netdev - Re: [PATCH] tcp: Export to userspace the TCP state names for the trace events

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Date:   Fri, 10 Nov 2017 12:56:06 +0800
From:   Yafang Shao <laoar.shao@...il.com>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     David Miller <davem@...emloft.net>,
        Song Liu <songliubraving@...com>,
        Alexei Starovoitov <alexei.starovoitov@...il.com>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] tcp: Export to userspace the TCP state names for the
 trace events

2017-11-10 8:57 GMT+08:00 Steven Rostedt <rostedt@...dmis.org>:
>
> From: "Steven Rostedt (VMware)" <rostedt@...dmis.org>
>
> The TCP trace events (specifically tcp_set_state), maps emums to symbol
> names via __print_symbolic(). But this only works for reading trace events
> from the tracefs trace files. If perf or trace-cmd were to record these
> events, the event format file does not convert the enum names into numbers,
> and you get something like:
>
> __print_symbolic(REC->oldstate,
>     { TCP_ESTABLISHED, "TCP_ESTABLISHED" },
>     { TCP_SYN_SENT, "TCP_SYN_SENT" },
>     { TCP_SYN_RECV, "TCP_SYN_RECV" },
>     { TCP_FIN_WAIT1, "TCP_FIN_WAIT1" },
>     { TCP_FIN_WAIT2, "TCP_FIN_WAIT2" },
>     { TCP_TIME_WAIT, "TCP_TIME_WAIT" },
>     { TCP_CLOSE, "TCP_CLOSE" },
>     { TCP_CLOSE_WAIT, "TCP_CLOSE_WAIT" },
>     { TCP_LAST_ACK, "TCP_LAST_ACK" },
>     { TCP_LISTEN, "TCP_LISTEN" },
>     { TCP_CLOSING, "TCP_CLOSING" },
>     { TCP_NEW_SYN_RECV, "TCP_NEW_SYN_RECV" })
>
> Where trace-cmd and perf do not know the values of those enums.
>
> Use the TRACE_DEFINE_ENUM() macros that will have the trace events convert
> the enum strings into their values at system boot. This will allow perf and
> trace-cmd to see actual numbers and not enums:
>
> __print_symbolic(REC->oldstate,
>     { 1, "TCP_ESTABLISHED" },
>     { 2, "TCP_SYN_SENT" },
>     { 3, "TCP_SYN_RECV" },
>     { 4, "TCP_FIN_WAIT1" },
>     { 5, "TCP_FIN_WAIT2" },
>     { 6, "TCP_TIME_WAIT" },
>     { 7, "TCP_CLOSE" },
>     { 8, "TCP_CLOSE_WAIT" },
>     { 9, "TCP_LAST_ACK" },
>     { 10, "TCP_LISTEN" },
>     { 11, "TCP_CLOSING" },
>     { 12, "TCP_NEW_SYN_RECV" })
>
> Signed-off-by: Steven Rostedt (VMware) <rostedt@...dmis.org>
> ---
>  include/trace/events/tcp.h | 41 ++++++++++++++++++++++++++++-------------
>  1 file changed, 28 insertions(+), 13 deletions(-)
>
> diff --git a/include/trace/events/tcp.h b/include/trace/events/tcp.h
> index 07cccca6cbf1..62e5bad7901f 100644
> --- a/include/trace/events/tcp.h
> +++ b/include/trace/events/tcp.h
> @@ -9,21 +9,36 @@
>  #include <linux/tracepoint.h>
>  #include <net/ipv6.h>
>
> +#define tcp_state_names                                \
> +       EM(TCP_ESTABLISHED)                     \
> +       EM(TCP_SYN_SENT)                        \
> +       EM(TCP_SYN_RECV)                        \
> +       EM(TCP_FIN_WAIT1)                       \
> +       EM(TCP_FIN_WAIT2)                       \
> +       EM(TCP_TIME_WAIT)                       \
> +       EM(TCP_CLOSE)                           \
> +       EM(TCP_CLOSE_WAIT)                      \
> +       EM(TCP_LAST_ACK)                        \
> +       EM(TCP_LISTEN)                          \
> +       EM(TCP_CLOSING)                         \
> +       EMe(TCP_NEW_SYN_RECV)
> +
> +/* enums need to be exported to user space */
> +#undef EM
> +#undef EMe
> +#define EM(a)         TRACE_DEFINE_ENUM(a);
> +#define EMe(a)        TRACE_DEFINE_ENUM(a);
> +
> +tcp_state_names
> +
> +#undef EM
> +#undef EMe
> +#define EM(a)         tcp_state_name(a),
> +#define EMe(a)        tcp_state_name(a)
> +
>  #define tcp_state_name(state)  { state, #state }
>  #define show_tcp_state_name(val)                       \
> -       __print_symbolic(val,                           \
> -               tcp_state_name(TCP_ESTABLISHED),        \
> -               tcp_state_name(TCP_SYN_SENT),           \
> -               tcp_state_name(TCP_SYN_RECV),           \
> -               tcp_state_name(TCP_FIN_WAIT1),          \
> -               tcp_state_name(TCP_FIN_WAIT2),          \
> -               tcp_state_name(TCP_TIME_WAIT),          \
> -               tcp_state_name(TCP_CLOSE),              \
> -               tcp_state_name(TCP_CLOSE_WAIT),         \
> -               tcp_state_name(TCP_LAST_ACK),           \
> -               tcp_state_name(TCP_LISTEN),             \
> -               tcp_state_name(TCP_CLOSING),            \
> -               tcp_state_name(TCP_NEW_SYN_RECV))
> +       __print_symbolic(val, tcp_state_names)
>
>  /*
>   * tcp event with arguments sk and skb
> --
> 2.13.6
>

Could the macro tcp_state_name() be renamed ？
If <trace/events/tcp.h> is included in include/net/tcp.h, it will
cause compile error, because there's another function tcp_state_name()
defined in net/netfilter/ipvs/ip_vs_proto_tcp.c.
    static const char * tcp_state_name(int state)
    {

        if (state >= IP_VS_TCP_S_LAST)

            return "ERR!";

        return tcp_state_name_table[state] ? tcp_state_name_table[state] : "?";

    }


Thanks
Yafang