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1.1 root 1: /*
2: * Copyright (c) 1982, 1988 Regents of the University of California.
3: * All rights reserved.
4: *
5: * Redistribution is only permitted until one year after the first shipment
6: * of 4.4BSD by the Regents. Otherwise, redistribution and use in source and
7: * binary forms are permitted provided that: (1) source distributions retain
8: * this entire copyright notice and comment, and (2) distributions including
9: * binaries display the following acknowledgement: This product includes
10: * software developed by the University of California, Berkeley and its
11: * contributors'' in the documentation or other materials provided with the
12: * distribution and in all advertising materials mentioning features or use
13: * of this software. Neither the name of the University nor the names of
14: * its contributors may be used to endorse or promote products derived from
15: * this software without specific prior written permission.
16: * THIS SOFTWARE IS PROVIDED AS IS'' AND WITHOUT ANY EXPRESS OR IMPLIED
17: * WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
18: * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
19: *
20: * @(#)ns_cksum.c 7.5 (Berkeley) 6/28/90
21: */
22:
23: #include "param.h"
24: #include "mbuf.h"
25: /*
26: * Checksum routine for Network Systems Protocol Packets (Big-Endian).
27: *
28: * This routine is very heavily used in the network
29: * code and should be modified for each CPU to be as fast as possible.
30: */
31:
32: #define ADDCARRY(x) { if ((x) > 65535) (x) -= 65535; }
33: #define FOLD(x) {l_util.l = (x); (x) = l_util.s[0] + l_util.s[1]; ADDCARRY(x);}
34:
35: u_short
36: ns_cksum(m, len)
37: register struct mbuf *m;
38: register int len;
39: {
40: register u_short *w;
41: register int sum = 0;
42: register int mlen = 0;
43: register int sum2;
44:
45: union {
46: u_short s[2];
47: long l;
48: } l_util;
49:
50: for (;m && len; m = m->m_next) {
51: if (m->m_len == 0)
52: continue;
53: /*
54: * Each trip around loop adds in
55: * word from one mbuf segment.
56: */
57: w = mtod(m, u_short *);
58: if (mlen == -1) {
59: /*
60: * There is a byte left from the last segment;
61: * ones-complement add it into the checksum.
62: */
63: sum += *(u_char *)w; /* Big-Endian, else << 8 */
64: sum += sum;
65: w = (u_short *)(1 + (char *)w);
66: mlen = m->m_len - 1;
67: len--;
68: FOLD(sum);
69: } else
70: mlen = m->m_len;
71: if (len < mlen)
72: mlen = len;
73: len -= mlen;
74: /*
75: * We can do a 16 bit ones complement sum using
76: * 32 bit arithmetic registers for adding,
77: * with carries from the low added
78: * into the high (by normal carry-chaining)
79: * so long as we fold back before 16 carries have occured.
80: */
81: if (1 & (int) w)
82: goto uuuuglyy;
83: #ifndef TINY
84: /* -DTINY reduces the size from 1250 to 550, but slows it down by 22% */
85: while ((mlen -= 32) >= 0) {
86: sum += w[0]; sum += sum; sum += w[1]; sum += sum;
87: sum += w[2]; sum += sum; sum += w[3]; sum += sum;
88: sum += w[4]; sum += sum; sum += w[5]; sum += sum;
89: sum += w[6]; sum += sum; sum += w[7]; sum += sum;
90: FOLD(sum);
91: sum += w[8]; sum += sum; sum += w[9]; sum += sum;
92: sum += w[10]; sum += sum; sum += w[11]; sum += sum;
93: sum += w[12]; sum += sum; sum += w[13]; sum += sum;
94: sum += w[14]; sum += sum; sum += w[15]; sum += sum;
95: FOLD(sum);
96: w += 16;
97: }
98: mlen += 32;
99: #endif
100: while ((mlen -= 8) >= 0) {
101: sum += w[0]; sum += sum; sum += w[1]; sum += sum;
102: sum += w[2]; sum += sum; sum += w[3]; sum += sum;
103: FOLD(sum);
104: w += 4;
105: }
106: mlen += 8;
107: while ((mlen -= 2) >= 0) {
108: sum += *w++; sum += sum;
109: }
110: goto commoncase;
111: uuuuglyy:
112: /* Big-Endian; else reverse ww and vv */
113: #define ww(n) (((u_char *)w)[n + n + 1])
114: #define vv(n) (((u_char *)w)[n + n])
115: sum2 = 0;
116: #ifndef TINY
117: while ((mlen -= 32) >= 0) {
118: sum += ww(0); sum += sum; sum += ww(1); sum += sum;
119: sum += ww(2); sum += sum; sum += ww(3); sum += sum;
120: sum += ww(4); sum += sum; sum += ww(5); sum += sum;
121: sum += ww(6); sum += sum; sum += ww(7); sum += sum;
122: FOLD(sum);
123: sum += ww(8); sum += sum; sum += ww(9); sum += sum;
124: sum += ww(10); sum += sum; sum += ww(11); sum += sum;
125: sum += ww(12); sum += sum; sum += ww(13); sum += sum;
126: sum += ww(14); sum += sum; sum += ww(15); sum += sum;
127: FOLD(sum);
128: sum2 += vv(0); sum2 += sum2; sum2 += vv(1); sum2 += sum2;
129: sum2 += vv(2); sum2 += sum2; sum2 += vv(3); sum2 += sum2;
130: sum2 += vv(4); sum2 += sum2; sum2 += vv(5); sum2 += sum2;
131: sum2 += vv(6); sum2 += sum2; sum2 += vv(7); sum2 += sum2;
132: FOLD(sum2);
133: sum2 += vv(8); sum2 += sum2; sum2 += vv(9); sum2 += sum2;
134: sum2 += vv(10); sum2 += sum2; sum2 += vv(11); sum2 += sum2;
135: sum2 += vv(12); sum2 += sum2; sum2 += vv(13); sum2 += sum2;
136: sum2 += vv(14); sum2 += sum2; sum2 += vv(15); sum2 += sum2;
137: FOLD(sum2);
138: w += 16;
139: }
140: mlen += 32;
141: #endif
142: while ((mlen -= 8) >= 0) {
143: sum += ww(0); sum += sum; sum += ww(1); sum += sum;
144: sum += ww(2); sum += sum; sum += ww(3); sum += sum;
145: FOLD(sum);
146: sum2 += vv(0); sum2 += sum2; sum2 += vv(1); sum2 += sum2;
147: sum2 += vv(2); sum2 += sum2; sum2 += vv(3); sum2 += sum2;
148: FOLD(sum2);
149: w += 4;
150: }
151: mlen += 8;
152: while ((mlen -= 2) >= 0) {
153: sum += ww(0); sum += sum;
154: sum2 += vv(0); sum2 += sum2;
155: w++;
156: }
157: sum += (sum2 << 8);
158: commoncase:
159: if (mlen == -1) {
160: sum += *(u_char *)w << 8; /* Big-Endian, else no << 8 */
161: }
162: FOLD(sum);
163: }
164: if (mlen == -1) {
165: /* We had an odd number of bytes to sum; assume a garbage
166: byte of zero and clean up */
167: sum += sum;
168: FOLD(sum);
169: }
170: /*
171: * sum has already been kept to low sixteen bits.
172: * just examine result and exit.
173: */
174: if(sum==0xffff) sum = 0;
175: return (sum);
176: }
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