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From:   Yafang Shao <laoar.shao@gmail.com>
Date:   Wed, 8 Nov 2017 18:48:50 +0800
Message-ID: <CALOAHbBZKuEpedxFLaMwVGn1Ps6ryiC=D_VO1gBCTonrCaHqCg@mail.gmail.com>
Subject: Re: [PATCH] net/tcp: track all ipv4/tcp state transition in tcp_set_state
To:     David Miller <davem@davemloft.net>
Cc:     Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>, yoshfuji@linux-ipv6.org,
        netdev@vger.kernel.org, linux-kernel@vger.kernel.org
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2017-11-08 14:51 GMT+08:00 David Miller <davem@davemloft.net>:
> From: Yafang Shao <laoar.shao@gmail.com>
> Date: Tue,  7 Nov 2017 18:36:28 +0800
>
>> When I hooked the function tcp_set_state with kprobe to track the ipv4/tcp
>> state transistion, I found state transition from TCP_LISTEN to TCP_SYN_RECV
>> is missed.
>>
>> I think it is better to use the helper to do state transition instead of
>> assigning the state to sk_state directly.
>> Then we can monitor the whole tcp lifespans with kprobe or ftrace easily.
>>
>> Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
>
> This is really heavy handed and excessive for these cases.
>
> They don't have to handle any of the issues dealt with in
> tcp_set_state().
>
> I would prefer if you made a special helper to net/tcp.h which did:
>
> static inline void __tcp_set_state(struct sock *sk, int state)
> {
>         trace_tcp_set_state(sk, sk->sk_state, state);
>         sk->sk_state = state;
> }

Good idea!
I will try to implement it.

Thanks
Yafang

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