/* * Copyright (c) 2000 Apple Computer, Inc. All rights reserved. * * @APPLE_LICENSE_HEADER_START@ * * Copyright (c) 1999-2003 Apple Computer, Inc. All Rights Reserved. * * This file contains Original Code and/or Modifications of Original Code * as defined in and that are subject to the Apple Public Source License * Version 2.0 (the 'License'). You may not use this file except in * compliance with the License. Please obtain a copy of the License at * http://www.opensource.apple.com/apsl/ and read it before using this * file. * * The Original Code and all software distributed under the License are * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES, * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY, * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT. * Please see the License for the specific language governing rights and * limitations under the License. * * @APPLE_LICENSE_HEADER_END@ */ /* * 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 * $FreeBSD: src/sys/netinet/tcp_timer.c,v 1.34.2.11 2001/08/22 00:59:12 silby Exp $ */ #include #include #include #include #include #include #include #include #include /* before tcp_seq.h, for tcp_random18() */ #include #include #include #include #if INET6 #include #endif #include #include #include #include #include #include #include #if TCPDEBUG #include #endif #include #define DBG_FNC_TCP_FAST NETDBG_CODE(DBG_NETTCP, (5 << 8)) #define DBG_FNC_TCP_SLOW NETDBG_CODE(DBG_NETTCP, (5 << 8) | 1) /* * NOTE - WARNING * * * * */ static int sysctl_msec_to_ticks SYSCTL_HANDLER_ARGS { int error, s, tt; tt = *(int *)oidp->oid_arg1; s = tt * 1000 / hz; error = sysctl_handle_int(oidp, &s, 0, req); if (error || !req->newptr) return (error); tt = s * hz / 1000; if (tt < 1) return (EINVAL); *(int *)oidp->oid_arg1 = tt; return (0); } 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"); static int always_keepalive = 0; 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; struct inpcbhead time_wait_slots[N_TIME_WAIT_SLOTS]; int cur_tw_slot = 0; u_long *delack_bitmask; void add_to_time_wait(tp) struct tcpcb *tp; { int tw_slot; LIST_REMOVE(tp->t_inpcb, inp_list); if (tp->t_timer[TCPT_2MSL] == 0) tp->t_timer[TCPT_2MSL] = 1; tp->t_rcvtime += tp->t_timer[TCPT_2MSL] & (N_TIME_WAIT_SLOTS - 1); tw_slot = (tp->t_timer[TCPT_2MSL] & (N_TIME_WAIT_SLOTS - 1)) + cur_tw_slot; if (tw_slot >= N_TIME_WAIT_SLOTS) tw_slot -= N_TIME_WAIT_SLOTS; LIST_INSERT_HEAD(&time_wait_slots[tw_slot], tp->t_inpcb, inp_list); } /* * Fast timeout routine for processing delayed acks */ void tcp_fasttimo() { register struct inpcb *inp; register struct tcpcb *tp; register u_long i,j; register u_long temp_mask; register u_long elem_base = 0; struct inpcbhead *head; int s = splnet(); static int delack_checked = 0; KERNEL_DEBUG(DBG_FNC_TCP_FAST | DBG_FUNC_START, 0,0,0,0,0); if (!tcp_delack_enabled) return; for (i=0; i < (tcbinfo.hashsize / 32); i++) { if (delack_bitmask[i]) { temp_mask = 1; for (j=0; j < 32; j++) { if (temp_mask & delack_bitmask[i]) { head = &tcbinfo.hashbase[elem_base + j]; for (inp=head->lh_first; inp != 0; inp = inp->inp_hash.le_next) { delack_checked++; if ((tp = (struct tcpcb *)inp->inp_ppcb) && (tp->t_flags & TF_DELACK)) { tp->t_flags &= ~TF_DELACK; tp->t_flags |= TF_ACKNOW; tcpstat.tcps_delack++; (void) tcp_output(tp); } } } temp_mask <<= 1; } delack_bitmask[i] = 0; } elem_base += 32; } KERNEL_DEBUG(DBG_FNC_TCP_FAST | DBG_FUNC_END, delack_checked,tcpstat.tcps_delack,0,0,0); 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 *ip, *ipnxt; register struct tcpcb *tp; register int i; int s; #if TCPDEBUG int ostate; #endif #if KDEBUG static int tws_checked; #endif KERNEL_DEBUG(DBG_FNC_TCP_SLOW | DBG_FUNC_START, 0,0,0,0,0); s = splnet(); tcp_maxidle = tcp_keepcnt * tcp_keepintvl; ip = tcb.lh_first; if (ip == NULL) { splx(s); return; } /* * Search through tcb's and update active timers. */ for (; ip != NULL; ip = ipnxt) { ipnxt = ip->inp_list.le_next; tp = intotcpcb(ip); if (tp == 0 || tp->t_state == TCPS_LISTEN) continue; /* * Bogus state when port owned by SharedIP with loopback as the * only configured interface: BlueBox does not filters loopback */ if (tp->t_state == TCP_NSTATES) continue; for (i = 0; i < TCPT_NTIMERS; i++) { if (tp->t_timer[i] && --tp->t_timer[i] == 0) { #if TCPDEBUG ostate = tp->t_state; #endif tp = tcp_timers(tp, i); if (tp == NULL) goto tpgone; #if TCPDEBUG if (tp->t_inpcb->inp_socket->so_options & SO_DEBUG) tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0, PRU_SLOWTIMO); #endif } } tp->t_rcvtime++; tp->t_starttime++; if (tp->t_rtttime) tp->t_rtttime++; tpgone: ; } #if KDEBUG tws_checked = 0; #endif KERNEL_DEBUG(DBG_FNC_TCP_SLOW | DBG_FUNC_NONE, tws_checked,0,0,0,0); /* * Process the items in the current time-wait slot */ for (ip = time_wait_slots[cur_tw_slot].lh_first; ip; ip = ipnxt) { #if KDEBUG tws_checked++; #endif ipnxt = ip->inp_list.le_next; tp = intotcpcb(ip); if (tp == NULL) { /* tp already closed, remove from list */ LIST_REMOVE(ip, inp_list); continue; } if (tp->t_timer[TCPT_2MSL] >= N_TIME_WAIT_SLOTS) { tp->t_timer[TCPT_2MSL] -= N_TIME_WAIT_SLOTS; tp->t_rcvtime += N_TIME_WAIT_SLOTS; } else tp->t_timer[TCPT_2MSL] = 0; if (tp->t_timer[TCPT_2MSL] == 0) tp = tcp_timers(tp, TCPT_2MSL); } if (++cur_tw_slot >= N_TIME_WAIT_SLOTS) cur_tw_slot = 0; tcp_now++; /* for timestamps */ splx(s); KERNEL_DEBUG(DBG_FNC_TCP_SLOW | DBG_FUNC_END, tws_checked, cur_tw_slot,0,0,0); } /* * Cancel all timers for TCP tp. */ void tcp_canceltimers(tp) struct tcpcb *tp; { register int i; for (i = 0; i < TCPT_NTIMERS; i++) tp->t_timer[i] = 0; } 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, 64, 64, 64, 64, 64, 64 }; static int tcp_totbackoff = 511; /* sum of tcp_backoff[] */ /* * TCP timer processing. */ struct tcpcb * tcp_timers(tp, timer) register struct tcpcb *tp; int timer; { register int rexmt; struct socket *so_tmp; struct tcptemp *t_template; #if TCPDEBUG int ostate; #endif #if INET6 int isipv6 = (tp->t_inpcb->inp_vflag & INP_IPV4) == 0; #endif /* INET6 */ 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_rcvtime <= tcp_maxidle) { tp->t_timer[TCPT_2MSL] = tcp_keepintvl; add_to_time_wait(tp); } 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++; so_tmp = tp->t_inpcb->inp_socket; tp = tcp_drop(tp, tp->t_softerror ? tp->t_softerror : ETIMEDOUT); postevent(so_tmp, 0, EV_TIMEOUT); break; } 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->t_badrxtwin = tcp_now + (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); tp->t_timer[TCPT_REXMT] = tp->t_rxtcur; /* * Disable rfc1323 and rfc1644 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|TF_REQ_CC); /* * 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) { #if INET6 if (isipv6) in6_losing(tp->t_inpcb); else #endif /* INET6 */ in_losing(tp->t_inpcb); tp->t_rttvar += (tp->t_srtt >> TCP_RTT_SHIFT); tp->t_srtt = 0; } tp->snd_nxt = tp->snd_una; /* * Note: We overload snd_recover to function also as the * snd_last variable described in RFC 2582 */ 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; } (void) tcp_output(tp); break; /* * Persistance timer into zero window. * Force a byte to be output, if possible. */ case TCPT_PERSIST: 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 && (tp->t_rcvtime >= tcp_maxpersistidle || tp->t_rcvtime >= TCP_REXMTVAL(tp) * tcp_totbackoff)) { tcpstat.tcps_persistdrop++; so_tmp = tp->t_inpcb->inp_socket; tp = tcp_drop(tp, ETIMEDOUT); postevent(so_tmp, 0, EV_TIMEOUT); break; } 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 (tp->t_state < TCPS_ESTABLISHED) goto dropit; if ((always_keepalive || tp->t_inpcb->inp_socket->so_options & SO_KEEPALIVE) && tp->t_state <= TCPS_CLOSING) { if (tp->t_rcvtime >= TCP_KEEPIDLE(tp) + 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 = tcp_maketemplate(tp); 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)); } tp->t_timer[TCPT_KEEP] = tcp_keepintvl; } else tp->t_timer[TCPT_KEEP] = TCP_KEEPIDLE(tp); break; #if TCPDEBUG if (tp->t_inpcb->inp_socket->so_options & SO_DEBUG) tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0, PRU_SLOWTIMO); #endif dropit: tcpstat.tcps_keepdrops++; so_tmp = tp->t_inpcb->inp_socket; tp = tcp_drop(tp, ETIMEDOUT); postevent(so_tmp, 0, EV_TIMEOUT); break; } return (tp); }