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/*

 * INET         An implementation of the TCP/IP protocol suite for the LINUX

 *              operating system.  INET is implemented using the  BSD Socket

 *              interface as the means of communication with the user level.

 *

 *              IP/TCP/UDP checksumming routines

 *

 * Authors:     Jorge Cwik, <jorge@laser.satlink.net>

 *              Arnt Gulbrandsen, <agulbra@nvg.unit.no>

 *              Tom May, <ftom@netcom.com>

 *              Lots of code moved from tcp.c and ip.c; see those files

 *              for more names.

 *

 * Adapted for PowerPC by Gary Thomas <gdt@mc.com>

 *

 *              This program is free software; you can redistribute it and/or

 *              modify it under the terms of the GNU General Public License

 *              as published by the Free Software Foundation; either version

 *              2 of the License, or (at your option) any later version.

 */

#include <net/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)

{

        unsigned long result = ~_csum_partial(buff, len, sum);

#if 0   

printk("Csum partial(%x, %d, %x) = %x\n", buff, len, sum, result);

dump_buf(buff, len);

#endif

        return result;

}

/*

 * the same as csum_partial, but copies from src while it

 * checksums

 *

 * here even more important to align src and dst on a 32-bit boundary

 */

unsigned int csum_partial_copy(const char *src, char *dst, int len, int sum)

{

        /*

         * The whole idea is to do the copy and the checksum at

         * the same time, but we do it the easy way now.

         *

         * At least csum on the source, not destination, for cache

         * reasons..

         */

        sum = csum_partial(src, len, sum);

        memcpy(dst, src, len);

        return sum;

}

extern unsigned short _ip_fast_csum(unsigned char *buf);

unsigned short

ip_fast_csum(unsigned char *buf, unsigned int len)

{

        unsigned short _val;

        _val = _ip_fast_csum(buf);

#if 0

        printk("IP CKSUM(%x, %d) = %x\n", buf, len, _val);

        dump_buf(buf, len*4);

#endif  

        return (_val);

}

extern unsigned short _ip_compute_csum(unsigned char *buf, int len);

unsigned short

ip_compute_csum(unsigned char *buf, int len)

{

        unsigned short _val;

        _val = _ip_compute_csum(buf, len);

#if 0

        printk("Compute IP CKSUM(%x, %d) = %x\n", buf, len, _val);

        dump_buf(buf, len);

#endif  

        return (_val);

}

unsigned short

_udp_check(unsigned char *buf, int len, int saddr, int daddr, int hdr);

unsigned short

udp_check(unsigned char *buf, int len, int saddr, int daddr)

{

        unsigned short _val;

        int hdr;

        hdr = (len << 16) + IPPROTO_UDP;

        _val = _udp_check(buf, len, saddr, daddr, hdr);

#if 0

        printk("UDP CSUM(%x,%d,%x,%x) = %x\n", buf, len, saddr, daddr, _val);

        dump_buf(buf, len);

#endif  

        return (_val);

}

unsigned short

_tcp_check(unsigned char *buf, int len, int saddr, int daddr, int hdr);

unsigned short

csum_tcpudp_magic(unsigned long saddr, unsigned long daddr, unsigned short len, unsigned short proto, unsigned int sum)

{

        unsigned short _val;

        _val = _csum_tcpudp_magic(saddr, daddr, sum, (len<<16)+proto);

#if 0

        printk("TCP Magic(%x, %x, %x, %x) = %x\n", saddr, daddr, (len<<16)+proto, sum, _val);

#endif

        return (_val);

}

/*

 *      Fold a partial checksum without adding pseudo headers

 */

unsigned short csum_fold(unsigned int sum)

{

        sum = (sum & 0xffff) + (sum >> 16);

        sum = (sum & 0xffff) + (sum >> 16);

        return ~sum;

}