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

[Bruce Richardson]

On Fri, Jun 17, 2022 at 01:16:08PM +0200, Morten Brørup wrote:
> > 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];
> > +}

According to the json spec at [1], the characters that need to be escaped
are:
a) any characters <0x20
b) inverted commas/quote character \"
c) the "reverse solidus character", better known to you and I as the
back-slash.

Therefore, I think this table generation could be simplified, but also
expanded using this. For completeness we should also see about handling all
control characters if they are encountered.

[1] https://www.rfc-editor.org/rfc/rfc8259.txt

/Bruce