60 lines
943 B
C
60 lines
943 B
C
/*
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* BIRD Library -- IP One-Complement Checksum
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*
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* (c) 1999 Martin Mares <mj@ucw.cz>
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*
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* Can be freely distributed and used under the terms of the GNU GPL.
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*/
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#include <stdarg.h>
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#include "nest/bird.h"
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#include "checksum.h"
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static u16
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ipsum_calc(void *frag, unsigned len, va_list args)
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{
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u16 sum = 0;
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for(;;)
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{
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u16 *x = frag;
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ASSERT(!(len % 2));
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while (len)
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{
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u16 z = sum + *x++;
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sum = z + (z < sum);
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len -= 2;
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}
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frag = va_arg(args, void *);
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if (!frag)
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break;
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len = va_arg(args, unsigned);
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}
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return sum;
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}
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int
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ipsum_verify(void *frag, unsigned len, ...)
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{
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va_list args;
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u16 sum;
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va_start(args, len);
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sum = ipsum_calc(frag, len, args);
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va_end(args);
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return sum == 0xffff;
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}
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u16
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ipsum_calculate(void *frag, unsigned len, ...)
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{
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va_list args;
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u16 sum;
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va_start(args, len);
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sum = ipsum_calc(frag, len, args);
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va_end(args);
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return 0xffff - sum;
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}
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