netdev - Re: [PATCH v2 bpf-next 06/11] bpf: Add sock

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Date:   Thu, 28 Dec 2017 09:57:42 -0800
From:   Yuchung Cheng <ycheng@...gle.com>
To:     Lawrence Brakmo <brakmo@...com>
Cc:     netdev <netdev@...r.kernel.org>, Kernel Team <kernel-team@...com>,
        Blake Matheny <bmatheny@...com>,
        Alexei Starovoitov <ast@...com>,
        Daniel Borkmann <daniel@...earbox.net>,
        Eric Dumazet <eric.dumazet@...il.com>,
        Neal Cardwell <ncardwell@...gle.com>
Subject: Re: [PATCH v2 bpf-next 06/11] bpf: Add sock_ops RTO callback

On Thu, Dec 21, 2017 at 5:20 PM, Lawrence Brakmo <brakmo@...com> wrote:
>
> Adds an optional call to sock_ops BPF program based on whether the
> BPF_SOCK_OPS_RTO_CB_FLAG is set in bpf_sock_ops_flags.
> The BPF program is passed 2 arguments: icsk_retransmits and whether the
> RTO has expired.
>
> Signed-off-by: Lawrence Brakmo <brakmo@...com>
> ---
>  include/uapi/linux/bpf.h | 5 +++++
>  include/uapi/linux/tcp.h | 3 +++
>  net/ipv4/tcp_timer.c     | 9 +++++++++
>  3 files changed, 17 insertions(+)
>
> diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
> index 62b2c89..3cf9014 100644
> --- a/include/uapi/linux/bpf.h
> +++ b/include/uapi/linux/bpf.h
> @@ -995,6 +995,11 @@ enum {
>                                          * a congestion threshold. RTTs above
>                                          * this indicate congestion
>                                          */
> +       BPF_SOCK_OPS_RTO_CB,            /* Called when an RTO has triggered.
> +                                        * Arg1: value of icsk_retransmits
> +                                        * Arg2: value of icsk_rto
> +                                        * Arg3: whether RTO has expired
> +                                        */
>  };
>
>  #define TCP_BPF_IW             1001    /* Set TCP initial congestion window */
> diff --git a/include/uapi/linux/tcp.h b/include/uapi/linux/tcp.h
> index b4a4f64..089c19e 100644
> --- a/include/uapi/linux/tcp.h
> +++ b/include/uapi/linux/tcp.h
> @@ -259,6 +259,9 @@ struct tcp_md5sig {
>         __u8    tcpm_key[TCP_MD5SIG_MAXKEYLEN];         /* key (binary) */
>  };
>
> +/* Definitions for bpf_sock_ops_flags */
> +#define BPF_SOCK_OPS_RTO_CB_FLAG       (1<<0)
> +
>  /* INET_DIAG_MD5SIG */
>  struct tcp_diag_md5sig {
>         __u8    tcpm_family;
> diff --git a/net/ipv4/tcp_timer.c b/net/ipv4/tcp_timer.c
> index 6db3124..f9c57e2 100644
> --- a/net/ipv4/tcp_timer.c
> +++ b/net/ipv4/tcp_timer.c
> @@ -215,9 +215,18 @@ static int tcp_write_timeout(struct sock *sk)
>         tcp_fastopen_active_detect_blackhole(sk, expired);
can't we just call it here once w/ 'expired' as a parameter, instead
of duplicating the code?

>         if (expired) {
>                 /* Has it gone just too far? */
> +               if (BPF_SOCK_OPS_TEST_FLAG(tp, BPF_SOCK_OPS_RTO_CB_FLAG))
> +                       tcp_call_bpf_3arg(sk, BPF_SOCK_OPS_RTO_CB,
> +                                         icsk->icsk_retransmits,
> +                                         icsk->icsk_rto, 1);
>                 tcp_write_err(sk);
>                 return 1;
>         }
> +
> +       if (BPF_SOCK_OPS_TEST_FLAG(tp, BPF_SOCK_OPS_RTO_CB_FLAG))
> +               tcp_call_bpf_3arg(sk, BPF_SOCK_OPS_RTO_CB,
> +                                 icsk->icsk_retransmits,
> +                                 icsk->icsk_rto, 0);
>         return 0;
>  }
>
> --
> 2.9.5
>