105 lines
3.0 KiB
C
105 lines
3.0 KiB
C
/* $NetBSD: in4_cksum.c,v 1.17 2008/02/12 13:05:55 joerg Exp $ */
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/*-
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* Copyright (c) 2008 Joerg Sonnenberger <joerg@NetBSD.org>.
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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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*
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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
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* the documentation and/or other materials provided with the
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* distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
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* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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* COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING,
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* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
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* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
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* 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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#include <sys/cdefs.h>
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__KERNEL_RCSID(0, "$NetBSD: in4_cksum.c,v 1.17 2008/02/12 13:05:55 joerg Exp $");
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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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#include <netinet/ip.h>
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/*
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* Checksum of the IPv4 pseudo header.
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*
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* off is supposed to be the skipped IPv4 header, len is the payload size.
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*/
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int
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in4_cksum(struct mbuf *m, u_int8_t nxt, int off, int len)
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{
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uint32_t sum;
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uint16_t *w;
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if (__predict_false(off < sizeof(struct ip)))
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panic("in4_cksum: offset too short for IP header");
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if (__predict_false(m->m_len < sizeof(struct ip)))
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panic("in4_cksum: mbuf too short for IP header");
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if (nxt == 0)
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return cpu_in_cksum(m, len, off, 0);
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/*
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* Compute the equivalent of:
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* struct ipovly ip;
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*
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* bzero(sizeof(*ip));
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* ip.ih_pr = nxt;
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* ip.ip_len = htons(len);
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* ip.ih_src = mtod(m, struct ip *)->ip_src;
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* ip.ih_dst = mtod(m, struct ip *)->ip_dst;
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* sum = one_add(&ip);
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*/
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#if BYTE_ORDER == LITTLE_ENDIAN
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sum = ((len & 0xffff) + nxt) << 8;
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#else
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sum = (len & 0xffff) + nxt;
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#endif
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w = (uint16_t *)(mtod(m, char *) + offsetof(struct ip, ip_src));
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if (__predict_true((uintptr_t)w % 2 == 0)) {
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sum += w[0];
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sum += w[1];
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sum += w[2];
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sum += w[3];
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} else {
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uint32_t partial;
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w = (void *)((uintptr_t)w - 1);
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#if BYTE_ORDER == LITTLE_ENDIAN
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partial = w[0] & 0xff00;
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#else
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partial = w[0] & 0x00ff;
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#endif
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partial += w[1];
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partial += w[2];
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partial += w[3];
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#if BYTE_ORDER == LITTLE_ENDIAN
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partial += w[4] & 0x00ff;
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#else
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partial += w[4] & 0xff00;
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#endif
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sum += partial << 8;
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}
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return cpu_in_cksum(m, len, off, sum);
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}
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