bpo-26227: Fixes decoding of host names on Windows from ANSI instead of UTF-8 (GH-25510)

(cherry picked from commit dc516ef)

Co-authored-by: Steve Dower <[email protected]>

Author: miss-islington

Misc/NEWS.d/next/Windows/2021-04-21-23-37-34.bpo-26227.QMY_eA.rst

@@ -0,0 +1,2 @@
+Fixed decoding of host names in :func:`socket.gethostbyaddr` and
+:func:`socket.gethostbyname_ex`.

Modules/socketmodule.c

@@ -5474,7 +5474,7 @@ sock_decode_hostname(const char *name)
 #ifdef MS_WINDOWS
     /* Issue #26227: gethostbyaddr() returns a string encoded
      * to the ANSI code page */
-    return PyUnicode_DecodeFSDefault(name);
+    return PyUnicode_DecodeMBCS(name, strlen(name), "surrogatepass");
 #else
     /* Decode from UTF-8 */
     return PyUnicode_FromString(name);