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33 * @(#)ns_cksum.c 8.1 (Berkeley) 6/10/93
34 * $FreeBSD: src/sys/netns/ns_cksum.c,v 1.7 1999/08/28 00:49:49 peter Exp $
35 * $DragonFly: src/sys/netproto/ns/ns_cksum.c,v 1.4 2004/06/02 14:19:11 joerg Exp $
38 #include <sys/param.h>
40 #include <sys/socketvar.h>
44 * Checksum routine for Network Systems Protocol Packets (Big-Endian).
46 * This routine is very heavily used in the network
47 * code and should be modified for each CPU to be as fast as possible.
50 #define ADDCARRY(x) { if ((x) > 65535) (x) -= 65535; }
51 #define FOLD(x) {l_util.l = (x); (x) = l_util.s[0] + l_util.s[1]; ADDCARRY(x);}
68 for (;m && len; m = m->m_next) {
72 * Each trip around loop adds in
73 * word from one mbuf segment.
75 w = mtod(m, u_short *);
78 * There is a byte left from the last segment;
79 * ones-complement add it into the checksum.
81 #if BYTE_ORDER == BIG_ENDIAN
84 sum += *(u_char *)w << 8;
87 w = (u_short *)(1 + (char *)w);
97 * We can do a 16 bit ones complement sum using
98 * 32 bit arithmetic registers for adding,
99 * with carries from the low added
100 * into the high (by normal carry-chaining)
101 * so long as we fold back before 16 carries have occured.
106 /* -DTINY reduces the size from 1250 to 550, but slows it down by 22% */
107 while ((mlen -= 32) >= 0) {
108 sum += w[0]; sum += sum; sum += w[1]; sum += sum;
109 sum += w[2]; sum += sum; sum += w[3]; sum += sum;
110 sum += w[4]; sum += sum; sum += w[5]; sum += sum;
111 sum += w[6]; sum += sum; sum += w[7]; sum += sum;
113 sum += w[8]; sum += sum; sum += w[9]; sum += sum;
114 sum += w[10]; sum += sum; sum += w[11]; sum += sum;
115 sum += w[12]; sum += sum; sum += w[13]; sum += sum;
116 sum += w[14]; sum += sum; sum += w[15]; sum += sum;
122 while ((mlen -= 8) >= 0) {
123 sum += w[0]; sum += sum; sum += w[1]; sum += sum;
124 sum += w[2]; sum += sum; sum += w[3]; sum += sum;
129 while ((mlen -= 2) >= 0) {
130 sum += *w++; sum += sum;
134 #if BYTE_ORDER == BIG_ENDIAN
135 #define ww(n) (((u_char *)w)[n + n + 1])
136 #define vv(n) (((u_char *)w)[n + n])
138 #if BYTE_ORDER == LITTLE_ENDIAN
139 #define vv(n) (((u_char *)w)[n + n + 1])
140 #define ww(n) (((u_char *)w)[n + n])
145 while ((mlen -= 32) >= 0) {
146 sum += ww(0); sum += sum; sum += ww(1); sum += sum;
147 sum += ww(2); sum += sum; sum += ww(3); sum += sum;
148 sum += ww(4); sum += sum; sum += ww(5); sum += sum;
149 sum += ww(6); sum += sum; sum += ww(7); sum += sum;
151 sum += ww(8); sum += sum; sum += ww(9); sum += sum;
152 sum += ww(10); sum += sum; sum += ww(11); sum += sum;
153 sum += ww(12); sum += sum; sum += ww(13); sum += sum;
154 sum += ww(14); sum += sum; sum += ww(15); sum += sum;
156 sum2 += vv(0); sum2 += sum2; sum2 += vv(1); sum2 += sum2;
157 sum2 += vv(2); sum2 += sum2; sum2 += vv(3); sum2 += sum2;
158 sum2 += vv(4); sum2 += sum2; sum2 += vv(5); sum2 += sum2;
159 sum2 += vv(6); sum2 += sum2; sum2 += vv(7); sum2 += sum2;
161 sum2 += vv(8); sum2 += sum2; sum2 += vv(9); sum2 += sum2;
162 sum2 += vv(10); sum2 += sum2; sum2 += vv(11); sum2 += sum2;
163 sum2 += vv(12); sum2 += sum2; sum2 += vv(13); sum2 += sum2;
164 sum2 += vv(14); sum2 += sum2; sum2 += vv(15); sum2 += sum2;
170 while ((mlen -= 8) >= 0) {
171 sum += ww(0); sum += sum; sum += ww(1); sum += sum;
172 sum += ww(2); sum += sum; sum += ww(3); sum += sum;
174 sum2 += vv(0); sum2 += sum2; sum2 += vv(1); sum2 += sum2;
175 sum2 += vv(2); sum2 += sum2; sum2 += vv(3); sum2 += sum2;
180 while ((mlen -= 2) >= 0) {
181 sum += ww(0); sum += sum;
182 sum2 += vv(0); sum2 += sum2;
188 #if BYTE_ORDER == BIG_ENDIAN
189 sum += *(u_char *)w << 8;
197 /* We had an odd number of bytes to sum; assume a garbage
198 byte of zero and clean up */
203 * sum has already been kept to low sixteen bits.
204 * just examine result and exit.
206 if(sum==0xffff) sum = 0;