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
|
/*-
* Copyright (c) 1990 The Regents of the University of California.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* This product includes software developed by the University of
* California, Berkeley and its contributors.
* 4. Neither the name of the University nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*
* from tahoe: in_cksum.c 1.2 86/01/05
* from: @(#)in_cksum.c 1.3 (Berkeley) 1/19/91
* $Id$
*/
#include "param.h"
#include "sys/mbuf.h"
/*
* Checksum routine for Internet Protocol family headers.
*
* This routine is very heavily used in the network
* code and should be modified for each CPU to be as fast as possible.
*
* This implementation is 386 version.
*/
#undef ADDCARRY
#define ADDCARRY(x) if ((x) > 0xffff) (x) -= 0xffff
#define REDUCE {sum = (sum & 0xffff) + (sum >> 16); ADDCARRY(sum);}
/*
* Thanks to gcc we don't have to guess
* which registers contain sum & w.
*/
#define CLC asm("clc")
#define ADD(n) asm("adcl " #n "(%2), %0": "=r"(sum): "0"(sum), "r"(w))
#define MOP asm("adcl $0, %0": "=r"(sum): "0"(sum))
in_cksum(m, len)
register struct mbuf *m;
register int len;
{
register u_short *w;
register unsigned sum = 0;
register int mlen = 0;
int byte_swapped = 0;
union { char c[2]; u_short s; } su;
for (;m && len; m = m->m_next) {
if (m->m_len == 0)
continue;
w = mtod(m, u_short *);
if (mlen == -1) {
/*
* The first byte of this mbuf is the continuation
* of a word spanning between this mbuf and the
* last mbuf.
*/
/* su.c[0] is already saved when scanning previous
* mbuf. sum was REDUCEd when we found mlen == -1
*/
su.c[1] = *(u_char *)w;
sum += su.s;
w = (u_short *)((char *)w + 1);
mlen = m->m_len - 1;
len--;
} else
mlen = m->m_len;
if (len < mlen)
mlen = len;
len -= mlen;
/*
* Force to long boundary so we do longword aligned
* memory operations
*/
if (3 & (int) w) {
REDUCE;
if ((1 & (int) w) && (mlen > 0)) {
sum <<= 8;
su.c[0] = *(char *)w;
w = (u_short *)((char *)w + 1);
mlen--;
byte_swapped = 1;
}
if ((2 & (int) w) && (mlen >= 2)) {
sum += *w++;
mlen -= 2;
}
}
/*
* Do as much of the checksum as possible 32 bits at at time.
* In fact, this loop is unrolled to make overhead from
* branches &c small.
*/
while ((mlen -= 32) >= 0) {
/*
* Clear the carry flag, add with carry 16 words
* and fold-in last carry by adding a 0 with carry.
*/
CLC;
ADD(0); ADD(4); ADD(8); ADD(12);
ADD(16); ADD(20); ADD(24); ADD(28);
MOP; w += 16;
}
mlen += 32;
while ((mlen -= 8) >= 0) {
CLC;
ADD(0); ADD(4);
MOP;
w += 4;
}
mlen += 8;
if (mlen == 0 && byte_swapped == 0)
continue; /* worth 1% maybe ?? */
REDUCE;
while ((mlen -= 2) >= 0) {
sum += *w++;
}
if (byte_swapped) {
sum <<= 8;
byte_swapped = 0;
if (mlen == -1) {
su.c[1] = *(char *)w;
sum += su.s;
mlen = 0;
} else
mlen = -1;
} else if (mlen == -1)
/*
* This mbuf has odd number of bytes.
* There could be a word split betwen
* this mbuf and the next mbuf.
* Save the last byte (to prepend to next mbuf).
*/
su.c[0] = *(char *)w;
}
if (len)
printf("cksum: out of data\n");
if (mlen == -1) {
/* The last mbuf has odd # of bytes. Follow the
standard (the odd byte is shifted left by 8 bits) */
su.c[1] = 0;
sum += su.s;
}
REDUCE;
return (~sum & 0xffff);
}
|
