diff options
Diffstat (limited to 'freebsd/sys/netinet/tcp_sack.c')
| -rw-r--r-- | freebsd/sys/netinet/tcp_sack.c | 687 |
1 files changed, 687 insertions, 0 deletions
diff --git a/freebsd/sys/netinet/tcp_sack.c b/freebsd/sys/netinet/tcp_sack.c new file mode 100644 index 00000000..94bae57b --- /dev/null +++ b/freebsd/sys/netinet/tcp_sack.c @@ -0,0 +1,687 @@ +#include <freebsd/machine/rtems-bsd-config.h> + +/*- + * 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. + * 4. 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 <freebsd/sys/cdefs.h> +__FBSDID("$FreeBSD$"); + +#include <freebsd/local/opt_inet.h> +#include <freebsd/local/opt_inet6.h> +#include <freebsd/local/opt_tcpdebug.h> + +#include <freebsd/sys/param.h> +#include <freebsd/sys/systm.h> +#include <freebsd/sys/kernel.h> +#include <freebsd/sys/sysctl.h> +#include <freebsd/sys/malloc.h> +#include <freebsd/sys/mbuf.h> +#include <freebsd/sys/proc.h> /* for proc0 declaration */ +#include <freebsd/sys/protosw.h> +#include <freebsd/sys/socket.h> +#include <freebsd/sys/socketvar.h> +#include <freebsd/sys/syslog.h> +#include <freebsd/sys/systm.h> + +#include <freebsd/machine/cpu.h> /* before tcp_seq.h, for tcp_random18() */ + +#include <freebsd/vm/uma.h> + +#include <freebsd/net/if.h> +#include <freebsd/net/route.h> +#include <freebsd/net/vnet.h> + +#include <freebsd/netinet/in.h> +#include <freebsd/netinet/in_systm.h> +#include <freebsd/netinet/ip.h> +#include <freebsd/netinet/in_var.h> +#include <freebsd/netinet/in_pcb.h> +#include <freebsd/netinet/ip_var.h> +#include <freebsd/netinet/ip6.h> +#include <freebsd/netinet/icmp6.h> +#include <freebsd/netinet6/nd6.h> +#include <freebsd/netinet6/ip6_var.h> +#include <freebsd/netinet6/in6_pcb.h> +#include <freebsd/netinet/tcp.h> +#include <freebsd/netinet/tcp_fsm.h> +#include <freebsd/netinet/tcp_seq.h> +#include <freebsd/netinet/tcp_timer.h> +#include <freebsd/netinet/tcp_var.h> +#include <freebsd/netinet6/tcp6_var.h> +#include <freebsd/netinet/tcpip.h> +#ifdef TCPDEBUG +#include <freebsd/netinet/tcp_debug.h> +#endif /* TCPDEBUG */ + +#include <freebsd/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, 0, "TCP SACK"); +VNET_DEFINE(int, tcp_do_sack) = 1; +#define V_tcp_do_sack VNET(tcp_do_sack) +SYSCTL_VNET_INT(_net_inet_tcp_sack, OID_AUTO, enable, CTLFLAG_RW, + &VNET_NAME(tcp_do_sack), 0, "Enable/Disable TCP SACK support"); + +VNET_DEFINE(int, tcp_sack_maxholes) = 128; +#define V_tcp_sack_maxholes VNET(tcp_sack_maxholes) +SYSCTL_VNET_INT(_net_inet_tcp_sack, OID_AUTO, maxholes, CTLFLAG_RW, + &VNET_NAME(tcp_sack_maxholes), 0, + "Maximum number of TCP SACK holes allowed per connection"); + +VNET_DEFINE(int, tcp_sack_globalmaxholes) = 65536; +#define V_tcp_sack_globalmaxholes VNET(tcp_sack_globalmaxholes) +SYSCTL_VNET_INT(_net_inet_tcp_sack, OID_AUTO, globalmaxholes, CTLFLAG_RW, + &VNET_NAME(tcp_sack_globalmaxholes), 0, + "Global maximum number of TCP SACK holes"); + +VNET_DEFINE(int, tcp_sack_globalholes) = 0; +#define V_tcp_sack_globalholes VNET(tcp_sack_globalholes) +SYSCTL_VNET_INT(_net_inet_tcp_sack, OID_AUTO, globalholes, CTLFLAG_RD, + &VNET_NAME(tcp_sack_globalholes), 0, + "Global number of TCP SACK holes currently allocated"); + +/* + * 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_LT(rcv_start, rcv_end), ("rcv_start < rcv_end")); + + /* 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. + */ + if (SEQ_GT(head_blk.start, start)) + head_blk.start = start; + if (SEQ_LT(head_blk.end, end)) + head_blk.end = end; + } else { + /* + * 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_GT(head_blk.start, tp->rcv_nxt)) { + /* + * 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 (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; +} + +/* + * 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). + */ +void +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; + + INP_WLOCK_ASSERT(tp->t_inpcb); + + num_sack_blks = 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. + */ + if (SEQ_LT(tp->snd_una, th_ack) && !TAILQ_EMPTY(&tp->snd_holes)) { + 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; + + /* + * Sort the SACK blocks so we can update the scoreboard with just one + * pass. The overhead of sorting upto 4+1 elements is less than + * making upto 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); + /* + * 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 */ + 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) { + tp->snd_fack = sblkp->end; + /* Go to the previous sack block. */ + sblkp--; + } 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)) + tp->snd_fack = sblkp->end; + } + } else if (SEQ_LT(tp->snd_fack, sblkp->end)) + /* fack is advanced. */ + tp->snd_fack = sblkp->end; + /* We must have at least one SACK hole in scoreboard. */ + KASSERT(!TAILQ_EMPTY(&tp->snd_holes), + ("SACK scoreboard must not be empty")); + 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")); + 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. */ + 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. */ + 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. */ + 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); + } + } + } + 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--; + } +} + +/* + * 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; + + 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 (((th->th_ack - tp->snd_una) / tp->t_maxseg) > 2) + num_segs = 2; + tp->snd_cwnd = (tp->sackhint.sack_bytes_rexmit + + (tp->snd_nxt - tp->sack_newdata) + num_segs * tp->t_maxseg); + if (tp->snd_cwnd > tp->snd_ssthresh) + tp->snd_cwnd = tp->snd_ssthresh; + tp->t_flags |= TF_ACKNOW; + (void) 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; +} |