724 lines
21 KiB
C
724 lines
21 KiB
C
/* $NetBSD: tcp_congctl.c,v 1.16 2011/04/08 11:15:11 yamt Exp $ */
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/*-
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* Copyright (c) 1997, 1998, 1999, 2001, 2005, 2006 The NetBSD Foundation, Inc.
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* All rights reserved.
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*
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* This code is derived from software contributed to The NetBSD Foundation
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* by Jason R. Thorpe and Kevin M. Lahey of the Numerical Aerospace Simulation
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* Facility, NASA Ames Research Center.
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* This code is derived from software contributed to The NetBSD Foundation
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* by Charles M. Hannum.
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* This code is derived from software contributed to The NetBSD Foundation
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* by Rui Paulo.
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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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*
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* THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
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* ``AS 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 PARTICULAR
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* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
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* BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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* POSSIBILITY OF SUCH DAMAGE.
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*/
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/*
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* Copyright (C) 1995, 1996, 1997, and 1998 WIDE Project.
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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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* 3. Neither the name of the project 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 PROJECT 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 PROJECT 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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/*
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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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/*
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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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* 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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* @(#)tcp_input.c 8.12 (Berkeley) 5/24/95
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*/
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#include <sys/cdefs.h>
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__KERNEL_RCSID(0, "$NetBSD: tcp_congctl.c,v 1.16 2011/04/08 11:15:11 yamt Exp $");
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#include "opt_inet.h"
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#include "opt_tcp_debug.h"
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#include "opt_tcp_congctl.h"
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#include <sys/param.h>
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#include <sys/systm.h>
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#include <sys/malloc.h>
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#include <sys/mbuf.h>
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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/errno.h>
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#include <sys/syslog.h>
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#include <sys/pool.h>
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#include <sys/domain.h>
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#include <sys/kernel.h>
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#include <sys/mutex.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_pcb.h>
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#include <netinet/in_var.h>
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#include <netinet/ip_var.h>
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#ifdef INET6
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#ifndef INET
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#include <netinet/in.h>
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#endif
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#include <netinet/ip6.h>
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#include <netinet6/ip6_var.h>
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#include <netinet6/in6_pcb.h>
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#include <netinet6/ip6_var.h>
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#include <netinet6/in6_var.h>
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#include <netinet/icmp6.h>
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#include <netinet6/nd6.h>
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#endif
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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 <netinet/tcpip.h>
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#include <netinet/tcp_congctl.h>
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#ifdef TCP_DEBUG
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#include <netinet/tcp_debug.h>
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#endif
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/*
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* TODO:
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* consider separating the actual implementations in another file.
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*/
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static int tcp_reno_fast_retransmit(struct tcpcb *, const struct tcphdr *);
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static void tcp_reno_slow_retransmit(struct tcpcb *);
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static void tcp_reno_fast_retransmit_newack(struct tcpcb *,
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const struct tcphdr *);
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static void tcp_reno_newack(struct tcpcb *, const struct tcphdr *);
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static void tcp_reno_congestion_exp(struct tcpcb *tp);
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static int tcp_newreno_fast_retransmit(struct tcpcb *, const struct tcphdr *);
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static void tcp_newreno_fast_retransmit_newack(struct tcpcb *,
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const struct tcphdr *);
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static void tcp_newreno_newack(struct tcpcb *, const struct tcphdr *);
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static void tcp_congctl_fillnames(void);
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extern int tcprexmtthresh;
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MALLOC_DEFINE(M_TCPCONGCTL, "tcpcongctl", "TCP congestion control structures");
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/* currently selected global congestion control */
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char tcp_congctl_global_name[TCPCC_MAXLEN];
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/* available global congestion control algorithms */
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char tcp_congctl_avail[10 * TCPCC_MAXLEN];
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/*
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* Used to list the available congestion control algorithms.
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*/
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TAILQ_HEAD(, tcp_congctlent) tcp_congctlhd =
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TAILQ_HEAD_INITIALIZER(tcp_congctlhd);
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static struct tcp_congctlent * tcp_congctl_global;
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static kmutex_t tcp_congctl_mtx;
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void
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tcp_congctl_init(void)
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{
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int r;
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mutex_init(&tcp_congctl_mtx, MUTEX_DEFAULT, IPL_NONE);
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/* Base algorithms. */
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r = tcp_congctl_register("reno", &tcp_reno_ctl);
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KASSERT(r == 0);
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r = tcp_congctl_register("newreno", &tcp_newreno_ctl);
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KASSERT(r == 0);
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/* NewReno is the default. */
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#ifndef TCP_CONGCTL_DEFAULT
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#define TCP_CONGCTL_DEFAULT "newreno"
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#endif
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r = tcp_congctl_select(NULL, TCP_CONGCTL_DEFAULT);
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KASSERT(r == 0);
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}
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/*
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* Register a congestion algorithm and select it if we have none.
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*/
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int
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tcp_congctl_register(const char *name, const struct tcp_congctl *tcc)
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{
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struct tcp_congctlent *ntcc, *tccp;
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TAILQ_FOREACH(tccp, &tcp_congctlhd, congctl_ent)
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if (!strcmp(name, tccp->congctl_name)) {
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/* name already registered */
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return EEXIST;
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}
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ntcc = malloc(sizeof(*ntcc), M_TCPCONGCTL, M_WAITOK|M_ZERO);
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strlcpy(ntcc->congctl_name, name, sizeof(ntcc->congctl_name) - 1);
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ntcc->congctl_ctl = tcc;
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TAILQ_INSERT_TAIL(&tcp_congctlhd, ntcc, congctl_ent);
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tcp_congctl_fillnames();
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if (TAILQ_FIRST(&tcp_congctlhd) == ntcc)
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tcp_congctl_select(NULL, name);
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return 0;
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}
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int
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tcp_congctl_unregister(const char *name)
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{
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struct tcp_congctlent *tccp, *rtccp;
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unsigned int size;
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rtccp = NULL;
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size = 0;
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TAILQ_FOREACH(tccp, &tcp_congctlhd, congctl_ent) {
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if (!strcmp(name, tccp->congctl_name))
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rtccp = tccp;
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size++;
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}
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if (!rtccp)
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return ENOENT;
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if (size <= 1 || tcp_congctl_global == rtccp || rtccp->congctl_refcnt)
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return EBUSY;
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TAILQ_REMOVE(&tcp_congctlhd, rtccp, congctl_ent);
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free(rtccp, M_TCPCONGCTL);
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tcp_congctl_fillnames();
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return 0;
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}
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/*
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* Select a congestion algorithm by name.
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*/
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int
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tcp_congctl_select(struct tcpcb *tp, const char *name)
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{
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struct tcp_congctlent *tccp, *old_tccp, *new_tccp;
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bool old_found, new_found;
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KASSERT(name);
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old_found = (tp == NULL || tp->t_congctl == NULL);
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old_tccp = NULL;
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new_found = false;
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new_tccp = NULL;
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TAILQ_FOREACH(tccp, &tcp_congctlhd, congctl_ent) {
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if (!old_found && tccp->congctl_ctl == tp->t_congctl) {
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old_tccp = tccp;
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old_found = true;
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}
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if (!new_found && !strcmp(name, tccp->congctl_name)) {
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new_tccp = tccp;
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new_found = true;
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}
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if (new_found && old_found) {
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if (tp) {
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mutex_enter(&tcp_congctl_mtx);
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if (old_tccp)
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old_tccp->congctl_refcnt--;
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tp->t_congctl = new_tccp->congctl_ctl;
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new_tccp->congctl_refcnt++;
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mutex_exit(&tcp_congctl_mtx);
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} else {
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tcp_congctl_global = new_tccp;
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strlcpy(tcp_congctl_global_name,
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new_tccp->congctl_name,
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sizeof(tcp_congctl_global_name) - 1);
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}
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return 0;
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}
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}
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return EINVAL;
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}
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void
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tcp_congctl_release(struct tcpcb *tp)
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{
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struct tcp_congctlent *tccp;
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KASSERT(tp->t_congctl);
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TAILQ_FOREACH(tccp, &tcp_congctlhd, congctl_ent) {
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if (tccp->congctl_ctl == tp->t_congctl) {
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tccp->congctl_refcnt--;
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return;
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}
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}
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}
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/*
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* Returns the name of a congestion algorithm.
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*/
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const char *
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tcp_congctl_bystruct(const struct tcp_congctl *tcc)
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{
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struct tcp_congctlent *tccp;
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KASSERT(tcc);
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TAILQ_FOREACH(tccp, &tcp_congctlhd, congctl_ent)
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if (tccp->congctl_ctl == tcc)
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return tccp->congctl_name;
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return NULL;
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}
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static void
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tcp_congctl_fillnames(void)
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{
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struct tcp_congctlent *tccp;
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const char *delim = " ";
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tcp_congctl_avail[0] = '\0';
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TAILQ_FOREACH(tccp, &tcp_congctlhd, congctl_ent) {
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strlcat(tcp_congctl_avail, tccp->congctl_name,
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sizeof(tcp_congctl_avail) - 1);
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if (TAILQ_NEXT(tccp, congctl_ent))
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strlcat(tcp_congctl_avail, delim,
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sizeof(tcp_congctl_avail) - 1);
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}
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}
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/* ------------------------------------------------------------------------ */
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/*
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* TCP/Reno congestion control.
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*/
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static void
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tcp_reno_congestion_exp(struct tcpcb *tp)
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{
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u_int win;
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/*
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* Halve the congestion window and reduce the
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* slow start threshold.
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*/
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win = min(tp->snd_wnd, tp->snd_cwnd) / 2 / tp->t_segsz;
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if (win < 2)
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win = 2;
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tp->snd_ssthresh = win * tp->t_segsz;
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tp->snd_recover = tp->snd_max;
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tp->snd_cwnd = tp->snd_ssthresh;
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/*
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* When using TCP ECN, notify the peer that
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* we reduced the cwnd.
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*/
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if (TCP_ECN_ALLOWED(tp))
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tp->t_flags |= TF_ECN_SND_CWR;
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}
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static int
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tcp_reno_fast_retransmit(struct tcpcb *tp, const struct tcphdr *th)
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{
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/*
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* We know we're losing at the current
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* window size so do congestion avoidance
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* (set ssthresh to half the current window
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* and pull our congestion window back to
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* the new ssthresh).
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*
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* Dup acks mean that packets have left the
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* network (they're now cached at the receiver)
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* so bump cwnd by the amount in the receiver
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* to keep a constant cwnd packets in the
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* network.
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*
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* If we are using TCP/SACK, then enter
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* Fast Recovery if the receiver SACKs
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* data that is tcprexmtthresh * MSS
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* bytes past the last ACKed segment,
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* irrespective of the number of DupAcks.
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*/
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tcp_seq onxt;
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onxt = tp->snd_nxt;
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tcp_reno_congestion_exp(tp);
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tp->t_partialacks = 0;
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TCP_TIMER_DISARM(tp, TCPT_REXMT);
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tp->t_rtttime = 0;
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if (TCP_SACK_ENABLED(tp)) {
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tp->t_dupacks = tcprexmtthresh;
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tp->sack_newdata = tp->snd_nxt;
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tp->snd_cwnd = tp->t_segsz;
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(void) tcp_output(tp);
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return 0;
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}
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tp->snd_nxt = th->th_ack;
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tp->snd_cwnd = tp->t_segsz;
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(void) tcp_output(tp);
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tp->snd_cwnd = tp->snd_ssthresh + tp->t_segsz * tp->t_dupacks;
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if (SEQ_GT(onxt, tp->snd_nxt))
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tp->snd_nxt = onxt;
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return 0;
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}
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static void
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tcp_reno_slow_retransmit(struct tcpcb *tp)
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{
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u_int win;
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/*
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* Close the congestion window down to one segment
|
|
* (we'll open it by one segment for each ack we get).
|
|
* Since we probably have a window's worth of unacked
|
|
* data accumulated, this "slow start" keeps us from
|
|
* dumping all that data as back-to-back packets (which
|
|
* might overwhelm an intermediate gateway).
|
|
*
|
|
* There are two phases to the opening: Initially we
|
|
* open by one mss on each ack. This makes the window
|
|
* size increase exponentially with time. If the
|
|
* window is larger than the path can handle, this
|
|
* exponential growth results in dropped packet(s)
|
|
* almost immediately. To get more time between
|
|
* drops but still "push" the network to take advantage
|
|
* of improving conditions, we switch from exponential
|
|
* to linear window opening at some threshhold size.
|
|
* For a threshhold, we use half the current window
|
|
* size, truncated to a multiple of the mss.
|
|
*
|
|
* (the minimum cwnd that will give us exponential
|
|
* growth is 2 mss. We don't allow the threshhold
|
|
* to go below this.)
|
|
*/
|
|
|
|
win = min(tp->snd_wnd, tp->snd_cwnd) / 2 / tp->t_segsz;
|
|
if (win < 2)
|
|
win = 2;
|
|
/* Loss Window MUST be one segment. */
|
|
tp->snd_cwnd = tp->t_segsz;
|
|
tp->snd_ssthresh = win * tp->t_segsz;
|
|
tp->t_partialacks = -1;
|
|
tp->t_dupacks = 0;
|
|
tp->t_bytes_acked = 0;
|
|
}
|
|
|
|
static void
|
|
tcp_reno_fast_retransmit_newack(struct tcpcb *tp,
|
|
const struct tcphdr *th)
|
|
{
|
|
if (tp->t_partialacks < 0) {
|
|
/*
|
|
* We were not in fast recovery. Reset the duplicate ack
|
|
* counter.
|
|
*/
|
|
tp->t_dupacks = 0;
|
|
} else {
|
|
/*
|
|
* Clamp the congestion window to the crossover point and
|
|
* exit fast recovery.
|
|
*/
|
|
if (tp->snd_cwnd > tp->snd_ssthresh)
|
|
tp->snd_cwnd = tp->snd_ssthresh;
|
|
tp->t_partialacks = -1;
|
|
tp->t_dupacks = 0;
|
|
tp->t_bytes_acked = 0;
|
|
}
|
|
}
|
|
|
|
static void
|
|
tcp_reno_newack(struct tcpcb *tp, const struct tcphdr *th)
|
|
{
|
|
/*
|
|
* When new data is acked, open the congestion window.
|
|
*/
|
|
|
|
u_int cw = tp->snd_cwnd;
|
|
u_int incr = tp->t_segsz;
|
|
|
|
if (tcp_do_abc) {
|
|
|
|
/*
|
|
* RFC 3465 Appropriate Byte Counting (ABC)
|
|
*/
|
|
|
|
int acked = th->th_ack - tp->snd_una;
|
|
|
|
if (cw >= tp->snd_ssthresh) {
|
|
tp->t_bytes_acked += acked;
|
|
if (tp->t_bytes_acked >= cw) {
|
|
/* Time to increase the window. */
|
|
tp->t_bytes_acked -= cw;
|
|
} else {
|
|
/* No need to increase yet. */
|
|
incr = 0;
|
|
}
|
|
} else {
|
|
/*
|
|
* use 2*SMSS or 1*SMSS for the "L" param,
|
|
* depending on sysctl setting.
|
|
*
|
|
* (See RFC 3465 2.3 Choosing the Limit)
|
|
*/
|
|
u_int abc_lim;
|
|
|
|
abc_lim = (tcp_abc_aggressive == 0 ||
|
|
tp->snd_nxt != tp->snd_max) ? incr : incr * 2;
|
|
incr = min(acked, abc_lim);
|
|
}
|
|
} else {
|
|
|
|
/*
|
|
* If the window gives us less than ssthresh packets
|
|
* in flight, open exponentially (segsz per packet).
|
|
* Otherwise open linearly: segsz per window
|
|
* (segsz^2 / cwnd per packet).
|
|
*/
|
|
|
|
if (cw >= tp->snd_ssthresh) {
|
|
incr = incr * incr / cw;
|
|
}
|
|
}
|
|
|
|
tp->snd_cwnd = min(cw + incr, TCP_MAXWIN << tp->snd_scale);
|
|
}
|
|
|
|
const struct tcp_congctl tcp_reno_ctl = {
|
|
.fast_retransmit = tcp_reno_fast_retransmit,
|
|
.slow_retransmit = tcp_reno_slow_retransmit,
|
|
.fast_retransmit_newack = tcp_reno_fast_retransmit_newack,
|
|
.newack = tcp_reno_newack,
|
|
.cong_exp = tcp_reno_congestion_exp,
|
|
};
|
|
|
|
/*
|
|
* TCP/NewReno Congestion control.
|
|
*/
|
|
static int
|
|
tcp_newreno_fast_retransmit(struct tcpcb *tp, const struct tcphdr *th)
|
|
{
|
|
|
|
if (SEQ_LT(th->th_ack, tp->snd_high)) {
|
|
/*
|
|
* False fast retransmit after timeout.
|
|
* Do not enter fast recovery
|
|
*/
|
|
tp->t_dupacks = 0;
|
|
return 1;
|
|
}
|
|
/*
|
|
* Fast retransmit is same as reno.
|
|
*/
|
|
return tcp_reno_fast_retransmit(tp, th);
|
|
}
|
|
|
|
/*
|
|
* Implement the NewReno response to a new ack, checking for partial acks in
|
|
* fast recovery.
|
|
*/
|
|
static void
|
|
tcp_newreno_fast_retransmit_newack(struct tcpcb *tp, const struct tcphdr *th)
|
|
{
|
|
if (tp->t_partialacks < 0) {
|
|
/*
|
|
* We were not in fast recovery. Reset the duplicate ack
|
|
* counter.
|
|
*/
|
|
tp->t_dupacks = 0;
|
|
} else if (SEQ_LT(th->th_ack, tp->snd_recover)) {
|
|
/*
|
|
* This is a partial ack. Retransmit the first unacknowledged
|
|
* segment and deflate the congestion window by the amount of
|
|
* acknowledged data. Do not exit fast recovery.
|
|
*/
|
|
tcp_seq onxt = tp->snd_nxt;
|
|
u_long ocwnd = tp->snd_cwnd;
|
|
|
|
/*
|
|
* snd_una has not yet been updated and the socket's send
|
|
* buffer has not yet drained off the ACK'd data, so we
|
|
* have to leave snd_una as it was to get the correct data
|
|
* offset in tcp_output().
|
|
*/
|
|
if (++tp->t_partialacks == 1)
|
|
TCP_TIMER_DISARM(tp, TCPT_REXMT);
|
|
tp->t_rtttime = 0;
|
|
tp->snd_nxt = th->th_ack;
|
|
/*
|
|
* Set snd_cwnd to one segment beyond ACK'd offset. snd_una
|
|
* is not yet updated when we're called.
|
|
*/
|
|
tp->snd_cwnd = tp->t_segsz + (th->th_ack - tp->snd_una);
|
|
(void) tcp_output(tp);
|
|
tp->snd_cwnd = ocwnd;
|
|
if (SEQ_GT(onxt, tp->snd_nxt))
|
|
tp->snd_nxt = onxt;
|
|
/*
|
|
* Partial window deflation. Relies on fact that tp->snd_una
|
|
* not updated yet.
|
|
*/
|
|
tp->snd_cwnd -= (th->th_ack - tp->snd_una - tp->t_segsz);
|
|
} else {
|
|
/*
|
|
* Complete ack. Inflate the congestion window to ssthresh
|
|
* and exit fast recovery.
|
|
*
|
|
* Window inflation should have left us with approx.
|
|
* snd_ssthresh outstanding data. But in case we
|
|
* would be inclined to send a burst, better to do
|
|
* it via the slow start mechanism.
|
|
*/
|
|
if (SEQ_SUB(tp->snd_max, th->th_ack) < tp->snd_ssthresh)
|
|
tp->snd_cwnd = SEQ_SUB(tp->snd_max, th->th_ack)
|
|
+ tp->t_segsz;
|
|
else
|
|
tp->snd_cwnd = tp->snd_ssthresh;
|
|
tp->t_partialacks = -1;
|
|
tp->t_dupacks = 0;
|
|
tp->t_bytes_acked = 0;
|
|
}
|
|
}
|
|
|
|
static void
|
|
tcp_newreno_newack(struct tcpcb *tp, const struct tcphdr *th)
|
|
{
|
|
/*
|
|
* If we are still in fast recovery (meaning we are using
|
|
* NewReno and we have only received partial acks), do not
|
|
* inflate the window yet.
|
|
*/
|
|
if (tp->t_partialacks < 0)
|
|
tcp_reno_newack(tp, th);
|
|
}
|
|
|
|
|
|
const struct tcp_congctl tcp_newreno_ctl = {
|
|
.fast_retransmit = tcp_newreno_fast_retransmit,
|
|
.slow_retransmit = tcp_reno_slow_retransmit,
|
|
.fast_retransmit_newack = tcp_newreno_fast_retransmit_newack,
|
|
.newack = tcp_newreno_newack,
|
|
.cong_exp = tcp_reno_congestion_exp,
|
|
};
|
|
|
|
|