[CRIU] [PATCH 2/2] tcp: refresh a data about tcp connection after blocking it (v4)

[Pavel Emelyanov]

On 11/15/2012 11:47 PM, Andrey Vagin wrote:
> We have a window between getting info about tcp connections
> and blocking them. States of tcp connections can be changes,
> so they should be refreshed after blocking.
> 
> https://bugzilla.openvz.org/show_bug.cgi?id=2419
> 
> v2: clean up
> v3: don't update lengthes of queues for listen sockets,
>     they don't used.
> v4: check that a state of a tcp connection is ESTABLISHED or CLOSE
> 
> Signed-off-by: Andrey Vagin <avagin at openvz.org>
> ---
>  sk-tcp.c | 47 +++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 47 insertions(+)
> 
> diff --git a/sk-tcp.c b/sk-tcp.c
> index cc1af80..ca14f47 100644
> --- a/sk-tcp.c
> +++ b/sk-tcp.c
> @@ -51,6 +51,38 @@ static int tcp_repair_on(int fd)
>  	return ret;
>  }
>  
> +static int refresh_inet_sk(int fd, struct inet_sk_desc *sk)
> +{
> +	int size;
> +	struct tcp_info info;
> +
> +	if (sk->state == TCP_CLOSE)
> +		return 0;

How can this be true?

> +
> +	if (dump_opt(fd, SOL_TCP, TCP_INFO, &info)) {
> +		pr_perror("Failt to obtain TCP_INFO");
> +		return -1;
> +	}
> +
> +	sk->state = info.tcpi_state;
> +
> +	if (ioctl(fd, SIOCOUTQ, &size) == -1) {
> +		pr_perror("Unable to get size of snd queue");
> +		return -1;
> +	}
> +
> +	sk->wqlen = size;
> +
> +	if (ioctl(fd, SIOCINQ, &size) == -1) {
> +		pr_perror("Unable to get size of recv queue");
> +		return -1;
> +	}
> +
> +	sk->rqlen = size;
> +
> +	return 0;
> +}
> +
>  static int tcp_repair_establised(int fd, struct inet_sk_desc *sk)
>  {
>  	int ret;
> @@ -298,6 +330,21 @@ int dump_one_tcp(int fd, struct inet_sk_desc *sk)
>  		ret = nf_lock_connection(sk);
>  		if (ret < 0)
>  			return -1;
> +
> +		/* A state of a tcp connection could be changed */
> +		ret = refresh_inet_sk(fd, sk);
> +		if (ret < 0)
> +			goto err;
> +
> +		if (sk->state == TCP_CLOSE) {

Socket cant change state from established to closed w/o task's will.

> +			nf_unlock_connection(sk);
> +			return 0;
> +		}
> +
> +		if (sk->state != TCP_ESTABLISHED) {
> +			pr_err("Unknown state %d\n", sk->state);
> +			goto err;
> +		}
>  	}
>  
>  	pr_info("Dumping TCP connection\n");
>