On Wed, Jul 28, 2021 at 07:55:53AM +0200, Greg Kroah-Hartman wrote:

quoted

 struct ethhdr {
-	unsigned char	h_dest[ETH_ALEN];	/* destination eth addr	*/
-	unsigned char	h_source[ETH_ALEN];	/* source ether addr	*/
+	union {
+		struct {
+			unsigned char h_dest[ETH_ALEN];	  /* destination eth addr */
+			unsigned char h_source[ETH_ALEN]; /* source ether addr	  */
+		};
+		struct {
+			unsigned char h_dest[ETH_ALEN];	  /* destination eth addr */
+			unsigned char h_source[ETH_ALEN]; /* source ether addr	  */
+		} addrs;

A union of the same fields in the same structure in the same way?

Ah, because struct_group() can not be used here?  Still feels odd to see
in a userspace-visible header.

Yeah, there is some inconsistency here. I will clean this up for v2.

Is there a place we can put kernel-specific macros for use in UAPI
headers? (I need to figure out where things like __kernel_size_t get
defined...)

-- 
Kees Cook