed correctly
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self.offset += length
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if rec is not None:
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self.answers.append(rec)
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def is_query(self):
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"""Returns true if this is a query"""
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return (self.flags & _FLAGS_QR_MASK) == _FLAGS_QR_QUERY
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def is_response(self):
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"""Returns true if this is a response"""
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return (self.flags & _FLAGS_QR_MASK) == _FLAGS_QR_RESPONSE
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def read_utf(self, offset, length):
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"""Reads a UTF-8 string of a given length from the packet"""
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return text_type(self.data[offset:offset + length], 'utf-8', 'replace')
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def read_name(self):
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"""Reads a domain name from the packet"""
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result = ''
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off = self.offset
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next = -1
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first = off
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|
|
while True:
|
|
length = indexbytes(self.data, off)
|
|
off += 1
|
|
if length == 0:
|
|
break
|
|
t = length & 0xC0
|
|
if t == 0x00:
|
|
result = ''.join((result, self.read_utf(off, length) + '.'))
|
|
off += length
|
|
elif t == 0xC0:
|
|
if next < 0:
|
|
next = off + 1
|
|
off = ((length & 0x3F) << 8) | indexbytes(self.data, off)
|
|
if off >= first:
|
|
# TODO raise more specific exception
|
|
raise Exception("Bad domain name (circular) at %s" % (off,))
|
|
first = off
|
|
else:
|
|
# TODO raise more specific exception
|
|
raise Exception("Bad domain name at %s" % (off,))
|
|
|
|
if next >= 0:
|
|
self.offset = next
|
|
else:
|
|
self.offset = off
|
|
|
|
return result
|
|
|
|
|
|
class DNSOutgoing(object):
|
|
|
|
"""Object representation of an outgoing packet"""
|
|
|
|
def __init__(self, flags, multicast=True):
|
|
self.finished = False
|
|
self.id = 0
|
|
self.multicast = multicast
|
|
self.flags = flags
|
|
self.names = {}
|
|
self.data = []
|
|
self.size = 12
|
|
|
|
self.questions = []
|
|
self.answers = []
|
|
self.authorities = []
|
|
self.additionals = []
|
|
|
|
def add_question(self, record):
|
|
"""Adds a question"""
|
|
self.questions.append(record)
|
|
|
|
def add_answer(self, inp, record):
|
|
"""Adds an answer"""
|
|
if not record.suppressed_by(inp):
|
|
self.add_answer_at_time(record, 0)
|
|
|
|
def add_answer_at_time(self, record, now):
|
|
"""Adds an answer if if does not expire by a certain time"""
|
|
if record is not None:
|
|
if now == 0 or not record.is_expired(now):
|
|
self.answers.append((record, now))
|
|
|
|
def add_authorative_answer(self, record):
|
|
"""Adds an authoritative answer"""
|
|
self.authorities.append(record)
|
|
|
|
def add_additional_answer(self, record):
|
|
"""Adds an additional answer"""
|
|
self.additionals.append(record)
|
|
|
|
def pack(self, format, value):
|
|
self.data.append(struct.pack(format, value))
|
|
self.size += struct.calcsize(format)
|
|
|
|
def write_byte(self, value):
|
|
"""Writes a single byte to the packet"""
|
|
self.pack(b'!c', int2byte(value))
|
|
|
|
def insert_short(self, index, value):
|
|
"""Inserts an unsigned short in a certain position in the packet"""
|
|
self.data.insert(index, struct.pack(b'!H', value))
|
|
self.size += 2
|
|
|
|
def write_short(self, value):
|
|
"""Writes an unsigned short to the packet"""
|
|
self.pack(b'!H', value)
|
|
|
|
def write_int(self, value):
|
|
"""Writes an unsigned integer to the packet"""
|
|
self.pack(b'!I', int(value))
|
|
|
|
def write_string(self, value):
|
|
"""Writes a string to the packet"""
|
|
assert isinstance(value, bytes)
|
|
self.data.append(value)
|
|
self.size += len(value)
|
|
|
|
def write_utf(self, s):
|
|
"""Writes a UTF-8 string of a given length to the packet"""
|
|
utfstr = s.encode('utf-8')
|
|
length = len(utfstr)
|
|
if length > 64:
|
|
raise NamePartTooLongException
|
|
self.write_byte(length)
|
|
self.write_string(utfstr)
|
|
|
|
def write_name(self, name):
|
|
"""Writes a domain name to the packet"""
|
|
|
|
if name in self.names:
|
|
# Find existing instance of this name in packet
|
|
#
|
|
index = self.names[name]
|
|
|
|
# An index was found, so write a pointer to it
|
|
#
|
|
self.write_byte((index >> 8) | 0xC0)
|
|
self.write_byte(index & 0xFF)
|
|
else:
|
|
# No record of this name already, so write it
|
|
# out as normal, recording the location of the name
|
|
# for future pointers to it.
|
|
#
|
|
self.names[name] = self.size
|
|
parts = name.split('.')
|
|
if parts[-1] == '':
|
|
parts = parts[:-1]
|
|
for part in parts:
|
|
self.write_utf(part)
|
|
self.write_byte(0)
|
|
|
|
def write_question(self, question):
|
|
"""Writes a question to the packet"""
|
|
self.write_name(question.name)
|
|
self.write_short(question.type)
|
|
self.write_short(question.class_)
|
|
|
|
def write_record(self, record, now):
|
|
"""Writes a record (answer, authoritative answer, additional) to
|
|
the packet"""
|
|
self.write_name(record.name)
|
|
self.write_short(record.type)
|
|
if record.unique and self.multicast:
|
|
self.write_short(record.class_ | _CLASS_UNIQUE)
|
|
else:
|
|
self.write_short(record.class_)
|
|
if now == 0:
|
|
self.write_int(record.ttl)
|
|
else:
|
|
self.write_int(record.get_remaining_ttl(now))
|
|
index = len(self.data)
|
|
# Adjust size for the short we will write before this record
|
|
#
|
|
self.size += 2
|
|
record.write(self)
|
|
self.size -= 2
|
|
|
|
length = len(b''.join(self.data[index:]))
|
|
self.insert_short(index, length) # Here is the short we adjusted for
|
|
|
|
def packet(self):
|
|
"""Returns a string containing the packet's bytes
|
|
|
|
No further parts should be added to the packet once this
|
|
is done."""
|
|
if not self.finished:
|
|
self.finished = True
|
|
for question in self.questions:
|
|
self.write_question(question)
|
|
for answer, time_ in self.answers:
|
|
self.write_record(answer, time_)
|
|
for authority in self.authorities:
|
|
self.write_record(authority, 0)
|
|
for additional in self.additionals:
|
|
self.write_record(additional, 0)
|
|
|
|
self.insert_short(0, len(self.additionals))
|
|
self.insert_short(0, len(self.authorities))
|
|
self.insert_short(0, len(self.answers))
|
|
self.insert_short(0, len(self.questions))
|
|
self.insert_short(0, self.flags)
|
|
if self.multicast:
|
|
self.insert_short(0, 0)
|
|
else:
|
|
self.insert_short(0, self.id)
|
|
return b''.join(self.data)
|
|
|
|
|
|
class DNSCache(object):
|
|
|
|
"""A cache of DNS entries"""
|
|
|
|
def __init__(self):
|
|
self.cache = {}
|
|
|
|
def add(self, entry):
|
|
"""Adds an entry"""
|
|
self.cache.setdefault(entry.key, []).append(entry)
|
|
|
|
def remove(self, entry):
|
|
"""Removes an entry"""
|
|
try:
|
|
list_ = self.cache[entry.key]
|
|
list_.remove(entry)
|
|
except (KeyError, ValueError):
|
|
pass
|
|
|
|
def get(self, entry):
|
|
"""Gets an entry by key. Will return None if there is no
|
|
matching entry."""
|
|
try:
|
|
list_ = self.cache[entry.key]
|
|
return list_[list_.index(entry)]
|
|
except (KeyError, ValueError):
|
|
return None
|
|
|
|
def get_by_details(self, name, type, class_):
|
|
"""Gets an entry by details. Will return None if there is
|
|
no matching entry."""
|
|
entry = DNSEntry(name, type, class_)
|
|
return self.get(entry)
|
|
|
|
def entries_with_name(self, name):
|
|
"""Returns a list of entries whose key matches the name."""
|
|
try:
|
|
return self.cache[name]
|
|
except KeyError:
|
|
return []
|
|
|
|
def entries(self):
|
|
"""Returns a list of all entries"""
|
|
if not self.cache:
|
|
return []
|
|
else:
|
|
return reduce(lambda a, b: a + b, self.cache.values())
|
|
|
|
|
|
class Engine(threading.Thread):
|
|
|
|
"""An engine wraps read access to sockets, allowing objects that
|
|
need to receive data from sockets to be called back when the
|
|
sockets are ready.
|
|
|
|
A reader needs a handle_read() method, which is called when the socket
|
|
it is interested in is ready for reading.
|
|
|
|
Writers are not implemented here, because we only send short
|
|
packets.
|
|
"""
|
|
|
|
def __init__(self, zc):
|
|
threading.Thread.__init__(self)
|
|
self.daemon = True
|
|
self.zc = zc
|
|
self.readers = {} # maps socket to reader
|
|
self.timeout = 5
|
|
self.condition = threading.Condition()
|
|
self.start()
|
|
|
|
def run(self):
|
|
while not _GLOBAL_DONE:
|
|
rs = self.get_readers()
|
|
if len(rs) == 0:
|
|
# No sockets to manage, but we wait for the timeout
|
|
# or addition of a socket
|
|
#
|
|
with self.condition:
|
|
self.condition.wait(self.timeout)
|
|
else:
|
|
try:
|
|
rr, wr, er = select.select(rs, [], [], self.timeout)
|
|
for socket_ in rr:
|
|
try:
|
|
self.readers[socket_].handle_read(socket_)
|
|
except Exception as e: # TODO stop catching all Exceptions
|
|
log.exception('Unknown error, possibly benign: %r', e)
|
|
except Exception as e: # TODO stop catching all Exceptions
|
|
log.exception('Unknown error, possibly benign: %r', e)
|
|
|
|
def get_readers(self):
|
|
result = []
|
|
with self.condition:
|
|
result = self.readers.keys()
|
|
return result
|
|
|
|
def add_reader(self, reader, socket):
|
|
with self.condition:
|
|
self.readers[socket] = reader
|
|
self.condition.notify()
|
|
|
|
def del_reader(self, socket):
|
|
with self.condition:
|
|
del self.readers[socket]
|
|
self.condition.notify()
|
|
|
|
def notify(self):
|
|
with self.condition:
|
|
self.condition.notify()
|
|
|
|
|
|
class Listener(object):
|
|
|
|
"""A Listener is used by this module to listen on the multicast
|
|
group to which DNS messages are sent, allowing the implementation
|
|
to cache information as it arrives.
|
|
|
|
It requires registration with an Engine object in order to have
|
|
the read() method called when a socket is availble for reading."""
|
|
|
|
def __init__(self, zc):
|
|
self.zc = zc
|
|
|
|
def handle_read(self, socket_):
|
|
try:
|
|
data, (addr, port) = socket_.recvfrom(_MAX_MSG_ABSOLUTE)
|
|
except socket.error as e:
|
|
# If the socket was closed by another thread -- which happens
|
|
# regularly on shutdown -- an EBADF exception is thrown here.
|
|
# Ignore it.
|
|
if e.errno == socket.EBADF:
|
|
return
|
|
else:
|
|
raise e
|
|
else:
|
|
log.debug('Received %r from %r:%r', data, addr, port)
|
|
|
|
self.data = data
|
|
msg = DNSIncoming(data)
|
|
if msg.is_query():
|
|
# Always multicast responses
|
|
#
|
|
if port == _MDNS_PORT:
|
|
self.zc.handle_query(msg, _MDNS_ADDR, _MDNS_PORT)
|
|
# If it's not a multicast query, reply via unicast
|
|
# and multicast
|
|
#
|
|
elif port == _DNS_PORT:
|
|
self.zc.handle_query(msg, addr, port)
|
|
self.zc.handle_query(msg, _MDNS_ADDR, _MDNS_PORT)
|
|
else:
|
|
self.zc.handle_response(msg)
|
|
|
|
|
|
class Reaper(threading.Thread):
|
|
|
|
"""A Reaper is used by this module to remove cache entries that
|
|
have expired."""
|
|
|
|
def __init__(self, zc):
|
|
threading.Thread.__init__(self)
|
|
self.daemon = True
|
|
self.zc = zc
|
|
self.start()
|
|
|
|
def run(self):
|
|
while True:
|
|
self.zc.wait(10 * 1000)
|
|
if _GLOBAL_DONE:
|
|
return
|
|
now = current_time_millis()
|
|
for record in self.zc.cache.entries():
|
|
if record.is_expired(now):
|
|
self.zc.update_record(now, record)
|
|
self.zc.cache.remove(record)
|
|
|
|
|
|
class Signal(object):
|
|
def __init__(self):
|
|
self._handlers = []
|
|
|
|
def fire(self, **kwargs):
|
|
for h in list(self._handlers):
|
|
h(**kwargs)
|
|
|
|
@property
|
|
def registration_interface(self):
|
|
return SignalRegistrationInterface(self._handlers)
|
|
|
|
|
|
class SignalRegistrationInterface(object):
|
|
|
|
def __init__(self, handlers):
|
|
self._handlers = handlers
|
|
|
|
def register_handler(self, handler):
|
|
self._handlers.append(handler)
|
|
return self
|
|
|
|
def unregister_handler(self, handler):
|
|
self._handlers.remove(handler)
|
|
return self
|
|
|
|
|
|
class ServiceBrowser(threading.Thread):
|
|
|
|
"""Used to browse for a service of a specific type.
|
|
|
|
The listener object will have its add_service() and
|
|
remove_service() methods called when this browser
|
|
discovers changes in the services availability."""
|
|
|
|
def __init__(self, zc, type_, handlers=None, listener=None):
|
|
"""Creates a browser for a specific type"""
|
|
assert handlers or listener, 'You need to specify at least one handler'
|
|
threading.Thread.__init__(self)
|
|
self.daemon = True
|
|
self.zc = zc
|
|
self.type = type_
|
|
self.services = {}
|
|
self.next_time = current_time_millis()
|
|
self.delay = _BROWSER_TIME
|
|
self._handlers_to_call = []
|
|
|
|
self.done = False
|
|
|
|
self.zc.add_listener(self, DNSQuestion(self.type, _TYPE_PTR, _CLASS_IN))
|
|
self.start()
|
|
|
|
self._service_state_changed = Signal()
|
|
|
|
if hasattr(handlers, 'add_service'):
|
|
listener = handlers
|
|
handlers = None
|
|
|
|
handlers = handlers or []
|
|
|
|
if listener:
|
|
def on_change(zeroconf, service_type, name, state_change):
|
|
args = (zeroconf, service_type, name)
|
|
if state_change is ServiceStateChange.Added:
|
|
listener.add_service(*args)
|
|
elif state_change is ServiceStateChange.Removed:
|
|
listener.remove_service(*args)
|
|
else:
|
|
raise NotImplementedError(state_change)
|
|
handlers.append(on_change)
|
|
|
|
for h in handlers:
|
|
self.service_state_changed.register_handler(h)
|
|
|
|
@property
|
|
def service_state_changed(self):
|
|
return self._service_state_changed.registration_interface
|
|
|
|
def update_record(self, zc, now, record):
|
|
"""Callback invoked by Zeroconf when new information arrives.
|
|
|
|
Updates information required by browser in the Zeroconf cache."""
|
|
|
|
def enqueue_callback(state_change, name):
|
|
self._handlers_to_call.append(
|
|
lambda zeroconf: self._service_state_changed.fire(
|
|
zeroconf=zeroconf,
|
|
service_type=self.type,
|
|
name=name,
|
|
state_change=state_change,
|
|
))
|
|
|
|
if record.type == _TYPE_PTR and record.name == self.type:
|
|
expired = record.is_expired(now)
|
|
service_key = record.alias.lower()
|
|
try:
|
|
old_record = self.services[service_key]
|
|
except KeyError:
|
|
if not expired:
|
|
self.services[service_key] = record
|
|
enqueue_callback(ServiceStateChange.Added, record.alias)
|
|
else:
|
|
if not expired:
|
|
old_record.reset_ttl(record)
|
|
else:
|
|
del self.services[service_key]
|
|
enqueue_callback(ServiceStateChange.Removed, record.alias)
|
|
return
|
|
|
|
expires = record.get_expiration_time(75)
|
|
if expires < self.next_time:
|
|
self.next_time = expires
|
|
|
|
def cancel(self):
|
|
self.done = True
|
|
self.zc.notify_all()
|
|
|
|
def run(self):
|
|
while True:
|
|
now = current_time_millis()
|
|
if len(self._handlers_to_call) == 0 and self.next_time > now:
|
|
self.zc.wait(self.next_time - now)
|
|
if _GLOBAL_DONE or self.done:
|
|
return
|
|
now = current_time_millis()
|
|
|
|
if self.next_time <= now:
|
|
out = DNSOutgoing(_FLAGS_QR_QUERY)
|
|
out.add_question(DNSQuestion(self.type, _TYPE_PTR, _CLASS_IN))
|
|
for record in self.services.values():
|
|
if not record.is_expired(now):
|
|
out.add_answer_at_time(record, now)
|
|
self.zc.send(out)
|
|
self.next_time = now + self.delay
|
|
self.delay = min(20 * 1000, self.delay * 2)
|
|
|
|
if len(self._handlers_to_call) > 0:
|
|
handler = self._handlers_to_call.pop(0)
|
|
handler(self.zc)
|
|
|
|
|
|
class ServiceInfo(object):
|
|
|
|
"""Service information"""
|
|
|
|
def __init__(self, type, name, address=None, port=None, weight=0,
|
|
priority=0, properties=None, server=None):
|
|
"""Create a service description.
|
|
|
|
type: fully qualified service type name
|
|
name: fully qualified service name
|
|
address: IP address as unsigned short, network byte order
|
|
port: port that the service runs on
|
|
weight: weight of the service
|
|
priority: priority of the service
|
|
properties: dictionary of properties (or a string holding the
|
|
bytes for the text field)
|
|
server: fully qualified name for service host (defaults to name)"""
|
|
|
|
if not name.endswith(type):
|
|
raise BadTypeInNameException
|
|
self.type = type
|
|
self.name = name
|
|
self.address = address
|
|
self.port = port
|
|
self.weight = weight
|
|
self.priority = priority
|
|
if server:
|
|
self.server = server
|
|
else:
|
|
self.server = name
|
|
self._set_properties(properties)
|
|
|
|
@property
|
|
def properties(self):
|
|
return self._properties
|
|
|
|
def _set_properties(self, properties):
|
|
"""Sets properties and text of this info from a dictionary"""
|
|
if isinstance(properties, dict):
|
|
self._properties = properties
|
|
list = []
|
|
result = b''
|
|
for key, value in iteritems(properties):
|
|
if isinstance(key, text_type):
|
|
key = key.encode('utf-8')
|
|
|
|
if value is None:
|
|
suffix = b''
|
|
elif isinstance(value, text_type):
|
|
suffix = value.encode('utf-8')
|
|
elif isinstance(value, binary_type):
|
|
suffix = value
|
|
elif isinstance(value, int):
|
|
if value:
|
|
suffix = b'true'
|
|
else:
|
|
suffix = b'false'
|
|
else:
|
|
suffix = b''
|
|
list.append(b'='.join((key, suffix)))
|
|
for item in list:
|
|
result = b''.join((result, int2byte(len(item)), item))
|
|
self.text = result
|
|
else:
|
|
self.text = properties
|
|
|
|
def _set_text(self, text):
|
|
"""Sets properties and text given a text field"""
|
|
self.text = text
|
|
result = {}
|
|
end = len(text)
|
|
index = 0
|
|
strs = []
|
|
while index < end:
|
|
length = indexbytes(text, index)
|
|
index += 1
|
|
strs.append(text[index:index + length])
|
|
index += length
|
|
|
|
for s in strs:
|
|
parts = s.split(b'=', 1)
|
|
try:
|
|
key, value = parts
|
|
except ValueError:
|
|
# No equals sign at all
|
|
key = s
|
|
value = False
|
|
else:
|
|
if value == b'true':
|
|
value = True
|
|
elif value == b'false' or not value:
|
|
value = False
|
|
|
|
# Only update non-existent properties
|
|
if key and result.get(key) is None:
|
|
result[key] = value
|
|
|
|
self._properties = result
|
|
|
|
def get_name(self):
|
|
"""Name accessor"""
|
|
if self.type is not None and self.name.endswith("." + self.type):
|
|
return self.name[:len(self.name) - len(self.type) - 1]
|
|
return self.name
|
|
|
|
def update_record(self, zc, now, record):
|
|
"""Updates service information from a DNS record"""
|
|
if record is not None and not record.is_expired(now):
|
|
if record.type == _TYPE_A:
|
|
# if record.name == self.name:
|
|
if record.name == self.server:
|
|
self.address = record.address
|
|
elif record.type == _TYPE_SRV:
|
|
if record.name == self.name:
|
|
self.server = record.server
|
|
self.port = record.port
|
|
self.weight = record.weight
|
|
self.priority = record.priority
|
|
# self.address = None
|
|
self.update_record(zc, now,
|
|
zc.cache.get_by_details(self.server, _TYPE_A, _CLASS_IN))
|
|
elif record.type == _TYPE_TXT:
|
|
if record.name == self.name:
|
|
self._set_text(record.text)
|
|
|
|
def request(self, zc, timeout):
|
|
"""Returns true if the service could be discovered on the
|
|
network, and updates this object with details discovered.
|
|
"""
|
|
now = current_time_millis()
|
|
delay = _LISTENER_TIME
|
|
next = now + delay
|
|
last = now + timeout
|
|
result = False
|
|
try:
|
|
zc.add_listener(self, DNSQuestion(self.name, _TYPE_ANY, _CLASS_IN))
|
|
while (self.server is None or self.address is None or
|
|
self.text is None):
|
|
if last <= now:
|
|
return False
|
|
if next <= now:
|
|
out = DNSOutgoing(_FLAGS_QR_QUERY)
|
|
out.add_question(DNSQuestion(self.name, _TYPE_SRV,
|
|
_CLASS_IN))
|
|
out.add_answer_at_time(zc.cache.get_by_details(self.name,
|
|
_TYPE_SRV, _CLASS_IN), now)
|
|
out.add_question(DNSQuestion(self.name, _TYPE_TXT,
|
|
_CLASS_IN))
|
|
out.add_answer_at_time(zc.cache.get_by_details(self.name,
|
|
_TYPE_TXT, _CLASS_IN), now)
|
|
if self.server is not None:
|
|
out.add_question(DNSQuestion(self.server,
|
|
_TYPE_A, _CLASS_IN))
|
|
out.add_answer_at_time(zc.cache.get_by_details(self.server,
|
|
_TYPE_A, _CLASS_IN), now)
|
|
zc.send(out)
|
|
next = now + delay
|
|
delay = delay * 2
|
|
|
|
zc.wait(min(next, last) - now)
|
|
now = current_time_millis()
|
|
result = True
|
|
finally:
|
|
zc.remove_listener(self)
|
|
|
|
return result
|
|
|
|
def __eq__(self, other):
|
|
"""Tests equality of service name"""
|
|
if isinstance(other, ServiceInfo):
|
|
return other.name == self.name
|
|
return False
|
|
|
|
def __ne__(self, other):
|
|
"""Non-equality test"""
|
|
return not self.__eq__(other)
|
|
|
|
def __repr__(self):
|
|
"""String representation"""
|
|
return '%s(%s)' % (
|
|
type(self).__name__,
|
|
', '.join(
|
|
'%s=%r' % (name, getattr(self, name))
|
|
for name in (
|
|
'type', 'name', 'address', 'port', 'weight', 'priority',
|
|
'server', 'properties',
|
|
)
|
|
)
|
|
)
|
|
|
|
|
|
@enum.unique
|
|
class InterfaceChoice(enum.Enum):
|
|
Default = 1
|
|
All = 2
|
|
|
|
|
|
@enum.unique
|
|
class ServiceStateChange(enum.Enum):
|
|
Added = 1
|
|
Removed = 2
|
|
|
|
|
|
HOST_ONLY_NETWORK_MASK = '255.255.255.255'
|
|
|
|
|
|
def get_all_addresses(address_family):
|
|
return list(set(
|
|
addr['addr']
|
|
for iface in netifaces.interfaces()
|
|
for addr in netifaces.ifaddresses(iface).get(address_family, [])
|
|
if addr.get('netmask') != HOST_ONLY_NETWORK_MASK
|
|
))
|
|
|
|
|
|
def normalize_interface_choice(choice, address_family):
|
|
if choice is InterfaceChoice.Default:
|
|
choice = ['0.0.0.0']
|
|
elif choice is InterfaceChoice.All:
|
|
choice = get_all_addresses(address_family)
|
|
return choice
|
|
|
|
|
|
def new_socket():
|
|
s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
|
|
s.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
|
|
|
|
# SO_REUSEADDR should be equivalent to SO_REUSEPORT for
|
|
# multicast UDP sockets (p 731, "TCP/IP Illustrated,
|
|
# Volume 2"), but some BSD-derived systems require
|
|
# SO_REUSEPORT to be specified explicity. Also, not all
|
|
# versions of Python have SO_REUSEPORT available.
|
|
# Catch OSError and socket.error for kernel versions <3.9 because lacking
|
|
# SO_REUSEPORT support.
|
|
try:
|
|
reuseport = socket.SO_REUSEPORT
|
|
except AttributeError:
|
|
pass
|
|
else:
|
|
try:
|
|
s.setsockopt(socket.SOL_SOCKET, reuseport, 1)
|
|
except (OSError, socket.error) as err: # OSError on python 3, socket.error on python 2
|
|
if not err.errno == errno.ENOPROTOOPT:
|
|
raise
|
|
|
|
s.setsockopt(socket.IPPROTO_IP, socket.IP_MULTICAST_TTL, 255)
|
|
s.setsockopt(socket.IPPROTO_IP, socket.IP_MULTICAST_LOOP, 1)
|
|
|
|
s.bind(('', _MDNS_PORT))
|
|
return s
|
|
|
|
|
|
def get_errno(e):
|
|
assert isinstance(e, socket.error)
|
|
return e.args[0]
|
|
|
|
|
|
class Zeroconf(object):
|
|
|
|
"""Implementation of Zeroconf Multicast DNS Service Discovery
|
|
|
|
Supports registration, unregistration, queries and browsing.
|
|
"""
|
|
|
|
def __init__(
|
|
self,
|
|
interfaces=InterfaceChoice.All,
|
|
):
|
|
"""Creates an instance of the Zeroconf class, establishing
|
|
multicast communications, listening and reaping threads.
|
|
|
|
:type interfaces: :class:`InterfaceChoice` or sequence of ip addresses
|
|
"""
|
|
global _GLOBAL_DONE
|
|
_GLOBAL_DONE = False
|
|
|
|
self._listen_socket = new_socket()
|
|
interfaces = normalize_interface_choice(interfaces, socket.AF_INET)
|
|
|
|
self._respond_sockets = []
|
|
|
|
for i in interfaces:
|
|
log.debug('Adding %r to multicast group', i)
|
|
try:
|
|
self._listen_socket.setsockopt(
|
|
socket.IPPROTO_IP, socket.IP_ADD_MEMBERSHIP,
|
|
socket.inet_aton(_MDNS_ADDR) + socket.inet_aton(i))
|
|
except socket.error as e:
|
|
if get_errno(e) == errno.EADDRINUSE:
|
|
log.info(
|
|
'Address in use when adding %s to multicast group, '
|
|
'it is expected to happen on some systems', i,
|
|
)
|
|
elif get_errno(e) == errno.EADDRNOTAVAIL:
|
|
log.info(
|
|
'Address not available when adding %s to multicast group, '
|
|
'it is expected to happen on some systems', i,
|
|
)
|
|
continue
|
|
else:
|
|
raise
|
|
|
|
respond_socket = new_socket()
|
|
respond_socket.setsockopt(
|
|
socket.IPPROTO_IP, socket.IP_MULTICAST_IF, socket.inet_aton(i))
|
|
|
|
self._respond_sockets.append(respond_socket)
|
|
|
|
self.listeners = []
|
|
self.browsers = []
|
|
self.services = {}
|
|
self.servicetypes = {}
|
|
|
|
self.cache = DNSCache()
|
|
|
|
self.condition = threading.Condition()
|
|
|
|
self.engine = Engine(self)
|
|
self.listener = Listener(self)
|
|
self.engine.add_reader(self.listener, self._listen_socket)
|
|
self.reaper = Reaper(self)
|
|
|
|
def wait(self, timeout):
|
|
"""Calling thread waits for a given number of milliseconds or
|
|
until notified."""
|
|
with self.condition:
|
|
self.condition.wait(timeout / 1000)
|
|
|
|
def notify_all(self):
|
|
"""Notifies all waiting threads"""
|
|
with self.condition:
|
|
self.condition.notify_all()
|
|
|
|
def get_service_info(self, type, name, timeout=3000):
|
|
"""Returns network's service information for a particular
|
|
name and type, or None if no service matches by the timeout,
|
|
which defaults to 3 seconds."""
|
|
info = ServiceInfo(type, name)
|
|
if info.request(self, timeout):
|
|
return info
|
|
return None
|
|
|
|
def add_service_listener(self, type, listener):
|
|
"""Adds a listener for a particular service type. This object
|
|
will then have its update_record method called when information
|
|
arrives for that type."""
|
|
self.remove_service_listener(listener)
|
|
self.browsers.append(ServiceBrowser(self, type, listener))
|
|
|
|
def remove_service_listener(self, listener):
|
|
"""Removes a listener from the set that is currently listening."""
|
|
for browser in self.browsers:
|
|
if browser.listener == listener:
|
|
browser.cancel()
|
|
del browser
|
|
|
|
def register_service(self, info, ttl=_DNS_TTL):
|
|
"""Registers service information to the network with a default TTL
|
|
of 60 seconds. Zeroconf will then respond to requests for
|
|
information for that service. The name of the service may be
|
|
changed if needed to make it unique on the network."""
|
|
self.check_service(info)
|
|
self.services[info.name.lower()] = info
|
|
if info.type in self.servicetypes:
|
|
self.servicetypes[info.type] += 1
|
|
else:
|
|
self.servicetypes[info.type] = 1
|
|
now = current_time_millis()
|
|
next_time = now
|
|
i = 0
|
|
while i < 3:
|
|
if now < next_time:
|
|
self.wait(next_time - now)
|
|
now = current_time_millis()
|
|
continue
|
|
out = DNSOutgoing(_FLAGS_QR_RESPONSE | _FLAGS_AA)
|
|
out.add_answer_at_time(DNSPointer(info.type, _TYPE_PTR,
|
|
_CLASS_IN, ttl, info.name), 0)
|
|
out.add_answer_at_time(DNSService(info.name, _TYPE_SRV,
|
|
_CLASS_IN, ttl, info.priority, info.weight, info.port,
|
|
info.server), 0)
|
|
out.add_answer_at_time(DNSText(info.name, _TYPE_TXT, _CLASS_IN,
|
|
ttl, info.text), 0)
|
|
if info.address:
|
|
out.add_answer_at_time(DNSAddress(info.server, _TYPE_A,
|
|
_CLASS_IN, ttl, info.address), 0)
|
|
self.send(out)
|
|
i += 1
|
|
next_time += _REGISTER_TIME
|
|
|
|
def unregister_service(self, info):
|
|
"""Unregister a service."""
|
|
try:
|
|
del self.services[info.name.lower()]
|
|
if self.servicetypes[info.type] > 1:
|
|
self.servicetypes[info.type] -= 1
|
|
else:
|
|
del self.servicetypes[info.type]
|
|
except Exception as e: # TODO stop catching all Exceptions
|
|
log.exception('Unknown error, possibly benign: %r', e)
|
|
now = current_time_millis()
|
|
next_time = now
|
|
i = 0
|
|
while i < 3:
|
|
if now < next_time:
|
|
self.wait(next_time - now)
|
|
now = current_time_millis()
|
|
continue
|
|
out = DNSOutgoing(_FLAGS_QR_RESPONSE | _FLAGS_AA)
|
|
out.add_answer_at_time(DNSPointer(info.type, _TYPE_PTR,
|
|
_CLASS_IN, 0, info.name), 0)
|
|
out.add_answer_at_time(DNSService(info.name, _TYPE_SRV,
|
|
_CLASS_IN, 0, info.priority, info.weight, info.port,
|
|
info.name), 0)
|
|
out.add_answer_at_time(DNSText(info.name, _TYPE_TXT, _CLASS_IN,
|
|
0, info.text), 0)
|
|
if info.address:
|
|
out.add_answer_at_time(DNSAddress(info.server, _TYPE_A,
|
|
_CLASS_IN, 0, info.address), 0)
|
|
self.send(out)
|
|
i += 1
|
|
next_time += _UNREGISTER_TIME
|
|
|
|
def unregister_all_services(self):
|
|
"""Unregister all registered services."""
|
|
if len(self.services) > 0:
|
|
now = current_time_millis()
|
|
next_time = now
|
|
i = 0
|
|
while i < 3:
|
|
if now < next_time:
|
|
self.wait(next_time - now)
|
|
now = current_time_millis()
|
|
continue
|
|
out = DNSOutgoing(_FLAGS_QR_RESPONSE | _FLAGS_AA)
|
|
for info in self.services.values():
|
|
out.add_answer_at_time(DNSPointer(info.type, _TYPE_PTR,
|
|
_CLASS_IN, 0, info.name), 0)
|
|
out.add_answer_at_time(DNSService(info.name, _TYPE_SRV,
|
|
_CLASS_IN, 0, info.priority, info.weight,
|
|
info.port, info.server), 0)
|
|
out.add_answer_at_time(DNSText(info.name, _TYPE_TXT,
|
|
_CLASS_IN, 0, info.text), 0)
|
|
if info.address:
|
|
out.add_answer_at_time(DNSAddress(info.server,
|
|
_TYPE_A, _CLASS_IN, 0, info.address), 0)
|
|
self.send(out)
|
|
i += 1
|
|
next_time += _UNREGISTER_TIME
|
|
|
|
def check_service(self, info):
|
|
"""Checks the network for a unique service name, modifying the
|
|
ServiceInfo passed in if it is not unique."""
|
|
now = current_time_millis()
|
|
next_time = now
|
|
i = 0
|
|
while i < 3:
|
|
for record in self.cache.entries_with_name(info.type):
|
|
if (record.type == _TYPE_PTR and
|
|
not record.is_expired(now) and
|
|
record.alias == info.name):
|
|
if info.name.find('.') < 0:
|
|
info.name = '%s.[%s:%s].%s' % (info.name,
|
|
info.address, info.port, info.type)
|
|
|
|
self.check_service(info)
|
|
return
|
|
raise NonUniqueNameException
|
|
if now < next_time:
|
|
self.wait(next_time - now)
|
|
now = current_time_millis()
|
|
continue
|
|
out = DNSOutgoing(_FLAGS_QR_QUERY | _FLAGS_AA)
|
|
self.debug = out
|
|
out.add_question(DNSQuestion(info.type, _TYPE_PTR, _CLASS_IN))
|
|
out.add_authorative_answer(DNSPointer(info.type, _TYPE_PTR,
|
|
_CLASS_IN, _DNS_TTL, info.name))
|
|
self.send(out)
|
|
i += 1
|
|
next_time += _CHECK_TIME
|
|
|
|
def add_listener(self, listener, question):
|
|
"""Adds a listener for a given question. The listener will have
|
|
its update_record method called when information is available to
|
|
answer the question."""
|
|
now = current_time_millis()
|
|
self.listeners.append(listener)
|
|
if question is not None:
|
|
for record in self.cache.entries_with_name(question.name):
|
|
if question.answered_by(record) and not record.is_expired(now):
|
|
listener.update_record(self, now, record)
|
|
self.notify_all()
|
|
|
|
def remove_listener(self, listener):
|
|
"""Removes a listener."""
|
|
try:
|
|
self.listeners.remove(listener)
|
|
self.notify_all()
|
|
except Exception as e: # TODO stop catching all Exceptions
|
|
log.exception('Unknown error, possibly benign: %r', e)
|
|
|
|
def update_record(self, now, rec):
|
|
"""Used to notify listeners of new information that has updated
|
|
a record."""
|
|
for listener in self.listeners:
|
|
listener.update_record(self, now, rec)
|
|
self.notify_all()
|
|
|
|
def handle_response(self, msg):
|
|
"""Deal with incoming response packets. All answers
|
|
are held in the cache, and listeners are notified."""
|
|
now = current_time_millis()
|
|
for record in msg.answers:
|
|
expired = record.is_expired(now)
|
|
if record in self.cache.entries():
|
|
if expired:
|
|
self.cache.remove(record)
|
|
else:
|
|
entry = self.cache.get(record)
|
|
if entry is not None:
|
|
entry.reset_ttl(record)
|
|
record = entry
|
|
else:
|
|
self.cache.add(record)
|
|
|
|
self.update_record(now, record)
|
|
|
|
def handle_query(self, msg, addr, port):
|
|
"""Deal with incoming query packets. Provides a response if
|
|
possible."""
|
|
out = None
|
|
|
|
# Support unicast client responses
|
|
#
|
|
if port != _MDNS_PORT:
|
|
out = DNSOutgoing(_FLAGS_QR_RESPONSE | _FLAGS_AA, False)
|
|
for question in msg.questions:
|
|
out.add_question(question)
|
|
|
|
for question in msg.questions:
|
|
if question.type == _TYPE_PTR:
|
|
if question.name == "_services._dns-sd._udp.local.":
|
|
for stype in self.servicetypes.keys():
|
|
if out is None:
|
|
out = DNSOutgoing(_FLAGS_QR_RESPONSE | _FLAGS_AA)
|
|
out.add_answer(msg,
|
|
DNSPointer("_services._dns-sd._udp.local.",
|
|
_TYPE_PTR, _CLASS_IN, _DNS_TTL, stype))
|
|
for service in self.services.values():
|
|
if question.name == service.type:
|
|
if out is None:
|
|
out = DNSOutgoing(_FLAGS_QR_RESPONSE | _FLAGS_AA)
|
|
out.add_answer(msg,
|
|
DNSPointer(service.type, _TYPE_PTR,
|
|
_CLASS_IN, _DNS_TTL, service.name))
|
|
else:
|
|
try:
|
|
if out is None:
|
|
out = DNSOutgoing(_FLAGS_QR_RESPONSE | _FLAGS_AA)
|
|
|
|
# Answer A record queries for any service addresses we know
|
|
if question.type in (_TYPE_A, _TYPE_ANY):
|
|
for service in self.services.values():
|
|
if service.server == question.name.lower():
|
|
out.add_answer(msg, DNSAddress(question.name,
|
|
_TYPE_A, _CLASS_IN | _CLASS_UNIQUE,
|
|
_DNS_TTL, service.address))
|
|
|
|
service = self.services.get(question.name.lower(), None)
|
|
if not service:
|
|
continue
|
|
|
|
if question.type in (_TYPE_SRV, _TYPE_ANY):
|
|
out.add_answer(msg, DNSService(question.name,
|
|
_TYPE_SRV, _CLASS_IN | _CLASS_UNIQUE,
|
|
_DNS_TTL, service.priority, service.weight,
|
|
service.port, service.server))
|
|
if question.type in (_TYPE_TXT, _TYPE_ANY):
|
|
out.add_answer(msg, DNSText(question.name,
|
|
_TYPE_TXT, _CLASS_IN | _CLASS_UNIQUE,
|
|
_DNS_TTL, service.text))
|
|
if question.type == _TYPE_SRV:
|
|
out.add_additional_answer(DNSAddress(service.server,
|
|
_TYPE_A, _CLASS_IN | _CLASS_UNIQUE,
|
|
_DNS_TTL, service.address))
|
|
except Exception as e: # TODO stop catching all Exceptions
|
|
log.exception('Unknown error, possibly benign: %r', e)
|
|
|
|
if out is not None and out.answers:
|
|
out.id = msg.id
|
|
self.send(out, addr, port)
|
|
|
|
def send(self, out, addr=_MDNS_ADDR, port=_MDNS_PORT):
|
|
"""Sends an outgoing packet."""
|
|
packet = out.packet()
|
|
log.debug('Sending %r as %r...', out, packet)
|
|
for s in self._respond_sockets:
|
|
bytes_sent = s.sendto(packet, 0, (addr, port))
|
|
if bytes_sent != len(packet):
|
|
raise Error(
|
|
'Should not happen, sent %d out of %d bytes' % (
|
|
bytes_sent, len(packet)))
|
|
|
|
def close(self):
|
|
"""Ends the background threads, and prevent this instance from
|
|
servicing further queries."""
|
|
global _GLOBAL_DONE
|
|
if not _GLOBAL_DONE:
|
|
_GLOBAL_DONE = True
|
|
self.notify_all()
|
|
self.engine.notify()
|
|
self.unregister_all_services()
|
|
for s in [self._listen_socket] + self._respond_sockets:
|
|
s.close()
|