WSAIoctl question.

[Scott Lindeneau]

I noticed a patch that was submitted by John Griffiths on the 13th of
July that forwards functions by mwsock.c using the following code:
(commit: 2da98052d90591474c65bed853ca75e1da714823)
+static void get_fn(SOCKET s, GUID* guid, FARPROC* fn)
+{
+    FARPROC func;
+    DWORD len;
+    if (!WSAIoctl(s, SIO_GET_EXTENSION_FUNCTION_POINTER, guid, sizeof(*guid),
+                  &func, sizeof(func), &len, NULL, NULL))
+        *fn = func;
+}

But wine's WSAIoctl does not support the
SIO_GET_EXTENSION_FUNCTION_POINTER. I was wondering how this works and
what its for? Is it for using native libraries?