LXR linux/arch/blackfin/lib/checksum.c

   1/*
   2 * File:         arch/blackfin/lib/checksum.c
   3 * Based on:     none - original work
   4 * Author:
   5 *
   6 * Created:
   7 * Description:  An implementation of the TCP/IP protocol suite for the LINUX
   8 *               operating system.  INET is implemented using the  BSD Socket
   9 *               interface as the means of communication with the user level.
  10 *
  11 * Modified:
  12 *               Copyright 2004-2006 Analog Devices Inc.
  13 *
  14 * Bugs:         Enter bugs at http://blackfin.uclinux.org/
  15 *
  16 * This program is free software; you can redistribute it and/or modify
  17 * it under the terms of the GNU General Public License as published by
  18 * the Free Software Foundation; either version 2 of the License, or
  19 * (at your option) any later version.
  20 *
  21 * This program is distributed in the hope that it will be useful,
  22 * but WITHOUT ANY WARRANTY; without even the implied warranty of
  23 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  24 * GNU General Public License for more details.
  25 *
  26 * You should have received a copy of the GNU General Public License
  27 * along with this program; if not, see the file COPYING, or write
  28 * to the Free Software Foundation, Inc.,
  29 * 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
  30 */
  31
  32#include <net/checksum.h>
  33#include <asm/checksum.h>
  34
  35#ifdef CONFIG_IP_CHECKSUM_L1
  36static unsigned short do_csum(const unsigned char *buff, int len)__attribute__((l1_text));
  37#endif
  38
  39static unsigned short do_csum(const unsigned char *buff, int len)
  40{
  41        register unsigned long sum = 0;
  42        int swappem = 0;
  43
  44        if (1 & (unsigned long)buff) {
  45                sum = *buff << 8;
  46                buff++;
  47                len--;
  48                ++swappem;
  49        }
  50
  51        while (len > 1) {
  52                sum += *(unsigned short *)buff;
  53                buff += 2;
  54                len -= 2;
  55        }
  56
  57        if (len > 0)
  58                sum += *buff;
  59
  60        /*  Fold 32-bit sum to 16 bits */
  61        while (sum >> 16)
  62                sum = (sum & 0xffff) + (sum >> 16);
  63
  64        if (swappem)
  65                sum = ((sum & 0xff00) >> 8) + ((sum & 0x00ff) << 8);
  66
  67        return sum;
  68
  69}
  70
  71/*
  72 *      This is a version of ip_compute_csum() optimized for IP headers,
  73 *      which always checksum on 4 octet boundaries.
  74 */
  75unsigned short ip_fast_csum(unsigned char *iph, unsigned int ihl)
  76{
  77        return ~do_csum(iph, ihl * 4);
  78}
  79
  80/*
  81 * computes the checksum of a memory block at buff, length len,
  82 * and adds in "sum" (32-bit)
  83 *
  84 * returns a 32-bit number suitable for feeding into itself
  85 * or csum_tcpudp_magic
  86 *
  87 * this function must be called with even lengths, except
  88 * for the last fragment, which may be odd
  89 *
  90 * it's best to have buff aligned on a 32-bit boundary
  91 */
  92unsigned int csum_partial(const unsigned char *buff, int len, unsigned int sum)
  93{
  94        /*
  95         * Just in case we get nasty checksum data...
  96         * Like 0xffff6ec3 in the case of our IPv6 multicast header.
  97         * We fold to begin with, as well as at the end.
  98         */
  99        sum = (sum & 0xffff) + (sum >> 16);
 100
 101        sum += do_csum(buff, len);
 102
 103        sum = (sum & 0xffff) + (sum >> 16);
 104
 105        return sum;
 106}
 107
 108/*
 109 * this routine is used for miscellaneous IP-like checksums, mainly
 110 * in icmp.c
 111 */
 112unsigned short ip_compute_csum(const unsigned char *buff, int len)
 113{
 114        return ~do_csum(buff, len);
 115}
 116
 117/*
 118 * copy from fs while checksumming, otherwise like csum_partial
 119 */
 120
 121unsigned int
 122csum_partial_copy_from_user(const unsigned char *src, unsigned char *dst,
 123                            int len, int sum, int *csum_err)
 124{
 125        if (csum_err)
 126                *csum_err = 0;
 127        memcpy(dst, src, len);
 128        return csum_partial(dst, len, sum);
 129}
 130
 131/*
 132 * copy from ds while checksumming, otherwise like csum_partial
 133 */
 134
 135unsigned int csum_partial_copy(const unsigned char *src, unsigned char *dst,
 136                               int len, int sum)
 137{
 138        memcpy(dst, src, len);
 139        return csum_partial(dst, len, sum);
 140}
 141