On Sat, Sep 7, 2024 at 7:24 AM Willem de Bruijn willemdebruijn.kernel@gmail.com wrote:
Jason Xing wrote:
From: Jason Xing kernelxing@tencent.com
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
High level: where is the harm in receiving unsolicited timestamps? A process can easily ignore them. I do wonder if the only use case is an overly strict testcase. Was reminded of this as I tried to write a more concise paragraph for the documentation.
You raised a good question.
I think It's more of a design consideration instead of a bugfix actually. So it is not solving a bug which makes the apps wrong but gives users a hint that we can explicitly and accurately do what we want and we expect.
Let's assume: if we remove all the report flags design, what will happen? It can work of course. I don't believe that people choose to enable the generation flag but are not willing to report it. Of course, It's another thing. I'm just saying.
I wonder if it makes sense to you :) ?
Otherwise implementation looks fine, only the tiniest nit.
@@ -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))) &&Nit: these statements should all align on the inner brace, so indent by one character.
I'm not that sure about the format, please help me to review here:
@@ -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)
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 ||
same here and the following two statements? Should I also indent by one char by the way?
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)-- 2.37.3