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 * 4. 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 __FBSDID("$FreeBSD$");
40
41 #include <sys/types.h>
42 #include <machine/endian.h>
43
44 #include "stand.h"
45
46 /*
47 * Checksum routine for Internet Protocol family headers.
48 * This routine is very heavily used in the network
49 * code and should be modified for each CPU to be as fast as possible.
50 * In particular, it should not be this one.
51 */
52 int
in_cksum(p,len)53 in_cksum(p, len)
54 void *p;
55 int len;
56 {
57 int sum = 0, oddbyte = 0, v = 0;
58 u_char *cp = p;
59
60 /* we assume < 2^16 bytes being summed */
61 while (len > 0) {
62 if (oddbyte) {
63 sum += v + *cp++;
64 len--;
65 }
66 if (((long)cp & 1) == 0) {
67 while ((len -= 2) >= 0) {
68 sum += *(u_short *)cp;
69 cp += 2;
70 }
71 } else {
72 while ((len -= 2) >= 0) {
73 #if BYTE_ORDER == BIG_ENDIAN
74 sum += *cp++ << 8;
75 sum += *cp++;
76 #else
77 sum += *cp++;
78 sum += *cp++ << 8;
79 #endif
80 }
81 }
82 if ((oddbyte = len & 1) != 0)
83 #if BYTE_ORDER == BIG_ENDIAN
84 v = *cp << 8;
85 #else
86 v = *cp;
87 #endif
88 }
89 if (oddbyte)
90 sum += v;
91 sum = (sum >> 16) + (sum & 0xffff); /* add in accumulated carries */
92 sum += sum >> 16; /* add potential last carry */
93 return (0xffff & ~sum);
94 }
95