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c-checksum.c

/*
 * arch/sh/lib64/c-checksum.c
 *
 * This file contains network checksum routines that are better done
 * in an architecture-specific manner due to speed..
 */
#include <linux/string.h>
#include <linux/errno.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <asm/byteorder.h>
#include <asm/uaccess.h>

static inline unsigned short from64to16(unsigned long long x)
{
      /* add up 32-bit words for 33 bits */
      x = (x & 0xffffffff) + (x >> 32);
      /* add up 16-bit and 17-bit words for 17+c bits */
      x = (x & 0xffff) + (x >> 16);
      /* add up 16-bit and 2-bit for 16+c bit */
      x = (x & 0xffff) + (x >> 16);
      /* add up carry.. */
      x = (x & 0xffff) + (x >> 16);
      return x;
}

static inline unsigned short foldto16(unsigned long x)
{
      /* add up 16-bit for 17 bits */
      x = (x & 0xffff) + (x >> 16);
      /* add up carry.. */
      x = (x & 0xffff) + (x >> 16);
      return x;
}

static inline unsigned short myfoldto16(unsigned long long x)
{
      /* Fold down to 32-bits so we don't loose in the typedef-less
         network stack.  */
      /* 64 to 33 */
      x = (x & 0xffffffff) + (x >> 32);
      /* 33 to 32 */
      x = (x & 0xffffffff) + (x >> 32);

      /* add up 16-bit for 17 bits */
      x = (x & 0xffff) + (x >> 16);
      /* add up carry.. */
      x = (x & 0xffff) + (x >> 16);
      return x;
}

#define odd(x) ((x)&1)
#define U16(x) ntohs(x)

static unsigned long do_csum(const unsigned char *buff, int len)
{
      int odd, count;
      unsigned long result = 0;

      pr_debug("do_csum buff %p, len %d (0x%x)\n", buff, len, len);
#ifdef DEBUG
      for (i = 0; i < len; i++) {
            if ((i % 26) == 0)
                  printk("\n");
            printk("%02X ", buff[i]);
      }
#endif

      if (len <= 0)
            goto out;

      odd = 1 & (unsigned long) buff;
      if (odd) {
            result = *buff << 8;
            len--;
            buff++;
      }
      count = len >> 1; /* nr of 16-bit words.. */
      if (count) {
            if (2 & (unsigned long) buff) {
                  result += *(unsigned short *) buff;
                  count--;
                  len -= 2;
                  buff += 2;
            }
            count >>= 1;      /* nr of 32-bit words.. */
            if (count) {
                  unsigned long carry = 0;
                  do {
                        unsigned long w = *(unsigned long *) buff;
                        buff += 4;
                        count--;
                        result += carry;
                        result += w;
                        carry = (w > result);
                  } while (count);
                  result += carry;
                  result = (result & 0xffff) + (result >> 16);
            }
            if (len & 2) {
                  result += *(unsigned short *) buff;
                  buff += 2;
            }
      }
      if (len & 1)
            result += *buff;
      result = foldto16(result);
      if (odd)
            result = ((result >> 8) & 0xff) | ((result & 0xff) << 8);

      pr_debug("\nCHECKSUM is 0x%lx\n", result);

      out:
      return result;
}

/* computes the checksum of a memory block at buff, length len,
   and adds in "sum" (32-bit)  */
__wsum csum_partial(const void *buff, int len, __wsum sum)
{
      unsigned long long result = do_csum(buff, len);

      /* add in old sum, and carry.. */
      result += (__force u32)sum;
      /* 32+c bits -> 32 bits */
      result = (result & 0xffffffff) + (result >> 32);

      pr_debug("csum_partial, buff %p len %d sum 0x%x result=0x%016Lx\n",
            buff, len, sum, result);

      return (__force __wsum)result;
}

/* Copy while checksumming, otherwise like csum_partial.  */
__wsum
csum_partial_copy_nocheck(const void *src, void *dst, int len, __wsum sum)
{
      sum = csum_partial(src, len, sum);
      memcpy(dst, src, len);

      return sum;
}

/* Copy from userspace and compute checksum.  If we catch an exception
   then zero the rest of the buffer.  */
__wsum
csum_partial_copy_from_user(const void __user *src, void *dst, int len,
                      __wsum sum, int *err_ptr)
{
      int missing;

      pr_debug
          ("csum_partial_copy_from_user src %p, dest %p, len %d, sum %08x, err_ptr %p\n",
           src, dst, len, sum, err_ptr);
      missing = copy_from_user(dst, src, len);
      pr_debug("  access_ok %d\n", __access_ok((unsigned long) src, len));
      pr_debug("  missing %d\n", missing);
      if (missing) {
            memset(dst + len - missing, 0, missing);
            *err_ptr = -EFAULT;
      }

      return csum_partial(dst, len, sum);
}

/* Copy to userspace and compute checksum.  */
__wsum
csum_partial_copy_to_user(const unsigned char *src, unsigned char *dst, int len,
                    __wsum sum, int *err_ptr)
{
      sum = csum_partial(src, len, sum);

      if (copy_to_user(dst, src, len))
            *err_ptr = -EFAULT;

      return sum;
}

/*
 *    This is a version of ip_compute_csum() optimized for IP headers,
 *    which always checksum on 4 octet boundaries.
 */
__sum16 ip_fast_csum(const void *iph, unsigned int ihl)
{
      pr_debug("ip_fast_csum %p,%d\n", iph, ihl);

      return (__force __sum16)~do_csum(iph, ihl * 4);
}

__wsum csum_tcpudp_nofold(__be32 saddr, __be32 daddr,
                        unsigned short len,
                        unsigned short proto, __wsum sum)
{
      unsigned long long result;

      pr_debug("ntohs(0x%x)=0x%x\n", 0xdead, ntohs(0xdead));
      pr_debug("htons(0x%x)=0x%x\n", 0xdead, htons(0xdead));

      result = (__force u64) saddr + (__force u64) daddr +
             (__force u64) sum + ((len + proto) << 8);

      /* Fold down to 32-bits so we don't loose in the typedef-less
         network stack.  */
      /* 64 to 33 */
      result = (result & 0xffffffff) + (result >> 32);
      /* 33 to 32 */
      result = (result & 0xffffffff) + (result >> 32);

      pr_debug("%s saddr %x daddr %x len %x proto %x sum %x result %08Lx\n",
            __func__, saddr, daddr, len, proto, sum, result);

      return (__wsum)result;
}
EXPORT_SYMBOL(csum_tcpudp_nofold);

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