gh-91968: Add socket constants SO_USER_COOKIE/SO_RTABLE from BSD (#91967)

Those are somewhat equivalent to Linux' SO_MARK.

Co-authored-by: Jelle Zijlstra <jelle.zijlstra@gmail.com>

Author: devnexen

Doc/library/socket.rst

@@ -392,6 +392,11 @@ Constants
       Added ``TCP_CONNECTION_INFO``. On MacOS this constant can be used in the
       same way that ``TCP_INFO`` is used on Linux and BSD.
 
+   .. versionchanged:: 3.12
+      Added ``SO_RTABLE`` and ``SO_USER_COOKIE``. On OpenBSD
+      and FreeBSD respectively those constants can be used in the same way that
+      ``SO_MARK`` is used on Linux.
+
 .. data:: AF_CAN
           PF_CAN
           SOL_CAN_*

Misc/NEWS.d/next/Library/2022-04-26-18-37-24.gh-issue-91968.fuuH1_.rst

@@ -0,0 +1 @@
+Add ``SO_RTABLE`` and ``SO_USER_COOKIE`` constants to :mod:`socket`.

Modules/socketmodule.c

@@ -7595,6 +7595,12 @@ PyInit__socket(void)
 #ifdef  SO_MARK
     PyModule_AddIntMacro(m, SO_MARK);
 #endif
+#ifdef  SO_USER_COOKIE
+    PyModule_AddIntMacro(m, SO_USER_COOKIE);
+#endif
+#ifdef  SO_RTABLE
+    PyModule_AddIntMacro(m, SO_RTABLE);
+#endif
 #ifdef SO_DOMAIN
     PyModule_AddIntMacro(m, SO_DOMAIN);
 #endif