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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 1.5 2006/01/14 13:36:40 swildner 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);}
54 ns_cksum(struct mbuf *m, int len)
66 for (;m && len; m = m->m_next) {
70 * Each trip around loop adds in
71 * word from one mbuf segment.
73 w = mtod(m, u_short *);
76 * There is a byte left from the last segment;
77 * ones-complement add it into the checksum.
79 #if BYTE_ORDER == BIG_ENDIAN
82 sum += *(u_char *)w << 8;
85 w = (u_short *)(1 + (char *)w);
95 * We can do a 16 bit ones complement sum using
96 * 32 bit arithmetic registers for adding,
97 * with carries from the low added
98 * into the high (by normal carry-chaining)
99 * so long as we fold back before 16 carries have occured.
104 /* -DTINY reduces the size from 1250 to 550, but slows it down by 22% */
105 while ((mlen -= 32) >= 0) {
106 sum += w[0]; sum += sum; sum += w[1]; sum += sum;
107 sum += w[2]; sum += sum; sum += w[3]; sum += sum;
108 sum += w[4]; sum += sum; sum += w[5]; sum += sum;
109 sum += w[6]; sum += sum; sum += w[7]; sum += sum;
111 sum += w[8]; sum += sum; sum += w[9]; sum += sum;
112 sum += w[10]; sum += sum; sum += w[11]; sum += sum;
113 sum += w[12]; sum += sum; sum += w[13]; sum += sum;
114 sum += w[14]; sum += sum; sum += w[15]; sum += sum;
120 while ((mlen -= 8) >= 0) {
121 sum += w[0]; sum += sum; sum += w[1]; sum += sum;
122 sum += w[2]; sum += sum; sum += w[3]; sum += sum;
127 while ((mlen -= 2) >= 0) {
128 sum += *w++; sum += sum;
132 #if BYTE_ORDER == BIG_ENDIAN
133 #define ww(n) (((u_char *)w)[n + n + 1])
134 #define vv(n) (((u_char *)w)[n + n])
136 #if BYTE_ORDER == LITTLE_ENDIAN
137 #define vv(n) (((u_char *)w)[n + n + 1])
138 #define ww(n) (((u_char *)w)[n + n])
143 while ((mlen -= 32) >= 0) {
144 sum += ww(0); sum += sum; sum += ww(1); sum += sum;
145 sum += ww(2); sum += sum; sum += ww(3); sum += sum;
146 sum += ww(4); sum += sum; sum += ww(5); sum += sum;
147 sum += ww(6); sum += sum; sum += ww(7); sum += sum;
149 sum += ww(8); sum += sum; sum += ww(9); sum += sum;
150 sum += ww(10); sum += sum; sum += ww(11); sum += sum;
151 sum += ww(12); sum += sum; sum += ww(13); sum += sum;
152 sum += ww(14); sum += sum; sum += ww(15); sum += sum;
154 sum2 += vv(0); sum2 += sum2; sum2 += vv(1); sum2 += sum2;
155 sum2 += vv(2); sum2 += sum2; sum2 += vv(3); sum2 += sum2;
156 sum2 += vv(4); sum2 += sum2; sum2 += vv(5); sum2 += sum2;
157 sum2 += vv(6); sum2 += sum2; sum2 += vv(7); sum2 += sum2;
159 sum2 += vv(8); sum2 += sum2; sum2 += vv(9); sum2 += sum2;
160 sum2 += vv(10); sum2 += sum2; sum2 += vv(11); sum2 += sum2;
161 sum2 += vv(12); sum2 += sum2; sum2 += vv(13); sum2 += sum2;
162 sum2 += vv(14); sum2 += sum2; sum2 += vv(15); sum2 += sum2;
168 while ((mlen -= 8) >= 0) {
169 sum += ww(0); sum += sum; sum += ww(1); sum += sum;
170 sum += ww(2); sum += sum; sum += ww(3); sum += sum;
172 sum2 += vv(0); sum2 += sum2; sum2 += vv(1); sum2 += sum2;
173 sum2 += vv(2); sum2 += sum2; sum2 += vv(3); sum2 += sum2;
178 while ((mlen -= 2) >= 0) {
179 sum += ww(0); sum += sum;
180 sum2 += vv(0); sum2 += sum2;
186 #if BYTE_ORDER == BIG_ENDIAN
187 sum += *(u_char *)w << 8;
195 /* We had an odd number of bytes to sum; assume a garbage
196 byte of zero and clean up */
201 * sum has already been kept to low sixteen bits.
202 * just examine result and exit.
204 if(sum==0xffff) sum = 0;