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Date:      Mon, 28 Jan 2019 12:45:31 +0000 (UTC)
From:      Michael Tuexen <tuexen@FreeBSD.org>
To:        src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org
Subject:   svn commit: r343525 - in head/sys/netinet: . tcp_stacks
Message-ID:  <201901281245.x0SCjVpw048723@repo.freebsd.org>
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Author: tuexen
Date: Mon Jan 28 12:45:31 2019
New Revision: 343525
URL: https://svnweb.freebsd.org/changeset/base/343525

Log:
  Fix the detection of ECN-setup SYN-ACK packets.
  
  RFC 3168 defines an ECN-setup SYN-ACK packet as on with the ECE flags
  set and the CWR flags not set. The code was only checking if ECE flag
  is set. This patch adds the check to verify that the CWR flags is not
  set.
  
  Submitted by:		Richard Scheffenegger
  Reviewed by:		tuexen@
  MFC after:		1 week
  Differential Revision:	https://reviews.freebsd.org/D18996

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

Modified: head/sys/netinet/tcp_input.c
==============================================================================
--- head/sys/netinet/tcp_input.c	Mon Jan 28 11:39:54 2019	(r343524)
+++ head/sys/netinet/tcp_input.c	Mon Jan 28 12:45:31 2019	(r343525)
@@ -2010,7 +2010,8 @@ tcp_do_segment(struct mbuf *m, struct tcphdr *th, stru
 			else
 				tp->t_flags |= TF_ACKNOW;
 
-			if ((thflags & TH_ECE) && V_tcp_do_ecn) {
+			if (((thflags & (TH_CWR | TH_ECE)) == TH_ECE) &&
+			    V_tcp_do_ecn) {
 				tp->t_flags |= TF_ECN_PERMIT;
 				TCPSTAT_INC(tcps_ecn_shs);
 			}

Modified: head/sys/netinet/tcp_stacks/rack.c
==============================================================================
--- head/sys/netinet/tcp_stacks/rack.c	Mon Jan 28 11:39:54 2019	(r343524)
+++ head/sys/netinet/tcp_stacks/rack.c	Mon Jan 28 12:45:31 2019	(r343525)
@@ -5233,7 +5233,8 @@ rack_do_syn_sent(struct mbuf *m, struct tcphdr *th, st
 			tp->t_flags |= TF_ACKNOW;
 		}
 
-		if ((thflags & TH_ECE) && V_tcp_do_ecn) {
+		if (((thflags & (TH_CWR | TH_ECE)) == TH_ECE) &&
+		    V_tcp_do_ecn) {
 			tp->t_flags |= TF_ECN_PERMIT;
 			TCPSTAT_INC(tcps_ecn_shs);
 		}

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