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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, <[email protected]>
9  * Arnt Gulbrandsen, <[email protected]>
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
29 static 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
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 
60 static 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 
67 static inline __wsum csum_sub(__wsum csum, __wsum addend)
68 {
69  return csum_add(csum, ~addend);
70 }
71 
72 static inline __wsum
73 csum_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 
81 static inline __wsum
82 csum_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 
90 static inline __wsum csum_unfold(__sum16 n)
91 {
92  return (__force __wsum)n;
93 }
94 
95 #define CSUM_MANGLED_0 ((__force __sum16)0xffff)
96 
97 static 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 
104 static inline void csum_replace2(__sum16 *sum, __be16 from, __be16 to)
105 {
106  csum_replace4(sum, (__force __be32)from, (__force __be32)to);
107 }
108 
109 struct sk_buff;
110 extern void inet_proto_csum_replace4(__sum16 *sum, struct sk_buff *skb,
111  __be32 from, __be32 to, int pseudohdr);
112 extern void inet_proto_csum_replace16(__sum16 *sum, struct sk_buff *skb,
113  const __be32 *from, const __be32 *to,
114  int pseudohdr);
115 
116 static 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