1/* $Id: old_checksum.c,v 1.1.1.1 2007-08-03 18:51:41 $
2 *
3 * INET		An implementation of the TCP/IP protocol suite for the LINUX
4 *		operating system.  INET is implemented using the  BSD Socket
5 *		interface as the means of communication with the user level.
6 *
7 *		IP/TCP/UDP checksumming routines
8 *
9 * Authors:	Jorge Cwik, <jorge@laser.satlink.net>
10 *		Arnt Gulbrandsen, <agulbra@nvg.unit.no>
11 *		Tom May, <ftom@netcom.com>
12 *		Lots of code moved from tcp.c and ip.c; see those files
13 *		for more names.
14 *
15 *		This program is free software; you can redistribute it and/or
16 *		modify it under the terms of the GNU General Public License
17 *		as published by the Free Software Foundation; either version
18 *		2 of the License, or (at your option) any later version.
19 */
20
21#include <net/checksum.h>
22#include <net/module.h>
23
24#undef PROFILE_CHECKSUM
25
26#ifdef PROFILE_CHECKSUM
27/* these are just for profiling the checksum code with an oscillioscope.. uh */
28#include <asm/io.h>
29#define CBITON LED_ACTIVE_SET(1)
30#define CBITOFF LED_ACTIVE_SET(0)
31#define BITOFF
32#define BITON
33#else
34#define BITOFF
35#define BITON
36#define CBITOFF
37#define CBITON
38#endif
39
40/*
41 * computes a partial checksum, e.g. for TCP/UDP fragments
42 */
43
44#include <asm/delay.h>
45
46__wsum csum_partial(const void *p, int len, __wsum __sum)
47{
48	u32 sum = (__force u32)__sum;
49	const u16 *buff = p;
50	/*
51	* Experiments with ethernet and slip connections show that buff
52	* is aligned on either a 2-byte or 4-byte boundary.
53	*/
54	const void *endMarker = p + len;
55	const void *marker = endMarker - (len % 16);
56	BITON;
57	while (buff < marker) {
58		sum += *buff++;
59		sum += *buff++;
60		sum += *buff++;
61		sum += *buff++;
62		sum += *buff++;
63		sum += *buff++;
64		sum += *buff++;
65		sum += *buff++;
66	}
67	marker = endMarker - (len % 2);
68	while (buff < marker)
69		sum += *buff++;
70
71	if (endMarker > buff)
72		sum += *(const u8 *)buff;	/* add extra byte seperately */
73
74	BITOFF;
75	return (__force __wsum)sum;
76}
77
78EXPORT_SYMBOL(csum_partial);
79