/* * Copyright (c) 2004 Apple Computer, Inc. All rights reserved. * * @APPLE_OSREFERENCE_LICENSE_HEADER_START@ * * This file contains Original Code and/or Modifications of Original Code * as defined in and that are subject to the Apple Public Source License * Version 2.0 (the 'License'). You may not use this file except in * compliance with the License. The rights granted to you under the License * may not be used to create, or enable the creation or redistribution of, * unlawful or unlicensed copies of an Apple operating system, or to * circumvent, violate, or enable the circumvention or violation of, any * terms of an Apple operating system software license agreement. * * Please obtain a copy of the License at * http://www.opensource.apple.com/apsl/ and read it before using this file. * * The Original Code and all software distributed under the License are * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES, * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY, * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT. * Please see the License for the specific language governing rights and * limitations under the License. * * @APPLE_OSREFERENCE_LICENSE_HEADER_END@ */ /* * Copyright (c) 1982, 1986, 1988, 1990, 1993, 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. All advertising materials mentioning features or use of this software * must display the following acknowledgement: * This product includes software developed by the University of * California, Berkeley and its contributors. * 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. * */ #define _IP_VHL #include <sys/param.h> #include <sys/systm.h> #include <sys/kernel.h> #include <sys/sysctl.h> #include <sys/mbuf.h> #include <sys/domain.h> #include <sys/protosw.h> #include <sys/socket.h> #include <sys/socketvar.h> #include <net/route.h> #include <netinet/in.h> #include <netinet/in_systm.h> #include <netinet/ip.h> #include <netinet/in_pcb.h> #include <netinet/ip_var.h> #if INET6 #include <netinet6/in6_pcb.h> #include <netinet/ip6.h> #include <netinet6/ip6_var.h> #endif #include <netinet/tcp.h> //#define TCPOUTFLAGS #include <netinet/tcp_fsm.h> #include <netinet/tcp_seq.h> #include <netinet/tcp_timer.h> #include <netinet/tcp_var.h> #include <netinet/tcpip.h> #if TCPDEBUG #include <netinet/tcp_debug.h> #endif #include <sys/kdebug.h> #if IPSEC #include <netinet6/ipsec.h> #endif /*IPSEC*/ int tcp_do_sack = 1; SYSCTL_INT(_net_inet_tcp, OID_AUTO, sack, CTLFLAG_RW, &tcp_do_sack, 0, "Enable/Disable TCP SACK support"); static int tcp_sack_maxholes = 128; SYSCTL_INT(_net_inet_tcp, OID_AUTO, sack_maxholes, CTLFLAG_RW, &tcp_sack_maxholes, 0, "Maximum number of TCP SACK holes allowed per connection"); static int tcp_sack_globalmaxholes = 65536; SYSCTL_INT(_net_inet_tcp, OID_AUTO, sack_globalmaxholes, CTLFLAG_RW, &tcp_sack_globalmaxholes, 0, "Global maximum number of TCP SACK holes"); static int tcp_sack_globalholes = 0; SYSCTL_INT(_net_inet_tcp, OID_AUTO, sack_globalholes, CTLFLAG_RD, &tcp_sack_globalholes, 0, "Global number of TCP SACK holes currently allocated"); extern struct zone *sack_hole_zone; /* * 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; /* 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; tp->rcv_numsacks = 0; for (i = 0; i < MAX_SACK_BLKS; i++) tp->sackblks[i].start = tp->sackblks[i].end=0; */ bzero(&tp->sackblks[0], sizeof (struct sackblk) * MAX_SACK_BLKS); } /* * 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 >= tcp_sack_maxholes || tcp_sack_globalholes >= tcp_sack_globalmaxholes) { tcpstat.tcps_sack_sboverflow++; return NULL; } hole = (struct sackhole *)zalloc_noblock(sack_hole_zone); if (hole == NULL) return NULL; hole->start = start; hole->end = end; hole->rxmit = start; tp->snd_numholes++; tcp_sack_globalholes++; return hole; } /* * Free struct sackhole. */ static void tcp_sackhole_free(struct tcpcb *tp, struct sackhole *hole) { zfree(sack_hole_zone, hole); tp->snd_numholes--; tcp_sack_globalholes--; } /* * 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; 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[]. */ 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_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 */ 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); 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; while ((q = TAILQ_FIRST(&tp->snd_holes)) != NULL) tcp_sackhole_remove(tp, q); tp->sackhint.sack_bytes_rexmit = 0; } /* * 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(tp, th) struct tcpcb *tp; struct tcphdr *th; { int num_segs = 1; tp->t_timer[TCPT_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); } /* * 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; *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); } /* * 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, *dbg_hole = NULL; int dbg_bytes_rexmt; dbg_hole = tcp_sack_output_debug(tp, &dbg_bytes_rexmt); *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: if (dbg_hole != hole) { printf("%s: Computed sack hole not the same as cached value\n", __func__); hole = dbg_hole; } if (*sack_bytes_rexmt != dbg_bytes_rexmt) { printf("%s: Computed sack_bytes_retransmitted (%d) not " "the same as cached value (%d)\n", __func__, dbg_bytes_rexmt, *sack_bytes_rexmt); *sack_bytes_rexmt = dbg_bytes_rexmt; } 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); 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; return; }