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Message-ID: <CAL+tcoCyu6w=O5y2fRSfrzDVm04SB2ycXB06uYn2+r2jSRhehA@mail.gmail.com>
Date: Fri, 13 Dec 2024 23:13:53 +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, bpf@...r.kernel.org,
netdev@...r.kernel.org, Jason Xing <kernelxing@...cent.com>
Subject: Re: [PATCH net-next v4 07/11] net-timestamp: support hwtstamp print
for bpf extension
On Fri, Dec 13, 2024 at 7:26 AM Martin KaFai Lau <martin.lau@...ux.dev> wrote:
>
> On 12/7/24 9:37 AM, Jason Xing wrote:
> > From: Jason Xing <kernelxing@...cent.com>
> >
> > Passing the hwtstamp to bpf prog which can print.
> >
> > Signed-off-by: Jason Xing <kernelxing@...cent.com>
> > ---
> > include/net/sock.h | 6 ++++--
> > net/core/skbuff.c | 17 +++++++++++++----
> > net/core/sock.c | 4 +++-
> > 3 files changed, 20 insertions(+), 7 deletions(-)
> >
> > diff --git a/include/net/sock.h b/include/net/sock.h
> > index f88a00108a2f..9bc883573208 100644
> > --- a/include/net/sock.h
> > +++ b/include/net/sock.h
> > @@ -2921,9 +2921,11 @@ int sock_set_timestamping(struct sock *sk, int optname,
> >
> > void sock_enable_timestamps(struct sock *sk);
> > #if defined(CONFIG_CGROUP_BPF) && defined(CONFIG_BPF_SYSCALL)
> > -void bpf_skops_tx_timestamping(struct sock *sk, struct sk_buff *skb, int op);
> > +void bpf_skops_tx_timestamping(struct sock *sk, struct sk_buff *skb, int op,
> > + u32 nargs, u32 *args);
> > #else
> > -static inline void bpf_skops_tx_timestamping(struct sock *sk, struct sk_buff *skb, int op)
> > +static inline void bpf_skops_tx_timestamping(struct sock *sk, struct sk_buff *skb, int op,
> > + u32 nargs, u32 *args)
> > {
> > }
> > #endif
> > diff --git a/net/core/skbuff.c b/net/core/skbuff.c
> > index 48b0c71e9522..182a44815630 100644
> > --- a/net/core/skbuff.c
> > +++ b/net/core/skbuff.c
> > @@ -5539,8 +5539,12 @@ void skb_complete_tx_timestamp(struct sk_buff *skb,
> > }
> > EXPORT_SYMBOL_GPL(skb_complete_tx_timestamp);
> >
> > -static void __skb_tstamp_tx_bpf(struct sock *sk, struct sk_buff *skb, int tstype)
> > +static void __skb_tstamp_tx_bpf(struct sock *sk, struct sk_buff *skb,
> > + struct skb_shared_hwtstamps *hwtstamps,
> > + int tstype)
> > {
> > + struct timespec64 tstamp;
> > + u32 args[2] = {0, 0};
> > int op;
> >
> > if (!sk)
> > @@ -5552,6 +5556,11 @@ static void __skb_tstamp_tx_bpf(struct sock *sk, struct sk_buff *skb, int tstype
> > break;
> > case SCM_TSTAMP_SND:
> > op = BPF_SOCK_OPS_TS_SW_OPT_CB;
>
> > + if (hwtstamps) {
> > + tstamp = ktime_to_timespec64(hwtstamps->hwtstamp);
>
> Avoid this conversion which is likely not useful to the bpf prog. Directly pass
> hwtstamps->hwtstamp (in ns?) to the bpf prog. Put lower 32bits in args[0] and
> higher 32bits in args[1].
It makes sense.
>
> Also, how about adding a BPF_SOCK_OPS_TS_"HW"_OPT_CB for the "hwtstamps != NULL"
> case instead of reusing the BPF_SOCK_OPS_TS_"SW"_OPT_CB?
Good suggestion. Will do that.
>
> A more subtle thing for the hwtstamps case is, afaik the bpf prog will not be
> called. All drivers are still only testing SKBTX_HW_TSTAMP instead of testing
> (SKBTX_HW_TSTAMP | SKBTX_BPF).
Ah, I didn't realize that!!
>
> There are a lot of drivers to change though. A quick thought is to rename the
> existing SKBTX_HW_TSTAMP (e.g. __SKBTX_HW_TSTAMP = 1 << 0) and define
> SKBTX_HW_TSTAMP like:
>
> #define SKBTX_HW_TSTAMP (__SKBTX_HW_TSTAMP | SKBTX_BPF)
I will take it, thanks!
>
> Then change some of the existing skb_shinfo(skb)->tx_flags "setting" site to use
> __SKBTX_HW_TSTAMP instead. e.g. in __sock_tx_timestamp(). Not very pretty but
> may be still better than changing many drivers. May be there is a better way...
I agree with your approach. Changing so many drivers would be a head-ache thing.
>
> While talking about where to test the SKBTX_BPF bit, I wonder if the new
> skb_tstamp_is_set() is needed. For the non SKBTX_HW_TSTAMP case, the number of
> tx_flags testing sites should be limited, so should be easy to add the SKBTX_BPF
> bit test. e.g. at the __dev_queue_xmit, test "if
> (unlikely(skb_shinfo(skb)->tx_flags & (SKBTX_SCHED_TSTAMP | SKBTX_BPF)))". Patch
> 6 has also tested the bpf specific bit at tcp_ack_tstamp() before calling the
> __skb_tstamp_tx().
>
> At the beginning of __skb_tstamp_tx(), do something like this:
>
> void __skb_tstamp_tx(struct sk_buff *orig_skb,
> const struct sk_buff *ack_skb,
> struct skb_shared_hwtstamps *hwtstamps,
> struct sock *sk, int tstype)
> {
> if (cgroup_bpf_enabled(CGROUP_SOCK_OPS) &&
> unlikely(skb_shinfo(skb)->tx_flags & SKBTX_BPF))
> __skb_tstamp_tx_bpf(sk, orig_skb, hwtstamps, tstype);
>
> if (unlikely(!(skb_shinfo(skb)->tx_flags & ~SKBTX_BPF)))
> return;
>
> Then the new skb_tstamp_tx_output() shuffle is probably not be needed also.
>
> > + args[0] = tstamp.tv_sec;
> > + args[1] = tstamp.tv_nsec;
> > + }
> > break;
> > case SCM_TSTAMP_ACK:
> > op = BPF_SOCK_OPS_TS_ACK_OPT_CB;
> > @@ -5560,7 +5569,7 @@ static void __skb_tstamp_tx_bpf(struct sock *sk, struct sk_buff *skb, int tstype
> > return;
> > }
> >
> > - bpf_skops_tx_timestamping(sk, skb, op);
> > + bpf_skops_tx_timestamping(sk, skb, op, 2, args);
> > }
> >
> > static void skb_tstamp_tx_output(struct sk_buff *orig_skb,
> > @@ -5651,7 +5660,7 @@ void __skb_tstamp_tx(struct sk_buff *orig_skb,
> > if (unlikely(skb_tstamp_is_set(orig_skb, tstype, false)))
> > skb_tstamp_tx_output(orig_skb, ack_skb, hwtstamps, sk, tstype);
> > if (unlikely(skb_tstamp_is_set(orig_skb, tstype, true)))
> > - __skb_tstamp_tx_bpf(sk, orig_skb, tstype);
> > + __skb_tstamp_tx_bpf(sk, orig_skb, hwtstamps, tstype);
> > }
> > EXPORT_SYMBOL_GPL(__skb_tstamp_tx);
> >
> > @@ -5662,7 +5671,7 @@ void skb_tstamp_tx(struct sk_buff *orig_skb,
> >
> > skb_tstamp_tx_output(orig_skb, NULL, hwtstamps, orig_skb->sk, tstype);
> > if (unlikely(skb_tstamp_is_set(orig_skb, tstype, true)))
> > - __skb_tstamp_tx_bpf(orig_skb->sk, orig_skb, tstype);
> > + __skb_tstamp_tx_bpf(orig_skb->sk, orig_skb, hwtstamps, tstype);
> > }
> > EXPORT_SYMBOL_GPL(skb_tstamp_tx);
> >
> > diff --git a/net/core/sock.c b/net/core/sock.c
> > index 79cb5c74c76c..504939bafe0c 100644
> > --- a/net/core/sock.c
> > +++ b/net/core/sock.c
> > @@ -942,7 +942,8 @@ int sock_set_timestamping(struct sock *sk, int optname,
> > }
> >
> > #if defined(CONFIG_CGROUP_BPF) && defined(CONFIG_BPF_SYSCALL)
> > -void bpf_skops_tx_timestamping(struct sock *sk, struct sk_buff *skb, int op)
> > +void bpf_skops_tx_timestamping(struct sock *sk, struct sk_buff *skb, int op,
> > + u32 nargs, u32 *args)
>
> Directly pass hwtstamps->hwtstamp instead of args and nargs. Save a memcpy below.
>
> > {
> > struct bpf_sock_ops_kern sock_ops;
> >
> > @@ -952,6 +953,7 @@ void bpf_skops_tx_timestamping(struct sock *sk, struct sk_buff *skb, int op)
> > sock_ops.op = op;
> > sock_ops.is_fullsock = 1;
> > sock_ops.sk = sk;
> > + memcpy(sock_ops.args, args, nargs * sizeof(*args));
> > __cgroup_bpf_run_filter_sock_ops(sk, &sock_ops, CGROUP_SOCK_OPS);
> > }
> > #endif
>
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