wsgi server: address family discovery is not quite right

[jclulow]

The code introduced to improve binding to an IPv6 address is based on similar code in Python itself, but is missing some critical arguments to the socket.getaddrinfo() call: in particular, the socket type must be set to SOCK_STREAM, because we want a TCP connection; the AI_PASSIVE flag should also be passed because we intend to use the result for binding a listen socket rather than making an outbound connection.

[jclulow]

By way of example, this is the output with and without the flags on an Ubuntu 22.04 system:

#!/usr/bin/env python3

import socket

print("WITH type set:")
print(socket.getaddrinfo("0.0.0.0", 9009,
    type=socket.SOCK_STREAM, flags=socket.AI_PASSIVE))

print("WITHOUT type set:")
print(socket.getaddrinfo("0.0.0.0", 9009))

WITH type set:
[(<AddressFamily.AF_INET: 2>, <SocketKind.SOCK_STREAM: 1>, 6, '', ('0.0.0.0', 9009))]
WITHOUT type set:
[(<AddressFamily.AF_INET: 2>, <SocketKind.SOCK_STREAM: 1>, 6, '', ('0.0.0.0', 9009)), (<AddressFamily.AF_INET: 2>, <SocketKind.SOCK_DGRAM: 2>, 17, '', ('0.0.0.0', 9009)), (<AddressFamily.AF_INET: 2>, <SocketKind.SOCK_RAW: 3>, 0, '', ('0.0.0.0', 9009))]

On some other platforms, getaddrinfo() requires at least the socket type to function as is expected here; e.g.,

WITH type set:
[(<AddressFamily.AF_INET: 2>, <SocketKind.SOCK_STREAM: 2>, 6, '', ('0.0.0.0', 9009))]
WITHOUT type set:
Traceback (most recent call last):
  File "/tmp/sigh_test.py", line 10, in <module>
    print(socket.getaddrinfo("0.0.0.0", 9009))
          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.11/socket.py", line 962, in getaddrinfo
    for res in _socket.getaddrinfo(host, port, family, type, proto, flags):
               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
socket.gaierror: [Errno 9] service name not available for the specified socket type

[csmarchbanks]

Thanks!