netdev - Re: [PATCH net-next v5 1/2] net-timestamp: introduce SOF_TIMESTAMPING_OPT_RX

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <CAL+tcoC9NoE3ws3nA-_ANAqD1cWpv9JDzFY11ACryZgg35dQrg@mail.gmail.com>
Date: Sat, 7 Sep 2024 09:23:35 +0800
From: Jason Xing <kerneljasonxing@...il.com>
To: Willem de Bruijn <willemdebruijn.kernel@...il.com>
Cc: davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org, 
	pabeni@...hat.com, dsahern@...nel.org, shuah@...nel.org, willemb@...gle.com, 
	linux-kselftest@...r.kernel.org, netdev@...r.kernel.org, 
	Jason Xing <kernelxing@...cent.com>
Subject: Re: [PATCH net-next v5 1/2] net-timestamp: introduce
 SOF_TIMESTAMPING_OPT_RX_FILTER flag

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