sys/netinet6/in6_cksum.c

   1 /*      $NetBSD: in6_cksum.c,v 1.26 2008/03/10 22:29:13 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 1.26 2008/03/10 22:29:13 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 }