tcp/sack: Use RFC3517bis IsLost(snd_una) as fallback of early retransmit
[dragonfly.git] / sys / netinet / tcp_sack.c
CommitLineData
91489f6b
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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 $
91489f6b
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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
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 76
12f68b86 77static MALLOC_DEFINE(M_SACKBLOCK, "sblk", "sackblock struct");
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78
79/*
80 * Per-tcpcb initialization.
81 */
82void
83tcp_sack_tcpcb_init(struct tcpcb *tp)
84{
85 struct scoreboard *scb = &tp->scb;
86
87 scb->nblocks = 0;
88 TAILQ_INIT(&scb->sackblocks);
89 scb->lastfound = NULL;
90}
91
92/*
93 * Find the SACK block containing or immediately preceding "seq".
94 * The boolean result indicates whether the sequence is actually
95 * contained in the SACK block.
96 */
97static boolean_t
98sack_block_lookup(struct scoreboard *scb, tcp_seq seq, struct sackblock **sb)
99{
100 struct sackblock *hint = scb->lastfound;
101 struct sackblock *cur, *last, *prev;
102
103 if (TAILQ_EMPTY(&scb->sackblocks)) {
104 *sb = NULL;
105 return FALSE;
106 }
107
108 if (hint == NULL) {
109 /* No hint. Search from start to end. */
110 cur = TAILQ_FIRST(&scb->sackblocks);
111 last = NULL;
112 prev = TAILQ_LAST(&scb->sackblocks, sackblock_list);
113 } else {
114 if (SEQ_GEQ(seq, hint->sblk_start)) {
115 /* Search from hint to end of list. */
116 cur = hint;
117 last = NULL;
118 prev = TAILQ_LAST(&scb->sackblocks, sackblock_list);
119 } else {
120 /* Search from front of list to hint. */
121 cur = TAILQ_FIRST(&scb->sackblocks);
122 last = hint;
123 prev = TAILQ_PREV(hint, sackblock_list, sblk_list);
124 }
125 }
126
127 do {
128 if (SEQ_GT(cur->sblk_end, seq)) {
129 if (SEQ_GEQ(seq, cur->sblk_start)) {
130 *sb = scb->lastfound = cur;
131 return TRUE;
132 } else {
133 *sb = scb->lastfound =
134 TAILQ_PREV(cur, sackblock_list, sblk_list);
135 return FALSE;
136 }
137 }
138 cur = TAILQ_NEXT(cur, sblk_list);
139 } while (cur != last);
140
141 *sb = scb->lastfound = prev;
142 return FALSE;
143}
144
145/*
146 * Allocate a SACK block.
147 */
148static __inline struct sackblock *
006af0db 149alloc_sackblock(struct scoreboard *scb, const struct raw_sackblock *raw_sb)
91489f6b 150{
26d3f1fb
SZ
151 struct sackblock *sb;
152
006af0db
SZ
153 if (scb->freecache != NULL) {
154 sb = scb->freecache;
155 scb->freecache = NULL;
156 tcpstat.tcps_sacksbfast++;
01d244e6 157 } else {
006af0db
SZ
158 sb = kmalloc(sizeof(struct sackblock), M_SACKBLOCK, M_NOWAIT);
159 if (sb == NULL) {
160 tcpstat.tcps_sacksbfailed++;
161 return NULL;
162 }
26d3f1fb 163 }
006af0db
SZ
164 sb->sblk_start = raw_sb->rblk_start;
165 sb->sblk_end = raw_sb->rblk_end;
26d3f1fb 166 return sb;
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167}
168
01d244e6
SZ
169static __inline struct sackblock *
170alloc_sackblock_limit(struct scoreboard *scb,
171 const struct raw_sackblock *raw_sb)
172{
173 if (scb->nblocks == MAXSAVEDBLOCKS) {
174 /*
175 * Should try to kick out older blocks XXX JH
176 * May be able to coalesce with existing block.
177 * Or, go other way and free all blocks if we hit
178 * this limit.
179 */
180 tcpstat.tcps_sacksboverflow++;
181 return NULL;
182 }
006af0db 183 return alloc_sackblock(scb, raw_sb);
01d244e6
SZ
184}
185
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186/*
187 * Free a SACK block.
188 */
189static __inline void
006af0db 190free_sackblock(struct scoreboard *scb, struct sackblock *s)
91489f6b 191{
006af0db
SZ
192 if (scb->freecache == NULL) {
193 /* YYY Maybe use the latest freed block? */
194 scb->freecache = s;
195 return;
196 }
12f68b86 197 kfree(s, M_SACKBLOCK);
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198}
199
200/*
201 * Free up SACK blocks for data that's been acked.
202 */
203static void
204tcp_sack_ack_blocks(struct scoreboard *scb, tcp_seq th_ack)
205{
206 struct sackblock *sb, *nb;
207
208 sb = TAILQ_FIRST(&scb->sackblocks);
209 while (sb && SEQ_LEQ(sb->sblk_end, th_ack)) {
210 nb = TAILQ_NEXT(sb, sblk_list);
9e3d6c96 211 if (scb->lastfound == sb)
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212 scb->lastfound = NULL;
213 TAILQ_REMOVE(&scb->sackblocks, sb, sblk_list);
006af0db 214 free_sackblock(scb, sb);
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215 --scb->nblocks;
216 KASSERT(scb->nblocks >= 0,
217 ("SACK block count underflow: %d < 0", scb->nblocks));
218 sb = nb;
219 }
220 if (sb && SEQ_GT(th_ack, sb->sblk_start))
221 sb->sblk_start = th_ack; /* other side reneged? XXX */
222}
223
224/*
225 * Delete and free SACK blocks saved in scoreboard.
226 */
227void
228tcp_sack_cleanup(struct scoreboard *scb)
229{
230 struct sackblock *sb, *nb;
231
232 TAILQ_FOREACH_MUTABLE(sb, &scb->sackblocks, sblk_list, nb) {
006af0db 233 free_sackblock(scb, sb);
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234 --scb->nblocks;
235 }
236 KASSERT(scb->nblocks == 0,
237 ("SACK block %d count not zero", scb->nblocks));
238 TAILQ_INIT(&scb->sackblocks);
239 scb->lastfound = NULL;
240}
241
242/*
006af0db
SZ
243 * Delete and free SACK blocks saved in scoreboard.
244 * Delete the one slot block cache.
245 */
246void
247tcp_sack_destroy(struct scoreboard *scb)
248{
249 tcp_sack_cleanup(scb);
250 if (scb->freecache != NULL) {
251 kfree(scb->freecache, M_SACKBLOCK);
252 scb->freecache = NULL;
253 }
254}
255
256/*
d58ca578
SZ
257 * Cleanup the reported SACK block information
258 */
259void
260tcp_sack_report_cleanup(struct tcpcb *tp)
261{
c7e6499a
SZ
262 tp->sack_flags &=
263 ~(TSACK_F_DUPSEG | TSACK_F_ENCLOSESEG | TSACK_F_SACKLEFT);
d58ca578
SZ
264 tp->reportblk.rblk_start = tp->reportblk.rblk_end;
265}
266
267/*
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268 * Returns 0 if not D-SACK block,
269 * 1 if D-SACK,
270 * 2 if duplicate of out-of-order D-SACK block.
271 */
272int
273tcp_sack_ndsack_blocks(struct raw_sackblock *blocks, const int numblocks,
274 tcp_seq snd_una)
275{
276 if (numblocks == 0)
277 return 0;
278
279 if (SEQ_LT(blocks[0].rblk_start, snd_una))
280 return 1;
281
282 /* block 0 inside block 1 */
283 if (numblocks > 1 &&
284 SEQ_GEQ(blocks[0].rblk_start, blocks[1].rblk_start) &&
285 SEQ_LEQ(blocks[0].rblk_end, blocks[1].rblk_end))
286 return 2;
287
288 return 0;
289}
290
291/*
292 * Update scoreboard on new incoming ACK.
293 */
294static void
295tcp_sack_add_blocks(struct tcpcb *tp, struct tcpopt *to)
296{
297 const int numblocks = to->to_nsackblocks;
298 struct raw_sackblock *blocks = to->to_sackblocks;
299 struct scoreboard *scb = &tp->scb;
6c1bbf57 300 int startblock, i;
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301
302 if (tcp_sack_ndsack_blocks(blocks, numblocks, tp->snd_una) > 0)
303 startblock = 1;
304 else
305 startblock = 0;
306
6c1bbf57 307 to->to_flags |= TOF_SACK_REDUNDANT;
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308 for (i = startblock; i < numblocks; i++) {
309 struct raw_sackblock *newsackblock = &blocks[i];
6c1bbf57
SZ
310 boolean_t update;
311 int error;
91489f6b 312
331721f5
SZ
313 /* Guard against ACK reordering */
314 if (SEQ_LT(newsackblock->rblk_start, tp->snd_una))
315 continue;
316
317 /* Don't accept bad SACK blocks */
02cc2f35
SZ
318 if (SEQ_GT(newsackblock->rblk_end, tp->snd_max)) {
319 tcpstat.tcps_rcvbadsackopt++;
91489f6b 320 break; /* skip all other blocks */
02cc2f35
SZ
321 }
322 tcpstat.tcps_sacksbupdate++;
91489f6b 323
6c1bbf57
SZ
324 error = insert_block(scb, newsackblock, &update);
325 if (update)
326 to->to_flags &= ~TOF_SACK_REDUNDANT;
327 if (error)
01d244e6 328 break;
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JH
329 }
330}
331
332void
333tcp_sack_update_scoreboard(struct tcpcb *tp, struct tcpopt *to)
334{
335 struct scoreboard *scb = &tp->scb;
a098966f 336 int rexmt_high_update = 0;
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337
338 tcp_sack_ack_blocks(scb, tp->snd_una);
339 tcp_sack_add_blocks(tp, to);
e2289e66
SZ
340 tcp_sack_update_lostseq(scb, tp->snd_una, tp->t_maxseg,
341 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 }
c7e6499a 346 if (tp->sack_flags & TSACK_F_SACKRESCUED) {
a098966f 347 if (SEQ_LT(tp->rexmt_rescue, tp->snd_una)) {
c7e6499a 348 tp->sack_flags &= ~TSACK_F_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 394 if (overlap_front || sb->sblk_end == raw_sb->rblk_start) {
f3c063ed
SZ
395 tcpstat.tcps_sacksbreused++;
396
01d244e6 397 /* Extend old block */
91489f6b 398 workingblock = sb;
f3c063ed 399 if (SEQ_GT(raw_sb->rblk_end, sb->sblk_end)) {
01d244e6 400 sb->sblk_end = raw_sb->rblk_end;
f3c063ed
SZ
401 } else {
402 /* Exact match, nothing to consolidate */
6c1bbf57 403 *update = FALSE;
f3c063ed
SZ
404 return 0;
405 }
91489f6b 406 } else {
01d244e6
SZ
407 workingblock = alloc_sackblock_limit(scb, raw_sb);
408 if (workingblock == NULL)
409 return ENOMEM;
410 TAILQ_INSERT_AFTER(&scb->sackblocks, sb, workingblock,
411 sblk_list);
91489f6b
JH
412 ++scb->nblocks;
413 }
414 }
415
416 /* Consolidate right-hand side. */
417 sb = TAILQ_NEXT(workingblock, sblk_list);
418 while (sb != NULL &&
419 SEQ_GEQ(workingblock->sblk_end, sb->sblk_end)) {
420 struct sackblock *nextblock;
421
422 nextblock = TAILQ_NEXT(sb, sblk_list);
9e3d6c96
MD
423 if (scb->lastfound == sb)
424 scb->lastfound = NULL;
91489f6b
JH
425 /* Remove completely overlapped block */
426 TAILQ_REMOVE(&scb->sackblocks, sb, sblk_list);
006af0db 427 free_sackblock(scb, sb);
91489f6b
JH
428 --scb->nblocks;
429 KASSERT(scb->nblocks > 0,
430 ("removed overlapped block: %d blocks left", scb->nblocks));
431 sb = nextblock;
432 }
433 if (sb != NULL &&
434 SEQ_GEQ(workingblock->sblk_end, sb->sblk_start)) {
435 /* Extend new block to cover partially overlapped old block. */
436 workingblock->sblk_end = sb->sblk_end;
9e3d6c96
MD
437 if (scb->lastfound == sb)
438 scb->lastfound = NULL;
91489f6b 439 TAILQ_REMOVE(&scb->sackblocks, sb, sblk_list);
006af0db 440 free_sackblock(scb, sb);
91489f6b
JH
441 --scb->nblocks;
442 KASSERT(scb->nblocks > 0,
443 ("removed partial right: %d blocks left", scb->nblocks));
444 }
01d244e6 445 return 0;
91489f6b
JH
446}
447
448#ifdef DEBUG_SACK_BLOCKS
449static void
450tcp_sack_dump_blocks(struct scoreboard *scb)
451{
452 struct sackblock *sb;
453
a6ec04bc 454 kprintf("%d blocks:", scb->nblocks);
91489f6b 455 TAILQ_FOREACH(sb, &scb->sackblocks, sblk_list)
a6ec04bc
SW
456 kprintf(" [%u, %u)", sb->sblk_start, sb->sblk_end);
457 kprintf("\n");
91489f6b
JH
458}
459#else
460static __inline void
461tcp_sack_dump_blocks(struct scoreboard *scb)
462{
463}
464#endif
465
466/*
467 * Optimization to quickly determine which packets are lost.
468 */
e2289e66
SZ
469void
470tcp_sack_update_lostseq(struct scoreboard *scb, tcp_seq snd_una, u_int maxseg,
7e4852bb 471 int rxtthresh)
91489f6b
JH
472{
473 struct sackblock *sb;
474 int nsackblocks = 0;
475 int bytes_sacked = 0;
ffe35e17
SZ
476 int rxtthresh_bytes;
477
ba0d6f99 478 if (tcp_do_rfc3517bis)
ffe35e17
SZ
479 rxtthresh_bytes = (rxtthresh - 1) * maxseg;
480 else
481 rxtthresh_bytes = rxtthresh * maxseg;
91489f6b
JH
482
483 sb = TAILQ_LAST(&scb->sackblocks, sackblock_list);
484 while (sb != NULL) {
485 ++nsackblocks;
486 bytes_sacked += sb->sblk_end - sb->sblk_start;
7e4852bb 487 if (nsackblocks == rxtthresh ||
ffe35e17 488 bytes_sacked >= rxtthresh_bytes) {
91489f6b
JH
489 scb->lostseq = sb->sblk_start;
490 return;
491 }
492 sb = TAILQ_PREV(sb, sackblock_list, sblk_list);
493 }
494 scb->lostseq = snd_una;
495}
496
497/*
498 * Return whether the given sequence number is considered lost.
499 */
ffe35e17
SZ
500boolean_t
501tcp_sack_islost(struct scoreboard *scb, tcp_seq seqnum)
91489f6b
JH
502{
503 return SEQ_LT(seqnum, scb->lostseq);
504}
505
506/*
507 * True if at least "amount" has been SACKed. Used by Early Retransmit.
508 */
509boolean_t
510tcp_sack_has_sacked(struct scoreboard *scb, u_int amount)
511{
512 struct sackblock *sb;
513 int bytes_sacked = 0;
514
515 TAILQ_FOREACH(sb, &scb->sackblocks, sblk_list) {
516 bytes_sacked += sb->sblk_end - sb->sblk_start;
517 if (bytes_sacked >= amount)
518 return TRUE;
519 }
520 return FALSE;
521}
522
523/*
9a5b142f
JH
524 * Number of bytes SACKed below seq.
525 */
526int
527tcp_sack_bytes_below(struct scoreboard *scb, tcp_seq seq)
528{
529 struct sackblock *sb;
530 int bytes_sacked = 0;
531
532 sb = TAILQ_FIRST(&scb->sackblocks);
533 while (sb && SEQ_GT(seq, sb->sblk_start)) {
534 bytes_sacked += seq_min(seq, sb->sblk_end) - sb->sblk_start;
535 sb = TAILQ_NEXT(sb, sblk_list);
536 }
537 return bytes_sacked;
538}
539
540/*
91489f6b
JH
541 * Return estimate of the number of bytes outstanding in the network.
542 */
543uint32_t
544tcp_sack_compute_pipe(struct tcpcb *tp)
545{
546 struct scoreboard *scb = &tp->scb;
547 struct sackblock *sb;
548 int nlost, nretransmitted;
549 tcp_seq end;
550
551 nlost = tp->snd_max - scb->lostseq;
552 nretransmitted = tp->rexmt_high - tp->snd_una;
553
554 TAILQ_FOREACH(sb, &scb->sackblocks, sblk_list) {
555 if (SEQ_LT(sb->sblk_start, tp->rexmt_high)) {
556 end = seq_min(sb->sblk_end, tp->rexmt_high);
557 nretransmitted -= end - sb->sblk_start;
558 }
559 if (SEQ_GEQ(sb->sblk_start, scb->lostseq))
560 nlost -= sb->sblk_end - sb->sblk_start;
561 }
562
563 return (nlost + nretransmitted);
564}
565
566/*
567 * Return the sequence number and length of the next segment to transmit
568 * when in Fast Recovery.
569 */
570boolean_t
571tcp_sack_nextseg(struct tcpcb *tp, tcp_seq *nextrexmt, uint32_t *plen,
1bdfd728 572 boolean_t *rescue)
91489f6b
JH
573{
574 struct scoreboard *scb = &tp->scb;
575 struct socket *so = tp->t_inpcb->inp_socket;
576 struct sackblock *sb;
577 const struct sackblock *lastblock =
578 TAILQ_LAST(&scb->sackblocks, sackblock_list);
579 tcp_seq torexmt;
580 long len, off;
581
582 /* skip SACKed data */
583 tcp_sack_skip_sacked(scb, &tp->rexmt_high);
584
585 /* Look for lost data. */
586 torexmt = tp->rexmt_high;
1bdfd728 587 *rescue = FALSE;
91489f6b
JH
588 if (lastblock != NULL) {
589 if (SEQ_LT(torexmt, lastblock->sblk_end) &&
ffe35e17 590 tcp_sack_islost(scb, torexmt)) {
91489f6b
JH
591sendunsacked:
592 *nextrexmt = torexmt;
593 /* If the left-hand edge has been SACKed, pull it in. */
594 if (sack_block_lookup(scb, torexmt + tp->t_maxseg, &sb))
595 *plen = sb->sblk_start - torexmt;
596 else
597 *plen = tp->t_maxseg;
598 return TRUE;
599 }
600 }
601
602 /* See if unsent data available within send window. */
603 off = tp->snd_max - tp->snd_una;
6d49aa6f 604 len = (long) ulmin(so->so_snd.ssb_cc, tp->snd_wnd) - off;
91489f6b
JH
605 if (len > 0) {
606 *nextrexmt = tp->snd_max; /* Send new data. */
607 *plen = tp->t_maxseg;
608 return TRUE;
609 }
610
611 /* We're less certain this data has been lost. */
1bdfd728 612 if (lastblock != NULL && SEQ_LT(torexmt, lastblock->sblk_end))
91489f6b
JH
613 goto sendunsacked;
614
a098966f 615 /* Rescue retransmission */
ffe35e17 616 if (tcp_do_rescuesack || tcp_do_rfc3517bis) {
1bdfd728 617 tcpstat.tcps_sackrescue_try++;
c7e6499a 618 if (tp->sack_flags & TSACK_F_SACKRESCUED) {
a098966f
SZ
619 if (!tcp_aggressive_rescuesack)
620 return FALSE;
1bdfd728 621
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622 /*
623 * Aggressive variant of the rescue retransmission.
624 *
625 * The idea of the rescue retransmission is to sustain
626 * the ACK clock thus to avoid timeout retransmission.
627 *
628 * Under some situations, the conservative approach
629 * suggested in the draft
630 * http://tools.ietf.org/html/
631 * draft-nishida-tcpm-rescue-retransmission-00
632 * could not sustain ACK clock, since it only allows
633 * one rescue retransmission before a cumulative ACK
634 * covers the segement transmitted by rescue
635 * retransmission.
636 *
637 * We try to locate the next unSACKed segment which
638 * follows the previously sent rescue segment. If
639 * there is no such segment, we loop back to the first
640 * unacknowledged segment.
641 */
642
643 /*
644 * Skip SACKed data, but here we follow
645 * the last transmitted rescue segment.
646 */
647 torexmt = tp->rexmt_rescue;
648 tcp_sack_skip_sacked(scb, &torexmt);
eb5f6cff
SZ
649 }
650 if (torexmt == tp->snd_max) {
651 /* Nothing left to retransmit; restart */
652 torexmt = tp->snd_una;
a098966f 653 }
1bdfd728 654 *rescue = TRUE;
1bdfd728
SZ
655 goto sendunsacked;
656 } else if (tcp_do_smartsack && lastblock == NULL) {
a098966f
SZ
657 tcpstat.tcps_sackrescue_try++;
658 *rescue = TRUE;
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SZ
659 goto sendunsacked;
660 }
661
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JH
662 return FALSE;
663}
664
665/*
666 * Return the next sequence number higher than "*prexmt" that has
667 * not been SACKed.
668 */
669void
670tcp_sack_skip_sacked(struct scoreboard *scb, tcp_seq *prexmt)
671{
672 struct sackblock *sb;
673
674 /* skip SACKed data */
675 if (sack_block_lookup(scb, *prexmt, &sb))
676 *prexmt = sb->sblk_end;
677}
678
679#ifdef later
680void
681tcp_sack_save_scoreboard(struct scoreboard *scb)
682{
683 struct scoreboard *scb = &tp->scb;
684
685 scb->sackblocks_prev = scb->sackblocks;
686 TAILQ_INIT(&scb->sackblocks);
687}
688
689void
690tcp_sack_revert_scoreboard(struct scoreboard *scb, tcp_seq snd_una,
691 u_int maxseg)
692{
693 struct sackblock *sb;
694
695 scb->sackblocks = scb->sackblocks_prev;
696 scb->nblocks = 0;
697 TAILQ_FOREACH(sb, &scb->sackblocks, sblk_list)
698 ++scb->nblocks;
699 tcp_sack_ack_blocks(scb, snd_una);
700 scb->lastfound = NULL;
701}
702#endif
703
704#ifdef DEBUG_SACK_HISTORY
705static void
706tcp_sack_dump_history(char *msg, struct tcpcb *tp)
707{
708 int i;
709 static int ndumped;
710
711 /* only need a couple of these to debug most problems */
712 if (++ndumped > 900)
713 return;
714
a6ec04bc 715 kprintf("%s:\tnsackhistory %d: ", msg, tp->nsackhistory);
91489f6b 716 for (i = 0; i < tp->nsackhistory; ++i)
a6ec04bc 717 kprintf("[%u, %u) ", tp->sackhistory[i].rblk_start,
91489f6b 718 tp->sackhistory[i].rblk_end);
a6ec04bc 719 kprintf("\n");
91489f6b
JH
720}
721#else
722static __inline void
723tcp_sack_dump_history(char *msg, struct tcpcb *tp)
724{
725}
726#endif
727
728/*
729 * Remove old SACK blocks from the SACK history that have already been ACKed.
730 */
731static void
732tcp_sack_ack_history(struct tcpcb *tp)
733{
734 int i, nblocks, openslot;
735
736 tcp_sack_dump_history("before tcp_sack_ack_history", tp);
737 nblocks = tp->nsackhistory;
738 for (i = openslot = 0; i < nblocks; ++i) {
739 if (SEQ_LEQ(tp->sackhistory[i].rblk_end, tp->rcv_nxt)) {
740 --tp->nsackhistory;
741 continue;
742 }
743 if (SEQ_LT(tp->sackhistory[i].rblk_start, tp->rcv_nxt))
744 tp->sackhistory[i].rblk_start = tp->rcv_nxt;
745 if (i == openslot)
746 ++openslot;
747 else
748 tp->sackhistory[openslot++] = tp->sackhistory[i];
749 }
750 tcp_sack_dump_history("after tcp_sack_ack_history", tp);
751 KASSERT(openslot == tp->nsackhistory,
752 ("tcp_sack_ack_history miscounted: %d != %d",
753 openslot, tp->nsackhistory));
754}
755
756/*
757 * Add or merge newblock into reported history.
758 * Also remove or update SACK blocks that will be acked.
759 */
760static void
761tcp_sack_update_reported_history(struct tcpcb *tp, tcp_seq start, tcp_seq end)
762{
763 struct raw_sackblock copy[MAX_SACK_REPORT_BLOCKS];
764 int i, cindex;
765
766 tcp_sack_dump_history("before tcp_sack_update_reported_history", tp);
767 /*
768 * Six cases:
769 * 0) no overlap
770 * 1) newblock == oldblock
771 * 2) oldblock contains newblock
772 * 3) newblock contains oldblock
773 * 4) tail of oldblock overlaps or abuts start of newblock
774 * 5) tail of newblock overlaps or abuts head of oldblock
775 */
776 for (i = cindex = 0; i < tp->nsackhistory; ++i) {
777 struct raw_sackblock *oldblock = &tp->sackhistory[i];
778 tcp_seq old_start = oldblock->rblk_start;
779 tcp_seq old_end = oldblock->rblk_end;
780
781 if (SEQ_LT(end, old_start) || SEQ_GT(start, old_end)) {
782 /* Case 0: no overlap. Copy old block. */
783 copy[cindex++] = *oldblock;
784 continue;
785 }
786
787 if (SEQ_GEQ(start, old_start) && SEQ_LEQ(end, old_end)) {
788 /* Cases 1 & 2. Move block to front of history. */
789 int j;
790
791 start = old_start;
792 end = old_end;
793 /* no need to check rest of blocks */
794 for (j = i + 1; j < tp->nsackhistory; ++j)
795 copy[cindex++] = tp->sackhistory[j];
796 break;
797 }
798
799 if (SEQ_GEQ(old_end, start) && SEQ_LT(old_start, start)) {
800 /* Case 4: extend start of new block. */
801 start = old_start;
802 } else if (SEQ_GEQ(end, old_start) && SEQ_GT(old_end, end)) {
803 /* Case 5: extend end of new block */
804 end = old_end;
805 } else {
806 /* Case 3. Delete old block by not copying it. */
807 KASSERT(SEQ_LEQ(start, old_start) &&
808 SEQ_GEQ(end, old_end),
809 ("bad logic: old [%u, %u), new [%u, %u)",
810 old_start, old_end, start, end));
811 }
812 }
813
814 /* insert new block */
815 tp->sackhistory[0].rblk_start = start;
816 tp->sackhistory[0].rblk_end = end;
817 cindex = min(cindex, MAX_SACK_REPORT_BLOCKS - 1);
818 for (i = 0; i < cindex; ++i)
819 tp->sackhistory[i + 1] = copy[i];
820 tp->nsackhistory = cindex + 1;
821 tcp_sack_dump_history("after tcp_sack_update_reported_history", tp);
822}
823
824/*
825 * Fill in SACK report to return to data sender.
826 */
827void
828tcp_sack_fill_report(struct tcpcb *tp, u_char *opt, u_int *plen)
829{
830 u_int optlen = *plen;
831 uint32_t *lp = (uint32_t *)(opt + optlen);
832 uint32_t *olp;
833 tcp_seq hstart = tp->rcv_nxt, hend;
834 int nblocks;
835
836 KASSERT(TCP_MAXOLEN - optlen >=
837 TCPOLEN_SACK_ALIGNED + TCPOLEN_SACK_BLOCK,
838 ("no room for SACK header and one block: optlen %d", optlen));
839
c7e6499a 840 if (tp->sack_flags & TSACK_F_DUPSEG)
02cc2f35
SZ
841 tcpstat.tcps_snddsackopt++;
842 else
843 tcpstat.tcps_sndsackopt++;
844
91489f6b
JH
845 olp = lp++;
846 optlen += TCPOLEN_SACK_ALIGNED;
847
848 tcp_sack_ack_history(tp);
849 if (tp->reportblk.rblk_start != tp->reportblk.rblk_end) {
850 *lp++ = htonl(tp->reportblk.rblk_start);
851 *lp++ = htonl(tp->reportblk.rblk_end);
852 optlen += TCPOLEN_SACK_BLOCK;
853 hstart = tp->reportblk.rblk_start;
854 hend = tp->reportblk.rblk_end;
c7e6499a 855 if (tp->sack_flags & TSACK_F_ENCLOSESEG) {
91489f6b
JH
856 KASSERT(TCP_MAXOLEN - optlen >= TCPOLEN_SACK_BLOCK,
857 ("no room for enclosing SACK block: oplen %d",
858 optlen));
859 *lp++ = htonl(tp->encloseblk.rblk_start);
860 *lp++ = htonl(tp->encloseblk.rblk_end);
861 optlen += TCPOLEN_SACK_BLOCK;
862 hstart = tp->encloseblk.rblk_start;
863 hend = tp->encloseblk.rblk_end;
864 }
865 if (SEQ_GT(hstart, tp->rcv_nxt))
866 tcp_sack_update_reported_history(tp, hstart, hend);
867 }
c7e6499a 868 if (tcp_do_smartsack && (tp->sack_flags & TSACK_F_SACKLEFT)) {
91489f6b
JH
869 /* Fill in from left! Walk re-assembly queue. */
870 struct tseg_qent *q;
871
0f9e45de 872 q = TAILQ_FIRST(&tp->t_segq);
91489f6b
JH
873 while (q != NULL &&
874 TCP_MAXOLEN - optlen >= TCPOLEN_SACK_BLOCK) {
875 *lp++ = htonl(q->tqe_th->th_seq);
3a5d999b
SZ
876 *lp++ = htonl(TCP_SACK_BLKEND(
877 q->tqe_th->th_seq + q->tqe_len,
878 q->tqe_th->th_flags));
91489f6b 879 optlen += TCPOLEN_SACK_BLOCK;
0f9e45de 880 q = TAILQ_NEXT(q, tqe_q);
91489f6b
JH
881 }
882 } else {
883 int n = 0;
884
885 /* Fill in SACK blocks from right side. */
886 while (n < tp->nsackhistory &&
887 TCP_MAXOLEN - optlen >= TCPOLEN_SACK_BLOCK) {
888 if (tp->sackhistory[n].rblk_start != hstart) {
889 *lp++ = htonl(tp->sackhistory[n].rblk_start);
890 *lp++ = htonl(tp->sackhistory[n].rblk_end);
891 optlen += TCPOLEN_SACK_BLOCK;
892 }
893 ++n;
894 }
895 }
896 tp->reportblk.rblk_start = tp->reportblk.rblk_end;
c7e6499a
SZ
897 tp->sack_flags &=
898 ~(TSACK_F_DUPSEG | TSACK_F_ENCLOSESEG | TSACK_F_SACKLEFT);
91489f6b
JH
899 nblocks = (lp - olp - 1) / 2;
900 *olp = htonl(TCPOPT_SACK_ALIGNED |
901 (TCPOLEN_SACK + nblocks * TCPOLEN_SACK_BLOCK));
902 *plen = optlen;
903}