1 /* $OpenBSD: in_cksum.c,v 1.3 2003/08/11 06:23:09 deraadt Exp $ */
2 /* $NetBSD: in_cksum.c,v 1.3 1995/04/22 13:53:48 cgd Exp $ */
3
4 /*
5 * Copyright (c) 1992 Regents of the University of California.
6 * All rights reserved.
7 *
8 * This software was developed by the Computer Systems Engineering group
9 * at Lawrence Berkeley Laboratory under DARPA contract BG 91-66 and
10 * contributed to Berkeley.
11 *
12 * Redistribution and use in source and binary forms, with or without
13 * modification, are permitted provided that the following conditions
14 * are met:
15 * 1. Redistributions of source code must retain the above copyright
16 * notice, this list of conditions and the following disclaimer.
17 * 2. Redistributions in binary form must reproduce the above copyright
18 * notice, this list of conditions and the following disclaimer in the
19 * documentation and/or other materials provided with the distribution.
20 * 3. All advertising materials mentioning features or use of this software
21 * must display the following acknowledgement:
22 * This product includes software developed by the University of
23 * California, Lawrence Berkeley Laboratory and its contributors.
24 * 4. Neither the name of the University nor the names of its contributors
25 * may be used to endorse or promote products derived from this software
26 * without specific prior written permission.
27 *
28 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
29 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
30 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
31 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
32 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
33 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
34 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
35 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
36 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
37 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
38 * SUCH DAMAGE.
39 *
40 * @(#) Header: in_cksum.c,v 1.1 92/09/11 01:15:55 leres Exp (LBL)
41 */
42
43 #include <sys/types.h>
44 #include <sys/socket.h>
45 #include <net/if.h>
46 #include <netinet/in.h>
47
48 #include <netinet/if_ether.h>
49 #include <netinet/in_systm.h>
50
51 #include "stand.h"
52 #include "net.h"
53
54 /*
55 * Checksum routine for Internet Protocol family headers.
56 * This routine is very heavily used in the network
57 * code and should be modified for each CPU to be as fast as possible.
58 * In particular, it should not be this one.
59 */
60 int
61 in_cksum(void *p, int len)
62 {
63 int sum = 0, oddbyte = 0, v = 0;
64 u_char *cp = p;
65
66 /* we assume < 2^16 bytes being summed */
67 while (len > 0) {
68 if (oddbyte) {
69 sum += v + *cp++;
70 len--;
71 }
72 if (((long)cp & 1) == 0) {
73 while ((len -= 2) >= 0) {
74 sum += *(u_short *)cp;
75 cp += 2;
76 }
77 } else {
78 while ((len -= 2) >= 0) {
79 sum += *cp++ << 8;
80 sum += *cp++;
81 }
82 }
83 if ((oddbyte = len & 1) != 0)
84 v = *cp << 8;
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 }