Fix a bug with transmitter restart after receiving a 0 window. The

receiver was not sending an immediate ack with delayed acks turned on
when the input buffer is drained, preventing the transmitter from
restarting immediately.

Propogate the TCP_NODELAY option to accept()ed sockets.  (Helps tbench and
is a good idea anyway).

Some cleanup.  Identify additonal issues in comments.

MFC after:	1 day

1 files changed, 7 insertions, 2 deletions

diff --git a/sys/netinet/tcp_input.c b/sys/netinet/tcp_input.c
index 6740ebe..d8ece0b 100644
--- a/sys/netinet/tcp_input.c
+++ b/sys/netinet/tcp_input.c
@@ -152,10 +152,15 @@ do { \
 #endif
 
 /*
- * Indicate whether this ack should be delayed.
+ * Indicate whether this ack should be delayed.  We can delay the ack if
+ *     - delayed acks are enabled and
+ *     - there is no delayed ack timer in progress and
+ *     - our last ack wasn't a 0-sized window.  We never want to delay
+ *       the ack that opens up a 0-sized window.
  */
 #define DELAY_ACK(tp) \
-	(tcp_delack_enabled && !callout_pending(tp->tt_delack))
+	(tcp_delack_enabled && !callout_pending(tp->tt_delack) && \
+	(tp->t_flags & TF_RXWIN0SENT) == 0)
 
 static int
 tcp_reass(tp, th, tlenp, m)