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/*

 * 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));

}

/*

 * Do a 64-bit checksum on an arbitrary memory area..

 *

 * This isn't a great routine, but it's not _horrible_ either. The

 * inner loop could be unrolled a bit further, and there are better

 * ways to do the carry, but this is reasonable.

 */

static inline unsigned long do_csum(unsigned char * buff, int len)

{

        int odd, count;

        unsigned long result = 0;

        if (len <= 0)

                goto out;

        odd = 1 & (unsigned long) buff;

        if (odd) {

                result = *buff << 8;

                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) {

                        if (4 & (unsigned long) buff) {

                                result += *(unsigned int *) buff;

                                count--;

                                len -= 4;

                                buff += 4;

                        }

                        count >>= 1;    /* nr of 64-bit words.. */

                        if (count) {

                                unsigned long carry = 0;

                                do {

                                        unsigned long w = *(unsigned long *) buff;

                                        count--;

                                        buff += 8;

                                        result += carry;

                                        result += w;

                                        carry = (w > result);

                                } while (count);

                                result += carry;

                                result = (result & 0xffffffff) + (result >> 32);

                        }

                        if (len & 4) {

                                result += *(unsigned int *) buff;

                                buff += 4;

                        }

                }

                if (len & 2) {

                        result += *(unsigned short *) buff;

                        buff += 2;

                }

        }

        if (len & 1)

                result += *buff;

        result = from64to16(result);

        if (odd)

                result = ((result >> 8) & 0xff) | ((result & 0xff) << 8);

out:

        return result;

}

/*

 *      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(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 ~from64to16(do_csum(buff,len));

}