1e77c1056a
ever actually used. Rename VNET_GET() to VNET() to shorten variable references. Discussed with: bz, julian Reviewed by: bz Approved by: re (kensmith, kib)
687 lines
21 KiB
C
687 lines
21 KiB
C
/*-
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* Copyright (c) 1982, 1986, 1988, 1990, 1993, 1994, 1995
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* The Regents of the University of California.
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 4. Neither the name of the University nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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* @(#)tcp_sack.c 8.12 (Berkeley) 5/24/95
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*/
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/*-
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* @@(#)COPYRIGHT 1.1 (NRL) 17 January 1995
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*
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* NRL grants permission for redistribution and use in source and binary
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* forms, with or without modification, of the software and documentation
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* created at NRL provided that the following conditions are met:
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*
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. All advertising materials mentioning features or use of this software
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* must display the following acknowledgements:
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* This product includes software developed by the University of
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* California, Berkeley and its contributors.
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* This product includes software developed at the Information
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* Technology Division, US Naval Research Laboratory.
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* 4. Neither the name of the NRL nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THE SOFTWARE PROVIDED BY NRL IS PROVIDED BY NRL AND CONTRIBUTORS ``AS
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* IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
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* TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
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* PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL NRL OR
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* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
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* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
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* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
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* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
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* LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
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* NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
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* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*
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* The views and conclusions contained in the software and documentation
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* are those of the authors and should not be interpreted as representing
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* official policies, either expressed or implied, of the US Naval
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* Research Laboratory (NRL).
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*/
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#include <sys/cdefs.h>
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__FBSDID("$FreeBSD$");
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#include "opt_inet.h"
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#include "opt_inet6.h"
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#include "opt_tcpdebug.h"
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#include <sys/param.h>
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#include <sys/systm.h>
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#include <sys/kernel.h>
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#include <sys/sysctl.h>
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#include <sys/malloc.h>
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#include <sys/mbuf.h>
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#include <sys/proc.h> /* for proc0 declaration */
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#include <sys/protosw.h>
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#include <sys/socket.h>
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#include <sys/socketvar.h>
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#include <sys/syslog.h>
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#include <sys/systm.h>
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#include <sys/vimage.h>
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#include <machine/cpu.h> /* before tcp_seq.h, for tcp_random18() */
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#include <vm/uma.h>
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#include <net/if.h>
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#include <net/route.h>
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#include <netinet/in.h>
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#include <netinet/in_systm.h>
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#include <netinet/ip.h>
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#include <netinet/in_var.h>
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#include <netinet/in_pcb.h>
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#include <netinet/ip_var.h>
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#include <netinet/ip6.h>
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#include <netinet/icmp6.h>
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#include <netinet6/nd6.h>
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#include <netinet6/ip6_var.h>
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#include <netinet6/in6_pcb.h>
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#include <netinet/tcp.h>
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#include <netinet/tcp_fsm.h>
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#include <netinet/tcp_seq.h>
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#include <netinet/tcp_timer.h>
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#include <netinet/tcp_var.h>
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#include <netinet6/tcp6_var.h>
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#include <netinet/tcpip.h>
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#ifdef TCPDEBUG
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#include <netinet/tcp_debug.h>
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#endif /* TCPDEBUG */
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#include <machine/in_cksum.h>
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VNET_DECLARE(struct uma_zone *, sack_hole_zone);
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VNET_DEFINE(int, tcp_do_sack);
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VNET_DEFINE(int, tcp_sack_maxholes);
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VNET_DEFINE(int, tcp_sack_globalmaxholes);
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VNET_DEFINE(int, tcp_sack_globalholes);
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#define V_sack_hole_zone VNET(sack_hole_zone)
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#define V_tcp_do_sack VNET(tcp_do_sack)
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#define V_tcp_sack_maxholes VNET(tcp_sack_maxholes)
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#define V_tcp_sack_globalmaxholes VNET(tcp_sack_globalmaxholes)
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#define V_tcp_sack_globalholes VNET(tcp_sack_globalholes)
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SYSCTL_NODE(_net_inet_tcp, OID_AUTO, sack, CTLFLAG_RW, 0, "TCP SACK");
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SYSCTL_VNET_INT(_net_inet_tcp_sack, OID_AUTO, enable, CTLFLAG_RW,
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&VNET_NAME(tcp_do_sack), 0, "Enable/Disable TCP SACK support");
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SYSCTL_VNET_INT(_net_inet_tcp_sack, OID_AUTO, maxholes, CTLFLAG_RW,
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&VNET_NAME(tcp_sack_maxholes), 0,
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"Maximum number of TCP SACK holes allowed per connection");
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SYSCTL_VNET_INT(_net_inet_tcp_sack, OID_AUTO, globalmaxholes, CTLFLAG_RW,
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&VNET_NAME(tcp_sack_globalmaxholes), 0,
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"Global maximum number of TCP SACK holes");
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SYSCTL_VNET_INT(_net_inet_tcp_sack, OID_AUTO, globalholes, CTLFLAG_RD,
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&VNET_NAME(tcp_sack_globalholes), 0,
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"Global number of TCP SACK holes currently allocated");
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/*
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* This function is called upon receipt of new valid data (while not in
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* header prediction mode), and it updates the ordered list of sacks.
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*/
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void
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tcp_update_sack_list(struct tcpcb *tp, tcp_seq rcv_start, tcp_seq rcv_end)
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{
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/*
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* First reported block MUST be the most recent one. Subsequent
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* blocks SHOULD be in the order in which they arrived at the
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* receiver. These two conditions make the implementation fully
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* compliant with RFC 2018.
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*/
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struct sackblk head_blk, saved_blks[MAX_SACK_BLKS];
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int num_head, num_saved, i;
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INP_WLOCK_ASSERT(tp->t_inpcb);
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/* Check arguments. */
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KASSERT(SEQ_LT(rcv_start, rcv_end), ("rcv_start < rcv_end"));
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/* SACK block for the received segment. */
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head_blk.start = rcv_start;
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head_blk.end = rcv_end;
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/*
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* Merge updated SACK blocks into head_blk, and save unchanged SACK
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* blocks into saved_blks[]. num_saved will have the number of the
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* saved SACK blocks.
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*/
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num_saved = 0;
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for (i = 0; i < tp->rcv_numsacks; i++) {
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tcp_seq start = tp->sackblks[i].start;
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tcp_seq end = tp->sackblks[i].end;
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if (SEQ_GEQ(start, end) || SEQ_LEQ(start, tp->rcv_nxt)) {
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/*
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* Discard this SACK block.
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*/
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} else if (SEQ_LEQ(head_blk.start, end) &&
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SEQ_GEQ(head_blk.end, start)) {
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/*
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* Merge this SACK block into head_blk. This SACK
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* block itself will be discarded.
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*/
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if (SEQ_GT(head_blk.start, start))
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head_blk.start = start;
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if (SEQ_LT(head_blk.end, end))
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head_blk.end = end;
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} else {
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/*
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* Save this SACK block.
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*/
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saved_blks[num_saved].start = start;
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saved_blks[num_saved].end = end;
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num_saved++;
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}
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}
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/*
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* Update SACK list in tp->sackblks[].
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*/
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num_head = 0;
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if (SEQ_GT(head_blk.start, tp->rcv_nxt)) {
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/*
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* The received data segment is an out-of-order segment. Put
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* head_blk at the top of SACK list.
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*/
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tp->sackblks[0] = head_blk;
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num_head = 1;
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/*
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* If the number of saved SACK blocks exceeds its limit,
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* discard the last SACK block.
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*/
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if (num_saved >= MAX_SACK_BLKS)
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num_saved--;
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}
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if (num_saved > 0) {
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/*
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* Copy the saved SACK blocks back.
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*/
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bcopy(saved_blks, &tp->sackblks[num_head],
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sizeof(struct sackblk) * num_saved);
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}
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/* Save the number of SACK blocks. */
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tp->rcv_numsacks = num_head + num_saved;
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}
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/*
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* Delete all receiver-side SACK information.
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*/
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void
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tcp_clean_sackreport(struct tcpcb *tp)
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{
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int i;
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INP_WLOCK_ASSERT(tp->t_inpcb);
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tp->rcv_numsacks = 0;
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for (i = 0; i < MAX_SACK_BLKS; i++)
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tp->sackblks[i].start = tp->sackblks[i].end=0;
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}
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/*
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* Allocate struct sackhole.
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*/
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static struct sackhole *
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tcp_sackhole_alloc(struct tcpcb *tp, tcp_seq start, tcp_seq end)
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{
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struct sackhole *hole;
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if (tp->snd_numholes >= V_tcp_sack_maxholes ||
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V_tcp_sack_globalholes >= V_tcp_sack_globalmaxholes) {
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TCPSTAT_INC(tcps_sack_sboverflow);
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return NULL;
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}
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hole = (struct sackhole *)uma_zalloc(V_sack_hole_zone, M_NOWAIT);
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if (hole == NULL)
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return NULL;
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hole->start = start;
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hole->end = end;
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hole->rxmit = start;
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tp->snd_numholes++;
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atomic_add_int(&V_tcp_sack_globalholes, 1);
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return hole;
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}
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/*
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* Free struct sackhole.
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*/
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static void
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tcp_sackhole_free(struct tcpcb *tp, struct sackhole *hole)
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{
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uma_zfree(V_sack_hole_zone, hole);
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tp->snd_numholes--;
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atomic_subtract_int(&V_tcp_sack_globalholes, 1);
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KASSERT(tp->snd_numholes >= 0, ("tp->snd_numholes >= 0"));
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KASSERT(V_tcp_sack_globalholes >= 0, ("tcp_sack_globalholes >= 0"));
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}
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/*
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* Insert new SACK hole into scoreboard.
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*/
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static struct sackhole *
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tcp_sackhole_insert(struct tcpcb *tp, tcp_seq start, tcp_seq end,
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struct sackhole *after)
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{
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struct sackhole *hole;
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/* Allocate a new SACK hole. */
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hole = tcp_sackhole_alloc(tp, start, end);
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if (hole == NULL)
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return NULL;
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/* Insert the new SACK hole into scoreboard. */
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if (after != NULL)
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TAILQ_INSERT_AFTER(&tp->snd_holes, after, hole, scblink);
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else
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TAILQ_INSERT_TAIL(&tp->snd_holes, hole, scblink);
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/* Update SACK hint. */
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if (tp->sackhint.nexthole == NULL)
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tp->sackhint.nexthole = hole;
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return hole;
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}
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/*
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* Remove SACK hole from scoreboard.
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*/
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static void
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tcp_sackhole_remove(struct tcpcb *tp, struct sackhole *hole)
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{
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/* Update SACK hint. */
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if (tp->sackhint.nexthole == hole)
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tp->sackhint.nexthole = TAILQ_NEXT(hole, scblink);
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/* Remove this SACK hole. */
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TAILQ_REMOVE(&tp->snd_holes, hole, scblink);
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/* Free this SACK hole. */
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tcp_sackhole_free(tp, hole);
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}
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/*
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* Process cumulative ACK and the TCP SACK option to update the scoreboard.
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* tp->snd_holes is an ordered list of holes (oldest to newest, in terms of
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* the sequence space).
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*/
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void
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tcp_sack_doack(struct tcpcb *tp, struct tcpopt *to, tcp_seq th_ack)
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{
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struct sackhole *cur, *temp;
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struct sackblk sack, sack_blocks[TCP_MAX_SACK + 1], *sblkp;
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int i, j, num_sack_blks;
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INP_WLOCK_ASSERT(tp->t_inpcb);
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num_sack_blks = 0;
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/*
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* If SND.UNA will be advanced by SEG.ACK, and if SACK holes exist,
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* treat [SND.UNA, SEG.ACK) as if it is a SACK block.
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*/
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if (SEQ_LT(tp->snd_una, th_ack) && !TAILQ_EMPTY(&tp->snd_holes)) {
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sack_blocks[num_sack_blks].start = tp->snd_una;
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sack_blocks[num_sack_blks++].end = th_ack;
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}
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/*
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* Append received valid SACK blocks to sack_blocks[], but only if we
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* received new blocks from the other side.
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*/
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if (to->to_flags & TOF_SACK) {
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for (i = 0; i < to->to_nsacks; i++) {
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bcopy((to->to_sacks + i * TCPOLEN_SACK),
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&sack, sizeof(sack));
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sack.start = ntohl(sack.start);
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sack.end = ntohl(sack.end);
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if (SEQ_GT(sack.end, sack.start) &&
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SEQ_GT(sack.start, tp->snd_una) &&
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SEQ_GT(sack.start, th_ack) &&
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SEQ_LT(sack.start, tp->snd_max) &&
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SEQ_GT(sack.end, tp->snd_una) &&
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SEQ_LEQ(sack.end, tp->snd_max))
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sack_blocks[num_sack_blks++] = sack;
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}
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}
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/*
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* Return if SND.UNA is not advanced and no valid SACK block is
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* received.
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*/
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if (num_sack_blks == 0)
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return;
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/*
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* Sort the SACK blocks so we can update the scoreboard with just one
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* pass. The overhead of sorting upto 4+1 elements is less than
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* making upto 4+1 passes over the scoreboard.
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*/
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for (i = 0; i < num_sack_blks; i++) {
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for (j = i + 1; j < num_sack_blks; j++) {
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if (SEQ_GT(sack_blocks[i].end, sack_blocks[j].end)) {
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sack = sack_blocks[i];
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sack_blocks[i] = sack_blocks[j];
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sack_blocks[j] = sack;
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}
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}
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}
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if (TAILQ_EMPTY(&tp->snd_holes))
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/*
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* Empty scoreboard. Need to initialize snd_fack (it may be
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* uninitialized or have a bogus value). Scoreboard holes
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* (from the sack blocks received) are created later below
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* (in the logic that adds holes to the tail of the
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* scoreboard).
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*/
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tp->snd_fack = SEQ_MAX(tp->snd_una, th_ack);
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/*
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* In the while-loop below, incoming SACK blocks (sack_blocks[]) and
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* SACK holes (snd_holes) are traversed from their tails with just
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* one pass in order to reduce the number of compares especially when
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* the bandwidth-delay product is large.
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*
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* Note: Typically, in the first RTT of SACK recovery, the highest
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* three or four SACK blocks with the same ack number are received.
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* In the second RTT, if retransmitted data segments are not lost,
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* the highest three or four SACK blocks with ack number advancing
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* are received.
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*/
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sblkp = &sack_blocks[num_sack_blks - 1]; /* Last SACK block */
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if (SEQ_LT(tp->snd_fack, sblkp->start)) {
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/*
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* The highest SACK block is beyond fack. Append new SACK
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* hole at the tail. If the second or later highest SACK
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* blocks are also beyond the current fack, they will be
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* inserted by way of hole splitting in the while-loop below.
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*/
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temp = tcp_sackhole_insert(tp, tp->snd_fack,sblkp->start,NULL);
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if (temp != NULL) {
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tp->snd_fack = sblkp->end;
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/* Go to the previous sack block. */
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sblkp--;
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} else {
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/*
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* We failed to add a new hole based on the current
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* sack block. Skip over all the sack blocks that
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* fall completely to the right of snd_fack and
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* proceed to trim the scoreboard based on the
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* remaining sack blocks. This also trims the
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* scoreboard for th_ack (which is sack_blocks[0]).
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*/
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while (sblkp >= sack_blocks &&
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SEQ_LT(tp->snd_fack, sblkp->start))
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sblkp--;
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if (sblkp >= sack_blocks &&
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SEQ_LT(tp->snd_fack, sblkp->end))
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tp->snd_fack = sblkp->end;
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}
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} else if (SEQ_LT(tp->snd_fack, sblkp->end))
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/* fack is advanced. */
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tp->snd_fack = sblkp->end;
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/* We must have at least one SACK hole in scoreboard. */
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KASSERT(!TAILQ_EMPTY(&tp->snd_holes),
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("SACK scoreboard must not be empty"));
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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;
|
|
}
|