netlink: add macro for checking dump ctx size

We encourage casting struct netlink_callback::ctx to a local
struct (in a comment above the field). Provide a convenience
macro for checking if the local struct fits into the ctx.

Reviewed-by: Jacob Keller <[email protected]>
Reviewed-by: Jiri Pirko <[email protected]>
Signed-off-by: Jakub Kicinski <[email protected]>

1 files changed, 4 insertions, 0 deletions

diff --git a/include/linux/netlink.h b/include/linux/netlink.h
index d81bde5a5844..38f6334f408c 100644
--- a/include/linux/netlink.h
+++ b/include/linux/netlink.h
@@ -263,6 +263,10 @@ struct netlink_callback {
 	};
 };
 
+#define NL_ASSET_DUMP_CTX_FITS(type_name)				\
+	BUILD_BUG_ON(sizeof(type_name) >				\
+		     sizeof_field(struct netlink_callback, ctx))
+
 struct netlink_notify {
 	struct net *net;
 	u32 portid;