2 * Copyright (c) 2003, 2004 Jeffrey M. Hsu. All rights reserved.
3 * Copyright (c) 2003, 2004 The DragonFly Project. All rights reserved.
5 * This code is derived from software contributed to The DragonFly Project
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
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12 * notice, this list of conditions and the following disclaimer.
13 * 2. Redistributions in binary form must reproduce the above copyright
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20 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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33 * $DragonFly: src/sys/netinet/tcp_sack.c,v 1.8 2008/08/15 21:37:16 nth Exp $
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>
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>
69 TAILQ_ENTRY(sackblock) sblk_list;
72 #define MAXSAVEDBLOCKS 8 /* per connection limit */
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, int rxtthresh);
79 static MALLOC_DEFINE(M_SACKBLOCK, "sblk", "sackblock struct");
82 * Per-tcpcb initialization.
85 tcp_sack_tcpcb_init(struct tcpcb *tp)
87 struct scoreboard *scb = &tp->scb;
90 TAILQ_INIT(&scb->sackblocks);
91 scb->lastfound = NULL;
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.
100 sack_block_lookup(struct scoreboard *scb, tcp_seq seq, struct sackblock **sb)
102 struct sackblock *hint = scb->lastfound;
103 struct sackblock *cur, *last, *prev;
105 if (TAILQ_EMPTY(&scb->sackblocks)) {
111 /* No hint. Search from start to end. */
112 cur = TAILQ_FIRST(&scb->sackblocks);
114 prev = TAILQ_LAST(&scb->sackblocks, sackblock_list);
116 if (SEQ_GEQ(seq, hint->sblk_start)) {
117 /* Search from hint to end of list. */
120 prev = TAILQ_LAST(&scb->sackblocks, sackblock_list);
122 /* Search from front of list to hint. */
123 cur = TAILQ_FIRST(&scb->sackblocks);
125 prev = TAILQ_PREV(hint, sackblock_list, sblk_list);
130 if (SEQ_GT(cur->sblk_end, seq)) {
131 if (SEQ_GEQ(seq, cur->sblk_start)) {
132 *sb = scb->lastfound = cur;
135 *sb = scb->lastfound =
136 TAILQ_PREV(cur, sackblock_list, sblk_list);
140 cur = TAILQ_NEXT(cur, sblk_list);
141 } while (cur != last);
143 *sb = scb->lastfound = prev;
148 * Allocate a SACK block.
150 static __inline struct sackblock *
151 alloc_sackblock(struct scoreboard *scb, const struct raw_sackblock *raw_sb)
153 struct sackblock *sb;
155 if (scb->freecache != NULL) {
157 scb->freecache = NULL;
158 tcpstat.tcps_sacksbfast++;
160 sb = kmalloc(sizeof(struct sackblock), M_SACKBLOCK, M_NOWAIT);
162 tcpstat.tcps_sacksbfailed++;
166 sb->sblk_start = raw_sb->rblk_start;
167 sb->sblk_end = raw_sb->rblk_end;
171 static __inline struct sackblock *
172 alloc_sackblock_limit(struct scoreboard *scb,
173 const struct raw_sackblock *raw_sb)
175 if (scb->nblocks == MAXSAVEDBLOCKS) {
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
182 tcpstat.tcps_sacksboverflow++;
185 return alloc_sackblock(scb, raw_sb);
192 free_sackblock(struct scoreboard *scb, struct sackblock *s)
194 if (scb->freecache == NULL) {
195 /* YYY Maybe use the latest freed block? */
199 kfree(s, M_SACKBLOCK);
203 * Free up SACK blocks for data that's been acked.
206 tcp_sack_ack_blocks(struct scoreboard *scb, tcp_seq th_ack)
208 struct sackblock *sb, *nb;
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);
218 KASSERT(scb->nblocks >= 0,
219 ("SACK block count underflow: %d < 0", scb->nblocks));
222 if (sb && SEQ_GT(th_ack, sb->sblk_start))
223 sb->sblk_start = th_ack; /* other side reneged? XXX */
227 * Delete and free SACK blocks saved in scoreboard.
230 tcp_sack_cleanup(struct scoreboard *scb)
232 struct sackblock *sb, *nb;
234 TAILQ_FOREACH_MUTABLE(sb, &scb->sackblocks, sblk_list, nb) {
235 free_sackblock(scb, sb);
238 KASSERT(scb->nblocks == 0,
239 ("SACK block %d count not zero", scb->nblocks));
240 TAILQ_INIT(&scb->sackblocks);
241 scb->lastfound = NULL;
245 * Delete and free SACK blocks saved in scoreboard.
246 * Delete the one slot block cache.
249 tcp_sack_destroy(struct scoreboard *scb)
251 tcp_sack_cleanup(scb);
252 if (scb->freecache != NULL) {
253 kfree(scb->freecache, M_SACKBLOCK);
254 scb->freecache = NULL;
259 * Cleanup the reported SACK block information
262 tcp_sack_report_cleanup(struct tcpcb *tp)
264 tp->t_flags &= ~(TF_DUPSEG | TF_ENCLOSESEG | TF_SACKLEFT);
265 tp->reportblk.rblk_start = tp->reportblk.rblk_end;
269 * Returns 0 if not D-SACK block,
271 * 2 if duplicate of out-of-order D-SACK block.
274 tcp_sack_ndsack_blocks(struct raw_sackblock *blocks, const int numblocks,
280 if (SEQ_LT(blocks[0].rblk_start, snd_una))
283 /* block 0 inside block 1 */
285 SEQ_GEQ(blocks[0].rblk_start, blocks[1].rblk_start) &&
286 SEQ_LEQ(blocks[0].rblk_end, blocks[1].rblk_end))
293 * Update scoreboard on new incoming ACK.
296 tcp_sack_add_blocks(struct tcpcb *tp, struct tcpopt *to)
298 const int numblocks = to->to_nsackblocks;
299 struct raw_sackblock *blocks = to->to_sackblocks;
300 struct scoreboard *scb = &tp->scb;
303 if (tcp_sack_ndsack_blocks(blocks, numblocks, tp->snd_una) > 0)
308 to->to_flags |= TOF_SACK_REDUNDANT;
309 for (i = startblock; i < numblocks; i++) {
310 struct raw_sackblock *newsackblock = &blocks[i];
314 /* Guard against ACK reordering */
315 if (SEQ_LT(newsackblock->rblk_start, tp->snd_una))
318 /* Don't accept bad SACK blocks */
319 if (SEQ_GT(newsackblock->rblk_end, tp->snd_max)) {
320 tcpstat.tcps_rcvbadsackopt++;
321 break; /* skip all other blocks */
323 tcpstat.tcps_sacksbupdate++;
325 error = insert_block(scb, newsackblock, &update);
327 to->to_flags &= ~TOF_SACK_REDUNDANT;
334 tcp_sack_update_scoreboard(struct tcpcb *tp, struct tcpopt *to)
336 struct scoreboard *scb = &tp->scb;
337 int rexmt_high_update = 0;
339 tcp_sack_ack_blocks(scb, tp->snd_una);
340 tcp_sack_add_blocks(tp, to);
341 update_lostseq(scb, tp->snd_una, tp->t_maxseg, tp->t_rxtthresh);
342 if (SEQ_LT(tp->rexmt_high, tp->snd_una)) {
343 tp->rexmt_high = tp->snd_una;
344 rexmt_high_update = 1;
346 if (tp->t_flags & TF_SACKRESCUED) {
347 if (SEQ_LT(tp->rexmt_rescue, tp->snd_una)) {
348 tp->t_flags &= ~TF_SACKRESCUED;
349 } else if (tcp_aggressive_rescuesack && rexmt_high_update &&
350 SEQ_LT(tp->rexmt_rescue, tp->rexmt_high)) {
351 /* Drag RescueRxt along with HighRxt */
352 tp->rexmt_rescue = tp->rexmt_high;
358 * Insert SACK block into sender's scoreboard.
361 insert_block(struct scoreboard *scb, const struct raw_sackblock *raw_sb,
364 struct sackblock *sb, *workingblock;
365 boolean_t overlap_front;
368 if (TAILQ_EMPTY(&scb->sackblocks)) {
369 struct sackblock *newblock;
371 KASSERT(scb->nblocks == 0, ("emply scb w/ blocks"));
373 newblock = alloc_sackblock(scb, raw_sb);
374 if (newblock == NULL)
376 TAILQ_INSERT_HEAD(&scb->sackblocks, newblock, sblk_list);
381 KASSERT(scb->nblocks > 0, ("insert_block() called w/ no blocks"));
382 KASSERT(scb->nblocks <= MAXSAVEDBLOCKS,
383 ("too many SACK blocks %d", scb->nblocks));
385 overlap_front = sack_block_lookup(scb, raw_sb->rblk_start, &sb);
388 workingblock = alloc_sackblock_limit(scb, raw_sb);
389 if (workingblock == NULL)
391 TAILQ_INSERT_HEAD(&scb->sackblocks, workingblock, sblk_list);
394 if (overlap_front || sb->sblk_end == raw_sb->rblk_start) {
395 /* Extend old block */
397 if (SEQ_GT(raw_sb->rblk_end, sb->sblk_end))
398 sb->sblk_end = raw_sb->rblk_end;
401 tcpstat.tcps_sacksbreused++;
403 workingblock = alloc_sackblock_limit(scb, raw_sb);
404 if (workingblock == NULL)
406 TAILQ_INSERT_AFTER(&scb->sackblocks, sb, workingblock,
412 /* Consolidate right-hand side. */
413 sb = TAILQ_NEXT(workingblock, sblk_list);
415 SEQ_GEQ(workingblock->sblk_end, sb->sblk_end)) {
416 struct sackblock *nextblock;
418 nextblock = TAILQ_NEXT(sb, sblk_list);
419 if (scb->lastfound == sb)
420 scb->lastfound = NULL;
421 /* Remove completely overlapped block */
422 TAILQ_REMOVE(&scb->sackblocks, sb, sblk_list);
423 free_sackblock(scb, sb);
425 KASSERT(scb->nblocks > 0,
426 ("removed overlapped block: %d blocks left", scb->nblocks));
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;
433 if (scb->lastfound == sb)
434 scb->lastfound = NULL;
435 TAILQ_REMOVE(&scb->sackblocks, sb, sblk_list);
436 free_sackblock(scb, sb);
438 KASSERT(scb->nblocks > 0,
439 ("removed partial right: %d blocks left", scb->nblocks));
444 #ifdef DEBUG_SACK_BLOCKS
446 tcp_sack_dump_blocks(struct scoreboard *scb)
448 struct sackblock *sb;
450 kprintf("%d blocks:", scb->nblocks);
451 TAILQ_FOREACH(sb, &scb->sackblocks, sblk_list)
452 kprintf(" [%u, %u)", sb->sblk_start, sb->sblk_end);
457 tcp_sack_dump_blocks(struct scoreboard *scb)
463 * Optimization to quickly determine which packets are lost.
466 update_lostseq(struct scoreboard *scb, tcp_seq snd_una, u_int maxseg,
469 struct sackblock *sb;
471 int bytes_sacked = 0;
473 sb = TAILQ_LAST(&scb->sackblocks, sackblock_list);
476 bytes_sacked += sb->sblk_end - sb->sblk_start;
477 if (nsackblocks == rxtthresh ||
478 bytes_sacked >= rxtthresh * maxseg) {
479 scb->lostseq = sb->sblk_start;
482 sb = TAILQ_PREV(sb, sackblock_list, sblk_list);
484 scb->lostseq = snd_una;
488 * Return whether the given sequence number is considered lost.
491 scb_islost(struct scoreboard *scb, tcp_seq seqnum)
493 return SEQ_LT(seqnum, scb->lostseq);
497 * True if at least "amount" has been SACKed. Used by Early Retransmit.
500 tcp_sack_has_sacked(struct scoreboard *scb, u_int amount)
502 struct sackblock *sb;
503 int bytes_sacked = 0;
505 TAILQ_FOREACH(sb, &scb->sackblocks, sblk_list) {
506 bytes_sacked += sb->sblk_end - sb->sblk_start;
507 if (bytes_sacked >= amount)
514 * Number of bytes SACKed below seq.
517 tcp_sack_bytes_below(struct scoreboard *scb, tcp_seq seq)
519 struct sackblock *sb;
520 int bytes_sacked = 0;
522 sb = TAILQ_FIRST(&scb->sackblocks);
523 while (sb && SEQ_GT(seq, sb->sblk_start)) {
524 bytes_sacked += seq_min(seq, sb->sblk_end) - sb->sblk_start;
525 sb = TAILQ_NEXT(sb, sblk_list);
531 * Return estimate of the number of bytes outstanding in the network.
534 tcp_sack_compute_pipe(struct tcpcb *tp)
536 struct scoreboard *scb = &tp->scb;
537 struct sackblock *sb;
538 int nlost, nretransmitted;
541 nlost = tp->snd_max - scb->lostseq;
542 nretransmitted = tp->rexmt_high - tp->snd_una;
544 TAILQ_FOREACH(sb, &scb->sackblocks, sblk_list) {
545 if (SEQ_LT(sb->sblk_start, tp->rexmt_high)) {
546 end = seq_min(sb->sblk_end, tp->rexmt_high);
547 nretransmitted -= end - sb->sblk_start;
549 if (SEQ_GEQ(sb->sblk_start, scb->lostseq))
550 nlost -= sb->sblk_end - sb->sblk_start;
553 return (nlost + nretransmitted);
557 * Return the sequence number and length of the next segment to transmit
558 * when in Fast Recovery.
561 tcp_sack_nextseg(struct tcpcb *tp, tcp_seq *nextrexmt, uint32_t *plen,
564 struct scoreboard *scb = &tp->scb;
565 struct socket *so = tp->t_inpcb->inp_socket;
566 struct sackblock *sb;
567 const struct sackblock *lastblock =
568 TAILQ_LAST(&scb->sackblocks, sackblock_list);
572 /* skip SACKed data */
573 tcp_sack_skip_sacked(scb, &tp->rexmt_high);
575 /* Look for lost data. */
576 torexmt = tp->rexmt_high;
578 if (lastblock != NULL) {
579 if (SEQ_LT(torexmt, lastblock->sblk_end) &&
580 scb_islost(scb, torexmt)) {
582 *nextrexmt = torexmt;
583 /* If the left-hand edge has been SACKed, pull it in. */
584 if (sack_block_lookup(scb, torexmt + tp->t_maxseg, &sb))
585 *plen = sb->sblk_start - torexmt;
587 *plen = tp->t_maxseg;
592 /* See if unsent data available within send window. */
593 off = tp->snd_max - tp->snd_una;
594 len = (long) ulmin(so->so_snd.ssb_cc, tp->snd_wnd) - off;
596 *nextrexmt = tp->snd_max; /* Send new data. */
597 *plen = tp->t_maxseg;
601 /* We're less certain this data has been lost. */
602 if (lastblock != NULL && SEQ_LT(torexmt, lastblock->sblk_end))
605 /* Rescue retransmission */
606 if (tcp_do_rescuesack) {
607 tcpstat.tcps_sackrescue_try++;
608 if (tp->t_flags & TF_SACKRESCUED) {
609 if (!tcp_aggressive_rescuesack)
613 * Aggressive variant of the rescue retransmission.
615 * The idea of the rescue retransmission is to sustain
616 * the ACK clock thus to avoid timeout retransmission.
618 * Under some situations, the conservative approach
619 * suggested in the draft
620 * http://tools.ietf.org/html/
621 * draft-nishida-tcpm-rescue-retransmission-00
622 * could not sustain ACK clock, since it only allows
623 * one rescue retransmission before a cumulative ACK
624 * covers the segement transmitted by rescue
627 * We try to locate the next unSACKed segment which
628 * follows the previously sent rescue segment. If
629 * there is no such segment, we loop back to the first
630 * unacknowledged segment.
634 * Skip SACKed data, but here we follow
635 * the last transmitted rescue segment.
637 torexmt = tp->rexmt_rescue;
638 tcp_sack_skip_sacked(scb, &torexmt);
639 if (torexmt == tp->snd_max) {
640 /* Nothing left to retransmit; restart */
641 torexmt = tp->snd_una;
646 } else if (tcp_do_smartsack && lastblock == NULL) {
647 tcpstat.tcps_sackrescue_try++;
656 * Return the next sequence number higher than "*prexmt" that has
660 tcp_sack_skip_sacked(struct scoreboard *scb, tcp_seq *prexmt)
662 struct sackblock *sb;
664 /* skip SACKed data */
665 if (sack_block_lookup(scb, *prexmt, &sb))
666 *prexmt = sb->sblk_end;
671 tcp_sack_save_scoreboard(struct scoreboard *scb)
673 struct scoreboard *scb = &tp->scb;
675 scb->sackblocks_prev = scb->sackblocks;
676 TAILQ_INIT(&scb->sackblocks);
680 tcp_sack_revert_scoreboard(struct scoreboard *scb, tcp_seq snd_una,
683 struct sackblock *sb;
685 scb->sackblocks = scb->sackblocks_prev;
687 TAILQ_FOREACH(sb, &scb->sackblocks, sblk_list)
689 tcp_sack_ack_blocks(scb, snd_una);
690 scb->lastfound = NULL;
694 #ifdef DEBUG_SACK_HISTORY
696 tcp_sack_dump_history(char *msg, struct tcpcb *tp)
701 /* only need a couple of these to debug most problems */
705 kprintf("%s:\tnsackhistory %d: ", msg, tp->nsackhistory);
706 for (i = 0; i < tp->nsackhistory; ++i)
707 kprintf("[%u, %u) ", tp->sackhistory[i].rblk_start,
708 tp->sackhistory[i].rblk_end);
713 tcp_sack_dump_history(char *msg, struct tcpcb *tp)
719 * Remove old SACK blocks from the SACK history that have already been ACKed.
722 tcp_sack_ack_history(struct tcpcb *tp)
724 int i, nblocks, openslot;
726 tcp_sack_dump_history("before tcp_sack_ack_history", tp);
727 nblocks = tp->nsackhistory;
728 for (i = openslot = 0; i < nblocks; ++i) {
729 if (SEQ_LEQ(tp->sackhistory[i].rblk_end, tp->rcv_nxt)) {
733 if (SEQ_LT(tp->sackhistory[i].rblk_start, tp->rcv_nxt))
734 tp->sackhistory[i].rblk_start = tp->rcv_nxt;
738 tp->sackhistory[openslot++] = tp->sackhistory[i];
740 tcp_sack_dump_history("after tcp_sack_ack_history", tp);
741 KASSERT(openslot == tp->nsackhistory,
742 ("tcp_sack_ack_history miscounted: %d != %d",
743 openslot, tp->nsackhistory));
747 * Add or merge newblock into reported history.
748 * Also remove or update SACK blocks that will be acked.
751 tcp_sack_update_reported_history(struct tcpcb *tp, tcp_seq start, tcp_seq end)
753 struct raw_sackblock copy[MAX_SACK_REPORT_BLOCKS];
756 tcp_sack_dump_history("before tcp_sack_update_reported_history", tp);
760 * 1) newblock == oldblock
761 * 2) oldblock contains newblock
762 * 3) newblock contains oldblock
763 * 4) tail of oldblock overlaps or abuts start of newblock
764 * 5) tail of newblock overlaps or abuts head of oldblock
766 for (i = cindex = 0; i < tp->nsackhistory; ++i) {
767 struct raw_sackblock *oldblock = &tp->sackhistory[i];
768 tcp_seq old_start = oldblock->rblk_start;
769 tcp_seq old_end = oldblock->rblk_end;
771 if (SEQ_LT(end, old_start) || SEQ_GT(start, old_end)) {
772 /* Case 0: no overlap. Copy old block. */
773 copy[cindex++] = *oldblock;
777 if (SEQ_GEQ(start, old_start) && SEQ_LEQ(end, old_end)) {
778 /* Cases 1 & 2. Move block to front of history. */
783 /* no need to check rest of blocks */
784 for (j = i + 1; j < tp->nsackhistory; ++j)
785 copy[cindex++] = tp->sackhistory[j];
789 if (SEQ_GEQ(old_end, start) && SEQ_LT(old_start, start)) {
790 /* Case 4: extend start of new block. */
792 } else if (SEQ_GEQ(end, old_start) && SEQ_GT(old_end, end)) {
793 /* Case 5: extend end of new block */
796 /* Case 3. Delete old block by not copying it. */
797 KASSERT(SEQ_LEQ(start, old_start) &&
798 SEQ_GEQ(end, old_end),
799 ("bad logic: old [%u, %u), new [%u, %u)",
800 old_start, old_end, start, end));
804 /* insert new block */
805 tp->sackhistory[0].rblk_start = start;
806 tp->sackhistory[0].rblk_end = end;
807 cindex = min(cindex, MAX_SACK_REPORT_BLOCKS - 1);
808 for (i = 0; i < cindex; ++i)
809 tp->sackhistory[i + 1] = copy[i];
810 tp->nsackhistory = cindex + 1;
811 tcp_sack_dump_history("after tcp_sack_update_reported_history", tp);
815 * Fill in SACK report to return to data sender.
818 tcp_sack_fill_report(struct tcpcb *tp, u_char *opt, u_int *plen)
820 u_int optlen = *plen;
821 uint32_t *lp = (uint32_t *)(opt + optlen);
823 tcp_seq hstart = tp->rcv_nxt, hend;
826 KASSERT(TCP_MAXOLEN - optlen >=
827 TCPOLEN_SACK_ALIGNED + TCPOLEN_SACK_BLOCK,
828 ("no room for SACK header and one block: optlen %d", optlen));
830 if (tp->t_flags & TF_DUPSEG)
831 tcpstat.tcps_snddsackopt++;
833 tcpstat.tcps_sndsackopt++;
836 optlen += TCPOLEN_SACK_ALIGNED;
838 tcp_sack_ack_history(tp);
839 if (tp->reportblk.rblk_start != tp->reportblk.rblk_end) {
840 *lp++ = htonl(tp->reportblk.rblk_start);
841 *lp++ = htonl(tp->reportblk.rblk_end);
842 optlen += TCPOLEN_SACK_BLOCK;
843 hstart = tp->reportblk.rblk_start;
844 hend = tp->reportblk.rblk_end;
845 if (tp->t_flags & TF_ENCLOSESEG) {
846 KASSERT(TCP_MAXOLEN - optlen >= TCPOLEN_SACK_BLOCK,
847 ("no room for enclosing SACK block: oplen %d",
849 *lp++ = htonl(tp->encloseblk.rblk_start);
850 *lp++ = htonl(tp->encloseblk.rblk_end);
851 optlen += TCPOLEN_SACK_BLOCK;
852 hstart = tp->encloseblk.rblk_start;
853 hend = tp->encloseblk.rblk_end;
855 if (SEQ_GT(hstart, tp->rcv_nxt))
856 tcp_sack_update_reported_history(tp, hstart, hend);
858 if (tcp_do_smartsack && (tp->t_flags & TF_SACKLEFT)) {
859 /* Fill in from left! Walk re-assembly queue. */
862 q = LIST_FIRST(&tp->t_segq);
864 TCP_MAXOLEN - optlen >= TCPOLEN_SACK_BLOCK) {
865 *lp++ = htonl(q->tqe_th->th_seq);
866 *lp++ = htonl(TCP_SACK_BLKEND(
867 q->tqe_th->th_seq + q->tqe_len,
868 q->tqe_th->th_flags));
869 optlen += TCPOLEN_SACK_BLOCK;
870 q = LIST_NEXT(q, tqe_q);
875 /* Fill in SACK blocks from right side. */
876 while (n < tp->nsackhistory &&
877 TCP_MAXOLEN - optlen >= TCPOLEN_SACK_BLOCK) {
878 if (tp->sackhistory[n].rblk_start != hstart) {
879 *lp++ = htonl(tp->sackhistory[n].rblk_start);
880 *lp++ = htonl(tp->sackhistory[n].rblk_end);
881 optlen += TCPOLEN_SACK_BLOCK;
886 tp->reportblk.rblk_start = tp->reportblk.rblk_end;
887 tp->t_flags &= ~(TF_DUPSEG | TF_ENCLOSESEG | TF_SACKLEFT);
888 nblocks = (lp - olp - 1) / 2;
889 *olp = htonl(TCPOPT_SACK_ALIGNED |
890 (TCPOLEN_SACK + nblocks * TCPOLEN_SACK_BLOCK));