/* * Copyright (c) 1986 Regents of the University of California. * All rights reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * 3. All advertising materials mentioning features or use of this software * must display the following acknowledgement: * This product includes software developed by the University of * California, Berkeley and its contributors. * 4. Neither the name of the University nor the names of its contributors * may be used to endorse or promote products derived from this software * without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF * SUCH DAMAGE. */ #ifndef lint static char sccsid[] = "@(#)cksum.tahoe.c 2.4 (Berkeley) 6/1/90"; #endif /* not lint */ #include <sys/types.h> /* * Checksum routine for Internet Protocol family headers. * * This routine is very heavily used in the network * code and should be modified for each CPU to be as fast as possible. * * This implementation is TAHOE version. */ #undef ADDCARRY #define ADDCARRY(sum) { \ if (sum & 0xffff0000) { \ sum &= 0xffff; \ sum++; \ } \ } in_cksum(addr, len) register u_short *addr; register int len; { union word { char c[2]; u_short s; } u; register int sum = 0; while (len > 0) { /* * add by words. */ while ((len -= 2) >= 0) { if ((int)addr & 0x1) { /* word is not aligned */ u.c[0] = *(char *)addr; u.c[1] = *((char *)addr+1); sum += u.s; addr++; } else sum += *addr++; ADDCARRY(sum); } if (len == -1) /* * Odd number of bytes. */ u.c[0] = *(u_char *)addr; } if (len == -1) { /* The last mbuf has odd # of bytes. Follow the standard (the odd byte is shifted left by 8 bits) */ u.c[1] = 0; sum += u.s; ADDCARRY(sum); } return (~sum & 0xffff); }