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Annotation of XNU/bsd/netinet/in_cksum.c, revision 1.1

1.1     ! root        1: /*
        !             2:  * Copyright (c) 2000 Apple Computer, Inc. All rights reserved.
        !             3:  *
        !             4:  * @APPLE_LICENSE_HEADER_START@
        !             5:  * 
        !             6:  * The contents of this file constitute Original Code as defined in and
        !             7:  * are subject to the Apple Public Source License Version 1.1 (the
        !             8:  * "License").  You may not use this file except in compliance with the
        !             9:  * License.  Please obtain a copy of the License at
        !            10:  * http://www.apple.com/publicsource and read it before using this file.
        !            11:  * 
        !            12:  * This Original Code and all software distributed under the License are
        !            13:  * distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, EITHER
        !            14:  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
        !            15:  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
        !            16:  * FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT.  Please see the
        !            17:  * License for the specific language governing rights and limitations
        !            18:  * under the License.
        !            19:  * 
        !            20:  * @APPLE_LICENSE_HEADER_END@
        !            21:  */
        !            22: /*
        !            23:  * Copyright (c) 1988, 1992, 1993
        !            24:  *     The Regents of the University of California.  All rights reserved.
        !            25:  *
        !            26:  * Redistribution and use in source and binary forms, with or without
        !            27:  * modification, are permitted provided that the following conditions
        !            28:  * are met:
        !            29:  * 1. Redistributions of source code must retain the above copyright
        !            30:  *    notice, this list of conditions and the following disclaimer.
        !            31:  * 2. Redistributions in binary form must reproduce the above copyright
        !            32:  *    notice, this list of conditions and the following disclaimer in the
        !            33:  *    documentation and/or other materials provided with the distribution.
        !            34:  * 3. All advertising materials mentioning features or use of this software
        !            35:  *    must display the following acknowledgement:
        !            36:  *     This product includes software developed by the University of
        !            37:  *     California, Berkeley and its contributors.
        !            38:  * 4. Neither the name of the University nor the names of its contributors
        !            39:  *    may be used to endorse or promote products derived from this software
        !            40:  *    without specific prior written permission.
        !            41:  *
        !            42:  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
        !            43:  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
        !            44:  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
        !            45:  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
        !            46:  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
        !            47:  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
        !            48:  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
        !            49:  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
        !            50:  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
        !            51:  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
        !            52:  * SUCH DAMAGE.
        !            53:  *
        !            54:  *     @(#)in_cksum.c  8.1 (Berkeley) 6/10/93
        !            55:  */
        !            56: 
        !            57: #include <sys/param.h>
        !            58: #include <sys/mbuf.h>
        !            59: #include <sys/kdebug.h>
        !            60: 
        !            61: /*
        !            62:  * Checksum routine for Internet Protocol family headers (Portable Version).
        !            63:  *
        !            64:  * This routine is very heavily used in the network
        !            65:  * code and should be modified for each CPU to be as fast as possible.
        !            66:  */
        !            67: 
        !            68: 
        !            69: 
        !            70: #if defined(ppc)
        !            71: 
        !            72: int
        !            73: in_cksum(m, len)
        !            74:        register struct mbuf *m;
        !            75:        register int len;
        !            76: {
        !            77:        register u_short *w;
        !            78:        register int sum = 0;
        !            79:        register int mlen = 0;
        !            80:        int starting_on_odd  = 0;
        !            81: 
        !            82: 
        !            83:        KERNEL_DEBUG(DBG_FNC_IN_CKSUM | DBG_FUNC_START, len,0,0,0,0);
        !            84: 
        !            85:        for (;m && len; m = m->m_next) {
        !            86:                if (m->m_len == 0)
        !            87:                        continue;
        !            88:                mlen = m->m_len;
        !            89:                w = mtod(m, u_short *);
        !            90: 
        !            91:                if (len < mlen)
        !            92:                        mlen = len;
        !            93: 
        !            94:                sum = xsum_assym(w, mlen, sum, starting_on_odd);
        !            95:                len -= mlen;
        !            96:                if (mlen & 0x1)
        !            97:                {
        !            98:                    if (starting_on_odd)
        !            99:                        starting_on_odd = 0;
        !           100:                    else
        !           101:                        starting_on_odd = 1;
        !           102:                }
        !           103:        }
        !           104: 
        !           105:        KERNEL_DEBUG(DBG_FNC_IN_CKSUM | DBG_FUNC_END, 0,0,0,0,0);
        !           106:        return (~sum & 0xffff);
        !           107: }
        !           108: 
        !           109: #else
        !           110: 
        !           111: 
        !           112: #define ADDCARRY(x)  (x > 65535 ? x -= 65535 : x)
        !           113: #define REDUCE {l_util.l = sum; sum = l_util.s[0] + l_util.s[1]; ADDCARRY(sum);}
        !           114: 
        !           115: 
        !           116: 
        !           117: int
        !           118: in_cksum(m, len)
        !           119:        register struct mbuf *m;
        !           120:        register int len;
        !           121: {
        !           122:        register u_short *w;
        !           123:        register int sum = 0;
        !           124:        register int mlen = 0;
        !           125:        int byte_swapped = 0;
        !           126: 
        !           127:        union {
        !           128:                char    c[2];
        !           129:                u_short s;
        !           130:        } s_util;
        !           131:        union {
        !           132:                u_short s[2];
        !           133:                long    l;
        !           134:        } l_util;
        !           135: 
        !           136:        for (;m && len; m = m->m_next) {
        !           137:                if (m->m_len == 0)
        !           138:                        continue;
        !           139:                w = mtod(m, u_short *);
        !           140:                if (mlen == -1) {
        !           141:                        /*
        !           142:                         * The first byte of this mbuf is the continuation
        !           143:                         * of a word spanning between this mbuf and the
        !           144:                         * last mbuf.
        !           145:                         *
        !           146:                         * s_util.c[0] is already saved when scanning previous
        !           147:                         * mbuf.
        !           148:                         */
        !           149:                        s_util.c[1] = *(char *)w;
        !           150:                        sum += s_util.s;
        !           151:                        w = (u_short *)((char *)w + 1);
        !           152:                        mlen = m->m_len - 1;
        !           153:                        len--;
        !           154:                } else
        !           155:                        mlen = m->m_len;
        !           156:                if (len < mlen)
        !           157:                        mlen = len;
        !           158:                len -= mlen;
        !           159:                /*
        !           160:                 * Force to even boundary.
        !           161:                 */
        !           162:                if ((1 & (int) w) && (mlen > 0)) {
        !           163:                        REDUCE;
        !           164:                        sum <<= 8;
        !           165:                        s_util.c[0] = *(u_char *)w;
        !           166:                        w = (u_short *)((char *)w + 1);
        !           167:                        mlen--;
        !           168:                        byte_swapped = 1;
        !           169:                }
        !           170:                /*
        !           171:                 * Unroll the loop to make overhead from
        !           172:                 * branches &c small.
        !           173:                 */
        !           174:                while ((mlen -= 32) >= 0) {
        !           175:                        sum += w[0]; sum += w[1]; sum += w[2]; sum += w[3];
        !           176:                        sum += w[4]; sum += w[5]; sum += w[6]; sum += w[7];
        !           177:                        sum += w[8]; sum += w[9]; sum += w[10]; sum += w[11];
        !           178:                        sum += w[12]; sum += w[13]; sum += w[14]; sum += w[15];
        !           179:                        w += 16;
        !           180:                }
        !           181:                mlen += 32;
        !           182:                while ((mlen -= 8) >= 0) {
        !           183:                        sum += w[0]; sum += w[1]; sum += w[2]; sum += w[3];
        !           184:                        w += 4;
        !           185:                }
        !           186:                mlen += 8;
        !           187:                if (mlen == 0 && byte_swapped == 0)
        !           188:                        continue;
        !           189:                REDUCE;
        !           190:                while ((mlen -= 2) >= 0) {
        !           191:                        sum += *w++;
        !           192:                }
        !           193:                if (byte_swapped) {
        !           194:                        REDUCE;
        !           195:                        sum <<= 8;
        !           196:                        byte_swapped = 0;
        !           197:                        if (mlen == -1) {
        !           198:                                s_util.c[1] = *(char *)w;
        !           199:                                sum += s_util.s;
        !           200:                                mlen = 0;
        !           201:                        } else
        !           202:                                mlen = -1;
        !           203:                } else if (mlen == -1)
        !           204:                        s_util.c[0] = *(char *)w;
        !           205:        }
        !           206:        if (len)
        !           207:                printf("cksum: out of data\n");
        !           208:        if (mlen == -1) {
        !           209:                /* The last mbuf has odd # of bytes. Follow the
        !           210:                   standard (the odd byte may be shifted left by 8 bits
        !           211:                   or not as determined by endian-ness of the machine) */
        !           212:                s_util.c[1] = 0;
        !           213:                sum += s_util.s;
        !           214:        }
        !           215:        REDUCE;
        !           216:        return (~sum & 0xffff);
        !           217: }
        !           218: 
        !           219: #endif

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