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
|
#ifndef _I386_CHECKSUM_H
#define _I386_CHECKSUM_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
*/
unsigned int csum_partial(const unsigned char * buff, int len, unsigned int sum);
/*
* the same as csum_partial, but copies from src while it
* checksums
*
* here even more important to align src and dst on a 32-bit (or even
* better 64-bit) boundary
*/
unsigned int csum_partial_copy( const char *src, char *dst, int len, int sum);
/*
* the same as csum_partial_copy, but copies from user space.
*
* here even more important to align src and dst on a 32-bit (or even
* better 64-bit) boundary
*/
unsigned int csum_partial_copy_fromuser(const char *src, char *dst, int len, int 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 unsigned short ip_fast_csum(unsigned char * iph,
unsigned int ihl) {
unsigned int sum;
__asm__ __volatile__("
movl (%1), %0
subl $4, %2
jbe 2f
addl 4(%1), %0
adcl 8(%1), %0
adcl 12(%1), %0
1: adcl 16(%1), %0
lea 4(%1), %1
decl %2
jne 1b
adcl $0, %0
movl %0, %2
shrl $16, %0
addw %w2, %w0
adcl $0, %0
notl %0
2:
"
/* Since the input registers which are loaded with iph and ipl
are modified, we must also specify them as outputs, or gcc
will assume they contain their original values. */
: "=r" (sum), "=r" (iph), "=r" (ihl)
: "1" (iph), "2" (ihl));
return(sum);
}
/*
* Fold a partial checksum
*/
static inline unsigned int csum_fold(unsigned int sum)
{
__asm__("
addl %1, %0
adcl $0xffff, %0
"
: "=r" (sum)
: "r" (sum << 16), "0" (sum & 0xffff0000)
);
return (~sum) >> 16;
}
/*
* computes the checksum of the TCP/UDP pseudo-header
* returns a 16-bit checksum, already complemented
*/
static inline unsigned short int csum_tcpudp_magic(unsigned long saddr,
unsigned long daddr,
unsigned short len,
unsigned short proto,
unsigned int sum) {
__asm__("
addl %1, %0
adcl %2, %0
adcl %3, %0
adcl $0, %0
"
: "=r" (sum)
: "g" (daddr), "g"(saddr), "g"((ntohs(len)<<16)+proto*256), "0"(sum));
return csum_fold(sum);
}
/*
* this routine is used for miscellaneous IP-like checksums, mainly
* in icmp.c
*/
static inline unsigned short ip_compute_csum(unsigned char * buff, int len) {
return csum_fold (csum_partial(buff, len, 0));
}
#endif
|
