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Message-ID: <67a384ea2d547_14e0832942c@willemb.c.googlers.com.notmuch>
Date: Wed, 05 Feb 2025 10:34:02 -0500
From: Willem de Bruijn <willemdebruijn.kernel@...il.com>
To: Jason Xing <kerneljasonxing@...il.com>,
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,
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
Cc: bpf@...r.kernel.org,
netdev@...r.kernel.org,
Jason Xing <kerneljasonxing@...il.com>
Subject: Re: [PATCH bpf-next v8 05/12] net-timestamp: prepare for isolating
two modes of SO_TIMESTAMPING
Jason Xing wrote:
> No functional changes here, only add skb_enable_app_tstamp() to test
> if the orig_skb matches the usage of application SO_TIMESTAMPING
> or its bpf extension. And it's good to support two modes in
> parallel later in this series.
>
> Also, this patch deliberately distinguish the software and
> hardware SCM_TSTAMP_SND timestamp by passing 'sw' parameter in order
> to avoid such a case where hardware may go wrong and pass a NULL
> hwstamps, which is even though unlikely to happen. If it really
> happens, bpf prog will finally consider it as a software timestamp.
> It will be hardly recognized. Let's make the timestamping part
> more robust.
Disagree. Don't add a crutch that has not shown to be necessary for
all this time.
Just infer hw from hwtstamps != NULL.
> Signed-off-by: Jason Xing <kerneljasonxing@...il.com>
> ---
> include/linux/skbuff.h | 13 +++++++------
> net/core/dev.c | 2 +-
> net/core/skbuff.c | 32 ++++++++++++++++++++++++++++++--
> net/ipv4/tcp_input.c | 3 ++-
> 4 files changed, 40 insertions(+), 10 deletions(-)
>
> diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
> index bb2b751d274a..dfc419281cc9 100644
> --- a/include/linux/skbuff.h
> +++ b/include/linux/skbuff.h
> @@ -39,6 +39,7 @@
> #include <net/net_debug.h>
> #include <net/dropreason-core.h>
> #include <net/netmem.h>
> +#include <uapi/linux/errqueue.h>
>
> /**
> * DOC: skb checksums
> @@ -4533,18 +4534,18 @@ void skb_complete_tx_timestamp(struct sk_buff *skb,
>
> 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);
> + struct sock *sk, bool sw, int tstype);
>
> /**
> - * skb_tstamp_tx - queue clone of skb with send time stamps
> + * skb_tstamp_tx - queue clone of skb with send HARDWARE timestamps
Unfortunately this cannot be modified to skb_tstamp_tx_hw, as that
would require updating way too many callers.
> * @orig_skb: the original outgoing packet
> * @hwtstamps: hardware time stamps, may be NULL if not available
> *
> * If the skb has a socket associated, then this function clones the
> * skb (thus sharing the actual data and optional structures), stores
> - * the optional hardware time stamping information (if non NULL) or
> - * generates a software time stamp (otherwise), then queues the clone
> - * to the error queue of the socket. Errors are silently ignored.
> + * the optional hardware time stamping information (if non NULL) then
> + * queues the clone to the error queue of the socket. Errors are
> + * silently ignored.
> */
> void skb_tstamp_tx(struct sk_buff *orig_skb,
> struct skb_shared_hwtstamps *hwtstamps);
> @@ -4565,7 +4566,7 @@ static inline void skb_tx_timestamp(struct sk_buff *skb)
> {
> skb_clone_tx_timestamp(skb);
> if (skb_shinfo(skb)->tx_flags & SKBTX_SW_TSTAMP)
> - skb_tstamp_tx(skb, NULL);
> + __skb_tstamp_tx(skb, NULL, NULL, skb->sk, true, SCM_TSTAMP_SND);
If a separate version for software timestamps were needed, I'd suggest
adding a skb_tstamp_tx_sw() wrapper. But see first comment.
> }
>
> /**
> diff --git a/net/core/dev.c b/net/core/dev.c
> index afa2282f2604..d77b8389753e 100644
> --- a/net/core/dev.c
> +++ b/net/core/dev.c
> @@ -4501,7 +4501,7 @@ int __dev_queue_xmit(struct sk_buff *skb, struct net_device *sb_dev)
> skb_assert_len(skb);
>
> if (unlikely(skb_shinfo(skb)->tx_flags & SKBTX_SCHED_TSTAMP))
> - __skb_tstamp_tx(skb, NULL, NULL, skb->sk, SCM_TSTAMP_SCHED);
> + __skb_tstamp_tx(skb, NULL, NULL, skb->sk, true, SCM_TSTAMP_SCHED);
>
> /* Disable soft irqs for various locks below. Also
> * stops preemption for RCU.
> diff --git a/net/core/skbuff.c b/net/core/skbuff.c
> index a441613a1e6c..6042961dfc02 100644
> --- a/net/core/skbuff.c
> +++ b/net/core/skbuff.c
> @@ -5539,10 +5539,35 @@ void skb_complete_tx_timestamp(struct sk_buff *skb,
> }
> EXPORT_SYMBOL_GPL(skb_complete_tx_timestamp);
>
> +static bool skb_enable_app_tstamp(struct sk_buff *skb, int tstype, bool sw)
app is a bit vague. I suggest
skb_tstamp_tx_report_so_timestamping
and
skb_tstamp_tx_report_bpf_timestamping
> +{
> + int flag;
> +
> + switch (tstype) {
> + case SCM_TSTAMP_SCHED:
> + flag = SKBTX_SCHED_TSTAMP;
> + break;
Please just have a one line statements in the case directly:
case SCM_TSTAMP_SCHED:
return skb_shinfo(skb)->tx_flags & SKBTX_SCHED_TSTAMP;
case SCM_TSTAMP_SND:
return skb_shinfo(skb)->tx_flags & (sw ? SKBTX_SW_TSTAMP :
SKBTX_HW_TSTAMP);
case SCM_TSTAMP_ACK:
return TCP_SKB_CB(skb)->txstamp_ack;
> + case SCM_TSTAMP_SND:
> + flag = sw ? SKBTX_SW_TSTAMP : SKBTX_HW_TSTAMP;
> + break;
> + case SCM_TSTAMP_ACK:
> + if (TCP_SKB_CB(skb)->txstamp_ack)
> + return true;
> + fallthrough;
> + default:
> + return false;
> + }
> +
> + if (skb_shinfo(skb)->tx_flags & flag)
> + return true;
> +
> + return false;
> +}
> +
> 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)
> + struct sock *sk, bool sw, int tstype)
> {
> struct sk_buff *skb;
> bool tsonly, opt_stats = false;
> @@ -5551,6 +5576,9 @@ void __skb_tstamp_tx(struct sk_buff *orig_skb,
> if (!sk)
> return;
>
> + if (!skb_enable_app_tstamp(orig_skb, tstype, sw))
> + return;
> +
> tsflags = READ_ONCE(sk->sk_tsflags);
> if (!hwtstamps && !(tsflags & SOF_TIMESTAMPING_OPT_TX_SWHW) &&
> skb_shinfo(orig_skb)->tx_flags & SKBTX_IN_PROGRESS)
> @@ -5599,7 +5627,7 @@ EXPORT_SYMBOL_GPL(__skb_tstamp_tx);
> void skb_tstamp_tx(struct sk_buff *orig_skb,
> struct skb_shared_hwtstamps *hwtstamps)
> {
> - return __skb_tstamp_tx(orig_skb, NULL, hwtstamps, orig_skb->sk,
> + return __skb_tstamp_tx(orig_skb, NULL, hwtstamps, orig_skb->sk, false,
> SCM_TSTAMP_SND);
> }
> EXPORT_SYMBOL_GPL(skb_tstamp_tx);
> diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
> index 77185479ed5e..62252702929d 100644
> --- a/net/ipv4/tcp_input.c
> +++ b/net/ipv4/tcp_input.c
> @@ -3330,7 +3330,8 @@ static void tcp_ack_tstamp(struct sock *sk, struct sk_buff *skb,
> if (!before(shinfo->tskey, prior_snd_una) &&
> before(shinfo->tskey, tcp_sk(sk)->snd_una)) {
> tcp_skb_tsorted_save(skb) {
> - __skb_tstamp_tx(skb, ack_skb, NULL, sk, SCM_TSTAMP_ACK);
> + __skb_tstamp_tx(skb, ack_skb, NULL, sk, true,
> + SCM_TSTAMP_ACK);
> } tcp_skb_tsorted_restore(skb);
> }
> }
> --
> 2.43.5
>
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