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7c060394 MK |
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 are permitted | |
6 | * provided that this notice is preserved and that due credit is given | |
7 | * to the University of California at Berkeley. The name of the University | |
8 | * may not be used to endorse or promote products derived from this | |
9 | * software without specific prior written permission. This software | |
10 | * is provided ``as is'' without express or implied warranty. | |
11 | * | |
12 | * @(#)in_cksum.c 7.1 (Berkeley) %G% | |
13 | */ | |
14 | ||
15 | #include "../h/types.h" | |
16 | #include "../h/mbuf.h" | |
17 | ||
18 | /* | |
19 | * Checksum routine for Internet Protocol family headers (Portable Version). | |
20 | * | |
21 | * This routine is very heavily used in the network | |
22 | * code and should be modified for each CPU to be as fast as possible. | |
23 | */ | |
24 | ||
25 | #define ADDCARRY(x) (x > 65535 ? x -= 65535 : x) | |
26 | #define REDUCE {l_util.l = sum; sum = l_util.s[0] + l_util.s[1]; ADDCARRY(sum);} | |
27 | ||
28 | in_cksum_c(m, len) | |
29 | register struct mbuf *m; | |
30 | register int len; | |
31 | { | |
32 | register u_short *w; | |
33 | register int sum = 0; | |
34 | register int mlen = 0; | |
35 | int byte_swapped = 0; | |
36 | ||
37 | union { | |
38 | char c[2]; | |
39 | u_short s; | |
40 | } s_util; | |
41 | union { | |
42 | u_short s[2]; | |
43 | long l; | |
44 | } l_util; | |
45 | ||
46 | for (;m && len; m = m->m_next) { | |
47 | if (m->m_len == 0) | |
48 | continue; | |
49 | w = mtod(m, u_short *); | |
50 | if (mlen == -1) { | |
51 | /* | |
52 | * The first byte of this mbuf is the continuation | |
53 | * of a word spanning between this mbuf and the | |
54 | * last mbuf. | |
55 | * | |
56 | * s_util.c[0] is already saved when scanning previous | |
57 | * mbuf. | |
58 | */ | |
59 | s_util.c[1] = *(char *)w; | |
60 | sum += s_util.s; | |
61 | w = (u_short *)((char *)w + 1); | |
62 | mlen = m->m_len - 1; | |
63 | len--; | |
64 | } else | |
65 | mlen = m->m_len; | |
66 | if (len < mlen) | |
67 | mlen = len; | |
68 | len -= mlen; | |
69 | /* | |
70 | * Force to even boundary. | |
71 | */ | |
72 | if ((1 & (int) w) && (mlen > 0)) { | |
73 | REDUCE; | |
74 | sum <<= 8; | |
75 | s_util.c[0] = *(u_char *)w; | |
76 | w = (u_short *)((char *)w + 1); | |
77 | mlen--; | |
78 | byte_swapped = 1; | |
79 | } | |
80 | /* | |
81 | * Unroll the loop to make overhead from | |
82 | * branches &c small. | |
83 | */ | |
84 | while ((mlen -= 32) >= 0) { | |
85 | sum += w[0]; sum += w[1]; sum += w[2]; sum += w[3]; | |
86 | sum += w[4]; sum += w[5]; sum += w[6]; sum += w[7]; | |
87 | sum += w[8]; sum += w[9]; sum += w[10]; sum += w[11]; | |
88 | sum += w[12]; sum += w[13]; sum += w[14]; sum += w[15]; | |
89 | w += 16; | |
90 | } | |
91 | mlen += 32; | |
92 | while ((mlen -= 8) >= 0) { | |
93 | sum += w[0]; sum += w[1]; sum += w[2]; sum += w[3]; | |
94 | w += 4; | |
95 | } | |
96 | mlen += 8; | |
97 | if (mlen == 0 && byte_swapped == 0) | |
98 | continue; | |
99 | REDUCE; | |
100 | while ((mlen -= 2) >= 0) { | |
101 | sum += *w++; | |
102 | } | |
103 | if (byte_swapped) { | |
104 | REDUCE; | |
105 | sum <<= 8; | |
106 | byte_swapped = 0; | |
107 | if (mlen == -1) { | |
108 | s_util.c[1] = *(char *)w; | |
109 | sum += s_util.s; | |
110 | mlen = 0; | |
111 | } else | |
112 | mlen = -1; | |
113 | } else if (mlen == -1) | |
114 | s_util.c[0] = *(char *)w; | |
115 | } | |
116 | if (len) | |
117 | printf("cksum: out of data\n"); | |
118 | if (mlen == -1) { | |
119 | /* The last mbuf has odd # of bytes. Follow the | |
120 | standard (the odd byte may be shifted left by 8 bits | |
121 | or not as determined by endian-ness of the machine) */ | |
122 | s_util.c[1] = 0; | |
123 | sum += s_util.s; | |
124 | } | |
125 | REDUCE; | |
126 | return (~sum & 0xffff); | |
127 | } |