linux/include/net/checksum.h
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   1/*
   2 * INET         An implementation of the TCP/IP protocol suite for the LINUX
   3 *              operating system.  INET is implemented using the  BSD Socket
   4 *              interface as the means of communication with the user level.
   5 *
   6 *              Checksumming functions for IP, TCP, UDP and so on
   7 *
   8 * Authors:     Jorge Cwik, <jorge@laser.satlink.net>
   9 *              Arnt Gulbrandsen, <agulbra@nvg.unit.no>
  10 *              Borrows very liberally from tcp.c and ip.c, see those
  11 *              files for more names.
  12 *
  13 *              This program is free software; you can redistribute it and/or
  14 *              modify it under the terms of the GNU General Public License
  15 *              as published by the Free Software Foundation; either version
  16 *              2 of the License, or (at your option) any later version.
  17 */
  18
  19#ifndef _CHECKSUM_H
  20#define _CHECKSUM_H
  21
  22#include <linux/errno.h>
  23#include <asm/types.h>
  24#include <asm/byteorder.h>
  25#include <asm/uaccess.h>
  26#include <asm/checksum.h>
  27
  28#ifndef _HAVE_ARCH_COPY_AND_CSUM_FROM_USER
  29static inline
  30__wsum csum_and_copy_from_user (const void __user *src, void *dst,
  31                                      int len, __wsum sum, int *err_ptr)
  32{
  33        if (access_ok(VERIFY_READ, src, len))
  34                return csum_partial_copy_from_user(src, dst, len, sum, err_ptr);
  35
  36        if (len)
  37                *err_ptr = -EFAULT;
  38
  39        return sum;
  40}
  41#endif
  42
  43#ifndef HAVE_CSUM_COPY_USER
  44static __inline__ __wsum csum_and_copy_to_user
  45(const void *src, void __user *dst, int len, __wsum sum, int *err_ptr)
  46{
  47        sum = csum_partial(src, len, sum);
  48
  49        if (access_ok(VERIFY_WRITE, dst, len)) {
  50                if (copy_to_user(dst, src, len) == 0)
  51                        return sum;
  52        }
  53        if (len)
  54                *err_ptr = -EFAULT;
  55
  56        return (__force __wsum)-1; /* invalid checksum */
  57}
  58#endif
  59
  60static inline __wsum csum_add(__wsum csum, __wsum addend)
  61{
  62        u32 res = (__force u32)csum;
  63        res += (__force u32)addend;
  64        return (__force __wsum)(res + (res < (__force u32)addend));
  65}
  66
  67static inline __wsum csum_sub(__wsum csum, __wsum addend)
  68{
  69        return csum_add(csum, ~addend);
  70}
  71
  72static inline __wsum
  73csum_block_add(__wsum csum, __wsum csum2, int offset)
  74{
  75        u32 sum = (__force u32)csum2;
  76        if (offset&1)
  77                sum = ((sum&0xFF00FF)<<8)+((sum>>8)&0xFF00FF);
  78        return csum_add(csum, (__force __wsum)sum);
  79}
  80
  81static inline __wsum
  82csum_block_sub(__wsum csum, __wsum csum2, int offset)
  83{
  84        u32 sum = (__force u32)csum2;
  85        if (offset&1)
  86                sum = ((sum&0xFF00FF)<<8)+((sum>>8)&0xFF00FF);
  87        return csum_sub(csum, (__force __wsum)sum);
  88}
  89
  90static inline __wsum csum_unfold(__sum16 n)
  91{
  92        return (__force __wsum)n;
  93}
  94
  95#define CSUM_MANGLED_0 ((__force __sum16)0xffff)
  96
  97static inline void csum_replace4(__sum16 *sum, __be32 from, __be32 to)
  98{
  99        __be32 diff[] = { ~from, to };
 100
 101        *sum = csum_fold(csum_partial(diff, sizeof(diff), ~csum_unfold(*sum)));
 102}
 103
 104static inline void csum_replace2(__sum16 *sum, __be16 from, __be16 to)
 105{
 106        csum_replace4(sum, (__force __be32)from, (__force __be32)to);
 107}
 108
 109struct sk_buff;
 110extern void inet_proto_csum_replace4(__sum16 *sum, struct sk_buff *skb,
 111                                     __be32 from, __be32 to, int pseudohdr);
 112extern void inet_proto_csum_replace16(__sum16 *sum, struct sk_buff *skb,
 113                                      const __be32 *from, const __be32 *to,
 114                                      int pseudohdr);
 115
 116static inline void inet_proto_csum_replace2(__sum16 *sum, struct sk_buff *skb,
 117                                            __be16 from, __be16 to,
 118                                            int pseudohdr)
 119{
 120        inet_proto_csum_replace4(sum, skb, (__force __be32)from,
 121                                 (__force __be32)to, pseudohdr);
 122}
 123
 124#endif
 125
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