/* * tcp_timer.c * * Derived from: * * Copyright (c) 1982, 1986 Regents of the University of California. * All rights reserved. * * Redistribution and use in source and binary forms are permitted * provided that this notice is preserved and that due credit is given * to the University of California at Berkeley. The name of the University * may not be used to endorse or promote products derived from this * software without specific prior written permission. This software * is provided ``as is'' without express or implied warranty. * * @(#)tcp_timer.c 7.11 (Berkeley) 12/7/87 * * Modified for x-kernel v3.3 * Modifications Copyright (c) 1996,1991 Arizona Board of Regents * * $Revision: 1.4 $ * $Date: 1996/06/14 21:31:50 $ */ #include "xkernel.h" #include "tcp_internal.h" #include "tcp_fsm.h" #include "tcp_seq.h" #include "tcp_timer.h" #include "tcp_var.h" #include "tcpip.h" static int mytrace = 0; /* * Fast timeout routine for processing delayed acks */ void vtcp_fasttimo( ev, arg ) Event ev; VOID *arg; { register struct inpcb *inp; register struct tcpcb *tp; struct tcpstate *tcpst; int currentTime; PSTATE *ps=(PSTATE *)arg; /* * The original code protected this routine with splnet(). If * the timeout thread blocks, there could be a problem. */ /* int s = splnet(); */ DO_TRACE(ps, TCP_EVENT_FAST_TO, (currentTime=tcpGetTime()), 0, 0); inp = ps->tcb.inp_next; if (inp) for (; inp != &ps->tcb; inp = inp->inp_next) { tp = (struct tcpcb *)inp->inp_ppcb; /* LSB ... */ if (tp) { if (tp->t_flags & TF_DELACK) { tp->t_flags &= ~TF_DELACK; tp->t_flags |= TF_ACKNOW; ps->tcpstat.tcps_delack++; /* * What if this blocks??? */ (void) vtcp_output(tp); } } } /* splx(s); */ evDetach(evSchedule(vtcp_fasttimo, (void *)ps, TCP_FAST_INTERVAL)); } /* * 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 vtcp_slowtimo(ev, arg) Event ev; VOID *arg; { register struct inpcb *ip, *ipnxt; register struct tcpcb *tp; PSTATE *ps=(PSTATE *)arg; /* * The original code protected this routine with splnet(). If * the timeout thread blocks, there could be a problem. */ /* int s = splnet(); */ register int i; DO_TRACE(ps, TCP_EVENT_SLOW_TO, tcpGetTime(), 0, 0); /* * Search through tcb's and update active timers. */ ip = ps->tcb.inp_next; if (ip != 0) { for (; ip != &ps->tcb; ip = ipnxt) { ipnxt = ip->inp_next; tp = intotcpcb(ip); if (tp == 0) continue; for (i = 0; i < TCPT_NTIMERS; i++) { if (tp->t_timer[i] && --tp->t_timer[i] == 0) { /* * What if this blocks??? */ (void) tcp_usrreq(tp->t_inpcb->inp_session, PRU_SLOWTIMO, (Msg *)0, (Msg *)i, 1); if (ipnxt->inp_prev != ip) goto tpgone; } } tp->t_idle++; if (tp->t_rtt) tp->t_rtt++; tpgone: ; } ps->tcp_iss += TCP_ISSINCR/PR_SLOWHZ; /* increment iss */ #ifdef TCP_COMPAT_42 if ((int)ps->tcp_iss < 0) ps->tcp_iss = 0; /* XXX */ #endif } /* splx(s); */ evDetach(evSchedule(vtcp_slowtimo, (void *)ps, TCP_SLOW_INTERVAL)); } /* * Cancel all timers for TCP tp. */ void vtcp_canceltimers(tp) struct tcpcb *tp; { register int i; for (i = 0; i < TCPT_NTIMERS; i++) tp->t_timer[i] = 0; } int tcp_backoff[TCP_MAXRXTSHIFT + 1] = { 1, 2, 4, 8, 16, 32, 64, 64, 64, 64, 64, 64, 64 }; /* * TCP timer processing. */ struct tcpcb * vtcp_timers(tp, timer, arg) register struct tcpcb *tp; int timer; void *arg; { register int rexmt; PSTATE *ps=(PSTATE *)arg; Protl self=tp->t_inpcb->inp_session->myprotl; DO_TRACE(ps, TCP_EVENT_TIMER, tcpGetTime(), timer, 0); 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 && tp->t_idle <= TCPTV_MAXIDLE) tp->t_timer[TCPT_2MSL] = TCPTV_KEEP; else tp = tcp_destroy(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: xTrace1(tcpp, 4, "Retransmission timeout (%d)", tp->t_rxtshift); if (tp->v_other14 < tp->t_rxtcur) tp->v_other14 = tp->t_rxtcur; if (mytrace) printf("Retransmission timeout \n"); if (++tp->t_rxtshift > TCP_MAXRXTSHIFT) { xTrace0(tcpp, 4, "Too many rexmits, dropping"); tp->t_rxtshift = TCP_MAXRXTSHIFT; ps->tcpstat.tcps_timeoutdrop++; tp = tcp_drop(tp, ETIMEDOUT); break; } ps->tcpstat.tcps_rexmttimeo++; rexmt = ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1; rexmt *= tcp_backoff[tp->t_rxtshift]; TCPT_RANGESET(tp->t_rxtcur, rexmt, TCPTV_MIN, TCPTV_REXMTMAX); DO_TRACE(ps, TCP_EVENT_OTHER9, tp->t_rxtcur, 4, 0); tp->t_timer[TCPT_REXMT] = tp->t_rxtcur; /* * 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) { tp->t_rttvar += (tp->t_srtt >> 2); tp->t_srtt = 0; } tp->snd_nxt = tp->snd_una; /* * If timing a segment in this window, stop the timer. */ tp->t_rtt = 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_short win = MIN(tp->snd_wnd, tp->snd_cwnd) / 2 / tp->t_maxseg; if (win < 2) win = 2; tp->snd_cwnd = tp->t_slowstart * tp->t_maxseg; tp->snd_ssthresh = win * tp->t_maxseg; tp->t_dupacks = 0; } (void) (ps->tcp_output)(tp); break; /* * Persistance timer into zero window. * Force a byte to be output, if possible. */ case TCPT_PERSIST: ps->tcpstat.tcps_persisttimeo++; tcp_setpersist(tp); tp->t_force = 1; (void) (ps->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: ps->tcpstat.tcps_keeptimeo++; if (tp->t_state < TCPS_ESTABLISHED) goto dropit; #define SHOULDDOKEEPS(X) 0 if (SHOULDDOKEEPS(tp->t_inpcb->inp_session) && tp->t_state <= TCPS_CLOSE_WAIT) { if (tp->t_idle >= TCPTV_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. */ ps->tcpstat.tcps_keepprobe++; #ifdef TCP_COMPAT_42 /* * The keepalive packet must have nonzero length * to get a 4.2 host to respond. */ tcp_respond(self, tp, &tp->t_template->ti_t, &tp->t_template->ti_p, tp->rcv_nxt - 1, tp->snd_una - 1, 0); #else tcp_respond(self, tp, &tp->t_template->ti_t, &tp->t_template->ti_p, tp->rcv_nxt, tp->snd_una - 1, 0); #endif } tp->t_timer[TCPT_KEEP] = TCPTV_KEEP; break; dropit: ps->tcpstat.tcps_keepdrops++; tp = tcp_drop(tp, ETIMEDOUT); break; } return (tp); }