Re: [PATCH net-next v2 11/12] net-timestamp: add bpf framework for rx timestamps

[Willem de Bruijn <willemdebruijn.kernel@gmail.com>]

Jason Xing wrote:
> From: Jason Xing <kernelxing@tencent.com>
> 
> Prepare for later changes in this series. Here I use u32 for
> bpf_sock_ops_cb_flags for better extension and introduce a new
> rx bpf flag to control separately.
> 
> Main change is let userside set through bpf_setsockopt() for
> SO_TIMESTAMPING feature.
> 
> Signed-off-by: Jason Xing <kernelxing@tencent.com>
> ---
>  include/linux/tcp.h            |  2 +-
>  include/net/tcp.h              |  2 +-
>  include/uapi/linux/bpf.h       |  5 ++++-
>  net/core/filter.c              |  6 +++++-
>  net/ipv4/tcp.c                 | 13 ++++++++++++-
>  tools/include/uapi/linux/bpf.h |  5 ++++-
>  6 files changed, 27 insertions(+), 6 deletions(-)
> 
> diff --git a/include/linux/tcp.h b/include/linux/tcp.h
> index 6a5e08b937b3..e21fd3035962 100644
> --- a/include/linux/tcp.h
> +++ b/include/linux/tcp.h
> @@ -446,7 +446,7 @@ struct tcp_sock {
>  
>  /* Sock_ops bpf program related variables */
>  #ifdef CONFIG_BPF
> -	u8	bpf_sock_ops_cb_flags;  /* Control calling BPF programs
> +	u32	bpf_sock_ops_cb_flags;  /* Control calling BPF programs
>  					 * values defined in uapi/linux/tcp.h
>  					 */
>  	u8	bpf_chg_cc_inprogress:1; /* In the middle of
> diff --git a/include/net/tcp.h b/include/net/tcp.h
> index 739a9fb83d0c..728db7107074 100644
> --- a/include/net/tcp.h
> +++ b/include/net/tcp.h
> @@ -423,7 +423,7 @@ int tcp_set_rcvlowat(struct sock *sk, int val);
>  int tcp_set_window_clamp(struct sock *sk, int val);
>  void tcp_update_recv_tstamps(struct sk_buff *skb,
>  			     struct scm_timestamping_internal *tss);
> -void tcp_recv_timestamp(struct msghdr *msg, const struct sock *sk,
> +void tcp_recv_timestamp(struct msghdr *msg, struct sock *sk,
>  			struct scm_timestamping_internal *tss);
>  void tcp_data_ready(struct sock *sk);
>  #ifdef CONFIG_MMU
> diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
> index 1b478ec18ac2..d2754f155cf7 100644
> --- a/include/uapi/linux/bpf.h
> +++ b/include/uapi/linux/bpf.h
> @@ -6903,8 +6903,11 @@ enum {
>  	/* Call bpf when the kernel is generating tx timestamps.
>  	 */
>  	BPF_SOCK_OPS_TX_TIMESTAMPING_OPT_CB_FLAG = (1<<7),
> +	/* Call bpf when the kernel is generating rx timestamps.
> +	 */
> +	BPF_SOCK_OPS_RX_TIMESTAMPING_OPT_CB_FLAG = (1<<8),
>  /* Mask of all currently supported cb flags */
> -	BPF_SOCK_OPS_ALL_CB_FLAGS       = 0xFF,
> +	BPF_SOCK_OPS_ALL_CB_FLAGS       = 0x1FF,
>  };
>  
>  /* List of known BPF sock_ops operators.
> diff --git a/net/core/filter.c b/net/core/filter.c
> index 3b4afaa273d9..36b357b76f4a 100644
> --- a/net/core/filter.c
> +++ b/net/core/filter.c
> @@ -5216,14 +5216,18 @@ static int bpf_sock_set_timestamping(struct sock *sk,
>  		return -EINVAL;
>  
>  	if (!(flags & (SOF_TIMESTAMPING_TX_SCHED | SOF_TIMESTAMPING_TX_SOFTWARE |
> -	      SOF_TIMESTAMPING_TX_ACK)))
> +	      SOF_TIMESTAMPING_TX_ACK | SOF_TIMESTAMPING_RX_SOFTWARE)))
>  		return -EINVAL;
>  
>  	ret = sock_set_tskey(sk, flags, BPFPROG_TS_REQUESTOR);
>  	if (ret)
>  		return ret;
>  
> +	if (flags & SOF_TIMESTAMPING_RX_SOFTWARE)
> +		sock_enable_timestamp(sk, SOCK_TIMESTAMPING_RX_SOFTWARE);
> +
>  	WRITE_ONCE(sk->sk_tsflags[BPFPROG_TS_REQUESTOR], flags);
> +
>  	static_branch_enable(&bpf_tstamp_control);
>  
>  	return 0;
> diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
> index d37e231b2737..0891b41bc745 100644
> --- a/net/ipv4/tcp.c
> +++ b/net/ipv4/tcp.c
> @@ -2260,14 +2260,25 @@ static int tcp_zerocopy_receive(struct sock *sk,
>  }
>  #endif
>  
> +static void tcp_bpf_recv_timestamp(struct sock *sk, struct scm_timestamping_internal *tss)
> +{
> +	struct tcp_sock *tp = tcp_sk(sk);
> +
> +	if (BPF_SOCK_OPS_TEST_FLAG(tp, BPF_SOCK_OPS_RX_TIMESTAMPING_OPT_CB_FLAG))
> +		return;
> +}
> +
>  /* Similar to __sock_recv_timestamp, but does not require an skb */
> -void tcp_recv_timestamp(struct msghdr *msg, const struct sock *sk,
> +void tcp_recv_timestamp(struct msghdr *msg, struct sock *sk,
>  			struct scm_timestamping_internal *tss)
>  {
>  	int new_tstamp = sock_flag(sk, SOCK_TSTAMP_NEW);
>  	u32 tsflags = READ_ONCE(sk->sk_tsflags[SOCKETOPT_TS_REQUESTOR]);
>  	bool has_timestamping = false;
>  
> +	if (static_branch_unlikely(&bpf_tstamp_control))
> +		tcp_bpf_recv_timestamp(sk, tss);
> +
>  	if (tss->ts[0].tv_sec || tss->ts[0].tv_nsec) {
>  		if (sock_flag(sk, SOCK_RCVTSTAMP)) {
>  			if (sock_flag(sk, SOCK_RCVTSTAMPNS)) {

tcp_recv_timestamp is called from tcp_recvmsg only conditionally:

        if ((cmsg_flags || msg->msg_get_inq) && ret >= 0) {
                if (cmsg_flags & TCP_CMSG_TS)
                        tcp_recv_timestamp(msg, sk, &tss);

How do you get this triggered for your BPF program?

And also check the other caller, tcp_zc_finalize_rx_tstamp.