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 4/9/2019 8:38 AM, Zhao1, Wei wrote:
> Hi,  Ferruh
> 
>> -----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 ;) )
>>
>> <...>
> 
> 
> 
> I have change code style as your guide as bellow, 
> but strtoul() seems do not work, it return c with a none-null every time.
> you can have a try yourself.

Hi Wei,

Yes it return 'c' none-null, which is OK/expected.

According man page:
"
If endptr is not NULL, strtol() stores the address of the first invalid
character in *endptr. If there were no digits at all, strtol() stores the
original value of nptr in *endptr (and returns 0). In particular, if *nptr is
not '\0' but **endptr is '\0' on return, the entire string is valid.
"

First invalid char in below is 'tmp[2]', which is '0', so 'strtol' returns
'&tmp[2]', this is aligned with what described above.

It says, "if *nptr is not '\0' but **endptr is '\0' on return, the entire string
is valid.", beware it says "**endptr is '\0'", so following check should work:

if (*c != 0) {
  len--;
  dst[len] = 0;
  *size = len;
  return -1;
}

> 
> 
> static int
> parse_hex_string(const char *src, uint8_t *dst, uint32_t *size)
> {
> 	char *c = NULL;
> 	uint32_t i, len;
> 	char tmp[3];
> 
> 	/* Check input parameters */
> 	if ((src == NULL) ||
> 		(dst == NULL) ||
> 		(size == NULL) ||
> 		(*size == 0))
> 		return -1;
> 
> 	/* Convert chars to bytes */
> 	for (i = 0, len = 0; i < *size; i += 2) {
> 		snprintf(tmp, 3, "%s" ,src + i);
> 		dst[len++] = strtoul(tmp, &c, 16);
> 		if(c)
> 			return -1;	
>  	}
> 	dst[len] = 0;
> 	*size = len;
> 
> 	return 0;
> }
> 
>>
>>> +	/* 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"