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Member "slirp-1.0.16/src/cksum.c" of archive slirp-1.0.16.tar.gz:
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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 * 3. All advertising materials mentioning features or use of this software
14 * must display the following acknowledgement:
15 * This product includes software developed by the University of
16 * California, Berkeley and its contributors.
17 * 4. Neither the name of the University nor the names of its contributors
18 * may be used to endorse or promote products derived from this software
19 * without specific prior written permission.
20 *
21 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
22 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
23 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
24 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
25 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
26 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
27 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
28 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
29 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
30 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
31 * SUCH DAMAGE.
32 *
33 * @(#)in_cksum.c 8.1 (Berkeley) 6/10/93
34 * in_cksum.c,v 1.2 1994/08/02 07:48:16 davidg Exp
35 */
36
37 #include <slirp.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 * XXX Since we will never span more than 1 mbuf, we can optimise this
46 */
47
48 #define ADDCARRY(x) (x > 65535 ? x -= 65535 : x)
49 #define REDUCE {l_util.l = sum; sum = l_util.s[0] + l_util.s[1]; ADDCARRY(sum);}
50
51 int
52 cksum(m, len)
53 register struct mbuf *m;
54 register int len;
55 {
56 register u_int16_t *w;
57 register int sum = 0;
58 register int mlen = 0;
59 int byte_swapped = 0;
60
61 union {
62 u_int8_t c[2];
63 u_int16_t s;
64 } s_util;
65 union {
66 u_int16_t s[2];
67 u_int32_t l;
68 } l_util;
69
70 if (m->m_len == 0)
71 goto cont;
72 w = mtod(m, u_int16_t *);
73
74 mlen = m->m_len;
75
76 if (len < mlen)
77 mlen = len;
78 len -= mlen;
79 /*
80 * Force to even boundary.
81 */
82 if ((1 & (long) w) && (mlen > 0)) {
83 REDUCE;
84 sum <<= 8;
85 s_util.c[0] = *(u_int8_t *)w;
86 w = (u_int16_t *)((int8_t *)w + 1);
87 mlen--;
88 byte_swapped = 1;
89 }
90 /*
91 * Unroll the loop to make overhead from
92 * branches &c small.
93 */
94 while ((mlen -= 32) >= 0) {
95 sum += w[0]; sum += w[1]; sum += w[2]; sum += w[3];
96 sum += w[4]; sum += w[5]; sum += w[6]; sum += w[7];
97 sum += w[8]; sum += w[9]; sum += w[10]; sum += w[11];
98 sum += w[12]; sum += w[13]; sum += w[14]; sum += w[15];
99 w += 16;
100 }
101 mlen += 32;
102 while ((mlen -= 8) >= 0) {
103 sum += w[0]; sum += w[1]; sum += w[2]; sum += w[3];
104 w += 4;
105 }
106 mlen += 8;
107 if (mlen == 0 && byte_swapped == 0)
108 goto cont;
109 REDUCE;
110 while ((mlen -= 2) >= 0) {
111 sum += *w++;
112 }
113
114 if (byte_swapped) {
115 REDUCE;
116 sum <<= 8;
117 byte_swapped = 0;
118 if (mlen == -1) {
119 s_util.c[1] = *(u_int8_t *)w;
120 sum += s_util.s;
121 mlen = 0;
122 } else
123
124 mlen = -1;
125 } else if (mlen == -1)
126 s_util.c[0] = *(u_int8_t *)w;
127
128 cont:
129 #ifdef DEBUG
130 if (len) {
131 DEBUG_ERROR((dfd, "cksum: out of data\n"));
132 DEBUG_ERROR((dfd, " len = %d\n", len));
133 }
134 #endif
135 if (mlen == -1) {
136 /* The last mbuf has odd # of bytes. Follow the
137 standard (the odd byte may be shifted left by 8 bits
138 or not as determined by endian-ness of the machine) */
139 s_util.c[1] = 0;
140 sum += s_util.s;
141 }
142 REDUCE;
143 return (~sum & 0xffff);
144 }