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/*
*
* ===================================
* HARP | Host ATM Research Platform
* ===================================
*
*
* This Host ATM Research Platform ("HARP") file (the "Software") is
* made available by Network Computing Services, Inc. ("NetworkCS")
* "AS IS". NetworkCS does not provide maintenance, improvements or
* support of any kind.
*
* NETWORKCS MAKES NO WARRANTIES OR REPRESENTATIONS, EXPRESS OR IMPLIED,
* INCLUDING, BUT NOT LIMITED TO, IMPLIED WARRANTIES OF MERCHANTABILITY
* AND FITNESS FOR A PARTICULAR PURPOSE, AS TO ANY ELEMENT OF THE
* SOFTWARE OR ANY SUPPORT PROVIDED IN CONNECTION WITH THIS SOFTWARE.
* In no event shall NetworkCS be responsible for any damages, including
* but not limited to consequential damages, arising from or relating to
* any use of the Software or related support.
*
* Copyright 1994-1998 Network Computing Services, Inc.
*
* Copies of this Software may be made, however, the above copyright
* notice must be reproduced on all copies.
*
* @(#) $FreeBSD$
*
*/
/*
* User Space Library Functions
* ----------------------------
*
* IP checksum computation
*
*/
#include <sys/types.h>
#include <sys/param.h>
#include <sys/socket.h>
#include <net/if.h>
#include <netinet/in.h>
#include <netatm/port.h>
#include <netatm/atm.h>
#include <netatm/atm_if.h>
#include <netatm/atm_sap.h>
#include <netatm/atm_sys.h>
#include <netatm/atm_ioctl.h>
#include "libatm.h"
#ifndef lint
__RCSID("@(#) $FreeBSD$");
#endif
/*
* Compute an IP checksum
*
* This code was taken from RFC 1071.
*
* "The following "C" code algorithm computes the checksum with an inner
* loop that sums 16 bits at a time in a 32-bit accumulator."
*
* Arguments:
* addr pointer to the buffer whose checksum is to be computed
* count number of bytes to include in the checksum
*
* Returns:
* the computed checksum
*
*/
short
ip_checksum(addr, count)
char *addr;
int count;
{
/* Compute Internet Checksum for "count" bytes
* beginning at location "addr".
*/
register long sum = 0;
while( count > 1 ) {
/* This is the inner loop */
sum += ntohs(* (unsigned short *) addr);
addr += sizeof(unsigned short);
count -= sizeof(unsigned short);
}
/* Add left-over byte, if any */
if( count > 0 )
sum += * (unsigned char *) addr;
/* Fold 32-bit sum to 16 bits */
while (sum>>16)
sum = (sum & 0xffff) + (sum >> 16);
return((short)~sum);
}
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