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: releng/5.4/sys/netinet/tcp_sack.c 155190 2006-02-01 19:43:36Z cperciva $
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 tmp_cp = cp + 2;
305 tmp_olen = optlen - 2;
306 tcpstat.tcps_sack_rcv_blocks++;
307 if (tp->snd_numholes < 0)
308 tp->snd_numholes = 0;
309 if (tp->t_maxseg == 0)
310 panic("tcp_sack_option"); /* Should never happen */
311 next_block:
312 while (tmp_olen > 0) {
313 struct sackblk sack;
314
315 bcopy(tmp_cp, (char *) &(sack.start), sizeof(tcp_seq));
316 sack.start = ntohl(sack.start);
317 bcopy(tmp_cp + sizeof(tcp_seq),
318 (char *) &(sack.end), sizeof(tcp_seq));
319 sack.end = ntohl(sack.end);
320 tmp_olen -= TCPOLEN_SACK;
321 tmp_cp += TCPOLEN_SACK;
322 if (SEQ_LEQ(sack.end, sack.start))
323 continue; /* bad SACK fields */
324 if (SEQ_LEQ(sack.end, tp->snd_una))
325 continue; /* old block */
326 if (SEQ_GT(th->th_ack, tp->snd_una)) {
327 if (SEQ_LT(sack.start, th->th_ack))
328 continue;
329 }
330 if (SEQ_GT(sack.end, tp->snd_max))
331 continue;
332 if (tp->snd_holes == NULL) { /* first hole */
333 tp->snd_holes = (struct sackhole *)
334 uma_zalloc(sack_hole_zone,M_NOWAIT);
335 if (tp->snd_holes == NULL) {
336 /* ENOBUFS, so ignore SACKed block for now*/
337 continue;
338 }
339 cur = tp->snd_holes;
340 cur->start = th->th_ack;
341 cur->end = sack.start;
342 cur->rxmit = cur->start;
343 cur->next = NULL;
344 tp->snd_numholes = 1;
345 tp->rcv_lastsack = sack.end;
346 continue; /* with next sack block */
347 }
348 /* Go thru list of holes: p = previous, cur = current */
349 p = cur = tp->snd_holes;
350 while (cur) {
351 if (SEQ_LEQ(sack.end, cur->start))
352 /* SACKs data before the current hole */
353 break; /* no use going through more holes */
354 if (SEQ_GEQ(sack.start, cur->end)) {
355 /* SACKs data beyond the current hole */
356 p = cur;
357 cur = cur->next;
358 continue;
359 }
360 if (SEQ_LEQ(sack.start, cur->start)) {
361 /* Data acks at least the beginning of hole */
362 if (SEQ_GEQ(sack.end, cur->end)) {
363 /* Acks entire hole, so delete hole */
364 if (p != cur) {
365 p->next = cur->next;
366 uma_zfree(sack_hole_zone, cur);
367 cur = p->next;
368 } else {
369 cur = cur->next;
370 uma_zfree(sack_hole_zone, p);
371 p = cur;
372 tp->snd_holes = p;
373 }
374 tp->snd_numholes--;
375 continue;
376 }
377 /* otherwise, move start of hole forward */
378 cur->start = sack.end;
379 cur->rxmit = SEQ_MAX(cur->rxmit, cur->start);
380 p = cur;
381 cur = cur->next;
382 continue;
383 }
384 /* move end of hole backward */
385 if (SEQ_GEQ(sack.end, cur->end)) {
386 cur->end = sack.start;
387 cur->rxmit = SEQ_MIN(cur->rxmit, cur->end);
388 p = cur;
389 cur = cur->next;
390 continue;
391 }
392 if (SEQ_LT(cur->start, sack.start) &&
393 SEQ_GT(cur->end, sack.end)) {
394 /*
395 * ACKs some data in middle of a hole; need to
396 * split current hole
397 */
398 temp = (struct sackhole *)
399 uma_zalloc(sack_hole_zone,M_NOWAIT);
400 if (temp == NULL)
401 goto next_block; /* ENOBUFS */
402 temp->next = cur->next;
403 temp->start = sack.end;
404 temp->end = cur->end;
405 temp->rxmit = SEQ_MAX(cur->rxmit, temp->start);
406 cur->end = sack.start;
407 cur->rxmit = SEQ_MIN(cur->rxmit, cur->end);
408 cur->next = temp;
409 p = temp;
410 cur = p->next;
411 tp->snd_numholes++;
412 }
413 }
414 /* At this point, p points to the last hole on the list */
415 if (SEQ_LT(tp->rcv_lastsack, sack.start)) {
416 /*
417 * Need to append new hole at end.
418 * Last hole is p (and it's not NULL).
419 */
420 temp = (struct sackhole *)
421 uma_zalloc(sack_hole_zone,M_NOWAIT);
422 if (temp == NULL)
423 continue; /* ENOBUFS */
424 temp->start = tp->rcv_lastsack;
425 temp->end = sack.start;
426 temp->rxmit = temp->start;
427 temp->next = 0;
428 p->next = temp;
429 tp->rcv_lastsack = sack.end;
430 tp->snd_numholes++;
431 }
432 }
433 return (0);
434 }
435
436 /*
437 * Delete stale (i.e, cumulatively ack'd) holes. Hole is deleted only if
438 * it is completely acked; otherwise, tcp_sack_option(), called from
439 * tcp_dooptions(), will fix up the hole.
440 */
441 void
442 tcp_del_sackholes(tp, th)
443 struct tcpcb *tp;
444 struct tcphdr *th;
445 {
446 INP_LOCK_ASSERT(tp->t_inpcb);
447 if (tp->sack_enable && tp->t_state != TCPS_LISTEN) {
448 /* max because this could be an older ack just arrived */
449 tcp_seq lastack = SEQ_GT(th->th_ack, tp->snd_una) ?
450 th->th_ack : tp->snd_una;
451 struct sackhole *cur = tp->snd_holes;
452 struct sackhole *prev;
453 while (cur)
454 if (SEQ_LEQ(cur->end, lastack)) {
455 prev = cur;
456 cur = cur->next;
457 uma_zfree(sack_hole_zone, prev);
458 tp->snd_numholes--;
459 } else if (SEQ_LT(cur->start, lastack)) {
460 cur->start = lastack;
461 if (SEQ_LT(cur->rxmit, cur->start))
462 cur->rxmit = cur->start;
463 break;
464 } else
465 break;
466 tp->snd_holes = cur;
467 }
468 }
469
470 void
471 tcp_free_sackholes(struct tcpcb *tp)
472 {
473 struct sackhole *p, *q;
474
475 INP_LOCK_ASSERT(tp->t_inpcb);
476 q = tp->snd_holes;
477 while (q != NULL) {
478 p = q;
479 q = q->next;
480 uma_zfree(sack_hole_zone, p);
481 }
482 tp->snd_holes = 0;
483 }
484
485 /*
486 * Partial ack handling within a sack recovery episode.
487 * Keeping this very simple for now. When a partial ack
488 * is received, force snd_cwnd to a value that will allow
489 * the sender to transmit no more than 2 segments.
490 * If necessary, a better scheme can be adopted at a
491 * later point, but for now, the goal is to prevent the
492 * sender from bursting a large amount of data in the midst
493 * of sack recovery.
494 */
495 void
496 tcp_sack_partialack(tp, th)
497 struct tcpcb *tp;
498 struct tcphdr *th;
499 {
500 INP_LOCK_ASSERT(tp->t_inpcb);
501 int num_segs = 1;
502 int sack_bytes_rxmt = 0;
503
504 callout_stop(tp->tt_rexmt);
505 tp->t_rtttime = 0;
506 /* send one or 2 segments based on how much new data was acked */
507 if (((th->th_ack - tp->snd_una) / tp->t_maxseg) > 2)
508 num_segs = 2;
509 (void)tcp_sack_output(tp, &sack_bytes_rxmt);
510 tp->snd_cwnd = sack_bytes_rxmt + (tp->snd_nxt - tp->sack_newdata) +
511 num_segs * tp->t_maxseg;
512 tp->t_flags |= TF_ACKNOW;
513 (void) tcp_output(tp);
514 }
515
516 #ifdef TCP_SACK_DEBUG
517 void
518 tcp_print_holes(struct tcpcb *tp)
519 {
520 struct sackhole *p = tp->snd_holes;
521 if (p == 0)
522 return;
523 printf("Hole report: start--end dups rxmit\n");
524 while (p) {
525 printf("%x--%x r %x\n", p->start, p->end, p->rxmit);
526 p = p->next;
527 }
528 printf("\n");
529 }
530 #endif /* TCP_SACK_DEBUG */
531
532 /*
533 * Returns pointer to a sackhole if there are any pending retransmissions;
534 * NULL otherwise.
535 */
536 struct sackhole *
537 tcp_sack_output(struct tcpcb *tp, int *sack_bytes_rexmt)
538 {
539 struct sackhole *p = NULL;
540
541 INP_LOCK_ASSERT(tp->t_inpcb);
542 if (!tp->sack_enable)
543 return (NULL);
544 *sack_bytes_rexmt = 0;
545 for (p = tp->snd_holes; p ; p = p->next) {
546 if (SEQ_LT(p->rxmit, p->end)) {
547 if (SEQ_LT(p->rxmit, tp->snd_una)) {/* old SACK hole */
548 continue;
549 }
550 #ifdef TCP_SACK_DEBUG
551 if (p)
552 tcp_print_holes(tp);
553 #endif
554 *sack_bytes_rexmt += (p->rxmit - p->start);
555 break;
556 }
557 *sack_bytes_rexmt += (p->rxmit - p->start);
558 }
559 return (p);
560 }
561
562 /*
563 * After a timeout, the SACK list may be rebuilt. This SACK information
564 * should be used to avoid retransmitting SACKed data. This function
565 * traverses the SACK list to see if snd_nxt should be moved forward.
566 */
567 void
568 tcp_sack_adjust(struct tcpcb *tp)
569 {
570 INP_LOCK_ASSERT(tp->t_inpcb);
571 struct sackhole *cur = tp->snd_holes;
572 if (cur == NULL)
573 return; /* No holes */
574 if (SEQ_GEQ(tp->snd_nxt, tp->rcv_lastsack))
575 return; /* We're already beyond any SACKed blocks */
576 /*
577 * Two cases for which we want to advance snd_nxt:
578 * i) snd_nxt lies between end of one hole and beginning of another
579 * ii) snd_nxt lies between end of last hole and rcv_lastsack
580 */
581 while (cur->next) {
582 if (SEQ_LT(tp->snd_nxt, cur->end))
583 return;
584 if (SEQ_GEQ(tp->snd_nxt, cur->next->start))
585 cur = cur->next;
586 else {
587 tp->snd_nxt = cur->next->start;
588 return;
589 }
590 }
591 if (SEQ_LT(tp->snd_nxt, cur->end))
592 return;
593 tp->snd_nxt = tp->rcv_lastsack;
594 return;
595 }
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