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 * Process the TCP SACK option. Returns 1 if tcp_dooptions() should continue, 290 * and 0 otherwise, if the option was fine. tp->snd_holes is an ordered list 291 * of holes (oldest to newest, in terms of the sequence space). 292 */ 293 int 294 tcp_sack_option(struct tcpcb *tp, struct tcphdr *th, u_char *cp, int optlen) 295 { 296 int tmp_olen; 297 u_char *tmp_cp; 298 struct sackhole *cur, *temp; 299 300 INP_LOCK_ASSERT(tp->t_inpcb); 301 if (!tp->sack_enable) 302 return (1); 303 if ((th->th_flags & TH_ACK) == 0) 304 return (1); 305 /* Note: TCPOLEN_SACK must be 2*sizeof(tcp_seq) */ 306 if (optlen <= 2 || (optlen - 2) % TCPOLEN_SACK != 0) 307 return (1); 308 /* If ack is outside [snd_una, snd_max], ignore the SACK options */ 309 if (SEQ_LT(th->th_ack, tp->snd_una) || SEQ_GT(th->th_ack, tp->snd_max)) 310 return (1); 311 tmp_cp = cp + 2; 312 tmp_olen = optlen - 2; 313 tcpstat.tcps_sack_rcv_blocks++; 314 if (tp->snd_numholes < 0) /* XXX panic? */ 315 tp->snd_numholes = 0; 316 if (tp->t_maxseg == 0) 317 panic("tcp_sack_option"); /* Should never happen */ 318 while (tmp_olen > 0) { 319 struct sackblk sack; 320 321 bcopy(tmp_cp, (char *) &(sack.start), sizeof(tcp_seq)); 322 sack.start = ntohl(sack.start); 323 bcopy(tmp_cp + sizeof(tcp_seq), 324 (char *) &(sack.end), sizeof(tcp_seq)); 325 sack.end = ntohl(sack.end); 326 tmp_olen -= TCPOLEN_SACK; 327 tmp_cp += TCPOLEN_SACK; 328 if (SEQ_LEQ(sack.end, sack.start)) 329 continue; /* bad SACK fields */ 330 if (SEQ_LEQ(sack.end, tp->snd_una)) 331 continue; /* old block */ 332 if (SEQ_GT(th->th_ack, tp->snd_una)) { 333 if (SEQ_LT(sack.start, th->th_ack)) 334 continue; 335 } 336 if (SEQ_GT(sack.end, tp->snd_max)) 337 continue; 338 if (TAILQ_EMPTY(&tp->snd_holes)) { /* first hole */ 339 if (tcp_sack_globalholes >= tcp_sack_globalmaxholes || 340 tcp_sack_maxholes == 0) { 341 tcpstat.tcps_sack_sboverflow++; 342 continue; 343 } 344 cur = (struct sackhole *) 345 uma_zalloc(sack_hole_zone,M_NOWAIT); 346 if (cur == NULL) { 347 /* ENOBUFS, so ignore SACKed block for now*/ 348 continue; 349 } 350 cur->start = th->th_ack; 351 cur->end = sack.start; 352 cur->rxmit = cur->start; 353 tp->snd_numholes = 1; 354 tcp_sack_globalholes++; 355 /* Update the sack scoreboard "cache" */ 356 tp->sackhint.nexthole = cur; 357 tp->rcv_lastsack = sack.end; 358 TAILQ_INSERT_HEAD(&tp->snd_holes, cur, scblink); 359 continue; /* with next sack block */ 360 } 361 /* Go thru list of holes. */ 362 cur = TAILQ_FIRST(&tp->snd_holes); 363 while (cur) { 364 if (SEQ_LEQ(sack.end, cur->start)) 365 /* SACKs data before the current hole */ 366 break; /* no use going through more holes */ 367 if (SEQ_GEQ(sack.start, cur->end)) { 368 /* SACKs data beyond the current hole */ 369 cur = TAILQ_NEXT(cur, scblink); 370 continue; 371 } 372 tp->sackhint.sack_bytes_rexmit -= 373 (cur->rxmit - cur->start); 374 KASSERT(tp->sackhint.sack_bytes_rexmit >= 0, 375 ("sackhint bytes rtx >= 0")); 376 if (SEQ_LEQ(sack.start, cur->start)) { 377 /* Data acks at least the beginning of hole */ 378 if (SEQ_GEQ(sack.end, cur->end)) { 379 /* Acks entire hole, so delete hole */ 380 if (tp->sackhint.nexthole == cur) 381 tp->sackhint.nexthole = 382 TAILQ_NEXT(cur, scblink); 383 temp = cur; 384 cur = TAILQ_NEXT(cur, scblink); 385 TAILQ_REMOVE(&tp->snd_holes, 386 temp, scblink); 387 uma_zfree(sack_hole_zone, temp); 388 tp->snd_numholes--; 389 tcp_sack_globalholes--; 390 continue; 391 } else { 392 /* Move start of hole forward */ 393 cur->start = sack.end; 394 cur->rxmit = SEQ_MAX(cur->rxmit, cur->start); 395 } 396 } else if (SEQ_GEQ(sack.end, cur->end)) { 397 /* Move end of hole backward */ 398 cur->end = sack.start; 399 cur->rxmit = SEQ_MIN(cur->rxmit, cur->end); 400 } else { 401 /* 402 * ACKs some data in middle of a hole; need to 403 * split current hole 404 */ 405 if (tp->snd_numholes >= tcp_sack_maxholes || 406 tcp_sack_globalholes >= 407 tcp_sack_globalmaxholes) { 408 tcpstat.tcps_sack_sboverflow++; 409 temp = NULL; 410 } else { 411 temp = (struct sackhole *) 412 uma_zalloc(sack_hole_zone, 413 M_NOWAIT); 414 } 415 if (temp != NULL) { 416 temp->start = sack.end; 417 temp->end = cur->end; 418 temp->rxmit = SEQ_MAX(cur->rxmit, 419 temp->start); 420 cur->end = sack.start; 421 cur->rxmit = SEQ_MIN(cur->rxmit, 422 cur->end); 423 tp->sackhint.sack_bytes_rexmit += 424 (cur->rxmit - cur->start); 425 TAILQ_INSERT_AFTER(&tp->snd_holes, 426 cur, temp, scblink); 427 cur = temp; 428 tp->snd_numholes++; 429 tcp_sack_globalholes++; 430 } 431 } 432 tp->sackhint.sack_bytes_rexmit += 433 (cur->rxmit - cur->start); 434 cur = TAILQ_NEXT(cur, scblink); 435 } 436 /* At this point, we have iterated the whole scoreboard. */ 437 if (SEQ_LT(tp->rcv_lastsack, sack.start)) { 438 /* Need to append new hole at end. */ 439 if (tp->snd_numholes >= tcp_sack_maxholes || 440 tcp_sack_globalholes >= tcp_sack_globalmaxholes) { 441 tcpstat.tcps_sack_sboverflow++; 442 continue; 443 } 444 temp = (struct sackhole *) 445 uma_zalloc(sack_hole_zone,M_NOWAIT); 446 if (temp == NULL) 447 continue; /* ENOBUFS */ 448 temp->start = tp->rcv_lastsack; 449 temp->end = sack.start; 450 temp->rxmit = temp->start; 451 tp->rcv_lastsack = sack.end; 452 tp->snd_numholes++; 453 tcp_sack_globalholes++; 454 TAILQ_INSERT_TAIL(&tp->snd_holes, temp, scblink); 455 if (tp->sackhint.nexthole == NULL) 456 tp->sackhint.nexthole = temp; 457 } 458 if (SEQ_LT(tp->rcv_lastsack, sack.end)) 459 tp->rcv_lastsack = sack.end; 460 } 461 return (0); 462 } 463 464 /* 465 * Delete stale (i.e, cumulatively ack'd) holes. Hole is deleted only if 466 * it is completely acked; otherwise, tcp_sack_option(), called from 467 * tcp_dooptions(), will fix up the hole. 468 */ 469 void 470 tcp_del_sackholes(tp, th) 471 struct tcpcb *tp; 472 struct tcphdr *th; 473 { 474 INP_LOCK_ASSERT(tp->t_inpcb); 475 if (tp->sack_enable && tp->t_state != TCPS_LISTEN) { 476 /* max because this could be an older ack just arrived */ 477 tcp_seq lastack = SEQ_GT(th->th_ack, tp->snd_una) ? 478 th->th_ack : tp->snd_una; 479 struct sackhole *cur = TAILQ_FIRST(&tp->snd_holes); 480 struct sackhole *prev; 481 while (cur) 482 if (SEQ_LEQ(cur->end, lastack)) { 483 prev = cur; 484 tp->sackhint.sack_bytes_rexmit -= 485 (cur->rxmit - cur->start); 486 if (tp->sackhint.nexthole == cur) 487 tp->sackhint.nexthole = 488 TAILQ_NEXT(cur, scblink); 489 cur = TAILQ_NEXT(cur, scblink); 490 TAILQ_REMOVE(&tp->snd_holes, prev, scblink); 491 uma_zfree(sack_hole_zone, prev); 492 tp->snd_numholes--; 493 tcp_sack_globalholes--; 494 } else if (SEQ_LT(cur->start, lastack)) { 495 if (SEQ_LT(cur->rxmit, lastack)) { 496 tp->sackhint.sack_bytes_rexmit -= 497 (cur->rxmit - cur->start); 498 cur->rxmit = lastack; 499 } else 500 tp->sackhint.sack_bytes_rexmit -= 501 (lastack - cur->start); 502 cur->start = lastack; 503 break; 504 } else 505 break; 506 } 507 } 508 509 void 510 tcp_free_sackholes(struct tcpcb *tp) 511 { 512 struct sackhole *q; 513 514 INP_LOCK_ASSERT(tp->t_inpcb); 515 while ((q = TAILQ_FIRST(&tp->snd_holes)) != NULL) { 516 TAILQ_REMOVE(&tp->snd_holes, q, scblink); 517 uma_zfree(sack_hole_zone, q); 518 tcp_sack_globalholes--; 519 } 520 tp->snd_numholes = 0; 521 tp->sackhint.nexthole = NULL; 522 tp->sackhint.sack_bytes_rexmit = 0; 523 } 524 525 /* 526 * Partial ack handling within a sack recovery episode. 527 * Keeping this very simple for now. When a partial ack 528 * is received, force snd_cwnd to a value that will allow 529 * the sender to transmit no more than 2 segments. 530 * If necessary, a better scheme can be adopted at a 531 * later point, but for now, the goal is to prevent the 532 * sender from bursting a large amount of data in the midst 533 * of sack recovery. 534 */ 535 void 536 tcp_sack_partialack(tp, th) 537 struct tcpcb *tp; 538 struct tcphdr *th; 539 { 540 int num_segs = 1; 541 542 INP_LOCK_ASSERT(tp->t_inpcb); 543 callout_stop(tp->tt_rexmt); 544 tp->t_rtttime = 0; 545 /* send one or 2 segments based on how much new data was acked */ 546 if (((th->th_ack - tp->snd_una) / tp->t_maxseg) > 2) 547 num_segs = 2; 548 tp->snd_cwnd = (tp->sackhint.sack_bytes_rexmit + 549 (tp->snd_nxt - tp->sack_newdata) + 550 num_segs * tp->t_maxseg); 551 if (tp->snd_cwnd > tp->snd_ssthresh) 552 tp->snd_cwnd = tp->snd_ssthresh; 553 tp->t_flags |= TF_ACKNOW; 554 (void) tcp_output(tp); 555 } 556 557 /* 558 * Debug version of tcp_sack_output() that walks the scoreboard. Used for 559 * now to sanity check the hint. 560 */ 561 static struct sackhole * 562 tcp_sack_output_debug(struct tcpcb *tp, int *sack_bytes_rexmt) 563 { 564 struct sackhole *p; 565 566 INP_LOCK_ASSERT(tp->t_inpcb); 567 *sack_bytes_rexmt = 0; 568 TAILQ_FOREACH(p, &tp->snd_holes, scblink) { 569 if (SEQ_LT(p->rxmit, p->end)) { 570 if (SEQ_LT(p->rxmit, tp->snd_una)) {/* old SACK hole */ 571 continue; 572 } 573 *sack_bytes_rexmt += (p->rxmit - p->start); 574 break; 575 } 576 *sack_bytes_rexmt += (p->rxmit - p->start); 577 } 578 return (p); 579 } 580 581 /* 582 * Returns the next hole to retransmit and the number of retransmitted bytes 583 * from the scoreboard. We store both the next hole and the number of 584 * retransmitted bytes as hints (and recompute these on the fly upon SACK/ACK 585 * reception). This avoids scoreboard traversals completely. 586 * 587 * The loop here will traverse *at most* one link. Here's the argument. 588 * For the loop to traverse more than 1 link before finding the next hole to 589 * retransmit, we would need to have at least 1 node following the current hint 590 * with (rxmit == end). But, for all holes following the current hint, 591 * (start == rxmit), since we have not yet retransmitted from them. Therefore, 592 * in order to traverse more 1 link in the loop below, we need to have at least 593 * one node following the current hint with (start == rxmit == end). 594 * But that can't happen, (start == end) means that all the data in that hole 595 * has been sacked, in which case, the hole would have been removed from the 596 * scoreboard. 597 */ 598 struct sackhole * 599 tcp_sack_output(struct tcpcb *tp, int *sack_bytes_rexmt) 600 { 601 struct sackhole *hole = NULL, *dbg_hole = NULL; 602 int dbg_bytes_rexmt; 603 604 INP_LOCK_ASSERT(tp->t_inpcb); 605 dbg_hole = tcp_sack_output_debug(tp, &dbg_bytes_rexmt); 606 *sack_bytes_rexmt = tp->sackhint.sack_bytes_rexmit; 607 hole = tp->sackhint.nexthole; 608 if (hole == NULL || SEQ_LT(hole->rxmit, hole->end)) 609 goto out; 610 while ((hole = TAILQ_NEXT(hole, scblink)) != NULL) { 611 if (SEQ_LT(hole->rxmit, hole->end)) { 612 tp->sackhint.nexthole = hole; 613 break; 614 } 615 } 616 out: 617 if (dbg_hole != hole) { 618 printf("%s: Computed sack hole not the same as cached value\n", __func__); 619 hole = dbg_hole; 620 } 621 if (*sack_bytes_rexmt != dbg_bytes_rexmt) { 622 printf("%s: Computed sack_bytes_retransmitted (%d) not" 623 "the same as cached value (%d)\n", 624 __func__, dbg_bytes_rexmt, *sack_bytes_rexmt); 625 *sack_bytes_rexmt = dbg_bytes_rexmt; 626 } 627 return (hole); 628 } 629 630 /* 631 * After a timeout, the SACK list may be rebuilt. This SACK information 632 * should be used to avoid retransmitting SACKed data. This function 633 * traverses the SACK list to see if snd_nxt should be moved forward. 634 */ 635 void 636 tcp_sack_adjust(struct tcpcb *tp) 637 { 638 struct sackhole *p, *cur = TAILQ_FIRST(&tp->snd_holes); 639 640 INP_LOCK_ASSERT(tp->t_inpcb); 641 if (cur == NULL) 642 return; /* No holes */ 643 if (SEQ_GEQ(tp->snd_nxt, tp->rcv_lastsack)) 644 return; /* We're already beyond any SACKed blocks */ 645 /* 646 * Two cases for which we want to advance snd_nxt: 647 * i) snd_nxt lies between end of one hole and beginning of another 648 * ii) snd_nxt lies between end of last hole and rcv_lastsack 649 */ 650 while ((p = TAILQ_NEXT(cur, scblink)) != NULL) { 651 if (SEQ_LT(tp->snd_nxt, cur->end)) 652 return; 653 if (SEQ_GEQ(tp->snd_nxt, p->start)) 654 cur = p; 655 else { 656 tp->snd_nxt = p->start; 657 return; 658 } 659 } 660 if (SEQ_LT(tp->snd_nxt, cur->end)) 661 return; 662 tp->snd_nxt = tp->rcv_lastsack; 663 return; 664 } 665