1 /* $OpenBSD: in_cksum.c,v 1.7 2020/05/19 12:54:37 patrick 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. Neither the name of the University nor the names of its contributors
21 * may be used to endorse or promote products derived from this software
22 * without specific prior written permission.
23 *
24 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
25 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
26 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
27 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
28 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
29 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
30 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
31 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
32 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
33 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
34 * SUCH DAMAGE.
35 *
36 * @(#) Header: in_cksum.c,v 1.1 92/09/11 01:15:55 leres Exp (LBL)
37 */
38
39 #include <sys/types.h>
40 #include <sys/socket.h>
41 #include <net/if.h>
42 #include <netinet/in.h>
43
44 #include <netinet/if_ether.h>
45
46 #include "stand.h"
47 #include "net.h"
48
49 /*
50 * Checksum routine for Internet Protocol family headers.
51 * This routine is very heavily used in the network
52 * code and should be modified for each CPU to be as fast as possible.
53 * In particular, it should not be this one.
54 */
55 u_int16_t
in_cksum(const void * p,size_t l)56 in_cksum(const void *p, size_t l)
57 {
58 unsigned int sum = 0;
59 int len;
60 const u_char *cp = p;
61
62 /* ensure that < 2^16 bytes being summed */
63 if (l >= (1 << 16))
64 panic("in_cksum: packet too big");
65 len = (int)l;
66
67 if (((long)cp & 1) == 0) {
68 while (len > 1) {
69 sum += htons(*(const u_short *)cp);
70 cp += 2;
71 len -= 2;
72 }
73 } else {
74 while (len > 1) {
75 sum += *cp++ << 8;
76 sum += *cp++;
77 len -= 2;
78 }
79 }
80 if (len == 1)
81 sum += *cp << 8;
82
83 sum = (sum >> 16) + (sum & 0xffff); /* add in accumulated carries */
84 sum += sum >> 16; /* add potential last carry */
85 sum = ntohs(sum);
86 return (0xffff & ~sum);
87 }
88