2 * Copyright (c) 1990 The Regents of the University of California.
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6 * modification, are permitted provided that the following conditions
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29 * from tahoe: in_cksum.c 1.2 86/01/05
30 * from: @(#)in_cksum.c 1.3 (Berkeley) 1/19/91
33 #include <sys/cdefs.h>
34 __FBSDID("$FreeBSD$");
39 #include <sys/param.h>
40 #include <sys/systm.h>
43 #include <netinet/in.h>
44 #include <netinet/in_systm.h>
45 #include <netinet/ip.h>
47 #include <machine/in_cksum.h>
50 * Checksum routine for Internet Protocol family headers.
52 * This routine is very heavily used in the network
53 * code and should be modified for each CPU to be as fast as possible.
55 * This implementation is 386 version.
59 #define ADDCARRY(x) if ((x) > 0xffff) (x) -= 0xffff
61 * icc needs to be special cased here, as the asm code below results
62 * in broken code if compiled with icc.
64 #if !defined(__GNUCLIKE_ASM) || defined(__INTEL_COMPILER)
65 /* non gcc parts stolen from sys/alpha/alpha/in_cksum.c */
69 sum = q_util.s[0] + q_util.s[1] + q_util.s[2] + q_util.s[3]; \
74 l_util.l = q_util.s[0] + q_util.s[1] + q_util.s[2] + q_util.s[3]; \
75 sum = l_util.s[0] + l_util.s[1]; \
79 #define REDUCE {sum = (sum & 0xffff) + (sum >> 16); ADDCARRY(sum);}
81 #if !defined(__GNUCLIKE_ASM) || defined(__INTEL_COMPILER)
82 static const u_int32_t in_masks[] = {
83 /*0 bytes*/ /*1 byte*/ /*2 bytes*/ /*3 bytes*/
84 0x00000000, 0x000000FF, 0x0000FFFF, 0x00FFFFFF, /* offset 0 */
85 0x00000000, 0x0000FF00, 0x00FFFF00, 0xFFFFFF00, /* offset 1 */
86 0x00000000, 0x00FF0000, 0xFFFF0000, 0xFFFF0000, /* offset 2 */
87 0x00000000, 0xFF000000, 0xFF000000, 0xFF000000, /* offset 3 */
101 in_cksumdata(const u_int32_t *lw, int len)
108 if ((3 & (long) lw) == 0 && len == 20) {
109 sum = (u_int64_t) lw[0] + lw[1] + lw[2] + lw[3] + lw[4];
114 if ((offset = 3 & (long) lw) != 0) {
115 const u_int32_t *masks = in_masks + (offset << 2);
116 lw = (u_int32_t *) (((long) lw) - offset);
117 sum = *lw++ & masks[len >= 3 ? 3 : len];
126 * Force to cache line boundary.
128 offset = 32 - (0x1f & (long) lw);
129 if (offset < 32 && len > offset) {
132 sum += (u_int64_t) lw[0];
136 sum += (u_int64_t) lw[0] + lw[1];
140 sum += (u_int64_t) lw[0] + lw[1] + lw[2] + lw[3];
146 * access prefilling to start load of next cache line.
147 * then add current cache line
148 * save result of prefilling for loop iteration.
151 while ((len -= 32) >= 4) {
152 u_int64_t prefilling = lw[8];
153 sum += prefilled + lw[1] + lw[2] + lw[3]
154 + lw[4] + lw[5] + lw[6] + lw[7];
156 prefilled = prefilling;
159 sum += prefilled + lw[1] + lw[2] + lw[3]
160 + lw[4] + lw[5] + lw[6] + lw[7];
165 while ((len -= 16) >= 0) {
166 sum += (u_int64_t) lw[0] + lw[1] + lw[2] + lw[3];
170 while ((len -= 4) >= 0) {
171 sum += (u_int64_t) *lw++;
175 sum += (u_int64_t) (in_masks[len] & *lw);
181 in_addword(u_short a, u_short b)
183 u_int64_t sum = a + b;
190 in_pseudo(u_int32_t a, u_int32_t b, u_int32_t c)
196 sum = (u_int64_t) a + b + c;
202 in_cksum_skip(struct mbuf *m, int len, int skip)
212 for (; skip && m; m = m->m_next) {
213 if (m->m_len > skip) {
214 mlen = m->m_len - skip;
215 addr = mtod(m, caddr_t) + skip;
222 for (; m && len; m = m->m_next) {
226 addr = mtod(m, caddr_t);
230 if ((clen ^ (long) addr) & 1)
231 sum += in_cksumdata((const u_int32_t *)addr, mlen) << 8;
233 sum += in_cksumdata((const u_int32_t *)addr, mlen);
239 return (~sum & 0xffff);
242 u_int in_cksum_hdr(const struct ip *ip)
244 u_int64_t sum = in_cksumdata((const u_int32_t *)ip, sizeof(struct ip));
249 return (~sum & 0xffff);
254 * These asm statements require __volatile because they pass information
255 * via the condition codes. GCC does not currently provide a way to specify
256 * the condition codes as an input or output operand.
258 * The LOAD macro below is effectively a prefetch into cache. GCC will
259 * load the value into a register but will not use it. Since modern CPUs
260 * reorder operations, this will generally take place in parallel with
261 * other calculations.
264 in_cksum_skip(m, len, skip)
270 register unsigned sum = 0;
271 register int mlen = 0;
272 int byte_swapped = 0;
273 union { char c[2]; u_short s; } su;
276 for (; skip && m; m = m->m_next) {
277 if (m->m_len > skip) {
278 mlen = m->m_len - skip;
279 w = (u_short *)(mtod(m, u_char *) + skip);
286 for (;m && len; m = m->m_next) {
289 w = mtod(m, u_short *);
292 * The first byte of this mbuf is the continuation
293 * of a word spanning between this mbuf and the
297 /* su.c[0] is already saved when scanning previous
298 * mbuf. sum was REDUCEd when we found mlen == -1
300 su.c[1] = *(u_char *)w;
302 w = (u_short *)((char *)w + 1);
312 * Force to long boundary so we do longword aligned
317 if ((1 & (int) w) && (mlen > 0)) {
319 su.c[0] = *(char *)w;
320 w = (u_short *)((char *)w + 1);
324 if ((2 & (int) w) && (mlen >= 2)) {
330 * Advance to a 486 cache line boundary.
332 if (4 & (int) w && mlen >= 4) {
337 : "g" (((const u_int32_t *)w)[0])
342 if (8 & (int) w && mlen >= 8) {
348 : "g" (((const u_int32_t *)w)[0]),
349 "g" (((const u_int32_t *)w)[1])
355 * Do as much of the checksum as possible 32 bits at at time.
356 * In fact, this loop is unrolled to make overhead from
360 while ((mlen -= 32) >= 0) {
362 * Add with carry 16 words and fold in the last
363 * carry by adding a 0 with carry.
365 * The early ADD(16) and the LOAD(32) are to load
366 * the next 2 cache lines in advance on 486's. The
367 * 486 has a penalty of 2 clock cycles for loading
368 * a cache line, plus whatever time the external
369 * memory takes to load the first word(s) addressed.
370 * These penalties are unavoidable. Subsequent
371 * accesses to a cache line being loaded (and to
372 * other external memory?) are delayed until the
373 * whole load finishes. These penalties are mostly
374 * avoided by not accessing external memory for
375 * 8 cycles after the ADD(16) and 12 cycles after
376 * the LOAD(32). The loop terminates when mlen
377 * is initially 33 (not 32) to guaranteed that
378 * the LOAD(32) is within bounds.
392 : "g" (((const u_int32_t *)w)[4]),
393 "g" (((const u_int32_t *)w)[0]),
394 "g" (((const u_int32_t *)w)[1]),
395 "g" (((const u_int32_t *)w)[2]),
396 "g" (((const u_int32_t *)w)[3]),
397 "g" (((const u_int32_t *)w)[8]),
398 "g" (((const u_int32_t *)w)[5]),
399 "g" (((const u_int32_t *)w)[6]),
400 "g" (((const u_int32_t *)w)[7])
418 : "g" (((const u_int32_t *)w)[4]),
419 "g" (((const u_int32_t *)w)[0]),
420 "g" (((const u_int32_t *)w)[1]),
421 "g" (((const u_int32_t *)w)[2]),
422 "g" (((const u_int32_t *)w)[3]),
423 "g" (((const u_int32_t *)w)[5]),
424 "g" (((const u_int32_t *)w)[6]),
425 "g" (((const u_int32_t *)w)[7])
438 : "g" (((const u_int32_t *)w)[0]),
439 "g" (((const u_int32_t *)w)[1]),
440 "g" (((const u_int32_t *)w)[2]),
441 "g" (((const u_int32_t *)w)[3])
452 : "g" (((const u_int32_t *)w)[0]),
453 "g" (((const u_int32_t *)w)[1])
458 if (mlen == 0 && byte_swapped == 0)
459 continue; /* worth 1% maybe ?? */
461 while ((mlen -= 2) >= 0) {
468 su.c[1] = *(char *)w;
473 } else if (mlen == -1)
475 * This mbuf has odd number of bytes.
476 * There could be a word split betwen
477 * this mbuf and the next mbuf.
478 * Save the last byte (to prepend to next mbuf).
480 su.c[0] = *(char *)w;
484 printf("%s: out of data by %d\n", __func__, len);
486 /* The last mbuf has odd # of bytes. Follow the
487 standard (the odd byte is shifted left by 8 bits) */
492 return (~sum & 0xffff);