Merge upstream QEMU 10.0.50 into the Android source tree.

This change integrates many changes from the upstream QEMU sources.
Its main purpose is to enable correct ARMv6 and ARMv7 support to the
Android emulator. Due to the nature of the upstream code base, this
unfortunately also required changes to many other parts of the source.

Note that to ensure easier integrations in the future, some source files
and directories that have heavy Android-specific customization have been
renamed with an -android suffix. The original files are still there for
easier integration tracking, but *never* compiled. For example:

  net.c        net-android.c
  qemu-char.c  qemu-char-android.c
  slirp/       slirp-android/
  etc...

Tested on linux-x86, darwin-x86 and windows host machines.

1 files changed, 599 insertions, 0 deletions

diff --git a/slirp-android/tcp_output.c b/slirp-android/tcp_output.c
new file mode 100644
index 0000000..9ed50f5
--- /dev/null
+++ b/slirp-android/tcp_output.c
@@ -0,0 +1,599 @@
+/*
+ * 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_output.c	8.3 (Berkeley) 12/30/93
+ * tcp_output.c,v 1.3 1994/09/15 10:36:55 davidg Exp
+ */
+
+/*
+ * Changes and additions relating to SLiRP
+ * Copyright (c) 1995 Danny Gasparovski.
+ *
+ * Please read the file COPYRIGHT for the
+ * terms and conditions of the copyright.
+ */
+
+#include <slirp.h>
+
+/*
+ * Since this is only used in "stats socket", we give meaning
+ * names instead of the REAL names
+ */
+const char * const tcpstates[] = {
+/*	"CLOSED",       "LISTEN",       "SYN_SENT",     "SYN_RCVD", */
+	"REDIRECT",	"LISTEN",	"SYN_SENT",     "SYN_RCVD",
+	"ESTABLISHED",  "CLOSE_WAIT",   "FIN_WAIT_1",   "CLOSING",
+	"LAST_ACK",     "FIN_WAIT_2",   "TIME_WAIT",
+};
+
+static const u_char  tcp_outflags[TCP_NSTATES] = {
+	TH_RST|TH_ACK, 0,      TH_SYN,        TH_SYN|TH_ACK,
+	TH_ACK,        TH_ACK, TH_FIN|TH_ACK, TH_FIN|TH_ACK,
+	TH_FIN|TH_ACK, TH_ACK, TH_ACK,
+};
+
+
+#define MAX_TCPOPTLEN	32	/* max # bytes that go in options */
+
+/*
+ * Tcp output routine: figure out what should be sent and send it.
+ */
+int
+tcp_output(struct tcpcb *tp)
+{
+	register struct socket *so = tp->t_socket;
+	register long len, win;
+	int off, flags, error;
+	register struct mbuf *m;
+	register struct tcpiphdr *ti;
+	u_char opt[MAX_TCPOPTLEN];
+	unsigned optlen, hdrlen;
+	int idle, sendalot;
+
+	DEBUG_CALL("tcp_output");
+	DEBUG_ARG("tp = %lx", (long )tp);
+
+	/*
+	 * Determine length of data that should be transmitted,
+	 * and flags that will be used.
+	 * If there is some data or critical controls (SYN, RST)
+	 * to send, then transmit; otherwise, investigate further.
+	 */
+	idle = (tp->snd_max == tp->snd_una);
+	if (idle && tp->t_idle >= tp->t_rxtcur)
+		/*
+		 * We have been idle for "a while" and no acks are
+		 * expected to clock out any data we send --
+		 * slow start to get ack "clock" running again.
+		 */
+		tp->snd_cwnd = tp->t_maxseg;
+again:
+	sendalot = 0;
+	off = tp->snd_nxt - tp->snd_una;
+	win = min(tp->snd_wnd, tp->snd_cwnd);
+
+	flags = tcp_outflags[tp->t_state];
+
+	DEBUG_MISC((dfd, " --- tcp_output flags = 0x%x\n",flags));
+
+	/*
+	 * If in persist timeout with window of 0, send 1 byte.
+	 * Otherwise, if window is small but nonzero
+	 * and timer expired, we will send what we can
+	 * and go to transmit state.
+	 */
+	if (tp->t_force) {
+		if (win == 0) {
+			/*
+			 * If we still have some data to send, then
+			 * clear the FIN bit.  Usually this would
+			 * happen below when it realizes that we
+			 * aren't sending all the data.  However,
+			 * if we have exactly 1 byte of unset data,
+			 * then it won't clear the FIN bit below,
+			 * and if we are in persist state, we wind
+			 * up sending the packet without recording
+			 * that we sent the FIN bit.
+			 *
+			 * We can't just blindly clear the FIN bit,
+			 * because if we don't have any more data
+			 * to send then the probe will be the FIN
+			 * itself.
+			 */
+			if (off < so->so_snd.sb_cc)
+				flags &= ~TH_FIN;
+			win = 1;
+		} else {
+			tp->t_timer[TCPT_PERSIST] = 0;
+			tp->t_rxtshift = 0;
+		}
+	}
+
+	len = min(so->so_snd.sb_cc, win) - off;
+
+	if (len < 0) {
+		/*
+		 * If FIN has been sent but not acked,
+		 * but we haven't been called to retransmit,
+		 * len will be -1.  Otherwise, window shrank
+		 * after we sent into it.  If window shrank to 0,
+		 * cancel pending retransmit and pull snd_nxt
+		 * back to (closed) window.  We will enter persist
+		 * state below.  If the window didn't close completely,
+		 * just wait for an ACK.
+		 */
+		len = 0;
+		if (win == 0) {
+			tp->t_timer[TCPT_REXMT] = 0;
+			tp->snd_nxt = tp->snd_una;
+		}
+	}
+
+	if (len > tp->t_maxseg) {
+		len = tp->t_maxseg;
+		sendalot = 1;
+	}
+	if (SEQ_LT(tp->snd_nxt + len, tp->snd_una + so->so_snd.sb_cc))
+		flags &= ~TH_FIN;
+
+	win = sbspace(&so->so_rcv);
+
+	/*
+	 * Sender silly window avoidance.  If connection is idle
+	 * and can send all data, a maximum segment,
+	 * at least a maximum default-size segment do it,
+	 * or are forced, do it; otherwise don't bother.
+	 * If peer's buffer is tiny, then send
+	 * when window is at least half open.
+	 * If retransmitting (possibly after persist timer forced us
+	 * to send into a small window), then must resend.
+	 */
+	if (len) {
+		if (len == tp->t_maxseg)
+			goto send;
+		if ((1 || idle || tp->t_flags & TF_NODELAY) &&
+		    len + off >= so->so_snd.sb_cc)
+			goto send;
+		if (tp->t_force)
+			goto send;
+		if (len >= tp->max_sndwnd / 2 && tp->max_sndwnd > 0)
+			goto send;
+		if (SEQ_LT(tp->snd_nxt, tp->snd_max))
+			goto send;
+	}
+
+	/*
+	 * Compare available window to amount of window
+	 * known to peer (as advertised window less
+	 * next expected input).  If the difference is at least two
+	 * max size segments, or at least 50% of the maximum possible
+	 * window, then want to send a window update to peer.
+	 */
+	if (win > 0) {
+		/*
+		 * "adv" is the amount we can increase the window,
+		 * taking into account that we are limited by
+		 * TCP_MAXWIN << tp->rcv_scale.
+		 */
+		long adv = min(win, (long)TCP_MAXWIN << tp->rcv_scale) -
+			(tp->rcv_adv - tp->rcv_nxt);
+
+		if (adv >= (long) (2 * tp->t_maxseg))
+			goto send;
+		if (2 * adv >= (long) so->so_rcv.sb_datalen)
+			goto send;
+	}
+
+	/*
+	 * Send if we owe peer an ACK.
+	 */
+	if (tp->t_flags & TF_ACKNOW)
+		goto send;
+	if (flags & (TH_SYN|TH_RST))
+		goto send;
+	if (SEQ_GT(tp->snd_up, tp->snd_una))
+		goto send;
+	/*
+	 * If our state indicates that FIN should be sent
+	 * and we have not yet done so, or we're retransmitting the FIN,
+	 * then we need to send.
+	 */
+	if (flags & TH_FIN &&
+	    ((tp->t_flags & TF_SENTFIN) == 0 || tp->snd_nxt == tp->snd_una))
+		goto send;
+
+	/*
+	 * TCP window updates are not reliable, rather a polling protocol
+	 * using ``persist'' packets is used to insure receipt of window
+	 * updates.  The three ``states'' for the output side are:
+	 *	idle			not doing retransmits or persists
+	 *	persisting		to move a small or zero window
+	 *	(re)transmitting	and thereby not persisting
+	 *
+	 * tp->t_timer[TCPT_PERSIST]
+	 *	is set when we are in persist state.
+	 * tp->t_force
+	 *	is set when we are called to send a persist packet.
+	 * tp->t_timer[TCPT_REXMT]
+	 *	is set when we are retransmitting
+	 * The output side is idle when both timers are zero.
+	 *
+	 * If send window is too small, there is data to transmit, and no
+	 * retransmit or persist is pending, then go to persist state.
+	 * If nothing happens soon, send when timer expires:
+	 * if window is nonzero, transmit what we can,
+	 * otherwise force out a byte.
+	 */
+	if (so->so_snd.sb_cc && tp->t_timer[TCPT_REXMT] == 0 &&
+	    tp->t_timer[TCPT_PERSIST] == 0) {
+		tp->t_rxtshift = 0;
+		tcp_setpersist(tp);
+	}
+
+	/*
+	 * No reason to send a segment, just return.
+	 */
+	STAT(tcpstat.tcps_didnuttin++);
+
+	return (0);
+
+send:
+	/*
+	 * Before ESTABLISHED, force sending of initial options
+	 * unless TCP set not to do any options.
+	 * NOTE: we assume that the IP/TCP header plus TCP options
+	 * always fit in a single mbuf, leaving room for a maximum
+	 * link header, i.e.
+	 *	max_linkhdr + sizeof (struct tcpiphdr) + optlen <= MHLEN
+	 */
+	optlen = 0;
+	hdrlen = sizeof (struct tcpiphdr);
+	if (flags & TH_SYN) {
+		tp->snd_nxt = tp->iss;
+		if ((tp->t_flags & TF_NOOPT) == 0) {
+			u_int16_t mss;
+
+			opt[0] = TCPOPT_MAXSEG;
+			opt[1] = 4;
+			mss = htons((u_int16_t) tcp_mss(tp, 0));
+			memcpy((caddr_t)(opt + 2), (caddr_t)&mss, sizeof(mss));
+			optlen = 4;
+
+/*			if ((tp->t_flags & TF_REQ_SCALE) &&
+ *			    ((flags & TH_ACK) == 0 ||
+ *			    (tp->t_flags & TF_RCVD_SCALE))) {
+ *				*((u_int32_t *) (opt + optlen)) = htonl(
+ *					TCPOPT_NOP << 24 |
+ *					TCPOPT_WINDOW << 16 |
+ *					TCPOLEN_WINDOW << 8 |
+ *					tp->request_r_scale);
+ *				optlen += 4;
+ *			}
+ */
+		}
+ 	}
+
+ 	/*
+	 * Send a timestamp and echo-reply if this is a SYN and our side
+	 * wants to use timestamps (TF_REQ_TSTMP is set) or both our side
+	 * and our peer have sent timestamps in our SYN's.
+ 	 */
+/* 	if ((tp->t_flags & (TF_REQ_TSTMP|TF_NOOPT)) == TF_REQ_TSTMP &&
+ *	     (flags & TH_RST) == 0 &&
+ *	    ((flags & (TH_SYN|TH_ACK)) == TH_SYN ||
+ *	     (tp->t_flags & TF_RCVD_TSTMP))) {
+ *		u_int32_t *lp = (u_int32_t *)(opt + optlen);
+ *
+ *		/ * Form timestamp option as shown in appendix A of RFC 1323. *  /
+ *		*lp++ = htonl(TCPOPT_TSTAMP_HDR);
+ *		*lp++ = htonl(tcp_now);
+ *		*lp   = htonl(tp->ts_recent);
+ *		optlen += TCPOLEN_TSTAMP_APPA;
+ *	}
+ */
+ 	hdrlen += optlen;
+
+	/*
+	 * Adjust data length if insertion of options will
+	 * bump the packet length beyond the t_maxseg length.
+	 */
+	 if (len > tp->t_maxseg - optlen) {
+		len = tp->t_maxseg - optlen;
+		sendalot = 1;
+	 }
+
+	/*
+	 * Grab a header mbuf, attaching a copy of data to
+	 * be transmitted, and initialize the header from
+	 * the template for sends on this connection.
+	 */
+	if (len) {
+		if (tp->t_force && len == 1)
+			STAT(tcpstat.tcps_sndprobe++);
+		else if (SEQ_LT(tp->snd_nxt, tp->snd_max)) {
+			STAT(tcpstat.tcps_sndrexmitpack++);
+			STAT(tcpstat.tcps_sndrexmitbyte += len);
+		} else {
+			STAT(tcpstat.tcps_sndpack++);
+			STAT(tcpstat.tcps_sndbyte += len);
+		}
+
+		m = m_get();
+		if (m == NULL) {
+/*			error = ENOBUFS; */
+			error = 1;
+			goto out;
+		}
+		m->m_data += IF_MAXLINKHDR;
+		m->m_len = hdrlen;
+
+		/*
+		 * This will always succeed, since we make sure our mbufs
+		 * are big enough to hold one MSS packet + header + ... etc.
+		 */
+/*		if (len <= MHLEN - hdrlen - max_linkhdr) { */
+
+			sbcopy(&so->so_snd, off, (int) len, mtod(m, caddr_t) + hdrlen);
+			m->m_len += len;
+
+/*		} else {
+ *			m->m_next = m_copy(so->so_snd.sb_mb, off, (int) len);
+ *			if (m->m_next == 0)
+ *				len = 0;
+ *		}
+ */
+		/*
+		 * If we're sending everything we've got, set PUSH.
+		 * (This will keep happy those implementations which only
+		 * give data to the user when a buffer fills or
+		 * a PUSH comes in.)
+		 */
+		if (off + len == so->so_snd.sb_cc)
+			flags |= TH_PUSH;
+	} else {
+		if (tp->t_flags & TF_ACKNOW)
+			STAT(tcpstat.tcps_sndacks++);
+		else if (flags & (TH_SYN|TH_FIN|TH_RST))
+			STAT(tcpstat.tcps_sndctrl++);
+		else if (SEQ_GT(tp->snd_up, tp->snd_una))
+			STAT(tcpstat.tcps_sndurg++);
+		else
+			STAT(tcpstat.tcps_sndwinup++);
+
+		m = m_get();
+		if (m == NULL) {
+/*			error = ENOBUFS; */
+			error = 1;
+			goto out;
+		}
+		m->m_data += IF_MAXLINKHDR;
+		m->m_len = hdrlen;
+	}
+
+	ti = mtod(m, struct tcpiphdr *);
+
+	memcpy((caddr_t)ti, &tp->t_template, sizeof (struct tcpiphdr));
+
+	/*
+	 * Fill in fields, remembering maximum advertised
+	 * window for use in delaying messages about window sizes.
+	 * If resending a FIN, be sure not to use a new sequence number.
+	 */
+	if (flags & TH_FIN && tp->t_flags & TF_SENTFIN &&
+	    tp->snd_nxt == tp->snd_max)
+		tp->snd_nxt--;
+	/*
+	 * If we are doing retransmissions, then snd_nxt will
+	 * not reflect the first unsent octet.  For ACK only
+	 * packets, we do not want the sequence number of the
+	 * retransmitted packet, we want the sequence number
+	 * of the next unsent octet.  So, if there is no data
+	 * (and no SYN or FIN), use snd_max instead of snd_nxt
+	 * when filling in ti_seq.  But if we are in persist
+	 * state, snd_max might reflect one byte beyond the
+	 * right edge of the window, so use snd_nxt in that
+	 * case, since we know we aren't doing a retransmission.
+	 * (retransmit and persist are mutually exclusive...)
+	 */
+	if (len || (flags & (TH_SYN|TH_FIN)) || tp->t_timer[TCPT_PERSIST])
+		ti->ti_seq = htonl(tp->snd_nxt);
+	else
+		ti->ti_seq = htonl(tp->snd_max);
+	ti->ti_ack = htonl(tp->rcv_nxt);
+	if (optlen) {
+		memcpy((caddr_t)(ti + 1), (caddr_t)opt, optlen);
+		ti->ti_off = (sizeof (struct tcphdr) + optlen) >> 2;
+	}
+	ti->ti_flags = flags;
+	/*
+	 * Calculate receive window.  Don't shrink window,
+	 * but avoid silly window syndrome.
+	 */
+	if (win < (long)(so->so_rcv.sb_datalen / 4) && win < (long)tp->t_maxseg)
+		win = 0;
+	if (win > (long)TCP_MAXWIN << tp->rcv_scale)
+		win = (long)TCP_MAXWIN << tp->rcv_scale;
+	if (win < (long)(tp->rcv_adv - tp->rcv_nxt))
+		win = (long)(tp->rcv_adv - tp->rcv_nxt);
+	ti->ti_win = htons((u_int16_t) (win>>tp->rcv_scale));
+
+	if (SEQ_GT(tp->snd_up, tp->snd_una)) {
+		ti->ti_urp = htons((u_int16_t)(tp->snd_up - ntohl(ti->ti_seq)));
+#ifdef notdef
+	if (SEQ_GT(tp->snd_up, tp->snd_nxt)) {
+		ti->ti_urp = htons((u_int16_t)(tp->snd_up - tp->snd_nxt));
+#endif
+		ti->ti_flags |= TH_URG;
+	} else
+		/*
+		 * If no urgent pointer to send, then we pull
+		 * the urgent pointer to the left edge of the send window
+		 * so that it doesn't drift into the send window on sequence
+		 * number wraparound.
+		 */
+		tp->snd_up = tp->snd_una;		/* drag it along */
+
+	/*
+	 * Put TCP length in extended header, and then
+	 * checksum extended header and data.
+	 */
+	if (len + optlen)
+		ti->ti_len = htons((u_int16_t)(sizeof (struct tcphdr) +
+		    optlen + len));
+	ti->ti_sum = cksum(m, (int)(hdrlen + len));
+
+	/*
+	 * In transmit state, time the transmission and arrange for
+	 * the retransmit.  In persist state, just set snd_max.
+	 */
+	if (tp->t_force == 0 || tp->t_timer[TCPT_PERSIST] == 0) {
+		tcp_seq startseq = tp->snd_nxt;
+
+		/*
+		 * Advance snd_nxt over sequence space of this segment.
+		 */
+		if (flags & (TH_SYN|TH_FIN)) {
+			if (flags & TH_SYN)
+				tp->snd_nxt++;
+			if (flags & TH_FIN) {
+				tp->snd_nxt++;
+				tp->t_flags |= TF_SENTFIN;
+			}
+		}
+		tp->snd_nxt += len;
+		if (SEQ_GT(tp->snd_nxt, tp->snd_max)) {
+			tp->snd_max = tp->snd_nxt;
+			/*
+			 * Time this transmission if not a retransmission and
+			 * not currently timing anything.
+			 */
+			if (tp->t_rtt == 0) {
+				tp->t_rtt = 1;
+				tp->t_rtseq = startseq;
+				STAT(tcpstat.tcps_segstimed++);
+			}
+		}
+
+		/*
+		 * Set retransmit timer if not currently set,
+		 * and not doing an ack or a keep-alive probe.
+		 * Initial value for retransmit timer is smoothed
+		 * round-trip time + 2 * round-trip time variance.
+		 * Initialize shift counter which is used for backoff
+		 * of retransmit time.
+		 */
+		if (tp->t_timer[TCPT_REXMT] == 0 &&
+		    tp->snd_nxt != tp->snd_una) {
+			tp->t_timer[TCPT_REXMT] = tp->t_rxtcur;
+			if (tp->t_timer[TCPT_PERSIST]) {
+				tp->t_timer[TCPT_PERSIST] = 0;
+				tp->t_rxtshift = 0;
+			}
+		}
+	} else
+		if (SEQ_GT(tp->snd_nxt + len, tp->snd_max))
+			tp->snd_max = tp->snd_nxt + len;
+
+	/*
+	 * Fill in IP length and desired time to live and
+	 * send to IP level.  There should be a better way
+	 * to handle ttl and tos; we could keep them in
+	 * the template, but need a way to checksum without them.
+	 */
+	m->m_len = hdrlen + len; /* XXX Needed? m_len should be correct */
+
+    {
+
+	((struct ip *)ti)->ip_len = m->m_len;
+
+	((struct ip *)ti)->ip_ttl = IPDEFTTL;
+	((struct ip *)ti)->ip_tos = so->so_iptos;
+
+/* #if BSD >= 43 */
+	/* Don't do IP options... */
+/*	error = ip_output(m, tp->t_inpcb->inp_options, &tp->t_inpcb->inp_route,
+ *	    so->so_options & SO_DONTROUTE, 0);
+ */
+	error = ip_output(so, m);
+
+/* #else
+ *	error = ip_output(m, (struct mbuf *)0, &tp->t_inpcb->inp_route,
+ *	    so->so_options & SO_DONTROUTE);
+ * #endif
+ */
+    }
+	if (error) {
+out:
+/*		if (error == ENOBUFS) {
+ *			tcp_quench(tp->t_inpcb, 0);
+ *			return (0);
+ *		}
+ */
+/*		if ((error == EHOSTUNREACH || error == ENETDOWN)
+ *		    && TCPS_HAVERCVDSYN(tp->t_state)) {
+ *			tp->t_softerror = error;
+ *			return (0);
+ *		}
+ */
+		return (error);
+	}
+	STAT(tcpstat.tcps_sndtotal++);
+
+	/*
+	 * Data sent (as far as we can tell).
+	 * If this advertises a larger window than any other segment,
+	 * then remember the size of the advertised window.
+	 * Any pending ACK has now been sent.
+	 */
+	if (win > 0 && SEQ_GT(tp->rcv_nxt+win, tp->rcv_adv))
+		tp->rcv_adv = tp->rcv_nxt + win;
+	tp->last_ack_sent = tp->rcv_nxt;
+	tp->t_flags &= ~(TF_ACKNOW|TF_DELACK);
+	if (sendalot)
+		goto again;
+
+	return (0);
+}
+
+void
+tcp_setpersist(struct tcpcb *tp)
+{
+    int t = ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1;
+
+/*	if (tp->t_timer[TCPT_REXMT])
+ *		panic("tcp_output REXMT");
+ */
+	/*
+	 * Start/restart persistence timer.
+	 */
+	TCPT_RANGESET(tp->t_timer[TCPT_PERSIST],
+	    t * tcp_backoff[tp->t_rxtshift],
+	    TCPTV_PERSMIN, TCPTV_PERSMAX);
+	if (tp->t_rxtshift < TCP_MAXRXTSHIFT)
+		tp->t_rxtshift++;
+}