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/*

 * Copyright (c) 1988, 1992, 1993

 *      The Regents of the University of California.  All rights reserved.

 *

 * Redistribution and use in source and binary forms, with or without

 * modification, are permitted provided that the following conditions

 * are met:

 * 1. Redistributions of source code must retain the above copyright

 *    notice, this list of conditions and the following disclaimer.

 * 2. Redistributions in binary form must reproduce the above copyright

 *    notice, this list of conditions and the following disclaimer in the

 *    documentation and/or other materials provided with the distribution.

 * 3. All advertising materials mentioning features or use of this software

 *    must display the following acknowledgement:

 *      This product includes software developed by the University of

 *      California, Berkeley and its contributors.

 * 4. Neither the name of the University nor the names of its contributors

 *    may be used to endorse or promote products derived from this software

 *    without specific prior written permission.

 *

 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND

 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE

 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE

 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE

 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL

 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS

 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)

 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT

 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY

 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF

 * SUCH DAMAGE.

 *

 *      @(#)in_cksum.c  8.1 (Berkeley) 6/10/93

 * $Id: in_cksum.c,v 1.2 2001-09-27 12:01:55 chris Exp $

 */

#include <sys/param.h>

#include <sys/mbuf.h>

/*

 *  Try to use a CPU specific version, then punt to the portable C one.

 */

#if (defined(__GNUC__) && (defined(__mc68000__) || defined(__m68k__)))

#include "in_cksum_m68k.c"

#elif (defined(__GNUC__) && defined(__i386__))

#include "in_cksum_i386.c"

#elif (defined(__GNUC__) && defined(__PPC__))

#include "in_cksum_powerpc.c"

#else

/*

 * Checksum routine for Internet Protocol family headers (Portable Version).

 *

 * This routine is very heavily used in the network

 * code and should be modified for each CPU to be as fast as possible.

 */

#define ADDCARRY(x)  (x > 65535 ? x -= 65535 : x)

#define REDUCE \

  {l_util.l = sum; sum = l_util.s[0] + l_util.s[1];  ADDCARRY(sum);}

int

in_cksum(m, len)

        register struct mbuf *m;

        register int len;

{

        register u_short *w;

        register int sum = 0;

        register int mlen = 0;

        int byte_swapped = 0;

        union {

                char    c[2];

                u_short s;

        } s_util;

        union {

                u_short s[2];

                long    l;

        } l_util;

        for (;m && len; m = m->m_next) {

                if (m->m_len == 0)

                        continue;

                w = mtod(m, u_short *);

                if (mlen == -1) {

                        /*

                         * The first byte of this mbuf is the continuation

                         * of a word spanning between this mbuf and the

                         * last mbuf.

                         *

                         * s_util.c[0] is already saved when scanning previous

                         * mbuf.

                         */

                        s_util.c[1] = *(char *)w;

                        sum += s_util.s;

                        w = (u_short *)((char *)w + 1);

                        mlen = m->m_len - 1;

                        len--;

                } else

                        mlen = m->m_len;

                if (len < mlen)

                        mlen = len;

                len -= mlen;

                /*

                 * Force to even boundary.

                 */

                if ((1 & (int) w) && (mlen > 0)) {

                        REDUCE;

                        sum <<= 8;

                        s_util.c[0] = *(u_char *)w;

                        w = (u_short *)((char *)w + 1);

                        mlen--;

                        byte_swapped = 1;

                }

                /*

                 * Unroll the loop to make overhead from

                 * branches &c small.

                 */

                while ((mlen -= 32) >= 0) {

                        sum += w[0]; sum += w[1]; sum += w[2]; sum += w[3];

                        sum += w[4]; sum += w[5]; sum += w[6]; sum += w[7];

                        sum += w[8]; sum += w[9]; sum += w[10]; sum += w[11];

                        sum += w[12]; sum += w[13]; sum += w[14]; sum += w[15];

                        w += 16;

                }

                mlen += 32;

                while ((mlen -= 8) >= 0) {

                        sum += w[0]; sum += w[1]; sum += w[2]; sum += w[3];

                        w += 4;

                }

                mlen += 8;

                if (mlen == 0 && byte_swapped == 0)

                        continue;

                REDUCE;

                while ((mlen -= 2) >= 0) {

                        sum += *w++;

                }

                if (byte_swapped) {

                        REDUCE;

                        sum <<= 8;

                        byte_swapped = 0;

                        if (mlen == -1) {

                                s_util.c[1] = *(char *)w;

                                sum += s_util.s;

                                mlen = 0;

                        } else

                                mlen = -1;

                } else if (mlen == -1)

                        s_util.c[0] = *(char *)w;

        }

        if (len)

                puts("cksum: out of data");

        if (mlen == -1) {

                /* The last mbuf has odd # of bytes. Follow the

                   standard (the odd byte may be shifted left by 8 bits

                   or not as determined by endian-ness of the machine) */

                s_util.c[1] = 0;

                sum += s_util.s;

        }

        REDUCE;

        return (~sum & 0xffff);

}

#endif