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Message-Id: <20240828160145.68805-2-kerneljasonxing@gmail.com>
Date: Thu, 29 Aug 2024 00:01:44 +0800
From: Jason Xing <kerneljasonxing@...il.com>
To: davem@...emloft.net,
edumazet@...gle.com,
kuba@...nel.org,
pabeni@...hat.com,
dsahern@...nel.org,
willemb@...gle.com
Cc: netdev@...r.kernel.org,
Jason Xing <kernelxing@...cent.com>,
Willem de Bruijn <willemdebruijn.kernel@...il.com>
Subject: [PATCH net-next v2 1/2] tcp: make SOF_TIMESTAMPING_RX_SOFTWARE feature per socket
From: Jason Xing <kernelxing@...cent.com>
Normally, if we want to record and print the rx timestamp after
tcp_recvmsg_locked(), we must enable both SOF_TIMESTAMPING_SOFTWARE
and SOF_TIMESTAMPING_RX_SOFTWARE flags, from which we also can notice
through running rxtimestamp binary in selftests (see testcase 7).
However, there is one particular case that fails the selftests with
"./rxtimestamp: Expected swtstamp to not be set." error printing in
testcase 6.
How does it happen? When we keep running a thread starting a socket
and set SOF_TIMESTAMPING_RX_SOFTWARE option first, then running
./rxtimestamp, it will fail. The reason is the former thread
switching on netstamp_needed_key that makes the feature global,
every skb going through netif_receive_skb_list_internal() function
will get a current timestamp in net_timestamp_check(). So the skb
will have timestamp regardless of whether its socket option has
SOF_TIMESTAMPING_RX_SOFTWARE or not.
After this patch, we can pass the selftest and control each socket
as we want when using rx timestamp feature.
Cc: Willem de Bruijn <willemdebruijn.kernel@...il.com>
Signed-off-by: Jason Xing <kernelxing@...cent.com>
---
net/ipv4/tcp.c | 11 +++++++++--
1 file changed, 9 insertions(+), 2 deletions(-)
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 8514257f4ecd..5e88c765b9a1 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -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 +2275,20 @@ void tcp_recv_timestamp(struct msghdr *msg, const struct sock *sk,
}
}
- if (READ_ONCE(sk->sk_tsflags) & SOF_TIMESTAMPING_SOFTWARE)
+ /* We have to use the generation flag here to test if we
+ * allow the corresponding application to receive the rx
+ * timestamp. Only using report flag does not hold for
+ * receive timestamping case.
+ */
+ if (tsflags & SOF_TIMESTAMPING_SOFTWARE &&
+ tsflags & SOF_TIMESTAMPING_RX_SOFTWARE)
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)
has_timestamping = true;
else
tss->ts[2] = (struct timespec64) {0};
--
2.37.3
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