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340 lines
12 KiB
Python
340 lines
12 KiB
Python
5 years ago
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# Copyright (c) 2011-2015 Denis Bilenko. See LICENSE for details.
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"""
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c-ares based hostname resolver.
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"""
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from __future__ import absolute_import, print_function, division
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import os
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from _socket import gaierror
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from _socket import herror
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from _socket import error
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from _socket import EAI_NONAME
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from gevent._compat import text_type
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from gevent._compat import integer_types
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from gevent._compat import PY3
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from gevent.hub import Waiter
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from gevent.hub import get_hub
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from gevent.socket import AF_UNSPEC
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from gevent.socket import AF_INET
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from gevent.socket import AF_INET6
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from gevent.socket import SOCK_DGRAM
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from gevent.socket import SOCK_STREAM
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from gevent.socket import SOL_TCP
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from gevent.socket import SOL_UDP
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from gevent._config import config
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from gevent._config import AresSettingMixin
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from .cares import channel, InvalidIP # pylint:disable=import-error,no-name-in-module
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from . import _lookup_port as lookup_port
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from . import AbstractResolver
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__all__ = ['Resolver']
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class Resolver(AbstractResolver):
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"""
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Implementation of the resolver API using the `c-ares`_ library.
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This implementation uses the c-ares library to handle name
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resolution. c-ares is natively asynchronous at the socket level
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and so integrates well into gevent's event loop.
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In comparison to :class:`gevent.resolver_thread.Resolver` (which
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delegates to the native system resolver), the implementation is
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much more complex. In addition, there have been reports of it not
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properly honoring certain system configurations (for example, the
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order in which IPv4 and IPv6 results are returned may not match
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the threaded resolver). However, because it does not use threads,
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it may scale better for applications that make many lookups.
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There are some known differences from the system resolver.
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- ``gethostbyname_ex`` and ``gethostbyaddr`` may return
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different for the ``aliaslist`` tuple member. (Sometimes the
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same, sometimes in a different order, sometimes a different
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alias altogether.)
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- ``gethostbyname_ex`` may return the ``ipaddrlist`` in a
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different order.
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- ``getaddrinfo`` does not return ``SOCK_RAW`` results.
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- ``getaddrinfo`` may return results in a different order.
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- Handling of ``.local`` (mDNS) names may be different, even
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if they are listed in the hosts file.
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- c-ares will not resolve ``broadcasthost``, even if listed in
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the hosts file prior to 2020-04-30.
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- This implementation may raise ``gaierror(4)`` where the
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system implementation would raise ``herror(1)`` or vice versa,
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with different error numbers. However, after 2020-04-30, this should be
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much reduced.
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- The results for ``localhost`` may be different. In
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particular, some system resolvers will return more results
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from ``getaddrinfo`` than c-ares does, such as SOCK_DGRAM
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results, and c-ares may report more ips on a multi-homed
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host.
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- The system implementation may return some names fully qualified, where
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this implementation returns only the host name. This appears to be
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the case only with entries found in ``/etc/hosts``.
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- c-ares supports a limited set of flags for ``getnameinfo`` and
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``getaddrinfo``; unknown flags are ignored. System-specific flags
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such as ``AI_V4MAPPED_CFG`` are not supported.
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- ``getaddrinfo`` may return canonical names even without the ``AI_CANONNAME``
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being set.
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.. caution::
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This module is considered extremely experimental on PyPy, and
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due to its implementation in cython, it may be slower. It may also lead to
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interpreter crashes.
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.. versionchanged:: 1.5.0
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This version of gevent typically embeds c-ares 1.15.0 or newer. In
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that version of c-ares, domains ending in ``.onion`` `are never
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resolved <https://github.com/c-ares/c-ares/issues/196>`_ or even
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sent to the DNS server.
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.. versionchanged:: 20.5.0
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``getaddrinfo`` is now implemented using the native c-ares function
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from c-ares 1.16 or newer.
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.. versionchanged:: 20.5.0
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Now ``herror`` and ``gaierror`` are raised more consistently with
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the standard library resolver, and have more consistent errno values.
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Handling of localhost and broadcast names is now more consistent.
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.. _c-ares: http://c-ares.haxx.se
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"""
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cares_class = channel
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def __init__(self, hub=None, use_environ=True, **kwargs):
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if hub is None:
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hub = get_hub()
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self.hub = hub
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if use_environ:
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for setting in config.settings.values():
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if isinstance(setting, AresSettingMixin):
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value = setting.get()
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if value is not None:
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kwargs.setdefault(setting.kwarg_name, value)
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self.cares = self.cares_class(hub.loop, **kwargs)
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self.pid = os.getpid()
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self.params = kwargs
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self.fork_watcher = hub.loop.fork(ref=False)
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self.fork_watcher.start(self._on_fork)
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def __repr__(self):
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return '<gevent.resolver_ares.Resolver at 0x%x ares=%r>' % (id(self), self.cares)
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def _on_fork(self):
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# NOTE: See comment in gevent.hub.reinit.
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pid = os.getpid()
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if pid != self.pid:
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self.hub.loop.run_callback(self.cares.destroy)
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self.cares = self.cares_class(self.hub.loop, **self.params)
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self.pid = pid
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def close(self):
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if self.cares is not None:
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self.hub.loop.run_callback(self.cares.destroy)
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self.cares = None
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self.fork_watcher.stop()
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def _gethostbyname_ex(self, hostname_bytes, family):
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while True:
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ares = self.cares
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try:
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waiter = Waiter(self.hub)
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ares.gethostbyname(waiter, hostname_bytes, family)
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result = waiter.get()
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if not result[-1]:
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raise herror(EAI_NONAME, self.EAI_NONAME_MSG)
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return result
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except herror as ex:
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if ares is self.cares:
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if ex.args[0] == 1:
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# Somewhere along the line, the internal
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# implementation of gethostbyname_ex changed to invoke
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# getaddrinfo() as a first pass, much like we do for ``getnameinfo()``;
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# this means it raises a different error for not-found hosts.
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raise gaierror(EAI_NONAME, self.EAI_NONAME_MSG)
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raise
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# "self.cares is not ares" means channel was destroyed (because we were forked)
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def _lookup_port(self, port, socktype):
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return lookup_port(port, socktype)
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def __getaddrinfo(
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self, host, port,
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family=0, socktype=0, proto=0, flags=0,
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fill_in_type_proto=True
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):
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"""
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Returns a list ``(family, socktype, proto, canonname, sockaddr)``
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:raises gaierror: If no results are found.
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"""
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# pylint:disable=too-many-locals,too-many-branches
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if isinstance(host, text_type):
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host = host.encode('idna')
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if isinstance(port, text_type):
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port = port.encode('ascii')
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elif isinstance(port, integer_types):
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if port == 0:
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port = None
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else:
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port = str(port).encode('ascii')
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waiter = Waiter(self.hub)
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self.cares.getaddrinfo(
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waiter,
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host,
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port,
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family,
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socktype,
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proto,
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flags,
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)
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# Result is a list of:
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# (family, socktype, proto, canonname, sockaddr)
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# Where sockaddr depends on family; for INET it is
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# (address, port)
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# and INET6 is
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# (address, port, flow info, scope id)
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result = waiter.get()
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if not result:
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raise gaierror(EAI_NONAME, self.EAI_NONAME_MSG)
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if fill_in_type_proto:
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# c-ares 1.16 DOES NOT fill in socktype or proto in the results,
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# ever. It's at least supposed to do that if they were given as
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# hints, but it doesn't (https://github.com/c-ares/c-ares/issues/317)
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# Sigh.
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# The SOL_* constants are another (older?) name for IPPROTO_*
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if socktype:
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hard_type_proto = [
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(socktype, SOL_TCP if socktype == SOCK_STREAM else SOL_UDP),
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]
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elif proto:
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hard_type_proto = [
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(SOCK_STREAM if proto == SOL_TCP else SOCK_DGRAM, proto),
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]
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else:
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hard_type_proto = [
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(SOCK_STREAM, SOL_TCP),
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(SOCK_DGRAM, SOL_UDP),
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]
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result = [
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(rfamily,
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hard_type if not rtype else rtype,
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hard_proto if not rproto else rproto,
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rcanon,
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raddr)
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for rfamily, rtype, rproto, rcanon, raddr
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in result
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for hard_type, hard_proto
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in hard_type_proto
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]
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return result
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def _getaddrinfo(self, host_bytes, port, family, socktype, proto, flags):
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while True:
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ares = self.cares
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try:
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return self.__getaddrinfo(host_bytes, port, family, socktype, proto, flags)
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except gaierror:
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if ares is self.cares:
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raise
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def __gethostbyaddr(self, ip_address):
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waiter = Waiter(self.hub)
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try:
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self.cares.gethostbyaddr(waiter, ip_address)
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return waiter.get()
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except InvalidIP:
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result = self._getaddrinfo(ip_address, None,
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family=AF_UNSPEC, socktype=SOCK_DGRAM,
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proto=0, flags=0)
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if not result:
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raise
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_ip_address = result[0][-1][0]
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if isinstance(_ip_address, text_type):
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_ip_address = _ip_address.encode('ascii')
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if _ip_address == ip_address:
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raise
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waiter.clear()
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self.cares.gethostbyaddr(waiter, _ip_address)
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return waiter.get()
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def _gethostbyaddr(self, ip_address_bytes):
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while True:
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ares = self.cares
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try:
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return self.__gethostbyaddr(ip_address_bytes)
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except herror:
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if ares is self.cares:
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raise
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def __getnameinfo(self, hostname, port, sockaddr, flags):
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result = self.__getaddrinfo(
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hostname, port,
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family=AF_UNSPEC, socktype=SOCK_DGRAM,
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proto=0, flags=0,
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fill_in_type_proto=False)
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if len(result) != 1:
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raise error('sockaddr resolved to multiple addresses')
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family, _socktype, _proto, _name, address = result[0]
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if family == AF_INET:
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if len(sockaddr) != 2:
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raise error("IPv4 sockaddr must be 2 tuple")
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elif family == AF_INET6:
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address = address[:2] + sockaddr[2:]
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waiter = Waiter(self.hub)
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self.cares.getnameinfo(waiter, address, flags)
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node, service = waiter.get()
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if service is None and PY3:
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# ares docs: "If the query did not complete
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# successfully, or one of the values was not
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# requested, node or service will be NULL ". Python 2
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# allows that for the service, but Python 3 raises
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# an error. This is tested by test_socket in py 3.4
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err = gaierror(EAI_NONAME, self.EAI_NONAME_MSG)
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err.errno = EAI_NONAME
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raise err
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return node, service or '0'
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def _getnameinfo(self, address_bytes, port, sockaddr, flags):
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while True:
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ares = self.cares
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try:
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return self.__getnameinfo(address_bytes, port, sockaddr, flags)
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except gaierror:
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if ares is self.cares:
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raise
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# # Things that need proper error handling
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# gethostbyaddr = AbstractResolver.convert_gaierror_to_herror(AbstractResolver.gethostbyaddr)
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