diff --git a/include/net/tcp.h b/include/net/tcp.h
index 8c05c25..8e9c28d 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -1573,6 +1573,8 @@
 void tcp4_proc_exit(void);
 #endif
 
+int tcp_rtx_synack(struct sock *sk, struct request_sock *req);
+
 /* TCP af-specific functions */
 struct tcp_sock_af_ops {
 #ifdef CONFIG_TCP_MD5SIG