Annotation of sys/lib/libsa/in_cksum.c, Revision 1.1.1.1
1.1 nbrk 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: }
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