1 /*-
2 * SPDX-License-Identifier: BSD-3-Clause
3 *
4 * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1994, 1995
5 * The Regents of the University of California.
6 * All rights reserved.
7 *
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
10 * are met:
11 * 1. Redistributions of source code must retain the above copyright
12 * notice, this list of conditions and the following disclaimer.
13 * 2. Redistributions in binary form must reproduce the above copyright
14 * notice, this list of conditions and the following disclaimer in the
15 * documentation and/or other materials provided with the distribution.
16 * 3. Neither the name of the University nor the names of its contributors
17 * may be used to endorse or promote products derived from this software
18 * without specific prior written permission.
19 *
20 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
21 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
22 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
23 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
24 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
25 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
26 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
27 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
28 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
29 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
30 * SUCH DAMAGE.
31 *
32 * @(#)tcp_sack.c 8.12 (Berkeley) 5/24/95
33 */
34
35 /*-
36 * @@(#)COPYRIGHT 1.1 (NRL) 17 January 1995
37 *
38 * NRL grants permission for redistribution and use in source and binary
39 * forms, with or without modification, of the software and documentation
40 * created at NRL provided that the following conditions are met:
41 *
42 * 1. Redistributions of source code must retain the above copyright
43 * notice, this list of conditions and the following disclaimer.
44 * 2. Redistributions in binary form must reproduce the above copyright
45 * notice, this list of conditions and the following disclaimer in the
46 * documentation and/or other materials provided with the distribution.
47 * 3. All advertising materials mentioning features or use of this software
48 * must display the following acknowledgements:
49 * This product includes software developed by the University of
50 * California, Berkeley and its contributors.
51 * This product includes software developed at the Information
52 * Technology Division, US Naval Research Laboratory.
53 * 4. Neither the name of the NRL nor the names of its contributors
54 * may be used to endorse or promote products derived from this software
55 * without specific prior written permission.
56 *
57 * THE SOFTWARE PROVIDED BY NRL IS PROVIDED BY NRL AND CONTRIBUTORS ``AS
58 * IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
59 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
60 * PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL NRL OR
61 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
62 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
63 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
64 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
65 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
66 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
67 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
68 *
69 * The views and conclusions contained in the software and documentation
70 * are those of the authors and should not be interpreted as representing
71 * official policies, either expressed or implied, of the US Naval
72 * Research Laboratory (NRL).
73 */
74
75 #include <sys/cdefs.h>
76 __FBSDID("$FreeBSD$");
77
78 #include "opt_inet.h"
79 #include "opt_inet6.h"
80 #include "opt_tcpdebug.h"
81
82 #include <sys/param.h>
83 #include <sys/systm.h>
84 #include <sys/kernel.h>
85 #include <sys/sysctl.h>
86 #include <sys/malloc.h>
87 #include <sys/mbuf.h>
88 #include <sys/proc.h> /* for proc0 declaration */
89 #include <sys/protosw.h>
90 #include <sys/socket.h>
91 #include <sys/socketvar.h>
92 #include <sys/syslog.h>
93 #include <sys/systm.h>
94
95 #include <machine/cpu.h> /* before tcp_seq.h, for tcp_random18() */
96
97 #include <vm/uma.h>
98
99 #include <net/if.h>
100 #include <net/if_var.h>
101 #include <net/route.h>
102 #include <net/vnet.h>
103
104 #include <netinet/in.h>
105 #include <netinet/in_systm.h>
106 #include <netinet/ip.h>
107 #include <netinet/in_var.h>
108 #include <netinet/in_pcb.h>
109 #include <netinet/ip_var.h>
110 #include <netinet/ip6.h>
111 #include <netinet/icmp6.h>
112 #include <netinet6/nd6.h>
113 #include <netinet6/ip6_var.h>
114 #include <netinet6/in6_pcb.h>
115 #include <netinet/tcp.h>
116 #include <netinet/tcp_fsm.h>
117 #include <netinet/tcp_seq.h>
118 #include <netinet/tcp_timer.h>
119 #include <netinet/tcp_var.h>
120 #include <netinet6/tcp6_var.h>
121 #include <netinet/tcpip.h>
122 #ifdef TCPDEBUG
123 #include <netinet/tcp_debug.h>
124 #endif /* TCPDEBUG */
125
126 #include <machine/in_cksum.h>
127
128 VNET_DECLARE(struct uma_zone *, sack_hole_zone);
129 #define V_sack_hole_zone VNET(sack_hole_zone)
130
131 SYSCTL_NODE(_net_inet_tcp, OID_AUTO, sack, CTLFLAG_RW, 0, "TCP SACK");
132 VNET_DEFINE(int, tcp_do_sack) = 1;
133 #define V_tcp_do_sack VNET(tcp_do_sack)
134 SYSCTL_INT(_net_inet_tcp_sack, OID_AUTO, enable, CTLFLAG_VNET | CTLFLAG_RW,
135 &VNET_NAME(tcp_do_sack), 0, "Enable/Disable TCP SACK support");
136
137 VNET_DEFINE(int, tcp_sack_maxholes) = 128;
138 SYSCTL_INT(_net_inet_tcp_sack, OID_AUTO, maxholes, CTLFLAG_VNET | CTLFLAG_RW,
139 &VNET_NAME(tcp_sack_maxholes), 0,
140 "Maximum number of TCP SACK holes allowed per connection");
141
142 VNET_DEFINE(int, tcp_sack_globalmaxholes) = 65536;
143 SYSCTL_INT(_net_inet_tcp_sack, OID_AUTO, globalmaxholes, CTLFLAG_VNET | CTLFLAG_RW,
144 &VNET_NAME(tcp_sack_globalmaxholes), 0,
145 "Global maximum number of TCP SACK holes");
146
147 VNET_DEFINE(int, tcp_sack_globalholes) = 0;
148 SYSCTL_INT(_net_inet_tcp_sack, OID_AUTO, globalholes, CTLFLAG_VNET | CTLFLAG_RD,
149 &VNET_NAME(tcp_sack_globalholes), 0,
150 "Global number of TCP SACK holes currently allocated");
151
152
153 /*
154 * This function will find overlaps with the currently stored sackblocks
155 * and add any overlap as a dsack block upfront
156 */
157 void
158 tcp_update_dsack_list(struct tcpcb *tp, tcp_seq rcv_start, tcp_seq rcv_end)
159 {
160 struct sackblk head_blk,mid_blk,saved_blks[MAX_SACK_BLKS];
161 int i, j, n, identical;
162 tcp_seq start, end;
163
164 INP_WLOCK_ASSERT(tp->t_inpcb);
165
166 KASSERT(SEQ_LT(rcv_start, rcv_end), ("rcv_start < rcv_end"));
167
168 if (SEQ_LT(rcv_end, tp->rcv_nxt) ||
169 ((rcv_end == tp->rcv_nxt) &&
170 (tp->rcv_numsacks > 0 ) &&
171 (tp->sackblks[0].end == tp->rcv_nxt))) {
172 saved_blks[0].start = rcv_start;
173 saved_blks[0].end = rcv_end;
174 } else {
175 saved_blks[0].start = saved_blks[0].end = 0;
176 }
177
178 head_blk.start = head_blk.end = 0;
179 mid_blk.start = rcv_start;
180 mid_blk.end = rcv_end;
181 identical = 0;
182
183 for (i = 0; i < tp->rcv_numsacks; i++) {
184 start = tp->sackblks[i].start;
185 end = tp->sackblks[i].end;
186 if (SEQ_LT(rcv_end, start)) {
187 /* pkt left to sack blk */
188 continue;
189 }
190 if (SEQ_GT(rcv_start, end)) {
191 /* pkt right to sack blk */
192 continue;
193 }
194 if (SEQ_GT(tp->rcv_nxt, end)) {
195 if ((SEQ_MAX(rcv_start, start) != SEQ_MIN(rcv_end, end)) &&
196 (SEQ_GT(head_blk.start, SEQ_MAX(rcv_start, start)) ||
197 (head_blk.start == head_blk.end))) {
198 head_blk.start = SEQ_MAX(rcv_start, start);
199 head_blk.end = SEQ_MIN(rcv_end, end);
200 }
201 continue;
202 }
203 if (((head_blk.start == head_blk.end) ||
204 SEQ_LT(start, head_blk.start)) &&
205 (SEQ_GT(end, rcv_start) &&
206 SEQ_LEQ(start, rcv_end))) {
207 head_blk.start = start;
208 head_blk.end = end;
209 }
210 mid_blk.start = SEQ_MIN(mid_blk.start, start);
211 mid_blk.end = SEQ_MAX(mid_blk.end, end);
212 if ((mid_blk.start == start) &&
213 (mid_blk.end == end))
214 identical = 1;
215 }
216 if (SEQ_LT(head_blk.start, head_blk.end)) {
217 /* store overlapping range */
218 saved_blks[0].start = SEQ_MAX(rcv_start, head_blk.start);
219 saved_blks[0].end = SEQ_MIN(rcv_end, head_blk.end);
220 }
221 n = 1;
222 /*
223 * Second, if not ACKed, store the SACK block that
224 * overlaps with the DSACK block unless it is identical
225 */
226 if ((SEQ_LT(tp->rcv_nxt, mid_blk.end) &&
227 !((mid_blk.start == saved_blks[0].start) &&
228 (mid_blk.end == saved_blks[0].end))) ||
229 identical == 1) {
230 saved_blks[n].start = mid_blk.start;
231 saved_blks[n++].end = mid_blk.end;
232 }
233 for (j = 0; (j < tp->rcv_numsacks) && (n < MAX_SACK_BLKS); j++) {
234 if (((SEQ_LT(tp->sackblks[j].end, mid_blk.start) ||
235 SEQ_GT(tp->sackblks[j].start, mid_blk.end)) &&
236 (SEQ_GT(tp->sackblks[j].start, tp->rcv_nxt))))
237 saved_blks[n++] = tp->sackblks[j];
238 }
239 j = 0;
240 for (i = 0; i < n; i++) {
241 /* we can end up with a stale inital entry */
242 if (SEQ_LT(saved_blks[i].start, saved_blks[i].end)) {
243 tp->sackblks[j++] = saved_blks[i];
244 }
245 }
246 tp->rcv_numsacks = j;
247 }
248
249 /*
250 * This function is called upon receipt of new valid data (while not in
251 * header prediction mode), and it updates the ordered list of sacks.
252 */
253 void
254 tcp_update_sack_list(struct tcpcb *tp, tcp_seq rcv_start, tcp_seq rcv_end)
255 {
256 /*
257 * First reported block MUST be the most recent one. Subsequent
258 * blocks SHOULD be in the order in which they arrived at the
259 * receiver. These two conditions make the implementation fully
260 * compliant with RFC 2018.
261 */
262 struct sackblk head_blk, saved_blks[MAX_SACK_BLKS];
263 int num_head, num_saved, i;
264
265 INP_WLOCK_ASSERT(tp->t_inpcb);
266
267 /* Check arguments. */
268 KASSERT(SEQ_LEQ(rcv_start, rcv_end), ("rcv_start <= rcv_end"));
269
270 if ((rcv_start == rcv_end) &&
271 (tp->rcv_numsacks >= 1) &&
272 (rcv_end == tp->sackblks[0].end)) {
273 /* retaining DSACK block below rcv_nxt (todrop) */
274 head_blk = tp->sackblks[0];
275 } else {
276 /* SACK block for the received segment. */
277 head_blk.start = rcv_start;
278 head_blk.end = rcv_end;
279 }
280
281 /*
282 * Merge updated SACK blocks into head_blk, and save unchanged SACK
283 * blocks into saved_blks[]. num_saved will have the number of the
284 * saved SACK blocks.
285 */
286 num_saved = 0;
287 for (i = 0; i < tp->rcv_numsacks; i++) {
288 tcp_seq start = tp->sackblks[i].start;
289 tcp_seq end = tp->sackblks[i].end;
290 if (SEQ_GEQ(start, end) || SEQ_LEQ(start, tp->rcv_nxt)) {
291 /*
292 * Discard this SACK block.
293 */
294 } else if (SEQ_LEQ(head_blk.start, end) &&
295 SEQ_GEQ(head_blk.end, start)) {
296 /*
297 * Merge this SACK block into head_blk. This SACK
298 * block itself will be discarded.
299 */
300 /*
301 * |-|
302 * |---| merge
303 *
304 * |-|
305 * |---| merge
306 *
307 * |-----|
308 * |-| DSACK smaller
309 *
310 * |-|
311 * |-----| DSACK smaller
312 */
313 if (head_blk.start == end)
314 head_blk.start = start;
315 else if (head_blk.end == start)
316 head_blk.end = end;
317 else {
318 if (SEQ_LT(head_blk.start, start)) {
319 tcp_seq temp = start;
320 start = head_blk.start;
321 head_blk.start = temp;
322 }
323 if (SEQ_GT(head_blk.end, end)) {
324 tcp_seq temp = end;
325 end = head_blk.end;
326 head_blk.end = temp;
327 }
328 if ((head_blk.start != start) ||
329 (head_blk.end != end)) {
330 if ((num_saved >= 1) &&
331 SEQ_GEQ(saved_blks[num_saved-1].start, start) &&
332 SEQ_LEQ(saved_blks[num_saved-1].end, end))
333 num_saved--;
334 saved_blks[num_saved].start = start;
335 saved_blks[num_saved].end = end;
336 num_saved++;
337 }
338 }
339 } else {
340 /*
341 * This block supercedes the prior block
342 */
343 if ((num_saved >= 1) &&
344 SEQ_GEQ(saved_blks[num_saved-1].start, start) &&
345 SEQ_LEQ(saved_blks[num_saved-1].end, end))
346 num_saved--;
347 /*
348 * Save this SACK block.
349 */
350 saved_blks[num_saved].start = start;
351 saved_blks[num_saved].end = end;
352 num_saved++;
353 }
354 }
355
356 /*
357 * Update SACK list in tp->sackblks[].
358 */
359 num_head = 0;
360 if (SEQ_LT(rcv_start, rcv_end)) {
361 /*
362 * The received data segment is an out-of-order segment. Put
363 * head_blk at the top of SACK list.
364 */
365 tp->sackblks[0] = head_blk;
366 num_head = 1;
367 /*
368 * If the number of saved SACK blocks exceeds its limit,
369 * discard the last SACK block.
370 */
371 if (num_saved >= MAX_SACK_BLKS)
372 num_saved--;
373 }
374 if ((rcv_start == rcv_end) &&
375 (rcv_start == tp->sackblks[0].end)) {
376 num_head = 1;
377 }
378 if (num_saved > 0) {
379 /*
380 * Copy the saved SACK blocks back.
381 */
382 bcopy(saved_blks, &tp->sackblks[num_head],
383 sizeof(struct sackblk) * num_saved);
384 }
385
386 /* Save the number of SACK blocks. */
387 tp->rcv_numsacks = num_head + num_saved;
388 }
389
390 void
391 tcp_clean_dsack_blocks(struct tcpcb *tp)
392 {
393 struct sackblk saved_blks[MAX_SACK_BLKS];
394 int num_saved, i;
395
396 INP_WLOCK_ASSERT(tp->t_inpcb);
397 /*
398 * Clean up any DSACK blocks that
399 * are in our queue of sack blocks.
400 *
401 */
402 num_saved = 0;
403 for (i = 0; i < tp->rcv_numsacks; i++) {
404 tcp_seq start = tp->sackblks[i].start;
405 tcp_seq end = tp->sackblks[i].end;
406 if (SEQ_GEQ(start, end) || SEQ_LEQ(start, tp->rcv_nxt)) {
407 /*
408 * Discard this D-SACK block.
409 */
410 continue;
411 }
412 /*
413 * Save this SACK block.
414 */
415 saved_blks[num_saved].start = start;
416 saved_blks[num_saved].end = end;
417 num_saved++;
418 }
419 if (num_saved > 0) {
420 /*
421 * Copy the saved SACK blocks back.
422 */
423 bcopy(saved_blks, &tp->sackblks[0],
424 sizeof(struct sackblk) * num_saved);
425 }
426 tp->rcv_numsacks = num_saved;
427 }
428
429 /*
430 * Delete all receiver-side SACK information.
431 */
432 void
433 tcp_clean_sackreport(struct tcpcb *tp)
434 {
435 int i;
436
437 INP_WLOCK_ASSERT(tp->t_inpcb);
438 tp->rcv_numsacks = 0;
439 for (i = 0; i < MAX_SACK_BLKS; i++)
440 tp->sackblks[i].start = tp->sackblks[i].end=0;
441 }
442
443 /*
444 * Allocate struct sackhole.
445 */
446 static struct sackhole *
447 tcp_sackhole_alloc(struct tcpcb *tp, tcp_seq start, tcp_seq end)
448 {
449 struct sackhole *hole;
450
451 if (tp->snd_numholes >= V_tcp_sack_maxholes ||
452 V_tcp_sack_globalholes >= V_tcp_sack_globalmaxholes) {
453 TCPSTAT_INC(tcps_sack_sboverflow);
454 return NULL;
455 }
456
457 hole = (struct sackhole *)uma_zalloc(V_sack_hole_zone, M_NOWAIT);
458 if (hole == NULL)
459 return NULL;
460
461 hole->start = start;
462 hole->end = end;
463 hole->rxmit = start;
464
465 tp->snd_numholes++;
466 atomic_add_int(&V_tcp_sack_globalholes, 1);
467
468 return hole;
469 }
470
471 /*
472 * Free struct sackhole.
473 */
474 static void
475 tcp_sackhole_free(struct tcpcb *tp, struct sackhole *hole)
476 {
477
478 uma_zfree(V_sack_hole_zone, hole);
479
480 tp->snd_numholes--;
481 atomic_subtract_int(&V_tcp_sack_globalholes, 1);
482
483 KASSERT(tp->snd_numholes >= 0, ("tp->snd_numholes >= 0"));
484 KASSERT(V_tcp_sack_globalholes >= 0, ("tcp_sack_globalholes >= 0"));
485 }
486
487 /*
488 * Insert new SACK hole into scoreboard.
489 */
490 static struct sackhole *
491 tcp_sackhole_insert(struct tcpcb *tp, tcp_seq start, tcp_seq end,
492 struct sackhole *after)
493 {
494 struct sackhole *hole;
495
496 /* Allocate a new SACK hole. */
497 hole = tcp_sackhole_alloc(tp, start, end);
498 if (hole == NULL)
499 return NULL;
500
501 /* Insert the new SACK hole into scoreboard. */
502 if (after != NULL)
503 TAILQ_INSERT_AFTER(&tp->snd_holes, after, hole, scblink);
504 else
505 TAILQ_INSERT_TAIL(&tp->snd_holes, hole, scblink);
506
507 /* Update SACK hint. */
508 if (tp->sackhint.nexthole == NULL)
509 tp->sackhint.nexthole = hole;
510
511 return hole;
512 }
513
514 /*
515 * Remove SACK hole from scoreboard.
516 */
517 static void
518 tcp_sackhole_remove(struct tcpcb *tp, struct sackhole *hole)
519 {
520
521 /* Update SACK hint. */
522 if (tp->sackhint.nexthole == hole)
523 tp->sackhint.nexthole = TAILQ_NEXT(hole, scblink);
524
525 /* Remove this SACK hole. */
526 TAILQ_REMOVE(&tp->snd_holes, hole, scblink);
527
528 /* Free this SACK hole. */
529 tcp_sackhole_free(tp, hole);
530 }
531
532 /*
533 * Process cumulative ACK and the TCP SACK option to update the scoreboard.
534 * tp->snd_holes is an ordered list of holes (oldest to newest, in terms of
535 * the sequence space).
536 * Returns 1 if incoming ACK has previously unknown SACK information,
537 * 0 otherwise.
538 */
539 int
540 tcp_sack_doack(struct tcpcb *tp, struct tcpopt *to, tcp_seq th_ack)
541 {
542 struct sackhole *cur, *temp;
543 struct sackblk sack, sack_blocks[TCP_MAX_SACK + 1], *sblkp;
544 int i, j, num_sack_blks, sack_changed;
545 int delivered_data, left_edge_delta;
546
547 INP_WLOCK_ASSERT(tp->t_inpcb);
548
549 num_sack_blks = 0;
550 sack_changed = 0;
551 delivered_data = 0;
552 left_edge_delta = 0;
553 /*
554 * If SND.UNA will be advanced by SEG.ACK, and if SACK holes exist,
555 * treat [SND.UNA, SEG.ACK) as if it is a SACK block.
556 * Account changes to SND.UNA always in delivered data.
557 */
558 if (SEQ_LT(tp->snd_una, th_ack) && !TAILQ_EMPTY(&tp->snd_holes)) {
559 left_edge_delta = th_ack - tp->snd_una;
560 sack_blocks[num_sack_blks].start = tp->snd_una;
561 sack_blocks[num_sack_blks++].end = th_ack;
562 }
563 /*
564 * Append received valid SACK blocks to sack_blocks[], but only if we
565 * received new blocks from the other side.
566 */
567 if (to->to_flags & TOF_SACK) {
568 for (i = 0; i < to->to_nsacks; i++) {
569 bcopy((to->to_sacks + i * TCPOLEN_SACK),
570 &sack, sizeof(sack));
571 sack.start = ntohl(sack.start);
572 sack.end = ntohl(sack.end);
573 if (SEQ_GT(sack.end, sack.start) &&
574 SEQ_GT(sack.start, tp->snd_una) &&
575 SEQ_GT(sack.start, th_ack) &&
576 SEQ_LT(sack.start, tp->snd_max) &&
577 SEQ_GT(sack.end, tp->snd_una) &&
578 SEQ_LEQ(sack.end, tp->snd_max)) {
579 sack_blocks[num_sack_blks++] = sack;
580 }
581 }
582 }
583 /*
584 * Return if SND.UNA is not advanced and no valid SACK block is
585 * received.
586 */
587 if (num_sack_blks == 0)
588 return (sack_changed);
589
590 /*
591 * Sort the SACK blocks so we can update the scoreboard with just one
592 * pass. The overhead of sorting up to 4+1 elements is less than
593 * making up to 4+1 passes over the scoreboard.
594 */
595 for (i = 0; i < num_sack_blks; i++) {
596 for (j = i + 1; j < num_sack_blks; j++) {
597 if (SEQ_GT(sack_blocks[i].end, sack_blocks[j].end)) {
598 sack = sack_blocks[i];
599 sack_blocks[i] = sack_blocks[j];
600 sack_blocks[j] = sack;
601 }
602 }
603 }
604 if (TAILQ_EMPTY(&tp->snd_holes)) {
605 /*
606 * Empty scoreboard. Need to initialize snd_fack (it may be
607 * uninitialized or have a bogus value). Scoreboard holes
608 * (from the sack blocks received) are created later below
609 * (in the logic that adds holes to the tail of the
610 * scoreboard).
611 */
612 tp->snd_fack = SEQ_MAX(tp->snd_una, th_ack);
613 tp->sackhint.sacked_bytes = 0; /* reset */
614 }
615 /*
616 * In the while-loop below, incoming SACK blocks (sack_blocks[]) and
617 * SACK holes (snd_holes) are traversed from their tails with just
618 * one pass in order to reduce the number of compares especially when
619 * the bandwidth-delay product is large.
620 *
621 * Note: Typically, in the first RTT of SACK recovery, the highest
622 * three or four SACK blocks with the same ack number are received.
623 * In the second RTT, if retransmitted data segments are not lost,
624 * the highest three or four SACK blocks with ack number advancing
625 * are received.
626 */
627 sblkp = &sack_blocks[num_sack_blks - 1]; /* Last SACK block */
628 tp->sackhint.last_sack_ack = sblkp->end;
629 if (SEQ_LT(tp->snd_fack, sblkp->start)) {
630 /*
631 * The highest SACK block is beyond fack. Append new SACK
632 * hole at the tail. If the second or later highest SACK
633 * blocks are also beyond the current fack, they will be
634 * inserted by way of hole splitting in the while-loop below.
635 */
636 temp = tcp_sackhole_insert(tp, tp->snd_fack,sblkp->start,NULL);
637 if (temp != NULL) {
638 delivered_data += sblkp->end - sblkp->start;
639 tp->snd_fack = sblkp->end;
640 /* Go to the previous sack block. */
641 sblkp--;
642 sack_changed = 1;
643 } else {
644 /*
645 * We failed to add a new hole based on the current
646 * sack block. Skip over all the sack blocks that
647 * fall completely to the right of snd_fack and
648 * proceed to trim the scoreboard based on the
649 * remaining sack blocks. This also trims the
650 * scoreboard for th_ack (which is sack_blocks[0]).
651 */
652 while (sblkp >= sack_blocks &&
653 SEQ_LT(tp->snd_fack, sblkp->start))
654 sblkp--;
655 if (sblkp >= sack_blocks &&
656 SEQ_LT(tp->snd_fack, sblkp->end)) {
657 delivered_data += sblkp->end - tp->snd_fack;
658 tp->snd_fack = sblkp->end;
659 sack_changed = 1;
660 }
661 }
662 } else if (SEQ_LT(tp->snd_fack, sblkp->end)) {
663 /* fack is advanced. */
664 delivered_data += sblkp->end - tp->snd_fack;
665 tp->snd_fack = sblkp->end;
666 sack_changed = 1;
667 }
668 cur = TAILQ_LAST(&tp->snd_holes, sackhole_head); /* Last SACK hole. */
669 /*
670 * Since the incoming sack blocks are sorted, we can process them
671 * making one sweep of the scoreboard.
672 */
673 while (sblkp >= sack_blocks && cur != NULL) {
674 if (SEQ_GEQ(sblkp->start, cur->end)) {
675 /*
676 * SACKs data beyond the current hole. Go to the
677 * previous sack block.
678 */
679 sblkp--;
680 continue;
681 }
682 if (SEQ_LEQ(sblkp->end, cur->start)) {
683 /*
684 * SACKs data before the current hole. Go to the
685 * previous hole.
686 */
687 cur = TAILQ_PREV(cur, sackhole_head, scblink);
688 continue;
689 }
690 tp->sackhint.sack_bytes_rexmit -= (cur->rxmit - cur->start);
691 KASSERT(tp->sackhint.sack_bytes_rexmit >= 0,
692 ("sackhint bytes rtx >= 0"));
693 sack_changed = 1;
694 if (SEQ_LEQ(sblkp->start, cur->start)) {
695 /* Data acks at least the beginning of hole. */
696 if (SEQ_GEQ(sblkp->end, cur->end)) {
697 /* Acks entire hole, so delete hole. */
698 delivered_data += (cur->end - cur->start);
699 temp = cur;
700 cur = TAILQ_PREV(cur, sackhole_head, scblink);
701 tcp_sackhole_remove(tp, temp);
702 /*
703 * The sack block may ack all or part of the
704 * next hole too, so continue onto the next
705 * hole.
706 */
707 continue;
708 } else {
709 /* Move start of hole forward. */
710 delivered_data += (sblkp->end - cur->start);
711 cur->start = sblkp->end;
712 cur->rxmit = SEQ_MAX(cur->rxmit, cur->start);
713 }
714 } else {
715 /* Data acks at least the end of hole. */
716 if (SEQ_GEQ(sblkp->end, cur->end)) {
717 /* Move end of hole backward. */
718 delivered_data += (cur->end - sblkp->start);
719 cur->end = sblkp->start;
720 cur->rxmit = SEQ_MIN(cur->rxmit, cur->end);
721 } else {
722 /*
723 * ACKs some data in middle of a hole; need
724 * to split current hole
725 */
726 temp = tcp_sackhole_insert(tp, sblkp->end,
727 cur->end, cur);
728 if (temp != NULL) {
729 if (SEQ_GT(cur->rxmit, temp->rxmit)) {
730 temp->rxmit = cur->rxmit;
731 tp->sackhint.sack_bytes_rexmit
732 += (temp->rxmit
733 - temp->start);
734 }
735 cur->end = sblkp->start;
736 cur->rxmit = SEQ_MIN(cur->rxmit,
737 cur->end);
738 delivered_data += (sblkp->end - sblkp->start);
739 }
740 }
741 }
742 tp->sackhint.sack_bytes_rexmit += (cur->rxmit - cur->start);
743 /*
744 * Testing sblkp->start against cur->start tells us whether
745 * we're done with the sack block or the sack hole.
746 * Accordingly, we advance one or the other.
747 */
748 if (SEQ_LEQ(sblkp->start, cur->start))
749 cur = TAILQ_PREV(cur, sackhole_head, scblink);
750 else
751 sblkp--;
752 }
753 tp->sackhint.delivered_data = delivered_data;
754 tp->sackhint.sacked_bytes += delivered_data - left_edge_delta;
755 KASSERT((delivered_data >= 0), ("delivered_data < 0"));
756 KASSERT((tp->sackhint.sacked_bytes >= 0), ("sacked_bytes < 0"));
757 return (sack_changed);
758 }
759
760 /*
761 * Free all SACK holes to clear the scoreboard.
762 */
763 void
764 tcp_free_sackholes(struct tcpcb *tp)
765 {
766 struct sackhole *q;
767
768 INP_WLOCK_ASSERT(tp->t_inpcb);
769 while ((q = TAILQ_FIRST(&tp->snd_holes)) != NULL)
770 tcp_sackhole_remove(tp, q);
771 tp->sackhint.sack_bytes_rexmit = 0;
772
773 KASSERT(tp->snd_numholes == 0, ("tp->snd_numholes == 0"));
774 KASSERT(tp->sackhint.nexthole == NULL,
775 ("tp->sackhint.nexthole == NULL"));
776 }
777
778 /*
779 * Partial ack handling within a sack recovery episode. Keeping this very
780 * simple for now. When a partial ack is received, force snd_cwnd to a value
781 * that will allow the sender to transmit no more than 2 segments. If
782 * necessary, a better scheme can be adopted at a later point, but for now,
783 * the goal is to prevent the sender from bursting a large amount of data in
784 * the midst of sack recovery.
785 */
786 void
787 tcp_sack_partialack(struct tcpcb *tp, struct tcphdr *th)
788 {
789 int num_segs = 1;
790 u_int maxseg = tcp_maxseg(tp);
791
792 INP_WLOCK_ASSERT(tp->t_inpcb);
793 tcp_timer_activate(tp, TT_REXMT, 0);
794 tp->t_rtttime = 0;
795 /* Send one or 2 segments based on how much new data was acked. */
796 if ((BYTES_THIS_ACK(tp, th) / maxseg) >= 2)
797 num_segs = 2;
798 tp->snd_cwnd = (tp->sackhint.sack_bytes_rexmit +
799 (tp->snd_nxt - tp->sack_newdata) + num_segs * maxseg);
800 if (tp->snd_cwnd > tp->snd_ssthresh)
801 tp->snd_cwnd = tp->snd_ssthresh;
802 tp->t_flags |= TF_ACKNOW;
803 (void) tp->t_fb->tfb_tcp_output(tp);
804 }
805
806 #if 0
807 /*
808 * Debug version of tcp_sack_output() that walks the scoreboard. Used for
809 * now to sanity check the hint.
810 */
811 static struct sackhole *
812 tcp_sack_output_debug(struct tcpcb *tp, int *sack_bytes_rexmt)
813 {
814 struct sackhole *p;
815
816 INP_WLOCK_ASSERT(tp->t_inpcb);
817 *sack_bytes_rexmt = 0;
818 TAILQ_FOREACH(p, &tp->snd_holes, scblink) {
819 if (SEQ_LT(p->rxmit, p->end)) {
820 if (SEQ_LT(p->rxmit, tp->snd_una)) {/* old SACK hole */
821 continue;
822 }
823 *sack_bytes_rexmt += (p->rxmit - p->start);
824 break;
825 }
826 *sack_bytes_rexmt += (p->rxmit - p->start);
827 }
828 return (p);
829 }
830 #endif
831
832 /*
833 * Returns the next hole to retransmit and the number of retransmitted bytes
834 * from the scoreboard. We store both the next hole and the number of
835 * retransmitted bytes as hints (and recompute these on the fly upon SACK/ACK
836 * reception). This avoids scoreboard traversals completely.
837 *
838 * The loop here will traverse *at most* one link. Here's the argument. For
839 * the loop to traverse more than 1 link before finding the next hole to
840 * retransmit, we would need to have at least 1 node following the current
841 * hint with (rxmit == end). But, for all holes following the current hint,
842 * (start == rxmit), since we have not yet retransmitted from them.
843 * Therefore, in order to traverse more 1 link in the loop below, we need to
844 * have at least one node following the current hint with (start == rxmit ==
845 * end). But that can't happen, (start == end) means that all the data in
846 * that hole has been sacked, in which case, the hole would have been removed
847 * from the scoreboard.
848 */
849 struct sackhole *
850 tcp_sack_output(struct tcpcb *tp, int *sack_bytes_rexmt)
851 {
852 struct sackhole *hole = NULL;
853
854 INP_WLOCK_ASSERT(tp->t_inpcb);
855 *sack_bytes_rexmt = tp->sackhint.sack_bytes_rexmit;
856 hole = tp->sackhint.nexthole;
857 if (hole == NULL || SEQ_LT(hole->rxmit, hole->end))
858 goto out;
859 while ((hole = TAILQ_NEXT(hole, scblink)) != NULL) {
860 if (SEQ_LT(hole->rxmit, hole->end)) {
861 tp->sackhint.nexthole = hole;
862 break;
863 }
864 }
865 out:
866 return (hole);
867 }
868
869 /*
870 * After a timeout, the SACK list may be rebuilt. This SACK information
871 * should be used to avoid retransmitting SACKed data. This function
872 * traverses the SACK list to see if snd_nxt should be moved forward.
873 */
874 void
875 tcp_sack_adjust(struct tcpcb *tp)
876 {
877 struct sackhole *p, *cur = TAILQ_FIRST(&tp->snd_holes);
878
879 INP_WLOCK_ASSERT(tp->t_inpcb);
880 if (cur == NULL)
881 return; /* No holes */
882 if (SEQ_GEQ(tp->snd_nxt, tp->snd_fack))
883 return; /* We're already beyond any SACKed blocks */
884 /*-
885 * Two cases for which we want to advance snd_nxt:
886 * i) snd_nxt lies between end of one hole and beginning of another
887 * ii) snd_nxt lies between end of last hole and snd_fack
888 */
889 while ((p = TAILQ_NEXT(cur, scblink)) != NULL) {
890 if (SEQ_LT(tp->snd_nxt, cur->end))
891 return;
892 if (SEQ_GEQ(tp->snd_nxt, p->start))
893 cur = p;
894 else {
895 tp->snd_nxt = p->start;
896 return;
897 }
898 }
899 if (SEQ_LT(tp->snd_nxt, cur->end))
900 return;
901 tp->snd_nxt = tp->snd_fack;
902 }
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