tcp/sack: Implement RFC3517bis
[dragonfly.git] / sys / netinet / tcp_sack.c
CommitLineData
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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 $
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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
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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");
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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
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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;
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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
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186}
187
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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);
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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)
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214 scb->lastfound = NULL;
215 TAILQ_REMOVE(&scb->sackblocks, sb, sblk_list);
006af0db 216 free_sackblock(scb, sb);
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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);
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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
244/*
006af0db
SZ
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
258/*
d58ca578
SZ
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
268/*
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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;
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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;
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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;
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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;
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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 }
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355}
356
357/*
358 * Insert SACK block into sender's scoreboard.
359 */
01d244e6 360static int
6c1bbf57
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361insert_block(struct scoreboard *scb, const struct raw_sackblock *raw_sb,
362 boolean_t *update)
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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,
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JH
383 ("too many SACK blocks %d", scb->nblocks));
384
01d244e6 385 overlap_front = sack_block_lookup(scb, raw_sb->rblk_start, &sb);
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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);
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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);
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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);
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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;
ffe35e17
SZ
472 int rxtthresh_bytes;
473
474 if (tcp_do_rfc3517bis)
475 rxtthresh_bytes = (rxtthresh - 1) * maxseg;
476 else
477 rxtthresh_bytes = rxtthresh * maxseg;
91489f6b
JH
478
479 sb = TAILQ_LAST(&scb->sackblocks, sackblock_list);
480 while (sb != NULL) {
481 ++nsackblocks;
482 bytes_sacked += sb->sblk_end - sb->sblk_start;
7e4852bb 483 if (nsackblocks == rxtthresh ||
ffe35e17 484 bytes_sacked >= rxtthresh_bytes) {
91489f6b
JH
485 scb->lostseq = sb->sblk_start;
486 return;
487 }
488 sb = TAILQ_PREV(sb, sackblock_list, sblk_list);
489 }
490 scb->lostseq = snd_una;
491}
492
493/*
494 * Return whether the given sequence number is considered lost.
495 */
ffe35e17
SZ
496boolean_t
497tcp_sack_islost(struct scoreboard *scb, tcp_seq seqnum)
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JH
498{
499 return SEQ_LT(seqnum, scb->lostseq);
500}
501
502/*
503 * True if at least "amount" has been SACKed. Used by Early Retransmit.
504 */
505boolean_t
506tcp_sack_has_sacked(struct scoreboard *scb, u_int amount)
507{
508 struct sackblock *sb;
509 int bytes_sacked = 0;
510
511 TAILQ_FOREACH(sb, &scb->sackblocks, sblk_list) {
512 bytes_sacked += sb->sblk_end - sb->sblk_start;
513 if (bytes_sacked >= amount)
514 return TRUE;
515 }
516 return FALSE;
517}
518
519/*
9a5b142f
JH
520 * Number of bytes SACKed below seq.
521 */
522int
523tcp_sack_bytes_below(struct scoreboard *scb, tcp_seq seq)
524{
525 struct sackblock *sb;
526 int bytes_sacked = 0;
527
528 sb = TAILQ_FIRST(&scb->sackblocks);
529 while (sb && SEQ_GT(seq, sb->sblk_start)) {
530 bytes_sacked += seq_min(seq, sb->sblk_end) - sb->sblk_start;
531 sb = TAILQ_NEXT(sb, sblk_list);
532 }
533 return bytes_sacked;
534}
535
536/*
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JH
537 * Return estimate of the number of bytes outstanding in the network.
538 */
539uint32_t
540tcp_sack_compute_pipe(struct tcpcb *tp)
541{
542 struct scoreboard *scb = &tp->scb;
543 struct sackblock *sb;
544 int nlost, nretransmitted;
545 tcp_seq end;
546
547 nlost = tp->snd_max - scb->lostseq;
548 nretransmitted = tp->rexmt_high - tp->snd_una;
549
550 TAILQ_FOREACH(sb, &scb->sackblocks, sblk_list) {
551 if (SEQ_LT(sb->sblk_start, tp->rexmt_high)) {
552 end = seq_min(sb->sblk_end, tp->rexmt_high);
553 nretransmitted -= end - sb->sblk_start;
554 }
555 if (SEQ_GEQ(sb->sblk_start, scb->lostseq))
556 nlost -= sb->sblk_end - sb->sblk_start;
557 }
558
559 return (nlost + nretransmitted);
560}
561
562/*
563 * Return the sequence number and length of the next segment to transmit
564 * when in Fast Recovery.
565 */
566boolean_t
567tcp_sack_nextseg(struct tcpcb *tp, tcp_seq *nextrexmt, uint32_t *plen,
1bdfd728 568 boolean_t *rescue)
91489f6b
JH
569{
570 struct scoreboard *scb = &tp->scb;
571 struct socket *so = tp->t_inpcb->inp_socket;
572 struct sackblock *sb;
573 const struct sackblock *lastblock =
574 TAILQ_LAST(&scb->sackblocks, sackblock_list);
575 tcp_seq torexmt;
576 long len, off;
577
578 /* skip SACKed data */
579 tcp_sack_skip_sacked(scb, &tp->rexmt_high);
580
581 /* Look for lost data. */
582 torexmt = tp->rexmt_high;
1bdfd728 583 *rescue = FALSE;
91489f6b
JH
584 if (lastblock != NULL) {
585 if (SEQ_LT(torexmt, lastblock->sblk_end) &&
ffe35e17 586 tcp_sack_islost(scb, torexmt)) {
91489f6b
JH
587sendunsacked:
588 *nextrexmt = torexmt;
589 /* If the left-hand edge has been SACKed, pull it in. */
590 if (sack_block_lookup(scb, torexmt + tp->t_maxseg, &sb))
591 *plen = sb->sblk_start - torexmt;
592 else
593 *plen = tp->t_maxseg;
594 return TRUE;
595 }
596 }
597
598 /* See if unsent data available within send window. */
599 off = tp->snd_max - tp->snd_una;
6d49aa6f 600 len = (long) ulmin(so->so_snd.ssb_cc, tp->snd_wnd) - off;
91489f6b
JH
601 if (len > 0) {
602 *nextrexmt = tp->snd_max; /* Send new data. */
603 *plen = tp->t_maxseg;
604 return TRUE;
605 }
606
607 /* We're less certain this data has been lost. */
1bdfd728 608 if (lastblock != NULL && SEQ_LT(torexmt, lastblock->sblk_end))
91489f6b
JH
609 goto sendunsacked;
610
a098966f 611 /* Rescue retransmission */
ffe35e17 612 if (tcp_do_rescuesack || tcp_do_rfc3517bis) {
1bdfd728 613 tcpstat.tcps_sackrescue_try++;
a098966f
SZ
614 if (tp->t_flags & TF_SACKRESCUED) {
615 if (!tcp_aggressive_rescuesack)
616 return FALSE;
1bdfd728 617
a098966f
SZ
618 /*
619 * Aggressive variant of the rescue retransmission.
620 *
621 * The idea of the rescue retransmission is to sustain
622 * the ACK clock thus to avoid timeout retransmission.
623 *
624 * Under some situations, the conservative approach
625 * suggested in the draft
626 * http://tools.ietf.org/html/
627 * draft-nishida-tcpm-rescue-retransmission-00
628 * could not sustain ACK clock, since it only allows
629 * one rescue retransmission before a cumulative ACK
630 * covers the segement transmitted by rescue
631 * retransmission.
632 *
633 * We try to locate the next unSACKed segment which
634 * follows the previously sent rescue segment. If
635 * there is no such segment, we loop back to the first
636 * unacknowledged segment.
637 */
638
639 /*
640 * Skip SACKed data, but here we follow
641 * the last transmitted rescue segment.
642 */
643 torexmt = tp->rexmt_rescue;
644 tcp_sack_skip_sacked(scb, &torexmt);
645 if (torexmt == tp->snd_max) {
646 /* Nothing left to retransmit; restart */
647 torexmt = tp->snd_una;
648 }
649 }
1bdfd728 650 *rescue = TRUE;
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SZ
651 goto sendunsacked;
652 } else if (tcp_do_smartsack && lastblock == NULL) {
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SZ
653 tcpstat.tcps_sackrescue_try++;
654 *rescue = TRUE;
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SZ
655 goto sendunsacked;
656 }
657
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JH
658 return FALSE;
659}
660
661/*
662 * Return the next sequence number higher than "*prexmt" that has
663 * not been SACKed.
664 */
665void
666tcp_sack_skip_sacked(struct scoreboard *scb, tcp_seq *prexmt)
667{
668 struct sackblock *sb;
669
670 /* skip SACKed data */
671 if (sack_block_lookup(scb, *prexmt, &sb))
672 *prexmt = sb->sblk_end;
673}
674
675#ifdef later
676void
677tcp_sack_save_scoreboard(struct scoreboard *scb)
678{
679 struct scoreboard *scb = &tp->scb;
680
681 scb->sackblocks_prev = scb->sackblocks;
682 TAILQ_INIT(&scb->sackblocks);
683}
684
685void
686tcp_sack_revert_scoreboard(struct scoreboard *scb, tcp_seq snd_una,
687 u_int maxseg)
688{
689 struct sackblock *sb;
690
691 scb->sackblocks = scb->sackblocks_prev;
692 scb->nblocks = 0;
693 TAILQ_FOREACH(sb, &scb->sackblocks, sblk_list)
694 ++scb->nblocks;
695 tcp_sack_ack_blocks(scb, snd_una);
696 scb->lastfound = NULL;
697}
698#endif
699
700#ifdef DEBUG_SACK_HISTORY
701static void
702tcp_sack_dump_history(char *msg, struct tcpcb *tp)
703{
704 int i;
705 static int ndumped;
706
707 /* only need a couple of these to debug most problems */
708 if (++ndumped > 900)
709 return;
710
a6ec04bc 711 kprintf("%s:\tnsackhistory %d: ", msg, tp->nsackhistory);
91489f6b 712 for (i = 0; i < tp->nsackhistory; ++i)
a6ec04bc 713 kprintf("[%u, %u) ", tp->sackhistory[i].rblk_start,
91489f6b 714 tp->sackhistory[i].rblk_end);
a6ec04bc 715 kprintf("\n");
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JH
716}
717#else
718static __inline void
719tcp_sack_dump_history(char *msg, struct tcpcb *tp)
720{
721}
722#endif
723
724/*
725 * Remove old SACK blocks from the SACK history that have already been ACKed.
726 */
727static void
728tcp_sack_ack_history(struct tcpcb *tp)
729{
730 int i, nblocks, openslot;
731
732 tcp_sack_dump_history("before tcp_sack_ack_history", tp);
733 nblocks = tp->nsackhistory;
734 for (i = openslot = 0; i < nblocks; ++i) {
735 if (SEQ_LEQ(tp->sackhistory[i].rblk_end, tp->rcv_nxt)) {
736 --tp->nsackhistory;
737 continue;
738 }
739 if (SEQ_LT(tp->sackhistory[i].rblk_start, tp->rcv_nxt))
740 tp->sackhistory[i].rblk_start = tp->rcv_nxt;
741 if (i == openslot)
742 ++openslot;
743 else
744 tp->sackhistory[openslot++] = tp->sackhistory[i];
745 }
746 tcp_sack_dump_history("after tcp_sack_ack_history", tp);
747 KASSERT(openslot == tp->nsackhistory,
748 ("tcp_sack_ack_history miscounted: %d != %d",
749 openslot, tp->nsackhistory));
750}
751
752/*
753 * Add or merge newblock into reported history.
754 * Also remove or update SACK blocks that will be acked.
755 */
756static void
757tcp_sack_update_reported_history(struct tcpcb *tp, tcp_seq start, tcp_seq end)
758{
759 struct raw_sackblock copy[MAX_SACK_REPORT_BLOCKS];
760 int i, cindex;
761
762 tcp_sack_dump_history("before tcp_sack_update_reported_history", tp);
763 /*
764 * Six cases:
765 * 0) no overlap
766 * 1) newblock == oldblock
767 * 2) oldblock contains newblock
768 * 3) newblock contains oldblock
769 * 4) tail of oldblock overlaps or abuts start of newblock
770 * 5) tail of newblock overlaps or abuts head of oldblock
771 */
772 for (i = cindex = 0; i < tp->nsackhistory; ++i) {
773 struct raw_sackblock *oldblock = &tp->sackhistory[i];
774 tcp_seq old_start = oldblock->rblk_start;
775 tcp_seq old_end = oldblock->rblk_end;
776
777 if (SEQ_LT(end, old_start) || SEQ_GT(start, old_end)) {
778 /* Case 0: no overlap. Copy old block. */
779 copy[cindex++] = *oldblock;
780 continue;
781 }
782
783 if (SEQ_GEQ(start, old_start) && SEQ_LEQ(end, old_end)) {
784 /* Cases 1 & 2. Move block to front of history. */
785 int j;
786
787 start = old_start;
788 end = old_end;
789 /* no need to check rest of blocks */
790 for (j = i + 1; j < tp->nsackhistory; ++j)
791 copy[cindex++] = tp->sackhistory[j];
792 break;
793 }
794
795 if (SEQ_GEQ(old_end, start) && SEQ_LT(old_start, start)) {
796 /* Case 4: extend start of new block. */
797 start = old_start;
798 } else if (SEQ_GEQ(end, old_start) && SEQ_GT(old_end, end)) {
799 /* Case 5: extend end of new block */
800 end = old_end;
801 } else {
802 /* Case 3. Delete old block by not copying it. */
803 KASSERT(SEQ_LEQ(start, old_start) &&
804 SEQ_GEQ(end, old_end),
805 ("bad logic: old [%u, %u), new [%u, %u)",
806 old_start, old_end, start, end));
807 }
808 }
809
810 /* insert new block */
811 tp->sackhistory[0].rblk_start = start;
812 tp->sackhistory[0].rblk_end = end;
813 cindex = min(cindex, MAX_SACK_REPORT_BLOCKS - 1);
814 for (i = 0; i < cindex; ++i)
815 tp->sackhistory[i + 1] = copy[i];
816 tp->nsackhistory = cindex + 1;
817 tcp_sack_dump_history("after tcp_sack_update_reported_history", tp);
818}
819
820/*
821 * Fill in SACK report to return to data sender.
822 */
823void
824tcp_sack_fill_report(struct tcpcb *tp, u_char *opt, u_int *plen)
825{
826 u_int optlen = *plen;
827 uint32_t *lp = (uint32_t *)(opt + optlen);
828 uint32_t *olp;
829 tcp_seq hstart = tp->rcv_nxt, hend;
830 int nblocks;
831
832 KASSERT(TCP_MAXOLEN - optlen >=
833 TCPOLEN_SACK_ALIGNED + TCPOLEN_SACK_BLOCK,
834 ("no room for SACK header and one block: optlen %d", optlen));
835
02cc2f35
SZ
836 if (tp->t_flags & TF_DUPSEG)
837 tcpstat.tcps_snddsackopt++;
838 else
839 tcpstat.tcps_sndsackopt++;
840
91489f6b
JH
841 olp = lp++;
842 optlen += TCPOLEN_SACK_ALIGNED;
843
844 tcp_sack_ack_history(tp);
845 if (tp->reportblk.rblk_start != tp->reportblk.rblk_end) {
846 *lp++ = htonl(tp->reportblk.rblk_start);
847 *lp++ = htonl(tp->reportblk.rblk_end);
848 optlen += TCPOLEN_SACK_BLOCK;
849 hstart = tp->reportblk.rblk_start;
850 hend = tp->reportblk.rblk_end;
851 if (tp->t_flags & TF_ENCLOSESEG) {
852 KASSERT(TCP_MAXOLEN - optlen >= TCPOLEN_SACK_BLOCK,
853 ("no room for enclosing SACK block: oplen %d",
854 optlen));
855 *lp++ = htonl(tp->encloseblk.rblk_start);
856 *lp++ = htonl(tp->encloseblk.rblk_end);
857 optlen += TCPOLEN_SACK_BLOCK;
858 hstart = tp->encloseblk.rblk_start;
859 hend = tp->encloseblk.rblk_end;
860 }
861 if (SEQ_GT(hstart, tp->rcv_nxt))
862 tcp_sack_update_reported_history(tp, hstart, hend);
863 }
864 if (tcp_do_smartsack && (tp->t_flags & TF_SACKLEFT)) {
865 /* Fill in from left! Walk re-assembly queue. */
866 struct tseg_qent *q;
867
868 q = LIST_FIRST(&tp->t_segq);
869 while (q != NULL &&
870 TCP_MAXOLEN - optlen >= TCPOLEN_SACK_BLOCK) {
871 *lp++ = htonl(q->tqe_th->th_seq);
3a5d999b
SZ
872 *lp++ = htonl(TCP_SACK_BLKEND(
873 q->tqe_th->th_seq + q->tqe_len,
874 q->tqe_th->th_flags));
91489f6b
JH
875 optlen += TCPOLEN_SACK_BLOCK;
876 q = LIST_NEXT(q, tqe_q);
877 }
878 } else {
879 int n = 0;
880
881 /* Fill in SACK blocks from right side. */
882 while (n < tp->nsackhistory &&
883 TCP_MAXOLEN - optlen >= TCPOLEN_SACK_BLOCK) {
884 if (tp->sackhistory[n].rblk_start != hstart) {
885 *lp++ = htonl(tp->sackhistory[n].rblk_start);
886 *lp++ = htonl(tp->sackhistory[n].rblk_end);
887 optlen += TCPOLEN_SACK_BLOCK;
888 }
889 ++n;
890 }
891 }
892 tp->reportblk.rblk_start = tp->reportblk.rblk_end;
893 tp->t_flags &= ~(TF_DUPSEG | TF_ENCLOSESEG | TF_SACKLEFT);
894 nblocks = (lp - olp - 1) / 2;
895 *olp = htonl(TCPOPT_SACK_ALIGNED |
896 (TCPOLEN_SACK + nblocks * TCPOLEN_SACK_BLOCK));
897 *plen = optlen;
898}