1 /*
2 * Copyright (c) 1982, 1988 Regents of the University of California.
3 * All rights reserved.
4 *
5 * %sccs.include.redist.c%
6 *
7 * @(#)in_cksum.c 7.6 (Berkeley) 12/16/90
8 */
9
10 #include "sys/param.h"
11 #include "sys/mbuf.h"
12
13 /*
14 * Checksum routine for Internet Protocol family headers (CCI Version).
15 *
16 * This routine is very heavily used in the network
17 * code and should be modified for each CPU to be as fast as possible.
18 */
19
20 #define ADDCARRY(x) { if ((x) > 65535) (x) -= 65535; }
21 #define REDUCE {l_util.l = sum; sum = l_util.s[0] + l_util.s[1]; ADDCARRY(sum);}
22
23 #define ADD(n) asm("adwc n (r10),r9")
24 #define MOP asm("adwc $0,r9")
25 #define BOTCH asm("addl2 r7,r9")
26
in_cksum(m,len)27 in_cksum(m, len)
28 register struct mbuf *m;
29 register int len;
30 {
31 register u_short *w; /* On CCI, known to be r10 */
32 register int sum = 0; /* On CCI, known to be r9 */
33 register int mlen = 0;
34 #ifndef lint
35 register int ClearCarry = 0; /* On CCI, known to be r7; see BOTCH */
36 #endif
37 int byte_swapped = 0;
38
39 union {
40 char c[2];
41 u_short s;
42 } s_util;
43 union {
44 u_short s[2];
45 long l;
46 } l_util;
47
48 for (;m && len; m = m->m_next) {
49 if (m->m_len == 0)
50 continue;
51 w = mtod(m, u_short *);
52 if (mlen == -1) {
53 /*
54 * The first byte of this mbuf is the continuation
55 * of a word spanning between this mbuf and the
56 * last mbuf.
57 *
58 * s_util.c[0] is already saved when scanning previous
59 * mbuf. sum was REDUCEd when we found mlen == -1.
60 */
61 s_util.c[1] = *(char *)w;
62 sum += s_util.s;
63 w = (u_short *)((char *)w + 1);
64 mlen = m->m_len - 1;
65 len--;
66 } else
67 mlen = m->m_len;
68 if (len < mlen)
69 mlen = len;
70 len -= mlen;
71 /*
72 * Force to long boundary so we do longword aligned
73 * memory operations.
74 */
75 if (3 & (int) w) {
76 REDUCE;
77 if ((1 & (int) w) && (mlen > 0)) {
78 sum <<= 8;
79 s_util.c[0] = *(char *)w;
80 w = (u_short *)((char *)w + 1);
81 mlen--;
82 byte_swapped = 1;
83 }
84 if ((2 & (int) w) && (mlen >= 2)) {
85 sum += *w++;
86 mlen -= 2;
87 }
88 }
89 /*
90 * Do as much of the checksum as possible 32 bits at at time.
91 * In fact, this loop is unrolled to make overhead from
92 * branches &c small.
93 */
94 while ((mlen -= 32) >= 0) {
95 /*
96 * The loop construct clears carry for us
97 * on vaxen, however, on the CCI machine subtracting
98 * a small postive number from a larger one doesn't.
99 *
100 * Doing a bicpsw is very slow (slows down the routine
101 * by a factor of 2); explicitly adding an immediate
102 * 0 to a register is optimized out; so we fake out
103 * the optimizer and add a register whose contents
104 * is always zero.
105 */
106 BOTCH;
107 ADD(0); ADD(4); ADD(8); ADD(12);
108 ADD(16); ADD(20); ADD(24); ADD(28);
109 MOP; w += 16;
110 }
111 mlen += 32;
112 while ((mlen -= 8) >= 0) {
113 BOTCH;
114 ADD(0); ADD(4);
115 MOP;
116 w += 4;
117 }
118 mlen += 8;
119 if (mlen == 0 && byte_swapped == 0)
120 continue; /* worth 1% maybe ?? */
121 REDUCE;
122 while ((mlen -= 2) >= 0) {
123 sum += *w++;
124 }
125 if (byte_swapped) {
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 /*
136 * This mbuf has odd number of bytes.
137 * There could be a word split betwen
138 * this mbuf and the next mbuf.
139 * Save the last byte (to prepend to next mbuf).
140 */
141 s_util.c[0] = *(char *)w;
142 }
143 if (len)
144 printf("cksum: out of data\n");
145 if (mlen == -1) {
146 /* The last mbuf has odd # of bytes. Follow the
147 standard (the odd byte is shifted left by 8 bits) */
148 s_util.c[1] = 0;
149 sum += s_util.s;
150 }
151 REDUCE;
152 return (~sum & 0xffff);
153 }
154