101 lines
3.4 KiB
C
101 lines
3.4 KiB
C
/*
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* Copyright (c) 1988, 1990 Regents of the University of California.
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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 the University of
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* California, Berkeley and its contributors.
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* 4. Neither the name of the University nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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* from: Utah $Hdr: in_cksum.c 1.1 90/07/09$
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*
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* @(#)in_cksum.c 7.3 (Berkeley) 12/16/90
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*/
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/*
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* in_cksum - checksum routine for the Internet Protocol family.
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*/
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#include "sys/param.h"
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#include "sys/mbuf.h"
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#include "netinet/in.h"
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#include "netinet/in_systm.h"
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extern int oc_cksum();
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/*
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* Checksum routine for the Internet Protocol family.
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*
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* This isn't as bad as it looks. For ip headers the "while" isn't
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* executed and we just drop through to the return statement at the
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* end. For the usual tcp or udp packet (a single header mbuf
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* chained onto a cluster of data, we make exactly one trip through
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* the while (for the header mbuf) and never do the hairy code
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* inside the "if". If fact, if m_copydata & sb_compact are doing
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* their job, we should never do the hairy code inside the "if".
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*/
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in_cksum(m, len)
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register struct mbuf *m;
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register int len;
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{
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register int sum = 0;
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register int i;
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while (len > m->m_len) {
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sum = oc_cksum(mtod(m, u_char *), i = m->m_len, sum);
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m = m->m_next;
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len -= i;
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if (i & 1) {
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/*
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* ouch - we ended on an odd byte with more
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* to do. This xfer is obviously not interested
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* in performance so finish things slowly.
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*/
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register u_char *cp;
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while (len > m->m_len) {
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cp = mtod(m, u_char *);
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if (i & 1) {
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i = m->m_len - 1;
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--len;
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sum += *cp++;
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} else
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i = m->m_len;
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sum = oc_cksum(cp, i, sum);
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m = m->m_next;
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len -= i;
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}
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if (i & 1) {
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cp = mtod(m, u_char *);
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sum += *cp++;
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return (0xffff & ~oc_cksum(cp, len - 1, sum));
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}
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}
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}
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return (0xffff & ~oc_cksum(mtod(m, u_char *), len, sum));
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}
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