Re: [PATCH net-next v2 5/6] bpf: enable bpf timestamping rx in TCP layer

On Sat, May 23, 2026 at 11:45 AM Kuniyuki Iwashima [off-list ref] wrote:

On Thu, May 21, 2026 at 6:53 AM Jason Xing [off-list ref] wrote:

quoted

From: Jason Xing <kernelxing@tencent.com>

Add two if statements to accurately isolate bpf timestamping and so
timestamping. They can work respectively.

As to so_timestamping, only add a loose condition via report flags
to avoid duplicate strict checks that is done in tcp_recv_timestamp()
and performance impact. If the loose condition is hit,
tcp_recv_timestamp() is able to handle the exact case and doesn't
hamper the existing timestamping feature.

Make it work in TCP protocol.

Signed-off-by: Jason Xing <kernelxing@tencent.com>
---
 net/ipv4/tcp.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 21ece4c71612..7ad3561dc8cd 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c

@@ -2353,6 +2353,16 @@ void tcp_recv_timestamp(struct msghdr *msg, const struct sock *sk,

Simply drop const from here rather than casting to
non-const for bpf_skops_rx_timestamping().

sk in all callers of tcp_recv_timestamp() is not const.

Will do that. Thanks.

quoted

        int new_tstamp = sock_flag(sk, SOCK_TSTAMP_NEW);
        u32 tsflags = READ_ONCE(sk->sk_tsflags);

+       if (cgroup_bpf_enabled(CGROUP_SOCK_OPS) &&
+           SK_BPF_CB_FLAG_TEST(sk, SK_BPF_CB_RX_TIMESTAMPING))
+               bpf_skops_rx_timestamping((struct sock *)sk, tss,
+                                         BPF_SOCK_OPS_TSTAMP_RCV_CB);
+
+       if (!sock_flag(sk, SOCK_RCVTSTAMP) &&
+           !(tsflags & SOF_TIMESTAMPING_SOFTWARE) &&
+           !(tsflags & SOF_TIMESTAMPING_RAW_HARDWARE))
+               return;
+
        if (tss->ts[0]) {
                if (sock_flag(sk, SOCK_RCVTSTAMP)) {
                        struct timespec64 tv = ktime_to_timespec64(tss->ts[0]);
--
2.43.7