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python3.10
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support
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socket_helper.py
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import contextlib import errno import socket import unittest import sys from .. import support HOST = "localhost" HOSTv4 = "127.0.0.1" HOSTv6 = "::1" def find_unused_port(family=socket.AF_INET, socktype=socket.SOCK_STREAM): """Returns an unused port that should be suitable for binding. This is achieved by creating a temporary socket with the same family and type as the 'sock' parameter (default is AF_INET, SOCK_STREAM), and binding it to the specified host address (defaults to 0.0.0.0) with the port set to 0, eliciting an unused ephemeral port from the OS. The temporary socket is then closed and deleted, and the ephemeral port is returned. Either this method or bind_port() should be used for any tests where a server socket needs to be bound to a particular port for the duration of the test. Which one to use depends on whether the calling code is creating a python socket, or if an unused port needs to be provided in a constructor or passed to an external program (i.e. the -accept argument to openssl's s_server mode). Always prefer bind_port() over find_unused_port() where possible. Hard coded ports should *NEVER* be used. As soon as a server socket is bound to a hard coded port, the ability to run multiple instances of the test simultaneously on the same host is compromised, which makes the test a ticking time bomb in a buildbot environment. On Unix buildbots, this may simply manifest as a failed test, which can be recovered from without intervention in most cases, but on Windows, the entire python process can completely and utterly wedge, requiring someone to log in to the buildbot and manually kill the affected process. (This is easy to reproduce on Windows, unfortunately, and can be traced to the SO_REUSEADDR socket option having different semantics on Windows versus Unix/Linux. On Unix, you can't have two AF_INET SOCK_STREAM sockets bind, listen and then accept connections on identical host/ports. An EADDRINUSE OSError will be raised at some point (depending on the platform and the order bind and listen were called on each socket). However, on Windows, if SO_REUSEADDR is set on the sockets, no EADDRINUSE will ever be raised when attempting to bind two identical host/ports. When accept() is called on each socket, the second caller's process will steal the port from the first caller, leaving them both in an awkwardly wedged state where they'll no longer respond to any signals or graceful kills, and must be forcibly killed via OpenProcess()/TerminateProcess(). The solution on Windows is to use the SO_EXCLUSIVEADDRUSE socket option instead of SO_REUSEADDR, which effectively affords the same semantics as SO_REUSEADDR on Unix. Given the propensity of Unix developers in the Open Source world compared to Windows ones, this is a common mistake. A quick look over OpenSSL's 0.9.8g source shows that they use SO_REUSEADDR when openssl.exe is called with the 's_server' option, for example. See http://bugs.python.org/issue2550 for more info. The following site also has a very thorough description about the implications of both REUSEADDR and EXCLUSIVEADDRUSE on Windows: https://learn.microsoft.com/windows/win32/winsock/using-so-reuseaddr-and-so-exclusiveaddruse XXX: although this approach is a vast improvement on previous attempts to elicit unused ports, it rests heavily on the assumption that the ephemeral port returned to us by the OS won't immediately be dished back out to some other process when we close and delete our temporary socket but before our calling code has a chance to bind the returned port. We can deal with this issue if/when we come across it. """ with socket.socket(family, socktype) as tempsock: port = bind_port(tempsock) del tempsock return port def bind_port(sock, host=HOST): """Bind the socket to a free port and return the port number. Relies on ephemeral ports in order to ensure we are using an unbound port. This is important as many tests may be running simultaneously, especially in a buildbot environment. This method raises an exception if the sock.family is AF_INET and sock.type is SOCK_STREAM, *and* the socket has SO_REUSEADDR or SO_REUSEPORT set on it. Tests should *never* set these socket options for TCP/IP sockets. The only case for setting these options is testing multicasting via multiple UDP sockets. Additionally, if the SO_EXCLUSIVEADDRUSE socket option is available (i.e. on Windows), it will be set on the socket. This will prevent anyone else from bind()'ing to our host/port for the duration of the test. """ if sock.family == socket.AF_INET and sock.type == socket.SOCK_STREAM: if hasattr(socket, 'SO_REUSEADDR'): if sock.getsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR) == 1: raise support.TestFailed("tests should never set the " "SO_REUSEADDR socket option on " "TCP/IP sockets!") if hasattr(socket, 'SO_REUSEPORT'): try: if sock.getsockopt(socket.SOL_SOCKET, socket.SO_REUSEPORT) == 1: raise support.TestFailed("tests should never set the " "SO_REUSEPORT socket option on " "TCP/IP sockets!") except OSError: # Python's socket module was compiled using modern headers # thus defining SO_REUSEPORT but this process is running # under an older kernel that does not support SO_REUSEPORT. pass if hasattr(socket, 'SO_EXCLUSIVEADDRUSE'): sock.setsockopt(socket.SOL_SOCKET, socket.SO_EXCLUSIVEADDRUSE, 1) sock.bind((host, 0)) port = sock.getsockname()[1] return port def bind_unix_socket(sock, addr): """Bind a unix socket, raising SkipTest if PermissionError is raised.""" assert sock.family == socket.AF_UNIX try: sock.bind(addr) except PermissionError: sock.close() raise unittest.SkipTest('cannot bind AF_UNIX sockets') def _is_ipv6_enabled(): """Check whether IPv6 is enabled on this host.""" if socket.has_ipv6: sock = None try: sock = socket.socket(socket.AF_INET6, socket.SOCK_STREAM) sock.bind((HOSTv6, 0)) return True except OSError: pass finally: if sock: sock.close() return False IPV6_ENABLED = _is_ipv6_enabled() _bind_nix_socket_error = None def skip_unless_bind_unix_socket(test): """Decorator for tests requiring a functional bind() for unix sockets.""" if not hasattr(socket, 'AF_UNIX'): return unittest.skip('No UNIX Sockets')(test) global _bind_nix_socket_error if _bind_nix_socket_error is None: from .os_helper import TESTFN, unlink path = TESTFN + "can_bind_unix_socket" with socket.socket(socket.AF_UNIX) as sock: try: sock.bind(path) _bind_nix_socket_error = False except OSError as e: _bind_nix_socket_error = e finally: unlink(path) if _bind_nix_socket_error: msg = 'Requires a functional unix bind(): %s' % _bind_nix_socket_error return unittest.skip(msg)(test) else: return test def get_socket_conn_refused_errs(): """ Get the different socket error numbers ('errno') which can be received when a connection is refused. """ errors = [errno.ECONNREFUSED] if hasattr(errno, 'ENETUNREACH'): # On Solaris, ENETUNREACH is returned sometimes instead of ECONNREFUSED errors.append(errno.ENETUNREACH) if hasattr(errno, 'EADDRNOTAVAIL'): # bpo-31910: socket.create_connection() fails randomly # with EADDRNOTAVAIL on Travis CI errors.append(errno.EADDRNOTAVAIL) if hasattr(errno, 'EHOSTUNREACH'): # bpo-37583: The destination host cannot be reached errors.append(errno.EHOSTUNREACH) if not IPV6_ENABLED: errors.append(errno.EAFNOSUPPORT) return errors _NOT_SET = object() @contextlib.contextmanager def transient_internet(resource_name, *, timeout=_NOT_SET, errnos=()): """Return a context manager that raises ResourceDenied when various issues with the internet connection manifest themselves as exceptions.""" import nntplib import urllib.error if timeout is _NOT_SET: timeout = support.INTERNET_TIMEOUT default_errnos = [ ('ECONNREFUSED', 111), ('ECONNRESET', 104), ('EHOSTUNREACH', 113), ('ENETUNREACH', 101), ('ETIMEDOUT', 110), # socket.create_connection() fails randomly with # EADDRNOTAVAIL on Travis CI. ('EADDRNOTAVAIL', 99), ] default_gai_errnos = [ ('EAI_AGAIN', -3), ('EAI_FAIL', -4), ('EAI_NONAME', -2), ('EAI_NODATA', -5), # Encountered when trying to resolve IPv6-only hostnames ('WSANO_DATA', 11004), ] denied = support.ResourceDenied("Resource %r is not available" % resource_name) captured_errnos = errnos gai_errnos = [] if not captured_errnos: captured_errnos = [getattr(errno, name, num) for (name, num) in default_errnos] gai_errnos = [getattr(socket, name, num) for (name, num) in default_gai_errnos] def filter_error(err): n = getattr(err, 'errno', None) if (isinstance(err, TimeoutError) or (isinstance(err, socket.gaierror) and n in gai_errnos) or (isinstance(err, urllib.error.HTTPError) and 500 <= err.code <= 599) or (isinstance(err, urllib.error.URLError) and (("ConnectionRefusedError" in err.reason) or ("TimeoutError" in err.reason) or ("EOFError" in err.reason))) or n in captured_errnos): if not support.verbose: sys.stderr.write(denied.args[0] + "\n") raise denied from err old_timeout = socket.getdefaulttimeout() try: if timeout is not None: socket.setdefaulttimeout(timeout) yield except nntplib.NNTPTemporaryError as err: if support.verbose: sys.stderr.write(denied.args[0] + "\n") raise denied from err except OSError as err: # urllib can wrap original socket errors multiple times (!), we must # unwrap to get at the original error. while True: a = err.args if len(a) >= 1 and isinstance(a[0], OSError): err = a[0] # The error can also be wrapped as args[1]: # except socket.error as msg: # raise OSError('socket error', msg).with_traceback(sys.exc_info()[2]) elif len(a) >= 2 and isinstance(a[1], OSError): err = a[1] else: break filter_error(err) raise # XXX should we catch generic exceptions and look for their # __cause__ or __context__? finally: socket.setdefaulttimeout(old_timeout)