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 * Insert new SACK hole into scoreboard. 333 */ 334 static struct sackhole * 335 tcp_sackhole_insert(struct tcpcb *tp, tcp_seq start, tcp_seq end, 336 struct sackhole *after) 337 { 338 struct sackhole *hole; 339 340 /* Allocate a new SACK hole. */ 341 hole = tcp_sackhole_alloc(tp, start, end); 342 if (hole == NULL) 343 return NULL; 344 345 /* Insert the new SACK hole into scoreboard */ 346 if (after != NULL) 347 TAILQ_INSERT_AFTER(&tp->snd_holes, after, hole, scblink); 348 else 349 TAILQ_INSERT_TAIL(&tp->snd_holes, hole, scblink); 350 351 /* Update SACK hint. */ 352 if (tp->sackhint.nexthole == NULL) 353 tp->sackhint.nexthole = hole; 354 355 return hole; 356 } 357 358 /* 359 * Remove SACK hole from scoreboard. 360 */ 361 static void 362 tcp_sackhole_remove(struct tcpcb *tp, struct sackhole *hole) 363 { 364 /* Update SACK hint. */ 365 if (tp->sackhint.nexthole == hole) 366 tp->sackhint.nexthole = TAILQ_NEXT(hole, scblink); 367 368 /* Remove this SACK hole. */ 369 TAILQ_REMOVE(&tp->snd_holes, hole, scblink); 370 371 /* Free this SACK hole. */ 372 tcp_sackhole_free(tp, hole); 373 } 374 375 /* 376 * Process the TCP SACK option. Returns 1 if tcp_dooptions() should continue, 377 * and 0 otherwise, if the option was fine. tp->snd_holes is an ordered list 378 * of holes (oldest to newest, in terms of the sequence space). 379 */ 380 int 381 tcp_sack_option(struct tcpcb *tp, struct tcphdr *th, u_char *cp, int optlen) 382 { 383 int tmp_olen; 384 u_char *tmp_cp; 385 struct sackhole *cur, *temp; 386 struct sackblk sack, sack_blocks[TCP_MAX_SACK], *sblkp; 387 int i, j, num_sack_blks; 388 389 INP_LOCK_ASSERT(tp->t_inpcb); 390 if (!tp->sack_enable) 391 return (1); 392 if ((th->th_flags & TH_ACK) == 0) 393 return (1); 394 /* Note: TCPOLEN_SACK must be 2*sizeof(tcp_seq) */ 395 if (optlen <= 2 || (optlen - 2) % TCPOLEN_SACK != 0) 396 return (1); 397 /* If ack is outside [snd_una, snd_max], ignore the SACK options */ 398 if (SEQ_LT(th->th_ack, tp->snd_una) || SEQ_GT(th->th_ack, tp->snd_max)) 399 return (1); 400 tmp_cp = cp + 2; 401 tmp_olen = optlen - 2; 402 tcpstat.tcps_sack_rcv_blocks++; 403 /* 404 * Sort the SACK blocks so we can update the scoreboard 405 * with just one pass. The overhead of sorting upto 4 elements 406 * is less than making upto 4 passes over the scoreboard. 407 */ 408 num_sack_blks = 0; 409 while (tmp_olen > 0) { 410 bcopy(tmp_cp, &sack, sizeof(sack)); 411 sack.start = ntohl(sack.start); 412 sack.end = ntohl(sack.end); 413 if (SEQ_GT(sack.end, sack.start) && 414 SEQ_GT(sack.start, tp->snd_una) && 415 SEQ_GT(sack.start, th->th_ack) && 416 SEQ_LEQ(sack.end, tp->snd_max)) 417 sack_blocks[num_sack_blks++] = sack; 418 tmp_olen -= TCPOLEN_SACK; 419 tmp_cp += TCPOLEN_SACK; 420 } 421 if (num_sack_blks == 0) 422 return 0; 423 /* Bubble sort */ 424 for (i = 0; i < num_sack_blks; i++) { 425 for (j = i + 1; j < num_sack_blks; j++) { 426 if (SEQ_GT(sack_blocks[i].end, sack_blocks[j].end)) { 427 sack = sack_blocks[i]; 428 sack_blocks[i] = sack_blocks[j]; 429 sack_blocks[j] = sack; 430 } 431 } 432 } 433 if (TAILQ_EMPTY(&tp->snd_holes)) 434 /* 435 * Empty scoreboard. Need to initialize snd_fack (it may be 436 * uninitialized or have a bogus value). Scoreboard holes 437 * (from the sack blocks received) are created later below (in 438 * the logic that adds holes to the tail of the scoreboard). 439 */ 440 tp->snd_fack = tp->snd_una; 441 /* 442 * In the while-loop below, incoming SACK blocks (sack_blocks[]) 443 * and SACK holes (snd_holes) are traversed from their tails with 444 * just one pass in order to reduce the number of compares especially 445 * when the bandwidth-delay product is large. 446 * Note: Typically, in the first RTT of SACK recovery, the highest 447 * three or four SACK blocks with the same ack number are received. 448 * In the second RTT, if retransmitted data segments are not lost, 449 * the highest three or four SACK blocks with ack number advancing 450 * are received. 451 */ 452 sblkp = &sack_blocks[num_sack_blks - 1]; /* Last SACK block */ 453 if (SEQ_LT(tp->snd_fack, sblkp->start)) { 454 /* 455 * The highest SACK block is beyond fack. 456 * Append new SACK hole at the tail. 457 * If the second or later highest SACK blocks are also 458 * beyond the current fack, they will be inserted by 459 * way of hole splitting in the while-loop below. 460 */ 461 tcp_sackhole_insert(tp, tp->snd_fack, sblkp->start, NULL); 462 tp->snd_fack = sblkp->end; 463 /* Go to the previous sack block. */ 464 sblkp--; 465 } else if (SEQ_LT(tp->snd_fack, sblkp->end)) 466 /* fack is advanced. */ 467 tp->snd_fack = sblkp->end; 468 cur = TAILQ_LAST(&tp->snd_holes, sackhole_head); /* Last SACK hole */ 469 /* 470 * Since the incoming sack blocks are sorted, we can process them 471 * making one sweep of the scoreboard. 472 */ 473 while (sblkp - sack_blocks >= 0) { 474 KASSERT(cur != NULL, ("cur != NULL")); 475 if (SEQ_GEQ(sblkp->start, cur->end)) { 476 /* 477 * SACKs data beyond the current hole. 478 * Go to the previous sack block. 479 */ 480 sblkp--; 481 continue; 482 } 483 if (SEQ_LEQ(sblkp->end, cur->start)) { 484 /* 485 * SACKs data before the current hole. 486 * Go to the previous hole. 487 */ 488 cur = TAILQ_PREV(cur, sackhole_head, scblink); 489 continue; 490 } 491 tp->sackhint.sack_bytes_rexmit -= (cur->rxmit - cur->start); 492 KASSERT(tp->sackhint.sack_bytes_rexmit >= 0, 493 ("sackhint bytes rtx >= 0")); 494 if (SEQ_LEQ(sblkp->start, cur->start)) { 495 /* Data acks at least the beginning of hole */ 496 if (SEQ_GEQ(sblkp->end, cur->end)) { 497 /* Acks entire hole, so delete hole */ 498 temp = cur; 499 cur = TAILQ_PREV(cur, sackhole_head, scblink); 500 tcp_sackhole_remove(tp, temp); 501 /* 502 * The sack block may ack all or part of the next 503 * hole too, so continue onto the next hole. 504 */ 505 continue; 506 } else { 507 /* Move start of hole forward */ 508 cur->start = sblkp->end; 509 cur->rxmit = SEQ_MAX(cur->rxmit, cur->start); 510 } 511 /* Go to the previous hole. */ 512 cur = TAILQ_PREV(cur, sackhole_head, scblink); 513 } else { 514 /* Data acks at least the end of hole */ 515 if (SEQ_GEQ(sblkp->end, cur->end)) { 516 /* Move end of hole backward */ 517 cur->end = sblkp->start; 518 cur->rxmit = SEQ_MIN(cur->rxmit, cur->end); 519 } else { 520 /* 521 * ACKs some data in middle of a hole; need to 522 * split current hole 523 */ 524 temp = tcp_sackhole_insert(tp, sblkp->end, 525 cur->end, cur); 526 if (temp != NULL) { 527 if (SEQ_GT(cur->rxmit, temp->rxmit)) { 528 temp->rxmit = cur->rxmit; 529 tp->sackhint.sack_bytes_rexmit 530 += (temp->rxmit 531 - temp->start); 532 } 533 cur->end = sblkp->start; 534 cur->rxmit = SEQ_MIN(cur->rxmit, 535 cur->end); 536 } 537 } 538 /* Go to the previous sack block. */ 539 sblkp--; 540 } 541 tp->sackhint.sack_bytes_rexmit += (cur->rxmit - cur->start); 542 } 543 return (0); 544 } 545 546 /* 547 * Delete stale (i.e, cumulatively ack'd) holes. Hole is deleted only if 548 * it is completely acked; otherwise, tcp_sack_option(), called from 549 * tcp_dooptions(), will fix up the hole. 550 */ 551 void 552 tcp_del_sackholes(tp, th) 553 struct tcpcb *tp; 554 struct tcphdr *th; 555 { 556 INP_LOCK_ASSERT(tp->t_inpcb); 557 if (tp->sack_enable && tp->t_state != TCPS_LISTEN) { 558 /* max because this could be an older ack just arrived */ 559 tcp_seq lastack = SEQ_GT(th->th_ack, tp->snd_una) ? 560 th->th_ack : tp->snd_una; 561 struct sackhole *cur = TAILQ_FIRST(&tp->snd_holes); 562 struct sackhole *prev; 563 while (cur) 564 if (SEQ_LEQ(cur->end, lastack)) { 565 prev = cur; 566 cur = TAILQ_NEXT(cur, scblink); 567 tp->sackhint.sack_bytes_rexmit -= 568 (prev->rxmit - prev->start); 569 tcp_sackhole_remove(tp, prev); 570 } else if (SEQ_LT(cur->start, lastack)) { 571 if (SEQ_LT(cur->rxmit, lastack)) { 572 tp->sackhint.sack_bytes_rexmit -= 573 (cur->rxmit - cur->start); 574 cur->rxmit = lastack; 575 } else 576 tp->sackhint.sack_bytes_rexmit -= 577 (lastack - cur->start); 578 cur->start = lastack; 579 break; 580 } else 581 break; 582 } 583 } 584 585 void 586 tcp_free_sackholes(struct tcpcb *tp) 587 { 588 struct sackhole *q; 589 590 INP_LOCK_ASSERT(tp->t_inpcb); 591 while ((q = TAILQ_FIRST(&tp->snd_holes)) != NULL) 592 tcp_sackhole_remove(tp, q); 593 tp->sackhint.sack_bytes_rexmit = 0; 594 595 KASSERT(tp->snd_numholes == 0, ("tp->snd_numholes == 0")); 596 KASSERT(tp->sackhint.nexthole == NULL, 597 ("tp->sackhint.nexthole == NULL")); 598 } 599 600 /* 601 * Partial ack handling within a sack recovery episode. 602 * Keeping this very simple for now. When a partial ack 603 * is received, force snd_cwnd to a value that will allow 604 * the sender to transmit no more than 2 segments. 605 * If necessary, a better scheme can be adopted at a 606 * later point, but for now, the goal is to prevent the 607 * sender from bursting a large amount of data in the midst 608 * of sack recovery. 609 */ 610 void 611 tcp_sack_partialack(tp, th) 612 struct tcpcb *tp; 613 struct tcphdr *th; 614 { 615 int num_segs = 1; 616 617 INP_LOCK_ASSERT(tp->t_inpcb); 618 callout_stop(tp->tt_rexmt); 619 tp->t_rtttime = 0; 620 /* send one or 2 segments based on how much new data was acked */ 621 if (((th->th_ack - tp->snd_una) / tp->t_maxseg) > 2) 622 num_segs = 2; 623 tp->snd_cwnd = (tp->sackhint.sack_bytes_rexmit + 624 (tp->snd_nxt - tp->sack_newdata) + 625 num_segs * tp->t_maxseg); 626 if (tp->snd_cwnd > tp->snd_ssthresh) 627 tp->snd_cwnd = tp->snd_ssthresh; 628 tp->t_flags |= TF_ACKNOW; 629 (void) tcp_output(tp); 630 } 631 632 /* 633 * Debug version of tcp_sack_output() that walks the scoreboard. Used for 634 * now to sanity check the hint. 635 */ 636 static struct sackhole * 637 tcp_sack_output_debug(struct tcpcb *tp, int *sack_bytes_rexmt) 638 { 639 struct sackhole *p; 640 641 INP_LOCK_ASSERT(tp->t_inpcb); 642 *sack_bytes_rexmt = 0; 643 TAILQ_FOREACH(p, &tp->snd_holes, scblink) { 644 if (SEQ_LT(p->rxmit, p->end)) { 645 if (SEQ_LT(p->rxmit, tp->snd_una)) {/* old SACK hole */ 646 continue; 647 } 648 *sack_bytes_rexmt += (p->rxmit - p->start); 649 break; 650 } 651 *sack_bytes_rexmt += (p->rxmit - p->start); 652 } 653 return (p); 654 } 655 656 /* 657 * Returns the next hole to retransmit and the number of retransmitted bytes 658 * from the scoreboard. We store both the next hole and the number of 659 * retransmitted bytes as hints (and recompute these on the fly upon SACK/ACK 660 * reception). This avoids scoreboard traversals completely. 661 * 662 * The loop here will traverse *at most* one link. Here's the argument. 663 * For the loop to traverse more than 1 link before finding the next hole to 664 * retransmit, we would need to have at least 1 node following the current hint 665 * with (rxmit == end). But, for all holes following the current hint, 666 * (start == rxmit), since we have not yet retransmitted from them. Therefore, 667 * in order to traverse more 1 link in the loop below, we need to have at least 668 * one node following the current hint with (start == rxmit == end). 669 * But that can't happen, (start == end) means that all the data in that hole 670 * has been sacked, in which case, the hole would have been removed from the 671 * scoreboard. 672 */ 673 struct sackhole * 674 tcp_sack_output(struct tcpcb *tp, int *sack_bytes_rexmt) 675 { 676 struct sackhole *hole = NULL, *dbg_hole = NULL; 677 int dbg_bytes_rexmt; 678 679 INP_LOCK_ASSERT(tp->t_inpcb); 680 dbg_hole = tcp_sack_output_debug(tp, &dbg_bytes_rexmt); 681 *sack_bytes_rexmt = tp->sackhint.sack_bytes_rexmit; 682 hole = tp->sackhint.nexthole; 683 if (hole == NULL || SEQ_LT(hole->rxmit, hole->end)) 684 goto out; 685 while ((hole = TAILQ_NEXT(hole, scblink)) != NULL) { 686 if (SEQ_LT(hole->rxmit, hole->end)) { 687 tp->sackhint.nexthole = hole; 688 break; 689 } 690 } 691 out: 692 if (dbg_hole != hole) { 693 printf("%s: Computed sack hole not the same as cached value\n", __func__); 694 hole = dbg_hole; 695 } 696 if (*sack_bytes_rexmt != dbg_bytes_rexmt) { 697 printf("%s: Computed sack_bytes_retransmitted (%d) not " 698 "the same as cached value (%d)\n", 699 __func__, dbg_bytes_rexmt, *sack_bytes_rexmt); 700 *sack_bytes_rexmt = dbg_bytes_rexmt; 701 } 702 return (hole); 703 } 704 705 /* 706 * After a timeout, the SACK list may be rebuilt. This SACK information 707 * should be used to avoid retransmitting SACKed data. This function 708 * traverses the SACK list to see if snd_nxt should be moved forward. 709 */ 710 void 711 tcp_sack_adjust(struct tcpcb *tp) 712 { 713 struct sackhole *p, *cur = TAILQ_FIRST(&tp->snd_holes); 714 715 INP_LOCK_ASSERT(tp->t_inpcb); 716 if (cur == NULL) 717 return; /* No holes */ 718 if (SEQ_GEQ(tp->snd_nxt, tp->snd_fack)) 719 return; /* We're already beyond any SACKed blocks */ 720 /* 721 * Two cases for which we want to advance snd_nxt: 722 * i) snd_nxt lies between end of one hole and beginning of another 723 * ii) snd_nxt lies between end of last hole and snd_fack 724 */ 725 while ((p = TAILQ_NEXT(cur, scblink)) != NULL) { 726 if (SEQ_LT(tp->snd_nxt, cur->end)) 727 return; 728 if (SEQ_GEQ(tp->snd_nxt, p->start)) 729 cur = p; 730 else { 731 tp->snd_nxt = p->start; 732 return; 733 } 734 } 735 if (SEQ_LT(tp->snd_nxt, cur->end)) 736 return; 737 tp->snd_nxt = tp->snd_fack; 738 return; 739 } 740