Add a flag TF_LASTIDLE, that forces a previously idle connection

to send all its data, especially when the data is less than one MSS.
This fixes an issue where the stack was delaying the sending
of data, eventhough there was enough window to send all the data and
the sending of data was emptying the socket buffer.

Problem found by Yoshihiro Tsuchiya (tsuchiya@flab.fujitsu.co.jp)

Submitted by: Jayanth Vijayaraghavan

1 files changed, 8 insertions, 1 deletions

diff --git a/sys/netinet/tcp_output.c b/sys/netinet/tcp_output.c
index 2740c72..e473b8e 100644
--- a/sys/netinet/tcp_output.c
+++ b/sys/netinet/tcp_output.c
@@ -135,7 +135,7 @@ tcp_output(tp)
 	 * If there is some data or critical controls (SYN, RST)
 	 * to send, then transmit; otherwise, investigate further.
 	 */
-	idle = (tp->snd_max == tp->snd_una);
+	idle = (tp->t_flags & TF_LASTIDLE) || (tp->snd_max == tp->snd_una);
 	if (idle && (ticks - tp->t_rcvtime) >= tp->t_rxtcur) {
 		/*
 		 * We have been idle for "a while" and no acks are
@@ -159,6 +159,13 @@ tcp_output(tp)
 		else     
 			tp->snd_cwnd = tp->t_maxseg * ss_fltsz;
 	}
+	tp->t_flags &= ~TF_LASTIDLE;
+	if (idle) {
+		if (tp->t_flags & TF_MORETOCOME) {
+			tp->t_flags |= TF_LASTIDLE;
+			idle = 0;
+		}
+	}
 again:
 	sendalot = 0;
 	off = tp->snd_nxt - tp->snd_una;