in_cksum.h revision 21673 
1/*-
2 * Copyright (c) 1990 The Regents of the University of California.
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 *    notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 *    notice, this list of conditions and the following disclaimer in the
12 *    documentation and/or other materials provided with the distribution.
13 * 3. All advertising materials mentioning features or use of this software
14 *    must display the following acknowledgement:
15 *	This product includes software developed by the University of
16 *	California, Berkeley and its contributors.
17 * 4. Neither the name of the University nor the names of its contributors
18 *    may be used to endorse or promote products derived from this software
19 *    without specific prior written permission.
20 *
21 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
22 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
23 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
24 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
25 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
26 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
27 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
28 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
29 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
30 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
31 * SUCH DAMAGE.
32 *
33 *	from tahoe:	in_cksum.c	1.2	86/01/05
34 *	from:		@(#)in_cksum.c	1.3 (Berkeley) 1/19/91
35 *	from: Id: in_cksum.c,v 1.8 1995/12/03 18:35:19 bde Exp
36 *	$FreeBSD: head/sys/i386/include/in_cksum.h 21673 1997-01-14 07:20:47Z jkh $
37 */
38
39#ifndef _MACHINE_IN_CKSUM_H_
40#define	_MACHINE_IN_CKSUM_H_	1
41
42#include <sys/cdefs.h>
43
44/*
45 * It it useful to have an Internet checksum routine which is inlineable
46 * and optimized specifically for the task of computing IP header checksums
47 * in the normal case (where there are no options and the header length is
48 * therefore always exactly five 32-bit words.
49 */
50#ifdef __GNUC__
51static __inline u_int
52in_cksum_hdr(const struct ip *ip)
53{
54	register u_int sum = 0;
55
56#define ADD(n)	__asm("addl " #n "(%2), %0" : "=r" (sum) : "0" (sum), "r" (ip))
57#define ADDC(n)	__asm("adcl " #n "(%2), %0" : "=r" (sum) : "0" (sum), "r" (ip))
58#define MOP	__asm("adcl         $0, %0" : "=r" (sum) : "0" (sum))
59
60	ADD(0);
61	ADDC(4);
62	ADDC(8);
63	ADDC(12);
64	ADDC(16);
65	MOP;
66	sum = (sum & 0xffff) + (sum >> 16);
67	if (sum > 0xffff)
68		sum -= 0xffff;
69
70	return ~sum & 0xffff;
71}
72
73static __inline void
74in_cksum_update(struct ip *ip)
75{
76	int __tmpsum;
77	__tmpsum = (int)ntohs(ip->ip_sum) + 256;
78	ip->ip_sum = htons(__tmpsum + (__tmpsum >> 16));
79}
80
81#else
82u_int in_cksum_hdr __P((const struct ip *));
83#define	in_cksum_update(ip) \
84	do { \
85		int __tmpsum; \
86		__tmpsum = (int)ntohs(ip->ip_sum) + 256; \
87		ip->ip_sum = htons(__tmpsum + (__tmpsum >> 16)); \
88	} while(0)
89
90#endif
91
92#endif /* _MACHINE_IN_CKSUM_H_ */
93