bpo-24209: In http.server script, rely on getaddrinfo to bind to preferred address based on the bind parameter. (#11767)

In http.server script, rely on getaddrinfo to bind to preferred address based on the bind parameter.

As a result, now IPv6 is used as the default (including IPv4 on dual-stack systems). Enhanced tests.

1 files changed, 20 insertions, 10 deletions

diff --git a/Lib/http/server.py b/Lib/http/server.py
index 29c720e..b247675 100644
--- a/Lib/http/server.py
+++ b/Lib/http/server.py
@@ -1224,24 +1224,34 @@ class CGIHTTPRequestHandler(SimpleHTTPRequestHandler):
                 self.log_message("CGI script exited OK")
 
 
+def _get_best_family(*address):
+    infos = socket.getaddrinfo(
+        *address,
+        type=socket.SOCK_STREAM,
+        flags=socket.AI_PASSIVE,
+    )
+    family, type, proto, canonname, sockaddr = next(iter(infos))
+    return family, sockaddr
+
+
 def test(HandlerClass=BaseHTTPRequestHandler,
          ServerClass=ThreadingHTTPServer,
-         protocol="HTTP/1.0", port=8000, bind=""):
+         protocol="HTTP/1.0", port=8000, bind=None):
     """Test the HTTP request handler class.
 
     This runs an HTTP server on port 8000 (or the port argument).
 
     """
-    server_address = (bind, port)
-
-    if ':' in bind:
-        ServerClass.address_family = socket.AF_INET6
+    ServerClass.address_family, addr = _get_best_family(bind, port)
 
     HandlerClass.protocol_version = protocol
-    with ServerClass(server_address, HandlerClass) as httpd:
-        sa = httpd.socket.getsockname()
-        serve_message = "Serving HTTP on {host} port {port} (http://{host}:{port}/) ..."
-        print(serve_message.format(host=sa[0], port=sa[1]))
+    with ServerClass(addr, HandlerClass) as httpd:
+        host, port = httpd.socket.getsockname()[:2]
+        url_host = f'[{host}]' if ':' in host else host
+        print(
+            f"Serving HTTP on {host} port {port} "
+            f"(http://{url_host}:{port}/) ..."
+        )
         try:
             httpd.serve_forever()
         except KeyboardInterrupt:
@@ -1254,7 +1264,7 @@ if __name__ == '__main__':
     parser = argparse.ArgumentParser()
     parser.add_argument('--cgi', action='store_true',
                        help='Run as CGI Server')
-    parser.add_argument('--bind', '-b', default='', metavar='ADDRESS',
+    parser.add_argument('--bind', '-b', metavar='ADDRESS',
                         help='Specify alternate bind address '
                              '[default: all interfaces]')
     parser.add_argument('--directory', '-d', default=os.getcwd(),