arch/ia64/lib/checksum.c

   1 /*
   2  * Network checksum routines
   3  *
   4  * Copyright (C) 1999, 2003 Hewlett-Packard Co
   5  *      Stephane Eranian <eranian@hpl.hp.com>
   6  *
   7  * Most of the code coming from arch/alpha/lib/checksum.c
   8  *
   9  * This file contains network checksum routines that are better done
  10  * in an architecture-specific manner due to speed..
  11  */
  12
  13 #include <linux/module.h>
  14 #include <linux/string.h>
  15
  16 #include <asm/byteorder.h>
  17
  18 static inline unsigned short
  19 from64to16 (unsigned long x)
  20 {
  21         /* add up 32-bit words for 33 bits */
  22         x = (x & 0xffffffff) + (x >> 32);
  23         /* add up 16-bit and 17-bit words for 17+c bits */
  24         x = (x & 0xffff) + (x >> 16);
  25         /* add up 16-bit and 2-bit for 16+c bit */
  26         x = (x & 0xffff) + (x >> 16);
  27         /* add up carry.. */
  28         x = (x & 0xffff) + (x >> 16);
  29         return x;
  30 }
  31
  32 /*
  33  * computes the checksum of the TCP/UDP pseudo-header
  34  * returns a 16-bit checksum, already complemented.
  35  */
  36 unsigned short int
  37 csum_tcpudp_magic (unsigned long saddr, unsigned long daddr, unsigned short len,
  38                    unsigned short proto, unsigned int sum)
  39 {
  40         return ~from64to16(saddr + daddr + sum + ((unsigned long) ntohs(len) << 16) +
  41                            ((unsigned long) proto << 8));
  42 }
  43
  44 EXPORT_SYMBOL(csum_tcpudp_magic);
  45
  46 unsigned int
  47 csum_tcpudp_nofold (unsigned long saddr, unsigned long daddr, unsigned short len,
  48                     unsigned short proto, unsigned int sum)
  49 {
  50         unsigned long result;
  51
  52         result = (saddr + daddr + sum +
  53                   ((unsigned long) ntohs(len) << 16) +
  54                   ((unsigned long) proto << 8));
  55
  56         /* Fold down to 32-bits so we don't lose in the typedef-less network stack.  */
  57         /* 64 to 33 */
  58         result = (result & 0xffffffff) + (result >> 32);
  59         /* 33 to 32 */
  60         result = (result & 0xffffffff) + (result >> 32);
  61         return result;
  62 }
  63
  64 extern unsigned long do_csum (const unsigned char *, long);
  65
  66 /*
  67  * computes the checksum of a memory block at buff, length len,
  68  * and adds in "sum" (32-bit)
  69  *
  70  * returns a 32-bit number suitable for feeding into itself
  71  * or csum_tcpudp_magic
  72  *
  73  * this function must be called with even lengths, except
  74  * for the last fragment, which may be odd
  75  *
  76  * it's best to have buff aligned on a 32-bit boundary
  77  */
  78 unsigned int
  79 csum_partial (const unsigned char * buff, int len, unsigned int sum)
  80 {
  81         unsigned long result = do_csum(buff, len);
  82
  83         /* add in old sum, and carry.. */
  84         result += sum;
  85         /* 32+c bits -> 32 bits */
  86         result = (result & 0xffffffff) + (result >> 32);
  87         return result;
  88 }
  89
  90 EXPORT_SYMBOL(csum_partial);
  91
  92 /*
  93  * this routine is used for miscellaneous IP-like checksums, mainly
  94  * in icmp.c
  95  */
  96 unsigned short
  97 ip_compute_csum (unsigned char * buff, int len)
  98 {
  99         return ~do_csum(buff,len);
 100 }
 101
 102 EXPORT_SYMBOL(ip_compute_csum);