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

["Zhao1, Wei" <wei.zhao1@intel.com>]

Hi，Ferruh

> -----Original Message-----
> From: Yigit, Ferruh
> Sent: Monday, March 25, 2019 4:46 PM
> To: Zhao1, Wei <wei.zhao1@intel.com>; dev@dpdk.org
> Cc: stable@dpdk.org; stephen@networkplumber.org; Ananyev, Konstantin
> <konstantin.ananyev@intel.com>
> Subject: Re: [dpdk-stable] [PATCH v3] app/testpmd: fix support of hex string
> parser for flow API
> 
> On 3/25/2019 3:39 AM, Zhao1, Wei wrote:
> > Hi,
> >
> >> -----Original Message-----
> >> From: Yigit, Ferruh
> >> Sent: Friday, March 22, 2019 10:56 PM
> >> To: Zhao1, Wei <wei.zhao1@intel.com>; dev@dpdk.org
> >> Cc: stable@dpdk.org; stephen@networkplumber.org; Ananyev,
> Konstantin
> >> <konstantin.ananyev@intel.com>
> >> Subject: Re: [dpdk-stable] [PATCH v3] app/testpmd: fix support of hex
> >> string parser for flow API
> >>
> >> 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 ;) )
> >
> >
> > Why delete these check from parse_hex_string()?
> 
> The point is using 'strtoul' instead of your functions, so that you won't need
> 'get_hex_val()' at all, or won't need 'isxdigit()' because 'strtoul' will check it,
> won't need size should be multiply of two restriction '(*size & 1)' because of
> implementation change. Probably you will need NULL checks, but again point
> is why not using 'strtoul' instead of writing your version of it?

Yes, we can use 'strtoul' , but my point is that  I think we need these check code even  if we use the code 'strtoul' .
isxdigit(*c)) is need because  *c may be sring "0xrgh" which is not hex.
If we use strtoul  will return 0 for that ,we can not distinguish between error or input is zero.  
'(*size & 1) can be delete, I agree.

	/* Check input parameters */
	if ((src == NULL) ||
	(dst == NULL) ||
		(size == NULL) ||
		(*size == 0))
		return -1;
	for (c = src, i = 0; i < *size; c++, i++) {
		if (isxdigit(*c))
			continue;
		else
			return -1;
	}


> >
> > 	/* 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;
> > 	}
> >
> >
> >
> >>
> >> <...>
> >>
> >>> +	/* 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"