checksum.h

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/* $Id: checksum.h,v 1.8 2000/02/18 00:24:48 ralf Exp $
 *
 * This file is subject to the terms and conditions of the GNU General Public
 * License.  See the file "COPYING" in the main directory of this archive
 * for more details.
 *
 * Copyright (C) 1995, 1996, 1997, 1998 by Ralf Baechle
 */
#ifndef _ASM_CHECKSUM_H
#define _ASM_CHECKSUM_H

#include <asm/uaccess.h>

/*
 * 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);

/*
 * this is a new version of the above that records errors it finds in *errp,
 * but continues and zeros the rest of the buffer.
 */
#define csum_partial_copy_nocheck csum_partial_copy

/*
 * this is a new version of the above that records errors it finds in *errp,
 * but continues and zeros the rest of the buffer.
 */
unsigned int csum_partial_copy_from_user(const char *src, char *dst, int len,
                                         unsigned int sum, int *errp);

/*
 * Copy and checksum to user
 */
#define HAVE_CSUM_COPY_USER
extern inline unsigned int
csum_and_copy_to_user (const char *src, char *dst,
                       int len, int sum, int *err_ptr)
{
	sum = csum_partial(src, len, sum);

	if (copy_to_user(dst, src, len)) {
		*err_ptr = -EFAULT;
		return -1;
	}

	return sum;
}

/*
 * the same as csum_partial, but copies from user space (but on MIPS
 * we have just one address space, so this is identical to the above)
 *
 * this is obsolete and will go away.
 */
#define csum_partial_copy_fromuser csum_partial_copy
unsigned int csum_partial_copy(const char *src, char *dst, int len, unsigned int sum);
  
/*
 *	Fold a partial checksum without adding pseudo headers
 */
static inline unsigned short int csum_fold(unsigned int sum)
{
	__asm__("
	.set	noat            
	sll	$1,%0,16
	addu	%0,$1
	sltu	$1,%0,$1
	srl	%0,%0,16
	addu	%0,$1
	xori	%0,0xffff
	.set	at"
	: "=r" (sum)
	: "0" (sum)
	: "$1");

 	return sum;
}
 
/*
 *	This is a version of ip_compute_csum() optimized for IP headers,
 *	which always checksum on 4 octet boundaries.
 *
 *	By Jorge Cwik <[e-mail]>, adapted for linux by
 *	Arnt Gulbrandsen.
 */
static inline unsigned short ip_fast_csum(unsigned char * iph,
					  unsigned int ihl)
{
	unsigned int sum;
	unsigned long dummy;

	/*
	 * This is for 32-bit MIPS processors.
	 */
	__asm__ __volatile__("
	.set	noreorder
	.set	noat
	lw	%0,(%1)
	subu	%2,4
	#blez	%2,2f
	sll	%2,2			# delay slot

	lw	%3,4(%1)
	addu	%2,%1			# delay slot
	addu	%0,%3
	sltu	$1,%0,%3
	lw	%3,8(%1)
	addu	%0,$1
	addu	%0,%3
	sltu	$1,%0,%3
	lw	%3,12(%1)
	addu	%0,$1
	addu	%0,%3
	sltu	$1,%0,%3
	addu	%0,$1

1:	lw	%3,16(%1)
	addiu	%1,4
	addu	%0,%3
	sltu	$1,%0,%3
	bne	%2,%1,1b
	addu	%0,$1			# delay slot

2:	.set	at
	.set	reorder"
	: "=&r" (sum), "=&r" (iph), "=&r" (ihl), "=&r" (dummy)
	: "1" (iph), "2" (ihl)
	: "$1");

	return csum_fold(sum);
}

/*
 * computes the checksum of the TCP/UDP pseudo-header
 * returns a 16-bit checksum, already complemented
 */
static inline unsigned long csum_tcpudp_nofold(unsigned long saddr,
                                               unsigned long daddr,
                                               unsigned short len,
                                               unsigned short proto,
                                               unsigned int sum)
{
    __asm__("
	.set	noat
	addu	%0,%2
	sltu	$1,%0,%2
	addu	%0,$1

	addu	%0,%3
	sltu	$1,%0,%3
	addu	%0,$1

	addu	%0,%4
	sltu	$1,%0,%4
	addu	%0,$1
	.set	at"
	: "=r" (sum)
	: "0" (daddr), "r"(saddr),
#ifdef __MIPSEL__
	    "r" ((ntohs(len)<<16)+proto*256),
#else
	    "r" (((proto)<<16)+len),
#endif
	    "r"(sum)
	: "$1");

	return sum;
}

/*
 * computes the checksum of the TCP/UDP pseudo-header
 * returns a 16-bit checksum, already complemented
 */
static inline unsigned short int csum_tcpudp_magic(unsigned long saddr,
						   unsigned long daddr,
						   unsigned short len,
						   unsigned short proto,
						   unsigned int sum)
{
	return csum_fold(csum_tcpudp_nofold(saddr,daddr,len,proto,sum));
}

/*
 * this routine is used for miscellaneous IP-like checksums, mainly
 * in icmp.c
 */
static inline unsigned short ip_compute_csum(unsigned char * buff, int len)
{
	return csum_fold(csum_partial(buff, len, 0));
}

#define _HAVE_ARCH_IPV6_CSUM
static __inline__ unsigned short int csum_ipv6_magic(struct in6_addr *saddr,
						     struct in6_addr *daddr,
						     __u32 len,
						     unsigned short proto,
						     unsigned int sum) 
{
	__asm__("
		.set	noreorder
		.set	noat
		addu	%0,%5		# proto (long in network byte order)
		sltu	$1,%0,%5
		addu	%0,$1

		addu	%0,%6		# csum
		sltu	$1,%0,%6
		lw	%1,0(%2)	# four words source address
		addu	%0,$1
		addu	%0,%1
		sltu	$1,%0,$1

		lw	%1,4(%2)
		addu	%0,$1
		addu	%0,%1
		sltu	$1,%0,$1

		lw	%1,8(%2)
		addu	%0,$1
		addu	%0,%1
		sltu	$1,%0,$1

		lw	%1,12(%2)
		addu	%0,$1
		addu	%0,%1
		sltu	$1,%0,$1

		lw	%1,0(%3)
		addu	%0,$1
		addu	%0,%1
		sltu	$1,%0,$1

		lw	%1,4(%3)
		addu	%0,$1
		addu	%0,%1
		sltu	$1,%0,$1

		lw	%1,8(%3)
		addu	%0,$1
		addu	%0,%1
		sltu	$1,%0,$1

		lw	%1,12(%3)
		addu	%0,$1
		addu	%0,%1
		sltu	$1,%0,$1
		.set	noat
		.set	noreorder"
		: "=r" (sum),
		  "=r" (proto)
		: "r" (saddr),
		  "r" (daddr),
		  "0" (htonl(len)),
		  "1" (htonl(proto)),
		  "r"(sum)
		: "$1");

	return csum_fold(sum);
}

#endif /* _ASM_CHECKSUM_H */