Line data Source code
1 : /* $OpenBSD: in_cksum.c,v 1.8 2015/07/17 23:49:03 tedu Exp $ */
2 : /* $NetBSD: in_cksum.c,v 1.11 1996/04/08 19:55:37 jonathan Exp $ */
3 :
4 : /*
5 : * Copyright (c) 1988, 1992, 1993
6 : * The Regents of the University of California. All rights reserved.
7 : *
8 : * Redistribution and use in source and binary forms, with or without
9 : * modification, are permitted provided that the following conditions
10 : * are met:
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 the
15 : * documentation and/or other materials provided with the distribution.
16 : * 3. Neither the name of the University nor the names of its contributors
17 : * may be used to endorse or promote products derived from this software
18 : * without specific prior written permission.
19 : *
20 : * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
21 : * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
22 : * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
23 : * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
24 : * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
25 : * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
26 : * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
27 : * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
28 : * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
29 : * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
30 : * SUCH DAMAGE.
31 : *
32 : * @(#)in_cksum.c 8.1 (Berkeley) 6/10/93
33 : */
34 :
35 : #include <sys/param.h>
36 : #include <sys/mbuf.h>
37 : #include <sys/systm.h>
38 :
39 : /*
40 : * Checksum routine for Internet Protocol family headers (Portable Version).
41 : *
42 : * This routine is very heavily used in the network
43 : * code and should be modified for each CPU to be as fast as possible.
44 : */
45 :
46 : #define ADDCARRY(x) (x > 65535 ? x -= 65535 : x)
47 : #define REDUCE {l_util.l = sum; sum = l_util.s[0] + l_util.s[1]; ADDCARRY(sum);}
48 :
49 : int
50 0 : in_cksum(struct mbuf *m, int len)
51 : {
52 : u_int16_t *w;
53 : int sum = 0;
54 : int mlen = 0;
55 : int byte_swapped = 0;
56 :
57 : union {
58 : u_int8_t c[2];
59 : u_int16_t s;
60 : } s_util;
61 : union {
62 : u_int16_t s[2];
63 : u_int32_t l;
64 : } l_util;
65 :
66 0 : for (;m && len; m = m->m_next) {
67 0 : if (m->m_len == 0)
68 : continue;
69 0 : w = mtod(m, u_int16_t *);
70 0 : if (mlen == -1) {
71 : /*
72 : * The first byte of this mbuf is the continuation
73 : * of a word spanning between this mbuf and the
74 : * last mbuf.
75 : *
76 : * s_util.c[0] is already saved when scanning previous
77 : * mbuf.
78 : */
79 0 : s_util.c[1] = *(u_int8_t *)w;
80 0 : sum += s_util.s;
81 0 : w = (u_int16_t *)((u_int8_t *)w + 1);
82 0 : mlen = m->m_len - 1;
83 0 : len--;
84 0 : } else
85 : mlen = m->m_len;
86 0 : if (len < mlen)
87 0 : mlen = len;
88 0 : len -= mlen;
89 : /*
90 : * Force to even boundary.
91 : */
92 0 : if ((1 & (long) w) && (mlen > 0)) {
93 0 : REDUCE;
94 0 : sum <<= 8;
95 0 : s_util.c[0] = *(u_int8_t *)w;
96 0 : w = (u_int16_t *)((int8_t *)w + 1);
97 0 : mlen--;
98 : byte_swapped = 1;
99 0 : }
100 : /*
101 : * Unroll the loop to make overhead from
102 : * branches &c small.
103 : */
104 0 : while ((mlen -= 32) >= 0) {
105 0 : sum += w[0]; sum += w[1]; sum += w[2]; sum += w[3];
106 0 : sum += w[4]; sum += w[5]; sum += w[6]; sum += w[7];
107 0 : sum += w[8]; sum += w[9]; sum += w[10]; sum += w[11];
108 0 : sum += w[12]; sum += w[13]; sum += w[14]; sum += w[15];
109 0 : w += 16;
110 : }
111 : mlen += 32;
112 0 : while ((mlen -= 8) >= 0) {
113 0 : sum += w[0]; sum += w[1]; sum += w[2]; sum += w[3];
114 0 : w += 4;
115 : }
116 : mlen += 8;
117 0 : if (mlen == 0 && byte_swapped == 0)
118 : continue;
119 0 : REDUCE;
120 0 : while ((mlen -= 2) >= 0) {
121 0 : sum += *w++;
122 : }
123 0 : if (byte_swapped) {
124 0 : REDUCE;
125 0 : sum <<= 8;
126 : byte_swapped = 0;
127 0 : if (mlen == -1) {
128 0 : s_util.c[1] = *(u_int8_t *)w;
129 0 : sum += s_util.s;
130 : mlen = 0;
131 0 : } else
132 : mlen = -1;
133 0 : } else if (mlen == -1)
134 0 : s_util.c[0] = *(u_int8_t *)w;
135 : }
136 0 : if (len)
137 0 : printf("cksum: out of data\n");
138 0 : if (mlen == -1) {
139 : /* The last mbuf has odd # of bytes. Follow the
140 : standard (the odd byte may be shifted left by 8 bits
141 : or not as determined by endian-ness of the machine) */
142 : s_util.c[1] = 0;
143 0 : sum += s_util.s;
144 0 : }
145 0 : REDUCE;
146 0 : return (~sum & 0xffff);
147 : }
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