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 33 /*- 34 * 35 * NRL grants permission for redistribution and use in source and binary 36 * forms, with or without modification, of the software and documentation 37 * created at NRL provided that the following conditions are met: 38 * 39 * 1. Redistributions of source code must retain the above copyright 40 * notice, this list of conditions and the following disclaimer. 41 * 2. Redistributions in binary form must reproduce the above copyright 42 * notice, this list of conditions and the following disclaimer in the 43 * documentation and/or other materials provided with the distribution. 44 * 3. All advertising materials mentioning features or use of this software 45 * must display the following acknowledgements: 46 * This product includes software developed by the University of 47 * California, Berkeley and its contributors. 48 * This product includes software developed at the Information 49 * Technology Division, US Naval Research Laboratory. 50 * 4. Neither the name of the NRL nor the names of its contributors 51 * may be used to endorse or promote products derived from this software 52 * without specific prior written permission. 53 * 54 * THE SOFTWARE PROVIDED BY NRL IS PROVIDED BY NRL AND CONTRIBUTORS ``AS 55 * IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 56 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A 57 * PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL NRL OR 58 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, 59 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, 60 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR 61 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF 62 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING 63 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS 64 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 65 * 66 * The views and conclusions contained in the software and documentation 67 * are those of the authors and should not be interpreted as representing 68 * official policies, either expressed or implied, of the US Naval 69 * Research Laboratory (NRL). 70 */ 71 72 #include <sys/cdefs.h> 73 #include "opt_inet.h" 74 #include "opt_inet6.h" 75 76 #include <sys/param.h> 77 #include <sys/systm.h> 78 #include <sys/kernel.h> 79 #include <sys/sysctl.h> 80 #include <sys/malloc.h> 81 #include <sys/mbuf.h> 82 #include <sys/proc.h> /* for proc0 declaration */ 83 #include <sys/protosw.h> 84 #include <sys/socket.h> 85 #include <sys/socketvar.h> 86 #include <sys/syslog.h> 87 #include <sys/systm.h> 88 89 #include <machine/cpu.h> /* before tcp_seq.h, for tcp_random18() */ 90 91 #include <vm/uma.h> 92 93 #include <net/if.h> 94 #include <net/if_var.h> 95 #include <net/route.h> 96 #include <net/vnet.h> 97 98 #include <netinet/in.h> 99 #include <netinet/in_systm.h> 100 #include <netinet/ip.h> 101 #include <netinet/in_var.h> 102 #include <netinet/in_pcb.h> 103 #include <netinet/ip_var.h> 104 #include <netinet/ip6.h> 105 #include <netinet/icmp6.h> 106 #include <netinet6/nd6.h> 107 #include <netinet6/ip6_var.h> 108 #include <netinet6/in6_pcb.h> 109 #include <netinet/tcp.h> 110 #include <netinet/tcp_fsm.h> 111 #include <netinet/tcp_seq.h> 112 #include <netinet/tcp_timer.h> 113 #include <netinet/tcp_var.h> 114 #include <netinet/tcpip.h> 115 #include <netinet/cc/cc.h> 116 117 #include <machine/in_cksum.h> 118 119 VNET_DECLARE(struct uma_zone *, sack_hole_zone); 120 #define V_sack_hole_zone VNET(sack_hole_zone) 121 122 SYSCTL_NODE(_net_inet_tcp, OID_AUTO, sack, CTLFLAG_RW | CTLFLAG_MPSAFE, 0, 123 "TCP SACK"); 124 125 VNET_DEFINE(int, tcp_do_sack) = 1; 126 SYSCTL_INT(_net_inet_tcp_sack, OID_AUTO, enable, CTLFLAG_VNET | CTLFLAG_RW, 127 &VNET_NAME(tcp_do_sack), 0, 128 "Enable/Disable TCP SACK support"); 129 130 VNET_DEFINE(int, tcp_do_newsack) = 1; 131 132 static int 133 sysctl_net_inet_tcp_sack_revised(SYSCTL_HANDLER_ARGS) 134 { 135 int error; 136 int new; 137 138 new = V_tcp_do_newsack; 139 error = sysctl_handle_int(oidp, &new, 0, req); 140 if (error == 0 && req->newptr) { 141 V_tcp_do_newsack = new; 142 gone_in(16, "net.inet.tcp.sack.revised will be deprecated." 143 " net.inet.tcp.sack.enable will always follow RFC6675 SACK.\n"); 144 } 145 return (error); 146 } 147 148 SYSCTL_PROC(_net_inet_tcp_sack, OID_AUTO, revised, CTLFLAG_VNET | CTLFLAG_RW | CTLTYPE_INT, 149 &VNET_NAME(tcp_do_newsack), 0, sysctl_net_inet_tcp_sack_revised, "CU", 150 "Use revised SACK loss recovery per RFC 6675"); 151 152 VNET_DEFINE(int, tcp_do_lrd) = 1; 153 SYSCTL_INT(_net_inet_tcp_sack, OID_AUTO, lrd, CTLFLAG_VNET | CTLFLAG_RW, 154 &VNET_NAME(tcp_do_lrd), 1, 155 "Perform Lost Retransmission Detection"); 156 157 VNET_DEFINE(int, tcp_sack_tso) = 0; 158 SYSCTL_INT(_net_inet_tcp_sack, OID_AUTO, tso, CTLFLAG_VNET | CTLFLAG_RW, 159 &VNET_NAME(tcp_sack_tso), 0, 160 "Allow TSO during SACK loss recovery"); 161 162 VNET_DEFINE(int, tcp_sack_maxholes) = 128; 163 SYSCTL_INT(_net_inet_tcp_sack, OID_AUTO, maxholes, CTLFLAG_VNET | CTLFLAG_RW, 164 &VNET_NAME(tcp_sack_maxholes), 0, 165 "Maximum number of TCP SACK holes allowed per connection"); 166 167 VNET_DEFINE(int, tcp_sack_globalmaxholes) = 65536; 168 SYSCTL_INT(_net_inet_tcp_sack, OID_AUTO, globalmaxholes, CTLFLAG_VNET | CTLFLAG_RW, 169 &VNET_NAME(tcp_sack_globalmaxholes), 0, 170 "Global maximum number of TCP SACK holes"); 171 172 VNET_DEFINE(int, tcp_sack_globalholes) = 0; 173 SYSCTL_INT(_net_inet_tcp_sack, OID_AUTO, globalholes, CTLFLAG_VNET | CTLFLAG_RD, 174 &VNET_NAME(tcp_sack_globalholes), 0, 175 "Global number of TCP SACK holes currently allocated"); 176 177 int 178 tcp_dsack_block_exists(struct tcpcb *tp) 179 { 180 /* Return true if a DSACK block exists */ 181 if (tp->rcv_numsacks == 0) 182 return (0); 183 if (SEQ_LEQ(tp->sackblks[0].end, tp->rcv_nxt)) 184 return(1); 185 return (0); 186 } 187 188 /* 189 * This function will find overlaps with the currently stored sackblocks 190 * and add any overlap as a dsack block upfront 191 */ 192 void 193 tcp_update_dsack_list(struct tcpcb *tp, tcp_seq rcv_start, tcp_seq rcv_end) 194 { 195 struct sackblk head_blk,mid_blk,saved_blks[MAX_SACK_BLKS]; 196 int i, j, n, identical; 197 tcp_seq start, end; 198 199 INP_WLOCK_ASSERT(tptoinpcb(tp)); 200 201 KASSERT(SEQ_LT(rcv_start, rcv_end), ("rcv_start < rcv_end")); 202 203 if (SEQ_LT(rcv_end, tp->rcv_nxt) || 204 ((rcv_end == tp->rcv_nxt) && 205 (tp->rcv_numsacks > 0 ) && 206 (tp->sackblks[0].end == tp->rcv_nxt))) { 207 saved_blks[0].start = rcv_start; 208 saved_blks[0].end = rcv_end; 209 } else { 210 saved_blks[0].start = saved_blks[0].end = 0; 211 } 212 213 head_blk.start = head_blk.end = 0; 214 mid_blk.start = rcv_start; 215 mid_blk.end = rcv_end; 216 identical = 0; 217 218 for (i = 0; i < tp->rcv_numsacks; i++) { 219 start = tp->sackblks[i].start; 220 end = tp->sackblks[i].end; 221 if (SEQ_LT(rcv_end, start)) { 222 /* pkt left to sack blk */ 223 continue; 224 } 225 if (SEQ_GT(rcv_start, end)) { 226 /* pkt right to sack blk */ 227 continue; 228 } 229 if (SEQ_GT(tp->rcv_nxt, end)) { 230 if ((SEQ_MAX(rcv_start, start) != SEQ_MIN(rcv_end, end)) && 231 (SEQ_GT(head_blk.start, SEQ_MAX(rcv_start, start)) || 232 (head_blk.start == head_blk.end))) { 233 head_blk.start = SEQ_MAX(rcv_start, start); 234 head_blk.end = SEQ_MIN(rcv_end, end); 235 } 236 continue; 237 } 238 if (((head_blk.start == head_blk.end) || 239 SEQ_LT(start, head_blk.start)) && 240 (SEQ_GT(end, rcv_start) && 241 SEQ_LEQ(start, rcv_end))) { 242 head_blk.start = start; 243 head_blk.end = end; 244 } 245 mid_blk.start = SEQ_MIN(mid_blk.start, start); 246 mid_blk.end = SEQ_MAX(mid_blk.end, end); 247 if ((mid_blk.start == start) && 248 (mid_blk.end == end)) 249 identical = 1; 250 } 251 if (SEQ_LT(head_blk.start, head_blk.end)) { 252 /* store overlapping range */ 253 saved_blks[0].start = SEQ_MAX(rcv_start, head_blk.start); 254 saved_blks[0].end = SEQ_MIN(rcv_end, head_blk.end); 255 } 256 n = 1; 257 /* 258 * Second, if not ACKed, store the SACK block that 259 * overlaps with the DSACK block unless it is identical 260 */ 261 if ((SEQ_LT(tp->rcv_nxt, mid_blk.end) && 262 !((mid_blk.start == saved_blks[0].start) && 263 (mid_blk.end == saved_blks[0].end))) || 264 identical == 1) { 265 saved_blks[n].start = mid_blk.start; 266 saved_blks[n++].end = mid_blk.end; 267 } 268 for (j = 0; (j < tp->rcv_numsacks) && (n < MAX_SACK_BLKS); j++) { 269 if (((SEQ_LT(tp->sackblks[j].end, mid_blk.start) || 270 SEQ_GT(tp->sackblks[j].start, mid_blk.end)) && 271 (SEQ_GT(tp->sackblks[j].start, tp->rcv_nxt)))) 272 saved_blks[n++] = tp->sackblks[j]; 273 } 274 j = 0; 275 for (i = 0; i < n; i++) { 276 /* we can end up with a stale initial entry */ 277 if (SEQ_LT(saved_blks[i].start, saved_blks[i].end)) { 278 tp->sackblks[j++] = saved_blks[i]; 279 } 280 } 281 tp->rcv_numsacks = j; 282 } 283 284 /* 285 * This function is called upon receipt of new valid data (while not in 286 * header prediction mode), and it updates the ordered list of sacks. 287 */ 288 void 289 tcp_update_sack_list(struct tcpcb *tp, tcp_seq rcv_start, tcp_seq rcv_end) 290 { 291 /* 292 * First reported block MUST be the most recent one. Subsequent 293 * blocks SHOULD be in the order in which they arrived at the 294 * receiver. These two conditions make the implementation fully 295 * compliant with RFC 2018. 296 */ 297 struct sackblk head_blk, saved_blks[MAX_SACK_BLKS]; 298 int num_head, num_saved, i; 299 300 INP_WLOCK_ASSERT(tptoinpcb(tp)); 301 302 /* Check arguments. */ 303 KASSERT(SEQ_LEQ(rcv_start, rcv_end), ("SEG_GT(rcv_start, rcv_end)")); 304 305 if ((rcv_start == rcv_end) && 306 (tp->rcv_numsacks >= 1) && 307 (rcv_end == tp->sackblks[0].end)) { 308 /* retaining DSACK block below rcv_nxt (todrop) */ 309 head_blk = tp->sackblks[0]; 310 } else { 311 /* SACK block for the received segment. */ 312 head_blk.start = rcv_start; 313 head_blk.end = rcv_end; 314 } 315 316 /* 317 * Merge updated SACK blocks into head_blk, and save unchanged SACK 318 * blocks into saved_blks[]. num_saved will have the number of the 319 * saved SACK blocks. 320 */ 321 num_saved = 0; 322 for (i = 0; i < tp->rcv_numsacks; i++) { 323 tcp_seq start = tp->sackblks[i].start; 324 tcp_seq end = tp->sackblks[i].end; 325 if (SEQ_GEQ(start, end) || SEQ_LEQ(start, tp->rcv_nxt)) { 326 /* 327 * Discard this SACK block. 328 */ 329 } else if (SEQ_LEQ(head_blk.start, end) && 330 SEQ_GEQ(head_blk.end, start)) { 331 /* 332 * Merge this SACK block into head_blk. This SACK 333 * block itself will be discarded. 334 */ 335 /* 336 * |-| 337 * |---| merge 338 * 339 * |-| 340 * |---| merge 341 * 342 * |-----| 343 * |-| DSACK smaller 344 * 345 * |-| 346 * |-----| DSACK smaller 347 */ 348 if (head_blk.start == end) 349 head_blk.start = start; 350 else if (head_blk.end == start) 351 head_blk.end = end; 352 else { 353 if (SEQ_LT(head_blk.start, start)) { 354 tcp_seq temp = start; 355 start = head_blk.start; 356 head_blk.start = temp; 357 } 358 if (SEQ_GT(head_blk.end, end)) { 359 tcp_seq temp = end; 360 end = head_blk.end; 361 head_blk.end = temp; 362 } 363 if ((head_blk.start != start) || 364 (head_blk.end != end)) { 365 if ((num_saved >= 1) && 366 SEQ_GEQ(saved_blks[num_saved-1].start, start) && 367 SEQ_LEQ(saved_blks[num_saved-1].end, end)) 368 num_saved--; 369 saved_blks[num_saved].start = start; 370 saved_blks[num_saved].end = end; 371 num_saved++; 372 } 373 } 374 } else { 375 /* 376 * This block supercedes the prior block 377 */ 378 if ((num_saved >= 1) && 379 SEQ_GEQ(saved_blks[num_saved-1].start, start) && 380 SEQ_LEQ(saved_blks[num_saved-1].end, end)) 381 num_saved--; 382 /* 383 * Save this SACK block. 384 */ 385 saved_blks[num_saved].start = start; 386 saved_blks[num_saved].end = end; 387 num_saved++; 388 } 389 } 390 391 /* 392 * Update SACK list in tp->sackblks[]. 393 */ 394 num_head = 0; 395 if (SEQ_LT(rcv_start, rcv_end)) { 396 /* 397 * The received data segment is an out-of-order segment. Put 398 * head_blk at the top of SACK list. 399 */ 400 tp->sackblks[0] = head_blk; 401 num_head = 1; 402 /* 403 * If the number of saved SACK blocks exceeds its limit, 404 * discard the last SACK block. 405 */ 406 if (num_saved >= MAX_SACK_BLKS) 407 num_saved--; 408 } 409 if ((rcv_start == rcv_end) && 410 (rcv_start == tp->sackblks[0].end)) { 411 num_head = 1; 412 } 413 if (num_saved > 0) { 414 /* 415 * Copy the saved SACK blocks back. 416 */ 417 bcopy(saved_blks, &tp->sackblks[num_head], 418 sizeof(struct sackblk) * num_saved); 419 } 420 421 /* Save the number of SACK blocks. */ 422 tp->rcv_numsacks = num_head + num_saved; 423 } 424 425 void 426 tcp_clean_dsack_blocks(struct tcpcb *tp) 427 { 428 struct sackblk saved_blks[MAX_SACK_BLKS]; 429 int num_saved, i; 430 431 INP_WLOCK_ASSERT(tptoinpcb(tp)); 432 /* 433 * Clean up any DSACK blocks that 434 * are in our queue of sack blocks. 435 * 436 */ 437 num_saved = 0; 438 for (i = 0; i < tp->rcv_numsacks; i++) { 439 tcp_seq start = tp->sackblks[i].start; 440 tcp_seq end = tp->sackblks[i].end; 441 if (SEQ_GEQ(start, end) || SEQ_LEQ(start, tp->rcv_nxt)) { 442 /* 443 * Discard this D-SACK block. 444 */ 445 continue; 446 } 447 /* 448 * Save this SACK block. 449 */ 450 saved_blks[num_saved].start = start; 451 saved_blks[num_saved].end = end; 452 num_saved++; 453 } 454 if (num_saved > 0) { 455 /* 456 * Copy the saved SACK blocks back. 457 */ 458 bcopy(saved_blks, &tp->sackblks[0], 459 sizeof(struct sackblk) * num_saved); 460 } 461 tp->rcv_numsacks = num_saved; 462 } 463 464 /* 465 * Delete all receiver-side SACK information. 466 */ 467 void 468 tcp_clean_sackreport(struct tcpcb *tp) 469 { 470 int i; 471 472 INP_WLOCK_ASSERT(tptoinpcb(tp)); 473 tp->rcv_numsacks = 0; 474 for (i = 0; i < MAX_SACK_BLKS; i++) 475 tp->sackblks[i].start = tp->sackblks[i].end=0; 476 } 477 478 /* 479 * Allocate struct sackhole. 480 */ 481 static struct sackhole * 482 tcp_sackhole_alloc(struct tcpcb *tp, tcp_seq start, tcp_seq end) 483 { 484 struct sackhole *hole; 485 486 if (tp->snd_numholes >= V_tcp_sack_maxholes || 487 V_tcp_sack_globalholes >= V_tcp_sack_globalmaxholes) { 488 TCPSTAT_INC(tcps_sack_sboverflow); 489 return NULL; 490 } 491 492 hole = (struct sackhole *)uma_zalloc(V_sack_hole_zone, M_NOWAIT); 493 if (hole == NULL) 494 return NULL; 495 496 hole->start = start; 497 hole->end = end; 498 hole->rxmit = start; 499 500 tp->snd_numholes++; 501 atomic_add_int(&V_tcp_sack_globalholes, 1); 502 503 return hole; 504 } 505 506 /* 507 * Free struct sackhole. 508 */ 509 static void 510 tcp_sackhole_free(struct tcpcb *tp, struct sackhole *hole) 511 { 512 513 uma_zfree(V_sack_hole_zone, hole); 514 515 tp->snd_numholes--; 516 atomic_subtract_int(&V_tcp_sack_globalholes, 1); 517 518 KASSERT(tp->snd_numholes >= 0, ("tp->snd_numholes < 0")); 519 KASSERT(V_tcp_sack_globalholes >= 0, ("tcp_sack_globalholes < 0")); 520 } 521 522 /* 523 * Insert new SACK hole into scoreboard. 524 */ 525 static struct sackhole * 526 tcp_sackhole_insert(struct tcpcb *tp, tcp_seq start, tcp_seq end, 527 struct sackhole *after) 528 { 529 struct sackhole *hole; 530 531 /* Allocate a new SACK hole. */ 532 hole = tcp_sackhole_alloc(tp, start, end); 533 if (hole == NULL) 534 return NULL; 535 536 /* Insert the new SACK hole into scoreboard. */ 537 if (after != NULL) 538 TAILQ_INSERT_AFTER(&tp->snd_holes, after, hole, scblink); 539 else 540 TAILQ_INSERT_TAIL(&tp->snd_holes, hole, scblink); 541 542 /* Update SACK hint. */ 543 if (tp->sackhint.nexthole == NULL) 544 tp->sackhint.nexthole = hole; 545 546 return hole; 547 } 548 549 /* 550 * Remove SACK hole from scoreboard. 551 */ 552 static void 553 tcp_sackhole_remove(struct tcpcb *tp, struct sackhole *hole) 554 { 555 556 /* Update SACK hint. */ 557 if (tp->sackhint.nexthole == hole) 558 tp->sackhint.nexthole = TAILQ_NEXT(hole, scblink); 559 560 /* Remove this SACK hole. */ 561 TAILQ_REMOVE(&tp->snd_holes, hole, scblink); 562 563 /* Free this SACK hole. */ 564 tcp_sackhole_free(tp, hole); 565 } 566 567 /* 568 * Process cumulative ACK and the TCP SACK option to update the scoreboard. 569 * tp->snd_holes is an ordered list of holes (oldest to newest, in terms of 570 * the sequence space). 571 * Returns SACK_NEWLOSS if incoming ACK indicates ongoing loss (hole split, new hole), 572 * SACK_CHANGE if incoming ACK has previously unknown SACK information, 573 * SACK_NOCHANGE otherwise. 574 */ 575 sackstatus_t 576 tcp_sack_doack(struct tcpcb *tp, struct tcpopt *to, tcp_seq th_ack) 577 { 578 struct sackhole *cur, *temp; 579 struct sackblk sack, sack_blocks[TCP_MAX_SACK + 1], *sblkp; 580 int i, j, num_sack_blks; 581 sackstatus_t sack_changed; 582 int delivered_data, left_edge_delta; 583 int maxseg = tp->t_maxseg - MAX_TCPOPTLEN; 584 585 tcp_seq loss_hiack = 0; 586 int loss_thresh = 0; 587 int loss_sblks = 0; 588 int notlost_bytes = 0; 589 590 INP_WLOCK_ASSERT(tptoinpcb(tp)); 591 592 num_sack_blks = 0; 593 sack_changed = SACK_NOCHANGE; 594 delivered_data = 0; 595 left_edge_delta = 0; 596 /* 597 * If SND.UNA will be advanced by SEG.ACK, and if SACK holes exist, 598 * treat [SND.UNA, SEG.ACK) as if it is a SACK block. 599 * Account changes to SND.UNA always in delivered data. 600 */ 601 if (SEQ_LT(tp->snd_una, th_ack) && !TAILQ_EMPTY(&tp->snd_holes)) { 602 left_edge_delta = th_ack - tp->snd_una; 603 delivered_data += left_edge_delta; 604 sack_blocks[num_sack_blks].start = tp->snd_una; 605 sack_blocks[num_sack_blks++].end = th_ack; 606 /* 607 * Pulling snd_fack forward if we got here 608 * due to DSACK blocks 609 */ 610 if (SEQ_LT(tp->snd_fack, th_ack)) { 611 tp->snd_fack = th_ack; 612 sack_changed = SACK_CHANGE; 613 } 614 } 615 /* 616 * Append received valid SACK blocks to sack_blocks[], but only if we 617 * received new blocks from the other side. 618 */ 619 if (to->to_flags & TOF_SACK) { 620 for (i = 0; i < to->to_nsacks; i++) { 621 bcopy((to->to_sacks + i * TCPOLEN_SACK), 622 &sack, sizeof(sack)); 623 sack.start = ntohl(sack.start); 624 sack.end = ntohl(sack.end); 625 if (SEQ_GT(sack.end, sack.start) && 626 SEQ_GT(sack.start, tp->snd_una) && 627 SEQ_GT(sack.start, th_ack) && 628 SEQ_LT(sack.start, tp->snd_max) && 629 SEQ_GT(sack.end, tp->snd_una) && 630 SEQ_LEQ(sack.end, tp->snd_max) && 631 ((sack.end - sack.start) >= maxseg || 632 SEQ_GEQ(sack.end, tp->snd_max))) { 633 sack_blocks[num_sack_blks++] = sack; 634 } else if (SEQ_LEQ(sack.start, th_ack) && 635 SEQ_LEQ(sack.end, th_ack)) { 636 /* 637 * Its a D-SACK block. 638 */ 639 tcp_record_dsack(tp, sack.start, sack.end, 0); 640 } 641 } 642 } 643 /* 644 * Return if SND.UNA is not advanced and no valid SACK block is 645 * received. 646 */ 647 if (num_sack_blks == 0) 648 return (sack_changed); 649 650 /* 651 * Sort the SACK blocks so we can update the scoreboard with just one 652 * pass. The overhead of sorting up to 4+1 elements is less than 653 * making up to 4+1 passes over the scoreboard. 654 */ 655 for (i = 0; i < num_sack_blks; i++) { 656 for (j = i + 1; j < num_sack_blks; j++) { 657 if (SEQ_GT(sack_blocks[i].end, sack_blocks[j].end)) { 658 sack = sack_blocks[i]; 659 sack_blocks[i] = sack_blocks[j]; 660 sack_blocks[j] = sack; 661 } 662 } 663 } 664 if (TAILQ_EMPTY(&tp->snd_holes)) { 665 /* 666 * Empty scoreboard. Need to initialize snd_fack (it may be 667 * uninitialized or have a bogus value). Scoreboard holes 668 * (from the sack blocks received) are created later below 669 * (in the logic that adds holes to the tail of the 670 * scoreboard). 671 */ 672 tp->snd_fack = SEQ_MAX(tp->snd_una, th_ack); 673 } 674 /* 675 * In the while-loop below, incoming SACK blocks (sack_blocks[]) and 676 * SACK holes (snd_holes) are traversed from their tails with just 677 * one pass in order to reduce the number of compares especially when 678 * the bandwidth-delay product is large. 679 * 680 * Note: Typically, in the first RTT of SACK recovery, the highest 681 * three or four SACK blocks with the same ack number are received. 682 * In the second RTT, if retransmitted data segments are not lost, 683 * the highest three or four SACK blocks with ack number advancing 684 * are received. 685 */ 686 sblkp = &sack_blocks[num_sack_blks - 1]; /* Last SACK block */ 687 tp->sackhint.last_sack_ack = sblkp->end; 688 if (SEQ_LT(tp->snd_fack, sblkp->start)) { 689 /* 690 * The highest SACK block is beyond fack. First, 691 * check if there was a successful Rescue Retransmission, 692 * and move this hole left. With normal holes, snd_fack 693 * is always to the right of the end. 694 */ 695 if (((temp = TAILQ_LAST(&tp->snd_holes, sackhole_head)) != NULL) && 696 SEQ_LEQ(tp->snd_fack,temp->end)) { 697 tp->sackhint.hole_bytes -= temp->end - temp->start; 698 temp->start = SEQ_MAX(tp->snd_fack, SEQ_MAX(tp->snd_una, th_ack)); 699 temp->end = sblkp->start; 700 temp->rxmit = temp->start; 701 delivered_data += sblkp->end - sblkp->start; 702 tp->sackhint.hole_bytes += temp->end - temp->start; 703 KASSERT(tp->sackhint.hole_bytes >= 0, 704 ("sackhint hole bytes < 0")); 705 tp->snd_fack = sblkp->end; 706 sblkp--; 707 sack_changed = SACK_NEWLOSS; 708 } else { 709 /* 710 * Append a new SACK hole at the tail. If the 711 * second or later highest SACK blocks are also 712 * beyond the current fack, they will be inserted 713 * by way of hole splitting in the while-loop below. 714 */ 715 temp = tcp_sackhole_insert(tp, tp->snd_fack,sblkp->start,NULL); 716 if (temp != NULL) { 717 delivered_data += sblkp->end - sblkp->start; 718 tp->sackhint.hole_bytes += temp->end - temp->start; 719 tp->snd_fack = sblkp->end; 720 /* Go to the previous sack block. */ 721 sblkp--; 722 sack_changed = SACK_CHANGE; 723 } else { 724 /* 725 * We failed to add a new hole based on the current 726 * sack block. Skip over all the sack blocks that 727 * fall completely to the right of snd_fack and 728 * proceed to trim the scoreboard based on the 729 * remaining sack blocks. This also trims the 730 * scoreboard for th_ack (which is sack_blocks[0]). 731 */ 732 while (sblkp >= sack_blocks && 733 SEQ_LT(tp->snd_fack, sblkp->start)) 734 sblkp--; 735 if (sblkp >= sack_blocks && 736 SEQ_LT(tp->snd_fack, sblkp->end)) { 737 delivered_data += sblkp->end - tp->snd_fack; 738 tp->snd_fack = sblkp->end; 739 /* 740 * While the Scoreboard didn't change in 741 * size, we only ended up here because 742 * some SACK data had to be dismissed. 743 */ 744 sack_changed = SACK_NEWLOSS; 745 } 746 } 747 } 748 } else if (SEQ_LT(tp->snd_fack, sblkp->end)) { 749 /* fack is advanced. */ 750 delivered_data += sblkp->end - tp->snd_fack; 751 tp->snd_fack = sblkp->end; 752 sack_changed = SACK_CHANGE; 753 } 754 cur = TAILQ_LAST(&tp->snd_holes, sackhole_head); /* Last SACK hole. */ 755 loss_hiack = tp->snd_fack; 756 757 /* 758 * Since the incoming sack blocks are sorted, we can process them 759 * making one sweep of the scoreboard. 760 */ 761 while (cur != NULL) { 762 if (!(sblkp >= sack_blocks)) { 763 if (((loss_sblks >= tcprexmtthresh) || 764 (loss_thresh > (tcprexmtthresh-1)*tp->t_maxseg))) 765 break; 766 loss_thresh += loss_hiack - cur->end; 767 loss_hiack = cur->start; 768 loss_sblks++; 769 if (!((loss_sblks >= tcprexmtthresh) || 770 (loss_thresh > (tcprexmtthresh-1)*tp->t_maxseg))) { 771 notlost_bytes += cur->end - cur->start; 772 } else { 773 break; 774 } 775 cur = TAILQ_PREV(cur, sackhole_head, scblink); 776 continue; 777 } 778 if (SEQ_GEQ(sblkp->start, cur->end)) { 779 /* 780 * SACKs data beyond the current hole. Go to the 781 * previous sack block. 782 */ 783 sblkp--; 784 continue; 785 } 786 if (SEQ_LEQ(sblkp->end, cur->start)) { 787 /* 788 * SACKs data before the current hole. Go to the 789 * previous hole. 790 */ 791 loss_thresh += loss_hiack - cur->end; 792 loss_hiack = cur->start; 793 loss_sblks++; 794 if (!((loss_sblks >= tcprexmtthresh) || 795 (loss_thresh > (tcprexmtthresh-1)*tp->t_maxseg))) 796 notlost_bytes += cur->end - cur->start; 797 cur = TAILQ_PREV(cur, sackhole_head, scblink); 798 continue; 799 } 800 tp->sackhint.sack_bytes_rexmit -= 801 (SEQ_MIN(cur->rxmit, cur->end) - cur->start); 802 KASSERT(tp->sackhint.sack_bytes_rexmit >= 0, 803 ("sackhint bytes rtx < 0")); 804 sack_changed = SACK_CHANGE; 805 if (SEQ_LEQ(sblkp->start, cur->start)) { 806 /* Data acks at least the beginning of hole. */ 807 if (SEQ_GEQ(sblkp->end, cur->end)) { 808 /* Acks entire hole, so delete hole. */ 809 delivered_data += (cur->end - cur->start); 810 temp = cur; 811 cur = TAILQ_PREV(cur, sackhole_head, scblink); 812 tp->sackhint.hole_bytes -= temp->end - temp->start; 813 tcp_sackhole_remove(tp, temp); 814 /* 815 * The sack block may ack all or part of the 816 * next hole too, so continue onto the next 817 * hole. 818 */ 819 continue; 820 } else { 821 /* Move start of hole forward. */ 822 delivered_data += (sblkp->end - cur->start); 823 tp->sackhint.hole_bytes -= sblkp->end - cur->start; 824 cur->start = sblkp->end; 825 cur->rxmit = SEQ_MAX(cur->rxmit, cur->start); 826 } 827 } else { 828 /* Data acks at least the end of hole. */ 829 if (SEQ_GEQ(sblkp->end, cur->end)) { 830 /* Move end of hole backward. */ 831 delivered_data += (cur->end - sblkp->start); 832 tp->sackhint.hole_bytes -= cur->end - sblkp->start; 833 cur->end = sblkp->start; 834 cur->rxmit = SEQ_MIN(cur->rxmit, cur->end); 835 if ((tp->t_flags & TF_LRD) && SEQ_GEQ(cur->rxmit, cur->end)) 836 cur->rxmit = SEQ_MAX(cur->rxmit, tp->snd_recover); 837 } else { 838 /* 839 * ACKs some data in middle of a hole; need 840 * to split current hole 841 */ 842 temp = tcp_sackhole_insert(tp, sblkp->end, 843 cur->end, cur); 844 sack_changed = SACK_NEWLOSS; 845 if (temp != NULL) { 846 if (SEQ_GT(cur->rxmit, temp->rxmit)) { 847 temp->rxmit = cur->rxmit; 848 tp->sackhint.sack_bytes_rexmit += 849 (SEQ_MIN(temp->rxmit, 850 temp->end) - temp->start); 851 } 852 tp->sackhint.hole_bytes -= sblkp->end - sblkp->start; 853 loss_thresh += loss_hiack - temp->end; 854 loss_hiack = temp->start; 855 loss_sblks++; 856 if (!((loss_sblks >= tcprexmtthresh) || 857 (loss_thresh > (tcprexmtthresh-1)*tp->t_maxseg))) 858 notlost_bytes += temp->end - temp->start; 859 cur->end = sblkp->start; 860 cur->rxmit = SEQ_MIN(cur->rxmit, 861 cur->end); 862 if ((tp->t_flags & TF_LRD) && SEQ_GEQ(cur->rxmit, cur->end)) 863 cur->rxmit = SEQ_MAX(cur->rxmit, tp->snd_recover); 864 delivered_data += (sblkp->end - sblkp->start); 865 } 866 } 867 } 868 tp->sackhint.sack_bytes_rexmit += 869 (SEQ_MIN(cur->rxmit, cur->end) - cur->start); 870 /* 871 * Testing sblkp->start against cur->start tells us whether 872 * we're done with the sack block or the sack hole. 873 * Accordingly, we advance one or the other. 874 */ 875 if (SEQ_LEQ(sblkp->start, cur->start)) { 876 loss_thresh += loss_hiack - cur->end; 877 loss_hiack = cur->start; 878 loss_sblks++; 879 if (!((loss_sblks >= tcprexmtthresh) || 880 (loss_thresh > (tcprexmtthresh-1)*tp->t_maxseg))) 881 notlost_bytes += cur->end - cur->start; 882 cur = TAILQ_PREV(cur, sackhole_head, scblink); 883 } else { 884 sblkp--; 885 } 886 } 887 888 KASSERT(delivered_data >= 0, ("delivered_data < 0")); 889 KASSERT(notlost_bytes <= tp->sackhint.hole_bytes, 890 ("SACK: more bytes marked notlost than in scoreboard holes")); 891 892 if (TAILQ_EMPTY(&tp->snd_holes)) { 893 KASSERT(tp->sackhint.hole_bytes == 0, 894 ("SACK scoreboard empty, but sackhint hole bytes != 0")); 895 tp->sackhint.sack_bytes_rexmit = 0; 896 tp->sackhint.sacked_bytes = 0; 897 tp->sackhint.lost_bytes = 0; 898 } else { 899 KASSERT(tp->sackhint.hole_bytes > 0, 900 ("SACK scoreboard not empty, but sackhint hole bytes <= 0")); 901 tp->sackhint.delivered_data = delivered_data; 902 tp->sackhint.sacked_bytes += delivered_data - left_edge_delta; 903 KASSERT((tp->sackhint.sacked_bytes >= 0), ("sacked_bytes < 0")); 904 tp->sackhint.lost_bytes = tp->sackhint.hole_bytes - 905 notlost_bytes; 906 } 907 908 if (!(to->to_flags & TOF_SACK)) 909 /* 910 * If this ACK did not contain any 911 * SACK blocks, any only moved the 912 * left edge right, it is a pure 913 * cumulative ACK. Do not count 914 * DupAck for this. Also required 915 * for RFC6675 rescue retransmission. 916 */ 917 sack_changed = SACK_NOCHANGE; 918 return (sack_changed); 919 } 920 921 /* 922 * Free all SACK holes to clear the scoreboard. 923 */ 924 void 925 tcp_free_sackholes(struct tcpcb *tp) 926 { 927 struct sackhole *q; 928 929 INP_WLOCK_ASSERT(tptoinpcb(tp)); 930 while ((q = TAILQ_FIRST(&tp->snd_holes)) != NULL) 931 tcp_sackhole_remove(tp, q); 932 tp->sackhint.sack_bytes_rexmit = 0; 933 tp->sackhint.delivered_data = 0; 934 tp->sackhint.sacked_bytes = 0; 935 tp->sackhint.hole_bytes = 0; 936 tp->sackhint.lost_bytes = 0; 937 938 KASSERT(tp->snd_numholes == 0, ("tp->snd_numholes != 0")); 939 KASSERT(tp->sackhint.nexthole == NULL, 940 ("tp->sackhint.nexthole != NULL")); 941 } 942 943 /* 944 * Resend all the currently existing SACK holes of 945 * the scoreboard. This is in line with the Errata to 946 * RFC 2018, which allows the use of SACK data past 947 * an RTO to good effect typically. 948 */ 949 void 950 tcp_resend_sackholes(struct tcpcb *tp) 951 { 952 struct sackhole *p; 953 954 INP_WLOCK_ASSERT(tptoinpcb(tp)); 955 TAILQ_FOREACH(p, &tp->snd_holes, scblink) { 956 p->rxmit = p->start; 957 } 958 tp->sackhint.nexthole = TAILQ_FIRST(&tp->snd_holes); 959 tp->sackhint.sack_bytes_rexmit = 0; 960 } 961 962 /* 963 * Partial ack handling within a sack recovery episode. Keeping this very 964 * simple for now. When a partial ack is received, force snd_cwnd to a value 965 * that will allow the sender to transmit no more than 2 segments. If 966 * necessary, a better scheme can be adopted at a later point, but for now, 967 * the goal is to prevent the sender from bursting a large amount of data in 968 * the midst of sack recovery. 969 */ 970 void 971 tcp_sack_partialack(struct tcpcb *tp, struct tcphdr *th, u_int *maxsegp) 972 { 973 struct sackhole *temp; 974 int num_segs = 1; 975 u_int maxseg; 976 977 INP_WLOCK_ASSERT(tptoinpcb(tp)); 978 979 if (*maxsegp == 0) { 980 *maxsegp = tcp_maxseg(tp); 981 } 982 maxseg = *maxsegp; 983 tcp_timer_activate(tp, TT_REXMT, 0); 984 tp->t_rtttime = 0; 985 /* Send one or 2 segments based on how much new data was acked. */ 986 if ((BYTES_THIS_ACK(tp, th) / maxseg) >= 2) 987 num_segs = 2; 988 if (tp->snd_nxt == tp->snd_max) { 989 tp->snd_cwnd = (tp->sackhint.sack_bytes_rexmit + 990 (tp->snd_nxt - tp->snd_recover) + num_segs * maxseg); 991 } else { 992 /* 993 * Since cwnd is not the expected flightsize during 994 * SACK LR, not deflating cwnd allows the partial 995 * ACKed amount to be sent. 996 */ 997 } 998 if (tp->snd_cwnd > tp->snd_ssthresh) 999 tp->snd_cwnd = tp->snd_ssthresh; 1000 tp->t_flags |= TF_ACKNOW; 1001 /* 1002 * RFC6675 rescue retransmission 1003 * Add a hole between th_ack (snd_una is not yet set) and snd_max, 1004 * if this was a pure cumulative ACK and no data was send beyond 1005 * recovery point. Since the data in the socket has not been freed 1006 * at this point, we check if the scoreboard is empty, and the ACK 1007 * delivered some new data, indicating a full ACK. Also, if the 1008 * recovery point is still at snd_max, we are probably application 1009 * limited. However, this inference might not always be true. The 1010 * rescue retransmission may rarely be slightly premature 1011 * compared to RFC6675. 1012 * The corresponding ACK+SACK will cause any further outstanding 1013 * segments to be retransmitted. This addresses a corner case, when 1014 * the trailing packets of a window are lost and no further data 1015 * is available for sending. 1016 */ 1017 if ((V_tcp_do_newsack) && 1018 SEQ_LT(th->th_ack, tp->snd_recover) && 1019 TAILQ_EMPTY(&tp->snd_holes) && 1020 (tp->sackhint.delivered_data > 0)) { 1021 /* 1022 * Exclude FIN sequence space in 1023 * the hole for the rescue retransmission, 1024 * and also don't create a hole, if only 1025 * the ACK for a FIN is outstanding. 1026 */ 1027 tcp_seq highdata = tp->snd_max; 1028 if (tp->t_flags & TF_SENTFIN) 1029 highdata--; 1030 highdata = SEQ_MIN(highdata, tp->snd_recover); 1031 if (SEQ_LT(th->th_ack, highdata)) { 1032 tp->snd_fack = SEQ_MAX(th->th_ack, tp->snd_fack); 1033 if ((temp = tcp_sackhole_insert(tp, SEQ_MAX(th->th_ack, 1034 highdata - maxseg), highdata, NULL)) != NULL) { 1035 tp->sackhint.hole_bytes += 1036 temp->end - temp->start; 1037 } 1038 } 1039 } 1040 (void) tcp_output(tp); 1041 } 1042 1043 /* 1044 * Returns the next hole to retransmit and the number of retransmitted bytes 1045 * from the scoreboard. We store both the next hole and the number of 1046 * retransmitted bytes as hints (and recompute these on the fly upon SACK/ACK 1047 * reception). This avoids scoreboard traversals completely. 1048 * 1049 * The loop here will traverse *at most* one link. Here's the argument. For 1050 * the loop to traverse more than 1 link before finding the next hole to 1051 * retransmit, we would need to have at least 1 node following the current 1052 * hint with (rxmit == end). But, for all holes following the current hint, 1053 * (start == rxmit), since we have not yet retransmitted from them. 1054 * Therefore, in order to traverse more 1 link in the loop below, we need to 1055 * have at least one node following the current hint with (start == rxmit == 1056 * end). But that can't happen, (start == end) means that all the data in 1057 * that hole has been sacked, in which case, the hole would have been removed 1058 * from the scoreboard. 1059 */ 1060 struct sackhole * 1061 tcp_sack_output(struct tcpcb *tp, int *sack_bytes_rexmt) 1062 { 1063 struct sackhole *hole = NULL; 1064 1065 INP_WLOCK_ASSERT(tptoinpcb(tp)); 1066 *sack_bytes_rexmt = tp->sackhint.sack_bytes_rexmit; 1067 hole = tp->sackhint.nexthole; 1068 if (hole == NULL) 1069 return (hole); 1070 if (SEQ_GEQ(hole->rxmit, hole->end)) { 1071 for (;;) { 1072 hole = TAILQ_NEXT(hole, scblink); 1073 if (hole == NULL) 1074 return (hole); 1075 if (SEQ_LT(hole->rxmit, hole->end)) { 1076 tp->sackhint.nexthole = hole; 1077 break; 1078 } 1079 } 1080 } 1081 KASSERT(SEQ_LT(hole->start, hole->end), 1082 ("%s: SEQ_GEQ(hole.start, hole.end)", __func__)); 1083 if (!(V_tcp_do_newsack)) { 1084 KASSERT(SEQ_LT(hole->start, tp->snd_fack), 1085 ("%s: SEG_GEQ(hole.start, snd.fack)", __func__)); 1086 KASSERT(SEQ_LT(hole->end, tp->snd_fack), 1087 ("%s: SEG_GEQ(hole.end, snd.fack)", __func__)); 1088 KASSERT(SEQ_LT(hole->rxmit, tp->snd_fack), 1089 ("%s: SEQ_GEQ(hole.rxmit, snd.fack)", __func__)); 1090 if (SEQ_GEQ(hole->start, hole->end) || 1091 SEQ_GEQ(hole->start, tp->snd_fack) || 1092 SEQ_GEQ(hole->end, tp->snd_fack) || 1093 SEQ_GEQ(hole->rxmit, tp->snd_fack)) { 1094 log(LOG_CRIT,"tcp: invalid SACK hole (%u-%u,%u) vs fwd ack %u, ignoring.\n", 1095 hole->start, hole->end, hole->rxmit, tp->snd_fack); 1096 return (NULL); 1097 } 1098 } 1099 return (hole); 1100 } 1101 1102 /* 1103 * After a timeout, the SACK list may be rebuilt. This SACK information 1104 * should be used to avoid retransmitting SACKed data. This function 1105 * traverses the SACK list to see if snd_nxt should be moved forward. 1106 * In addition, cwnd will be inflated by the sacked bytes traversed when 1107 * moving snd_nxt forward. This prevents a traffic burst after the final 1108 * full ACK, and also keeps ACKs coming back. 1109 */ 1110 int 1111 tcp_sack_adjust(struct tcpcb *tp) 1112 { 1113 int sacked = 0; 1114 struct sackhole *p, *cur = TAILQ_FIRST(&tp->snd_holes); 1115 1116 INP_WLOCK_ASSERT(tptoinpcb(tp)); 1117 if (cur == NULL) { 1118 /* No holes */ 1119 return (0); 1120 } 1121 if (SEQ_GEQ(tp->snd_nxt, tp->snd_fack)) { 1122 /* We're already beyond any SACKed blocks */ 1123 return (tp->sackhint.sacked_bytes); 1124 } 1125 /* 1126 * Two cases for which we want to advance snd_nxt: 1127 * i) snd_nxt lies between end of one hole and beginning of another 1128 * ii) snd_nxt lies between end of last hole and snd_fack 1129 */ 1130 while ((p = TAILQ_NEXT(cur, scblink)) != NULL) { 1131 if (SEQ_LT(tp->snd_nxt, cur->end)) { 1132 return (sacked); 1133 } 1134 sacked += p->start - cur->end; 1135 if (SEQ_GEQ(tp->snd_nxt, p->start)) { 1136 cur = p; 1137 } else { 1138 tp->snd_nxt = p->start; 1139 return (sacked); 1140 } 1141 } 1142 if (SEQ_LT(tp->snd_nxt, cur->end)) { 1143 return (sacked); 1144 } 1145 tp->snd_nxt = tp->snd_fack; 1146 return (tp->sackhint.sacked_bytes); 1147 } 1148 1149 /* 1150 * Lost Retransmission Detection 1151 * Check is FACK is beyond the rexmit of the leftmost hole. 1152 * If yes, we restart sending from still existing holes, 1153 * and adjust cwnd via the congestion control module. 1154 */ 1155 void 1156 tcp_sack_lost_retransmission(struct tcpcb *tp, struct tcphdr *th) 1157 { 1158 struct sackhole *temp; 1159 1160 if (IN_RECOVERY(tp->t_flags) && 1161 SEQ_GT(tp->snd_fack, tp->snd_recover) && 1162 ((temp = TAILQ_FIRST(&tp->snd_holes)) != NULL) && 1163 SEQ_GEQ(temp->rxmit, temp->end) && 1164 SEQ_GEQ(tp->snd_fack, temp->rxmit)) { 1165 TCPSTAT_INC(tcps_sack_lostrexmt); 1166 /* 1167 * Start retransmissions from the first hole, and 1168 * subsequently all other remaining holes, including 1169 * those, which had been sent completely before. 1170 */ 1171 tp->sackhint.nexthole = temp; 1172 TAILQ_FOREACH(temp, &tp->snd_holes, scblink) { 1173 if (SEQ_GEQ(tp->snd_fack, temp->rxmit) && 1174 SEQ_GEQ(temp->rxmit, temp->end)) 1175 temp->rxmit = temp->start; 1176 } 1177 /* 1178 * Remember the old ssthresh, to deduct the beta factor used 1179 * by the CC module. Finally, set cwnd to ssthresh just 1180 * prior to invoking another cwnd reduction by the CC 1181 * module, to not shrink it excessively. 1182 */ 1183 tp->snd_cwnd = tp->snd_ssthresh; 1184 /* 1185 * Formally exit recovery, and let the CC module adjust 1186 * ssthresh as intended. 1187 */ 1188 EXIT_RECOVERY(tp->t_flags); 1189 cc_cong_signal(tp, th, CC_NDUPACK); 1190 /* 1191 * For PRR, adjust recover_fs as if this new reduction 1192 * initialized this variable. 1193 * cwnd will be adjusted by SACK or PRR processing 1194 * subsequently, only set it to a safe value here. 1195 */ 1196 tp->snd_cwnd = tcp_maxseg(tp); 1197 tp->sackhint.recover_fs = (tp->snd_max - tp->snd_una) - 1198 tp->sackhint.recover_fs; 1199 } 1200 } 1201