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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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17
Documentation/networking/timestamping.rst
View File

@ -267,6 +267,23 @@ SOF_TIMESTAMPING_OPT_TX_SWHW:
two separate messages will be looped to the socket's error queue,
each containing just one timestamp.
SOF_TIMESTAMPING_OPT_RX_FILTER:
Filter out spurious receive timestamps: report a receive timestamp
only if the matching timestamp generation flag is enabled.
Receive timestamps are generated early in the ingress path, before a
packet's destination socket is known. If any socket enables receive
timestamps, packets for all socket will receive timestamped packets.
Including those that request timestamp reporting with
SOF_TIMESTAMPING_SOFTWARE and/or SOF_TIMESTAMPING_RAW_HARDWARE, but
do not request receive timestamp generation. This can happen when
requesting transmit timestamps only.
Receiving spurious timestamps is generally benign. A process can
ignore the unexpected non-zero value. But it makes behavior subtly
dependent on other sockets. This flag isolates the socket for more
deterministic behavior.
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.

3
include/uapi/linux/net_tstamp.h
View File

@ -32,8 +32,9 @@ enum {
SOF_TIMESTAMPING_OPT_TX_SWHW = (1<<14),
SOF_TIMESTAMPING_BIND_PHC = (1 << 15),
SOF_TIMESTAMPING_OPT_ID_TCP = (1 << 16),
SOF_TIMESTAMPING_OPT_RX_FILTER = (1 << 17),
SOF_TIMESTAMPING_LAST = SOF_TIMESTAMPING_OPT_ID_TCP,
SOF_TIMESTAMPING_LAST = SOF_TIMESTAMPING_OPT_RX_FILTER,
SOF_TIMESTAMPING_MASK = (SOF_TIMESTAMPING_LAST - 1) |
SOF_TIMESTAMPING_LAST
};

1
net/ethtool/common.c
View File

@ -427,6 +427,7 @@ const char sof_timestamping_names[][ETH_GSTRING_LEN] = {
[const_ilog2(SOF_TIMESTAMPING_OPT_TX_SWHW)] = "option-tx-swhw",
[const_ilog2(SOF_TIMESTAMPING_BIND_PHC)] = "bind-phc",
[const_ilog2(SOF_TIMESTAMPING_OPT_ID_TCP)] = "option-id-tcp",
[const_ilog2(SOF_TIMESTAMPING_OPT_RX_FILTER)] = "option-rx-filter",
};
static_assert(ARRAY_SIZE(sof_timestamping_names) == __SOF_TIMESTAMPING_CNT);

9
net/ipv4/tcp.c
View File

@ -2235,6 +2235,7 @@ void tcp_recv_timestamp(struct msghdr *msg, const struct sock *sk,
struct scm_timestamping_internal *tss)
{
int new_tstamp = sock_flag(sk, SOCK_TSTAMP_NEW);
u32 tsflags = READ_ONCE(sk->sk_tsflags);
bool has_timestamping = false;
if (tss->ts[0].tv_sec || tss->ts[0].tv_nsec) {
@ -2274,14 +2275,18 @@ void tcp_recv_timestamp(struct msghdr *msg, const struct sock *sk,
}
}
if (READ_ONCE(sk->sk_tsflags) & SOF_TIMESTAMPING_SOFTWARE)
if (tsflags & SOF_TIMESTAMPING_SOFTWARE &&
(tsflags & SOF_TIMESTAMPING_RX_SOFTWARE ||
!(tsflags & SOF_TIMESTAMPING_OPT_RX_FILTER)))
has_timestamping = true;
else
tss->ts[0] = (struct timespec64) {0};
}
if (tss->ts[2].tv_sec || tss->ts[2].tv_nsec) {
if (READ_ONCE(sk->sk_tsflags) & SOF_TIMESTAMPING_RAW_HARDWARE)
if (tsflags & SOF_TIMESTAMPING_RAW_HARDWARE &&
(tsflags & SOF_TIMESTAMPING_RX_HARDWARE ||
!(tsflags & SOF_TIMESTAMPING_OPT_RX_FILTER)))
has_timestamping = true;
else
tss->ts[2] = (struct timespec64) {0};

10
net/socket.c
View File

@ -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)