tcp_timer.c

eCos/RedBoot for勤研ARM AnywhereII(4510) 含全部源代码

}

void
tcp_timer_keep(xtp)
	void *xtp;
{
	struct tcpcb *tp = xtp;
	struct tcptemp *t_template;
	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++;
		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));
		}
		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_rexmit_shift_max &&
	    ((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_rexmit_shift_max) {
		tp->t_rxtshift = tcp_rexmit_shift_max;
		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);
	/*
	 * 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_rexmit_shift_max / 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);
}