tcp_sack.c revision 293710
1/*- 2 * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1994, 1995 3 * The Regents of the University of California. 4 * All rights reserved. 5 * 6 * Redistribution and use in source and binary forms, with or without 7 * modification, are permitted provided that the following conditions 8 * are met: 9 * 1. Redistributions of source code must retain the above copyright 10 * notice, this list of conditions and the following disclaimer. 11 * 2. Redistributions in binary form must reproduce the above copyright 12 * notice, this list of conditions and the following disclaimer in the 13 * documentation and/or other materials provided with the distribution. 14 * 4. Neither the name of the University nor the names of its contributors 15 * may be used to endorse or promote products derived from this software 16 * without specific prior written permission. 17 * 18 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 19 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 20 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 21 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 22 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 23 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 24 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 25 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 26 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 27 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 28 * SUCH DAMAGE. 29 * 30 * @(#)tcp_sack.c 8.12 (Berkeley) 5/24/95 31 */ 32 33/*- 34 * @@(#)COPYRIGHT 1.1 (NRL) 17 January 1995 35 * 36 * NRL grants permission for redistribution and use in source and binary 37 * forms, with or without modification, of the software and documentation 38 * created at NRL provided that the following conditions are met: 39 * 40 * 1. Redistributions of source code must retain the above copyright 41 * notice, this list of conditions and the following disclaimer. 42 * 2. Redistributions in binary form must reproduce the above copyright 43 * notice, this list of conditions and the following disclaimer in the 44 * documentation and/or other materials provided with the distribution. 45 * 3. All advertising materials mentioning features or use of this software 46 * must display the following acknowledgements: 47 * This product includes software developed by the University of 48 * California, Berkeley and its contributors. 49 * This product includes software developed at the Information 50 * Technology Division, US Naval Research Laboratory. 51 * 4. Neither the name of the NRL nor the names of its contributors 52 * may be used to endorse or promote products derived from this software 53 * without specific prior written permission. 54 * 55 * THE SOFTWARE PROVIDED BY NRL IS PROVIDED BY NRL AND CONTRIBUTORS ``AS 56 * IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 57 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A 58 * PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL NRL OR 59 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, 60 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, 61 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR 62 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF 63 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING 64 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS 65 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 66 * 67 * The views and conclusions contained in the software and documentation 68 * are those of the authors and should not be interpreted as representing 69 * official policies, either expressed or implied, of the US Naval 70 * Research Laboratory (NRL). 71 */ 72 73#include <sys/cdefs.h> 74__FBSDID("$FreeBSD: stable/10/sys/netinet/tcp_sack.c 293710 2016-01-11 23:34:29Z hiren $"); 75 76#include "opt_inet.h" 77#include "opt_inet6.h" 78#include "opt_tcpdebug.h" 79 80#include <sys/param.h> 81#include <sys/systm.h> 82#include <sys/kernel.h> 83#include <sys/sysctl.h> 84#include <sys/malloc.h> 85#include <sys/mbuf.h> 86#include <sys/proc.h> /* for proc0 declaration */ 87#include <sys/protosw.h> 88#include <sys/socket.h> 89#include <sys/socketvar.h> 90#include <sys/syslog.h> 91#include <sys/systm.h> 92 93#include <machine/cpu.h> /* before tcp_seq.h, for tcp_random18() */ 94 95#include <vm/uma.h> 96 97#include <net/if.h> 98#include <net/route.h> 99#include <net/vnet.h> 100 101#include <netinet/in.h> 102#include <netinet/in_systm.h> 103#include <netinet/ip.h> 104#include <netinet/in_var.h> 105#include <netinet/in_pcb.h> 106#include <netinet/ip_var.h> 107#include <netinet/ip6.h> 108#include <netinet/icmp6.h> 109#include <netinet6/nd6.h> 110#include <netinet6/ip6_var.h> 111#include <netinet6/in6_pcb.h> 112#include <netinet/tcp.h> 113#include <netinet/tcp_fsm.h> 114#include <netinet/tcp_seq.h> 115#include <netinet/tcp_timer.h> 116#include <netinet/tcp_var.h> 117#include <netinet6/tcp6_var.h> 118#include <netinet/tcpip.h> 119#ifdef TCPDEBUG 120#include <netinet/tcp_debug.h> 121#endif /* TCPDEBUG */ 122 123#include <machine/in_cksum.h> 124 125VNET_DECLARE(struct uma_zone *, sack_hole_zone); 126#define V_sack_hole_zone VNET(sack_hole_zone) 127 128SYSCTL_NODE(_net_inet_tcp, OID_AUTO, sack, CTLFLAG_RW, 0, "TCP SACK"); 129VNET_DEFINE(int, tcp_do_sack) = 1; 130#define V_tcp_do_sack VNET(tcp_do_sack) 131SYSCTL_VNET_INT(_net_inet_tcp_sack, OID_AUTO, enable, CTLFLAG_RW, 132 &VNET_NAME(tcp_do_sack), 0, "Enable/Disable TCP SACK support"); 133 134VNET_DEFINE(int, tcp_sack_maxholes) = 128; 135#define V_tcp_sack_maxholes VNET(tcp_sack_maxholes) 136SYSCTL_VNET_INT(_net_inet_tcp_sack, OID_AUTO, maxholes, CTLFLAG_RW, 137 &VNET_NAME(tcp_sack_maxholes), 0, 138 "Maximum number of TCP SACK holes allowed per connection"); 139 140VNET_DEFINE(int, tcp_sack_globalmaxholes) = 65536; 141#define V_tcp_sack_globalmaxholes VNET(tcp_sack_globalmaxholes) 142SYSCTL_VNET_INT(_net_inet_tcp_sack, OID_AUTO, globalmaxholes, CTLFLAG_RW, 143 &VNET_NAME(tcp_sack_globalmaxholes), 0, 144 "Global maximum number of TCP SACK holes"); 145 146VNET_DEFINE(int, tcp_sack_globalholes) = 0; 147#define V_tcp_sack_globalholes VNET(tcp_sack_globalholes) 148SYSCTL_VNET_INT(_net_inet_tcp_sack, OID_AUTO, globalholes, CTLFLAG_RD, 149 &VNET_NAME(tcp_sack_globalholes), 0, 150 "Global number of TCP SACK holes currently allocated"); 151 152/* 153 * This function is called upon receipt of new valid data (while not in 154 * header prediction mode), and it updates the ordered list of sacks. 155 */ 156void 157tcp_update_sack_list(struct tcpcb *tp, tcp_seq rcv_start, tcp_seq rcv_end) 158{ 159 /* 160 * First reported block MUST be the most recent one. Subsequent 161 * blocks SHOULD be in the order in which they arrived at the 162 * receiver. These two conditions make the implementation fully 163 * compliant with RFC 2018. 164 */ 165 struct sackblk head_blk, saved_blks[MAX_SACK_BLKS]; 166 int num_head, num_saved, i; 167 168 INP_WLOCK_ASSERT(tp->t_inpcb); 169 170 /* Check arguments. */ 171 KASSERT(SEQ_LT(rcv_start, rcv_end), ("rcv_start < rcv_end")); 172 173 /* SACK block for the received segment. */ 174 head_blk.start = rcv_start; 175 head_blk.end = rcv_end; 176 177 /* 178 * Merge updated SACK blocks into head_blk, and save unchanged SACK 179 * blocks into saved_blks[]. num_saved will have the number of the 180 * saved SACK blocks. 181 */ 182 num_saved = 0; 183 for (i = 0; i < tp->rcv_numsacks; i++) { 184 tcp_seq start = tp->sackblks[i].start; 185 tcp_seq end = tp->sackblks[i].end; 186 if (SEQ_GEQ(start, end) || SEQ_LEQ(start, tp->rcv_nxt)) { 187 /* 188 * Discard this SACK block. 189 */ 190 } else if (SEQ_LEQ(head_blk.start, end) && 191 SEQ_GEQ(head_blk.end, start)) { 192 /* 193 * Merge this SACK block into head_blk. This SACK 194 * block itself will be discarded. 195 */ 196 if (SEQ_GT(head_blk.start, start)) 197 head_blk.start = start; 198 if (SEQ_LT(head_blk.end, end)) 199 head_blk.end = end; 200 } else { 201 /* 202 * Save this SACK block. 203 */ 204 saved_blks[num_saved].start = start; 205 saved_blks[num_saved].end = end; 206 num_saved++; 207 } 208 } 209 210 /* 211 * Update SACK list in tp->sackblks[]. 212 */ 213 num_head = 0; 214 if (SEQ_GT(head_blk.start, tp->rcv_nxt)) { 215 /* 216 * The received data segment is an out-of-order segment. Put 217 * head_blk at the top of SACK list. 218 */ 219 tp->sackblks[0] = head_blk; 220 num_head = 1; 221 /* 222 * If the number of saved SACK blocks exceeds its limit, 223 * discard the last SACK block. 224 */ 225 if (num_saved >= MAX_SACK_BLKS) 226 num_saved--; 227 } 228 if (num_saved > 0) { 229 /* 230 * Copy the saved SACK blocks back. 231 */ 232 bcopy(saved_blks, &tp->sackblks[num_head], 233 sizeof(struct sackblk) * num_saved); 234 } 235 236 /* Save the number of SACK blocks. */ 237 tp->rcv_numsacks = num_head + num_saved; 238} 239 240/* 241 * Delete all receiver-side SACK information. 242 */ 243void 244tcp_clean_sackreport(struct tcpcb *tp) 245{ 246 int i; 247 248 INP_WLOCK_ASSERT(tp->t_inpcb); 249 tp->rcv_numsacks = 0; 250 for (i = 0; i < MAX_SACK_BLKS; i++) 251 tp->sackblks[i].start = tp->sackblks[i].end=0; 252} 253 254/* 255 * Allocate struct sackhole. 256 */ 257static struct sackhole * 258tcp_sackhole_alloc(struct tcpcb *tp, tcp_seq start, tcp_seq end) 259{ 260 struct sackhole *hole; 261 262 if (tp->snd_numholes >= V_tcp_sack_maxholes || 263 V_tcp_sack_globalholes >= V_tcp_sack_globalmaxholes) { 264 TCPSTAT_INC(tcps_sack_sboverflow); 265 return NULL; 266 } 267 268 hole = (struct sackhole *)uma_zalloc(V_sack_hole_zone, M_NOWAIT); 269 if (hole == NULL) 270 return NULL; 271 272 hole->start = start; 273 hole->end = end; 274 hole->rxmit = start; 275 276 tp->snd_numholes++; 277 atomic_add_int(&V_tcp_sack_globalholes, 1); 278 279 return hole; 280} 281 282/* 283 * Free struct sackhole. 284 */ 285static void 286tcp_sackhole_free(struct tcpcb *tp, struct sackhole *hole) 287{ 288 289 uma_zfree(V_sack_hole_zone, hole); 290 291 tp->snd_numholes--; 292 atomic_subtract_int(&V_tcp_sack_globalholes, 1); 293 294 KASSERT(tp->snd_numholes >= 0, ("tp->snd_numholes >= 0")); 295 KASSERT(V_tcp_sack_globalholes >= 0, ("tcp_sack_globalholes >= 0")); 296} 297 298/* 299 * Insert new SACK hole into scoreboard. 300 */ 301static struct sackhole * 302tcp_sackhole_insert(struct tcpcb *tp, tcp_seq start, tcp_seq end, 303 struct sackhole *after) 304{ 305 struct sackhole *hole; 306 307 /* Allocate a new SACK hole. */ 308 hole = tcp_sackhole_alloc(tp, start, end); 309 if (hole == NULL) 310 return NULL; 311 312 /* Insert the new SACK hole into scoreboard. */ 313 if (after != NULL) 314 TAILQ_INSERT_AFTER(&tp->snd_holes, after, hole, scblink); 315 else 316 TAILQ_INSERT_TAIL(&tp->snd_holes, hole, scblink); 317 318 /* Update SACK hint. */ 319 if (tp->sackhint.nexthole == NULL) 320 tp->sackhint.nexthole = hole; 321 322 return hole; 323} 324 325/* 326 * Remove SACK hole from scoreboard. 327 */ 328static void 329tcp_sackhole_remove(struct tcpcb *tp, struct sackhole *hole) 330{ 331 332 /* Update SACK hint. */ 333 if (tp->sackhint.nexthole == hole) 334 tp->sackhint.nexthole = TAILQ_NEXT(hole, scblink); 335 336 /* Remove this SACK hole. */ 337 TAILQ_REMOVE(&tp->snd_holes, hole, scblink); 338 339 /* Free this SACK hole. */ 340 tcp_sackhole_free(tp, hole); 341} 342 343/* 344 * Process cumulative ACK and the TCP SACK option to update the scoreboard. 345 * tp->snd_holes is an ordered list of holes (oldest to newest, in terms of 346 * the sequence space). 347 * Returns 1 if incoming ACK has previously unknown SACK information, 348 * 0 otherwise. Note: We treat (snd_una, th_ack) as a sack block so any changes 349 * to that (i.e. left edge moving) would also be considered a change in SACK 350 * information which is slightly different than rfc6675. 351 */ 352int 353tcp_sack_doack(struct tcpcb *tp, struct tcpopt *to, tcp_seq th_ack) 354{ 355 struct sackhole *cur, *temp; 356 struct sackblk sack, sack_blocks[TCP_MAX_SACK + 1], *sblkp; 357 int i, j, num_sack_blks, sack_changed; 358 359 INP_WLOCK_ASSERT(tp->t_inpcb); 360 361 num_sack_blks = 0; 362 sack_changed = 0; 363 /* 364 * If SND.UNA will be advanced by SEG.ACK, and if SACK holes exist, 365 * treat [SND.UNA, SEG.ACK) as if it is a SACK block. 366 */ 367 if (SEQ_LT(tp->snd_una, th_ack) && !TAILQ_EMPTY(&tp->snd_holes)) { 368 sack_blocks[num_sack_blks].start = tp->snd_una; 369 sack_blocks[num_sack_blks++].end = th_ack; 370 } 371 /* 372 * Append received valid SACK blocks to sack_blocks[], but only if we 373 * received new blocks from the other side. 374 */ 375 if (to->to_flags & TOF_SACK) { 376 tp->sackhint.sacked_bytes = 0; /* reset */ 377 for (i = 0; i < to->to_nsacks; i++) { 378 bcopy((to->to_sacks + i * TCPOLEN_SACK), 379 &sack, sizeof(sack)); 380 sack.start = ntohl(sack.start); 381 sack.end = ntohl(sack.end); 382 if (SEQ_GT(sack.end, sack.start) && 383 SEQ_GT(sack.start, tp->snd_una) && 384 SEQ_GT(sack.start, th_ack) && 385 SEQ_LT(sack.start, tp->snd_max) && 386 SEQ_GT(sack.end, tp->snd_una) && 387 SEQ_LEQ(sack.end, tp->snd_max)) { 388 sack_blocks[num_sack_blks++] = sack; 389 tp->sackhint.sacked_bytes += 390 (sack.end-sack.start); 391 } 392 } 393 } 394 /* 395 * Return if SND.UNA is not advanced and no valid SACK block is 396 * received. 397 */ 398 if (num_sack_blks == 0) 399 return (sack_changed); 400 401 /* 402 * Sort the SACK blocks so we can update the scoreboard with just one 403 * pass. The overhead of sorting upto 4+1 elements is less than 404 * making upto 4+1 passes over the scoreboard. 405 */ 406 for (i = 0; i < num_sack_blks; i++) { 407 for (j = i + 1; j < num_sack_blks; j++) { 408 if (SEQ_GT(sack_blocks[i].end, sack_blocks[j].end)) { 409 sack = sack_blocks[i]; 410 sack_blocks[i] = sack_blocks[j]; 411 sack_blocks[j] = sack; 412 } 413 } 414 } 415 if (TAILQ_EMPTY(&tp->snd_holes)) 416 /* 417 * Empty scoreboard. Need to initialize snd_fack (it may be 418 * uninitialized or have a bogus value). Scoreboard holes 419 * (from the sack blocks received) are created later below 420 * (in the logic that adds holes to the tail of the 421 * scoreboard). 422 */ 423 tp->snd_fack = SEQ_MAX(tp->snd_una, th_ack); 424 /* 425 * In the while-loop below, incoming SACK blocks (sack_blocks[]) and 426 * SACK holes (snd_holes) are traversed from their tails with just 427 * one pass in order to reduce the number of compares especially when 428 * the bandwidth-delay product is large. 429 * 430 * Note: Typically, in the first RTT of SACK recovery, the highest 431 * three or four SACK blocks with the same ack number are received. 432 * In the second RTT, if retransmitted data segments are not lost, 433 * the highest three or four SACK blocks with ack number advancing 434 * are received. 435 */ 436 sblkp = &sack_blocks[num_sack_blks - 1]; /* Last SACK block */ 437 tp->sackhint.last_sack_ack = sblkp->end; 438 if (SEQ_LT(tp->snd_fack, sblkp->start)) { 439 /* 440 * The highest SACK block is beyond fack. Append new SACK 441 * hole at the tail. If the second or later highest SACK 442 * blocks are also beyond the current fack, they will be 443 * inserted by way of hole splitting in the while-loop below. 444 */ 445 temp = tcp_sackhole_insert(tp, tp->snd_fack,sblkp->start,NULL); 446 if (temp != NULL) { 447 tp->snd_fack = sblkp->end; 448 /* Go to the previous sack block. */ 449 sblkp--; 450 sack_changed = 1; 451 } else { 452 /* 453 * We failed to add a new hole based on the current 454 * sack block. Skip over all the sack blocks that 455 * fall completely to the right of snd_fack and 456 * proceed to trim the scoreboard based on the 457 * remaining sack blocks. This also trims the 458 * scoreboard for th_ack (which is sack_blocks[0]). 459 */ 460 while (sblkp >= sack_blocks && 461 SEQ_LT(tp->snd_fack, sblkp->start)) 462 sblkp--; 463 if (sblkp >= sack_blocks && 464 SEQ_LT(tp->snd_fack, sblkp->end)) 465 tp->snd_fack = sblkp->end; 466 } 467 } else if (SEQ_LT(tp->snd_fack, sblkp->end)) { 468 /* fack is advanced. */ 469 tp->snd_fack = sblkp->end; 470 sack_changed = 1; 471 } 472 /* We must have at least one SACK hole in scoreboard. */ 473 KASSERT(!TAILQ_EMPTY(&tp->snd_holes), 474 ("SACK scoreboard must not be empty")); 475 cur = TAILQ_LAST(&tp->snd_holes, sackhole_head); /* Last SACK hole. */ 476 /* 477 * Since the incoming sack blocks are sorted, we can process them 478 * making one sweep of the scoreboard. 479 */ 480 while (sblkp >= sack_blocks && cur != NULL) { 481 if (SEQ_GEQ(sblkp->start, cur->end)) { 482 /* 483 * SACKs data beyond the current hole. Go to the 484 * previous sack block. 485 */ 486 sblkp--; 487 continue; 488 } 489 if (SEQ_LEQ(sblkp->end, cur->start)) { 490 /* 491 * SACKs data before the current hole. Go to the 492 * previous hole. 493 */ 494 cur = TAILQ_PREV(cur, sackhole_head, scblink); 495 continue; 496 } 497 tp->sackhint.sack_bytes_rexmit -= (cur->rxmit - cur->start); 498 KASSERT(tp->sackhint.sack_bytes_rexmit >= 0, 499 ("sackhint bytes rtx >= 0")); 500 sack_changed = 1; 501 if (SEQ_LEQ(sblkp->start, cur->start)) { 502 /* Data acks at least the beginning of hole. */ 503 if (SEQ_GEQ(sblkp->end, cur->end)) { 504 /* Acks entire hole, so delete hole. */ 505 temp = cur; 506 cur = TAILQ_PREV(cur, sackhole_head, scblink); 507 tcp_sackhole_remove(tp, temp); 508 /* 509 * The sack block may ack all or part of the 510 * next hole too, so continue onto the next 511 * hole. 512 */ 513 continue; 514 } else { 515 /* Move start of hole forward. */ 516 cur->start = sblkp->end; 517 cur->rxmit = SEQ_MAX(cur->rxmit, cur->start); 518 } 519 } else { 520 /* Data acks at least the end of hole. */ 521 if (SEQ_GEQ(sblkp->end, cur->end)) { 522 /* Move end of hole backward. */ 523 cur->end = sblkp->start; 524 cur->rxmit = SEQ_MIN(cur->rxmit, cur->end); 525 } else { 526 /* 527 * ACKs some data in middle of a hole; need 528 * to split current hole 529 */ 530 temp = tcp_sackhole_insert(tp, sblkp->end, 531 cur->end, cur); 532 if (temp != NULL) { 533 if (SEQ_GT(cur->rxmit, temp->rxmit)) { 534 temp->rxmit = cur->rxmit; 535 tp->sackhint.sack_bytes_rexmit 536 += (temp->rxmit 537 - temp->start); 538 } 539 cur->end = sblkp->start; 540 cur->rxmit = SEQ_MIN(cur->rxmit, 541 cur->end); 542 } 543 } 544 } 545 tp->sackhint.sack_bytes_rexmit += (cur->rxmit - cur->start); 546 /* 547 * Testing sblkp->start against cur->start tells us whether 548 * we're done with the sack block or the sack hole. 549 * Accordingly, we advance one or the other. 550 */ 551 if (SEQ_LEQ(sblkp->start, cur->start)) 552 cur = TAILQ_PREV(cur, sackhole_head, scblink); 553 else 554 sblkp--; 555 } 556 return (sack_changed); 557} 558 559/* 560 * Free all SACK holes to clear the scoreboard. 561 */ 562void 563tcp_free_sackholes(struct tcpcb *tp) 564{ 565 struct sackhole *q; 566 567 INP_WLOCK_ASSERT(tp->t_inpcb); 568 while ((q = TAILQ_FIRST(&tp->snd_holes)) != NULL) 569 tcp_sackhole_remove(tp, q); 570 tp->sackhint.sack_bytes_rexmit = 0; 571 572 KASSERT(tp->snd_numholes == 0, ("tp->snd_numholes == 0")); 573 KASSERT(tp->sackhint.nexthole == NULL, 574 ("tp->sackhint.nexthole == NULL")); 575} 576 577/* 578 * Partial ack handling within a sack recovery episode. Keeping this very 579 * simple for now. When a partial ack is received, force snd_cwnd to a value 580 * that will allow the sender to transmit no more than 2 segments. If 581 * necessary, a better scheme can be adopted at a later point, but for now, 582 * the goal is to prevent the sender from bursting a large amount of data in 583 * the midst of sack recovery. 584 */ 585void 586tcp_sack_partialack(struct tcpcb *tp, struct tcphdr *th) 587{ 588 int num_segs = 1; 589 590 INP_WLOCK_ASSERT(tp->t_inpcb); 591 tcp_timer_activate(tp, TT_REXMT, 0); 592 tp->t_rtttime = 0; 593 /* Send one or 2 segments based on how much new data was acked. */ 594 if ((BYTES_THIS_ACK(tp, th) / tp->t_maxseg) >= 2) 595 num_segs = 2; 596 tp->snd_cwnd = (tp->sackhint.sack_bytes_rexmit + 597 (tp->snd_nxt - tp->sack_newdata) + num_segs * tp->t_maxseg); 598 if (tp->snd_cwnd > tp->snd_ssthresh) 599 tp->snd_cwnd = tp->snd_ssthresh; 600 tp->t_flags |= TF_ACKNOW; 601 (void) tcp_output(tp); 602} 603 604#if 0 605/* 606 * Debug version of tcp_sack_output() that walks the scoreboard. Used for 607 * now to sanity check the hint. 608 */ 609static struct sackhole * 610tcp_sack_output_debug(struct tcpcb *tp, int *sack_bytes_rexmt) 611{ 612 struct sackhole *p; 613 614 INP_WLOCK_ASSERT(tp->t_inpcb); 615 *sack_bytes_rexmt = 0; 616 TAILQ_FOREACH(p, &tp->snd_holes, scblink) { 617 if (SEQ_LT(p->rxmit, p->end)) { 618 if (SEQ_LT(p->rxmit, tp->snd_una)) {/* old SACK hole */ 619 continue; 620 } 621 *sack_bytes_rexmt += (p->rxmit - p->start); 622 break; 623 } 624 *sack_bytes_rexmt += (p->rxmit - p->start); 625 } 626 return (p); 627} 628#endif 629 630/* 631 * Returns the next hole to retransmit and the number of retransmitted bytes 632 * from the scoreboard. We store both the next hole and the number of 633 * retransmitted bytes as hints (and recompute these on the fly upon SACK/ACK 634 * reception). This avoids scoreboard traversals completely. 635 * 636 * The loop here will traverse *at most* one link. Here's the argument. For 637 * the loop to traverse more than 1 link before finding the next hole to 638 * retransmit, we would need to have at least 1 node following the current 639 * hint with (rxmit == end). But, for all holes following the current hint, 640 * (start == rxmit), since we have not yet retransmitted from them. 641 * Therefore, in order to traverse more 1 link in the loop below, we need to 642 * have at least one node following the current hint with (start == rxmit == 643 * end). But that can't happen, (start == end) means that all the data in 644 * that hole has been sacked, in which case, the hole would have been removed 645 * from the scoreboard. 646 */ 647struct sackhole * 648tcp_sack_output(struct tcpcb *tp, int *sack_bytes_rexmt) 649{ 650 struct sackhole *hole = NULL; 651 652 INP_WLOCK_ASSERT(tp->t_inpcb); 653 *sack_bytes_rexmt = tp->sackhint.sack_bytes_rexmit; 654 hole = tp->sackhint.nexthole; 655 if (hole == NULL || SEQ_LT(hole->rxmit, hole->end)) 656 goto out; 657 while ((hole = TAILQ_NEXT(hole, scblink)) != NULL) { 658 if (SEQ_LT(hole->rxmit, hole->end)) { 659 tp->sackhint.nexthole = hole; 660 break; 661 } 662 } 663out: 664 return (hole); 665} 666 667/* 668 * After a timeout, the SACK list may be rebuilt. This SACK information 669 * should be used to avoid retransmitting SACKed data. This function 670 * traverses the SACK list to see if snd_nxt should be moved forward. 671 */ 672void 673tcp_sack_adjust(struct tcpcb *tp) 674{ 675 struct sackhole *p, *cur = TAILQ_FIRST(&tp->snd_holes); 676 677 INP_WLOCK_ASSERT(tp->t_inpcb); 678 if (cur == NULL) 679 return; /* No holes */ 680 if (SEQ_GEQ(tp->snd_nxt, tp->snd_fack)) 681 return; /* We're already beyond any SACKed blocks */ 682 /*- 683 * Two cases for which we want to advance snd_nxt: 684 * i) snd_nxt lies between end of one hole and beginning of another 685 * ii) snd_nxt lies between end of last hole and snd_fack 686 */ 687 while ((p = TAILQ_NEXT(cur, scblink)) != NULL) { 688 if (SEQ_LT(tp->snd_nxt, cur->end)) 689 return; 690 if (SEQ_GEQ(tp->snd_nxt, p->start)) 691 cur = p; 692 else { 693 tp->snd_nxt = p->start; 694 return; 695 } 696 } 697 if (SEQ_LT(tp->snd_nxt, cur->end)) 698 return; 699 tp->snd_nxt = tp->snd_fack; 700} 701