in4_cksum.c

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    1 /*      $OpenBSD: in4_cksum.c,v 1.11 2022/02/01 15:30:10 miod Exp $     */
    2 /*      $KAME: in4_cksum.c,v 1.10 2001/11/30 10:06:15 itojun Exp $      */
    3 /*      $NetBSD: in_cksum.c,v 1.13 1996/10/13 02:03:03 christos Exp $   */
    4 
    5 /*
    6  * Copyright (C) 1999 WIDE Project.
    7  * All rights reserved.
    8  *
    9  * Redistribution and use in source and binary forms, with or without
   10  * modification, are permitted provided that the following conditions
   11  * are met:
   12  * 1. Redistributions of source code must retain the above copyright
   13  *    notice, this list of conditions and the following disclaimer.
   14  * 2. Redistributions in binary form must reproduce the above copyright
   15  *    notice, this list of conditions and the following disclaimer in the
   16  *    documentation and/or other materials provided with the distribution.
   17  * 3. Neither the name of the project 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 PROJECT 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 PROJECT 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 
   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/param.h>
   66 #include <sys/mbuf.h>
   67 #include <sys/systm.h>
   68 #include <sys/socket.h>
   69 #include <sys/socketvar.h>
   70 #include <netinet/in.h>
   71 #include <netinet/ip.h>
   72 #include <netinet/ip_var.h>
   73 
   74 /*
   75  * Checksum routine for Internet Protocol family headers (Portable Version).
   76  * This is only for IPv4 pseudo header checksum.
   77  * No need to clear non-pseudo-header fields in IPv4 header.
   78  * len is for actual payload size, and does not include IPv4 header and
   79  * skipped header chain (off + len should be equal to the whole packet).
   80  *
   81  * This routine is very heavily used in the network
   82  * code and should be modified for each CPU to be as fast as possible.
   83  */
   84 
   85 #define ADDCARRY(x)  (x > 65535 ? x -= 65535 : x)
   86 #define REDUCE {l_util.l = sum; sum = l_util.s[0] + l_util.s[1]; ADDCARRY(sum);}
   87 
   88 int
   89 in4_cksum(struct mbuf *m, u_int8_t nxt, int off, int len)
   90 {
   91         u_int16_t *w;
   92         int sum = 0;
   93         int mlen = 0;
   94         int byte_swapped = 0;
   95         union {
   96                 struct ipovly ipov;
   97                 u_int16_t w[10];
   98         } u;
   99         union {
  100                 u_int8_t  c[2];
  101                 u_int16_t s;
  102         } s_util;
  103         union {
  104                 u_int16_t s[2];
  105                 u_int32_t l;
  106         } l_util;
  107 
  108         if (nxt != 0) {
  109                 /* pseudo header */
  110                 if (off < sizeof(struct ipovly))
  111                         panic("in4_cksum: offset too short");
  112                 if (m->m_len < sizeof(struct ip))
  113                         panic("in4_cksum: bad mbuf chain");
  114                 u.ipov.ih_x1[8] = 0;
  115                 u.ipov.ih_pr = nxt;
  116                 u.ipov.ih_len = htons(len);
  117                 u.ipov.ih_src = mtod(m, struct ip *)->ip_src;
  118                 u.ipov.ih_dst = mtod(m, struct ip *)->ip_dst;
  119                 w = u.w;
  120                 /* assumes sizeof(ipov) == 20 and first 8 bytes are zeroes */
  121                 sum += w[4]; sum += w[5]; sum += w[6];
  122                 sum += w[7]; sum += w[8]; sum += w[9];
  123         }
  124 
  125         /* skip unnecessary part */
  126         while (m && off > 0) {
  127                 if (m->m_len > off)
  128                         break;
  129                 off -= m->m_len;
  130                 m = m->m_next;
  131         }
  132 
  133         for (;m && len; m = m->m_next) {
  134                 if (m->m_len == 0)
  135                         continue;
  136                 w = (u_int16_t *)(mtod(m, caddr_t) + off);
  137                 if (mlen == -1) {
  138                         /*
  139                          * The first byte of this mbuf is the continuation
  140                          * of a word spanning between this mbuf and the
  141                          * last mbuf.
  142                          *
  143                          * s_util.c[0] is already saved when scanning previous
  144                          * mbuf.
  145                          */
  146                         s_util.c[1] = *(u_int8_t *)w;
  147                         sum += s_util.s;
  148                         w = (u_int16_t *)((u_int8_t *)w + 1);
  149                         mlen = m->m_len - off - 1;
  150                         len--;
  151                 } else
  152                         mlen = m->m_len - off;
  153                 off = 0;
  154                 if (len < mlen)
  155                         mlen = len;
  156                 len -= mlen;
  157                 /*
  158                  * Force to even boundary.
  159                  */
  160                 if ((1 & (long) w) && (mlen > 0)) {
  161                         REDUCE;
  162                         sum <<= 8;
  163                         s_util.c[0] = *(u_int8_t *)w;
  164                         w = (u_int16_t *)((int8_t *)w + 1);
  165                         mlen--;
  166                         byte_swapped = 1;
  167                 }
  168                 /*
  169                  * Unroll the loop to make overhead from
  170                  * branches &c small.
  171                  */
  172                 while ((mlen -= 32) >= 0) {
  173                         sum += w[0]; sum += w[1]; sum += w[2]; sum += w[3];
  174                         sum += w[4]; sum += w[5]; sum += w[6]; sum += w[7];
  175                         sum += w[8]; sum += w[9]; sum += w[10]; sum += w[11];
  176                         sum += w[12]; sum += w[13]; sum += w[14]; sum += w[15];
  177                         w += 16;
  178                 }
  179                 mlen += 32;
  180                 while ((mlen -= 8) >= 0) {
  181                         sum += w[0]; sum += w[1]; sum += w[2]; sum += w[3];
  182                         w += 4;
  183                 }
  184                 mlen += 8;
  185                 if (mlen == 0 && byte_swapped == 0)
  186                         continue;
  187                 REDUCE;
  188                 while ((mlen -= 2) >= 0) {
  189                         sum += *w++;
  190                 }
  191                 if (byte_swapped) {
  192                         REDUCE;
  193                         sum <<= 8;
  194                         byte_swapped = 0;
  195                         if (mlen == -1) {
  196                                 s_util.c[1] = *(u_int8_t *)w;
  197                                 sum += s_util.s;
  198                                 mlen = 0;
  199                         } else
  200                                 mlen = -1;
  201                 } else if (mlen == -1)
  202                         s_util.c[0] = *(u_int8_t *)w;
  203         }
  204         if (len)
  205                 printf("cksum4: out of data\n");
  206         if (mlen == -1) {
  207                 /* The last mbuf has odd # of bytes. Follow the
  208                    standard (the odd byte may be shifted left by 8 bits
  209                    or not as determined by endian-ness of the machine) */
  210                 s_util.c[1] = 0;
  211                 sum += s_util.s;
  212         }
  213         REDUCE;
  214         return (~sum & 0xffff);
  215 }

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FreeBSD/Linux Kernel Cross Reference sys/netinet/in4_cksum.c

FreeBSD/Linux Kernel Cross Reference
sys/netinet/in4_cksum.c