1 /*-
2 * Copyright (c) 1988, 1992, 1993
3 * The Regents of the University of California. All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 * notice, this list of conditions and the following disclaimer in the
12 * documentation and/or other materials provided with the distribution.
13 * 4. Neither the name of the University nor the names of its contributors
14 * may be used to endorse or promote products derived from this software
15 * without specific prior written permission.
16 *
17 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
18 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
19 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
20 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
21 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
22 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
23 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
24 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
25 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
26 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
27 * SUCH DAMAGE.
28 *
29 * @(#)in_cksum.c 8.1 (Berkeley) 6/10/93
30 */
31
32 #include <sys/cdefs.h>
33 __FBSDID("$FreeBSD: src/sys/netinet/in_cksum.c,v 1.10 2007/10/07 20:44:22 silby Exp $");
34
35 #include <sys/param.h>
36 #include <sys/mbuf.h>
37
38 /*
39 * Checksum routine for Internet Protocol family headers (Portable Version).
40 *
41 * This routine is very heavily used in the network
42 * code and should be modified for each CPU to be as fast as possible.
43 */
44
45 #define ADDCARRY(x) (x > 65535 ? x -= 65535 : x)
46 #define REDUCE {l_util.l = sum; sum = l_util.s[0] + l_util.s[1]; ADDCARRY(sum);}
47
48 int
49 in_cksum(struct mbuf *m, int len)
50 {
51 register u_short *w;
52 register int sum = 0;
53 register int mlen = 0;
54 int byte_swapped = 0;
55
56 union {
57 char c[2];
58 u_short s;
59 } s_util;
60 union {
61 u_short s[2];
62 long l;
63 } l_util;
64
65 for (;m && len; m = m->m_next) {
66 if (m->m_len == 0)
67 continue;
68 w = mtod(m, u_short *);
69 if (mlen == -1) {
70 /*
71 * The first byte of this mbuf is the continuation
72 * of a word spanning between this mbuf and the
73 * last mbuf.
74 *
75 * s_util.c[0] is already saved when scanning previous
76 * mbuf.
77 */
78 s_util.c[1] = *(char *)w;
79 sum += s_util.s;
80 w = (u_short *)((char *)w + 1);
81 mlen = m->m_len - 1;
82 len--;
83 } else
84 mlen = m->m_len;
85 if (len < mlen)
86 mlen = len;
87 len -= mlen;
88 /*
89 * Force to even boundary.
90 */
91 if ((1 & (int) w) && (mlen > 0)) {
92 REDUCE;
93 sum <<= 8;
94 s_util.c[0] = *(u_char *)w;
95 w = (u_short *)((char *)w + 1);
96 mlen--;
97 byte_swapped = 1;
98 }
99 /*
100 * Unroll the loop to make overhead from
101 * branches &c small.
102 */
103 while ((mlen -= 32) >= 0) {
104 sum += w[0]; sum += w[1]; sum += w[2]; sum += w[3];
105 sum += w[4]; sum += w[5]; sum += w[6]; sum += w[7];
106 sum += w[8]; sum += w[9]; sum += w[10]; sum += w[11];
107 sum += w[12]; sum += w[13]; sum += w[14]; sum += w[15];
108 w += 16;
109 }
110 mlen += 32;
111 while ((mlen -= 8) >= 0) {
112 sum += w[0]; sum += w[1]; sum += w[2]; sum += w[3];
113 w += 4;
114 }
115 mlen += 8;
116 if (mlen == 0 && byte_swapped == 0)
117 continue;
118 REDUCE;
119 while ((mlen -= 2) >= 0) {
120 sum += *w++;
121 }
122 if (byte_swapped) {
123 REDUCE;
124 sum <<= 8;
125 byte_swapped = 0;
126 if (mlen == -1) {
127 s_util.c[1] = *(char *)w;
128 sum += s_util.s;
129 mlen = 0;
130 } else
131 mlen = -1;
132 } else if (mlen == -1)
133 s_util.c[0] = *(char *)w;
134 }
135 if (len)
136 printf("cksum: out of data\n");
137 if (mlen == -1) {
138 /* The last mbuf has odd # of bytes. Follow the
139 standard (the odd byte may be shifted left by 8 bits
140 or not as determined by endian-ness of the machine) */
141 s_util.c[1] = 0;
142 sum += s_util.s;
143 }
144 REDUCE;
145 return (~sum & 0xffff);
146 }
147
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