socket_helper.py

importcontextlib
importerrno
importos.path
importsocket
importsys
importsubprocess
importtempfile
importunittest

from .. importsupport

HOST="localhost"
HOSTv4="127.0.0.1"
HOSTv6="::1"

# WASI SDK 15.0 does not provide gethostname, stub raises OSError ENOTSUP.
has_gethostname=notsupport.is_wasi


deffind_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.
 """

withsocket.socket(family, socktype) astempsock:
port=bind_port(tempsock)
deltempsock
returnport

defbind_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.
 """

ifsock.family==socket.AF_INETandsock.type==socket.SOCK_STREAM:
ifhasattr(socket, 'SO_REUSEADDR'):
ifsock.getsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR) ==1:
raisesupport.TestFailed("tests should never set the "
"SO_REUSEADDR socket option on "
"TCP/IP sockets!")
ifhasattr(socket, 'SO_REUSEPORT'):
try:
ifsock.getsockopt(socket.SOL_SOCKET, socket.SO_REUSEPORT) ==1:
raisesupport.TestFailed("tests should never set the "
"SO_REUSEPORT socket option on "
"TCP/IP sockets!")
exceptOSError:
# 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
ifhasattr(socket, 'SO_EXCLUSIVEADDRUSE'):
sock.setsockopt(socket.SOL_SOCKET, socket.SO_EXCLUSIVEADDRUSE, 1)

sock.bind((host, 0))
port=sock.getsockname()[1]
returnport

defbind_unix_socket(sock, addr):
"""Bind a unix socket, raising SkipTest if PermissionError is raised."""
assertsock.family==socket.AF_UNIX
try:
sock.bind(addr)
exceptPermissionError:
sock.close()
raiseunittest.SkipTest('cannot bind AF_UNIX sockets')

def_is_ipv6_enabled():
"""Check whether IPv6 is enabled on this host."""
ifsocket.has_ipv6:
sock=None
try:
sock=socket.socket(socket.AF_INET6, socket.SOCK_STREAM)
sock.bind((HOSTv6, 0))
returnTrue
exceptOSError:
pass
finally:
ifsock:
sock.close()
returnFalse

IPV6_ENABLED=_is_ipv6_enabled()


_bind_nix_socket_error=None
defskip_unless_bind_unix_socket(test):
"""Decorator for tests requiring a functional bind() for unix sockets."""
ifnothasattr(socket, 'AF_UNIX'):
returnunittest.skip('No UNIX Sockets')(test)
global_bind_nix_socket_error
if_bind_nix_socket_errorisNone:
from .os_helperimportTESTFN, unlink
path=TESTFN+"can_bind_unix_socket"
withsocket.socket(socket.AF_UNIX) assock:
try:
sock.bind(path)
_bind_nix_socket_error=False
exceptOSErrorase:
_bind_nix_socket_error=e
finally:
unlink(path)
if_bind_nix_socket_error:
msg='Requires a functional unix bind(): %s'%_bind_nix_socket_error
returnunittest.skip(msg)(test)
else:
returntest


defget_socket_conn_refused_errs():
"""
 Get the different socket error numbers ('errno') which can be received
 when a connection is refused.
 """
errors= [errno.ECONNREFUSED]
ifhasattr(errno, 'ENETUNREACH'):
# On Solaris, ENETUNREACH is returned sometimes instead of ECONNREFUSED
errors.append(errno.ENETUNREACH)
ifhasattr(errno, 'EADDRNOTAVAIL'):
# bpo-31910: socket.create_connection() fails randomly
# with EADDRNOTAVAIL on Travis CI
errors.append(errno.EADDRNOTAVAIL)
ifhasattr(errno, 'EHOSTUNREACH'):
# bpo-37583: The destination host cannot be reached
errors.append(errno.EHOSTUNREACH)
ifnotIPV6_ENABLED:
errors.append(errno.EAFNOSUPPORT)
returnerrors


_NOT_SET=object()

@contextlib.contextmanager
deftransient_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."""
importurllib.error
iftimeoutis_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= []
ifnotcaptured_errnos:
captured_errnos= [getattr(errno, name, num)
for (name, num) indefault_errnos]
gai_errnos= [getattr(socket, name, num)
for (name, num) indefault_gai_errnos]

deffilter_error(err):
n=getattr(err, 'errno', None)
if (isinstance(err, TimeoutError) or
 (isinstance(err, socket.gaierror) andningai_errnos) or
 (isinstance(err, urllib.error.HTTPError) and
500<=err.code<=599) or
 (isinstance(err, urllib.error.URLError) and
 (("ConnectionRefusedError"inerr.reason) or
 ("TimeoutError"inerr.reason) or
 ("EOFError"inerr.reason))) or
nincaptured_errnos):
ifnotsupport.verbose:
sys.stderr.write(denied.args[0] +"\n")
raisedeniedfromerr

old_timeout=socket.getdefaulttimeout()
try:
iftimeoutisnotNone:
socket.setdefaulttimeout(timeout)
yield
exceptOSErroraserr:
# urllib can wrap original socket errors multiple times (!), we must
# unwrap to get at the original error.
whileTrue:
a=err.args
iflen(a) >=1andisinstance(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) from msg
eliflen(a) >=2andisinstance(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)


defcreate_unix_domain_name():
"""
 Create a UNIX domain name: socket.bind() argument of a AF_UNIX socket.

 Return a path relative to the current directory to get a short path
 (around 27 ASCII characters).
 """
returntempfile.mktemp(prefix="test_python_", suffix='.sock',
dir=os.path.curdir)


# consider that sysctl values should not change while tests are running
_sysctl_cache= {}

def_get_sysctl(name):
"""Get a sysctl value as an integer."""
try:
return_sysctl_cache[name]
exceptKeyError:
pass

# At least Linux and FreeBSD support the "-n" option
cmd= ['sysctl', '-n', name]
proc=subprocess.run(cmd,
stdout=subprocess.PIPE,
stderr=subprocess.STDOUT,
text=True)
ifproc.returncode:
support.print_warning(f'{' '.join(cmd)!r} command failed with '
f'exit code {proc.returncode}')
# cache the error to only log the warning once
_sysctl_cache[name] =None
returnNone
output=proc.stdout

# Parse '0\n' to get '0'
try:
value=int(output.strip())
exceptExceptionasexc:
support.print_warning(f'Failed to parse {' '.join(cmd)!r} '
f'command output {output!r}: {exc!r}')
# cache the error to only log the warning once
_sysctl_cache[name] =None
returnNone

_sysctl_cache[name] =value
returnvalue


deftcp_blackhole():
ifnotsys.platform.startswith('freebsd'):
returnFalse

# gh-109015: test if FreeBSD TCP blackhole is enabled
value=_get_sysctl('net.inet.tcp.blackhole')
ifvalueisNone:
# don't skip if we fail to get the sysctl value
returnFalse
return (value!=0)


defskip_if_tcp_blackhole(test):
"""Decorator skipping test if TCP blackhole is enabled."""
skip_if=unittest.skipIf(
tcp_blackhole(),
"TCP blackhole is enabled (sysctl net.inet.tcp.blackhole)"
 )
returnskip_if(test)