net: allow simultaneous SW and HW transmit timestamping
Add SOF_TIMESTAMPING_OPT_TX_SWHW option to allow an outgoing packet to
be looped to the socket's error queue with a software timestamp even
when a hardware transmit timestamp is expected to be provided by the
driver.
Applications using this option will receive two separate messages from
the error queue, one with a software timestamp and the other with a
hardware timestamp. As the hardware timestamp is saved to the shared skb
info, which may happen before the first message with software timestamp
is received by the application, the hardware timestamp is copied to the
SCM_TIMESTAMPING control message only when the skb has no software
timestamp or it is an incoming packet.
While changing sw_tx_timestamp(), inline it in skb_tx_timestamp() as
there are no other users.
CC: Richard Cochran <richardcochran@gmail.com>
CC: Willem de Bruijn <willemb@google.com>
Signed-off-by: Miroslav Lichvar <mlichvar@redhat.com>
Acked-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/Documentation/networking/timestamping.txt b/Documentation/networking/timestamping.txt
index 50eb0e5..196ba17 100644
--- a/Documentation/networking/timestamping.txt
+++ b/Documentation/networking/timestamping.txt
@@ -203,6 +203,14 @@
enabled and the driver is using NAPI. The struct contains also two
other fields, but they are reserved and undefined.
+SOF_TIMESTAMPING_OPT_TX_SWHW:
+
+ Request both hardware and software timestamps for outgoing packets
+ when SOF_TIMESTAMPING_TX_HARDWARE and SOF_TIMESTAMPING_TX_SOFTWARE
+ are enabled at the same time. If both timestamps are generated,
+ two separate messages will be looped to the socket's error queue,
+ each containing just one timestamp.
+
New applications are encouraged to pass SOF_TIMESTAMPING_OPT_ID to
disambiguate timestamps and SOF_TIMESTAMPING_OPT_TSONLY to operate
regardless of the setting of sysctl net.core.tstamp_allow_data.