various fixes to SACK and FACK from adesai@cisco.com, tomh@tomh.org and

osuga@mml.yrp.nttdocomo.co.jp

2 files changed, 41 insertions, 11 deletions

diff --git a/sys/netinet/tcp_input.c b/sys/netinet/tcp_input.c
index e84f649e326..33a38b7dee4 100644
--- a/sys/netinet/tcp_input.c
+++ b/sys/netinet/tcp_input.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: tcp_input.c,v 1.68 2000/07/27 04:05:26 itojun Exp $	*/
+/*	$OpenBSD: tcp_input.c,v 1.69 2000/09/05 21:57:41 provos Exp $	*/
 /*	$NetBSD: tcp_input.c,v 1.23 1996/02/13 23:43:44 christos Exp $	*/
 
 /*
@@ -1563,9 +1563,7 @@ trimthenstep6:
 						 * False fast retx after 
 						 * timeout.  Do not cut window.
 						 */
-						tp->snd_cwnd += tp->t_maxseg;
 						tp->t_dupacks = 0;
-						(void) tcp_output(tp); 
 						goto drop;
 					}
 #endif
@@ -1581,13 +1579,13 @@ trimthenstep6:
 						tp->t_rtt = 0;
 						tcpstat.tcps_sndrexmitfast++;
 #if defined(TCP_SACK) && defined(TCP_FACK) 
+						tp->t_dupacks = tcprexmtthresh;
 						(void) tcp_output(tp);
 						/*
 						 * During FR, snd_cwnd is held
 						 * constant for FACK.
 						 */
 						tp->snd_cwnd = tp->snd_ssthresh;
-						tp->t_dupacks = tcprexmtthresh;
 #else
 						/* 
 						 * tcp_output() will send
@@ -1663,7 +1661,7 @@ trimthenstep6:
 					    th->th_ack) < tp->snd_ssthresh)
 						tp->snd_cwnd = 
 						   tcp_seq_subtract(tp->snd_max,
-					           th->th_ack) + tp->t_maxseg;
+					           th->th_ack);
 					tp->t_dupacks = 0;
 #if defined(TCP_SACK) && defined(TCP_FACK)
 					if (SEQ_GT(th->th_ack, tp->snd_fack))
@@ -1680,7 +1678,7 @@ trimthenstep6:
 			  	    tp->snd_ssthresh)
 					tp->snd_cwnd = 
 					    tcp_seq_subtract(tp->snd_max,
-					    th->th_ack) + tp->t_maxseg;
+					    th->th_ack);
 				tp->t_dupacks = 0;
 			}
 		}
@@ -1739,7 +1737,7 @@ trimthenstep6:
 		if (cw > tp->snd_ssthresh)
 			incr = incr * incr / cw;
 #if defined (TCP_SACK)
-		if (SEQ_GEQ(th->th_ack, tp->snd_last)) 
+		if (tp->t_dupacks < tcprexmtthresh)
 #endif
 		tp->snd_cwnd = min(cw + incr, TCP_MAXWIN<<tp->snd_scale);
 		}
@@ -1759,8 +1757,14 @@ trimthenstep6:
 		if (SEQ_LT(tp->snd_nxt, tp->snd_una))
 			tp->snd_nxt = tp->snd_una;
 #if defined (TCP_SACK) && defined (TCP_FACK)
-		if (SEQ_GT(tp->snd_una, tp->snd_fack))
+		if (SEQ_GT(tp->snd_una, tp->snd_fack)) {
 			tp->snd_fack = tp->snd_una;
+			/* Update snd_awnd for partial ACK
+			 * without any SACK blocks.
+			 */
+			tp->snd_awnd = tcp_seq_subtract(tp->snd_nxt,
+				tp->snd_fack) + tp->retran_data;
+		}
 #endif
 
 		switch (tp->t_state) {
@@ -2546,6 +2550,8 @@ tcp_del_sackholes(tp, th)
 				tp->snd_numholes--;
 			} else if (SEQ_LT(cur->start, lastack)) {
 				cur->start = lastack;
+				if (SEQ_LT(cur->rxmit, cur->start))
+					cur->rxmit = cur->start;
 				break;
 			} else
 				break;
@@ -2588,7 +2594,11 @@ tcp_sack_partialack(tp, th)
 		 * fact that tp->snd_una has not been updated yet.  In FACK
 		 * hold snd_cwnd constant during fast recovery.
 		 */
-		tp->snd_cwnd -= (th->th_ack - tp->snd_una - tp->t_maxseg);
+		if (tp->snd_cwnd > (th->th_ack - tp->snd_una)) {
+			tp->snd_cwnd -= th->th_ack - tp->snd_una;
+			tp->snd_cwnd += tp->t_maxseg;
+		} else
+			tp->snd_cwnd = tp->t_maxseg;
 #endif
 		return 1;
 	}
diff --git a/sys/netinet/tcp_output.c b/sys/netinet/tcp_output.c
index 07164c6ff8a..a746eea1b41 100644
--- a/sys/netinet/tcp_output.c
+++ b/sys/netinet/tcp_output.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: tcp_output.c,v 1.30 2000/02/21 21:42:13 provos Exp $	*/
+/*	$OpenBSD: tcp_output.c,v 1.31 2000/09/05 21:57:41 provos Exp $	*/
 /*	$NetBSD: tcp_output.c,v 1.16 1997/06/03 16:17:09 kml Exp $	*/
 
 /*
@@ -127,7 +127,17 @@ register struct tcpcb *tp;
 		return 0;
 	p = tp->snd_holes;
 	while (p) {
+#ifndef TCP_FACK
 		if (p->dups >= tcprexmtthresh && SEQ_LT(p->rxmit, p->end)) {
+#else
+		/* In FACK, if p->dups is less than tcprexmtthresh, but
+		 * snd_fack advances more than tcprextmtthresh * tp->t_maxseg,
+		 * tcp_input() will try fast retransmit. This forces output.
+		 */
+		if ((p->dups >= tcprexmtthresh ||
+		     tp->t_dupacks == tcprexmtthresh) &&
+		    SEQ_LT(p->rxmit, p->end)) {
+#endif /* TCP_FACK */
 			if (SEQ_LT(p->rxmit, tp->snd_una)) {/* old SACK hole */
 				p = p->next;
 				continue;
@@ -235,6 +245,15 @@ again:
 		tcp_sack_adjust(tp);
 #endif
 	off = tp->snd_nxt - tp->snd_una;
+#if defined(TCP_SACK) && defined(TCP_FACK)
+	/* Normally, sendable data is limited by off < tp->snd_cwnd.
+	 * But in FACK, sendable data is limited by snd_awnd < snd_cwnd,
+	 * regardless of offset.
+	 */
+	if (!tp->sack_disable && (tp->t_dupacks > tcprexmtthresh))
+		win = tp->snd_wnd;
+	else
+#endif
 	win = ulmin(tp->snd_wnd, tp->snd_cwnd);
 
 	flags = tcp_outflags[tp->t_state];
@@ -248,7 +267,8 @@ again:
 	 * now, and we previously incremented snd_cwnd in tcp_input().
 	 */
 	if (!tp->sack_disable && !sendalot) {
-		if ((p = tcp_sack_output(tp))) {
+		if (tp->t_dupacks >= tcprexmtthresh &&
+		    (p = tcp_sack_output(tp))) {
 			off = p->rxmit - tp->snd_una;
 			sack_rxmit = 1;
 #if 0