1 /* 2 * Copyright (c) 2003, 2004 Jeffrey M. Hsu. All rights reserved. 3 * Copyright (c) 2003, 2004 The DragonFly Project. All rights reserved. 4 * 5 * This code is derived from software contributed to The DragonFly Project 6 * by Jeffrey M. Hsu. 7 * 8 * Redistribution and use in source and binary forms, with or without 9 * modification, are permitted provided that the following conditions 10 * are met: 11 * 1. Redistributions of source code must retain the above copyright 12 * notice, this list of conditions and the following disclaimer. 13 * 2. Redistributions in binary form must reproduce the above copyright 14 * notice, this list of conditions and the following disclaimer in the 15 * documentation and/or other materials provided with the distribution. 16 * 3. Neither the name of The DragonFly Project nor the names of its 17 * contributors may be used to endorse or promote products derived 18 * from this software without specific, prior written permission. 19 * 20 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 21 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 22 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS 23 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE 24 * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, 25 * INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING, 26 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; 27 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED 28 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, 29 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT 30 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 31 * SUCH DAMAGE. 32 * 33 * $DragonFly: src/sys/netinet/tcp_sack.c,v 1.8 2008/08/15 21:37:16 nth Exp $ 34 */ 35 36 #include <sys/param.h> 37 #include <sys/systm.h> 38 #include <sys/kernel.h> 39 #include <sys/malloc.h> 40 #include <sys/queue.h> 41 #include <sys/thread.h> 42 #include <sys/types.h> 43 #include <sys/socket.h> 44 #include <sys/socketvar.h> 45 #include <sys/resourcevar.h> 46 47 #include <net/if.h> 48 49 #include <netinet/in.h> 50 #include <netinet/in_systm.h> 51 #include <netinet/ip.h> 52 #include <netinet/in_var.h> 53 #include <netinet/in_pcb.h> 54 #include <netinet/ip_var.h> 55 #include <netinet/tcp.h> 56 #include <netinet/tcp_seq.h> 57 #include <netinet/tcp_var.h> 58 59 /* 60 * Implemented: 61 * 62 * RFC 2018 63 * RFC 2883 64 * RFC 3517 65 * RFC 6675 66 */ 67 68 struct sackblock { 69 tcp_seq sblk_start; 70 tcp_seq sblk_end; 71 TAILQ_ENTRY(sackblock) sblk_list; 72 }; 73 74 #define MAXSAVEDBLOCKS 8 /* per connection limit */ 75 76 static int insert_block(struct scoreboard *scb, 77 const struct raw_sackblock *raw_sb, boolean_t *update); 78 79 static MALLOC_DEFINE(M_SACKBLOCK, "sblk", "sackblock struct"); 80 81 /* 82 * Per-tcpcb initialization. 83 */ 84 void 85 tcp_sack_tcpcb_init(struct tcpcb *tp) 86 { 87 struct scoreboard *scb = &tp->scb; 88 89 scb->nblocks = 0; 90 TAILQ_INIT(&scb->sackblocks); 91 scb->lastfound = NULL; 92 } 93 94 /* 95 * Find the SACK block containing or immediately preceding "seq". 96 * The boolean result indicates whether the sequence is actually 97 * contained in the SACK block. 98 */ 99 static boolean_t 100 sack_block_lookup(struct scoreboard *scb, tcp_seq seq, struct sackblock **sb) 101 { 102 static struct krate sackkrate = { .freq = 1 }; 103 struct sackblock *hint = scb->lastfound; 104 struct sackblock *cur, *last, *prev; 105 106 if (TAILQ_EMPTY(&scb->sackblocks)) { 107 *sb = NULL; 108 return FALSE; 109 } 110 111 if (hint == NULL) { 112 /* No hint. Search from start to end. */ 113 cur = TAILQ_FIRST(&scb->sackblocks); 114 last = NULL; 115 prev = TAILQ_LAST(&scb->sackblocks, sackblock_list); 116 } else { 117 if (SEQ_GEQ(seq, hint->sblk_start)) { 118 /* Search from hint to end of list. */ 119 cur = hint; 120 last = NULL; 121 prev = TAILQ_LAST(&scb->sackblocks, sackblock_list); 122 } else { 123 /* Search from front of list to hint. */ 124 cur = TAILQ_FIRST(&scb->sackblocks); 125 last = hint; 126 prev = TAILQ_PREV(hint, sackblock_list, sblk_list); 127 } 128 } 129 130 do { 131 /* 132 * Ensure we can't crash if the list really blows up due to 133 * delta sign wraps when comparing seq against sblk_start vs 134 * sblk_end. 135 */ 136 if (cur == NULL) { 137 krateprintf(&sackkrate, 138 "tcp_sack: fatal corrupt seq\n"); 139 *sb = NULL; 140 return FALSE; 141 } 142 143 /* 144 * Check completion 145 */ 146 if (SEQ_GT(cur->sblk_end, seq)) { 147 if (SEQ_GEQ(seq, cur->sblk_start)) { 148 *sb = scb->lastfound = cur; 149 return TRUE; 150 } else { 151 *sb = scb->lastfound = 152 TAILQ_PREV(cur, sackblock_list, sblk_list); 153 return FALSE; 154 } 155 } 156 157 /* 158 * seq is greater than sblk_end, nominally proceed to the 159 * next block. 160 * 161 * It is possible for an overflow to cause the comparison 162 * between seq an sblk_start vs sblk_end to make it appear 163 * that seq is less than sblk_start and also greater than 164 * sblk_end. If we allow the case to fall through we can 165 * end up with cur == NULL on the next loop. 166 */ 167 if (SEQ_LT(seq, cur->sblk_start)) { 168 krateprintf(&sackkrate, 169 "tcp_sack: corrupt seq " 170 "0x%08x vs 0x%08x-0x%08x\n", 171 seq, cur->sblk_start, cur->sblk_end); 172 if (SEQ_GEQ(seq, cur->sblk_start)) { 173 *sb = scb->lastfound = cur; 174 return TRUE; 175 } else { 176 *sb = scb->lastfound = 177 TAILQ_PREV(cur, sackblock_list, sblk_list); 178 return FALSE; 179 } 180 } 181 cur = TAILQ_NEXT(cur, sblk_list); 182 } while (cur != last); 183 184 *sb = scb->lastfound = prev; 185 return FALSE; 186 } 187 188 /* 189 * Allocate a SACK block. 190 */ 191 static __inline struct sackblock * 192 alloc_sackblock(struct scoreboard *scb, const struct raw_sackblock *raw_sb) 193 { 194 struct sackblock *sb; 195 196 if (scb->freecache != NULL) { 197 sb = scb->freecache; 198 scb->freecache = NULL; 199 tcpstat.tcps_sacksbfast++; 200 } else { 201 sb = kmalloc(sizeof(struct sackblock), M_SACKBLOCK, M_NOWAIT); 202 if (sb == NULL) { 203 tcpstat.tcps_sacksbfailed++; 204 return NULL; 205 } 206 } 207 sb->sblk_start = raw_sb->rblk_start; 208 sb->sblk_end = raw_sb->rblk_end; 209 return sb; 210 } 211 212 static __inline struct sackblock * 213 alloc_sackblock_limit(struct scoreboard *scb, 214 const struct raw_sackblock *raw_sb) 215 { 216 if (scb->nblocks == MAXSAVEDBLOCKS) { 217 /* 218 * Should try to kick out older blocks XXX JH 219 * May be able to coalesce with existing block. 220 * Or, go other way and free all blocks if we hit 221 * this limit. 222 */ 223 tcpstat.tcps_sacksboverflow++; 224 return NULL; 225 } 226 return alloc_sackblock(scb, raw_sb); 227 } 228 229 /* 230 * Free a SACK block. 231 */ 232 static __inline void 233 free_sackblock(struct scoreboard *scb, struct sackblock *s) 234 { 235 if (scb->freecache == NULL) { 236 /* YYY Maybe use the latest freed block? */ 237 scb->freecache = s; 238 return; 239 } 240 kfree(s, M_SACKBLOCK); 241 } 242 243 /* 244 * Free up SACK blocks for data that's been acked. 245 */ 246 static void 247 tcp_sack_ack_blocks(struct tcpcb *tp, tcp_seq th_ack) 248 { 249 struct scoreboard *scb = &tp->scb; 250 struct sackblock *sb, *nb; 251 252 sb = TAILQ_FIRST(&scb->sackblocks); 253 while (sb && SEQ_LEQ(sb->sblk_end, th_ack)) { 254 nb = TAILQ_NEXT(sb, sblk_list); 255 if (scb->lastfound == sb) 256 scb->lastfound = NULL; 257 TAILQ_REMOVE(&scb->sackblocks, sb, sblk_list); 258 free_sackblock(scb, sb); 259 --scb->nblocks; 260 KASSERT(scb->nblocks >= 0, 261 ("SACK block count underflow: %d < 0", scb->nblocks)); 262 sb = nb; 263 } 264 if (sb && SEQ_GEQ(th_ack, sb->sblk_start)) { 265 /* Other side reneged? XXX */ 266 tcpstat.tcps_sackrenege++; 267 tcp_sack_discard(tp); 268 } 269 } 270 271 /* 272 * Delete and free SACK blocks saved in scoreboard. 273 */ 274 static void 275 tcp_sack_cleanup(struct scoreboard *scb) 276 { 277 struct sackblock *sb, *nb; 278 279 TAILQ_FOREACH_MUTABLE(sb, &scb->sackblocks, sblk_list, nb) { 280 free_sackblock(scb, sb); 281 --scb->nblocks; 282 } 283 KASSERT(scb->nblocks == 0, 284 ("SACK block %d count not zero", scb->nblocks)); 285 TAILQ_INIT(&scb->sackblocks); 286 scb->lastfound = NULL; 287 } 288 289 /* 290 * Discard SACK scoreboard, HighRxt, RescueRxt and LostSeq. 291 */ 292 void 293 tcp_sack_discard(struct tcpcb *tp) 294 { 295 tcp_sack_cleanup(&tp->scb); 296 tp->rexmt_high = tp->snd_una; 297 tp->sack_flags &= ~TSACK_F_SACKRESCUED; 298 tp->scb.lostseq = tp->snd_una; 299 } 300 301 /* 302 * Delete and free SACK blocks saved in scoreboard. 303 * Delete the one slot block cache. 304 */ 305 void 306 tcp_sack_destroy(struct scoreboard *scb) 307 { 308 tcp_sack_cleanup(scb); 309 if (scb->freecache != NULL) { 310 kfree(scb->freecache, M_SACKBLOCK); 311 scb->freecache = NULL; 312 } 313 } 314 315 /* 316 * Cleanup the reported SACK block information 317 */ 318 void 319 tcp_sack_report_cleanup(struct tcpcb *tp) 320 { 321 tp->sack_flags &= 322 ~(TSACK_F_DUPSEG | TSACK_F_ENCLOSESEG | TSACK_F_SACKLEFT); 323 tp->reportblk.rblk_start = tp->reportblk.rblk_end; 324 } 325 326 /* 327 * Whether SACK report is needed or not 328 */ 329 boolean_t 330 tcp_sack_report_needed(const struct tcpcb *tp) 331 { 332 if ((tp->sack_flags & 333 (TSACK_F_DUPSEG | TSACK_F_ENCLOSESEG | TSACK_F_SACKLEFT)) || 334 tp->reportblk.rblk_start != tp->reportblk.rblk_end) 335 return TRUE; 336 else 337 return FALSE; 338 } 339 340 /* 341 * Returns 0 if not D-SACK block, 342 * 1 if D-SACK, 343 * 2 if duplicate of out-of-order D-SACK block. 344 */ 345 int 346 tcp_sack_ndsack_blocks(const struct raw_sackblock *blocks, const int numblocks, 347 tcp_seq snd_una) 348 { 349 if (numblocks == 0) 350 return 0; 351 352 if (SEQ_LT(blocks[0].rblk_start, snd_una)) 353 return 1; 354 355 /* block 0 inside block 1 */ 356 if (numblocks > 1 && 357 SEQ_GEQ(blocks[0].rblk_start, blocks[1].rblk_start) && 358 SEQ_LEQ(blocks[0].rblk_end, blocks[1].rblk_end)) 359 return 2; 360 361 return 0; 362 } 363 364 /* 365 * Update scoreboard on new incoming ACK. 366 */ 367 static void 368 tcp_sack_add_blocks(struct tcpcb *tp, struct tcpopt *to) 369 { 370 const int numblocks = to->to_nsackblocks; 371 struct raw_sackblock *blocks = to->to_sackblocks; 372 struct scoreboard *scb = &tp->scb; 373 int startblock, i; 374 375 if (tcp_sack_ndsack_blocks(blocks, numblocks, tp->snd_una) > 0) 376 startblock = 1; 377 else 378 startblock = 0; 379 380 to->to_flags |= TOF_SACK_REDUNDANT; 381 for (i = startblock; i < numblocks; i++) { 382 struct raw_sackblock *newsackblock = &blocks[i]; 383 boolean_t update; 384 int error; 385 386 /* Guard against ACK reordering */ 387 if (SEQ_LEQ(newsackblock->rblk_start, tp->snd_una)) 388 continue; 389 390 /* Don't accept bad SACK blocks */ 391 if (SEQ_GT(newsackblock->rblk_end, tp->snd_max)) { 392 tcpstat.tcps_rcvbadsackopt++; 393 break; /* skip all other blocks */ 394 } 395 tcpstat.tcps_sacksbupdate++; 396 397 error = insert_block(scb, newsackblock, &update); 398 if (update) 399 to->to_flags &= ~TOF_SACK_REDUNDANT; 400 if (error) 401 break; 402 } 403 } 404 405 void 406 tcp_sack_update_scoreboard(struct tcpcb *tp, struct tcpopt *to) 407 { 408 struct scoreboard *scb = &tp->scb; 409 int rexmt_high_update = 0; 410 411 tcp_sack_ack_blocks(tp, tp->snd_una); 412 tcp_sack_add_blocks(tp, to); 413 tcp_sack_update_lostseq(scb, tp->snd_una, tp->t_maxseg, 414 tp->t_rxtthresh); 415 if (SEQ_LT(tp->rexmt_high, tp->snd_una)) { 416 tp->rexmt_high = tp->snd_una; 417 rexmt_high_update = 1; 418 } 419 if (tp->sack_flags & TSACK_F_SACKRESCUED) { 420 if (SEQ_LEQ(tp->rexmt_rescue, tp->snd_una)) { 421 tp->sack_flags &= ~TSACK_F_SACKRESCUED; 422 } else if (tcp_aggressive_rescuesack && rexmt_high_update && 423 SEQ_LT(tp->rexmt_rescue, tp->rexmt_high)) { 424 /* Drag RescueRxt along with HighRxt */ 425 tp->rexmt_rescue = tp->rexmt_high; 426 } 427 } 428 } 429 430 /* 431 * Insert SACK block into sender's scoreboard. 432 */ 433 static int 434 insert_block(struct scoreboard *scb, const struct raw_sackblock *raw_sb, 435 boolean_t *update) 436 { 437 struct sackblock *sb, *workingblock; 438 boolean_t overlap_front; 439 440 *update = TRUE; 441 if (TAILQ_EMPTY(&scb->sackblocks)) { 442 struct sackblock *newblock; 443 444 KASSERT(scb->nblocks == 0, ("emply scb w/ blocks")); 445 446 newblock = alloc_sackblock(scb, raw_sb); 447 if (newblock == NULL) 448 return ENOMEM; 449 TAILQ_INSERT_HEAD(&scb->sackblocks, newblock, sblk_list); 450 scb->nblocks = 1; 451 return 0; 452 } 453 454 KASSERT(scb->nblocks > 0, ("insert_block() called w/ no blocks")); 455 KASSERT(scb->nblocks <= MAXSAVEDBLOCKS, 456 ("too many SACK blocks %d", scb->nblocks)); 457 458 overlap_front = sack_block_lookup(scb, raw_sb->rblk_start, &sb); 459 460 if (sb == NULL) { 461 workingblock = alloc_sackblock_limit(scb, raw_sb); 462 if (workingblock == NULL) 463 return ENOMEM; 464 TAILQ_INSERT_HEAD(&scb->sackblocks, workingblock, sblk_list); 465 ++scb->nblocks; 466 } else { 467 if (overlap_front || sb->sblk_end == raw_sb->rblk_start) { 468 tcpstat.tcps_sacksbreused++; 469 470 /* Extend old block */ 471 workingblock = sb; 472 if (SEQ_GT(raw_sb->rblk_end, sb->sblk_end)) { 473 sb->sblk_end = raw_sb->rblk_end; 474 } else { 475 /* Exact match, nothing to consolidate */ 476 *update = FALSE; 477 return 0; 478 } 479 } else { 480 workingblock = alloc_sackblock_limit(scb, raw_sb); 481 if (workingblock == NULL) 482 return ENOMEM; 483 TAILQ_INSERT_AFTER(&scb->sackblocks, sb, workingblock, 484 sblk_list); 485 ++scb->nblocks; 486 } 487 } 488 489 /* Consolidate right-hand side. */ 490 sb = TAILQ_NEXT(workingblock, sblk_list); 491 while (sb != NULL && 492 SEQ_GEQ(workingblock->sblk_end, sb->sblk_end)) { 493 struct sackblock *nextblock; 494 495 nextblock = TAILQ_NEXT(sb, sblk_list); 496 if (scb->lastfound == sb) 497 scb->lastfound = NULL; 498 /* Remove completely overlapped block */ 499 TAILQ_REMOVE(&scb->sackblocks, sb, sblk_list); 500 free_sackblock(scb, sb); 501 --scb->nblocks; 502 KASSERT(scb->nblocks > 0, 503 ("removed overlapped block: %d blocks left", scb->nblocks)); 504 sb = nextblock; 505 } 506 if (sb != NULL && 507 SEQ_GEQ(workingblock->sblk_end, sb->sblk_start)) { 508 /* Extend new block to cover partially overlapped old block. */ 509 workingblock->sblk_end = sb->sblk_end; 510 if (scb->lastfound == sb) 511 scb->lastfound = NULL; 512 TAILQ_REMOVE(&scb->sackblocks, sb, sblk_list); 513 free_sackblock(scb, sb); 514 --scb->nblocks; 515 KASSERT(scb->nblocks > 0, 516 ("removed partial right: %d blocks left", scb->nblocks)); 517 } 518 return 0; 519 } 520 521 #ifdef DEBUG_SACK_BLOCKS 522 static void 523 tcp_sack_dump_blocks(const struct scoreboard *scb) 524 { 525 const struct sackblock *sb; 526 527 kprintf("%d blocks:", scb->nblocks); 528 TAILQ_FOREACH(sb, &scb->sackblocks, sblk_list) 529 kprintf(" [%u, %u)", sb->sblk_start, sb->sblk_end); 530 kprintf("\n"); 531 } 532 #else 533 static __inline void 534 tcp_sack_dump_blocks(const struct scoreboard *scb) 535 { 536 } 537 #endif 538 539 /* 540 * Optimization to quickly determine which packets are lost. 541 */ 542 void 543 tcp_sack_update_lostseq(struct scoreboard *scb, tcp_seq snd_una, u_int maxseg, 544 int rxtthresh) 545 { 546 struct sackblock *sb; 547 int nsackblocks = 0; 548 int bytes_sacked = 0; 549 int rxtthresh_bytes; 550 551 if (tcp_do_rfc6675) 552 rxtthresh_bytes = (rxtthresh - 1) * maxseg; 553 else 554 rxtthresh_bytes = rxtthresh * maxseg; 555 556 sb = TAILQ_LAST(&scb->sackblocks, sackblock_list); 557 while (sb != NULL) { 558 ++nsackblocks; 559 bytes_sacked += sb->sblk_end - sb->sblk_start; 560 if (nsackblocks == rxtthresh || 561 bytes_sacked >= rxtthresh_bytes) { 562 scb->lostseq = sb->sblk_start; 563 return; 564 } 565 sb = TAILQ_PREV(sb, sackblock_list, sblk_list); 566 } 567 scb->lostseq = snd_una; 568 } 569 570 /* 571 * Return whether the given sequence number is considered lost. 572 */ 573 boolean_t 574 tcp_sack_islost(const struct scoreboard *scb, tcp_seq seqnum) 575 { 576 return SEQ_LT(seqnum, scb->lostseq); 577 } 578 579 /* 580 * True if at least "amount" has been SACKed. Used by Early Retransmit. 581 */ 582 boolean_t 583 tcp_sack_has_sacked(const struct scoreboard *scb, u_int amount) 584 { 585 const struct sackblock *sb; 586 int bytes_sacked = 0; 587 588 TAILQ_FOREACH(sb, &scb->sackblocks, sblk_list) { 589 bytes_sacked += sb->sblk_end - sb->sblk_start; 590 if (bytes_sacked >= amount) 591 return TRUE; 592 } 593 return FALSE; 594 } 595 596 /* 597 * Number of bytes SACKed below seq. 598 */ 599 int 600 tcp_sack_bytes_below(const struct scoreboard *scb, tcp_seq seq) 601 { 602 const struct sackblock *sb; 603 int bytes_sacked = 0; 604 605 sb = TAILQ_FIRST(&scb->sackblocks); 606 while (sb && SEQ_GT(seq, sb->sblk_start)) { 607 bytes_sacked += seq_min(seq, sb->sblk_end) - sb->sblk_start; 608 sb = TAILQ_NEXT(sb, sblk_list); 609 } 610 return bytes_sacked; 611 } 612 613 /* 614 * Return estimate of the number of bytes outstanding in the network. 615 */ 616 uint32_t 617 tcp_sack_compute_pipe(const struct tcpcb *tp) 618 { 619 const struct scoreboard *scb = &tp->scb; 620 const struct sackblock *sb; 621 int nlost, nretransmitted; 622 tcp_seq end; 623 624 nlost = tp->snd_max - scb->lostseq; 625 nretransmitted = tp->rexmt_high - tp->snd_una; 626 627 TAILQ_FOREACH(sb, &scb->sackblocks, sblk_list) { 628 if (SEQ_LT(sb->sblk_start, tp->rexmt_high)) { 629 end = seq_min(sb->sblk_end, tp->rexmt_high); 630 nretransmitted -= end - sb->sblk_start; 631 } 632 if (SEQ_GEQ(sb->sblk_start, scb->lostseq)) 633 nlost -= sb->sblk_end - sb->sblk_start; 634 } 635 636 return (nlost + nretransmitted); 637 } 638 639 /* 640 * Return the sequence number and length of the next segment to transmit 641 * when in Fast Recovery. 642 */ 643 boolean_t 644 tcp_sack_nextseg(struct tcpcb *tp, tcp_seq *nextrexmt, uint32_t *plen, 645 boolean_t *rescue) 646 { 647 struct scoreboard *scb = &tp->scb; 648 struct socket *so = tp->t_inpcb->inp_socket; 649 struct sackblock *sb; 650 const struct sackblock *lastblock = 651 TAILQ_LAST(&scb->sackblocks, sackblock_list); 652 tcp_seq torexmt; 653 long len, off, sendwin; 654 655 /* skip SACKed data */ 656 tcp_sack_skip_sacked(scb, &tp->rexmt_high); 657 658 /* Look for lost data. */ 659 torexmt = tp->rexmt_high; 660 *rescue = FALSE; 661 if (lastblock != NULL) { 662 if (SEQ_LT(torexmt, lastblock->sblk_end) && 663 tcp_sack_islost(scb, torexmt)) { 664 sendunsacked: 665 *nextrexmt = torexmt; 666 /* If the left-hand edge has been SACKed, pull it in. */ 667 if (sack_block_lookup(scb, torexmt + tp->t_maxseg, &sb)) 668 *plen = sb->sblk_start - torexmt; 669 else 670 *plen = tp->t_maxseg; 671 return TRUE; 672 } 673 } 674 675 /* See if unsent data available within send window. */ 676 off = tp->snd_max - tp->snd_una; 677 sendwin = min(tp->snd_wnd, tp->snd_bwnd); 678 len = (long) ulmin(so->so_snd.ssb_cc, sendwin) - off; 679 if (len > 0) { 680 *nextrexmt = tp->snd_max; /* Send new data. */ 681 *plen = tp->t_maxseg; 682 return TRUE; 683 } 684 685 /* We're less certain this data has been lost. */ 686 if (lastblock != NULL && SEQ_LT(torexmt, lastblock->sblk_end)) 687 goto sendunsacked; 688 689 /* Rescue retransmission */ 690 if (tcp_do_rescuesack || tcp_do_rfc6675) { 691 tcpstat.tcps_sackrescue_try++; 692 if (tp->sack_flags & TSACK_F_SACKRESCUED) { 693 if (!tcp_aggressive_rescuesack) 694 return FALSE; 695 696 /* 697 * Aggressive variant of the rescue retransmission. 698 * 699 * The idea of the rescue retransmission is to sustain 700 * the ACK clock thus to avoid timeout retransmission. 701 * 702 * Under some situations, the conservative approach 703 * suggested in the draft 704 * http://tools.ietf.org/html/ 705 * draft-nishida-tcpm-rescue-retransmission-00 706 * could not sustain ACK clock, since it only allows 707 * one rescue retransmission before a cumulative ACK 708 * covers the segement transmitted by rescue 709 * retransmission. 710 * 711 * We try to locate the next unSACKed segment which 712 * follows the previously sent rescue segment. If 713 * there is no such segment, we loop back to the first 714 * unacknowledged segment. 715 */ 716 717 /* 718 * Skip SACKed data, but here we follow 719 * the last transmitted rescue segment. 720 */ 721 torexmt = tp->rexmt_rescue; 722 tcp_sack_skip_sacked(scb, &torexmt); 723 } 724 if (torexmt == tp->snd_max) { 725 /* Nothing left to retransmit; restart */ 726 torexmt = tp->snd_una; 727 } 728 *rescue = TRUE; 729 goto sendunsacked; 730 } else if (tcp_do_smartsack && lastblock == NULL) { 731 tcpstat.tcps_sackrescue_try++; 732 *rescue = TRUE; 733 goto sendunsacked; 734 } 735 736 return FALSE; 737 } 738 739 /* 740 * Return the next sequence number higher than "*prexmt" that has 741 * not been SACKed. 742 */ 743 void 744 tcp_sack_skip_sacked(struct scoreboard *scb, tcp_seq *prexmt) 745 { 746 struct sackblock *sb; 747 748 /* skip SACKed data */ 749 if (sack_block_lookup(scb, *prexmt, &sb)) 750 *prexmt = sb->sblk_end; 751 } 752 753 /* 754 * The length of the first amount of unSACKed data 755 */ 756 uint32_t 757 tcp_sack_first_unsacked_len(const struct tcpcb *tp) 758 { 759 const struct sackblock *sb; 760 761 sb = TAILQ_FIRST(&tp->scb.sackblocks); 762 if (sb == NULL) 763 return tp->t_maxseg; 764 765 KASSERT(SEQ_LT(tp->snd_una, sb->sblk_start), 766 ("invalid sb start %u, snd_una %u", 767 sb->sblk_start, tp->snd_una)); 768 return (sb->sblk_start - tp->snd_una); 769 } 770 771 #ifdef later 772 void 773 tcp_sack_save_scoreboard(struct scoreboard *scb) 774 { 775 struct scoreboard *scb = &tp->scb; 776 777 scb->sackblocks_prev = scb->sackblocks; 778 TAILQ_INIT(&scb->sackblocks); 779 } 780 781 void 782 tcp_sack_revert_scoreboard(struct scoreboard *scb, tcp_seq snd_una, 783 u_int maxseg) 784 { 785 struct sackblock *sb; 786 787 scb->sackblocks = scb->sackblocks_prev; 788 scb->nblocks = 0; 789 TAILQ_FOREACH(sb, &scb->sackblocks, sblk_list) 790 ++scb->nblocks; 791 tcp_sack_ack_blocks(scb, snd_una); 792 scb->lastfound = NULL; 793 } 794 #endif 795 796 #ifdef DEBUG_SACK_HISTORY 797 static void 798 tcp_sack_dump_history(const char *msg, const struct tcpcb *tp) 799 { 800 int i; 801 static int ndumped; 802 803 /* only need a couple of these to debug most problems */ 804 if (++ndumped > 900) 805 return; 806 807 kprintf("%s:\tnsackhistory %d: ", msg, tp->nsackhistory); 808 for (i = 0; i < tp->nsackhistory; ++i) 809 kprintf("[%u, %u) ", tp->sackhistory[i].rblk_start, 810 tp->sackhistory[i].rblk_end); 811 kprintf("\n"); 812 } 813 #else 814 static __inline void 815 tcp_sack_dump_history(const char *msg, const struct tcpcb *tp) 816 { 817 } 818 #endif 819 820 /* 821 * Remove old SACK blocks from the SACK history that have already been ACKed. 822 */ 823 static void 824 tcp_sack_ack_history(struct tcpcb *tp) 825 { 826 int i, nblocks, openslot; 827 828 tcp_sack_dump_history("before tcp_sack_ack_history", tp); 829 nblocks = tp->nsackhistory; 830 for (i = openslot = 0; i < nblocks; ++i) { 831 if (SEQ_LEQ(tp->sackhistory[i].rblk_end, tp->rcv_nxt)) { 832 --tp->nsackhistory; 833 continue; 834 } 835 if (SEQ_LT(tp->sackhistory[i].rblk_start, tp->rcv_nxt)) 836 tp->sackhistory[i].rblk_start = tp->rcv_nxt; 837 if (i == openslot) 838 ++openslot; 839 else 840 tp->sackhistory[openslot++] = tp->sackhistory[i]; 841 } 842 tcp_sack_dump_history("after tcp_sack_ack_history", tp); 843 KASSERT(openslot == tp->nsackhistory, 844 ("tcp_sack_ack_history miscounted: %d != %d", 845 openslot, tp->nsackhistory)); 846 } 847 848 /* 849 * Add or merge newblock into reported history. 850 * Also remove or update SACK blocks that will be acked. 851 */ 852 static void 853 tcp_sack_update_reported_history(struct tcpcb *tp, tcp_seq start, tcp_seq end) 854 { 855 struct raw_sackblock copy[MAX_SACK_REPORT_BLOCKS]; 856 int i, cindex; 857 858 tcp_sack_dump_history("before tcp_sack_update_reported_history", tp); 859 /* 860 * Six cases: 861 * 0) no overlap 862 * 1) newblock == oldblock 863 * 2) oldblock contains newblock 864 * 3) newblock contains oldblock 865 * 4) tail of oldblock overlaps or abuts start of newblock 866 * 5) tail of newblock overlaps or abuts head of oldblock 867 */ 868 for (i = cindex = 0; i < tp->nsackhistory; ++i) { 869 struct raw_sackblock *oldblock = &tp->sackhistory[i]; 870 tcp_seq old_start = oldblock->rblk_start; 871 tcp_seq old_end = oldblock->rblk_end; 872 873 if (SEQ_LT(end, old_start) || SEQ_GT(start, old_end)) { 874 /* Case 0: no overlap. Copy old block. */ 875 copy[cindex++] = *oldblock; 876 continue; 877 } 878 879 if (SEQ_GEQ(start, old_start) && SEQ_LEQ(end, old_end)) { 880 /* Cases 1 & 2. Move block to front of history. */ 881 int j; 882 883 start = old_start; 884 end = old_end; 885 /* no need to check rest of blocks */ 886 for (j = i + 1; j < tp->nsackhistory; ++j) 887 copy[cindex++] = tp->sackhistory[j]; 888 break; 889 } 890 891 if (SEQ_GEQ(old_end, start) && SEQ_LT(old_start, start)) { 892 /* Case 4: extend start of new block. */ 893 start = old_start; 894 } else if (SEQ_GEQ(end, old_start) && SEQ_GT(old_end, end)) { 895 /* Case 5: extend end of new block */ 896 end = old_end; 897 } else { 898 /* Case 3. Delete old block by not copying it. */ 899 KASSERT(SEQ_LEQ(start, old_start) && 900 SEQ_GEQ(end, old_end), 901 ("bad logic: old [%u, %u), new [%u, %u)", 902 old_start, old_end, start, end)); 903 } 904 } 905 906 /* insert new block */ 907 tp->sackhistory[0].rblk_start = start; 908 tp->sackhistory[0].rblk_end = end; 909 cindex = min(cindex, MAX_SACK_REPORT_BLOCKS - 1); 910 for (i = 0; i < cindex; ++i) 911 tp->sackhistory[i + 1] = copy[i]; 912 tp->nsackhistory = cindex + 1; 913 tcp_sack_dump_history("after tcp_sack_update_reported_history", tp); 914 } 915 916 /* 917 * Fill in SACK report to return to data sender. 918 */ 919 void 920 tcp_sack_fill_report(struct tcpcb *tp, u_char *opt, u_int *plen) 921 { 922 u_int optlen = *plen; 923 uint32_t *lp = (uint32_t *)(opt + optlen); 924 uint32_t *olp; 925 tcp_seq hstart = tp->rcv_nxt, hend; 926 int nblocks; 927 928 KASSERT(TCP_MAXOLEN - optlen >= 929 TCPOLEN_SACK_ALIGNED + TCPOLEN_SACK_BLOCK, 930 ("no room for SACK header and one block: optlen %d", optlen)); 931 932 if (tp->sack_flags & TSACK_F_DUPSEG) 933 tcpstat.tcps_snddsackopt++; 934 else 935 tcpstat.tcps_sndsackopt++; 936 937 olp = lp++; 938 optlen += TCPOLEN_SACK_ALIGNED; 939 940 tcp_sack_ack_history(tp); 941 if (tp->reportblk.rblk_start != tp->reportblk.rblk_end) { 942 *lp++ = htonl(tp->reportblk.rblk_start); 943 *lp++ = htonl(tp->reportblk.rblk_end); 944 optlen += TCPOLEN_SACK_BLOCK; 945 hstart = tp->reportblk.rblk_start; 946 hend = tp->reportblk.rblk_end; 947 if (tp->sack_flags & TSACK_F_ENCLOSESEG) { 948 KASSERT(TCP_MAXOLEN - optlen >= TCPOLEN_SACK_BLOCK, 949 ("no room for enclosing SACK block: oplen %d", 950 optlen)); 951 *lp++ = htonl(tp->encloseblk.rblk_start); 952 *lp++ = htonl(tp->encloseblk.rblk_end); 953 optlen += TCPOLEN_SACK_BLOCK; 954 hstart = tp->encloseblk.rblk_start; 955 hend = tp->encloseblk.rblk_end; 956 } 957 if (SEQ_GT(hstart, tp->rcv_nxt)) 958 tcp_sack_update_reported_history(tp, hstart, hend); 959 } 960 if (tcp_do_smartsack && (tp->sack_flags & TSACK_F_SACKLEFT)) { 961 /* Fill in from left! Walk re-assembly queue. */ 962 struct tseg_qent *q; 963 964 q = TAILQ_FIRST(&tp->t_segq); 965 while (q != NULL && 966 TCP_MAXOLEN - optlen >= TCPOLEN_SACK_BLOCK) { 967 *lp++ = htonl(q->tqe_th->th_seq); 968 *lp++ = htonl(TCP_SACK_BLKEND( 969 q->tqe_th->th_seq + q->tqe_len, 970 q->tqe_th->th_flags)); 971 optlen += TCPOLEN_SACK_BLOCK; 972 q = TAILQ_NEXT(q, tqe_q); 973 } 974 } else { 975 int n = 0; 976 977 /* Fill in SACK blocks from right side. */ 978 while (n < tp->nsackhistory && 979 TCP_MAXOLEN - optlen >= TCPOLEN_SACK_BLOCK) { 980 if (tp->sackhistory[n].rblk_start != hstart) { 981 *lp++ = htonl(tp->sackhistory[n].rblk_start); 982 *lp++ = htonl(tp->sackhistory[n].rblk_end); 983 optlen += TCPOLEN_SACK_BLOCK; 984 } 985 ++n; 986 } 987 } 988 tp->reportblk.rblk_start = tp->reportblk.rblk_end; 989 tp->sack_flags &= 990 ~(TSACK_F_DUPSEG | TSACK_F_ENCLOSESEG | TSACK_F_SACKLEFT); 991 nblocks = (lp - olp - 1) / 2; 992 *olp = htonl(TCPOPT_SACK_ALIGNED | 993 (TCPOLEN_SACK + nblocks * TCPOLEN_SACK_BLOCK)); 994 *plen = optlen; 995 } 996