net-timestamp: introduce SOF_TIMESTAMPING_OPT_RX_FILTER flag
authorJason Xing <kernelxing@tencent.com>
Mon, 9 Sep 2024 01:56:11 +0000 (09:56 +0800)
committerJakub Kicinski <kuba@kernel.org>
Tue, 10 Sep 2024 23:55:23 +0000 (16:55 -0700)
commitbe8e9eb3750639aa5cffb3f764ca080caed41bd0
treeab6a286d9ab8afbdf8b77668935b8b7864bbb8b5
parente503f82e304b039332226008addac9d13ac68cb9
net-timestamp: introduce SOF_TIMESTAMPING_OPT_RX_FILTER flag

introduce a new flag SOF_TIMESTAMPING_OPT_RX_FILTER in the receive
path. User can set it with SOF_TIMESTAMPING_SOFTWARE to filter
out rx software timestamp report, especially after a process turns on
netstamp_needed_key which can time stamp every incoming skb.

Previously, we found out if an application starts first which turns on
netstamp_needed_key, then another one only passing SOF_TIMESTAMPING_SOFTWARE
could also get rx timestamp. Now we handle this case by introducing this
new flag without breaking users.

Quoting Willem to explain why we need the flag:
"why a process would want to request software timestamp reporting, but
not receive software timestamp generation. The only use I see is when
the application does request
SOF_TIMESTAMPING_SOFTWARE | SOF_TIMESTAMPING_TX_SOFTWARE."

Similarly, this new flag could also be used for hardware case where we
can set it with SOF_TIMESTAMPING_RAW_HARDWARE, then we won't receive
hardware receive timestamp.

Another thing about errqueue in this patch I have a few words to say:
In this case, we need to handle the egress path carefully, or else
reporting the tx timestamp will fail. Egress path and ingress path will
finally call sock_recv_timestamp(). We have to distinguish them.
Errqueue is a good indicator to reflect the flow direction.

Suggested-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: Jason Xing <kernelxing@tencent.com>
Reviewed-by: Willem de Bruijn <willemb@google.com>
Link: https://patch.msgid.link/20240909015612.3856-2-kerneljasonxing@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Documentation/networking/timestamping.rst
include/uapi/linux/net_tstamp.h
net/ethtool/common.c
net/ipv4/tcp.c
net/socket.c