1 /*
2 * Copyright (c) 1995, Mike Mitchell
3 * Copyright (c) 1982, 1992, 1993
4 * The Regents of the University of California. All rights reserved.
5 *
6 * Redistribution and use in source and binary forms, with or without
7 * modification, are permitted provided that the following conditions
8 * are met:
9 * 1. Redistributions of source code must retain the above copyright
10 * notice, this list of conditions and the following disclaimer.
11 * 2. Redistributions in binary form must reproduce the above copyright
12 * notice, this list of conditions and the following disclaimer in the
13 * documentation and/or other materials provided with the distribution.
14 * 3. All advertising materials mentioning features or use of this software
15 * must display the following acknowledgement:
16 * This product includes software developed by the University of
17 * California, Berkeley and its contributors.
18 * 4. Neither the name of the University nor the names of its contributors
19 * may be used to endorse or promote products derived from this software
20 * without specific prior written permission.
21 *
22 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
23 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
24 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
25 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
26 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
27 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
28 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
29 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
30 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
31 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
32 * SUCH DAMAGE.
33 *
34 * @(#)ipx_cksum.c
35 *
36 * $FreeBSD: releng/5.0/sys/netipx/ipx_cksum.c 50519 1999-08-28 18:21:55Z jhay $
37 */
38
39 #include <sys/param.h>
40 #include <sys/mbuf.h>
41 #include <sys/libkern.h>
42
43 #include <netipx/ipx.h>
44 #include <netipx/ipx_var.h>
45
46
47 #define SUMADV sum += *w++
48
49 u_short
50 ipx_cksum(struct mbuf *m, int len) {
51 u_int32_t sum = 0;
52 u_short *w;
53 u_char oldtc;
54 int mlen, words;
55 struct ipx *ipx;
56 union {
57 u_char b[2];
58 u_short w;
59 } buf;
60
61 ipx = mtod(m, struct ipx*);
62 oldtc = ipx->ipx_tc;
63 ipx->ipx_tc = 0;
64 w = &ipx->ipx_len;
65 len -= 2;
66 mlen = 2;
67
68 for(;;) {
69 mlen = imin(m->m_len - mlen, len);
70 words = mlen / 2;
71 len -= mlen & ~1;
72 while (words >= 16) {
73 SUMADV; SUMADV; SUMADV; SUMADV;
74 SUMADV; SUMADV; SUMADV; SUMADV;
75 SUMADV; SUMADV; SUMADV; SUMADV;
76 SUMADV; SUMADV; SUMADV; SUMADV;
77 words -= 16;
78 }
79 while (words--)
80 SUMADV;
81 if (len == 0)
82 break;
83 mlen &= 1;
84 if (mlen) {
85 buf.b[0] = *(u_char*)w;
86 if (--len == 0) {
87 buf.b[1] = 0;
88 sum += buf.w;
89 break;
90 }
91 }
92 m = m->m_next;
93 if (m == NULL)
94 break;
95 w = mtod(m, u_short*);
96 if (mlen) {
97 buf.b[1] = *(u_char*)w;
98 sum += buf.w;
99 ((u_char*)w)++;
100 if (--len == 0)
101 break;
102 }
103 }
104
105 ipx->ipx_tc = oldtc;
106
107 sum = (sum & 0xffff) + (sum >> 16);
108 if (sum >= 0x10000)
109 sum++;
110 if (sum)
111 sum = ~sum;
112 return (sum);
113 }
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