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-rw-r--r--sys/netinet/tcp_input.c57
-rw-r--r--sys/netinet/tcp_reass.c57
-rw-r--r--sys/netinet/tcp_var.h24
3 files changed, 131 insertions, 7 deletions
diff --git a/sys/netinet/tcp_input.c b/sys/netinet/tcp_input.c
index 177b98f48c6f..8c6928bf1d50 100644
--- a/sys/netinet/tcp_input.c
+++ b/sys/netinet/tcp_input.c
@@ -31,7 +31,7 @@
* SUCH DAMAGE.
*
* @(#)tcp_input.c 8.12 (Berkeley) 5/24/95
- * $Id: tcp_input.c,v 1.37 1996/02/26 21:47:10 guido Exp $
+ * $Id: tcp_input.c,v 1.38 1996/03/11 15:13:29 davidg Exp $
*/
#ifndef TUBA_INCLUDE
@@ -492,7 +492,8 @@ findpcb:
if (ti->ti_len == 0) {
if (SEQ_GT(ti->ti_ack, tp->snd_una) &&
SEQ_LEQ(ti->ti_ack, tp->snd_max) &&
- tp->snd_cwnd >= tp->snd_wnd) {
+ tp->snd_cwnd >= tp->snd_wnd &&
+ tp->t_dupacks < tcprexmtthresh) {
/*
* this is a pure ack for outstanding data.
*/
@@ -1257,7 +1258,7 @@ trimthenstep6:
* If the congestion window was inflated to account
* for the other side's cached packets, retract it.
*/
- if (tp->t_dupacks > tcprexmtthresh &&
+ if (tp->t_dupacks >= tcprexmtthresh &&
tp->snd_cwnd > tp->snd_ssthresh)
tp->snd_cwnd = tp->snd_ssthresh;
tp->t_dupacks = 0;
@@ -1819,6 +1820,7 @@ tcp_xmit_timer(tp, rtt)
register struct tcpcb *tp;
short rtt;
{
+#ifdef notdef
register short delta;
tcpstat.tcps_rttupdated++;
@@ -1858,6 +1860,50 @@ tcp_xmit_timer(tp, rtt)
tp->t_srtt = rtt << TCP_RTT_SHIFT;
tp->t_rttvar = rtt << (TCP_RTTVAR_SHIFT - 1);
}
+#else /* Peterson paper */
+ register int delta;
+
+ tcpstat.tcps_rttupdated++;
+ tp->t_rttupdated++;
+ if (tp->t_srtt != 0) {
+ /*
+ * srtt is stored as fixed point with 5 bits after the
+ * binary point (i.e., scaled by 8). The following magic
+ * is equivalent to the smoothing algorithm in rfc793 with
+ * an alpha of .875 (srtt = rtt/8 + srtt*7/8 in fixed
+ * point). Adjust rtt to origin 0.
+ */
+ delta = ((rtt - 1) << TCP_DELTA_SHIFT)
+ - (tp->t_srtt >> (TCP_RTT_SHIFT - TCP_DELTA_SHIFT));
+
+ if ((tp->t_srtt += delta) <= 0)
+ tp->t_srtt = 1;
+
+ /*
+ * We accumulate a smoothed rtt variance (actually, a
+ * smoothed mean difference), then set the retransmit
+ * timer to smoothed rtt + 4 times the smoothed variance.
+ * rttvar is stored as fixed point with 4 bits after the
+ * binary point (scaled by 16). The following is
+ * equivalent to rfc793 smoothing with an alpha of .75
+ * (rttvar = rttvar*3/4 + |delta| / 4). This replaces
+ * rfc793's wired-in beta.
+ */
+ if (delta < 0)
+ delta = -delta;
+ delta -= tp->t_rttvar >> (TCP_RTTVAR_SHIFT - TCP_DELTA_SHIFT);
+ if ((tp->t_rttvar += delta) <= 0)
+ tp->t_rttvar = 1;
+ } else {
+ /*
+ * No rtt measurement yet - use the unsmoothed rtt.
+ * Set the variance to half the rtt (so our first
+ * retransmit happens at 3*rtt).
+ */
+ tp->t_srtt = rtt << TCP_RTT_SHIFT;
+ tp->t_rttvar = rtt << (TCP_RTTVAR_SHIFT - 1);
+ }
+#endif
tp->t_rtt = 0;
tp->t_rxtshift = 0;
@@ -1872,8 +1918,13 @@ tcp_xmit_timer(tp, rtt)
* statistical, we have to test that we don't drop below
* the minimum feasible timer (which is 2 ticks).
*/
+#ifdef notdef
TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp),
tp->t_rttmin, TCPTV_REXMTMAX);
+#else /* Peterson */
+ TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp),
+ max(tp->t_rttmin, TCPTV_MIN + rtt - 1), TCPTV_REXMTMAX);
+#endif
/*
* We received an ack for a packet that wasn't retransmitted;
diff --git a/sys/netinet/tcp_reass.c b/sys/netinet/tcp_reass.c
index 177b98f48c6f..8c6928bf1d50 100644
--- a/sys/netinet/tcp_reass.c
+++ b/sys/netinet/tcp_reass.c
@@ -31,7 +31,7 @@
* SUCH DAMAGE.
*
* @(#)tcp_input.c 8.12 (Berkeley) 5/24/95
- * $Id: tcp_input.c,v 1.37 1996/02/26 21:47:10 guido Exp $
+ * $Id: tcp_input.c,v 1.38 1996/03/11 15:13:29 davidg Exp $
*/
#ifndef TUBA_INCLUDE
@@ -492,7 +492,8 @@ findpcb:
if (ti->ti_len == 0) {
if (SEQ_GT(ti->ti_ack, tp->snd_una) &&
SEQ_LEQ(ti->ti_ack, tp->snd_max) &&
- tp->snd_cwnd >= tp->snd_wnd) {
+ tp->snd_cwnd >= tp->snd_wnd &&
+ tp->t_dupacks < tcprexmtthresh) {
/*
* this is a pure ack for outstanding data.
*/
@@ -1257,7 +1258,7 @@ trimthenstep6:
* If the congestion window was inflated to account
* for the other side's cached packets, retract it.
*/
- if (tp->t_dupacks > tcprexmtthresh &&
+ if (tp->t_dupacks >= tcprexmtthresh &&
tp->snd_cwnd > tp->snd_ssthresh)
tp->snd_cwnd = tp->snd_ssthresh;
tp->t_dupacks = 0;
@@ -1819,6 +1820,7 @@ tcp_xmit_timer(tp, rtt)
register struct tcpcb *tp;
short rtt;
{
+#ifdef notdef
register short delta;
tcpstat.tcps_rttupdated++;
@@ -1858,6 +1860,50 @@ tcp_xmit_timer(tp, rtt)
tp->t_srtt = rtt << TCP_RTT_SHIFT;
tp->t_rttvar = rtt << (TCP_RTTVAR_SHIFT - 1);
}
+#else /* Peterson paper */
+ register int delta;
+
+ tcpstat.tcps_rttupdated++;
+ tp->t_rttupdated++;
+ if (tp->t_srtt != 0) {
+ /*
+ * srtt is stored as fixed point with 5 bits after the
+ * binary point (i.e., scaled by 8). The following magic
+ * is equivalent to the smoothing algorithm in rfc793 with
+ * an alpha of .875 (srtt = rtt/8 + srtt*7/8 in fixed
+ * point). Adjust rtt to origin 0.
+ */
+ delta = ((rtt - 1) << TCP_DELTA_SHIFT)
+ - (tp->t_srtt >> (TCP_RTT_SHIFT - TCP_DELTA_SHIFT));
+
+ if ((tp->t_srtt += delta) <= 0)
+ tp->t_srtt = 1;
+
+ /*
+ * We accumulate a smoothed rtt variance (actually, a
+ * smoothed mean difference), then set the retransmit
+ * timer to smoothed rtt + 4 times the smoothed variance.
+ * rttvar is stored as fixed point with 4 bits after the
+ * binary point (scaled by 16). The following is
+ * equivalent to rfc793 smoothing with an alpha of .75
+ * (rttvar = rttvar*3/4 + |delta| / 4). This replaces
+ * rfc793's wired-in beta.
+ */
+ if (delta < 0)
+ delta = -delta;
+ delta -= tp->t_rttvar >> (TCP_RTTVAR_SHIFT - TCP_DELTA_SHIFT);
+ if ((tp->t_rttvar += delta) <= 0)
+ tp->t_rttvar = 1;
+ } else {
+ /*
+ * No rtt measurement yet - use the unsmoothed rtt.
+ * Set the variance to half the rtt (so our first
+ * retransmit happens at 3*rtt).
+ */
+ tp->t_srtt = rtt << TCP_RTT_SHIFT;
+ tp->t_rttvar = rtt << (TCP_RTTVAR_SHIFT - 1);
+ }
+#endif
tp->t_rtt = 0;
tp->t_rxtshift = 0;
@@ -1872,8 +1918,13 @@ tcp_xmit_timer(tp, rtt)
* statistical, we have to test that we don't drop below
* the minimum feasible timer (which is 2 ticks).
*/
+#ifdef notdef
TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp),
tp->t_rttmin, TCPTV_REXMTMAX);
+#else /* Peterson */
+ TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp),
+ max(tp->t_rttmin, TCPTV_MIN + rtt - 1), TCPTV_REXMTMAX);
+#endif
/*
* We received an ack for a packet that wasn't retransmitted;
diff --git a/sys/netinet/tcp_var.h b/sys/netinet/tcp_var.h
index d53251a071e1..30351439d603 100644
--- a/sys/netinet/tcp_var.h
+++ b/sys/netinet/tcp_var.h
@@ -31,7 +31,7 @@
* SUCH DAMAGE.
*
* @(#)tcp_var.h 8.4 (Berkeley) 5/24/95
- * $Id: tcp_var.h,v 1.29 1996/02/26 21:47:13 guido Exp $
+ * $Id: tcp_var.h,v 1.30 1996/02/27 15:12:53 bde Exp $
*/
#ifndef _NETINET_TCP_VAR_H_
@@ -191,10 +191,18 @@ struct rmxp_tao {
* and thus an "ALPHA" of 0.875. rttvar has 2 bits to the right of the
* binary point, and is smoothed with an ALPHA of 0.75.
*/
+#ifdef notdef
#define TCP_RTT_SCALE 8 /* multiplier for srtt; 3 bits frac. */
#define TCP_RTT_SHIFT 3 /* shift for srtt; 3 bits frac. */
#define TCP_RTTVAR_SCALE 4 /* multiplier for rttvar; 2 bits */
#define TCP_RTTVAR_SHIFT 2 /* shift for rttvar; 2 bits */
+#else
+#define TCP_RTT_SCALE 32 /* multiplier for srtt; 3 bits frac. */
+#define TCP_RTT_SHIFT 5 /* shift for srtt; 3 bits frac. */
+#define TCP_RTTVAR_SCALE 16 /* multiplier for rttvar; 2 bits */
+#define TCP_RTTVAR_SHIFT 4 /* shift for rttvar; 2 bits */
+#define TCP_DELTA_SHIFT 2 /* see tcp_input.c */
+#endif
/*
* The initial retransmission should happen at rtt + 4 * rttvar.
@@ -206,11 +214,25 @@ struct rmxp_tao {
* 1.5 tick we need. But, because the bias is
* statistical, we have to test that we don't drop below
* the minimum feasible timer (which is 2 ticks).
+#ifdef notdef
* This macro assumes that the value of TCP_RTTVAR_SCALE
* is the same as the multiplier for rttvar.
+#else
+ * This version of the macro adapted from a paper by Lawrence
+ * Brakmo and Larry Peterson which outlines a problem caused
+ * by insufficient precision in the original implementation,
+ * which results in inappropriately large RTO values for very
+ * fast networks.
+#endif
*/
+#ifdef notdef
#define TCP_REXMTVAL(tp) \
(((tp)->t_srtt >> TCP_RTT_SHIFT) + (tp)->t_rttvar)
+#else
+#define TCP_REXMTVAL(tp) \
+ ((((tp)->t_srtt >> (TCP_RTT_SHIFT - TCP_RTTVAR_SHIFT)) \
+ + ((tp)->t_rttvar) >> TCP_RTTVAR_SHIFT))
+#endif
/* XXX
* We want to avoid doing m_pullup on incoming packets but that
generated by cgit v1.2.3 (git 2.25.1) at 2024-10-07 19:48:04 +0000