sock: add MSG_ZEROCOPY
The kernel supports zerocopy sendmsg in virtio and tap. Expand the
infrastructure to support other socket types. Introduce a completion
notification channel over the socket error queue. Notifications are
returned with ee_origin SO_EE_ORIGIN_ZEROCOPY. ee_errno is 0 to avoid
blocking the send/recv path on receiving notifications.
Add reference counting, to support the skb split, merge, resize and
clone operations possible with SOCK_STREAM and other socket types.
The patch does not yet modify any datapaths.
Signed-off-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/uapi/linux/errqueue.h b/include/uapi/linux/errqueue.h
index 07bdce1..78fdf52 100644
--- a/include/uapi/linux/errqueue.h
+++ b/include/uapi/linux/errqueue.h
@@ -18,10 +18,13 @@ struct sock_extended_err {
#define SO_EE_ORIGIN_ICMP 2
#define SO_EE_ORIGIN_ICMP6 3
#define SO_EE_ORIGIN_TXSTATUS 4
+#define SO_EE_ORIGIN_ZEROCOPY 5
#define SO_EE_ORIGIN_TIMESTAMPING SO_EE_ORIGIN_TXSTATUS
#define SO_EE_OFFENDER(ee) ((struct sockaddr*)((ee)+1))
+#define SO_EE_CODE_ZEROCOPY_COPIED 1
+
/**
* struct scm_timestamping - timestamps exposed through cmsg
*