Index: sys/netinet/tcp.h
===================================================================
--- sys/netinet/tcp.h
+++ sys/netinet/tcp.h
@@ -71,8 +71,9 @@
 #define	TH_URG	0x20
 #define	TH_ECE	0x40
 #define	TH_CWR	0x80
+#define	TH_AE	0x100			/* maps into th_x2 */
 #define	TH_FLAGS	(TH_FIN|TH_SYN|TH_RST|TH_PUSH|TH_ACK|TH_URG|TH_ECE|TH_CWR)
-#define	PRINT_TH_FLAGS	"\20\1FIN\2SYN\3RST\4PUSH\5ACK\6URG\7ECE\10CWR"
+#define	PRINT_TH_FLAGS	"\20\1FIN\2SYN\3RST\4PUSH\5ACK\6URG\7ECE\10CWR\11AE"
 
 	u_short	th_win;			/* window */
 	u_short	th_sum;			/* checksum */
Index: sys/netinet/tcp_syncache.h
===================================================================
--- sys/netinet/tcp_syncache.h
+++ sys/netinet/tcp_syncache.h
@@ -90,6 +90,10 @@
 #define SCF_SIGNATURE	0x20			/* send MD5 digests */
 #define SCF_SACK	0x80			/* send SACK option */
 #define SCF_ECN		0x100			/* send ECN setup packet */
+#define SCF_ACE_N	0x200			/* send ACE non-ECT setup */
+#define SCF_ACE_0	0x400			/* send ACE ECT0 setup */
+#define SCF_ACE_1	0x800			/* send ACE ECT1 setup */
+#define SCF_ACE_CE	0x1000			/* send ACE CE setup */
 
 struct syncache_head {
 	struct mtx	sch_mtx;
Index: sys/netinet/tcp_var.h
===================================================================
--- sys/netinet/tcp_var.h
+++ sys/netinet/tcp_var.h
@@ -326,6 +326,8 @@
 #define	TF_NEEDFIN	0x000800	/* send FIN (implicit state) */
 #define	TF_NOPUSH	0x001000	/* don't push */
 #define	TF_PREVVALID	0x002000	/* saved values for bad rxmit valid */
+#define	TF_ACE_PERMIT	0x00004000	/* Accurate ECN mode */
+#define	TF_UNUSED1	0x00008000	/* unused flag bit 1 */
 #define	TF_MORETOCOME	0x010000	/* More data to be appended to sock */
 #define	TF_LQ_OVERFLOW	0x020000	/* listen queue overflow */
 #define	TF_LASTIDLE	0x040000	/* connection was previously idle */