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Annotation of Net2/netiso/iso_chksum.c, revision 1.1

1.1     ! root        1: /*-
        !             2:  * Copyright (c) 1991 The Regents of the University of California.
        !             3:  * All rights reserved.
        !             4:  *
        !             5:  * Redistribution and use in source and binary forms, with or without
        !             6:  * modification, are permitted provided that the following conditions
        !             7:  * are met:
        !             8:  * 1. Redistributions of source code must retain the above copyright
        !             9:  *    notice, this list of conditions and the following disclaimer.
        !            10:  * 2. Redistributions in binary form must reproduce the above copyright
        !            11:  *    notice, this list of conditions and the following disclaimer in the
        !            12:  *    documentation and/or other materials provided with the distribution.
        !            13:  * 3. All advertising materials mentioning features or use of this software
        !            14:  *    must display the following acknowledgement:
        !            15:  *     This product includes software developed by the University of
        !            16:  *     California, Berkeley and its contributors.
        !            17:  * 4. Neither the name of the University nor the names of its contributors
        !            18:  *    may be used to endorse or promote products derived from this software
        !            19:  *    without specific prior written permission.
        !            20:  *
        !            21:  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
        !            22:  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
        !            23:  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
        !            24:  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
        !            25:  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
        !            26:  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
        !            27:  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
        !            28:  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
        !            29:  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
        !            30:  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
        !            31:  * SUCH DAMAGE.
        !            32:  *
        !            33:  *     @(#)iso_chksum.c        7.5 (Berkeley) 5/6/91
        !            34:  */
        !            35: 
        !            36: /***********************************************************
        !            37:                Copyright IBM Corporation 1987
        !            38: 
        !            39:                       All Rights Reserved
        !            40: 
        !            41: Permission to use, copy, modify, and distribute this software and its 
        !            42: documentation for any purpose and without fee is hereby granted, 
        !            43: provided that the above copyright notice appear in all copies and that
        !            44: both that copyright notice and this permission notice appear in 
        !            45: supporting documentation, and that the name of IBM not be
        !            46: used in advertising or publicity pertaining to distribution of the
        !            47: software without specific, written prior permission.  
        !            48: 
        !            49: IBM DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING
        !            50: ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO EVENT SHALL
        !            51: IBM BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR
        !            52: ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS,
        !            53: WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION,
        !            54: ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
        !            55: SOFTWARE.
        !            56: 
        !            57: ******************************************************************/
        !            58: 
        !            59: /*
        !            60:  * ARGO Project, Computer Sciences Dept., University of Wisconsin - Madison
        !            61:  */
        !            62: /* 
        !            63:  * $Header: iso_chksum.c,v 4.7 88/07/29 15:31:26 nhall Exp $
        !            64:  * $Source: /usr/argo/sys/netiso/RCS/iso_chksum.c,v $
        !            65:  *
        !            66:  * ISO CHECKSUM
        !            67:  *
        !            68:  * The checksum generation and check routines are here.
        !            69:  * The checksum is 2 bytes such that the sum of all the bytes b(i) == 0
        !            70:  * and the sum of i * b(i) == 0.
        !            71:  * The whole thing is complicated by the fact that the data are in mbuf
        !            72:  * chains.
        !            73:  * Furthermore, there is the possibility of wraparound in the running
        !            74:  * sums after adding up 4102 octets.  In order to avoid doing a mod
        !            75:  * operation after EACH add, we have restricted this implementation to 
        !            76:  * negotiating a maximum of 4096-octets per TPDU (for the transport layer).
        !            77:  * The routine iso_check_csum doesn't need to know where the checksum
        !            78:  * octets are.
        !            79:  * The routine iso_gen_csum takes a pointer to an mbuf chain (logically
        !            80:  * a chunk of data), an offset into the chunk at which the 2 octets are to
        !            81:  * be stuffed, and the length of the chunk.  The 2 octets have to be
        !            82:  * logically adjacent, but may be physically located in separate mbufs.
        !            83:  */
        !            84: 
        !            85: #ifdef ISO
        !            86: #include "argo_debug.h"
        !            87: #include "param.h"
        !            88: #include "mbuf.h"
        !            89: #endif ISO
        !            90: 
        !            91: #ifndef MNULL
        !            92: #define MNULL (struct mbuf *)0
        !            93: #endif MNULL
        !            94: 
        !            95: /*
        !            96:  * FUNCTION:   iso_check_csum
        !            97:  *
        !            98:  * PURPOSE:            To check the checksum of the packet in the mbuf chain (m).
        !            99:  *                             The total length of the packet is (len).
        !           100:  *                             Called from tp_input() and clnp_intr()
        !           101:  *
        !           102:  * RETURNS:             TRUE (something non-zero) if there is a checksum error,
        !           103:  *                              FALSE if there was NO checksum error.
        !           104:  *
        !           105:  * SIDE EFFECTS:  none
        !           106:  *
        !           107:  * NOTES:               It might be possible to gain something by optimizing
        !           108:  *               this routine (unrolling loops, etc). But it is such
        !           109:  *                              a horrible thing to fiddle with anyway, it probably
        !           110:  *                              isn't worth it.
        !           111:  */
        !           112: int 
        !           113: iso_check_csum(m, len)
        !           114:        struct mbuf *m;
        !           115:        int len;
        !           116: {
        !           117:        register u_char *p = mtod(m, u_char *);
        !           118:        register u_long c0=0, c1=0;
        !           119:        register int i=0;
        !           120:        int cum = 0; /* cumulative length */
        !           121:        int l;
        !           122: 
        !           123:        l = len;
        !           124:        len = MIN(m->m_len, len);
        !           125:        i = 0;
        !           126: 
        !           127:        IFDEBUG(D_CHKSUM)
        !           128:                printf("iso_check_csum: m x%x, l x%x, m->m_len x%x\n", m, l, m->m_len);
        !           129:        ENDDEBUG
        !           130: 
        !           131:        while( i<l ) {
        !           132:                cum += len;
        !           133:                while (i<cum) {
        !           134:                        c0 = c0 + *(p++);
        !           135:                        c1 += c0;
        !           136:                        i++;
        !           137:                }
        !           138:                if(i < l) {
        !           139:                        m = m->m_next;
        !           140:                        IFDEBUG(D_CHKSUM)
        !           141:                                printf("iso_check_csum: new mbuf\n");
        !           142:                                if(l-i < m->m_len)
        !           143:                                        printf(
        !           144:                                        "bad mbuf chain in check csum l 0x%x i 0x%x m_data 0x%x",
        !           145:                                                l,i,m->m_data);
        !           146:                        ENDDEBUG
        !           147:                        ASSERT( m != MNULL);
        !           148:                        len = MIN( m->m_len, l-i);
        !           149:                        p = mtod(m, u_char *);
        !           150:                }
        !           151:        }
        !           152:        if ( ((int)c0 % 255) || ((int)c1 % 255) ) {
        !           153:                IFDEBUG(D_CHKSUM)
        !           154:                        printf("BAD iso_check_csum l 0x%x cum 0x%x len 0x%x, i 0x%x", 
        !           155:                                l, cum, len, i);
        !           156:                ENDDEBUG
        !           157:                return ((int)c0 % 255)<<8 | ((int)c1 % 255);
        !           158:        }
        !           159:        return 0;
        !           160: }
        !           161: 
        !           162: /*
        !           163:  * FUNCTION:   iso_gen_csum
        !           164:  *
        !           165:  * PURPOSE:            To generate the checksum of the packet in the mbuf chain (m).
        !           166:  *                             The first of the 2 (logically) adjacent checksum bytes 
        !           167:  *                             (x and y) go at offset (n).
        !           168:  *                             (n) is an offset relative to the beginning of the data, 
        !           169:  *                             not the beginning of the mbuf.
        !           170:  *                             (l) is the length of the total mbuf chain's data.
        !           171:  *                             Called from tp_emit(), tp_error_emit()
        !           172:  *                             clnp_emit_er(), clnp_forward(), clnp_output().
        !           173:  *
        !           174:  * RETURNS:            Rien
        !           175:  *
        !           176:  * SIDE EFFECTS: Puts the 2 checksum bytes into the packet.
        !           177:  *
        !           178:  * NOTES:              Ditto the note for iso_check_csum().
        !           179:  */
        !           180: 
        !           181: void
        !           182: iso_gen_csum(m,n,l)
        !           183:        struct mbuf *m;
        !           184:        int n; /* offset of 2 checksum bytes */
        !           185:        int l;
        !           186: {
        !           187:        register u_char *p = mtod(m, u_char *);
        !           188:        register int c0=0, c1=0;
        !           189:        register int i=0;
        !           190:        int loc = n++, len=0; /* n is position, loc is offset */
        !           191:        u_char *xloc;
        !           192:        u_char *yloc;
        !           193:        int cum=0;      /* cum == cumulative length */
        !           194: 
        !           195:        IFDEBUG(D_CHKSUM)
        !           196:                printf("enter gen csum m 0x%x n 0x%x l 0x%x\n",m, n-1 ,l );
        !           197:        ENDDEBUG
        !           198: 
        !           199:        while(i < l) {
        !           200:                len = MIN(m->m_len, CLBYTES);
        !           201:                /* RAH: don't cksum more than l bytes */
        !           202:                len = MIN(len, l - i);
        !           203: 
        !           204:                cum +=len;
        !           205:                p = mtod(m, u_char *);
        !           206: 
        !           207:                if(loc>=0) {
        !           208:                        if (loc < len) {
        !           209:                                xloc = loc + mtod(m, u_char *);
        !           210:                                IFDEBUG(D_CHKSUM)
        !           211:                                        printf("1: zeroing xloc 0x%x loc 0x%x\n",xloc, loc );
        !           212:                                ENDDEBUG
        !           213:                                *xloc = (u_char)0;
        !           214:                                if (loc+1 < len) {
        !           215:                                        /* both xloc and yloc are in same mbuf */
        !           216:                                        yloc = 1  + xloc;
        !           217:                                        IFDEBUG(D_CHKSUM)
        !           218:                                                printf("2: zeroing yloc 0x%x loc 0x%x\n",yloc, loc );
        !           219:                                        ENDDEBUG
        !           220:                                        *yloc = (u_char)0;
        !           221:                                } else {
        !           222:                                        /* crosses boundary of mbufs */
        !           223:                                        yloc = mtod(m->m_next, u_char *);
        !           224:                                        IFDEBUG(D_CHKSUM)
        !           225:                                                printf("3: zeroing yloc 0x%x \n",yloc );
        !           226:                                        ENDDEBUG
        !           227:                                        *yloc = (u_char)0;
        !           228:                                }
        !           229:                        }
        !           230:                        loc -= len;
        !           231:                }
        !           232: 
        !           233:                while(i < cum) {
        !           234:                        c0 = (c0 + *p);
        !           235:                        c1 += c0 ;
        !           236:                        i++; 
        !           237:                        p++;
        !           238:                }
        !           239:                m = m->m_next;
        !           240:        }
        !           241:        IFDEBUG(D_CHKSUM)
        !           242:                printf("gen csum final xloc 0x%x yloc 0x%x\n",xloc, yloc );
        !           243:        ENDDEBUG
        !           244: 
        !           245:        c1 = (((c0 * (l-n))-c1)%255) ;
        !           246:        *xloc = (u_char) ((c1 < 0)? c1+255 : c1);
        !           247: 
        !           248:        c1 = (-(int)(c1+c0))%255;
        !           249:        *yloc = (u_char) (c1 < 0? c1 + 255 : c1);
        !           250: 
        !           251:        IFDEBUG(D_CHKSUM)
        !           252:                printf("gen csum end \n");
        !           253:        ENDDEBUG
        !           254: }
        !           255: 
        !           256: struct mbuf  *
        !           257: m_append(head, m)
        !           258:        struct mbuf *head, *m;
        !           259: {
        !           260:        register struct mbuf *n;
        !           261: 
        !           262:        if (m == 0)
        !           263:                return head;
        !           264:        if (head == 0)
        !           265:                return m;
        !           266:        n = head;
        !           267:        while (n->m_next)
        !           268:                n = n->m_next;
        !           269:        n->m_next = m;
        !           270:        return head;
        !           271: }
        !           272: /*
        !           273:  * FUNCTION:   m_datalen
        !           274:  *
        !           275:  * PURPOSE:            returns length of the mbuf chain.
        !           276:  *                             used all over the iso code.
        !           277:  *
        !           278:  * RETURNS:            integer
        !           279:  *
        !           280:  * SIDE EFFECTS: none
        !           281:  *
        !           282:  * NOTES:              
        !           283:  */
        !           284: 
        !           285: int
        !           286: m_datalen (morig)
        !           287:        struct mbuf *morig;
        !           288: {      
        !           289:        int     s = splimp();
        !           290:        register struct mbuf *n=morig;
        !           291:        register int datalen = 0;
        !           292: 
        !           293:        if( morig == (struct mbuf *)0)
        !           294:                return 0;
        !           295:        for(;;) {
        !           296:                datalen += n->m_len;
        !           297:                if (n->m_next == (struct mbuf *)0 ) {
        !           298:                        break;
        !           299:                }
        !           300:                n = n->m_next;
        !           301:        }
        !           302:        splx(s);
        !           303:        return datalen;
        !           304: }
        !           305: 
        !           306: int
        !           307: m_compress(in, out)
        !           308:        register struct mbuf *in, **out;
        !           309: {
        !           310:        register        int datalen = 0;
        !           311:        int     s = splimp();
        !           312: 
        !           313:        if( in->m_next == MNULL ) {
        !           314:                *out = in;
        !           315:                IFDEBUG(D_REQUEST)
        !           316:                        printf("m_compress returning 0x%x: A\n", in->m_len);
        !           317:                ENDDEBUG
        !           318:                splx(s);
        !           319:                return in->m_len;
        !           320:        }
        !           321:        MGET((*out), M_DONTWAIT, MT_DATA);
        !           322:        if((*out) == MNULL) {
        !           323:                *out = in;
        !           324:                IFDEBUG(D_REQUEST)
        !           325:                        printf("m_compress returning -1: B\n");
        !           326:                ENDDEBUG
        !           327:                splx(s);
        !           328:                return -1; 
        !           329:        }
        !           330:        (*out)->m_len = 0;
        !           331:        (*out)->m_act = MNULL;
        !           332: 
        !           333:        while (in) {
        !           334:                IFDEBUG(D_REQUEST)
        !           335:                        printf("m_compress in 0x%x *out 0x%x\n", in, *out);
        !           336:                        printf("m_compress in: len 0x%x, off 0x%x\n", in->m_len, in->m_data);
        !           337:                        printf("m_compress *out: len 0x%x, off 0x%x\n", (*out)->m_len, 
        !           338:                                (*out)->m_data);
        !           339:                ENDDEBUG
        !           340:                if (in->m_flags & M_EXT) {
        !           341:                        ASSERT(in->m_len == 0);
        !           342:                }
        !           343:                if ( in->m_len == 0) {
        !           344:                        in = in->m_next;
        !           345:                        continue;
        !           346:                }
        !           347:                if (((*out)->m_flags & M_EXT) == 0) {
        !           348:                        int len;
        !           349: 
        !           350:                        len = M_TRAILINGSPACE(*out);
        !           351:                        len = MIN(len, in->m_len);
        !           352:                        datalen += len;
        !           353: 
        !           354:                        IFDEBUG(D_REQUEST)
        !           355:                                printf("m_compress copying len %d\n", len);
        !           356:                        ENDDEBUG
        !           357:                        bcopy(mtod(in, caddr_t), mtod((*out), caddr_t) + (*out)->m_len,
        !           358:                                                (unsigned)len);
        !           359: 
        !           360:                        (*out)->m_len += len;
        !           361:                        in->m_len -= len;
        !           362:                        continue;
        !           363:                } else {
        !           364:                        /* (*out) is full */
        !           365:                        if(( (*out)->m_next = m_get(M_DONTWAIT, MT_DATA) ) == MNULL) {
        !           366:                                m_freem(*out);
        !           367:                                *out = in;
        !           368:                                IFDEBUG(D_REQUEST)
        !           369:                                        printf("m_compress returning -1: B\n");
        !           370:                                ENDDEBUG
        !           371:                                splx(s);
        !           372:                                return -1;
        !           373:                        }
        !           374:                        (*out)->m_len = 0;
        !           375:                        (*out)->m_act = MNULL;
        !           376:                        *out = (*out)->m_next;
        !           377:                }
        !           378:        }
        !           379:        m_freem(in);
        !           380:        IFDEBUG(D_REQUEST)
        !           381:                printf("m_compress returning 0x%x: A\n", datalen);
        !           382:        ENDDEBUG
        !           383:        splx(s);
        !           384:        return datalen;
        !           385: }

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