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Message-ID: <CAL+tcoAH6OYNOvUg8LDYw_b+ar3bo2AXqq0=oHgb-ogEYAeHZA@mail.gmail.com>
Date: Thu, 6 Feb 2025 00:03:27 +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, willemb@...gle.com, ast@...nel.org,
daniel@...earbox.net, andrii@...nel.org, martin.lau@...ux.dev,
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 v8 08/12] bpf: support hw SCM_TSTAMP_SND of SO_TIMESTAMPING
On Wed, Feb 5, 2025 at 11:45 PM Willem de Bruijn
<willemdebruijn.kernel@...il.com> wrote:
>
> Jason Xing wrote:
> > Patch finishes the hardware part.
>
> For consistency with previous patches, and to make sense of this
> commit message on its own, when stumbling on it, e.g., through
> git blame, replace the above with
>
> Support hw SCM_TSTAMP_SND case.
>
> > 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.
>
> Which simple modification? Please state explicitly.
>
> > Signed-off-by: Jason Xing <kerneljasonxing@...il.com>
> > ---
> > include/linux/skbuff.h | 4 +++-
> > include/uapi/linux/bpf.h | 7 +++++++
> > net/core/skbuff.c | 13 +++++++------
> > net/dsa/user.c | 2 +-
> > net/socket.c | 2 +-
> > tools/include/uapi/linux/bpf.h | 7 +++++++
> > 6 files changed, 26 insertions(+), 9 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,
>
> Perhaps we can have a more descriptive name. SKBTX_HW_TSTAMP_NOBPF?
Good suggestion.
>
> >
> > /* 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.
>
> "hwtstamp of skb is initialized" is this something new? Or are you
> just conveying that when this callback is called, skb_hwtstamps(skb)
> is non-zero? If the latter, drop, because the wording is confusing.
I will update it.
>
> > + */
> > };
> >
> > /* 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 b22d079e7143..264435f989ad 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;
> >
> > @@ -5574,9 +5575,9 @@ 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:
> > - if (!sw)
> > - return;
> > - op = BPF_SOCK_OPS_TS_SW_OPT_CB;
> > + op = sw ? BPF_SOCK_OPS_TS_SW_OPT_CB : BPF_SOCK_OPS_TS_HW_OPT_CB;
> > + if (!sw && hwtstamps)
> > + *skb_hwtstamps(skb) = *hwtstamps;
>
> Isn't this called by drivers that have actually set skb_hwtstamps?
Oops, somehow my mind has gone blank :( Will remove it. Thanks for
correcting me!
> > break;
> > default:
> > return;
> > @@ -5599,7 +5600,7 @@ void __skb_tstamp_tx(struct sk_buff *orig_skb,
> >
> > /* bpf extension feature entry */
> > if (skb_shinfo(orig_skb)->tx_flags & SKBTX_BPF)
> > - skb_tstamp_tx_bpf(orig_skb, sk, tstype, sw);
> > + skb_tstamp_tx_bpf(orig_skb, sk, tstype, sw, hwtstamps);
> >
> > /* application feature entry */
> > if (!skb_enable_app_tstamp(orig_skb, tstype, sw))
> > diff --git a/net/dsa/user.c b/net/dsa/user.c
> > index 291ab1b4acc4..ae715bf0ae75 100644
> > --- a/net/dsa/user.c
> > +++ b/net/dsa/user.c
> > @@ -897,7 +897,7 @@ static void dsa_skb_tx_timestamp(struct dsa_user_priv *p,
> > {
> > struct dsa_switch *ds = p->dp->ds;
> >
> > - if (!(skb_shinfo(skb)->tx_flags & SKBTX_HW_TSTAMP))
> > + if (!(skb_shinfo(skb)->tx_flags & __SKBTX_HW_TSTAMP))
> > return;
> >
> > if (!ds->ops->port_txtstamp)
> > diff --git a/net/socket.c b/net/socket.c
> > index 262a28b59c7f..70eabb510ce6 100644
> > --- a/net/socket.c
> > +++ b/net/socket.c
> > @@ -676,7 +676,7 @@ void __sock_tx_timestamp(__u32 tsflags, __u8 *tx_flags)
> > u8 flags = *tx_flags;
> >
> > if (tsflags & SOF_TIMESTAMPING_TX_HARDWARE) {
> > - flags |= SKBTX_HW_TSTAMP;
> > + flags |= __SKBTX_HW_TSTAMP;
> >
> > /* PTP hardware clocks can provide a free running cycle counter
> > * as a time base for virtual clocks. Tell driver to use the
> > diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
> > index 9bd1c7c77b17..974b7f61d11f 100644
> > --- a/tools/include/uapi/linux/bpf.h
> > +++ b/tools/include/uapi/linux/bpf.h
> > @@ -7033,6 +7033,13 @@ 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
> > --
> > 2.43.5
> >
>
>
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