--- /dev/null
+/*
+ * Copyright (c) 1982, 1986, 1988, 1990, 1993
+ * 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 8.1 (Berkeley) 6/10/93
+ * tcp_timer.c,v 1.2 1994/08/02 07:49:10 davidg Exp
+ */
+
+#include <slirp.h>
+
+static struct tcpcb *tcp_timers(register struct tcpcb *tp, int timer);
+
+/*
+ * Fast timeout routine for processing delayed acks
+ */
+void
+tcp_fasttimo(Slirp *slirp)
+{
+ register struct socket *so;
+ register struct tcpcb *tp;
+
+ DEBUG_CALL("tcp_fasttimo");
+
+ so = slirp->tcb.so_next;
+ if (so)
+ for (; so != &slirp->tcb; so = so->so_next)
+ if ((tp = (struct tcpcb *)so->so_tcpcb) &&
+ (tp->t_flags & TF_DELACK)) {
+ tp->t_flags &= ~TF_DELACK;
+ tp->t_flags |= TF_ACKNOW;
+ (void) tcp_output(tp);
+ }
+}
+
+/*
+ * 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(Slirp *slirp)
+{
+ register struct socket *ip, *ipnxt;
+ register struct tcpcb *tp;
+ register int i;
+
+ DEBUG_CALL("tcp_slowtimo");
+
+ /*
+ * Search through tcb's and update active timers.
+ */
+ ip = slirp->tcb.so_next;
+ if (ip == NULL) {
+ return;
+ }
+ for (; ip != &slirp->tcb; ip = ipnxt) {
+ ipnxt = ip->so_next;
+ tp = sototcpcb(ip);
+ if (tp == NULL) {
+ continue;
+ }
+ for (i = 0; i < TCPT_NTIMERS; i++) {
+ if (tp->t_timer[i] && --tp->t_timer[i] == 0) {
+ tcp_timers(tp,i);
+ if (ipnxt->so_prev != ip)
+ goto tpgone;
+ }
+ }
+ tp->t_idle++;
+ if (tp->t_rtt)
+ tp->t_rtt++;
+tpgone:
+ ;
+ }
+ slirp->tcp_iss += TCP_ISSINCR/PR_SLOWHZ; /* increment iss */
+ slirp->tcp_now++; /* for timestamps */
+}
+
+/*
+ * Cancel all timers for TCP tp.
+ */
+void
+tcp_canceltimers(struct tcpcb *tp)
+{
+ register int i;
+
+ for (i = 0; i < TCPT_NTIMERS; i++)
+ tp->t_timer[i] = 0;
+}
+
+const int tcp_backoff[TCP_MAXRXTSHIFT + 1] =
+ { 1, 2, 4, 8, 16, 32, 64, 64, 64, 64, 64, 64, 64 };
+
+/*
+ * TCP timer processing.
+ */
+static struct tcpcb *
+tcp_timers(register struct tcpcb *tp, int timer)
+{
+ register int rexmt;
+
+ DEBUG_CALL("tcp_timers");
+
+ 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 <= TCP_MAXIDLE)
+ tp->t_timer[TCPT_2MSL] = TCPTV_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:
+
+ /*
+ * XXXXX If a packet has timed out, then remove all the queued
+ * packets for that session.
+ */
+
+ if (++tp->t_rxtshift > TCP_MAXRXTSHIFT) {
+ /*
+ * This is a hack to suit our terminal server here at the uni of canberra
+ * since they have trouble with zeroes... It usually lets them through
+ * unharmed, but under some conditions, it'll eat the zeros. If we
+ * keep retransmitting it, it'll keep eating the zeroes, so we keep
+ * retransmitting, and eventually the connection dies...
+ * (this only happens on incoming data)
+ *
+ * So, if we were gonna drop the connection from too many retransmits,
+ * don't... instead halve the t_maxseg, which might break up the NULLs and
+ * let them through
+ *
+ * *sigh*
+ */
+
+ tp->t_maxseg >>= 1;
+ if (tp->t_maxseg < 32) {
+ /*
+ * We tried our best, now the connection must die!
+ */
+ tp->t_rxtshift = TCP_MAXRXTSHIFT;
+ tp = tcp_drop(tp, tp->t_softerror);
+ /* tp->t_softerror : ETIMEDOUT); */ /* XXX */
+ return (tp); /* XXX */
+ }
+
+ /*
+ * Set rxtshift to 6, which is still at the maximum
+ * backoff time
+ */
+ tp->t_rxtshift = 6;
+ }
+ rexmt = TCP_REXMTVAL(tp) * tcp_backoff[tp->t_rxtshift];
+ TCPT_RANGESET(tp->t_rxtcur, rexmt,
+ (short)tp->t_rttmin, TCPTV_REXMTMAX); /* XXX */
+ 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 >> 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;
+ /*
+ * 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 threshold size.
+ * For a threshold, 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 threshold
+ * 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;
+
+ /*
+ * Persistence timer into zero window.
+ * Force a byte to be output, if possible.
+ */
+ case TCPT_PERSIST:
+ 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:
+ if (tp->t_state < TCPS_ESTABLISHED)
+ goto dropit;
+
+ if ((SO_OPTIONS) && tp->t_state <= TCPS_CLOSE_WAIT) {
+ if (tp->t_idle >= TCPTV_KEEP_IDLE + 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.
+ */
+ tcp_respond(tp, &tp->t_template, (struct mbuf *)NULL,
+ tp->rcv_nxt, tp->snd_una - 1, 0);
+ tp->t_timer[TCPT_KEEP] = TCPTV_KEEPINTVL;
+ } else
+ tp->t_timer[TCPT_KEEP] = TCPTV_KEEP_IDLE;
+ break;
+
+ dropit:
+ tp = tcp_drop(tp, 0);
+ break;
+ }
+
+ return (tp);
+}
Code Review / kvmfornfv.git / blobdiff