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Annotation of kernel/machdep/i386/in_cksum.c, revision 1.1

1.1     ! root        1: /*
        !             2:  * Copyright (c) 1999 Apple Computer, Inc. All rights reserved.
        !             3:  *
        !             4:  * @APPLE_LICENSE_HEADER_START@
        !             5:  * 
        !             6:  * Portions Copyright (c) 1999 Apple Computer, Inc.  All Rights
        !             7:  * Reserved.  This file contains Original Code and/or Modifications of
        !             8:  * Original Code as defined in and that are subject to the Apple Public
        !             9:  * Source License Version 1.1 (the "License").  You may not use this file
        !            10:  * except in compliance with the License.  Please obtain a copy of the
        !            11:  * License at http://www.apple.com/publicsource and read it before using
        !            12:  * this file.
        !            13:  * 
        !            14:  * The Original Code and all software distributed under the License are
        !            15:  * distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, EITHER
        !            16:  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
        !            17:  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
        !            18:  * FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT.  Please see the
        !            19:  * License for the specific language governing rights and limitations
        !            20:  * under the License.
        !            21:  * 
        !            22:  * @APPLE_LICENSE_HEADER_END@
        !            23:  */
        !            24: 
        !            25: /*
        !            26:  * Copyright (c) 1988 Regents of the University of California.
        !            27:  * All rights reserved.
        !            28:  *
        !            29:  * Redistribution and use in source and binary forms are permitted
        !            30:  * provided that this notice is preserved and that due credit is given
        !            31:  * to the University of California at Berkeley. The name of the University
        !            32:  * may not be used to endorse or promote products derived from this
        !            33:  * software without specific prior written permission. This software
        !            34:  * is provided ``as is'' without express or implied warranty.
        !            35:  *
        !            36:  *     @(#)in_cksum.c  7.1 (Berkeley) 3/29/88
        !            37:  */
        !            38: 
        !            39: /* HISTORY
        !            40:  * 26-May-94 Curtis Galloway at NeXT
        !            41:  *     Grabbed the m68k code and added a Pentium-optimized checksummer.
        !            42:  *     (See RFC 1107 for the checksum algorithm.)
        !            43:  *
        !            44:  * 06-Dec-92 Mac Gillon (mgillon) at NeXT
        !            45:  *     Lifted the '020 code from 4.4. The compiler generates crummy
        !            46:  *      code for the portable version. 
        !            47:  */
        !            48: 
        !            49: #include <sys/param.h>
        !            50: #include <sys/mbuf.h>
        !            51: #include <netinet/in.h>
        !            52: #include <netinet/in_systm.h>
        !            53: 
        !            54: #if defined(NX_CURRENT_COMPILER_RELEASE) && (NX_CURRENT_COMPILER_RELEASE < 320)
        !            55: #define SIREG "e"
        !            56: #else
        !            57: #define SIREG "S"
        !            58: #endif
        !            59: 
        !            60: 
        !            61: #if    DEBUG_OC
        !            62: 
        !            63: static inline int
        !            64: oc_cksum(
        !            65:     unsigned char *buf,
        !            66:     int len,
        !            67:     unsigned long oldsum
        !            68: )
        !            69: {
        !            70:     unsigned short *p = (unsigned short *)buf;
        !            71:     
        !            72:     for (; len>1; len -=2)
        !            73:        oldsum += *p++;
        !            74: #if __BIG_ENDIAN__
        !            75:     if (len > 0)
        !            76:        oldsum += (*(unsigned char *)p) << 8;
        !            77: #else
        !            78:     if (len > 0)
        !            79:        oldsum += *(unsigned char *)p;
        !            80: #endif
        !            81:     oldsum = (oldsum >> 16) + (oldsum & 0xffff);
        !            82:     oldsum = (oldsum >> 16) + (oldsum & 0xffff);
        !            83:     return oldsum;     
        !            84: }
        !            85: 
        !            86: #else  DEBUG_OC
        !            87: 
        !            88: static inline int
        !            89: oc_cksum(
        !            90:     unsigned char *buf,
        !            91:     int len,
        !            92:     unsigned long oldsum
        !            93: )
        !            94: {
        !            95:     unsigned short sum;
        !            96:        
        !            97:     asm("
        !            98:        testb   $1, %%ecx
        !            99:        jne     5f                      // one or three extra bytes
        !           100:        testb   $2, %%ecx
        !           101:        jne     7f                      // two extra bytes
        !           102: 0:
        !           103:         adc     $0,%%eax               //add carry if extra bytes
        !           104:         shr     $3,%%ecx               //we'll do two dwords per loop
        !           105:         jnc     1f                     //is there an odd dword in buffer?
        !           106:         add     (%%esi),%%eax          //checksum the odd dword
        !           107:         adc     $0,%%eax               //add carry if needed
        !           108:         add     $4,%%esi               //point to the next dword
        !           109: 1:
        !           110:        test    %%ecx, %%ecx
        !           111:        jz      4f
        !           112:         mov     (%%esi),%%edx          //preload the first dword
        !           113:         mov     4(%%esi),%%ebx         //preload the second dword
        !           114:         dec     %%ecx                  //we'll do 1 checksum outside the loop
        !           115:         jz      3f                     //only 1 checksum to do
        !           116:         add     $8, %%esi              //point to the next dword
        !           117: 
        !           118: 2:
        !           119:         add     %%edx,%%eax            //cycle 1 U-pipe
        !           120:         mov     (%%esi),%%edx          //cycle 1 V-pipe
        !           121:         adc     %%ebx,%%eax            //cycle 2 U-pipe
        !           122:         mov     4(%%esi),%%ebx         //cycle 2 V-pipe
        !           123:         adc     $0,%%eax               //cycle 3 U-pipe
        !           124:         add     $8,%%esi               //cycle 3 V-pipe
        !           125:         dec     %%ecx                  //cycle 4 U-pipe
        !           126:         jnz     2b                     //cycle 4 V-pipe
        !           127: 
        !           128: 3:
        !           129:         add     %%edx,%%eax            //checksum the last two dwords
        !           130:         adc     %%ebx,%%eax
        !           131:         adc     $0,%%eax
        !           132: 4:
        !           133:         mov     %%eax,%%edx            //compress the 32-bit checksum
        !           134:         shr     $16,%%edx              //into a 16-bit checksum
        !           135:         add     %%dx,%%ax
        !           136:         adc     $0,%%eax
        !           137:        jmp     8f
        !           138:        
        !           139: 5:
        !           140:        testb   $2, %%ecx
        !           141:        je      6f                      // do one byte
        !           142:        
        !           143:        movzwl  -3(%%esi,%%ecx),%%ebx
        !           144:        add     %%ebx,%%eax             // pick up two bytes and fall through
        !           145: 
        !           146: 6:
        !           147:        movzbl  -1(%%esi,%%ecx),%%ebx
        !           148:        adc     %%ebx,%%eax
        !           149:        jmp     0b
        !           150:        
        !           151: 7:
        !           152:        movzwl  -2(%%esi,%%ecx),%%ebx
        !           153:        add     %%ebx, %%eax
        !           154:        jmp     0b
        !           155: 
        !           156: 8:     
        !           157:     " : "=a" (sum) : "c" (len), SIREG (buf), "a" (oldsum) :
        !           158:     "eax", "ebx", "ecx", "edx", "esi");
        !           159: 
        !           160:     return sum;
        !           161: }
        !           162: 
        !           163: #endif DEBUG_OC
        !           164: 
        !           165: 
        !           166: 
        !           167: /*
        !           168:  * Checksum routine for the Internet Protocol family.
        !           169:  *
        !           170:  * This isn't as bad as it looks.  For ip headers the "while" isn't
        !           171:  * executed and we just drop through to the return statement at the
        !           172:  * end.  For the usual tcp or udp packet (a single header mbuf
        !           173:  * chained onto a cluster of data, we make exactly one trip through
        !           174:  * the while (for the header mbuf) and never do the hairy code
        !           175:  * inside the "if".  If fact, if m_copydata & sb_compact are doing
        !           176:  * their job, we should never do the hairy code inside the "if".
        !           177:  */
        !           178: in_cksum(m, len)
        !           179:        register struct mbuf *m;
        !           180:        register int len;
        !           181: {
        !           182:        register int sum = 0;
        !           183:        register int i;
        !           184: 
        !           185:        while (len > m->m_len) {
        !           186:                sum = oc_cksum(mtod(m, u_char *), i = m->m_len, sum);
        !           187:                m = m->m_next;
        !           188:                len -= i;
        !           189:                if (i & 1) {
        !           190:                        /*
        !           191:                         * ouch - we ended on an odd byte with more
        !           192:                         * to do.  This xfer is obviously not interested
        !           193:                         * in performance so finish things slowly.
        !           194:                         */
        !           195:                        register u_char *cp;
        !           196: 
        !           197:                        while (len > m->m_len) {
        !           198:                                cp = mtod(m, u_char *);
        !           199:                                if (i & 1) {
        !           200:                                        i = m->m_len - 1;
        !           201:                                        --len;
        !           202: #if __BIG_ENDIAN__
        !           203:                                        sum += *cp++;
        !           204: #else
        !           205:                                        sum += (*cp++) << 8;
        !           206: #endif
        !           207:                                } else
        !           208:                                        i = m->m_len;
        !           209: 
        !           210:                                sum = oc_cksum(cp, i, sum);
        !           211:                                m = m->m_next;
        !           212:                                len -= i;
        !           213:                        }
        !           214:                        if (i & 1) {
        !           215:                                cp =  mtod(m, u_char *);
        !           216: #if __BIG_ENDIAN__
        !           217:                                sum += *cp++;
        !           218: #else
        !           219:                                sum += (*cp++) << 8;
        !           220: #endif
        !           221:                                return (0xffff & ~oc_cksum(cp, len - 1, sum));
        !           222:                        }
        !           223:                }
        !           224:        }
        !           225:        return (0xffff & ~oc_cksum(mtod(m, u_char *), len, sum));
        !           226: }
        !           227: 
        !           228: 
        !           229: /*
        !           230:  * Checksum routine for Internet Protocol family headers (Portable Version).
        !           231:  *
        !           232:  * This routine is very heavily used in the network
        !           233:  * code and should be modified for each CPU to be as fast as possible.
        !           234:  */
        !           235: 
        !           236: #ifdef notdef
        !           237: 
        !           238: #define ADDCARRY(x)  (x > 65535 ? x -= 65535 : x)
        !           239: #define REDUCE {l_util.l = sum; sum = l_util.s[0] + l_util.s[1]; ADDCARRY(sum);}
        !           240: 
        !           241: in_cksum(m, len)
        !           242:        register struct mbuf *m;
        !           243:        register int len;
        !           244: {
        !           245:        register u_short *w;
        !           246:        register int sum = 0;
        !           247:        register int mlen = 0;
        !           248:        int byte_swapped = 0;
        !           249: 
        !           250:        union {
        !           251:                char    c[2];
        !           252:                u_short s;
        !           253:        } s_util;
        !           254:        union {
        !           255:                u_short s[2];
        !           256:                long    l;
        !           257:        } l_util;
        !           258: 
        !           259:        for (;m && len; m = m->m_next) {
        !           260:                if (m->m_len == 0)
        !           261:                        continue;
        !           262:                w = mtod(m, u_short *);
        !           263:                if (mlen == -1) {
        !           264:                        /*
        !           265:                         * The first byte of this mbuf is the continuation
        !           266:                         * of a word spanning between this mbuf and the
        !           267:                         * last mbuf.
        !           268:                         *
        !           269:                         * s_util.c[0] is already saved when scanning previous 
        !           270:                         * mbuf.
        !           271:                         */
        !           272:                        s_util.c[1] = *(char *)w;
        !           273:                        sum += s_util.s;
        !           274:                        w = (u_short *)((char *)w + 1);
        !           275:                        mlen = m->m_len - 1;
        !           276:                        len--;
        !           277:                } else
        !           278:                        mlen = m->m_len;
        !           279:                if (len < mlen)
        !           280:                        mlen = len;
        !           281:                len -= mlen;
        !           282:                /*
        !           283:                 * Force to even boundary.
        !           284:                 */
        !           285:                if ((1 & (int) w) && (mlen > 0)) {
        !           286:                        REDUCE;
        !           287:                        sum <<= 8;
        !           288:                        s_util.c[0] = *(u_char *)w;
        !           289:                        w = (u_short *)((char *)w + 1);
        !           290:                        mlen--;
        !           291:                        byte_swapped = 1;
        !           292:                }
        !           293:                /*
        !           294:                 * Unroll the loop to make overhead from
        !           295:                 * branches &c small.
        !           296:                 */
        !           297:                while ((mlen -= 32) >= 0) {
        !           298:                        sum += w[0]; sum += w[1]; sum += w[2]; sum += w[3];
        !           299:                        sum += w[4]; sum += w[5]; sum += w[6]; sum += w[7];
        !           300:                        sum += w[8]; sum += w[9]; sum += w[10]; sum += w[11];
        !           301:                        sum += w[12]; sum += w[13]; sum += w[14]; sum += w[15];
        !           302:                        w += 16;
        !           303:                }
        !           304:                mlen += 32;
        !           305:                while ((mlen -= 8) >= 0) {
        !           306:                        sum += w[0]; sum += w[1]; sum += w[2]; sum += w[3];
        !           307:                        w += 4;
        !           308:                }
        !           309:                mlen += 8;
        !           310:                if (mlen == 0 && byte_swapped == 0)
        !           311:                        continue;
        !           312:                REDUCE;
        !           313:                while ((mlen -= 2) >= 0) {
        !           314:                        sum += *w++;
        !           315:                }
        !           316:                if (byte_swapped) {
        !           317:                        REDUCE;
        !           318:                        sum <<= 8;
        !           319:                        byte_swapped = 0;
        !           320:                        if (mlen == -1) {
        !           321:                                s_util.c[1] = *(char *)w;
        !           322:                                sum += s_util.s;
        !           323:                                mlen = 0;
        !           324:                        } else
        !           325:                                mlen = -1;
        !           326:                } else if (mlen == -1)
        !           327:                        s_util.c[0] = *(char *)w;
        !           328:        }
        !           329:        if (len)
        !           330:                printf("cksum: out of data\n");
        !           331:        if (mlen == -1) {
        !           332:                /* The last mbuf has odd # of bytes. Follow the
        !           333:                   standard (the odd byte may be shifted left by 8 bits
        !           334:                   or not as determined by endian-ness of the machine) */
        !           335:                s_util.c[1] = 0;
        !           336:                sum += s_util.s;
        !           337:        }
        !           338:        REDUCE;
        !           339:        return (~sum & 0xffff);
        !           340: }
        !           341: #endif

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