Index: tcp_input.c
===================================================================
--- tcp_input.c
+++ tcp_input.c
@@ -2989,7 +2989,7 @@
 	 */
 	tfo_syn = ((tp->t_state == TCPS_SYN_RECEIVED) &&
 		   IS_FASTOPEN(tp->t_flags));
-	if ((tlen || (thflags & TH_FIN) || tfo_syn) &&
+	if ((tlen || (thflags & TH_FIN) || (tfo_syn && tlen > 0)) &&
 	    TCPS_HAVERCVDFIN(tp->t_state) == 0) {
 		tcp_seq save_start = th->th_seq;
 		tcp_seq save_rnxt  = tp->rcv_nxt;
Index: tcp_stacks/bbr.c
===================================================================
--- tcp_stacks/bbr.c
+++ tcp_stacks/bbr.c
@@ -6028,7 +6028,7 @@
 		 * or FIN if seq_out is adding more on and a FIN is present
 		 * (and we are not resending).
 		 */
-		if (th_flags & TH_SYN)
+		if ((th_flags & TH_SYN) && (tp->iss == seq_out))
 			len++;
 		if (th_flags & TH_FIN)
 			len++;
@@ -8369,7 +8369,7 @@
 	 */
 	tfo_syn = ((tp->t_state == TCPS_SYN_RECEIVED) &&
 		   IS_FASTOPEN(tp->t_flags));
-	if ((tlen || (thflags & TH_FIN) || tfo_syn) &&
+	if ((tlen || (thflags & TH_FIN) || (tfo_syn && tlen > 0)) &&
 	    TCPS_HAVERCVDFIN(tp->t_state) == 0) {
 		tcp_seq save_start = th->th_seq;
 		tcp_seq save_rnxt  = tp->rcv_nxt;
Index: tcp_stacks/rack.c
===================================================================
--- tcp_stacks/rack.c
+++ tcp_stacks/rack.c
@@ -6237,7 +6237,7 @@
 		 * or FIN if seq_out is adding more on and a FIN is present
 		 * (and we are not resending).
 		 */
-		if (th_flags & TH_SYN)
+		if ((th_flags & TH_SYN) && (seq_out == tp->iss)) 
 			len++;
 		if (th_flags & TH_FIN)
 			len++;
@@ -6280,6 +6280,7 @@
 		rsm->usec_orig_send = us_cts;
 		if (th_flags & TH_SYN) {
 			/* The data space is one beyond snd_una */
+			rsm->r_flags |= RACK_HAS_SIN;
 			rsm->r_start = seq_out + 1;
 			rsm->r_end = rsm->r_start + (len - 1);
 		} else {
@@ -8724,7 +8725,7 @@
 	 */
 	tfo_syn = ((tp->t_state == TCPS_SYN_RECEIVED) &&
 		   IS_FASTOPEN(tp->t_flags));
-	if ((tlen || (thflags & TH_FIN) || tfo_syn) &&
+	if ((tlen || (thflags & TH_FIN) || (tfo_syn && tlen > 0)) &&
 	    TCPS_HAVERCVDFIN(tp->t_state) == 0) {
 		tcp_seq save_start = th->th_seq;
 		tcp_seq save_rnxt  = tp->rcv_nxt;
@@ -12563,8 +12564,10 @@
 		len = 0;
 	}
 	/* Without fast-open there should never be data sent on a SYN */
-	if ((flags & TH_SYN) && (!IS_FASTOPEN(tp->t_flags)))
+	if ((flags & TH_SYN) && (!IS_FASTOPEN(tp->t_flags))) {
+		tp->snd_nxt = tp->iss;
 		len = 0;
+	}
 	orig_len = len;
 	if (len <= 0) {
 		/*
Index: tcp_stacks/tcp_rack.h
===================================================================
--- tcp_stacks/tcp_rack.h
+++ tcp_stacks/tcp_rack.h
@@ -39,6 +39,7 @@
 #define RACK_RWND_COLLAPSED 0x0100/* The peer collapsed the rwnd on the segment */
 #define RACK_APP_LIMITED    0x0200/* We went app limited after this send */
 #define RACK_WAS_ACKED	    0x0400/* a RTO undid the ack, but it already had a rtt calc done */
+#define RACK_HAS_SIN	    0x0800/* SIN is on this guy */
 #define RACK_NUM_OF_RETRANS 3
 
 #define RACK_INITIAL_RTO 1000 /* 1 second in milli seconds */