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1.1 root 1: /*
2: * Copyright (c) 1988 Regents of the University of California.
3: * 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: * @(#)in_cksum.c 7.3 (Berkeley) 6/28/90
34: */
35:
36: #include "../h/types.h"
37: #include "../h/mbuf.h"
38:
39: /*
40: * Checksum routine for Internet Protocol family headers (Portable Version).
41: *
42: * This routine is very heavily used in the network
43: * code and should be modified for each CPU to be as fast as possible.
44: */
45:
46: #define ADDCARRY(x) (x > 65535 ? x -= 65535 : x)
47: #define REDUCE {l_util.l = sum; sum = l_util.s[0] + l_util.s[1]; ADDCARRY(sum);}
48:
49: in_cksum_c(m, len)
50: register struct mbuf *m;
51: register int len;
52: {
53: register u_short *w;
54: register int sum = 0;
55: register int mlen = 0;
56: int byte_swapped = 0;
57:
58: union {
59: char c[2];
60: u_short s;
61: } s_util;
62: union {
63: u_short s[2];
64: long l;
65: } l_util;
66:
67: for (;m && len; m = m->m_next) {
68: if (m->m_len == 0)
69: continue;
70: w = mtod(m, u_short *);
71: if (mlen == -1) {
72: /*
73: * The first byte of this mbuf is the continuation
74: * of a word spanning between this mbuf and the
75: * last mbuf.
76: *
77: * s_util.c[0] is already saved when scanning previous
78: * mbuf.
79: */
80: s_util.c[1] = *(char *)w;
81: sum += s_util.s;
82: w = (u_short *)((char *)w + 1);
83: mlen = m->m_len - 1;
84: len--;
85: } else
86: mlen = m->m_len;
87: if (len < mlen)
88: mlen = len;
89: len -= mlen;
90: /*
91: * Force to even boundary.
92: */
93: if ((1 & (int) w) && (mlen > 0)) {
94: REDUCE;
95: sum <<= 8;
96: s_util.c[0] = *(u_char *)w;
97: w = (u_short *)((char *)w + 1);
98: mlen--;
99: byte_swapped = 1;
100: }
101: /*
102: * Unroll the loop to make overhead from
103: * branches &c small.
104: */
105: while ((mlen -= 32) >= 0) {
106: sum += w[0]; sum += w[1]; sum += w[2]; sum += w[3];
107: sum += w[4]; sum += w[5]; sum += w[6]; sum += w[7];
108: sum += w[8]; sum += w[9]; sum += w[10]; sum += w[11];
109: sum += w[12]; sum += w[13]; sum += w[14]; sum += w[15];
110: w += 16;
111: }
112: mlen += 32;
113: while ((mlen -= 8) >= 0) {
114: sum += w[0]; sum += w[1]; sum += w[2]; sum += w[3];
115: w += 4;
116: }
117: mlen += 8;
118: if (mlen == 0 && byte_swapped == 0)
119: continue;
120: REDUCE;
121: while ((mlen -= 2) >= 0) {
122: sum += *w++;
123: }
124: if (byte_swapped) {
125: REDUCE;
126: sum <<= 8;
127: byte_swapped = 0;
128: if (mlen == -1) {
129: s_util.c[1] = *(char *)w;
130: sum += s_util.s;
131: mlen = 0;
132: } else
133: mlen = -1;
134: } else if (mlen == -1)
135: s_util.c[0] = *(char *)w;
136: }
137: if (len)
138: printf("cksum: out of data\n");
139: if (mlen == -1) {
140: /* The last mbuf has odd # of bytes. Follow the
141: standard (the odd byte may be shifted left by 8 bits
142: or not as determined by endian-ness of the machine) */
143: s_util.c[1] = 0;
144: sum += s_util.s;
145: }
146: REDUCE;
147: return (~sum & 0xffff);
148: }
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