--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/planemo/lib/python3.7/site-packages/urllib3/util/connection.py	Fri Jul 31 00:32:28 2020 -0400
@@ -0,0 +1,138 @@
+from __future__ import absolute_import
+import socket
+from .wait import NoWayToWaitForSocketError, wait_for_read
+from ..contrib import _appengine_environ
+
+
+def is_connection_dropped(conn):  # Platform-specific
+    """
+    Returns True if the connection is dropped and should be closed.
+
+    :param conn:
+        :class:`httplib.HTTPConnection` object.
+
+    Note: For platforms like AppEngine, this will always return ``False`` to
+    let the platform handle connection recycling transparently for us.
+    """
+    sock = getattr(conn, "sock", False)
+    if sock is False:  # Platform-specific: AppEngine
+        return False
+    if sock is None:  # Connection already closed (such as by httplib).
+        return True
+    try:
+        # Returns True if readable, which here means it's been dropped
+        return wait_for_read(sock, timeout=0.0)
+    except NoWayToWaitForSocketError:  # Platform-specific: AppEngine
+        return False
+
+
+# This function is copied from socket.py in the Python 2.7 standard
+# library test suite. Added to its signature is only `socket_options`.
+# One additional modification is that we avoid binding to IPv6 servers
+# discovered in DNS if the system doesn't have IPv6 functionality.
+def create_connection(
+    address,
+    timeout=socket._GLOBAL_DEFAULT_TIMEOUT,
+    source_address=None,
+    socket_options=None,
+):
+    """Connect to *address* and return the socket object.
+
+    Convenience function.  Connect to *address* (a 2-tuple ``(host,
+    port)``) and return the socket object.  Passing the optional
+    *timeout* parameter will set the timeout on the socket instance
+    before attempting to connect.  If no *timeout* is supplied, the
+    global default timeout setting returned by :func:`getdefaulttimeout`
+    is used.  If *source_address* is set it must be a tuple of (host, port)
+    for the socket to bind as a source address before making the connection.
+    An host of '' or port 0 tells the OS to use the default.
+    """
+
+    host, port = address
+    if host.startswith("["):
+        host = host.strip("[]")
+    err = None
+
+    # Using the value from allowed_gai_family() in the context of getaddrinfo lets
+    # us select whether to work with IPv4 DNS records, IPv6 records, or both.
+    # The original create_connection function always returns all records.
+    family = allowed_gai_family()
+
+    for res in socket.getaddrinfo(host, port, family, socket.SOCK_STREAM):
+        af, socktype, proto, canonname, sa = res
+        sock = None
+        try:
+            sock = socket.socket(af, socktype, proto)
+
+            # If provided, set socket level options before connecting.
+            _set_socket_options(sock, socket_options)
+
+            if timeout is not socket._GLOBAL_DEFAULT_TIMEOUT:
+                sock.settimeout(timeout)
+            if source_address:
+                sock.bind(source_address)
+            sock.connect(sa)
+            return sock
+
+        except socket.error as e:
+            err = e
+            if sock is not None:
+                sock.close()
+                sock = None
+
+    if err is not None:
+        raise err
+
+    raise socket.error("getaddrinfo returns an empty list")
+
+
+def _set_socket_options(sock, options):
+    if options is None:
+        return
+
+    for opt in options:
+        sock.setsockopt(*opt)
+
+
+def allowed_gai_family():
+    """This function is designed to work in the context of
+    getaddrinfo, where family=socket.AF_UNSPEC is the default and
+    will perform a DNS search for both IPv6 and IPv4 records."""
+
+    family = socket.AF_INET
+    if HAS_IPV6:
+        family = socket.AF_UNSPEC
+    return family
+
+
+def _has_ipv6(host):
+    """ Returns True if the system can bind an IPv6 address. """
+    sock = None
+    has_ipv6 = False
+
+    # App Engine doesn't support IPV6 sockets and actually has a quota on the
+    # number of sockets that can be used, so just early out here instead of
+    # creating a socket needlessly.
+    # See https://github.com/urllib3/urllib3/issues/1446
+    if _appengine_environ.is_appengine_sandbox():
+        return False
+
+    if socket.has_ipv6:
+        # has_ipv6 returns true if cPython was compiled with IPv6 support.
+        # It does not tell us if the system has IPv6 support enabled. To
+        # determine that we must bind to an IPv6 address.
+        # https://github.com/urllib3/urllib3/pull/611
+        # https://bugs.python.org/issue658327
+        try:
+            sock = socket.socket(socket.AF_INET6)
+            sock.bind((host, 0))
+            has_ipv6 = True
+        except Exception:
+            pass
+
+    if sock:
+        sock.close()
+    return has_ipv6
+
+
+HAS_IPV6 = _has_ipv6("::1")