/* $NetBSD: tcp_timer.c,v 1.65 2003/10/27 07:43:01 itojun Exp $ */ /* * Copyright (C) 1995, 1996, 1997, and 1998 WIDE Project. * 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 project 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 PROJECT 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 PROJECT 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) 1997, 1998, 2001 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. 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 __KERNEL_RCSID(0, "$NetBSD: tcp_timer.c,v 1.65 2003/10/27 07:43:01 itojun Exp $"); #include "opt_inet.h" #include "opt_tcp_debug.h" #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #ifdef INET6 #ifndef INET #include #endif #include #include #endif #include #include #include #include #include #include #ifdef TCP_DEBUG #include #endif /* * Various tunable timer parameters. These are initialized in tcp_init(), * unless they are patched. */ int tcp_keepidle = 0; int tcp_keepintvl = 0; int tcp_keepcnt = 0; /* max idle probes */ int tcp_maxpersistidle = 0; /* max idle time in persist */ int tcp_maxidle; /* computed in tcp_slowtimo() */ /* * Time to delay the ACK. This is initialized in tcp_init(), unless * its patched. */ int tcp_delack_ticks = 0; void tcp_timer_rexmt(void *); void tcp_timer_persist(void *); void tcp_timer_keep(void *); void tcp_timer_2msl(void *); const tcp_timer_func_t tcp_timer_funcs[TCPT_NTIMERS] = { tcp_timer_rexmt, tcp_timer_persist, tcp_timer_keep, tcp_timer_2msl, }; /* * Timer state initialization, called from tcp_init(). */ void tcp_timer_init(void) { if (tcp_keepidle == 0) tcp_keepidle = TCPTV_KEEP_IDLE; if (tcp_keepintvl == 0) tcp_keepintvl = TCPTV_KEEPINTVL; if (tcp_keepcnt == 0) tcp_keepcnt = TCPTV_KEEPCNT; if (tcp_maxpersistidle == 0) tcp_maxpersistidle = TCPTV_KEEP_IDLE; if (tcp_delack_ticks == 0) tcp_delack_ticks = TCP_DELACK_TICKS; } /* * Return how many timers are currently being invoked. */ int tcp_timers_invoking(struct tcpcb *tp) { int i; int count = 0; for (i = 0; i < TCPT_NTIMERS; i++) if (callout_invoking(&tp->t_timer[i])) count++; if (callout_invoking(&tp->t_delack_ch)) count++; return count; } /* * Callout to process delayed ACKs for a TCPCB. */ void tcp_delack(void *arg) { struct tcpcb *tp = arg; int s; /* * If tcp_output() wasn't able to transmit the ACK * for whatever reason, it will restart the delayed * ACK callout. */ s = splsoftnet(); callout_ack(&tp->t_delack_ch); if (tcp_isdead(tp)) { splx(s); return; } 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() { int s; s = splsoftnet(); tcp_maxidle = tcp_keepcnt * tcp_keepintvl; tcp_iss_seq += TCP_ISSINCR; /* increment iss */ tcp_now++; /* for timestamps */ splx(s); } /* * Cancel all timers for TCP tp. */ void tcp_canceltimers(tp) struct tcpcb *tp; { int i; for (i = 0; i < TCPT_NTIMERS; i++) TCP_TIMER_DISARM(tp, i); } const int tcp_backoff[TCP_MAXRXTSHIFT + 1] = { 1, 2, 4, 8, 16, 32, 64, 64, 64, 64, 64, 64, 64 }; const int tcp_totbackoff = 511; /* sum of tcp_backoff[] */ /* * TCP timer processing. */ void tcp_timer_rexmt(void *arg) { struct tcpcb *tp = arg; uint32_t rto; int s; #ifdef TCP_DEBUG struct socket *so = NULL; short ostate; #endif s = splsoftnet(); callout_ack(&tp->t_timer[TCPT_KEEP]); if (tcp_isdead(tp)) { splx(s); return; } #ifdef TCP_DEBUG #ifdef INET if (tp->t_inpcb) so = tp->t_inpcb->inp_socket; #endif #ifdef INET6 if (tp->t_in6pcb) so = tp->t_in6pcb->in6p_socket; #endif ostate = tp->t_state; #endif /* TCP_DEBUG */ /* * 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; } 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 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 (tp->t_mtudisc && tp->t_rxtshift > TCP_MAXRXTSHIFT / 6) { tcpstat.tcps_pmtublackhole++; #ifdef INET /* try turning PMTUD off */ if (tp->t_inpcb) tp->t_mtudisc = 0; #endif #ifdef INET6 /* try using IPv6 minimum MTU */ if (tp->t_in6pcb) tp->t_mtudisc = 0; #endif /* XXX: more sophisticated Black hole recovery code? */ } /* * 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) { #ifdef INET if (tp->t_inpcb) in_losing(tp->t_inpcb); #endif #ifdef INET6 if (tp->t_in6pcb) in6_losing(tp->t_in6pcb); #endif 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_rtttime = 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); out: #ifdef TCP_DEBUG if (tp && so->so_options & SO_DEBUG) tcp_trace(TA_USER, ostate, tp, NULL, PRU_SLOWTIMO | (TCPT_REXMT << 8)); #endif splx(s); } void tcp_timer_persist(void *arg) { struct tcpcb *tp = arg; uint32_t rto; int s; #ifdef TCP_DEBUG struct socket *so = NULL; short ostate; #endif s = splsoftnet(); callout_ack(&tp->t_timer[TCPT_PERSIST]); if (tcp_isdead(tp)) { splx(s); return; } #ifdef TCP_DEBUG #ifdef INET if (tp->t_inpcb) so = tp->t_inpcb->inp_socket; #endif #ifdef INET6 if (tp->t_in6pcb) so = tp->t_in6pcb->in6p_socket; #endif ostate = tp->t_state; #endif /* TCP_DEBUG */ /* * Persistance timer into zero window. * Force a byte to be output, if possible. */ /* * 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 && ((tcp_now - tp->t_rcvtime) >= tcp_maxpersistidle || (tcp_now - tp->t_rcvtime) >= rto * tcp_totbackoff)) { tcpstat.tcps_persistdrops++; tp = tcp_drop(tp, ETIMEDOUT); goto out; } tcpstat.tcps_persisttimeo++; tcp_setpersist(tp); tp->t_force = 1; (void) tcp_output(tp); tp->t_force = 0; out: #ifdef TCP_DEBUG if (tp && so->so_options & SO_DEBUG) tcp_trace(TA_USER, ostate, tp, NULL, PRU_SLOWTIMO | (TCPT_PERSIST << 8)); #endif splx(s); } void tcp_timer_keep(void *arg) { struct tcpcb *tp = arg; struct socket *so = NULL; /* Quell compiler warning */ int s; #ifdef TCP_DEBUG short ostate; #endif s = splsoftnet(); callout_ack(&tp->t_timer[TCPT_KEEP]); if (tcp_isdead(tp)) { splx(s); return; } #ifdef TCP_DEBUG ostate = tp->t_state; #endif /* TCP_DEBUG */ /* * Keep-alive timer went off; send something * or drop connection if idle for too long. */ tcpstat.tcps_keeptimeo++; if (TCPS_HAVEESTABLISHED(tp->t_state) == 0) goto dropit; #ifdef INET if (tp->t_inpcb) so = tp->t_inpcb->inp_socket; #endif #ifdef INET6 if (tp->t_in6pcb) so = tp->t_in6pcb->in6p_socket; #endif if (so->so_options & SO_KEEPALIVE && tp->t_state <= TCPS_CLOSE_WAIT) { if ((tcp_maxidle > 0) && ((tcp_now - 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++; 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, NULL, tp->rcv_nxt - 1, tp->snd_una - 1, 0); } else { (void)tcp_respond(tp, tp->t_template, (struct mbuf *)NULL, 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); #ifdef TCP_DEBUG if (tp && so->so_options & SO_DEBUG) tcp_trace(TA_USER, ostate, tp, NULL, PRU_SLOWTIMO | (TCPT_KEEP << 8)); #endif splx(s); return; dropit: tcpstat.tcps_keepdrops++; (void) tcp_drop(tp, ETIMEDOUT); splx(s); } void tcp_timer_2msl(void *arg) { struct tcpcb *tp = arg; int s; #ifdef TCP_DEBUG struct socket *so = NULL; short ostate; #endif s = splsoftnet(); callout_ack(&tp->t_timer[TCPT_2MSL]); if (tcp_isdead(tp)) { splx(s); return; } #ifdef TCP_DEBUG #ifdef INET if (tp->t_inpcb) so = tp->t_inpcb->inp_socket; #endif #ifdef INET6 if (tp->t_in6pcb) so = tp->t_in6pcb->in6p_socket; #endif ostate = tp->t_state; #endif /* TCP_DEBUG */ /* * 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 && ((tcp_maxidle == 0) || ((tcp_now - tp->t_rcvtime) <= tcp_maxidle))) TCP_TIMER_ARM(tp, TCPT_2MSL, tcp_keepintvl); else tp = tcp_close(tp); #ifdef TCP_DEBUG if (tp && so->so_options & SO_DEBUG) tcp_trace(TA_USER, ostate, tp, NULL, PRU_SLOWTIMO | (TCPT_2MSL << 8)); #endif splx(s); }