67 lines
2.1 KiB
C
67 lines
2.1 KiB
C
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/*
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Cubesat Space Protocol - A small network-layer protocol designed for Cubesats
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Copyright (C) 2012 GomSpace ApS (http://www.gomspace.com)
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Copyright (C) 2012 AAUSAT3 Project (http://aausat3.space.aau.dk)
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This library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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This library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with this library; if not, write to the Free Software
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Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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*/
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#include <stdlib.h>
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#include <stddef.h>
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#include <stdio.h>
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#include <inttypes.h>
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#include <csp/csp.h>
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#include <csp/arch/csp_time.h>
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#include <csp/csp_crc32.h>
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#include "csp_dedup.h"
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/* Check the last CSP_DEDUP_COUNT packets for duplicates */
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#define CSP_DEDUP_COUNT 16
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/* Only consider packet a duplicate if received under CSP_DEDUP_WINDOW_MS ago */
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#define CSP_DEDUP_WINDOW_MS 1000
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/* Store packet CRC's in a ringbuffer */
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static uint32_t csp_dedup_array[CSP_DEDUP_COUNT] = {};
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static uint32_t csp_dedup_timestamp[CSP_DEDUP_COUNT] = {};
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static int csp_dedup_in = 0;
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bool csp_dedup_is_duplicate(csp_packet_t *packet)
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{
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/* Calculate CRC32 for packet */
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uint32_t crc = csp_crc32_memory((const uint8_t *) &packet->id, packet->length + sizeof(packet->id));
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/* Check if we have received this packet before */
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for (int i = 0; i < CSP_DEDUP_COUNT; i++) {
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/* Check for match */
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if (crc == csp_dedup_array[i]) {
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/* Check the timestamp */
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if (csp_get_ms() < csp_dedup_timestamp[i] + CSP_DEDUP_WINDOW_MS)
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return true;
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}
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}
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/* If not, insert packet into duplicate list */
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csp_dedup_array[csp_dedup_in] = crc;
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csp_dedup_timestamp[csp_dedup_in] = csp_get_ms();
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csp_dedup_in = (csp_dedup_in + 1) % CSP_DEDUP_COUNT;
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return false;
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}
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