Method testConnectTimeout

Lib/test/test_timeout.py:145–216

(self)

        self.addr_remote = resolve_address('www.python.org.', 80)

    def testConnectTimeout(self):
        # Testing connect timeout is tricky: we need to have IP connectivity
        # to a host that silently drops our packets.  We can't simulate this
        # from Python because it's a function of the underlying TCP/IP stack.
        # So, the following port on the pythontest.net host has been defined:
        blackhole = resolve_address('pythontest.net', 56666)

        # Blackhole has been configured to silently drop any incoming packets.
        # No RSTs (for TCP) or ICMP UNREACH (for UDP/ICMP) will be sent back
        # to hosts that attempt to connect to this address: which is exactly
        # what we need to confidently test connect timeout.

        # However, we want to prevent false positives.  It's not unreasonable
        # to expect certain hosts may not be able to reach the blackhole, due
        # to firewalling or general network configuration.  In order to improve
        # our confidence in testing the blackhole, a corresponding 'whitehole'
        # has also been set up using one port higher:
        whitehole = resolve_address('pythontest.net', 56667)

        # This address has been configured to immediately drop any incoming
        # packets as well, but it does it respectfully with regards to the
        # incoming protocol.  RSTs are sent for TCP packets, and ICMP UNREACH
        # is sent for UDP/ICMP packets.  This means our attempts to connect to
        # it should be met immediately with ECONNREFUSED.  The test case has
        # been structured around this premise: if we get an ECONNREFUSED from
        # the whitehole, we proceed with testing connect timeout against the
        # blackhole.  If we don't, we skip the test (with a message about not
        # getting the required RST from the whitehole within the required
        # timeframe).

        # For the records, the whitehole/blackhole configuration has been set
        # up using the 'iptables' firewall, using the following rules:
        #
        # -A INPUT -p tcp --destination-port 56666 -j DROP
        # -A INPUT -p udp --destination-port 56666 -j DROP
        # -A INPUT -p tcp --destination-port 56667 -j REJECT
        # -A INPUT -p udp --destination-port 56667 -j REJECT
        #
        # See https://github.com/python/psf-salt/blob/main/pillar/base/firewall/snakebite.sls
        # for the current configuration.

        skip = True
        with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as sock:
            try:
                timeout = support.LOOPBACK_TIMEOUT
                sock.settimeout(timeout)
                sock.connect((whitehole))
            except TimeoutError:
                pass
            except OSError as err:
                if err.errno == errno.ECONNREFUSED:
                    skip = False

        if skip:
            self.skipTest(
                "We didn't receive a connection reset (RST) packet from "
                "{}:{} within {} seconds, so we're unable to test connect "
                "timeout against the corresponding {}:{} (which is "