M.Mathis and J.Mahdavi, "Forward Acknowledgement: Refining TCP Congestion Control" SIGCOMM'96, August 1996. Submitted by: Noritoshi Demizu, Raja Mukerji
714 lines
22 KiB
C
714 lines
22 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. 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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* $FreeBSD$
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*/
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/*-
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* Copyright (c) 1982, 1986, 1988, 1990, 1993, 1994
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* The Regents of the University of California. 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
|
|
* 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
|
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* documentation and/or other materials provided with the distribution.
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* 3. 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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* @@(#)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 "opt_inet.h"
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#include "opt_inet6.h"
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#include "opt_ipsec.h"
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#include "opt_tcpdebug.h"
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#include "opt_tcp_input.h"
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#include "opt_tcp_sack.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 <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/ip_icmp.h> /* for ICMP_BANDLIM */
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#include <netinet/in_var.h>
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#include <netinet/icmp_var.h> /* for ICMP_BANDLIM */
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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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#ifdef FAST_IPSEC
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#include <netipsec/ipsec.h>
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#include <netipsec/ipsec6.h>
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#endif
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#ifdef IPSEC
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#include <netinet6/ipsec.h>
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#include <netinet6/ipsec6.h>
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#include <netkey/key.h>
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#endif /*IPSEC*/
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#include <machine/in_cksum.h>
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extern struct uma_zone *sack_hole_zone;
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SYSCTL_NODE(_net_inet_tcp, OID_AUTO, sack, CTLFLAG_RW, 0, "TCP SACK");
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int tcp_do_sack = 1;
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SYSCTL_INT(_net_inet_tcp_sack, OID_AUTO, enable, CTLFLAG_RW,
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&tcp_do_sack, 0, "Enable/Disable TCP SACK support");
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TUNABLE_INT("net.inet.tcp.sack.enable", &tcp_do_sack);
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static int tcp_sack_maxholes = 128;
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SYSCTL_INT(_net_inet_tcp_sack, OID_AUTO, maxholes, CTLFLAG_RW,
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&tcp_sack_maxholes, 0,
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"Maximum number of TCP SACK holes allowed per connection");
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static int tcp_sack_globalmaxholes = 65536;
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SYSCTL_INT(_net_inet_tcp_sack, OID_AUTO, globalmaxholes, CTLFLAG_RW,
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&tcp_sack_globalmaxholes, 0,
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"Global maximum number of TCP SACK holes");
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static int tcp_sack_globalholes = 0;
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SYSCTL_INT(_net_inet_tcp_sack, OID_AUTO, globalholes, CTLFLAG_RD,
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&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 header
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* 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_LOCK_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
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* save unchanged SACK blocks into saved_blks[].
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* num_saved will have the number of the 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.
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* This SACK 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.
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* Put 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(tp)
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struct tcpcb *tp;
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{
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int i;
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INP_LOCK_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 >= tcp_sack_maxholes ||
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tcp_sack_globalholes >= tcp_sack_globalmaxholes) {
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tcpstat.tcps_sack_sboverflow++;
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return NULL;
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}
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hole = (struct sackhole *)uma_zalloc(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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tcp_sack_globalholes++;
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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(sack_hole_zone, hole);
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tp->snd_numholes--;
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tcp_sack_globalholes--;
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KASSERT(tp->snd_numholes >= 0, ("tp->snd_numholes >= 0"));
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KASSERT(tcp_sack_globalholes >= 0, ("tcp_sack_globalholes >= 0"));
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}
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/*
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* Process the TCP SACK option. Returns 1 if tcp_dooptions() should continue,
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* and 0 otherwise, if the option was fine. tp->snd_holes is an ordered list
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* of holes (oldest to newest, in terms of the sequence space).
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*/
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int
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tcp_sack_option(struct tcpcb *tp, struct tcphdr *th, u_char *cp, int optlen)
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{
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int tmp_olen;
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u_char *tmp_cp;
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struct sackhole *cur, *temp;
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struct sackblk sack, sack_blocks[TCP_MAX_SACK];
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int i, j, next_sack_blk, num_sack_blks;
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INP_LOCK_ASSERT(tp->t_inpcb);
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if (!tp->sack_enable)
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return (1);
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if ((th->th_flags & TH_ACK) == 0)
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return (1);
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/* Note: TCPOLEN_SACK must be 2*sizeof(tcp_seq) */
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if (optlen <= 2 || (optlen - 2) % TCPOLEN_SACK != 0)
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return (1);
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/* If ack is outside [snd_una, snd_max], ignore the SACK options */
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if (SEQ_LT(th->th_ack, tp->snd_una) || SEQ_GT(th->th_ack, tp->snd_max))
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return (1);
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tmp_cp = cp + 2;
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tmp_olen = optlen - 2;
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tcpstat.tcps_sack_rcv_blocks++;
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/*
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* Sort the SACK blocks so we can update the scoreboard
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* with just one pass. The overhead of sorting upto 4 elements
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* is less than making 3 passes over the scoreboard.
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*/
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num_sack_blks = 0;
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while (tmp_olen > 0) {
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bcopy(tmp_cp, &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->th_ack) &&
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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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tmp_olen -= TCPOLEN_SACK;
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tmp_cp += TCPOLEN_SACK;
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}
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if (num_sack_blks == 0)
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return 0;
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/* Bubble sort */
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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].start,
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sack_blocks[j].start)){
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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 (in
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* the logic that adds holes to the tail of the scoreboard).
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*/
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tp->snd_fack = tp->snd_una;
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next_sack_blk = 0;
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cur = TAILQ_FIRST(&tp->snd_holes);
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/*
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* Since the incoming sack blocks are sorted, we can process them
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* making one sweep of the scoreboard.
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*/
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while ((next_sack_blk < num_sack_blks) && (cur != NULL)) {
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sack = sack_blocks[next_sack_blk];
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if (SEQ_LT(tp->snd_fack, sack.start))
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/*
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* The sack block acks data to the right of all the holes
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* in the scoreboard. No need to iterate over the
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* scoreboard anymore.
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*/
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break;
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if (SEQ_LEQ(sack.end, cur->start)) {
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/*
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* SACKs data before the current hole.
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* Ignore the sack block. Go to the next sack
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* block.
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*/
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next_sack_blk++;
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continue;
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}
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if (SEQ_GEQ(sack.start, cur->end)) {
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/*
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* SACKs data beyond the current hole.
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* Go to the next hole.
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*/
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cur = TAILQ_NEXT(cur, scblink);
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continue;
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}
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tp->sackhint.sack_bytes_rexmit -= (cur->rxmit - cur->start);
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KASSERT(tp->sackhint.sack_bytes_rexmit >= 0,
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("sackhint bytes rtx >= 0"));
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if (SEQ_LEQ(sack.start, cur->start)) {
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/* Data acks at least the beginning of hole */
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if (SEQ_GEQ(sack.end, cur->end)) {
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/* Acks entire hole, so delete hole */
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if (tp->sackhint.nexthole == cur)
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tp->sackhint.nexthole =
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TAILQ_NEXT(cur, scblink);
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temp = cur;
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cur = TAILQ_NEXT(cur, scblink);
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TAILQ_REMOVE(&tp->snd_holes, temp, scblink);
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tcp_sackhole_free(tp, temp);
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/*
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* The sack block may ack all or part of the next
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* hole too, so continue onto the next hole.
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*/
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continue;
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} else {
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/* Move start of hole forward */
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cur->start = sack.end;
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cur->rxmit = SEQ_MAX(cur->rxmit, cur->start);
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}
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} else {
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if (SEQ_GEQ(sack.end, cur->end)) {
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/* Move end of hole backward */
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cur->end = sack.start;
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cur->rxmit = SEQ_MIN(cur->rxmit, cur->end);
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} else {
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/*
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* ACKs some data in middle of a hole; need to
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* split current hole
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*/
|
|
temp = tcp_sackhole_alloc(tp, sack.end,
|
|
cur->end);
|
|
if (temp != NULL) {
|
|
if (SEQ_GT(cur->rxmit, temp->rxmit))
|
|
temp->rxmit = cur->rxmit;
|
|
TAILQ_INSERT_AFTER(&tp->snd_holes,
|
|
cur, temp, scblink);
|
|
cur->end = sack.start;
|
|
cur->rxmit = SEQ_MIN(cur->rxmit, cur->end);
|
|
tp->sackhint.sack_bytes_rexmit +=
|
|
(cur->rxmit - cur->start);
|
|
cur = temp;
|
|
}
|
|
}
|
|
}
|
|
tp->sackhint.sack_bytes_rexmit += (cur->rxmit - cur->start);
|
|
/*
|
|
* Testing sack.end against cur->end tells us whether we're done
|
|
* with the sack block or the sack hole. Accordingly, we advance
|
|
* one or the other.
|
|
*/
|
|
if (SEQ_GEQ(sack.end, cur->end))
|
|
cur = TAILQ_NEXT(cur, scblink);
|
|
else
|
|
next_sack_blk++;
|
|
}
|
|
/* Iterated all the holes in the scoreboard. Add new holes. */
|
|
for ( ; next_sack_blk < num_sack_blks ; next_sack_blk++) {
|
|
sack = sack_blocks[next_sack_blk];
|
|
/*
|
|
* The two SEQ_LT() checks here that test rcv_laststart against
|
|
* sack.start and sack.end seem redundant, but they're necessary
|
|
* to deal with overlapping sack blocks.
|
|
*/
|
|
if (SEQ_LT(tp->snd_fack, sack.start)) {
|
|
/* Need to append new hole at end. */
|
|
temp = tcp_sackhole_alloc(tp, tp->snd_fack,
|
|
sack.start);
|
|
if (temp == NULL)
|
|
continue; /* ENOBUFS */
|
|
TAILQ_INSERT_TAIL(&tp->snd_holes, temp, scblink);
|
|
tp->snd_fack = sack.end;
|
|
if (tp->sackhint.nexthole == NULL)
|
|
tp->sackhint.nexthole = temp;
|
|
}
|
|
if (SEQ_LT(tp->snd_fack, sack.end))
|
|
tp->snd_fack = sack.end;
|
|
}
|
|
return (0);
|
|
}
|
|
|
|
/*
|
|
* Delete stale (i.e, cumulatively ack'd) holes. Hole is deleted only if
|
|
* it is completely acked; otherwise, tcp_sack_option(), called from
|
|
* tcp_dooptions(), will fix up the hole.
|
|
*/
|
|
void
|
|
tcp_del_sackholes(tp, th)
|
|
struct tcpcb *tp;
|
|
struct tcphdr *th;
|
|
{
|
|
INP_LOCK_ASSERT(tp->t_inpcb);
|
|
if (tp->sack_enable && tp->t_state != TCPS_LISTEN) {
|
|
/* max because this could be an older ack just arrived */
|
|
tcp_seq lastack = SEQ_GT(th->th_ack, tp->snd_una) ?
|
|
th->th_ack : tp->snd_una;
|
|
struct sackhole *cur = TAILQ_FIRST(&tp->snd_holes);
|
|
struct sackhole *prev;
|
|
while (cur)
|
|
if (SEQ_LEQ(cur->end, lastack)) {
|
|
prev = cur;
|
|
tp->sackhint.sack_bytes_rexmit -=
|
|
(cur->rxmit - cur->start);
|
|
if (tp->sackhint.nexthole == cur)
|
|
tp->sackhint.nexthole =
|
|
TAILQ_NEXT(cur, scblink);
|
|
cur = TAILQ_NEXT(cur, scblink);
|
|
TAILQ_REMOVE(&tp->snd_holes, prev, scblink);
|
|
tcp_sackhole_free(tp, prev);
|
|
} else if (SEQ_LT(cur->start, lastack)) {
|
|
if (SEQ_LT(cur->rxmit, lastack)) {
|
|
tp->sackhint.sack_bytes_rexmit -=
|
|
(cur->rxmit - cur->start);
|
|
cur->rxmit = lastack;
|
|
} else
|
|
tp->sackhint.sack_bytes_rexmit -=
|
|
(lastack - cur->start);
|
|
cur->start = lastack;
|
|
break;
|
|
} else
|
|
break;
|
|
}
|
|
}
|
|
|
|
void
|
|
tcp_free_sackholes(struct tcpcb *tp)
|
|
{
|
|
struct sackhole *q;
|
|
|
|
INP_LOCK_ASSERT(tp->t_inpcb);
|
|
while ((q = TAILQ_FIRST(&tp->snd_holes)) != NULL) {
|
|
TAILQ_REMOVE(&tp->snd_holes, q, scblink);
|
|
tcp_sackhole_free(tp, q);
|
|
}
|
|
tp->sackhint.nexthole = NULL;
|
|
tp->sackhint.sack_bytes_rexmit = 0;
|
|
|
|
KASSERT(tp->snd_numholes == 0, ("tp->snd_numholes == 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;
|
|
|
|
INP_LOCK_ASSERT(tp->t_inpcb);
|
|
callout_stop(tp->tt_rexmt);
|
|
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;
|
|
|
|
INP_LOCK_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);
|
|
}
|
|
|
|
/*
|
|
* 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;
|
|
|
|
INP_LOCK_ASSERT(tp->t_inpcb);
|
|
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);
|
|
|
|
INP_LOCK_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;
|
|
return;
|
|
}
|