9eb0e8326d
There should be no functional changes with this commit. Reviewed by: rscheff Differential revision: https://reviews.freebsd.org/D37123
315 lines
8.5 KiB
C
315 lines
8.5 KiB
C
/*-
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* SPDX-License-Identifier: BSD-3-Clause
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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. 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_subr.c 8.2 (Berkeley) 5/24/95
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*/
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#include <sys/cdefs.h>
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__FBSDID("$FreeBSD$");
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#include "opt_inet.h"
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#include "opt_inet6.h"
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#include "opt_ipsec.h"
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#include "opt_tcpdebug.h"
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#include <sys/param.h>
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#include <sys/systm.h>
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#include <sys/callout.h>
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#include <sys/kernel.h>
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#include <sys/sysctl.h>
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#include <sys/malloc.h>
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#include <sys/mbuf.h>
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#include <sys/priv.h>
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#include <sys/proc.h>
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#include <sys/socket.h>
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#include <sys/socketvar.h>
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#include <sys/syslog.h>
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#include <sys/protosw.h>
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#include <sys/random.h>
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#include <vm/uma.h>
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#include <net/route.h>
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#include <net/if.h>
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#include <net/if_var.h>
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#include <net/vnet.h>
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#include <netinet/in.h>
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#include <netinet/in_kdtrace.h>
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#include <netinet/in_pcb.h>
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#include <netinet/in_systm.h>
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#include <netinet/in_var.h>
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#include <netinet/ip.h>
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#include <netinet/ip_icmp.h>
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#include <netinet/ip_var.h>
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#ifdef INET6
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#include <netinet/ip6.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/scope6_var.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/tcp_hpts.h>
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#include <netinet/tcpip.h>
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#ifdef TCPDEBUG
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#include <netinet/tcp_debug.h>
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#endif
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#include <netinet/udp.h>
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#include <netinet/udp_var.h>
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#include <netipsec/ipsec_support.h>
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#include <machine/in_cksum.h>
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#include <security/mac/mac_framework.h>
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VNET_DEFINE_STATIC(bool, nolocaltimewait) = true;
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#define V_nolocaltimewait VNET(nolocaltimewait)
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SYSCTL_BOOL(_net_inet_tcp, OID_AUTO, nolocaltimewait,
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CTLFLAG_VNET | CTLFLAG_RW, &VNET_NAME(nolocaltimewait), true,
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"Do not create TCP TIME_WAIT state for local connections");
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/*
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* Move a TCP connection into TIME_WAIT state.
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* inp is locked, and is unlocked before returning.
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*
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* This function used to free tcpcb and allocate a compressed TCP time-wait
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* structure tcptw. This served well for 20 years but is no longer relevant
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* on modern machines in the modern internet. However, the function remains
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* so that TCP stacks require less modification and we don't burn the bridge
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* to go back to using compressed time-wait.
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*/
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void
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tcp_twstart(struct tcpcb *tp)
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{
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struct inpcb *inp = tptoinpcb(tp);
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#ifdef INET6
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bool isipv6 = inp->inp_inc.inc_flags & INC_ISIPV6;
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#endif
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NET_EPOCH_ASSERT();
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INP_WLOCK_ASSERT(inp);
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/* A dropped inp should never transition to TIME_WAIT state. */
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KASSERT((inp->inp_flags & INP_DROPPED) == 0, ("tcp_twstart: "
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"(inp->inp_flags & INP_DROPPED) != 0"));
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tcp_state_change(tp, TCPS_TIME_WAIT);
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soisdisconnected(inp->inp_socket);
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if (tp->t_flags & TF_ACKNOW)
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tcp_output(tp);
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if (V_nolocaltimewait && (
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#ifdef INET6
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isipv6 ? in6_localaddr(&inp->in6p_faddr) :
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#endif
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#ifdef INET
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in_localip(inp->inp_faddr)
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#else
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false
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#endif
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)) {
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if ((tp = tcp_close(tp)) != NULL)
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INP_WUNLOCK(inp);
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return;
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}
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tcp_timer_activate(tp, TT_2MSL, 2 * V_tcp_msl);
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INP_WUNLOCK(inp);
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}
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/*
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* Returns true if the TIME_WAIT state was killed and we should start over,
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* looking for a pcb in the listen state. Otherwise returns false and frees
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* the mbuf.
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*
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* For pure SYN-segments the PCB shall be read-locked and the tcpopt pointer
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* may be NULL. For the rest write-lock and valid tcpopt.
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*/
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bool
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tcp_twcheck(struct inpcb *inp, struct tcpopt *to, struct tcphdr *th,
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struct mbuf *m, int tlen)
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{
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struct tcpcb *tp = intotcpcb(inp);
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char *s;
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int thflags;
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tcp_seq seq;
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NET_EPOCH_ASSERT();
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INP_LOCK_ASSERT(inp);
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thflags = tcp_get_flags(th);
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#ifdef INVARIANTS
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if ((thflags & (TH_SYN | TH_ACK)) == TH_SYN)
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INP_RLOCK_ASSERT(inp);
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else {
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INP_WLOCK_ASSERT(inp);
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KASSERT(to != NULL,
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("%s: called without options on a non-SYN segment",
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__func__));
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}
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#endif
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/*
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* NOTE: for FIN_WAIT_2 (to be added later),
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* must validate sequence number before accepting RST
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*/
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/*
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* If the segment contains RST:
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* Drop the segment - see Stevens, vol. 2, p. 964 and
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* RFC 1337.
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*/
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if (thflags & TH_RST)
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goto drop;
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#if 0
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/* PAWS not needed at the moment */
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/*
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* RFC 1323 PAWS: If we have a timestamp reply on this segment
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* and it's less than ts_recent, drop it.
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*/
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if ((to.to_flags & TOF_TS) != 0 && tp->ts_recent &&
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TSTMP_LT(to.to_tsval, tp->ts_recent)) {
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if ((thflags & TH_ACK) == 0)
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goto drop;
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goto ack;
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}
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/*
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* ts_recent is never updated because we never accept new segments.
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*/
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#endif
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/* Honor the drop_synfin sysctl variable. */
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if ((thflags & TH_SYN) && (thflags & TH_FIN) && V_drop_synfin) {
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if ((s = tcp_log_addrs(&inp->inp_inc, th, NULL, NULL))) {
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log(LOG_DEBUG, "%s; %s: "
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"SYN|FIN segment ignored (based on "
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"sysctl setting)\n", s, __func__);
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free(s, M_TCPLOG);
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}
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goto drop;
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}
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/*
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* If a new connection request is received
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* while in TIME_WAIT, drop the old connection
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* and start over if the sequence numbers
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* are above the previous ones.
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* Allow UDP port number changes in this case.
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*/
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if (((thflags & (TH_SYN | TH_ACK)) == TH_SYN) &&
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SEQ_GT(th->th_seq, tp->rcv_nxt)) {
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/*
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* In case we can't upgrade our lock just pretend we have
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* lost this packet.
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*/
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if (INP_TRY_UPGRADE(inp) == 0)
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goto drop;
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if ((tp = tcp_close(tp)) != NULL)
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INP_WUNLOCK(inp);
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TCPSTAT_INC(tcps_tw_recycles);
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return (true);
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}
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/*
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* Send RST if UDP port numbers don't match
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*/
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if (tp->t_port != m->m_pkthdr.tcp_tun_port) {
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if (tcp_get_flags(th) & TH_ACK) {
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tcp_respond(tp, mtod(m, void *), th, m,
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(tcp_seq)0, th->th_ack, TH_RST);
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} else {
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if (tcp_get_flags(th) & TH_SYN)
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tlen++;
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if (tcp_get_flags(th) & TH_FIN)
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tlen++;
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tcp_respond(tp, mtod(m, void *), th, m,
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th->th_seq+tlen, (tcp_seq)0, TH_RST|TH_ACK);
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}
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INP_UNLOCK(inp);
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TCPSTAT_INC(tcps_tw_resets);
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return (false);
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}
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/*
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* Drop the segment if it does not contain an ACK.
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*/
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if ((thflags & TH_ACK) == 0)
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goto drop;
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INP_WLOCK_ASSERT(inp);
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/*
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* If timestamps were negotiated during SYN/ACK and a
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* segment without a timestamp is received, silently drop
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* the segment, unless the missing timestamps are tolerated.
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* See section 3.2 of RFC 7323.
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*/
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if (((to->to_flags & TOF_TS) == 0) && (tp->ts_recent != 0) &&
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(V_tcp_tolerate_missing_ts == 0)) {
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goto drop;
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}
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/*
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* Reset the 2MSL timer if this is a duplicate FIN.
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*/
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if (thflags & TH_FIN) {
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seq = th->th_seq + tlen + (thflags & TH_SYN ? 1 : 0);
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if (seq + 1 == tp->rcv_nxt)
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tcp_timer_activate(tp, TT_2MSL, 2 * V_tcp_msl);
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}
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/*
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* Acknowledge the segment if it has data or is not a duplicate ACK.
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*/
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if (thflags != TH_ACK || tlen != 0 ||
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th->th_seq != tp->rcv_nxt || th->th_ack != tp->snd_nxt) {
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TCP_PROBE5(receive, NULL, NULL, m, NULL, th);
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tcp_respond(tp, mtod(m, void *), th, m, tp->rcv_nxt,
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tp->snd_nxt, TH_ACK);
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INP_UNLOCK(inp);
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TCPSTAT_INC(tcps_tw_responds);
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return (false);
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}
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drop:
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TCP_PROBE5(receive, NULL, NULL, m, NULL, th);
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INP_UNLOCK(inp);
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m_freem(m);
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return (false);
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}
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