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1.1 root 1: /*
2: * Copyright (c) 1988, 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: * @(#)in_cksum.c 8.1 (Berkeley) 6/10/93
34: * in_cksum.c,v 1.2 1994/08/02 07:48:16 davidg Exp
35: */
36:
37: #include <slirp.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: * XXX Since we will never span more than 1 mbuf, we can optimise this
46: */
47:
48: #define ADDCARRY(x) (x > 65535 ? x -= 65535 : x)
49: #define REDUCE {l_util.l = sum; sum = l_util.s[0] + l_util.s[1]; ADDCARRY(sum);}
50:
51: int cksum(struct mbuf *m, int len)
52: {
53: register u_int16_t *w;
54: register int sum = 0;
55: register int mlen = 0;
56: int byte_swapped = 0;
57:
58: union {
59: u_int8_t c[2];
60: u_int16_t s;
61: } s_util;
62: union {
63: u_int16_t s[2];
64: u_int32_t l;
65: } l_util;
66:
67: if (m->m_len == 0)
68: goto cont;
69: w = mtod(m, u_int16_t *);
70:
71: mlen = m->m_len;
72:
73: if (len < mlen)
74: mlen = len;
75: len -= mlen;
76: /*
77: * Force to even boundary.
78: */
79: if ((1 & (long) w) && (mlen > 0)) {
80: REDUCE;
81: sum <<= 8;
82: s_util.c[0] = *(u_int8_t *)w;
83: w = (u_int16_t *)((int8_t *)w + 1);
84: mlen--;
85: byte_swapped = 1;
86: }
87: /*
88: * Unroll the loop to make overhead from
89: * branches &c small.
90: */
91: while ((mlen -= 32) >= 0) {
92: sum += w[0]; sum += w[1]; sum += w[2]; sum += w[3];
93: sum += w[4]; sum += w[5]; sum += w[6]; sum += w[7];
94: sum += w[8]; sum += w[9]; sum += w[10]; sum += w[11];
95: sum += w[12]; sum += w[13]; sum += w[14]; sum += w[15];
96: w += 16;
97: }
98: mlen += 32;
99: while ((mlen -= 8) >= 0) {
100: sum += w[0]; sum += w[1]; sum += w[2]; sum += w[3];
101: w += 4;
102: }
103: mlen += 8;
104: if (mlen == 0 && byte_swapped == 0)
105: goto cont;
106: REDUCE;
107: while ((mlen -= 2) >= 0) {
108: sum += *w++;
109: }
110:
111: if (byte_swapped) {
112: REDUCE;
113: sum <<= 8;
114: byte_swapped = 0;
115: if (mlen == -1) {
116: s_util.c[1] = *(u_int8_t *)w;
117: sum += s_util.s;
118: mlen = 0;
119: } else
120:
121: mlen = -1;
122: } else if (mlen == -1)
123: s_util.c[0] = *(u_int8_t *)w;
124:
125: cont:
126: #ifdef DEBUG
127: if (len) {
128: DEBUG_ERROR((dfd, "cksum: out of data\n"));
129: DEBUG_ERROR((dfd, " len = %d\n", len));
130: }
131: #endif
132: if (mlen == -1) {
133: /* The last mbuf has odd # of bytes. Follow the
134: standard (the odd byte may be shifted left by 8 bits
135: or not as determined by endian-ness of the machine) */
136: s_util.c[1] = 0;
137: sum += s_util.s;
138: }
139: REDUCE;
140: return (~sum & 0xffff);
141: }
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