checksum.c
2.54 KB
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
/*
* Network checksum routines
*
* Copyright (C) 1999, 2003 Hewlett-Packard Co
* Stephane Eranian <eranian@hpl.hp.com>
*
* Most of the code coming from arch/alpha/lib/checksum.c
*
* This file contains network checksum routines that are better done
* in an architecture-specific manner due to speed..
*/
#include <linux/module.h>
#include <linux/string.h>
#include <asm/byteorder.h>
static inline unsigned short
from64to16 (unsigned long x)
{
/* add up 32-bit words for 33 bits */
x = (x & 0xffffffff) + (x >> 32);
/* add up 16-bit and 17-bit words for 17+c bits */
x = (x & 0xffff) + (x >> 16);
/* add up 16-bit and 2-bit for 16+c bit */
x = (x & 0xffff) + (x >> 16);
/* add up carry.. */
x = (x & 0xffff) + (x >> 16);
return x;
}
/*
* computes the checksum of the TCP/UDP pseudo-header
* returns a 16-bit checksum, already complemented.
*/
__sum16
csum_tcpudp_magic (__be32 saddr, __be32 daddr, unsigned short len,
unsigned short proto, __wsum sum)
{
return (__force __sum16)~from64to16(
(__force u64)saddr + (__force u64)daddr +
(__force u64)sum + ((len + proto) << 8));
}
EXPORT_SYMBOL(csum_tcpudp_magic);
__wsum
csum_tcpudp_nofold (__be32 saddr, __be32 daddr, unsigned short len,
unsigned short proto, __wsum sum)
{
unsigned long result;
result = (__force u64)saddr + (__force u64)daddr +
(__force u64)sum + ((len + proto) << 8);
/* Fold down to 32-bits so we don't lose in the typedef-less network stack. */
/* 64 to 33 */
result = (result & 0xffffffff) + (result >> 32);
/* 33 to 32 */
result = (result & 0xffffffff) + (result >> 32);
return (__force __wsum)result;
}
EXPORT_SYMBOL(csum_tcpudp_nofold);
extern unsigned long do_csum (const unsigned char *, long);
/*
* 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
*/
__wsum csum_partial(const void *buff, int len, __wsum sum)
{
u64 result = do_csum(buff, len);
/* add in old sum, and carry.. */
result += (__force u32)sum;
/* 32+c bits -> 32 bits */
result = (result & 0xffffffff) + (result >> 32);
return (__force __wsum)result;
}
EXPORT_SYMBOL(csum_partial);
/*
* this routine is used for miscellaneous IP-like checksums, mainly
* in icmp.c
*/
__sum16 ip_compute_csum (const void *buff, int len)
{
return (__force __sum16)~do_csum(buff,len);
}
EXPORT_SYMBOL(ip_compute_csum);