FreeBSD/Linux Kernel Cross Reference
sys/netns/ns_cksum.c
1 /* $NetBSD: ns_cksum.c,v 1.10 2004/04/19 00:10:48 matt Exp $ */
2
3 /*
4 * Copyright (c) 1982, 1992, 1993
5 * The Regents of the University of California. All rights reserved.
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
9 * are met:
10 * 1. Redistributions of source code must retain the above copyright
11 * notice, this list of conditions and the following disclaimer.
12 * 2. Redistributions in binary form must reproduce the above copyright
13 * notice, this list of conditions and the following disclaimer in the
14 * documentation and/or other materials provided with the distribution.
15 * 3. Neither the name of the University nor the names of its contributors
16 * may be used to endorse or promote products derived from this software
17 * without specific prior written permission.
18 *
19 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
20 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
21 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
22 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
23 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
24 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
25 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
26 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
27 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
28 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
29 * SUCH DAMAGE.
30 *
31 * @(#)ns_cksum.c 8.1 (Berkeley) 6/10/93
32 */
33
34 #include <sys/cdefs.h>
35 __KERNEL_RCSID(0, "$NetBSD: ns_cksum.c,v 1.10 2004/04/19 00:10:48 matt Exp $");
36
37 #include <sys/param.h>
38 #include <sys/mbuf.h>
39 #include <netns/ns_var.h>
40
41 /*
42 * Checksum routine for Network Systems Protocol Packets (Big-Endian).
43 *
44 * This routine is very heavily used in the network
45 * code and should be modified for each CPU to be as fast as possible.
46 */
47
48 #define ADDCARRY(x) { if ((x) > 65535) (x) -= 65535; }
49 #define FOLD(x) {l_util.l = (x); (x) = l_util.s[0] + l_util.s[1]; ADDCARRY(x);}
50
51 u_int16_t
52 ns_cksum(struct mbuf *m, int len)
53 {
54 u_int16_t *w;
55 int sum = 0;
56 int mlen = 0;
57 int sum2;
58
59 union {
60 u_int16_t s[2];
61 int32_t l;
62 } l_util;
63
64 for (;m && len; m = m->m_next) {
65 if (m->m_len == 0)
66 continue;
67 /*
68 * Each trip around loop adds in
69 * word from one mbuf segment.
70 */
71 w = mtod(m, u_int16_t *);
72 if (mlen == -1) {
73 /*
74 * There is a byte left from the last segment;
75 * ones-complement add it into the checksum.
76 */
77 #if BYTE_ORDER == BIG_ENDIAN
78 sum += *(u_int8_t *)w;
79 #else
80 sum += *(u_int8_t *)w << 8;
81 #endif
82 sum += sum;
83 w = (u_int16_t *)(1 + (char *)w);
84 mlen = m->m_len - 1;
85 len--;
86 FOLD(sum);
87 } else
88 mlen = m->m_len;
89 if (len < mlen)
90 mlen = len;
91 len -= mlen;
92 /*
93 * We can do a 16 bit ones complement sum using
94 * 32 bit arithmetic registers for adding,
95 * with carries from the low added
96 * into the high (by normal carry-chaining)
97 * so long as we fold back before 16 carries have occurred.
98 */
99 if (1 & (long) w)
100 goto uuuuglyy;
101 #ifndef TINY
102 /* -DTINY reduces the size from 1250 to 550, but slows it down by 22% */
103 while ((mlen -= 32) >= 0) {
104 sum += w[0]; sum += sum; sum += w[1]; sum += sum;
105 sum += w[2]; sum += sum; sum += w[3]; sum += sum;
106 sum += w[4]; sum += sum; sum += w[5]; sum += sum;
107 sum += w[6]; sum += sum; sum += w[7]; sum += sum;
108 FOLD(sum);
109 sum += w[8]; sum += sum; sum += w[9]; sum += sum;
110 sum += w[10]; sum += sum; sum += w[11]; sum += sum;
111 sum += w[12]; sum += sum; sum += w[13]; sum += sum;
112 sum += w[14]; sum += sum; sum += w[15]; sum += sum;
113 FOLD(sum);
114 w += 16;
115 }
116 mlen += 32;
117 #endif
118 while ((mlen -= 8) >= 0) {
119 sum += w[0]; sum += sum; sum += w[1]; sum += sum;
120 sum += w[2]; sum += sum; sum += w[3]; sum += sum;
121 FOLD(sum);
122 w += 4;
123 }
124 mlen += 8;
125 while ((mlen -= 2) >= 0) {
126 sum += *w++; sum += sum;
127 }
128 goto commoncase;
129 uuuuglyy:
130 #if BYTE_ORDER == BIG_ENDIAN
131 #define ww(n) (((u_int8_t *)w)[n + n + 1])
132 #define vv(n) (((u_int8_t *)w)[n + n])
133 #else
134 #if BYTE_ORDER == LITTLE_ENDIAN
135 #define vv(n) (((u_int8_t *)w)[n + n + 1])
136 #define ww(n) (((u_int8_t *)w)[n + n])
137 #endif
138 #endif
139 sum2 = 0;
140 #ifndef TINY
141 while ((mlen -= 32) >= 0) {
142 sum += ww(0); sum += sum; sum += ww(1); sum += sum;
143 sum += ww(2); sum += sum; sum += ww(3); sum += sum;
144 sum += ww(4); sum += sum; sum += ww(5); sum += sum;
145 sum += ww(6); sum += sum; sum += ww(7); sum += sum;
146 FOLD(sum);
147 sum += ww(8); sum += sum; sum += ww(9); sum += sum;
148 sum += ww(10); sum += sum; sum += ww(11); sum += sum;
149 sum += ww(12); sum += sum; sum += ww(13); sum += sum;
150 sum += ww(14); sum += sum; sum += ww(15); sum += sum;
151 FOLD(sum);
152 sum2 += vv(0); sum2 += sum2; sum2 += vv(1); sum2 += sum2;
153 sum2 += vv(2); sum2 += sum2; sum2 += vv(3); sum2 += sum2;
154 sum2 += vv(4); sum2 += sum2; sum2 += vv(5); sum2 += sum2;
155 sum2 += vv(6); sum2 += sum2; sum2 += vv(7); sum2 += sum2;
156 FOLD(sum2);
157 sum2 += vv(8); sum2 += sum2; sum2 += vv(9); sum2 += sum2;
158 sum2 += vv(10); sum2 += sum2; sum2 += vv(11); sum2 += sum2;
159 sum2 += vv(12); sum2 += sum2; sum2 += vv(13); sum2 += sum2;
160 sum2 += vv(14); sum2 += sum2; sum2 += vv(15); sum2 += sum2;
161 FOLD(sum2);
162 w += 16;
163 }
164 mlen += 32;
165 #endif
166 while ((mlen -= 8) >= 0) {
167 sum += ww(0); sum += sum; sum += ww(1); sum += sum;
168 sum += ww(2); sum += sum; sum += ww(3); sum += sum;
169 FOLD(sum);
170 sum2 += vv(0); sum2 += sum2; sum2 += vv(1); sum2 += sum2;
171 sum2 += vv(2); sum2 += sum2; sum2 += vv(3); sum2 += sum2;
172 FOLD(sum2);
173 w += 4;
174 }
175 mlen += 8;
176 while ((mlen -= 2) >= 0) {
177 sum += ww(0); sum += sum;
178 sum2 += vv(0); sum2 += sum2;
179 w++;
180 }
181 sum += (sum2 << 8);
182 commoncase:
183 if (mlen == -1) {
184 #if BYTE_ORDER == BIG_ENDIAN
185 sum += *(u_int8_t *)w << 8;
186 #else
187 sum += *(u_int8_t *)w;
188 #endif
189 }
190 FOLD(sum);
191 }
192 if (mlen == -1) {
193 /* We had an odd number of bytes to sum; assume a garbage
194 byte of zero and clean up */
195 sum += sum;
196 FOLD(sum);
197 }
198 /*
199 * sum has already been kept to low sixteen bits.
200 * just examine result and exit.
201 */
202 if(sum==0xffff) sum = 0;
203 return (sum);
204 }
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