diff --git a/sys/netinet/tcp_input.c b/sys/netinet/tcp_input.c
--- a/sys/netinet/tcp_input.c
+++ b/sys/netinet/tcp_input.c
@@ -633,6 +633,7 @@
 	to.to_flags = 0;
 	TCPSTAT_INC(tcps_rcvtotal);
 
+	m->m_pkthdr.tcp_tun_port = port;
 #ifdef INET6
 	if (isipv6) {
 		ip6 = mtod(m, struct ip6_hdr *);