2014-08-24 20:50:33 +02:00
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/*
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This file is part of libcapwap.
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libcapwap is free software: you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation, either version 3 of the License, or
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(at your option) any later version.
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libcapwap 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
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with Foobar. If not, see <http://www.gnu.org/licenses/>.
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*/
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2015-03-23 07:48:27 +01:00
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/**
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*@file
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*@brief Implements lw_checksum.
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2016-03-05 10:24:08 +01:00
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*@addtogroup LW
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2015-04-14 07:42:23 +02:00
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*@{
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2015-03-23 07:48:27 +01:00
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*/
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2018-03-17 17:29:09 +01:00
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2016-03-05 21:49:45 +01:00
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#include "lw.h"
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2014-08-24 20:50:33 +02:00
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/**
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2015-04-05 02:07:59 +02:00
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* Calculate the 16-bit checksum for LWAPP Image Data message
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* elements with opcode 3 (see RFC5412)
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* This is also used by Cisco in CAPWAP
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2015-03-23 07:48:27 +01:00
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* @param d pointer to data to calulate the checksum for
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* @param len length of data
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* @return the calculated checksum.
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2014-08-24 20:50:33 +02:00
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*/
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2014-08-26 07:42:56 +02:00
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uint16_t lw_checksum(uint8_t * d, int len)
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{
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2015-01-04 10:01:04 +01:00
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int32_t sum = 0;
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uint16_t *w = (uint16_t *) d;
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2014-08-26 07:42:56 +02:00
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2015-01-04 10:01:04 +01:00
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while (len > 1) {
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sum += ntohs(*w++);
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len -= 2;
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}
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2014-08-25 07:56:14 +02:00
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2015-01-05 23:06:59 +01:00
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if (len)
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2015-01-04 10:01:04 +01:00
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sum += (*(uint8_t *) w) << 8;
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2014-08-25 07:56:14 +02:00
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2015-01-04 10:01:04 +01:00
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sum = (sum >> 16) + (sum & 0xffff);
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sum += (sum >> 16);
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return (~sum) & 0xffff;
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2014-08-26 07:42:56 +02:00
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}
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2015-04-05 02:07:59 +02:00
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2015-04-14 07:42:23 +02:00
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/**
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*@}
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*/
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