[RFC PATCH] uapi: fix linux/packet_diag.h userspace compilation error

Replace MAX_ADDR_LEN with its numeric value to fix the following
linux/packet_diag.h userspace compilation error:

/usr/include/linux/packet_diag.h:67:17: error: 'MAX_ADDR_LEN' undeclared here (not in a function)
  __u8 pdmc_addr[MAX_ADDR_LEN];

This is not the first case in the UAPI where the numeric value
of MAX_ADDR_LEN is used, uapi/linux/if_link.h already does the same,
and there are no UAPI headers besides these two that use MAX_ADDR_LEN.

The alternative fix would be to include <linux/netdevice.h> which
pulls in other headers and a lot of definitions with them.

Signed-off-by: Dmitry V. Levin <redacted>
---
I'm not quite comfortable with this approach but the alternative
has its own drawbacks.

 include/uapi/linux/packet_diag.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/uapi/linux/packet_diag.h b/include/uapi/linux/packet_diag.h
index d08c63f..0c5d5dd 100644
--- a/include/uapi/linux/packet_diag.h
+++ b/include/uapi/linux/packet_diag.h

@@ -64,7 +64,7 @@ struct packet_diag_mclist {
 	__u32	pdmc_count;
 	__u16	pdmc_type;
 	__u16	pdmc_alen;
-	__u8	pdmc_addr[MAX_ADDR_LEN];
+	__u8	pdmc_addr[32]; /* MAX_ADDR_LEN */
 };
 
 struct packet_diag_ring {

-- 
ldv