1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
|
/*
* netsniff-ng - the packet sniffing beast
* Copyright 2010 Emmanuel Roullit.
* Subject to the GPL, version 2.
*/
#ifndef CSUM_H
#define CSUM_H
#include <netinet/in.h>
#include <netinet/ip.h>
#include "built_in.h"
static inline unsigned short csum(unsigned short *buf, int nwords)
{
unsigned long sum;
for (sum = 0; nwords > 0; nwords--)
sum += *buf++;
sum = (sum >> 16) + (sum & 0xffff);
sum += (sum >> 16);
return ~sum;
}
static inline uint16_t calc_csum(void *addr, size_t len, int ccsum)
{
return csum(addr, len >> 1);
}
static inline uint16_t csum_expected(uint16_t sum, uint16_t computed_sum)
{
uint32_t shouldbe;
shouldbe = sum;
shouldbe += ntohs(computed_sum);
shouldbe = (shouldbe & 0xFFFF) + (shouldbe >> 16);
shouldbe = (shouldbe & 0xFFFF) + (shouldbe >> 16);
return shouldbe;
}
/* Taken and modified from tcpdump, Copyright belongs to them! */
struct cksum_vec {
const u8 *ptr;
int len;
};
#define ADDCARRY(x) \
do { if ((x) > 65535) \
(x) -= 65535; \
} while (0)
#define REDUCE \
do { \
l_util.l = sum; \
sum = l_util.s[0] + l_util.s[1]; \
ADDCARRY(sum); \
} while (0)
static inline u16 __in_cksum(const struct cksum_vec *vec, int veclen)
{
const u16 *w;
int sum = 0, mlen = 0;
int byte_swapped = 0;
union {
u8 c[2];
u16 s;
} s_util;
union {
u16 s[2];
u32 l;
} l_util;
for (; veclen != 0; vec++, veclen--) {
if (vec->len == 0)
continue;
w = (const u16 *) (void *) vec->ptr;
if (mlen == -1) {
s_util.c[1] = *(const u8 *) w;
sum += s_util.s;
w = (const u16 *) (void *) ((const u8 *) w + 1);
mlen = vec->len - 1;
} else
mlen = vec->len;
if ((1 & (unsigned long) w) && (mlen > 0)) {
REDUCE;
sum <<= 8;
s_util.c[0] = *(const u8 *) w;
w = (const u16 *) (void *) ((const u8 *) w + 1);
mlen--;
byte_swapped = 1;
}
while ((mlen -= 32) >= 0) {
sum += w[0]; sum += w[1]; sum += w[2]; sum += w[3];
sum += w[4]; sum += w[5]; sum += w[6]; sum += w[7];
sum += w[8]; sum += w[9]; sum += w[10]; sum += w[11];
sum += w[12]; sum += w[13]; sum += w[14]; sum += w[15];
w += 16;
}
mlen += 32;
while ((mlen -= 8) >= 0) {
sum += w[0]; sum += w[1]; sum += w[2]; sum += w[3];
w += 4;
}
mlen += 8;
if (mlen == 0 && byte_swapped == 0)
continue;
REDUCE;
while ((mlen -= 2) >= 0) {
sum += *w++;
}
if (byte_swapped) {
REDUCE;
sum <<= 8;
byte_swapped = 0;
if (mlen == -1) {
s_util.c[1] = *(const u8 *) w;
sum += s_util.s;
mlen = 0;
} else
mlen = -1;
} else if (mlen == -1)
s_util.c[0] = *(const u8 *) w;
}
if (mlen == -1) {
s_util.c[1] = 0;
sum += s_util.s;
}
REDUCE;
return (~sum & 0xffff);
}
static inline u16 p4_csum(const struct ip *ip, const u8 *data, u16 len,
u8 next_proto)
{
struct cksum_vec vec[2];
struct pseudo_hdr {
u32 src;
u32 dst;
u8 mbz;
u8 proto;
u16 len;
} ph;
memset(&ph, 0, sizeof(ph));
ph.len = htons(len);
ph.mbz = 0;
ph.proto = next_proto;
ph.src = ip->ip_src.s_addr;
ph.dst = ip->ip_dst.s_addr;
vec[0].ptr = (const u8 *) (void *) &ph;
vec[0].len = sizeof(ph);
vec[1].ptr = data;
vec[1].len = len;
return __in_cksum(vec, 2);
}
#endif /* CSUM_H */
|
