75 lines
2.9 KiB
Python
75 lines
2.9 KiB
Python
import pycares
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import socket
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from tornado import gen
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from tornado.ioloop import IOLoop
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from tornado.netutil import Resolver, is_valid_ip
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class CaresResolver(Resolver):
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"""Name resolver based on the c-ares library.
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This is a non-blocking and non-threaded resolver. It may not produce
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the same results as the system resolver, but can be used for non-blocking
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resolution when threads cannot be used.
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c-ares fails to resolve some names when ``family`` is ``AF_UNSPEC``,
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so it is only recommended for use in ``AF_INET`` (i.e. IPv4). This is
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the default for ``tornado.simple_httpclient``, but other libraries
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may default to ``AF_UNSPEC``.
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"""
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def initialize(self, io_loop=None):
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self.io_loop = io_loop or IOLoop.current()
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self.channel = pycares.Channel(sock_state_cb=self._sock_state_cb)
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self.fds = {}
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def _sock_state_cb(self, fd, readable, writable):
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state = ((IOLoop.READ if readable else 0) |
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(IOLoop.WRITE if writable else 0))
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if not state:
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self.io_loop.remove_handler(fd)
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del self.fds[fd]
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elif fd in self.fds:
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self.io_loop.update_handler(fd, state)
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self.fds[fd] = state
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else:
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self.io_loop.add_handler(fd, self._handle_events, state)
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self.fds[fd] = state
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def _handle_events(self, fd, events):
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read_fd = pycares.ARES_SOCKET_BAD
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write_fd = pycares.ARES_SOCKET_BAD
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if events & IOLoop.READ:
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read_fd = fd
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if events & IOLoop.WRITE:
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write_fd = fd
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self.channel.process_fd(read_fd, write_fd)
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@gen.coroutine
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def resolve(self, host, port, family=0):
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if is_valid_ip(host):
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addresses = [host]
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else:
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# gethostbyname doesn't take callback as a kwarg
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self.channel.gethostbyname(host, family, (yield gen.Callback(1)))
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callback_args = yield gen.Wait(1)
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assert isinstance(callback_args, gen.Arguments)
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assert not callback_args.kwargs
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result, error = callback_args.args
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if error:
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raise Exception('C-Ares returned error %s: %s while resolving %s' %
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(error, pycares.errno.strerror(error), host))
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addresses = result.addresses
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addrinfo = []
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for address in addresses:
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if '.' in address:
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address_family = socket.AF_INET
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elif ':' in address:
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address_family = socket.AF_INET6
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else:
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address_family = socket.AF_UNSPEC
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if family != socket.AF_UNSPEC and family != address_family:
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raise Exception('Requested socket family %d but got %d' %
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(family, address_family))
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addrinfo.append((address_family, (address, port)))
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raise gen.Return(addrinfo)
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