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Annotation of 43BSDReno/sys/hp300/in_cksum.c, revision 1.1

1.1     ! root        1: /*
        !             2:  * Copyright (c) 1988, 1990 Regents of the University of California.
        !             3:  * All rights reserved.
        !             4:  *
        !             5:  * Redistribution is only permitted until one year after the first shipment
        !             6:  * of 4.4BSD by the Regents.  Otherwise, redistribution and use in source and
        !             7:  * binary forms are permitted provided that: (1) source distributions retain
        !             8:  * this entire copyright notice and comment, and (2) distributions including
        !             9:  * binaries display the following acknowledgement:  This product includes
        !            10:  * software developed by the University of California, Berkeley and its
        !            11:  * contributors'' in the documentation or other materials provided with the
        !            12:  * distribution and in all advertising materials mentioning features or use
        !            13:  * of this software.  Neither the name of the University nor the names of
        !            14:  * its contributors may be used to endorse or promote products derived from
        !            15:  * this software without specific prior written permission.
        !            16:  * THIS SOFTWARE IS PROVIDED AS IS'' AND WITHOUT ANY EXPRESS OR IMPLIED
        !            17:  * WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
        !            18:  * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
        !            19:  *
        !            20:  * from: Utah $Hdr: in_cksum.c 1.6 89/08/24$
        !            21:  *
        !            22:  *     @(#)in_cksum.c  7.1 (Berkeley) 5/8/90
        !            23:  */
        !            24: 
        !            25: /*
        !            26:  * in_cksum - checksum routine for the Internet Protocol family.
        !            27:  */
        !            28: 
        !            29: #include "param.h"
        !            30: #include "mbuf.h"
        !            31: #include "../netinet/in.h"
        !            32: #include "../netinet/in_systm.h"
        !            33: 
        !            34: extern int oc_cksum();
        !            35: 
        !            36: /*
        !            37:  * Checksum routine for the Internet Protocol family.
        !            38:  *
        !            39:  * This isn't as bad as it looks.  For ip headers the "while" isn't
        !            40:  * executed and we just drop through to the return statement at the
        !            41:  * end.  For the usual tcp or udp packet (a single header mbuf
        !            42:  * chained onto a cluster of data, we make exactly one trip through
        !            43:  * the while (for the header mbuf) and never do the hairy code
        !            44:  * inside the "if".  If fact, if m_copydata & sb_compact are doing
        !            45:  * their job, we should never do the hairy code inside the "if".
        !            46:  */
        !            47: in_cksum(m, len)
        !            48:        register struct mbuf *m;
        !            49:        register int len;
        !            50: {
        !            51:        register int sum = 0;
        !            52:        register int i;
        !            53: 
        !            54:        while (len > m->m_len) {
        !            55:                sum = oc_cksum(mtod(m, u_char *), i = m->m_len, sum);
        !            56:                m = m->m_next;
        !            57:                len -= i;
        !            58:                if (i & 1) {
        !            59:                        /*
        !            60:                         * ouch - we ended on an odd byte with more
        !            61:                         * to do.  This xfer is obviously not interested
        !            62:                         * in performance so finish things slowly.
        !            63:                         */
        !            64:                        register u_char *cp;
        !            65: 
        !            66:                        while (len > m->m_len) {
        !            67:                                cp = mtod(m, u_char *);
        !            68:                                if (i & 1) {
        !            69:                                        i = m->m_len - 1;
        !            70:                                        --len;
        !            71:                                        sum += *cp++;
        !            72:                                } else
        !            73:                                        i = m->m_len;
        !            74: 
        !            75:                                sum = oc_cksum(cp, i, sum);
        !            76:                                m = m->m_next;
        !            77:                                len -= i;
        !            78:                        }
        !            79:                        if (i & 1) {
        !            80:                                cp =  mtod(m, u_char *);
        !            81:                                sum += *cp++;
        !            82:                                return (0xffff & ~oc_cksum(cp, len - 1, sum));
        !            83:                        }
        !            84:                }
        !            85:        }
        !            86:        return (0xffff & ~oc_cksum(mtod(m, u_char *), len, sum));
        !            87: }

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