Re: [PATCH] net/tcp: track all ipv4/tcp state transition in tcp_set_state

[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;
}