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net-timestamp: introduce SOF_TIMESTAMPING_OPT_RX_FILTER flag

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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>
This commit is contained in:
Jason Xing
2024-09-09 09:56:11 +08:00
committed by Jakub Kicinski
parent e503f82e30
commit be8e9eb375
5 changed files with 35 additions and 5 deletions
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10
net/socket.c
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@@ -946,11 +946,17 @@ void __sock_recv_timestamp(struct msghdr *msg, struct sock *sk,
memset(&tss, 0, sizeof(tss));
tsflags = READ_ONCE(sk->sk_tsflags);
if ((tsflags & SOF_TIMESTAMPING_SOFTWARE) &&
if ((tsflags & SOF_TIMESTAMPING_SOFTWARE &&
(tsflags & SOF_TIMESTAMPING_RX_SOFTWARE ||
skb_is_err_queue(skb) ||
!(tsflags & SOF_TIMESTAMPING_OPT_RX_FILTER))) &&
ktime_to_timespec64_cond(skb->tstamp, tss.ts + 0))
empty = 0;
if (shhwtstamps &&
(tsflags & SOF_TIMESTAMPING_RAW_HARDWARE) &&
(tsflags & SOF_TIMESTAMPING_RAW_HARDWARE &&
(tsflags & SOF_TIMESTAMPING_RX_HARDWARE ||
skb_is_err_queue(skb) ||
!(tsflags & SOF_TIMESTAMPING_OPT_RX_FILTER))) &&
!skb_is_swtx_tstamp(skb, false_tstamp)) {
if_index = 0;
if (skb_shinfo(skb)->tx_flags & SKBTX_HW_TSTAMP_NETDEV)