sys/netinet/tcp_sack.c

   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
  46 #include <net/if.h>
  47
  48 #include <netinet/in.h>
  49 #include <netinet/in_systm.h>
  50 #include <netinet/ip.h>
  51 #include <netinet/in_var.h>
  52 #include <netinet/in_pcb.h>
  53 #include <netinet/ip_var.h>
  54 #include <netinet/tcp.h>
  55 #include <netinet/tcp_seq.h>
  56 #include <netinet/tcp_var.h>
  57
  58 /*
  59  * Implemented:
  60  *
  61  * RFC 2018
  62  * RFC 2883
  63  * RFC 3517
  64  */
  65
  66 struct sackblock {
  67         tcp_seq                 sblk_start;
  68         tcp_seq                 sblk_end;
  69         TAILQ_ENTRY(sackblock)  sblk_list;
  70 };
  71
  72 #define MAXSAVEDBLOCKS  8                       /* per connection limit */
  73
  74 static int insert_block(struct scoreboard *scb,
  75                         const struct raw_sackblock *raw_sb);
  76 static void update_lostseq(struct scoreboard *scb, tcp_seq snd_una,
  77                            u_int maxseg);
  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         struct sackblock *hint = scb->lastfound;
 103         struct sackblock *cur, *last, *prev;
 104
 105         if (TAILQ_EMPTY(&scb->sackblocks)) {
 106                 *sb = NULL;
 107                 return FALSE;
 108         }
 109
 110         if (hint == NULL) {
 111                 /* No hint.  Search from start to end. */
 112                 cur = TAILQ_FIRST(&scb->sackblocks);
 113                 last = NULL;
 114                 prev = TAILQ_LAST(&scb->sackblocks, sackblock_list);
 115         } else  {
 116                 if (SEQ_GEQ(seq, hint->sblk_start)) {
 117                         /* Search from hint to end of list. */
 118                         cur = hint;
 119                         last = NULL;
 120                         prev = TAILQ_LAST(&scb->sackblocks, sackblock_list);
 121                 } else {
 122                         /* Search from front of list to hint. */
 123                         cur = TAILQ_FIRST(&scb->sackblocks);
 124                         last = hint;
 125                         prev = TAILQ_PREV(hint, sackblock_list, sblk_list);
 126                 }
 127         }
 128
 129         do {
 130                 if (SEQ_GT(cur->sblk_end, seq)) {
 131                         if (SEQ_GEQ(seq, cur->sblk_start)) {
 132                                 *sb = scb->lastfound = cur;
 133                                 return TRUE;
 134                         } else {
 135                                 *sb = scb->lastfound =
 136                                     TAILQ_PREV(cur, sackblock_list, sblk_list);
 137                                 return FALSE;
 138                         }
 139                 }
 140                 cur = TAILQ_NEXT(cur, sblk_list);
 141         } while (cur != last);
 142
 143         *sb = scb->lastfound = prev;
 144         return FALSE;
 145 }
 146
 147 /*
 148  * Allocate a SACK block.
 149  */
 150 static __inline struct sackblock *
 151 alloc_sackblock(struct scoreboard *scb, const struct raw_sackblock *raw_sb)
 152 {
 153         struct sackblock *sb;
 154
 155         if (scb->freecache != NULL) {
 156                 sb = scb->freecache;
 157                 scb->freecache = NULL;
 158                 tcpstat.tcps_sacksbfast++;
 159         } else {
 160                 sb = kmalloc(sizeof(struct sackblock), M_SACKBLOCK, M_NOWAIT);
 161                 if (sb == NULL) {
 162                         tcpstat.tcps_sacksbfailed++;
 163                         return NULL;
 164                 }
 165         }
 166         sb->sblk_start = raw_sb->rblk_start;
 167         sb->sblk_end = raw_sb->rblk_end;
 168         return sb;
 169 }
 170
 171 static __inline struct sackblock *
 172 alloc_sackblock_limit(struct scoreboard *scb,
 173     const struct raw_sackblock *raw_sb)
 174 {
 175         if (scb->nblocks == MAXSAVEDBLOCKS) {
 176                 /*
 177                  * Should try to kick out older blocks XXX JH
 178                  * May be able to coalesce with existing block.
 179                  * Or, go other way and free all blocks if we hit
 180                  * this limit.
 181                  */
 182                 tcpstat.tcps_sacksboverflow++;
 183                 return NULL;
 184         }
 185         return alloc_sackblock(scb, raw_sb);
 186 }
 187
 188 /*
 189  * Free a SACK block.
 190  */
 191 static __inline void
 192 free_sackblock(struct scoreboard *scb, struct sackblock *s)
 193 {
 194         if (scb->freecache == NULL) {
 195                 /* YYY Maybe use the latest freed block? */
 196                 scb->freecache = s;
 197                 return;
 198         }
 199         kfree(s, M_SACKBLOCK);
 200 }
 201
 202 /*
 203  * Free up SACK blocks for data that's been acked.
 204  */
 205 static void
 206 tcp_sack_ack_blocks(struct scoreboard *scb, tcp_seq th_ack)
 207 {
 208         struct sackblock *sb, *nb;
 209
 210         sb = TAILQ_FIRST(&scb->sackblocks);
 211         while (sb && SEQ_LEQ(sb->sblk_end, th_ack)) {
 212                 nb = TAILQ_NEXT(sb, sblk_list);
 213                 if (scb->lastfound == sb)
 214                         scb->lastfound = NULL;
 215                 TAILQ_REMOVE(&scb->sackblocks, sb, sblk_list);
 216                 free_sackblock(scb, sb);
 217                 --scb->nblocks;
 218                 KASSERT(scb->nblocks >= 0,
 219                     ("SACK block count underflow: %d < 0", scb->nblocks));
 220                 sb = nb;
 221         }
 222         if (sb && SEQ_GT(th_ack, sb->sblk_start))
 223                 sb->sblk_start = th_ack;        /* other side reneged? XXX */
 224 }
 225
 226 /*
 227  * Delete and free SACK blocks saved in scoreboard.
 228  */
 229 void
 230 tcp_sack_cleanup(struct scoreboard *scb)
 231 {
 232         struct sackblock *sb, *nb;
 233
 234         TAILQ_FOREACH_MUTABLE(sb, &scb->sackblocks, sblk_list, nb) {
 235                 free_sackblock(scb, sb);
 236                 --scb->nblocks;
 237         }
 238         KASSERT(scb->nblocks == 0,
 239             ("SACK block %d count not zero", scb->nblocks));
 240         TAILQ_INIT(&scb->sackblocks);
 241         scb->lastfound = NULL;
 242 }
 243
 244 /*
 245  * Delete and free SACK blocks saved in scoreboard.
 246  * Delete the one slot block cache.
 247  */
 248 void
 249 tcp_sack_destroy(struct scoreboard *scb)
 250 {
 251         tcp_sack_cleanup(scb);
 252         if (scb->freecache != NULL) {
 253                 kfree(scb->freecache, M_SACKBLOCK);
 254                 scb->freecache = NULL;
 255         }
 256 }
 257
 258 /*
 259  * Cleanup the reported SACK block information
 260  */
 261 void
 262 tcp_sack_report_cleanup(struct tcpcb *tp)
 263 {
 264         tp->t_flags &= ~(TF_DUPSEG | TF_ENCLOSESEG | TF_SACKLEFT);
 265         tp->reportblk.rblk_start = tp->reportblk.rblk_end;
 266 }
 267
 268 /*
 269  * Returns      0 if not D-SACK block,
 270  *              1 if D-SACK,
 271  *              2 if duplicate of out-of-order D-SACK block.
 272  */
 273 int
 274 tcp_sack_ndsack_blocks(struct raw_sackblock *blocks, const int numblocks,
 275                        tcp_seq snd_una)
 276 {
 277         if (numblocks == 0)
 278                 return 0;
 279
 280         if (SEQ_LT(blocks[0].rblk_start, snd_una))
 281                 return 1;
 282
 283         /* block 0 inside block 1 */
 284         if (numblocks > 1 &&
 285             SEQ_GEQ(blocks[0].rblk_start, blocks[1].rblk_start) &&
 286             SEQ_LEQ(blocks[0].rblk_end, blocks[1].rblk_end))
 287                 return 2;
 288
 289         return 0;
 290 }
 291
 292 /*
 293  * Update scoreboard on new incoming ACK.
 294  */
 295 static void
 296 tcp_sack_add_blocks(struct tcpcb *tp, struct tcpopt *to)
 297 {
 298         const int numblocks = to->to_nsackblocks;
 299         struct raw_sackblock *blocks = to->to_sackblocks;
 300         struct scoreboard *scb = &tp->scb;
 301         int startblock;
 302         int i;
 303
 304         if (tcp_sack_ndsack_blocks(blocks, numblocks, tp->snd_una) > 0)
 305                 startblock = 1;
 306         else
 307                 startblock = 0;
 308
 309         for (i = startblock; i < numblocks; i++) {
 310                 struct raw_sackblock *newsackblock = &blocks[i];
 311
 312                 /* don't accept bad SACK blocks */
 313                 if (SEQ_GT(newsackblock->rblk_end, tp->snd_max)) {
 314                         tcpstat.tcps_rcvbadsackopt++;
 315                         break;          /* skip all other blocks */
 316                 }
 317                 tcpstat.tcps_sacksbupdate++;
 318
 319                 if (insert_block(scb, newsackblock))
 320                         break;
 321         }
 322 }
 323
 324 void
 325 tcp_sack_update_scoreboard(struct tcpcb *tp, struct tcpopt *to)
 326 {
 327         struct scoreboard *scb = &tp->scb;
 328
 329         tcp_sack_ack_blocks(scb, tp->snd_una);
 330         tcp_sack_add_blocks(tp, to);
 331         update_lostseq(scb, tp->snd_una, tp->t_maxseg);
 332         if (SEQ_LT(tp->rexmt_high, tp->snd_una))
 333                 tp->rexmt_high = tp->snd_una;
 334         if ((tp->t_flags & TF_SACKRESCUED) &&
 335             SEQ_LT(tp->rexmt_rescue, tp->snd_una))
 336                 tp->t_flags &= ~TF_SACKRESCUED;
 337 }
 338
 339 /*
 340  * Insert SACK block into sender's scoreboard.
 341  */
 342 static int
 343 insert_block(struct scoreboard *scb, const struct raw_sackblock *raw_sb)
 344 {
 345         struct sackblock *sb, *workingblock;
 346         boolean_t overlap_front;
 347
 348         if (TAILQ_EMPTY(&scb->sackblocks)) {
 349                 struct sackblock *newblock;
 350
 351                 KASSERT(scb->nblocks == 0, ("emply scb w/ blocks"));
 352
 353                 newblock = alloc_sackblock(scb, raw_sb);
 354                 if (newblock == NULL)
 355                         return ENOMEM;
 356                 TAILQ_INSERT_HEAD(&scb->sackblocks, newblock, sblk_list);
 357                 scb->nblocks = 1;
 358                 return 0;
 359         }
 360
 361         KASSERT(scb->nblocks > 0, ("insert_block() called w/ no blocks"));
 362         KASSERT(scb->nblocks <= MAXSAVEDBLOCKS,
 363             ("too many SACK blocks %d", scb->nblocks));
 364
 365         overlap_front = sack_block_lookup(scb, raw_sb->rblk_start, &sb);
 366
 367         if (sb == NULL) {
 368                 workingblock = alloc_sackblock_limit(scb, raw_sb);
 369                 if (workingblock == NULL)
 370                         return ENOMEM;
 371                 TAILQ_INSERT_HEAD(&scb->sackblocks, workingblock, sblk_list);
 372                 ++scb->nblocks;
 373         } else {
 374                 if (overlap_front || sb->sblk_end == raw_sb->rblk_start) {
 375                         /* Extend old block */
 376                         workingblock = sb;
 377                         if (SEQ_GT(raw_sb->rblk_end, sb->sblk_end))
 378                                 sb->sblk_end = raw_sb->rblk_end;
 379                         tcpstat.tcps_sacksbreused++;
 380                 } else {
 381                         workingblock = alloc_sackblock_limit(scb, raw_sb);
 382                         if (workingblock == NULL)
 383                                 return ENOMEM;
 384                         TAILQ_INSERT_AFTER(&scb->sackblocks, sb, workingblock,
 385                             sblk_list);
 386                         ++scb->nblocks;
 387                 }
 388         }
 389
 390         /* Consolidate right-hand side. */
 391         sb = TAILQ_NEXT(workingblock, sblk_list);
 392         while (sb != NULL &&
 393             SEQ_GEQ(workingblock->sblk_end, sb->sblk_end)) {
 394                 struct sackblock *nextblock;
 395
 396                 nextblock = TAILQ_NEXT(sb, sblk_list);
 397                 if (scb->lastfound == sb)
 398                         scb->lastfound = NULL;
 399                 /* Remove completely overlapped block */
 400                 TAILQ_REMOVE(&scb->sackblocks, sb, sblk_list);
 401                 free_sackblock(scb, sb);
 402                 --scb->nblocks;
 403                 KASSERT(scb->nblocks > 0,
 404                     ("removed overlapped block: %d blocks left", scb->nblocks));
 405                 sb = nextblock;
 406         }
 407         if (sb != NULL &&
 408             SEQ_GEQ(workingblock->sblk_end, sb->sblk_start)) {
 409                 /* Extend new block to cover partially overlapped old block. */
 410                 workingblock->sblk_end = sb->sblk_end;
 411                 if (scb->lastfound == sb)
 412                         scb->lastfound = NULL;
 413                 TAILQ_REMOVE(&scb->sackblocks, sb, sblk_list);
 414                 free_sackblock(scb, sb);
 415                 --scb->nblocks;
 416                 KASSERT(scb->nblocks > 0,
 417                     ("removed partial right: %d blocks left", scb->nblocks));
 418         }
 419         return 0;
 420 }
 421
 422 #ifdef DEBUG_SACK_BLOCKS
 423 static void
 424 tcp_sack_dump_blocks(struct scoreboard *scb)
 425 {
 426         struct sackblock *sb;
 427
 428         kprintf("%d blocks:", scb->nblocks);
 429         TAILQ_FOREACH(sb, &scb->sackblocks, sblk_list)
 430                 kprintf(" [%u, %u)", sb->sblk_start, sb->sblk_end);
 431         kprintf("\n");
 432 }
 433 #else
 434 static __inline void
 435 tcp_sack_dump_blocks(struct scoreboard *scb)
 436 {
 437 }
 438 #endif
 439
 440 /*
 441  * Optimization to quickly determine which packets are lost.
 442  */
 443 static void
 444 update_lostseq(struct scoreboard *scb, tcp_seq snd_una, u_int maxseg)
 445 {
 446         struct sackblock *sb;
 447         int nsackblocks = 0;
 448         int bytes_sacked = 0;
 449
 450         sb = TAILQ_LAST(&scb->sackblocks, sackblock_list);
 451         while (sb != NULL) {
 452                 ++nsackblocks;
 453                 bytes_sacked += sb->sblk_end - sb->sblk_start;
 454                 if (nsackblocks == tcprexmtthresh ||
 455                     bytes_sacked >= tcprexmtthresh * maxseg) {
 456                         scb->lostseq = sb->sblk_start;
 457                         return;
 458                 }
 459                 sb = TAILQ_PREV(sb, sackblock_list, sblk_list);
 460         }
 461         scb->lostseq = snd_una;
 462 }
 463
 464 /*
 465  * Return whether the given sequence number is considered lost.
 466  */
 467 static boolean_t
 468 scb_islost(struct scoreboard *scb, tcp_seq seqnum)
 469 {
 470         return SEQ_LT(seqnum, scb->lostseq);
 471 }
 472
 473 /*
 474  * True if at least "amount" has been SACKed.  Used by Early Retransmit.
 475  */
 476 boolean_t
 477 tcp_sack_has_sacked(struct scoreboard *scb, u_int amount)
 478 {
 479         struct sackblock *sb;
 480         int bytes_sacked = 0;
 481
 482         TAILQ_FOREACH(sb, &scb->sackblocks, sblk_list) {
 483                 bytes_sacked += sb->sblk_end - sb->sblk_start;
 484                 if (bytes_sacked >= amount)
 485                         return TRUE;
 486         }
 487         return FALSE;
 488 }
 489
 490 /*
 491  * Number of bytes SACKed below seq.
 492  */
 493 int
 494 tcp_sack_bytes_below(struct scoreboard *scb, tcp_seq seq)
 495 {
 496         struct sackblock *sb;
 497         int bytes_sacked = 0;
 498
 499         sb = TAILQ_FIRST(&scb->sackblocks);
 500         while (sb && SEQ_GT(seq, sb->sblk_start)) {
 501                 bytes_sacked += seq_min(seq, sb->sblk_end) - sb->sblk_start;
 502                 sb = TAILQ_NEXT(sb, sblk_list);
 503         }
 504         return bytes_sacked;
 505 }
 506
 507 /*
 508  * Return estimate of the number of bytes outstanding in the network.
 509  */
 510 uint32_t
 511 tcp_sack_compute_pipe(struct tcpcb *tp)
 512 {
 513         struct scoreboard *scb = &tp->scb;
 514         struct sackblock *sb;
 515         int nlost, nretransmitted;
 516         tcp_seq end;
 517
 518         nlost = tp->snd_max - scb->lostseq;
 519         nretransmitted = tp->rexmt_high - tp->snd_una;
 520
 521         TAILQ_FOREACH(sb, &scb->sackblocks, sblk_list) {
 522                 if (SEQ_LT(sb->sblk_start, tp->rexmt_high)) {
 523                         end = seq_min(sb->sblk_end, tp->rexmt_high);
 524                         nretransmitted -= end - sb->sblk_start;
 525                 }
 526                 if (SEQ_GEQ(sb->sblk_start, scb->lostseq))
 527                         nlost -= sb->sblk_end - sb->sblk_start;
 528         }
 529
 530         return (nlost + nretransmitted);
 531 }
 532
 533 /*
 534  * Return the sequence number and length of the next segment to transmit
 535  * when in Fast Recovery.
 536  */
 537 boolean_t
 538 tcp_sack_nextseg(struct tcpcb *tp, tcp_seq *nextrexmt, uint32_t *plen,
 539     boolean_t *rescue)
 540 {
 541         struct scoreboard *scb = &tp->scb;
 542         struct socket *so = tp->t_inpcb->inp_socket;
 543         struct sackblock *sb;
 544         const struct sackblock *lastblock =
 545             TAILQ_LAST(&scb->sackblocks, sackblock_list);
 546         tcp_seq torexmt;
 547         long len, off;
 548
 549         /* skip SACKed data */
 550         tcp_sack_skip_sacked(scb, &tp->rexmt_high);
 551
 552         /* Look for lost data. */
 553         torexmt = tp->rexmt_high;
 554         *rescue = FALSE;
 555         if (lastblock != NULL) {
 556                 if (SEQ_LT(torexmt, lastblock->sblk_end) &&
 557                     scb_islost(scb, torexmt)) {
 558 sendunsacked:
 559                         *nextrexmt = torexmt;
 560                         /* If the left-hand edge has been SACKed, pull it in. */
 561                         if (sack_block_lookup(scb, torexmt + tp->t_maxseg, &sb))
 562                                 *plen = sb->sblk_start - torexmt;
 563                         else
 564                                 *plen = tp->t_maxseg;
 565                         return TRUE;
 566                 }
 567         }
 568
 569         /* See if unsent data available within send window. */
 570         off = tp->snd_max - tp->snd_una;
 571         len = (long) ulmin(so->so_snd.ssb_cc, tp->snd_wnd) - off;
 572         if (len > 0) {
 573                 *nextrexmt = tp->snd_max;       /* Send new data. */
 574                 *plen = tp->t_maxseg;
 575                 return TRUE;
 576         }
 577
 578         /* We're less certain this data has been lost. */
 579         if (lastblock != NULL && SEQ_LT(torexmt, lastblock->sblk_end))
 580                 goto sendunsacked;
 581
 582         if (tcp_do_rescuesack) {
 583                 tcpstat.tcps_sackrescue_try++;
 584                 if (lastblock == NULL)
 585                         tcpstat.tcps_sackrescue_smart++;
 586
 587                 if (tp->t_flags & TF_SACKRESCUED)
 588                         return FALSE;
 589                 *rescue = TRUE;
 590                 tcpstat.tcps_sackrescue++;
 591                 goto sendunsacked;
 592         } else if (tcp_do_smartsack && lastblock == NULL) {
 593                 goto sendunsacked;
 594         }
 595
 596         return FALSE;
 597 }
 598
 599 /*
 600  * Return the next sequence number higher than "*prexmt" that has
 601  * not been SACKed.
 602  */
 603 void
 604 tcp_sack_skip_sacked(struct scoreboard *scb, tcp_seq *prexmt)
 605 {
 606         struct sackblock *sb;
 607
 608         /* skip SACKed data */
 609         if (sack_block_lookup(scb, *prexmt, &sb))
 610                 *prexmt = sb->sblk_end;
 611 }
 612
 613 #ifdef later
 614 void
 615 tcp_sack_save_scoreboard(struct scoreboard *scb)
 616 {
 617         struct scoreboard *scb = &tp->scb;
 618
 619         scb->sackblocks_prev = scb->sackblocks;
 620         TAILQ_INIT(&scb->sackblocks);
 621 }
 622
 623 void
 624 tcp_sack_revert_scoreboard(struct scoreboard *scb, tcp_seq snd_una,
 625                            u_int maxseg)
 626 {
 627         struct sackblock *sb;
 628
 629         scb->sackblocks = scb->sackblocks_prev;
 630         scb->nblocks = 0;
 631         TAILQ_FOREACH(sb, &scb->sackblocks, sblk_list)
 632                 ++scb->nblocks;
 633         tcp_sack_ack_blocks(scb, snd_una);
 634         scb->lastfound = NULL;
 635 }
 636 #endif
 637
 638 #ifdef DEBUG_SACK_HISTORY
 639 static void
 640 tcp_sack_dump_history(char *msg, struct tcpcb *tp)
 641 {
 642         int i;
 643         static int ndumped;
 644
 645         /* only need a couple of these to debug most problems */
 646         if (++ndumped > 900)
 647                 return;
 648
 649         kprintf("%s:\tnsackhistory %d: ", msg, tp->nsackhistory);
 650         for (i = 0; i < tp->nsackhistory; ++i)
 651                 kprintf("[%u, %u) ", tp->sackhistory[i].rblk_start,
 652                     tp->sackhistory[i].rblk_end);
 653         kprintf("\n");
 654 }
 655 #else
 656 static __inline void
 657 tcp_sack_dump_history(char *msg, struct tcpcb *tp)
 658 {
 659 }
 660 #endif
 661
 662 /*
 663  * Remove old SACK blocks from the SACK history that have already been ACKed.
 664  */
 665 static void
 666 tcp_sack_ack_history(struct tcpcb *tp)
 667 {
 668         int i, nblocks, openslot;
 669
 670         tcp_sack_dump_history("before tcp_sack_ack_history", tp);
 671         nblocks = tp->nsackhistory;
 672         for (i = openslot = 0; i < nblocks; ++i) {
 673                 if (SEQ_LEQ(tp->sackhistory[i].rblk_end, tp->rcv_nxt)) {
 674                         --tp->nsackhistory;
 675                         continue;
 676                 }
 677                 if (SEQ_LT(tp->sackhistory[i].rblk_start, tp->rcv_nxt))
 678                         tp->sackhistory[i].rblk_start = tp->rcv_nxt;
 679                 if (i == openslot)
 680                         ++openslot;
 681                 else
 682                         tp->sackhistory[openslot++] = tp->sackhistory[i];
 683         }
 684         tcp_sack_dump_history("after tcp_sack_ack_history", tp);
 685         KASSERT(openslot == tp->nsackhistory,
 686             ("tcp_sack_ack_history miscounted: %d != %d",
 687             openslot, tp->nsackhistory));
 688 }
 689
 690 /*
 691  * Add or merge newblock into reported history.
 692  * Also remove or update SACK blocks that will be acked.
 693  */
 694 static void
 695 tcp_sack_update_reported_history(struct tcpcb *tp, tcp_seq start, tcp_seq end)
 696 {
 697         struct raw_sackblock copy[MAX_SACK_REPORT_BLOCKS];
 698         int i, cindex;
 699
 700         tcp_sack_dump_history("before tcp_sack_update_reported_history", tp);
 701         /*
 702          * Six cases:
 703          *      0) no overlap
 704          *      1) newblock == oldblock
 705          *      2) oldblock contains newblock
 706          *      3) newblock contains oldblock
 707          *      4) tail of oldblock overlaps or abuts start of newblock
 708          *      5) tail of newblock overlaps or abuts head of oldblock
 709          */
 710         for (i = cindex = 0; i < tp->nsackhistory; ++i) {
 711                 struct raw_sackblock *oldblock = &tp->sackhistory[i];
 712                 tcp_seq old_start = oldblock->rblk_start;
 713                 tcp_seq old_end = oldblock->rblk_end;
 714
 715                 if (SEQ_LT(end, old_start) || SEQ_GT(start, old_end)) {
 716                         /* Case 0:  no overlap.  Copy old block. */
 717                         copy[cindex++] = *oldblock;
 718                         continue;
 719                 }
 720
 721                 if (SEQ_GEQ(start, old_start) && SEQ_LEQ(end, old_end)) {
 722                         /* Cases 1 & 2.  Move block to front of history. */
 723                         int j;
 724
 725                         start = old_start;
 726                         end = old_end;
 727                         /* no need to check rest of blocks */
 728                         for (j = i + 1; j < tp->nsackhistory; ++j)
 729                                 copy[cindex++] = tp->sackhistory[j];
 730                         break;
 731                 }
 732
 733                 if (SEQ_GEQ(old_end, start) && SEQ_LT(old_start, start)) {
 734                         /* Case 4:  extend start of new block. */
 735                         start = old_start;
 736                 } else if (SEQ_GEQ(end, old_start) && SEQ_GT(old_end, end)) {
 737                         /* Case 5: extend end of new block */
 738                         end = old_end;
 739                 } else {
 740                         /* Case 3.  Delete old block by not copying it. */
 741                         KASSERT(SEQ_LEQ(start, old_start) &&
 742                                 SEQ_GEQ(end, old_end),
 743                             ("bad logic: old [%u, %u), new [%u, %u)",
 744                              old_start, old_end, start, end));
 745                 }
 746         }
 747
 748         /* insert new block */
 749         tp->sackhistory[0].rblk_start = start;
 750         tp->sackhistory[0].rblk_end = end;
 751         cindex = min(cindex, MAX_SACK_REPORT_BLOCKS - 1);
 752         for (i = 0; i < cindex; ++i)
 753                 tp->sackhistory[i + 1] = copy[i];
 754         tp->nsackhistory = cindex + 1;
 755         tcp_sack_dump_history("after tcp_sack_update_reported_history", tp);
 756 }
 757
 758 /*
 759  * Fill in SACK report to return to data sender.
 760  */
 761 void
 762 tcp_sack_fill_report(struct tcpcb *tp, u_char *opt, u_int *plen)
 763 {
 764         u_int optlen = *plen;
 765         uint32_t *lp = (uint32_t *)(opt + optlen);
 766         uint32_t *olp;
 767         tcp_seq hstart = tp->rcv_nxt, hend;
 768         int nblocks;
 769
 770         KASSERT(TCP_MAXOLEN - optlen >=
 771             TCPOLEN_SACK_ALIGNED + TCPOLEN_SACK_BLOCK,
 772             ("no room for SACK header and one block: optlen %d", optlen));
 773
 774         if (tp->t_flags & TF_DUPSEG)
 775                 tcpstat.tcps_snddsackopt++;
 776         else
 777                 tcpstat.tcps_sndsackopt++;
 778
 779         olp = lp++;
 780         optlen += TCPOLEN_SACK_ALIGNED;
 781
 782         tcp_sack_ack_history(tp);
 783         if (tp->reportblk.rblk_start != tp->reportblk.rblk_end) {
 784                 *lp++ = htonl(tp->reportblk.rblk_start);
 785                 *lp++ = htonl(tp->reportblk.rblk_end);
 786                 optlen += TCPOLEN_SACK_BLOCK;
 787                 hstart = tp->reportblk.rblk_start;
 788                 hend = tp->reportblk.rblk_end;
 789                 if (tp->t_flags & TF_ENCLOSESEG) {
 790                         KASSERT(TCP_MAXOLEN - optlen >= TCPOLEN_SACK_BLOCK,
 791                             ("no room for enclosing SACK block: oplen %d",
 792                             optlen));
 793                         *lp++ = htonl(tp->encloseblk.rblk_start);
 794                         *lp++ = htonl(tp->encloseblk.rblk_end);
 795                         optlen += TCPOLEN_SACK_BLOCK;
 796                         hstart = tp->encloseblk.rblk_start;
 797                         hend = tp->encloseblk.rblk_end;
 798                 }
 799                 if (SEQ_GT(hstart, tp->rcv_nxt))
 800                         tcp_sack_update_reported_history(tp, hstart, hend);
 801         }
 802         if (tcp_do_smartsack && (tp->t_flags & TF_SACKLEFT)) {
 803                 /* Fill in from left!  Walk re-assembly queue. */
 804                 struct tseg_qent *q;
 805
 806                 q = LIST_FIRST(&tp->t_segq);
 807                 while (q != NULL &&
 808                     TCP_MAXOLEN - optlen >= TCPOLEN_SACK_BLOCK) {
 809                         *lp++ = htonl(q->tqe_th->th_seq);
 810                         *lp++ = htonl(TCP_SACK_BLKEND(
 811                             q->tqe_th->th_seq + q->tqe_len,
 812                             q->tqe_th->th_flags));
 813                         optlen += TCPOLEN_SACK_BLOCK;
 814                         q = LIST_NEXT(q, tqe_q);
 815                 }
 816         } else {
 817                 int n = 0;
 818
 819                 /* Fill in SACK blocks from right side. */
 820                 while (n < tp->nsackhistory &&
 821                     TCP_MAXOLEN - optlen >= TCPOLEN_SACK_BLOCK) {
 822                         if (tp->sackhistory[n].rblk_start != hstart) {
 823                                 *lp++ = htonl(tp->sackhistory[n].rblk_start);
 824                                 *lp++ = htonl(tp->sackhistory[n].rblk_end);
 825                                 optlen += TCPOLEN_SACK_BLOCK;
 826                         }
 827                         ++n;
 828                 }
 829         }
 830         tp->reportblk.rblk_start = tp->reportblk.rblk_end;
 831         tp->t_flags &= ~(TF_DUPSEG | TF_ENCLOSESEG | TF_SACKLEFT);
 832         nblocks = (lp - olp - 1) / 2;
 833         *olp = htonl(TCPOPT_SACK_ALIGNED |
 834                      (TCPOLEN_SACK + nblocks * TCPOLEN_SACK_BLOCK));
 835         *plen = optlen;
 836 }