LXR linux/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
  18static inline unsigned short
  19from64to16 (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__sum16
  37csum_tcpudp_magic (__be32 saddr, __be32 daddr, unsigned short len,
  38                   unsigned short proto, __wsum sum)
  39{
  40        return (__force __sum16)~from64to16(
  41                (__force u64)saddr + (__force u64)daddr +
  42                (__force u64)sum + ((len + proto) << 8));
  43}
  44
  45EXPORT_SYMBOL(csum_tcpudp_magic);
  46
  47__wsum
  48csum_tcpudp_nofold (__be32 saddr, __be32 daddr, unsigned short len,
  49                    unsigned short proto, __wsum sum)
  50{
  51        unsigned long result;
  52
  53        result = (__force u64)saddr + (__force u64)daddr +
  54                 (__force u64)sum + ((len + 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 (__force __wsum)result;
  62}
  63EXPORT_SYMBOL(csum_tcpudp_nofold);
  64
  65extern unsigned long do_csum (const unsigned char *, long);
  66
  67/*
  68 * computes the checksum of a memory block at buff, length len,
  69 * and adds in "sum" (32-bit)
  70 *
  71 * returns a 32-bit number suitable for feeding into itself
  72 * or csum_tcpudp_magic
  73 *
  74 * this function must be called with even lengths, except
  75 * for the last fragment, which may be odd
  76 *
  77 * it's best to have buff aligned on a 32-bit boundary
  78 */
  79__wsum csum_partial(const void *buff, int len, __wsum sum)
  80{
  81        u64 result = do_csum(buff, len);
  82
  83        /* add in old sum, and carry.. */
  84        result += (__force u32)sum;
  85        /* 32+c bits -> 32 bits */
  86        result = (result & 0xffffffff) + (result >> 32);
  87        return (__force __wsum)result;
  88}
  89
  90EXPORT_SYMBOL(csum_partial);
  91
  92/*
  93 * this routine is used for miscellaneous IP-like checksums, mainly
  94 * in icmp.c
  95 */
  96__sum16 ip_compute_csum (const void *buff, int len)
  97{
  98        return (__force __sum16)~do_csum(buff,len);
  99}
 100
 101EXPORT_SYMBOL(ip_compute_csum);
 102