diff --git a/include/net/tcp.h b/include/net/tcp.h
index 5173fec..2b89f1a 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -840,6 +840,16 @@ static inline bool inet_exact_dif_match(struct net *net, struct sk_buff *skb)
 	return false;
 }
 
+/* TCP_SKB_CB reference means this can not be used from early demux */
+static inline int tcp_v4_sdif(struct sk_buff *skb)
+{
+#if IS_ENABLED(CONFIG_NET_L3_MASTER_DEV)
+	if (skb && ipv4_l3mdev_skb(TCP_SKB_CB(skb)->header.h4.flags))
+		return TCP_SKB_CB(skb)->header.h4.iif;
+#endif
+	return 0;
+}
+
 /* Due to TSO, an SKB can be composed of multiple actual
  * packets.  To keep these tracked properly, we use this.
  */