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skrzyp |
//==========================================================================
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//
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// net/cksum.c
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//
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// Stand-alone network checksum support for RedBoot
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//
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//==========================================================================
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// ####ECOSGPLCOPYRIGHTBEGIN####
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// -------------------------------------------
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// This file is part of eCos, the Embedded Configurable Operating System.
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// Copyright (C) 1998, 1999, 2000, 2001, 2002 Free Software Foundation, Inc.
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//
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// eCos is free software; you can redistribute it and/or modify it under
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// the terms of the GNU General Public License as published by the Free
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// Software Foundation; either version 2 or (at your option) any later
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// version.
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//
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// eCos is distributed in the hope that it will be useful, but WITHOUT
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// ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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// FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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// for more details.
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//
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// You should have received a copy of the GNU General Public License
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// along with eCos; if not, write to the Free Software Foundation, Inc.,
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// 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
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//
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// As a special exception, if other files instantiate templates or use
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// macros or inline functions from this file, or you compile this file
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// and link it with other works to produce a work based on this file,
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// this file does not by itself cause the resulting work to be covered by
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// the GNU General Public License. However the source code for this file
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// must still be made available in accordance with section (3) of the GNU
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// General Public License v2.
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//
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// This exception does not invalidate any other reasons why a work based
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// on this file might be covered by the GNU General Public License.
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// -------------------------------------------
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// ####ECOSGPLCOPYRIGHTEND####
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//==========================================================================
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//#####DESCRIPTIONBEGIN####
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//
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// Author(s): gthomas
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// Contributors: gthomas
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// Date: 2000-07-14
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// Purpose:
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// Description:
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//
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// This code is part of RedBoot (tm).
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//
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//####DESCRIPTIONEND####
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//
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//==========================================================================
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#include <net/net.h>
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/*
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* Do a one's complement checksum.
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* The data being checksum'd is in network byte order.
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* The returned checksum is in network byte order.
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*/
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unsigned short
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__sum(word *w, int len, int init_sum)
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{
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int sum = init_sum;
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union {
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volatile unsigned char c[2];
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volatile unsigned short s;
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} su;
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union {
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volatile unsigned short s[2];
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volatile int i;
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} iu;
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while ((len -= 2) >= 0)
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sum += *w++;
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if (len == -1) {
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su.c[0] = *(char *)w;
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su.c[1] = 0;
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sum += su.s;
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}
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iu.i = sum;
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sum = iu.s[0] + iu.s[1];
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if (sum > 65535)
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sum -= 65535;
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su.s = ~sum;
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return (su.c[0] << 8) | su.c[1];
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}
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/*
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* Compute a partial checksum for the UDP/TCP pseudo header.
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*/
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int
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__pseudo_sum(ip_header_t *ip)
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{
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int sum;
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word *p;
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union {
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volatile unsigned char c[2];
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volatile unsigned short s;
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} su;
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p = (word *)ip->source;
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sum = *p++;
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sum += *p++;
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sum += *p++;
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sum += *p++;
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su.c[0] = 0;
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su.c[1] = ip->protocol;
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sum += su.s;
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sum += ip->length;
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return sum;
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}
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