1/*
2 * INET		An implementation of the TCP/IP protocol suite for the LINUX
3 *		operating system.  INET is implemented using the  BSD Socket
4 *		interface as the means of communication with the user level.
5 *
6 *		IP/TCP/UDP checksumming routines
7 *
8 * Authors:	Jorge Cwik, <jorge@laser.satlink.net>
9 *		Arnt Gulbrandsen, <agulbra@nvg.unit.no>
10 *		Tom May, <ftom@netcom.com>
11 *		Lots of code moved from tcp.c and ip.c; see those files
12 *		for more names.
13 *
14 *		This program is free software; you can redistribute it and/or
15 *		modify it under the terms of the GNU General Public License
16 *		as published by the Free Software Foundation; either version
17 *		2 of the License, or (at your option) any later version.
18 */
19
20#include <net/checksum.h>
21#include <net/module.h>
22
23#undef PROFILE_CHECKSUM
24
25#ifdef PROFILE_CHECKSUM
26/* these are just for profiling the checksum code with an oscillioscope.. uh */
27#if 0
28#define BITOFF *((unsigned char *)0xb0000030) = 0xff
29#define BITON *((unsigned char *)0xb0000030) = 0x0
30#endif
31#include <asm/io.h>
32#define CBITON LED_ACTIVE_SET(1)
33#define CBITOFF LED_ACTIVE_SET(0)
34#define BITOFF
35#define BITON
36#else
37#define BITOFF
38#define BITON
39#define CBITOFF
40#define CBITON
41#endif
42
43/*
44 * computes a partial checksum, e.g. for TCP/UDP fragments
45 */
46
47#include <asm/delay.h>
48
49__wsum csum_partial(const void *p, int len, __wsum __sum)
50{
51	u32 sum = (__force u32)__sum;
52	const u16 *buff = p;
53	/*
54	* Experiments with ethernet and slip connections show that buff
55	* is aligned on either a 2-byte or 4-byte boundary.
56	*/
57	const void *endMarker = p + len;
58	const void *marker = endMarker - (len % 16);
59#if 0
60	if((int)buff & 0x3)
61		printk("unaligned buff %p\n", buff);
62	__delay(900); /* extra delay of 90 us to test performance hit */
63#endif
64	BITON;
65	while (buff < marker) {
66		sum += *buff++;
67		sum += *buff++;
68		sum += *buff++;
69		sum += *buff++;
70		sum += *buff++;
71		sum += *buff++;
72		sum += *buff++;
73		sum += *buff++;
74	}
75	marker = endMarker - (len % 2);
76	while (buff < marker)
77		sum += *buff++;
78
79	if (endMarker > buff)
80		sum += *(const u8 *)buff;	/* add extra byte separately */
81
82	BITOFF;
83	return (__force __wsum)sum;
84}
85
86EXPORT_SYMBOL(csum_partial);
87