Subject: Re: [PATCH v2 net-next] net/tcp: trace all TCP/IP state transition with tcp_set_state tracepoint

From: Marcelo Ricardo Leitner <[email-masked]>
Date: Mon, 4 Dec 2017 17:28:06 -0200

On Sat, Dec 02, 2017 at 09:36:41AM +0000, Yafang Shao wrote:
> The TCP/IP transition from TCP_LISTEN to TCP_SYN_RECV and some other
> transitions are not traced with tcp_set_state tracepoint.
> 
> In order to trace the whole tcp lifespans, two helpers are introduced,
> void __tcp_set_state(struct sock *sk, int state)
> void __sk_state_store(struct sock *sk, int newstate)
> 
> When do TCP/IP state transition, we should use these two helpers or use
> tcp_set_state() other than assigning a value to sk_state directly.
> 
> Signed-off-by: Yafang Shao <[email-masked]>
> 
> ---
> v2: test
> ---
>  include/net/tcp.h               |  2 ++
>  net/ipv4/inet_connection_sock.c |  6 +++---
>  net/ipv4/inet_hashtables.c      |  2 +-
>  net/ipv4/tcp.c                  | 12 ++++++++++++
>  4 files changed, 18 insertions(+), 4 deletions(-)
> 
> diff --git a/include/net/tcp.h b/include/net/tcp.h
> index 85ea578..4f2d015 100644
> --- a/include/net/tcp.h
> +++ b/include/net/tcp.h
> @@ -1247,6 +1247,8 @@ static inline bool tcp_checksum_complete(struct sk_buff *skb)
>  	"Close Wait","Last ACK","Listen","Closing"
>  };
>  #endif
> +void __sk_state_store(struct sock *sk, int newstate);
> +void __tcp_set_state(struct sock *sk, int state);
>  void tcp_set_state(struct sock *sk, int state);
>  
>  void tcp_done(struct sock *sk);
> diff --git a/net/ipv4/inet_connection_sock.c b/net/ipv4/inet_connection_sock.c
> index 4ca46dc..f3967f1 100644
> --- a/net/ipv4/inet_connection_sock.c
> +++ b/net/ipv4/inet_connection_sock.c
> @@ -783,7 +783,7 @@ struct sock *inet_csk_clone_lock(const struct sock *sk,
>  	if (newsk) {
>  		struct inet_connection_sock *newicsk = inet_csk(newsk);
>  
> -		newsk->sk_state = TCP_SYN_RECV;
> +		__tcp_set_state(newsk, TCP_SYN_RECV);
>  		newicsk->icsk_bind_hash = NULL;
>  
>  		inet_sk(newsk)->inet_dport = inet_rsk(req)->ir_rmt_port;
> @@ -877,7 +877,7 @@ int inet_csk_listen_start(struct sock *sk, int backlog)
>  	 * It is OK, because this socket enters to hash table only
>  	 * after validation is complete.
>  	 */
> -	sk_state_store(sk, TCP_LISTEN);
> +	__sk_state_store(sk, TCP_LISTEN);
>  	if (!sk->sk_prot->get_port(sk, inet->inet_num)) {
>  		inet->inet_sport = htons(inet->inet_num);
>  
> @@ -888,7 +888,7 @@ int inet_csk_listen_start(struct sock *sk, int backlog)
>  			return 0;
>  	}
>  
> -	sk->sk_state = TCP_CLOSE;
> +	__tcp_set_state(sk, TCP_CLOSE);
>  	return err;
>  }
>  EXPORT_SYMBOL_GPL(inet_csk_listen_start);
> diff --git a/net/ipv4/inet_hashtables.c b/net/ipv4/inet_hashtables.c
> index e7d15fb..72c15b6 100644
> --- a/net/ipv4/inet_hashtables.c
> +++ b/net/ipv4/inet_hashtables.c
> @@ -430,7 +430,7 @@ bool inet_ehash_nolisten(struct sock *sk, struct sock *osk)
>  		sock_prot_inuse_add(sock_net(sk), sk->sk_prot, 1);
>  	} else {
>  		percpu_counter_inc(sk->sk_prot->orphan_count);
> -		sk->sk_state = TCP_CLOSE;
> +		__tcp_set_state(sk, TCP_CLOSE);
>  		sock_set_flag(sk, SOCK_DEAD);
>  		inet_csk_destroy_sock(sk);
>  	}
> diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
> index bf97317..2bc7e04 100644
> --- a/net/ipv4/tcp.c
> +++ b/net/ipv4/tcp.c
> @@ -2036,6 +2036,18 @@ int tcp_recvmsg(struct sock *sk, struct msghdr *msg, size_t len, int nonblock,
>  }
>  EXPORT_SYMBOL(tcp_recvmsg);
>  
> +void __sk_state_store(struct sock *sk, int newstate)
> +{
> +	trace_tcp_set_state(sk, sk->sk_state, newstate);
> +	sk_state_store(sk, newstate);

This sounds counter-intuitive, to have a __func() to call func(). It's
usually the other way around.
There is only 1 call to sk_state_store in the stack, what about
inverting these __ ?

I guess you applied the same standard as to the one below, but it's a
different case.

> +}
> +
> +void __tcp_set_state(struct sock *sk, int state)
> +{
> +	trace_tcp_set_state(sk, sk->sk_state, state);
> +	sk->sk_state = state;
> +}
> +
>  void tcp_set_state(struct sock *sk, int state)
>  {
>  	int oldstate = sk->sk_state;
> -- 
> 1.8.3.1
>