| 1 | /*- |
| 2 | * Copyright (c) 1990 The Regents of the University of California. |
| 3 | * All rights reserved. |
| 4 | * |
| 5 | * Redistribution and use in source and binary forms, with or without |
| 6 | * modification, are permitted provided that the following conditions |
| 7 | * are met: |
| 8 | * 1. Redistributions of source code must retain the above copyright |
| 9 | * notice, this list of conditions and the following disclaimer. |
| 10 | * 2. Redistributions in binary form must reproduce the above copyright |
| 11 | * notice, this list of conditions and the following disclaimer in the |
| 12 | * documentation and/or other materials provided with the distribution. |
| 13 | * 3. All advertising materials mentioning features or use of this software |
| 14 | * must display the following acknowledgement: |
| 15 | * This product includes software developed by the University of |
| 16 | * California, Berkeley and its contributors. |
| 17 | * 4. Neither the name of the University nor the names of its contributors |
| 18 | * may be used to endorse or promote products derived from this software |
| 19 | * without specific prior written permission. |
| 20 | * |
| 21 | * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND |
| 22 | * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE |
| 23 | * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE |
| 24 | * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE |
| 25 | * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL |
| 26 | * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS |
| 27 | * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) |
| 28 | * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT |
| 29 | * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY |
| 30 | * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF |
| 31 | * SUCH DAMAGE. |
| 32 | * |
| 33 | * from tahoe: in_cksum.c 1.2 86/01/05 |
| 34 | * from: @(#)in_cksum.c 1.3 (Berkeley) 1/19/91 |
| 35 | * $FreeBSD: src/sys/i386/i386/in_cksum.c,v 1.17.2.3 2002/07/02 04:03:00 jdp Exp $ |
| 36 | * $DragonFly: src/sys/i386/i386/Attic/in_cksum.c,v 1.3 2003/07/26 19:07:47 rob Exp $ |
| 37 | */ |
| 38 | |
| 39 | #include <sys/param.h> |
| 40 | #include <sys/systm.h> |
| 41 | #include <sys/mbuf.h> |
| 42 | |
| 43 | #include <netinet/in.h> |
| 44 | #include <netinet/in_systm.h> |
| 45 | #include <netinet/ip.h> |
| 46 | |
| 47 | #include <machine/in_cksum.h> |
| 48 | |
| 49 | /* |
| 50 | * Checksum routine for Internet Protocol family headers. |
| 51 | * |
| 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. |
| 54 | * |
| 55 | * This implementation is 386 version. |
| 56 | */ |
| 57 | |
| 58 | #undef ADDCARRY |
| 59 | #define ADDCARRY(x) if ((x) > 0xffff) (x) -= 0xffff |
| 60 | #define REDUCE {sum = (sum & 0xffff) + (sum >> 16); ADDCARRY(sum);} |
| 61 | |
| 62 | /* |
| 63 | * These asm statements require __volatile because they pass information |
| 64 | * via the condition codes. GCC does not currently provide a way to specify |
| 65 | * the condition codes as an input or output operand. |
| 66 | * |
| 67 | * The LOAD macro below is effectively a prefetch into cache. GCC will |
| 68 | * load the value into a register but will not use it. Since modern CPUs |
| 69 | * reorder operations, this will generally take place in parallel with |
| 70 | * other calculations. |
| 71 | */ |
| 72 | #define ADD(n) __asm __volatile \ |
| 73 | ("addl %1, %0" : "+r" (sum) : \ |
| 74 | "g" (((const u_int32_t *)w)[n / 4])) |
| 75 | #define ADDC(n) __asm __volatile \ |
| 76 | ("adcl %1, %0" : "+r" (sum) : \ |
| 77 | "g" (((const u_int32_t *)w)[n / 4])) |
| 78 | #define LOAD(n) __asm __volatile \ |
| 79 | ("" : : "r" (((const u_int32_t *)w)[n / 4])) |
| 80 | #define MOP __asm __volatile \ |
| 81 | ("adcl $0, %0" : "+r" (sum)) |
| 82 | |
| 83 | int |
| 84 | in_cksum(m, len) |
| 85 | struct mbuf *m; |
| 86 | int len; |
| 87 | { |
| 88 | u_short *w; |
| 89 | unsigned sum = 0; |
| 90 | int mlen = 0; |
| 91 | int byte_swapped = 0; |
| 92 | union { char c[2]; u_short s; } su; |
| 93 | |
| 94 | for (;m && len; m = m->m_next) { |
| 95 | if (m->m_len == 0) |
| 96 | continue; |
| 97 | w = mtod(m, u_short *); |
| 98 | if (mlen == -1) { |
| 99 | /* |
| 100 | * The first byte of this mbuf is the continuation |
| 101 | * of a word spanning between this mbuf and the |
| 102 | * last mbuf. |
| 103 | */ |
| 104 | |
| 105 | /* su.c[0] is already saved when scanning previous |
| 106 | * mbuf. sum was REDUCEd when we found mlen == -1 |
| 107 | */ |
| 108 | su.c[1] = *(u_char *)w; |
| 109 | sum += su.s; |
| 110 | w = (u_short *)((char *)w + 1); |
| 111 | mlen = m->m_len - 1; |
| 112 | len--; |
| 113 | } else |
| 114 | mlen = m->m_len; |
| 115 | if (len < mlen) |
| 116 | mlen = len; |
| 117 | len -= mlen; |
| 118 | /* |
| 119 | * Force to long boundary so we do longword aligned |
| 120 | * memory operations |
| 121 | */ |
| 122 | if (3 & (int) w) { |
| 123 | REDUCE; |
| 124 | if ((1 & (int) w) && (mlen > 0)) { |
| 125 | sum <<= 8; |
| 126 | su.c[0] = *(char *)w; |
| 127 | w = (u_short *)((char *)w + 1); |
| 128 | mlen--; |
| 129 | byte_swapped = 1; |
| 130 | } |
| 131 | if ((2 & (int) w) && (mlen >= 2)) { |
| 132 | sum += *w++; |
| 133 | mlen -= 2; |
| 134 | } |
| 135 | } |
| 136 | /* |
| 137 | * Advance to a 486 cache line boundary. |
| 138 | */ |
| 139 | if (4 & (int) w && mlen >= 4) { |
| 140 | ADD(0); |
| 141 | MOP; |
| 142 | w += 2; |
| 143 | mlen -= 4; |
| 144 | } |
| 145 | if (8 & (int) w && mlen >= 8) { |
| 146 | ADD(0); |
| 147 | ADDC(4); |
| 148 | MOP; |
| 149 | w += 4; |
| 150 | mlen -= 8; |
| 151 | } |
| 152 | /* |
| 153 | * Do as much of the checksum as possible 32 bits at at time. |
| 154 | * In fact, this loop is unrolled to make overhead from |
| 155 | * branches &c small. |
| 156 | */ |
| 157 | mlen -= 1; |
| 158 | while ((mlen -= 32) >= 0) { |
| 159 | /* |
| 160 | * Add with carry 16 words and fold in the last |
| 161 | * carry by adding a 0 with carry. |
| 162 | * |
| 163 | * The early ADD(16) and the LOAD(32) are to load |
| 164 | * the next 2 cache lines in advance on 486's. The |
| 165 | * 486 has a penalty of 2 clock cycles for loading |
| 166 | * a cache line, plus whatever time the external |
| 167 | * memory takes to load the first word(s) addressed. |
| 168 | * These penalties are unavoidable. Subsequent |
| 169 | * accesses to a cache line being loaded (and to |
| 170 | * other external memory?) are delayed until the |
| 171 | * whole load finishes. These penalties are mostly |
| 172 | * avoided by not accessing external memory for |
| 173 | * 8 cycles after the ADD(16) and 12 cycles after |
| 174 | * the LOAD(32). The loop terminates when mlen |
| 175 | * is initially 33 (not 32) to guaranteed that |
| 176 | * the LOAD(32) is within bounds. |
| 177 | */ |
| 178 | ADD(16); |
| 179 | ADDC(0); |
| 180 | ADDC(4); |
| 181 | ADDC(8); |
| 182 | ADDC(12); |
| 183 | LOAD(32); |
| 184 | ADDC(20); |
| 185 | ADDC(24); |
| 186 | ADDC(28); |
| 187 | MOP; |
| 188 | w += 16; |
| 189 | } |
| 190 | mlen += 32 + 1; |
| 191 | if (mlen >= 32) { |
| 192 | ADD(16); |
| 193 | ADDC(0); |
| 194 | ADDC(4); |
| 195 | ADDC(8); |
| 196 | ADDC(12); |
| 197 | ADDC(20); |
| 198 | ADDC(24); |
| 199 | ADDC(28); |
| 200 | MOP; |
| 201 | w += 16; |
| 202 | mlen -= 32; |
| 203 | } |
| 204 | if (mlen >= 16) { |
| 205 | ADD(0); |
| 206 | ADDC(4); |
| 207 | ADDC(8); |
| 208 | ADDC(12); |
| 209 | MOP; |
| 210 | w += 8; |
| 211 | mlen -= 16; |
| 212 | } |
| 213 | if (mlen >= 8) { |
| 214 | ADD(0); |
| 215 | ADDC(4); |
| 216 | MOP; |
| 217 | w += 4; |
| 218 | mlen -= 8; |
| 219 | } |
| 220 | if (mlen == 0 && byte_swapped == 0) |
| 221 | continue; /* worth 1% maybe ?? */ |
| 222 | REDUCE; |
| 223 | while ((mlen -= 2) >= 0) { |
| 224 | sum += *w++; |
| 225 | } |
| 226 | if (byte_swapped) { |
| 227 | sum <<= 8; |
| 228 | byte_swapped = 0; |
| 229 | if (mlen == -1) { |
| 230 | su.c[1] = *(char *)w; |
| 231 | sum += su.s; |
| 232 | mlen = 0; |
| 233 | } else |
| 234 | mlen = -1; |
| 235 | } else if (mlen == -1) |
| 236 | /* |
| 237 | * This mbuf has odd number of bytes. |
| 238 | * There could be a word split betwen |
| 239 | * this mbuf and the next mbuf. |
| 240 | * Save the last byte (to prepend to next mbuf). |
| 241 | */ |
| 242 | su.c[0] = *(char *)w; |
| 243 | } |
| 244 | |
| 245 | if (len) |
| 246 | printf("%s: out of data by %d\n", __func__, len); |
| 247 | if (mlen == -1) { |
| 248 | /* The last mbuf has odd # of bytes. Follow the |
| 249 | standard (the odd byte is shifted left by 8 bits) */ |
| 250 | su.c[1] = 0; |
| 251 | sum += su.s; |
| 252 | } |
| 253 | REDUCE; |
| 254 | return (~sum & 0xffff); |
| 255 | } |
| 256 | |
| 257 | u_short |
| 258 | in_cksum_skip(m, len, skip) |
| 259 | struct mbuf *m; |
| 260 | int len; |
| 261 | int skip; |
| 262 | { |
| 263 | u_short *w; |
| 264 | unsigned sum = 0; |
| 265 | int mlen = 0; |
| 266 | int byte_swapped = 0; |
| 267 | union { char c[2]; u_short s; } su; |
| 268 | |
| 269 | len -= skip; |
| 270 | for (; skip && m; m = m->m_next) { |
| 271 | if (m->m_len > skip) { |
| 272 | mlen = m->m_len - skip; |
| 273 | w = (u_short *)(mtod(m, u_char *) + skip); |
| 274 | goto skip_start; |
| 275 | } else { |
| 276 | skip -= m->m_len; |
| 277 | } |
| 278 | } |
| 279 | |
| 280 | for (;m && len; m = m->m_next) { |
| 281 | if (m->m_len == 0) |
| 282 | continue; |
| 283 | w = mtod(m, u_short *); |
| 284 | if (mlen == -1) { |
| 285 | /* |
| 286 | * The first byte of this mbuf is the continuation |
| 287 | * of a word spanning between this mbuf and the |
| 288 | * last mbuf. |
| 289 | */ |
| 290 | |
| 291 | /* su.c[0] is already saved when scanning previous |
| 292 | * mbuf. sum was REDUCEd when we found mlen == -1 |
| 293 | */ |
| 294 | su.c[1] = *(u_char *)w; |
| 295 | sum += su.s; |
| 296 | w = (u_short *)((char *)w + 1); |
| 297 | mlen = m->m_len - 1; |
| 298 | len--; |
| 299 | } else |
| 300 | mlen = m->m_len; |
| 301 | skip_start: |
| 302 | if (len < mlen) |
| 303 | mlen = len; |
| 304 | len -= mlen; |
| 305 | /* |
| 306 | * Force to long boundary so we do longword aligned |
| 307 | * memory operations |
| 308 | */ |
| 309 | if (3 & (int) w) { |
| 310 | REDUCE; |
| 311 | if ((1 & (int) w) && (mlen > 0)) { |
| 312 | sum <<= 8; |
| 313 | su.c[0] = *(char *)w; |
| 314 | w = (u_short *)((char *)w + 1); |
| 315 | mlen--; |
| 316 | byte_swapped = 1; |
| 317 | } |
| 318 | if ((2 & (int) w) && (mlen >= 2)) { |
| 319 | sum += *w++; |
| 320 | mlen -= 2; |
| 321 | } |
| 322 | } |
| 323 | /* |
| 324 | * Advance to a 486 cache line boundary. |
| 325 | */ |
| 326 | if (4 & (int) w && mlen >= 4) { |
| 327 | ADD(0); |
| 328 | MOP; |
| 329 | w += 2; |
| 330 | mlen -= 4; |
| 331 | } |
| 332 | if (8 & (int) w && mlen >= 8) { |
| 333 | ADD(0); |
| 334 | ADDC(4); |
| 335 | MOP; |
| 336 | w += 4; |
| 337 | mlen -= 8; |
| 338 | } |
| 339 | /* |
| 340 | * Do as much of the checksum as possible 32 bits at at time. |
| 341 | * In fact, this loop is unrolled to make overhead from |
| 342 | * branches &c small. |
| 343 | */ |
| 344 | mlen -= 1; |
| 345 | while ((mlen -= 32) >= 0) { |
| 346 | /* |
| 347 | * Add with carry 16 words and fold in the last |
| 348 | * carry by adding a 0 with carry. |
| 349 | * |
| 350 | * The early ADD(16) and the LOAD(32) are to load |
| 351 | * the next 2 cache lines in advance on 486's. The |
| 352 | * 486 has a penalty of 2 clock cycles for loading |
| 353 | * a cache line, plus whatever time the external |
| 354 | * memory takes to load the first word(s) addressed. |
| 355 | * These penalties are unavoidable. Subsequent |
| 356 | * accesses to a cache line being loaded (and to |
| 357 | * other external memory?) are delayed until the |
| 358 | * whole load finishes. These penalties are mostly |
| 359 | * avoided by not accessing external memory for |
| 360 | * 8 cycles after the ADD(16) and 12 cycles after |
| 361 | * the LOAD(32). The loop terminates when mlen |
| 362 | * is initially 33 (not 32) to guaranteed that |
| 363 | * the LOAD(32) is within bounds. |
| 364 | */ |
| 365 | ADD(16); |
| 366 | ADDC(0); |
| 367 | ADDC(4); |
| 368 | ADDC(8); |
| 369 | ADDC(12); |
| 370 | LOAD(32); |
| 371 | ADDC(20); |
| 372 | ADDC(24); |
| 373 | ADDC(28); |
| 374 | MOP; |
| 375 | w += 16; |
| 376 | } |
| 377 | mlen += 32 + 1; |
| 378 | if (mlen >= 32) { |
| 379 | ADD(16); |
| 380 | ADDC(0); |
| 381 | ADDC(4); |
| 382 | ADDC(8); |
| 383 | ADDC(12); |
| 384 | ADDC(20); |
| 385 | ADDC(24); |
| 386 | ADDC(28); |
| 387 | MOP; |
| 388 | w += 16; |
| 389 | mlen -= 32; |
| 390 | } |
| 391 | if (mlen >= 16) { |
| 392 | ADD(0); |
| 393 | ADDC(4); |
| 394 | ADDC(8); |
| 395 | ADDC(12); |
| 396 | MOP; |
| 397 | w += 8; |
| 398 | mlen -= 16; |
| 399 | } |
| 400 | if (mlen >= 8) { |
| 401 | ADD(0); |
| 402 | ADDC(4); |
| 403 | MOP; |
| 404 | w += 4; |
| 405 | mlen -= 8; |
| 406 | } |
| 407 | if (mlen == 0 && byte_swapped == 0) |
| 408 | continue; /* worth 1% maybe ?? */ |
| 409 | REDUCE; |
| 410 | while ((mlen -= 2) >= 0) { |
| 411 | sum += *w++; |
| 412 | } |
| 413 | if (byte_swapped) { |
| 414 | sum <<= 8; |
| 415 | byte_swapped = 0; |
| 416 | if (mlen == -1) { |
| 417 | su.c[1] = *(char *)w; |
| 418 | sum += su.s; |
| 419 | mlen = 0; |
| 420 | } else |
| 421 | mlen = -1; |
| 422 | } else if (mlen == -1) |
| 423 | /* |
| 424 | * This mbuf has odd number of bytes. |
| 425 | * There could be a word split betwen |
| 426 | * this mbuf and the next mbuf. |
| 427 | * Save the last byte (to prepend to next mbuf). |
| 428 | */ |
| 429 | su.c[0] = *(char *)w; |
| 430 | } |
| 431 | |
| 432 | if (len) |
| 433 | printf("%s: out of data by %d\n", __func__, len); |
| 434 | if (mlen == -1) { |
| 435 | /* The last mbuf has odd # of bytes. Follow the |
| 436 | standard (the odd byte is shifted left by 8 bits) */ |
| 437 | su.c[1] = 0; |
| 438 | sum += su.s; |
| 439 | } |
| 440 | REDUCE; |
| 441 | return (~sum & 0xffff); |
| 442 | } |
| 443 | |
| 444 | /* |
| 445 | * This is the exact same algorithm as above with a few exceptions: |
| 446 | * (1) it is designed to operate on buffers, not mbufs |
| 447 | * (2) it returns an intermediate form of the sum which has to be |
| 448 | * explicitly finalized (but this can be delayed) |
| 449 | * (3) it accepts an intermediate sum |
| 450 | * |
| 451 | * This is particularly useful when building packets quickly, |
| 452 | * since one can compute the checksum of the pseudoheader ahead of |
| 453 | * time and then use this function to complete the work. That way, |
| 454 | * the pseudoheader never actually has to exist in the packet buffer, |
| 455 | * which avoids needless duplication of work. |
| 456 | */ |
| 457 | in_psum_t |
| 458 | in_cksum_partial(psum, w, len) |
| 459 | in_psum_t psum; |
| 460 | const u_short *w; |
| 461 | int len; |
| 462 | { |
| 463 | in_psum_t sum = psum; |
| 464 | int byte_swapped = 0; |
| 465 | union { char c[2]; u_short s; } su; |
| 466 | |
| 467 | /* |
| 468 | * Force to long boundary so we do longword aligned |
| 469 | * memory operations |
| 470 | */ |
| 471 | if (3 & (int) w) { |
| 472 | REDUCE; |
| 473 | if ((1 & (int) w) && (len > 0)) { |
| 474 | sum <<= 8; |
| 475 | su.c[0] = *(const char *)w; |
| 476 | w = (const u_short *)((const char *)w + 1); |
| 477 | len--; |
| 478 | byte_swapped = 1; |
| 479 | } |
| 480 | if ((2 & (int) w) && (len >= 2)) { |
| 481 | sum += *w++; |
| 482 | len -= 2; |
| 483 | } |
| 484 | } |
| 485 | /* |
| 486 | * Advance to a 486 cache line boundary. |
| 487 | */ |
| 488 | if (4 & (int) w && len >= 4) { |
| 489 | ADD(0); |
| 490 | MOP; |
| 491 | w += 2; |
| 492 | len -= 4; |
| 493 | } |
| 494 | if (8 & (int) w && len >= 8) { |
| 495 | ADD(0); |
| 496 | ADDC(4); |
| 497 | MOP; |
| 498 | w += 4; |
| 499 | len -= 8; |
| 500 | } |
| 501 | /* |
| 502 | * Do as much of the checksum as possible 32 bits at at time. |
| 503 | * In fact, this loop is unrolled to make overhead from |
| 504 | * branches &c small. |
| 505 | */ |
| 506 | len -= 1; |
| 507 | while ((len -= 32) >= 0) { |
| 508 | /* |
| 509 | * Add with carry 16 words and fold in the last |
| 510 | * carry by adding a 0 with carry. |
| 511 | * |
| 512 | * The early ADD(16) and the LOAD(32) are to load |
| 513 | * the next 2 cache lines in advance on 486's. The |
| 514 | * 486 has a penalty of 2 clock cycles for loading |
| 515 | * a cache line, plus whatever time the external |
| 516 | * memory takes to load the first word(s) addressed. |
| 517 | * These penalties are unavoidable. Subsequent |
| 518 | * accesses to a cache line being loaded (and to |
| 519 | * other external memory?) are delayed until the |
| 520 | * whole load finishes. These penalties are mostly |
| 521 | * avoided by not accessing external memory for |
| 522 | * 8 cycles after the ADD(16) and 12 cycles after |
| 523 | * the LOAD(32). The loop terminates when len |
| 524 | * is initially 33 (not 32) to guaranteed that |
| 525 | * the LOAD(32) is within bounds. |
| 526 | */ |
| 527 | ADD(16); |
| 528 | ADDC(0); |
| 529 | ADDC(4); |
| 530 | ADDC(8); |
| 531 | ADDC(12); |
| 532 | LOAD(32); |
| 533 | ADDC(20); |
| 534 | ADDC(24); |
| 535 | ADDC(28); |
| 536 | MOP; |
| 537 | w += 16; |
| 538 | } |
| 539 | len += 32 + 1; |
| 540 | if (len >= 32) { |
| 541 | ADD(16); |
| 542 | ADDC(0); |
| 543 | ADDC(4); |
| 544 | ADDC(8); |
| 545 | ADDC(12); |
| 546 | ADDC(20); |
| 547 | ADDC(24); |
| 548 | ADDC(28); |
| 549 | MOP; |
| 550 | w += 16; |
| 551 | len -= 32; |
| 552 | } |
| 553 | if (len >= 16) { |
| 554 | ADD(0); |
| 555 | ADDC(4); |
| 556 | ADDC(8); |
| 557 | ADDC(12); |
| 558 | MOP; |
| 559 | w += 8; |
| 560 | len -= 16; |
| 561 | } |
| 562 | if (len >= 8) { |
| 563 | ADD(0); |
| 564 | ADDC(4); |
| 565 | MOP; |
| 566 | w += 4; |
| 567 | len -= 8; |
| 568 | } |
| 569 | if (len == 0 && byte_swapped == 0) |
| 570 | goto out; |
| 571 | REDUCE; |
| 572 | while ((len -= 2) >= 0) { |
| 573 | sum += *w++; |
| 574 | } |
| 575 | if (byte_swapped) { |
| 576 | sum <<= 8; |
| 577 | byte_swapped = 0; |
| 578 | if (len == -1) { |
| 579 | su.c[1] = *(const char *)w; |
| 580 | sum += su.s; |
| 581 | len = 0; |
| 582 | } else |
| 583 | len = -1; |
| 584 | } else if (len == -1) { |
| 585 | /* |
| 586 | * This buffer has odd number of bytes. |
| 587 | * There could be a word split betwen |
| 588 | * this buffer and the next. |
| 589 | */ |
| 590 | su.c[0] = *(const char *)w; |
| 591 | } |
| 592 | out: |
| 593 | if (len == -1) { |
| 594 | /* The last buffer has odd # of bytes. Follow the |
| 595 | standard (the odd byte is shifted left by 8 bits) */ |
| 596 | su.c[1] = 0; |
| 597 | sum += su.s; |
| 598 | } |
| 599 | return sum; |
| 600 | } |
| 601 | |
| 602 | int |
| 603 | in_cksum_finalize(psum) |
| 604 | in_psum_t psum; |
| 605 | { |
| 606 | in_psum_t sum = psum; |
| 607 | REDUCE; |
| 608 | return (~sum & 0xffff); |
| 609 | } |