from __future__ import (
absolute_import, division, print_function, unicode_literals)
""" 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 enum
import errno
import logging
import re
import select
import socket
import struct
import sys
import threading
import time
from functools import reduce
import netifaces
from six import binary_type, indexbytes, int2byte, iteritems, text_type
from six.moves import xrange
__author__ = 'Paul Scott-Murphy, William McBrine'
__maintainer__ = 'Jakub Stasiak <jakub@stasiak.at>'
__version__ = '0.17.7'
__license__ = 'LGPL'
try:
NullHandler = logging.NullHandler
except AttributeError:
# Python 2.6 fallback
class NullHandler(logging.Handler):
def emit(self, record):
pass
__all__ = [
"__version__",
"Zeroconf", "ServiceInfo", "ServiceBrowser",
"Error", "InterfaceChoice", "ServiceStateChange",
]
log = logging.getLogger(__name__)
log.addHandler(NullHandler())
if log.level == logging.NOTSET:
log.setLevel(logging.WARN)
# Some timing constants
_UNREGISTER_TIME = 125
_CHECK_TIME = 175
_REGISTER_TIME = 225
_LISTENER_TIME = 200
_BROWSER_TIME = 500
# Some DNS constants
_MDNS_ADDR = '224.0.0.251'
_MDNS_PORT = 5353
_DNS_PORT = 53
_DNS_TTL = 60 * 60 # one hour default TTL
_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_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"}
_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_ASCII_CONTROL_CHARS = re.compile(r'[\x00-\x1f\x7f]')
@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'
# utility functions
def current_time_millis():
"""Current system time in milliseconds"""
return time.time() * 1000
def service_type_name(type_):
"""
Validate a fully qualified service name, instance or subtype. [rfc6763]
Returns fully qualified service name.
Domain names used by mDNS-SD take the following forms:
<sn> . <_tcp|_udp> . local.
<Instance> . <sn> . <_tcp|_udp> . local.
<sub>._sub . <sn> . <_tcp|_udp> . local.
1) must end with 'local.'
This is true because we are implementing mDNS and since the 'm' means
multi-cast, the 'local.' domain is mandatory.
2) local is preceded with either '_udp.' or '_tcp.'
3) service name <sn> precedes <_tcp|_udp>
The rules for Service Names [RFC6335] state that they may be no more
than fifteen characters long (not counting the mandatory underscore),
consisting of only letters, digits, and hyphens, must begin and end
with a letter or digit, must not contain consecutive hyphens, and
must contain at least one letter.
The instance name <Instance> and sub type <sub> may be up to 63 bytes.
The portion of the Service Instance Name is a user-
friendly name consisting of arbitrary Net-Unicode text [RFC5198]. It
MUST NOT contain ASCII control characters (byte values 0x00-0x1F and
0x7F) [RFC20] but otherwise is allowed to contain any characters,
without restriction, including spaces, uppercase, lowercase,
punctuation -- including dots -- accented characters, non-Roman text,
and anything else that may be represented using Net-Unicode.
:param type_: Type, SubType or service name to validate
:return: fully qualified service name (eg: _http._tcp.local.)
"""
if not (type_.endswith('._tcp.local.') or type_.endswith('._udp.local.')):
raise BadTypeInNameException(
"Type '%s' must end with '._tcp.local.' or '._udp.local.'" %
type_)
remaining = type_[:-len('._tcp.local.')].split('.')
name = remaining.pop()
if not name:
raise BadTypeInNameException("No Service name found")
if len(remaining) == 1 and len(remaining[0]) == 0:
raise BadTypeInNameException(
"Type '%s' must not start with '.'" % type_)
if name[0] != '_':
raise BadTypeInNameException(
"Service name (%s) must start with '_'" % name)
# remove leading underscore
name = name[1:]
if len(name) > 15:
raise BadTypeInNameException(
"Service name (%s) must be <= 15 bytes" % name)
if '--' in name:
raise BadTypeInNameException(
"Service name (%s) must not contain '--'" % name)
if '-' in (name[0], name[-1]):
raise BadTypeInNameException(
"Service name (%s) may not start or end with '-'" % name)
if not _HAS_A_TO_Z.search(name):
raise BadTypeInNameException(
"Service name (%s) must contain at least one letter (eg: 'A-Z')" %
name)
if not _HAS_ONLY_A_TO_Z_NUM_HYPHEN.search(name):
raise BadTypeInNameException(
"Service name (%s) must contain only these characters: "
"A-Z, a-z, 0-9, hyphen ('-')" % name)
if remaining and remaining[-1] == '_sub':
remaining.pop()
if len(remaining) == 0 or len(remaining[0]) == 0:
raise BadTypeInNameException(
"_sub requires a subtype name")
if len(remaining) > 1:
remaining = ['.'.join(remaining)]
if remaining:
length = len(remaining[0].encode('utf-8'))
if length > 63:
raise BadTypeInNameException("Too long: '%s'" % remaining[0])
if _HAS_ASCII_CONTROL_CHARS.search(remaining[0]):
raise BadTypeInNameException(
"Ascii control character 0x00-0x1F and 0x7F illegal in '%s'" %
remaining[0])
return '_' + name + type_[-len('._tcp.local.'):]
# Exceptions
class Error(Exception):
pass
class IncomingDecodeError(Error):
pass
class NonUniqueNameException(Error):
pass
class NamePartTooLongException(Error):
pass
class AbstractMethodException(Error):
pass
class BadTypeInNameException(Error):
pass
# implementation classes
class QuietLogger(object):
_seen_logs = {}
@classmethod
def log_exception_warning(cls, logger_data=None):
exc_info = sys.exc_info()
exc_str = str(exc_info[1])
if exc_str not in cls._seen_logs:
# log at warning level the first time this is seen
cls._seen_logs[exc_str] = exc_info
logger = log.warning
else:
logger = log.debug
if logger_data is not None:
logger(*logger_data)
logger('Exception occurred:', exc_info=exc_info)
@classmethod
def log_warning_once(cls, *args):
msg_str = args[0]
if msg_str not in cls._seen_logs:
cls._seen_logs[msg_str] = 0
logger = log.warning
else:
logger = log.debug
cls._seen_logs[msg_str] += 1
logger(*args)
class DNSEntry(object):
"""A DNS entry"""
def __init__(self, name, type_, class_):
self.key = name.lower()
self.name = name
self.type = type_
self.class_ = class_ & _CLASS_MASK
self.unique = (class_ & _CLASS_UNIQUE) != 0
def __eq__(self, other):
"""Equality test on name, type, and class"""
return (isinstance(other, DNSEntry) and
self.name == other.name and
self.type == other.type and
self.class_ == other.class_)
def __ne__(self, other):
"""Non-equality test"""
return not self.__eq__(other)
@staticmethod
def get_class_(class_):
"""Class accessor"""
return _CLASSES.get(class_, "?(%s)" % class_)
@staticmethod
def get_type(t):
"""Type accessor"""
return _TYPES.get(t, "?(%s)" % t)
def to_string(self, hdr, other):
"""String representation with additional information"""
result = "%s[%s,%s" % (hdr, self.get_type(self.type),
self.get_class_(self.class_))
if self.unique:
result += "-unique,"
else:
result += ","
result += self.name
if other is not None:
result += ",%s]" % other
else:
result += "]"
return result
class DNSQuestion(DNSEntry):
"""A DNS question entry"""
def __init__(self, name, type_, class_):
DNSEntry.__init__(self, name, type_, class_)
def answered_by(self, rec):
"""Returns true if the question is answered by the record"""
return (self.class_ == rec.class_ and
(self.type == rec.type or self.type == _TYPE_ANY) and
self.name == rec.name)
def __repr__(self):
"""String representation"""
return DNSEntry.to_string(self, "question", None)
class DNSRecord(DNSEntry):
"""A DNS record - like a DNS entry, but has a TTL"""
def __init__(self, name, type_, class_, ttl):
DNSEntry.__init__(self, name, type_, class_)
self.ttl = ttl
self.created = current_time_millis()
def __eq__(self, other):
"""Abstract method"""
raise AbstractMethodException
def suppressed_by(self, msg):
"""Returns true if any answer in a message can suffice for the
information held in this record."""
for record in msg.answers:
if self.suppressed_by_answer(record):
return True
return False
def suppressed_by_answer(self, other):
"""Returns true if another record has same name, type and class,
and if its TTL is at least half of this record's."""
return self == other and other.ttl > (self.ttl / 2)
def get_expiration_time(self, percent):
"""Returns the time at which this record will have expired
by a certain percentage."""
return self.created + (percent * self.ttl * 10)
def get_remaining_ttl(self, now):
"""Returns the remaining TTL in seconds."""
return max(0, (self.get_expiration_time(100) - now) / 1000.0)
def is_expired(self, now):
"""Returns true if this record has expired."""
return self.get_expiration_time(100) <= now
def is_stale(self, now):
"""Returns true if this record is at least half way expired."""
return self.get_expiration_time(50) <= now
def reset_ttl(self, other):
"""Sets this record's TTL and created time to that of
another record."""
self.created = other.created
self.ttl = other.ttl
def write(self, out):
"""Abstract method"""
raise AbstractMethodException
def to_string(self, other):
"""String representation with additional information"""
arg = "%s/%s,%s" % (
self.ttl, self.get_remaining_ttl(current_time_millis()), other)
return DNSEntry.to_string(self, "record", arg)
class DNSAddress(DNSRecord):
"""A DNS address record"""
def __init__(self, name, type_, class_, ttl, address):
DNSRecord.__init__(self, name, type_, class_, ttl)
self.address = address
def write(self, out):
"""Used in constructing an outgoing packet"""
out.write_string(self.address)
def __eq__(self, other):
"""Tests equality on address"""
return isinstance(other, DNSAddress) and self.address == other.address
def __repr__(self):
"""String representation"""
try:
return str(socket.inet_ntoa(self.address))
except Exception: # TODO stop catching all Exceptions
return str(self.address)
class DNSHinfo(DNSRecord):
"""A DNS host information record"""
def __init__(self, name, type_, class_, ttl, cpu, os):
DNSRecord.__init__(self, name, type_, class_, ttl)
try:
self.cpu = cpu.decode('utf-8')
except AttributeError:
self.cpu = cpu
try:
self.os = os.decode('utf-8')
except AttributeError:
self.os = os
def write(self, out):
"""Used in constructing an outgoing packet"""
out.write_character_string(self.cpu.encode('utf-8'))
out.write_character_string(self.os.encode('utf-8'))
def __eq__(self, other):
"""Tests equality on cpu and os"""
return (isinstance(other, DNSHinfo) and
self.cpu == other.cpu and self.os == other.os)
def __repr__(self):
"""String representation"""
return self.cpu + " " + self.os
class DNSPointer(DNSRecord):
"""A DNS pointer record"""
def __init__(self, name, type_, class_, ttl, alias):
DNSRecord.__init__(self, name, type_, class_, ttl)
self.alias = alias
def write(self, out):
"""Used in constructing an outgoing packet"""
out.write_name(self.alias)
def __eq__(self, other):
"""Tests equality on alias"""
return isinstance(other, DNSPointer) and self.alias == other.alias
def __repr__(self):
"""String representation"""
return self.to_string(self.alias)
class DNSText(DNSRecord):
"""A DNS text record"""
def __init__(self, name, type_, class_, ttl, text):
assert isinstance(text, (bytes, type(None)))
DNSRecord.__init__(self, name, type_, class_, ttl)
self.text = text
def write(self, out):
"""Used in constructing an outgoing packet"""
out.write_string(self.text)
def __eq__(self, other):
"""Tests equality on text"""
return isinstance(other, DNSText) and self.text == other.text
def __repr__(self):
"""String representation"""
if len(self.text) > 10:
return self.to_string(self.text[:7]) + "..."
else:
return self.to_string(self.text)
class DNSService(DNSRecord):
"""A DNS service record"""
def __init__(self, name, type_, class_, ttl,
priority, weight, port, server):
DNSRecord.__init__(self, name, type_, class_, ttl)
self.priority = priority
self.weight = weight
self.port = port
self.server = server
def write(self, out):
"""Used in constructing an outgoing packet"""
out.write_short(self.priority)
out.write_short(self.weight)
out.write_short(self.port)
out.write_name(self.server)
def __eq__(self, other):
"""Tests equality on priority, weight, port and server"""
return (isinstance(other, DNSService) and
self.priority == other.priority and
self.weight == other.weight and
self.port == other.port and
self.server == other.server)
def __repr__(self):
"""String representation"""
return self.to_string("%s:%s" % (self.server, self.port))
class DNSIncoming(QuietLogger):
"""Object representation of an incoming DNS packet"""
def __init__(self, data):
"""Constructor from string holding bytes of packet"""
self.offset = 0
self.data = data
self.questions = []
self.answers = []
self.id = 0
self.flags = 0
self.num_questions = 0
self.num_answers = 0
self.num_authorities = 0
self.num_additionals = 0
self.valid = False
try:
self.read_header()
self.read_questions()
self.read_others()
self.valid = True
except (IndexError, struct.error, IncomingDecodeError):
self.log_exception_warning((
'Choked at offset %d while unpacking %r', self.offset, data))
def unpack(self, format_):
length = struct.calcsize(format_)
info = struct.unpack(
format_, self.data[self.offset:self.offset + length])
self.offset += length
return info
def read_header(self):
"""Reads header portion of packet"""
(self.id, self.flags, self.num_questions, self.num_answers,
self.num_authorities, self.num_additionals) = self.unpack(b'!6H')
def read_questions(self):
"""Reads questions section of packet"""
for i in xrange(self.num_questions):
name = self.read_name()
type_, class_ = self.unpack(b'!HH')
question = DNSQuestion(name, type_, class_)
self.questions.append(question)
# def read_int(self):
# """Reads an integer from the packet"""
# return self.unpack(b'!I')[0]
def read_character_string(self):
"""Reads a character string from the packet"""
length = indexbytes(self.data, self.offset)
self.offset += 1
return self.read_string(length)
def read_string(self, length):
"""Reads a string of a given length from the packet"""
info = self.data[self.offset:self.offset + length]
self.offset += length
return info
def read_unsigned_short(self):
"""Reads an unsigned short from the packet"""
return self.unpack(b'!H')[0]
def read_others(self):
"""Reads the answers, authorities and additionals section of the
packet"""
n = self.num_answers + self.num_authorities + self.num_additionals
for i in xrange(n):
domain = self.read_name()
type_, class_, ttl, length = self.unpack(b'!HHiH')
rec = None
if type_ == _TYPE_A:
rec = DNSAddress(
domain, type_, class_, ttl, self.read_string(4))
elif type_ == _TYPE_CNAME or type_ == _TYPE_PTR:
rec = DNSPointer(
domain, type_, class_, ttl, self.read_name())
elif type_ == _TYPE_TXT:
rec = DNSText(
domain, type_, class_, ttl, self.read_string(length))
elif type_ == _TYPE_SRV:
rec = DNSService(
domain, type_, class_, ttl,
self.read_unsigned_short(), self.read_unsigned_short(),
self.read_unsigned_short(), self.read_name())
elif type_ == _TYPE_HINFO:
rec = DNSHinfo(
domain, type_, class_, ttl,
self.read_character_string(), self.read_character_string())
elif type_ == _TYPE_AAAA:
rec = DNSAddress(
domain, type_, class_, ttl, self.read_string(16))
else:
# Try to ignore types we don't know about
# Skip the payload for the resource record so the next
# records can be parsed correctly
self.offset += length
if rec is not None:
self.answers.append(rec)
def is_query(self):
"""Returns true if this is a query"""
return (self.flags & _FLAGS_QR_MASK) == _FLAGS_QR_QUERY
def is_response(self):
"""Returns true if this is a response"""
return (self.flags & _FLAGS_QR_MASK) == _FLAGS_QR_RESPONSE
def read_utf(self, offset, length):
"""Reads a UTF-8 string of a given length from the packet"""
return text_type(self.data[offset:offset + length], 'utf-8', 'replace')
def read_name(self):
"""Reads a domain name from the packet"""
result = ''
off = self.offset
next_ = -1
first = off
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:
raise IncomingDecodeError(
"Bad domain name (circular) at %s" % (off,))
first = off
else:
raise IncomingDecodeError("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.state = self.State.init
self.questions = []
self.answers = []
self.authorities = []
self.additionals = []
def __repr__(self):
return '<DNSOutgoing:{%s}>' % ', '.join([
'multicast=%s' % self.multicast,
'flags=%s' % self.flags,
'questions=%s' % self.questions,
'answers=%s' % self.answers,
'authorities=%s' % self.authorities,
'additionals=%s' % self.additionals,
])
class State(enum.Enum):
init = 0
finished = 1
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 it 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
From: RFC 6763, DNS-Based Service Discovery, February 2013
12. DNS Additional Record Generation
DNS has an efficiency feature whereby a DNS server may place
additional records in the additional section of the DNS message.
These additional records are records that the client did not
explicitly request, but the server has reasonable grounds to expect
that the client might request them shortly, so including them can
save the client from having to issue additional queries.
This section recommends which additional records SHOULD be generated
to improve network efficiency, for both Unicast and Multicast DNS-SD
responses.
12.1. PTR Records
When including a DNS-SD Service Instance Enumeration or Selective
Instance Enumeration (subtype) PTR record in a response packet, the
server/responder SHOULD include the following additional records:
o The SRV record(s) named in the PTR rdata.
o The TXT record(s) named in the PTR rdata.
o All address records (type "A" and "AAAA") named in the SRV rdata.
12.2. SRV Records
When including an SRV record in a response packet, the
server/responder SHOULD include the following additional records:
o All address records (type "A" and "AAAA") named in the SRV rdata.
"""
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_character_string(self, value):
assert isinstance(value, bytes)
length = len(value)
if length > 256:
raise NamePartTooLongException
self.write_byte(length)
self.write_string(value)
def write_name(self, name):
"""
Write names to packet
18.14. Name Compression
When generating Multicast DNS messages, implementations SHOULD use
name compression wherever possible to compress the names of resource
records, by replacing some or all of the resource record name with a
compact two-byte reference to an appearance of that data somewhere
earlier in the message [RFC1035].
"""
# split name into each label
parts = name.split('.')
if not parts[-1]:
parts.pop()
# construct each suffix
name_suffices = ['.'.join(parts[i:]) for i in range(len(parts))]
# look for an existing name or suffix
for count, sub_name in enumerate(name_suffices):
if sub_name in self.names:
break
else:
count += 1
# note the new names we are saving into the packet
for suffix in name_suffices[:count]:
self.names[suffix] = self.size + len(name) - len(suffix) - 1
# write the new names out.
for part in parts[:count]:
self.write_utf(part)
# if we wrote part of the name, create a pointer to the rest
if count != len(name_suffices):
# Found substring in packet, create pointer
index = self.names[name_suffices[count]]
self.write_byte((index >> 8) | 0xC0)
self.write_byte(index & 0xFF)
else:
# this is the end of a name
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"""
if self.state == self.State.finished:
return 1
start_data_length, start_size = len(self.data), self.size
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 = sum((len(d) for d in self.data[index:]))
# Here is the short we adjusted for
self.insert_short(index, length)
# if we go over, then rollback and quit
if self.size > _MAX_MSG_ABSOLUTE:
while len(self.data) > start_data_length:
self.data.pop()
self.size = start_size
self.state = self.State.finished
return 1
return 0
def packet(self):
"""Returns a string containing the packet's bytes
No further parts should be added to the packet once this
is done."""
overrun_answers, overrun_authorities, overrun_additionals = 0, 0, 0
if self.state != self.State.finished:
for question in self.questions:
self.write_question(question)
for answer, time_ in self.answers:
overrun_answers += self.write_record(answer, time_)
for authority in self.authorities:
overrun_authorities += self.write_record(authority, 0)
for additional in self.additionals:
overrun_additionals += self.write_record(additional, 0)
self.state = self.State.finished
self.insert_short(0, len(self.additionals) - overrun_additionals)
self.insert_short(0, len(self.authorities) - overrun_authorities)
self.insert_short(0, len(self.answers) - overrun_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]
for cached_entry in list_:
if entry.__eq__(cached_entry):
return cached_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.lower()]
except KeyError:
return []
def current_entry_with_name_and_alias(self, name, alias):
now = current_time_millis()
for record in self.entries_with_name(name):
if (record.type == _TYPE_PTR and
not record.is_expired(now) and
record.alias == alias):
return record
def entries(self):
"""Returns a list of all entries"""
if not self.cache:
return []
else:
# avoid size change during iteration by copying the cache
values = list(self.cache.values())
return reduce(lambda a, b: a + b, 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, name='zeroconf-Engine')
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 self.zc.done:
with self.condition:
rs = self.readers.keys()
if len(rs) == 0:
# No sockets to manage, but we wait for the timeout
# or addition of a socket
self.condition.wait(self.timeout)
if len(rs) != 0:
try:
rr, wr, er = select.select(rs, [], [], self.timeout)
if not self.zc.done:
for socket_ in rr:
reader = self.readers.get(socket_)
if reader:
reader.handle_read(socket_)
except socket.error as e:
# If the socket was closed by another thread, during
# shutdown, ignore it and exit
if e.errno != socket.EBADF or not self.zc.done:
raise
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()
class Listener(QuietLogger):
"""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 available for reading."""
def __init__(self, zc):
self.zc = zc
self.data = None
def handle_read(self, socket_):
try:
data, (addr, port) = socket_.recvfrom(_MAX_MSG_ABSOLUTE)
except Exception:
self.log_exception_warning()
return
log.debug('Received from %r:%r: %r ', addr, port, data)
self.data = data
msg = DNSIncoming(data)
if not msg.valid:
pass
elif 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, name='zeroconf-Reaper')
self.daemon = True
self.zc = zc
self.start()
def run(self):
while True:
self.zc.wait(10 * 1000)
if self.zc.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'
if not type_.endswith(service_type_name(type_)):
raise BadTypeInNameException
threading.Thread.__init__(
self, name='zeroconf-ServiceBrowser_' + type_)
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._service_state_changed = Signal()
self.done = False
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)
self.start()
@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.remove_listener(self)
self.join()
def run(self):
self.zc.add_listener(self, DNSQuestion(self.type, _TYPE_PTR, _CLASS_IN))
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 self.zc.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 and not self.zc.done:
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 type_.endswith(service_type_name(name)):
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._properties = {}
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
record_types_for_check_cache = [
(_TYPE_SRV, _CLASS_IN),
(_TYPE_TXT, _CLASS_IN),
]
if self.server is not None:
record_types_for_check_cache.append((_TYPE_A, _CLASS_IN))
for record_type in record_types_for_check_cache:
cached = zc.cache.get_by_details(self.name, *record_type)
if cached:
self.update_record(zc, now, cached)
if None not in (self.server, self.address, self.text):
return True
try:
zc.add_listener(self, DNSQuestion(self.name, _TYPE_ANY, _CLASS_IN))
while None in (self.server, self.address, self.text):
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 *= 2
zc.wait(min(next_, last) - now)
now = current_time_millis()
finally:
zc.remove_listener(self)
return True
def __eq__(self, other):
"""Tests equality of service name"""
return isinstance(other, ServiceInfo) and other.name == self.name
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',
)
)
)
class ZeroconfServiceTypes(object):
"""
Return all of the advertised services on any local networks
"""
def __init__(self):
self.found_services = set()
def add_service(self, zc, type_, name):
self.found_services.add(name)
def remove_service(self, zc, type_, name):
pass
@classmethod
def find(cls, zc=None, timeout=5, interfaces=InterfaceChoice.All):
"""
Return all of the advertised services on any local networks.
:param zc: Zeroconf() instance. Pass in if already have an
instance running or if non-default interfaces are needed
:param timeout: seconds to wait for any responses
:return: tuple of service type strings
"""
local_zc = zc or Zeroconf(interfaces=interfaces)
listener = cls()
browser = ServiceBrowser(
local_zc, '_services._dns-sd._udp.local.', listener=listener)
# wait for responses
time.sleep(timeout)
# close down anything we opened
if zc is None:
local_zc.close()
else:
browser.cancel()
return tuple(sorted(listener.found_services))
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
# OpenBSD needs the ttl and loop values for the IP_MULTICAST_TTL and
# IP_MULTICAST_LOOP socket options as an unsigned char.
ttl = struct.pack(b'B', 255)
s.setsockopt(socket.IPPROTO_IP, socket.IP_MULTICAST_TTL, ttl)
loop = struct.pack(b'B', 1)
s.setsockopt(socket.IPPROTO_IP, socket.IP_MULTICAST_LOOP, loop)
s.bind(('', _MDNS_PORT))
return s
def get_errno(e):
assert isinstance(e, socket.error)
return e.args[0]
class Zeroconf(QuietLogger):
"""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
"""
# hook for threads
self._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)
self.debug = None
@property
def done(self):
return self._GLOBAL_DONE
def wait(self, timeout):
"""Calling thread waits for a given number of milliseconds or
until notified."""
with self.condition:
self.condition.wait(timeout / 1000.0)
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
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[listener] = ServiceBrowser(self, type_, listener)
def remove_service_listener(self, listener):
"""Removes a listener from the set that is currently listening."""
if listener in self.browsers:
self.browsers[listener].cancel()
del self.browsers[listener]
def remove_all_service_listeners(self):
"""Removes a listener from the set that is currently listening."""
for listener in [k for k in self.browsers]:
self.remove_service_listener(listener)
def register_service(self, info, ttl=_DNS_TTL, allow_name_change=False):
"""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, allow_name_change)
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, allow_name_change):
"""Checks the network for a unique service name, modifying the
ServiceInfo passed in if it is not unique."""
# This is kind of funky because of the subtype based tests
# need to make subtypes a first class citizen
service_name = service_type_name(info.name)
if not info.type.endswith(service_name):
raise BadTypeInNameException
instance_name = info.name[:-len(service_name) - 1]
next_instance_number = 2
now = current_time_millis()
next_time = now
i = 0
while i < 3:
# check for a name conflict
while self.cache.current_entry_with_name_and_alias(
info.type, info.name):
if not allow_name_change:
raise NonUniqueNameException
# change the name and look for a conflict
info.name = '%s-%s.%s' % (
instance_name, next_instance_number, info.type)
next_instance_number += 1
service_type_name(info.name)
next_time = now
i = 0
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)
else:
self.cache.add(record)
for record in msg.answers:
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, multicast=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: # TODO stop catching all Exceptions
self.log_exception_warning()
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()
if len(packet) > _MAX_MSG_ABSOLUTE:
self.log_warning_once("Dropping %r over-sized packet (%d bytes) %r",
out, len(packet), packet)
return
log.debug('Sending %r (%d bytes) as %r...', out, len(packet), packet)
for s in self._respond_sockets:
if self._GLOBAL_DONE:
return
try:
bytes_sent = s.sendto(packet, 0, (addr, port))
except Exception: # TODO stop catching all Exceptions
# on send errors, log the exception and keep going
self.log_exception_warning()
else:
if bytes_sent != len(packet):
self.log_warning_once(
'!!! sent %d out of %d bytes to %r' % (
bytes_sent, len(packet)), s)
def close(self):
"""Ends the background threads, and prevent this instance from
servicing further queries."""
if not self._GLOBAL_DONE:
self._GLOBAL_DONE = True
# remove service listeners
self.remove_all_service_listeners()
self.unregister_all_services()
# shutdown recv socket and thread
self.engine.del_reader(self._listen_socket)
self._listen_socket.close()
self.engine.join()
# shutdown the rest
self.notify_all()
self.reaper.join()
for s in self._respond_sockets:
s.close()
