1 /* $OpenBSD: in_cksum.c,v 1.2 1996/09/23 14:18:55 mickey 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 45 /* 46 * Checksum routine for Internet Protocol family headers. 47 * This routine is very heavily used in the network 48 * code and should be modified for each CPU to be as fast as possible. 49 * In particular, it should not be this one. 50 */ 51 int 52 in_cksum(p, len) 53 register void *p; 54 register int len; 55 { 56 register int sum = 0, oddbyte = 0, v = 0; 57 register u_char *cp = p; 58 59 /* we assume < 2^16 bytes being summed */ 60 while (len > 0) { 61 if (oddbyte) { 62 sum += v + *cp++; 63 len--; 64 } 65 if (((long)cp & 1) == 0) { 66 while ((len -= 2) >= 0) { 67 sum += *(u_short *)cp; 68 cp += 2; 69 } 70 } else { 71 while ((len -= 2) >= 0) { 72 sum += *cp++ << 8; 73 sum += *cp++; 74 } 75 } 76 if ((oddbyte = len & 1) != 0) 77 v = *cp << 8; 78 } 79 if (oddbyte) 80 sum += v; 81 sum = (sum >> 16) + (sum & 0xffff); /* add in accumulated carries */ 82 sum += sum >> 16; /* add potential last carry */ 83 return (0xffff & ~sum); 84 } 85