1 /* $NetBSD: ip_cksum.c,v 1.2 2006/01/25 13:46:09 christos 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. All advertising materials mentioning features or use of this software
20 * must display the following acknowledgement:
21 * This product includes software developed by the University of
22 * California, Lawrence Berkeley Laboratory and its contributors.
23 * 4. Neither the name of the University nor the names of its contributors
24 * may be used to endorse or promote products derived from this software
25 * without specific prior written permission.
26 *
27 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
28 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
29 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
30 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
31 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
32 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
33 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
34 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
35 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
36 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
37 * SUCH DAMAGE.
38 *
39 * @(#) Header: in_cksum.c,v 1.1 92/09/11 01:15:55 leres Exp (LBL)
40 */
41
42 #include <sys/types.h>
43 #include <sys/socket.h>
44
45 #include <net/if.h>
46 #include <net/if_ether.h>
47
48 #include <netinet/in.h>
49 #include <netinet/in_systm.h>
50 #include <netinet/ip.h>
51 #include <netinet/ip_var.h>
52 #include <netinet/udp.h>
53 #include <netinet/udp_var.h>
54
55 #include <machine/endian.h>
56
57 #include "stand.h"
58 #include "net.h"
59
60 /*
61 * Checksum routine for Internet Protocol family headers.
62 * This routine is very heavily used in the network
63 * code and should be modified for each CPU to be as fast as possible.
64 * In particular, it should not be this one.
65 */
66 int
ip_cksum(const void * p,size_t llen)67 ip_cksum(const void *p, size_t llen)
68 {
69 int sum = 0, oddbyte = 0, v = 0, len = (int)llen;
70 const u_char *cp = p;
71
72 /* we assume < 2^16 bytes being summed */
73 while (len > 0) {
74 if (oddbyte) {
75 sum += v + *cp++;
76 len--;
77 }
78 if (((long)cp & 1) == 0) {
79 while ((len -= 2) >= 0) {
80 sum += *(const u_short *)cp;
81 cp += 2;
82 }
83 } else {
84 while ((len -= 2) >= 0) {
85 #if BYTE_ORDER == BIG_ENDIAN
86 sum += *cp++ << 8;
87 sum += *cp++;
88 #else
89 sum += *cp++;
90 sum += *cp++ << 8;
91 #endif
92 }
93 }
94 if ((oddbyte = len & 1) != 0)
95 #if BYTE_ORDER == BIG_ENDIAN
96 v = *cp << 8;
97 #else
98 v = *cp;
99 #endif
100 }
101 if (oddbyte)
102 sum += v;
103 sum = (sum >> 16) + (sum & 0xffff); /* add in accumulated carries */
104 sum += sum >> 16; /* add potential last carry */
105 return (0xffff & ~sum);
106 }
107