Subject: Re: [PATCH net-next v3 02/14] net-timestamp: allow two features to work parallelly

From: Martin KaFai Lau <[email-masked]>
Date: Tue, 29 Oct 2024 16:00:22 -0700

On 10/28/24 4:05 AM, Jason Xing wrote:
> From: Jason Xing <[email-masked]>
> 
> This patch has introduced a separate sk_tsflags_bpf for bpf
> extension, which helps us let two feature work nearly at the
> same time.
> 
> Each feature will finally take effect on skb_shinfo(skb)->tx_flags,
> say, tcp_tx_timestamp() for TCP or skb_setup_tx_timestamp() for
> other types, so in __skb_tstamp_tx() we are unable to know which
> feature is turned on, unless we check each feature's own socket
> flag field.
> 
> Signed-off-by: Jason Xing <[email-masked]>
> ---
>   include/net/sock.h |  1 +
>   net/core/skbuff.c  | 39 +++++++++++++++++++++++++++++++++++++++
>   2 files changed, 40 insertions(+)
> 
> diff --git a/include/net/sock.h b/include/net/sock.h
> index 7464e9f9f47c..5384f1e49f5c 100644
> --- a/include/net/sock.h
> +++ b/include/net/sock.h
> @@ -445,6 +445,7 @@ struct sock {
>   	u32			sk_reserved_mem;
>   	int			sk_forward_alloc;
>   	u32			sk_tsflags;
> +	u32			sk_tsflags_bpf;
>   	__cacheline_group_end(sock_write_rxtx);
>   
>   	__cacheline_group_begin(sock_write_tx);
> diff --git a/net/core/skbuff.c b/net/core/skbuff.c
> index 1cf8416f4123..39309f75e105 100644
> --- a/net/core/skbuff.c
> +++ b/net/core/skbuff.c
> @@ -5539,6 +5539,32 @@ void skb_complete_tx_timestamp(struct sk_buff *skb,
>   }
>   EXPORT_SYMBOL_GPL(skb_complete_tx_timestamp);
>   
> +/* This function is used to test if application SO_TIMESTAMPING feature
> + * or bpf SO_TIMESTAMPING feature is loaded by checking its own socket flags.
> + */
> +static bool sk_tstamp_tx_flags(struct sock *sk, u32 tsflags, int tstype)
> +{
> +	u32 testflag;
> +
> +	switch (tstype) {
> +	case SCM_TSTAMP_SCHED:
> +		testflag = SOF_TIMESTAMPING_TX_SCHED;
> +		break;
> +	case SCM_TSTAMP_SND:
> +		testflag = SOF_TIMESTAMPING_TX_SOFTWARE;
> +		break;
> +	case SCM_TSTAMP_ACK:
> +		testflag = SOF_TIMESTAMPING_TX_ACK;
> +		break;
> +	default:
> +		return false;
> +	}
> +	if (tsflags & testflag)
> +		return true;
> +
> +	return false;
> +}
> +
>   static void skb_tstamp_tx_output(struct sk_buff *orig_skb,
>   				 const struct sk_buff *ack_skb,
>   				 struct skb_shared_hwtstamps *hwtstamps,
> @@ -5549,6 +5575,9 @@ static void skb_tstamp_tx_output(struct sk_buff *orig_skb,
>   	u32 tsflags;
>   
>   	tsflags = READ_ONCE(sk->sk_tsflags);
> +	if (!sk_tstamp_tx_flags(sk, tsflags, tstype))

I still don't get this part since v2. How does it work with cmsg only 
SOF_TIMESTAMPING_TX_*?

I tried with "./txtimestamp -6 -c 1 -C -N -L ::1" and it does not return any tx 
time stamp after this patch.

I am likely missing something
or v2 concluded that this behavior change is acceptable?

> +		return;
> +
>   	if (!hwtstamps && !(tsflags & SOF_TIMESTAMPING_OPT_TX_SWHW) &&
>   	    skb_shinfo(orig_skb)->tx_flags & SKBTX_IN_PROGRESS)
>   		return;
> @@ -5592,6 +5621,15 @@ static void skb_tstamp_tx_output(struct sk_buff *orig_skb,
>   	__skb_complete_tx_timestamp(skb, sk, tstype, opt_stats);
>   }
>   
> +static void skb_tstamp_tx_output_bpf(struct sock *sk, int tstype)
> +{
> +	u32 tsflags;
> +
> +	tsflags = READ_ONCE(sk->sk_tsflags_bpf);
> +	if (!sk_tstamp_tx_flags(sk, tsflags, tstype))
> +		return;
> +}
> +
>   void __skb_tstamp_tx(struct sk_buff *orig_skb,
>   		     const struct sk_buff *ack_skb,
>   		     struct skb_shared_hwtstamps *hwtstamps,
> @@ -5600,6 +5638,7 @@ void __skb_tstamp_tx(struct sk_buff *orig_skb,
>   	if (!sk)
>   		return;
>   
> +	skb_tstamp_tx_output_bpf(sk, tstype);
>   	skb_tstamp_tx_output(orig_skb, ack_skb, hwtstamps, sk, tstype);
>   }
>   EXPORT_SYMBOL_GPL(__skb_tstamp_tx);