tcp/sack: Guard against ACK reordering when adding SACK blocks
[dragonfly.git] / sys / netinet / tcp_sack.c
CommitLineData
91489f6b
JH
1/*
2 * Copyright (c) 2003, 2004 Jeffrey M. Hsu. All rights reserved.
3 * Copyright (c) 2003, 2004 The DragonFly Project. All rights reserved.
4 *
5 * This code is derived from software contributed to The DragonFly Project
6 * by Jeffrey M. Hsu.
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 DragonFly Project nor the names of its
17 * contributors may be used to endorse or promote products derived
18 * from this software without specific, prior written permission.
19 *
20 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
21 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
22 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
23 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
24 * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
25 * INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING,
26 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
27 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
28 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
29 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
30 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
31 * SUCH DAMAGE.
32 *
12f68b86 33 * $DragonFly: src/sys/netinet/tcp_sack.c,v 1.8 2008/08/15 21:37:16 nth Exp $
91489f6b
JH
34 */
35
36#include <sys/param.h>
37#include <sys/systm.h>
38#include <sys/kernel.h>
39#include <sys/malloc.h>
40#include <sys/queue.h>
41#include <sys/thread.h>
42#include <sys/types.h>
43#include <sys/socket.h>
44#include <sys/socketvar.h>
45
46#include <net/if.h>
47
48#include <netinet/in.h>
49#include <netinet/in_systm.h>
50#include <netinet/ip.h>
51#include <netinet/in_var.h>
52#include <netinet/in_pcb.h>
53#include <netinet/ip_var.h>
54#include <netinet/tcp.h>
55#include <netinet/tcp_seq.h>
56#include <netinet/tcp_var.h>
57
bf55dc6d
SZ
58/*
59 * Implemented:
60 *
61 * RFC 2018
62 * RFC 2883
63 * RFC 3517
64 */
65
91489f6b
JH
66struct sackblock {
67 tcp_seq sblk_start;
68 tcp_seq sblk_end;
69 TAILQ_ENTRY(sackblock) sblk_list;
70};
71
72#define MAXSAVEDBLOCKS 8 /* per connection limit */
73
01d244e6 74static int insert_block(struct scoreboard *scb,
6c1bbf57 75 const struct raw_sackblock *raw_sb, boolean_t *update);
91489f6b 76static void update_lostseq(struct scoreboard *scb, tcp_seq snd_una,
7e4852bb 77 u_int maxseg, int rxtthresh);
91489f6b 78
12f68b86 79static MALLOC_DEFINE(M_SACKBLOCK, "sblk", "sackblock struct");
91489f6b
JH
80
81/*
82 * Per-tcpcb initialization.
83 */
84void
85tcp_sack_tcpcb_init(struct tcpcb *tp)
86{
87 struct scoreboard *scb = &tp->scb;
88
89 scb->nblocks = 0;
90 TAILQ_INIT(&scb->sackblocks);
91 scb->lastfound = NULL;
92}
93
94/*
95 * Find the SACK block containing or immediately preceding "seq".
96 * The boolean result indicates whether the sequence is actually
97 * contained in the SACK block.
98 */
99static boolean_t
100sack_block_lookup(struct scoreboard *scb, tcp_seq seq, struct sackblock **sb)
101{
102 struct sackblock *hint = scb->lastfound;
103 struct sackblock *cur, *last, *prev;
104
105 if (TAILQ_EMPTY(&scb->sackblocks)) {
106 *sb = NULL;
107 return FALSE;
108 }
109
110 if (hint == NULL) {
111 /* No hint. Search from start to end. */
112 cur = TAILQ_FIRST(&scb->sackblocks);
113 last = NULL;
114 prev = TAILQ_LAST(&scb->sackblocks, sackblock_list);
115 } else {
116 if (SEQ_GEQ(seq, hint->sblk_start)) {
117 /* Search from hint to end of list. */
118 cur = hint;
119 last = NULL;
120 prev = TAILQ_LAST(&scb->sackblocks, sackblock_list);
121 } else {
122 /* Search from front of list to hint. */
123 cur = TAILQ_FIRST(&scb->sackblocks);
124 last = hint;
125 prev = TAILQ_PREV(hint, sackblock_list, sblk_list);
126 }
127 }
128
129 do {
130 if (SEQ_GT(cur->sblk_end, seq)) {
131 if (SEQ_GEQ(seq, cur->sblk_start)) {
132 *sb = scb->lastfound = cur;
133 return TRUE;
134 } else {
135 *sb = scb->lastfound =
136 TAILQ_PREV(cur, sackblock_list, sblk_list);
137 return FALSE;
138 }
139 }
140 cur = TAILQ_NEXT(cur, sblk_list);
141 } while (cur != last);
142
143 *sb = scb->lastfound = prev;
144 return FALSE;
145}
146
147/*
148 * Allocate a SACK block.
149 */
150static __inline struct sackblock *
006af0db 151alloc_sackblock(struct scoreboard *scb, const struct raw_sackblock *raw_sb)
91489f6b 152{
26d3f1fb
SZ
153 struct sackblock *sb;
154
006af0db
SZ
155 if (scb->freecache != NULL) {
156 sb = scb->freecache;
157 scb->freecache = NULL;
158 tcpstat.tcps_sacksbfast++;
01d244e6 159 } else {
006af0db
SZ
160 sb = kmalloc(sizeof(struct sackblock), M_SACKBLOCK, M_NOWAIT);
161 if (sb == NULL) {
162 tcpstat.tcps_sacksbfailed++;
163 return NULL;
164 }
26d3f1fb 165 }
006af0db
SZ
166 sb->sblk_start = raw_sb->rblk_start;
167 sb->sblk_end = raw_sb->rblk_end;
26d3f1fb 168 return sb;
91489f6b
JH
169}
170
01d244e6
SZ
171static __inline struct sackblock *
172alloc_sackblock_limit(struct scoreboard *scb,
173 const struct raw_sackblock *raw_sb)
174{
175 if (scb->nblocks == MAXSAVEDBLOCKS) {
176 /*
177 * Should try to kick out older blocks XXX JH
178 * May be able to coalesce with existing block.
179 * Or, go other way and free all blocks if we hit
180 * this limit.
181 */
182 tcpstat.tcps_sacksboverflow++;
183 return NULL;
184 }
006af0db 185 return alloc_sackblock(scb, raw_sb);
01d244e6
SZ
186}
187
91489f6b
JH
188/*
189 * Free a SACK block.
190 */
191static __inline void
006af0db 192free_sackblock(struct scoreboard *scb, struct sackblock *s)
91489f6b 193{
006af0db
SZ
194 if (scb->freecache == NULL) {
195 /* YYY Maybe use the latest freed block? */
196 scb->freecache = s;
197 return;
198 }
12f68b86 199 kfree(s, M_SACKBLOCK);
91489f6b
JH
200}
201
202/*
203 * Free up SACK blocks for data that's been acked.
204 */
205static void
206tcp_sack_ack_blocks(struct scoreboard *scb, tcp_seq th_ack)
207{
208 struct sackblock *sb, *nb;
209
210 sb = TAILQ_FIRST(&scb->sackblocks);
211 while (sb && SEQ_LEQ(sb->sblk_end, th_ack)) {
212 nb = TAILQ_NEXT(sb, sblk_list);
9e3d6c96 213 if (scb->lastfound == sb)
91489f6b
JH
214 scb->lastfound = NULL;
215 TAILQ_REMOVE(&scb->sackblocks, sb, sblk_list);
006af0db 216 free_sackblock(scb, sb);
91489f6b
JH
217 --scb->nblocks;
218 KASSERT(scb->nblocks >= 0,
219 ("SACK block count underflow: %d < 0", scb->nblocks));
220 sb = nb;
221 }
222 if (sb && SEQ_GT(th_ack, sb->sblk_start))
223 sb->sblk_start = th_ack; /* other side reneged? XXX */
224}
225
226/*
227 * Delete and free SACK blocks saved in scoreboard.
228 */
229void
230tcp_sack_cleanup(struct scoreboard *scb)
231{
232 struct sackblock *sb, *nb;
233
234 TAILQ_FOREACH_MUTABLE(sb, &scb->sackblocks, sblk_list, nb) {
006af0db 235 free_sackblock(scb, sb);
91489f6b
JH
236 --scb->nblocks;
237 }
238 KASSERT(scb->nblocks == 0,
239 ("SACK block %d count not zero", scb->nblocks));
240 TAILQ_INIT(&scb->sackblocks);
241 scb->lastfound = NULL;
242}
243
006af0db
SZ
244/*
245 * Delete and free SACK blocks saved in scoreboard.
246 * Delete the one slot block cache.
247 */
248void
249tcp_sack_destroy(struct scoreboard *scb)
250{
251 tcp_sack_cleanup(scb);
252 if (scb->freecache != NULL) {
253 kfree(scb->freecache, M_SACKBLOCK);
254 scb->freecache = NULL;
255 }
256}
257
d58ca578
SZ
258/*
259 * Cleanup the reported SACK block information
260 */
261void
262tcp_sack_report_cleanup(struct tcpcb *tp)
263{
264 tp->t_flags &= ~(TF_DUPSEG | TF_ENCLOSESEG | TF_SACKLEFT);
265 tp->reportblk.rblk_start = tp->reportblk.rblk_end;
266}
267
91489f6b
JH
268/*
269 * Returns 0 if not D-SACK block,
270 * 1 if D-SACK,
271 * 2 if duplicate of out-of-order D-SACK block.
272 */
273int
274tcp_sack_ndsack_blocks(struct raw_sackblock *blocks, const int numblocks,
275 tcp_seq snd_una)
276{
277 if (numblocks == 0)
278 return 0;
279
280 if (SEQ_LT(blocks[0].rblk_start, snd_una))
281 return 1;
282
283 /* block 0 inside block 1 */
284 if (numblocks > 1 &&
285 SEQ_GEQ(blocks[0].rblk_start, blocks[1].rblk_start) &&
286 SEQ_LEQ(blocks[0].rblk_end, blocks[1].rblk_end))
287 return 2;
288
289 return 0;
290}
291
292/*
293 * Update scoreboard on new incoming ACK.
294 */
295static void
296tcp_sack_add_blocks(struct tcpcb *tp, struct tcpopt *to)
297{
298 const int numblocks = to->to_nsackblocks;
299 struct raw_sackblock *blocks = to->to_sackblocks;
300 struct scoreboard *scb = &tp->scb;
6c1bbf57 301 int startblock, i;
91489f6b
JH
302
303 if (tcp_sack_ndsack_blocks(blocks, numblocks, tp->snd_una) > 0)
304 startblock = 1;
305 else
306 startblock = 0;
307
6c1bbf57 308 to->to_flags |= TOF_SACK_REDUNDANT;
91489f6b
JH
309 for (i = startblock; i < numblocks; i++) {
310 struct raw_sackblock *newsackblock = &blocks[i];
6c1bbf57
SZ
311 boolean_t update;
312 int error;
91489f6b 313
331721f5
SZ
314 /* Guard against ACK reordering */
315 if (SEQ_LT(newsackblock->rblk_start, tp->snd_una))
316 continue;
317
318 /* Don't accept bad SACK blocks */
02cc2f35
SZ
319 if (SEQ_GT(newsackblock->rblk_end, tp->snd_max)) {
320 tcpstat.tcps_rcvbadsackopt++;
91489f6b 321 break; /* skip all other blocks */
02cc2f35
SZ
322 }
323 tcpstat.tcps_sacksbupdate++;
91489f6b 324
6c1bbf57
SZ
325 error = insert_block(scb, newsackblock, &update);
326 if (update)
327 to->to_flags &= ~TOF_SACK_REDUNDANT;
328 if (error)
01d244e6 329 break;
91489f6b
JH
330 }
331}
332
333void
334tcp_sack_update_scoreboard(struct tcpcb *tp, struct tcpopt *to)
335{
336 struct scoreboard *scb = &tp->scb;
a098966f 337 int rexmt_high_update = 0;
91489f6b
JH
338
339 tcp_sack_ack_blocks(scb, tp->snd_una);
340 tcp_sack_add_blocks(tp, to);
7e4852bb 341 update_lostseq(scb, tp->snd_una, tp->t_maxseg, tp->t_rxtthresh);
a098966f 342 if (SEQ_LT(tp->rexmt_high, tp->snd_una)) {
91489f6b 343 tp->rexmt_high = tp->snd_una;
a098966f
SZ
344 rexmt_high_update = 1;
345 }
346 if (tp->t_flags & TF_SACKRESCUED) {
347 if (SEQ_LT(tp->rexmt_rescue, tp->snd_una)) {
348 tp->t_flags &= ~TF_SACKRESCUED;
21f337ca 349 } else if (tcp_aggressive_rescuesack && rexmt_high_update &&
a098966f
SZ
350 SEQ_LT(tp->rexmt_rescue, tp->rexmt_high)) {
351 /* Drag RescueRxt along with HighRxt */
352 tp->rexmt_rescue = tp->rexmt_high;
353 }
354 }
91489f6b
JH
355}
356
357/*
358 * Insert SACK block into sender's scoreboard.
359 */
01d244e6 360static int
6c1bbf57
SZ
361insert_block(struct scoreboard *scb, const struct raw_sackblock *raw_sb,
362 boolean_t *update)
91489f6b
JH
363{
364 struct sackblock *sb, *workingblock;
365 boolean_t overlap_front;
366
6c1bbf57 367 *update = TRUE;
2ed615e0 368 if (TAILQ_EMPTY(&scb->sackblocks)) {
01d244e6
SZ
369 struct sackblock *newblock;
370
2ed615e0 371 KASSERT(scb->nblocks == 0, ("emply scb w/ blocks"));
01d244e6 372
006af0db 373 newblock = alloc_sackblock(scb, raw_sb);
01d244e6
SZ
374 if (newblock == NULL)
375 return ENOMEM;
2ed615e0 376 TAILQ_INSERT_HEAD(&scb->sackblocks, newblock, sblk_list);
01d244e6
SZ
377 scb->nblocks = 1;
378 return 0;
2ed615e0 379 }
91489f6b 380
01d244e6
SZ
381 KASSERT(scb->nblocks > 0, ("insert_block() called w/ no blocks"));
382 KASSERT(scb->nblocks <= MAXSAVEDBLOCKS,
91489f6b
JH
383 ("too many SACK blocks %d", scb->nblocks));
384
01d244e6 385 overlap_front = sack_block_lookup(scb, raw_sb->rblk_start, &sb);
91489f6b
JH
386
387 if (sb == NULL) {
01d244e6
SZ
388 workingblock = alloc_sackblock_limit(scb, raw_sb);
389 if (workingblock == NULL)
390 return ENOMEM;
391 TAILQ_INSERT_HEAD(&scb->sackblocks, workingblock, sblk_list);
91489f6b
JH
392 ++scb->nblocks;
393 } else {
01d244e6
SZ
394 if (overlap_front || sb->sblk_end == raw_sb->rblk_start) {
395 /* Extend old block */
91489f6b 396 workingblock = sb;
01d244e6
SZ
397 if (SEQ_GT(raw_sb->rblk_end, sb->sblk_end))
398 sb->sblk_end = raw_sb->rblk_end;
6c1bbf57
SZ
399 else
400 *update = FALSE;
02cc2f35 401 tcpstat.tcps_sacksbreused++;
91489f6b 402 } else {
01d244e6
SZ
403 workingblock = alloc_sackblock_limit(scb, raw_sb);
404 if (workingblock == NULL)
405 return ENOMEM;
406 TAILQ_INSERT_AFTER(&scb->sackblocks, sb, workingblock,
407 sblk_list);
91489f6b
JH
408 ++scb->nblocks;
409 }
410 }
411
412 /* Consolidate right-hand side. */
413 sb = TAILQ_NEXT(workingblock, sblk_list);
414 while (sb != NULL &&
415 SEQ_GEQ(workingblock->sblk_end, sb->sblk_end)) {
416 struct sackblock *nextblock;
417
418 nextblock = TAILQ_NEXT(sb, sblk_list);
9e3d6c96
MD
419 if (scb->lastfound == sb)
420 scb->lastfound = NULL;
91489f6b
JH
421 /* Remove completely overlapped block */
422 TAILQ_REMOVE(&scb->sackblocks, sb, sblk_list);
006af0db 423 free_sackblock(scb, sb);
91489f6b
JH
424 --scb->nblocks;
425 KASSERT(scb->nblocks > 0,
426 ("removed overlapped block: %d blocks left", scb->nblocks));
427 sb = nextblock;
428 }
429 if (sb != NULL &&
430 SEQ_GEQ(workingblock->sblk_end, sb->sblk_start)) {
431 /* Extend new block to cover partially overlapped old block. */
432 workingblock->sblk_end = sb->sblk_end;
9e3d6c96
MD
433 if (scb->lastfound == sb)
434 scb->lastfound = NULL;
91489f6b 435 TAILQ_REMOVE(&scb->sackblocks, sb, sblk_list);
006af0db 436 free_sackblock(scb, sb);
91489f6b
JH
437 --scb->nblocks;
438 KASSERT(scb->nblocks > 0,
439 ("removed partial right: %d blocks left", scb->nblocks));
440 }
01d244e6 441 return 0;
91489f6b
JH
442}
443
444#ifdef DEBUG_SACK_BLOCKS
445static void
446tcp_sack_dump_blocks(struct scoreboard *scb)
447{
448 struct sackblock *sb;
449
a6ec04bc 450 kprintf("%d blocks:", scb->nblocks);
91489f6b 451 TAILQ_FOREACH(sb, &scb->sackblocks, sblk_list)
a6ec04bc
SW
452 kprintf(" [%u, %u)", sb->sblk_start, sb->sblk_end);
453 kprintf("\n");
91489f6b
JH
454}
455#else
456static __inline void
457tcp_sack_dump_blocks(struct scoreboard *scb)
458{
459}
460#endif
461
462/*
463 * Optimization to quickly determine which packets are lost.
464 */
465static void
7e4852bb
SZ
466update_lostseq(struct scoreboard *scb, tcp_seq snd_una, u_int maxseg,
467 int rxtthresh)
91489f6b
JH
468{
469 struct sackblock *sb;
470 int nsackblocks = 0;
471 int bytes_sacked = 0;
472
473 sb = TAILQ_LAST(&scb->sackblocks, sackblock_list);
474 while (sb != NULL) {
475 ++nsackblocks;
476 bytes_sacked += sb->sblk_end - sb->sblk_start;
7e4852bb
SZ
477 if (nsackblocks == rxtthresh ||
478 bytes_sacked >= rxtthresh * maxseg) {
91489f6b
JH
479 scb->lostseq = sb->sblk_start;
480 return;
481 }
482 sb = TAILQ_PREV(sb, sackblock_list, sblk_list);
483 }
484 scb->lostseq = snd_una;
485}
486
487/*
488 * Return whether the given sequence number is considered lost.
489 */
490static boolean_t
491scb_islost(struct scoreboard *scb, tcp_seq seqnum)
492{
493 return SEQ_LT(seqnum, scb->lostseq);
494}
495
496/*
497 * True if at least "amount" has been SACKed. Used by Early Retransmit.
498 */
499boolean_t
500tcp_sack_has_sacked(struct scoreboard *scb, u_int amount)
501{
502 struct sackblock *sb;
503 int bytes_sacked = 0;
504
505 TAILQ_FOREACH(sb, &scb->sackblocks, sblk_list) {
506 bytes_sacked += sb->sblk_end - sb->sblk_start;
507 if (bytes_sacked >= amount)
508 return TRUE;
509 }
510 return FALSE;
511}
512
9a5b142f
JH
513/*
514 * Number of bytes SACKed below seq.
515 */
516int
517tcp_sack_bytes_below(struct scoreboard *scb, tcp_seq seq)
518{
519 struct sackblock *sb;
520 int bytes_sacked = 0;
521
522 sb = TAILQ_FIRST(&scb->sackblocks);
523 while (sb && SEQ_GT(seq, sb->sblk_start)) {
524 bytes_sacked += seq_min(seq, sb->sblk_end) - sb->sblk_start;
525 sb = TAILQ_NEXT(sb, sblk_list);
526 }
527 return bytes_sacked;
528}
529
91489f6b
JH
530/*
531 * Return estimate of the number of bytes outstanding in the network.
532 */
533uint32_t
534tcp_sack_compute_pipe(struct tcpcb *tp)
535{
536 struct scoreboard *scb = &tp->scb;
537 struct sackblock *sb;
538 int nlost, nretransmitted;
539 tcp_seq end;
540
541 nlost = tp->snd_max - scb->lostseq;
542 nretransmitted = tp->rexmt_high - tp->snd_una;
543
544 TAILQ_FOREACH(sb, &scb->sackblocks, sblk_list) {
545 if (SEQ_LT(sb->sblk_start, tp->rexmt_high)) {
546 end = seq_min(sb->sblk_end, tp->rexmt_high);
547 nretransmitted -= end - sb->sblk_start;
548 }
549 if (SEQ_GEQ(sb->sblk_start, scb->lostseq))
550 nlost -= sb->sblk_end - sb->sblk_start;
551 }
552
553 return (nlost + nretransmitted);
554}
555
556/*
557 * Return the sequence number and length of the next segment to transmit
558 * when in Fast Recovery.
559 */
560boolean_t
561tcp_sack_nextseg(struct tcpcb *tp, tcp_seq *nextrexmt, uint32_t *plen,
1bdfd728 562 boolean_t *rescue)
91489f6b
JH
563{
564 struct scoreboard *scb = &tp->scb;
565 struct socket *so = tp->t_inpcb->inp_socket;
566 struct sackblock *sb;
567 const struct sackblock *lastblock =
568 TAILQ_LAST(&scb->sackblocks, sackblock_list);
569 tcp_seq torexmt;
570 long len, off;
571
572 /* skip SACKed data */
573 tcp_sack_skip_sacked(scb, &tp->rexmt_high);
574
575 /* Look for lost data. */
576 torexmt = tp->rexmt_high;
1bdfd728 577 *rescue = FALSE;
91489f6b
JH
578 if (lastblock != NULL) {
579 if (SEQ_LT(torexmt, lastblock->sblk_end) &&
580 scb_islost(scb, torexmt)) {
581sendunsacked:
582 *nextrexmt = torexmt;
583 /* If the left-hand edge has been SACKed, pull it in. */
584 if (sack_block_lookup(scb, torexmt + tp->t_maxseg, &sb))
585 *plen = sb->sblk_start - torexmt;
586 else
587 *plen = tp->t_maxseg;
588 return TRUE;
589 }
590 }
591
592 /* See if unsent data available within send window. */
593 off = tp->snd_max - tp->snd_una;
6d49aa6f 594 len = (long) ulmin(so->so_snd.ssb_cc, tp->snd_wnd) - off;
91489f6b
JH
595 if (len > 0) {
596 *nextrexmt = tp->snd_max; /* Send new data. */
597 *plen = tp->t_maxseg;
598 return TRUE;
599 }
600
601 /* We're less certain this data has been lost. */
1bdfd728 602 if (lastblock != NULL && SEQ_LT(torexmt, lastblock->sblk_end))
91489f6b
JH
603 goto sendunsacked;
604
a098966f 605 /* Rescue retransmission */
1bdfd728
SZ
606 if (tcp_do_rescuesack) {
607 tcpstat.tcps_sackrescue_try++;
a098966f
SZ
608 if (tp->t_flags & TF_SACKRESCUED) {
609 if (!tcp_aggressive_rescuesack)
610 return FALSE;
1bdfd728 611
a098966f
SZ
612 /*
613 * Aggressive variant of the rescue retransmission.
614 *
615 * The idea of the rescue retransmission is to sustain
616 * the ACK clock thus to avoid timeout retransmission.
617 *
618 * Under some situations, the conservative approach
619 * suggested in the draft
620 * http://tools.ietf.org/html/
621 * draft-nishida-tcpm-rescue-retransmission-00
622 * could not sustain ACK clock, since it only allows
623 * one rescue retransmission before a cumulative ACK
624 * covers the segement transmitted by rescue
625 * retransmission.
626 *
627 * We try to locate the next unSACKed segment which
628 * follows the previously sent rescue segment. If
629 * there is no such segment, we loop back to the first
630 * unacknowledged segment.
631 */
632
633 /*
634 * Skip SACKed data, but here we follow
635 * the last transmitted rescue segment.
636 */
637 torexmt = tp->rexmt_rescue;
638 tcp_sack_skip_sacked(scb, &torexmt);
639 if (torexmt == tp->snd_max) {
640 /* Nothing left to retransmit; restart */
641 torexmt = tp->snd_una;
642 }
643 }
1bdfd728 644 *rescue = TRUE;
1bdfd728
SZ
645 goto sendunsacked;
646 } else if (tcp_do_smartsack && lastblock == NULL) {
a098966f
SZ
647 tcpstat.tcps_sackrescue_try++;
648 *rescue = TRUE;
1bdfd728
SZ
649 goto sendunsacked;
650 }
651
91489f6b
JH
652 return FALSE;
653}
654
655/*
656 * Return the next sequence number higher than "*prexmt" that has
657 * not been SACKed.
658 */
659void
660tcp_sack_skip_sacked(struct scoreboard *scb, tcp_seq *prexmt)
661{
662 struct sackblock *sb;
663
664 /* skip SACKed data */
665 if (sack_block_lookup(scb, *prexmt, &sb))
666 *prexmt = sb->sblk_end;
667}
668
669#ifdef later
670void
671tcp_sack_save_scoreboard(struct scoreboard *scb)
672{
673 struct scoreboard *scb = &tp->scb;
674
675 scb->sackblocks_prev = scb->sackblocks;
676 TAILQ_INIT(&scb->sackblocks);
677}
678
679void
680tcp_sack_revert_scoreboard(struct scoreboard *scb, tcp_seq snd_una,
681 u_int maxseg)
682{
683 struct sackblock *sb;
684
685 scb->sackblocks = scb->sackblocks_prev;
686 scb->nblocks = 0;
687 TAILQ_FOREACH(sb, &scb->sackblocks, sblk_list)
688 ++scb->nblocks;
689 tcp_sack_ack_blocks(scb, snd_una);
690 scb->lastfound = NULL;
691}
692#endif
693
694#ifdef DEBUG_SACK_HISTORY
695static void
696tcp_sack_dump_history(char *msg, struct tcpcb *tp)
697{
698 int i;
699 static int ndumped;
700
701 /* only need a couple of these to debug most problems */
702 if (++ndumped > 900)
703 return;
704
a6ec04bc 705 kprintf("%s:\tnsackhistory %d: ", msg, tp->nsackhistory);
91489f6b 706 for (i = 0; i < tp->nsackhistory; ++i)
a6ec04bc 707 kprintf("[%u, %u) ", tp->sackhistory[i].rblk_start,
91489f6b 708 tp->sackhistory[i].rblk_end);
a6ec04bc 709 kprintf("\n");
91489f6b
JH
710}
711#else
712static __inline void
713tcp_sack_dump_history(char *msg, struct tcpcb *tp)
714{
715}
716#endif
717
718/*
719 * Remove old SACK blocks from the SACK history that have already been ACKed.
720 */
721static void
722tcp_sack_ack_history(struct tcpcb *tp)
723{
724 int i, nblocks, openslot;
725
726 tcp_sack_dump_history("before tcp_sack_ack_history", tp);
727 nblocks = tp->nsackhistory;
728 for (i = openslot = 0; i < nblocks; ++i) {
729 if (SEQ_LEQ(tp->sackhistory[i].rblk_end, tp->rcv_nxt)) {
730 --tp->nsackhistory;
731 continue;
732 }
733 if (SEQ_LT(tp->sackhistory[i].rblk_start, tp->rcv_nxt))
734 tp->sackhistory[i].rblk_start = tp->rcv_nxt;
735 if (i == openslot)
736 ++openslot;
737 else
738 tp->sackhistory[openslot++] = tp->sackhistory[i];
739 }
740 tcp_sack_dump_history("after tcp_sack_ack_history", tp);
741 KASSERT(openslot == tp->nsackhistory,
742 ("tcp_sack_ack_history miscounted: %d != %d",
743 openslot, tp->nsackhistory));
744}
745
746/*
747 * Add or merge newblock into reported history.
748 * Also remove or update SACK blocks that will be acked.
749 */
750static void
751tcp_sack_update_reported_history(struct tcpcb *tp, tcp_seq start, tcp_seq end)
752{
753 struct raw_sackblock copy[MAX_SACK_REPORT_BLOCKS];
754 int i, cindex;
755
756 tcp_sack_dump_history("before tcp_sack_update_reported_history", tp);
757 /*
758 * Six cases:
759 * 0) no overlap
760 * 1) newblock == oldblock
761 * 2) oldblock contains newblock
762 * 3) newblock contains oldblock
763 * 4) tail of oldblock overlaps or abuts start of newblock
764 * 5) tail of newblock overlaps or abuts head of oldblock
765 */
766 for (i = cindex = 0; i < tp->nsackhistory; ++i) {
767 struct raw_sackblock *oldblock = &tp->sackhistory[i];
768 tcp_seq old_start = oldblock->rblk_start;
769 tcp_seq old_end = oldblock->rblk_end;
770
771 if (SEQ_LT(end, old_start) || SEQ_GT(start, old_end)) {
772 /* Case 0: no overlap. Copy old block. */
773 copy[cindex++] = *oldblock;
774 continue;
775 }
776
777 if (SEQ_GEQ(start, old_start) && SEQ_LEQ(end, old_end)) {
778 /* Cases 1 & 2. Move block to front of history. */
779 int j;
780
781 start = old_start;
782 end = old_end;
783 /* no need to check rest of blocks */
784 for (j = i + 1; j < tp->nsackhistory; ++j)
785 copy[cindex++] = tp->sackhistory[j];
786 break;
787 }
788
789 if (SEQ_GEQ(old_end, start) && SEQ_LT(old_start, start)) {
790 /* Case 4: extend start of new block. */
791 start = old_start;
792 } else if (SEQ_GEQ(end, old_start) && SEQ_GT(old_end, end)) {
793 /* Case 5: extend end of new block */
794 end = old_end;
795 } else {
796 /* Case 3. Delete old block by not copying it. */
797 KASSERT(SEQ_LEQ(start, old_start) &&
798 SEQ_GEQ(end, old_end),
799 ("bad logic: old [%u, %u), new [%u, %u)",
800 old_start, old_end, start, end));
801 }
802 }
803
804 /* insert new block */
805 tp->sackhistory[0].rblk_start = start;
806 tp->sackhistory[0].rblk_end = end;
807 cindex = min(cindex, MAX_SACK_REPORT_BLOCKS - 1);
808 for (i = 0; i < cindex; ++i)
809 tp->sackhistory[i + 1] = copy[i];
810 tp->nsackhistory = cindex + 1;
811 tcp_sack_dump_history("after tcp_sack_update_reported_history", tp);
812}
813
814/*
815 * Fill in SACK report to return to data sender.
816 */
817void
818tcp_sack_fill_report(struct tcpcb *tp, u_char *opt, u_int *plen)
819{
820 u_int optlen = *plen;
821 uint32_t *lp = (uint32_t *)(opt + optlen);
822 uint32_t *olp;
823 tcp_seq hstart = tp->rcv_nxt, hend;
824 int nblocks;
825
826 KASSERT(TCP_MAXOLEN - optlen >=
827 TCPOLEN_SACK_ALIGNED + TCPOLEN_SACK_BLOCK,
828 ("no room for SACK header and one block: optlen %d", optlen));
829
02cc2f35
SZ
830 if (tp->t_flags & TF_DUPSEG)
831 tcpstat.tcps_snddsackopt++;
832 else
833 tcpstat.tcps_sndsackopt++;
834
91489f6b
JH
835 olp = lp++;
836 optlen += TCPOLEN_SACK_ALIGNED;
837
838 tcp_sack_ack_history(tp);
839 if (tp->reportblk.rblk_start != tp->reportblk.rblk_end) {
840 *lp++ = htonl(tp->reportblk.rblk_start);
841 *lp++ = htonl(tp->reportblk.rblk_end);
842 optlen += TCPOLEN_SACK_BLOCK;
843 hstart = tp->reportblk.rblk_start;
844 hend = tp->reportblk.rblk_end;
845 if (tp->t_flags & TF_ENCLOSESEG) {
846 KASSERT(TCP_MAXOLEN - optlen >= TCPOLEN_SACK_BLOCK,
847 ("no room for enclosing SACK block: oplen %d",
848 optlen));
849 *lp++ = htonl(tp->encloseblk.rblk_start);
850 *lp++ = htonl(tp->encloseblk.rblk_end);
851 optlen += TCPOLEN_SACK_BLOCK;
852 hstart = tp->encloseblk.rblk_start;
853 hend = tp->encloseblk.rblk_end;
854 }
855 if (SEQ_GT(hstart, tp->rcv_nxt))
856 tcp_sack_update_reported_history(tp, hstart, hend);
857 }
858 if (tcp_do_smartsack && (tp->t_flags & TF_SACKLEFT)) {
859 /* Fill in from left! Walk re-assembly queue. */
860 struct tseg_qent *q;
861
862 q = LIST_FIRST(&tp->t_segq);
863 while (q != NULL &&
864 TCP_MAXOLEN - optlen >= TCPOLEN_SACK_BLOCK) {
865 *lp++ = htonl(q->tqe_th->th_seq);
3a5d999b
SZ
866 *lp++ = htonl(TCP_SACK_BLKEND(
867 q->tqe_th->th_seq + q->tqe_len,
868 q->tqe_th->th_flags));
91489f6b
JH
869 optlen += TCPOLEN_SACK_BLOCK;
870 q = LIST_NEXT(q, tqe_q);
871 }
872 } else {
873 int n = 0;
874
875 /* Fill in SACK blocks from right side. */
876 while (n < tp->nsackhistory &&
877 TCP_MAXOLEN - optlen >= TCPOLEN_SACK_BLOCK) {
878 if (tp->sackhistory[n].rblk_start != hstart) {
879 *lp++ = htonl(tp->sackhistory[n].rblk_start);
880 *lp++ = htonl(tp->sackhistory[n].rblk_end);
881 optlen += TCPOLEN_SACK_BLOCK;
882 }
883 ++n;
884 }
885 }
886 tp->reportblk.rblk_start = tp->reportblk.rblk_end;
887 tp->t_flags &= ~(TF_DUPSEG | TF_ENCLOSESEG | TF_SACKLEFT);
888 nblocks = (lp - olp - 1) / 2;
889 *olp = htonl(TCPOPT_SACK_ALIGNED |
890 (TCPOLEN_SACK + nblocks * TCPOLEN_SACK_BLOCK));
891 *plen = optlen;
892}