/* $NetBSD: tcp_timer.c,v 1.43 1998/09/10 10:47:00 mouse Exp $ */ /*- * Copyright (c) 1997, 1998 The NetBSD Foundation, Inc. * All rights reserved. * * This code is derived from software contributed to The NetBSD Foundation * by Jason R. Thorpe and Kevin M. Lahey of the Numerical Aerospace Simulation * Facility, NASA Ames Research Center. * * 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. All advertising materials mentioning features or use of this software * must display the following acknowledgement: * This product includes software developed by the NetBSD * Foundation, Inc. and its contributors. * 4. Neither the name of The NetBSD Foundation 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 NETBSD FOUNDATION, INC. 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 FOUNDATION 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. */ /* * 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. All advertising materials mentioning features or use of this software * must display the following acknowledgement: * This product includes software developed by the University of * California, Berkeley and its contributors. * 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 */ #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include int tcp_keepidle = TCPTV_KEEP_IDLE; int tcp_keepintvl = TCPTV_KEEPINTVL; int tcp_keepcnt = TCPTV_KEEPCNT; /* max idle probes */ int tcp_maxpersistidle = TCPTV_KEEP_IDLE; /* max idle time in persist */ int tcp_maxidle; struct tcp_delack_head tcp_delacks; /* * Fast timeout routine for processing delayed acks */ void tcp_fasttimo() { register struct tcpcb *tp, *ntp; int s; s = splsoftnet(); for (tp = tcp_delacks.lh_first; tp != NULL; tp = ntp) { /* * If tcp_output() can't transmit the ACK for whatever * reason, it will remain on the queue for the next * time the heartbeat ticks. */ ntp = tp->t_delack.le_next; tp->t_flags |= TF_ACKNOW; (void) tcp_output(tp); } splx(s); } /* * Tcp protocol timeout routine called every 500 ms. * Updates the timers in all active tcb's and * causes finite state machine actions if timers expire. */ void tcp_slowtimo() { register struct inpcb *inp, *ninp; register struct tcpcb *tp; int s; register long i; static int syn_cache_last = 0; s = splsoftnet(); tcp_maxidle = tcp_keepcnt * tcp_keepintvl; /* * Search through tcb's and update active timers. */ inp = tcbtable.inpt_queue.cqh_first; if (inp == (struct inpcb *)0) { /* XXX */ splx(s); return; } for (; inp != (struct inpcb *)&tcbtable.inpt_queue; inp = ninp) { ninp = inp->inp_queue.cqe_next; tp = intotcpcb(inp); if (tp == 0 || tp->t_state == TCPS_LISTEN) continue; for (i = 0; i < TCPT_NTIMERS; i++) { if (TCP_TIMER_ISEXPIRED(tp, i)) { TCP_TIMER_DISARM(tp, i); (void) tcp_usrreq(tp->t_inpcb->inp_socket, PRU_SLOWTIMO, (struct mbuf *)0, (struct mbuf *)i, (struct mbuf *)0, (struct proc *)0); /* XXX NOT MP SAFE */ if ((ninp == (void *)&tcbtable.inpt_queue && tcbtable.inpt_queue.cqh_last != inp) || ninp->inp_queue.cqe_prev != inp) goto tpgone; } } tp->t_idle++; if (tp->t_rtt) tp->t_rtt++; tpgone: ; } tcp_iss_seq += TCP_ISSINCR; /* increment iss */ tcp_now++; /* for timestamps */ if (++syn_cache_last >= tcp_syn_cache_interval) { syn_cache_timer(); syn_cache_last = 0; } splx(s); } /* * Cancel all timers for TCP tp. */ void tcp_canceltimers(tp) struct tcpcb *tp; { register int i; for (i = 0; i < TCPT_NTIMERS; i++) TCP_TIMER_DISARM(tp, i); } int tcp_backoff[TCP_MAXRXTSHIFT + 1] = { 1, 2, 4, 8, 16, 32, 64, 64, 64, 64, 64, 64, 64 }; int tcp_totbackoff = 511; /* sum of tcp_backoff[] */ /* * TCP timer processing. */ struct tcpcb * tcp_timers(tp, timer) register struct tcpcb *tp; int timer; { short rto; switch (timer) { /* * 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. */ case TCPT_2MSL: if (tp->t_state != TCPS_TIME_WAIT && ((tcp_maxidle == 0) || (tp->t_idle <= tcp_maxidle))) TCP_TIMER_ARM(tp, TCPT_2MSL, tcp_keepintvl); else tp = tcp_close(tp); break; /* * Retransmission timer went off. Message has not * been acked within retransmit interval. Back off * to a longer retransmit interval and retransmit one segment. */ case TCPT_REXMT: 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); break; } tcpstat.tcps_rexmttimeo++; rto = TCP_REXMTVAL(tp); if (rto < tp->t_rttmin) rto = tp->t_rttmin; TCPT_RANGESET(tp->t_rxtcur, rto * tcp_backoff[tp->t_rxtshift], tp->t_rttmin, TCPTV_REXMTMAX); TCP_TIMER_ARM(tp, TCPT_REXMT, tp->t_rxtcur); #if 0 /* * If we are losing and we are trying path MTU discovery, * try turning it off. This will avoid black holes in * the network which suppress or fail to send "packet * too big" ICMP messages. We should ideally do * lots more sophisticated searching to find the right * value here... */ if (ip_mtudisc && tp->t_rxtshift > TCP_MAXRXTSHIFT / 6) { struct inpcb *inp = tp->t_inpcb; struct rtentry *rt = in_pcbrtentry(inp); /* XXX: Black hole recovery code goes here */ } #endif /* * If losing, let the lower level know and try for * a better route. Also, 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) { in_losing(tp->t_inpcb); tp->t_rttvar += (tp->t_srtt >> TCP_RTT_SHIFT); tp->t_srtt = 0; } tp->snd_nxt = tp->snd_una; /* * If timing a segment in this window, stop the timer. */ tp->t_rtt = 0; /* * Remember if we are retransmitting a SYN, because if * we do, set the initial congestion window must be set * to 1 segment. */ if (tp->t_state == TCPS_SYN_SENT) tp->t_flags |= TF_SYN_REXMT; /* * 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_segsz; if (win < 2) win = 2; /* Loss Window MUST be one segment. */ tp->snd_cwnd = tp->t_segsz; tp->snd_ssthresh = win * tp->t_segsz; tp->t_dupacks = 0; } (void) tcp_output(tp); break; /* * Persistance timer into zero window. * Force a byte to be output, if possible. */ case TCPT_PERSIST: /* * 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. */ rto = TCP_REXMTVAL(tp); if (rto < tp->t_rttmin) rto = tp->t_rttmin; if (tp->t_rxtshift == TCP_MAXRXTSHIFT && (tp->t_idle >= tcp_maxpersistidle || tp->t_idle >= rto * tcp_totbackoff)) { tcpstat.tcps_persistdrops++; tp = tcp_drop(tp, ETIMEDOUT); break; } tcpstat.tcps_persisttimeo++; tcp_setpersist(tp); tp->t_force = 1; (void) tcp_output(tp); tp->t_force = 0; break; /* * Keep-alive timer went off; send something * or drop connection if idle for too long. */ case TCPT_KEEP: tcpstat.tcps_keeptimeo++; if (TCPS_HAVEESTABLISHED(tp->t_state) == 0) goto dropit; if (tp->t_inpcb->inp_socket->so_options & SO_KEEPALIVE && tp->t_state <= TCPS_CLOSE_WAIT) { if ((tcp_maxidle > 0) && (tp->t_idle >= 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++; if (tcp_compat_42) { /* * The keepalive packet must have nonzero * length to get a 4.2 host to respond. */ (void)tcp_respond(tp, tp->t_template, (struct mbuf *)NULL, tp->rcv_nxt - 1, tp->snd_una - 1, 0); } else { (void)tcp_respond(tp, tp->t_template, (struct mbuf *)NULL, tp->rcv_nxt, tp->snd_una - 1, 0); } TCP_TIMER_ARM(tp, TCPT_KEEP, tcp_keepintvl); } else TCP_TIMER_ARM(tp, TCPT_KEEP, tcp_keepidle); break; dropit: tcpstat.tcps_keepdrops++; tp = tcp_drop(tp, ETIMEDOUT); break; } return (tp); }