1 /*- 2 * SPDX-License-Identifier: BSD-3-Clause 3 * 4 * Copyright (c) 1989, 1993 5 * The Regents of the University of California. All rights reserved. 6 * 7 * This code is derived from software contributed to Berkeley by 8 * Mike Muuss. 9 * 10 * Redistribution and use in source and binary forms, with or without 11 * modification, are permitted provided that the following conditions 12 * are met: 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. 21 * 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 32 * SUCH DAMAGE. 33 */ 34 35 #if 0 36 #ifndef lint 37 static const char copyright[] = 38 "@(#) Copyright (c) 1989, 1993\n\ 39 The Regents of the University of California. All rights reserved.\n"; 40 #endif /* not lint */ 41 42 #ifndef lint 43 static char sccsid[] = "@(#)ping.c 8.1 (Berkeley) 6/5/93"; 44 #endif /* not lint */ 45 #endif 46 #include <sys/cdefs.h> 47 __FBSDID("$FreeBSD$"); 48 49 #include <string.h> 50 51 #include "utils.h" 52 53 /* 54 * in_cksum -- 55 * Checksum routine for Internet Protocol family headers (C Version) 56 */ 57 u_short 58 in_cksum(u_char *addr, int len) 59 { 60 int nleft, sum; 61 u_char *w; 62 union { 63 u_short us; 64 u_char uc[2]; 65 } last; 66 u_short answer; 67 68 nleft = len; 69 sum = 0; 70 w = addr; 71 72 /* 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. 76 */ 77 while (nleft > 1) { 78 u_short data; 79 80 memcpy(&data, w, sizeof(data)); 81 sum += data; 82 w += sizeof(data); 83 nleft -= sizeof(data); 84 } 85 86 /* mop up an odd byte, if necessary */ 87 if (nleft == 1) { 88 last.uc[0] = *w; 89 last.uc[1] = 0; 90 sum += last.us; 91 } 92 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 */ 97 return(answer); 98 } 99