diff options
Diffstat (limited to 'sys/netinet/tcp_timer.c')
| -rw-r--r-- | sys/netinet/tcp_timer.c | 463 |
1 files changed, 463 insertions, 0 deletions
diff --git a/sys/netinet/tcp_timer.c b/sys/netinet/tcp_timer.c new file mode 100644 index 0000000..0a85cf8 --- /dev/null +++ b/sys/netinet/tcp_timer.c @@ -0,0 +1,463 @@ +/* + * 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 + * $FreeBSD$ + */ + +#include "opt_compat.h" +#include "opt_inet6.h" +#include "opt_tcpdebug.h" + +#include <sys/param.h> +#include <sys/systm.h> +#include <sys/kernel.h> +#include <sys/sysctl.h> +#include <sys/socket.h> +#include <sys/socketvar.h> +#include <sys/protosw.h> + +#include <machine/cpu.h> /* before tcp_seq.h, for tcp_random18() */ + +#include <net/route.h> + +#include <netinet/in.h> +#include <netinet/in_systm.h> +#include <netinet/in_pcb.h> +#ifdef INET6 +#include <netinet6/in6_pcb.h> +#endif +#include <netinet/ip_var.h> +#include <netinet/tcp.h> +#include <netinet/tcp_fsm.h> +#include <netinet/tcp_seq.h> +#include <netinet/tcp_timer.h> +#include <netinet/tcp_var.h> +#include <netinet/tcpip.h> +#ifdef TCPDEBUG +#include <netinet/tcp_debug.h> +#endif + +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; + +/* + * Tcp protocol timeout routine called every 500 ms. + * Updates timestamps used for TCP + * causes finite state machine actions if timers expire. + */ +void +tcp_slowtimo() +{ + int s; + + s = splnet(); + + tcp_maxidle = tcp_keepcnt * tcp_keepintvl; + + splx(s); +} + +/* + * Cancel all timers for TCP tp. + */ +void +tcp_canceltimers(tp) + struct tcpcb *tp; +{ + callout_stop(tp->tt_2msl); + callout_stop(tp->tt_persist); + callout_stop(tp->tt_keep); + callout_stop(tp->tt_rexmt); +} + +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. + */ +void +tcp_timer_delack(xtp) + void *xtp; +{ + struct tcpcb *tp = xtp; + int s; + + s = splnet(); + if (callout_pending(tp->tt_delack) || !callout_active(tp->tt_delack)) { + splx(s); + return; + } + callout_deactivate(tp->tt_delack); + + tp->t_flags |= TF_ACKNOW; + tcpstat.tcps_delack++; + (void) tcp_output(tp); + splx(s); +} + +void +tcp_timer_2msl(xtp) + void *xtp; +{ + struct tcpcb *tp = xtp; + int s; +#ifdef TCPDEBUG + int ostate; + + ostate = tp->t_state; +#endif + s = splnet(); + if (callout_pending(tp->tt_2msl) || !callout_active(tp->tt_2msl)) { + splx(s); + 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 && (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) + tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0, + PRU_SLOWTIMO); +#endif + splx(s); +} + +void +tcp_timer_keep(xtp) + void *xtp; +{ + struct tcpcb *tp = xtp; + int s; +#ifdef TCPDEBUG + int ostate; + + ostate = tp->t_state; +#endif + s = splnet(); + if (callout_pending(tp->tt_keep) || !callout_active(tp->tt_keep)) { + splx(s); + 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 || + tp->t_inpcb->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++; + tcp_respond(tp, tp->t_template->tt_ipgen, + &tp->t_template->tt_t, (struct mbuf *)NULL, + tp->rcv_nxt, tp->snd_una - 1, 0); + 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 (tp->t_inpcb->inp_socket->so_options & SO_DEBUG) + tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0, + PRU_SLOWTIMO); +#endif + splx(s); + return; + +dropit: + tcpstat.tcps_keepdrops++; + tp = tcp_drop(tp, ETIMEDOUT); + +#ifdef TCPDEBUG + if (tp && (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) + tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0, + PRU_SLOWTIMO); +#endif + splx(s); +} + +void +tcp_timer_persist(xtp) + void *xtp; +{ + struct tcpcb *tp = xtp; + int s; +#ifdef TCPDEBUG + int ostate; + + ostate = tp->t_state; +#endif + s = splnet(); + if (callout_pending(tp->tt_persist) || !callout_active(tp->tt_persist)){ + splx(s); + 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_force = 1; + (void) tcp_output(tp); + tp->t_force = 0; + +out: +#ifdef TCPDEBUG + if (tp && tp->t_inpcb->inp_socket->so_options & SO_DEBUG) + tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0, + PRU_SLOWTIMO); +#endif + splx(s); +} + +void +tcp_timer_rexmt(xtp) + void *xtp; +{ + struct tcpcb *tp = xtp; + int s; + int rexmt; +#ifdef TCPDEBUG + int ostate; + + ostate = tp->t_state; +#endif + s = splnet(); + if (callout_pending(tp->tt_rexmt) || !callout_active(tp->tt_rexmt)) { + splx(s); + return; + } + callout_deactivate(tp->tt_rexmt); + /* + * 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; + } + 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 = 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); + /* + * 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 INET6 + if ((tp->t_inpcb->inp_vflag & INP_IPV6) != 0) + in6_losing(tp->t_inpcb); + else +#endif + 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); + +out: +#ifdef TCPDEBUG + if (tp && (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) + tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0, + PRU_SLOWTIMO); +#endif + splx(s); +} |
