--- linux-4.9.37/include/linux/tcp.h	2017-07-12 16:42:41.000000000 +0300
+++ linux-4.9.y/include/linux/tcp.h	2021-06-07 13:01:34.000000000 +0300
@@ -432,4 +432,7 @@
 	tp->saved_syn = NULL;
 }
 
+int tcp_skb_shift(struct sk_buff *to, struct sk_buff *from, int pcount,
+		  int shiftlen);
+
 #endif	/* _LINUX_TCP_H */