1 /*- 2 * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1994, 1995 3 * The Regents of the University of California. All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 1. Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * 2. Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in the 12 * documentation and/or other materials provided with the distribution. 13 * 4. Neither the name of the University nor the names of its contributors 14 * may be used to endorse or promote products derived from this software 15 * without specific prior written permission. 16 * 17 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 18 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 19 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 20 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 21 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 22 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 23 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 24 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 25 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 26 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 27 * SUCH DAMAGE. 28 * 29 * @(#)tcp_sack.c 8.12 (Berkeley) 5/24/95 30 * $FreeBSD$ 31 */ 32 33 /*- 34 * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1994 35 * The Regents of the University of California. All rights reserved. 36 * 37 * Redistribution and use in source and binary forms, with or without 38 * modification, are permitted provided that the following conditions 39 * are met: 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. Neither the name of the University nor the names of its contributors 46 * may be used to endorse or promote products derived from this software 47 * without specific prior written permission. 48 * 49 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 50 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 51 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 52 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 53 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 54 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 55 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 56 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 57 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 58 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 59 * SUCH DAMAGE. 60 * 61 * @@(#)COPYRIGHT 1.1 (NRL) 17 January 1995 62 * 63 * NRL grants permission for redistribution and use in source and binary 64 * forms, with or without modification, of the software and documentation 65 * created at NRL provided that the following conditions are met: 66 * 67 * 1. Redistributions of source code must retain the above copyright 68 * notice, this list of conditions and the following disclaimer. 69 * 2. Redistributions in binary form must reproduce the above copyright 70 * notice, this list of conditions and the following disclaimer in the 71 * documentation and/or other materials provided with the distribution. 72 * 3. All advertising materials mentioning features or use of this software 73 * must display the following acknowledgements: 74 * This product includes software developed by the University of 75 * California, Berkeley and its contributors. 76 * This product includes software developed at the Information 77 * Technology Division, US Naval Research Laboratory. 78 * 4. Neither the name of the NRL nor the names of its contributors 79 * may be used to endorse or promote products derived from this software 80 * without specific prior written permission. 81 * 82 * THE SOFTWARE PROVIDED BY NRL IS PROVIDED BY NRL AND CONTRIBUTORS ``AS 83 * IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 84 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A 85 * PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL NRL OR 86 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, 87 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, 88 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR 89 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF 90 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING 91 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS 92 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 93 * 94 * The views and conclusions contained in the software and documentation 95 * are those of the authors and should not be interpreted as representing 96 * official policies, either expressed or implied, of the US Naval 97 * Research Laboratory (NRL). 98 */ 99 #include "opt_inet.h" 100 #include "opt_inet6.h" 101 #include "opt_ipsec.h" 102 #include "opt_tcpdebug.h" 103 #include "opt_tcp_input.h" 104 #include "opt_tcp_sack.h" 105 106 #include <sys/param.h> 107 #include <sys/systm.h> 108 #include <sys/kernel.h> 109 #include <sys/sysctl.h> 110 #include <sys/malloc.h> 111 #include <sys/mbuf.h> 112 #include <sys/proc.h> /* for proc0 declaration */ 113 #include <sys/protosw.h> 114 #include <sys/socket.h> 115 #include <sys/socketvar.h> 116 #include <sys/syslog.h> 117 #include <sys/systm.h> 118 119 #include <machine/cpu.h> /* before tcp_seq.h, for tcp_random18() */ 120 121 #include <vm/uma.h> 122 123 #include <net/if.h> 124 #include <net/route.h> 125 126 #include <netinet/in.h> 127 #include <netinet/in_systm.h> 128 #include <netinet/ip.h> 129 #include <netinet/ip_icmp.h> /* for ICMP_BANDLIM */ 130 #include <netinet/in_var.h> 131 #include <netinet/icmp_var.h> /* for ICMP_BANDLIM */ 132 #include <netinet/in_pcb.h> 133 #include <netinet/ip_var.h> 134 #include <netinet/ip6.h> 135 #include <netinet/icmp6.h> 136 #include <netinet6/nd6.h> 137 #include <netinet6/ip6_var.h> 138 #include <netinet6/in6_pcb.h> 139 #include <netinet/tcp.h> 140 #include <netinet/tcp_fsm.h> 141 #include <netinet/tcp_seq.h> 142 #include <netinet/tcp_timer.h> 143 #include <netinet/tcp_var.h> 144 #include <netinet6/tcp6_var.h> 145 #include <netinet/tcpip.h> 146 #ifdef TCPDEBUG 147 #include <netinet/tcp_debug.h> 148 #endif /* TCPDEBUG */ 149 150 #ifdef FAST_IPSEC 151 #include <netipsec/ipsec.h> 152 #include <netipsec/ipsec6.h> 153 #endif 154 155 #ifdef IPSEC 156 #include <netinet6/ipsec.h> 157 #include <netinet6/ipsec6.h> 158 #include <netkey/key.h> 159 #endif /*IPSEC*/ 160 #include <machine/in_cksum.h> 161 162 extern struct uma_zone *sack_hole_zone; 163 164 SYSCTL_NODE(_net_inet_tcp, OID_AUTO, sack, CTLFLAG_RW, 0, "TCP SACK"); 165 int tcp_do_sack = 1; 166 SYSCTL_INT(_net_inet_tcp_sack, OID_AUTO, enable, CTLFLAG_RW, 167 &tcp_do_sack, 0, "Enable/Disable TCP SACK support"); 168 TUNABLE_INT("net.inet.tcp.sack.enable", &tcp_do_sack); 169 170 static int tcp_sack_maxholes = 128; 171 SYSCTL_INT(_net_inet_tcp_sack, OID_AUTO, maxholes, CTLFLAG_RW, 172 &tcp_sack_maxholes, 0, 173 "Maximum number of TCP SACK holes allowed per connection"); 174 175 static int tcp_sack_globalmaxholes = 65536; 176 SYSCTL_INT(_net_inet_tcp_sack, OID_AUTO, globalmaxholes, CTLFLAG_RW, 177 &tcp_sack_globalmaxholes, 0, 178 "Global maximum number of TCP SACK holes"); 179 180 static int tcp_sack_globalholes = 0; 181 SYSCTL_INT(_net_inet_tcp_sack, OID_AUTO, globalholes, CTLFLAG_RD, 182 &tcp_sack_globalholes, 0, 183 "Global number of TCP SACK holes currently allocated"); 184 185 /* 186 * This function is called upon receipt of new valid data (while not in header 187 * prediction mode), and it updates the ordered list of sacks. 188 */ 189 void 190 tcp_update_sack_list(struct tcpcb *tp, tcp_seq rcv_start, tcp_seq rcv_end) 191 { 192 /* 193 * First reported block MUST be the most recent one. Subsequent 194 * blocks SHOULD be in the order in which they arrived at the 195 * receiver. These two conditions make the implementation fully 196 * compliant with RFC 2018. 197 */ 198 struct sackblk head_blk, saved_blks[MAX_SACK_BLKS]; 199 int num_head, num_saved, i; 200 201 INP_LOCK_ASSERT(tp->t_inpcb); 202 203 /* Check arguments */ 204 KASSERT(SEQ_LT(rcv_start, rcv_end), ("rcv_start < rcv_end")); 205 206 /* SACK block for the received segment. */ 207 head_blk.start = rcv_start; 208 head_blk.end = rcv_end; 209 210 /* 211 * Merge updated SACK blocks into head_blk, and 212 * save unchanged SACK blocks into saved_blks[]. 213 * num_saved will have the number of the saved SACK blocks. 214 */ 215 num_saved = 0; 216 for (i = 0; i < tp->rcv_numsacks; i++) { 217 tcp_seq start = tp->sackblks[i].start; 218 tcp_seq end = tp->sackblks[i].end; 219 if (SEQ_GEQ(start, end) || SEQ_LEQ(start, tp->rcv_nxt)) { 220 /* 221 * Discard this SACK block. 222 */ 223 } else if (SEQ_LEQ(head_blk.start, end) && 224 SEQ_GEQ(head_blk.end, start)) { 225 /* 226 * Merge this SACK block into head_blk. 227 * This SACK block itself will be discarded. 228 */ 229 if (SEQ_GT(head_blk.start, start)) 230 head_blk.start = start; 231 if (SEQ_LT(head_blk.end, end)) 232 head_blk.end = end; 233 } else { 234 /* 235 * Save this SACK block. 236 */ 237 saved_blks[num_saved].start = start; 238 saved_blks[num_saved].end = end; 239 num_saved++; 240 } 241 } 242 243 /* 244 * Update SACK list in tp->sackblks[]. 245 */ 246 num_head = 0; 247 if (SEQ_GT(head_blk.start, tp->rcv_nxt)) { 248 /* 249 * The received data segment is an out-of-order segment. 250 * Put head_blk at the top of SACK list. 251 */ 252 tp->sackblks[0] = head_blk; 253 num_head = 1; 254 /* 255 * If the number of saved SACK blocks exceeds its limit, 256 * discard the last SACK block. 257 */ 258 if (num_saved >= MAX_SACK_BLKS) 259 num_saved--; 260 } 261 if (num_saved > 0) { 262 /* 263 * Copy the saved SACK blocks back. 264 */ 265 bcopy(saved_blks, &tp->sackblks[num_head], 266 sizeof(struct sackblk) * num_saved); 267 } 268 269 /* Save the number of SACK blocks. */ 270 tp->rcv_numsacks = num_head + num_saved; 271 } 272 273 /* 274 * Delete all receiver-side SACK information. 275 */ 276 void 277 tcp_clean_sackreport(tp) 278 struct tcpcb *tp; 279 { 280 int i; 281 282 INP_LOCK_ASSERT(tp->t_inpcb); 283 tp->rcv_numsacks = 0; 284 for (i = 0; i < MAX_SACK_BLKS; i++) 285 tp->sackblks[i].start = tp->sackblks[i].end=0; 286 } 287 288 /* 289 * Allocate struct sackhole. 290 */ 291 static struct sackhole * 292 tcp_sackhole_alloc(struct tcpcb *tp, tcp_seq start, tcp_seq end) 293 { 294 struct sackhole *hole; 295 296 if (tp->snd_numholes >= tcp_sack_maxholes || 297 tcp_sack_globalholes >= tcp_sack_globalmaxholes) { 298 tcpstat.tcps_sack_sboverflow++; 299 return NULL; 300 } 301 302 hole = (struct sackhole *)uma_zalloc(sack_hole_zone, M_NOWAIT); 303 if (hole == NULL) 304 return NULL; 305 306 hole->start = start; 307 hole->end = end; 308 hole->rxmit = start; 309 310 tp->snd_numholes++; 311 tcp_sack_globalholes++; 312 313 return hole; 314 } 315 316 /* 317 * Free struct sackhole. 318 */ 319 static void 320 tcp_sackhole_free(struct tcpcb *tp, struct sackhole *hole) 321 { 322 uma_zfree(sack_hole_zone, hole); 323 324 tp->snd_numholes--; 325 tcp_sack_globalholes--; 326 327 KASSERT(tp->snd_numholes >= 0, ("tp->snd_numholes >= 0")); 328 KASSERT(tcp_sack_globalholes >= 0, ("tcp_sack_globalholes >= 0")); 329 } 330 331 /* 332 * Process the TCP SACK option. Returns 1 if tcp_dooptions() should continue, 333 * and 0 otherwise, if the option was fine. tp->snd_holes is an ordered list 334 * of holes (oldest to newest, in terms of the sequence space). 335 */ 336 int 337 tcp_sack_option(struct tcpcb *tp, struct tcphdr *th, u_char *cp, int optlen) 338 { 339 int tmp_olen; 340 u_char *tmp_cp; 341 struct sackhole *cur, *temp; 342 343 INP_LOCK_ASSERT(tp->t_inpcb); 344 if (!tp->sack_enable) 345 return (1); 346 if ((th->th_flags & TH_ACK) == 0) 347 return (1); 348 /* Note: TCPOLEN_SACK must be 2*sizeof(tcp_seq) */ 349 if (optlen <= 2 || (optlen - 2) % TCPOLEN_SACK != 0) 350 return (1); 351 /* If ack is outside [snd_una, snd_max], ignore the SACK options */ 352 if (SEQ_LT(th->th_ack, tp->snd_una) || SEQ_GT(th->th_ack, tp->snd_max)) 353 return (1); 354 tmp_cp = cp + 2; 355 tmp_olen = optlen - 2; 356 tcpstat.tcps_sack_rcv_blocks++; 357 if (tp->t_maxseg == 0) 358 panic("tcp_sack_option"); /* Should never happen */ 359 while (tmp_olen > 0) { 360 struct sackblk sack; 361 362 bcopy(tmp_cp, (char *) &(sack.start), sizeof(tcp_seq)); 363 sack.start = ntohl(sack.start); 364 bcopy(tmp_cp + sizeof(tcp_seq), 365 (char *) &(sack.end), sizeof(tcp_seq)); 366 sack.end = ntohl(sack.end); 367 tmp_olen -= TCPOLEN_SACK; 368 tmp_cp += TCPOLEN_SACK; 369 if (SEQ_LEQ(sack.end, sack.start)) 370 continue; /* bad SACK fields */ 371 if (SEQ_LEQ(sack.end, tp->snd_una)) 372 continue; /* old block */ 373 if (SEQ_GT(th->th_ack, tp->snd_una)) { 374 if (SEQ_LT(sack.start, th->th_ack)) 375 continue; 376 } 377 if (SEQ_GT(sack.end, tp->snd_max)) 378 continue; 379 if (TAILQ_EMPTY(&tp->snd_holes)) { /* first hole */ 380 cur = tcp_sackhole_alloc(tp, th->th_ack, sack.start); 381 if (cur == NULL) { 382 /* ENOBUFS, so ignore SACKed block for now*/ 383 continue; 384 } 385 TAILQ_INSERT_HEAD(&tp->snd_holes, cur, scblink); 386 tp->rcv_lastsack = sack.end; 387 /* Update the sack scoreboard "cache" */ 388 tp->sackhint.nexthole = cur; 389 continue; /* with next sack block */ 390 } 391 /* Go thru list of holes. */ 392 cur = TAILQ_FIRST(&tp->snd_holes); 393 while (cur) { 394 if (SEQ_LEQ(sack.end, cur->start)) 395 /* SACKs data before the current hole */ 396 break; /* no use going through more holes */ 397 if (SEQ_GEQ(sack.start, cur->end)) { 398 /* SACKs data beyond the current hole */ 399 cur = TAILQ_NEXT(cur, scblink); 400 continue; 401 } 402 tp->sackhint.sack_bytes_rexmit -= 403 (cur->rxmit - cur->start); 404 KASSERT(tp->sackhint.sack_bytes_rexmit >= 0, 405 ("sackhint bytes rtx >= 0")); 406 if (SEQ_LEQ(sack.start, cur->start)) { 407 /* Data acks at least the beginning of hole */ 408 if (SEQ_GEQ(sack.end, cur->end)) { 409 /* Acks entire hole, so delete hole */ 410 if (tp->sackhint.nexthole == cur) 411 tp->sackhint.nexthole = 412 TAILQ_NEXT(cur, scblink); 413 temp = cur; 414 cur = TAILQ_NEXT(cur, scblink); 415 TAILQ_REMOVE(&tp->snd_holes, 416 temp, scblink); 417 tcp_sackhole_free(tp, temp); 418 continue; 419 } else { 420 /* Move start of hole forward */ 421 cur->start = sack.end; 422 cur->rxmit = SEQ_MAX(cur->rxmit, cur->start); 423 } 424 } else if (SEQ_GEQ(sack.end, cur->end)) { 425 /* Move end of hole backward */ 426 cur->end = sack.start; 427 cur->rxmit = SEQ_MIN(cur->rxmit, cur->end); 428 } else { 429 /* 430 * ACKs some data in middle of a hole; need to 431 * split current hole 432 */ 433 temp = tcp_sackhole_alloc(tp, sack.end, 434 cur->end); 435 if (temp != NULL) { 436 if (SEQ_GT(cur->rxmit, temp->rxmit)) 437 temp->rxmit = cur->rxmit; 438 TAILQ_INSERT_AFTER(&tp->snd_holes, 439 cur, temp, scblink); 440 cur->end = sack.start; 441 cur->rxmit = SEQ_MIN(cur->rxmit, 442 cur->end); 443 tp->sackhint.sack_bytes_rexmit += 444 (cur->rxmit - cur->start); 445 cur = temp; 446 } 447 } 448 tp->sackhint.sack_bytes_rexmit += 449 (cur->rxmit - cur->start); 450 cur = TAILQ_NEXT(cur, scblink); 451 } 452 /* At this point, we have iterated the whole scoreboard. */ 453 if (SEQ_LT(tp->rcv_lastsack, sack.start)) { 454 /* Need to append new hole at end. */ 455 temp = tcp_sackhole_alloc(tp, tp->rcv_lastsack, 456 sack.start); 457 if (temp == NULL) 458 continue; /* ENOBUFS */ 459 TAILQ_INSERT_TAIL(&tp->snd_holes, temp, scblink); 460 tp->rcv_lastsack = sack.end; 461 if (tp->sackhint.nexthole == NULL) 462 tp->sackhint.nexthole = temp; 463 } 464 if (SEQ_LT(tp->rcv_lastsack, sack.end)) 465 tp->rcv_lastsack = sack.end; 466 } 467 return (0); 468 } 469 470 /* 471 * Delete stale (i.e, cumulatively ack'd) holes. Hole is deleted only if 472 * it is completely acked; otherwise, tcp_sack_option(), called from 473 * tcp_dooptions(), will fix up the hole. 474 */ 475 void 476 tcp_del_sackholes(tp, th) 477 struct tcpcb *tp; 478 struct tcphdr *th; 479 { 480 INP_LOCK_ASSERT(tp->t_inpcb); 481 if (tp->sack_enable && tp->t_state != TCPS_LISTEN) { 482 /* max because this could be an older ack just arrived */ 483 tcp_seq lastack = SEQ_GT(th->th_ack, tp->snd_una) ? 484 th->th_ack : tp->snd_una; 485 struct sackhole *cur = TAILQ_FIRST(&tp->snd_holes); 486 struct sackhole *prev; 487 while (cur) 488 if (SEQ_LEQ(cur->end, lastack)) { 489 prev = cur; 490 tp->sackhint.sack_bytes_rexmit -= 491 (cur->rxmit - cur->start); 492 if (tp->sackhint.nexthole == cur) 493 tp->sackhint.nexthole = 494 TAILQ_NEXT(cur, scblink); 495 cur = TAILQ_NEXT(cur, scblink); 496 TAILQ_REMOVE(&tp->snd_holes, prev, scblink); 497 tcp_sackhole_free(tp, prev); 498 } else if (SEQ_LT(cur->start, lastack)) { 499 if (SEQ_LT(cur->rxmit, lastack)) { 500 tp->sackhint.sack_bytes_rexmit -= 501 (cur->rxmit - cur->start); 502 cur->rxmit = lastack; 503 } else 504 tp->sackhint.sack_bytes_rexmit -= 505 (lastack - cur->start); 506 cur->start = lastack; 507 break; 508 } else 509 break; 510 } 511 } 512 513 void 514 tcp_free_sackholes(struct tcpcb *tp) 515 { 516 struct sackhole *q; 517 518 INP_LOCK_ASSERT(tp->t_inpcb); 519 while ((q = TAILQ_FIRST(&tp->snd_holes)) != NULL) { 520 TAILQ_REMOVE(&tp->snd_holes, q, scblink); 521 tcp_sackhole_free(tp, q); 522 } 523 tp->sackhint.nexthole = NULL; 524 tp->sackhint.sack_bytes_rexmit = 0; 525 526 KASSERT(tp->snd_numholes == 0, ("tp->snd_numholes == 0")); 527 } 528 529 /* 530 * Partial ack handling within a sack recovery episode. 531 * Keeping this very simple for now. When a partial ack 532 * is received, force snd_cwnd to a value that will allow 533 * the sender to transmit no more than 2 segments. 534 * If necessary, a better scheme can be adopted at a 535 * later point, but for now, the goal is to prevent the 536 * sender from bursting a large amount of data in the midst 537 * of sack recovery. 538 */ 539 void 540 tcp_sack_partialack(tp, th) 541 struct tcpcb *tp; 542 struct tcphdr *th; 543 { 544 int num_segs = 1; 545 546 INP_LOCK_ASSERT(tp->t_inpcb); 547 callout_stop(tp->tt_rexmt); 548 tp->t_rtttime = 0; 549 /* send one or 2 segments based on how much new data was acked */ 550 if (((th->th_ack - tp->snd_una) / tp->t_maxseg) > 2) 551 num_segs = 2; 552 tp->snd_cwnd = (tp->sackhint.sack_bytes_rexmit + 553 (tp->snd_nxt - tp->sack_newdata) + 554 num_segs * tp->t_maxseg); 555 if (tp->snd_cwnd > tp->snd_ssthresh) 556 tp->snd_cwnd = tp->snd_ssthresh; 557 tp->t_flags |= TF_ACKNOW; 558 (void) tcp_output(tp); 559 } 560 561 /* 562 * Debug version of tcp_sack_output() that walks the scoreboard. Used for 563 * now to sanity check the hint. 564 */ 565 static struct sackhole * 566 tcp_sack_output_debug(struct tcpcb *tp, int *sack_bytes_rexmt) 567 { 568 struct sackhole *p; 569 570 INP_LOCK_ASSERT(tp->t_inpcb); 571 *sack_bytes_rexmt = 0; 572 TAILQ_FOREACH(p, &tp->snd_holes, scblink) { 573 if (SEQ_LT(p->rxmit, p->end)) { 574 if (SEQ_LT(p->rxmit, tp->snd_una)) {/* old SACK hole */ 575 continue; 576 } 577 *sack_bytes_rexmt += (p->rxmit - p->start); 578 break; 579 } 580 *sack_bytes_rexmt += (p->rxmit - p->start); 581 } 582 return (p); 583 } 584 585 /* 586 * Returns the next hole to retransmit and the number of retransmitted bytes 587 * from the scoreboard. We store both the next hole and the number of 588 * retransmitted bytes as hints (and recompute these on the fly upon SACK/ACK 589 * reception). This avoids scoreboard traversals completely. 590 * 591 * The loop here will traverse *at most* one link. Here's the argument. 592 * For the loop to traverse more than 1 link before finding the next hole to 593 * retransmit, we would need to have at least 1 node following the current hint 594 * with (rxmit == end). But, for all holes following the current hint, 595 * (start == rxmit), since we have not yet retransmitted from them. Therefore, 596 * in order to traverse more 1 link in the loop below, we need to have at least 597 * one node following the current hint with (start == rxmit == end). 598 * But that can't happen, (start == end) means that all the data in that hole 599 * has been sacked, in which case, the hole would have been removed from the 600 * scoreboard. 601 */ 602 struct sackhole * 603 tcp_sack_output(struct tcpcb *tp, int *sack_bytes_rexmt) 604 { 605 struct sackhole *hole = NULL, *dbg_hole = NULL; 606 int dbg_bytes_rexmt; 607 608 INP_LOCK_ASSERT(tp->t_inpcb); 609 dbg_hole = tcp_sack_output_debug(tp, &dbg_bytes_rexmt); 610 *sack_bytes_rexmt = tp->sackhint.sack_bytes_rexmit; 611 hole = tp->sackhint.nexthole; 612 if (hole == NULL || SEQ_LT(hole->rxmit, hole->end)) 613 goto out; 614 while ((hole = TAILQ_NEXT(hole, scblink)) != NULL) { 615 if (SEQ_LT(hole->rxmit, hole->end)) { 616 tp->sackhint.nexthole = hole; 617 break; 618 } 619 } 620 out: 621 if (dbg_hole != hole) { 622 printf("%s: Computed sack hole not the same as cached value\n", __func__); 623 hole = dbg_hole; 624 } 625 if (*sack_bytes_rexmt != dbg_bytes_rexmt) { 626 printf("%s: Computed sack_bytes_retransmitted (%d) not" 627 "the same as cached value (%d)\n", 628 __func__, dbg_bytes_rexmt, *sack_bytes_rexmt); 629 *sack_bytes_rexmt = dbg_bytes_rexmt; 630 } 631 return (hole); 632 } 633 634 /* 635 * After a timeout, the SACK list may be rebuilt. This SACK information 636 * should be used to avoid retransmitting SACKed data. This function 637 * traverses the SACK list to see if snd_nxt should be moved forward. 638 */ 639 void 640 tcp_sack_adjust(struct tcpcb *tp) 641 { 642 struct sackhole *p, *cur = TAILQ_FIRST(&tp->snd_holes); 643 644 INP_LOCK_ASSERT(tp->t_inpcb); 645 if (cur == NULL) 646 return; /* No holes */ 647 if (SEQ_GEQ(tp->snd_nxt, tp->rcv_lastsack)) 648 return; /* We're already beyond any SACKed blocks */ 649 /* 650 * Two cases for which we want to advance snd_nxt: 651 * i) snd_nxt lies between end of one hole and beginning of another 652 * ii) snd_nxt lies between end of last hole and rcv_lastsack 653 */ 654 while ((p = TAILQ_NEXT(cur, scblink)) != NULL) { 655 if (SEQ_LT(tp->snd_nxt, cur->end)) 656 return; 657 if (SEQ_GEQ(tp->snd_nxt, p->start)) 658 cur = p; 659 else { 660 tp->snd_nxt = p->start; 661 return; 662 } 663 } 664 if (SEQ_LT(tp->snd_nxt, cur->end)) 665 return; 666 tp->snd_nxt = tp->rcv_lastsack; 667 return; 668 } 669