On Sat, Sep 7, 2024 at 7:24 AM Willem de Bruijn
<willemdebruijn.kernel@xxxxxxxxx> wrote:
>
> Jason Xing wrote:
> > From: Jason Xing <kernelxing@xxxxxxxxxxx>
> >
> > 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@xxxxxxxxxx>
> > Signed-off-by: Jason Xing <kernelxing@xxxxxxxxxxx>
>
> 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
> >
>
>
