From: Hasso Tepper <hasso@estpak.ee>

Add the 'no interface' command to all the daemons and vtysh. now it's
possible to delete interface from routeing daemons as well only if it
doesn't exist in os.

http://hasso.linux.ee/zebra/ht-no_interface_fix.patch
diff --git a/lib/if.c b/lib/if.c
index e1a1839..2ca8c94 100644
--- a/lib/if.c
+++ b/lib/if.c
@@ -440,6 +440,32 @@
   return CMD_SUCCESS;
 }
 
+DEFUN_NOSH (no_interface,
+           no_interface_cmd,
+           "no interface IFNAME",
+           NO_STR
+           "Delete a pseudo interface's configuration\n"
+           "Interface's name\n")
+{
+  // deleting interface
+  struct interface *ifp;
+
+  ifp = if_lookup_by_name (argv[0]);
+
+  if (ifp == NULL)
+    return CMD_SUCCESS;
+
+  if (if_is_up(ifp)) {
+    vty_out (vty, "%% Only inactive interfaces can be deleted%s",
+            VTY_NEWLINE);
+    return CMD_WARNING;
+  }
+
+  if_delete(ifp);
+
+  return CMD_SUCCESS;
+}
+
 /* For debug purpose. */
 DEFUN (show_address,
        show_address_cmd,