zebra: mark multicast commands experimental

depending on feedback from actually having these commands in a released
version, we may want to adjust them.  Thus, mark them as experimental so
users are aware of this.

Cc: Everton Marques <everton.marques@gmail.com>
Cc: Balaji G <balajig81@gmail.com>
Signed-off-by: David Lamparter <equinox@opensourcerouting.org>
diff --git a/lib/vty.h b/lib/vty.h
index 4d6048c..f31f4b5 100644
--- a/lib/vty.h
+++ b/lib/vty.h
@@ -217,6 +217,14 @@
     }                                                                         \
 } while (0)
 
+#define VTY_WARN_EXPERIMENTAL()                                               \
+do {                                                                          \
+  vty_out (vty, "%% WARNING: this command is experimental. Both its name and" \
+                " parameters may%s%% change in a future version of Quagga,"   \
+                " possibly breaking your configuration!%s",                   \
+                VTY_NEWLINE, VTY_NEWLINE);                                    \
+} while (0)
+
 /* Exported variables */
 extern char integrate_default[];
 
diff --git a/zebra/zebra_vty.c b/zebra/zebra_vty.c
index 29c01c3..598b40d 100644
--- a/zebra/zebra_vty.c
+++ b/zebra/zebra_vty.c
@@ -154,6 +154,7 @@
        "Nexthop interface name\n"
        "Distance\n")
 {
+  VTY_WARN_EXPERIMENTAL();
   return zebra_static_ipv4_safi(vty, SAFI_MULTICAST, 1, argv[0], NULL, argv[1],
                                 NULL, argc > 2 ? argv[2] : NULL);
 }
@@ -177,6 +178,7 @@
        "Nexthop interface name\n"
        "Distance\n")
 {
+  VTY_WARN_EXPERIMENTAL();
   return zebra_static_ipv4_safi(vty, SAFI_MULTICAST, 0, argv[0], NULL, argv[1],
                                 NULL, argc > 2 ? argv[2] : NULL);
 }
@@ -203,6 +205,8 @@
        "Lookup both, use entry with lower distance\n"
        "Lookup both, use entry with longer prefix\n")
 {
+  VTY_WARN_EXPERIMENTAL();
+
   if (!strncmp (argv[0], "u", 1))
     multicast_mode_ipv4_set (MCAST_URIB_ONLY);
   else if (!strncmp (argv[0], "mrib-o", 6))
@@ -254,6 +258,7 @@
        IP_STR
        "Display RPF information for multicast source\n")
 {
+  VTY_WARN_EXPERIMENTAL();
   return do_show_ip_route(vty, SAFI_MULTICAST);
 }
 
@@ -270,6 +275,8 @@
   struct rib *rib;
   int ret;
 
+  VTY_WARN_EXPERIMENTAL();
+
   ret = inet_aton (argv[0], &addr);
   if (ret == 0)
     {