1 /* $NetBSD: in6_cksum.c,v 1.28 2011/04/25 22:05:05 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 1.28 2011/04/25 22:05:05 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
in6_cksum(struct mbuf * m,u_int8_t nxt,uint32_t off,uint32_t len)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 (nxt == 0)
64 return cpu_in_cksum(m, len, off, 0);
65
66 if (__predict_false(off < sizeof(struct ip6_hdr)))
67 panic("in6_cksum: offset too short for IPv6 header");
68 if (__predict_false(m->m_len < sizeof(struct ip6_hdr)))
69 panic("in6_cksum: mbuf too short for IPv6 header");
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 }
125