linux-kernel - Re: [PATCH] net/tcp: introduce TRACE_EVENT for TCP/IPv4 state transition

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Date:   Thu, 9 Nov 2017 15:43:29 +0900
From:   Alexei Starovoitov <alexei.starovoitov@...il.com>
To:     Yafang Shao <laoar.shao@...il.com>
Cc:     davem@...emloft.net, rostedt@...dmis.org, mingo@...hat.com,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        songliubraving@...com
Subject: Re: [PATCH] net/tcp: introduce TRACE_EVENT for TCP/IPv4 state
 transition

On Thu, Nov 09, 2017 at 02:01:38PM +0800, Yafang Shao wrote:
> With this newly introduced TRACE_EVENT, it will be very easy to minotor
> TCP/IPv4 state transition.
> 
> A new TRACE_SYSTEM named tcp is added, in which we can trace other TCP
> event as well.
> 
> Two helpers are added,
> static inline void __tcp_set_state(struct sock *sk, int state)
> static inline void __sk_state_store(struct sock *sk, int newstate)
> 
> When do TCP/IPv4 state transition, we should use these two helpers or
> use tcp_set_state() instead of assign a value to sk_state directly.
> 
> Signed-off-by: Yafang Shao <laoar.shao@...il.com>

when you submit a patch pls make it clear which tree this patch is targeting.
In this case it should have been net-next,
but the patch clearly conflicts with it.
Make sure to rebase.

> +/*
> + * To trace TCP state transition.
> + */
> +static inline void __tcp_set_state(struct sock *sk, int state)
> +{
> +	trace_tcp_set_state(sk, sk->sk_state, state);
> +	sk->sk_state = state;
> +}
> +
> +static inline void __sk_state_store(struct sock *sk, int newstate)
> +{
> +	trace_tcp_set_state(sk, sk->sk_state, newstate);
> +	sk_state_store(sk, newstate);
> +}
> +
>  void tcp_done(struct sock *sk);
>  
>  int tcp_abort(struct sock *sk, int err);
> diff --git a/include/trace/events/tcp.h b/include/trace/events/tcp.h
> new file mode 100644
> index 0000000..abf65af
> --- /dev/null
> +++ b/include/trace/events/tcp.h
> @@ -0,0 +1,58 @@
> +#undef TRACE_SYSTEM
> +#define TRACE_SYSTEM tcp
> +
> +#if !defined(_TRACE_TCP_H) || defined(TRACE_HEADER_MULTI_READ)
> +#define _TRACE_TCP_H
> +
> +#include <linux/tracepoint.h>
> +#include <net/sock.h>
> +#include <net/inet_timewait_sock.h>
> +#include <net/request_sock.h>
> +#include <net/inet_sock.h>
> +#include <net/tcp_states.h>
> +
> +TRACE_EVENT(tcp_set_state,
> +	TP_PROTO(struct sock *sk, int oldstate, int newstate),
> +	TP_ARGS(sk, oldstate, newstate),
> +
> +	TP_STRUCT__entry(
> +		__field(__be32, dst)
> +		__field(__be32, src)
> +		__field(__u16, dport)
> +		__field(__u16, sport)
> +		__field(int, oldstate)
> +		__field(int, newstate)
> +	),
> +
> +	TP_fast_assign(
> +		if (oldstate == TCP_TIME_WAIT) {
> +			__entry->dst = inet_twsk(sk)->tw_daddr;
> +			__entry->src = inet_twsk(sk)->tw_rcv_saddr;
> +			__entry->dport = ntohs(inet_twsk(sk)->tw_dport);
> +			__entry->sport = ntohs(inet_twsk(sk)->tw_sport);
> +		} else if (oldstate == TCP_NEW_SYN_RECV) {
> +			__entry->dst = inet_rsk(inet_reqsk(sk))->ir_rmt_addr;
> +			__entry->src = inet_rsk(inet_reqsk(sk))->ir_loc_addr;
> +			__entry->dport =
> +				ntohs(inet_rsk(inet_reqsk(sk))->ir_rmt_port);
> +			__entry->sport = inet_rsk(inet_reqsk(sk))->ir_num;
> +		} else {
> +			__entry->dst = inet_sk(sk)->inet_daddr;
> +			__entry->src = inet_sk(sk)->inet_rcv_saddr;
> +			__entry->dport = ntohs(inet_sk(sk)->inet_dport);
> +			__entry->sport = ntohs(inet_sk(sk)->inet_sport);
> +		}
> +
> +		__entry->oldstate = oldstate;
> +		__entry->newstate = newstate;
> +	),
> +
> +	TP_printk("%08X:%04X %08X:%04X, %02x %02x",
> +		__entry->src, __entry->sport, __entry->dst, __entry->dport,
> +		__entry->oldstate, __entry->newstate)

direct %x of state is not allowed.
This has to use show_tcp_state_name() like it's done in trace_tcp_set_state

Also I'm missing the reason to introduce another tracepoint
that looks just like trace_tcp_set_state.