netdev - Re: [PATCH v2 bpf 2/2] bpf, sockmap: sk_prot needs inuse

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Message-ID: <CAM_iQpWZnQ7A=U9JmzGZrOcOB2V1f22NmbFkcJ0SVdA3iHgSGA@mail.gmail.com>
Date:   Fri, 2 Jul 2021 12:50:47 -0700
From:   Cong Wang <xiyou.wangcong@...il.com>
To:     John Fastabend <john.fastabend@...il.com>
Cc:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andriin@...com>, bpf <bpf@...r.kernel.org>,
        Linux Kernel Network Developers <netdev@...r.kernel.org>
Subject: Re: [PATCH v2 bpf 2/2] bpf, sockmap: sk_prot needs inuse_idx for proc stats

On Thu, Jul 1, 2021 at 5:12 PM John Fastabend <john.fastabend@...il.com> wrote:
>
> Proc socket stats use sk_prot->inuse_idx value to record inuse sock stats.
> We currently do not set this correctly from sockmap side. The result is
> reading sock stats '/proc/net/sockstat' gives incorrect values. The
> socket counter is incremented correctly, but because we don't set the
> counter correctly when we replace sk_prot we may omit the decrement.
>
> Fixes: 604326b41a6fb ("bpf, sockmap: convert to generic sk_msg interface")
> Signed-off-by: John Fastabend <john.fastabend@...il.com>
> ---
>  net/core/sock_map.c | 9 +++++++++
>  1 file changed, 9 insertions(+)
>
> diff --git a/net/core/sock_map.c b/net/core/sock_map.c
> index 60decd6420ca..016ea5460f8f 100644
> --- a/net/core/sock_map.c
> +++ b/net/core/sock_map.c
> @@ -222,6 +222,9 @@ static int sock_map_link(struct bpf_map *map, struct sock *sk)
>         struct bpf_prog *msg_parser = NULL;
>         struct sk_psock *psock;
>         int ret;
> +#ifdef CONFIG_PROC_FS
> +       int idx;
> +#endif
>
>         /* Only sockets we can redirect into/from in BPF need to hold
>          * refs to parser/verdict progs and have their sk_data_ready
> @@ -293,9 +296,15 @@ static int sock_map_link(struct bpf_map *map, struct sock *sk)
>         if (msg_parser)
>                 psock_set_prog(&psock->progs.msg_parser, msg_parser);
>
> +#ifdef CONFIG_PROC_FS
> +       idx = sk->sk_prot->inuse_idx;
> +#endif
>         ret = sock_map_init_proto(sk, psock);
>         if (ret < 0)
>                 goto out_drop;
> +#ifdef CONFIG_PROC_FS
> +       sk->sk_prot->inuse_idx = idx;
> +#endif

I think it is better to put these into sock_map_init_proto()
so that sock_map_link() does not need to worry about the sk_prot
details.

Thanks.