diff --git a/include/net/tcp.h b/include/net/tcp.h
index 304a8e1..123979f 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -1220,6 +1220,7 @@
 
 bool tcp_prequeue(struct sock *sk, struct sk_buff *skb);
 bool tcp_add_backlog(struct sock *sk, struct sk_buff *skb);
+int tcp_filter(struct sock *sk, struct sk_buff *skb);
 
 #undef STATE_TRACE