aboutsummaryrefslogtreecommitdiff
path: root/arch/alpha/lib/checksum.c
blob: ab3761c437a848f7ca965d62f5945a93ade945d0 (plain)
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
180
181
182
183
/*
 * arch/alpha/lib/checksum.c
 *
 * This file contains network checksum routines that are better done
 * in an architecture-specific manner due to speed..
 * Comments in other versions indicate that the algorithms are from RFC1071
 *
 * accellerated versions (and 21264 assembly versions ) contributed by
 *	Rick Gorton	<rick.gorton@alpha-processor.com>
 */
 
#include <linux/module.h>
#include <linux/string.h>

#include <asm/byteorder.h>

static inline unsigned short from64to16(unsigned long x)
{
	/* Using extract instructions is a bit more efficient
	   than the original shift/bitmask version.  */

	union {
		unsigned long	ul;
		unsigned int	ui[2];
		unsigned short	us[4];
	} in_v, tmp_v, out_v;

	in_v.ul = x;
	tmp_v.ul = (unsigned long) in_v.ui[0] + (unsigned long) in_v.ui[1];

	/* Since the bits of tmp_v.sh[3] are going to always be zero,
	   we don't have to bother to add that in.  */
	out_v.ul = (unsigned long) tmp_v.us[0] + (unsigned long) tmp_v.us[1]
			+ (unsigned long) tmp_v.us[2];

	/* Similarly, out_v.us[2] is always zero for the final add.  */
	return out_v.us[0] + out_v.us[1];
}

/*
 * 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));
}

__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;
}

/*
 * Do a 64-bit checksum on an arbitrary memory area..
 *
 * This isn't a great routine, but it's not _horrible_ either. The
 * inner loop could be unrolled a bit further, and there are better
 * ways to do the carry, but this is reasonable.
 */
static inline unsigned long do_csum(const unsigned char * buff, int len)
{
	int odd, count;
	unsigned long result = 0;

	if (len <= 0)
		goto out;
	odd = 1 & (unsigned long) buff;
	if (odd) {
		result = *buff << 8;
		len--;
		buff++;
	}
	count = len >> 1;		/* nr of 16-bit words.. */
	if (count) {
		if (2 & (unsigned long) buff) {
			result += *(unsigned short *) buff;
			count--;
			len -= 2;
			buff += 2;
		}
		count >>= 1;		/* nr of 32-bit words.. */
		if (count) {
			if (4 & (unsigned long) buff) {
				result += *(unsigned int *) buff;
				count--;
				len -= 4;
				buff += 4;
			}
			count >>= 1;	/* nr of 64-bit words.. */
			if (count) {
				unsigned long carry = 0;
				do {
					unsigned long w = *(unsigned long *) buff;
					count--;
					buff += 8;
					result += carry;
					result += w;
					carry = (w > result);
				} while (count);
				result += carry;
				result = (result & 0xffffffff) + (result >> 32);
			}
			if (len & 4) {
				result += *(unsigned int *) buff;
				buff += 4;
			}
		}
		if (len & 2) {
			result += *(unsigned short *) buff;
			buff += 2;
		}
	}
	if (len & 1)
		result += *buff;
	result = from64to16(result);
	if (odd)
		result = ((result >> 8) & 0xff) | ((result & 0xff) << 8);
out:
	return result;
}

/*
 *	This is a version of ip_compute_csum() optimized for IP headers,
 *	which always checksum on 4 octet boundaries.
 */
__sum16 ip_fast_csum(const void *iph, unsigned int ihl)
{
	return (__force __sum16)~do_csum(iph,ihl*4);
}

/*
 * 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)
{
	unsigned long 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)~from64to16(do_csum(buff,len));
}