Re: [dpdk-dev] [dpdk-stable] [PATCH v3] app/testpmd: fix support of hex string parser for flow API

[Ferruh Yigit <ferruh.yigit@intel.com>]

On 3/22/2019 3:15 AM, Wei Zhao wrote:
> There is need for users to set configuration of HEX number for RSS
> key. The key byte should be pass down as hex number not as char
> string. This patch enable cmdline flow parse HEX number,
> in order to not using string which pass ASIC number.
> 
> Fixes: f4d623f96119 ("app/testpmd: fix missing RSS fields in flow action")
> Cc: stable@dpdk.org
> 
> Signed-off-by: Wei Zhao <wei.zhao1@intel.com>
> Tested-by: Peng Yuan <yuan.peng@intel.com>

<...>

> @@ -4475,6 +4486,138 @@ parse_string(struct context *ctx, const struct token *token,
>  	return -1;
>  }
>  
> +static uint32_t
> +get_hex_val(char c)
> +{
> +	switch (c) {
> +	case '0': case '1': case '2': case '3': case '4': case '5':
> +	case '6': case '7': case '8': case '9':
> +		return c - '0';
> +	case 'A': case 'B': case 'C': case 'D': case 'E': case 'F':
> +		return c - 'A' + 10;
> +	case 'a': case 'b': case 'c': case 'd': case 'e': case 'f':
> +		return c - 'a' + 10;
> +	default:
> +		return 0;
> +	}
> +}
> +
> +static int
> +parse_hex_string(const char *src, uint8_t *dst, uint32_t *size)
> +{
> +	const char *c;
> +	uint32_t i;
> +
> +	/* Check input parameters */
> +	if ((src == NULL) ||
> +		(dst == NULL) ||
> +		(size == NULL) ||
> +		(*size == 0))
> +		return -1;
> +	if ((*size & 1) != 0)
> +		return -1;
> +
> +	for (c = src, i = 0; i < *size; c++, i++) {
> +		if (isxdigit(*c))
> +			continue;
> +		else
> +			return -1;
> +	}
> +
> +	*size = *size / 2;
> +
> +	/* Convert chars to bytes */
> +	for (i = 0; i < *size; i++)
> +		dst[i] = get_hex_val(src[2 * i]) * 16 +
> +			get_hex_val(src[2 * i + 1]);
> +
> +	return 0;
> +}

I can see this has been discussed already but what would you think updating the
'parse_hex_string' something like following, it is less code to maintain:

static int
parse_hex_string(const char *src, uint8_t *dst, uint32_t *size)
{
  int len;
  int i
  for (i = 0, len = 0; i < *size; i += 2) {
    char tmp[3];
    snprintf(tmp, 3, src + i);
    dst[len++] = strtoul(tmp, NULL, 16);
  }
  dst[len] = 0;
  *size = len;
  return 0;
}

(indeed with better error checking on strtoul ;) )

<...>

> +	/* Output buffer is not necessarily NUL-terminated. */
> +	memcpy(buf, hex_tmp, hexlen);
> +	memset((uint8_t *)buf + len, 0x00, size - hexlen);

Can't this overflow the 'buf'? since "len = 2 * hexlen"
I guess intention is "buf + hexlen"