2 * SPDX-License-Identifier: BSD-3-Clause
4 * Copyright (c) 1989, 1993
5 * The Regents of the University of California. All rights reserved.
7 * This code is derived from software contributed to Berkeley by
10 * Redistribution and use in source and binary forms, with or without
11 * modification, are permitted provided that the following conditions
13 * 1. Redistributions of source code must retain the above copyright
14 * notice, this list of conditions and the following disclaimer.
15 * 2. Redistributions in binary form must reproduce the above copyright
16 * notice, this list of conditions and the following disclaimer in the
17 * documentation and/or other materials provided with the distribution.
18 * 3. Neither the name of the University nor the names of its contributors
19 * may be used to endorse or promote products derived from this software
20 * without specific prior written permission.
22 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
23 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
24 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
25 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
26 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
27 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
28 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
29 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
30 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
31 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
37 static const char copyright[] =
38 "@(#) Copyright (c) 1989, 1993\n\
39 The Regents of the University of California. All rights reserved.\n";
43 static char sccsid[] = "@(#)ping.c 8.1 (Berkeley) 6/5/93";
46 #include <sys/cdefs.h>
47 __FBSDID("$FreeBSD$");
55 * Checksum routine for Internet Protocol family headers (C Version)
58 in_cksum(u_char *addr, int len)
73 * Our algorithm is simple, using a 32 bit accumulator (sum), we add
74 * sequential 16 bit words to it, and at the end, fold back all the
75 * carry bits from the top 16 bits into the lower 16 bits.
80 memcpy(&data, w, sizeof(data));
83 nleft -= sizeof(data);
86 /* mop up an odd byte, if necessary */
93 /* add back carry outs from top 16 bits to low 16 bits */
94 sum = (sum >> 16) + (sum & 0xffff); /* add hi 16 to low 16 */
95 sum += (sum >> 16); /* add carry */
96 answer = ~sum; /* truncate to 16 bits */