61 lines
1.3 KiB
C
61 lines
1.3 KiB
C
/*
|
|
This file is part of libcapwap.
|
|
|
|
libcapwap 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
|
|
(at your option) any later version.
|
|
|
|
libcapwap 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 Foobar. If not, see <http://www.gnu.org/licenses/>.
|
|
|
|
*/
|
|
|
|
/**
|
|
*@file
|
|
*@brief Implements lw_checksum.
|
|
*@addtogroup LW
|
|
*@{
|
|
*/
|
|
|
|
#include "lw.h"
|
|
|
|
|
|
/**
|
|
* Calculate the 16-bit checksum for LWAPP Image Data message
|
|
* elements with opcode 3 (see RFC5412)
|
|
* This is also used by Cisco in CAPWAP
|
|
* @param d pointer to data to calulate the checksum for
|
|
* @param len length of data
|
|
* @return the calculated checksum.
|
|
*/
|
|
uint16_t lw_checksum(uint8_t * d, int len)
|
|
{
|
|
int32_t sum = 0;
|
|
uint16_t *w = (uint16_t *) d;
|
|
|
|
while (len > 1) {
|
|
sum += ntohs(*w++);
|
|
len -= 2;
|
|
}
|
|
|
|
if (len)
|
|
sum += (*(uint8_t *) w) << 8;
|
|
|
|
sum = (sum >> 16) + (sum & 0xffff);
|
|
sum += (sum >> 16);
|
|
|
|
return (~sum) & 0xffff;
|
|
}
|
|
|
|
|
|
/**
|
|
*@}
|
|
*/
|
|
|