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. 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 * in_cksum.c,v 1.2 1994/08/02 07:48:16 davidg Exp
31 */
32
33 #include <slirp.h>
34
35 /*
36 * Checksum routine for Internet Protocol family headers (Portable Version).
37 *
38 * This routine is very heavily used in the network
39 * code and should be modified for each CPU to be as fast as possible.
40 *
41 * XXX Since we will never span more than 1 mbuf, we can optimise this
42 */
43
44 #define ADDCARRY(x) (x > 65535 ? x -= 65535 : x)
45 #define REDUCE {l_util.l = sum; sum = l_util.s[0] + l_util.s[1]; ADDCARRY(sum);}
46
cksum(struct mbuf * m,int len)47 int cksum(struct mbuf *m, int len)
48 {
49 register u_int16_t *w;
50 register int sum = 0;
51 register int mlen = 0;
52 int byte_swapped = 0;
53
54 union {
55 u_int8_t c[2];
56 u_int16_t s;
57 } s_util;
58 union {
59 u_int16_t s[2];
60 u_int32_t l;
61 } l_util;
62
63 if (m->m_len == 0)
64 goto cont;
65 w = mtod(m, u_int16_t *);
66
67 mlen = m->m_len;
68
69 if (len < mlen)
70 mlen = len;
71 len -= mlen;
72 /*
73 * Force to even boundary.
74 */
75 if ((1 & (long) w) && (mlen > 0)) {
76 REDUCE;
77 sum <<= 8;
78 s_util.c[0] = *(u_int8_t *)w;
79 w = (u_int16_t *)((int8_t *)w + 1);
80 mlen--;
81 byte_swapped = 1;
82 }
83 /*
84 * Unroll the loop to make overhead from
85 * branches &c small.
86 */
87 while ((mlen -= 32) >= 0) {
88 sum += w[0]; sum += w[1]; sum += w[2]; sum += w[3];
89 sum += w[4]; sum += w[5]; sum += w[6]; sum += w[7];
90 sum += w[8]; sum += w[9]; sum += w[10]; sum += w[11];
91 sum += w[12]; sum += w[13]; sum += w[14]; sum += w[15];
92 w += 16;
93 }
94 mlen += 32;
95 while ((mlen -= 8) >= 0) {
96 sum += w[0]; sum += w[1]; sum += w[2]; sum += w[3];
97 w += 4;
98 }
99 mlen += 8;
100 if (mlen == 0 && byte_swapped == 0)
101 goto cont;
102 REDUCE;
103 while ((mlen -= 2) >= 0) {
104 sum += *w++;
105 }
106
107 if (byte_swapped) {
108 REDUCE;
109 sum <<= 8;
110 byte_swapped = 0;
111 if (mlen == -1) {
112 s_util.c[1] = *(u_int8_t *)w;
113 sum += s_util.s;
114 mlen = 0;
115 } else
116
117 mlen = -1;
118 } else if (mlen == -1)
119 s_util.c[0] = *(u_int8_t *)w;
120
121 cont:
122 #ifdef DEBUG
123 if (len) {
124 DEBUG_ERROR((dfd, "cksum: out of data\n"));
125 DEBUG_ERROR((dfd, " len = %d\n", len));
126 }
127 #endif
128 if (mlen == -1) {
129 /* The last mbuf has odd # of bytes. Follow the
130 standard (the odd byte may be shifted left by 8 bits
131 or not as determined by endian-ness of the machine) */
132 s_util.c[1] = 0;
133 sum += s_util.s;
134 }
135 REDUCE;
136 return (~sum & 0xffff);
137 }
138