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Add an inline function to compute the common-case IP header checksum.

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Garrett Wollman 1996-04-18 15:39:27 +00:00
parent 806a609d46
commit 97f588a78b
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=15291
1 changed files with 76 additions and 0 deletions
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sys/i386/include/in_cksum.h Normal file
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/*-
* Copyright (c) 1990 The Regents of the University of California.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* This product includes software developed by the University of
* California, Berkeley and its contributors.
* 4. Neither the name of the University nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*
* from tahoe: in_cksum.c 1.2 86/01/05
* from: @(#)in_cksum.c 1.3 (Berkeley) 1/19/91
* from: Id: in_cksum.c,v 1.8 1995/12/03 18:35:19 bde Exp
* $Id$
*/
#ifndef _MACHINE_IN_CKSUM_H_
#define _MACHINE_IN_CKSUM_H_ 1
#include <sys/cdefs.h>
/*
* It it useful to have an Internet checksum routine which is inlineable
* and optimized specifically for the task of computing IP header checksums
* in the normal case (where there are no options and the header length is
* therefore always exactly five 32-bit words.
*/
#ifdef __GNUC__
static __inline u_int
in_cksum_hdr(const struct ip *ip)
{
register u_int sum = 0;
#define ADD(n) __asm("addl " #n "(%2), %0" : "=r" (sum) : "0" (sum), "r" (ip))
#define ADDC(n) __asm("adcl " #n "(%2), %0" : "=r" (sum) : "0" (sum), "r" (ip))
#define MOP __asm("adcl $0, %0" : "=r" (sum) : "0" (sum))
ADD(0);
ADDC(4);
ADDC(8);
ADDC(12);
ADDC(16);
MOP;
sum = (sum & 0xffff) + (sum >> 16);
if (sum > 0xffff)
sum -= 0xffff;
return ~sum & 0xffff;
}
#else
u_int in_cksum_hdr __P((const struct ip *));
#endif
#endif /* _MACHINE_IN_CKSUM_H_ */