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, 1 insertions, 0 deletions

diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index c1a33033cbe2..c9f68802e992 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -3521,6 +3521,7 @@ void skb_tstamp_tx(struct sk_buff *orig_skb,
         memset(serr, 0, sizeof(*serr));
         serr->ee.ee_errno = ENOMSG;
         serr->ee.ee_origin = SO_EE_ORIGIN_TIMESTAMPING;
+        serr->ee.ee_info = SCM_TSTAMP_SND;
 
         err = sock_queue_err_skb(sk, skb);