103 lines
2.5 KiB
C
103 lines
2.5 KiB
C
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/*
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*
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* ===================================
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* HARP | Host ATM Research Platform
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* ===================================
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*
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*
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* This Host ATM Research Platform ("HARP") file (the "Software") is
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* made available by Network Computing Services, Inc. ("NetworkCS")
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* "AS IS". NetworkCS does not provide maintenance, improvements or
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* support of any kind.
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*
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* NETWORKCS MAKES NO WARRANTIES OR REPRESENTATIONS, EXPRESS OR IMPLIED,
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* INCLUDING, BUT NOT LIMITED TO, IMPLIED WARRANTIES OF MERCHANTABILITY
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* AND FITNESS FOR A PARTICULAR PURPOSE, AS TO ANY ELEMENT OF THE
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* SOFTWARE OR ANY SUPPORT PROVIDED IN CONNECTION WITH THIS SOFTWARE.
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* In no event shall NetworkCS be responsible for any damages, including
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* but not limited to consequential damages, arising from or relating to
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* any use of the Software or related support.
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*
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* Copyright 1994-1998 Network Computing Services, Inc.
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*
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* Copies of this Software may be made, however, the above copyright
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* notice must be reproduced on all copies.
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*
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* @(#) $Id: ip_checksum.c,v 1.4 1998/08/11 18:11:48 johnc Exp $
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*
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*/
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/*
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* User Space Library Functions
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* ----------------------------
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*
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* IP checksum computation
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*
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*/
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#ifndef lint
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static char *RCSid = "@(#) $Id: ip_checksum.c,v 1.4 1998/08/11 18:11:48 johnc Exp $";
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#endif
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#include <sys/types.h>
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#include <sys/param.h>
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#include <sys/socket.h>
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#include <net/if.h>
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#include <netinet/in.h>
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#include <netatm/port.h>
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#include <netatm/atm.h>
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#include <netatm/atm_if.h>
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#include <netatm/atm_sap.h>
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#include <netatm/atm_sys.h>
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#include <netatm/atm_ioctl.h>
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#include "libatm.h"
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/*
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* Compute an IP checksum
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*
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* This code was taken from RFC 1071.
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*
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* "The following "C" code algorithm computes the checksum with an inner
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* loop that sums 16 bits at a time in a 32-bit accumulator."
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*
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* Arguments:
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* addr pointer to the buffer whose checksum is to be computed
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* count number of bytes to include in the checksum
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*
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* Returns:
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* the computed checksum
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*
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*/
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short
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ip_checksum(addr, count)
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char *addr;
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int count;
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{
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/* Compute Internet Checksum for "count" bytes
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* beginning at location "addr".
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*/
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register long sum = 0;
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while( count > 1 ) {
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/* This is the inner loop */
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sum += ntohs(* (unsigned short *) addr);
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addr += sizeof(unsigned short);
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count -= sizeof(unsigned short);
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}
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/* Add left-over byte, if any */
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if( count > 0 )
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sum += * (unsigned char *) addr;
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/* Fold 32-bit sum to 16 bits */
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while (sum>>16)
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sum = (sum & 0xffff) + (sum >> 16);
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return((short)~sum);
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}
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