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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);

/*

 * 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);

}