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/*
* INET An implementation of the TCP/IP protocol suite for the LINUX
* operating system. INET is implemented using the BSD Socket
* interface as the means of communication with the user level.
*
* IP/TCP/UDP checksumming routines
*
* Authors: Jorge Cwik, <jorge@laser.satlink.net>
* Arnt Gulbrandsen, <agulbra@nvg.unit.no>
* Tom May, <ftom@netcom.com>
* Lots of code moved from tcp.c and ip.c; see those files
* for more names.
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version
* 2 of the License, or (at your option) any later version.
*/
#include <net/checksum.h>
#include <net/module.h>
#undef PROFILE_CHECKSUM
#ifdef PROFILE_CHECKSUM
/* these are just for profiling the checksum code with an oscillioscope.. uh */
#if 0
#define BITOFF *((unsigned char *)0xb0000030) = 0xff
#define BITON *((unsigned char *)0xb0000030) = 0x0
#endif
#include <asm/io.h>
#define CBITON LED_ACTIVE_SET(1)
#define CBITOFF LED_ACTIVE_SET(0)
#define BITOFF
#define BITON
#else
#define BITOFF
#define BITON
#define CBITOFF
#define CBITON
#endif
/*
* computes a partial checksum, e.g. for TCP/UDP fragments
*/
#include <asm/delay.h>
__wsum csum_partial(const void *p, int len, __wsum __sum)
{
u32 sum = (__force u32)__sum;
const u16 *buff = p;
/*
* Experiments with ethernet and slip connections show that buff
* is aligned on either a 2-byte or 4-byte boundary.
*/
const void *endMarker = p + len;
const void *marker = endMarker - (len % 16);
#if 0
if((int)buff & 0x3)
printk("unaligned buff %p\n", buff);
__delay(900); /* extra delay of 90 us to test performance hit */
#endif
BITON;
while (buff < marker) {
sum += *buff++;
sum += *buff++;
sum += *buff++;
sum += *buff++;
sum += *buff++;
sum += *buff++;
sum += *buff++;
sum += *buff++;
}
marker = endMarker - (len % 2);
while (buff < marker)
sum += *buff++;
if (endMarker > buff)
sum += *(const u8 *)buff; /* add extra byte separately */
BITOFF;
return (__force __wsum)sum;
}
EXPORT_SYMBOL(csum_partial);
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