FreeBSD/Linux Kernel Cross Reference
sys/netns/ns_cksum.c
1 /*
2 * Copyright (c) 1982, 1992, 1993
3 * The Regents of the University of California. All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 * notice, this list of conditions and the following disclaimer in the
12 * documentation and/or other materials provided with the distribution.
13 * 3. All advertising materials mentioning features or use of this software
14 * must display the following acknowledgement:
15 * This product includes software developed by the University of
16 * California, Berkeley and its contributors.
17 * 4. Neither the name of the University nor the names of its contributors
18 * may be used to endorse or promote products derived from this software
19 * without specific prior written permission.
20 *
21 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
22 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
23 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
24 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
25 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
26 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
27 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
28 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
29 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
30 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
31 * SUCH DAMAGE.
32 *
33 * @(#)ns_cksum.c 8.1 (Berkeley) 6/10/93
34 * $FreeBSD$
35 */
36
37 #include <sys/param.h>
38 #include <sys/mbuf.h>
39
40 /*
41 * Checksum routine for Network Systems Protocol Packets (Big-Endian).
42 *
43 * This routine is very heavily used in the network
44 * code and should be modified for each CPU to be as fast as possible.
45 */
46
47 #define ADDCARRY(x) { if ((x) > 65535) (x) -= 65535; }
48 #define FOLD(x) {l_util.l = (x); (x) = l_util.s[0] + l_util.s[1]; ADDCARRY(x);}
49
50 u_short
51 ns_cksum(m, len)
52 register struct mbuf *m;
53 register int len;
54 {
55 register u_short *w;
56 register int sum = 0;
57 register int mlen = 0;
58 register int sum2;
59
60 union {
61 u_short s[2];
62 long l;
63 } l_util;
64
65 for (;m && len; m = m->m_next) {
66 if (m->m_len == 0)
67 continue;
68 /*
69 * Each trip around loop adds in
70 * word from one mbuf segment.
71 */
72 w = mtod(m, u_short *);
73 if (mlen == -1) {
74 /*
75 * There is a byte left from the last segment;
76 * ones-complement add it into the checksum.
77 */
78 #if BYTE_ORDER == BIG_ENDIAN
79 sum += *(u_char *)w;
80 #else
81 sum += *(u_char *)w << 8;
82 #endif
83 sum += sum;
84 w = (u_short *)(1 + (char *)w);
85 mlen = m->m_len - 1;
86 len--;
87 FOLD(sum);
88 } else
89 mlen = m->m_len;
90 if (len < mlen)
91 mlen = len;
92 len -= mlen;
93 /*
94 * We can do a 16 bit ones complement sum using
95 * 32 bit arithmetic registers for adding,
96 * with carries from the low added
97 * into the high (by normal carry-chaining)
98 * so long as we fold back before 16 carries have occured.
99 */
100 if (1 & (int) w)
101 goto uuuuglyy;
102 #ifndef TINY
103 /* -DTINY reduces the size from 1250 to 550, but slows it down by 22% */
104 while ((mlen -= 32) >= 0) {
105 sum += w[0]; sum += sum; sum += w[1]; sum += sum;
106 sum += w[2]; sum += sum; sum += w[3]; sum += sum;
107 sum += w[4]; sum += sum; sum += w[5]; sum += sum;
108 sum += w[6]; sum += sum; sum += w[7]; sum += sum;
109 FOLD(sum);
110 sum += w[8]; sum += sum; sum += w[9]; sum += sum;
111 sum += w[10]; sum += sum; sum += w[11]; sum += sum;
112 sum += w[12]; sum += sum; sum += w[13]; sum += sum;
113 sum += w[14]; sum += sum; sum += w[15]; sum += sum;
114 FOLD(sum);
115 w += 16;
116 }
117 mlen += 32;
118 #endif
119 while ((mlen -= 8) >= 0) {
120 sum += w[0]; sum += sum; sum += w[1]; sum += sum;
121 sum += w[2]; sum += sum; sum += w[3]; sum += sum;
122 FOLD(sum);
123 w += 4;
124 }
125 mlen += 8;
126 while ((mlen -= 2) >= 0) {
127 sum += *w++; sum += sum;
128 }
129 goto commoncase;
130 uuuuglyy:
131 #if BYTE_ORDER == BIG_ENDIAN
132 #define ww(n) (((u_char *)w)[n + n + 1])
133 #define vv(n) (((u_char *)w)[n + n])
134 #else
135 #if BYTE_ORDER == LITTLE_ENDIAN
136 #define vv(n) (((u_char *)w)[n + n + 1])
137 #define ww(n) (((u_char *)w)[n + n])
138 #endif
139 #endif
140 sum2 = 0;
141 #ifndef TINY
142 while ((mlen -= 32) >= 0) {
143 sum += ww(0); sum += sum; sum += ww(1); sum += sum;
144 sum += ww(2); sum += sum; sum += ww(3); sum += sum;
145 sum += ww(4); sum += sum; sum += ww(5); sum += sum;
146 sum += ww(6); sum += sum; sum += ww(7); sum += sum;
147 FOLD(sum);
148 sum += ww(8); sum += sum; sum += ww(9); sum += sum;
149 sum += ww(10); sum += sum; sum += ww(11); sum += sum;
150 sum += ww(12); sum += sum; sum += ww(13); sum += sum;
151 sum += ww(14); sum += sum; sum += ww(15); sum += sum;
152 FOLD(sum);
153 sum2 += vv(0); sum2 += sum2; sum2 += vv(1); sum2 += sum2;
154 sum2 += vv(2); sum2 += sum2; sum2 += vv(3); sum2 += sum2;
155 sum2 += vv(4); sum2 += sum2; sum2 += vv(5); sum2 += sum2;
156 sum2 += vv(6); sum2 += sum2; sum2 += vv(7); sum2 += sum2;
157 FOLD(sum2);
158 sum2 += vv(8); sum2 += sum2; sum2 += vv(9); sum2 += sum2;
159 sum2 += vv(10); sum2 += sum2; sum2 += vv(11); sum2 += sum2;
160 sum2 += vv(12); sum2 += sum2; sum2 += vv(13); sum2 += sum2;
161 sum2 += vv(14); sum2 += sum2; sum2 += vv(15); sum2 += sum2;
162 FOLD(sum2);
163 w += 16;
164 }
165 mlen += 32;
166 #endif
167 while ((mlen -= 8) >= 0) {
168 sum += ww(0); sum += sum; sum += ww(1); sum += sum;
169 sum += ww(2); sum += sum; sum += ww(3); sum += sum;
170 FOLD(sum);
171 sum2 += vv(0); sum2 += sum2; sum2 += vv(1); sum2 += sum2;
172 sum2 += vv(2); sum2 += sum2; sum2 += vv(3); sum2 += sum2;
173 FOLD(sum2);
174 w += 4;
175 }
176 mlen += 8;
177 while ((mlen -= 2) >= 0) {
178 sum += ww(0); sum += sum;
179 sum2 += vv(0); sum2 += sum2;
180 w++;
181 }
182 sum += (sum2 << 8);
183 commoncase:
184 if (mlen == -1) {
185 #if BYTE_ORDER == BIG_ENDIAN
186 sum += *(u_char *)w << 8;
187 #else
188 sum += *(u_char *)w;
189 #endif
190 }
191 FOLD(sum);
192 }
193 if (mlen == -1) {
194 /* We had an odd number of bytes to sum; assume a garbage
195 byte of zero and clean up */
196 sum += sum;
197 FOLD(sum);
198 }
199 /*
200 * sum has already been kept to low sixteen bits.
201 * just examine result and exit.
202 */
203 if(sum==0xffff) sum = 0;
204 return (sum);
205 }
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