1/* 2 * Copyright (c) 2004,2007 Apple Inc. All rights reserved. 3 * 4 * @APPLE_OSREFERENCE_LICENSE_HEADER_START@ 5 * 6 * This file contains Original Code and/or Modifications of Original Code 7 * as defined in and that are subject to the Apple Public Source License 8 * Version 2.0 (the 'License'). You may not use this file except in 9 * compliance with the License. The rights granted to you under the License 10 * may not be used to create, or enable the creation or redistribution of, 11 * unlawful or unlicensed copies of an Apple operating system, or to 12 * circumvent, violate, or enable the circumvention or violation of, any 13 * terms of an Apple operating system software license agreement. 14 * 15 * Please obtain a copy of the License at 16 * http://www.opensource.apple.com/apsl/ and read it before using this file. 17 * 18 * The Original Code and all software distributed under the License are 19 * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER 20 * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES, 21 * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY, 22 * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT. 23 * Please see the License for the specific language governing rights and 24 * limitations under the License. 25 * 26 * @APPLE_OSREFERENCE_LICENSE_HEADER_END@ 27 */ 28/* 29 * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1995 30 * The Regents of the University of California. All rights reserved. 31 * 32 * Redistribution and use in source and binary forms, with or without 33 * modification, are permitted provided that the following conditions 34 * are met: 35 * 1. Redistributions of source code must retain the above copyright 36 * notice, this list of conditions and the following disclaimer. 37 * 2. Redistributions in binary form must reproduce the above copyright 38 * notice, this list of conditions and the following disclaimer in the 39 * documentation and/or other materials provided with the distribution. 40 * 3. All advertising materials mentioning features or use of this software 41 * must display the following acknowledgement: 42 * This product includes software developed by the University of 43 * California, Berkeley and its contributors. 44 * 4. Neither the name of the University nor the names of its contributors 45 * may be used to endorse or promote products derived from this software 46 * without specific prior written permission. 47 * 48 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 49 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 50 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 51 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 52 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 53 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 54 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 55 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 56 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 57 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 58 * SUCH DAMAGE. 59 * 60 */ 61 62#define _IP_VHL 63 64 65#include <sys/param.h> 66#include <sys/systm.h> 67#include <sys/kernel.h> 68#include <sys/sysctl.h> 69#include <sys/mbuf.h> 70#include <sys/domain.h> 71#include <sys/protosw.h> 72#include <sys/socket.h> 73#include <sys/socketvar.h> 74 75#include <kern/zalloc.h> 76 77#include <net/route.h> 78 79#include <netinet/in.h> 80#include <netinet/in_systm.h> 81#include <netinet/ip.h> 82#include <netinet/in_pcb.h> 83#include <netinet/ip_var.h> 84#if INET6 85#include <netinet6/in6_pcb.h> 86#include <netinet/ip6.h> 87#include <netinet6/ip6_var.h> 88#endif 89#include <netinet/tcp.h> 90//#define TCPOUTFLAGS 91#include <netinet/tcp_fsm.h> 92#include <netinet/tcp_seq.h> 93#include <netinet/tcp_timer.h> 94#include <netinet/tcp_var.h> 95#include <netinet/tcpip.h> 96#if TCPDEBUG 97#include <netinet/tcp_debug.h> 98#endif 99#include <sys/kdebug.h> 100 101#if IPSEC 102#include <netinet6/ipsec.h> 103#endif /*IPSEC*/ 104 105int tcp_do_sack = 1; 106SYSCTL_INT(_net_inet_tcp, OID_AUTO, sack, CTLFLAG_RW | CTLFLAG_LOCKED, &tcp_do_sack, 0, 107 "Enable/Disable TCP SACK support"); 108static int tcp_sack_maxholes = 128; 109SYSCTL_INT(_net_inet_tcp, OID_AUTO, sack_maxholes, CTLFLAG_RW | CTLFLAG_LOCKED, 110 &tcp_sack_maxholes, 0, 111 "Maximum number of TCP SACK holes allowed per connection"); 112 113static int tcp_sack_globalmaxholes = 65536; 114SYSCTL_INT(_net_inet_tcp, OID_AUTO, sack_globalmaxholes, CTLFLAG_RW | CTLFLAG_LOCKED, 115 &tcp_sack_globalmaxholes, 0, 116 "Global maximum number of TCP SACK holes"); 117 118static int tcp_sack_globalholes = 0; 119SYSCTL_INT(_net_inet_tcp, OID_AUTO, sack_globalholes, CTLFLAG_RD | CTLFLAG_LOCKED, 120 &tcp_sack_globalholes, 0, 121 "Global number of TCP SACK holes currently allocated"); 122 123extern struct zone *sack_hole_zone; 124 125/* 126 * This function is called upon receipt of new valid data (while not in header 127 * prediction mode), and it updates the ordered list of sacks. 128 */ 129void 130tcp_update_sack_list(struct tcpcb *tp, tcp_seq rcv_start, tcp_seq rcv_end) 131{ 132 /* 133 * First reported block MUST be the most recent one. Subsequent 134 * blocks SHOULD be in the order in which they arrived at the 135 * receiver. These two conditions make the implementation fully 136 * compliant with RFC 2018. 137 */ 138 struct sackblk head_blk, saved_blks[MAX_SACK_BLKS]; 139 int num_head, num_saved, i; 140 141 /* SACK block for the received segment. */ 142 head_blk.start = rcv_start; 143 head_blk.end = rcv_end; 144 145 /* 146 * Merge updated SACK blocks into head_blk, and 147 * save unchanged SACK blocks into saved_blks[]. 148 * num_saved will have the number of the saved SACK blocks. 149 */ 150 num_saved = 0; 151 for (i = 0; i < tp->rcv_numsacks; i++) { 152 tcp_seq start = tp->sackblks[i].start; 153 tcp_seq end = tp->sackblks[i].end; 154 if (SEQ_GEQ(start, end) || SEQ_LEQ(start, tp->rcv_nxt)) { 155 /* 156 * Discard this SACK block. 157 */ 158 } else if (SEQ_LEQ(head_blk.start, end) && 159 SEQ_GEQ(head_blk.end, start)) { 160 /* 161 * Merge this SACK block into head_blk. 162 * This SACK block itself will be discarded. 163 */ 164 if (SEQ_GT(head_blk.start, start)) 165 head_blk.start = start; 166 if (SEQ_LT(head_blk.end, end)) 167 head_blk.end = end; 168 } else { 169 /* 170 * Save this SACK block. 171 */ 172 saved_blks[num_saved].start = start; 173 saved_blks[num_saved].end = end; 174 num_saved++; 175 } 176 } 177 178 /* 179 * Update SACK list in tp->sackblks[]. 180 */ 181 num_head = 0; 182 if (SEQ_GT(head_blk.start, tp->rcv_nxt)) { 183 /* 184 * The received data segment is an out-of-order segment. 185 * Put head_blk at the top of SACK list. 186 */ 187 tp->sackblks[0] = head_blk; 188 num_head = 1; 189 /* 190 * If the number of saved SACK blocks exceeds its limit, 191 * discard the last SACK block. 192 */ 193 if (num_saved >= MAX_SACK_BLKS) 194 num_saved--; 195 } 196 if (num_saved > 0) { 197 /* 198 * Copy the saved SACK blocks back. 199 */ 200 bcopy(saved_blks, &tp->sackblks[num_head], 201 sizeof(struct sackblk) * num_saved); 202 } 203 204 /* Save the number of SACK blocks. */ 205 tp->rcv_numsacks = num_head + num_saved; 206 207 /* If we are requesting SACK recovery, reset the stretch-ack state 208 * so that connection will generate more acks after recovery and 209 * sender's cwnd will open. 210 */ 211 if ((tp->t_flags & TF_STRETCHACK) != 0 && tp->rcv_numsacks > 0) 212 tcp_reset_stretch_ack(tp); 213 214#if TRAFFIC_MGT 215 if (tp->acc_iaj > 0 && tp->rcv_numsacks > 0) 216 reset_acc_iaj(tp); 217#endif /* TRAFFIC_MGT */ 218} 219 220/* 221 * Delete all receiver-side SACK information. 222 */ 223void 224tcp_clean_sackreport( struct tcpcb *tp) 225{ 226 227 tp->rcv_numsacks = 0; 228 bzero(&tp->sackblks[0], sizeof (struct sackblk) * MAX_SACK_BLKS); 229} 230 231/* 232 * Allocate struct sackhole. 233 */ 234static struct sackhole * 235tcp_sackhole_alloc(struct tcpcb *tp, tcp_seq start, tcp_seq end) 236{ 237 struct sackhole *hole; 238 239 if (tp->snd_numholes >= tcp_sack_maxholes || 240 tcp_sack_globalholes >= tcp_sack_globalmaxholes) { 241 tcpstat.tcps_sack_sboverflow++; 242 return NULL; 243 } 244 245 hole = (struct sackhole *)zalloc_noblock(sack_hole_zone); 246 if (hole == NULL) 247 return NULL; 248 249 hole->start = start; 250 hole->end = end; 251 hole->rxmit = start; 252 253 tp->snd_numholes++; 254 tcp_sack_globalholes++; 255 256 return hole; 257} 258 259/* 260 * Free struct sackhole. 261 */ 262static void 263tcp_sackhole_free(struct tcpcb *tp, struct sackhole *hole) 264{ 265 zfree(sack_hole_zone, hole); 266 267 tp->snd_numholes--; 268 tcp_sack_globalholes--; 269} 270 271/* 272 * Insert new SACK hole into scoreboard. 273 */ 274static struct sackhole * 275tcp_sackhole_insert(struct tcpcb *tp, tcp_seq start, tcp_seq end, 276 struct sackhole *after) 277{ 278 struct sackhole *hole; 279 280 /* Allocate a new SACK hole. */ 281 hole = tcp_sackhole_alloc(tp, start, end); 282 if (hole == NULL) 283 return NULL; 284 285 /* Insert the new SACK hole into scoreboard */ 286 if (after != NULL) 287 TAILQ_INSERT_AFTER(&tp->snd_holes, after, hole, scblink); 288 else 289 TAILQ_INSERT_TAIL(&tp->snd_holes, hole, scblink); 290 291 /* Update SACK hint. */ 292 if (tp->sackhint.nexthole == NULL) 293 tp->sackhint.nexthole = hole; 294 295 return hole; 296} 297 298/* 299 * Remove SACK hole from scoreboard. 300 */ 301static void 302tcp_sackhole_remove(struct tcpcb *tp, struct sackhole *hole) 303{ 304 /* Update SACK hint. */ 305 if (tp->sackhint.nexthole == hole) 306 tp->sackhint.nexthole = TAILQ_NEXT(hole, scblink); 307 308 /* Remove this SACK hole. */ 309 TAILQ_REMOVE(&tp->snd_holes, hole, scblink); 310 311 /* Free this SACK hole. */ 312 tcp_sackhole_free(tp, hole); 313} 314 315/* 316 * Process cumulative ACK and the TCP SACK option to update the scoreboard. 317 * tp->snd_holes is an ordered list of holes (oldest to newest, in terms of 318 * the sequence space). 319 */ 320void 321tcp_sack_doack(struct tcpcb *tp, struct tcpopt *to, tcp_seq th_ack) 322{ 323 struct sackhole *cur, *temp; 324 struct sackblk sack, sack_blocks[TCP_MAX_SACK + 1], *sblkp; 325 int i, j, num_sack_blks; 326 327 num_sack_blks = 0; 328 /* 329 * If SND.UNA will be advanced by SEG.ACK, and if SACK holes exist, 330 * treat [SND.UNA, SEG.ACK) as if it is a SACK block. 331 */ 332 if (SEQ_LT(tp->snd_una, th_ack) && !TAILQ_EMPTY(&tp->snd_holes)) { 333 sack_blocks[num_sack_blks].start = tp->snd_una; 334 sack_blocks[num_sack_blks++].end = th_ack; 335 } 336 /* 337 * Append received valid SACK blocks to sack_blocks[]. 338 * Check that the SACK block range is valid. 339 */ 340 for (i = 0; i < to->to_nsacks; i++) { 341 bcopy((to->to_sacks + i * TCPOLEN_SACK), 342 &sack, sizeof(sack)); 343 sack.start = ntohl(sack.start); 344 sack.end = ntohl(sack.end); 345 if (SEQ_GT(sack.end, sack.start) && 346 SEQ_GT(sack.start, tp->snd_una) && 347 SEQ_GT(sack.start, th_ack) && 348 SEQ_LT(sack.start, tp->snd_max) && 349 SEQ_GT(sack.end, tp->snd_una) && 350 SEQ_LEQ(sack.end, tp->snd_max)) 351 sack_blocks[num_sack_blks++] = sack; 352 } 353 354 /* 355 * Return if SND.UNA is not advanced and no valid SACK block 356 * is received. 357 */ 358 if (num_sack_blks == 0) 359 return; 360 361 /* 362 * Sort the SACK blocks so we can update the scoreboard 363 * with just one pass. The overhead of sorting upto 4+1 elements 364 * is less than making upto 4+1 passes over the scoreboard. 365 */ 366 for (i = 0; i < num_sack_blks; i++) { 367 for (j = i + 1; j < num_sack_blks; j++) { 368 if (SEQ_GT(sack_blocks[i].end, sack_blocks[j].end)) { 369 sack = sack_blocks[i]; 370 sack_blocks[i] = sack_blocks[j]; 371 sack_blocks[j] = sack; 372 } 373 } 374 } 375 if (TAILQ_EMPTY(&tp->snd_holes)) 376 /* 377 * Empty scoreboard. Need to initialize snd_fack (it may be 378 * uninitialized or have a bogus value). Scoreboard holes 379 * (from the sack blocks received) are created later below (in 380 * the logic that adds holes to the tail of the scoreboard). 381 */ 382 tp->snd_fack = SEQ_MAX(tp->snd_una, th_ack); 383 /* 384 * In the while-loop below, incoming SACK blocks (sack_blocks[]) 385 * and SACK holes (snd_holes) are traversed from their tails with 386 * just one pass in order to reduce the number of compares especially 387 * when the bandwidth-delay product is large. 388 * Note: Typically, in the first RTT of SACK recovery, the highest 389 * three or four SACK blocks with the same ack number are received. 390 * In the second RTT, if retransmitted data segments are not lost, 391 * the highest three or four SACK blocks with ack number advancing 392 * are received. 393 */ 394 sblkp = &sack_blocks[num_sack_blks - 1]; /* Last SACK block */ 395 if (SEQ_LT(tp->snd_fack, sblkp->start)) { 396 /* 397 * The highest SACK block is beyond fack. 398 * Append new SACK hole at the tail. 399 * If the second or later highest SACK blocks are also 400 * beyond the current fack, they will be inserted by 401 * way of hole splitting in the while-loop below. 402 */ 403 temp = tcp_sackhole_insert(tp, tp->snd_fack,sblkp->start,NULL); 404 if (temp != NULL) { 405 tp->snd_fack = sblkp->end; 406 /* Go to the previous sack block. */ 407 sblkp--; 408 } else { 409 /* 410 * We failed to add a new hole based on the current 411 * sack block. Skip over all the sack blocks that 412 * fall completely to the right of snd_fack and proceed 413 * to trim the scoreboard based on the remaining sack 414 * blocks. This also trims the scoreboard for th_ack 415 * (which is sack_blocks[0]). 416 */ 417 while (sblkp >= sack_blocks && 418 SEQ_LT(tp->snd_fack, sblkp->start)) 419 sblkp--; 420 if (sblkp >= sack_blocks && 421 SEQ_LT(tp->snd_fack, sblkp->end)) 422 tp->snd_fack = sblkp->end; 423 } 424 } else if (SEQ_LT(tp->snd_fack, sblkp->end)) 425 /* fack is advanced. */ 426 tp->snd_fack = sblkp->end; 427 /* We must have at least one SACK hole in scoreboard */ 428 cur = TAILQ_LAST(&tp->snd_holes, sackhole_head); /* Last SACK hole */ 429 /* 430 * Since the incoming sack blocks are sorted, we can process them 431 * making one sweep of the scoreboard. 432 */ 433 while (sblkp >= sack_blocks && cur != NULL) { 434 if (SEQ_GEQ(sblkp->start, cur->end)) { 435 /* 436 * SACKs data beyond the current hole. 437 * Go to the previous sack block. 438 */ 439 sblkp--; 440 continue; 441 } 442 if (SEQ_LEQ(sblkp->end, cur->start)) { 443 /* 444 * SACKs data before the current hole. 445 * Go to the previous hole. 446 */ 447 cur = TAILQ_PREV(cur, sackhole_head, scblink); 448 continue; 449 } 450 tp->sackhint.sack_bytes_rexmit -= (cur->rxmit - cur->start); 451 if (SEQ_LEQ(sblkp->start, cur->start)) { 452 /* Data acks at least the beginning of hole */ 453 if (SEQ_GEQ(sblkp->end, cur->end)) { 454 /* Acks entire hole, so delete hole */ 455 temp = cur; 456 cur = TAILQ_PREV(cur, sackhole_head, scblink); 457 tcp_sackhole_remove(tp, temp); 458 /* 459 * The sack block may ack all or part of the next 460 * hole too, so continue onto the next hole. 461 */ 462 continue; 463 } else { 464 /* Move start of hole forward */ 465 cur->start = sblkp->end; 466 cur->rxmit = SEQ_MAX(cur->rxmit, cur->start); 467 } 468 } else { 469 /* Data acks at least the end of hole */ 470 if (SEQ_GEQ(sblkp->end, cur->end)) { 471 /* Move end of hole backward */ 472 cur->end = sblkp->start; 473 cur->rxmit = SEQ_MIN(cur->rxmit, cur->end); 474 } else { 475 /* 476 * ACKs some data in middle of a hole; need to 477 * split current hole 478 */ 479 temp = tcp_sackhole_insert(tp, sblkp->end, 480 cur->end, cur); 481 if (temp != NULL) { 482 if (SEQ_GT(cur->rxmit, temp->rxmit)) { 483 temp->rxmit = cur->rxmit; 484 tp->sackhint.sack_bytes_rexmit 485 += (temp->rxmit 486 - temp->start); 487 } 488 cur->end = sblkp->start; 489 cur->rxmit = SEQ_MIN(cur->rxmit, 490 cur->end); 491 } 492 } 493 } 494 tp->sackhint.sack_bytes_rexmit += (cur->rxmit - cur->start); 495 /* 496 * Testing sblkp->start against cur->start tells us whether 497 * we're done with the sack block or the sack hole. 498 * Accordingly, we advance one or the other. 499 */ 500 if (SEQ_LEQ(sblkp->start, cur->start)) 501 cur = TAILQ_PREV(cur, sackhole_head, scblink); 502 else 503 sblkp--; 504 } 505} 506 507/* 508 * Free all SACK holes to clear the scoreboard. 509 */ 510void 511tcp_free_sackholes(struct tcpcb *tp) 512{ 513 struct sackhole *q; 514 515 while ((q = TAILQ_FIRST(&tp->snd_holes)) != NULL) 516 tcp_sackhole_remove(tp, q); 517 tp->sackhint.sack_bytes_rexmit = 0; 518 tp->sackhint.nexthole = NULL; 519 tp->sack_newdata = 0; 520 521} 522 523/* 524 * Partial ack handling within a sack recovery episode. 525 * Keeping this very simple for now. When a partial ack 526 * is received, force snd_cwnd to a value that will allow 527 * the sender to transmit no more than 2 segments. 528 * If necessary, a better scheme can be adopted at a 529 * later point, but for now, the goal is to prevent the 530 * sender from bursting a large amount of data in the midst 531 * of sack recovery. 532 */ 533void 534tcp_sack_partialack(tp, th) 535 struct tcpcb *tp; 536 struct tcphdr *th; 537{ 538 int num_segs = 1; 539 540 tp->t_timer[TCPT_REXMT] = 0; 541 tp->t_rtttime = 0; 542 /* send one or 2 segments based on how much new data was acked */ 543 if (((th->th_ack - tp->snd_una) / tp->t_maxseg) > 2) 544 num_segs = 2; 545 tp->snd_cwnd = (tp->sackhint.sack_bytes_rexmit + 546 (tp->snd_nxt - tp->sack_newdata) + 547 num_segs * tp->t_maxseg); 548 if (tp->snd_cwnd > tp->snd_ssthresh) 549 tp->snd_cwnd = tp->snd_ssthresh; 550 tp->t_flags |= TF_ACKNOW; 551 (void) tcp_output(tp); 552} 553 554/* 555 * Debug version of tcp_sack_output() that walks the scoreboard. Used for 556 * now to sanity check the hint. 557 */ 558static struct sackhole * 559tcp_sack_output_debug(struct tcpcb *tp, int *sack_bytes_rexmt) 560{ 561 struct sackhole *p; 562 563 *sack_bytes_rexmt = 0; 564 TAILQ_FOREACH(p, &tp->snd_holes, scblink) { 565 if (SEQ_LT(p->rxmit, p->end)) { 566 if (SEQ_LT(p->rxmit, tp->snd_una)) {/* old SACK hole */ 567 continue; 568 } 569 *sack_bytes_rexmt += (p->rxmit - p->start); 570 break; 571 } 572 *sack_bytes_rexmt += (p->rxmit - p->start); 573 } 574 return (p); 575} 576 577/* 578 * Returns the next hole to retransmit and the number of retransmitted bytes 579 * from the scoreboard. We store both the next hole and the number of 580 * retransmitted bytes as hints (and recompute these on the fly upon SACK/ACK 581 * reception). This avoids scoreboard traversals completely. 582 * 583 * The loop here will traverse *at most* one link. Here's the argument. 584 * For the loop to traverse more than 1 link before finding the next hole to 585 * retransmit, we would need to have at least 1 node following the current hint 586 * with (rxmit == end). But, for all holes following the current hint, 587 * (start == rxmit), since we have not yet retransmitted from them. Therefore, 588 * in order to traverse more 1 link in the loop below, we need to have at least 589 * one node following the current hint with (start == rxmit == end). 590 * But that can't happen, (start == end) means that all the data in that hole 591 * has been sacked, in which case, the hole would have been removed from the 592 * scoreboard. 593 */ 594struct sackhole * 595tcp_sack_output(struct tcpcb *tp, int *sack_bytes_rexmt) 596{ 597 struct sackhole *hole = NULL, *dbg_hole = NULL; 598 int dbg_bytes_rexmt; 599 600 dbg_hole = tcp_sack_output_debug(tp, &dbg_bytes_rexmt); 601 *sack_bytes_rexmt = tp->sackhint.sack_bytes_rexmit; 602 hole = tp->sackhint.nexthole; 603 if (hole == NULL || SEQ_LT(hole->rxmit, hole->end)) 604 goto out; 605 while ((hole = TAILQ_NEXT(hole, scblink)) != NULL) { 606 if (SEQ_LT(hole->rxmit, hole->end)) { 607 tp->sackhint.nexthole = hole; 608 break; 609 } 610 } 611out: 612 if (dbg_hole != hole) { 613 printf("%s: Computed sack hole not the same as cached value\n", __func__); 614 hole = dbg_hole; 615 } 616 if (*sack_bytes_rexmt != dbg_bytes_rexmt) { 617 printf("%s: Computed sack_bytes_retransmitted (%d) not " 618 "the same as cached value (%d)\n", 619 __func__, dbg_bytes_rexmt, *sack_bytes_rexmt); 620 *sack_bytes_rexmt = dbg_bytes_rexmt; 621 } 622 return (hole); 623} 624 625/* 626 * After a timeout, the SACK list may be rebuilt. This SACK information 627 * should be used to avoid retransmitting SACKed data. This function 628 * traverses the SACK list to see if snd_nxt should be moved forward. 629 */ 630void 631tcp_sack_adjust(struct tcpcb *tp) 632{ 633 struct sackhole *p, *cur = TAILQ_FIRST(&tp->snd_holes); 634 635 if (cur == NULL) 636 return; /* No holes */ 637 if (SEQ_GEQ(tp->snd_nxt, tp->snd_fack)) 638 return; /* We're already beyond any SACKed blocks */ 639 /* 640 * Two cases for which we want to advance snd_nxt: 641 * i) snd_nxt lies between end of one hole and beginning of another 642 * ii) snd_nxt lies between end of last hole and snd_fack 643 */ 644 while ((p = TAILQ_NEXT(cur, scblink)) != NULL) { 645 if (SEQ_LT(tp->snd_nxt, cur->end)) 646 return; 647 if (SEQ_GEQ(tp->snd_nxt, p->start)) 648 cur = p; 649 else { 650 tp->snd_nxt = p->start; 651 return; 652 } 653 } 654 if (SEQ_LT(tp->snd_nxt, cur->end)) 655 return; 656 tp->snd_nxt = tp->snd_fack; 657 return; 658} 659