/usr/lib/python3/dist-packages/tornado/platform/caresresolver.py is in python3-tornado 4.5.3-1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 | from __future__ import absolute_import, division, print_function
import pycares # type: ignore
import socket
from tornado import gen
from tornado.ioloop import IOLoop
from tornado.netutil import Resolver, is_valid_ip
class CaresResolver(Resolver):
"""Name resolver based on the c-ares library.
This is a non-blocking and non-threaded resolver. It may not produce
the same results as the system resolver, but can be used for non-blocking
resolution when threads cannot be used.
c-ares fails to resolve some names when ``family`` is ``AF_UNSPEC``,
so it is only recommended for use in ``AF_INET`` (i.e. IPv4). This is
the default for ``tornado.simple_httpclient``, but other libraries
may default to ``AF_UNSPEC``.
.. versionchanged:: 4.1
The ``io_loop`` argument is deprecated.
"""
def initialize(self, io_loop=None):
self.io_loop = io_loop or IOLoop.current()
self.channel = pycares.Channel(sock_state_cb=self._sock_state_cb)
self.fds = {}
def _sock_state_cb(self, fd, readable, writable):
state = ((IOLoop.READ if readable else 0) |
(IOLoop.WRITE if writable else 0))
if not state:
self.io_loop.remove_handler(fd)
del self.fds[fd]
elif fd in self.fds:
self.io_loop.update_handler(fd, state)
self.fds[fd] = state
else:
self.io_loop.add_handler(fd, self._handle_events, state)
self.fds[fd] = state
def _handle_events(self, fd, events):
read_fd = pycares.ARES_SOCKET_BAD
write_fd = pycares.ARES_SOCKET_BAD
if events & IOLoop.READ:
read_fd = fd
if events & IOLoop.WRITE:
write_fd = fd
self.channel.process_fd(read_fd, write_fd)
@gen.coroutine
def resolve(self, host, port, family=0):
if is_valid_ip(host):
addresses = [host]
else:
# gethostbyname doesn't take callback as a kwarg
self.channel.gethostbyname(host, family, (yield gen.Callback(1)))
callback_args = yield gen.Wait(1)
assert isinstance(callback_args, gen.Arguments)
assert not callback_args.kwargs
result, error = callback_args.args
if error:
raise IOError('C-Ares returned error %s: %s while resolving %s' %
(error, pycares.errno.strerror(error), host))
addresses = result.addresses
addrinfo = []
for address in addresses:
if '.' in address:
address_family = socket.AF_INET
elif ':' in address:
address_family = socket.AF_INET6
else:
address_family = socket.AF_UNSPEC
if family != socket.AF_UNSPEC and family != address_family:
raise IOError('Requested socket family %d but got %d' %
(family, address_family))
addrinfo.append((address_family, (address, port)))
raise gen.Return(addrinfo)
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