Re: [PATCH mptcp-next] selftests: mptcp: print stats before socket closure

On 8/14/26 4:07 PM, Matthieu Baerts (NGI0) wrote:
> In case of poll timeout, it might be too late to print the stats after
> the socket closure.
> 
> Now, in case of poll timeout, 'ss' and 'nstat' are invoked from
> mptcp_connect to print the stats before exiting. This should help
> debugging poll timeout issues.
> 
> Note: for this "workaround", system() is used for debugging purposes
> only. The returned result can then be safely ignored.
> 
> Signed-off-by: Matthieu Baerts (NGI0) <[email protected]>
> ---
>  tools/testing/selftests/net/mptcp/mptcp_connect.c | 15 +++++++++++++++
>  1 file changed, 15 insertions(+)
> 
> diff --git a/tools/testing/selftests/net/mptcp/mptcp_connect.c b/tools/testing/selftests/net/mptcp/mptcp_connect.c
> index ea4cb6c1bd5e..842c0eb99aa9 100644
> --- a/tools/testing/selftests/net/mptcp/mptcp_connect.c
> +++ b/tools/testing/selftests/net/mptcp/mptcp_connect.c
> @@ -210,6 +210,19 @@ static void xgetaddrinfo(const char *node, const char *service,
>  	}
>  }
>  
> +static void print_err_stats(void)
> +{
> +	char cmd[128];
> +
> +	snprintf(cmd, sizeof(cmd), "ss -Menitam -o '%cport = :%s' >&2",
> +		 listen_mode ? 's' : 'd', cfg_port);
> +
> +	fprintf(stderr, "socket stats before socket closure:\n");
> +	(void)!system(cmd);
> +	(void)!system("NSTAT_HISTORY='/tmp/$(ip netns id).nstat' nstat -s | "
> +		      "grep Tcp >&2");

Overall LGTM. I tried something similar in the past, but the correct
redirection always fouled me. A couple of questions:
- Is the '!' operator needed?
- Can we avoid the pipe? with something alike the following:
	(void)system("NSTAT_HISTORY='/tmp/$(ip netns id).nstat' nstat -s *Tcp*
>&2");

/P