On Wed, Feb 5, 2025 at 11:34 PM Willem de Bruijn
<willemdebruijn.kernel@xxxxxxxxx> wrote:
>
> 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@xxxxxxxxx>
> > ---
> > 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
Good name. I like them.
>
> > +{
> > + 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;
>
Thanks for the re-arrangement!
> > + 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
> >
>
>
