linux-kernel - Re: [PATCH] samples/bpf: Update sockex2: get the expected output results

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Message-ID: <ZMGOqYG8oCAQmMtq@fjasle.eu>
Date:   Wed, 26 Jul 2023 23:22:49 +0200
From:   Nicolas Schier <nicolas@...sle.eu>
To:     George Guo <guodongtai@...inos.cn>
Cc:     masahiroy@...nel.org, ndesaulniers@...gle.com, nathan@...nel.org,
        linux-kbuild@...r.kernel.org, linux-kernel@...r.kernel.org,
        bpf@...r.kernel.org
Subject: Re: [PATCH] samples/bpf: Update sockex2: get the expected output
 results

On Wed, Jul 26, 2023 at 03:09:55PM +0800 George Guo wrote:
> Running "ping -4 -c5 localhost" only shows 4 times prints not 5:
> 
> $ sudo ./samples/bpf/sockex2
> ip 127.0.0.1 bytes 392 packets 4
> ip 127.0.0.1 bytes 784 packets 8
> ip 127.0.0.1 bytes 1176 packets 12
> ip 127.0.0.1 bytes 1568 packets 16
> 
> debug it with num prints:
> $ sudo ./samples/bpf/sockex2
> num = 1: ip 127.0.0.1 bytes 392 packets 4
> num = 2: ip 127.0.0.1 bytes 784 packets 8
> num = 3: ip 127.0.0.1 bytes 1176 packets 12
> num = 4: ip 127.0.0.1 bytes 1568 packets 16
> 
> The reason is that we check it faster, just put sleep(1) before check
> while(bpf_map_get_next_key(map_fd, &key, &next_key) == 0).
> Now we get the expected results:
> 
> $ sudo ./samples/bpf/sockex2
> num = 0: ip 127.0.0.1 bytes 392 packets 4
> num = 1: ip 127.0.0.1 bytes 784 packets 8
> num = 2: ip 127.0.0.1 bytes 1176 packets 12
> num = 3: ip 127.0.0.1 bytes 1568 packets 16
> num = 4: ip 127.0.0.1 bytes 1960 packets 20
> 
> Signed-off-by: George Guo <guodongtai@...inos.cn>
> ---

Thanks, sounds reasonable to me (but I haven't checked it).  Might you want to
minimize the diff to only contain the move of the sleep call?

Kind regards,
Nicolas


>  samples/bpf/sockex2_user.c | 13 +++++++------
>  1 file changed, 7 insertions(+), 6 deletions(-)
> 
> diff --git a/samples/bpf/sockex2_user.c b/samples/bpf/sockex2_user.c
> index 2c18471336f0..84bf1ab77649 100644
> --- a/samples/bpf/sockex2_user.c
> +++ b/samples/bpf/sockex2_user.c
> @@ -18,8 +18,8 @@ int main(int ac, char **argv)
>  	struct bpf_program *prog;
>  	struct bpf_object *obj;
>  	int map_fd, prog_fd;
> -	char filename[256];
> -	int i, sock, err;
> +	char filename[256], command[64];
> +	int i, sock, err, num = 5;
>  	FILE *f;
>  
>  	snprintf(filename, sizeof(filename), "%s_kern.o", argv[0]);
> @@ -42,21 +42,22 @@ int main(int ac, char **argv)
>  	assert(setsockopt(sock, SOL_SOCKET, SO_ATTACH_BPF, &prog_fd,
>  			  sizeof(prog_fd)) == 0);
>  
> -	f = popen("ping -4 -c5 localhost", "r");
> +	snprintf(command, sizeof(command), "ping -4 -c%d localhost", num);
> +	f = popen(command, "r");
>  	(void) f;
>  
> -	for (i = 0; i < 5; i++) {
> +	for (i = 0; i < num; i++) {
>  		int key = 0, next_key;
>  		struct pair value;
>  
> +		sleep(1);
>  		while (bpf_map_get_next_key(map_fd, &key, &next_key) == 0) {
>  			bpf_map_lookup_elem(map_fd, &next_key, &value);
> -			printf("ip %s bytes %lld packets %lld\n",
> +			printf("num = %d: ip %s bytes %lld packets %lld\n", i,
>  			       inet_ntoa((struct in_addr){htonl(next_key)}),
>  			       value.bytes, value.packets);
>  			key = next_key;
>  		}
> -		sleep(1);
>  	}
>  	return 0;
>  }
> -- 
> 2.34.1

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