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 <linux/module.h>
  33 #include <net/checksum.h>
  34 #include <asm/checksum.h>
  35
  36 #ifdef CONFIG_IP_CHECKSUM_L1
  37 static unsigned short do_csum(const unsigned char *buff, int len)__attribute__((l1_text));
  38 #endif
  39
  40 static unsigned short do_csum(const unsigned char *buff, int len)
  41 {
  42         register unsigned long sum = 0;
  43         int swappem = 0;
  44
  45         if (1 & (unsigned long)buff) {
  46                 sum = *buff << 8;
  47                 buff++;
  48                 len--;
  49                 ++swappem;
  50         }
  51
  52         while (len > 1) {
  53                 sum += *(unsigned short *)buff;
  54                 buff += 2;
  55                 len -= 2;
  56         }
  57
  58         if (len > 0)
  59                 sum += *buff;
  60
  61         /*  Fold 32-bit sum to 16 bits */
  62         while (sum >> 16)
  63                 sum = (sum & 0xffff) + (sum >> 16);
  64
  65         if (swappem)
  66                 sum = ((sum & 0xff00) >> 8) + ((sum & 0x00ff) << 8);
  67
  68         return sum;
  69
  70 }
  71
  72 /*
  73  *      This is a version of ip_compute_csum() optimized for IP headers,
  74  *      which always checksum on 4 octet boundaries.
  75  */
  76 __sum16 ip_fast_csum(unsigned char *iph, unsigned int ihl)
  77 {
  78         return (__force __sum16)~do_csum(iph, ihl * 4);
  79 }
  80 EXPORT_SYMBOL(ip_fast_csum);
  81
  82 /*
  83  * computes the checksum of a memory block at buff, length len,
  84  * and adds in "sum" (32-bit)
  85  *
  86  * returns a 32-bit number suitable for feeding into itself
  87  * or csum_tcpudp_magic
  88  *
  89  * this function must be called with even lengths, except
  90  * for the last fragment, which may be odd
  91  *
  92  * it's best to have buff aligned on a 32-bit boundary
  93  */
  94 __wsum csum_partial(const void *buff, int len, __wsum sum)
  95 {
  96         /*
  97          * Just in case we get nasty checksum data...
  98          * Like 0xffff6ec3 in the case of our IPv6 multicast header.
  99          * We fold to begin with, as well as at the end.
 100          */
 101         sum = (sum & 0xffff) + (sum >> 16);
 102
 103         sum += do_csum(buff, len);
 104
 105         sum = (sum & 0xffff) + (sum >> 16);
 106
 107         return sum;
 108 }
 109 EXPORT_SYMBOL(csum_partial);
 110
 111 /*
 112  * this routine is used for miscellaneous IP-like checksums, mainly
 113  * in icmp.c
 114  */
 115 __sum16 ip_compute_csum(const void *buff, int len)
 116 {
 117         return (__force __sum16)~do_csum(buff, len);
 118 }
 119
 120 /*
 121  * copy from fs while checksumming, otherwise like csum_partial
 122  */
 123
 124 __wsum
 125 csum_partial_copy_from_user(const void __user *src, void *dst,
 126                             int len, __wsum sum, int *csum_err)
 127 {
 128         if (csum_err)
 129                 *csum_err = 0;
 130         memcpy(dst, (__force void *)src, len);
 131         return csum_partial(dst, len, sum);
 132 }
 133
 134 /*
 135  * copy from ds while checksumming, otherwise like csum_partial
 136  */
 137
 138 __wsum csum_partial_copy(const void *src, void *dst, int len, __wsum sum)
 139 {
 140         memcpy(dst, src, len);
 141         return csum_partial(dst, len, sum);
 142 }
 143 EXPORT_SYMBOL(csum_partial_copy);