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Date:      Thu, 7 May 2020 20:29:38 +0000 (UTC)
From:      Randall Stewart <rrs@FreeBSD.org>
To:        src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org
Subject:   svn commit: r360798 - head/sys/netinet/tcp_stacks
Message-ID:  <202005072029.047KTcft063304@repo.freebsd.org>
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Author: rrs
Date: Thu May  7 20:29:38 2020
New Revision: 360798
URL: https://svnweb.freebsd.org/changeset/base/360798

Log:
  When in the SYN-SENT state bbr and rack will not properly send an ACK but instead start the D-ACK timer. This
  causes so_reuseport_lb_test to fail since it slows down how quickly the program runs until the timeout occurs
  and fails the test
  
  Sponsored by: Netflix inc.
  Differential Revision:	https://reviews.freebsd.org/D24747

Modified:
  head/sys/netinet/tcp_stacks/bbr.c
  head/sys/netinet/tcp_stacks/rack.c

Modified: head/sys/netinet/tcp_stacks/bbr.c
==============================================================================
--- head/sys/netinet/tcp_stacks/bbr.c	Thu May  7 20:27:32 2020	(r360797)
+++ head/sys/netinet/tcp_stacks/bbr.c	Thu May  7 20:29:38 2020	(r360798)
@@ -4078,6 +4078,7 @@ bbr_cong_signal(struct tcpcb *tp, struct tcphdr *th, u
  */
 #define DELAY_ACK(tp, bbr, nsegs)				\
 	(((tp->t_flags & TF_RXWIN0SENT) == 0) &&		\
+	 ((tp->t_flags & TF_DELACK) == 0) && 		 	\
 	 ((bbr->bbr_segs_rcvd + nsegs) < tp->t_delayed_ack) &&	\
 	 (tp->t_delayed_ack || (tp->t_flags & TF_NEEDSYN)))
 
@@ -8992,7 +8993,7 @@ bbr_do_syn_sent(struct mbuf *m, struct tcphdr *th, str
 		 * If there's data, delay ACK; if there's also a FIN ACKNOW
 		 * will be turned on later.
 		 */
-		if (DELAY_ACK(tp, bbr, 1) && tlen != 0 && (tfo_partial == 0)) {
+		if (DELAY_ACK(tp, bbr, 1) && tlen != 0 && !tfo_partial) {
 			bbr->bbr_segs_rcvd += 1;
 			tp->t_flags |= TF_DELACK;
 			bbr_timer_cancel(bbr, __LINE__, bbr->r_ctl.rc_rcvtime);

Modified: head/sys/netinet/tcp_stacks/rack.c
==============================================================================
--- head/sys/netinet/tcp_stacks/rack.c	Thu May  7 20:27:32 2020	(r360797)
+++ head/sys/netinet/tcp_stacks/rack.c	Thu May  7 20:29:38 2020	(r360798)
@@ -9320,7 +9320,15 @@ rack_do_syn_sent(struct mbuf *m, struct tcphdr *th, st
 		 * If there's data, delay ACK; if there's also a FIN ACKNOW
 		 * will be turned on later.
 		 */
-		rack_handle_delayed_ack(tp, rack, tlen, tfo_partial);
+		if (DELAY_ACK(tp, tlen) && tlen != 0 && !tfo_partial) {
+			rack_timer_cancel(tp, rack,
+					  rack->r_ctl.rc_rcvtime, __LINE__);
+			tp->t_flags |= TF_DELACK;
+		} else {
+			rack->r_wanted_output = 1;
+			tp->t_flags |= TF_ACKNOW;
+			rack->rc_dack_toggle = 0;
+		}
 		if (((thflags & (TH_CWR | TH_ECE)) == TH_ECE) &&
 		    (V_tcp_do_ecn == 1)) {
 			tp->t_flags2 |= TF2_ECN_PERMIT;

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