Subject: Re: [PATCH net-next v5 1/2] pktgen: Automate flag enumeration for unknown flag handling

From: Benjamin Poirier <[email-masked]>
Date: Thu, 28 Sep 2023 09:18:08 -0400

On 2023-09-28 13:21 +0200, Simon Horman wrote:
> On Wed, Sep 20, 2023 at 08:56:57PM +0800, Liang Chen wrote:
> > When specifying an unknown flag, it will print all available flags.
> > Currently, these flags are provided as fixed strings, which requires
> > manual updates when flags change. Replacing it with automated flag
> > enumeration.
> > 
> > Signed-off-by: Liang Chen <[email-masked]>
> > Signed-off-by: Benjamin Poirier <[email-masked]>
> > ---
> >  Changes from v3:
> > - check "n == IPSEC_SHIFT" instead of string comparison
> > - use snprintf and check that the result does not overrun pkg_dev->result[]
> > - avoid double '\n' at the end

      ^

[...]

> > -		} else {
> > -			sprintf(pg_result,
> > -				"Flag -:%s:- unknown\nAvailable flags, (prepend ! to un-set flag):\n%s",
> > -				f,
> > -				"IPSRC_RND, IPDST_RND, UDPSRC_RND, UDPDST_RND, "
> > -				"MACSRC_RND, MACDST_RND, TXSIZE_RND, IPV6, "
> > -				"MPLS_RND, VID_RND, SVID_RND, FLOW_SEQ, "
> > -				"QUEUE_MAP_RND, QUEUE_MAP_CPU, UDPCSUM, "
> > -				"NO_TIMESTAMP, "
> > -#ifdef CONFIG_XFRM
> > -				"IPSEC, "
> > -#endif
> > -				"NODE_ALLOC\n");
> > +
> > +			sprintf(pg_result, "OK: flags=0x%x", pkt_dev->flags);
> >  			return count;
> >  		}
> > -		sprintf(pg_result, "OK: flags=0x%x", pkt_dev->flags);
> > +
> > +		/* Unknown flag */
> > +		end = pkt_dev->result + sizeof(pkt_dev->result);
> > +		pg_result += sprintf(pg_result,
> > +			"Flag -:%s:- unknown\n"
> > +			"Available flags, (prepend ! to un-set flag):\n", f);
> > +
> > +		for (int n = 0; n < NR_PKT_FLAGS && pg_result < end; n++) {
> > +			if (!IS_ENABLED(CONFIG_XFRM) && n == IPSEC_SHIFT)
> > +				continue;
> > +			pg_result += snprintf(pg_result, end - pg_result,
> > +					      "%s, ", pkt_flag_names[n]);
> > +		}
> > +		if (!WARN_ON_ONCE(pg_result >= end)) {
> > +			/* Remove the comma and whitespace at the end */
> > +			*(pg_result - 2) = '\0';
> 
> Hi Liang Chen,
> 
> Should the string have a trailing '\n' in keeping with the current formatting?

A '\n' is already added when the string is output by pktgen_if_show() so
if the string above has a trailing '\n', it leads to an empty line in
the output.

If my count is correct, before this patch there are 56 cases that output
to pkt_dev->result/pg_result in pktgen_if_write() and only 3 of them
include a trailing '\n', arguably by mistake.

So, I think it's better to remove the empty line than to keep the
current formatting.