Index: sys/netinet/tcp_output.c
===================================================================
--- sys/netinet/tcp_output.c
+++ sys/netinet/tcp_output.c
@@ -194,7 +194,7 @@
  * Tcp output routine: figure out what should be sent and send it.
  */
 int
-tcp_output(struct tcpcb *tp)
+tcp_default_output(struct tcpcb *tp)
 {
 	struct socket *so = tp->t_inpcb->inp_socket;
 	int32_t len;
Index: sys/netinet/tcp_subr.c
===================================================================
--- sys/netinet/tcp_subr.c
+++ sys/netinet/tcp_subr.c
@@ -381,7 +381,7 @@
 
 static struct tcp_function_block tcp_def_funcblk = {
 	.tfb_tcp_block_name = "freebsd",
-	.tfb_tcp_output = tcp_output,
+	.tfb_tcp_output = tcp_default_output,
 	.tfb_tcp_do_segment = tcp_do_segment,
 	.tfb_tcp_ctloutput = tcp_default_ctloutput,
 	.tfb_tcp_handoff_ok = tcp_default_handoff_ok,
Index: sys/netinet/tcp_var.h
===================================================================
--- sys/netinet/tcp_var.h
+++ sys/netinet/tcp_var.h
@@ -385,6 +385,13 @@
 };
 
 TAILQ_HEAD(tcp_funchead, tcp_function);
+
+static inline int
+tcp_output(struct tcpcb *tp)
+{
+
+	return (tp->t_fb->tfb_tcp_output(tp));
+}
 #endif	/* _KERNEL */
 
 /*
@@ -1063,7 +1070,7 @@
 	 tcp_drop_syn_sent(struct inpcb *, int);
 struct tcpcb *
 	 tcp_newtcpcb(struct inpcb *);
-int	 tcp_output(struct tcpcb *);
+int	 tcp_default_output(struct tcpcb *);
 void	 tcp_state_change(struct tcpcb *, int);
 void	 tcp_respond(struct tcpcb *, void *,
 	    struct tcphdr *, struct mbuf *, tcp_seq, tcp_seq, int);