1 /* $NetBSD: in_cksum.c,v 1.6 2000/03/31 19:55:09 castor 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. Neither the name of the University nor the names of its contributors 20 * may be used to endorse or promote products derived from this software 21 * without specific prior written permission. 22 * 23 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 24 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 25 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 26 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 27 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 28 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 29 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 30 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 31 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 32 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 33 * SUCH DAMAGE. 34 * 35 * @(#) Header: in_cksum.c,v 1.1 92/09/11 01:15:55 leres Exp (LBL) 36 */ 37 38 #include <sys/cdefs.h> 39 __FBSDID("$FreeBSD$"); 40 41 #include <sys/types.h> 42 #include <machine/endian.h> 43 44 #include "stand.h" 45 46 /* 47 * Checksum routine for Internet Protocol family headers. 48 * This routine is very heavily used in the network 49 * code and should be modified for each CPU to be as fast as possible. 50 * In particular, it should not be this one. 51 */ 52 int 53 in_cksum(p, len) 54 void *p; 55 int len; 56 { 57 int sum = 0, oddbyte = 0, v = 0; 58 u_char *cp = p; 59 60 /* we assume < 2^16 bytes being summed */ 61 while (len > 0) { 62 if (oddbyte) { 63 sum += v + *cp++; 64 len--; 65 } 66 if (((long)cp & 1) == 0) { 67 while ((len -= 2) >= 0) { 68 sum += *(u_short *)cp; 69 cp += 2; 70 } 71 } else { 72 while ((len -= 2) >= 0) { 73 #if BYTE_ORDER == BIG_ENDIAN 74 sum += *cp++ << 8; 75 sum += *cp++; 76 #else 77 sum += *cp++; 78 sum += *cp++ << 8; 79 #endif 80 } 81 } 82 if ((oddbyte = len & 1) != 0) 83 #if BYTE_ORDER == BIG_ENDIAN 84 v = *cp << 8; 85 #else 86 v = *cp; 87 #endif 88 } 89 if (oddbyte) 90 sum += v; 91 sum = (sum >> 16) + (sum & 0xffff); /* add in accumulated carries */ 92 sum += sum >> 16; /* add potential last carry */ 93 return (0xffff & ~sum); 94 } 95