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/*
* Network checksum routines
*
* Copyright (C) 1999 Hewlett-Packard Co
* Copyright (C) 1999 Stephane Eranian <eranian@hpl.hp.com>
*
* Most of the code coming from arch/alpha/lib/checksum.c
*
* This file contains network checksum routines that are better done
* in an architecture-specific manner due to speed..
*/
#include <linux/string.h>
#include <asm/byteorder.h>
static inline unsigned short
from64to16(unsigned long x)
{
/* add up 32-bit words for 33 bits */
x = (x & 0xffffffff) + (x >> 32);
/* add up 16-bit and 17-bit words for 17+c bits */
x = (x & 0xffff) + (x >> 16);
/* add up 16-bit and 2-bit for 16+c bit */
x = (x & 0xffff) + (x >> 16);
/* add up carry.. */
x = (x & 0xffff) + (x >> 16);
return x;
}
/*
* computes the checksum of the TCP/UDP pseudo-header
* returns a 16-bit checksum, already complemented.
*/
unsigned short int csum_tcpudp_magic(unsigned long saddr,
unsigned long daddr,
unsigned short len,
unsigned short proto,
unsigned int sum)
{
return ~from64to16(saddr + daddr + sum +
((unsigned long) ntohs(len) << 16) +
((unsigned long) proto << 8));
}
unsigned int csum_tcpudp_nofold(unsigned long saddr,
unsigned long daddr,
unsigned short len,
unsigned short proto,
unsigned int sum)
{
unsigned long result;
result = (saddr + daddr + sum +
((unsigned long) ntohs(len) << 16) +
((unsigned long) proto << 8));
/* Fold down to 32-bits so we don't loose in the typedef-less network stack. */
/* 64 to 33 */
result = (result & 0xffffffff) + (result >> 32);
/* 33 to 32 */
result = (result & 0xffffffff) + (result >> 32);
return result;
}
extern unsigned long do_csum (const unsigned char *, long);
/*
* This is a version of ip_compute_csum() optimized for IP headers,
* which always checksum on 4 octet boundaries.
*/
unsigned short ip_fast_csum(unsigned char * iph, unsigned int ihl)
{
return ~do_csum(iph, ihl*4);
}
/*
* computes the checksum of a memory block at buff, length len,
* and adds in "sum" (32-bit)
*
* returns a 32-bit number suitable for feeding into itself
* or csum_tcpudp_magic
*
* this function must be called with even lengths, except
* for the last fragment, which may be odd
*
* it's best to have buff aligned on a 32-bit boundary
*/
unsigned int csum_partial(const unsigned char * buff, int len, unsigned int sum)
{
unsigned long result = do_csum(buff, len);
/* add in old sum, and carry.. */
result += sum;
/* 32+c bits -> 32 bits */
result = (result & 0xffffffff) + (result >> 32);
return result;
}
/*
* this routine is used for miscellaneous IP-like checksums, mainly
* in icmp.c
*/
unsigned short ip_compute_csum(unsigned char * buff, int len)
{
return ~do_csum(buff,len);
}
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