1231 lines
34 KiB
C
1231 lines
34 KiB
C
/* $NetBSD: tcp_output.c,v 1.91 2003/05/17 17:16:20 itojun Exp $ */
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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) 1997, 1998, 2001 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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*
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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. All advertising materials mentioning features or use of this software
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* must display the following acknowledgement:
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* This product includes software developed by the NetBSD
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* Foundation, Inc. and its contributors.
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* 4. Neither the name of The NetBSD Foundation nor the names of its
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* contributors may be used to endorse or promote products derived
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* from this software without specific prior written permission.
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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) 1982, 1986, 1988, 1990, 1993, 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. All advertising materials mentioning features or use of this software
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* must display the following acknowledgement:
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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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* 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_output.c 8.4 (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_output.c,v 1.91 2003/05/17 17:16:20 itojun Exp $");
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#include "opt_inet.h"
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#include "opt_ipsec.h"
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#include "opt_tcp_debug.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/domain.h>
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#include <sys/kernel.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/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/in6_var.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/nd6.h>
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#endif
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#ifdef IPSEC
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#include <netinet6/ipsec.h>
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#endif
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#include <netinet/tcp.h>
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#define TCPOUTFLAGS
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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_debug.h>
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#ifdef notyet
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extern struct mbuf *m_copypack();
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#endif
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#define MAX_TCPOPTLEN 32 /* max # bytes that go in options */
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/*
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* Knob to enable Congestion Window Monitoring, and control the
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* the burst size it allows. Default burst is 4 packets, per
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* the Internet draft.
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*/
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int tcp_cwm = 0;
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int tcp_cwm_burstsize = 4;
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#ifdef TCP_OUTPUT_COUNTERS
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#include <sys/device.h>
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extern struct evcnt tcp_output_bigheader;
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extern struct evcnt tcp_output_copysmall;
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extern struct evcnt tcp_output_copybig;
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extern struct evcnt tcp_output_refbig;
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#define TCP_OUTPUT_COUNTER_INCR(ev) (ev)->ev_count++
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#else
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#define TCP_OUTPUT_COUNTER_INCR(ev) /* nothing */
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#endif /* TCP_OUTPUT_COUNTERS */
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static
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#ifndef GPROF
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__inline
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#endif
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void
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tcp_segsize(struct tcpcb *tp, int *txsegsizep, int *rxsegsizep)
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{
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#ifdef INET
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struct inpcb *inp = tp->t_inpcb;
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#endif
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#ifdef INET6
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struct in6pcb *in6p = tp->t_in6pcb;
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#endif
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struct socket *so = NULL;
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struct rtentry *rt;
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struct ifnet *ifp;
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int size;
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int iphlen;
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int optlen;
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#ifdef DIAGNOSTIC
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if (tp->t_inpcb && tp->t_in6pcb)
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panic("tcp_segsize: both t_inpcb and t_in6pcb are set");
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#endif
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switch (tp->t_family) {
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#ifdef INET
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case AF_INET:
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iphlen = sizeof(struct ip);
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break;
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#endif
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#ifdef INET6
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case AF_INET6:
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iphlen = sizeof(struct ip6_hdr);
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break;
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#endif
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default:
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size = tcp_mssdflt;
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goto out;
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}
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rt = NULL;
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#ifdef INET
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if (inp) {
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rt = in_pcbrtentry(inp);
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so = inp->inp_socket;
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}
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#endif
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#ifdef INET6
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if (in6p) {
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rt = in6_pcbrtentry(in6p);
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so = in6p->in6p_socket;
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}
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#endif
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if (rt == NULL) {
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size = tcp_mssdflt;
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goto out;
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}
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ifp = rt->rt_ifp;
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size = tcp_mssdflt;
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if (tp->t_mtudisc && rt->rt_rmx.rmx_mtu != 0)
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size = rt->rt_rmx.rmx_mtu - iphlen - sizeof(struct tcphdr);
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else if (ifp->if_flags & IFF_LOOPBACK)
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size = ifp->if_mtu - iphlen - sizeof(struct tcphdr);
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#ifdef INET
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else if (inp && tp->t_mtudisc)
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size = ifp->if_mtu - iphlen - sizeof(struct tcphdr);
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else if (inp && in_localaddr(inp->inp_faddr))
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size = ifp->if_mtu - iphlen - sizeof(struct tcphdr);
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#endif
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#ifdef INET6
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else if (in6p) {
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#ifdef INET
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if (IN6_IS_ADDR_V4MAPPED(&in6p->in6p_faddr)) {
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/* mapped addr case */
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struct in_addr d;
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bcopy(&in6p->in6p_faddr.s6_addr32[3], &d, sizeof(d));
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if (tp->t_mtudisc || in_localaddr(d))
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size = ifp->if_mtu - iphlen - sizeof(struct tcphdr);
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} else
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#endif
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{
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/*
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* for IPv6, path MTU discovery is always turned on,
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* or the node must use packet size <= 1280.
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*/
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size = tp->t_mtudisc ? IN6_LINKMTU(ifp) : IPV6_MMTU;
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size -= (iphlen + sizeof(struct tcphdr));
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}
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}
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#endif
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out:
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/*
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* Now we must make room for whatever extra TCP/IP options are in
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* the packet.
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*/
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optlen = tcp_optlen(tp);
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/*
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* XXX tp->t_ourmss should have the right size, but without this code
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* fragmentation will occur... need more investigation
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*/
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#ifdef INET
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if (inp) {
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#ifdef IPSEC
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optlen += ipsec4_hdrsiz_tcp(tp);
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#endif
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optlen += ip_optlen(inp);
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}
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#endif
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#ifdef INET6
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#ifdef INET
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if (in6p && tp->t_family == AF_INET) {
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#ifdef IPSEC
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optlen += ipsec4_hdrsiz_tcp(tp);
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#endif
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/* XXX size -= ip_optlen(in6p); */
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} else
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#endif
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if (in6p && tp->t_family == AF_INET6) {
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#ifdef IPSEC
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optlen += ipsec6_hdrsiz_tcp(tp);
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#endif
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optlen += ip6_optlen(in6p);
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}
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#endif
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size -= optlen;
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/*
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* *rxsegsizep holds *estimated* inbound segment size (estimation
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* assumes that path MTU is the same for both ways). this is only
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* for silly window avoidance, do not use the value for other purposes.
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*
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* ipseclen is subtracted from both sides, this may not be right.
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* I'm not quite sure about this (could someone comment).
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*/
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*txsegsizep = min(tp->t_peermss - optlen, size);
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/*
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* Never send more than half a buffer full. This insures that we can
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* always keep 2 packets on the wire, no matter what SO_SNDBUF is, and
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* therefore acks will never be delayed unless we run out of data to
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* transmit.
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*/
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if (so)
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*txsegsizep = min(so->so_snd.sb_hiwat >> 1, *txsegsizep);
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*rxsegsizep = min(tp->t_ourmss - optlen, size);
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if (*txsegsizep != tp->t_segsz) {
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/*
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* If the new segment size is larger, we don't want to
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* mess up the congestion window, but if it is smaller
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* we'll have to reduce the congestion window to ensure
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* that we don't get into trouble with initial windows
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* and the rest. In any case, if the segment size
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* has changed, chances are the path has, too, and
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* our congestion window will be different.
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*/
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if (*txsegsizep < tp->t_segsz) {
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tp->snd_cwnd = max((tp->snd_cwnd / tp->t_segsz)
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* *txsegsizep, *txsegsizep);
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tp->snd_ssthresh = max((tp->snd_ssthresh / tp->t_segsz)
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* *txsegsizep, *txsegsizep);
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}
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tp->t_segsz = *txsegsizep;
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}
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}
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static
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#ifndef GPROF
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__inline
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#endif
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int
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tcp_build_datapkt(struct tcpcb *tp, struct socket *so, int off,
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long len, int hdrlen, struct mbuf **mp)
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{
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struct mbuf *m;
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if (tp->t_force && len == 1)
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tcpstat.tcps_sndprobe++;
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else if (SEQ_LT(tp->snd_nxt, tp->snd_max)) {
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tcpstat.tcps_sndrexmitpack++;
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tcpstat.tcps_sndrexmitbyte += len;
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} else {
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tcpstat.tcps_sndpack++;
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tcpstat.tcps_sndbyte += len;
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}
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#ifdef notyet
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if ((m = m_copypack(so->so_snd.sb_mb, off,
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(int)len, max_linkhdr + hdrlen)) == 0)
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return (ENOBUFS);
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/*
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* m_copypack left space for our hdr; use it.
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*/
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m->m_len += hdrlen;
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m->m_data -= hdrlen;
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#else
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MGETHDR(m, M_DONTWAIT, MT_HEADER);
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if (__predict_false(m == NULL))
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return (ENOBUFS);
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MCLAIM(m, &tcp_tx_mowner);
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|
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/*
|
|
* XXX Because other code assumes headers will fit in
|
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* XXX one header mbuf.
|
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*
|
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* (This code should almost *never* be run.)
|
|
*/
|
|
if (__predict_false((max_linkhdr + hdrlen) > MHLEN)) {
|
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TCP_OUTPUT_COUNTER_INCR(&tcp_output_bigheader);
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MCLGET(m, M_DONTWAIT);
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|
if ((m->m_flags & M_EXT) == 0) {
|
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m_freem(m);
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return (ENOBUFS);
|
|
}
|
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}
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|
|
|
m->m_data += max_linkhdr;
|
|
m->m_len = hdrlen;
|
|
if (len <= M_TRAILINGSPACE(m)) {
|
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m_copydata(so->so_snd.sb_mb, off, (int) len,
|
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mtod(m, caddr_t) + hdrlen);
|
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m->m_len += len;
|
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TCP_OUTPUT_COUNTER_INCR(&tcp_output_copysmall);
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} else {
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m->m_next = m_copy(so->so_snd.sb_mb, off, (int) len);
|
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if (m->m_next == NULL) {
|
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m_freem(m);
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return (ENOBUFS);
|
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}
|
|
#ifdef TCP_OUTPUT_COUNTERS
|
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if (m->m_next->m_flags & M_EXT)
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TCP_OUTPUT_COUNTER_INCR(&tcp_output_refbig);
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else
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TCP_OUTPUT_COUNTER_INCR(&tcp_output_copybig);
|
|
#endif /* TCP_OUTPUT_COUNTERS */
|
|
}
|
|
#endif
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|
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*mp = m;
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return (0);
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}
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|
|
/*
|
|
* Tcp output routine: figure out what should be sent and send it.
|
|
*/
|
|
int
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|
tcp_output(tp)
|
|
struct tcpcb *tp;
|
|
{
|
|
struct socket *so;
|
|
struct route *ro;
|
|
long len, win;
|
|
int off, flags, error;
|
|
struct mbuf *m;
|
|
struct ip *ip;
|
|
#ifdef INET6
|
|
struct ip6_hdr *ip6;
|
|
#endif
|
|
struct tcphdr *th;
|
|
u_char opt[MAX_TCPOPTLEN];
|
|
unsigned optlen, hdrlen;
|
|
int idle, sendalot, txsegsize, rxsegsize;
|
|
int maxburst = TCP_MAXBURST;
|
|
int af; /* address family on the wire */
|
|
int iphdrlen;
|
|
|
|
#ifdef DIAGNOSTIC
|
|
if (tp->t_inpcb && tp->t_in6pcb)
|
|
panic("tcp_output: both t_inpcb and t_in6pcb are set");
|
|
#endif
|
|
so = NULL;
|
|
ro = NULL;
|
|
if (tp->t_inpcb) {
|
|
so = tp->t_inpcb->inp_socket;
|
|
ro = &tp->t_inpcb->inp_route;
|
|
}
|
|
#ifdef INET6
|
|
else if (tp->t_in6pcb) {
|
|
so = tp->t_in6pcb->in6p_socket;
|
|
ro = (struct route *)&tp->t_in6pcb->in6p_route;
|
|
}
|
|
#endif
|
|
|
|
switch (af = tp->t_family) {
|
|
#ifdef INET
|
|
case AF_INET:
|
|
if (tp->t_inpcb)
|
|
break;
|
|
#ifdef INET6
|
|
/* mapped addr case */
|
|
if (tp->t_in6pcb)
|
|
break;
|
|
#endif
|
|
return EINVAL;
|
|
#endif
|
|
#ifdef INET6
|
|
case AF_INET6:
|
|
if (tp->t_in6pcb)
|
|
break;
|
|
return EINVAL;
|
|
#endif
|
|
default:
|
|
return EAFNOSUPPORT;
|
|
}
|
|
|
|
tcp_segsize(tp, &txsegsize, &rxsegsize);
|
|
|
|
idle = (tp->snd_max == tp->snd_una);
|
|
|
|
/*
|
|
* Restart Window computation. From draft-floyd-incr-init-win-03:
|
|
*
|
|
* Optionally, a TCP MAY set the restart window to the
|
|
* minimum of the value used for the initial window and
|
|
* the current value of cwnd (in other words, using a
|
|
* larger value for the restart window should never increase
|
|
* the size of cwnd).
|
|
*/
|
|
if (tcp_cwm) {
|
|
/*
|
|
* Hughes/Touch/Heidemann Congestion Window Monitoring.
|
|
* Count the number of packets currently pending
|
|
* acknowledgement, and limit our congestion window
|
|
* to a pre-determined allowed burst size plus that count.
|
|
* This prevents bursting once all pending packets have
|
|
* been acknowledged (i.e. transmission is idle).
|
|
*
|
|
* XXX Link this to Initial Window?
|
|
*/
|
|
tp->snd_cwnd = min(tp->snd_cwnd,
|
|
(tcp_cwm_burstsize * txsegsize) +
|
|
(tp->snd_nxt - tp->snd_una));
|
|
} else {
|
|
if (idle && (tcp_now - tp->t_rcvtime) >= tp->t_rxtcur) {
|
|
/*
|
|
* We have been idle for "a while" and no acks are
|
|
* expected to clock out any data we send --
|
|
* slow start to get ack "clock" running again.
|
|
*/
|
|
int ss = tcp_init_win;
|
|
#ifdef INET
|
|
if (tp->t_inpcb &&
|
|
in_localaddr(tp->t_inpcb->inp_faddr))
|
|
ss = tcp_init_win_local;
|
|
#endif
|
|
#ifdef INET6
|
|
if (tp->t_in6pcb &&
|
|
in6_localaddr(&tp->t_in6pcb->in6p_faddr))
|
|
ss = tcp_init_win_local;
|
|
#endif
|
|
tp->snd_cwnd = min(tp->snd_cwnd,
|
|
TCP_INITIAL_WINDOW(ss, txsegsize));
|
|
}
|
|
}
|
|
|
|
again:
|
|
/*
|
|
* Determine length of data that should be transmitted, and
|
|
* flags that should be used. If there is some data or critical
|
|
* controls (SYN, RST) to send, then transmit; otherwise,
|
|
* investigate further.
|
|
*/
|
|
sendalot = 0;
|
|
off = tp->snd_nxt - tp->snd_una;
|
|
win = min(tp->snd_wnd, tp->snd_cwnd);
|
|
|
|
flags = tcp_outflags[tp->t_state];
|
|
/*
|
|
* If in persist timeout with window of 0, send 1 byte.
|
|
* Otherwise, if window is small but nonzero
|
|
* and timer expired, we will send what we can
|
|
* and go to transmit state.
|
|
*/
|
|
if (tp->t_force) {
|
|
if (win == 0) {
|
|
/*
|
|
* If we still have some data to send, then
|
|
* clear the FIN bit. Usually this would
|
|
* happen below when it realizes that we
|
|
* aren't sending all the data. However,
|
|
* if we have exactly 1 byte of unset data,
|
|
* then it won't clear the FIN bit below,
|
|
* and if we are in persist state, we wind
|
|
* up sending the packet without recording
|
|
* that we sent the FIN bit.
|
|
*
|
|
* We can't just blindly clear the FIN bit,
|
|
* because if we don't have any more data
|
|
* to send then the probe will be the FIN
|
|
* itself.
|
|
*/
|
|
if (off < so->so_snd.sb_cc)
|
|
flags &= ~TH_FIN;
|
|
win = 1;
|
|
} else {
|
|
TCP_TIMER_DISARM(tp, TCPT_PERSIST);
|
|
tp->t_rxtshift = 0;
|
|
}
|
|
}
|
|
|
|
if (win < so->so_snd.sb_cc) {
|
|
len = win - off;
|
|
flags &= ~TH_FIN;
|
|
} else
|
|
len = so->so_snd.sb_cc - off;
|
|
|
|
if (len < 0) {
|
|
/*
|
|
* If FIN has been sent but not acked,
|
|
* but we haven't been called to retransmit,
|
|
* len will be -1. Otherwise, window shrank
|
|
* after we sent into it. If window shrank to 0,
|
|
* cancel pending retransmit, pull snd_nxt back
|
|
* to (closed) window, and set the persist timer
|
|
* if it isn't already going. If the window didn't
|
|
* close completely, just wait for an ACK.
|
|
*
|
|
* If we have a pending FIN, either it has already been
|
|
* transmitted or it is outside the window, so drop it.
|
|
* If the FIN has been transmitted, but this is not a
|
|
* retransmission, then len must be -1. Therefore we also
|
|
* prevent here the sending of `gratuitous FINs'. This
|
|
* eliminates the need to check for that case below (e.g.
|
|
* to back up snd_nxt before the FIN so that the sequence
|
|
* number is correct).
|
|
*/
|
|
len = 0;
|
|
flags &= ~TH_FIN;
|
|
if (win == 0) {
|
|
TCP_TIMER_DISARM(tp, TCPT_REXMT);
|
|
tp->t_rxtshift = 0;
|
|
tp->snd_nxt = tp->snd_una;
|
|
if (TCP_TIMER_ISARMED(tp, TCPT_PERSIST) == 0)
|
|
tcp_setpersist(tp);
|
|
}
|
|
}
|
|
if (len > txsegsize) {
|
|
len = txsegsize;
|
|
flags &= ~TH_FIN;
|
|
sendalot = 1;
|
|
}
|
|
|
|
win = sbspace(&so->so_rcv);
|
|
|
|
/*
|
|
* Sender silly window avoidance. If connection is idle
|
|
* and can send all data, a maximum segment,
|
|
* at least a maximum default-size segment do it,
|
|
* or are forced, do it; otherwise don't bother.
|
|
* If peer's buffer is tiny, then send
|
|
* when window is at least half open.
|
|
* If retransmitting (possibly after persist timer forced us
|
|
* to send into a small window), then must resend.
|
|
*/
|
|
if (len) {
|
|
if (len == txsegsize)
|
|
goto send;
|
|
if ((so->so_state & SS_MORETOCOME) == 0 &&
|
|
((idle || tp->t_flags & TF_NODELAY) &&
|
|
len + off >= so->so_snd.sb_cc))
|
|
goto send;
|
|
if (tp->t_force)
|
|
goto send;
|
|
if (len >= tp->max_sndwnd / 2)
|
|
goto send;
|
|
if (SEQ_LT(tp->snd_nxt, tp->snd_max))
|
|
goto send;
|
|
}
|
|
|
|
/*
|
|
* Compare available window to amount of window known to peer
|
|
* (as advertised window less next expected input). If the
|
|
* difference is at least twice the size of the largest segment
|
|
* we expect to receive (i.e. two segments) or at least 50% of
|
|
* the maximum possible window, then want to send a window update
|
|
* to peer.
|
|
*/
|
|
if (win > 0) {
|
|
/*
|
|
* "adv" is the amount we can increase the window,
|
|
* taking into account that we are limited by
|
|
* TCP_MAXWIN << tp->rcv_scale.
|
|
*/
|
|
long adv = min(win, (long)TCP_MAXWIN << tp->rcv_scale) -
|
|
(tp->rcv_adv - tp->rcv_nxt);
|
|
|
|
if (adv >= (long) (2 * rxsegsize))
|
|
goto send;
|
|
if (2 * adv >= (long) so->so_rcv.sb_hiwat)
|
|
goto send;
|
|
}
|
|
|
|
/*
|
|
* Send if we owe peer an ACK.
|
|
*/
|
|
if (tp->t_flags & TF_ACKNOW)
|
|
goto send;
|
|
if (flags & (TH_SYN|TH_FIN|TH_RST))
|
|
goto send;
|
|
if (SEQ_GT(tp->snd_up, tp->snd_una))
|
|
goto send;
|
|
|
|
/*
|
|
* TCP window updates are not reliable, rather a polling protocol
|
|
* using ``persist'' packets is used to insure receipt of window
|
|
* updates. The three ``states'' for the output side are:
|
|
* idle not doing retransmits or persists
|
|
* persisting to move a small or zero window
|
|
* (re)transmitting and thereby not persisting
|
|
*
|
|
* tp->t_timer[TCPT_PERSIST]
|
|
* is set when we are in persist state.
|
|
* tp->t_force
|
|
* is set when we are called to send a persist packet.
|
|
* tp->t_timer[TCPT_REXMT]
|
|
* is set when we are retransmitting
|
|
* The output side is idle when both timers are zero.
|
|
*
|
|
* If send window is too small, there is data to transmit, and no
|
|
* retransmit or persist is pending, then go to persist state.
|
|
* If nothing happens soon, send when timer expires:
|
|
* if window is nonzero, transmit what we can,
|
|
* otherwise force out a byte.
|
|
*/
|
|
if (so->so_snd.sb_cc && TCP_TIMER_ISARMED(tp, TCPT_REXMT) == 0 &&
|
|
TCP_TIMER_ISARMED(tp, TCPT_PERSIST) == 0) {
|
|
tp->t_rxtshift = 0;
|
|
tcp_setpersist(tp);
|
|
}
|
|
|
|
/*
|
|
* No reason to send a segment, just return.
|
|
*/
|
|
return (0);
|
|
|
|
send:
|
|
/*
|
|
* Before ESTABLISHED, force sending of initial options
|
|
* unless TCP set not to do any options.
|
|
* NOTE: we assume that the IP/TCP header plus TCP options
|
|
* always fit in a single mbuf, leaving room for a maximum
|
|
* link header, i.e.
|
|
* max_linkhdr + sizeof (struct tcpiphdr) + optlen <= MCLBYTES
|
|
*/
|
|
optlen = 0;
|
|
switch (af) {
|
|
#ifdef INET
|
|
case AF_INET:
|
|
iphdrlen = sizeof(struct ip) + sizeof(struct tcphdr);
|
|
break;
|
|
#endif
|
|
#ifdef INET6
|
|
case AF_INET6:
|
|
iphdrlen = sizeof(struct ip6_hdr) + sizeof(struct tcphdr);
|
|
break;
|
|
#endif
|
|
default: /*pacify gcc*/
|
|
iphdrlen = 0;
|
|
break;
|
|
}
|
|
hdrlen = iphdrlen;
|
|
if (flags & TH_SYN) {
|
|
struct rtentry *rt;
|
|
|
|
rt = NULL;
|
|
#ifdef INET
|
|
if (tp->t_inpcb)
|
|
rt = in_pcbrtentry(tp->t_inpcb);
|
|
#endif
|
|
#ifdef INET6
|
|
if (tp->t_in6pcb)
|
|
rt = in6_pcbrtentry(tp->t_in6pcb);
|
|
#endif
|
|
|
|
tp->snd_nxt = tp->iss;
|
|
tp->t_ourmss = tcp_mss_to_advertise(rt != NULL ?
|
|
rt->rt_ifp : NULL, af);
|
|
if ((tp->t_flags & TF_NOOPT) == 0) {
|
|
opt[0] = TCPOPT_MAXSEG;
|
|
opt[1] = 4;
|
|
opt[2] = (tp->t_ourmss >> 8) & 0xff;
|
|
opt[3] = tp->t_ourmss & 0xff;
|
|
optlen = 4;
|
|
|
|
if ((tp->t_flags & TF_REQ_SCALE) &&
|
|
((flags & TH_ACK) == 0 ||
|
|
(tp->t_flags & TF_RCVD_SCALE))) {
|
|
*((u_int32_t *) (opt + optlen)) = htonl(
|
|
TCPOPT_NOP << 24 |
|
|
TCPOPT_WINDOW << 16 |
|
|
TCPOLEN_WINDOW << 8 |
|
|
tp->request_r_scale);
|
|
optlen += 4;
|
|
}
|
|
}
|
|
}
|
|
|
|
/*
|
|
* Send a timestamp and echo-reply if this is a SYN and our side
|
|
* wants to use timestamps (TF_REQ_TSTMP is set) or both our side
|
|
* and our peer have sent timestamps in our SYN's.
|
|
*/
|
|
if ((tp->t_flags & (TF_REQ_TSTMP|TF_NOOPT)) == TF_REQ_TSTMP &&
|
|
(flags & TH_RST) == 0 &&
|
|
((flags & (TH_SYN|TH_ACK)) == TH_SYN ||
|
|
(tp->t_flags & TF_RCVD_TSTMP))) {
|
|
u_int32_t *lp = (u_int32_t *)(opt + optlen);
|
|
|
|
/* Form timestamp option as shown in appendix A of RFC 1323. */
|
|
*lp++ = htonl(TCPOPT_TSTAMP_HDR);
|
|
*lp++ = htonl(TCP_TIMESTAMP(tp));
|
|
*lp = htonl(tp->ts_recent);
|
|
optlen += TCPOLEN_TSTAMP_APPA;
|
|
}
|
|
|
|
hdrlen += optlen;
|
|
|
|
#ifdef DIAGNOSTIC
|
|
if (len > txsegsize)
|
|
panic("tcp data to be sent is larger than segment");
|
|
if (max_linkhdr + hdrlen > MCLBYTES)
|
|
panic("tcphdr too big");
|
|
#endif
|
|
|
|
/*
|
|
* Grab a header mbuf, attaching a copy of data to
|
|
* be transmitted, and initialize the header from
|
|
* the template for sends on this connection.
|
|
*/
|
|
if (len) {
|
|
error = tcp_build_datapkt(tp, so, off, len, hdrlen, &m);
|
|
if (error)
|
|
goto out;
|
|
/*
|
|
* If we're sending everything we've got, set PUSH.
|
|
* (This will keep happy those implementations which only
|
|
* give data to the user when a buffer fills or
|
|
* a PUSH comes in.)
|
|
*/
|
|
if (off + len == so->so_snd.sb_cc)
|
|
flags |= TH_PUSH;
|
|
} else {
|
|
if (tp->t_flags & TF_ACKNOW)
|
|
tcpstat.tcps_sndacks++;
|
|
else if (flags & (TH_SYN|TH_FIN|TH_RST))
|
|
tcpstat.tcps_sndctrl++;
|
|
else if (SEQ_GT(tp->snd_up, tp->snd_una))
|
|
tcpstat.tcps_sndurg++;
|
|
else
|
|
tcpstat.tcps_sndwinup++;
|
|
|
|
MGETHDR(m, M_DONTWAIT, MT_HEADER);
|
|
if (m != NULL && max_linkhdr + hdrlen > MHLEN) {
|
|
MCLGET(m, M_DONTWAIT);
|
|
if ((m->m_flags & M_EXT) == 0) {
|
|
m_freem(m);
|
|
m = NULL;
|
|
}
|
|
}
|
|
if (m == NULL) {
|
|
error = ENOBUFS;
|
|
goto out;
|
|
}
|
|
MCLAIM(m, &tcp_tx_mowner);
|
|
m->m_data += max_linkhdr;
|
|
m->m_len = hdrlen;
|
|
}
|
|
m->m_pkthdr.rcvif = (struct ifnet *)0;
|
|
switch (af) {
|
|
#ifdef INET
|
|
case AF_INET:
|
|
ip = mtod(m, struct ip *);
|
|
#ifdef INET6
|
|
ip6 = NULL;
|
|
#endif
|
|
th = (struct tcphdr *)(ip + 1);
|
|
break;
|
|
#endif
|
|
#ifdef INET6
|
|
case AF_INET6:
|
|
ip = NULL;
|
|
ip6 = mtod(m, struct ip6_hdr *);
|
|
th = (struct tcphdr *)(ip6 + 1);
|
|
break;
|
|
#endif
|
|
default: /*pacify gcc*/
|
|
ip = NULL;
|
|
#ifdef INET6
|
|
ip6 = NULL;
|
|
#endif
|
|
th = NULL;
|
|
break;
|
|
}
|
|
if (tp->t_template == 0)
|
|
panic("tcp_output");
|
|
if (tp->t_template->m_len < iphdrlen)
|
|
panic("tcp_output");
|
|
bcopy(mtod(tp->t_template, caddr_t), mtod(m, caddr_t), iphdrlen);
|
|
|
|
/*
|
|
* If we are doing retransmissions, then snd_nxt will
|
|
* not reflect the first unsent octet. For ACK only
|
|
* packets, we do not want the sequence number of the
|
|
* retransmitted packet, we want the sequence number
|
|
* of the next unsent octet. So, if there is no data
|
|
* (and no SYN or FIN), use snd_max instead of snd_nxt
|
|
* when filling in ti_seq. But if we are in persist
|
|
* state, snd_max might reflect one byte beyond the
|
|
* right edge of the window, so use snd_nxt in that
|
|
* case, since we know we aren't doing a retransmission.
|
|
* (retransmit and persist are mutually exclusive...)
|
|
*/
|
|
if (len || (flags & (TH_SYN|TH_FIN)) ||
|
|
TCP_TIMER_ISARMED(tp, TCPT_PERSIST))
|
|
th->th_seq = htonl(tp->snd_nxt);
|
|
else
|
|
th->th_seq = htonl(tp->snd_max);
|
|
th->th_ack = htonl(tp->rcv_nxt);
|
|
if (optlen) {
|
|
bcopy((caddr_t)opt, (caddr_t)(th + 1), optlen);
|
|
th->th_off = (sizeof (struct tcphdr) + optlen) >> 2;
|
|
}
|
|
th->th_flags = flags;
|
|
/*
|
|
* Calculate receive window. Don't shrink window,
|
|
* but avoid silly window syndrome.
|
|
*/
|
|
if (win < (long)(so->so_rcv.sb_hiwat / 4) && win < (long)rxsegsize)
|
|
win = 0;
|
|
if (win > (long)TCP_MAXWIN << tp->rcv_scale)
|
|
win = (long)TCP_MAXWIN << tp->rcv_scale;
|
|
if (win < (long)(tp->rcv_adv - tp->rcv_nxt))
|
|
win = (long)(tp->rcv_adv - tp->rcv_nxt);
|
|
th->th_win = htons((u_int16_t) (win>>tp->rcv_scale));
|
|
if (SEQ_GT(tp->snd_up, tp->snd_nxt)) {
|
|
u_int32_t urp = tp->snd_up - tp->snd_nxt;
|
|
if (urp > IP_MAXPACKET)
|
|
urp = IP_MAXPACKET;
|
|
th->th_urp = htons((u_int16_t)urp);
|
|
th->th_flags |= TH_URG;
|
|
} else
|
|
/*
|
|
* If no urgent pointer to send, then we pull
|
|
* the urgent pointer to the left edge of the send window
|
|
* so that it doesn't drift into the send window on sequence
|
|
* number wraparound.
|
|
*/
|
|
tp->snd_up = tp->snd_una; /* drag it along */
|
|
|
|
/*
|
|
* Set ourselves up to be checksummed just before the packet
|
|
* hits the wire.
|
|
*/
|
|
switch (af) {
|
|
#ifdef INET
|
|
case AF_INET:
|
|
m->m_pkthdr.csum_flags = M_CSUM_TCPv4;
|
|
m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum);
|
|
if (len + optlen) {
|
|
/* Fixup the pseudo-header checksum. */
|
|
/* XXXJRT Not IP Jumbogram safe. */
|
|
th->th_sum = in_cksum_addword(th->th_sum,
|
|
htons((u_int16_t) (len + optlen)));
|
|
}
|
|
break;
|
|
#endif
|
|
#ifdef INET6
|
|
case AF_INET6:
|
|
/*
|
|
* XXX Actually delaying the checksum is Hard
|
|
* XXX (well, maybe not for Itojun, but it is
|
|
* XXX for me), but we can still take advantage
|
|
* XXX of the cached pseudo-header checksum.
|
|
*/
|
|
/* equals to hdrlen + len */
|
|
m->m_pkthdr.len = sizeof(struct ip6_hdr)
|
|
+ sizeof(struct tcphdr) + optlen + len;
|
|
#ifdef notyet
|
|
m->m_pkthdr.csum_flags = M_CSUM_TCPv6;
|
|
m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum);
|
|
#endif
|
|
if (len + optlen) {
|
|
/* Fixup the pseudo-header checksum. */
|
|
/* XXXJRT: Not IPv6 Jumbogram safe. */
|
|
th->th_sum = in_cksum_addword(th->th_sum,
|
|
htons((u_int16_t) (len + optlen)));
|
|
}
|
|
#ifndef notyet
|
|
th->th_sum = in6_cksum(m, 0, sizeof(struct ip6_hdr),
|
|
sizeof(struct tcphdr) + optlen + len);
|
|
#endif
|
|
break;
|
|
#endif
|
|
}
|
|
|
|
/*
|
|
* In transmit state, time the transmission and arrange for
|
|
* the retransmit. In persist state, just set snd_max.
|
|
*/
|
|
if (tp->t_force == 0 || TCP_TIMER_ISARMED(tp, TCPT_PERSIST) == 0) {
|
|
tcp_seq startseq = tp->snd_nxt;
|
|
|
|
/*
|
|
* Advance snd_nxt over sequence space of this segment.
|
|
* There are no states in which we send both a SYN and a FIN,
|
|
* so we collapse the tests for these flags.
|
|
*/
|
|
if (flags & (TH_SYN|TH_FIN))
|
|
tp->snd_nxt++;
|
|
tp->snd_nxt += len;
|
|
if (SEQ_GT(tp->snd_nxt, tp->snd_max)) {
|
|
tp->snd_max = tp->snd_nxt;
|
|
/*
|
|
* Time this transmission if not a retransmission and
|
|
* not currently timing anything.
|
|
*/
|
|
if (tp->t_rtttime == 0) {
|
|
tp->t_rtttime = tcp_now;
|
|
tp->t_rtseq = startseq;
|
|
tcpstat.tcps_segstimed++;
|
|
}
|
|
}
|
|
|
|
/*
|
|
* Set retransmit timer if not currently set,
|
|
* and not doing an ack or a keep-alive probe.
|
|
* Initial value for retransmit timer is smoothed
|
|
* round-trip time + 2 * round-trip time variance.
|
|
* Initialize shift counter which is used for backoff
|
|
* of retransmit time.
|
|
*/
|
|
if (TCP_TIMER_ISARMED(tp, TCPT_REXMT) == 0 &&
|
|
tp->snd_nxt != tp->snd_una) {
|
|
TCP_TIMER_ARM(tp, TCPT_REXMT, tp->t_rxtcur);
|
|
if (TCP_TIMER_ISARMED(tp, TCPT_PERSIST)) {
|
|
TCP_TIMER_DISARM(tp, TCPT_PERSIST);
|
|
tp->t_rxtshift = 0;
|
|
}
|
|
}
|
|
} else
|
|
if (SEQ_GT(tp->snd_nxt + len, tp->snd_max))
|
|
tp->snd_max = tp->snd_nxt + len;
|
|
|
|
#ifdef TCP_DEBUG
|
|
/*
|
|
* Trace.
|
|
*/
|
|
if (so->so_options & SO_DEBUG)
|
|
tcp_trace(TA_OUTPUT, tp->t_state, tp, m, 0);
|
|
#endif
|
|
|
|
/*
|
|
* Fill in IP length and desired time to live and
|
|
* send to IP level. There should be a better way
|
|
* to handle ttl and tos; we could keep them in
|
|
* the template, but need a way to checksum without them.
|
|
*/
|
|
m->m_pkthdr.len = hdrlen + len;
|
|
|
|
switch (af) {
|
|
#ifdef INET
|
|
case AF_INET:
|
|
ip->ip_len = htons(m->m_pkthdr.len);
|
|
if (tp->t_inpcb) {
|
|
ip->ip_ttl = tp->t_inpcb->inp_ip.ip_ttl;
|
|
ip->ip_tos = tp->t_inpcb->inp_ip.ip_tos;
|
|
}
|
|
#ifdef INET6
|
|
else if (tp->t_in6pcb) {
|
|
ip->ip_ttl = in6_selecthlim(tp->t_in6pcb, NULL); /*XXX*/
|
|
ip->ip_tos = 0; /*XXX*/
|
|
}
|
|
#endif
|
|
break;
|
|
#endif
|
|
#ifdef INET6
|
|
case AF_INET6:
|
|
ip6->ip6_nxt = IPPROTO_TCP;
|
|
if (tp->t_in6pcb) {
|
|
/*
|
|
* we separately set hoplimit for every segment, since
|
|
* the user might want to change the value via
|
|
* setsockopt. Also, desired default hop limit might
|
|
* be changed via Neighbor Discovery.
|
|
*/
|
|
ip6->ip6_hlim = in6_selecthlim(tp->t_in6pcb,
|
|
ro->ro_rt ? ro->ro_rt->rt_ifp : NULL);
|
|
}
|
|
/* ip6->ip6_flow = ??? */
|
|
/* ip6_plen will be filled in ip6_output(). */
|
|
break;
|
|
#endif
|
|
}
|
|
|
|
#ifdef IPSEC
|
|
if (ipsec_setsocket(m, so) != 0) {
|
|
m_freem(m);
|
|
error = ENOBUFS;
|
|
goto out;
|
|
}
|
|
#endif /*IPSEC*/
|
|
|
|
switch (af) {
|
|
#ifdef INET
|
|
case AF_INET:
|
|
{
|
|
struct mbuf *opts;
|
|
|
|
if (tp->t_inpcb)
|
|
opts = tp->t_inpcb->inp_options;
|
|
else
|
|
opts = NULL;
|
|
error = ip_output(m, opts, ro,
|
|
(tp->t_mtudisc ? IP_MTUDISC : 0) |
|
|
(so->so_options & SO_DONTROUTE),
|
|
0);
|
|
break;
|
|
}
|
|
#endif
|
|
#ifdef INET6
|
|
case AF_INET6:
|
|
{
|
|
struct ip6_pktopts *opts;
|
|
|
|
if (tp->t_in6pcb)
|
|
opts = tp->t_in6pcb->in6p_outputopts;
|
|
else
|
|
opts = NULL;
|
|
error = ip6_output(m, opts, (struct route_in6 *)ro,
|
|
so->so_options & SO_DONTROUTE, 0, NULL);
|
|
break;
|
|
}
|
|
#endif
|
|
default:
|
|
error = EAFNOSUPPORT;
|
|
break;
|
|
}
|
|
if (error) {
|
|
out:
|
|
if (error == ENOBUFS) {
|
|
tcpstat.tcps_selfquench++;
|
|
#ifdef INET
|
|
if (tp->t_inpcb)
|
|
tcp_quench(tp->t_inpcb, 0);
|
|
#endif
|
|
#ifdef INET6
|
|
if (tp->t_in6pcb)
|
|
tcp6_quench(tp->t_in6pcb, 0);
|
|
#endif
|
|
error = 0;
|
|
} else if ((error == EHOSTUNREACH || error == ENETDOWN) &&
|
|
TCPS_HAVERCVDSYN(tp->t_state)) {
|
|
tp->t_softerror = error;
|
|
error = 0;
|
|
}
|
|
|
|
/* Restart the delayed ACK timer, if necessary. */
|
|
if (tp->t_flags & TF_DELACK)
|
|
TCP_RESTART_DELACK(tp);
|
|
|
|
return (error);
|
|
}
|
|
tcpstat.tcps_sndtotal++;
|
|
if (tp->t_flags & TF_DELACK)
|
|
tcpstat.tcps_delack++;
|
|
|
|
/*
|
|
* Data sent (as far as we can tell).
|
|
* If this advertises a larger window than any other segment,
|
|
* then remember the size of the advertised window.
|
|
* Any pending ACK has now been sent.
|
|
*/
|
|
if (win > 0 && SEQ_GT(tp->rcv_nxt+win, tp->rcv_adv))
|
|
tp->rcv_adv = tp->rcv_nxt + win;
|
|
tp->last_ack_sent = tp->rcv_nxt;
|
|
tp->t_flags &= ~TF_ACKNOW;
|
|
TCP_CLEAR_DELACK(tp);
|
|
#ifdef DIAGNOSTIC
|
|
if (maxburst < 0)
|
|
printf("tcp_output: maxburst exceeded by %d\n", -maxburst);
|
|
#endif
|
|
if (sendalot && (!tcp_do_newreno || --maxburst))
|
|
goto again;
|
|
return (0);
|
|
}
|
|
|
|
void
|
|
tcp_setpersist(tp)
|
|
struct tcpcb *tp;
|
|
{
|
|
int t = ((tp->t_srtt >> 2) + tp->t_rttvar) >> (1 + 2);
|
|
int nticks;
|
|
|
|
if (TCP_TIMER_ISARMED(tp, TCPT_REXMT))
|
|
panic("tcp_output REXMT");
|
|
/*
|
|
* Start/restart persistance timer.
|
|
*/
|
|
if (t < tp->t_rttmin)
|
|
t = tp->t_rttmin;
|
|
TCPT_RANGESET(nticks, t * tcp_backoff[tp->t_rxtshift],
|
|
TCPTV_PERSMIN, TCPTV_PERSMAX);
|
|
TCP_TIMER_ARM(tp, TCPT_PERSIST, nticks);
|
|
if (tp->t_rxtshift < TCP_MAXRXTSHIFT)
|
|
tp->t_rxtshift++;
|
|
}
|