[xdp-hints] Re: [PATCH bpf-next v5 2/4] selftests/bpf: Add launch time request to xdp_hw_metadata

[Daniel Borkmann <daniel@iogearbox.net>]

On 1/14/25 4:27 PM, Song Yoong Siang wrote:
[...]
> +	/* Add mqprio qdisc with TC and hardware queue one-to-one mapping */
> +	char map[256] = {0};
> +	char queues[256] = {0};
> +
> +	for (i = 0; i < rxq; i++) {
> +		char buf[8];
> +
> +		snprintf(buf, sizeof(buf), "%d ", i);
> +		strcat(map, buf);
> +
> +		snprintf(buf, sizeof(buf), "1@%d ", i);
> +		strcat(queues, buf);
> +	}
> +	run_command("sudo tc qdisc add dev %s handle 8001: parent root mqprio num_tc %d map %s queues %s hw 0",
> +		    ifname, rxq, map, queues);

Fyi, above triggers selftest build errors:

   xdp_hw_metadata.c: In function ‘main’:
   xdp_hw_metadata.c:763:45: error: ‘%d’ directive output may be truncated writing between 1 and 10 bytes into a region of size 8 [-Werror=format-truncation=]
     763 |                 snprintf(buf, sizeof(buf), "%d ", i);
         |                                             ^~
     TEST-OBJ [test_progs] arg_parsing.test.o
   xdp_hw_metadata.c:763:44: note: directive argument in the range [0, 2147483646]
     763 |                 snprintf(buf, sizeof(buf), "%d ", i);
         |                                            ^~~~~
   xdp_hw_metadata.c:763:17: note: ‘snprintf’ output between 3 and 12 bytes into a destination of size 8
     763 |                 snprintf(buf, sizeof(buf), "%d ", i);
         |                 ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   xdp_hw_metadata.c:766:47: error: ‘%d’ directive output may be truncated writing between 1 and 10 bytes into a region of size 6 [-Werror=format-truncation=]
     766 |                 snprintf(buf, sizeof(buf), "1@%d ", i);
         |                                               ^~
   xdp_hw_metadata.c:766:44: note: directive argument in the range [0, 2147483646]
     766 |                 snprintf(buf, sizeof(buf), "1@%d ", i);
         |                                            ^~~~~~~
   xdp_hw_metadata.c:766:17: note: ‘snprintf’ output between 5 and 14 bytes into a destination of size 8
     766 |                 snprintf(buf, sizeof(buf), "1@%d ", i);
         |                 ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~