""" 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 ipaddress import itertools import logging import os import platform import re import select import socket import struct import sys import threading import time import warnings from collections import OrderedDict from typing import Dict, List, Optional, Sequence, Union, cast from typing import Any, Callable, Set, Tuple # noqa # used in type hints import ifaddr __author__ = 'Paul Scott-Murphy, William McBrine' __maintainer__ = 'Jakub Stasiak ' __version__ = '0.26.1' __license__ = 'LGPL' __all__ = [ "__version__", "Zeroconf", "ServiceInfo", "ServiceBrowser", "Error", "InterfaceChoice", "ServiceStateChange", "IPVersion", ] if sys.version_info <= (3, 3): raise ImportError( ''' Python version > 3.3 required for python-zeroconf. If you need support for Python 2 or Python 3.3 please use version 19.1 ''' ) log = logging.getLogger(__name__) log.addHandler(logging.NullHandler()) if log.level == logging.NOTSET: log.setLevel(logging.WARN) # Some timing constants _UNREGISTER_TIME = 125 # ms _CHECK_TIME = 175 # ms _REGISTER_TIME = 225 # ms _LISTENER_TIME = 200 # ms _BROWSER_TIME = 1000 # ms _BROWSER_BACKOFF_LIMIT = 3600 # s # Some DNS constants _MDNS_ADDR = '224.0.0.251' _MDNS_ADDR_BYTES = socket.inet_aton(_MDNS_ADDR) _MDNS_ADDR6 = 'ff02::fb' _MDNS_ADDR6_BYTES = socket.inet_pton(socket.AF_INET6, _MDNS_ADDR6) _MDNS_PORT = 5353 _DNS_PORT = 53 _DNS_HOST_TTL = 120 # two minute for host records (A, SRV etc) as-per RFC6762 _DNS_OTHER_TTL = 4500 # 75 minutes for non-host records (PTR, TXT etc) as-per RFC6762 _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\-]+$') _HAS_ONLY_A_TO_Z_NUM_HYPHEN_UNDERSCORE = re.compile(r'^[A-Za-z0-9\-\_]+$') _HAS_ASCII_CONTROL_CHARS = re.compile(r'[\x00-\x1f\x7f]') try: _IPPROTO_IPV6 = socket.IPPROTO_IPV6 except AttributeError: # Sigh: https://bugs.python.org/issue29515 _IPPROTO_IPV6 = 41 int2byte = struct.Struct(">B").pack @enum.unique class InterfaceChoice(enum.Enum): Default = 1 All = 2 InterfacesType = Union[List[Union[str, int]], InterfaceChoice] @enum.unique class ServiceStateChange(enum.Enum): Added = 1 Removed = 2 Updated = 3 @enum.unique class IPVersion(enum.Enum): V4Only = 1 V6Only = 2 All = 3 # utility functions def current_time_millis() -> float: """Current system time in milliseconds""" return time.time() * 1000 def _is_v6_address(addr: bytes) -> bool: return len(addr) == 16 def service_type_name(type_: str, *, allow_underscores: bool = False) -> str: """ 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: . <_tcp|_udp> . local. . . <_tcp|_udp> . local. ._sub . . <_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 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 and sub type 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) allowed_characters_re = ( _HAS_ONLY_A_TO_Z_NUM_HYPHEN_UNDERSCORE if allow_underscores else _HAS_ONLY_A_TO_Z_NUM_HYPHEN ) if not allowed_characters_re.search(name): raise BadTypeInNameException( "Service name (%s) must contain only these characters: " "A-Z, a-z, 0-9, hyphen ('-')%s" % (name, ", underscore ('_')" if allow_underscores else "") ) 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: _seen_logs = {} # type: Dict[str, Union[int, tuple]] @classmethod def log_exception_warning(cls, logger_data: Optional[Tuple] = None) -> 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=True) @classmethod def log_warning_once(cls, *args: Any) -> None: 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] = cast(int, cls._seen_logs[msg_str]) + 1 logger(*args) class DNSEntry: """A DNS entry""" def __init__(self, name: str, type_: int, class_: int) -> None: 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: Any) -> bool: """Equality test on name, type, and class""" return ( self.name == other.name and self.type == other.type and self.class_ == other.class_ and isinstance(other, DNSEntry) ) def __ne__(self, other: Any) -> bool: """Non-equality test""" return not self.__eq__(other) @staticmethod def get_class_(class_: int) -> str: """Class accessor""" return _CLASSES.get(class_, "?(%s)" % class_) @staticmethod def get_type(t: int) -> str: """Type accessor""" return _TYPES.get(t, "?(%s)" % t) def entry_to_string(self, hdr: str, other: Optional[Union[bytes, str]]) -> str: """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" % cast(Any, other) else: result += "]" return result class DNSQuestion(DNSEntry): """A DNS question entry""" def __init__(self, name: str, type_: int, class_: int) -> None: DNSEntry.__init__(self, name, type_, class_) def answered_by(self, rec: 'DNSRecord') -> bool: """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) -> str: """String representation""" return DNSEntry.entry_to_string(self, "question", None) class DNSRecord(DNSEntry): """A DNS record - like a DNS entry, but has a TTL""" # TODO: Switch to just int ttl def __init__(self, name: str, type_: int, class_: int, ttl: Union[float, int]) -> None: DNSEntry.__init__(self, name, type_, class_) self.ttl = ttl self.created = current_time_millis() self._expiration_time = self.get_expiration_time(100) self._stale_time = self.get_expiration_time(50) def __eq__(self, other: Any) -> bool: """Abstract method""" raise AbstractMethodException def __ne__(self, other: Any) -> bool: """Non-equality test""" return not self.__eq__(other) def suppressed_by(self, msg: 'DNSIncoming') -> bool: """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: 'DNSRecord') -> bool: """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: int) -> float: """Returns the time at which this record will have expired by a certain percentage.""" return self.created + (percent * self.ttl * 10) # TODO: Switch to just int here def get_remaining_ttl(self, now: float) -> Union[int, float]: """Returns the remaining TTL in seconds.""" return max(0, (self._expiration_time - now) / 1000.0) def is_expired(self, now: float) -> bool: """Returns true if this record has expired.""" return self._expiration_time <= now def is_stale(self, now: float) -> bool: """Returns true if this record is at least half way expired.""" return self._stale_time <= now def reset_ttl(self, other: 'DNSRecord') -> None: """Sets this record's TTL and created time to that of another record.""" self.created = other.created self.ttl = other.ttl self._expiration_time = self.get_expiration_time(100) self._stale_time = self.get_expiration_time(50) def write(self, out: 'DNSOutgoing') -> None: """Abstract method""" raise AbstractMethodException def to_string(self, other: Union[bytes, str]) -> str: """String representation with additional information""" arg = "%s/%s,%s" % (self.ttl, int(self.get_remaining_ttl(current_time_millis())), cast(Any, other)) return DNSEntry.entry_to_string(self, "record", arg) class DNSAddress(DNSRecord): """A DNS address record""" def __init__(self, name: str, type_: int, class_: int, ttl: int, address: bytes) -> None: DNSRecord.__init__(self, name, type_, class_, ttl) self.address = address def write(self, out: 'DNSOutgoing') -> None: """Used in constructing an outgoing packet""" out.write_string(self.address) def __eq__(self, other: Any) -> bool: """Tests equality on address""" return ( isinstance(other, DNSAddress) and DNSEntry.__eq__(self, other) and self.address == other.address ) def __ne__(self, other: Any) -> bool: """Non-equality test""" return not self.__eq__(other) def __repr__(self) -> str: """String representation""" try: return self.to_string( socket.inet_ntop( socket.AF_INET6 if _is_v6_address(self.address) else socket.AF_INET, self.address ) ) except Exception: # TODO stop catching all Exceptions return self.to_string(str(self.address)) class DNSHinfo(DNSRecord): """A DNS host information record""" def __init__( self, name: str, type_: int, class_: int, ttl: int, cpu: Union[bytes, str], os: Union[bytes, str] ) -> None: DNSRecord.__init__(self, name, type_, class_, ttl) try: self.cpu = cast(bytes, cpu).decode('utf-8') except AttributeError: self.cpu = cast(str, cpu) try: self.os = cast(bytes, os).decode('utf-8') except AttributeError: self.os = cast(str, os) def write(self, out: 'DNSOutgoing') -> None: """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: Any) -> bool: """Tests equality on cpu and os""" return ( isinstance(other, DNSHinfo) and DNSEntry.__eq__(self, other) and self.cpu == other.cpu and self.os == other.os ) def __ne__(self, other: Any) -> bool: """Non-equality test""" return not self.__eq__(other) def __repr__(self) -> str: """String representation""" return self.to_string(self.cpu + " " + self.os) class DNSPointer(DNSRecord): """A DNS pointer record""" def __init__(self, name: str, type_: int, class_: int, ttl: int, alias: str) -> None: DNSRecord.__init__(self, name, type_, class_, ttl) self.alias = alias def write(self, out: 'DNSOutgoing') -> None: """Used in constructing an outgoing packet""" out.write_name(self.alias) def __eq__(self, other: Any) -> bool: """Tests equality on alias""" return isinstance(other, DNSPointer) and self.alias == other.alias and DNSEntry.__eq__(self, other) def __ne__(self, other: Any) -> bool: """Non-equality test""" return not self.__eq__(other) def __repr__(self) -> str: """String representation""" return self.to_string(self.alias) class DNSText(DNSRecord): """A DNS text record""" def __init__(self, name: str, type_: int, class_: int, ttl: int, text: bytes) -> None: assert isinstance(text, (bytes, type(None))) DNSRecord.__init__(self, name, type_, class_, ttl) self.text = text def write(self, out: 'DNSOutgoing') -> None: """Used in constructing an outgoing packet""" out.write_string(self.text) def __eq__(self, other: Any) -> bool: """Tests equality on text""" return isinstance(other, DNSText) and self.text == other.text and DNSEntry.__eq__(self, other) def __ne__(self, other: Any) -> bool: """Non-equality test""" return not self.__eq__(other) def __repr__(self) -> str: """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: str, type_: int, class_: int, ttl: Union[float, int], priority: int, weight: int, port: int, server: str, ) -> None: DNSRecord.__init__(self, name, type_, class_, ttl) self.priority = priority self.weight = weight self.port = port self.server = server def write(self, out: 'DNSOutgoing') -> None: """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: Any) -> bool: """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 and DNSEntry.__eq__(self, other) ) def __ne__(self, other: Any) -> bool: """Non-equality test""" return not self.__eq__(other) def __repr__(self) -> str: """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: bytes) -> None: """Constructor from string holding bytes of packet""" self.offset = 0 self.data = data self.questions = [] # type: List[DNSQuestion] self.answers = [] # type: List[DNSRecord] self.id = 0 self.flags = 0 # type: int 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_: bytes) -> tuple: length = struct.calcsize(format_) info = struct.unpack(format_, self.data[self.offset : self.offset + length]) self.offset += length return info def read_header(self) -> None: """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) -> None: """Reads questions section of packet""" for i in range(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) -> bytes: """Reads a character string from the packet""" length = self.data[self.offset] self.offset += 1 return self.read_string(length) def read_string(self, length: int) -> bytes: """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) -> int: """Reads an unsigned short from the packet""" return cast(int, self.unpack(b'!H')[0]) def read_others(self) -> None: """Reads the answers, authorities and additionals section of the packet""" n = self.num_answers + self.num_authorities + self.num_additionals for i in range(n): domain = self.read_name() type_, class_, ttl, length = self.unpack(b'!HHiH') rec = None # type: Optional[DNSRecord] 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) -> bool: """Returns true if this is a query""" return (self.flags & _FLAGS_QR_MASK) == _FLAGS_QR_QUERY def is_response(self) -> bool: """Returns true if this is a response""" return (self.flags & _FLAGS_QR_MASK) == _FLAGS_QR_RESPONSE def read_utf(self, offset: int, length: int) -> str: """Reads a UTF-8 string of a given length from the packet""" return str(self.data[offset : offset + length], 'utf-8', 'replace') def read_name(self) -> str: """Reads a domain name from the packet""" result = '' off = self.offset next_ = -1 first = off while True: length = 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) | 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 representation of an outgoing packet""" def __init__(self, flags: int, multicast: bool = True) -> None: self.finished = False self.id = 0 self.multicast = multicast self.flags = flags self.names = {} # type: Dict[str, int] self.data = [] # type: List[bytes] self.size = 12 self.state = self.State.init self.questions = [] # type: List[DNSQuestion] self.answers = [] # type: List[Tuple[DNSRecord, float]] self.authorities = [] # type: List[DNSPointer] self.additionals = [] # type: List[DNSRecord] def __repr__(self) -> str: return '' % ', '.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 @staticmethod def is_type_unique(type_: int) -> bool: return type_ == _TYPE_TXT or type_ == _TYPE_SRV or type_ == _TYPE_A or type_ == _TYPE_AAAA def add_question(self, record: DNSQuestion) -> None: """Adds a question""" self.questions.append(record) def add_answer(self, inp: DNSIncoming, record: DNSRecord) -> None: """Adds an answer""" if not record.suppressed_by(inp): self.add_answer_at_time(record, 0) def add_answer_at_time(self, record: Optional[DNSRecord], now: Union[float, int]) -> None: """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: DNSPointer) -> None: """Adds an authoritative answer""" self.authorities.append(record) def add_additional_answer(self, record: DNSRecord) -> None: """ 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_: Union[bytes, str], value: Any) -> None: self.data.append(struct.pack(format_, value)) self.size += struct.calcsize(format_) def write_byte(self, value: int) -> None: """Writes a single byte to the packet""" self.pack(b'!c', int2byte(value)) def insert_short(self, index: int, value: int) -> None: """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: int) -> None: """Writes an unsigned short to the packet""" self.pack(b'!H', value) def write_int(self, value: Union[float, int]) -> None: """Writes an unsigned integer to the packet""" self.pack(b'!I', int(value)) def write_string(self, value: bytes) -> None: """Writes a string to the packet""" assert isinstance(value, bytes) self.data.append(value) self.size += len(value) def write_utf(self, s: str) -> None: """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: bytes) -> None: 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: str) -> None: """ 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 = len(name_suffices) # note the new names we are saving into the packet name_length = len(name.encode('utf-8')) for suffix in name_suffices[:count]: self.names[suffix] = self.size + name_length - len(suffix.encode('utf-8')) - 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: DNSQuestion) -> None: """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: DNSRecord, now: float) -> int: """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) -> bytes: """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: """A cache of DNS entries""" def __init__(self) -> None: self.cache = {} # type: Dict[str, List[DNSRecord]] def add(self, entry: DNSRecord) -> None: """Adds an entry""" # Insert last in list, get will return newest entry # iteration will result in last update winning self.cache.setdefault(entry.key, []).append(entry) def remove(self, entry: DNSRecord) -> None: """Removes an entry""" try: list_ = self.cache[entry.key] list_.remove(entry) # If we remove the last entry in the list # we remove the key from the dict in order # to avoid leaking memory if not list_: del self.cache[entry.key] except (KeyError, ValueError): pass def get(self, entry: DNSEntry) -> Optional[DNSRecord]: """Gets an entry by key. Will return None if there is no matching entry.""" try: list_ = self.cache[entry.key] for cached_entry in reversed(list_): if entry.__eq__(cached_entry): return cached_entry return None except (KeyError, ValueError): return None def get_by_details(self, name: str, type_: int, class_: int) -> Optional[DNSRecord]: """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: str) -> List[DNSRecord]: """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: str, alias: str) -> Optional[DNSRecord]: now = current_time_millis() for record in reversed(self.entries_with_name(name)): if ( record.type == _TYPE_PTR and not record.is_expired(now) and cast(DNSPointer, record).alias == alias ): return record return None def entries(self) -> List[DNSRecord]: """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 list(itertools.chain.from_iterable(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: 'Zeroconf') -> None: threading.Thread.__init__(self, name='zeroconf-Engine') self.daemon = True self.zc = zc self.readers = {} # type: Dict[socket.socket, Listener] self.timeout = 5 self.condition = threading.Condition() self.socketpair = socket.socketpair() self.start() def run(self) -> None: while not self.zc.done: with self.condition: rs = list(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: rs = rs + [self.socketpair[0]] rr, wr, er = select.select(cast(Sequence[Any], rs), [], [], self.timeout) if not self.zc.done: for socket_ in rr: reader = self.readers.get(socket_) if reader: reader.handle_read(socket_) if self.socketpair[0] in rr: # Clear the socket's buffer self.socketpair[0].recv(128) except (select.error, socket.error) as e: # If the socket was closed by another thread, during # shutdown, ignore it and exit if e.args[0] not in (errno.EBADF, errno.ENOTCONN) or not self.zc.done: raise self.socketpair[0].close() self.socketpair[1].close() def _notify(self) -> None: self.condition.notify() try: self.socketpair[1].send(b'x') except socket.error: # The socketpair may already be closed during shutdown, ignore it if not self.zc.done: raise def add_reader(self, reader: 'Listener', socket_: socket.socket) -> None: with self.condition: self.readers[socket_] = reader self._notify() def del_reader(self, socket_: socket.socket) -> None: with self.condition: del self.readers[socket_] self._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: 'Zeroconf') -> None: self.zc = zc self.data = None # type: Optional[bytes] def handle_read(self, socket_: socket.socket) -> None: try: data, (addr, port, *_v6) = 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, None, _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, None, _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: 'Zeroconf') -> None: threading.Thread.__init__(self, name='zeroconf-Reaper') self.daemon = True self.zc = zc self.start() def run(self) -> None: 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: def __init__(self) -> None: self._handlers = [] # type: List[Callable[..., None]] def fire(self, **kwargs: Any) -> None: for h in list(self._handlers): h(**kwargs) @property def registration_interface(self) -> 'SignalRegistrationInterface': return SignalRegistrationInterface(self._handlers) # NOTE: Callable quoting needed on Python 3.5.2, see # https://github.com/jstasiak/python-zeroconf/issues/208 for details. class SignalRegistrationInterface: def __init__(self, handlers: List['Callable[..., None]']) -> None: self._handlers = handlers def register_handler(self, handler: 'Callable[..., None]') -> 'SignalRegistrationInterface': self._handlers.append(handler) return self def unregister_handler(self, handler: 'Callable[..., None]') -> 'SignalRegistrationInterface': self._handlers.remove(handler) return self class RecordUpdateListener: def update_record(self, zc: 'Zeroconf', now: float, record: DNSRecord) -> None: raise NotImplementedError() class ServiceListener: def add_service(self, zc: 'Zeroconf', type_: str, name: str) -> None: raise NotImplementedError() def remove_service(self, zc: 'Zeroconf', type_: str, name: str) -> None: raise NotImplementedError() def update_service(self, zc: 'Zeroconf', type_: str, name: str) -> None: raise NotImplementedError() class ServiceBrowser(RecordUpdateListener, 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: 'Zeroconf', type_: str, # NOTE: Callable quoting needed on Python 3.5.2, see # https://github.com/jstasiak/python-zeroconf/issues/208 for details. handlers: Optional[Union[ServiceListener, List['Callable[..., None]']]] = None, listener: Optional[ServiceListener] = None, addr: Optional[str] = None, port: int = _MDNS_PORT, delay: int = _BROWSER_TIME, ) -> 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_, allow_underscores=True)): raise BadTypeInNameException threading.Thread.__init__(self, name='zeroconf-ServiceBrowser_' + type_) self.daemon = True self.zc = zc self.type = type_ self.addr = addr self.port = port self.multicast = self.addr in (None, _MDNS_ADDR, _MDNS_ADDR6) self.services = {} # type: Dict[str, DNSRecord] self.next_time = current_time_millis() self.delay = delay self._handlers_to_call = OrderedDict() # type: OrderedDict[str, ServiceStateChange] self._service_state_changed = Signal() self.done = False if hasattr(handlers, 'add_service'): listener = cast(ServiceListener, handlers) handlers = None # NOTE: Callable quoting needed on Python 3.5.2, see # https://github.com/jstasiak/python-zeroconf/issues/208 for details. handlers = cast(List['Callable[..., None]'], handlers or []) if listener: def on_change( zeroconf: 'Zeroconf', service_type: str, name: str, state_change: ServiceStateChange ) -> None: assert listener is not None 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) elif state_change is ServiceStateChange.Updated: if hasattr(listener, 'update_service'): listener.update_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) -> SignalRegistrationInterface: return self._service_state_changed.registration_interface def update_record(self, zc: 'Zeroconf', now: float, record: DNSRecord) -> None: """Callback invoked by Zeroconf when new information arrives. Updates information required by browser in the Zeroconf cache. Ensures that there is are no unecessary duplicates in the list """ def enqueue_callback(state_change: ServiceStateChange, name: str) -> None: # Code to ensure we only do a single update message # Precedence is; Added, Remove, Update if ( state_change is ServiceStateChange.Added or ( state_change is ServiceStateChange.Removed and ( self._handlers_to_call.get(name) is ServiceStateChange.Updated or self._handlers_to_call.get(name) is ServiceStateChange.Added or self._handlers_to_call.get(name) is None ) ) or (state_change is ServiceStateChange.Updated and name not in self._handlers_to_call) ): self._handlers_to_call[name] = state_change if record.type == _TYPE_PTR and record.name == self.type: assert isinstance(record, DNSPointer) 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 elif record.type == _TYPE_A or record.type == _TYPE_AAAA: assert isinstance(record, DNSAddress) if record.is_expired(now): return address_changed = False for service in zc.cache.entries_with_name(record.name): if isinstance(service, DNSAddress) and service.address != record.address: address_changed = True break # Avoid iterating the entire DNSCache if the address has not changed # as this is an expensive operation when there many hosts # generating zeroconf traffic. if not address_changed: return # Iterate through the DNSCache and callback any services that use this address for service in zc.cache.entries(): if ( isinstance(service, DNSService) and service.name.endswith(self.type) and service.server == record.name ): enqueue_callback(ServiceStateChange.Updated, service.name) elif record.name.endswith(self.type): expired = record.is_expired(now) if not expired: enqueue_callback(ServiceStateChange.Updated, record.name) def cancel(self) -> None: self.done = True self.zc.remove_listener(self) self.join() def run(self) -> None: 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, multicast=self.multicast) out.add_question(DNSQuestion(self.type, _TYPE_PTR, _CLASS_IN)) for record in self.services.values(): if not record.is_stale(now): out.add_answer_at_time(record, now) self.zc.send(out, addr=self.addr, port=self.port) self.next_time = now + self.delay self.delay = min(_BROWSER_BACKOFF_LIMIT * 1000, self.delay * 2) if len(self._handlers_to_call) > 0 and not self.zc.done: with self.zc._handlers_lock: handler = self._handlers_to_call.popitem(False) self._service_state_changed.fire( zeroconf=self.zc, service_type=self.type, name=handler[0], state_change=handler[1] ) class ServiceInfo(RecordUpdateListener): """Service information. Constructor parameters are as follows: * type_: fully qualified service type name * name: fully qualified service name * address: IP address as unsigned short, network byte order (deprecated, use addresses) * port: port that the service runs on * weight: weight of the service * priority: priority of the service * properties: dictionary of properties (or a bytes object holding the contents of the `text` field). converted to str and then encoded to bytes using UTF-8. Keys with `None` values are converted to value-less attributes. * server: fully qualified name for service host (defaults to name) * host_ttl: ttl used for A/SRV records * other_ttl: ttl used for PTR/TXT records * addresses: List of IP addresses as unsigned short (IPv4) or unsigned 128 bit number (IPv6), network byte order """ text = b'' # FIXME(dtantsur): black 19.3b0 produces code that is not valid syntax on # Python 3.5: https://github.com/python/black/issues/759 # fmt: off def __init__( self, type_: str, name: str, address: Optional[Union[bytes, List[bytes]]] = None, port: Optional[int] = None, weight: int = 0, priority: int = 0, properties: Union[bytes, Dict] = b'', server: Optional[str] = None, host_ttl: int = _DNS_HOST_TTL, other_ttl: int = _DNS_OTHER_TTL, *, addresses: Optional[List[bytes]] = None ) -> None: # Accept both none, or one, but not both. if address is not None and addresses is not None: raise TypeError("address and addresses cannot be provided together") if not type_.endswith(service_type_name(name, allow_underscores=True)): raise BadTypeInNameException self.type = type_ self.name = name if addresses is not None: self._addresses = addresses elif address is not None: warnings.warn("address is deprecated, use addresses instead", DeprecationWarning) if isinstance(address, list): self._addresses = address else: self._addresses = [address] else: self._addresses = [] # This results in an ugly error when registering, better check now invalid = [a for a in self._addresses if not isinstance(a, bytes) or len(a) not in (4, 16)] if invalid: raise TypeError('Addresses must be bytes, got %s. Hint: convert string addresses ' 'with socket.inet_pton' % invalid) self.port = port self.weight = weight self.priority = priority if server: self.server = server else: self.server = name self._properties = {} # type: Dict self._set_properties(properties) self.host_ttl = host_ttl self.other_ttl = other_ttl # fmt: on @property def address(self) -> Optional[bytes]: warnings.warn("ServiceInfo.address is deprecated, use addresses instead", DeprecationWarning) try: # Return the first V4 address for compatibility return self.addresses[0] except IndexError: return None @address.setter def address(self, value: bytes) -> None: warnings.warn("ServiceInfo.address is deprecated, use addresses instead", DeprecationWarning) if value is None: self._addresses = [] else: self._addresses = [value] @property def addresses(self) -> List[bytes]: """IPv4 addresses of this service. Only IPv4 addresses are returned for backward compatibility. Use :meth:`addresses_by_version` or :meth:`parsed_addresses` to include IPv6 addresses as well. """ return self.addresses_by_version(IPVersion.V4Only) @addresses.setter def addresses(self, value: List[bytes]) -> None: """Replace the addresses list. This replaces all currently stored addresses, both IPv4 and IPv6. """ self._addresses = value @property def properties(self) -> Dict: """If properties were set in the constructor this property returns the original dictionary of type `Dict[Union[bytes, str], Any]`. If properties are coming from the network, after decoding a TXT record, the keys are always bytes and the values are either bytes, if there was a value, even empty, or `None`, if there was none. No further decoding is attempted. The type returned is `Dict[bytes, Optional[bytes]]`. """ return self._properties def addresses_by_version(self, version: IPVersion) -> List[bytes]: """List addresses matching IP version.""" if version == IPVersion.V4Only: return [addr for addr in self._addresses if not _is_v6_address(addr)] elif version == IPVersion.V6Only: return list(filter(_is_v6_address, self._addresses)) else: return self._addresses def parsed_addresses(self, version: IPVersion = IPVersion.All) -> List[str]: """List addresses in their parsed string form.""" result = self.addresses_by_version(version) return [ socket.inet_ntop(socket.AF_INET6 if _is_v6_address(addr) else socket.AF_INET, addr) for addr in result ] def _set_properties(self, properties: Union[bytes, Dict]) -> None: """Sets properties and text of this info from a dictionary""" if isinstance(properties, dict): self._properties = properties list_ = [] result = b'' for key, value in properties.items(): if isinstance(key, str): key = key.encode('utf-8') record = key if value is not None: if not isinstance(value, bytes): value = str(value).encode('utf-8') record += b'=' + value list_.append(record) for item in list_: result = b''.join((result, int2byte(len(item)), item)) self.text = result else: self.text = properties def _set_text(self, text: bytes) -> None: """Sets properties and text given a text field""" self.text = text result = {} # type: Dict end = len(text) index = 0 strs = [] while index < end: length = 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 # type: Tuple[bytes, Optional[bytes]] except ValueError: # No equals sign at all key = s value = None # Only update non-existent properties if key and result.get(key) is None: result[key] = value self._properties = result def get_name(self) -> str: """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: 'Zeroconf', now: float, record: Optional[DNSRecord]) -> None: """Updates service information from a DNS record""" if record is not None and not record.is_expired(now): if record.type in [_TYPE_A, _TYPE_AAAA]: assert isinstance(record, DNSAddress) # if record.name == self.name: if record.name == self.server: if record.address not in self._addresses: self._addresses.append(record.address) elif record.type == _TYPE_SRV: assert isinstance(record, DNSService) 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)) self.update_record(zc, now, zc.cache.get_by_details(self.server, _TYPE_AAAA, _CLASS_IN)) elif record.type == _TYPE_TXT: assert isinstance(record, DNSText) if record.name == self.name: self._set_text(record.text) def request(self, zc: 'Zeroconf', timeout: float) -> bool: """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)) record_types_for_check_cache.append((_TYPE_AAAA, _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 self.server is not None and self.text is not None and self._addresses: return True try: zc.add_listener(self, DNSQuestion(self.name, _TYPE_ANY, _CLASS_IN)) while self.server is None or self.text is None or not self._addresses: 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) out.add_question(DNSQuestion(self.server, _TYPE_AAAA, _CLASS_IN)) out.add_answer_at_time( zc.cache.get_by_details(self.server, _TYPE_AAAA, _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: object) -> bool: """Tests equality of service name""" return isinstance(other, ServiceInfo) and other.name == self.name def __ne__(self, other: object) -> bool: """Non-equality test""" return not self.__eq__(other) def __repr__(self) -> str: """String representation""" return '%s(%s)' % ( type(self).__name__, ', '.join( '%s=%r' % (name, getattr(self, name)) for name in ( 'type', 'name', 'addresses', 'port', 'weight', 'priority', 'server', 'properties', ) ), ) class ZeroconfServiceTypes(ServiceListener): """ Return all of the advertised services on any local networks """ def __init__(self) -> None: self.found_services = set() # type: Set[str] def add_service(self, zc: 'Zeroconf', type_: str, name: str) -> None: self.found_services.add(name) def remove_service(self, zc: 'Zeroconf', type_: str, name: str) -> None: pass @classmethod def find( cls, zc: Optional['Zeroconf'] = None, timeout: Union[int, float] = 5, interfaces: InterfacesType = InterfaceChoice.All, ip_version: Optional[IPVersion] = None, ) -> Tuple[str, ...]: """ 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 :param interfaces: interfaces to listen on. :param ip_version: IP protocol version to use. :return: tuple of service type strings """ local_zc = zc or Zeroconf(interfaces=interfaces, ip_version=ip_version) 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() -> List[str]: return list(set(addr.ip for iface in ifaddr.get_adapters() for addr in iface.ips if addr.is_IPv4)) def get_all_addresses_v6() -> List[int]: # IPv6 multicast uses positive indexes for interfaces try: nameindex = socket.if_nameindex except AttributeError: # Requires Python 3.8 on Windows. Fall back to Default. QuietLogger.log_warning_once( 'if_nameindex is not available, falling back to using the default IPv6 interface' ) return [0] return [tpl[0] for tpl in nameindex()] def ip_to_index(adapters: List[Any], ip: str) -> int: if os.name != 'posix': # Adapter names that ifaddr reports are not compatible with what if_nametoindex expects on Windows. # We need https://github.com/pydron/ifaddr/pull/21 but it seems stuck on review. raise RuntimeError('Converting from IP addresses to indexes is not supported on non-POSIX systems') ipaddr = ipaddress.ip_address(ip) for adapter in adapters: for adapter_ip in adapter.ips: # IPv6 addresses are represented as tuples if isinstance(adapter_ip.ip, tuple) and ipaddress.ip_address(adapter_ip.ip[0]) == ipaddr: return socket.if_nametoindex(adapter.name) raise RuntimeError('No adapter found for IP address %s' % ip) def ip6_addresses_to_indexes(interfaces: List[Union[str, int]]) -> List[int]: """Convert IPv6 interface addresses to interface indexes. IPv4 addresses are ignored. The conversion currently only works on POSIX systems. :param interfaces: List of IP addresses and indexes. :returns: List of indexes. """ result = [] adapters = ifaddr.get_adapters() for iface in interfaces: if isinstance(iface, int): result.append(iface) elif isinstance(iface, str) and ipaddress.ip_address(iface).version == 6: result.append(ip_to_index(adapters, iface)) return result def normalize_interface_choice( choice: InterfacesType, ip_version: IPVersion = IPVersion.V4Only ) -> List[Union[str, int]]: """Convert the interfaces choice into internal representation. :param choice: `InterfaceChoice` or list of interface addresses or indexes (IPv6 only). :param ip_address: IP version to use (ignored if `choice` is a list). :returns: List of IP addresses (for IPv4) and indexes (for IPv6). """ result = [] # type: List[Union[str, int]] if choice is InterfaceChoice.Default: if ip_version != IPVersion.V4Only: # IPv6 multicast uses interface 0 to mean the default result.append(0) if ip_version != IPVersion.V6Only: result.append('0.0.0.0') elif choice is InterfaceChoice.All: if ip_version != IPVersion.V4Only: result.extend(get_all_addresses_v6()) if ip_version != IPVersion.V6Only: result.extend(get_all_addresses()) if not result: raise RuntimeError( 'No interfaces to listen on, check that any interfaces have IP version %s' % ip_version ) elif isinstance(choice, list): # First, take IPv4 addresses. result = [i for i in choice if isinstance(i, str) and ipaddress.ip_address(i).version == 4] # Unlike IP_ADD_MEMBERSHIP, IPV6_JOIN_GROUP requires interface indexes. result += ip6_addresses_to_indexes(choice) else: raise TypeError("choice must be a list or InterfaceChoice, got %r" % choice) return result def new_socket( port: int = _MDNS_PORT, ip_version: IPVersion = IPVersion.V4Only, apple_p2p: bool = False ) -> socket.socket: if ip_version == IPVersion.V4Only: s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM) else: s = socket.socket(socket.AF_INET6, socket.SOCK_DGRAM) if ip_version == IPVersion.All: # make V6 sockets work for both V4 and V6 (required for Windows) try: s.setsockopt(_IPPROTO_IPV6, socket.IPV6_V6ONLY, False) except OSError: log.error('Support for dual V4-V6 sockets is not present, use IPVersion.V4 or IPVersion.V6') raise 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 explicitly. 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 if port is _MDNS_PORT: ttl = struct.pack(b'B', 255) loop = struct.pack(b'B', 1) if ip_version != IPVersion.V6Only: # OpenBSD needs the ttl and loop values for the IP_MULTICAST_TTL and # IP_MULTICAST_LOOP socket options as an unsigned char. s.setsockopt(socket.IPPROTO_IP, socket.IP_MULTICAST_TTL, ttl) s.setsockopt(socket.IPPROTO_IP, socket.IP_MULTICAST_LOOP, loop) if ip_version != IPVersion.V4Only: # However, char doesn't work here (at least on Linux) s.setsockopt(_IPPROTO_IPV6, socket.IPV6_MULTICAST_HOPS, 255) s.setsockopt(_IPPROTO_IPV6, socket.IPV6_MULTICAST_LOOP, True) if apple_p2p: # SO_RECV_ANYIF = 0x1104 # https://opensource.apple.com/source/xnu/xnu-4570.41.2/bsd/sys/socket.h s.setsockopt(socket.SOL_SOCKET, 0x1104, 1) s.bind(('', port)) return s def add_multicast_member( listen_socket: socket.socket, interface: Union[str, int], apple_p2p: bool = False ) -> Optional[socket.socket]: # This is based on assumptions in normalize_interface_choice is_v6 = isinstance(interface, int) log.debug('Adding %r to multicast group', interface) try: if is_v6: iface_bin = struct.pack('@I', cast(int, interface)) _value = _MDNS_ADDR6_BYTES + iface_bin listen_socket.setsockopt(_IPPROTO_IPV6, socket.IPV6_JOIN_GROUP, _value) else: _value = _MDNS_ADDR_BYTES + socket.inet_aton(cast(str, interface)) listen_socket.setsockopt(socket.IPPROTO_IP, socket.IP_ADD_MEMBERSHIP, _value) except socket.error as e: _errno = get_errno(e) if _errno == errno.EADDRINUSE: log.info( 'Address in use when adding %s to multicast group, ' 'it is expected to happen on some systems', interface, ) return None elif _errno == errno.EADDRNOTAVAIL: log.info( 'Address not available when adding %s to multicast ' 'group, it is expected to happen on some systems', interface, ) return None elif _errno == errno.EINVAL: log.info('Interface of %s does not support multicast, ' 'it is expected in WSL', interface) return None else: raise respond_socket = new_socket( ip_version=(IPVersion.V6Only if is_v6 else IPVersion.V4Only), apple_p2p=apple_p2p ) log.debug('Configuring %s with multicast interface %s', respond_socket, interface) if is_v6: respond_socket.setsockopt(_IPPROTO_IPV6, socket.IPV6_MULTICAST_IF, iface_bin) else: respond_socket.setsockopt( socket.IPPROTO_IP, socket.IP_MULTICAST_IF, socket.inet_aton(cast(str, interface)) ) return respond_socket def create_sockets( interfaces: InterfacesType = InterfaceChoice.All, unicast: bool = False, ip_version: IPVersion = IPVersion.V4Only, apple_p2p: bool = False, ) -> Tuple[Optional[socket.socket], List[socket.socket]]: if unicast: listen_socket = None else: listen_socket = new_socket(ip_version=ip_version, apple_p2p=apple_p2p) interfaces = normalize_interface_choice(interfaces, ip_version) respond_sockets = [] for i in interfaces: if not unicast: respond_socket = add_multicast_member(cast(socket.socket, listen_socket), i, apple_p2p=apple_p2p) else: respond_socket = new_socket(port=0, ip_version=ip_version, apple_p2p=apple_p2p) if respond_socket is not None: respond_sockets.append(respond_socket) return listen_socket, respond_sockets def get_errno(e: Exception) -> int: assert isinstance(e, socket.error) return cast(int, e.args[0]) def can_send_to(sock: socket.socket, address: str) -> bool: addr = ipaddress.ip_address(address) return cast(bool, addr.version == 6 if sock.family == socket.AF_INET6 else addr.version == 4) class Zeroconf(QuietLogger): """Implementation of Zeroconf Multicast DNS Service Discovery Supports registration, unregistration, queries and browsing. """ def __init__( self, interfaces: InterfacesType = InterfaceChoice.All, unicast: bool = False, ip_version: Optional[IPVersion] = None, apple_p2p: bool = False, ) -> None: """Creates an instance of the Zeroconf class, establishing multicast communications, listening and reaping threads. :param interfaces: :class:`InterfaceChoice` or a list of IP addresses (IPv4 and IPv6) and interface indexes (IPv6 only). IPv6 notes for non-POSIX systems: * IPv6 addresses are not supported, use indexes instead. * `InterfaceChoice.All` is an alias for `InterfaceChoice.Default` on Python versions before 3.8. Also listening on loopback (``::1``) doesn't work, use a real address. :param ip_version: IP versions to support. If `choice` is a list, the default is detected from it. Otherwise defaults to V4 only for backward compatibility. :param apple_p2p: use AWDL interface (only macOS) """ if ip_version is None and isinstance(interfaces, list): has_v6 = any( isinstance(i, int) or (isinstance(i, str) and ipaddress.ip_address(i).version == 6) for i in interfaces ) has_v4 = any(isinstance(i, str) and ipaddress.ip_address(i).version == 4 for i in interfaces) if has_v4 and has_v6: ip_version = IPVersion.All elif has_v6: ip_version = IPVersion.V6Only if ip_version is None: ip_version = IPVersion.V4Only # hook for threads self._GLOBAL_DONE = False self.unicast = unicast if apple_p2p and not platform.system() == 'Darwin': raise RuntimeError('Option `apple_p2p` is not supported on non-Apple platforms.') self._listen_socket, self._respond_sockets = create_sockets( interfaces, unicast, ip_version, apple_p2p=apple_p2p ) self.listeners = [] # type: List[RecordUpdateListener] self.browsers = {} # type: Dict[ServiceListener, ServiceBrowser] self.services = {} # type: Dict[str, ServiceInfo] self.servicetypes = {} # type: Dict[str, int] self.cache = DNSCache() self.condition = threading.Condition() self.engine = Engine(self) self.listener = Listener(self) if not unicast: self.engine.add_reader(self.listener, cast(socket.socket, self._listen_socket)) else: for s in self._respond_sockets: self.engine.add_reader(self.listener, s) self.reaper = Reaper(self) self.debug = None # type: Optional[DNSOutgoing] self._handlers_lock = threading.Lock() # ensure we process a full message in one go @property def done(self) -> bool: return self._GLOBAL_DONE def wait(self, timeout: float) -> None: """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) -> None: """Notifies all waiting threads""" with self.condition: self.condition.notify_all() def get_service_info(self, type_: str, name: str, timeout: int = 3000) -> Optional[ServiceInfo]: """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_: str, listener: ServiceListener) -> None: """Adds a listener for a particular service type. This object will then have its add_service and remove_service methods called when services of that type become available and unavailable.""" self.remove_service_listener(listener) self.browsers[listener] = ServiceBrowser(self, type_, listener) def remove_service_listener(self, listener: ServiceListener) -> None: """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) -> None: """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: ServiceInfo, ttl: Optional[int] = None, allow_name_change: bool = False, cooperating_responders: bool = False, ) -> None: """Registers service information to the network with a default TTL. 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. Additionally multiple cooperating responders can register the same service on the network for resilience (if you want this behavior set `cooperating_responders` to `True`).""" if ttl is not None: # ttl argument is used to maintain backward compatibility # Setting TTLs via ServiceInfo is preferred info.host_ttl = ttl info.other_ttl = ttl self.check_service(info, allow_name_change, cooperating_responders) self.services[info.name.lower()] = info if info.type in self.servicetypes: self.servicetypes[info.type] += 1 else: self.servicetypes[info.type] = 1 self._broadcast_service(info) def update_service(self, info: ServiceInfo) -> None: """Registers service information to the network with a default TTL. Zeroconf will then respond to requests for information for that service.""" assert self.services[info.name.lower()] is not None self.services[info.name.lower()] = info self._broadcast_service(info) def _broadcast_service(self, info: ServiceInfo) -> None: 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, info.other_ttl, info.name), 0) out.add_answer_at_time( DNSService( info.name, _TYPE_SRV, _CLASS_IN | _CLASS_UNIQUE, info.host_ttl, info.priority, info.weight, cast(int, info.port), info.server, ), 0, ) out.add_answer_at_time( DNSText(info.name, _TYPE_TXT, _CLASS_IN | _CLASS_UNIQUE, info.other_ttl, info.text), 0 ) for address in info.addresses_by_version(IPVersion.All): type_ = _TYPE_AAAA if _is_v6_address(address) else _TYPE_A out.add_answer_at_time( DNSAddress(info.server, type_, _CLASS_IN | _CLASS_UNIQUE, info.host_ttl, address), 0 ) self.send(out) i += 1 next_time += _REGISTER_TIME def unregister_service(self, info: ServiceInfo) -> None: """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 | _CLASS_UNIQUE, 0, info.priority, info.weight, cast(int, info.port), info.name, ), 0, ) out.add_answer_at_time(DNSText(info.name, _TYPE_TXT, _CLASS_IN | _CLASS_UNIQUE, 0, info.text), 0) for address in info.addresses_by_version(IPVersion.All): type_ = _TYPE_AAAA if _is_v6_address(address) else _TYPE_A out.add_answer_at_time( DNSAddress(info.server, type_, _CLASS_IN | _CLASS_UNIQUE, 0, address), 0 ) self.send(out) i += 1 next_time += _UNREGISTER_TIME def unregister_all_services(self) -> None: """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 | _CLASS_UNIQUE, 0, info.priority, info.weight, cast(int, info.port), info.server, ), 0, ) out.add_answer_at_time( DNSText(info.name, _TYPE_TXT, _CLASS_IN | _CLASS_UNIQUE, 0, info.text), 0 ) for address in info.addresses_by_version(IPVersion.All): type_ = _TYPE_AAAA if _is_v6_address(address) else _TYPE_A out.add_answer_at_time( DNSAddress(info.server, type_, _CLASS_IN | _CLASS_UNIQUE, 0, address), 0 ) self.send(out) i += 1 next_time += _UNREGISTER_TIME def check_service( self, info: ServiceInfo, allow_name_change: bool, cooperating_responders: bool = False ) -> None: """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: if not cooperating_responders: # 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, info.other_ttl, info.name)) self.send(out) i += 1 next_time += _CHECK_TIME def add_listener(self, listener: RecordUpdateListener, question: Optional[DNSQuestion]) -> None: """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: RecordUpdateListener) -> None: """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: float, rec: DNSRecord) -> None: """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: DNSIncoming) -> None: """Deal with incoming response packets. All answers are held in the cache, and listeners are notified.""" with self._handlers_lock: now = current_time_millis() for record in msg.answers: updated = True if record.unique: # https://tools.ietf.org/html/rfc6762#section-10.2 # Since the cache format is keyed on the lower case record name # we can avoid iterating everything in the cache and # only look though entries for the specific name. # entries_with_name will take care of converting to lowercase # # We make a copy of the list that entries_with_name returns # since we cannot iterate over something we might remove for entry in self.cache.entries_with_name(record.name).copy(): if entry == record: updated = False # Check the time first because it is far cheaper # than the __eq__ if (record.created - entry.created > 1000) and DNSEntry.__eq__(entry, record): self.cache.remove(entry) expired = record.is_expired(now) maybe_entry = self.cache.get(record) if not expired: if maybe_entry is not None: maybe_entry.reset_ttl(record) else: self.cache.add(record) if updated: self.update_record(now, record) else: if maybe_entry is not None: self.update_record(now, record) self.cache.remove(maybe_entry) def handle_query(self, msg: DNSIncoming, addr: Optional[str], port: int) -> None: """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_OTHER_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, service.other_ttl, service.name), ) # Add recommended additional answers according to # https://tools.ietf.org/html/rfc6763#section-12.1. out.add_additional_answer( DNSService( service.name, _TYPE_SRV, _CLASS_IN | _CLASS_UNIQUE, service.host_ttl, service.priority, service.weight, cast(int, service.port), service.server, ) ) out.add_additional_answer( DNSText( service.name, _TYPE_TXT, _CLASS_IN | _CLASS_UNIQUE, service.other_ttl, service.text, ) ) for address in service.addresses_by_version(IPVersion.All): type_ = _TYPE_AAAA if _is_v6_address(address) else _TYPE_A out.add_additional_answer( DNSAddress( service.server, type_, _CLASS_IN | _CLASS_UNIQUE, service.host_ttl, address, ) ) 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(): for address in service.addresses_by_version(IPVersion.All): type_ = _TYPE_AAAA if _is_v6_address(address) else _TYPE_A out.add_answer( msg, DNSAddress( question.name, type_, _CLASS_IN | _CLASS_UNIQUE, service.host_ttl, address, ), ) name_to_find = question.name.lower() if name_to_find not in self.services: continue service = self.services[name_to_find] if question.type in (_TYPE_SRV, _TYPE_ANY): out.add_answer( msg, DNSService( question.name, _TYPE_SRV, _CLASS_IN | _CLASS_UNIQUE, service.host_ttl, service.priority, service.weight, cast(int, 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, service.other_ttl, service.text, ), ) if question.type == _TYPE_SRV: for address in service.addresses_by_version(IPVersion.All): type_ = _TYPE_AAAA if _is_v6_address(address) else _TYPE_A out.add_additional_answer( DNSAddress( service.server, type_, _CLASS_IN | _CLASS_UNIQUE, service.host_ttl, 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: DNSOutgoing, addr: Optional[str] = None, port: int = _MDNS_PORT) -> None: """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: if addr is None: real_addr = _MDNS_ADDR6 if s.family == socket.AF_INET6 else _MDNS_ADDR elif not can_send_to(s, addr): continue else: real_addr = addr bytes_sent = s.sendto(packet, 0, (real_addr, port)) except Exception as exc: # TODO stop catching all Exceptions if ( isinstance(exc, OSError) and exc.errno == errno.ENETUNREACH and s.family == socket.AF_INET6 ): # with IPv6 we don't have a reliable way to determine if an interface actually has IPv6 # support, so we have to try and ignore errors. continue # 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) -> None: """Ends the background threads, and prevent this instance from servicing further queries.""" if not self._GLOBAL_DONE: # remove service listeners self.remove_all_service_listeners() self.unregister_all_services() self._GLOBAL_DONE = True # shutdown recv socket and thread if not self.unicast: self.engine.del_reader(cast(socket.socket, self._listen_socket)) cast(socket.socket, self._listen_socket).close() else: for s in self._respond_sockets: self.engine.del_reader(s) self.engine.join() # shutdown the rest self.notify_all() self.reaper.join() for s in self._respond_sockets: s.close()