1 /* 2 * Copyright (c) 1986 Regents of the University of California. 3 * All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 1. Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * 2. Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in the 12 * documentation and/or other materials provided with the distribution. 13 * 3. All advertising materials mentioning features or use of this software 14 * must display the following acknowledgement: 15 * This product includes software developed by the University of 16 * California, Berkeley and its contributors. 17 * 4. Neither the name of the University nor the names of its contributors 18 * may be used to endorse or promote products derived from this software 19 * without specific prior written permission. 20 * 21 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 22 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 23 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 24 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 25 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 26 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 27 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 28 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 29 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 30 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 31 * SUCH DAMAGE. 32 */ 33 34 #ifndef lint 35 static char sccsid[] = "@(#)cksum.tahoe.c 2.4 (Berkeley) 6/1/90"; 36 #endif /* not lint */ 37 38 #include <sys/types.h> 39 40 /* 41 * Checksum routine for Internet Protocol family headers. 42 * 43 * This routine is very heavily used in the network 44 * code and should be modified for each CPU to be as fast as possible. 45 * 46 * This implementation is TAHOE version. 47 */ 48 49 #undef ADDCARRY 50 #define ADDCARRY(sum) { \ 51 if (sum & 0xffff0000) { \ 52 sum &= 0xffff; \ 53 sum++; \ 54 } \ 55 } 56 57 in_cksum(addr, len) 58 register u_short *addr; 59 register int len; 60 { 61 union word { 62 char c[2]; 63 u_short s; 64 } u; 65 register int sum = 0; 66 67 while (len > 0) { 68 /* 69 * add by words. 70 */ 71 while ((len -= 2) >= 0) { 72 if ((int)addr & 0x1) { 73 /* word is not aligned */ 74 u.c[0] = *(char *)addr; 75 u.c[1] = *((char *)addr+1); 76 sum += u.s; 77 addr++; 78 } else 79 sum += *addr++; 80 ADDCARRY(sum); 81 } 82 if (len == -1) 83 /* 84 * Odd number of bytes. 85 */ 86 u.c[0] = *(u_char *)addr; 87 } 88 if (len == -1) { 89 /* The last mbuf has odd # of bytes. Follow the 90 standard (the odd byte is shifted left by 8 bits) */ 91 u.c[1] = 0; 92 sum += u.s; 93 ADDCARRY(sum); 94 } 95 return (~sum & 0xffff); 96 } 97