1/*- 2 * SPDX-License-Identifier: BSD-3-Clause 3 * 4 * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1994, 1995 5 * The Regents of the University of California. 6 * All rights reserved. 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 University nor the names of its contributors 17 * may be used to endorse or promote products derived from this software 18 * without specific prior written permission. 19 * 20 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 21 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 22 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 23 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 24 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 25 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30 * SUCH DAMAGE. 31 * 32 * @(#)tcp_sack.c 8.12 (Berkeley) 5/24/95 33 */ 34 35/*- 36 * @@(#)COPYRIGHT 1.1 (NRL) 17 January 1995 37 * 38 * NRL grants permission for redistribution and use in source and binary 39 * forms, with or without modification, of the software and documentation 40 * created at NRL provided that the following conditions are met: 41 * 42 * 1. Redistributions of source code must retain the above copyright 43 * notice, this list of conditions and the following disclaimer. 44 * 2. Redistributions in binary form must reproduce the above copyright 45 * notice, this list of conditions and the following disclaimer in the 46 * documentation and/or other materials provided with the distribution. 47 * 3. All advertising materials mentioning features or use of this software 48 * must display the following acknowledgements: 49 * This product includes software developed by the University of 50 * California, Berkeley and its contributors. 51 * This product includes software developed at the Information 52 * Technology Division, US Naval Research Laboratory. 53 * 4. Neither the name of the NRL nor the names of its contributors 54 * may be used to endorse or promote products derived from this software 55 * without specific prior written permission. 56 * 57 * THE SOFTWARE PROVIDED BY NRL IS PROVIDED BY NRL AND CONTRIBUTORS ``AS 58 * IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 59 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A 60 * PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL NRL OR 61 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, 62 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, 63 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR 64 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF 65 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING 66 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS 67 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 68 * 69 * The views and conclusions contained in the software and documentation 70 * are those of the authors and should not be interpreted as representing 71 * official policies, either expressed or implied, of the US Naval 72 * Research Laboratory (NRL). 73 */ 74 75#include <sys/cdefs.h> 76__FBSDID("$FreeBSD$"); 77 78#include "opt_inet.h" 79#include "opt_inet6.h" 80#include "opt_tcpdebug.h" 81 82#include <sys/param.h> 83#include <sys/systm.h> 84#include <sys/kernel.h> 85#include <sys/sysctl.h> 86#include <sys/malloc.h> 87#include <sys/mbuf.h> 88#include <sys/proc.h> /* for proc0 declaration */ 89#include <sys/protosw.h> 90#include <sys/socket.h> 91#include <sys/socketvar.h> 92#include <sys/syslog.h> 93#include <sys/systm.h> 94 95#include <machine/cpu.h> /* before tcp_seq.h, for tcp_random18() */ 96 97#include <vm/uma.h> 98 99#include <net/if.h> 100#include <net/if_var.h> 101#include <net/route.h> 102#include <net/vnet.h> 103 104#include <netinet/in.h> 105#include <netinet/in_systm.h> 106#include <netinet/ip.h> 107#include <netinet/in_var.h> 108#include <netinet/in_pcb.h> 109#include <netinet/ip_var.h> 110#include <netinet/ip6.h> 111#include <netinet/icmp6.h> 112#include <netinet6/nd6.h> 113#include <netinet6/ip6_var.h> 114#include <netinet6/in6_pcb.h> 115#include <netinet/tcp.h> 116#include <netinet/tcp_fsm.h> 117#include <netinet/tcp_seq.h> 118#include <netinet/tcp_timer.h> 119#include <netinet/tcp_var.h> 120#include <netinet6/tcp6_var.h> 121#include <netinet/tcpip.h> 122#ifdef TCPDEBUG 123#include <netinet/tcp_debug.h> 124#endif /* TCPDEBUG */ 125 126#include <machine/in_cksum.h> 127 128VNET_DECLARE(struct uma_zone *, sack_hole_zone); 129#define V_sack_hole_zone VNET(sack_hole_zone) 130 131SYSCTL_NODE(_net_inet_tcp, OID_AUTO, sack, CTLFLAG_RW | CTLFLAG_MPSAFE, 0, 132 "TCP SACK"); 133VNET_DEFINE(int, tcp_do_sack) = 1; 134#define V_tcp_do_sack VNET(tcp_do_sack) 135SYSCTL_INT(_net_inet_tcp_sack, OID_AUTO, enable, CTLFLAG_VNET | CTLFLAG_RW, 136 &VNET_NAME(tcp_do_sack), 0, "Enable/Disable TCP SACK support"); 137 138VNET_DEFINE(int, tcp_sack_maxholes) = 128; 139SYSCTL_INT(_net_inet_tcp_sack, OID_AUTO, maxholes, CTLFLAG_VNET | CTLFLAG_RW, 140 &VNET_NAME(tcp_sack_maxholes), 0, 141 "Maximum number of TCP SACK holes allowed per connection"); 142 143VNET_DEFINE(int, tcp_sack_globalmaxholes) = 65536; 144SYSCTL_INT(_net_inet_tcp_sack, OID_AUTO, globalmaxholes, CTLFLAG_VNET | CTLFLAG_RW, 145 &VNET_NAME(tcp_sack_globalmaxholes), 0, 146 "Global maximum number of TCP SACK holes"); 147 148VNET_DEFINE(int, tcp_sack_globalholes) = 0; 149SYSCTL_INT(_net_inet_tcp_sack, OID_AUTO, globalholes, CTLFLAG_VNET | CTLFLAG_RD, 150 &VNET_NAME(tcp_sack_globalholes), 0, 151 "Global number of TCP SACK holes currently allocated"); 152 153int 154tcp_dsack_block_exists(struct tcpcb *tp) 155{ 156 /* Return true if a DSACK block exists */ 157 if (tp->rcv_numsacks == 0) 158 return (0); 159 if (SEQ_LEQ(tp->sackblks[0].end, tp->rcv_nxt)) 160 return(1); 161 return (0); 162} 163 164/* 165 * This function will find overlaps with the currently stored sackblocks 166 * and add any overlap as a dsack block upfront 167 */ 168void 169tcp_update_dsack_list(struct tcpcb *tp, tcp_seq rcv_start, tcp_seq rcv_end) 170{ 171 struct sackblk head_blk,mid_blk,saved_blks[MAX_SACK_BLKS]; 172 int i, j, n, identical; 173 tcp_seq start, end; 174 175 INP_WLOCK_ASSERT(tp->t_inpcb); 176 177 KASSERT(SEQ_LT(rcv_start, rcv_end), ("rcv_start < rcv_end")); 178 179 if (SEQ_LT(rcv_end, tp->rcv_nxt) || 180 ((rcv_end == tp->rcv_nxt) && 181 (tp->rcv_numsacks > 0 ) && 182 (tp->sackblks[0].end == tp->rcv_nxt))) { 183 saved_blks[0].start = rcv_start; 184 saved_blks[0].end = rcv_end; 185 } else { 186 saved_blks[0].start = saved_blks[0].end = 0; 187 } 188 189 head_blk.start = head_blk.end = 0; 190 mid_blk.start = rcv_start; 191 mid_blk.end = rcv_end; 192 identical = 0; 193 194 for (i = 0; i < tp->rcv_numsacks; i++) { 195 start = tp->sackblks[i].start; 196 end = tp->sackblks[i].end; 197 if (SEQ_LT(rcv_end, start)) { 198 /* pkt left to sack blk */ 199 continue; 200 } 201 if (SEQ_GT(rcv_start, end)) { 202 /* pkt right to sack blk */ 203 continue; 204 } 205 if (SEQ_GT(tp->rcv_nxt, end)) { 206 if ((SEQ_MAX(rcv_start, start) != SEQ_MIN(rcv_end, end)) && 207 (SEQ_GT(head_blk.start, SEQ_MAX(rcv_start, start)) || 208 (head_blk.start == head_blk.end))) { 209 head_blk.start = SEQ_MAX(rcv_start, start); 210 head_blk.end = SEQ_MIN(rcv_end, end); 211 } 212 continue; 213 } 214 if (((head_blk.start == head_blk.end) || 215 SEQ_LT(start, head_blk.start)) && 216 (SEQ_GT(end, rcv_start) && 217 SEQ_LEQ(start, rcv_end))) { 218 head_blk.start = start; 219 head_blk.end = end; 220 } 221 mid_blk.start = SEQ_MIN(mid_blk.start, start); 222 mid_blk.end = SEQ_MAX(mid_blk.end, end); 223 if ((mid_blk.start == start) && 224 (mid_blk.end == end)) 225 identical = 1; 226 } 227 if (SEQ_LT(head_blk.start, head_blk.end)) { 228 /* store overlapping range */ 229 saved_blks[0].start = SEQ_MAX(rcv_start, head_blk.start); 230 saved_blks[0].end = SEQ_MIN(rcv_end, head_blk.end); 231 } 232 n = 1; 233 /* 234 * Second, if not ACKed, store the SACK block that 235 * overlaps with the DSACK block unless it is identical 236 */ 237 if ((SEQ_LT(tp->rcv_nxt, mid_blk.end) && 238 !((mid_blk.start == saved_blks[0].start) && 239 (mid_blk.end == saved_blks[0].end))) || 240 identical == 1) { 241 saved_blks[n].start = mid_blk.start; 242 saved_blks[n++].end = mid_blk.end; 243 } 244 for (j = 0; (j < tp->rcv_numsacks) && (n < MAX_SACK_BLKS); j++) { 245 if (((SEQ_LT(tp->sackblks[j].end, mid_blk.start) || 246 SEQ_GT(tp->sackblks[j].start, mid_blk.end)) && 247 (SEQ_GT(tp->sackblks[j].start, tp->rcv_nxt)))) 248 saved_blks[n++] = tp->sackblks[j]; 249 } 250 j = 0; 251 for (i = 0; i < n; i++) { 252 /* we can end up with a stale initial entry */ 253 if (SEQ_LT(saved_blks[i].start, saved_blks[i].end)) { 254 tp->sackblks[j++] = saved_blks[i]; 255 } 256 } 257 tp->rcv_numsacks = j; 258} 259 260/* 261 * This function is called upon receipt of new valid data (while not in 262 * header prediction mode), and it updates the ordered list of sacks. 263 */ 264void 265tcp_update_sack_list(struct tcpcb *tp, tcp_seq rcv_start, tcp_seq rcv_end) 266{ 267 /* 268 * First reported block MUST be the most recent one. Subsequent 269 * blocks SHOULD be in the order in which they arrived at the 270 * receiver. These two conditions make the implementation fully 271 * compliant with RFC 2018. 272 */ 273 struct sackblk head_blk, saved_blks[MAX_SACK_BLKS]; 274 int num_head, num_saved, i; 275 276 INP_WLOCK_ASSERT(tp->t_inpcb); 277 278 /* Check arguments. */ 279 KASSERT(SEQ_LEQ(rcv_start, rcv_end), ("rcv_start <= rcv_end")); 280 281 if ((rcv_start == rcv_end) && 282 (tp->rcv_numsacks >= 1) && 283 (rcv_end == tp->sackblks[0].end)) { 284 /* retaining DSACK block below rcv_nxt (todrop) */ 285 head_blk = tp->sackblks[0]; 286 } else { 287 /* SACK block for the received segment. */ 288 head_blk.start = rcv_start; 289 head_blk.end = rcv_end; 290 } 291 292 /* 293 * Merge updated SACK blocks into head_blk, and save unchanged SACK 294 * blocks into saved_blks[]. num_saved will have the number of the 295 * saved SACK blocks. 296 */ 297 num_saved = 0; 298 for (i = 0; i < tp->rcv_numsacks; i++) { 299 tcp_seq start = tp->sackblks[i].start; 300 tcp_seq end = tp->sackblks[i].end; 301 if (SEQ_GEQ(start, end) || SEQ_LEQ(start, tp->rcv_nxt)) { 302 /* 303 * Discard this SACK block. 304 */ 305 } else if (SEQ_LEQ(head_blk.start, end) && 306 SEQ_GEQ(head_blk.end, start)) { 307 /* 308 * Merge this SACK block into head_blk. This SACK 309 * block itself will be discarded. 310 */ 311 /* 312 * |-| 313 * |---| merge 314 * 315 * |-| 316 * |---| merge 317 * 318 * |-----| 319 * |-| DSACK smaller 320 * 321 * |-| 322 * |-----| DSACK smaller 323 */ 324 if (head_blk.start == end) 325 head_blk.start = start; 326 else if (head_blk.end == start) 327 head_blk.end = end; 328 else { 329 if (SEQ_LT(head_blk.start, start)) { 330 tcp_seq temp = start; 331 start = head_blk.start; 332 head_blk.start = temp; 333 } 334 if (SEQ_GT(head_blk.end, end)) { 335 tcp_seq temp = end; 336 end = head_blk.end; 337 head_blk.end = temp; 338 } 339 if ((head_blk.start != start) || 340 (head_blk.end != end)) { 341 if ((num_saved >= 1) && 342 SEQ_GEQ(saved_blks[num_saved-1].start, start) && 343 SEQ_LEQ(saved_blks[num_saved-1].end, end)) 344 num_saved--; 345 saved_blks[num_saved].start = start; 346 saved_blks[num_saved].end = end; 347 num_saved++; 348 } 349 } 350 } else { 351 /* 352 * This block supercedes the prior block 353 */ 354 if ((num_saved >= 1) && 355 SEQ_GEQ(saved_blks[num_saved-1].start, start) && 356 SEQ_LEQ(saved_blks[num_saved-1].end, end)) 357 num_saved--; 358 /* 359 * Save this SACK block. 360 */ 361 saved_blks[num_saved].start = start; 362 saved_blks[num_saved].end = end; 363 num_saved++; 364 } 365 } 366 367 /* 368 * Update SACK list in tp->sackblks[]. 369 */ 370 num_head = 0; 371 if (SEQ_LT(rcv_start, rcv_end)) { 372 /* 373 * The received data segment is an out-of-order segment. Put 374 * head_blk at the top of SACK list. 375 */ 376 tp->sackblks[0] = head_blk; 377 num_head = 1; 378 /* 379 * If the number of saved SACK blocks exceeds its limit, 380 * discard the last SACK block. 381 */ 382 if (num_saved >= MAX_SACK_BLKS) 383 num_saved--; 384 } 385 if ((rcv_start == rcv_end) && 386 (rcv_start == tp->sackblks[0].end)) { 387 num_head = 1; 388 } 389 if (num_saved > 0) { 390 /* 391 * Copy the saved SACK blocks back. 392 */ 393 bcopy(saved_blks, &tp->sackblks[num_head], 394 sizeof(struct sackblk) * num_saved); 395 } 396 397 /* Save the number of SACK blocks. */ 398 tp->rcv_numsacks = num_head + num_saved; 399} 400 401void 402tcp_clean_dsack_blocks(struct tcpcb *tp) 403{ 404 struct sackblk saved_blks[MAX_SACK_BLKS]; 405 int num_saved, i; 406 407 INP_WLOCK_ASSERT(tp->t_inpcb); 408 /* 409 * Clean up any DSACK blocks that 410 * are in our queue of sack blocks. 411 * 412 */ 413 num_saved = 0; 414 for (i = 0; i < tp->rcv_numsacks; i++) { 415 tcp_seq start = tp->sackblks[i].start; 416 tcp_seq end = tp->sackblks[i].end; 417 if (SEQ_GEQ(start, end) || SEQ_LEQ(start, tp->rcv_nxt)) { 418 /* 419 * Discard this D-SACK block. 420 */ 421 continue; 422 } 423 /* 424 * Save this SACK block. 425 */ 426 saved_blks[num_saved].start = start; 427 saved_blks[num_saved].end = end; 428 num_saved++; 429 } 430 if (num_saved > 0) { 431 /* 432 * Copy the saved SACK blocks back. 433 */ 434 bcopy(saved_blks, &tp->sackblks[0], 435 sizeof(struct sackblk) * num_saved); 436 } 437 tp->rcv_numsacks = num_saved; 438} 439 440/* 441 * Delete all receiver-side SACK information. 442 */ 443void 444tcp_clean_sackreport(struct tcpcb *tp) 445{ 446 int i; 447 448 INP_WLOCK_ASSERT(tp->t_inpcb); 449 tp->rcv_numsacks = 0; 450 for (i = 0; i < MAX_SACK_BLKS; i++) 451 tp->sackblks[i].start = tp->sackblks[i].end=0; 452} 453 454/* 455 * Allocate struct sackhole. 456 */ 457static struct sackhole * 458tcp_sackhole_alloc(struct tcpcb *tp, tcp_seq start, tcp_seq end) 459{ 460 struct sackhole *hole; 461 462 if (tp->snd_numholes >= V_tcp_sack_maxholes || 463 V_tcp_sack_globalholes >= V_tcp_sack_globalmaxholes) { 464 TCPSTAT_INC(tcps_sack_sboverflow); 465 return NULL; 466 } 467 468 hole = (struct sackhole *)uma_zalloc(V_sack_hole_zone, M_NOWAIT); 469 if (hole == NULL) 470 return NULL; 471 472 hole->start = start; 473 hole->end = end; 474 hole->rxmit = start; 475 476 tp->snd_numholes++; 477 atomic_add_int(&V_tcp_sack_globalholes, 1); 478 479 return hole; 480} 481 482/* 483 * Free struct sackhole. 484 */ 485static void 486tcp_sackhole_free(struct tcpcb *tp, struct sackhole *hole) 487{ 488 489 uma_zfree(V_sack_hole_zone, hole); 490 491 tp->snd_numholes--; 492 atomic_subtract_int(&V_tcp_sack_globalholes, 1); 493 494 KASSERT(tp->snd_numholes >= 0, ("tp->snd_numholes >= 0")); 495 KASSERT(V_tcp_sack_globalholes >= 0, ("tcp_sack_globalholes >= 0")); 496} 497 498/* 499 * Insert new SACK hole into scoreboard. 500 */ 501static struct sackhole * 502tcp_sackhole_insert(struct tcpcb *tp, tcp_seq start, tcp_seq end, 503 struct sackhole *after) 504{ 505 struct sackhole *hole; 506 507 /* Allocate a new SACK hole. */ 508 hole = tcp_sackhole_alloc(tp, start, end); 509 if (hole == NULL) 510 return NULL; 511 512 /* Insert the new SACK hole into scoreboard. */ 513 if (after != NULL) 514 TAILQ_INSERT_AFTER(&tp->snd_holes, after, hole, scblink); 515 else 516 TAILQ_INSERT_TAIL(&tp->snd_holes, hole, scblink); 517 518 /* Update SACK hint. */ 519 if (tp->sackhint.nexthole == NULL) 520 tp->sackhint.nexthole = hole; 521 522 return hole; 523} 524 525/* 526 * Remove SACK hole from scoreboard. 527 */ 528static void 529tcp_sackhole_remove(struct tcpcb *tp, struct sackhole *hole) 530{ 531 532 /* Update SACK hint. */ 533 if (tp->sackhint.nexthole == hole) 534 tp->sackhint.nexthole = TAILQ_NEXT(hole, scblink); 535 536 /* Remove this SACK hole. */ 537 TAILQ_REMOVE(&tp->snd_holes, hole, scblink); 538 539 /* Free this SACK hole. */ 540 tcp_sackhole_free(tp, hole); 541} 542 543/* 544 * Process cumulative ACK and the TCP SACK option to update the scoreboard. 545 * tp->snd_holes is an ordered list of holes (oldest to newest, in terms of 546 * the sequence space). 547 * Returns 1 if incoming ACK has previously unknown SACK information, 548 * 0 otherwise. 549 */ 550int 551tcp_sack_doack(struct tcpcb *tp, struct tcpopt *to, tcp_seq th_ack) 552{ 553 struct sackhole *cur, *temp; 554 struct sackblk sack, sack_blocks[TCP_MAX_SACK + 1], *sblkp; 555 int i, j, num_sack_blks, sack_changed; 556 int delivered_data, left_edge_delta; 557 558 INP_WLOCK_ASSERT(tp->t_inpcb); 559 560 num_sack_blks = 0; 561 sack_changed = 0; 562 delivered_data = 0; 563 left_edge_delta = 0; 564 /* 565 * If SND.UNA will be advanced by SEG.ACK, and if SACK holes exist, 566 * treat [SND.UNA, SEG.ACK) as if it is a SACK block. 567 * Account changes to SND.UNA always in delivered data. 568 */ 569 if (SEQ_LT(tp->snd_una, th_ack) && !TAILQ_EMPTY(&tp->snd_holes)) { 570 left_edge_delta = th_ack - tp->snd_una; 571 sack_blocks[num_sack_blks].start = tp->snd_una; 572 sack_blocks[num_sack_blks++].end = th_ack; 573 /* 574 * Pulling snd_fack forward if we got here 575 * due to DSACK blocks 576 */ 577 if (SEQ_LT(tp->snd_fack, th_ack)) { 578 delivered_data += th_ack - tp->snd_una; 579 tp->snd_fack = th_ack; 580 sack_changed = 1; 581 } 582 } 583 /* 584 * Append received valid SACK blocks to sack_blocks[], but only if we 585 * received new blocks from the other side. 586 */ 587 if (to->to_flags & TOF_SACK) { 588 for (i = 0; i < to->to_nsacks; i++) { 589 bcopy((to->to_sacks + i * TCPOLEN_SACK), 590 &sack, sizeof(sack)); 591 sack.start = ntohl(sack.start); 592 sack.end = ntohl(sack.end); 593 if (SEQ_GT(sack.end, sack.start) && 594 SEQ_GT(sack.start, tp->snd_una) && 595 SEQ_GT(sack.start, th_ack) && 596 SEQ_LT(sack.start, tp->snd_max) && 597 SEQ_GT(sack.end, tp->snd_una) && 598 SEQ_LEQ(sack.end, tp->snd_max)) { 599 sack_blocks[num_sack_blks++] = sack; 600 } 601 } 602 } 603 /* 604 * Return if SND.UNA is not advanced and no valid SACK block is 605 * received. 606 */ 607 if (num_sack_blks == 0) 608 return (sack_changed); 609 610 /* 611 * Sort the SACK blocks so we can update the scoreboard with just one 612 * pass. The overhead of sorting up to 4+1 elements is less than 613 * making up to 4+1 passes over the scoreboard. 614 */ 615 for (i = 0; i < num_sack_blks; i++) { 616 for (j = i + 1; j < num_sack_blks; j++) { 617 if (SEQ_GT(sack_blocks[i].end, sack_blocks[j].end)) { 618 sack = sack_blocks[i]; 619 sack_blocks[i] = sack_blocks[j]; 620 sack_blocks[j] = sack; 621 } 622 } 623 } 624 if (TAILQ_EMPTY(&tp->snd_holes)) { 625 /* 626 * Empty scoreboard. Need to initialize snd_fack (it may be 627 * uninitialized or have a bogus value). Scoreboard holes 628 * (from the sack blocks received) are created later below 629 * (in the logic that adds holes to the tail of the 630 * scoreboard). 631 */ 632 tp->snd_fack = SEQ_MAX(tp->snd_una, th_ack); 633 tp->sackhint.sacked_bytes = 0; /* reset */ 634 } 635 /* 636 * In the while-loop below, incoming SACK blocks (sack_blocks[]) and 637 * SACK holes (snd_holes) are traversed from their tails with just 638 * one pass in order to reduce the number of compares especially when 639 * the bandwidth-delay product is large. 640 * 641 * Note: Typically, in the first RTT of SACK recovery, the highest 642 * three or four SACK blocks with the same ack number are received. 643 * In the second RTT, if retransmitted data segments are not lost, 644 * the highest three or four SACK blocks with ack number advancing 645 * are received. 646 */ 647 sblkp = &sack_blocks[num_sack_blks - 1]; /* Last SACK block */ 648 tp->sackhint.last_sack_ack = sblkp->end; 649 if (SEQ_LT(tp->snd_fack, sblkp->start)) { 650 /* 651 * The highest SACK block is beyond fack. First, 652 * check if there was a successful Rescue Retransmission, 653 * and move this hole left. With normal holes, snd_fack 654 * is always to the right of the end. 655 */ 656 if (((temp = TAILQ_LAST(&tp->snd_holes, sackhole_head)) != NULL) && 657 SEQ_LEQ(tp->snd_fack,temp->end)) { 658 temp->start = SEQ_MAX(tp->snd_fack, SEQ_MAX(tp->snd_una, th_ack)); 659 temp->end = sblkp->start; 660 temp->rxmit = temp->start; 661 delivered_data += sblkp->end - sblkp->start; 662 tp->snd_fack = sblkp->end; 663 sblkp--; 664 sack_changed = 1; 665 } else { 666 /* 667 * Append a new SACK hole at the tail. If the 668 * second or later highest SACK blocks are also 669 * beyond the current fack, they will be inserted 670 * by way of hole splitting in the while-loop below. 671 */ 672 temp = tcp_sackhole_insert(tp, tp->snd_fack,sblkp->start,NULL); 673 if (temp != NULL) { 674 delivered_data += sblkp->end - sblkp->start; 675 tp->snd_fack = sblkp->end; 676 /* Go to the previous sack block. */ 677 sblkp--; 678 sack_changed = 1; 679 } else { 680 /* 681 * We failed to add a new hole based on the current 682 * sack block. Skip over all the sack blocks that 683 * fall completely to the right of snd_fack and 684 * proceed to trim the scoreboard based on the 685 * remaining sack blocks. This also trims the 686 * scoreboard for th_ack (which is sack_blocks[0]). 687 */ 688 while (sblkp >= sack_blocks && 689 SEQ_LT(tp->snd_fack, sblkp->start)) 690 sblkp--; 691 if (sblkp >= sack_blocks && 692 SEQ_LT(tp->snd_fack, sblkp->end)) { 693 delivered_data += sblkp->end - tp->snd_fack; 694 tp->snd_fack = sblkp->end; 695 sack_changed = 1; 696 } 697 } 698 } 699 } else if (SEQ_LT(tp->snd_fack, sblkp->end)) { 700 /* fack is advanced. */ 701 delivered_data += sblkp->end - tp->snd_fack; 702 tp->snd_fack = sblkp->end; 703 sack_changed = 1; 704 } 705 cur = TAILQ_LAST(&tp->snd_holes, sackhole_head); /* Last SACK hole. */ 706 /* 707 * Since the incoming sack blocks are sorted, we can process them 708 * making one sweep of the scoreboard. 709 */ 710 while (sblkp >= sack_blocks && cur != NULL) { 711 if (SEQ_GEQ(sblkp->start, cur->end)) { 712 /* 713 * SACKs data beyond the current hole. Go to the 714 * previous sack block. 715 */ 716 sblkp--; 717 continue; 718 } 719 if (SEQ_LEQ(sblkp->end, cur->start)) { 720 /* 721 * SACKs data before the current hole. Go to the 722 * previous hole. 723 */ 724 cur = TAILQ_PREV(cur, sackhole_head, scblink); 725 continue; 726 } 727 tp->sackhint.sack_bytes_rexmit -= (cur->rxmit - cur->start); 728 KASSERT(tp->sackhint.sack_bytes_rexmit >= 0, 729 ("sackhint bytes rtx >= 0")); 730 sack_changed = 1; 731 if (SEQ_LEQ(sblkp->start, cur->start)) { 732 /* Data acks at least the beginning of hole. */ 733 if (SEQ_GEQ(sblkp->end, cur->end)) { 734 /* Acks entire hole, so delete hole. */ 735 delivered_data += (cur->end - cur->start); 736 temp = cur; 737 cur = TAILQ_PREV(cur, sackhole_head, scblink); 738 tcp_sackhole_remove(tp, temp); 739 /* 740 * The sack block may ack all or part of the 741 * next hole too, so continue onto the next 742 * hole. 743 */ 744 continue; 745 } else { 746 /* Move start of hole forward. */ 747 delivered_data += (sblkp->end - cur->start); 748 cur->start = sblkp->end; 749 cur->rxmit = SEQ_MAX(cur->rxmit, cur->start); 750 } 751 } else { 752 /* Data acks at least the end of hole. */ 753 if (SEQ_GEQ(sblkp->end, cur->end)) { 754 /* Move end of hole backward. */ 755 delivered_data += (cur->end - sblkp->start); 756 cur->end = sblkp->start; 757 cur->rxmit = SEQ_MIN(cur->rxmit, cur->end); 758 } else { 759 /* 760 * ACKs some data in middle of a hole; need 761 * to split current hole 762 */ 763 temp = tcp_sackhole_insert(tp, sblkp->end, 764 cur->end, cur); 765 if (temp != NULL) { 766 if (SEQ_GT(cur->rxmit, temp->rxmit)) { 767 temp->rxmit = cur->rxmit; 768 tp->sackhint.sack_bytes_rexmit 769 += (temp->rxmit 770 - temp->start); 771 } 772 cur->end = sblkp->start; 773 cur->rxmit = SEQ_MIN(cur->rxmit, 774 cur->end); 775 delivered_data += (sblkp->end - sblkp->start); 776 } 777 } 778 } 779 tp->sackhint.sack_bytes_rexmit += (cur->rxmit - cur->start); 780 /* 781 * Testing sblkp->start against cur->start tells us whether 782 * we're done with the sack block or the sack hole. 783 * Accordingly, we advance one or the other. 784 */ 785 if (SEQ_LEQ(sblkp->start, cur->start)) 786 cur = TAILQ_PREV(cur, sackhole_head, scblink); 787 else 788 sblkp--; 789 } 790 if (!(to->to_flags & TOF_SACK)) 791 /* 792 * If this ACK did not contain any 793 * SACK blocks, any only moved the 794 * left edge right, it is a pure 795 * cumulative ACK. Do not count 796 * DupAck for this. Also required 797 * for RFC6675 rescue retransmission. 798 */ 799 sack_changed = 0; 800 tp->sackhint.delivered_data = delivered_data; 801 tp->sackhint.sacked_bytes += delivered_data - left_edge_delta; 802 KASSERT((delivered_data >= 0), ("delivered_data < 0")); 803 KASSERT((tp->sackhint.sacked_bytes >= 0), ("sacked_bytes < 0")); 804 return (sack_changed); 805} 806 807/* 808 * Free all SACK holes to clear the scoreboard. 809 */ 810void 811tcp_free_sackholes(struct tcpcb *tp) 812{ 813 struct sackhole *q; 814 815 INP_WLOCK_ASSERT(tp->t_inpcb); 816 while ((q = TAILQ_FIRST(&tp->snd_holes)) != NULL) 817 tcp_sackhole_remove(tp, q); 818 tp->sackhint.sack_bytes_rexmit = 0; 819 820 KASSERT(tp->snd_numholes == 0, ("tp->snd_numholes == 0")); 821 KASSERT(tp->sackhint.nexthole == NULL, 822 ("tp->sackhint.nexthole == NULL")); 823} 824 825/* 826 * Partial ack handling within a sack recovery episode. Keeping this very 827 * simple for now. When a partial ack is received, force snd_cwnd to a value 828 * that will allow the sender to transmit no more than 2 segments. If 829 * necessary, a better scheme can be adopted at a later point, but for now, 830 * the goal is to prevent the sender from bursting a large amount of data in 831 * the midst of sack recovery. 832 */ 833void 834tcp_sack_partialack(struct tcpcb *tp, struct tcphdr *th) 835{ 836 int num_segs = 1; 837 u_int maxseg = tcp_maxseg(tp); 838 839 INP_WLOCK_ASSERT(tp->t_inpcb); 840 tcp_timer_activate(tp, TT_REXMT, 0); 841 tp->t_rtttime = 0; 842 /* Send one or 2 segments based on how much new data was acked. */ 843 if ((BYTES_THIS_ACK(tp, th) / maxseg) >= 2) 844 num_segs = 2; 845 tp->snd_cwnd = (tp->sackhint.sack_bytes_rexmit + 846 (tp->snd_nxt - tp->snd_recover) + num_segs * maxseg); 847 if (tp->snd_cwnd > tp->snd_ssthresh) 848 tp->snd_cwnd = tp->snd_ssthresh; 849 tp->t_flags |= TF_ACKNOW; 850 /* 851 * RFC6675 rescue retransmission 852 * Add a hole between th_ack (snd_una is not yet set) and snd_max, 853 * if this was a pure cumulative ACK and no data was send beyond 854 * recovery point. Since the data in the socket has not been freed 855 * at this point, we check if the scoreboard is empty, and the ACK 856 * delivered some new data, indicating a full ACK. Also, if the 857 * recovery point is still at snd_max, we are probably application 858 * limited. However, this inference might not always be true. The 859 * rescue retransmission may rarely be slightly premature 860 * compared to RFC6675. 861 * The corresponding ACK+SACK will cause any further outstanding 862 * segments to be retransmitted. This addresses a corner case, when 863 * the trailing packets of a window are lost and no further data 864 * is available for sending. 865 */ 866 if ((V_tcp_do_rfc6675_pipe) && 867 SEQ_LT(th->th_ack, tp->snd_recover) && 868 (tp->snd_recover == tp->snd_max) && 869 TAILQ_EMPTY(&tp->snd_holes) && 870 (tp->sackhint.delivered_data > 0)) { 871 /* 872 * Exclude FIN sequence space in 873 * the hole for the rescue retransmission, 874 * and also don't create a hole, if only 875 * the ACK for a FIN is outstanding. 876 */ 877 tcp_seq highdata = tp->snd_max; 878 if (tp->t_flags & TF_SENTFIN) 879 highdata--; 880 if (th->th_ack != highdata) { 881 tp->snd_fack = th->th_ack; 882 (void)tcp_sackhole_insert(tp, SEQ_MAX(th->th_ack, 883 highdata - maxseg), highdata, NULL); 884 } 885 } 886 (void) tp->t_fb->tfb_tcp_output(tp); 887} 888 889#if 0 890/* 891 * Debug version of tcp_sack_output() that walks the scoreboard. Used for 892 * now to sanity check the hint. 893 */ 894static struct sackhole * 895tcp_sack_output_debug(struct tcpcb *tp, int *sack_bytes_rexmt) 896{ 897 struct sackhole *p; 898 899 INP_WLOCK_ASSERT(tp->t_inpcb); 900 *sack_bytes_rexmt = 0; 901 TAILQ_FOREACH(p, &tp->snd_holes, scblink) { 902 if (SEQ_LT(p->rxmit, p->end)) { 903 if (SEQ_LT(p->rxmit, tp->snd_una)) {/* old SACK hole */ 904 continue; 905 } 906 *sack_bytes_rexmt += (p->rxmit - p->start); 907 break; 908 } 909 *sack_bytes_rexmt += (p->rxmit - p->start); 910 } 911 return (p); 912} 913#endif 914 915/* 916 * Returns the next hole to retransmit and the number of retransmitted bytes 917 * from the scoreboard. We store both the next hole and the number of 918 * retransmitted bytes as hints (and recompute these on the fly upon SACK/ACK 919 * reception). This avoids scoreboard traversals completely. 920 * 921 * The loop here will traverse *at most* one link. Here's the argument. For 922 * the loop to traverse more than 1 link before finding the next hole to 923 * retransmit, we would need to have at least 1 node following the current 924 * hint with (rxmit == end). But, for all holes following the current hint, 925 * (start == rxmit), since we have not yet retransmitted from them. 926 * Therefore, in order to traverse more 1 link in the loop below, we need to 927 * have at least one node following the current hint with (start == rxmit == 928 * end). But that can't happen, (start == end) means that all the data in 929 * that hole has been sacked, in which case, the hole would have been removed 930 * from the scoreboard. 931 */ 932struct sackhole * 933tcp_sack_output(struct tcpcb *tp, int *sack_bytes_rexmt) 934{ 935 struct sackhole *hole = NULL; 936 937 INP_WLOCK_ASSERT(tp->t_inpcb); 938 *sack_bytes_rexmt = tp->sackhint.sack_bytes_rexmit; 939 hole = tp->sackhint.nexthole; 940 if (hole == NULL || SEQ_LT(hole->rxmit, hole->end)) 941 goto out; 942 while ((hole = TAILQ_NEXT(hole, scblink)) != NULL) { 943 if (SEQ_LT(hole->rxmit, hole->end)) { 944 tp->sackhint.nexthole = hole; 945 break; 946 } 947 } 948out: 949 return (hole); 950} 951 952/* 953 * After a timeout, the SACK list may be rebuilt. This SACK information 954 * should be used to avoid retransmitting SACKed data. This function 955 * traverses the SACK list to see if snd_nxt should be moved forward. 956 */ 957void 958tcp_sack_adjust(struct tcpcb *tp) 959{ 960 struct sackhole *p, *cur = TAILQ_FIRST(&tp->snd_holes); 961 962 INP_WLOCK_ASSERT(tp->t_inpcb); 963 if (cur == NULL) 964 return; /* No holes */ 965 if (SEQ_GEQ(tp->snd_nxt, tp->snd_fack)) 966 return; /* We're already beyond any SACKed blocks */ 967 /*- 968 * Two cases for which we want to advance snd_nxt: 969 * i) snd_nxt lies between end of one hole and beginning of another 970 * ii) snd_nxt lies between end of last hole and snd_fack 971 */ 972 while ((p = TAILQ_NEXT(cur, scblink)) != NULL) { 973 if (SEQ_LT(tp->snd_nxt, cur->end)) 974 return; 975 if (SEQ_GEQ(tp->snd_nxt, p->start)) 976 cur = p; 977 else { 978 tp->snd_nxt = p->start; 979 return; 980 } 981 } 982 if (SEQ_LT(tp->snd_nxt, cur->end)) 983 return; 984 tp->snd_nxt = tp->snd_fack; 985} 986