net-timestamp: extend SCM_TIMESTAMPING ancillary data struct

Applications that request kernel tx timestamps with SO_TIMESTAMPING
read timestamps as recvmsg() ancillary data. The response is defined
implicitly as timespec[3].

1) define struct scm_timestamping explicitly and

2) add support for new tstamp types. On tx, scm_timestamping always
   accompanies a sock_extended_err. Define previously unused field
   ee_info to signal the type of ts[0]. Introduce SCM_TSTAMP_SND to
   define the existing behavior.

The reception path is not modified. On rx, no struct similar to
sock_extended_err is passed along with SCM_TIMESTAMPING.

Signed-off-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 18 insertions, 0 deletions

diff --git a/include/uapi/linux/errqueue.h b/include/uapi/linux/errqueue.h
index aacd4fb7102a..accee72cae7c 100644
--- a/include/uapi/linux/errqueue.h
+++ b/include/uapi/linux/errqueue.h
@@ -22,5 +22,23 @@ struct sock_extended_err {
 
 #define SO_EE_OFFENDER(ee)      ((struct sockaddr*)((ee)+1))
 
+/**
+ *      struct scm_timestamping - timestamps exposed through cmsg
+ *
+ *      The timestamping interfaces SO_TIMESTAMPING, MSG_TSTAMP_*
+ *      communicate network timestamps by passing this struct in a cmsg with
+ *      recvmsg(). See Documentation/networking/timestamping.txt for details.
+ */
+struct scm_timestamping {
+        struct timespec ts[3];
+};
+
+/* The type of scm_timestamping, passed in sock_extended_err ee_info.
+ * This defines the type of ts[0]. For SCM_TSTAMP_SND only, if ts[0]
+ * is zero, then this is a hardware timestamp and recorded in ts[2].
+ */
+enum {
+        SCM_TSTAMP_SND,         /* driver passed skb to NIC, or HW */
+};
 
 #endif /* _UAPI_LINUX_ERRQUEUE_H */