[PATCH v2 1/5] telemetry: escape special char when tel string

[Morten Brørup]

> From: Chengwen Feng [mailto:fengchengwen at huawei.com]
> Sent: Friday, 17 June 2022 11.46
> 
> This patch supports escape special characters (including: \",\\,/,\b,
> /f,/n,/r,/t) when telemetry string.
> This patch is used to support telemetry xxx-dump commands which the
> string may include special characters.
> 
> Signed-off-by: Chengwen Feng <fengchengwen at huawei.com>
> ---
>  lib/telemetry/telemetry.c | 96 +++++++++++++++++++++++++++++++++++++--
>  1 file changed, 93 insertions(+), 3 deletions(-)
> 
> diff --git a/lib/telemetry/telemetry.c b/lib/telemetry/telemetry.c
> index c6fd03a5ab..0f762f633e 100644
> --- a/lib/telemetry/telemetry.c
> +++ b/lib/telemetry/telemetry.c
> @@ -215,6 +215,94 @@ container_to_json(const struct rte_tel_data *d,
> char *out_buf, size_t buf_len)
>  	return used;
>  }
> 
> +static bool
> +json_is_special_char(char ch)
> +{
> +	static unsigned char is_spec[256] = { 0 };
> +	static bool init_once;
> +
> +	if (!init_once) {
> +		is_spec['\"'] = 1;
> +		is_spec['\\'] = 1;
> +		is_spec['/'] = 1;
> +		is_spec['\b'] = 1;
> +		is_spec['\f'] = 1;
> +		is_spec['\n'] = 1;
> +		is_spec['\r'] = 1;
> +		is_spec['\t'] = 1;
> +		init_once = true;
> +	}
> +
> +	return (bool)is_spec[(unsigned char)ch];
> +}

Here's a suggestion for simplifying the code:

Remove json_is_special_char(), and update json_escape_special_char() and json_format_string() as follows:

> +
> +static size_t
> +json_escape_special_char(char *buf, const char ch)

Consider making this function inline.

> +{
> +	size_t used = 0;
> +
> +	switch (ch) {
> +	case '\"':
> +		buf[used++] = '\\';
> +		buf[used++] = '\"';
> +		break;
> +	case '\\':
> +		buf[used++] = '\\';
> +		buf[used++] = '\\';
> +		break;
> +	case '/':
> +		buf[used++] = '\\';
> +		buf[used++] = '/';
> +		break;
> +	case '\b':
> +		buf[used++] = '\\';
> +		buf[used++] = 'b';
> +		break;
> +	case '\f':
> +		buf[used++] = '\\';
> +		buf[used++] = 'f';
> +		break;
> +	case '\n':
> +		buf[used++] = '\\';
> +		buf[used++] = 'n';
> +		break;
> +	case '\r':
> +		buf[used++] = '\\';
> +		buf[used++] = 'r';
> +		break;
> +	case '\t':
> +		buf[used++] = '\\';
> +		buf[used++] = 't';
> +		break;
> +	default:

Handle non-escaped characters in the default case here instead:

+		buf[used++] = ch;

> +		break;
> +	}
> +
> +	return used;
> +}
> +
> +static size_t
> +json_format_string(char *buf, size_t len, const char *str)
> +{
> +	size_t used = 0;
> +
> +	while (*str) {
> +		if (unlikely(len < used + 2)) {
> +			TMTY_LOG(WARNING, "Insufficient buffer when json
> format string\n");
> +			break;
> +		}
> +

-- replace:
> +		if (json_is_special_char(*str))
> +			used += json_escape_special_char(buf + used, *str);
> +		else
> +			buf[used++] = *str;
> +
> +		str++;
-- by:
+		used += json_escape_special_char(buf + used, *str++);
--

End of suggestion. Feel free to use it or not. :-)

> +	}
> +
> +	return used;
> +}
> +
>  static void
>  output_json(const char *cmd, const struct rte_tel_data *d, int s)
>  {
> @@ -232,9 +320,11 @@ output_json(const char *cmd, const struct
> rte_tel_data *d, int s)
>  				MAX_CMD_LEN, cmd ? cmd : "none");
>  		break;
>  	case RTE_TEL_STRING:
> -		used = snprintf(out_buf, sizeof(out_buf),
> "{\"%.*s\":\"%.*s\"}",
> -				MAX_CMD_LEN, cmd,
> -				RTE_TEL_MAX_SINGLE_STRING_LEN, d->data.str);
> +		used = snprintf(out_buf, sizeof(out_buf), "{\"%.*s\":\"",
> +				MAX_CMD_LEN, cmd);
> +		used += json_format_string(out_buf + used,
> +				sizeof(out_buf) - used - 3, d->data.str);
> +		used += snprintf(out_buf + used, sizeof(out_buf) - used,
> "\"}");

I looked for missing 0-termination in json_format_string(), but that is not required due to the immediately following snprintf().

>  		break;
>  	case RTE_TEL_DICT:
>  		prefix_used = snprintf(out_buf, sizeof(out_buf),
> "{\"%.*s\":",
> --
> 2.33.0
> 

If you want to make it generic, these four cases in output_json() also need to JSON encode the strings:

case RTE_TEL_DICT:
	case RTE_TEL_STRING_VAL: ...
	case RTE_TEL_CONTAINER: ... (strings only)

case RTE_TEL_ARRAY_STRING:
	if (d->type == RTE_TEL_ARRAY_STRING) ...
	else if (d->type == RTE_TEL_ARRAY_CONTAINER) ... (strings only)


However, JSON encoding of strings inside arrays and containers is not required for the dump purposes addressed by this patch series, so I consider this patch complete without it. No need to add "feature creep" to this series.


Reviewed-by: Morten Brørup <mb at smartsharesystems.com>