VILLASnode/lib/hooks/drop.c

/** Drop hook.
 *
 * @author Steffen Vogel <stvogel@eonerc.rwth-aachen.de>
 * @copyright 2017, Institute for Automation of Complex Power Systems, EONERC
 * @license GNU General Public License (version 3)
 *
 * VILLASnode
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 *********************************************************************************/

/** @addtogroup hooks Hook functions
 * @{
 */

#include "hook.h"
#include "plugin.h"
#include "stats.h"
#include "path.h"

static int drop_read(struct hook *h, struct sample *smps[], size_t *cnt)
{
	int i, ok, dist;

	for (i = 0, ok = 0; i < *cnt; i++) {
		h->last = smps[i];

		if (h->prev) {
			dist = h->last->sequence - (int32_t) h->prev->sequence;
			if (dist <= 0) {
				warn("Dropped sample: sequence=%u, dist=%d, i=%d", h->last->sequence, dist, i);
				if (h->path && h->path->stats)
					stats_update(h->path->stats->delta, STATS_REORDERED, dist);
			}
			else {
				struct sample *tmp;

				tmp = smps[i];
				smps[i] = smps[ok];
				smps[ok++] = tmp;
			}

			/* To discard the first X samples in 'smps[]' we must
			 * shift them to the end of the 'smps[]' array.
			 * In case the hook returns a number 'ok' which is smaller than 'cnt',
			 * only the first 'ok' samples in 'smps[]' are accepted and further processed.
			 */
		}
		else {
			struct sample *tmp;

			tmp = smps[i];
			smps[i] = smps[ok];
			smps[ok++] = tmp;
		}

		h->prev = h->last;
	}

	*cnt = ok;

	return 0;
}

static struct plugin p = {
	.name		= "drop",
	.description	= "Drop messages with reordered sequence numbers",
	.type		= PLUGIN_TYPE_HOOK,
	.hook		= {
		.priority = 3,
		.builtin = true,
		.read	= drop_read
	}
};

REGISTER_PLUGIN(&p)

/** @} */