tcp/sack: Cleanup the SACK related bits when return from tcp_input slow path
[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 void insert_block(struct scoreboard *scb, struct sackblock *newblock);
75 static void update_lostseq(struct scoreboard *scb, tcp_seq snd_una,
76                            u_int maxseg);
77
78 static MALLOC_DEFINE(M_SACKBLOCK, "sblk", "sackblock struct");
79
80 /*
81  * Per-tcpcb initialization.
82  */
83 void
84 tcp_sack_tcpcb_init(struct tcpcb *tp)
85 {
86         struct scoreboard *scb = &tp->scb;
87
88         scb->nblocks = 0;
89         TAILQ_INIT(&scb->sackblocks);
90         scb->lastfound = NULL;
91 }
92
93 /*
94  * Find the SACK block containing or immediately preceding "seq".
95  * The boolean result indicates whether the sequence is actually
96  * contained in the SACK block.
97  */
98 static boolean_t
99 sack_block_lookup(struct scoreboard *scb, tcp_seq seq, struct sackblock **sb)
100 {
101         struct sackblock *hint = scb->lastfound;
102         struct sackblock *cur, *last, *prev;
103
104         if (TAILQ_EMPTY(&scb->sackblocks)) {
105                 *sb = NULL;
106                 return FALSE;
107         }
108
109         if (hint == NULL) {
110                 /* No hint.  Search from start to end. */
111                 cur = TAILQ_FIRST(&scb->sackblocks);
112                 last = NULL;
113                 prev = TAILQ_LAST(&scb->sackblocks, sackblock_list);
114         } else  {
115                 if (SEQ_GEQ(seq, hint->sblk_start)) {
116                         /* Search from hint to end of list. */
117                         cur = hint;
118                         last = NULL;
119                         prev = TAILQ_LAST(&scb->sackblocks, sackblock_list);
120                 } else {
121                         /* Search from front of list to hint. */
122                         cur = TAILQ_FIRST(&scb->sackblocks);
123                         last = hint;
124                         prev = TAILQ_PREV(hint, sackblock_list, sblk_list);
125                 }
126         }
127
128         do {
129                 if (SEQ_GT(cur->sblk_end, seq)) {
130                         if (SEQ_GEQ(seq, cur->sblk_start)) {
131                                 *sb = scb->lastfound = cur;
132                                 return TRUE;
133                         } else {
134                                 *sb = scb->lastfound =
135                                     TAILQ_PREV(cur, sackblock_list, sblk_list);
136                                 return FALSE;
137                         }
138                 }
139                 cur = TAILQ_NEXT(cur, sblk_list);
140         } while (cur != last);
141
142         *sb = scb->lastfound = prev;
143         return FALSE;
144 }
145
146 /*
147  * Allocate a SACK block.
148  */
149 static __inline struct sackblock *
150 alloc_sackblock(void)
151 {
152         return (kmalloc(sizeof(struct sackblock), M_SACKBLOCK, M_NOWAIT));
153 }
154
155 /*
156  * Free a SACK block.
157  */
158 static __inline void
159 free_sackblock(struct sackblock *s)
160 {
161         kfree(s, M_SACKBLOCK);
162 }
163
164 /*
165  * Free up SACK blocks for data that's been acked.
166  */
167 static void
168 tcp_sack_ack_blocks(struct scoreboard *scb, tcp_seq th_ack)
169 {
170         struct sackblock *sb, *nb;
171
172         sb = TAILQ_FIRST(&scb->sackblocks);
173         while (sb && SEQ_LEQ(sb->sblk_end, th_ack)) {
174                 nb = TAILQ_NEXT(sb, sblk_list);
175                 if (scb->lastfound == sb)
176                         scb->lastfound = NULL;
177                 TAILQ_REMOVE(&scb->sackblocks, sb, sblk_list);
178                 free_sackblock(sb);
179                 --scb->nblocks;
180                 KASSERT(scb->nblocks >= 0,
181                     ("SACK block count underflow: %d < 0", scb->nblocks));
182                 sb = nb;
183         }
184         if (sb && SEQ_GT(th_ack, sb->sblk_start))
185                 sb->sblk_start = th_ack;        /* other side reneged? XXX */
186 }
187
188 /*
189  * Delete and free SACK blocks saved in scoreboard.
190  */
191 void
192 tcp_sack_cleanup(struct scoreboard *scb)
193 {
194         struct sackblock *sb, *nb;
195
196         TAILQ_FOREACH_MUTABLE(sb, &scb->sackblocks, sblk_list, nb) {
197                 free_sackblock(sb);
198                 --scb->nblocks;
199         }
200         KASSERT(scb->nblocks == 0,
201             ("SACK block %d count not zero", scb->nblocks));
202         TAILQ_INIT(&scb->sackblocks);
203         scb->lastfound = NULL;
204 }
205
206 /*
207  * Cleanup the reported SACK block information
208  */
209 void
210 tcp_sack_report_cleanup(struct tcpcb *tp)
211 {
212         tp->t_flags &= ~(TF_DUPSEG | TF_ENCLOSESEG | TF_SACKLEFT);
213         tp->reportblk.rblk_start = tp->reportblk.rblk_end;
214 }
215
216 /*
217  * Returns      0 if not D-SACK block,
218  *              1 if D-SACK,
219  *              2 if duplicate of out-of-order D-SACK block.
220  */
221 int
222 tcp_sack_ndsack_blocks(struct raw_sackblock *blocks, const int numblocks,
223                        tcp_seq snd_una)
224 {
225         if (numblocks == 0)
226                 return 0;
227
228         if (SEQ_LT(blocks[0].rblk_start, snd_una))
229                 return 1;
230
231         /* block 0 inside block 1 */
232         if (numblocks > 1 &&
233             SEQ_GEQ(blocks[0].rblk_start, blocks[1].rblk_start) &&
234             SEQ_LEQ(blocks[0].rblk_end, blocks[1].rblk_end))
235                 return 2;
236
237         return 0;
238 }
239
240 /*
241  * Update scoreboard on new incoming ACK.
242  */
243 static void
244 tcp_sack_add_blocks(struct tcpcb *tp, struct tcpopt *to)
245 {
246         const int numblocks = to->to_nsackblocks;
247         struct raw_sackblock *blocks = to->to_sackblocks;
248         struct scoreboard *scb = &tp->scb;
249         struct sackblock *sb;
250         int startblock;
251         int i;
252
253         if (tcp_sack_ndsack_blocks(blocks, numblocks, tp->snd_una) > 0)
254                 startblock = 1;
255         else
256                 startblock = 0;
257
258         for (i = startblock; i < numblocks; i++) {
259                 struct raw_sackblock *newsackblock = &blocks[i];
260
261                 /* don't accept bad SACK blocks */
262                 if (SEQ_GT(newsackblock->rblk_end, tp->snd_max)) {
263                         tcpstat.tcps_rcvbadsackopt++;
264                         break;          /* skip all other blocks */
265                 }
266                 tcpstat.tcps_sacksbupdate++;
267
268                 sb = alloc_sackblock();
269                 if (sb == NULL) {       /* do some sort of cleanup? XXX */
270                         tcpstat.tcps_sacksbfailed++;
271                         break;          /* just skip rest of blocks */
272                 }
273                 sb->sblk_start = newsackblock->rblk_start;
274                 sb->sblk_end = newsackblock->rblk_end;
275                 if (TAILQ_EMPTY(&scb->sackblocks)) {
276                         KASSERT(scb->nblocks == 0, ("emply scb w/ blocks"));
277                         scb->nblocks = 1;
278                         TAILQ_INSERT_HEAD(&scb->sackblocks, sb, sblk_list);
279                 } else {
280                         insert_block(scb, sb);
281                 }
282         }
283 }
284
285 void
286 tcp_sack_update_scoreboard(struct tcpcb *tp, struct tcpopt *to)
287 {
288         struct scoreboard *scb = &tp->scb;
289
290         tcp_sack_ack_blocks(scb, tp->snd_una);
291         tcp_sack_add_blocks(tp, to);
292         update_lostseq(scb, tp->snd_una, tp->t_maxseg);
293         if (SEQ_LT(tp->rexmt_high, tp->snd_una))
294                 tp->rexmt_high = tp->snd_una;
295 }
296
297 /*
298  * Insert SACK block into sender's scoreboard.
299  */
300 static void
301 insert_block(struct scoreboard *scb, struct sackblock *newblock)
302 {
303         struct sackblock *sb, *workingblock;
304         boolean_t overlap_front;
305
306         KASSERT(scb->nblocks > 0, ("insert_block() called w/ no blocks"));
307
308         if (scb->nblocks == MAXSAVEDBLOCKS) {
309                 /*
310                  * Should try to kick out older blocks XXX JH
311                  * May be able to coalesce with existing block.
312                  * Or, go other way and free all blocks if we hit this limit.
313                  */
314                 free_sackblock(newblock);
315                 tcpstat.tcps_sacksboverflow++;
316                 return;
317         }
318         KASSERT(scb->nblocks < MAXSAVEDBLOCKS,
319             ("too many SACK blocks %d", scb->nblocks));
320
321         overlap_front = sack_block_lookup(scb, newblock->sblk_start,  &sb);
322
323         if (sb == NULL) {
324                 workingblock = newblock;
325                 TAILQ_INSERT_HEAD(&scb->sackblocks, newblock, sblk_list);
326                 ++scb->nblocks;
327         } else {
328                 if (overlap_front || sb->sblk_end == newblock->sblk_start) {
329                         /* extend old block and discard new one */
330                         workingblock = sb;
331                         if (SEQ_GT(newblock->sblk_end, sb->sblk_end))
332                                 sb->sblk_end = newblock->sblk_end;
333                         free_sackblock(newblock);
334                         tcpstat.tcps_sacksbreused++;
335                 } else {
336                         workingblock = newblock;
337                         TAILQ_INSERT_AFTER(&scb->sackblocks, sb, newblock,
338                                            sblk_list);
339                         ++scb->nblocks;
340                 }
341         }
342
343         /* Consolidate right-hand side. */
344         sb = TAILQ_NEXT(workingblock, sblk_list);
345         while (sb != NULL &&
346             SEQ_GEQ(workingblock->sblk_end, sb->sblk_end)) {
347                 struct sackblock *nextblock;
348
349                 nextblock = TAILQ_NEXT(sb, sblk_list);
350                 if (scb->lastfound == sb)
351                         scb->lastfound = NULL;
352                 /* Remove completely overlapped block */
353                 TAILQ_REMOVE(&scb->sackblocks, sb, sblk_list);
354                 free_sackblock(sb);
355                 --scb->nblocks;
356                 KASSERT(scb->nblocks > 0,
357                     ("removed overlapped block: %d blocks left", scb->nblocks));
358                 sb = nextblock;
359         }
360         if (sb != NULL &&
361             SEQ_GEQ(workingblock->sblk_end, sb->sblk_start)) {
362                 /* Extend new block to cover partially overlapped old block. */
363                 workingblock->sblk_end = sb->sblk_end;
364                 if (scb->lastfound == sb)
365                         scb->lastfound = NULL;
366                 TAILQ_REMOVE(&scb->sackblocks, sb, sblk_list);
367                 free_sackblock(sb);
368                 --scb->nblocks;
369                 KASSERT(scb->nblocks > 0,
370                     ("removed partial right: %d blocks left", scb->nblocks));
371         }
372 }
373
374 #ifdef DEBUG_SACK_BLOCKS
375 static void
376 tcp_sack_dump_blocks(struct scoreboard *scb)
377 {
378         struct sackblock *sb;
379
380         kprintf("%d blocks:", scb->nblocks);
381         TAILQ_FOREACH(sb, &scb->sackblocks, sblk_list)
382                 kprintf(" [%u, %u)", sb->sblk_start, sb->sblk_end);
383         kprintf("\n");
384 }
385 #else
386 static __inline void
387 tcp_sack_dump_blocks(struct scoreboard *scb)
388 {
389 }
390 #endif
391
392 /*
393  * Optimization to quickly determine which packets are lost.
394  */
395 static void
396 update_lostseq(struct scoreboard *scb, tcp_seq snd_una, u_int maxseg)
397 {
398         struct sackblock *sb;
399         int nsackblocks = 0;
400         int bytes_sacked = 0;
401
402         sb = TAILQ_LAST(&scb->sackblocks, sackblock_list);
403         while (sb != NULL) {
404                 ++nsackblocks;
405                 bytes_sacked += sb->sblk_end - sb->sblk_start;
406                 if (nsackblocks == tcprexmtthresh ||
407                     bytes_sacked >= tcprexmtthresh * maxseg) {
408                         scb->lostseq = sb->sblk_start;
409                         return;
410                 }
411                 sb = TAILQ_PREV(sb, sackblock_list, sblk_list);
412         }
413         scb->lostseq = snd_una;
414 }
415
416 /*
417  * Return whether the given sequence number is considered lost.
418  */
419 static boolean_t
420 scb_islost(struct scoreboard *scb, tcp_seq seqnum)
421 {
422         return SEQ_LT(seqnum, scb->lostseq);
423 }
424
425 /*
426  * True if at least "amount" has been SACKed.  Used by Early Retransmit.
427  */
428 boolean_t
429 tcp_sack_has_sacked(struct scoreboard *scb, u_int amount)
430 {
431         struct sackblock *sb;
432         int bytes_sacked = 0;
433
434         TAILQ_FOREACH(sb, &scb->sackblocks, sblk_list) {
435                 bytes_sacked += sb->sblk_end - sb->sblk_start;
436                 if (bytes_sacked >= amount)
437                         return TRUE;
438         }
439         return FALSE;
440 }
441
442 /*
443  * Number of bytes SACKed below seq.
444  */
445 int
446 tcp_sack_bytes_below(struct scoreboard *scb, tcp_seq seq)
447 {
448         struct sackblock *sb;
449         int bytes_sacked = 0;
450
451         sb = TAILQ_FIRST(&scb->sackblocks);
452         while (sb && SEQ_GT(seq, sb->sblk_start)) {
453                 bytes_sacked += seq_min(seq, sb->sblk_end) - sb->sblk_start;
454                 sb = TAILQ_NEXT(sb, sblk_list);
455         }
456         return bytes_sacked;
457 }
458
459 /*
460  * Return estimate of the number of bytes outstanding in the network.
461  */
462 uint32_t
463 tcp_sack_compute_pipe(struct tcpcb *tp)
464 {
465         struct scoreboard *scb = &tp->scb;
466         struct sackblock *sb;
467         int nlost, nretransmitted;
468         tcp_seq end;
469
470         nlost = tp->snd_max - scb->lostseq;
471         nretransmitted = tp->rexmt_high - tp->snd_una;
472
473         TAILQ_FOREACH(sb, &scb->sackblocks, sblk_list) {
474                 if (SEQ_LT(sb->sblk_start, tp->rexmt_high)) {
475                         end = seq_min(sb->sblk_end, tp->rexmt_high);
476                         nretransmitted -= end - sb->sblk_start;
477                 }
478                 if (SEQ_GEQ(sb->sblk_start, scb->lostseq))
479                         nlost -= sb->sblk_end - sb->sblk_start;
480         }
481
482         return (nlost + nretransmitted);
483 }
484
485 /*
486  * Return the sequence number and length of the next segment to transmit
487  * when in Fast Recovery.
488  */
489 boolean_t
490 tcp_sack_nextseg(struct tcpcb *tp, tcp_seq *nextrexmt, uint32_t *plen,
491                  boolean_t *lostdup)
492 {
493         struct scoreboard *scb = &tp->scb;
494         struct socket *so = tp->t_inpcb->inp_socket;
495         struct sackblock *sb;
496         const struct sackblock *lastblock =
497             TAILQ_LAST(&scb->sackblocks, sackblock_list);
498         tcp_seq torexmt;
499         long len, off;
500
501         /* skip SACKed data */
502         tcp_sack_skip_sacked(scb, &tp->rexmt_high);
503
504         /* Look for lost data. */
505         torexmt = tp->rexmt_high;
506         *lostdup = FALSE;
507         if (lastblock != NULL) {
508                 if (SEQ_LT(torexmt, lastblock->sblk_end) &&
509                     scb_islost(scb, torexmt)) {
510 sendunsacked:
511                         *nextrexmt = torexmt;
512                         /* If the left-hand edge has been SACKed, pull it in. */
513                         if (sack_block_lookup(scb, torexmt + tp->t_maxseg, &sb))
514                                 *plen = sb->sblk_start - torexmt;
515                         else
516                                 *plen = tp->t_maxseg;
517                         return TRUE;
518                 }
519         }
520
521         /* See if unsent data available within send window. */
522         off = tp->snd_max - tp->snd_una;
523         len = (long) ulmin(so->so_snd.ssb_cc, tp->snd_wnd) - off;
524         if (len > 0) {
525                 *nextrexmt = tp->snd_max;       /* Send new data. */
526                 *plen = tp->t_maxseg;
527                 return TRUE;
528         }
529
530         /* We're less certain this data has been lost. */
531         if (lastblock == NULL || SEQ_LT(torexmt, lastblock->sblk_end))
532                 goto sendunsacked;
533
534         return FALSE;
535 }
536
537 /*
538  * Return the next sequence number higher than "*prexmt" that has
539  * not been SACKed.
540  */
541 void
542 tcp_sack_skip_sacked(struct scoreboard *scb, tcp_seq *prexmt)
543 {
544         struct sackblock *sb;
545
546         /* skip SACKed data */
547         if (sack_block_lookup(scb, *prexmt, &sb))
548                 *prexmt = sb->sblk_end;
549 }
550
551 #ifdef later
552 void
553 tcp_sack_save_scoreboard(struct scoreboard *scb)
554 {
555         struct scoreboard *scb = &tp->scb;
556
557         scb->sackblocks_prev = scb->sackblocks;
558         TAILQ_INIT(&scb->sackblocks);
559 }
560
561 void
562 tcp_sack_revert_scoreboard(struct scoreboard *scb, tcp_seq snd_una,
563                            u_int maxseg)
564 {
565         struct sackblock *sb;
566
567         scb->sackblocks = scb->sackblocks_prev;
568         scb->nblocks = 0;
569         TAILQ_FOREACH(sb, &scb->sackblocks, sblk_list)
570                 ++scb->nblocks;
571         tcp_sack_ack_blocks(scb, snd_una);
572         scb->lastfound = NULL;
573 }
574 #endif
575
576 #ifdef DEBUG_SACK_HISTORY
577 static void
578 tcp_sack_dump_history(char *msg, struct tcpcb *tp)
579 {
580         int i;
581         static int ndumped;
582
583         /* only need a couple of these to debug most problems */
584         if (++ndumped > 900)
585                 return;
586
587         kprintf("%s:\tnsackhistory %d: ", msg, tp->nsackhistory);
588         for (i = 0; i < tp->nsackhistory; ++i)
589                 kprintf("[%u, %u) ", tp->sackhistory[i].rblk_start,
590                     tp->sackhistory[i].rblk_end);
591         kprintf("\n");
592 }
593 #else
594 static __inline void
595 tcp_sack_dump_history(char *msg, struct tcpcb *tp)
596 {
597 }
598 #endif
599
600 /*
601  * Remove old SACK blocks from the SACK history that have already been ACKed.
602  */
603 static void
604 tcp_sack_ack_history(struct tcpcb *tp)
605 {
606         int i, nblocks, openslot;
607
608         tcp_sack_dump_history("before tcp_sack_ack_history", tp);
609         nblocks = tp->nsackhistory;
610         for (i = openslot = 0; i < nblocks; ++i) {
611                 if (SEQ_LEQ(tp->sackhistory[i].rblk_end, tp->rcv_nxt)) {
612                         --tp->nsackhistory;
613                         continue;
614                 }
615                 if (SEQ_LT(tp->sackhistory[i].rblk_start, tp->rcv_nxt))
616                         tp->sackhistory[i].rblk_start = tp->rcv_nxt;
617                 if (i == openslot)
618                         ++openslot;
619                 else
620                         tp->sackhistory[openslot++] = tp->sackhistory[i];
621         }
622         tcp_sack_dump_history("after tcp_sack_ack_history", tp);
623         KASSERT(openslot == tp->nsackhistory,
624             ("tcp_sack_ack_history miscounted: %d != %d",
625             openslot, tp->nsackhistory));
626 }
627
628 /*
629  * Add or merge newblock into reported history.
630  * Also remove or update SACK blocks that will be acked.
631  */
632 static void
633 tcp_sack_update_reported_history(struct tcpcb *tp, tcp_seq start, tcp_seq end)
634 {
635         struct raw_sackblock copy[MAX_SACK_REPORT_BLOCKS];
636         int i, cindex;
637
638         tcp_sack_dump_history("before tcp_sack_update_reported_history", tp);
639         /*
640          * Six cases:
641          *      0) no overlap
642          *      1) newblock == oldblock
643          *      2) oldblock contains newblock
644          *      3) newblock contains oldblock
645          *      4) tail of oldblock overlaps or abuts start of newblock
646          *      5) tail of newblock overlaps or abuts head of oldblock
647          */
648         for (i = cindex = 0; i < tp->nsackhistory; ++i) {
649                 struct raw_sackblock *oldblock = &tp->sackhistory[i];
650                 tcp_seq old_start = oldblock->rblk_start;
651                 tcp_seq old_end = oldblock->rblk_end;
652
653                 if (SEQ_LT(end, old_start) || SEQ_GT(start, old_end)) {
654                         /* Case 0:  no overlap.  Copy old block. */
655                         copy[cindex++] = *oldblock;
656                         continue;
657                 }
658
659                 if (SEQ_GEQ(start, old_start) && SEQ_LEQ(end, old_end)) {
660                         /* Cases 1 & 2.  Move block to front of history. */
661                         int j;
662
663                         start = old_start;
664                         end = old_end;
665                         /* no need to check rest of blocks */
666                         for (j = i + 1; j < tp->nsackhistory; ++j)
667                                 copy[cindex++] = tp->sackhistory[j];
668                         break;
669                 }
670
671                 if (SEQ_GEQ(old_end, start) && SEQ_LT(old_start, start)) {
672                         /* Case 4:  extend start of new block. */
673                         start = old_start;
674                 } else if (SEQ_GEQ(end, old_start) && SEQ_GT(old_end, end)) {
675                         /* Case 5: extend end of new block */
676                         end = old_end;
677                 } else {
678                         /* Case 3.  Delete old block by not copying it. */
679                         KASSERT(SEQ_LEQ(start, old_start) &&
680                                 SEQ_GEQ(end, old_end),
681                             ("bad logic: old [%u, %u), new [%u, %u)",
682                              old_start, old_end, start, end));
683                 }
684         }
685
686         /* insert new block */
687         tp->sackhistory[0].rblk_start = start;
688         tp->sackhistory[0].rblk_end = end;
689         cindex = min(cindex, MAX_SACK_REPORT_BLOCKS - 1);
690         for (i = 0; i < cindex; ++i)
691                 tp->sackhistory[i + 1] = copy[i];
692         tp->nsackhistory = cindex + 1;
693         tcp_sack_dump_history("after tcp_sack_update_reported_history", tp);
694 }
695
696 /*
697  * Fill in SACK report to return to data sender.
698  */
699 void
700 tcp_sack_fill_report(struct tcpcb *tp, u_char *opt, u_int *plen)
701 {
702         u_int optlen = *plen;
703         uint32_t *lp = (uint32_t *)(opt + optlen);
704         uint32_t *olp;
705         tcp_seq hstart = tp->rcv_nxt, hend;
706         int nblocks;
707
708         KASSERT(TCP_MAXOLEN - optlen >=
709             TCPOLEN_SACK_ALIGNED + TCPOLEN_SACK_BLOCK,
710             ("no room for SACK header and one block: optlen %d", optlen));
711
712         if (tp->t_flags & TF_DUPSEG)
713                 tcpstat.tcps_snddsackopt++;
714         else
715                 tcpstat.tcps_sndsackopt++;
716
717         olp = lp++;
718         optlen += TCPOLEN_SACK_ALIGNED;
719
720         tcp_sack_ack_history(tp);
721         if (tp->reportblk.rblk_start != tp->reportblk.rblk_end) {
722                 *lp++ = htonl(tp->reportblk.rblk_start);
723                 *lp++ = htonl(tp->reportblk.rblk_end);
724                 optlen += TCPOLEN_SACK_BLOCK;
725                 hstart = tp->reportblk.rblk_start;
726                 hend = tp->reportblk.rblk_end;
727                 if (tp->t_flags & TF_ENCLOSESEG) {
728                         KASSERT(TCP_MAXOLEN - optlen >= TCPOLEN_SACK_BLOCK,
729                             ("no room for enclosing SACK block: oplen %d",
730                             optlen));
731                         *lp++ = htonl(tp->encloseblk.rblk_start);
732                         *lp++ = htonl(tp->encloseblk.rblk_end);
733                         optlen += TCPOLEN_SACK_BLOCK;
734                         hstart = tp->encloseblk.rblk_start;
735                         hend = tp->encloseblk.rblk_end;
736                 }
737                 if (SEQ_GT(hstart, tp->rcv_nxt))
738                         tcp_sack_update_reported_history(tp, hstart, hend);
739         }
740         if (tcp_do_smartsack && (tp->t_flags & TF_SACKLEFT)) {
741                 /* Fill in from left!  Walk re-assembly queue. */
742                 struct tseg_qent *q;
743
744                 q = LIST_FIRST(&tp->t_segq);
745                 while (q != NULL &&
746                     TCP_MAXOLEN - optlen >= TCPOLEN_SACK_BLOCK) {
747                         *lp++ = htonl(q->tqe_th->th_seq);
748                         *lp++ = htonl(TCP_SACK_BLKEND(
749                             q->tqe_th->th_seq + q->tqe_len,
750                             q->tqe_th->th_flags));
751                         optlen += TCPOLEN_SACK_BLOCK;
752                         q = LIST_NEXT(q, tqe_q);
753                 }
754         } else {
755                 int n = 0;
756
757                 /* Fill in SACK blocks from right side. */
758                 while (n < tp->nsackhistory &&
759                     TCP_MAXOLEN - optlen >= TCPOLEN_SACK_BLOCK) {
760                         if (tp->sackhistory[n].rblk_start != hstart) {
761                                 *lp++ = htonl(tp->sackhistory[n].rblk_start);
762                                 *lp++ = htonl(tp->sackhistory[n].rblk_end);
763                                 optlen += TCPOLEN_SACK_BLOCK;
764                         }
765                         ++n;
766                 }
767         }
768         tp->reportblk.rblk_start = tp->reportblk.rblk_end;
769         tp->t_flags &= ~(TF_DUPSEG | TF_ENCLOSESEG | TF_SACKLEFT);
770         nblocks = (lp - olp - 1) / 2;
771         *olp = htonl(TCPOPT_SACK_ALIGNED |
772                      (TCPOLEN_SACK + nblocks * TCPOLEN_SACK_BLOCK));
773         *plen = optlen;
774 }