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
  36 static unsigned short do_csum(const unsigned char *buff, int len)__attribute__((l1_text));
  37 #endif
  38
  39 static 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  */
  75 unsigned 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  */
  92 unsigned 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  */
 112 unsigned 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
 121 unsigned int
 122 csum_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
 135 unsigned 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 }