svn commit: r362577 - head/sys/netinet

[Richard Scheffenegger]

Author: rscheff
Date: Wed Jun 24 13:42:42 2020
New Revision: 362577
URL: https://svnweb.freebsd.org/changeset/base/362577

Log:
  TCP: make after-idle work for transactional sessions.
  
  The use of t_rcvtime as proxy for the last transmission
  fails for transactional IO, where the client requests
  data before the server can respond with a bulk transfer.
  
  Set aside a dedicated variable to actually track the last
  locally sent segment going forward.
  
  Reported by:	rrs
  Reviewed by:	rrs, tuexen (mentor)
  Approved by:	tuexen (mentor), rgrimes (mentor)
  MFC after:	2 weeks
  Sponsored by:	NetApp, Inc.
  Differential Revision:	https://reviews.freebsd.org/D25016

Modified:
  head/sys/netinet/tcp_output.c
  head/sys/netinet/tcp_var.h

Modified: head/sys/netinet/tcp_output.c
==============================================================================
--- head/sys/netinet/tcp_output.c	Wed Jun 24 13:11:19 2020	(r362576)
+++ head/sys/netinet/tcp_output.c	Wed Jun 24 13:42:42 2020	(r362577)
@@ -260,7 +260,8 @@ tcp_output(struct tcpcb *tp)
 	 * to send, then transmit; otherwise, investigate further.
 	 */
 	idle = (tp->t_flags & TF_LASTIDLE) || (tp->snd_max == tp->snd_una);
-	if (idle && ticks - tp->t_rcvtime >= tp->t_rxtcur)
+	if (idle && (((ticks - tp->t_rcvtime) >= tp->t_rxtcur) ||
+	    (tp->t_sndtime && ((ticks - tp->t_sndtime) >= tp->t_rxtcur))))
 		cc_after_idle(tp);
 	tp->t_flags &= ~TF_LASTIDLE;
 	if (idle) {
@@ -1502,6 +1503,7 @@ out:
 			 * Time this transmission if not a retransmission and
 			 * not currently timing anything.
 			 */
+			tp->t_sndtime = ticks;
 			if (tp->t_rtttime == 0) {
 				tp->t_rtttime = ticks;
 				tp->t_rtseq = startseq;

Modified: head/sys/netinet/tcp_var.h
==============================================================================
--- head/sys/netinet/tcp_var.h	Wed Jun 24 13:11:19 2020	(r362576)
+++ head/sys/netinet/tcp_var.h	Wed Jun 24 13:42:42 2020	(r362577)
@@ -188,8 +188,9 @@ struct tcpcb {
 	tcp_seq	snd_wl2;		/* window update seg ack number */
 
 	tcp_seq	irs;			/* initial receive sequence number */
-	tcp_seq	iss;		        /* initial send sequence number */
-	u_int   t_acktime;
+	tcp_seq	iss;			/* initial send sequence number */
+	u_int	t_acktime;		/* RACK and BBR incoming new data was acked */
+	u_int	t_sndtime;		/* time last data was sent */
 	u_int	ts_recent_age;		/* when last updated */
 	tcp_seq	snd_recover;		/* for use in NewReno Fast Recovery */
 	uint16_t cl4_spare;		/* Spare to adjust CL 4 */