python-zeroconf/src/zeroconf/_transport.py at master · python-zeroconf/python-zeroconf · GitHub

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

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

"""

from __future__ import annotations

import asyncio

import logging

import socket

import sys

from typing import cast

from ._logger import log

def _strip_zone(address: str) -> str:

"""Drop a ``%zone`` suffix from an IPv6 address string."""

percent = address.find("%")

return address[:percent] if percent != -1 else address

class _WrappedTransport:

"""A wrapper for transports."""

__slots__ = (

"fileno",

"is_ipv6",

"multicast_index",

"sock",

"sock_name",

"transport",

)

def __init__(

self,

transport: asyncio.DatagramTransport,

is_ipv6: bool,

sock: socket.socket,

fileno: int,

sock_name: tuple,

multicast_index: int = 0,

) -> None:

"""Initialize the wrapped transport.

``multicast_index`` is the IPV6_MULTICAST_IF interface index the

sender joined the group with, carried so a group leave uses the same

index the join did (the bound socket's scope_id is 0 for global IPv6).

"""

self.transport = transport

self.is_ipv6 = is_ipv6

self.sock = sock

self.fileno = fileno

self.sock_name = sock_name

self.multicast_index = multicast_index

@property

def interface_key(self) -> tuple[str, int]:

"""The bound (address, scope_id) identifying this sender's interface.

Used to diff senders against the desired interface set. The scope_id

keeps link-local IPv6 addresses that repeat across interfaces (same

address, different zone) from colliding to one key.

"""

sock_name = self.sock_name

if self.is_ipv6:

scope_id = cast(int, sock_name[3]) if len(sock_name) > 3 else 0

return (_strip_zone(sock_name[0]), scope_id)

return (cast(str, sock_name[0]), 0)

@property

def multicast_interface(self) -> str | tuple[tuple[str, int, int], int]:

"""The interface value a group leave takes for this transport.

For IPv6 this carries ``multicast_index`` (the index the join used),

not the bound scope_id, so leave and join stay symmetric.

"""

address, _scope_id = self.interface_key

if self.is_ipv6:

return ((address, 0, 0), self.multicast_index)

return address

def make_wrapped_transport(transport: asyncio.DatagramTransport) -> _WrappedTransport:

"""Make a wrapped transport."""

sock: socket.socket = transport.get_extra_info("socket")

is_ipv6 = sock.family == socket.AF_INET6

multicast_index = 0

if is_ipv6:

# IPV6_MULTICAST_IF holds the interface index new_respond_socket

# joined the group with; capture it so a later group leave uses the

# same index. This is on the startup/connection path, and the index

# only selects the interface for a future (benign) group leave, so a

# read failure (Windows rejects it with WSAEINVAL; other platforms

# shouldn't) keeps the default index 0 rather than aborting setup.

try:

multicast_index = sock.getsockopt(socket.IPPROTO_IPV6, socket.IPV6_MULTICAST_IF)

except OSError as exc:

# Windows rejects this read (WSAEINVAL) for every v6 socket, so it is

# expected and benign there; keep it at debug. Elsewhere a failure is

# unexpected and means a later group leave uses the wrong index (a

# benign no-op that leaks the membership), so surface it at warning.

level = logging.DEBUG if sys.platform == "win32" else logging.WARNING

log.log(level, "Unable to read IPV6_MULTICAST_IF, using default index 0: %s", exc)

return _WrappedTransport(

transport=transport,

is_ipv6=is_ipv6,

sock=sock,

fileno=sock.fileno(),

sock_name=sock.getsockname(),

multicast_index=multicast_index,

)

python-zeroconf/src/zeroconf/_transport.py at master · python-zeroconf/python-zeroconf · GitHub

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