On receiving 3 duplicate acknowledgements, SACK recovery was not being entered correctly.

Fix this problem by separating out the SACK and the newreno cases. Also, check
if we are in FASTRECOVERY for the sack case and if so, turn off dupacks.

Fix an issue where the congestion window was not being incremented by ssthresh.

Thanks to Mohan Srinivasan for finding this problem.

2 files changed, 40 insertions, 14 deletions

diff --git a/sys/netinet/tcp_input.c b/sys/netinet/tcp_input.c
index ee6d3ce..78b1fad 100644
--- a/sys/netinet/tcp_input.c
+++ b/sys/netinet/tcp_input.c
@@ -1931,12 +1931,25 @@ trimthenstep6:
 				} else if (tp->t_dupacks == tcprexmtthresh) {
 					tcp_seq onxt = tp->snd_nxt;
 					u_int win;
-					if ((tcp_do_newreno || 
-					    tp->sack_enable) &&
-					    SEQ_LEQ(th->th_ack,
-					            tp->snd_recover)) {
-						tp->t_dupacks = 0;
-						break;
+
+					/*
+					 * If we're doing sack, check to 
+					 * see if we're already in sack 
+					 * recovery. If we're not doing sack,
+					 * check to see if we're in newreno
+					 * recovery.
+					 */
+					if (tp->sack_enable) {
+						if (IN_FASTRECOVERY(tp)) {
+							tp->t_dupacks = 0;
+							break;
+						}
+					} else if (tcp_do_newreno) {
+						if (SEQ_LEQ(th->th_ack,
+						    tp->snd_recover)) {
+							tp->t_dupacks = 0;
+							break;
+						}
 					}
 					win = min(tp->snd_wnd, tp->snd_cwnd) /
 					    2 / tp->t_maxseg;
@@ -1953,7 +1966,7 @@ trimthenstep6:
 						    tp->t_maxseg * 
 						    tp->t_dupacks;
 						(void) tcp_output(tp);
-						tp->snd_cwnd = 
+						tp->snd_cwnd += 
 						    tp->snd_ssthresh;
 						goto drop;
 					}
diff --git a/sys/netinet/tcp_reass.c b/sys/netinet/tcp_reass.c
index ee6d3ce..78b1fad 100644
--- a/sys/netinet/tcp_reass.c
+++ b/sys/netinet/tcp_reass.c
@@ -1931,12 +1931,25 @@ trimthenstep6:
 				} else if (tp->t_dupacks == tcprexmtthresh) {
 					tcp_seq onxt = tp->snd_nxt;
 					u_int win;
-					if ((tcp_do_newreno || 
-					    tp->sack_enable) &&
-					    SEQ_LEQ(th->th_ack,
-					            tp->snd_recover)) {
-						tp->t_dupacks = 0;
-						break;
+
+					/*
+					 * If we're doing sack, check to 
+					 * see if we're already in sack 
+					 * recovery. If we're not doing sack,
+					 * check to see if we're in newreno
+					 * recovery.
+					 */
+					if (tp->sack_enable) {
+						if (IN_FASTRECOVERY(tp)) {
+							tp->t_dupacks = 0;
+							break;
+						}
+					} else if (tcp_do_newreno) {
+						if (SEQ_LEQ(th->th_ack,
+						    tp->snd_recover)) {
+							tp->t_dupacks = 0;
+							break;
+						}
 					}
 					win = min(tp->snd_wnd, tp->snd_cwnd) /
 					    2 / tp->t_maxseg;
@@ -1953,7 +1966,7 @@ trimthenstep6:
 						    tp->t_maxseg * 
 						    tp->t_dupacks;
 						(void) tcp_output(tp);
-						tp->snd_cwnd = 
+						tp->snd_cwnd += 
 						    tp->snd_ssthresh;
 						goto drop;
 					}