Re: [PATCH bpf-next v10 09/12] bpf: add BPF_SOCK_OPS_TS_ACK_OPT_CB callback

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

Jason Xing wrote:
> Support the ACK case for bpf timestamping.
> 
> Add a new sock_ops callback, BPF_SOCK_OPS_TS_ACK_OPT_CB. This
> callback will occur at the same timestamping point as the user
> space's SCM_TSTAMP_ACK. The BPF program can use it to get the
> same SCM_TSTAMP_ACK timestamp without modifying the user-space
> application.
> 
> This patch extends txstamp_ack to two bits: 1 stands for
> SO_TIMESTAMPING mode, 2 bpf extension.
> 
> Signed-off-by: Jason Xing <kerneljasonxing@gmail.com>
> ---
>  include/net/tcp.h              | 6 ++++--
>  include/uapi/linux/bpf.h       | 5 +++++
>  net/core/skbuff.c              | 5 ++++-
>  net/dsa/user.c                 | 2 +-
>  net/ipv4/tcp.c                 | 2 +-
>  net/socket.c                   | 2 +-
>  tools/include/uapi/linux/bpf.h | 5 +++++
>  7 files changed, 21 insertions(+), 6 deletions(-)

> diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
> index 0d704bda6c41..aa080f7ccea4 100644
> --- a/net/ipv4/tcp.c
> +++ b/net/ipv4/tcp.c
> @@ -488,7 +488,7 @@ static void tcp_tx_timestamp(struct sock *sk, struct sockcm_cookie *sockc)
>  
>  		sock_tx_timestamp(sk, sockc, &shinfo->tx_flags);
>  		if (tsflags & SOF_TIMESTAMPING_TX_ACK)
> -			tcb->txstamp_ack = 1;
> +			tcb->txstamp_ack = TSTAMP_ACK_SK;

Similar to the BPF code, should this by |= TSTAMP_ACK_SK?

Does not matter in practice if the BPF setter can never precede this.