/*- * 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. * 4. 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 * $FreeBSD$ */ #include "opt_inet6.h" #include "opt_tcpdebug.h" #include "opt_tcp_sack.h" #include #include #include #include #include #include #include #include #include #include #include #include #include #include #ifdef INET6 #include #endif #include #include #include #include #include #include #ifdef TCPDEBUG #include #endif int tcp_keepinit; SYSCTL_PROC(_net_inet_tcp, TCPCTL_KEEPINIT, keepinit, CTLTYPE_INT|CTLFLAG_RW, &tcp_keepinit, 0, sysctl_msec_to_ticks, "I", ""); int tcp_keepidle; SYSCTL_PROC(_net_inet_tcp, TCPCTL_KEEPIDLE, keepidle, CTLTYPE_INT|CTLFLAG_RW, &tcp_keepidle, 0, sysctl_msec_to_ticks, "I", ""); int tcp_keepintvl; SYSCTL_PROC(_net_inet_tcp, TCPCTL_KEEPINTVL, keepintvl, CTLTYPE_INT|CTLFLAG_RW, &tcp_keepintvl, 0, sysctl_msec_to_ticks, "I", ""); 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"); static int always_keepalive = 1; SYSCTL_INT(_net_inet_tcp, OID_AUTO, always_keepalive, CTLFLAG_RW, &always_keepalive , 0, "Assume SO_KEEPALIVE on all TCP connections"); static int tcp_keepcnt = TCPTV_KEEPCNT; /* max idle probes */ int tcp_maxpersistidle; /* max idle time in persist */ int tcp_maxidle; /* * Tcp protocol timeout routine called every 500 ms. * Updates timestamps used for TCP * causes finite state machine actions if timers expire. */ void tcp_slowtimo() { tcp_maxidle = tcp_keepcnt * tcp_keepintvl; INP_INFO_WLOCK(&tcbinfo); (void) tcp_timer_2msl_tw(0); INP_INFO_WUNLOCK(&tcbinfo); } 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[] */ static int tcp_timer_race; SYSCTL_INT(_net_inet_tcp, OID_AUTO, timer_race, CTLFLAG_RD, &tcp_timer_race, 0, "Count of t_inpcb races on tcp_discardcb"); /* * TCP timer processing. */ void tcp_timer_delack(xtp) void *xtp; { struct tcpcb *tp = xtp; struct inpcb *inp; INP_INFO_RLOCK(&tcbinfo); inp = tp->t_inpcb; /* * XXXRW: While this assert is in fact correct, bugs in the tcpcb * tear-down mean we need it as a work-around for races between * timers and tcp_discardcb(). * * KASSERT(inp != NULL, ("tcp_timer_delack: inp == NULL")); */ if (inp == NULL) { tcp_timer_race++; INP_INFO_RUNLOCK(&tcbinfo); return; } INP_LOCK(inp); INP_INFO_RUNLOCK(&tcbinfo); if (callout_pending(tp->tt_delack) || !callout_active(tp->tt_delack)) { INP_UNLOCK(inp); return; } callout_deactivate(tp->tt_delack); tp->t_flags |= TF_ACKNOW; tcpstat.tcps_delack++; (void) tcp_output(tp); INP_UNLOCK(inp); } void tcp_timer_2msl(xtp) void *xtp; { struct tcpcb *tp = xtp; struct inpcb *inp; #ifdef TCPDEBUG int ostate; ostate = tp->t_state; #endif /* * XXXRW: Does this actually happen? */ INP_INFO_WLOCK(&tcbinfo); inp = tp->t_inpcb; /* * XXXRW: While this assert is in fact correct, bugs in the tcpcb * tear-down mean we need it as a work-around for races between * timers and tcp_discardcb(). * * KASSERT(inp != NULL, ("tcp_timer_2msl: inp == NULL")); */ if (inp == NULL) { tcp_timer_race++; INP_INFO_RUNLOCK(&tcbinfo); return; } INP_LOCK(inp); tcp_free_sackholes(tp); if (callout_pending(tp->tt_2msl) || !callout_active(tp->tt_2msl)) { INP_UNLOCK(tp->t_inpcb); INP_INFO_WUNLOCK(&tcbinfo); return; } callout_deactivate(tp->tt_2msl); /* * 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, or if 2MSL time is up from TIME_WAIT, delete connection * control block. Otherwise, check again in a bit. */ if (tp->t_state != TCPS_TIME_WAIT && (ticks - tp->t_rcvtime) <= tcp_maxidle) callout_reset(tp->tt_2msl, tcp_keepintvl, tcp_timer_2msl, tp); else tp = tcp_close(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 if (tp != NULL) INP_UNLOCK(inp); INP_INFO_WUNLOCK(&tcbinfo); } /* * The timed wait lists contain references to each of the TCP sessions * currently TIME_WAIT state. The list pointers, including the list pointers * in each tcptw structure, are protected using the global tcbinfo lock, * which must be held over list iteration and modification. */ struct twlist { LIST_HEAD(, tcptw) tw_list; struct tcptw tw_tail; }; #define TWLIST_NLISTS 2 static struct twlist twl_2msl[TWLIST_NLISTS]; static struct twlist *tw_2msl_list[] = { &twl_2msl[0], &twl_2msl[1], NULL }; void tcp_timer_init(void) { int i; struct twlist *twl; for (i = 0; i < TWLIST_NLISTS; i++) { twl = &twl_2msl[i]; LIST_INIT(&twl->tw_list); LIST_INSERT_HEAD(&twl->tw_list, &twl->tw_tail, tw_2msl); } } void tcp_timer_2msl_reset(struct tcptw *tw, int timeo) { int i; struct tcptw *tw_tail; INP_INFO_WLOCK_ASSERT(&tcbinfo); INP_LOCK_ASSERT(tw->tw_inpcb); if (tw->tw_time != 0) LIST_REMOVE(tw, tw_2msl); tw->tw_time = timeo + ticks; i = timeo > tcp_msl ? 1 : 0; tw_tail = &twl_2msl[i].tw_tail; LIST_INSERT_BEFORE(tw_tail, tw, tw_2msl); } void tcp_timer_2msl_stop(struct tcptw *tw) { INP_INFO_WLOCK_ASSERT(&tcbinfo); if (tw->tw_time != 0) LIST_REMOVE(tw, tw_2msl); } struct tcptw * tcp_timer_2msl_tw(int reuse) { struct tcptw *tw, *tw_tail; struct twlist *twl; int i; INP_INFO_WLOCK_ASSERT(&tcbinfo); for (i = 0; i < 2; i++) { twl = tw_2msl_list[i]; tw_tail = &twl->tw_tail; tw = LIST_FIRST(&twl->tw_list); if (tw == tw_tail || (!reuse && tw->tw_time > ticks)) continue; INP_LOCK(tw->tw_inpcb); tcp_twclose(tw, reuse); return (reuse ? tw : NULL); } return (NULL); } void tcp_timer_keep(xtp) void *xtp; { struct tcpcb *tp = xtp; struct tcptemp *t_template; struct inpcb *inp; #ifdef TCPDEBUG int ostate; ostate = tp->t_state; #endif INP_INFO_WLOCK(&tcbinfo); inp = tp->t_inpcb; /* * XXXRW: While this assert is in fact correct, bugs in the tcpcb * tear-down mean we need it as a work-around for races between * timers and tcp_discardcb(). * * KASSERT(inp != NULL, ("tcp_timer_keep: inp == NULL")); */ if (inp == NULL) { tcp_timer_race++; INP_INFO_RUNLOCK(&tcbinfo); return; } INP_LOCK(inp); if (callout_pending(tp->tt_keep) || !callout_active(tp->tt_keep)) { INP_UNLOCK(inp); INP_INFO_WUNLOCK(&tcbinfo); return; } callout_deactivate(tp->tt_keep); /* * Keep-alive timer went off; send something * or drop connection if idle for too long. */ tcpstat.tcps_keeptimeo++; if (tp->t_state < TCPS_ESTABLISHED) goto dropit; if ((always_keepalive || inp->inp_socket->so_options & SO_KEEPALIVE) && tp->t_state <= TCPS_CLOSING) { if ((ticks - tp->t_rcvtime) >= tcp_keepidle + tcp_maxidle) 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.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); (void) m_free(dtom(t_template)); } callout_reset(tp->tt_keep, tcp_keepintvl, tcp_timer_keep, tp); } else callout_reset(tp->tt_keep, tcp_keepidle, 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 INP_UNLOCK(inp); INP_INFO_WUNLOCK(&tcbinfo); return; dropit: tcpstat.tcps_keepdrops++; 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 if (tp != NULL) INP_UNLOCK(tp->t_inpcb); INP_INFO_WUNLOCK(&tcbinfo); } void tcp_timer_persist(xtp) void *xtp; { struct tcpcb *tp = xtp; struct inpcb *inp; #ifdef TCPDEBUG int ostate; ostate = tp->t_state; #endif INP_INFO_WLOCK(&tcbinfo); inp = tp->t_inpcb; /* * XXXRW: While this assert is in fact correct, bugs in the tcpcb * tear-down mean we need it as a work-around for races between * timers and tcp_discardcb(). * * KASSERT(inp != NULL, ("tcp_timer_persist: inp == NULL")); */ if (inp == NULL) { tcp_timer_race++; INP_INFO_RUNLOCK(&tcbinfo); return; } INP_LOCK(inp); if (callout_pending(tp->tt_persist) || !callout_active(tp->tt_persist)){ INP_UNLOCK(inp); INP_INFO_WUNLOCK(&tcbinfo); return; } callout_deactivate(tp->tt_persist); /* * Persistance timer into zero window. * Force a byte to be output, if possible. */ tcpstat.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.tcps_persistdrop++; tp = tcp_drop(tp, ETIMEDOUT); goto out; } tcp_setpersist(tp); tp->t_flags |= TF_FORCEDATA; (void) tcp_output(tp); tp->t_flags &= ~TF_FORCEDATA; out: #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 if (tp != NULL) INP_UNLOCK(inp); INP_INFO_WUNLOCK(&tcbinfo); } void tcp_timer_rexmt(xtp) void *xtp; { struct tcpcb *tp = xtp; int rexmt; int headlocked; struct inpcb *inp; #ifdef TCPDEBUG int ostate; ostate = tp->t_state; #endif INP_INFO_WLOCK(&tcbinfo); headlocked = 1; inp = tp->t_inpcb; /* * XXXRW: While this assert is in fact correct, bugs in the tcpcb * tear-down mean we need it as a work-around for races between * timers and tcp_discardcb(). * * KASSERT(inp != NULL, ("tcp_timer_rexmt: inp == NULL")); */ if (inp == NULL) { tcp_timer_race++; INP_INFO_RUNLOCK(&tcbinfo); return; } INP_LOCK(inp); if (callout_pending(tp->tt_rexmt) || !callout_active(tp->tt_rexmt)) { INP_UNLOCK(inp); INP_INFO_WUNLOCK(&tcbinfo); return; } callout_deactivate(tp->tt_rexmt); tcp_free_sackholes(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.tcps_timeoutdrop++; tp = tcp_drop(tp, tp->t_softerror ? tp->t_softerror : ETIMEDOUT); goto out; } INP_INFO_WUNLOCK(&tcbinfo); headlocked = 0; 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)) tp->t_flags |= TF_WASFRECOVERY; else tp->t_flags &= ~TF_WASFRECOVERY; tp->t_badrxtwin = ticks + (tp->t_srtt >> (TCP_RTT_SHIFT + 1)); } tcpstat.tcps_rexmttimeo++; if (tp->t_state == TCPS_SYN_SENT) rexmt = TCP_REXMTVAL(tp) * 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); /* * Disable rfc1323 if we havn'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 ((tp->t_state == TCPS_SYN_SENT) && (tp->t_rxtshift == 3)) tp->t_flags &= ~(TF_REQ_SCALE|TF_REQ_TSTMP); /* * If we backed off this far, our srtt estimate is probably bogus. * Clobber it so we'll take the next rtt measurement as our srtt; * move the current srtt into rttvar to keep the current * retransmit times until then. */ if (tp->t_rxtshift > TCP_MAXRXTSHIFT / 4) { #ifdef INET6 if ((tp->t_inpcb->inp_vflag & INP_IPV6) != 0) in6_losing(tp->t_inpcb); else #endif tp->t_rttvar += (tp->t_srtt >> TCP_RTT_SHIFT); tp->t_srtt = 0; } 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; /* * Close the congestion window down to one segment * (we'll open it by one segment for each ack we get). * Since we probably have a window's worth of unacked * data accumulated, this "slow start" keeps us from * dumping all that data as back-to-back packets (which * might overwhelm an intermediate gateway). * * There are two phases to the opening: Initially we * open by one mss on each ack. This makes the window * size increase exponentially with time. If the * window is larger than the path can handle, this * exponential growth results in dropped packet(s) * almost immediately. To get more time between * drops but still "push" the network to take advantage * of improving conditions, we switch from exponential * to linear window opening at some threshhold size. * For a threshhold, we use half the current window * size, truncated to a multiple of the mss. * * (the minimum cwnd that will give us exponential * growth is 2 mss. We don't allow the threshhold * to go below this.) */ { u_int win = min(tp->snd_wnd, tp->snd_cwnd) / 2 / tp->t_maxseg; if (win < 2) win = 2; tp->snd_cwnd = tp->t_maxseg; tp->snd_ssthresh = win * tp->t_maxseg; tp->t_dupacks = 0; } EXIT_FASTRECOVERY(tp); (void) tcp_output(tp); 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 if (tp != NULL) INP_UNLOCK(inp); if (headlocked) INP_INFO_WUNLOCK(&tcbinfo); }