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checksum.h

/*
 * This file is subject to the terms and conditions of the GNU General Public
 * License.  See the file "COPYING" in the main directory of this archive
 * for more details.
 *
 * Copyright (C) 1995, 96, 97, 98, 99, 2001 by Ralf Baechle
 * Copyright (C) 1999 Silicon Graphics, Inc.
 * Copyright (C) 2001 Thiemo Seufer.
 * Copyright (C) 2002 Maciej W. Rozycki
 */
#ifndef _ASM_CHECKSUM_H
#define _ASM_CHECKSUM_H

#include <linux/in6.h>

#include <asm/uaccess.h>

/*
 * computes the checksum of a memory block at buff, length len,
 * and adds in "sum" (32-bit)
 *
 * returns a 32-bit number suitable for feeding into itself
 * or csum_tcpudp_magic
 *
 * this function must be called with even lengths, except
 * for the last fragment, which may be odd
 *
 * it's best to have buff aligned on a 32-bit boundary
 */
__wsum csum_partial(const void *buff, int len, __wsum sum);

__wsum __csum_partial_copy_user(const void *src, void *dst,
                        int len, __wsum sum, int *err_ptr);

/*
 * this is a new version of the above that records errors it finds in *errp,
 * but continues and zeros the rest of the buffer.
 */
static inline
__wsum csum_partial_copy_from_user(const void __user *src, void *dst, int len,
                           __wsum sum, int *err_ptr)
{
      might_sleep();
      return __csum_partial_copy_user((__force void *)src, dst,
                              len, sum, err_ptr);
}

/*
 * Copy and checksum to user
 */
#define HAVE_CSUM_COPY_USER
static inline
__wsum csum_and_copy_to_user(const void *src, void __user *dst, int len,
                       __wsum sum, int *err_ptr)
{
      might_sleep();
      if (access_ok(VERIFY_WRITE, dst, len))
            return __csum_partial_copy_user(src, (__force void *)dst,
                                    len, sum, err_ptr);
      if (len)
            *err_ptr = -EFAULT;

      return (__force __wsum)-1; /* invalid checksum */
}

/*
 * the same as csum_partial, but copies from user space (but on MIPS
 * we have just one address space, so this is identical to the above)
 */
__wsum csum_partial_copy_nocheck(const void *src, void *dst,
                               int len, __wsum sum);

/*
 *    Fold a partial checksum without adding pseudo headers
 */
static inline __sum16 csum_fold(__wsum sum)
{
      __asm__(
      "     .set  push        # csum_fold\n"
      "     .set  noat        \n"
      "     sll   $1, %0, 16  \n"
      "     addu  %0, $1            \n"
      "     sltu  $1, %0, $1  \n"
      "     srl   %0, %0, 16  \n"
      "     addu  %0, $1            \n"
      "     xori  %0, 0xffff  \n"
      "     .set  pop"
      : "=r" (sum)
      : "0" (sum));

      return (__force __sum16)sum;
}

/*
 *    This is a version of ip_compute_csum() optimized for IP headers,
 *    which always checksum on 4 octet boundaries.
 *
 *    By Jorge Cwik <jorge@laser.satlink.net>, adapted for linux by
 *    Arnt Gulbrandsen.
 */
static inline __sum16 ip_fast_csum(const void *iph, unsigned int ihl)
{
      const unsigned int *word = iph;
      const unsigned int *stop = word + ihl;
      unsigned int csum;
      int carry;

      csum = word[0];
      csum += word[1];
      carry = (csum < word[1]);
      csum += carry;

      csum += word[2];
      carry = (csum < word[2]);
      csum += carry;

      csum += word[3];
      carry = (csum < word[3]);
      csum += carry;

      word += 4;
      do {
            csum += *word;
            carry = (csum < *word);
            csum += carry;
            word++;
      } while (word != stop);

      return csum_fold(csum);
}

static inline __wsum csum_tcpudp_nofold(__be32 saddr,
      __be32 daddr, unsigned short len, unsigned short proto,
      __wsum sum)
{
      __asm__(
      "     .set  push        # csum_tcpudp_nofold\n"
      "     .set  noat        \n"
#ifdef CONFIG_32BIT
      "     addu  %0, %2            \n"
      "     sltu  $1, %0, %2  \n"
      "     addu  %0, $1            \n"

      "     addu  %0, %3            \n"
      "     sltu  $1, %0, %3  \n"
      "     addu  %0, $1            \n"

      "     addu  %0, %4            \n"
      "     sltu  $1, %0, %4  \n"
      "     addu  %0, $1            \n"
#endif
#ifdef CONFIG_64BIT
      "     daddu %0, %2            \n"
      "     daddu %0, %3            \n"
      "     daddu %0, %4            \n"
      "     dsll32      $1, %0, 0   \n"
      "     daddu %0, $1            \n"
      "     dsra32      %0, %0, 0   \n"
#endif
      "     .set  pop"
      : "=r" (sum)
      : "0" ((__force unsigned long)daddr),
        "r" ((__force unsigned long)saddr),
#ifdef __MIPSEL__
        "r" ((proto + len) << 8),
#else
        "r" (proto + len),
#endif
        "r" ((__force unsigned long)sum));

      return sum;
}

/*
 * computes the checksum of the TCP/UDP pseudo-header
 * returns a 16-bit checksum, already complemented
 */
static inline __sum16 csum_tcpudp_magic(__be32 saddr, __be32 daddr,
                                       unsigned short len,
                                       unsigned short proto,
                                       __wsum sum)
{
      return csum_fold(csum_tcpudp_nofold(saddr, daddr, len, proto, sum));
}

/*
 * this routine is used for miscellaneous IP-like checksums, mainly
 * in icmp.c
 */
static inline __sum16 ip_compute_csum(const void *buff, int len)
{
      return csum_fold(csum_partial(buff, len, 0));
}

#define _HAVE_ARCH_IPV6_CSUM
static __inline__ __sum16 csum_ipv6_magic(const struct in6_addr *saddr,
                                  const struct in6_addr *daddr,
                                __u32 len, unsigned short proto,
                                __wsum sum)
{
      __asm__(
      "     .set  push        # csum_ipv6_magic\n"
      "     .set  noreorder   \n"
      "     .set  noat        \n"
      "     addu  %0, %5            # proto (long in network byte order)\n"
      "     sltu  $1, %0, %5  \n"
      "     addu  %0, $1            \n"

      "     addu  %0, %6            # csum\n"
      "     sltu  $1, %0, %6  \n"
      "     lw    %1, 0(%2)   # four words source address\n"
      "     addu  %0, $1            \n"
      "     addu  %0, %1            \n"
      "     sltu  $1, %0, %1  \n"

      "     lw    %1, 4(%2)   \n"
      "     addu  %0, $1            \n"
      "     addu  %0, %1            \n"
      "     sltu  $1, %0, %1  \n"

      "     lw    %1, 8(%2)   \n"
      "     addu  %0, $1            \n"
      "     addu  %0, %1            \n"
      "     sltu  $1, %0, %1  \n"

      "     lw    %1, 12(%2)  \n"
      "     addu  %0, $1            \n"
      "     addu  %0, %1            \n"
      "     sltu  $1, %0, %1  \n"

      "     lw    %1, 0(%3)   \n"
      "     addu  %0, $1            \n"
      "     addu  %0, %1            \n"
      "     sltu  $1, %0, %1  \n"

      "     lw    %1, 4(%3)   \n"
      "     addu  %0, $1            \n"
      "     addu  %0, %1            \n"
      "     sltu  $1, %0, %1  \n"

      "     lw    %1, 8(%3)   \n"
      "     addu  %0, $1            \n"
      "     addu  %0, %1            \n"
      "     sltu  $1, %0, %1  \n"

      "     lw    %1, 12(%3)  \n"
      "     addu  %0, $1            \n"
      "     addu  %0, %1            \n"
      "     sltu  $1, %0, %1  \n"

      "     addu  %0, $1            # Add final carry\n"
      "     .set  pop"
      : "=r" (sum), "=r" (proto)
      : "r" (saddr), "r" (daddr),
        "0" (htonl(len)), "1" (htonl(proto)), "r" (sum));

      return csum_fold(sum);
}

#endif /* _ASM_CHECKSUM_H */

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