freebsd-dev/sys/netinet/tcp_timer.c
Matt Macy 10d20c84ed Fix spurious retransmit recovery on low latency networks
TCP's smoothed RTT (SRTT) can be much larger than an actual observed RTT. This can be either because of hz restricting the calculable RTT to 10ms in VMs or 1ms using the default 1000hz or simply because SRTT recently incorporated a larger value.

If an ACK arrives before the calculated badrxtwin (now + SRTT):
tp->t_badrxtwin = ticks + (tp->t_srtt >> (TCP_RTT_SHIFT + 1));

We'll erroneously reset snd_una to snd_max. If multiple segments were dropped and this happens repeatedly the transmit rate will be limited to 1MSS per RTO until we've retransmitted all drops.

Reported by:	rstone
Reviewed by:	hiren, transport
Approved by:	sbruno
MFC after:	1 month
Differential Revision:	https://reviews.freebsd.org/D8556
2018-05-08 02:22:34 +00:00

994 lines
28 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_timer.c 8.2 (Berkeley) 5/24/95
*/
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
#include "opt_inet.h"
#include "opt_inet6.h"
#include "opt_tcpdebug.h"
#include "opt_rss.h"
#include <sys/param.h>
#include <sys/kernel.h>
#include <sys/lock.h>
#include <sys/mbuf.h>
#include <sys/mutex.h>
#include <sys/protosw.h>
#include <sys/smp.h>
#include <sys/socket.h>
#include <sys/socketvar.h>
#include <sys/sysctl.h>
#include <sys/systm.h>
#include <net/if.h>
#include <net/route.h>
#include <net/rss_config.h>
#include <net/vnet.h>
#include <net/netisr.h>
#include <netinet/in.h>
#include <netinet/in_kdtrace.h>
#include <netinet/in_pcb.h>
#include <netinet/in_rss.h>
#include <netinet/in_systm.h>
#ifdef INET6
#include <netinet6/in6_pcb.h>
#endif
#include <netinet/ip_var.h>
#include <netinet/tcp.h>
#include <netinet/tcp_fsm.h>
#include <netinet/tcp_log_buf.h>
#include <netinet/tcp_timer.h>
#include <netinet/tcp_var.h>
#include <netinet/cc/cc.h>
#ifdef INET6
#include <netinet6/tcp6_var.h>
#endif
#include <netinet/tcpip.h>
#ifdef TCPDEBUG
#include <netinet/tcp_debug.h>
#endif
int tcp_persmin;
SYSCTL_PROC(_net_inet_tcp, OID_AUTO, persmin, CTLTYPE_INT|CTLFLAG_RW,
&tcp_persmin, 0, sysctl_msec_to_ticks, "I", "minimum persistence interval");
int tcp_persmax;
SYSCTL_PROC(_net_inet_tcp, OID_AUTO, persmax, CTLTYPE_INT|CTLFLAG_RW,
&tcp_persmax, 0, sysctl_msec_to_ticks, "I", "maximum persistence interval");
int tcp_keepinit;
SYSCTL_PROC(_net_inet_tcp, TCPCTL_KEEPINIT, keepinit, CTLTYPE_INT|CTLFLAG_RW,
&tcp_keepinit, 0, sysctl_msec_to_ticks, "I", "time to establish connection");
int tcp_keepidle;
SYSCTL_PROC(_net_inet_tcp, TCPCTL_KEEPIDLE, keepidle, CTLTYPE_INT|CTLFLAG_RW,
&tcp_keepidle, 0, sysctl_msec_to_ticks, "I", "time before keepalive probes begin");
int tcp_keepintvl;
SYSCTL_PROC(_net_inet_tcp, TCPCTL_KEEPINTVL, keepintvl, CTLTYPE_INT|CTLFLAG_RW,
&tcp_keepintvl, 0, sysctl_msec_to_ticks, "I", "time between keepalive probes");
int tcp_delacktime;
SYSCTL_PROC(_net_inet_tcp, TCPCTL_DELACKTIME, delacktime, CTLTYPE_INT|CTLFLAG_RW,
&tcp_delacktime, 0, sysctl_msec_to_ticks, "I",
"Time before a delayed ACK is sent");
int tcp_msl;
SYSCTL_PROC(_net_inet_tcp, OID_AUTO, msl, CTLTYPE_INT|CTLFLAG_RW,
&tcp_msl, 0, sysctl_msec_to_ticks, "I", "Maximum segment lifetime");
int tcp_rexmit_min;
SYSCTL_PROC(_net_inet_tcp, OID_AUTO, rexmit_min, CTLTYPE_INT|CTLFLAG_RW,
&tcp_rexmit_min, 0, sysctl_msec_to_ticks, "I",
"Minimum Retransmission Timeout");
int tcp_rexmit_slop;
SYSCTL_PROC(_net_inet_tcp, OID_AUTO, rexmit_slop, CTLTYPE_INT|CTLFLAG_RW,
&tcp_rexmit_slop, 0, sysctl_msec_to_ticks, "I",
"Retransmission Timer Slop");
int tcp_always_keepalive = 1;
SYSCTL_INT(_net_inet_tcp, OID_AUTO, always_keepalive, CTLFLAG_RW,
&tcp_always_keepalive , 0, "Assume SO_KEEPALIVE on all TCP connections");
int tcp_fast_finwait2_recycle = 0;
SYSCTL_INT(_net_inet_tcp, OID_AUTO, fast_finwait2_recycle, CTLFLAG_RW,
&tcp_fast_finwait2_recycle, 0,
"Recycle closed FIN_WAIT_2 connections faster");
int tcp_finwait2_timeout;
SYSCTL_PROC(_net_inet_tcp, OID_AUTO, finwait2_timeout, CTLTYPE_INT|CTLFLAG_RW,
&tcp_finwait2_timeout, 0, sysctl_msec_to_ticks, "I", "FIN-WAIT2 timeout");
int tcp_keepcnt = TCPTV_KEEPCNT;
SYSCTL_INT(_net_inet_tcp, OID_AUTO, keepcnt, CTLFLAG_RW, &tcp_keepcnt, 0,
"Number of keepalive probes to send");
/* max idle probes */
int tcp_maxpersistidle;
static int tcp_rexmit_drop_options = 0;
SYSCTL_INT(_net_inet_tcp, OID_AUTO, rexmit_drop_options, CTLFLAG_RW,
&tcp_rexmit_drop_options, 0,
"Drop TCP options from 3rd and later retransmitted SYN");
VNET_DEFINE(int, tcp_pmtud_blackhole_detect);
SYSCTL_INT(_net_inet_tcp, OID_AUTO, pmtud_blackhole_detection,
CTLFLAG_RW|CTLFLAG_VNET,
&VNET_NAME(tcp_pmtud_blackhole_detect), 0,
"Path MTU Discovery Black Hole Detection Enabled");
#ifdef INET
VNET_DEFINE(int, tcp_pmtud_blackhole_mss) = 1200;
SYSCTL_INT(_net_inet_tcp, OID_AUTO, pmtud_blackhole_mss,
CTLFLAG_RW|CTLFLAG_VNET,
&VNET_NAME(tcp_pmtud_blackhole_mss), 0,
"Path MTU Discovery Black Hole Detection lowered MSS");
#endif
#ifdef INET6
VNET_DEFINE(int, tcp_v6pmtud_blackhole_mss) = 1220;
SYSCTL_INT(_net_inet_tcp, OID_AUTO, v6pmtud_blackhole_mss,
CTLFLAG_RW|CTLFLAG_VNET,
&VNET_NAME(tcp_v6pmtud_blackhole_mss), 0,
"Path MTU Discovery IPv6 Black Hole Detection lowered MSS");
#endif
#ifdef RSS
static int per_cpu_timers = 1;
#else
static int per_cpu_timers = 0;
#endif
SYSCTL_INT(_net_inet_tcp, OID_AUTO, per_cpu_timers, CTLFLAG_RW,
&per_cpu_timers , 0, "run tcp timers on all cpus");
#if 0
#define INP_CPU(inp) (per_cpu_timers ? (!CPU_ABSENT(((inp)->inp_flowid % (mp_maxid+1))) ? \
((inp)->inp_flowid % (mp_maxid+1)) : curcpu) : 0)
#endif
/*
* Map the given inp to a CPU id.
*
* This queries RSS if it's compiled in, else it defaults to the current
* CPU ID.
*/
static inline int
inp_to_cpuid(struct inpcb *inp)
{
u_int cpuid;
#ifdef RSS
if (per_cpu_timers) {
cpuid = rss_hash2cpuid(inp->inp_flowid, inp->inp_flowtype);
if (cpuid == NETISR_CPUID_NONE)
return (curcpu); /* XXX */
else
return (cpuid);
}
#else
/* Legacy, pre-RSS behaviour */
if (per_cpu_timers) {
/*
* We don't have a flowid -> cpuid mapping, so cheat and
* just map unknown cpuids to curcpu. Not the best, but
* apparently better than defaulting to swi 0.
*/
cpuid = inp->inp_flowid % (mp_maxid + 1);
if (! CPU_ABSENT(cpuid))
return (cpuid);
return (curcpu);
}
#endif
/* Default for RSS and non-RSS - cpuid 0 */
else {
return (0);
}
}
/*
* Tcp protocol timeout routine called every 500 ms.
* Updates timestamps used for TCP
* causes finite state machine actions if timers expire.
*/
void
tcp_slowtimo(void)
{
VNET_ITERATOR_DECL(vnet_iter);
VNET_LIST_RLOCK_NOSLEEP();
VNET_FOREACH(vnet_iter) {
CURVNET_SET(vnet_iter);
(void) tcp_tw_2msl_scan(0);
CURVNET_RESTORE();
}
VNET_LIST_RUNLOCK_NOSLEEP();
}
int tcp_syn_backoff[TCP_MAXRXTSHIFT + 1] =
{ 1, 1, 1, 1, 1, 2, 4, 8, 16, 32, 64, 64, 64 };
int tcp_backoff[TCP_MAXRXTSHIFT + 1] =
{ 1, 2, 4, 8, 16, 32, 64, 128, 256, 512, 512, 512, 512 };
static int tcp_totbackoff = 2559; /* sum of tcp_backoff[] */
/*
* TCP timer processing.
*/
void
tcp_timer_delack(void *xtp)
{
struct tcpcb *tp = xtp;
struct inpcb *inp;
CURVNET_SET(tp->t_vnet);
inp = tp->t_inpcb;
KASSERT(inp != NULL, ("%s: tp %p tp->t_inpcb == NULL", __func__, tp));
INP_WLOCK(inp);
if (callout_pending(&tp->t_timers->tt_delack) ||
!callout_active(&tp->t_timers->tt_delack)) {
INP_WUNLOCK(inp);
CURVNET_RESTORE();
return;
}
callout_deactivate(&tp->t_timers->tt_delack);
if ((inp->inp_flags & INP_DROPPED) != 0) {
INP_WUNLOCK(inp);
CURVNET_RESTORE();
return;
}
tp->t_flags |= TF_ACKNOW;
TCPSTAT_INC(tcps_delack);
(void) tp->t_fb->tfb_tcp_output(tp);
INP_WUNLOCK(inp);
CURVNET_RESTORE();
}
/*
* When a timer wants to remove a TCB it must
* hold the INP_INFO_RLOCK(). The timer function
* should only have grabbed the INP_WLOCK() when
* it entered. To safely switch to holding both the
* INP_INFO_RLOCK() and the INP_WLOCK() we must first
* grab a reference on the inp, which will hold the inp
* so that it can't be removed. We then unlock the INP_WLOCK(),
* and grab the INP_INFO_RLOCK() lock. Once we have the INP_INFO_RLOCK()
* we proceed again to get the INP_WLOCK() (this preserves proper
* lock order). After acquiring the INP_WLOCK we must check if someone
* else deleted the pcb i.e. the inp_flags check.
* If so we return 1 otherwise we return 0.
*
* No matter what the tcp_inpinfo_lock_add() function
* returns the caller must afterwards call tcp_inpinfo_lock_del()
* to drop the locks and reference properly.
*/
int
tcp_inpinfo_lock_add(struct inpcb *inp)
{
in_pcbref(inp);
INP_WUNLOCK(inp);
INP_INFO_RLOCK(&V_tcbinfo);
INP_WLOCK(inp);
if (inp->inp_flags & (INP_TIMEWAIT | INP_DROPPED)) {
return(1);
}
return(0);
}
void
tcp_inpinfo_lock_del(struct inpcb *inp, struct tcpcb *tp)
{
INP_INFO_RUNLOCK(&V_tcbinfo);
if (inp && (tp == NULL)) {
/*
* If tcp_close/drop() gets called and tp
* returns NULL, then the function dropped
* the inp lock, we hold a reference keeping
* this around, so we must re-aquire the
* INP_WLOCK() in order to proceed with
* our dropping the inp reference.
*/
INP_WLOCK(inp);
}
if (inp && in_pcbrele_wlocked(inp) == 0)
INP_WUNLOCK(inp);
}
void
tcp_timer_2msl(void *xtp)
{
struct tcpcb *tp = xtp;
struct inpcb *inp;
CURVNET_SET(tp->t_vnet);
#ifdef TCPDEBUG
int ostate;
ostate = tp->t_state;
#endif
inp = tp->t_inpcb;
KASSERT(inp != NULL, ("%s: tp %p tp->t_inpcb == NULL", __func__, tp));
INP_WLOCK(inp);
tcp_free_sackholes(tp);
if (callout_pending(&tp->t_timers->tt_2msl) ||
!callout_active(&tp->t_timers->tt_2msl)) {
INP_WUNLOCK(tp->t_inpcb);
CURVNET_RESTORE();
return;
}
callout_deactivate(&tp->t_timers->tt_2msl);
if ((inp->inp_flags & INP_DROPPED) != 0) {
INP_WUNLOCK(inp);
CURVNET_RESTORE();
return;
}
KASSERT((tp->t_timers->tt_flags & TT_STOPPED) == 0,
("%s: tp %p tcpcb can't be stopped here", __func__, tp));
/*
* 2 MSL timeout in shutdown went off. If we're closed but
* still waiting for peer to close and connection has been idle
* too long delete connection control block. Otherwise, check
* again in a bit.
*
* If in TIME_WAIT state just ignore as this timeout is handled in
* tcp_tw_2msl_scan().
*
* If fastrecycle of FIN_WAIT_2, in FIN_WAIT_2 and receiver has closed,
* there's no point in hanging onto FIN_WAIT_2 socket. Just close it.
* Ignore fact that there were recent incoming segments.
*/
if ((inp->inp_flags & INP_TIMEWAIT) != 0) {
INP_WUNLOCK(inp);
CURVNET_RESTORE();
return;
}
if (tcp_fast_finwait2_recycle && tp->t_state == TCPS_FIN_WAIT_2 &&
tp->t_inpcb && tp->t_inpcb->inp_socket &&
(tp->t_inpcb->inp_socket->so_rcv.sb_state & SBS_CANTRCVMORE)) {
TCPSTAT_INC(tcps_finwait2_drops);
if (tcp_inpinfo_lock_add(inp)) {
tcp_inpinfo_lock_del(inp, tp);
goto out;
}
tp = tcp_close(tp);
tcp_inpinfo_lock_del(inp, tp);
goto out;
} else {
if (ticks - tp->t_rcvtime <= TP_MAXIDLE(tp)) {
callout_reset(&tp->t_timers->tt_2msl,
TP_KEEPINTVL(tp), tcp_timer_2msl, tp);
} else {
if (tcp_inpinfo_lock_add(inp)) {
tcp_inpinfo_lock_del(inp, tp);
goto out;
}
tp = tcp_close(tp);
tcp_inpinfo_lock_del(inp, tp);
goto out;
}
}
#ifdef TCPDEBUG
if (tp != NULL && (tp->t_inpcb->inp_socket->so_options & SO_DEBUG))
tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0,
PRU_SLOWTIMO);
#endif
TCP_PROBE2(debug__user, tp, PRU_SLOWTIMO);
if (tp != NULL)
INP_WUNLOCK(inp);
out:
CURVNET_RESTORE();
}
void
tcp_timer_keep(void *xtp)
{
struct tcpcb *tp = xtp;
struct tcptemp *t_template;
struct inpcb *inp;
CURVNET_SET(tp->t_vnet);
#ifdef TCPDEBUG
int ostate;
ostate = tp->t_state;
#endif
inp = tp->t_inpcb;
KASSERT(inp != NULL, ("%s: tp %p tp->t_inpcb == NULL", __func__, tp));
INP_WLOCK(inp);
if (callout_pending(&tp->t_timers->tt_keep) ||
!callout_active(&tp->t_timers->tt_keep)) {
INP_WUNLOCK(inp);
CURVNET_RESTORE();
return;
}
callout_deactivate(&tp->t_timers->tt_keep);
if ((inp->inp_flags & INP_DROPPED) != 0) {
INP_WUNLOCK(inp);
CURVNET_RESTORE();
return;
}
KASSERT((tp->t_timers->tt_flags & TT_STOPPED) == 0,
("%s: tp %p tcpcb can't be stopped here", __func__, tp));
/*
* Because we don't regularly reset the keepalive callout in
* the ESTABLISHED state, it may be that we don't actually need
* to send a keepalive yet. If that occurs, schedule another
* call for the next time the keepalive timer might expire.
*/
if (TCPS_HAVEESTABLISHED(tp->t_state)) {
u_int idletime;
idletime = ticks - tp->t_rcvtime;
if (idletime < TP_KEEPIDLE(tp)) {
callout_reset(&tp->t_timers->tt_keep,
TP_KEEPIDLE(tp) - idletime, tcp_timer_keep, tp);
INP_WUNLOCK(inp);
CURVNET_RESTORE();
return;
}
}
/*
* Keep-alive timer went off; send something
* or drop connection if idle for too long.
*/
TCPSTAT_INC(tcps_keeptimeo);
if (tp->t_state < TCPS_ESTABLISHED)
goto dropit;
if ((tcp_always_keepalive ||
inp->inp_socket->so_options & SO_KEEPALIVE) &&
tp->t_state <= TCPS_CLOSING) {
if (ticks - tp->t_rcvtime >= TP_KEEPIDLE(tp) + TP_MAXIDLE(tp))
goto dropit;
/*
* Send a packet designed to force a response
* if the peer is up and reachable:
* either an ACK if the connection is still alive,
* or an RST if the peer has closed the connection
* due to timeout or reboot.
* Using sequence number tp->snd_una-1
* causes the transmitted zero-length segment
* to lie outside the receive window;
* by the protocol spec, this requires the
* correspondent TCP to respond.
*/
TCPSTAT_INC(tcps_keepprobe);
t_template = tcpip_maketemplate(inp);
if (t_template) {
tcp_respond(tp, t_template->tt_ipgen,
&t_template->tt_t, (struct mbuf *)NULL,
tp->rcv_nxt, tp->snd_una - 1, 0);
free(t_template, M_TEMP);
}
callout_reset(&tp->t_timers->tt_keep, TP_KEEPINTVL(tp),
tcp_timer_keep, tp);
} else
callout_reset(&tp->t_timers->tt_keep, TP_KEEPIDLE(tp),
tcp_timer_keep, tp);
#ifdef TCPDEBUG
if (inp->inp_socket->so_options & SO_DEBUG)
tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0,
PRU_SLOWTIMO);
#endif
TCP_PROBE2(debug__user, tp, PRU_SLOWTIMO);
INP_WUNLOCK(inp);
CURVNET_RESTORE();
return;
dropit:
TCPSTAT_INC(tcps_keepdrops);
if (tcp_inpinfo_lock_add(inp)) {
tcp_inpinfo_lock_del(inp, tp);
goto out;
}
tp = tcp_drop(tp, ETIMEDOUT);
#ifdef TCPDEBUG
if (tp != NULL && (tp->t_inpcb->inp_socket->so_options & SO_DEBUG))
tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0,
PRU_SLOWTIMO);
#endif
TCP_PROBE2(debug__user, tp, PRU_SLOWTIMO);
tcp_inpinfo_lock_del(inp, tp);
out:
CURVNET_RESTORE();
}
void
tcp_timer_persist(void *xtp)
{
struct tcpcb *tp = xtp;
struct inpcb *inp;
CURVNET_SET(tp->t_vnet);
#ifdef TCPDEBUG
int ostate;
ostate = tp->t_state;
#endif
inp = tp->t_inpcb;
KASSERT(inp != NULL, ("%s: tp %p tp->t_inpcb == NULL", __func__, tp));
INP_WLOCK(inp);
if (callout_pending(&tp->t_timers->tt_persist) ||
!callout_active(&tp->t_timers->tt_persist)) {
INP_WUNLOCK(inp);
CURVNET_RESTORE();
return;
}
callout_deactivate(&tp->t_timers->tt_persist);
if ((inp->inp_flags & INP_DROPPED) != 0) {
INP_WUNLOCK(inp);
CURVNET_RESTORE();
return;
}
KASSERT((tp->t_timers->tt_flags & TT_STOPPED) == 0,
("%s: tp %p tcpcb can't be stopped here", __func__, tp));
/*
* Persistence timer into zero window.
* Force a byte to be output, if possible.
*/
TCPSTAT_INC(tcps_persisttimeo);
/*
* Hack: if the peer is dead/unreachable, we do not
* time out if the window is closed. After a full
* backoff, drop the connection if the idle time
* (no responses to probes) reaches the maximum
* backoff that we would use if retransmitting.
*/
if (tp->t_rxtshift == TCP_MAXRXTSHIFT &&
(ticks - tp->t_rcvtime >= tcp_maxpersistidle ||
ticks - tp->t_rcvtime >= TCP_REXMTVAL(tp) * tcp_totbackoff)) {
TCPSTAT_INC(tcps_persistdrop);
if (tcp_inpinfo_lock_add(inp)) {
tcp_inpinfo_lock_del(inp, tp);
goto out;
}
tp = tcp_drop(tp, ETIMEDOUT);
tcp_inpinfo_lock_del(inp, tp);
goto out;
}
/*
* If the user has closed the socket then drop a persisting
* connection after a much reduced timeout.
*/
if (tp->t_state > TCPS_CLOSE_WAIT &&
(ticks - tp->t_rcvtime) >= TCPTV_PERSMAX) {
TCPSTAT_INC(tcps_persistdrop);
if (tcp_inpinfo_lock_add(inp)) {
tcp_inpinfo_lock_del(inp, tp);
goto out;
}
tp = tcp_drop(tp, ETIMEDOUT);
tcp_inpinfo_lock_del(inp, tp);
goto out;
}
tcp_setpersist(tp);
tp->t_flags |= TF_FORCEDATA;
(void) tp->t_fb->tfb_tcp_output(tp);
tp->t_flags &= ~TF_FORCEDATA;
#ifdef TCPDEBUG
if (tp != NULL && tp->t_inpcb->inp_socket->so_options & SO_DEBUG)
tcp_trace(TA_USER, ostate, tp, NULL, NULL, PRU_SLOWTIMO);
#endif
TCP_PROBE2(debug__user, tp, PRU_SLOWTIMO);
INP_WUNLOCK(inp);
out:
CURVNET_RESTORE();
}
void
tcp_timer_rexmt(void * xtp)
{
struct tcpcb *tp = xtp;
CURVNET_SET(tp->t_vnet);
int rexmt;
struct inpcb *inp;
#ifdef TCPDEBUG
int ostate;
ostate = tp->t_state;
#endif
inp = tp->t_inpcb;
KASSERT(inp != NULL, ("%s: tp %p tp->t_inpcb == NULL", __func__, tp));
INP_WLOCK(inp);
if (callout_pending(&tp->t_timers->tt_rexmt) ||
!callout_active(&tp->t_timers->tt_rexmt)) {
INP_WUNLOCK(inp);
CURVNET_RESTORE();
return;
}
callout_deactivate(&tp->t_timers->tt_rexmt);
if ((inp->inp_flags & INP_DROPPED) != 0) {
INP_WUNLOCK(inp);
CURVNET_RESTORE();
return;
}
KASSERT((tp->t_timers->tt_flags & TT_STOPPED) == 0,
("%s: tp %p tcpcb can't be stopped here", __func__, tp));
tcp_free_sackholes(tp);
TCP_LOG_EVENT(tp, NULL, NULL, NULL, TCP_LOG_RTO, 0, 0, NULL, false);
if (tp->t_fb->tfb_tcp_rexmit_tmr) {
/* The stack has a timer action too. */
(*tp->t_fb->tfb_tcp_rexmit_tmr)(tp);
}
/*
* Retransmission timer went off. Message has not
* been acked within retransmit interval. Back off
* to a longer retransmit interval and retransmit one segment.
*/
if (++tp->t_rxtshift > TCP_MAXRXTSHIFT) {
tp->t_rxtshift = TCP_MAXRXTSHIFT;
TCPSTAT_INC(tcps_timeoutdrop);
if (tcp_inpinfo_lock_add(inp)) {
tcp_inpinfo_lock_del(inp, tp);
goto out;
}
tp = tcp_drop(tp, ETIMEDOUT);
tcp_inpinfo_lock_del(inp, tp);
goto out;
}
if (tp->t_state == TCPS_SYN_SENT) {
/*
* If the SYN was retransmitted, indicate CWND to be
* limited to 1 segment in cc_conn_init().
*/
tp->snd_cwnd = 1;
} else if (tp->t_rxtshift == 1) {
/*
* first retransmit; record ssthresh and cwnd so they can
* be recovered if this turns out to be a "bad" retransmit.
* A retransmit is considered "bad" if an ACK for this
* segment is received within RTT/2 interval; the assumption
* here is that the ACK was already in flight. See
* "On Estimating End-to-End Network Path Properties" by
* Allman and Paxson for more details.
*/
tp->snd_cwnd_prev = tp->snd_cwnd;
tp->snd_ssthresh_prev = tp->snd_ssthresh;
tp->snd_recover_prev = tp->snd_recover;
if (IN_FASTRECOVERY(tp->t_flags))
tp->t_flags |= TF_WASFRECOVERY;
else
tp->t_flags &= ~TF_WASFRECOVERY;
if (IN_CONGRECOVERY(tp->t_flags))
tp->t_flags |= TF_WASCRECOVERY;
else
tp->t_flags &= ~TF_WASCRECOVERY;
if ((tp->t_flags & TF_RCVD_TSTMP) == 0)
tp->t_badrxtwin = ticks + (tp->t_srtt >> (TCP_RTT_SHIFT + 1));
/* In the event that we've negotiated timestamps
* badrxtwin will be set to the value that we set
* the retransmitted packet's to_tsval to by tcp_output
*/
tp->t_flags |= TF_PREVVALID;
} else
tp->t_flags &= ~TF_PREVVALID;
TCPSTAT_INC(tcps_rexmttimeo);
if ((tp->t_state == TCPS_SYN_SENT) ||
(tp->t_state == TCPS_SYN_RECEIVED))
rexmt = TCPTV_RTOBASE * tcp_syn_backoff[tp->t_rxtshift];
else
rexmt = TCP_REXMTVAL(tp) * tcp_backoff[tp->t_rxtshift];
TCPT_RANGESET(tp->t_rxtcur, rexmt,
tp->t_rttmin, TCPTV_REXMTMAX);
/*
* We enter the path for PLMTUD if connection is established or, if
* connection is FIN_WAIT_1 status, reason for the last is that if
* amount of data we send is very small, we could send it in couple of
* packets and process straight to FIN. In that case we won't catch
* ESTABLISHED state.
*/
if (V_tcp_pmtud_blackhole_detect && (((tp->t_state == TCPS_ESTABLISHED))
|| (tp->t_state == TCPS_FIN_WAIT_1))) {
#ifdef INET6
int isipv6;
#endif
/*
* Idea here is that at each stage of mtu probe (usually, 1448
* -> 1188 -> 524) should be given 2 chances to recover before
* further clamping down. 'tp->t_rxtshift % 2 == 0' should
* take care of that.
*/
if (((tp->t_flags2 & (TF2_PLPMTU_PMTUD|TF2_PLPMTU_MAXSEGSNT)) ==
(TF2_PLPMTU_PMTUD|TF2_PLPMTU_MAXSEGSNT)) &&
(tp->t_rxtshift >= 2 && tp->t_rxtshift < 6 &&
tp->t_rxtshift % 2 == 0)) {
/*
* Enter Path MTU Black-hole Detection mechanism:
* - Disable Path MTU Discovery (IP "DF" bit).
* - Reduce MTU to lower value than what we
* negotiated with peer.
*/
if ((tp->t_flags2 & TF2_PLPMTU_BLACKHOLE) == 0) {
/* Record that we may have found a black hole. */
tp->t_flags2 |= TF2_PLPMTU_BLACKHOLE;
/* Keep track of previous MSS. */
tp->t_pmtud_saved_maxseg = tp->t_maxseg;
}
/*
* Reduce the MSS to blackhole value or to the default
* in an attempt to retransmit.
*/
#ifdef INET6
isipv6 = (tp->t_inpcb->inp_vflag & INP_IPV6) ? 1 : 0;
if (isipv6 &&
tp->t_maxseg > V_tcp_v6pmtud_blackhole_mss) {
/* Use the sysctl tuneable blackhole MSS. */
tp->t_maxseg = V_tcp_v6pmtud_blackhole_mss;
TCPSTAT_INC(tcps_pmtud_blackhole_activated);
} else if (isipv6) {
/* Use the default MSS. */
tp->t_maxseg = V_tcp_v6mssdflt;
/*
* Disable Path MTU Discovery when we switch to
* minmss.
*/
tp->t_flags2 &= ~TF2_PLPMTU_PMTUD;
TCPSTAT_INC(tcps_pmtud_blackhole_activated_min_mss);
}
#endif
#if defined(INET6) && defined(INET)
else
#endif
#ifdef INET
if (tp->t_maxseg > V_tcp_pmtud_blackhole_mss) {
/* Use the sysctl tuneable blackhole MSS. */
tp->t_maxseg = V_tcp_pmtud_blackhole_mss;
TCPSTAT_INC(tcps_pmtud_blackhole_activated);
} else {
/* Use the default MSS. */
tp->t_maxseg = V_tcp_mssdflt;
/*
* Disable Path MTU Discovery when we switch to
* minmss.
*/
tp->t_flags2 &= ~TF2_PLPMTU_PMTUD;
TCPSTAT_INC(tcps_pmtud_blackhole_activated_min_mss);
}
#endif
/*
* Reset the slow-start flight size
* as it may depend on the new MSS.
*/
if (CC_ALGO(tp)->conn_init != NULL)
CC_ALGO(tp)->conn_init(tp->ccv);
} else {
/*
* If further retransmissions are still unsuccessful
* with a lowered MTU, maybe this isn't a blackhole and
* we restore the previous MSS and blackhole detection
* flags.
* The limit '6' is determined by giving each probe
* stage (1448, 1188, 524) 2 chances to recover.
*/
if ((tp->t_flags2 & TF2_PLPMTU_BLACKHOLE) &&
(tp->t_rxtshift >= 6)) {
tp->t_flags2 |= TF2_PLPMTU_PMTUD;
tp->t_flags2 &= ~TF2_PLPMTU_BLACKHOLE;
tp->t_maxseg = tp->t_pmtud_saved_maxseg;
TCPSTAT_INC(tcps_pmtud_blackhole_failed);
/*
* Reset the slow-start flight size as it
* may depend on the new MSS.
*/
if (CC_ALGO(tp)->conn_init != NULL)
CC_ALGO(tp)->conn_init(tp->ccv);
}
}
}
/*
* Disable RFC1323 and SACK if we haven't got any response to
* our third SYN to work-around some broken terminal servers
* (most of which have hopefully been retired) that have bad VJ
* header compression code which trashes TCP segments containing
* unknown-to-them TCP options.
*/
if (tcp_rexmit_drop_options && (tp->t_state == TCPS_SYN_SENT) &&
(tp->t_rxtshift == 3))
tp->t_flags &= ~(TF_REQ_SCALE|TF_REQ_TSTMP|TF_SACK_PERMIT);
/*
* If we backed off this far, notify the L3 protocol that we're having
* connection problems.
*/
if (tp->t_rxtshift > TCP_RTT_INVALIDATE) {
#ifdef INET6
if ((tp->t_inpcb->inp_vflag & INP_IPV6) != 0)
in6_losing(tp->t_inpcb);
else
#endif
in_losing(tp->t_inpcb);
}
tp->snd_nxt = tp->snd_una;
tp->snd_recover = tp->snd_max;
/*
* Force a segment to be sent.
*/
tp->t_flags |= TF_ACKNOW;
/*
* If timing a segment in this window, stop the timer.
*/
tp->t_rtttime = 0;
cc_cong_signal(tp, NULL, CC_RTO);
(void) tp->t_fb->tfb_tcp_output(tp);
#ifdef TCPDEBUG
if (tp != NULL && (tp->t_inpcb->inp_socket->so_options & SO_DEBUG))
tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0,
PRU_SLOWTIMO);
#endif
TCP_PROBE2(debug__user, tp, PRU_SLOWTIMO);
INP_WUNLOCK(inp);
out:
CURVNET_RESTORE();
}
void
tcp_timer_activate(struct tcpcb *tp, uint32_t timer_type, u_int delta)
{
struct callout *t_callout;
timeout_t *f_callout;
struct inpcb *inp = tp->t_inpcb;
int cpu = inp_to_cpuid(inp);
#ifdef TCP_OFFLOAD
if (tp->t_flags & TF_TOE)
return;
#endif
if (tp->t_timers->tt_flags & TT_STOPPED)
return;
switch (timer_type) {
case TT_DELACK:
t_callout = &tp->t_timers->tt_delack;
f_callout = tcp_timer_delack;
break;
case TT_REXMT:
t_callout = &tp->t_timers->tt_rexmt;
f_callout = tcp_timer_rexmt;
break;
case TT_PERSIST:
t_callout = &tp->t_timers->tt_persist;
f_callout = tcp_timer_persist;
break;
case TT_KEEP:
t_callout = &tp->t_timers->tt_keep;
f_callout = tcp_timer_keep;
break;
case TT_2MSL:
t_callout = &tp->t_timers->tt_2msl;
f_callout = tcp_timer_2msl;
break;
default:
if (tp->t_fb->tfb_tcp_timer_activate) {
tp->t_fb->tfb_tcp_timer_activate(tp, timer_type, delta);
return;
}
panic("tp %p bad timer_type %#x", tp, timer_type);
}
if (delta == 0) {
callout_stop(t_callout);
} else {
callout_reset_on(t_callout, delta, f_callout, tp, cpu);
}
}
int
tcp_timer_active(struct tcpcb *tp, uint32_t timer_type)
{
struct callout *t_callout;
switch (timer_type) {
case TT_DELACK:
t_callout = &tp->t_timers->tt_delack;
break;
case TT_REXMT:
t_callout = &tp->t_timers->tt_rexmt;
break;
case TT_PERSIST:
t_callout = &tp->t_timers->tt_persist;
break;
case TT_KEEP:
t_callout = &tp->t_timers->tt_keep;
break;
case TT_2MSL:
t_callout = &tp->t_timers->tt_2msl;
break;
default:
if (tp->t_fb->tfb_tcp_timer_active) {
return(tp->t_fb->tfb_tcp_timer_active(tp, timer_type));
}
panic("tp %p bad timer_type %#x", tp, timer_type);
}
return callout_active(t_callout);
}
void
tcp_timer_stop(struct tcpcb *tp, uint32_t timer_type)
{
struct callout *t_callout;
tp->t_timers->tt_flags |= TT_STOPPED;
switch (timer_type) {
case TT_DELACK:
t_callout = &tp->t_timers->tt_delack;
break;
case TT_REXMT:
t_callout = &tp->t_timers->tt_rexmt;
break;
case TT_PERSIST:
t_callout = &tp->t_timers->tt_persist;
break;
case TT_KEEP:
t_callout = &tp->t_timers->tt_keep;
break;
case TT_2MSL:
t_callout = &tp->t_timers->tt_2msl;
break;
default:
if (tp->t_fb->tfb_tcp_timer_stop) {
/*
* XXXrrs we need to look at this with the
* stop case below (flags).
*/
tp->t_fb->tfb_tcp_timer_stop(tp, timer_type);
return;
}
panic("tp %p bad timer_type %#x", tp, timer_type);
}
if (callout_async_drain(t_callout, tcp_timer_discard) == 0) {
/*
* Can't stop the callout, defer tcpcb actual deletion
* to the last one. We do this using the async drain
* function and incrementing the count in
*/
tp->t_timers->tt_draincnt++;
}
}