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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.
*
* MIPS specific IP/TCP/UDP checksumming routines
*
* Authors: Ralf Baechle, <ralf@waldorf-gmbh.de>
* 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.
*
* $Id: checksum.c,v 1.3 1997/12/01 17:57:34 ralf Exp $
*/
#include <net/checksum.h>
#include <linux/types.h>
#include <asm/byteorder.h>
#include <asm/string.h>
#include <asm/uaccess.h>
static inline unsigned short from32to16(unsigned int x)
{
/* 32 bits --> 16 bits + carry */
x = (x & 0xffff) + (x >> 16);
/* 16 bits + carry --> 16 bits including carry */
x = (x & 0xffff) + (x >> 16);
return (unsigned short)x;
}
static inline unsigned int do_csum(const unsigned char * buff, int len)
{
int odd, count;
unsigned int result = 0;
if (len <= 0)
goto out;
odd = 1 & (unsigned long) buff;
if (odd) {
result = be16_to_cpu(*buff);
len--;
buff++;
}
count = len >> 1; /* nr of 16-bit words.. */
if (count) {
if (2 & (unsigned long) buff) {
result += *(unsigned short *) buff;
count--;
len -= 2;
buff += 2;
}
count >>= 1; /* nr of 32-bit words.. */
if (count) {
unsigned int carry = 0;
do {
unsigned int w = *(unsigned int *) buff;
count--;
buff += 4;
result += carry;
result += w;
carry = (w > result);
} while (count);
result += carry;
result = (result & 0xffff) + (result >> 16);
}
if (len & 2) {
result += *(unsigned short *) buff;
buff += 2;
}
}
if (len & 1)
result += le16_to_cpu(*buff);
result = from32to16(result);
if (odd)
result = ((result >> 8) & 0xff) | ((result & 0xff) << 8);
out:
return result;
}
/*
* computes a partial checksum, e.g. for TCP/UDP fragments
*/
unsigned int csum_partial(const unsigned char *buff, int len, unsigned int sum)
{
unsigned int result = do_csum(buff, len);
/* add in old sum, and carry.. */
result += sum;
if(sum > result)
result += 1;
return result;
}
/*
* copy while checksumming, otherwise like csum_partial
*/
unsigned int csum_partial_copy(const char *src, char *dst,
int len, unsigned int sum)
{
/*
* It's 2:30 am and I don't feel like doing it real ...
* This is lots slower than the real thing (tm)
*/
sum = csum_partial(src, len, sum);
memcpy(dst, src, len);
return sum;
}
/*
* Copy from userspace and compute checksum. If we catch an exception
* then zero the rest of the buffer.
*/
unsigned int csum_partial_copy_from_user (const char *src, char *dst,
int len, unsigned int sum,
int *err_ptr)
{
int missing;
missing = copy_from_user(dst, src, len);
if (missing) {
memset(dst + len - missing, 0, missing);
*err_ptr = -EFAULT;
}
return csum_partial(dst, len, sum);
}
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