# Copyright 2011 Facebook
# Licensed under the Apache License, Version 2.0 (the "License"); you may
# not use this file except in compliance with the License. You may obtain
# a copy of the License at
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
# License for the specific language governing permissions and limitations
# under the License.
"""Miscellaneous network utility code."""
from __future__ import absolute_import, division, print_function, with_statement
from tornado.concurrent import dummy_executor, run_on_executor
from tornado.ioloop import IOLoop
from tornado.platform.auto import set_close_exec
from tornado.util import u, Configurable, errno_from_exception
# ssl is not available on Google App Engine
ssl = None
xrange # py2
xrange = range # py3
if hasattr(ssl, 'match_hostname') and hasattr(ssl, 'CertificateError'): # python 3.2+
ssl_match_hostname = ssl.match_hostname
SSLCertificateError = ssl.CertificateError
elif ssl is None:
ssl_match_hostname = SSLCertificateError = None
ssl_match_hostname = backports.ssl_match_hostname.match_hostname
SSLCertificateError = backports.ssl_match_hostname.CertificateError
# ThreadedResolver runs getaddrinfo on a thread. If the hostname is unicode,
# getaddrinfo attempts to import encodings.idna. If this is done at
# module-import time, the import lock is already held by the main thread,
# leading to deadlock. Avoid it by caching the idna encoder on the main
# thread now.
# These errnos indicate that a non-blocking operation must be retried
# at a later time. On most platforms they're the same value, but on
# some they differ.
_ERRNO_WOULDBLOCK = (errno.EWOULDBLOCK, errno.EAGAIN)
if hasattr(errno, "WSAEWOULDBLOCK"):
_ERRNO_WOULDBLOCK += (errno.WSAEWOULDBLOCK,)
# Default backlog used when calling sock.listen()
_DEFAULT_BACKLOG = 128
[docs]def bind_sockets(port, address=None, family=socket.AF_UNSPEC,
"""Creates listening sockets bound to the given port and address.
Returns a list of socket objects (multiple sockets are returned if
the given address maps to multiple IP addresses, which is most common
for mixed IPv4 and IPv6 use).
Address may be either an IP address or hostname. If it's a hostname,
the server will listen on all IP addresses associated with the
name. Address may be an empty string or None to listen on all
available interfaces. Family may be set to either `socket.AF_INET`
or `socket.AF_INET6` to restrict to IPv4 or IPv6 addresses, otherwise
both will be used if available.
The ``backlog`` argument has the same meaning as for
``flags`` is a bitmask of AI_* flags to `~socket.getaddrinfo`, like
``socket.AI_PASSIVE | socket.AI_NUMERICHOST``.
sockets = 
if address == "":
address = None
if not socket.has_ipv6 and family == socket.AF_UNSPEC:
# Python can be compiled with --disable-ipv6, which causes
# operations on AF_INET6 sockets to fail, but does not
# automatically exclude those results from getaddrinfo
family = socket.AF_INET
if flags is None:
flags = socket.AI_PASSIVE
bound_port = None
for res in set(socket.getaddrinfo(address, port, family, socket.SOCK_STREAM,
af, socktype, proto, canonname, sockaddr = res
if (sys.platform == 'darwin' and address == 'localhost' and
af == socket.AF_INET6 and sockaddr != 0):
# Mac OS X includes a link-local address fe80::1%lo0 in the
# getaddrinfo results for 'localhost'. However, the firewall
# doesn't understand that this is a local address and will
# prompt for access (often repeatedly, due to an apparent
# bug in its ability to remember granting access to an
# application). Skip these addresses.
sock = socket.socket(af, socktype, proto)
except socket.error as e:
if errno_from_exception(e) == errno.EAFNOSUPPORT:
if os.name != 'nt':
sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
if af == socket.AF_INET6:
# On linux, ipv6 sockets accept ipv4 too by default,
# but this makes it impossible to bind to both
# 0.0.0.0 in ipv4 and :: in ipv6. On other systems,
# separate sockets *must* be used to listen for both ipv4
# and ipv6. For consistency, always disable ipv4 on our
# ipv6 sockets and use a separate ipv4 socket when needed.
# Python 2.x on windows doesn't have IPPROTO_IPV6.
if hasattr(socket, "IPPROTO_IPV6"):
sock.setsockopt(socket.IPPROTO_IPV6, socket.IPV6_V6ONLY, 1)
# automatic port allocation with port=None
# should bind on the same port on IPv4 and IPv6
host, requested_port = sockaddr[:2]
if requested_port == 0 and bound_port is not None:
sockaddr = tuple([host, bound_port] + list(sockaddr[2:]))
bound_port = sock.getsockname()
if hasattr(socket, 'AF_UNIX'):
[docs] def bind_unix_socket(file, mode=0o600, backlog=_DEFAULT_BACKLOG):
"""Creates a listening unix socket.
If a socket with the given name already exists, it will be deleted.
If any other file with that name exists, an exception will be
Returns a socket object (not a list of socket objects like
sock = socket.socket(socket.AF_UNIX, socket.SOCK_STREAM)
sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
st = os.stat(file)
except OSError as err:
if errno_from_exception(err) != errno.ENOENT:
raise ValueError("File %s exists and is not a socket", file)
[docs]def add_accept_handler(sock, callback, io_loop=None):
"""Adds an `.IOLoop` event handler to accept new connections on ``sock``.
When a connection is accepted, ``callback(connection, address)`` will
be run (``connection`` is a socket object, and ``address`` is the
address of the other end of the connection). Note that this signature
is different from the ``callback(fd, events)`` signature used for
if io_loop is None:
io_loop = IOLoop.current()
def accept_handler(fd, events):
# More connections may come in while we're handling callbacks;
# to prevent starvation of other tasks we must limit the number
# of connections we accept at a time. Ideally we would accept
# up to the number of connections that were waiting when we
# entered this method, but this information is not available
# (and rearranging this method to call accept() as many times
# as possible before running any callbacks would have adverse
# effects on load balancing in multiprocess configurations).
# Instead, we use the (default) listen backlog as a rough
# heuristic for the number of connections we can reasonably
# accept at once.
for i in xrange(_DEFAULT_BACKLOG):
connection, address = sock.accept()
except socket.error as e:
# _ERRNO_WOULDBLOCK indicate we have accepted every
# connection that is available.
if errno_from_exception(e) in _ERRNO_WOULDBLOCK:
# ECONNABORTED indicates that there was a connection
# but it was closed while still in the accept queue.
# (observed on FreeBSD).
if errno_from_exception(e) == errno.ECONNABORTED:
io_loop.add_handler(sock, accept_handler, IOLoop.READ)
"""Returns true if the given string is a well-formed IP address.
Supports IPv4 and IPv6.
if not ip or '\x00' in ip:
# getaddrinfo resolves empty strings to localhost, and truncates
# on zero bytes.
res = socket.getaddrinfo(ip, 0, socket.AF_UNSPEC,
except socket.gaierror as e:
if e.args == socket.EAI_NONAME:
"""Configurable asynchronous DNS resolver interface.
By default, a blocking implementation is used (which simply calls
`socket.getaddrinfo`). An alternative implementation can be
chosen with the `Resolver.configure <.Configurable.configure>`
The implementations of this interface included with Tornado are
[docs] def resolve(self, host, port, family=socket.AF_UNSPEC, callback=None):
"""Resolves an address.
The ``host`` argument is a string which may be a hostname or a
literal IP address.
Returns a `.Future` whose result is a list of (family,
address) pairs, where address is a tuple suitable to pass to
`socket.connect <socket.socket.connect>` (i.e. a ``(host,
port)`` pair for IPv4; additional fields may be present for
IPv6). If a ``callback`` is passed, it will be run with the
result as an argument when it is complete.
[docs] def close(self):
"""Closes the `Resolver`, freeing any resources used.
.. versionadded:: 3.1
"""Resolver implementation using a `concurrent.futures.Executor`.
Use this instead of `ThreadedResolver` when you require additional
control over the executor being used.
The executor will be shut down when the resolver is closed unless
``close_resolver=False``; use this if you want to reuse the same
def initialize(self, io_loop=None, executor=None, close_executor=True):
self.io_loop = io_loop or IOLoop.current()
if executor is not None:
self.executor = executor
self.close_executor = close_executor
self.executor = dummy_executor
self.close_executor = False
self.executor = None
def resolve(self, host, port, family=socket.AF_UNSPEC):
# On Solaris, getaddrinfo fails if the given port is not found
# in /etc/services and no socket type is given, so we must pass
# one here. The socket type used here doesn't seem to actually
# matter (we discard the one we get back in the results),
# so the addresses we return should still be usable with SOCK_DGRAM.
addrinfo = socket.getaddrinfo(host, port, family, socket.SOCK_STREAM)
results = 
for family, socktype, proto, canonname, address in addrinfo:
"""Default `Resolver` implementation, using `socket.getaddrinfo`.
The `.IOLoop` will be blocked during the resolution, although the
callback will not be run until the next `.IOLoop` iteration.
def initialize(self, io_loop=None):
"""Multithreaded non-blocking `Resolver` implementation.
Requires the `concurrent.futures` package to be installed
(available in the standard library since Python 3.2,
installable with ``pip install futures`` in older versions).
The thread pool size can be configured with::
.. versionchanged:: 3.1
All ``ThreadedResolvers`` share a single thread pool, whose
size is set by the first one to be created.
_threadpool = None
_threadpool_pid = None
def initialize(self, io_loop=None, num_threads=10):
threadpool = ThreadedResolver._create_threadpool(num_threads)
io_loop=io_loop, executor=threadpool, close_executor=False)
def _create_threadpool(cls, num_threads):
pid = os.getpid()
if cls._threadpool_pid != pid:
# Threads cannot survive after a fork, so if our pid isn't what it
# was when we created the pool then delete it.
cls._threadpool = None
if cls._threadpool is None:
from concurrent.futures import ThreadPoolExecutor
cls._threadpool = ThreadPoolExecutor(num_threads)
cls._threadpool_pid = pid
"""Wraps a resolver with a mapping of overrides.
This can be used to make local DNS changes (e.g. for testing)
without modifying system-wide settings.
The mapping can contain either host strings or host-port pairs.
def initialize(self, resolver, mapping):
self.resolver = resolver
self.mapping = mapping
def resolve(self, host, port, *args, **kwargs):
if (host, port) in self.mapping:
host, port = self.mapping[(host, port)]
elif host in self.mapping:
host = self.mapping[host]
return self.resolver.resolve(host, port, *args, **kwargs)
# These are the keyword arguments to ssl.wrap_socket that must be translated
# to their SSLContext equivalents (the other arguments are still passed
# to SSLContext.wrap_socket).
_SSL_CONTEXT_KEYWORDS = frozenset(['ssl_version', 'certfile', 'keyfile',
'cert_reqs', 'ca_certs', 'ciphers'])
"""Try to convert an ``ssl_options`` dictionary to an
The ``ssl_options`` dictionary contains keywords to be passed to
`ssl.wrap_socket`. In Python 3.2+, `ssl.SSLContext` objects can
be used instead. This function converts the dict form to its
`~ssl.SSLContext` equivalent, and may be used when a component which
accepts both forms needs to upgrade to the `~ssl.SSLContext` version
to use features like SNI or NPN.
if isinstance(ssl_options, dict):
assert all(k in _SSL_CONTEXT_KEYWORDS for k in ssl_options), ssl_options
if (not hasattr(ssl, 'SSLContext') or
context = ssl.SSLContext(
if 'certfile' in ssl_options:
context.load_cert_chain(ssl_options['certfile'], ssl_options.get('keyfile', None))
if 'cert_reqs' in ssl_options:
context.verify_mode = ssl_options['cert_reqs']
if 'ca_certs' in ssl_options:
if 'ciphers' in ssl_options:
if hasattr(ssl, 'OP_NO_COMPRESSION'):
# Disable TLS compression to avoid CRIME and related attacks.
# This constant wasn't added until python 3.3.
context.options |= ssl.OP_NO_COMPRESSION
[docs]def ssl_wrap_socket(socket, ssl_options, server_hostname=None, **kwargs):
"""Returns an ``ssl.SSLSocket`` wrapping the given socket.
``ssl_options`` may be either a dictionary (as accepted by
`ssl_options_to_context`) or an `ssl.SSLContext` object.
Additional keyword arguments are passed to ``wrap_socket``
(either the `~ssl.SSLContext` method or the `ssl` module function
context = ssl_options_to_context(ssl_options)
if hasattr(ssl, 'SSLContext') and isinstance(context, ssl.SSLContext):
if server_hostname is not None and getattr(ssl, 'HAS_SNI'):
# Python doesn't have server-side SNI support so we can't
# really unittest this, but it can be manually tested with
# python3.2 -m tornado.httpclient https://sni.velox.ch
return context.wrap_socket(socket, server_hostname=server_hostname,
return context.wrap_socket(socket, **kwargs)
return ssl.wrap_socket(socket, **dict(context, **kwargs))