GCC Code Coverage Report
Directory: ./ Exec Total Coverage
File: usr.sbin/ospf6d/iso_cksum.c Lines: 0 17 0.0 %
Date: 2017-11-07 Branches: 0 10 0.0 %

Line Branch Exec Source
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/*	$OpenBSD: iso_cksum.c,v 1.1 2007/10/08 10:44:50 norby Exp $ */
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/*
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 * Copyright (c) 2005 Claudio Jeker <claudio@openbsd.org>
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 *
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 * Permission to use, copy, modify, and distribute this software for any
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 * purpose with or without fee is hereby granted, provided that the above
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 * copyright notice and this permission notice appear in all copies.
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 *
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 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
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 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
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 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
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 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
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 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
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 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
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 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
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 */
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#include <sys/types.h>
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#include "ospf6d.h"
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/* implementation of Fletcher Checksum -- see RFC 1008 for more info */
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/* pos needs to be 0 for verify and 2 <= pos < len for calculation */
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u_int16_t
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iso_cksum(void *buf, u_int16_t len, u_int16_t pos)
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{
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	u_int8_t	*p = buf;
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	int		 c0 = 0, c1 = 0, x;	/* counters */
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	u_int16_t	 sop;
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	sop = len - pos - 1;	/* pos is an offset (pos 2 is 3rd element) */
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	p += 2;			/* jump over age field */
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	len -= 2;
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	while (len--) {
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		c0 += *p++;
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		c1 += c0;
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		if ((len & 0xfff) == 0) {
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			/* overflow protection */
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			c0 %= 255;
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			c1 %= 255;
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		}
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	}
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	if (pos) {
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		x = ((sop * c0 - c1)) % 255;
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		if (x <= 0)
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			x += 255;
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		c1 = 510 - c0 - x;
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		if (c1 > 255)
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			c1 -= 255;
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		c0 = x;
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	}
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	return (c0 << 8 | c1);
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}