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  * accellerated 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
  17 static 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 unsigned short int csum_tcpudp_magic(unsigned long saddr,
  45                                    unsigned long daddr,
  46                                    unsigned short len,
  47                                    unsigned short proto,
  48                                    unsigned int sum)
  49 {
  50         return ~from64to16(saddr + daddr + sum +
  51                 ((unsigned long) ntohs(len) << 16) +
  52                 ((unsigned long) proto << 8));
  53 }
  54
  55 unsigned int csum_tcpudp_nofold(unsigned long saddr,
  56                                    unsigned long daddr,
  57                                    unsigned short len,
  58                                    unsigned short proto,
  59                                    unsigned int sum)
  60 {
  61         unsigned long result;
  62
  63         result = (saddr + daddr + sum +
  64                   ((unsigned long) ntohs(len) << 16) +
  65                   ((unsigned long) proto << 8));
  66
  67         /* Fold down to 32-bits so we don't lose in the typedef-less
  68            network stack.  */
  69         /* 64 to 33 */
  70         result = (result & 0xffffffff) + (result >> 32);
  71         /* 33 to 32 */
  72         result = (result & 0xffffffff) + (result >> 32);
  73         return result;
  74 }
  75
  76 /*
  77  * Do a 64-bit checksum on an arbitrary memory area..
  78  *
  79  * This isn't a great routine, but it's not _horrible_ either. The
  80  * inner loop could be unrolled a bit further, and there are better
  81  * ways to do the carry, but this is reasonable.
  82  */
  83 static inline unsigned long do_csum(const unsigned char * buff, int len)
  84 {
  85         int odd, count;
  86         unsigned long result = 0;
  87
  88         if (len <= 0)
  89                 goto out;
  90         odd = 1 & (unsigned long) buff;
  91         if (odd) {
  92                 result = *buff << 8;
  93                 len--;
  94                 buff++;
  95         }
  96         count = len >> 1;               /* nr of 16-bit words.. */
  97         if (count) {
  98                 if (2 & (unsigned long) buff) {
  99                         result += *(unsigned short *) buff;
 100                         count--;
 101                         len -= 2;
 102                         buff += 2;
 103                 }
 104                 count >>= 1;            /* nr of 32-bit words.. */
 105                 if (count) {
 106                         if (4 & (unsigned long) buff) {
 107                                 result += *(unsigned int *) buff;
 108                                 count--;
 109                                 len -= 4;
 110                                 buff += 4;
 111                         }
 112                         count >>= 1;    /* nr of 64-bit words.. */
 113                         if (count) {
 114                                 unsigned long carry = 0;
 115                                 do {
 116                                         unsigned long w = *(unsigned long *) buff;
 117                                         count--;
 118                                         buff += 8;
 119                                         result += carry;
 120                                         result += w;
 121                                         carry = (w > result);
 122                                 } while (count);
 123                                 result += carry;
 124                                 result = (result & 0xffffffff) + (result >> 32);
 125                         }
 126                         if (len & 4) {
 127                                 result += *(unsigned int *) buff;
 128                                 buff += 4;
 129                         }
 130                 }
 131                 if (len & 2) {
 132                         result += *(unsigned short *) buff;
 133                         buff += 2;
 134                 }
 135         }
 136         if (len & 1)
 137                 result += *buff;
 138         result = from64to16(result);
 139         if (odd)
 140                 result = ((result >> 8) & 0xff) | ((result & 0xff) << 8);
 141 out:
 142         return result;
 143 }
 144
 145 /*
 146  *      This is a version of ip_compute_csum() optimized for IP headers,
 147  *      which always checksum on 4 octet boundaries.
 148  */
 149 unsigned short ip_fast_csum(unsigned char * iph, unsigned int ihl)
 150 {
 151         return ~do_csum(iph,ihl*4);
 152 }
 153
 154 /*
 155  * computes the checksum of a memory block at buff, length len,
 156  * and adds in "sum" (32-bit)
 157  *
 158  * returns a 32-bit number suitable for feeding into itself
 159  * or csum_tcpudp_magic
 160  *
 161  * this function must be called with even lengths, except
 162  * for the last fragment, which may be odd
 163  *
 164  * it's best to have buff aligned on a 32-bit boundary
 165  */
 166 unsigned int csum_partial(const unsigned char * buff, int len, unsigned int sum)
 167 {
 168         unsigned long result = do_csum(buff, len);
 169
 170         /* add in old sum, and carry.. */
 171         result += sum;
 172         /* 32+c bits -> 32 bits */
 173         result = (result & 0xffffffff) + (result >> 32);
 174         return result;
 175 }
 176
 177 EXPORT_SYMBOL(csum_partial);
 178
 179 /*
 180  * this routine is used for miscellaneous IP-like checksums, mainly
 181  * in icmp.c
 182  */
 183 unsigned short ip_compute_csum(unsigned char * buff, int len)
 184 {
 185         return ~from64to16(do_csum(buff,len));
 186 }