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SubjectRe: [bpf-next 2/2] bpf: add BPF_SOCK_OPS_STATS_CB for tcp_stats()
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On 02/12/2019 03:31 AM, Yafang Shao wrote:
> Introuce this new op BPF_SOCK_OPS_STATS_CB for tcp_stats() such that it
> can be traced via BPF on a per socket basis.
> There's one argument in BPF_SOCK_OPS_STATS_CB, which is Linux MIB index
> LINUX_MIB_* to indicate the TCP event.
> All these Linux MIBs are defined in include/uapi/linux/snmp.h.
>
> Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
> ---
> include/uapi/linux/bpf.h | 5 +++++
> net/ipv4/tcp_input.c | 1 +
> 2 files changed, 6 insertions(+)
>
> diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
> index 1777fa0..0314ddd 100644
> --- a/include/uapi/linux/bpf.h
> +++ b/include/uapi/linux/bpf.h
> @@ -2894,6 +2894,11 @@ enum {
> BPF_SOCK_OPS_TCP_LISTEN_CB, /* Called on listen(2), right after
> * socket transition to LISTEN state.
> */
> + BPF_SOCK_OPS_STATS_CB, /*
> + * Called on tcp_stats().
> + * Arg1: Linux MIB index
> + * LINUX_MIB_*
> + */
> };
>
> /* List of TCP states. There is a build check in net/ipv4/tcp.c to detect
> diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
> index 88deb1f..4acf458 100644
> --- a/net/ipv4/tcp_input.c
> +++ b/net/ipv4/tcp_input.c
> @@ -3557,6 +3557,7 @@ static u32 tcp_newly_delivered(struct sock *sk, u32 prior_delivered, int flag)
> static void tcp_stats(struct sock *sk, int mib_idx)
> {
> NET_INC_STATS(sock_net(sk), mib_idx);
> + tcp_call_bpf(sk, BPF_SOCK_OPS_STATS_CB, 1, &mib_idx);
> }
>
> /* This routine deals with incoming acks, but not outgoing ones. */
>

If the plan is to add to all NET_INC_STATS() calls in TCP an additional tcp_call_bpf()
I will say no.

So far, tcp_call_bpf() has not been used in fast path.

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