tcp: Dragging RescueRxt along with HighRxt should depend on tcp.rescuesack_agg
[dragonfly.git] / sys / netinet / tcp_sack.c
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  *
33  * $DragonFly: src/sys/netinet/tcp_sack.c,v 1.8 2008/08/15 21:37:16 nth Exp $
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
58 /*
59  * Implemented:
60  *
61  * RFC 2018
62  * RFC 2883
63  * RFC 3517
64  */
65
66 struct 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
74 static int insert_block(struct scoreboard *scb,
75                         const struct raw_sackblock *raw_sb, boolean_t *update);
76 static void update_lostseq(struct scoreboard *scb, tcp_seq snd_una,
77                            u_int maxseg);
78
79 static MALLOC_DEFINE(M_SACKBLOCK, "sblk", "sackblock struct");
80
81 /*
82  * Per-tcpcb initialization.
83  */
84 void
85 tcp_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  */
99 static boolean_t
100 sack_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  */
150 static __inline struct sackblock *
151 alloc_sackblock(struct scoreboard *scb, const struct raw_sackblock *raw_sb)
152 {
153         struct sackblock *sb;
154
155         if (scb->freecache != NULL) {
156                 sb = scb->freecache;
157                 scb->freecache = NULL;
158                 tcpstat.tcps_sacksbfast++;
159         } else {
160                 sb = kmalloc(sizeof(struct sackblock), M_SACKBLOCK, M_NOWAIT);
161                 if (sb == NULL) {
162                         tcpstat.tcps_sacksbfailed++;
163                         return NULL;
164                 }
165         }
166         sb->sblk_start = raw_sb->rblk_start;
167         sb->sblk_end = raw_sb->rblk_end;
168         return sb;
169 }
170
171 static __inline struct sackblock *
172 alloc_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         }
185         return alloc_sackblock(scb, raw_sb);
186 }
187
188 /*
189  * Free a SACK block.
190  */
191 static __inline void
192 free_sackblock(struct scoreboard *scb, struct sackblock *s)
193 {
194         if (scb->freecache == NULL) {
195                 /* YYY Maybe use the latest freed block? */
196                 scb->freecache = s;
197                 return;
198         }
199         kfree(s, M_SACKBLOCK);
200 }
201
202 /*
203  * Free up SACK blocks for data that's been acked.
204  */
205 static void
206 tcp_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);
213                 if (scb->lastfound == sb)
214                         scb->lastfound = NULL;
215                 TAILQ_REMOVE(&scb->sackblocks, sb, sblk_list);
216                 free_sackblock(scb, sb);
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  */
229 void
230 tcp_sack_cleanup(struct scoreboard *scb)
231 {
232         struct sackblock *sb, *nb;
233
234         TAILQ_FOREACH_MUTABLE(sb, &scb->sackblocks, sblk_list, nb) {
235                 free_sackblock(scb, sb);
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 /*
245  * Delete and free SACK blocks saved in scoreboard.
246  * Delete the one slot block cache.
247  */
248 void
249 tcp_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 /*
259  * Cleanup the reported SACK block information
260  */
261 void
262 tcp_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 /*
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  */
273 int
274 tcp_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  */
295 static void
296 tcp_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;
301         int startblock, i;
302
303         if (tcp_sack_ndsack_blocks(blocks, numblocks, tp->snd_una) > 0)
304                 startblock = 1;
305         else
306                 startblock = 0;
307
308         to->to_flags |= TOF_SACK_REDUNDANT;
309         for (i = startblock; i < numblocks; i++) {
310                 struct raw_sackblock *newsackblock = &blocks[i];
311                 boolean_t update;
312                 int error;
313
314                 /* don't accept bad SACK blocks */
315                 if (SEQ_GT(newsackblock->rblk_end, tp->snd_max)) {
316                         tcpstat.tcps_rcvbadsackopt++;
317                         break;          /* skip all other blocks */
318                 }
319                 tcpstat.tcps_sacksbupdate++;
320
321                 error = insert_block(scb, newsackblock, &update);
322                 if (update)
323                         to->to_flags &= ~TOF_SACK_REDUNDANT;
324                 if (error)
325                         break;
326         }
327 }
328
329 void
330 tcp_sack_update_scoreboard(struct tcpcb *tp, struct tcpopt *to)
331 {
332         struct scoreboard *scb = &tp->scb;
333         int rexmt_high_update = 0;
334
335         tcp_sack_ack_blocks(scb, tp->snd_una);
336         tcp_sack_add_blocks(tp, to);
337         update_lostseq(scb, tp->snd_una, tp->t_maxseg);
338         if (SEQ_LT(tp->rexmt_high, tp->snd_una)) {
339                 tp->rexmt_high = tp->snd_una;
340                 rexmt_high_update = 1;
341         }
342         if (tp->t_flags & TF_SACKRESCUED) {
343                 if (SEQ_LT(tp->rexmt_rescue, tp->snd_una)) {
344                         tp->t_flags &= ~TF_SACKRESCUED;
345                 } else if (tcp_aggressive_rescuesack && rexmt_high_update &&
346                     SEQ_LT(tp->rexmt_rescue, tp->rexmt_high)) {
347                         /* Drag RescueRxt along with HighRxt */
348                         tp->rexmt_rescue = tp->rexmt_high;
349                 }
350         }
351 }
352
353 /*
354  * Insert SACK block into sender's scoreboard.
355  */
356 static int
357 insert_block(struct scoreboard *scb, const struct raw_sackblock *raw_sb,
358     boolean_t *update)
359 {
360         struct sackblock *sb, *workingblock;
361         boolean_t overlap_front;
362
363         *update = TRUE;
364         if (TAILQ_EMPTY(&scb->sackblocks)) {
365                 struct sackblock *newblock;
366
367                 KASSERT(scb->nblocks == 0, ("emply scb w/ blocks"));
368
369                 newblock = alloc_sackblock(scb, raw_sb);
370                 if (newblock == NULL)
371                         return ENOMEM;
372                 TAILQ_INSERT_HEAD(&scb->sackblocks, newblock, sblk_list);
373                 scb->nblocks = 1;
374                 return 0;
375         }
376
377         KASSERT(scb->nblocks > 0, ("insert_block() called w/ no blocks"));
378         KASSERT(scb->nblocks <= MAXSAVEDBLOCKS,
379             ("too many SACK blocks %d", scb->nblocks));
380
381         overlap_front = sack_block_lookup(scb, raw_sb->rblk_start, &sb);
382
383         if (sb == NULL) {
384                 workingblock = alloc_sackblock_limit(scb, raw_sb);
385                 if (workingblock == NULL)
386                         return ENOMEM;
387                 TAILQ_INSERT_HEAD(&scb->sackblocks, workingblock, sblk_list);
388                 ++scb->nblocks;
389         } else {
390                 if (overlap_front || sb->sblk_end == raw_sb->rblk_start) {
391                         /* Extend old block */
392                         workingblock = sb;
393                         if (SEQ_GT(raw_sb->rblk_end, sb->sblk_end))
394                                 sb->sblk_end = raw_sb->rblk_end;
395                         else
396                                 *update = FALSE;
397                         tcpstat.tcps_sacksbreused++;
398                 } else {
399                         workingblock = alloc_sackblock_limit(scb, raw_sb);
400                         if (workingblock == NULL)
401                                 return ENOMEM;
402                         TAILQ_INSERT_AFTER(&scb->sackblocks, sb, workingblock,
403                             sblk_list);
404                         ++scb->nblocks;
405                 }
406         }
407
408         /* Consolidate right-hand side. */
409         sb = TAILQ_NEXT(workingblock, sblk_list);
410         while (sb != NULL &&
411             SEQ_GEQ(workingblock->sblk_end, sb->sblk_end)) {
412                 struct sackblock *nextblock;
413
414                 nextblock = TAILQ_NEXT(sb, sblk_list);
415                 if (scb->lastfound == sb)
416                         scb->lastfound = NULL;
417                 /* Remove completely overlapped block */
418                 TAILQ_REMOVE(&scb->sackblocks, sb, sblk_list);
419                 free_sackblock(scb, sb);
420                 --scb->nblocks;
421                 KASSERT(scb->nblocks > 0,
422                     ("removed overlapped block: %d blocks left", scb->nblocks));
423                 sb = nextblock;
424         }
425         if (sb != NULL &&
426             SEQ_GEQ(workingblock->sblk_end, sb->sblk_start)) {
427                 /* Extend new block to cover partially overlapped old block. */
428                 workingblock->sblk_end = sb->sblk_end;
429                 if (scb->lastfound == sb)
430                         scb->lastfound = NULL;
431                 TAILQ_REMOVE(&scb->sackblocks, sb, sblk_list);
432                 free_sackblock(scb, sb);
433                 --scb->nblocks;
434                 KASSERT(scb->nblocks > 0,
435                     ("removed partial right: %d blocks left", scb->nblocks));
436         }
437         return 0;
438 }
439
440 #ifdef DEBUG_SACK_BLOCKS
441 static void
442 tcp_sack_dump_blocks(struct scoreboard *scb)
443 {
444         struct sackblock *sb;
445
446         kprintf("%d blocks:", scb->nblocks);
447         TAILQ_FOREACH(sb, &scb->sackblocks, sblk_list)
448                 kprintf(" [%u, %u)", sb->sblk_start, sb->sblk_end);
449         kprintf("\n");
450 }
451 #else
452 static __inline void
453 tcp_sack_dump_blocks(struct scoreboard *scb)
454 {
455 }
456 #endif
457
458 /*
459  * Optimization to quickly determine which packets are lost.
460  */
461 static void
462 update_lostseq(struct scoreboard *scb, tcp_seq snd_una, u_int maxseg)
463 {
464         struct sackblock *sb;
465         int nsackblocks = 0;
466         int bytes_sacked = 0;
467
468         sb = TAILQ_LAST(&scb->sackblocks, sackblock_list);
469         while (sb != NULL) {
470                 ++nsackblocks;
471                 bytes_sacked += sb->sblk_end - sb->sblk_start;
472                 if (nsackblocks == tcprexmtthresh ||
473                     bytes_sacked >= tcprexmtthresh * maxseg) {
474                         scb->lostseq = sb->sblk_start;
475                         return;
476                 }
477                 sb = TAILQ_PREV(sb, sackblock_list, sblk_list);
478         }
479         scb->lostseq = snd_una;
480 }
481
482 /*
483  * Return whether the given sequence number is considered lost.
484  */
485 static boolean_t
486 scb_islost(struct scoreboard *scb, tcp_seq seqnum)
487 {
488         return SEQ_LT(seqnum, scb->lostseq);
489 }
490
491 /*
492  * True if at least "amount" has been SACKed.  Used by Early Retransmit.
493  */
494 boolean_t
495 tcp_sack_has_sacked(struct scoreboard *scb, u_int amount)
496 {
497         struct sackblock *sb;
498         int bytes_sacked = 0;
499
500         TAILQ_FOREACH(sb, &scb->sackblocks, sblk_list) {
501                 bytes_sacked += sb->sblk_end - sb->sblk_start;
502                 if (bytes_sacked >= amount)
503                         return TRUE;
504         }
505         return FALSE;
506 }
507
508 /*
509  * Number of bytes SACKed below seq.
510  */
511 int
512 tcp_sack_bytes_below(struct scoreboard *scb, tcp_seq seq)
513 {
514         struct sackblock *sb;
515         int bytes_sacked = 0;
516
517         sb = TAILQ_FIRST(&scb->sackblocks);
518         while (sb && SEQ_GT(seq, sb->sblk_start)) {
519                 bytes_sacked += seq_min(seq, sb->sblk_end) - sb->sblk_start;
520                 sb = TAILQ_NEXT(sb, sblk_list);
521         }
522         return bytes_sacked;
523 }
524
525 /*
526  * Return estimate of the number of bytes outstanding in the network.
527  */
528 uint32_t
529 tcp_sack_compute_pipe(struct tcpcb *tp)
530 {
531         struct scoreboard *scb = &tp->scb;
532         struct sackblock *sb;
533         int nlost, nretransmitted;
534         tcp_seq end;
535
536         nlost = tp->snd_max - scb->lostseq;
537         nretransmitted = tp->rexmt_high - tp->snd_una;
538
539         TAILQ_FOREACH(sb, &scb->sackblocks, sblk_list) {
540                 if (SEQ_LT(sb->sblk_start, tp->rexmt_high)) {
541                         end = seq_min(sb->sblk_end, tp->rexmt_high);
542                         nretransmitted -= end - sb->sblk_start;
543                 }
544                 if (SEQ_GEQ(sb->sblk_start, scb->lostseq))
545                         nlost -= sb->sblk_end - sb->sblk_start;
546         }
547
548         return (nlost + nretransmitted);
549 }
550
551 /*
552  * Return the sequence number and length of the next segment to transmit
553  * when in Fast Recovery.
554  */
555 boolean_t
556 tcp_sack_nextseg(struct tcpcb *tp, tcp_seq *nextrexmt, uint32_t *plen,
557     boolean_t *rescue)
558 {
559         struct scoreboard *scb = &tp->scb;
560         struct socket *so = tp->t_inpcb->inp_socket;
561         struct sackblock *sb;
562         const struct sackblock *lastblock =
563             TAILQ_LAST(&scb->sackblocks, sackblock_list);
564         tcp_seq torexmt;
565         long len, off;
566
567         /* skip SACKed data */
568         tcp_sack_skip_sacked(scb, &tp->rexmt_high);
569
570         /* Look for lost data. */
571         torexmt = tp->rexmt_high;
572         *rescue = FALSE;
573         if (lastblock != NULL) {
574                 if (SEQ_LT(torexmt, lastblock->sblk_end) &&
575                     scb_islost(scb, torexmt)) {
576 sendunsacked:
577                         *nextrexmt = torexmt;
578                         /* If the left-hand edge has been SACKed, pull it in. */
579                         if (sack_block_lookup(scb, torexmt + tp->t_maxseg, &sb))
580                                 *plen = sb->sblk_start - torexmt;
581                         else
582                                 *plen = tp->t_maxseg;
583                         return TRUE;
584                 }
585         }
586
587         /* See if unsent data available within send window. */
588         off = tp->snd_max - tp->snd_una;
589         len = (long) ulmin(so->so_snd.ssb_cc, tp->snd_wnd) - off;
590         if (len > 0) {
591                 *nextrexmt = tp->snd_max;       /* Send new data. */
592                 *plen = tp->t_maxseg;
593                 return TRUE;
594         }
595
596         /* We're less certain this data has been lost. */
597         if (lastblock != NULL && SEQ_LT(torexmt, lastblock->sblk_end))
598                 goto sendunsacked;
599
600         /* Rescue retransmission */
601         if (tcp_do_rescuesack) {
602                 tcpstat.tcps_sackrescue_try++;
603                 if (tp->t_flags & TF_SACKRESCUED) {
604                         if (!tcp_aggressive_rescuesack)
605                                 return FALSE;
606
607                         /*
608                          * Aggressive variant of the rescue retransmission.
609                          *
610                          * The idea of the rescue retransmission is to sustain
611                          * the ACK clock thus to avoid timeout retransmission.
612                          *
613                          * Under some situations, the conservative approach
614                          * suggested in the draft
615                          * http://tools.ietf.org/html/
616                          * draft-nishida-tcpm-rescue-retransmission-00
617                          * could not sustain ACK clock, since it only allows
618                          * one rescue retransmission before a cumulative ACK
619                          * covers the segement transmitted by rescue
620                          * retransmission.
621                          *
622                          * We try to locate the next unSACKed segment which
623                          * follows the previously sent rescue segment.  If
624                          * there is no such segment, we loop back to the first
625                          * unacknowledged segment.
626                          */
627
628                         /*
629                          * Skip SACKed data, but here we follow
630                          * the last transmitted rescue segment.
631                          */
632                         torexmt = tp->rexmt_rescue;
633                         tcp_sack_skip_sacked(scb, &torexmt);
634                         if (torexmt == tp->snd_max) {
635                                 /* Nothing left to retransmit; restart */
636                                 torexmt = tp->snd_una;
637                         }
638                 }
639                 *rescue = TRUE;
640                 goto sendunsacked;
641         } else if (tcp_do_smartsack && lastblock == NULL) {
642                 tcpstat.tcps_sackrescue_try++;
643                 *rescue = TRUE;
644                 goto sendunsacked;
645         }
646
647         return FALSE;
648 }
649
650 /*
651  * Return the next sequence number higher than "*prexmt" that has
652  * not been SACKed.
653  */
654 void
655 tcp_sack_skip_sacked(struct scoreboard *scb, tcp_seq *prexmt)
656 {
657         struct sackblock *sb;
658
659         /* skip SACKed data */
660         if (sack_block_lookup(scb, *prexmt, &sb))
661                 *prexmt = sb->sblk_end;
662 }
663
664 #ifdef later
665 void
666 tcp_sack_save_scoreboard(struct scoreboard *scb)
667 {
668         struct scoreboard *scb = &tp->scb;
669
670         scb->sackblocks_prev = scb->sackblocks;
671         TAILQ_INIT(&scb->sackblocks);
672 }
673
674 void
675 tcp_sack_revert_scoreboard(struct scoreboard *scb, tcp_seq snd_una,
676                            u_int maxseg)
677 {
678         struct sackblock *sb;
679
680         scb->sackblocks = scb->sackblocks_prev;
681         scb->nblocks = 0;
682         TAILQ_FOREACH(sb, &scb->sackblocks, sblk_list)
683                 ++scb->nblocks;
684         tcp_sack_ack_blocks(scb, snd_una);
685         scb->lastfound = NULL;
686 }
687 #endif
688
689 #ifdef DEBUG_SACK_HISTORY
690 static void
691 tcp_sack_dump_history(char *msg, struct tcpcb *tp)
692 {
693         int i;
694         static int ndumped;
695
696         /* only need a couple of these to debug most problems */
697         if (++ndumped > 900)
698                 return;
699
700         kprintf("%s:\tnsackhistory %d: ", msg, tp->nsackhistory);
701         for (i = 0; i < tp->nsackhistory; ++i)
702                 kprintf("[%u, %u) ", tp->sackhistory[i].rblk_start,
703                     tp->sackhistory[i].rblk_end);
704         kprintf("\n");
705 }
706 #else
707 static __inline void
708 tcp_sack_dump_history(char *msg, struct tcpcb *tp)
709 {
710 }
711 #endif
712
713 /*
714  * Remove old SACK blocks from the SACK history that have already been ACKed.
715  */
716 static void
717 tcp_sack_ack_history(struct tcpcb *tp)
718 {
719         int i, nblocks, openslot;
720
721         tcp_sack_dump_history("before tcp_sack_ack_history", tp);
722         nblocks = tp->nsackhistory;
723         for (i = openslot = 0; i < nblocks; ++i) {
724                 if (SEQ_LEQ(tp->sackhistory[i].rblk_end, tp->rcv_nxt)) {
725                         --tp->nsackhistory;
726                         continue;
727                 }
728                 if (SEQ_LT(tp->sackhistory[i].rblk_start, tp->rcv_nxt))
729                         tp->sackhistory[i].rblk_start = tp->rcv_nxt;
730                 if (i == openslot)
731                         ++openslot;
732                 else
733                         tp->sackhistory[openslot++] = tp->sackhistory[i];
734         }
735         tcp_sack_dump_history("after tcp_sack_ack_history", tp);
736         KASSERT(openslot == tp->nsackhistory,
737             ("tcp_sack_ack_history miscounted: %d != %d",
738             openslot, tp->nsackhistory));
739 }
740
741 /*
742  * Add or merge newblock into reported history.
743  * Also remove or update SACK blocks that will be acked.
744  */
745 static void
746 tcp_sack_update_reported_history(struct tcpcb *tp, tcp_seq start, tcp_seq end)
747 {
748         struct raw_sackblock copy[MAX_SACK_REPORT_BLOCKS];
749         int i, cindex;
750
751         tcp_sack_dump_history("before tcp_sack_update_reported_history", tp);
752         /*
753          * Six cases:
754          *      0) no overlap
755          *      1) newblock == oldblock
756          *      2) oldblock contains newblock
757          *      3) newblock contains oldblock
758          *      4) tail of oldblock overlaps or abuts start of newblock
759          *      5) tail of newblock overlaps or abuts head of oldblock
760          */
761         for (i = cindex = 0; i < tp->nsackhistory; ++i) {
762                 struct raw_sackblock *oldblock = &tp->sackhistory[i];
763                 tcp_seq old_start = oldblock->rblk_start;
764                 tcp_seq old_end = oldblock->rblk_end;
765
766                 if (SEQ_LT(end, old_start) || SEQ_GT(start, old_end)) {
767                         /* Case 0:  no overlap.  Copy old block. */
768                         copy[cindex++] = *oldblock;
769                         continue;
770                 }
771
772                 if (SEQ_GEQ(start, old_start) && SEQ_LEQ(end, old_end)) {
773                         /* Cases 1 & 2.  Move block to front of history. */
774                         int j;
775
776                         start = old_start;
777                         end = old_end;
778                         /* no need to check rest of blocks */
779                         for (j = i + 1; j < tp->nsackhistory; ++j)
780                                 copy[cindex++] = tp->sackhistory[j];
781                         break;
782                 }
783
784                 if (SEQ_GEQ(old_end, start) && SEQ_LT(old_start, start)) {
785                         /* Case 4:  extend start of new block. */
786                         start = old_start;
787                 } else if (SEQ_GEQ(end, old_start) && SEQ_GT(old_end, end)) {
788                         /* Case 5: extend end of new block */
789                         end = old_end;
790                 } else {
791                         /* Case 3.  Delete old block by not copying it. */
792                         KASSERT(SEQ_LEQ(start, old_start) &&
793                                 SEQ_GEQ(end, old_end),
794                             ("bad logic: old [%u, %u), new [%u, %u)",
795                              old_start, old_end, start, end));
796                 }
797         }
798
799         /* insert new block */
800         tp->sackhistory[0].rblk_start = start;
801         tp->sackhistory[0].rblk_end = end;
802         cindex = min(cindex, MAX_SACK_REPORT_BLOCKS - 1);
803         for (i = 0; i < cindex; ++i)
804                 tp->sackhistory[i + 1] = copy[i];
805         tp->nsackhistory = cindex + 1;
806         tcp_sack_dump_history("after tcp_sack_update_reported_history", tp);
807 }
808
809 /*
810  * Fill in SACK report to return to data sender.
811  */
812 void
813 tcp_sack_fill_report(struct tcpcb *tp, u_char *opt, u_int *plen)
814 {
815         u_int optlen = *plen;
816         uint32_t *lp = (uint32_t *)(opt + optlen);
817         uint32_t *olp;
818         tcp_seq hstart = tp->rcv_nxt, hend;
819         int nblocks;
820
821         KASSERT(TCP_MAXOLEN - optlen >=
822             TCPOLEN_SACK_ALIGNED + TCPOLEN_SACK_BLOCK,
823             ("no room for SACK header and one block: optlen %d", optlen));
824
825         if (tp->t_flags & TF_DUPSEG)
826                 tcpstat.tcps_snddsackopt++;
827         else
828                 tcpstat.tcps_sndsackopt++;
829
830         olp = lp++;
831         optlen += TCPOLEN_SACK_ALIGNED;
832
833         tcp_sack_ack_history(tp);
834         if (tp->reportblk.rblk_start != tp->reportblk.rblk_end) {
835                 *lp++ = htonl(tp->reportblk.rblk_start);
836                 *lp++ = htonl(tp->reportblk.rblk_end);
837                 optlen += TCPOLEN_SACK_BLOCK;
838                 hstart = tp->reportblk.rblk_start;
839                 hend = tp->reportblk.rblk_end;
840                 if (tp->t_flags & TF_ENCLOSESEG) {
841                         KASSERT(TCP_MAXOLEN - optlen >= TCPOLEN_SACK_BLOCK,
842                             ("no room for enclosing SACK block: oplen %d",
843                             optlen));
844                         *lp++ = htonl(tp->encloseblk.rblk_start);
845                         *lp++ = htonl(tp->encloseblk.rblk_end);
846                         optlen += TCPOLEN_SACK_BLOCK;
847                         hstart = tp->encloseblk.rblk_start;
848                         hend = tp->encloseblk.rblk_end;
849                 }
850                 if (SEQ_GT(hstart, tp->rcv_nxt))
851                         tcp_sack_update_reported_history(tp, hstart, hend);
852         }
853         if (tcp_do_smartsack && (tp->t_flags & TF_SACKLEFT)) {
854                 /* Fill in from left!  Walk re-assembly queue. */
855                 struct tseg_qent *q;
856
857                 q = LIST_FIRST(&tp->t_segq);
858                 while (q != NULL &&
859                     TCP_MAXOLEN - optlen >= TCPOLEN_SACK_BLOCK) {
860                         *lp++ = htonl(q->tqe_th->th_seq);
861                         *lp++ = htonl(TCP_SACK_BLKEND(
862                             q->tqe_th->th_seq + q->tqe_len,
863                             q->tqe_th->th_flags));
864                         optlen += TCPOLEN_SACK_BLOCK;
865                         q = LIST_NEXT(q, tqe_q);
866                 }
867         } else {
868                 int n = 0;
869
870                 /* Fill in SACK blocks from right side. */
871                 while (n < tp->nsackhistory &&
872                     TCP_MAXOLEN - optlen >= TCPOLEN_SACK_BLOCK) {
873                         if (tp->sackhistory[n].rblk_start != hstart) {
874                                 *lp++ = htonl(tp->sackhistory[n].rblk_start);
875                                 *lp++ = htonl(tp->sackhistory[n].rblk_end);
876                                 optlen += TCPOLEN_SACK_BLOCK;
877                         }
878                         ++n;
879                 }
880         }
881         tp->reportblk.rblk_start = tp->reportblk.rblk_end;
882         tp->t_flags &= ~(TF_DUPSEG | TF_ENCLOSESEG | TF_SACKLEFT);
883         nblocks = (lp - olp - 1) / 2;
884         *olp = htonl(TCPOPT_SACK_ALIGNED |
885                      (TCPOLEN_SACK + nblocks * TCPOLEN_SACK_BLOCK));
886         *plen = optlen;
887 }