checksum.h

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/* $Id: checksum.h,v 1.6 2000/02/18 22:06:19 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, 1999 by Ralf Baechle
 * Copyright (C) 1999 Silicon Graphics, Inc.
 */
#ifndef _ASM_CHECKSUM_H
#define _ASM_CHECKSUM_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 * this is obsolete and will go away.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 processors ...  but works just fine for 64-bit
	 * processors for now ...  XXX
	 */
	__asm__ __volatile__("
	.set	noreorder
	.set	noat
	lw	%0, (%1)
	subu	%2, 4
	dsll	%2, 2

	lw	%3, 4(%1)
	daddu	%2, %1
	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)
	daddiu	%1, 4
	addu	%0, %3
	sltu	$1, %0, %3
	bne	%2, %1, 1b
	 addu	%0, $1

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
	daddu	%0, %2
	daddu	%0, %3
	daddu	%0, %4
	dsll32	$1, %0, 0
	daddu	%0, $1		# never results in an overflow
	dsrl32	%0, %0, 0
	.set	at"
	: "=r" (sum)
	: "0" (sum), "r"(saddr), "r" (daddr),
#ifdef __MIPSEL__
	    "r" ((ntohs(len)<<16)+proto*256)
#else
	    "r" (((proto)<<16)+len)
#endif
	: "$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 */