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

   1/*
   2 * arch/alpha/lib/checksum.c
   3 *
   4 * This file contains network checksum routines that are better done
   5 * in an architecture-specific manner due to speed..
   6 * Comments in other versions indicate that the algorithms are from RFC1071
   7 *
   8 * accelerated versions (and 21264 assembly versions ) contributed by
   9 *      Rick Gorton     <rick.gorton@alpha-processor.com>
  10 */
  11 
  12#include <linux/module.h>
  13#include <linux/string.h>
  14
  15#include <asm/byteorder.h>
  16
  17static inline unsigned short from64to16(unsigned long x)
  18{
  19        /* Using extract instructions is a bit more efficient
  20           than the original shift/bitmask version.  */
  21
  22        union {
  23                unsigned long   ul;
  24                unsigned int    ui[2];
  25                unsigned short  us[4];
  26        } in_v, tmp_v, out_v;
  27
  28        in_v.ul = x;
  29        tmp_v.ul = (unsigned long) in_v.ui[0] + (unsigned long) in_v.ui[1];
  30
  31        /* Since the bits of tmp_v.sh[3] are going to always be zero,
  32           we don't have to bother to add that in.  */
  33        out_v.ul = (unsigned long) tmp_v.us[0] + (unsigned long) tmp_v.us[1]
  34                        + (unsigned long) tmp_v.us[2];
  35
  36        /* Similarly, out_v.us[2] is always zero for the final add.  */
  37        return out_v.us[0] + out_v.us[1];
  38}
  39
  40/*
  41 * computes the checksum of the TCP/UDP pseudo-header
  42 * returns a 16-bit checksum, already complemented.
  43 */
  44__sum16 csum_tcpudp_magic(__be32 saddr, __be32 daddr,
  45                                   unsigned short len,
  46                                   unsigned short proto,
  47                                   __wsum sum)
  48{
  49        return (__force __sum16)~from64to16(
  50                (__force u64)saddr + (__force u64)daddr +
  51                (__force u64)sum + ((len + proto) << 8));
  52}
  53
  54__wsum csum_tcpudp_nofold(__be32 saddr, __be32 daddr,
  55                                   unsigned short len,
  56                                   unsigned short proto,
  57                                   __wsum sum)
  58{
  59        unsigned long result;
  60
  61        result = (__force u64)saddr + (__force u64)daddr +
  62                 (__force u64)sum + ((len + proto) << 8);
  63
  64        /* Fold down to 32-bits so we don't lose in the typedef-less 
  65           network stack.  */
  66        /* 64 to 33 */
  67        result = (result & 0xffffffff) + (result >> 32);
  68        /* 33 to 32 */
  69        result = (result & 0xffffffff) + (result >> 32);
  70        return (__force __wsum)result;
  71}
  72EXPORT_SYMBOL(csum_tcpudp_nofold);
  73
  74/*
  75 * Do a 64-bit checksum on an arbitrary memory area..
  76 *
  77 * This isn't a great routine, but it's not _horrible_ either. The
  78 * inner loop could be unrolled a bit further, and there are better
  79 * ways to do the carry, but this is reasonable.
  80 */
  81static inline unsigned long do_csum(const unsigned char * buff, int len)
  82{
  83        int odd, count;
  84        unsigned long result = 0;
  85
  86        if (len <= 0)
  87                goto out;
  88        odd = 1 & (unsigned long) buff;
  89        if (odd) {
  90                result = *buff << 8;
  91                len--;
  92                buff++;
  93        }
  94        count = len >> 1;               /* nr of 16-bit words.. */
  95        if (count) {
  96                if (2 & (unsigned long) buff) {
  97                        result += *(unsigned short *) buff;
  98                        count--;
  99                        len -= 2;
 100                        buff += 2;
 101                }
 102                count >>= 1;            /* nr of 32-bit words.. */
 103                if (count) {
 104                        if (4 & (unsigned long) buff) {
 105                                result += *(unsigned int *) buff;
 106                                count--;
 107                                len -= 4;
 108                                buff += 4;
 109                        }
 110                        count >>= 1;    /* nr of 64-bit words.. */
 111                        if (count) {
 112                                unsigned long carry = 0;
 113                                do {
 114                                        unsigned long w = *(unsigned long *) buff;
 115                                        count--;
 116                                        buff += 8;
 117                                        result += carry;
 118                                        result += w;
 119                                        carry = (w > result);
 120                                } while (count);
 121                                result += carry;
 122                                result = (result & 0xffffffff) + (result >> 32);
 123                        }
 124                        if (len & 4) {
 125                                result += *(unsigned int *) buff;
 126                                buff += 4;
 127                        }
 128                }
 129                if (len & 2) {
 130                        result += *(unsigned short *) buff;
 131                        buff += 2;
 132                }
 133        }
 134        if (len & 1)
 135                result += *buff;
 136        result = from64to16(result);
 137        if (odd)
 138                result = ((result >> 8) & 0xff) | ((result & 0xff) << 8);
 139out:
 140        return result;
 141}
 142
 143/*
 144 *      This is a version of ip_compute_csum() optimized for IP headers,
 145 *      which always checksum on 4 octet boundaries.
 146 */
 147__sum16 ip_fast_csum(const void *iph, unsigned int ihl)
 148{
 149        return (__force __sum16)~do_csum(iph,ihl*4);
 150}
 151
 152/*
 153 * computes the checksum of a memory block at buff, length len,
 154 * and adds in "sum" (32-bit)
 155 *
 156 * returns a 32-bit number suitable for feeding into itself
 157 * or csum_tcpudp_magic
 158 *
 159 * this function must be called with even lengths, except
 160 * for the last fragment, which may be odd
 161 *
 162 * it's best to have buff aligned on a 32-bit boundary
 163 */
 164__wsum csum_partial(const void *buff, int len, __wsum sum)
 165{
 166        unsigned long result = do_csum(buff, len);
 167
 168        /* add in old sum, and carry.. */
 169        result += (__force u32)sum;
 170        /* 32+c bits -> 32 bits */
 171        result = (result & 0xffffffff) + (result >> 32);
 172        return (__force __wsum)result;
 173}
 174
 175EXPORT_SYMBOL(csum_partial);
 176
 177/*
 178 * this routine is used for miscellaneous IP-like checksums, mainly
 179 * in icmp.c
 180 */
 181__sum16 ip_compute_csum(const void *buff, int len)
 182{
 183        return (__force __sum16)~from64to16(do_csum(buff,len));
 184}
 185