The Design and Implementation of the FreeBSD Operating System, Second Edition
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FreeBSD/Linux Kernel Cross Reference
sys/netinet6/in6_cksum.c

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    1 /*-
    2  * SPDX-License-Identifier: BSD-3-Clause
    3  *
    4  * Copyright (C) 1995, 1996, 1997, and 1998 WIDE Project.
    5  * All rights reserved.
    6  *
    7  * Redistribution and use in source and binary forms, with or without
    8  * modification, are permitted provided that the following conditions
    9  * are met:
   10  * 1. Redistributions of source code must retain the above copyright
   11  *    notice, this list of conditions and the following disclaimer.
   12  * 2. Redistributions in binary form must reproduce the above copyright
   13  *    notice, this list of conditions and the following disclaimer in the
   14  *    documentation and/or other materials provided with the distribution.
   15  * 3. Neither the name of the project nor the names of its contributors
   16  *    may be used to endorse or promote products derived from this software
   17  *    without specific prior written permission.
   18  *
   19  * THIS SOFTWARE IS PROVIDED BY THE PROJECT AND CONTRIBUTORS ``AS IS'' AND
   20  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   21  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   22  * ARE DISCLAIMED.  IN NO EVENT SHALL THE PROJECT OR CONTRIBUTORS BE LIABLE
   23  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   24  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   25  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   26  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   27  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   28  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   29  * SUCH DAMAGE.
   30  *
   31  *      $KAME: in6_cksum.c,v 1.10 2000/12/03 00:53:59 itojun Exp $
   32  */
   33 
   34 /*-
   35  * Copyright (c) 1988, 1992, 1993
   36  *      The Regents of the University of California.  All rights reserved.
   37  *
   38  * Redistribution and use in source and binary forms, with or without
   39  * modification, are permitted provided that the following conditions
   40  * are met:
   41  * 1. Redistributions of source code must retain the above copyright
   42  *    notice, this list of conditions and the following disclaimer.
   43  * 2. Redistributions in binary form must reproduce the above copyright
   44  *    notice, this list of conditions and the following disclaimer in the
   45  *    documentation and/or other materials provided with the distribution.
   46  * 3. Neither the name of the University nor the names of its contributors
   47  *    may be used to endorse or promote products derived from this software
   48  *    without specific prior written permission.
   49  *
   50  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
   51  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   52  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   53  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
   54  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   55  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   56  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   57  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   58  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   59  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   60  * SUCH DAMAGE.
   61  *
   62  *      @(#)in_cksum.c  8.1 (Berkeley) 6/10/93
   63  */
   64 
   65 #include <sys/cdefs.h>
   66 __FBSDID("$FreeBSD$");
   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 #include <netinet6/scope6_var.h>
   74 
   75 /*
   76  * Checksum routine for Internet Protocol family headers (Portable Version).
   77  *
   78  * This routine is very heavily used in the network
   79  * code and should be modified for each CPU to be as fast as possible.
   80  */
   81 
   82 #define ADDCARRY(x)  (x > 65535 ? x -= 65535 : x)
   83 #define REDUCE {l_util.l = sum; sum = l_util.s[0] + l_util.s[1]; (void)ADDCARRY(sum);}
   84 
   85 static int
   86 _in6_cksum_pseudo(struct ip6_hdr *ip6, uint32_t len, uint8_t nxt, uint16_t csum)
   87 {
   88         int sum;
   89         uint16_t scope, *w;
   90         union {
   91                 u_int16_t phs[4];
   92                 struct {
   93                         u_int32_t       ph_len;
   94                         u_int8_t        ph_zero[3];
   95                         u_int8_t        ph_nxt;
   96                 } __packed ph;
   97         } uph;
   98 
   99         sum = csum;
  100 
  101         /*
  102          * First create IP6 pseudo header and calculate a summary.
  103          */
  104         uph.ph.ph_len = htonl(len);
  105         uph.ph.ph_zero[0] = uph.ph.ph_zero[1] = uph.ph.ph_zero[2] = 0;
  106         uph.ph.ph_nxt = nxt;
  107 
  108         /* Payload length and upper layer identifier. */
  109         sum += uph.phs[0];  sum += uph.phs[1];
  110         sum += uph.phs[2];  sum += uph.phs[3];
  111 
  112         /* IPv6 source address. */
  113         scope = in6_getscope(&ip6->ip6_src);
  114         w = (u_int16_t *)&ip6->ip6_src;
  115         sum += w[0]; sum += w[1]; sum += w[2]; sum += w[3];
  116         sum += w[4]; sum += w[5]; sum += w[6]; sum += w[7];
  117         if (scope != 0)
  118                 sum -= scope;
  119 
  120         /* IPv6 destination address. */
  121         scope = in6_getscope(&ip6->ip6_dst);
  122         w = (u_int16_t *)&ip6->ip6_dst;
  123         sum += w[0]; sum += w[1]; sum += w[2]; sum += w[3];
  124         sum += w[4]; sum += w[5]; sum += w[6]; sum += w[7];
  125         if (scope != 0)
  126                 sum -= scope;
  127 
  128         return (sum);
  129 }
  130 
  131 int
  132 in6_cksum_pseudo(struct ip6_hdr *ip6, uint32_t len, uint8_t nxt, uint16_t csum)
  133 {
  134         int sum;
  135         union {
  136                 u_int16_t s[2];
  137                 u_int32_t l;
  138         } l_util;
  139 
  140         sum = _in6_cksum_pseudo(ip6, len, nxt, csum);
  141         REDUCE;
  142         return (sum);
  143 }
  144 
  145 /*
  146  * m MUST contain a contiguous IP6 header.
  147  * off is an offset where TCP/UDP/ICMP6 header starts.
  148  * len is a total length of a transport segment.
  149  * (e.g. TCP header + TCP payload)
  150  * cov is the number of bytes to be taken into account for the checksum
  151  */
  152 int
  153 in6_cksum_partial(struct mbuf *m, u_int8_t nxt, u_int32_t off,
  154     u_int32_t len, u_int32_t cov)
  155 {
  156         struct ip6_hdr *ip6;
  157         u_int16_t *w, scope;
  158         int byte_swapped, mlen;
  159         int sum;
  160         union {
  161                 u_int16_t phs[4];
  162                 struct {
  163                         u_int32_t       ph_len;
  164                         u_int8_t        ph_zero[3];
  165                         u_int8_t        ph_nxt;
  166                 } __packed ph;
  167         } uph;
  168         union {
  169                 u_int8_t        c[2];
  170                 u_int16_t       s;
  171         } s_util;
  172         union {
  173                 u_int16_t s[2];
  174                 u_int32_t l;
  175         } l_util;
  176 
  177         /* Sanity check. */
  178         KASSERT(m->m_pkthdr.len >= off + len, ("%s: mbuf len (%d) < off(%d)+"
  179             "len(%d)", __func__, m->m_pkthdr.len, off, len));
  180 
  181         /*
  182          * First create IP6 pseudo header and calculate a summary.
  183          */
  184         uph.ph.ph_len = htonl(len);
  185         uph.ph.ph_zero[0] = uph.ph.ph_zero[1] = uph.ph.ph_zero[2] = 0;
  186         uph.ph.ph_nxt = nxt;
  187 
  188         /* Payload length and upper layer identifier. */
  189         sum = uph.phs[0];  sum += uph.phs[1];
  190         sum += uph.phs[2];  sum += uph.phs[3];
  191 
  192         ip6 = mtod(m, struct ip6_hdr *);
  193 
  194         /* IPv6 source address. */
  195         scope = in6_getscope(&ip6->ip6_src);
  196         w = (u_int16_t *)&ip6->ip6_src;
  197         sum += w[0]; sum += w[1]; sum += w[2]; sum += w[3];
  198         sum += w[4]; sum += w[5]; sum += w[6]; sum += w[7];
  199         if (scope != 0)
  200                 sum -= scope;
  201 
  202         /* IPv6 destination address. */
  203         scope = in6_getscope(&ip6->ip6_dst);
  204         w = (u_int16_t *)&ip6->ip6_dst;
  205         sum += w[0]; sum += w[1]; sum += w[2]; sum += w[3];
  206         sum += w[4]; sum += w[5]; sum += w[6]; sum += w[7];
  207         if (scope != 0)
  208                 sum -= scope;
  209 
  210         /*
  211          * Secondly calculate a summary of the first mbuf excluding offset.
  212          */
  213         while (off > 0) {
  214                 if (m->m_len <= off)
  215                         off -= m->m_len;
  216                 else
  217                         break;
  218                 m = m->m_next;
  219         }
  220         w = (u_int16_t *)(mtod(m, u_char *) + off);
  221         mlen = m->m_len - off;
  222         if (cov < mlen)
  223                 mlen = cov;
  224         cov -= mlen;
  225         /*
  226          * Force to even boundary.
  227          */
  228         if ((1 & (long)w) && (mlen > 0)) {
  229                 REDUCE;
  230                 sum <<= 8;
  231                 s_util.c[0] = *(u_char *)w;
  232                 w = (u_int16_t *)((char *)w + 1);
  233                 mlen--;
  234                 byte_swapped = 1;
  235         } else
  236                 byte_swapped = 0;
  237 
  238         /*
  239          * Unroll the loop to make overhead from
  240          * branches &c small.
  241          */
  242         while ((mlen -= 32) >= 0) {
  243                 sum += w[0]; sum += w[1]; sum += w[2]; sum += w[3];
  244                 sum += w[4]; sum += w[5]; sum += w[6]; sum += w[7];
  245                 sum += w[8]; sum += w[9]; sum += w[10]; sum += w[11];
  246                 sum += w[12]; sum += w[13]; sum += w[14]; sum += w[15];
  247                 w += 16;
  248         }
  249         mlen += 32;
  250         while ((mlen -= 8) >= 0) {
  251                 sum += w[0]; sum += w[1]; sum += w[2]; sum += w[3];
  252                 w += 4;
  253         }
  254         mlen += 8;
  255         if (mlen == 0 && byte_swapped == 0)
  256                 goto next;
  257         REDUCE;
  258         while ((mlen -= 2) >= 0) {
  259                 sum += *w++;
  260         }
  261         if (byte_swapped) {
  262                 REDUCE;
  263                 sum <<= 8;
  264                 byte_swapped = 0;
  265                 if (mlen == -1) {
  266                         s_util.c[1] = *(char *)w;
  267                         sum += s_util.s;
  268                         mlen = 0;
  269                 } else
  270                         mlen = -1;
  271         } else if (mlen == -1)
  272                 s_util.c[0] = *(char *)w;
  273  next:
  274         m = m->m_next;
  275 
  276         /*
  277          * Lastly calculate a summary of the rest of mbufs.
  278          */
  279 
  280         for (;m && cov; m = m->m_next) {
  281                 if (m->m_len == 0)
  282                         continue;
  283                 w = mtod(m, u_int16_t *);
  284                 if (mlen == -1) {
  285                         /*
  286                          * The first byte of this mbuf is the continuation
  287                          * of a word spanning between this mbuf and the
  288                          * last mbuf.
  289                          *
  290                          * s_util.c[0] is already saved when scanning previous
  291                          * mbuf.
  292                          */
  293                         s_util.c[1] = *(char *)w;
  294                         sum += s_util.s;
  295                         w = (u_int16_t *)((char *)w + 1);
  296                         mlen = m->m_len - 1;
  297                         cov--;
  298                 } else
  299                         mlen = m->m_len;
  300                 if (cov < mlen)
  301                         mlen = cov;
  302                 cov -= mlen;
  303                 /*
  304                  * Force to even boundary.
  305                  */
  306                 if ((1 & (long) w) && (mlen > 0)) {
  307                         REDUCE;
  308                         sum <<= 8;
  309                         s_util.c[0] = *(u_char *)w;
  310                         w = (u_int16_t *)((char *)w + 1);
  311                         mlen--;
  312                         byte_swapped = 1;
  313                 }
  314                 /*
  315                  * Unroll the loop to make overhead from
  316                  * branches &c small.
  317                  */
  318                 while ((mlen -= 32) >= 0) {
  319                         sum += w[0]; sum += w[1]; sum += w[2]; sum += w[3];
  320                         sum += w[4]; sum += w[5]; sum += w[6]; sum += w[7];
  321                         sum += w[8]; sum += w[9]; sum += w[10]; sum += w[11];
  322                         sum += w[12]; sum += w[13]; sum += w[14]; sum += w[15];
  323                         w += 16;
  324                 }
  325                 mlen += 32;
  326                 while ((mlen -= 8) >= 0) {
  327                         sum += w[0]; sum += w[1]; sum += w[2]; sum += w[3];
  328                         w += 4;
  329                 }
  330                 mlen += 8;
  331                 if (mlen == 0 && byte_swapped == 0)
  332                         continue;
  333                 REDUCE;
  334                 while ((mlen -= 2) >= 0) {
  335                         sum += *w++;
  336                 }
  337                 if (byte_swapped) {
  338                         REDUCE;
  339                         sum <<= 8;
  340                         byte_swapped = 0;
  341                         if (mlen == -1) {
  342                                 s_util.c[1] = *(char *)w;
  343                                 sum += s_util.s;
  344                                 mlen = 0;
  345                         } else
  346                                 mlen = -1;
  347                 } else if (mlen == -1)
  348                         s_util.c[0] = *(char *)w;
  349         }
  350         if (cov)
  351                 panic("in6_cksum: out of data");
  352         if (mlen == -1) {
  353                 /* The last mbuf has odd # of bytes. Follow the
  354                    standard (the odd byte may be shifted left by 8 bits
  355                    or not as determined by endian-ness of the machine) */
  356                 s_util.c[1] = 0;
  357                 sum += s_util.s;
  358         }
  359         REDUCE;
  360         return (~sum & 0xffff);
  361 }
  362 
  363 int
  364 in6_cksum(struct mbuf *m, u_int8_t nxt, u_int32_t off, u_int32_t len)
  365 {
  366         return (in6_cksum_partial(m, nxt, off, len, len));
  367 }

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