netdev - Re: [PATCH bpf-next v7 08/13] net-timestamp: support hw SCM_TSTAMP

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Message-ID: <CAL+tcoA5tSRNGOqP2tpNM_M4rRBQb2WSBcjEcVS5=JJSPPjRKQ@mail.gmail.com>
Date: Tue, 4 Feb 2025 09:13:47 +0800
From: Jason Xing <kerneljasonxing@...il.com>
To: Martin KaFai Lau <martin.lau@...ux.dev>
Cc: davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org, 
	pabeni@...hat.com, dsahern@...nel.org, willemdebruijn.kernel@...il.com, 
	willemb@...gle.com, ast@...nel.org, daniel@...earbox.net, andrii@...nel.org, 
	eddyz87@...il.com, song@...nel.org, yonghong.song@...ux.dev, 
	john.fastabend@...il.com, kpsingh@...nel.org, sdf@...ichev.me, 
	haoluo@...gle.com, jolsa@...nel.org, horms@...nel.org, bpf@...r.kernel.org, 
	netdev@...r.kernel.org
Subject: Re: [PATCH bpf-next v7 08/13] net-timestamp: support hw
 SCM_TSTAMP_SND for bpf extension

On Tue, Feb 4, 2025 at 8:56 AM Martin KaFai Lau <martin.lau@...ux.dev> wrote:
>
> On 1/28/25 12:46 AM, Jason Xing wrote:
> > In this patch, we finish the hardware part. Then bpf program can
> > fetch the hwstamp from skb directly.
> >
> > To avoid changing so many callers using SKBTX_HW_TSTAMP from drivers,
> > use this simple modification like this patch does to support printing
> > hardware timestamp.
> >
> > Signed-off-by: Jason Xing <kerneljasonxing@...il.com>
> > ---
> >   include/linux/skbuff.h         |  4 +++-
> >   include/uapi/linux/bpf.h       |  7 +++++++
> >   net/core/skbuff.c              | 11 ++++++-----
> >   net/dsa/user.c                 |  2 +-
> >   net/socket.c                   |  2 +-
> >   tools/include/uapi/linux/bpf.h |  7 +++++++
> >   6 files changed, 25 insertions(+), 8 deletions(-)
> >
> > diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
> > index de8d3bd311f5..df2d790ae36b 100644
> > --- a/include/linux/skbuff.h
> > +++ b/include/linux/skbuff.h
> > @@ -471,7 +471,7 @@ struct skb_shared_hwtstamps {
> >   /* Definitions for tx_flags in struct skb_shared_info */
> >   enum {
> >       /* generate hardware time stamp */
> > -     SKBTX_HW_TSTAMP = 1 << 0,
> > +     __SKBTX_HW_TSTAMP = 1 << 0,
> >
> >       /* generate software time stamp when queueing packet to NIC */
> >       SKBTX_SW_TSTAMP = 1 << 1,
> > @@ -495,6 +495,8 @@ enum {
> >       SKBTX_BPF = 1 << 7,
> >   };
> >
> > +#define SKBTX_HW_TSTAMP              (__SKBTX_HW_TSTAMP | SKBTX_BPF)
> > +
> >   #define SKBTX_ANY_SW_TSTAMP (SKBTX_SW_TSTAMP    | \
> >                                SKBTX_SCHED_TSTAMP | \
> >                                SKBTX_BPF)
> > diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
> > index 6a1083bcf779..4c3566f623c2 100644
> > --- a/include/uapi/linux/bpf.h
> > +++ b/include/uapi/linux/bpf.h
> > @@ -7040,6 +7040,13 @@ enum {
> >                                        * to the nic when SK_BPF_CB_TX_TIMESTAMPING
> >                                        * feature is on.
> >                                        */
> > +     BPF_SOCK_OPS_TS_HW_OPT_CB,      /* Called in hardware phase when
> > +                                      * SK_BPF_CB_TX_TIMESTAMPING feature
> > +                                      * is on. At the same time, hwtstamps
> > +                                      * of skb is initialized as the
> > +                                      * timestamp that hardware just
> > +                                      * generates.
> > +                                      */
> >   };
> >
> >   /* List of TCP states. There is a build check in net/ipv4/tcp.c to detect
> > diff --git a/net/core/skbuff.c b/net/core/skbuff.c
> > index 288eb9869827..c769feae5162 100644
> > --- a/net/core/skbuff.c
> > +++ b/net/core/skbuff.c
> > @@ -5548,7 +5548,7 @@ static bool skb_enable_app_tstamp(struct sk_buff *skb, int tstype, bool sw)
> >               flag = SKBTX_SCHED_TSTAMP;
> >               break;
> >       case SCM_TSTAMP_SND:
> > -             flag = sw ? SKBTX_SW_TSTAMP : SKBTX_HW_TSTAMP;
> > +             flag = sw ? SKBTX_SW_TSTAMP : __SKBTX_HW_TSTAMP;
> >               break;
> >       case SCM_TSTAMP_ACK:
> >               if (TCP_SKB_CB(skb)->txstamp_ack)
> > @@ -5565,7 +5565,8 @@ static bool skb_enable_app_tstamp(struct sk_buff *skb, int tstype, bool sw)
> >   }
> >
> >   static void skb_tstamp_tx_bpf(struct sk_buff *skb, struct sock *sk,
> > -                           int tstype, bool sw)
> > +                           int tstype, bool sw,
> > +                           struct skb_shared_hwtstamps *hwtstamps)
> >   {
> >       int op;
> >
> > @@ -5577,9 +5578,9 @@ static void skb_tstamp_tx_bpf(struct sk_buff *skb, struct sock *sk,
> >               op = BPF_SOCK_OPS_TS_SCHED_OPT_CB;
> >               break;
> >       case SCM_TSTAMP_SND:
> > +             op = sw ? BPF_SOCK_OPS_TS_SW_OPT_CB : BPF_SOCK_OPS_TS_HW_OPT_CB;
> >               if (!sw)
>
> Patch 5 mentioned hwtstamps could be NULL, so this should be "if (hwtstamps)" here.
>
> > -                     return;
> > -             op = BPF_SOCK_OPS_TS_SW_OPT_CB;
> > +                     *skb_hwtstamps(skb) = *hwtstamps;
>
> Otherwise, this will crash.

Sorry, I tested it in the wrong way... Will fix it soon!

>
> pw-bot: cr
>
>
> >               break;
> >       default:
> >               return;