85 lines
2.6 KiB
C
85 lines
2.6 KiB
C
/* $NetBSD: in_cksum.c,v 1.1 1996/09/30 16:34:47 ws Exp $ */
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/*
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* Copyright (C) 1995, 1996 Wolfgang Solfrank.
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* Copyright (C) 1995, 1996 TooLs GmbH.
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. All advertising materials mentioning features or use of this software
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* must display the following acknowledgement:
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* This product includes software developed by TooLs GmbH.
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* 4. The name of TooLs GmbH may not be used to endorse or promote products
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* derived from this software without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY TOOLS GMBH ``AS IS'' AND ANY EXPRESS OR
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* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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* IN NO EVENT SHALL TOOLS GMBH BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
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* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
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* OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
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* WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
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* OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
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* ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#include <sys/param.h>
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#include <sys/mbuf.h>
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/*
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* First cut for in_cksum.
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* This code is in C and should be optimized for PPC later.
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*/
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#define REDUCE (sum = (sum & 0xffff) + (sum >> 16))
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#define ROL (sum = sum << 8)
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#define ADDB (ROL, sum += *w, byte_swapped ^= 1)
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#define ADDS (sum += *(u_short *)w)
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#define SHIFT(n) (w += (n), mlen -= (n))
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#define ADDCARRY do { while (sum > 0xffff) REDUCE; } while (0)
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int
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in_cksum(m, len)
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struct mbuf *m;
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int len;
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{
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u_char *w;
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u_int sum = 0;
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int mlen;
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int byte_swapped = 0;
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for (; m && len; m = m->m_next) {
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if (m->m_len == 0)
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continue;
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w = mtod(m, u_char *);
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mlen = m->m_len;
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if (len < mlen)
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mlen = len;
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len -= mlen;
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if ((long)w & 1) {
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REDUCE;
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ADDB;
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SHIFT(1);
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}
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while (mlen >= 2) {
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ADDS;
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SHIFT(2);
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}
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REDUCE;
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if (mlen == 1)
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ADDB;
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}
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if (byte_swapped) {
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REDUCE;
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ROL;
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}
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ADDCARRY;
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return sum ^ 0xffff;
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}
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