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34#include <net/checksum.h>
35#include <linux/module.h>
36
37static inline unsigned short from32to16(unsigned long x)
38{
39
40 x = (x & 0xffff) + (x >> 16);
41
42 x = (x & 0xffff) + (x >> 16);
43 return x;
44}
45
46static unsigned long do_csum(const unsigned char * buff, int len)
47{
48 int odd, count;
49 unsigned long result = 0;
50
51 if (len <= 0)
52 goto out;
53 odd = 1 & (unsigned long) buff;
54 if (odd) {
55 result = *buff;
56 len--;
57 buff++;
58 }
59 count = len >> 1;
60 if (count) {
61 if (2 & (unsigned long) buff) {
62 result += *(unsigned short *) buff;
63 count--;
64 len -= 2;
65 buff += 2;
66 }
67 count >>= 1;
68 if (count) {
69 unsigned long carry = 0;
70 do {
71 unsigned long w = *(unsigned long *) buff;
72 count--;
73 buff += 4;
74 result += carry;
75 result += w;
76 carry = (w > result);
77 } while (count);
78 result += carry;
79 result = (result & 0xffff) + (result >> 16);
80 }
81 if (len & 2) {
82 result += *(unsigned short *) buff;
83 buff += 2;
84 }
85 }
86 if (len & 1)
87 result += (*buff << 8);
88 result = from32to16(result);
89 if (odd)
90 result = ((result >> 8) & 0xff) | ((result & 0xff) << 8);
91out:
92 return result;
93}
94
95
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97
98
99__sum16 ip_fast_csum(const void *iph, unsigned int ihl)
100{
101 return (__force __sum16)~do_csum(iph,ihl*4);
102}
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119
120__wsum csum_partial(const void *buff, int len, __wsum sum)
121{
122 unsigned int result = do_csum(buff, len);
123
124
125 result += (__force u32)sum;
126
127 result = (result & 0xffff) + (result >> 16);
128 return (__force __wsum)result;
129}
130
131EXPORT_SYMBOL(csum_partial);
132
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135
136
137__sum16 ip_compute_csum(const void *buff, int len)
138{
139 return (__force __sum16)~do_csum(buff,len);
140}
141
142
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144
145
146__wsum
147csum_partial_copy_from_user(const void __user *src, void *dst, int len,
148 __wsum sum, int *csum_err)
149{
150 if (csum_err) *csum_err = 0;
151 memcpy(dst, (__force const void *)src, len);
152 return csum_partial(dst, len, sum);
153}
154
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158
159__wsum
160csum_partial_copy_nocheck(const void *src, void *dst, int len, __wsum sum)
161{
162 memcpy(dst, src, len);
163 return csum_partial(dst, len, sum);
164}
165