1 /* $NetBSD: in_cksum.c,v 1.6 2000/03/31 19:55:09 castor Exp $ */
2
3 /*
4 * Copyright (c) 1992 Regents of the University of California.
5 * All rights reserved.
6 *
7 * This software was developed by the Computer Systems Engineering group
8 * at Lawrence Berkeley Laboratory under DARPA contract BG 91-66 and
9 * contributed to Berkeley.
10 *
11 * Redistribution and use in source and binary forms, with or without
12 * modification, are permitted provided that the following conditions
13 * are met:
14 * 1. Redistributions of source code must retain the above copyright
15 * notice, this list of conditions and the following disclaimer.
16 * 2. Redistributions in binary form must reproduce the above copyright
17 * notice, this list of conditions and the following disclaimer in the
18 * documentation and/or other materials provided with the distribution.
19 * 3. Neither the name of the University nor the names of its contributors
20 * may be used to endorse or promote products derived from this software
21 * without specific prior written permission.
22 *
23 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
24 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
25 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
26 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
27 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
28 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
29 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
30 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
31 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
32 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
33 * SUCH DAMAGE.
34 *
35 * @(#) Header: in_cksum.c,v 1.1 92/09/11 01:15:55 leres Exp (LBL)
36 */
37
38 #include <sys/cdefs.h>
39
40 #include <sys/types.h>
41 #include <machine/endian.h>
42
43 #include "stand.h"
44
45 /*
46 * Checksum routine for Internet Protocol family headers.
47 * This routine is very heavily used in the network
48 * code and should be modified for each CPU to be as fast as possible.
49 * In particular, it should not be this one.
50 */
51 int
in_cksum(void * p,int len)52 in_cksum(void *p, int len)
53 {
54 int sum = 0, oddbyte = 0, v = 0;
55 uchar_t *cp = p;
56
57 /* we assume < 2^16 bytes being summed */
58 while (len > 0) {
59 if (oddbyte) {
60 sum += v + *cp++;
61 len--;
62 }
63 if (((long)cp & 1) == 0) {
64 while ((len -= 2) >= 0) {
65 sum += *(ushort_t *)cp;
66 cp += 2;
67 }
68 } else {
69 while ((len -= 2) >= 0) {
70 #if BYTE_ORDER == BIG_ENDIAN
71 sum += *cp++ << 8;
72 sum += *cp++;
73 #else
74 sum += *cp++;
75 sum += *cp++ << 8;
76 #endif
77 }
78 }
79 if ((oddbyte = len & 1) != 0)
80 #if BYTE_ORDER == BIG_ENDIAN
81 v = *cp << 8;
82 #else
83 v = *cp;
84 #endif
85 }
86 if (oddbyte)
87 sum += v;
88 sum = (sum >> 16) + (sum & 0xffff); /* add in accumulated carries */
89 sum += sum >> 16; /* add potential last carry */
90 return (0xffff & ~sum);
91 }
92