sock.h: Add a new sock zero-copy flag

Signed-off-by: NShirley Ma <xma@us.ibm.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

include/net/sock.h

@@ -563,6 +563,7 @@ enum sock_flags {
 	SOCK_TIMESTAMPING_SYS_HARDWARE, /* %SOF_TIMESTAMPING_SYS_HARDWARE */
 	SOCK_FASYNC, /* fasync() active */
 	SOCK_RXQ_OVFL,
+	SOCK_ZEROCOPY, /* buffers from userspace */
 };
 
 static inline void sock_copy_flags(struct sock *nsk, struct sock *osk)