/*- * 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 __FBSDID("$FreeBSD$"); #include "opt_inet.h" #include "opt_inet6.h" #include "opt_tcpdebug.h" #include #include #include #include #include #include #include /* for proc0 declaration */ #include #include #include #include #include #include /* before tcp_seq.h, for tcp_random18() */ #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #ifdef TCPDEBUG #include #endif /* TCPDEBUG */ #include 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; }