Add test/support/socket_helper from CPython 3.10

fanninpm · fanninpm · commit ab556e2811d5 · 2022-02-12T19:37:44.000-05:00
diff --git a/Lib/test/support/socket_helper.py b/Lib/test/support/socket_helper.py
@@ -0,0 +1,269 @@
+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:
+    http://msdn2.microsoft.com/en-us/library/ms740621(VS.85).aspx)
+
+    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)
