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> 148 149 u_char tcp_saveipgen[40]; /* the size must be of max ip header, now IPv6 */ 150 struct tcphdr tcp_savetcp; 151 #endif /* TCPDEBUG */ 152 153 #ifdef FAST_IPSEC 154 #include <netipsec/ipsec.h> 155 #include <netipsec/ipsec6.h> 156 #endif 157 158 #ifdef IPSEC 159 #include <netinet6/ipsec.h> 160 #include <netinet6/ipsec6.h> 161 #include <netkey/key.h> 162 #endif /*IPSEC*/ 163 #include <machine/in_cksum.h> 164 165 extern struct uma_zone *sack_hole_zone; 166 167 SYSCTL_NODE(_net_inet_tcp, OID_AUTO, sack, CTLFLAG_RW, 0, "TCP SACK"); 168 int tcp_do_sack = 1; 169 SYSCTL_INT(_net_inet_tcp_sack, OID_AUTO, enable, CTLFLAG_RW, 170 &tcp_do_sack, 0, "Enable/Disable TCP SACK support"); 171 TUNABLE_INT("net.inet.tcp.sack.enable", &tcp_do_sack); 172 173 /* 174 * This function is called upon receipt of new valid data (while not in header 175 * prediction mode), and it updates the ordered list of sacks. 176 */ 177 void 178 tcp_update_sack_list(tp, rcv_laststart, rcv_lastend) 179 struct tcpcb *tp; 180 tcp_seq rcv_laststart, rcv_lastend; 181 { 182 /* 183 * First reported block MUST be the most recent one. Subsequent 184 * blocks SHOULD be in the order in which they arrived at the 185 * receiver. These two conditions make the implementation fully 186 * compliant with RFC 2018. 187 */ 188 int i, j = 0, count = 0, lastpos = -1; 189 struct sackblk sack, firstsack, temp[MAX_SACK_BLKS]; 190 191 INP_LOCK_ASSERT(tp->t_inpcb); 192 /* First clean up current list of sacks */ 193 for (i = 0; i < tp->rcv_numsacks; i++) { 194 sack = tp->sackblks[i]; 195 if (sack.start == 0 && sack.end == 0) { 196 count++; /* count = number of blocks to be discarded */ 197 continue; 198 } 199 if (SEQ_LEQ(sack.end, tp->rcv_nxt)) { 200 tp->sackblks[i].start = tp->sackblks[i].end = 0; 201 count++; 202 } else { 203 temp[j].start = tp->sackblks[i].start; 204 temp[j++].end = tp->sackblks[i].end; 205 } 206 } 207 tp->rcv_numsacks -= count; 208 if (tp->rcv_numsacks == 0) { /* no sack blocks currently (fast path) */ 209 tcp_clean_sackreport(tp); 210 if (SEQ_LT(tp->rcv_nxt, rcv_laststart)) { 211 /* ==> need first sack block */ 212 tp->sackblks[0].start = rcv_laststart; 213 tp->sackblks[0].end = rcv_lastend; 214 tp->rcv_numsacks = 1; 215 } 216 return; 217 } 218 /* Otherwise, sack blocks are already present. */ 219 for (i = 0; i < tp->rcv_numsacks; i++) 220 tp->sackblks[i] = temp[i]; /* first copy back sack list */ 221 if (SEQ_GEQ(tp->rcv_nxt, rcv_lastend)) 222 return; /* sack list remains unchanged */ 223 /* 224 * From here, segment just received should be (part of) the 1st sack. 225 * Go through list, possibly coalescing sack block entries. 226 */ 227 firstsack.start = rcv_laststart; 228 firstsack.end = rcv_lastend; 229 for (i = 0; i < tp->rcv_numsacks; i++) { 230 sack = tp->sackblks[i]; 231 if (SEQ_LT(sack.end, firstsack.start) || 232 SEQ_GT(sack.start, firstsack.end)) 233 continue; /* no overlap */ 234 if (sack.start == firstsack.start && sack.end == firstsack.end){ 235 /* 236 * identical block; delete it here since we will 237 * move it to the front of the list. 238 */ 239 tp->sackblks[i].start = tp->sackblks[i].end = 0; 240 lastpos = i; /* last posn with a zero entry */ 241 continue; 242 } 243 if (SEQ_LEQ(sack.start, firstsack.start)) 244 firstsack.start = sack.start; /* merge blocks */ 245 if (SEQ_GEQ(sack.end, firstsack.end)) 246 firstsack.end = sack.end; /* merge blocks */ 247 tp->sackblks[i].start = tp->sackblks[i].end = 0; 248 lastpos = i; /* last posn with a zero entry */ 249 } 250 if (lastpos != -1) { /* at least one merge */ 251 for (i = 0, j = 1; i < tp->rcv_numsacks; i++) { 252 sack = tp->sackblks[i]; 253 if (sack.start == 0 && sack.end == 0) 254 continue; 255 temp[j++] = sack; 256 } 257 tp->rcv_numsacks = j; /* including first blk (added later) */ 258 for (i = 1; i < tp->rcv_numsacks; i++) /* now copy back */ 259 tp->sackblks[i] = temp[i]; 260 } else { /* no merges -- shift sacks by 1 */ 261 if (tp->rcv_numsacks < MAX_SACK_BLKS) 262 tp->rcv_numsacks++; 263 for (i = tp->rcv_numsacks-1; i > 0; i--) 264 tp->sackblks[i] = tp->sackblks[i-1]; 265 } 266 tp->sackblks[0] = firstsack; 267 return; 268 } 269 270 /* 271 * Delete all receiver-side SACK information. 272 */ 273 void 274 tcp_clean_sackreport(tp) 275 struct tcpcb *tp; 276 { 277 int i; 278 279 INP_LOCK_ASSERT(tp->t_inpcb); 280 tp->rcv_numsacks = 0; 281 for (i = 0; i < MAX_SACK_BLKS; i++) 282 tp->sackblks[i].start = tp->sackblks[i].end=0; 283 } 284 285 /* 286 * Process the TCP SACK option. Returns 1 if tcp_dooptions() should continue, 287 * and 0 otherwise, if the option was fine. tp->snd_holes is an ordered list 288 * of holes (oldest to newest, in terms of the sequence space). 289 */ 290 int 291 tcp_sack_option(struct tcpcb *tp, struct tcphdr *th, u_char *cp, int optlen) 292 { 293 int tmp_olen; 294 u_char *tmp_cp; 295 struct sackhole *cur, *p, *temp; 296 297 INP_LOCK_ASSERT(tp->t_inpcb); 298 if (!tp->sack_enable) 299 return (1); 300 301 /* Note: TCPOLEN_SACK must be 2*sizeof(tcp_seq) */ 302 if (optlen <= 2 || (optlen - 2) % TCPOLEN_SACK != 0) 303 return (1); 304 /* If ack is outside window, ignore the SACK options */ 305 if (SEQ_LT(th->th_ack, tp->snd_una) || SEQ_GT(th->th_ack, tp->snd_max)) 306 return (1); 307 tmp_cp = cp + 2; 308 tmp_olen = optlen - 2; 309 tcpstat.tcps_sack_rcv_blocks++; 310 if (tp->snd_numholes < 0) 311 tp->snd_numholes = 0; 312 if (tp->t_maxseg == 0) 313 panic("tcp_sack_option"); /* Should never happen */ 314 while (tmp_olen > 0) { 315 struct sackblk sack; 316 317 bcopy(tmp_cp, (char *) &(sack.start), sizeof(tcp_seq)); 318 sack.start = ntohl(sack.start); 319 bcopy(tmp_cp + sizeof(tcp_seq), 320 (char *) &(sack.end), sizeof(tcp_seq)); 321 sack.end = ntohl(sack.end); 322 tmp_olen -= TCPOLEN_SACK; 323 tmp_cp += TCPOLEN_SACK; 324 if (SEQ_LEQ(sack.end, sack.start)) 325 continue; /* bad SACK fields */ 326 if (SEQ_LEQ(sack.end, tp->snd_una)) 327 continue; /* old block */ 328 if (SEQ_GT(th->th_ack, tp->snd_una)) { 329 if (SEQ_LT(sack.start, th->th_ack)) 330 continue; 331 } 332 if (SEQ_GT(sack.end, tp->snd_max)) 333 continue; 334 if (tp->snd_holes == NULL) { /* first hole */ 335 tp->snd_holes = (struct sackhole *) 336 uma_zalloc(sack_hole_zone,M_NOWAIT); 337 if (tp->snd_holes == NULL) { 338 /* ENOBUFS, so ignore SACKed block for now*/ 339 continue; 340 } 341 cur = tp->snd_holes; 342 cur->start = th->th_ack; 343 cur->end = sack.start; 344 cur->rxmit = cur->start; 345 cur->next = NULL; 346 tp->snd_numholes = 1; 347 tp->rcv_lastsack = sack.end; 348 continue; /* with next sack block */ 349 } 350 /* Go thru list of holes: p = previous, cur = current */ 351 p = cur = tp->snd_holes; 352 while (cur) { 353 if (SEQ_LEQ(sack.end, cur->start)) 354 /* SACKs data before the current hole */ 355 break; /* no use going through more holes */ 356 if (SEQ_GEQ(sack.start, cur->end)) { 357 /* SACKs data beyond the current hole */ 358 p = cur; 359 cur = cur->next; 360 continue; 361 } 362 if (SEQ_LEQ(sack.start, cur->start)) { 363 /* Data acks at least the beginning of hole */ 364 if (SEQ_GEQ(sack.end, cur->end)) { 365 /* Acks entire hole, so delete hole */ 366 if (p != cur) { 367 p->next = cur->next; 368 uma_zfree(sack_hole_zone, cur); 369 cur = p->next; 370 } else { 371 cur = cur->next; 372 uma_zfree(sack_hole_zone, p); 373 p = cur; 374 tp->snd_holes = p; 375 } 376 tp->snd_numholes--; 377 continue; 378 } 379 /* otherwise, move start of hole forward */ 380 cur->start = sack.end; 381 cur->rxmit = SEQ_MAX(cur->rxmit, cur->start); 382 p = cur; 383 cur = cur->next; 384 continue; 385 } 386 /* move end of hole backward */ 387 if (SEQ_GEQ(sack.end, cur->end)) { 388 cur->end = sack.start; 389 cur->rxmit = SEQ_MIN(cur->rxmit, cur->end); 390 p = cur; 391 cur = cur->next; 392 continue; 393 } 394 if (SEQ_LT(cur->start, sack.start) && 395 SEQ_GT(cur->end, sack.end)) { 396 /* 397 * ACKs some data in middle of a hole; need to 398 * split current hole 399 */ 400 temp = (struct sackhole *) 401 uma_zalloc(sack_hole_zone,M_NOWAIT); 402 if (temp == NULL) 403 continue; /* ENOBUFS */ 404 temp->next = cur->next; 405 temp->start = sack.end; 406 temp->end = cur->end; 407 temp->rxmit = SEQ_MAX(cur->rxmit, temp->start); 408 cur->end = sack.start; 409 cur->rxmit = SEQ_MIN(cur->rxmit, cur->end); 410 cur->next = temp; 411 p = temp; 412 cur = p->next; 413 tp->snd_numholes++; 414 } 415 } 416 /* At this point, p points to the last hole on the list */ 417 if (SEQ_LT(tp->rcv_lastsack, sack.start)) { 418 /* 419 * Need to append new hole at end. 420 * Last hole is p (and it's not NULL). 421 */ 422 temp = (struct sackhole *) 423 uma_zalloc(sack_hole_zone,M_NOWAIT); 424 if (temp == NULL) 425 continue; /* ENOBUFS */ 426 temp->start = tp->rcv_lastsack; 427 temp->end = sack.start; 428 temp->rxmit = temp->start; 429 temp->next = 0; 430 p->next = temp; 431 tp->rcv_lastsack = sack.end; 432 tp->snd_numholes++; 433 } 434 } 435 return (0); 436 } 437 438 /* 439 * Delete stale (i.e, cumulatively ack'd) holes. Hole is deleted only if 440 * it is completely acked; otherwise, tcp_sack_option(), called from 441 * tcp_dooptions(), will fix up the hole. 442 */ 443 void 444 tcp_del_sackholes(tp, th) 445 struct tcpcb *tp; 446 struct tcphdr *th; 447 { 448 INP_LOCK_ASSERT(tp->t_inpcb); 449 if (tp->sack_enable && tp->t_state != TCPS_LISTEN) { 450 /* max because this could be an older ack just arrived */ 451 tcp_seq lastack = SEQ_GT(th->th_ack, tp->snd_una) ? 452 th->th_ack : tp->snd_una; 453 struct sackhole *cur = tp->snd_holes; 454 struct sackhole *prev; 455 while (cur) 456 if (SEQ_LEQ(cur->end, lastack)) { 457 prev = cur; 458 cur = cur->next; 459 uma_zfree(sack_hole_zone, prev); 460 tp->snd_numholes--; 461 } else if (SEQ_LT(cur->start, lastack)) { 462 cur->start = lastack; 463 if (SEQ_LT(cur->rxmit, cur->start)) 464 cur->rxmit = cur->start; 465 break; 466 } else 467 break; 468 tp->snd_holes = cur; 469 } 470 } 471 472 void 473 tcp_free_sackholes(struct tcpcb *tp) 474 { 475 struct sackhole *p, *q; 476 477 INP_LOCK_ASSERT(tp->t_inpcb); 478 q = tp->snd_holes; 479 while (q != NULL) { 480 p = q; 481 q = q->next; 482 uma_zfree(sack_hole_zone, p); 483 } 484 tp->snd_holes = 0; 485 } 486 487 /* 488 * Partial ack handling within a sack recovery episode. 489 * Keeping this very simple for now. When a partial ack 490 * is received, force snd_cwnd to a value that will allow 491 * the sender to transmit no more than 2 segments. 492 * If necessary, a better scheme can be adopted at a 493 * later point, but for now, the goal is to prevent the 494 * sender from bursting a large amount of data in the midst 495 * of sack recovery. 496 */ 497 void 498 tcp_sack_partialack(tp, th) 499 struct tcpcb *tp; 500 struct tcphdr *th; 501 { 502 INP_LOCK_ASSERT(tp->t_inpcb); 503 int num_segs = 1; 504 int sack_bytes_rxmt = 0; 505 506 callout_stop(tp->tt_rexmt); 507 tp->t_rtttime = 0; 508 /* send one or 2 segments based on how much new data was acked */ 509 if (((th->th_ack - tp->snd_una) / tp->t_maxseg) > 2) 510 num_segs = 2; 511 (void)tcp_sack_output(tp, &sack_bytes_rxmt); 512 tp->snd_cwnd = sack_bytes_rxmt + (tp->snd_nxt - tp->sack_newdata) + 513 num_segs * tp->t_maxseg; 514 tp->t_flags |= TF_ACKNOW; 515 (void) tcp_output(tp); 516 } 517 518 #ifdef TCP_SACK_DEBUG 519 void 520 tcp_print_holes(struct tcpcb *tp) 521 { 522 struct sackhole *p = tp->snd_holes; 523 if (p == 0) 524 return; 525 printf("Hole report: start--end dups rxmit\n"); 526 while (p) { 527 printf("%x--%x r %x\n", p->start, p->end, p->rxmit); 528 p = p->next; 529 } 530 printf("\n"); 531 } 532 #endif /* TCP_SACK_DEBUG */ 533 534 /* 535 * Returns pointer to a sackhole if there are any pending retransmissions; 536 * NULL otherwise. 537 */ 538 struct sackhole * 539 tcp_sack_output(struct tcpcb *tp, int *sack_bytes_rexmt) 540 { 541 struct sackhole *p = NULL; 542 543 INP_LOCK_ASSERT(tp->t_inpcb); 544 if (!tp->sack_enable) 545 return (NULL); 546 *sack_bytes_rexmt = 0; 547 for (p = tp->snd_holes; p ; p = p->next) { 548 if (SEQ_LT(p->rxmit, p->end)) { 549 if (SEQ_LT(p->rxmit, tp->snd_una)) {/* old SACK hole */ 550 continue; 551 } 552 #ifdef TCP_SACK_DEBUG 553 if (p) 554 tcp_print_holes(tp); 555 #endif 556 *sack_bytes_rexmt += (p->rxmit - p->start); 557 break; 558 } 559 *sack_bytes_rexmt += (p->rxmit - p->start); 560 } 561 return (p); 562 } 563 564 /* 565 * After a timeout, the SACK list may be rebuilt. This SACK information 566 * should be used to avoid retransmitting SACKed data. This function 567 * traverses the SACK list to see if snd_nxt should be moved forward. 568 */ 569 void 570 tcp_sack_adjust(struct tcpcb *tp) 571 { 572 INP_LOCK_ASSERT(tp->t_inpcb); 573 struct sackhole *cur = tp->snd_holes; 574 if (cur == NULL) 575 return; /* No holes */ 576 if (SEQ_GEQ(tp->snd_nxt, tp->rcv_lastsack)) 577 return; /* We're already beyond any SACKed blocks */ 578 /* 579 * Two cases for which we want to advance snd_nxt: 580 * i) snd_nxt lies between end of one hole and beginning of another 581 * ii) snd_nxt lies between end of last hole and rcv_lastsack 582 */ 583 while (cur->next) { 584 if (SEQ_LT(tp->snd_nxt, cur->end)) 585 return; 586 if (SEQ_GEQ(tp->snd_nxt, cur->next->start)) 587 cur = cur->next; 588 else { 589 tp->snd_nxt = cur->next->start; 590 return; 591 } 592 } 593 if (SEQ_LT(tp->snd_nxt, cur->end)) 594 return; 595 tp->snd_nxt = tp->rcv_lastsack; 596 return; 597 } 598