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- /*-
- * SPDX-License-Identifier: BSD-3-Clause
- *
- * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1994, 1995
- * The Regents of the University of California.
- * All rights reserved.
- *
- * Redistribution and use in source and binary forms, with or without
- * modification, are permitted provided that the following conditions
- * are met:
- * 1. Redistributions of source code must retain the above copyright
- * notice, this list of conditions and the following disclaimer.
- * 2. Redistributions in binary form must reproduce the above copyright
- * notice, this list of conditions and the following disclaimer in the
- * documentation and/or other materials provided with the distribution.
- * 3. Neither the name of the University nor the names of its contributors
- * may be used to endorse or promote products derived from this software
- * without specific prior written permission.
- *
- * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
- * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
- * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
- * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
- * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
- * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
- * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
- * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
- * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
- * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
- * SUCH DAMAGE.
- *
- * @(#)tcp_sack.c 8.12 (Berkeley) 5/24/95
- */
- /*-
- * @@(#)COPYRIGHT 1.1 (NRL) 17 January 1995
- *
- * NRL grants permission for redistribution and use in source and binary
- * forms, with or without modification, of the software and documentation
- * created at NRL provided that the following conditions are met:
- *
- * 1. Redistributions of source code must retain the above copyright
- * notice, this list of conditions and the following disclaimer.
- * 2. Redistributions in binary form must reproduce the above copyright
- * notice, this list of conditions and the following disclaimer in the
- * documentation and/or other materials provided with the distribution.
- * 3. All advertising materials mentioning features or use of this software
- * must display the following acknowledgements:
- * This product includes software developed by the University of
- * California, Berkeley and its contributors.
- * This product includes software developed at the Information
- * Technology Division, US Naval Research Laboratory.
- * 4. Neither the name of the NRL nor the names of its contributors
- * may be used to endorse or promote products derived from this software
- * without specific prior written permission.
- *
- * THE SOFTWARE PROVIDED BY NRL IS PROVIDED BY NRL AND CONTRIBUTORS ``AS
- * IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
- * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
- * PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL NRL OR
- * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
- * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
- * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
- * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
- * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
- * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
- * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
- *
- * The views and conclusions contained in the software and documentation
- * are those of the authors and should not be interpreted as representing
- * official policies, either expressed or implied, of the US Naval
- * Research Laboratory (NRL).
- */
- #include <sys/cdefs.h>
- __FBSDID("$FreeBSD$");
- #include "opt_inet.h"
- #include "opt_inet6.h"
- #include "opt_tcpdebug.h"
- #include <sys/param.h>
- #include <sys/systm.h>
- #include <sys/kernel.h>
- #include <sys/sysctl.h>
- #include <sys/malloc.h>
- #include <sys/mbuf.h>
- #include <sys/proc.h> /* for proc0 declaration */
- #include <sys/protosw.h>
- #include <sys/socket.h>
- #include <sys/socketvar.h>
- #include <sys/syslog.h>
- #include <sys/systm.h>
- #include <machine/cpu.h> /* before tcp_seq.h, for tcp_random18() */
- #include <vm/uma.h>
- #include <net/if.h>
- #include <net/if_var.h>
- #include <net/route.h>
- #include <net/vnet.h>
- #include <netinet/in.h>
- #include <netinet/in_systm.h>
- #include <netinet/ip.h>
- #include <netinet/in_var.h>
- #include <netinet/in_pcb.h>
- #include <netinet/ip_var.h>
- #include <netinet/ip6.h>
- #include <netinet/icmp6.h>
- #include <netinet6/nd6.h>
- #include <netinet6/ip6_var.h>
- #include <netinet6/in6_pcb.h>
- #include <netinet/tcp.h>
- #include <netinet/tcp_fsm.h>
- #include <netinet/tcp_seq.h>
- #include <netinet/tcp_timer.h>
- #include <netinet/tcp_var.h>
- #include <netinet6/tcp6_var.h>
- #include <netinet/tcpip.h>
- #ifdef TCPDEBUG
- #include <netinet/tcp_debug.h>
- #endif /* TCPDEBUG */
- #include <machine/in_cksum.h>
- VNET_DECLARE(struct uma_zone *, sack_hole_zone);
- #define V_sack_hole_zone VNET(sack_hole_zone)
- SYSCTL_NODE(_net_inet_tcp, OID_AUTO, sack, CTLFLAG_RW | CTLFLAG_MPSAFE, 0,
- "TCP SACK");
- VNET_DEFINE(int, tcp_do_sack) = 1;
- #define V_tcp_do_sack VNET(tcp_do_sack)
- SYSCTL_INT(_net_inet_tcp_sack, OID_AUTO, enable, CTLFLAG_VNET | CTLFLAG_RW,
- &VNET_NAME(tcp_do_sack), 0, "Enable/Disable TCP SACK support");
- VNET_DEFINE(int, tcp_sack_maxholes) = 128;
- SYSCTL_INT(_net_inet_tcp_sack, OID_AUTO, maxholes, CTLFLAG_VNET | CTLFLAG_RW,
- &VNET_NAME(tcp_sack_maxholes), 0,
- "Maximum number of TCP SACK holes allowed per connection");
- VNET_DEFINE(int, tcp_sack_globalmaxholes) = 65536;
- SYSCTL_INT(_net_inet_tcp_sack, OID_AUTO, globalmaxholes, CTLFLAG_VNET | CTLFLAG_RW,
- &VNET_NAME(tcp_sack_globalmaxholes), 0,
- "Global maximum number of TCP SACK holes");
- VNET_DEFINE(int, tcp_sack_globalholes) = 0;
- SYSCTL_INT(_net_inet_tcp_sack, OID_AUTO, globalholes, CTLFLAG_VNET | CTLFLAG_RD,
- &VNET_NAME(tcp_sack_globalholes), 0,
- "Global number of TCP SACK holes currently allocated");
- /*
- * This function will find overlaps with the currently stored sackblocks
- * and add any overlap as a dsack block upfront
- */
- void
- tcp_update_dsack_list(struct tcpcb *tp, tcp_seq rcv_start, tcp_seq rcv_end)
- {
- struct sackblk head_blk,mid_blk,saved_blks[MAX_SACK_BLKS];
- int i, j, n, identical;
- tcp_seq start, end;
- INP_WLOCK_ASSERT(tp->t_inpcb);
- KASSERT(SEQ_LT(rcv_start, rcv_end), ("rcv_start < rcv_end"));
- if (SEQ_LT(rcv_end, tp->rcv_nxt) ||
- ((rcv_end == tp->rcv_nxt) &&
- (tp->rcv_numsacks > 0 ) &&
- (tp->sackblks[0].end == tp->rcv_nxt))) {
- saved_blks[0].start = rcv_start;
- saved_blks[0].end = rcv_end;
- } else {
- saved_blks[0].start = saved_blks[0].end = 0;
- }
- head_blk.start = head_blk.end = 0;
- mid_blk.start = rcv_start;
- mid_blk.end = rcv_end;
- identical = 0;
- for (i = 0; i < tp->rcv_numsacks; i++) {
- start = tp->sackblks[i].start;
- end = tp->sackblks[i].end;
- if (SEQ_LT(rcv_end, start)) {
- /* pkt left to sack blk */
- continue;
- }
- if (SEQ_GT(rcv_start, end)) {
- /* pkt right to sack blk */
- continue;
- }
- if (SEQ_GT(tp->rcv_nxt, end)) {
- if ((SEQ_MAX(rcv_start, start) != SEQ_MIN(rcv_end, end)) &&
- (SEQ_GT(head_blk.start, SEQ_MAX(rcv_start, start)) ||
- (head_blk.start == head_blk.end))) {
- head_blk.start = SEQ_MAX(rcv_start, start);
- head_blk.end = SEQ_MIN(rcv_end, end);
- }
- continue;
- }
- if (((head_blk.start == head_blk.end) ||
- SEQ_LT(start, head_blk.start)) &&
- (SEQ_GT(end, rcv_start) &&
- SEQ_LEQ(start, rcv_end))) {
- head_blk.start = start;
- head_blk.end = end;
- }
- mid_blk.start = SEQ_MIN(mid_blk.start, start);
- mid_blk.end = SEQ_MAX(mid_blk.end, end);
- if ((mid_blk.start == start) &&
- (mid_blk.end == end))
- identical = 1;
- }
- if (SEQ_LT(head_blk.start, head_blk.end)) {
- /* store overlapping range */
- saved_blks[0].start = SEQ_MAX(rcv_start, head_blk.start);
- saved_blks[0].end = SEQ_MIN(rcv_end, head_blk.end);
- }
- n = 1;
- /*
- * Second, if not ACKed, store the SACK block that
- * overlaps with the DSACK block unless it is identical
- */
- if ((SEQ_LT(tp->rcv_nxt, mid_blk.end) &&
- !((mid_blk.start == saved_blks[0].start) &&
- (mid_blk.end == saved_blks[0].end))) ||
- identical == 1) {
- saved_blks[n].start = mid_blk.start;
- saved_blks[n++].end = mid_blk.end;
- }
- for (j = 0; (j < tp->rcv_numsacks) && (n < MAX_SACK_BLKS); j++) {
- if (((SEQ_LT(tp->sackblks[j].end, mid_blk.start) ||
- SEQ_GT(tp->sackblks[j].start, mid_blk.end)) &&
- (SEQ_GT(tp->sackblks[j].start, tp->rcv_nxt))))
- saved_blks[n++] = tp->sackblks[j];
- }
- j = 0;
- for (i = 0; i < n; i++) {
- /* we can end up with a stale initial entry */
- if (SEQ_LT(saved_blks[i].start, saved_blks[i].end)) {
- tp->sackblks[j++] = saved_blks[i];
- }
- }
- tp->rcv_numsacks = j;
- }
- /*
- * This function is called upon receipt of new valid data (while not in
- * header prediction mode), and it updates the ordered list of sacks.
- */
- void
- tcp_update_sack_list(struct tcpcb *tp, tcp_seq rcv_start, tcp_seq rcv_end)
- {
- /*
- * First reported block MUST be the most recent one. Subsequent
- * blocks SHOULD be in the order in which they arrived at the
- * receiver. These two conditions make the implementation fully
- * compliant with RFC 2018.
- */
- struct sackblk head_blk, saved_blks[MAX_SACK_BLKS];
- int num_head, num_saved, i;
- INP_WLOCK_ASSERT(tp->t_inpcb);
- /* Check arguments. */
- KASSERT(SEQ_LEQ(rcv_start, rcv_end), ("rcv_start <= rcv_end"));
- if ((rcv_start == rcv_end) &&
- (tp->rcv_numsacks >= 1) &&
- (rcv_end == tp->sackblks[0].end)) {
- /* retaining DSACK block below rcv_nxt (todrop) */
- head_blk = tp->sackblks[0];
- } else {
- /* SACK block for the received segment. */
- head_blk.start = rcv_start;
- head_blk.end = rcv_end;
- }
- /*
- * Merge updated SACK blocks into head_blk, and save unchanged SACK
- * blocks into saved_blks[]. num_saved will have the number of the
- * saved SACK blocks.
- */
- num_saved = 0;
- for (i = 0; i < tp->rcv_numsacks; i++) {
- tcp_seq start = tp->sackblks[i].start;
- tcp_seq end = tp->sackblks[i].end;
- if (SEQ_GEQ(start, end) || SEQ_LEQ(start, tp->rcv_nxt)) {
- /*
- * Discard this SACK block.
- */
- } else if (SEQ_LEQ(head_blk.start, end) &&
- SEQ_GEQ(head_blk.end, start)) {
- /*
- * Merge this SACK block into head_blk. This SACK
- * block itself will be discarded.
- */
- /*
- * |-|
- * |---| merge
- *
- * |-|
- * |---| merge
- *
- * |-----|
- * |-| DSACK smaller
- *
- * |-|
- * |-----| DSACK smaller
- */
- if (head_blk.start == end)
- head_blk.start = start;
- else if (head_blk.end == start)
- head_blk.end = end;
- else {
- if (SEQ_LT(head_blk.start, start)) {
- tcp_seq temp = start;
- start = head_blk.start;
- head_blk.start = temp;
- }
- if (SEQ_GT(head_blk.end, end)) {
- tcp_seq temp = end;
- end = head_blk.end;
- head_blk.end = temp;
- }
- if ((head_blk.start != start) ||
- (head_blk.end != end)) {
- if ((num_saved >= 1) &&
- SEQ_GEQ(saved_blks[num_saved-1].start, start) &&
- SEQ_LEQ(saved_blks[num_saved-1].end, end))
- num_saved--;
- saved_blks[num_saved].start = start;
- saved_blks[num_saved].end = end;
- num_saved++;
- }
- }
- } else {
- /*
- * This block supercedes the prior block
- */
- if ((num_saved >= 1) &&
- SEQ_GEQ(saved_blks[num_saved-1].start, start) &&
- SEQ_LEQ(saved_blks[num_saved-1].end, end))
- num_saved--;
- /*
- * Save this SACK block.
- */
- saved_blks[num_saved].start = start;
- saved_blks[num_saved].end = end;
- num_saved++;
- }
- }
- /*
- * Update SACK list in tp->sackblks[].
- */
- num_head = 0;
- if (SEQ_LT(rcv_start, rcv_end)) {
- /*
- * The received data segment is an out-of-order segment. Put
- * head_blk at the top of SACK list.
- */
- tp->sackblks[0] = head_blk;
- num_head = 1;
- /*
- * If the number of saved SACK blocks exceeds its limit,
- * discard the last SACK block.
- */
- if (num_saved >= MAX_SACK_BLKS)
- num_saved--;
- }
- if ((rcv_start == rcv_end) &&
- (rcv_start == tp->sackblks[0].end)) {
- num_head = 1;
- }
- if (num_saved > 0) {
- /*
- * Copy the saved SACK blocks back.
- */
- bcopy(saved_blks, &tp->sackblks[num_head],
- sizeof(struct sackblk) * num_saved);
- }
- /* Save the number of SACK blocks. */
- tp->rcv_numsacks = num_head + num_saved;
- }
- void
- tcp_clean_dsack_blocks(struct tcpcb *tp)
- {
- struct sackblk saved_blks[MAX_SACK_BLKS];
- int num_saved, i;
- INP_WLOCK_ASSERT(tp->t_inpcb);
- /*
- * Clean up any DSACK blocks that
- * are in our queue of sack blocks.
- *
- */
- num_saved = 0;
- for (i = 0; i < tp->rcv_numsacks; i++) {
- tcp_seq start = tp->sackblks[i].start;
- tcp_seq end = tp->sackblks[i].end;
- if (SEQ_GEQ(start, end) || SEQ_LEQ(start, tp->rcv_nxt)) {
- /*
- * Discard this D-SACK block.
- */
- continue;
- }
- /*
- * Save this SACK block.
- */
- saved_blks[num_saved].start = start;
- saved_blks[num_saved].end = end;
- num_saved++;
- }
- if (num_saved > 0) {
- /*
- * Copy the saved SACK blocks back.
- */
- bcopy(saved_blks, &tp->sackblks[0],
- sizeof(struct sackblk) * num_saved);
- }
- tp->rcv_numsacks = num_saved;
- }
- /*
- * Delete all receiver-side SACK information.
- */
- void
- tcp_clean_sackreport(struct tcpcb *tp)
- {
- int i;
- INP_WLOCK_ASSERT(tp->t_inpcb);
- tp->rcv_numsacks = 0;
- for (i = 0; i < MAX_SACK_BLKS; i++)
- tp->sackblks[i].start = tp->sackblks[i].end=0;
- }
- /*
- * Allocate struct sackhole.
- */
- static struct sackhole *
- tcp_sackhole_alloc(struct tcpcb *tp, tcp_seq start, tcp_seq end)
- {
- struct sackhole *hole;
- if (tp->snd_numholes >= V_tcp_sack_maxholes ||
- V_tcp_sack_globalholes >= V_tcp_sack_globalmaxholes) {
- TCPSTAT_INC(tcps_sack_sboverflow);
- return NULL;
- }
- hole = (struct sackhole *)uma_zalloc(V_sack_hole_zone, M_NOWAIT);
- if (hole == NULL)
- return NULL;
- hole->start = start;
- hole->end = end;
- hole->rxmit = start;
- tp->snd_numholes++;
- atomic_add_int(&V_tcp_sack_globalholes, 1);
- return hole;
- }
- /*
- * Free struct sackhole.
- */
- static void
- tcp_sackhole_free(struct tcpcb *tp, struct sackhole *hole)
- {
- uma_zfree(V_sack_hole_zone, hole);
- tp->snd_numholes--;
- atomic_subtract_int(&V_tcp_sack_globalholes, 1);
- KASSERT(tp->snd_numholes >= 0, ("tp->snd_numholes >= 0"));
- KASSERT(V_tcp_sack_globalholes >= 0, ("tcp_sack_globalholes >= 0"));
- }
- /*
- * Insert new SACK hole into scoreboard.
- */
- static struct sackhole *
- tcp_sackhole_insert(struct tcpcb *tp, tcp_seq start, tcp_seq end,
- struct sackhole *after)
- {
- struct sackhole *hole;
- /* Allocate a new SACK hole. */
- hole = tcp_sackhole_alloc(tp, start, end);
- if (hole == NULL)
- return NULL;
- /* Insert the new SACK hole into scoreboard. */
- if (after != NULL)
- TAILQ_INSERT_AFTER(&tp->snd_holes, after, hole, scblink);
- else
- TAILQ_INSERT_TAIL(&tp->snd_holes, hole, scblink);
- /* Update SACK hint. */
- if (tp->sackhint.nexthole == NULL)
- tp->sackhint.nexthole = hole;
- return hole;
- }
- /*
- * Remove SACK hole from scoreboard.
- */
- static void
- tcp_sackhole_remove(struct tcpcb *tp, struct sackhole *hole)
- {
- /* Update SACK hint. */
- if (tp->sackhint.nexthole == hole)
- tp->sackhint.nexthole = TAILQ_NEXT(hole, scblink);
- /* Remove this SACK hole. */
- TAILQ_REMOVE(&tp->snd_holes, hole, scblink);
- /* Free this SACK hole. */
- tcp_sackhole_free(tp, hole);
- }
- /*
- * Process cumulative ACK and the TCP SACK option to update the scoreboard.
- * tp->snd_holes is an ordered list of holes (oldest to newest, in terms of
- * the sequence space).
- * Returns 1 if incoming ACK has previously unknown SACK information,
- * 0 otherwise.
- */
- int
- tcp_sack_doack(struct tcpcb *tp, struct tcpopt *to, tcp_seq th_ack)
- {
- struct sackhole *cur, *temp;
- struct sackblk sack, sack_blocks[TCP_MAX_SACK + 1], *sblkp;
- int i, j, num_sack_blks, sack_changed;
- int delivered_data, left_edge_delta;
- INP_WLOCK_ASSERT(tp->t_inpcb);
- num_sack_blks = 0;
- sack_changed = 0;
- delivered_data = 0;
- left_edge_delta = 0;
- /*
- * If SND.UNA will be advanced by SEG.ACK, and if SACK holes exist,
- * treat [SND.UNA, SEG.ACK) as if it is a SACK block.
- * Account changes to SND.UNA always in delivered data.
- */
- if (SEQ_LT(tp->snd_una, th_ack) && !TAILQ_EMPTY(&tp->snd_holes)) {
- left_edge_delta = th_ack - tp->snd_una;
- sack_blocks[num_sack_blks].start = tp->snd_una;
- sack_blocks[num_sack_blks++].end = th_ack;
- }
- /*
- * Append received valid SACK blocks to sack_blocks[], but only if we
- * received new blocks from the other side.
- */
- if (to->to_flags & TOF_SACK) {
- for (i = 0; i < to->to_nsacks; i++) {
- bcopy((to->to_sacks + i * TCPOLEN_SACK),
- &sack, sizeof(sack));
- sack.start = ntohl(sack.start);
- sack.end = ntohl(sack.end);
- if (SEQ_GT(sack.end, sack.start) &&
- SEQ_GT(sack.start, tp->snd_una) &&
- SEQ_GT(sack.start, th_ack) &&
- SEQ_LT(sack.start, tp->snd_max) &&
- SEQ_GT(sack.end, tp->snd_una) &&
- SEQ_LEQ(sack.end, tp->snd_max)) {
- sack_blocks[num_sack_blks++] = sack;
- }
- }
- }
- /*
- * Return if SND.UNA is not advanced and no valid SACK block is
- * received.
- */
- if (num_sack_blks == 0)
- return (sack_changed);
- /*
- * Sort the SACK blocks so we can update the scoreboard with just one
- * pass. The overhead of sorting up to 4+1 elements is less than
- * making up to 4+1 passes over the scoreboard.
- */
- for (i = 0; i < num_sack_blks; i++) {
- for (j = i + 1; j < num_sack_blks; j++) {
- if (SEQ_GT(sack_blocks[i].end, sack_blocks[j].end)) {
- sack = sack_blocks[i];
- sack_blocks[i] = sack_blocks[j];
- sack_blocks[j] = sack;
- }
- }
- }
- if (TAILQ_EMPTY(&tp->snd_holes)) {
- /*
- * Empty scoreboard. Need to initialize snd_fack (it may be
- * uninitialized or have a bogus value). Scoreboard holes
- * (from the sack blocks received) are created later below
- * (in the logic that adds holes to the tail of the
- * scoreboard).
- */
- tp->snd_fack = SEQ_MAX(tp->snd_una, th_ack);
- tp->sackhint.sacked_bytes = 0; /* reset */
- }
- /*
- * In the while-loop below, incoming SACK blocks (sack_blocks[]) and
- * SACK holes (snd_holes) are traversed from their tails with just
- * one pass in order to reduce the number of compares especially when
- * the bandwidth-delay product is large.
- *
- * Note: Typically, in the first RTT of SACK recovery, the highest
- * three or four SACK blocks with the same ack number are received.
- * In the second RTT, if retransmitted data segments are not lost,
- * the highest three or four SACK blocks with ack number advancing
- * are received.
- */
- sblkp = &sack_blocks[num_sack_blks - 1]; /* Last SACK block */
- tp->sackhint.last_sack_ack = sblkp->end;
- if (SEQ_LT(tp->snd_fack, sblkp->start)) {
- /*
- * The highest SACK block is beyond fack. Append new SACK
- * hole at the tail. If the second or later highest SACK
- * blocks are also beyond the current fack, they will be
- * inserted by way of hole splitting in the while-loop below.
- */
- temp = tcp_sackhole_insert(tp, tp->snd_fack,sblkp->start,NULL);
- if (temp != NULL) {
- delivered_data += sblkp->end - sblkp->start;
- tp->snd_fack = sblkp->end;
- /* Go to the previous sack block. */
- sblkp--;
- sack_changed = 1;
- } else {
- /*
- * We failed to add a new hole based on the current
- * sack block. Skip over all the sack blocks that
- * fall completely to the right of snd_fack and
- * proceed to trim the scoreboard based on the
- * remaining sack blocks. This also trims the
- * scoreboard for th_ack (which is sack_blocks[0]).
- */
- while (sblkp >= sack_blocks &&
- SEQ_LT(tp->snd_fack, sblkp->start))
- sblkp--;
- if (sblkp >= sack_blocks &&
- SEQ_LT(tp->snd_fack, sblkp->end)) {
- delivered_data += sblkp->end - tp->snd_fack;
- tp->snd_fack = sblkp->end;
- sack_changed = 1;
- }
- }
- } else if (SEQ_LT(tp->snd_fack, sblkp->end)) {
- /* fack is advanced. */
- delivered_data += sblkp->end - tp->snd_fack;
- tp->snd_fack = sblkp->end;
- sack_changed = 1;
- }
- cur = TAILQ_LAST(&tp->snd_holes, sackhole_head); /* Last SACK hole. */
- /*
- * Since the incoming sack blocks are sorted, we can process them
- * making one sweep of the scoreboard.
- */
- while (sblkp >= sack_blocks && cur != NULL) {
- if (SEQ_GEQ(sblkp->start, cur->end)) {
- /*
- * SACKs data beyond the current hole. Go to the
- * previous sack block.
- */
- sblkp--;
- continue;
- }
- if (SEQ_LEQ(sblkp->end, cur->start)) {
- /*
- * SACKs data before the current hole. Go to the
- * previous hole.
- */
- cur = TAILQ_PREV(cur, sackhole_head, scblink);
- continue;
- }
- tp->sackhint.sack_bytes_rexmit -= (cur->rxmit - cur->start);
- KASSERT(tp->sackhint.sack_bytes_rexmit >= 0,
- ("sackhint bytes rtx >= 0"));
- sack_changed = 1;
- if (SEQ_LEQ(sblkp->start, cur->start)) {
- /* Data acks at least the beginning of hole. */
- if (SEQ_GEQ(sblkp->end, cur->end)) {
- /* Acks entire hole, so delete hole. */
- delivered_data += (cur->end - cur->start);
- temp = cur;
- cur = TAILQ_PREV(cur, sackhole_head, scblink);
- tcp_sackhole_remove(tp, temp);
- /*
- * The sack block may ack all or part of the
- * next hole too, so continue onto the next
- * hole.
- */
- continue;
- } else {
- /* Move start of hole forward. */
- delivered_data += (sblkp->end - cur->start);
- cur->start = sblkp->end;
- cur->rxmit = SEQ_MAX(cur->rxmit, cur->start);
- }
- } else {
- /* Data acks at least the end of hole. */
- if (SEQ_GEQ(sblkp->end, cur->end)) {
- /* Move end of hole backward. */
- delivered_data += (cur->end - sblkp->start);
- cur->end = sblkp->start;
- cur->rxmit = SEQ_MIN(cur->rxmit, cur->end);
- } else {
- /*
- * ACKs some data in middle of a hole; need
- * to split current hole
- */
- temp = tcp_sackhole_insert(tp, sblkp->end,
- cur->end, cur);
- if (temp != NULL) {
- if (SEQ_GT(cur->rxmit, temp->rxmit)) {
- temp->rxmit = cur->rxmit;
- tp->sackhint.sack_bytes_rexmit
- += (temp->rxmit
- - temp->start);
- }
- cur->end = sblkp->start;
- cur->rxmit = SEQ_MIN(cur->rxmit,
- cur->end);
- delivered_data += (sblkp->end - sblkp->start);
- }
- }
- }
- tp->sackhint.sack_bytes_rexmit += (cur->rxmit - cur->start);
- /*
- * Testing sblkp->start against cur->start tells us whether
- * we're done with the sack block or the sack hole.
- * Accordingly, we advance one or the other.
- */
- if (SEQ_LEQ(sblkp->start, cur->start))
- cur = TAILQ_PREV(cur, sackhole_head, scblink);
- else
- sblkp--;
- }
- tp->sackhint.delivered_data = delivered_data;
- tp->sackhint.sacked_bytes += delivered_data - left_edge_delta;
- KASSERT((delivered_data >= 0), ("delivered_data < 0"));
- KASSERT((tp->sackhint.sacked_bytes >= 0), ("sacked_bytes < 0"));
- return (sack_changed);
- }
- /*
- * Free all SACK holes to clear the scoreboard.
- */
- void
- tcp_free_sackholes(struct tcpcb *tp)
- {
- struct sackhole *q;
- INP_WLOCK_ASSERT(tp->t_inpcb);
- while ((q = TAILQ_FIRST(&tp->snd_holes)) != NULL)
- tcp_sackhole_remove(tp, q);
- tp->sackhint.sack_bytes_rexmit = 0;
- KASSERT(tp->snd_numholes == 0, ("tp->snd_numholes == 0"));
- KASSERT(tp->sackhint.nexthole == NULL,
- ("tp->sackhint.nexthole == NULL"));
- }
- /*
- * Partial ack handling within a sack recovery episode. Keeping this very
- * simple for now. When a partial ack is received, force snd_cwnd to a value
- * that will allow the sender to transmit no more than 2 segments. If
- * necessary, a better scheme can be adopted at a later point, but for now,
- * the goal is to prevent the sender from bursting a large amount of data in
- * the midst of sack recovery.
- */
- void
- tcp_sack_partialack(struct tcpcb *tp, struct tcphdr *th)
- {
- int num_segs = 1;
- u_int maxseg = tcp_maxseg(tp);
- INP_WLOCK_ASSERT(tp->t_inpcb);
- tcp_timer_activate(tp, TT_REXMT, 0);
- tp->t_rtttime = 0;
- /* Send one or 2 segments based on how much new data was acked. */
- if ((BYTES_THIS_ACK(tp, th) / maxseg) >= 2)
- num_segs = 2;
- tp->snd_cwnd = (tp->sackhint.sack_bytes_rexmit +
- (tp->snd_nxt - tp->snd_recover) + num_segs * maxseg);
- if (tp->snd_cwnd > tp->snd_ssthresh)
- tp->snd_cwnd = tp->snd_ssthresh;
- tp->t_flags |= TF_ACKNOW;
- (void) tp->t_fb->tfb_tcp_output(tp);
- }
- #if 0
- /*
- * Debug version of tcp_sack_output() that walks the scoreboard. Used for
- * now to sanity check the hint.
- */
- static struct sackhole *
- tcp_sack_output_debug(struct tcpcb *tp, int *sack_bytes_rexmt)
- {
- struct sackhole *p;
- INP_WLOCK_ASSERT(tp->t_inpcb);
- *sack_bytes_rexmt = 0;
- TAILQ_FOREACH(p, &tp->snd_holes, scblink) {
- if (SEQ_LT(p->rxmit, p->end)) {
- if (SEQ_LT(p->rxmit, tp->snd_una)) {/* old SACK hole */
- continue;
- }
- *sack_bytes_rexmt += (p->rxmit - p->start);
- break;
- }
- *sack_bytes_rexmt += (p->rxmit - p->start);
- }
- return (p);
- }
- #endif
- /*
- * Returns the next hole to retransmit and the number of retransmitted bytes
- * from the scoreboard. We store both the next hole and the number of
- * retransmitted bytes as hints (and recompute these on the fly upon SACK/ACK
- * reception). This avoids scoreboard traversals completely.
- *
- * The loop here will traverse *at most* one link. Here's the argument. For
- * the loop to traverse more than 1 link before finding the next hole to
- * retransmit, we would need to have at least 1 node following the current
- * hint with (rxmit == end). But, for all holes following the current hint,
- * (start == rxmit), since we have not yet retransmitted from them.
- * Therefore, in order to traverse more 1 link in the loop below, we need to
- * have at least one node following the current hint with (start == rxmit ==
- * end). But that can't happen, (start == end) means that all the data in
- * that hole has been sacked, in which case, the hole would have been removed
- * from the scoreboard.
- */
- struct sackhole *
- tcp_sack_output(struct tcpcb *tp, int *sack_bytes_rexmt)
- {
- struct sackhole *hole = NULL;
- INP_WLOCK_ASSERT(tp->t_inpcb);
- *sack_bytes_rexmt = tp->sackhint.sack_bytes_rexmit;
- hole = tp->sackhint.nexthole;
- if (hole == NULL || SEQ_LT(hole->rxmit, hole->end))
- goto out;
- while ((hole = TAILQ_NEXT(hole, scblink)) != NULL) {
- if (SEQ_LT(hole->rxmit, hole->end)) {
- tp->sackhint.nexthole = hole;
- break;
- }
- }
- out:
- return (hole);
- }
- /*
- * After a timeout, the SACK list may be rebuilt. This SACK information
- * should be used to avoid retransmitting SACKed data. This function
- * traverses the SACK list to see if snd_nxt should be moved forward.
- */
- void
- tcp_sack_adjust(struct tcpcb *tp)
- {
- struct sackhole *p, *cur = TAILQ_FIRST(&tp->snd_holes);
- INP_WLOCK_ASSERT(tp->t_inpcb);
- if (cur == NULL)
- return; /* No holes */
- if (SEQ_GEQ(tp->snd_nxt, tp->snd_fack))
- return; /* We're already beyond any SACKed blocks */
- /*-
- * Two cases for which we want to advance snd_nxt:
- * i) snd_nxt lies between end of one hole and beginning of another
- * ii) snd_nxt lies between end of last hole and snd_fack
- */
- while ((p = TAILQ_NEXT(cur, scblink)) != NULL) {
- if (SEQ_LT(tp->snd_nxt, cur->end))
- return;
- if (SEQ_GEQ(tp->snd_nxt, p->start))
- cur = p;
- else {
- tp->snd_nxt = p->start;
- return;
- }
- }
- if (SEQ_LT(tp->snd_nxt, cur->end))
- return;
- tp->snd_nxt = tp->snd_fack;
- }
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