1 /*-
2 * SPDX-License-Identifier: BSD-3-Clause
3 *
4 * Copyright (c) 1988, 1992, 1993
5 * The Regents of the University of California. 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 * 1. Redistributions of source code must retain the above copyright
11 * notice, this list of conditions and the following disclaimer.
12 * 2. Redistributions in binary form must reproduce the above copyright
13 * notice, this list of conditions and the following disclaimer in the
14 * documentation and/or other materials provided with the distribution.
15 * 3. Neither the name of the University nor the names of its contributors
16 * may be used to endorse or promote products derived from this software
17 * without specific prior written permission.
18 *
19 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
20 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
21 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
22 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
23 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
24 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
25 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
26 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
27 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
28 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
29 * SUCH DAMAGE.
30 *
31 * @(#)in_cksum.c 8.1 (Berkeley) 6/10/93
32 */
33
34 #include <sys/cdefs.h>
35 __FBSDID("$FreeBSD$");
36
37 #include <sys/param.h>
38 #include <sys/mbuf.h>
39
40 /*
41 * Checksum routine for Internet Protocol family headers (Portable Version).
42 *
43 * This routine is very heavily used in the network
44 * code and should be modified for each CPU to be as fast as possible.
45 */
46
47 #define ADDCARRY(x) (x > 65535 ? x -= 65535 : x)
48 #define REDUCE {l_util.l = sum; sum = l_util.s[0] + l_util.s[1]; ADDCARRY(sum);}
49
50 int
51 in_cksum(struct mbuf *m, int len)
52 {
53 u_short *w;
54 int sum = 0;
55 int mlen = 0;
56 int byte_swapped = 0;
57
58 union {
59 char c[2];
60 u_short s;
61 } s_util;
62 union {
63 u_short s[2];
64 long l;
65 } l_util;
66
67 for (;m && len; m = m->m_next) {
68 if (m->m_len == 0)
69 continue;
70 w = mtod(m, u_short *);
71 if (mlen == -1) {
72 /*
73 * The first byte of this mbuf is the continuation
74 * of a word spanning between this mbuf and the
75 * last mbuf.
76 *
77 * s_util.c[0] is already saved when scanning previous
78 * mbuf.
79 */
80 s_util.c[1] = *(char *)w;
81 sum += s_util.s;
82 w = (u_short *)((char *)w + 1);
83 mlen = m->m_len - 1;
84 len--;
85 } else
86 mlen = m->m_len;
87 if (len < mlen)
88 mlen = len;
89 len -= mlen;
90 /*
91 * Force to even boundary.
92 */
93 if ((1 & (uintptr_t) w) && (mlen > 0)) {
94 REDUCE;
95 sum <<= 8;
96 s_util.c[0] = *(u_char *)w;
97 w = (u_short *)((char *)w + 1);
98 mlen--;
99 byte_swapped = 1;
100 }
101 /*
102 * Unroll the loop to make overhead from
103 * branches &c small.
104 */
105 while ((mlen -= 32) >= 0) {
106 sum += w[0]; sum += w[1]; sum += w[2]; sum += w[3];
107 sum += w[4]; sum += w[5]; sum += w[6]; sum += w[7];
108 sum += w[8]; sum += w[9]; sum += w[10]; sum += w[11];
109 sum += w[12]; sum += w[13]; sum += w[14]; sum += w[15];
110 w += 16;
111 }
112 mlen += 32;
113 while ((mlen -= 8) >= 0) {
114 sum += w[0]; sum += w[1]; sum += w[2]; sum += w[3];
115 w += 4;
116 }
117 mlen += 8;
118 if (mlen == 0 && byte_swapped == 0)
119 continue;
120 REDUCE;
121 while ((mlen -= 2) >= 0) {
122 sum += *w++;
123 }
124 if (byte_swapped) {
125 REDUCE;
126 sum <<= 8;
127 byte_swapped = 0;
128 if (mlen == -1) {
129 s_util.c[1] = *(char *)w;
130 sum += s_util.s;
131 mlen = 0;
132 } else
133 mlen = -1;
134 } else if (mlen == -1)
135 s_util.c[0] = *(char *)w;
136 }
137 if (len)
138 printf("cksum: out of data\n");
139 if (mlen == -1) {
140 /* The last mbuf has odd # of bytes. Follow the
141 standard (the odd byte may be shifted left by 8 bits
142 or not as determined by endian-ness of the machine) */
143 s_util.c[1] = 0;
144 sum += s_util.s;
145 }
146 REDUCE;
147 return (~sum & 0xffff);
148 }
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