1 /* $OpenBSD: in_cksum.c,v 1.5 2014/11/19 20:28:56 miod 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 #include <sys/socket.h> 45 #include <net/if.h> 46 #include <netinet/in.h> 47 48 #include <netinet/if_ether.h> 49 50 #include "stand.h" 51 #include "net.h" 52 53 /* 54 * Checksum routine for Internet Protocol family headers. 55 * This routine is very heavily used in the network 56 * code and should be modified for each CPU to be as fast as possible. 57 * In particular, it should not be this one. 58 */ 59 int 60 in_cksum(const void *p, int len) 61 { 62 int sum = 0, oddbyte = 0, v = 0; 63 const u_char *cp = p; 64 65 /* we assume < 2^16 bytes being summed */ 66 while (len > 0) { 67 if (oddbyte) { 68 sum += v + *cp++; 69 len--; 70 } 71 if (((long)cp & 1) == 0) { 72 while ((len -= 2) >= 0) { 73 sum += *(const u_short *)cp; 74 cp += 2; 75 } 76 } else { 77 while ((len -= 2) >= 0) { 78 sum += *cp++ << 8; 79 sum += *cp++; 80 } 81 } 82 if ((oddbyte = len & 1) != 0) 83 v = *cp << 8; 84 } 85 if (oddbyte) 86 sum += v; 87 sum = (sum >> 16) + (sum & 0xffff); /* add in accumulated carries */ 88 sum += sum >> 16; /* add potential last carry */ 89 return (0xffff & ~sum); 90 } 91