| /*- |
| * 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 <sys/bsd_cdefs.h> |
| //__FBSDID("$FreeBSD$"); |
| |
| #include "bsd_opt_inet.h" |
| #include "bsd_opt_inet6.h" |
| #include "bsd_opt_tcpdebug.h" |
| |
| #include <sys/bsd_param.h> |
| #include <sys/bsd_systm.h> |
| #include <sys/bsd_kernel.h> |
| //baoyg//#include <sys/bsd_sysctl.h> |
| #include <sys/bsd_malloc.h> |
| #include <sys/bsd_mbuf.h> |
| ////#include <sys/bsd_proc.h> /* for proc0 declaration */ |
| #include <sys/bsd_protosw.h> |
| #include <sys/bsd_socket.h> |
| #include <sys/bsd_socketvar.h> |
| #include <sys/bsd_syslog.h> |
| #include <sys/bsd_systm.h> |
| |
| #include <machine/bsd_cpu.h> /* before tcp_seq.h, for tcp_random18() */ |
| |
| #include <vm/bsd_uma.h> |
| |
| #include <net/bsd_if.h> |
| #include <net/bsd_route.h> |
| #include <net/bsd_vnet.h> |
| |
| #include <netinet/bsd_in.h> |
| #include <netinet/bsd_in_systm.h> |
| #include <netinet/bsd_ip.h> |
| #include <netinet/bsd_in_var.h> |
| #include <netinet/bsd_in_pcb.h> |
| #include <netinet/bsd_ip_var.h> |
| #include <netinet/bsd_ip6.h> |
| #include <netinet/bsd_icmp6.h> |
| #include <netinet6/bsd_nd6.h> |
| #include <netinet6/bsd_ip6_var.h> |
| #include <netinet6/bsd_in6_pcb.h> |
| #include <netinet/bsd_tcp.h> |
| #include <netinet/bsd_tcp_fsm.h> |
| #include <netinet/bsd_tcp_seq.h> |
| #include <netinet/bsd_tcp_timer.h> |
| #include <netinet/bsd_tcp_var.h> |
| #include <netinet6/bsd_tcp6_var.h> |
| #include <netinet/bsd_tcpip.h> |
| #ifdef TCPDEBUG |
| #include <netinet/bsd_tcp_debug.h> |
| #endif /* TCPDEBUG */ |
| |
| #include <machine/bsd_in_cksum.h> |
| |
| VNET_DECLARE(struct uma_zone *, sack_hole_zone); |
| VNET_DEFINE(int, tcp_do_sack); |
| VNET_DEFINE(int, tcp_sack_maxholes); |
| VNET_DEFINE(int, tcp_sack_globalmaxholes); |
| VNET_DEFINE(int, tcp_sack_globalholes); |
| |
| #define V_sack_hole_zone VNET(sack_hole_zone) |
| #define V_tcp_do_sack VNET(tcp_do_sack) |
| #define V_tcp_sack_maxholes VNET(tcp_sack_maxholes) |
| #define V_tcp_sack_globalmaxholes VNET(tcp_sack_globalmaxholes) |
| #define V_tcp_sack_globalholes VNET(tcp_sack_globalholes) |
| /* |
| SYSCTL_NODE(_net_inet_tcp, OID_AUTO, sack, CTLFLAG_RW, 0, "TCP SACK"); |
| SYSCTL_VNET_INT(_net_inet_tcp_sack, OID_AUTO, enable, CTLFLAG_RW, |
| &VNET_NAME(tcp_do_sack), 0, "Enable/Disable TCP SACK support"); |
| |
| 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"); |
| |
| 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"); |
| |
| 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((u_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((u_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; |
| } |