1 /* $OpenBSD: in_cksum.c,v 1.7 2020/05/19 12:54:37 patrick 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. Neither the name of the University nor the names of its contributors 21 * may be used to endorse or promote products derived from this software 22 * without specific prior written permission. 23 * 24 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 25 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 26 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 27 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 28 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 29 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 30 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 31 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 32 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 33 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 34 * SUCH DAMAGE. 35 * 36 * @(#) Header: in_cksum.c,v 1.1 92/09/11 01:15:55 leres Exp (LBL) 37 */ 38 39 #include <sys/types.h> 40 #include <sys/socket.h> 41 #include <net/if.h> 42 #include <netinet/in.h> 43 44 #include <netinet/if_ether.h> 45 46 #include "stand.h" 47 #include "net.h" 48 49 /* 50 * Checksum routine for Internet Protocol family headers. 51 * This routine is very heavily used in the network 52 * code and should be modified for each CPU to be as fast as possible. 53 * In particular, it should not be this one. 54 */ 55 u_int16_t 56 in_cksum(const void *p, size_t l) 57 { 58 unsigned int sum = 0; 59 int len; 60 const u_char *cp = p; 61 62 /* ensure that < 2^16 bytes being summed */ 63 if (l >= (1 << 16)) 64 panic("in_cksum: packet too big"); 65 len = (int)l; 66 67 if (((long)cp & 1) == 0) { 68 while (len > 1) { 69 sum += htons(*(const u_short *)cp); 70 cp += 2; 71 len -= 2; 72 } 73 } else { 74 while (len > 1) { 75 sum += *cp++ << 8; 76 sum += *cp++; 77 len -= 2; 78 } 79 } 80 if (len == 1) 81 sum += *cp << 8; 82 83 sum = (sum >> 16) + (sum & 0xffff); /* add in accumulated carries */ 84 sum += sum >> 16; /* add potential last carry */ 85 sum = ntohs(sum); 86 return (0xffff & ~sum); 87 } 88