freebsd-dev/sys/netinet/tcp_timewait.c
Gleb Smirnoff eaabc93764 tcp: retire TCPDEBUG
This subsystem is superseded by modern debugging facilities,
e.g. DTrace probes and TCP black box logging.

We intentionally leave SO_DEBUG in place, as many utilities may
set it on a socket.  Also the tcp::debug DTrace probes look at
this flag on a socket.

Reviewed by:		gnn, tuexen
Discussed with:		rscheff, rrs, jtl
Differential revision:	https://reviews.freebsd.org/D37694
2022-12-14 09:54:06 -08:00

311 lines
8.4 KiB
C

/*-
* SPDX-License-Identifier: BSD-3-Clause
*
* Copyright (c) 1982, 1986, 1988, 1990, 1993, 1995
* The Regents of the University of California. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. Neither the name of the University nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*
* @(#)tcp_subr.c 8.2 (Berkeley) 5/24/95
*/
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
#include "opt_inet.h"
#include "opt_inet6.h"
#include "opt_ipsec.h"
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/callout.h>
#include <sys/kernel.h>
#include <sys/sysctl.h>
#include <sys/malloc.h>
#include <sys/mbuf.h>
#include <sys/priv.h>
#include <sys/proc.h>
#include <sys/socket.h>
#include <sys/socketvar.h>
#include <sys/syslog.h>
#include <sys/protosw.h>
#include <sys/random.h>
#include <vm/uma.h>
#include <net/route.h>
#include <net/if.h>
#include <net/if_var.h>
#include <net/vnet.h>
#include <netinet/in.h>
#include <netinet/in_kdtrace.h>
#include <netinet/in_pcb.h>
#include <netinet/in_systm.h>
#include <netinet/in_var.h>
#include <netinet/ip.h>
#include <netinet/ip_icmp.h>
#include <netinet/ip_var.h>
#ifdef INET6
#include <netinet/ip6.h>
#include <netinet6/in6_pcb.h>
#include <netinet6/ip6_var.h>
#include <netinet6/scope6_var.h>
#include <netinet6/nd6.h>
#endif
#include <netinet/tcp.h>
#include <netinet/tcp_fsm.h>
#include <netinet/tcp_seq.h>
#include <netinet/tcp_timer.h>
#include <netinet/tcp_var.h>
#include <netinet/tcp_hpts.h>
#include <netinet/tcpip.h>
#include <netinet/udp.h>
#include <netinet/udp_var.h>
#include <netipsec/ipsec_support.h>
#include <machine/in_cksum.h>
#include <security/mac/mac_framework.h>
VNET_DEFINE_STATIC(bool, nolocaltimewait) = true;
#define V_nolocaltimewait VNET(nolocaltimewait)
SYSCTL_BOOL(_net_inet_tcp, OID_AUTO, nolocaltimewait,
CTLFLAG_VNET | CTLFLAG_RW, &VNET_NAME(nolocaltimewait), true,
"Do not create TCP TIME_WAIT state for local connections");
/*
* Move a TCP connection into TIME_WAIT state.
* inp is locked, and is unlocked before returning.
*
* This function used to free tcpcb and allocate a compressed TCP time-wait
* structure tcptw. This served well for 20 years but is no longer relevant
* on modern machines in the modern internet. However, the function remains
* so that TCP stacks require less modification and we don't burn the bridge
* to go back to using compressed time-wait.
*/
void
tcp_twstart(struct tcpcb *tp)
{
struct inpcb *inp = tptoinpcb(tp);
#ifdef INET6
bool isipv6 = inp->inp_inc.inc_flags & INC_ISIPV6;
#endif
NET_EPOCH_ASSERT();
INP_WLOCK_ASSERT(inp);
/* A dropped inp should never transition to TIME_WAIT state. */
KASSERT((inp->inp_flags & INP_DROPPED) == 0, ("tcp_twstart: "
"(inp->inp_flags & INP_DROPPED) != 0"));
tcp_state_change(tp, TCPS_TIME_WAIT);
soisdisconnected(inp->inp_socket);
if (tp->t_flags & TF_ACKNOW)
tcp_output(tp);
if (V_nolocaltimewait && (
#ifdef INET6
isipv6 ? in6_localaddr(&inp->in6p_faddr) :
#endif
#ifdef INET
in_localip(inp->inp_faddr)
#else
false
#endif
)) {
if ((tp = tcp_close(tp)) != NULL)
INP_WUNLOCK(inp);
return;
}
tcp_timer_activate(tp, TT_2MSL, 2 * V_tcp_msl);
INP_WUNLOCK(inp);
}
/*
* Returns true if the TIME_WAIT state was killed and we should start over,
* looking for a pcb in the listen state. Otherwise returns false and frees
* the mbuf.
*
* For pure SYN-segments the PCB shall be read-locked and the tcpopt pointer
* may be NULL. For the rest write-lock and valid tcpopt.
*/
bool
tcp_twcheck(struct inpcb *inp, struct tcpopt *to, struct tcphdr *th,
struct mbuf *m, int tlen)
{
struct tcpcb *tp = intotcpcb(inp);
char *s;
int thflags;
tcp_seq seq;
NET_EPOCH_ASSERT();
INP_LOCK_ASSERT(inp);
thflags = tcp_get_flags(th);
#ifdef INVARIANTS
if ((thflags & (TH_SYN | TH_ACK)) == TH_SYN)
INP_RLOCK_ASSERT(inp);
else {
INP_WLOCK_ASSERT(inp);
KASSERT(to != NULL,
("%s: called without options on a non-SYN segment",
__func__));
}
#endif
/*
* NOTE: for FIN_WAIT_2 (to be added later),
* must validate sequence number before accepting RST
*/
/*
* If the segment contains RST:
* Drop the segment - see Stevens, vol. 2, p. 964 and
* RFC 1337.
*/
if (thflags & TH_RST)
goto drop;
#if 0
/* PAWS not needed at the moment */
/*
* RFC 1323 PAWS: If we have a timestamp reply on this segment
* and it's less than ts_recent, drop it.
*/
if ((to.to_flags & TOF_TS) != 0 && tp->ts_recent &&
TSTMP_LT(to.to_tsval, tp->ts_recent)) {
if ((thflags & TH_ACK) == 0)
goto drop;
goto ack;
}
/*
* ts_recent is never updated because we never accept new segments.
*/
#endif
/* Honor the drop_synfin sysctl variable. */
if ((thflags & TH_SYN) && (thflags & TH_FIN) && V_drop_synfin) {
if ((s = tcp_log_addrs(&inp->inp_inc, th, NULL, NULL))) {
log(LOG_DEBUG, "%s; %s: "
"SYN|FIN segment ignored (based on "
"sysctl setting)\n", s, __func__);
free(s, M_TCPLOG);
}
goto drop;
}
/*
* If a new connection request is received
* while in TIME_WAIT, drop the old connection
* and start over if the sequence numbers
* are above the previous ones.
* Allow UDP port number changes in this case.
*/
if (((thflags & (TH_SYN | TH_ACK)) == TH_SYN) &&
SEQ_GT(th->th_seq, tp->rcv_nxt)) {
/*
* In case we can't upgrade our lock just pretend we have
* lost this packet.
*/
if (INP_TRY_UPGRADE(inp) == 0)
goto drop;
if ((tp = tcp_close(tp)) != NULL)
INP_WUNLOCK(inp);
TCPSTAT_INC(tcps_tw_recycles);
return (true);
}
/*
* Send RST if UDP port numbers don't match
*/
if (tp->t_port != m->m_pkthdr.tcp_tun_port) {
if (tcp_get_flags(th) & TH_ACK) {
tcp_respond(tp, mtod(m, void *), th, m,
(tcp_seq)0, th->th_ack, TH_RST);
} else {
if (tcp_get_flags(th) & TH_SYN)
tlen++;
if (tcp_get_flags(th) & TH_FIN)
tlen++;
tcp_respond(tp, mtod(m, void *), th, m,
th->th_seq+tlen, (tcp_seq)0, TH_RST|TH_ACK);
}
INP_UNLOCK(inp);
TCPSTAT_INC(tcps_tw_resets);
return (false);
}
/*
* Drop the segment if it does not contain an ACK.
*/
if ((thflags & TH_ACK) == 0)
goto drop;
INP_WLOCK_ASSERT(inp);
/*
* If timestamps were negotiated during SYN/ACK and a
* segment without a timestamp is received, silently drop
* the segment, unless the missing timestamps are tolerated.
* See section 3.2 of RFC 7323.
*/
if (((to->to_flags & TOF_TS) == 0) && (tp->ts_recent != 0) &&
(V_tcp_tolerate_missing_ts == 0)) {
goto drop;
}
/*
* Reset the 2MSL timer if this is a duplicate FIN.
*/
if (thflags & TH_FIN) {
seq = th->th_seq + tlen + (thflags & TH_SYN ? 1 : 0);
if (seq + 1 == tp->rcv_nxt)
tcp_timer_activate(tp, TT_2MSL, 2 * V_tcp_msl);
}
/*
* Acknowledge the segment if it has data or is not a duplicate ACK.
*/
if (thflags != TH_ACK || tlen != 0 ||
th->th_seq != tp->rcv_nxt || th->th_ack != tp->snd_nxt) {
TCP_PROBE5(receive, NULL, NULL, m, NULL, th);
tcp_respond(tp, mtod(m, void *), th, m, tp->rcv_nxt,
tp->snd_nxt, TH_ACK);
INP_UNLOCK(inp);
TCPSTAT_INC(tcps_tw_responds);
return (false);
}
drop:
TCP_PROBE5(receive, NULL, NULL, m, NULL, th);
INP_UNLOCK(inp);
m_freem(m);
return (false);
}