The Design and Implementation of the FreeBSD Operating System, Second Edition
Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)


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FreeBSD/Linux Kernel Cross Reference
sys/bsd/netinet6/in6_cksum.c

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    1 /*      $FreeBSD: src/sys/netinet6/in6_cksum.c,v 1.1.2.3 2001/07/03 11:01:52 ume Exp $  */
    2 /*      $KAME: in6_cksum.c,v 1.10 2000/12/03 00:53:59 itojun Exp $      */
    3 
    4 /*
    5  * Copyright (C) 1995, 1996, 1997, and 1998 WIDE Project.
    6  * All rights reserved.
    7  *
    8  * Redistribution and use in source and binary forms, with or without
    9  * modification, are permitted provided that the following conditions
   10  * are met:
   11  * 1. Redistributions of source code must retain the above copyright
   12  *    notice, this list of conditions and the following disclaimer.
   13  * 2. Redistributions in binary form must reproduce the above copyright
   14  *    notice, this list of conditions and the following disclaimer in the
   15  *    documentation and/or other materials provided with the distribution.
   16  * 3. Neither the name of the project nor the names of its contributors
   17  *    may be used to endorse or promote products derived from this software
   18  *    without specific prior written permission.
   19  *
   20  * THIS SOFTWARE IS PROVIDED BY THE PROJECT AND CONTRIBUTORS ``AS IS'' AND
   21  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   22  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   23  * ARE DISCLAIMED.  IN NO EVENT SHALL THE PROJECT OR CONTRIBUTORS BE LIABLE
   24  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   25  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   26  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   27  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   28  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   29  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   30  * SUCH DAMAGE.
   31  */
   32 
   33 /*
   34  * Copyright (c) 1988, 1992, 1993
   35  *      The Regents of the University of California.  All rights reserved.
   36  *
   37  * Redistribution and use in source and binary forms, with or without
   38  * modification, are permitted provided that the following conditions
   39  * are met:
   40  * 1. Redistributions of source code must retain the above copyright
   41  *    notice, this list of conditions and the following disclaimer.
   42  * 2. Redistributions in binary form must reproduce the above copyright
   43  *    notice, this list of conditions and the following disclaimer in the
   44  *    documentation and/or other materials provided with the distribution.
   45  * 3. All advertising materials mentioning features or use of this software
   46  *    must display the following acknowledgement:
   47  *      This product includes software developed by the University of
   48  *      California, Berkeley and its contributors.
   49  * 4. Neither the name of the University nor the names of its contributors
   50  *    may be used to endorse or promote products derived from this software
   51  *    without specific prior written permission.
   52  *
   53  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
   54  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   55  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   56  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
   57  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   58  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   59  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   60  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   61  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   62  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   63  * SUCH DAMAGE.
   64  *
   65  *      @(#)in_cksum.c  8.1 (Berkeley) 6/10/93
   66  */
   67 
   68 #include <sys/param.h>
   69 #include <sys/mbuf.h>
   70 #include <sys/systm.h>
   71 #include <netinet/in.h>
   72 #include <netinet/ip6.h>
   73 
   74 #include <net/net_osdep.h>
   75 
   76 /*
   77  * Checksum routine for Internet Protocol family headers (Portable Version).
   78  *
   79  * This routine is very heavily used in the network
   80  * code and should be modified for each CPU to be as fast as possible.
   81  */
   82 
   83 #define ADDCARRY(x)  (x > 65535 ? x -= 65535 : x)
   84 #define REDUCE {l_util.l = sum; sum = l_util.s[0] + l_util.s[1]; ADDCARRY(sum);}
   85 
   86 /*
   87  * m MUST contain a continuous IP6 header.
   88  * off is a offset where TCP/UDP/ICMP6 header starts.
   89  * len is a total length of a transport segment.
   90  * (e.g. TCP header + TCP payload)
   91  */
   92 
   93 int
   94 in6_cksum(m, nxt, off, len)
   95         struct mbuf *m;
   96         u_int8_t nxt;
   97         u_int32_t off, len;
   98 {
   99         u_int16_t *w;
  100         int sum = 0;
  101         int mlen = 0;
  102         int byte_swapped = 0;
  103 #if 0
  104         int srcifid = 0, dstifid = 0;
  105 #endif
  106         struct ip6_hdr *ip6;    
  107         union {
  108                 u_int16_t phs[4];
  109                 struct {
  110                         u_int32_t       ph_len;
  111                         u_int8_t        ph_zero[3];
  112                         u_int8_t        ph_nxt;
  113                 } ph __attribute__((__packed__));
  114         } uph;
  115         union {
  116                 u_int8_t        c[2];
  117                 u_int16_t       s;
  118         } s_util;
  119         union {
  120                 u_int16_t s[2];
  121                 u_int32_t l;
  122         } l_util;
  123 
  124         /* sanity check */
  125         if (m->m_pkthdr.len < off + len) {
  126                 panic("in6_cksum: mbuf len (%d) < off+len (%d+%d)\n",
  127                         m->m_pkthdr.len, off, len);
  128         }
  129 
  130         bzero(&uph, sizeof(uph));
  131 
  132         /*
  133          * First create IP6 pseudo header and calculate a summary.
  134          */
  135         ip6 = mtod(m, struct ip6_hdr *);
  136 #if 0
  137         if (IN6_IS_SCOPE_LINKLOCAL(&ip6->ip6_src)) {
  138                 srcifid = ip6->ip6_src.s6_addr16[1];
  139                 ip6->ip6_src.s6_addr16[1] = 0;
  140         }
  141         if (IN6_IS_SCOPE_LINKLOCAL(&ip6->ip6_dst)) {
  142                 dstifid = ip6->ip6_dst.s6_addr16[1];
  143                 ip6->ip6_dst.s6_addr16[1] = 0;
  144         }
  145 #endif
  146         w = (u_int16_t *)&ip6->ip6_src;
  147         uph.ph.ph_len = htonl(len);
  148         uph.ph.ph_nxt = nxt;
  149 
  150         /* IPv6 source address */
  151         sum += w[0];
  152         if (!IN6_IS_SCOPE_LINKLOCAL(&ip6->ip6_src))
  153                 sum += w[1];
  154         sum += w[2]; sum += w[3]; sum += w[4]; sum += w[5];
  155         sum += w[6]; sum += w[7];
  156         /* IPv6 destination address */
  157         sum += w[8];
  158         if (!IN6_IS_SCOPE_LINKLOCAL(&ip6->ip6_dst))
  159                 sum += w[9];
  160         sum += w[10]; sum += w[11]; sum += w[12]; sum += w[13];
  161         sum += w[14]; sum += w[15];
  162         /* Payload length and upper layer identifier */
  163         sum += uph.phs[0];  sum += uph.phs[1];
  164         sum += uph.phs[2];  sum += uph.phs[3];
  165 
  166 #if 0
  167         if (srcifid)
  168                 ip6->ip6_src.s6_addr16[1] = srcifid;
  169         if (dstifid)
  170                 ip6->ip6_dst.s6_addr16[1] = dstifid;
  171 #endif
  172         /*
  173          * Secondly calculate a summary of the first mbuf excluding offset.
  174          */
  175         while (m != NULL && off > 0) {
  176                 if (m->m_len <= off)
  177                         off -= m->m_len;
  178                 else
  179                         break;
  180                 m = m->m_next;
  181         }
  182         w = (u_int16_t *)(mtod(m, u_char *) + off);
  183         mlen = m->m_len - off;
  184         if (len < mlen)
  185                 mlen = len;
  186         len -= mlen;
  187         /*
  188          * Force to even boundary.
  189          */
  190         if ((1 & (long) w) && (mlen > 0)) {
  191                 REDUCE;
  192                 sum <<= 8;
  193                 s_util.c[0] = *(u_char *)w;
  194                 w = (u_int16_t *)((char *)w + 1);
  195                 mlen--;
  196                 byte_swapped = 1;
  197         }
  198         /*
  199          * Unroll the loop to make overhead from
  200          * branches &c small.
  201          */
  202         while ((mlen -= 32) >= 0) {
  203                 sum += w[0]; sum += w[1]; sum += w[2]; sum += w[3];
  204                 sum += w[4]; sum += w[5]; sum += w[6]; sum += w[7];
  205                 sum += w[8]; sum += w[9]; sum += w[10]; sum += w[11];
  206                 sum += w[12]; sum += w[13]; sum += w[14]; sum += w[15];
  207                 w += 16;
  208         }
  209         mlen += 32;
  210         while ((mlen -= 8) >= 0) {
  211                 sum += w[0]; sum += w[1]; sum += w[2]; sum += w[3];
  212                 w += 4;
  213         }
  214         mlen += 8;
  215         if (mlen == 0 && byte_swapped == 0)
  216                 goto next;
  217         REDUCE;
  218         while ((mlen -= 2) >= 0) {
  219                 sum += *w++;
  220         }
  221         if (byte_swapped) {
  222                 REDUCE;
  223                 sum <<= 8;
  224                 byte_swapped = 0;
  225                 if (mlen == -1) {
  226                         s_util.c[1] = *(char *)w;
  227                         sum += s_util.s;
  228                         mlen = 0;
  229                 } else
  230                         mlen = -1;
  231         } else if (mlen == -1)
  232                 s_util.c[0] = *(char *)w;
  233  next:
  234         m = m->m_next;
  235 
  236         /*
  237          * Lastly calculate a summary of the rest of mbufs.
  238          */
  239         
  240         for (;m && len; m = m->m_next) {
  241                 if (m->m_len == 0)
  242                         continue;
  243                 w = mtod(m, u_int16_t *);
  244                 if (mlen == -1) {
  245                         /*
  246                          * The first byte of this mbuf is the continuation
  247                          * of a word spanning between this mbuf and the
  248                          * last mbuf.
  249                          *
  250                          * s_util.c[0] is already saved when scanning previous
  251                          * mbuf.
  252                          */
  253                         s_util.c[1] = *(char *)w;
  254                         sum += s_util.s;
  255                         w = (u_int16_t *)((char *)w + 1);
  256                         mlen = m->m_len - 1;
  257                         len--;
  258                 } else
  259                         mlen = m->m_len;
  260                 if (len < mlen)
  261                         mlen = len;
  262                 len -= mlen;
  263                 /*
  264                  * Force to even boundary.
  265                  */
  266                 if ((1 & (long) w) && (mlen > 0)) {
  267                         REDUCE;
  268                         sum <<= 8;
  269                         s_util.c[0] = *(u_char *)w;
  270                         w = (u_int16_t *)((char *)w + 1);
  271                         mlen--;
  272                         byte_swapped = 1;
  273                 }
  274                 /*
  275                  * Unroll the loop to make overhead from
  276                  * branches &c small.
  277                  */
  278                 while ((mlen -= 32) >= 0) {
  279                         sum += w[0]; sum += w[1]; sum += w[2]; sum += w[3];
  280                         sum += w[4]; sum += w[5]; sum += w[6]; sum += w[7];
  281                         sum += w[8]; sum += w[9]; sum += w[10]; sum += w[11];
  282                         sum += w[12]; sum += w[13]; sum += w[14]; sum += w[15];
  283                         w += 16;
  284                 }
  285                 mlen += 32;
  286                 while ((mlen -= 8) >= 0) {
  287                         sum += w[0]; sum += w[1]; sum += w[2]; sum += w[3];
  288                         w += 4;
  289                 }
  290                 mlen += 8;
  291                 if (mlen == 0 && byte_swapped == 0)
  292                         continue;
  293                 REDUCE;
  294                 while ((mlen -= 2) >= 0) {
  295                         sum += *w++;
  296                 }
  297                 if (byte_swapped) {
  298                         REDUCE;
  299                         sum <<= 8;
  300                         byte_swapped = 0;
  301                         if (mlen == -1) {
  302                                 s_util.c[1] = *(char *)w;
  303                                 sum += s_util.s;
  304                                 mlen = 0;
  305                         } else
  306                                 mlen = -1;
  307                 } else if (mlen == -1)
  308                         s_util.c[0] = *(char *)w;
  309         }
  310         if (len)
  311                 panic("in6_cksum: out of data\n");
  312         if (mlen == -1) {
  313                 /* The last mbuf has odd # of bytes. Follow the
  314                    standard (the odd byte may be shifted left by 8 bits
  315                    or not as determined by endian-ness of the machine) */
  316                 s_util.c[1] = 0;
  317                 sum += s_util.s;
  318         }
  319         REDUCE;
  320         return (~sum & 0xffff);
  321 }

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