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/netinet6/in6_cksum.c

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    1 /*      $NetBSD: in6_cksum.c,v 1.27 2008/03/10 22:34:40 yamt Exp $      */
    2 
    3 /*-
    4  * Copyright (c) 2008 Joerg Sonnenberger <joerg@NetBSD.org>.
    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  *
   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
   15  *    the documentation and/or other materials provided with the
   16  *    distribution.
   17  *
   18  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
   19  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
   20  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
   21  * FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE
   22  * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
   23  * INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING,
   24  * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
   25  * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
   26  * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
   27  * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
   28  * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   29  * SUCH DAMAGE.
   30  */
   31 
   32 #include <sys/cdefs.h>
   33 __KERNEL_RCSID(0, "$NetBSD: in6_cksum.c,v 1.27 2008/03/10 22:34:40 yamt Exp $");
   34 
   35 #include <sys/param.h>
   36 #include <sys/mbuf.h>
   37 #include <netinet/in.h>
   38 #include <netinet/ip6.h>
   39 
   40 /*
   41  * Checksum of the IPv6 pseudo header.
   42  *
   43  * off is supposed to be the skipped IPv6 header, len is the payload size.
   44  */
   45 
   46 int
   47 in6_cksum(struct mbuf *m, u_int8_t nxt, uint32_t off, uint32_t len)
   48 {
   49         union {
   50                 uint16_t words[16];
   51                 struct {
   52                         struct in6_addr ip6_src;
   53                         struct in6_addr ip6_dst;
   54                 } addrs;
   55         } u;
   56         const struct in6_addr *in6_src;
   57         const struct in6_addr *in6_dst;
   58         const struct ip6_hdr *ip6;
   59         uint32_t sum;
   60         const uint16_t *w;
   61         const char *cp;
   62 
   63         if (__predict_false(off < sizeof(struct ip6_hdr)))
   64                 panic("in6_cksum: offset too short for IPv6 header");
   65         if (__predict_false(m->m_len < sizeof(struct ip6_hdr)))
   66                 panic("in6_cksum: mbuf too short for IPv6 header");
   67 
   68         if (nxt == 0)
   69                 return cpu_in_cksum(m, len, off, 0);
   70 
   71         /*
   72          * Compute the equivalent of:
   73          * struct ip6_hdr_pseudo ip6;
   74          *
   75          * bzero(sizeof(*ip6));
   76          * ip6.ip6ph_nxt = nxt;
   77          * ip6.ip6ph_len = htonl(len);
   78          * ipv6.ip6ph_src = mtod(m, struct ip6_hdr *)->ip6_src;
   79          * in6_clearscope(&ip6->ip6ph_src);
   80          * ipv6.ip6ph_dst = mtod(m, struct ip6_hdr *)->ip6_dst;
   81          * in6_clearscope(&ip6->ip6ph_dst);
   82          * sum = one_add(&ip6);
   83          */
   84 
   85 #if BYTE_ORDER == LITTLE_ENDIAN
   86         sum = ((len & 0xffff) + ((len >> 16) & 0xffff) + nxt) << 8;
   87 #else
   88         sum = (len & 0xffff) + ((len >> 16) & 0xffff) + nxt;
   89 #endif
   90         cp = mtod(m, const char *);
   91         w = (const uint16_t *)(cp + offsetof(struct ip6_hdr, ip6_src));
   92         ip6 = (const void *)cp;
   93         if (__predict_true((uintptr_t)w % 2 == 0)) {
   94                 in6_src = &ip6->ip6_src;
   95                 in6_dst = &ip6->ip6_dst;
   96         } else {
   97                 memcpy(&u, &ip6->ip6_src, 32);
   98                 w = u.words;
   99                 in6_src = &u.addrs.ip6_src;
  100                 in6_dst = &u.addrs.ip6_dst;
  101         }
  102 
  103         sum += w[0];
  104         if (!IN6_IS_SCOPE_EMBEDDABLE(in6_src))
  105                 sum += w[1];
  106         sum += w[2];
  107         sum += w[3];
  108         sum += w[4];
  109         sum += w[5];
  110         sum += w[6];
  111         sum += w[7];
  112         w += 8;
  113         sum += w[0];
  114         if (!IN6_IS_SCOPE_EMBEDDABLE(in6_dst))
  115                 sum += w[1];
  116         sum += w[2];
  117         sum += w[3];
  118         sum += w[4];
  119         sum += w[5];
  120         sum += w[6];
  121         sum += w[7];
  122 
  123         return cpu_in_cksum(m, len, off, sum);
  124 }

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