[PATCH net-next v5 0/2] net-timestamp: introduce a flag to filter out rx software and hardware report

[Jason Xing <kerneljasonxing@gmail.com>]

From: Jason Xing <kernelxing@tencent.com>

When one socket is set SOF_TIMESTAMPING_RX_SOFTWARE which means the
whole system turns on the netstamp_needed_key button, other sockets
that only have SOF_TIMESTAMPING_SOFTWARE will be affected and then
print the rx timestamp information even without setting
SOF_TIMESTAMPING_RX_SOFTWARE generation flag.

How to solve it without breaking users?
We introduce a new flag named SOF_TIMESTAMPING_OPT_RX_FILTER. Using
it together with SOF_TIMESTAMPING_SOFTWARE can stop reporting the
rx software timestamp.

Similarly, we also filter out the hardware case where one process
enables the rx hardware generation flag, then another process only
passing SOF_TIMESTAMPING_RAW_HARDWARE gets the timestamp. So we can set
both SOF_TIMESTAMPING_RAW_HARDWARE and SOF_TIMESTAMPING_OPT_RX_FILTER
to stop reporting rx hardware timestamp after this patch applied.

v5
Link: https://lore.kernel.org/all/20240905071738.3725-1-kerneljasonxing@gmail.com/
1. squash the hardware case patch into this one (Willem)
2. update corresponding commit message and doc (Willem)
3. remove the limitation in sock_set_timestamping() and restore the
simplification branches. (Willem)
4. add missing type and another test in selftests

v4
Link: https://lore.kernel.org/all/20240830153751.86895-1-kerneljasonxing@gmail.com/
1. revise the doc and commit message (Willem)
2. add patch [2/4] to make the doc right (Willem)
3. add patch [3/4] to cover the hardware use (Willem)
4. add testcase for hardware use.
Note: the reason why I split into 4 patches is try to make each commit
clean, atomic, easy to review.

v3
Link: https://lore.kernel.org/all/20240828160145.68805-1-kerneljasonxing@gmail.com/
1. introduce a new flag to avoid application breakage, suggested by
Willem.
2. add it into the selftests.

v2
Link: https://lore.kernel.org/all/20240825152440.93054-1-kerneljasonxing@gmail.com/
Discussed with Willem
1. update the documentation accordingly
2. add more comments in each patch
3. remove the previous test statements in __sock_recv_timestamp()

Jason Xing (2):
  net-timestamp: introduce SOF_TIMESTAMPING_OPT_RX_FILTER flag
  net-timestamp: add selftests for SOF_TIMESTAMPING_OPT_RX_FILTER

 Documentation/networking/timestamping.rst | 27 +++++++++++++++++++++++
 include/uapi/linux/net_tstamp.h           |  3 ++-
 net/ethtool/common.c                      |  1 +
 net/ipv4/tcp.c                            |  9 ++++++--
 net/socket.c                              | 10 +++++++--
 tools/testing/selftests/net/rxtimestamp.c | 18 +++++++++++++++
 6 files changed, 63 insertions(+), 5 deletions(-)

-- 
2.37.3