1import contextlib
2import errno
3import socket
4import unittest
5import sys
6
7from .. import support
8from . import warnings_helper
9
10HOST = "localhost"
11HOSTv4 = "127.0.0.1"
12HOSTv6 = "::1"
13
14# WASI SDK 15.0 does not provide gethostname, stub raises OSError ENOTSUP.
15has_gethostname = not support.is_wasi
16
17
18def find_unused_port(family=socket.AF_INET, socktype=socket.SOCK_STREAM):
19    """Returns an unused port that should be suitable for binding.  This is
20    achieved by creating a temporary socket with the same family and type as
21    the 'sock' parameter (default is AF_INET, SOCK_STREAM), and binding it to
22    the specified host address (defaults to 0.0.0.0) with the port set to 0,
23    eliciting an unused ephemeral port from the OS.  The temporary socket is
24    then closed and deleted, and the ephemeral port is returned.
25
26    Either this method or bind_port() should be used for any tests where a
27    server socket needs to be bound to a particular port for the duration of
28    the test.  Which one to use depends on whether the calling code is creating
29    a python socket, or if an unused port needs to be provided in a constructor
30    or passed to an external program (i.e. the -accept argument to openssl's
31    s_server mode).  Always prefer bind_port() over find_unused_port() where
32    possible.  Hard coded ports should *NEVER* be used.  As soon as a server
33    socket is bound to a hard coded port, the ability to run multiple instances
34    of the test simultaneously on the same host is compromised, which makes the
35    test a ticking time bomb in a buildbot environment. On Unix buildbots, this
36    may simply manifest as a failed test, which can be recovered from without
37    intervention in most cases, but on Windows, the entire python process can
38    completely and utterly wedge, requiring someone to log in to the buildbot
39    and manually kill the affected process.
40
41    (This is easy to reproduce on Windows, unfortunately, and can be traced to
42    the SO_REUSEADDR socket option having different semantics on Windows versus
43    Unix/Linux.  On Unix, you can't have two AF_INET SOCK_STREAM sockets bind,
44    listen and then accept connections on identical host/ports.  An EADDRINUSE
45    OSError will be raised at some point (depending on the platform and
46    the order bind and listen were called on each socket).
47
48    However, on Windows, if SO_REUSEADDR is set on the sockets, no EADDRINUSE
49    will ever be raised when attempting to bind two identical host/ports. When
50    accept() is called on each socket, the second caller's process will steal
51    the port from the first caller, leaving them both in an awkwardly wedged
52    state where they'll no longer respond to any signals or graceful kills, and
53    must be forcibly killed via OpenProcess()/TerminateProcess().
54
55    The solution on Windows is to use the SO_EXCLUSIVEADDRUSE socket option
56    instead of SO_REUSEADDR, which effectively affords the same semantics as
57    SO_REUSEADDR on Unix.  Given the propensity of Unix developers in the Open
58    Source world compared to Windows ones, this is a common mistake.  A quick
59    look over OpenSSL's 0.9.8g source shows that they use SO_REUSEADDR when
60    openssl.exe is called with the 's_server' option, for example. See
61    http://bugs.python.org/issue2550 for more info.  The following site also
62    has a very thorough description about the implications of both REUSEADDR
63    and EXCLUSIVEADDRUSE on Windows:
64    https://learn.microsoft.com/windows/win32/winsock/using-so-reuseaddr-and-so-exclusiveaddruse
65
66    XXX: although this approach is a vast improvement on previous attempts to
67    elicit unused ports, it rests heavily on the assumption that the ephemeral
68    port returned to us by the OS won't immediately be dished back out to some
69    other process when we close and delete our temporary socket but before our
70    calling code has a chance to bind the returned port.  We can deal with this
71    issue if/when we come across it.
72    """
73
74    with socket.socket(family, socktype) as tempsock:
75        port = bind_port(tempsock)
76    del tempsock
77    return port
78
79def bind_port(sock, host=HOST):
80    """Bind the socket to a free port and return the port number.  Relies on
81    ephemeral ports in order to ensure we are using an unbound port.  This is
82    important as many tests may be running simultaneously, especially in a
83    buildbot environment.  This method raises an exception if the sock.family
84    is AF_INET and sock.type is SOCK_STREAM, *and* the socket has SO_REUSEADDR
85    or SO_REUSEPORT set on it.  Tests should *never* set these socket options
86    for TCP/IP sockets.  The only case for setting these options is testing
87    multicasting via multiple UDP sockets.
88
89    Additionally, if the SO_EXCLUSIVEADDRUSE socket option is available (i.e.
90    on Windows), it will be set on the socket.  This will prevent anyone else
91    from bind()'ing to our host/port for the duration of the test.
92    """
93
94    if sock.family == socket.AF_INET and sock.type == socket.SOCK_STREAM:
95        if hasattr(socket, 'SO_REUSEADDR'):
96            if sock.getsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR) == 1:
97                raise support.TestFailed("tests should never set the "
98                                         "SO_REUSEADDR socket option on "
99                                         "TCP/IP sockets!")
100        if hasattr(socket, 'SO_REUSEPORT'):
101            try:
102                if sock.getsockopt(socket.SOL_SOCKET, socket.SO_REUSEPORT) == 1:
103                    raise support.TestFailed("tests should never set the "
104                                             "SO_REUSEPORT socket option on "
105                                             "TCP/IP sockets!")
106            except OSError:
107                # Python's socket module was compiled using modern headers
108                # thus defining SO_REUSEPORT but this process is running
109                # under an older kernel that does not support SO_REUSEPORT.
110                pass
111        if hasattr(socket, 'SO_EXCLUSIVEADDRUSE'):
112            sock.setsockopt(socket.SOL_SOCKET, socket.SO_EXCLUSIVEADDRUSE, 1)
113
114    sock.bind((host, 0))
115    port = sock.getsockname()[1]
116    return port
117
118def bind_unix_socket(sock, addr):
119    """Bind a unix socket, raising SkipTest if PermissionError is raised."""
120    assert sock.family == socket.AF_UNIX
121    try:
122        sock.bind(addr)
123    except PermissionError:
124        sock.close()
125        raise unittest.SkipTest('cannot bind AF_UNIX sockets')
126
127def _is_ipv6_enabled():
128    """Check whether IPv6 is enabled on this host."""
129    if socket.has_ipv6:
130        sock = None
131        try:
132            sock = socket.socket(socket.AF_INET6, socket.SOCK_STREAM)
133            sock.bind((HOSTv6, 0))
134            return True
135        except OSError:
136            pass
137        finally:
138            if sock:
139                sock.close()
140    return False
141
142IPV6_ENABLED = _is_ipv6_enabled()
143
144
145_bind_nix_socket_error = None
146def skip_unless_bind_unix_socket(test):
147    """Decorator for tests requiring a functional bind() for unix sockets."""
148    if not hasattr(socket, 'AF_UNIX'):
149        return unittest.skip('No UNIX Sockets')(test)
150    global _bind_nix_socket_error
151    if _bind_nix_socket_error is None:
152        from .os_helper import TESTFN, unlink
153        path = TESTFN + "can_bind_unix_socket"
154        with socket.socket(socket.AF_UNIX) as sock:
155            try:
156                sock.bind(path)
157                _bind_nix_socket_error = False
158            except OSError as e:
159                _bind_nix_socket_error = e
160            finally:
161                unlink(path)
162    if _bind_nix_socket_error:
163        msg = 'Requires a functional unix bind(): %s' % _bind_nix_socket_error
164        return unittest.skip(msg)(test)
165    else:
166        return test
167
168
169def get_socket_conn_refused_errs():
170    """
171    Get the different socket error numbers ('errno') which can be received
172    when a connection is refused.
173    """
174    errors = [errno.ECONNREFUSED]
175    if hasattr(errno, 'ENETUNREACH'):
176        # On Solaris, ENETUNREACH is returned sometimes instead of ECONNREFUSED
177        errors.append(errno.ENETUNREACH)
178    if hasattr(errno, 'EADDRNOTAVAIL'):
179        # bpo-31910: socket.create_connection() fails randomly
180        # with EADDRNOTAVAIL on Travis CI
181        errors.append(errno.EADDRNOTAVAIL)
182    if hasattr(errno, 'EHOSTUNREACH'):
183        # bpo-37583: The destination host cannot be reached
184        errors.append(errno.EHOSTUNREACH)
185    if not IPV6_ENABLED:
186        errors.append(errno.EAFNOSUPPORT)
187    return errors
188
189
190_NOT_SET = object()
191
192@contextlib.contextmanager
193def transient_internet(resource_name, *, timeout=_NOT_SET, errnos=()):
194    """Return a context manager that raises ResourceDenied when various issues
195    with the internet connection manifest themselves as exceptions."""
196    nntplib = warnings_helper.import_deprecated("nntplib")
197    import urllib.error
198    if timeout is _NOT_SET:
199        timeout = support.INTERNET_TIMEOUT
200
201    default_errnos = [
202        ('ECONNREFUSED', 111),
203        ('ECONNRESET', 104),
204        ('EHOSTUNREACH', 113),
205        ('ENETUNREACH', 101),
206        ('ETIMEDOUT', 110),
207        # socket.create_connection() fails randomly with
208        # EADDRNOTAVAIL on Travis CI.
209        ('EADDRNOTAVAIL', 99),
210    ]
211    default_gai_errnos = [
212        ('EAI_AGAIN', -3),
213        ('EAI_FAIL', -4),
214        ('EAI_NONAME', -2),
215        ('EAI_NODATA', -5),
216        # Encountered when trying to resolve IPv6-only hostnames
217        ('WSANO_DATA', 11004),
218    ]
219
220    denied = support.ResourceDenied("Resource %r is not available" % resource_name)
221    captured_errnos = errnos
222    gai_errnos = []
223    if not captured_errnos:
224        captured_errnos = [getattr(errno, name, num)
225                           for (name, num) in default_errnos]
226        gai_errnos = [getattr(socket, name, num)
227                      for (name, num) in default_gai_errnos]
228
229    def filter_error(err):
230        n = getattr(err, 'errno', None)
231        if (isinstance(err, TimeoutError) or
232            (isinstance(err, socket.gaierror) and n in gai_errnos) or
233            (isinstance(err, urllib.error.HTTPError) and
234             500 <= err.code <= 599) or
235            (isinstance(err, urllib.error.URLError) and
236                 (("ConnectionRefusedError" in err.reason) or
237                  ("TimeoutError" in err.reason) or
238                  ("EOFError" in err.reason))) or
239            n in captured_errnos):
240            if not support.verbose:
241                sys.stderr.write(denied.args[0] + "\n")
242            raise denied from err
243
244    old_timeout = socket.getdefaulttimeout()
245    try:
246        if timeout is not None:
247            socket.setdefaulttimeout(timeout)
248        yield
249    except nntplib.NNTPTemporaryError as err:
250        if support.verbose:
251            sys.stderr.write(denied.args[0] + "\n")
252        raise denied from err
253    except OSError as err:
254        # urllib can wrap original socket errors multiple times (!), we must
255        # unwrap to get at the original error.
256        while True:
257            a = err.args
258            if len(a) >= 1 and isinstance(a[0], OSError):
259                err = a[0]
260            # The error can also be wrapped as args[1]:
261            #    except socket.error as msg:
262            #        raise OSError('socket error', msg) from msg
263            elif len(a) >= 2 and isinstance(a[1], OSError):
264                err = a[1]
265            else:
266                break
267        filter_error(err)
268        raise
269    # XXX should we catch generic exceptions and look for their
270    # __cause__ or __context__?
271    finally:
272        socket.setdefaulttimeout(old_timeout)
273