diff --git a/share/man/man4/tcp.4 b/share/man/man4/tcp.4
index cbb8021226fe..873cfe4b822a 100644
--- a/share/man/man4/tcp.4
+++ b/share/man/man4/tcp.4
@@ -34,7 +34,7 @@
 .\"     From: @(#)tcp.4	8.1 (Berkeley) 6/5/93
 .\" $FreeBSD$
 .\"
-.Dd April 17, 2021
+.Dd April 18, 2021
 .Dt TCP 4
 .Os
 .Sh NAME
@@ -329,6 +329,9 @@ currently executing.
 This is typically used after a process or thread inherits a listen
 socket from its parent, and sets its CPU affinity to a particular core.
 .El
+.It Dv TCP_REMOTE_UDP_ENCAPS_PORT
+Set and get the remote UDP encapsulation port.
+It can only be set on a closed TCP socket.
 .El
 .Pp
 The option level for the
@@ -755,6 +758,16 @@ A CSV list of template_spec=percent key-value pairs which controls the per
 template sampling rates when
 .Xr stats 3
 sampling is enabled.
+.It Va udp_tunneling_port
+The local UDP encapsulation port.
+A value of 0 indicates that UDP encapsulation is disabled.
+The default is 0.
+.It Va udp_tunneling_overhead
+The overhead taken into account when using UDP encapsulation.
+Since MSS clamping by middleboxes will most likely not work, values larger than
+8 (the size of the UDP header) are also supported.
+Supported values are between 8 and 1024.
+The default is 8.
 .El
 .Sh ERRORS
 A socket operation may fail with one of the following errors returned:
diff --git a/sys/netinet/tcp.h b/sys/netinet/tcp.h
index 0b71bd4658f8..d2bf1f8431fd 100644
--- a/sys/netinet/tcp.h
+++ b/sys/netinet/tcp.h
@@ -183,6 +183,7 @@ struct tcphdr {
 #define	TCP_RXTLS_MODE	42	/* Receive TLS mode */
 #define	TCP_CONGESTION	64	/* get/set congestion control algorithm */
 #define	TCP_CCALGOOPT	65	/* get/set cc algorithm specific options */
+#define TCP_REMOTE_UDP_ENCAPS_PORT 71	/* Enable TCP over UDP tunneling via the specified port */
 #define TCP_DELACK  	72	/* socket option for delayed ack */
 #define TCP_FIN_IS_RST 73	/* A fin from the peer is treated has a RST */
 #define TCP_LOG_LIMIT  74	/* Limit to number of records in tcp-log */
diff --git a/sys/netinet/tcp_input.c b/sys/netinet/tcp_input.c
index ed184de4a4bf..8592f3313725 100644
--- a/sys/netinet/tcp_input.c
+++ b/sys/netinet/tcp_input.c
@@ -123,6 +123,7 @@ __FBSDID("$FreeBSD$");
 #ifdef TCP_OFFLOAD
 #include <netinet/tcp_offload.h>
 #endif
+#include <netinet/udp.h>
 
 #include <netipsec/ipsec_support.h>
 
@@ -567,7 +568,7 @@ cc_ecnpkt_handler(struct tcpcb *tp, struct tcphdr *th, uint8_t iptos)
  */
 #ifdef INET6
 int
-tcp6_input(struct mbuf **mp, int *offp, int proto)
+tcp6_input_with_port(struct mbuf **mp, int *offp, int proto, uint16_t port)
 {
 	struct mbuf *m;
 	struct in6_ifaddr *ia6;
@@ -597,12 +598,19 @@ tcp6_input(struct mbuf **mp, int *offp, int proto)
 	}
 
 	*mp = m;
-	return (tcp_input(mp, offp, proto));
+	return (tcp_input_with_port(mp, offp, proto, port));
+}
+
+int
+tcp6_input(struct mbuf **mp, int *offp, int proto)
+{
+
+	return(tcp6_input_with_port(mp, offp, proto, 0));
 }
 #endif /* INET6 */
 
 int
-tcp_input(struct mbuf **mp, int *offp, int proto)
+tcp_input_with_port(struct mbuf **mp, int *offp, int proto, uint16_t port)
 {
 	struct mbuf *m = *mp;
 	struct tcphdr *th = NULL;
@@ -659,6 +667,8 @@ tcp_input(struct mbuf **mp, int *offp, int proto)
 		ip6 = mtod(m, struct ip6_hdr *);
 		th = (struct tcphdr *)((caddr_t)ip6 + off0);
 		tlen = sizeof(*ip6) + ntohs(ip6->ip6_plen) - off0;
+		if (port)
+			goto skip6_csum;
 		if (m->m_pkthdr.csum_flags & CSUM_DATA_VALID_IPV6) {
 			if (m->m_pkthdr.csum_flags & CSUM_PSEUDO_HDR)
 				th->th_sum = m->m_pkthdr.csum_data;
@@ -672,7 +682,7 @@ tcp_input(struct mbuf **mp, int *offp, int proto)
 			TCPSTAT_INC(tcps_rcvbadsum);
 			goto drop;
 		}
-
+	skip6_csum:
 		/*
 		 * Be proactive about unspecified IPv6 address in source.
 		 * As we use all-zero to indicate unbounded/unconnected pcb,
@@ -713,6 +723,8 @@ tcp_input(struct mbuf **mp, int *offp, int proto)
 		tlen = ntohs(ip->ip_len) - off0;
 
 		iptos = ip->ip_tos;
+		if (port)
+			goto skip_csum;
 		if (m->m_pkthdr.csum_flags & CSUM_DATA_VALID) {
 			if (m->m_pkthdr.csum_flags & CSUM_PSEUDO_HDR)
 				th->th_sum = m->m_pkthdr.csum_data;
@@ -742,8 +754,8 @@ tcp_input(struct mbuf **mp, int *offp, int proto)
 			ip->ip_v = IPVERSION;
 			ip->ip_hl = off0 >> 2;
 		}
-
-		if (th->th_sum) {
+	skip_csum:
+		if (th->th_sum && (port == 0)) {
 			TCPSTAT_INC(tcps_rcvbadsum);
 			goto drop;
 		}
@@ -1004,6 +1016,11 @@ tcp_input(struct mbuf **mp, int *offp, int proto)
 		goto dropwithreset;
 	}
 
+	if ((tp->t_port != port) && (tp->t_state > TCPS_LISTEN)) {
+		rstreason = BANDLIM_RST_CLOSEDPORT;
+		goto dropwithreset;
+	}
+
 #ifdef TCP_OFFLOAD
 	if (tp->t_flags & TF_TOE) {
 		tcp_offload_input(tp, m);
@@ -1074,7 +1091,7 @@ tcp_input(struct mbuf **mp, int *offp, int proto)
 			 * NB: syncache_expand() doesn't unlock
 			 * inp and tcpinfo locks.
 			 */
-			rstreason = syncache_expand(&inc, &to, th, &so, m);
+			rstreason = syncache_expand(&inc, &to, th, &so, m, port);
 			if (rstreason < 0) {
 				/*
 				 * A failing TCP MD5 signature comparison
@@ -1156,7 +1173,7 @@ tcp_input(struct mbuf **mp, int *offp, int proto)
 		 * causes.
 		 */
 		if (thflags & TH_RST) {
-			syncache_chkrst(&inc, th, m);
+			syncache_chkrst(&inc, th, m, port);
 			goto dropunlock;
 		}
 		/*
@@ -1178,7 +1195,7 @@ tcp_input(struct mbuf **mp, int *offp, int proto)
 				log(LOG_DEBUG, "%s; %s: Listen socket: "
 				    "SYN|ACK invalid, segment rejected\n",
 				    s, __func__);
-			syncache_badack(&inc);	/* XXX: Not needed! */
+			syncache_badack(&inc, port);	/* XXX: Not needed! */
 			TCPSTAT_INC(tcps_badsyn);
 			rstreason = BANDLIM_RST_OPENPORT;
 			goto dropwithreset;
@@ -1337,7 +1354,7 @@ tcp_input(struct mbuf **mp, int *offp, int proto)
 		TCP_PROBE3(debug__input, tp, th, m);
 		tcp_dooptions(&to, optp, optlen, TO_SYN);
 		if ((so = syncache_add(&inc, &to, th, inp, so, m, NULL, NULL,
-		    iptos)) != NULL)
+		    iptos, port)) != NULL)
 			goto tfo_socket_result;
 
 		/*
@@ -1468,6 +1485,12 @@ tcp_autorcvbuf(struct mbuf *m, struct tcphdr *th, struct socket *so,
 	return (newsize);
 }
 
+int
+tcp_input(struct mbuf **mp, int *offp, int proto)
+{
+	return(tcp_input_with_port(mp, offp, proto, 0));
+}
+
 void
 tcp_handle_wakeup(struct tcpcb *tp, struct socket *so)
 {
@@ -3672,11 +3695,13 @@ tcp_mss_update(struct tcpcb *tp, int offer, int mtuoffer,
 			    sizeof (struct ip6_hdr) + sizeof (struct tcphdr) :
 			    sizeof (struct tcpiphdr);
 #else
-	const size_t min_protoh = sizeof(struct tcpiphdr);
+	 size_t min_protoh = sizeof(struct tcpiphdr);
 #endif
 
 	INP_WLOCK_ASSERT(tp->t_inpcb);
 
+	if (tp->t_port)
+		min_protoh += V_tcp_udp_tunneling_overhead;
 	if (mtuoffer != -1) {
 		KASSERT(offer == -1, ("%s: conflict", __func__));
 		offer = mtuoffer - min_protoh;
diff --git a/sys/netinet/tcp_output.c b/sys/netinet/tcp_output.c
index e23cdc749e98..5bda2be14df0 100644
--- a/sys/netinet/tcp_output.c
+++ b/sys/netinet/tcp_output.c
@@ -101,6 +101,8 @@ __FBSDID("$FreeBSD$");
 
 #include <netipsec/ipsec_support.h>
 
+#include <netinet/udp.h>
+#include <netinet/udp_var.h>
 #include <machine/in_cksum.h>
 
 #include <security/mac/mac_framework.h>
@@ -207,7 +209,7 @@ tcp_output(struct tcpcb *tp)
 #endif
 	struct tcphdr *th;
 	u_char opt[TCP_MAXOLEN];
-	unsigned ipoptlen, optlen, hdrlen;
+	unsigned ipoptlen, optlen, hdrlen, ulen;
 #if defined(IPSEC) || defined(IPSEC_SUPPORT)
 	unsigned ipsec_optlen = 0;
 #endif
@@ -216,6 +218,7 @@ tcp_output(struct tcpcb *tp)
 	struct sackhole *p;
 	int tso, mtu;
 	struct tcpopt to;
+	struct udphdr *udp = NULL;
 	unsigned int wanted_cookie = 0;
 	unsigned int dont_sendalot = 0;
 #if 0
@@ -558,6 +561,7 @@ tcp_output(struct tcpcb *tp)
 #endif
 
 	if ((tp->t_flags & TF_TSO) && V_tcp_do_tso && len > tp->t_maxseg &&
+	    (tp->t_port == 0) &&
 	    ((tp->t_flags & TF_SIGNATURE) == 0) &&
 	    tp->rcv_numsacks == 0 && sack_rxmit == 0 &&
 	    ipoptlen == 0 && !(flags & TH_SYN))
@@ -800,6 +804,8 @@ tcp_output(struct tcpcb *tp)
 		/* Maximum segment size. */
 		if (flags & TH_SYN) {
 			to.to_mss = tcp_mssopt(&tp->t_inpcb->inp_inc);
+			if (tp->t_port)
+				to.to_mss -= V_tcp_udp_tunneling_overhead;
 			to.to_flags |= TOF_MSS;
 
 			/*
@@ -887,7 +893,14 @@ tcp_output(struct tcpcb *tp)
 		    !(to.to_flags & TOF_FASTOPEN))
 			len = 0;
 	}
-
+	if (tp->t_port) {
+		if (V_tcp_udp_tunneling_port == 0) {
+			/* The port was removed?? */
+			SOCKBUF_UNLOCK(&so->so_snd);
+			return (EHOSTUNREACH);
+		}
+		hdrlen += sizeof(struct udphdr);
+	}
 	/*
 	 * Adjust data length if insertion of options will
 	 * bump the packet length beyond the t_maxseg length.
@@ -1140,8 +1153,17 @@ tcp_output(struct tcpcb *tp)
 #ifdef INET6
 	if (isipv6) {
 		ip6 = mtod(m, struct ip6_hdr *);
-		th = (struct tcphdr *)(ip6 + 1);
-		tcpip_fillheaders(tp->t_inpcb, ip6, th);
+		if (tp->t_port) {
+			udp = (struct udphdr *)((caddr_t)ip6 + ipoptlen + sizeof(struct ip6_hdr));
+			udp->uh_sport = htons(V_tcp_udp_tunneling_port);
+			udp->uh_dport = tp->t_port;
+			ulen = hdrlen + len - sizeof(struct ip6_hdr);
+			udp->uh_ulen = htons(ulen);
+			th = (struct tcphdr *)(udp + 1);
+		} else {
+			th = (struct tcphdr *)(ip6 + 1);
+		}
+		tcpip_fillheaders(tp->t_inpcb, tp->t_port, ip6, th);
 	} else
 #endif /* INET6 */
 	{
@@ -1149,8 +1171,16 @@ tcp_output(struct tcpcb *tp)
 #ifdef TCPDEBUG
 		ipov = (struct ipovly *)ip;
 #endif
-		th = (struct tcphdr *)(ip + 1);
-		tcpip_fillheaders(tp->t_inpcb, ip, th);
+		if (tp->t_port) {
+			udp = (struct udphdr *)((caddr_t)ip + ipoptlen + sizeof(struct ip));
+			udp->uh_sport = htons(V_tcp_udp_tunneling_port);
+			udp->uh_dport = tp->t_port;
+			ulen = hdrlen + len - sizeof(struct ip);
+			udp->uh_ulen = htons(ulen);
+			th = (struct tcphdr *)(udp + 1);
+		} else
+			th = (struct tcphdr *)(ip + 1);
+		tcpip_fillheaders(tp->t_inpcb, tp->t_port, ip, th);
 	}
 
 	/*
@@ -1309,7 +1339,6 @@ tcp_output(struct tcpcb *tp)
 	 * checksum extended header and data.
 	 */
 	m->m_pkthdr.len = hdrlen + len; /* in6_cksum() need this */
-	m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum);
 
 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE)
 	if (to.to_flags & TOF_SIGNATURE) {
@@ -1336,9 +1365,19 @@ tcp_output(struct tcpcb *tp)
 		 * There is no need to fill in ip6_plen right now.
 		 * It will be filled later by ip6_output.
 		 */
-		m->m_pkthdr.csum_flags = CSUM_TCP_IPV6;
-		th->th_sum = in6_cksum_pseudo(ip6, sizeof(struct tcphdr) +
-		    optlen + len, IPPROTO_TCP, 0);
+		if (tp->t_port) {
+			m->m_pkthdr.csum_flags = CSUM_UDP_IPV6;
+			m->m_pkthdr.csum_data = offsetof(struct udphdr, uh_sum);
+			udp->uh_sum = in6_cksum_pseudo(ip6, ulen, IPPROTO_UDP, 0);
+			th->th_sum = htons(0);
+			UDPSTAT_INC(udps_opackets);
+		} else {
+			m->m_pkthdr.csum_flags = CSUM_TCP_IPV6;
+			m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum);
+			th->th_sum = in6_cksum_pseudo(ip6,
+			    sizeof(struct tcphdr) + optlen + len, IPPROTO_TCP,
+			    0);
+		}
 	}
 #endif
 #if defined(INET6) && defined(INET)
@@ -1346,9 +1385,20 @@ tcp_output(struct tcpcb *tp)
 #endif
 #ifdef INET
 	{
-		m->m_pkthdr.csum_flags = CSUM_TCP;
-		th->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr,
-		    htons(sizeof(struct tcphdr) + IPPROTO_TCP + len + optlen));
+		if (tp->t_port) {
+			m->m_pkthdr.csum_flags = CSUM_UDP;
+			m->m_pkthdr.csum_data = offsetof(struct udphdr, uh_sum);
+			udp->uh_sum = in_pseudo(ip->ip_src.s_addr,
+			   ip->ip_dst.s_addr, htons(ulen + IPPROTO_UDP));
+			th->th_sum = htons(0);
+			UDPSTAT_INC(udps_opackets);
+		} else {
+			m->m_pkthdr.csum_flags = CSUM_TCP;
+			m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum);
+			th->th_sum = in_pseudo(ip->ip_src.s_addr,
+			    ip->ip_dst.s_addr, htons(sizeof(struct tcphdr) +
+			    IPPROTO_TCP + len + optlen));
+		}
 
 		/* IP version must be set here for ipv4/ipv6 checking later */
 		KASSERT(ip->ip_v == IPVERSION,
@@ -1473,8 +1523,10 @@ tcp_output(struct tcpcb *tp)
 	 * NB: Don't set DF on small MTU/MSS to have a safe fallback.
 	 */
 	if (V_path_mtu_discovery && tp->t_maxseg > V_tcp_minmss) {
-		ip->ip_off |= htons(IP_DF);
 		tp->t_flags2 |= TF2_PLPMTU_PMTUD;
+		if (tp->t_port == 0 || len < V_tcp_minmss) {
+			ip->ip_off |= htons(IP_DF);
+		}
 	} else {
 		tp->t_flags2 &= ~TF2_PLPMTU_PMTUD;
 	}
diff --git a/sys/netinet/tcp_stacks/bbr.c b/sys/netinet/tcp_stacks/bbr.c
index 673dee911c87..febac7ad424c 100644
--- a/sys/netinet/tcp_stacks/bbr.c
+++ b/sys/netinet/tcp_stacks/bbr.c
@@ -11969,14 +11969,10 @@ bbr_output_wtime(struct tcpcb *tp, const struct timeval *tv)
 #endif
 	struct tcp_bbr *bbr;
 	struct tcphdr *th;
-#ifdef NETFLIX_TCPOUDP
 	struct udphdr *udp = NULL;
-#endif
 	u_char opt[TCP_MAXOLEN];
 	unsigned ipoptlen, optlen, hdrlen;
-#ifdef NETFLIX_TCPOUDP
 	unsigned ulen;
-#endif
 	uint32_t bbr_seq;
 	uint32_t delay_calc=0;
 	uint8_t doing_tlp = 0;
@@ -12991,10 +12987,8 @@ bbr_output_wtime(struct tcpcb *tp, const struct timeval *tv)
 		/* Maximum segment size. */
 		if (flags & TH_SYN) {
 			to.to_mss = tcp_mssopt(&inp->inp_inc);
-#ifdef NETFLIX_TCPOUDP
 			if (tp->t_port)
 				to.to_mss -= V_tcp_udp_tunneling_overhead;
-#endif
 			to.to_flags |= TOF_MSS;
 			/*
 			 * On SYN or SYN|ACK transmits on TFO connections,
@@ -13063,7 +13057,6 @@ bbr_output_wtime(struct tcpcb *tp, const struct timeval *tv)
 		    !(to.to_flags & TOF_FASTOPEN))
 			len = 0;
 	}
-#ifdef NETFLIX_TCPOUDP
 	if (tp->t_port) {
 		if (V_tcp_udp_tunneling_port == 0) {
 			/* The port was removed?? */
@@ -13072,7 +13065,6 @@ bbr_output_wtime(struct tcpcb *tp, const struct timeval *tv)
 		}
 		hdrlen += sizeof(struct udphdr);
 	}
-#endif
 #ifdef INET6
 	if (isipv6)
 		ipoptlen = ip6_optlen(tp->t_inpcb);
@@ -13408,7 +13400,6 @@ bbr_output_wtime(struct tcpcb *tp, const struct timeval *tv)
 #ifdef INET6
 	if (isipv6) {
 		ip6 = mtod(m, struct ip6_hdr *);
-#ifdef NETFLIX_TCPOUDP
 		if (tp->t_port) {
 			udp = (struct udphdr *)((caddr_t)ip6 + ipoptlen + sizeof(struct ip6_hdr));
 			udp->uh_sport = htons(V_tcp_udp_tunneling_port);
@@ -13417,17 +13408,9 @@ bbr_output_wtime(struct tcpcb *tp, const struct timeval *tv)
 			udp->uh_ulen = htons(ulen);
 			th = (struct tcphdr *)(udp + 1);
 		} else {
-#endif
 			th = (struct tcphdr *)(ip6 + 1);
-
-#ifdef NETFLIX_TCPOUDP
 		}
-#endif
-		tcpip_fillheaders(inp,
-#ifdef NETFLIX_TCPOUDP
-				  tp->t_port,
-#endif
-				  ip6, th);
+		tcpip_fillheaders(inp, tp->t_port, ip6, th);
 	} else
 #endif				/* INET6 */
 	{
@@ -13435,7 +13418,6 @@ bbr_output_wtime(struct tcpcb *tp, const struct timeval *tv)
 #ifdef TCPDEBUG
 		ipov = (struct ipovly *)ip;
 #endif
-#ifdef NETFLIX_TCPOUDP
 		if (tp->t_port) {
 			udp = (struct udphdr *)((caddr_t)ip + ipoptlen + sizeof(struct ip));
 			udp->uh_sport = htons(V_tcp_udp_tunneling_port);
@@ -13443,14 +13425,10 @@ bbr_output_wtime(struct tcpcb *tp, const struct timeval *tv)
 			ulen = hdrlen + len - sizeof(struct ip);
 			udp->uh_ulen = htons(ulen);
 			th = (struct tcphdr *)(udp + 1);
-		} else
-#endif
+		} else {
 			th = (struct tcphdr *)(ip + 1);
-		tcpip_fillheaders(inp,
-#ifdef NETFLIX_TCPOUDP
-				  tp->t_port,
-#endif
-				  ip, th);
+		}
+		tcpip_fillheaders(inp, tp->t_port, ip, th);
 	}
 	/*
 	 * If we are doing retransmissions, then snd_nxt will not reflect
@@ -13600,7 +13578,6 @@ bbr_output_wtime(struct tcpcb *tp, const struct timeval *tv)
 		 * ip6_plen is not need to be filled now, and will be filled
 		 * in ip6_output.
 		 */
-#ifdef NETFLIX_TCPOUDP
 		if (tp->t_port) {
 			m->m_pkthdr.csum_flags = CSUM_UDP_IPV6;
 			m->m_pkthdr.csum_data = offsetof(struct udphdr, uh_sum);
@@ -13608,14 +13585,11 @@ bbr_output_wtime(struct tcpcb *tp, const struct timeval *tv)
 			th->th_sum = htons(0);
 			UDPSTAT_INC(udps_opackets);
 		} else {
-#endif
 			csum_flags = m->m_pkthdr.csum_flags = CSUM_TCP_IPV6;
 			m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum);
 			th->th_sum = in6_cksum_pseudo(ip6, sizeof(struct tcphdr) +
 			    optlen + len, IPPROTO_TCP, 0);
-#ifdef NETFLIX_TCPOUDP
 		}
-#endif
 	}
 #endif
 #if defined(INET6) && defined(INET)
@@ -13623,7 +13597,6 @@ bbr_output_wtime(struct tcpcb *tp, const struct timeval *tv)
 #endif
 #ifdef INET
 	{
-#ifdef NETFLIX_TCPOUDP
 		if (tp->t_port) {
 			m->m_pkthdr.csum_flags = CSUM_UDP;
 			m->m_pkthdr.csum_data = offsetof(struct udphdr, uh_sum);
@@ -13632,15 +13605,12 @@ bbr_output_wtime(struct tcpcb *tp, const struct timeval *tv)
 			th->th_sum = htons(0);
 			UDPSTAT_INC(udps_opackets);
 		} else {
-#endif
 			csum_flags = m->m_pkthdr.csum_flags = CSUM_TCP;
 			m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum);
 			th->th_sum = in_pseudo(ip->ip_src.s_addr,
 			    ip->ip_dst.s_addr, htons(sizeof(struct tcphdr) +
 			    IPPROTO_TCP + len + optlen));
-#ifdef NETFLIX_TCPOUDP
 		}
-#endif
 		/* IP version must be set here for ipv4/ipv6 checking later */
 		KASSERT(ip->ip_v == IPVERSION,
 		    ("%s: IP version incorrect: %d", __func__, ip->ip_v));
diff --git a/sys/netinet/tcp_stacks/rack.c b/sys/netinet/tcp_stacks/rack.c
index 0079bf8b6400..d2093e1afab7 100644
--- a/sys/netinet/tcp_stacks/rack.c
+++ b/sys/netinet/tcp_stacks/rack.c
@@ -13008,10 +13008,8 @@ rack_output(struct tcpcb *tp)
 		if (flags & TH_SYN) {
 			tp->snd_nxt = tp->iss;
 			to.to_mss = tcp_mssopt(&inp->inp_inc);
-#ifdef NETFLIX_TCPOUDP
 			if (tp->t_port)
 				to.to_mss -= V_tcp_udp_tunneling_overhead;
-#endif
 			to.to_flags |= TOF_MSS;
 
 			/*
@@ -13088,7 +13086,6 @@ rack_output(struct tcpcb *tp)
 		    !(to.to_flags & TOF_FASTOPEN))
 			len = 0;
 	}
-#ifdef NETFLIX_TCPOUDP
 	if (tp->t_port) {
 		if (V_tcp_udp_tunneling_port == 0) {
 			/* The port was removed?? */
@@ -13097,7 +13094,6 @@ rack_output(struct tcpcb *tp)
 		}
 		hdrlen += sizeof(struct udphdr);
 	}
-#endif
 #ifdef INET6
 	if (isipv6)
 		ipoptlen = ip6_optlen(tp->t_inpcb);
@@ -13372,7 +13368,6 @@ rack_output(struct tcpcb *tp)
 #ifdef INET6
 	if (isipv6) {
 		ip6 = mtod(m, struct ip6_hdr *);
-#ifdef NETFLIX_TCPOUDP
 		if (tp->t_port) {
 			udp = (struct udphdr *)((caddr_t)ip6 + ipoptlen + sizeof(struct ip6_hdr));
 			udp->uh_sport = htons(V_tcp_udp_tunneling_port);
@@ -13380,14 +13375,10 @@ rack_output(struct tcpcb *tp)
 			ulen = hdrlen + len - sizeof(struct ip6_hdr);
 			udp->uh_ulen = htons(ulen);
 			th = (struct tcphdr *)(udp + 1);
-		} else
-#endif
+		} else {
 			th = (struct tcphdr *)(ip6 + 1);
-		tcpip_fillheaders(inp,
-#ifdef NETFLIX_TCPOUDP
-				  tp->t_port,
-#endif
-				  ip6, th);
+		}
+		tcpip_fillheaders(inp, tp->t_port, ip6, th);
 	} else
 #endif				/* INET6 */
 	{
@@ -13395,7 +13386,6 @@ rack_output(struct tcpcb *tp)
 #ifdef TCPDEBUG
 		ipov = (struct ipovly *)ip;
 #endif
-#ifdef NETFLIX_TCPOUDP
 		if (tp->t_port) {
 			udp = (struct udphdr *)((caddr_t)ip + ipoptlen + sizeof(struct ip));
 			udp->uh_sport = htons(V_tcp_udp_tunneling_port);
@@ -13403,14 +13393,10 @@ rack_output(struct tcpcb *tp)
 			ulen = hdrlen + len - sizeof(struct ip);
 			udp->uh_ulen = htons(ulen);
 			th = (struct tcphdr *)(udp + 1);
-		} else
-#endif
+		} else {
 			th = (struct tcphdr *)(ip + 1);
-		tcpip_fillheaders(inp,
-#ifdef NETFLIX_TCPOUDP
-				  tp->t_port,
-#endif
-				  ip, th);
+		}
+		tcpip_fillheaders(inp, tp->t_port, ip, th);
 	}
 	/*
 	 * Fill in fields, remembering maximum advertised window for use in
diff --git a/sys/netinet/tcp_subr.c b/sys/netinet/tcp_subr.c
index e973555efbcb..1ebc7357def3 100644
--- a/sys/netinet/tcp_subr.c
+++ b/sys/netinet/tcp_subr.c
@@ -126,6 +126,8 @@ __FBSDID("$FreeBSD$");
 #ifdef TCP_OFFLOAD
 #include <netinet/tcp_offload.h>
 #endif
+#include <netinet/udp.h>
+#include <netinet/udp_var.h>
 
 #include <netipsec/ipsec_support.h>
 
@@ -501,6 +503,80 @@ tcp_switch_back_to_default(struct tcpcb *tp)
 	}
 }
 
+static void
+tcp_recv_udp_tunneled_packet(struct mbuf *m, int off, struct inpcb *inp,
+    const struct sockaddr *sa, void *ctx)
+{
+	struct ip *iph;
+#ifdef INET6
+	struct ip6_hdr *ip6;
+#endif
+	struct udphdr *uh;
+	struct tcphdr *th;
+	int thlen;
+	uint16_t port;
+
+	TCPSTAT_INC(tcps_tunneled_pkts);
+	if ((m->m_flags & M_PKTHDR) == 0) {
+		/* Can't handle one that is not a pkt hdr */
+		TCPSTAT_INC(tcps_tunneled_errs);
+		goto out;
+	}
+	thlen = sizeof(struct tcphdr);
+	if (m->m_len < off + sizeof(struct udphdr) + thlen &&
+	    (m =  m_pullup(m, off + sizeof(struct udphdr) + thlen)) == NULL) {
+		TCPSTAT_INC(tcps_tunneled_errs);
+		goto out;
+	}
+	iph = mtod(m, struct ip *);
+	uh = (struct udphdr *)((caddr_t)iph + off);
+	th = (struct tcphdr *)(uh + 1);
+	thlen = th->th_off << 2;
+	if (m->m_len < off + sizeof(struct udphdr) + thlen) {
+		m =  m_pullup(m, off + sizeof(struct udphdr) + thlen);
+		if (m == NULL) {
+			TCPSTAT_INC(tcps_tunneled_errs);
+			goto out;
+		} else {
+			iph = mtod(m, struct ip *);
+			uh = (struct udphdr *)((caddr_t)iph + off);
+			th = (struct tcphdr *)(uh + 1);
+		}
+	}
+	m->m_pkthdr.tcp_tun_port = port = uh->uh_sport;
+	bcopy(th, uh, m->m_len - off);
+	m->m_len -= sizeof(struct udphdr);
+	m->m_pkthdr.len -= sizeof(struct udphdr);
+	/*
+	 * We use the same algorithm for
+	 * both UDP and TCP for c-sum. So
+	 * the code in tcp_input will skip
+	 * the checksum. So we do nothing
+	 * with the flag (m->m_pkthdr.csum_flags).
+	 */
+	switch (iph->ip_v) {
+#ifdef INET
+	case IPVERSION:
+		iph->ip_len = htons(ntohs(iph->ip_len) - sizeof(struct udphdr));
+		tcp_input_with_port(&m, &off, IPPROTO_TCP, port);
+		break;
+#endif
+#ifdef INET6
+	case IPV6_VERSION >> 4:
+		ip6 = mtod(m, struct ip6_hdr *);
+		ip6->ip6_plen = htons(ntohs(ip6->ip6_plen) - sizeof(struct udphdr));
+		tcp6_input_with_port(&m, &off, IPPROTO_TCP, port);
+		break;
+#endif
+	default:
+		goto out;
+		break;
+	}
+	return;
+out:
+	m_freem(m);
+}
+
 static int
 sysctl_net_inet_default_tcp_functions(SYSCTL_HANDLER_ARGS)
 {
@@ -598,6 +674,183 @@ SYSCTL_PROC(_net_inet_tcp, OID_AUTO, functions_available,
     NULL, 0, sysctl_net_inet_list_available, "A",
     "list available TCP Function sets");
 
+VNET_DEFINE(int, tcp_udp_tunneling_port) = TCP_TUNNELING_PORT_DEFAULT;
+
+#ifdef INET
+VNET_DEFINE(struct socket *, udp4_tun_socket) = NULL;
+#define	V_udp4_tun_socket	VNET(udp4_tun_socket)
+#endif
+#ifdef INET6
+VNET_DEFINE(struct socket *, udp6_tun_socket) = NULL;
+#define	V_udp6_tun_socket	VNET(udp6_tun_socket)
+#endif
+
+static void
+tcp_over_udp_stop(void)
+{
+	/*
+	 * This function assumes sysctl caller holds inp_rinfo_lock()
+	 * for writting!
+	 */
+#ifdef INET
+	if (V_udp4_tun_socket != NULL) {
+		soclose(V_udp4_tun_socket);
+		V_udp4_tun_socket = NULL;
+	}
+#endif
+#ifdef INET6
+	if (V_udp6_tun_socket != NULL) {
+		soclose(V_udp6_tun_socket);
+		V_udp6_tun_socket = NULL;
+	}
+#endif
+}
+
+static int
+tcp_over_udp_start(void)
+{
+	uint16_t port;
+	int ret;
+#ifdef INET
+	struct sockaddr_in sin;
+#endif
+#ifdef INET6
+	struct sockaddr_in6 sin6;
+#endif
+	/*
+	 * This function assumes sysctl caller holds inp_info_rlock()
+	 * for writting!
+	 */
+	port = V_tcp_udp_tunneling_port;
+	if (ntohs(port) == 0) {
+		/* Must have a port set */
+		return (EINVAL);
+	}
+#ifdef INET
+	if (V_udp4_tun_socket != NULL) {
+		/* Already running -- must stop first */
+		return (EALREADY);
+	}
+#endif
+#ifdef INET6
+	if (V_udp6_tun_socket != NULL) {
+		/* Already running -- must stop first */
+		return (EALREADY);
+	}
+#endif
+#ifdef INET
+	if ((ret = socreate(PF_INET, &V_udp4_tun_socket,
+	    SOCK_DGRAM, IPPROTO_UDP,
+	    curthread->td_ucred, curthread))) {
+		tcp_over_udp_stop();
+		return (ret);
+	}
+	/* Call the special UDP hook. */
+	if ((ret = udp_set_kernel_tunneling(V_udp4_tun_socket,
+	    tcp_recv_udp_tunneled_packet,
+	    tcp_ctlinput_viaudp,
+	    NULL))) {
+		tcp_over_udp_stop();
+		return (ret);
+	}
+	/* Ok, we have a socket, bind it to the port. */
+	memset(&sin, 0, sizeof(struct sockaddr_in));
+	sin.sin_len = sizeof(struct sockaddr_in);
+	sin.sin_family = AF_INET;
+	sin.sin_port = htons(port);
+	if ((ret = sobind(V_udp4_tun_socket,
+	    (struct sockaddr *)&sin, curthread))) {
+		tcp_over_udp_stop();
+		return (ret);
+	}
+#endif
+#ifdef INET6
+	if ((ret = socreate(PF_INET6, &V_udp6_tun_socket,
+	    SOCK_DGRAM, IPPROTO_UDP,
+	    curthread->td_ucred, curthread))) {
+		tcp_over_udp_stop();
+		return (ret);
+	}
+	/* Call the special UDP hook. */
+	if ((ret = udp_set_kernel_tunneling(V_udp6_tun_socket,
+	    tcp_recv_udp_tunneled_packet,
+	    tcp6_ctlinput_viaudp,
+	    NULL))) {
+		tcp_over_udp_stop();
+		return (ret);
+	}
+	/* Ok, we have a socket, bind it to the port. */
+	memset(&sin6, 0, sizeof(struct sockaddr_in6));
+	sin6.sin6_len = sizeof(struct sockaddr_in6);
+	sin6.sin6_family = AF_INET6;
+	sin6.sin6_port = htons(port);
+	if ((ret = sobind(V_udp6_tun_socket,
+	    (struct sockaddr *)&sin6, curthread))) {
+		tcp_over_udp_stop();
+		return (ret);
+	}
+#endif
+	return (0);
+}
+
+static int
+sysctl_net_inet_tcp_udp_tunneling_port_check(SYSCTL_HANDLER_ARGS)
+{
+	int error;
+	uint32_t old, new;
+
+	old = V_tcp_udp_tunneling_port;
+	new = old;
+	error = sysctl_handle_int(oidp, &new, 0, req);
+	if ((error == 0) &&
+	    (req->newptr != NULL)) {
+		if ((new < TCP_TUNNELING_PORT_MIN) ||
+		    (new > TCP_TUNNELING_PORT_MAX)) {
+			error = EINVAL;
+		} else {
+			V_tcp_udp_tunneling_port = new;
+			if (old != 0) {
+				tcp_over_udp_stop();
+			}
+			if (new != 0) {
+				error = tcp_over_udp_start();
+			}
+		}
+	}
+	return (error);
+}
+
+SYSCTL_PROC(_net_inet_tcp, OID_AUTO, udp_tunneling_port,
+    CTLFLAG_VNET | CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_MPSAFE,
+    &VNET_NAME(tcp_udp_tunneling_port),
+    0, &sysctl_net_inet_tcp_udp_tunneling_port_check, "IU",
+    "Tunneling port for tcp over udp");
+
+VNET_DEFINE(int, tcp_udp_tunneling_overhead) = TCP_TUNNELING_OVERHEAD_DEFAULT;
+
+static int
+sysctl_net_inet_tcp_udp_tunneling_overhead_check(SYSCTL_HANDLER_ARGS)
+{
+	int error, new;
+
+	new = V_tcp_udp_tunneling_overhead;
+	error = sysctl_handle_int(oidp, &new, 0, req);
+	if (error == 0 && req->newptr) {
+		if ((new < TCP_TUNNELING_OVERHEAD_MIN) ||
+		    (new > TCP_TUNNELING_OVERHEAD_MAX))
+			error = EINVAL;
+		else
+			V_tcp_udp_tunneling_overhead = new;
+	}
+	return (error);
+}
+
+SYSCTL_PROC(_net_inet_tcp, OID_AUTO, udp_tunneling_overhead,
+    CTLFLAG_VNET | CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_MPSAFE,
+    &VNET_NAME(tcp_udp_tunneling_overhead),
+    0, &sysctl_net_inet_tcp_udp_tunneling_overhead_check, "IU",
+    "MSS reduction when using tcp over udp");
+
 /*
  * Exports one (struct tcp_function_info) for each alias/name.
  */
@@ -1314,7 +1567,7 @@ tcp_fini(void *xtp)
  * of the tcpcb each time to conserve mbufs.
  */
 void
-tcpip_fillheaders(struct inpcb *inp, void *ip_ptr, void *tcp_ptr)
+tcpip_fillheaders(struct inpcb *inp, uint16_t port, void *ip_ptr, void *tcp_ptr)
 {
 	struct tcphdr *th = (struct tcphdr *)tcp_ptr;
 
@@ -1329,7 +1582,10 @@ tcpip_fillheaders(struct inpcb *inp, void *ip_ptr, void *tcp_ptr)
 			(inp->inp_flow & IPV6_FLOWINFO_MASK);
 		ip6->ip6_vfc = (ip6->ip6_vfc & ~IPV6_VERSION_MASK) |
 			(IPV6_VERSION & IPV6_VERSION_MASK);
-		ip6->ip6_nxt = IPPROTO_TCP;
+		if (port == 0)
+			ip6->ip6_nxt = IPPROTO_TCP;
+		else
+			ip6->ip6_nxt = IPPROTO_UDP;
 		ip6->ip6_plen = htons(sizeof(struct tcphdr));
 		ip6->ip6_src = inp->in6p_laddr;
 		ip6->ip6_dst = inp->in6p_faddr;
@@ -1351,7 +1607,10 @@ tcpip_fillheaders(struct inpcb *inp, void *ip_ptr, void *tcp_ptr)
 		ip->ip_off = 0;
 		ip->ip_ttl = inp->inp_ip_ttl;
 		ip->ip_sum = 0;
-		ip->ip_p = IPPROTO_TCP;
+		if (port == 0)
+			ip->ip_p = IPPROTO_TCP;
+		else
+			ip->ip_p = IPPROTO_UDP;
 		ip->ip_src = inp->inp_laddr;
 		ip->ip_dst = inp->inp_faddr;
 	}
@@ -1381,7 +1640,7 @@ tcpip_maketemplate(struct inpcb *inp)
 	t = malloc(sizeof(*t), M_TEMP, M_NOWAIT);
 	if (t == NULL)
 		return (NULL);
-	tcpip_fillheaders(inp, (void *)&t->tt_ipgen, (void *)&t->tt_t);
+	tcpip_fillheaders(inp, 0, (void *)&t->tt_ipgen, (void *)&t->tt_t);
 	return (t);
 }
 
@@ -1407,14 +1666,16 @@ tcp_respond(struct tcpcb *tp, void *ipgen, struct tcphdr *th, struct mbuf *m,
 	struct inpcb *inp;
 	struct ip *ip;
 	struct mbuf *optm;
+	struct udphdr *uh = NULL;
 	struct tcphdr *nth;
 	u_char *optp;
 #ifdef INET6
 	struct ip6_hdr *ip6;
 	int isipv6;
 #endif /* INET6 */
-	int optlen, tlen, win;
+	int optlen, tlen, win, ulen;
 	bool incl_opts;
+	uint16_t port;
 
 	KASSERT(tp != NULL || m != NULL, ("tcp_respond: tp and m both NULL"));
 	NET_EPOCH_ASSERT();
@@ -1432,6 +1693,19 @@ tcp_respond(struct tcpcb *tp, void *ipgen, struct tcphdr *th, struct mbuf *m,
 	} else
 		inp = NULL;
 
+	if (m != NULL) {
+#ifdef INET6
+		if (isipv6 && ip6 && (ip6->ip6_nxt == IPPROTO_UDP))
+			port = m->m_pkthdr.tcp_tun_port;
+		else
+#endif
+		if (ip && (ip->ip_p == IPPROTO_UDP))
+			port = m->m_pkthdr.tcp_tun_port;
+		else
+			port = 0;
+	} else
+		port = tp->t_port;
+
 	incl_opts = false;
 	win = 0;
 	if (tp != NULL) {
@@ -1454,16 +1728,30 @@ tcp_respond(struct tcpcb *tp, void *ipgen, struct tcphdr *th, struct mbuf *m,
 			      sizeof(struct ip6_hdr));
 			ip6 = mtod(m, struct ip6_hdr *);
 			nth = (struct tcphdr *)(ip6 + 1);
+			if (port) {
+				/* Insert a UDP header */
+				uh = (struct udphdr *)nth;
+				uh->uh_sport = htons(V_tcp_udp_tunneling_port);
+				uh->uh_dport = port;
+				nth = (struct tcphdr *)(uh + 1);
+			}
 		} else
 #endif /* INET6 */
 		{
 			bcopy((caddr_t)ip, mtod(m, caddr_t), sizeof(struct ip));
 			ip = mtod(m, struct ip *);
 			nth = (struct tcphdr *)(ip + 1);
+			if (port) {
+				/* Insert a UDP header */
+				uh = (struct udphdr *)nth;
+				uh->uh_sport = htons(V_tcp_udp_tunneling_port);
+				uh->uh_dport = port;
+				nth = (struct tcphdr *)(uh + 1);
+			}
 		}
 		bcopy((caddr_t)th, (caddr_t)nth, sizeof(struct tcphdr));
 		flags = TH_ACK;
-	} else if (!M_WRITABLE(m)) {
+	} else if ((!M_WRITABLE(m)) || (port != 0)) {
 		struct mbuf *n;
 
 		/* Can't reuse 'm', allocate a new mbuf. */
@@ -1489,6 +1777,13 @@ tcp_respond(struct tcpcb *tp, void *ipgen, struct tcphdr *th, struct mbuf *m,
 			ip6 = mtod(n, struct ip6_hdr *);
 			xchg(ip6->ip6_dst, ip6->ip6_src, struct in6_addr);
 			nth = (struct tcphdr *)(ip6 + 1);
+			if (port) {
+				/* Insert a UDP header */
+				uh = (struct udphdr *)nth;
+				uh->uh_sport = htons(V_tcp_udp_tunneling_port);
+				uh->uh_dport = port;
+				nth = (struct tcphdr *)(uh + 1);
+			}
 		} else
 #endif /* INET6 */
 		{
@@ -1496,6 +1791,13 @@ tcp_respond(struct tcpcb *tp, void *ipgen, struct tcphdr *th, struct mbuf *m,
 			ip = mtod(n, struct ip *);
 			xchg(ip->ip_dst.s_addr, ip->ip_src.s_addr, uint32_t);
 			nth = (struct tcphdr *)(ip + 1);
+			if (port) {
+				/* Insert a UDP header */
+				uh = (struct udphdr *)nth;
+				uh->uh_sport = htons(V_tcp_udp_tunneling_port);
+				uh->uh_dport = port;
+				nth = (struct tcphdr *)(uh + 1);
+			}
 		}
 		bcopy((caddr_t)th, (caddr_t)nth, sizeof(struct tcphdr));
 		xchg(nth->th_dport, nth->th_sport, uint16_t);
@@ -1544,6 +1846,8 @@ tcp_respond(struct tcpcb *tp, void *ipgen, struct tcphdr *th, struct mbuf *m,
 #ifdef INET
 		tlen = sizeof (struct tcpiphdr);
 #endif
+	if (port)
+		tlen += sizeof (struct udphdr);
 #ifdef INVARIANTS
 	m->m_len = 0;
 	KASSERT(M_TRAILINGSPACE(m) >= tlen,
@@ -1587,9 +1891,16 @@ tcp_respond(struct tcpcb *tp, void *ipgen, struct tcphdr *th, struct mbuf *m,
 		optlen = 0;
 #ifdef INET6
 	if (isipv6) {
+		if (uh) {
+			ulen = tlen - sizeof(struct ip6_hdr);
+			uh->uh_ulen = htons(ulen);
+		}
 		ip6->ip6_flow = 0;
 		ip6->ip6_vfc = IPV6_VERSION;
-		ip6->ip6_nxt = IPPROTO_TCP;
+		if (port)
+			ip6->ip6_nxt = IPPROTO_UDP;
+		else
+			ip6->ip6_nxt = IPPROTO_TCP;
 		ip6->ip6_plen = htons(tlen - sizeof(*ip6));
 	}
 #endif
@@ -1598,8 +1909,17 @@ tcp_respond(struct tcpcb *tp, void *ipgen, struct tcphdr *th, struct mbuf *m,
 #endif
 #ifdef INET
 	{
+		if (uh) {
+			ulen = tlen - sizeof(struct ip);
+			uh->uh_ulen = htons(ulen);
+		}
 		ip->ip_len = htons(tlen);
 		ip->ip_ttl = V_ip_defttl;
+		if (port) {
+			ip->ip_p = IPPROTO_UDP;
+		} else {
+			ip->ip_p = IPPROTO_TCP;
+		}
 		if (V_path_mtu_discovery)
 			ip->ip_off |= htons(IP_DF);
 	}
@@ -1643,12 +1963,19 @@ tcp_respond(struct tcpcb *tp, void *ipgen, struct tcphdr *th, struct mbuf *m,
 	}
 #endif
 
-	m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum);
 #ifdef INET6
 	if (isipv6) {
-		m->m_pkthdr.csum_flags = CSUM_TCP_IPV6;
-		nth->th_sum = in6_cksum_pseudo(ip6,
-		    tlen - sizeof(struct ip6_hdr), IPPROTO_TCP, 0);
+		if (port) {
+			m->m_pkthdr.csum_flags = CSUM_UDP_IPV6;
+			m->m_pkthdr.csum_data = offsetof(struct udphdr, uh_sum);
+			uh->uh_sum = in6_cksum_pseudo(ip6, ulen, IPPROTO_UDP, 0);
+			nth->th_sum = 0;
+		} else {
+			m->m_pkthdr.csum_flags = CSUM_TCP_IPV6;
+			m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum);
+			nth->th_sum = in6_cksum_pseudo(ip6,
+			    tlen - sizeof(struct ip6_hdr), IPPROTO_TCP, 0);
+		}
 		ip6->ip6_hlim = in6_selecthlim(tp != NULL ? tp->t_inpcb :
 		    NULL, NULL);
 	}
@@ -1658,9 +1985,18 @@ tcp_respond(struct tcpcb *tp, void *ipgen, struct tcphdr *th, struct mbuf *m,
 #endif
 #ifdef INET
 	{
-		m->m_pkthdr.csum_flags = CSUM_TCP;
-		nth->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr,
-		    htons((u_short)(tlen - sizeof(struct ip) + ip->ip_p)));
+		if (port) {
+			uh->uh_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr,
+			    htons(ulen + IPPROTO_UDP));
+			m->m_pkthdr.csum_flags = CSUM_UDP;
+			m->m_pkthdr.csum_data = offsetof(struct udphdr, uh_sum);
+			nth->th_sum = 0;
+		} else {
+			m->m_pkthdr.csum_flags = CSUM_TCP;
+			m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum);
+			nth->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr,
+			    htons((u_short)(tlen - sizeof(struct ip) + ip->ip_p)));
+		}
 	}
 #endif /* INET */
 #ifdef TCPDEBUG
@@ -2460,8 +2796,8 @@ SYSCTL_PROC(_net_inet6_tcp6, OID_AUTO, getcred,
 #endif /* INET6 */
 
 #ifdef INET
-void
-tcp_ctlinput(int cmd, struct sockaddr *sa, void *vip)
+static void
+tcp_ctlinput_with_port(int cmd, struct sockaddr *sa, void *vip, uint16_t port)
 {
 	struct ip *ip = vip;
 	struct tcphdr *th;
@@ -2515,6 +2851,9 @@ tcp_ctlinput(int cmd, struct sockaddr *sa, void *vip)
 		    !(inp->inp_flags & INP_DROPPED) &&
 		    !(inp->inp_socket == NULL)) {
 			tp = intotcpcb(inp);
+			if (tp->t_port != port) {
+				goto out;
+			}
 			if (SEQ_GEQ(ntohl(icmp_tcp_seq), tp->snd_una) &&
 			    SEQ_LT(ntohl(icmp_tcp_seq), tp->snd_max)) {
 				if (cmd == PRC_MSGSIZE) {
@@ -2561,17 +2900,61 @@ tcp_ctlinput(int cmd, struct sockaddr *sa, void *vip)
 		inc.inc_lport = th->th_sport;
 		inc.inc_faddr = faddr;
 		inc.inc_laddr = ip->ip_src;
-		syncache_unreach(&inc, icmp_tcp_seq);
+		syncache_unreach(&inc, icmp_tcp_seq, port);
 	}
 out:
 	if (inp != NULL)
 		INP_WUNLOCK(inp);
 }
+
+void
+tcp_ctlinput(int cmd, struct sockaddr *sa, void *vip)
+{
+	tcp_ctlinput_with_port(cmd, sa, vip, htons(0));
+}
+
+void
+tcp_ctlinput_viaudp(int cmd, struct sockaddr *sa, void *vip, void *unused)
+{
+	/* Its a tunneled TCP over UDP icmp */
+	struct ip *outer_ip, *inner_ip;
+	struct icmp *icmp;
+	struct udphdr *udp;
+	struct tcphdr *th, ttemp;
+	int i_hlen, o_len;
+	uint16_t port;
+
+	inner_ip = (struct ip *)vip;
+	icmp = (struct icmp *)((caddr_t)inner_ip -
+	    (sizeof(struct icmp) - sizeof(struct ip)));
+	outer_ip = (struct ip *)((caddr_t)icmp - sizeof(struct ip));
+	i_hlen = inner_ip->ip_hl << 2;
+	o_len = ntohs(outer_ip->ip_len);
+	if (o_len <
+	    (sizeof(struct ip) + 8 + i_hlen + sizeof(struct udphdr) + offsetof(struct tcphdr, th_ack))) {
+		/* Not enough data present */
+		return;
+	}
+	/* Ok lets strip out the inner udphdr header by copying up on top of it the tcp hdr */
+	udp = (struct udphdr *)(((caddr_t)inner_ip) + i_hlen);
+	if (ntohs(udp->uh_sport) != V_tcp_udp_tunneling_port) {
+		return;
+	}
+	port = udp->uh_dport;
+	th = (struct tcphdr *)(udp + 1);
+	memcpy(&ttemp, th, sizeof(struct tcphdr));
+	memcpy(udp, &ttemp, sizeof(struct tcphdr));
+	/* Now adjust down the size of the outer IP header */
+	o_len -= sizeof(struct udphdr);
+	outer_ip->ip_len = htons(o_len);
+	/* Now call in to the normal handling code */
+	tcp_ctlinput_with_port(cmd, sa, vip, port);
+}
 #endif /* INET */
 
 #ifdef INET6
-void
-tcp6_ctlinput(int cmd, struct sockaddr *sa, void *d)
+static void
+tcp6_ctlinput_with_port(int cmd, struct sockaddr *sa, void *d, uint16_t port)
 {
 	struct in6_addr *dst;
 	struct inpcb *(*notify)(struct inpcb *, int) = tcp_notify;
@@ -2661,6 +3044,9 @@ tcp6_ctlinput(int cmd, struct sockaddr *sa, void *d)
 		    !(inp->inp_flags & INP_DROPPED) &&
 		    !(inp->inp_socket == NULL)) {
 			tp = intotcpcb(inp);
+			if (tp->t_port != port) {
+				goto out;
+			}
 			if (SEQ_GEQ(ntohl(icmp_tcp_seq), tp->snd_una) &&
 			    SEQ_LT(ntohl(icmp_tcp_seq), tp->snd_max)) {
 				if (cmd == PRC_MSGSIZE) {
@@ -2710,12 +3096,45 @@ tcp6_ctlinput(int cmd, struct sockaddr *sa, void *d)
 		inc.inc_lport = t_ports.th_sport;
 		inc.inc6_faddr = *dst;
 		inc.inc6_laddr = ip6->ip6_src;
-		syncache_unreach(&inc, icmp_tcp_seq);
+		syncache_unreach(&inc, icmp_tcp_seq, port);
 	}
 out:
 	if (inp != NULL)
 		INP_WUNLOCK(inp);
 }
+
+void
+tcp6_ctlinput(int cmd, struct sockaddr *sa, void *d)
+{
+	tcp6_ctlinput_with_port(cmd, sa, d, htons(0));
+}
+
+void
+tcp6_ctlinput_viaudp(int cmd, struct sockaddr *sa, void *d, void *unused)
+{
+	struct ip6ctlparam *ip6cp;
+	struct mbuf *m;
+	struct udphdr *udp;
+	uint16_t port;
+
+	ip6cp = (struct ip6ctlparam *)d;
+	m = m_pulldown(ip6cp->ip6c_m, ip6cp->ip6c_off, sizeof(struct udphdr), NULL);
+	if (m == NULL) {
+		return;
+	}
+	udp = mtod(m, struct udphdr *);
+	if (ntohs(udp->uh_sport) != V_tcp_udp_tunneling_port) {
+		return;
+	}
+	port = udp->uh_dport;
+	m_adj(m, sizeof(struct udphdr));
+	if ((m->m_flags & M_PKTHDR) == 0) {
+		ip6cp->ip6c_m->m_pkthdr.len -= sizeof(struct udphdr);
+	}
+	/* Now call in to the normal handling code */
+	tcp6_ctlinput_with_port(cmd, sa, d, port);
+}
+
 #endif /* INET6 */
 
 static uint32_t
@@ -3448,11 +3867,13 @@ void
 tcp_inptoxtp(const struct inpcb *inp, struct xtcpcb *xt)
 {
 	struct tcpcb *tp = intotcpcb(inp);
+	struct tcptw *tw = intotw(inp);
 	sbintime_t now;
 
 	bzero(xt, sizeof(*xt));
 	if (inp->inp_flags & INP_TIMEWAIT) {
 		xt->t_state = TCPS_TIME_WAIT;
+		xt->xt_encaps_port = tw->t_port;
 	} else {
 		xt->t_state = tp->t_state;
 		xt->t_logstate = tp->t_logstate;
@@ -3484,6 +3905,7 @@ tcp_inptoxtp(const struct inpcb *inp, struct xtcpcb *xt)
 #undef COPYTIMER
 		xt->t_rcvtime = 1000 * (ticks - tp->t_rcvtime) / hz;
 
+		xt->xt_encaps_port = tp->t_port;
 		bcopy(tp->t_fb->tfb_tcp_block_name, xt->xt_stack,
 		    TCP_FUNCTION_NAME_LEN_MAX);
 		bcopy(CC_ALGO(tp)->name, xt->xt_cc,
diff --git a/sys/netinet/tcp_syncache.c b/sys/netinet/tcp_syncache.c
index 4cd8411af8d5..35d9c091ab96 100644
--- a/sys/netinet/tcp_syncache.c
+++ b/sys/netinet/tcp_syncache.c
@@ -96,6 +96,8 @@ __FBSDID("$FreeBSD$");
 #ifdef TCP_OFFLOAD
 #include <netinet/toecore.h>
 #endif
+#include <netinet/udp.h>
+#include <netinet/udp_var.h>
 
 #include <netipsec/ipsec_support.h>
 
@@ -143,14 +145,14 @@ static tcp_seq	 syncookie_generate(struct syncache_head *, struct syncache *);
 static struct syncache
 		*syncookie_lookup(struct in_conninfo *, struct syncache_head *,
 		    struct syncache *, struct tcphdr *, struct tcpopt *,
-		    struct socket *);
+		    struct socket *, uint16_t);
 static void	syncache_pause(struct in_conninfo *);
 static void	syncache_unpause(void *);
 static void	 syncookie_reseed(void *);
 #ifdef INVARIANTS
 static int	 syncookie_cmp(struct in_conninfo *inc, struct syncache_head *sch,
 		    struct syncache *sc, struct tcphdr *th, struct tcpopt *to,
-		    struct socket *lso);
+		    struct socket *lso, uint16_t port);
 #endif
 
 /*
@@ -610,7 +612,8 @@ syncache_lookup(struct in_conninfo *inc, struct syncache_head **schp)
  * If required send a challenge ACK.
  */
 void
-syncache_chkrst(struct in_conninfo *inc, struct tcphdr *th, struct mbuf *m)
+syncache_chkrst(struct in_conninfo *inc, struct tcphdr *th, struct mbuf *m,
+    uint16_t port)
 {
 	struct syncache *sc;
 	struct syncache_head *sch;
@@ -650,6 +653,16 @@ syncache_chkrst(struct in_conninfo *inc, struct tcphdr *th, struct mbuf *m)
 		goto done;
 	}
 
+	/* The remote UDP encaps port does not match. */
+	if (sc->sc_port != port) {
+		if ((s = tcp_log_addrs(inc, th, NULL, NULL)))
+			log(LOG_DEBUG, "%s; %s: Spurious RST with matching "
+			    "syncache entry but non-matching UDP encaps port, "
+			    "segment ignored\n", s, __func__);
+		TCPSTAT_INC(tcps_badrst);
+		goto done;
+	}
+
 	/*
 	 * If the RST bit is set, check the sequence number to see
 	 * if this is a valid reset segment.
@@ -716,7 +729,7 @@ syncache_chkrst(struct in_conninfo *inc, struct tcphdr *th, struct mbuf *m)
 }
 
 void
-syncache_badack(struct in_conninfo *inc)
+syncache_badack(struct in_conninfo *inc, uint16_t port)
 {
 	struct syncache *sc;
 	struct syncache_head *sch;
@@ -725,7 +738,7 @@ syncache_badack(struct in_conninfo *inc)
 		return;
 	sc = syncache_lookup(inc, &sch);	/* returns locked sch */
 	SCH_LOCK_ASSERT(sch);
-	if (sc != NULL) {
+	if ((sc != NULL) && (sc->sc_port == port)) {
 		syncache_drop(sc, sch);
 		TCPSTAT_INC(tcps_sc_badack);
 	}
@@ -733,7 +746,7 @@ syncache_badack(struct in_conninfo *inc)
 }
 
 void
-syncache_unreach(struct in_conninfo *inc, tcp_seq th_seq)
+syncache_unreach(struct in_conninfo *inc, tcp_seq th_seq, uint16_t port)
 {
 	struct syncache *sc;
 	struct syncache_head *sch;
@@ -745,6 +758,10 @@ syncache_unreach(struct in_conninfo *inc, tcp_seq th_seq)
 	if (sc == NULL)
 		goto done;
 
+	/* If the port != sc_port, then it's a bogus ICMP msg */
+	if (port != sc->sc_port)
+		goto done;
+
 	/* If the sequence number != sc_iss, then it's a bogus ICMP msg */
 	if (ntohl(th_seq) != sc->sc_iss)
 		goto done;
@@ -951,6 +968,7 @@ syncache_socket(struct syncache *sc, struct socket *lso, struct mbuf *m)
 	tcp_state_change(tp, TCPS_SYN_RECEIVED);
 	tp->iss = sc->sc_iss;
 	tp->irs = sc->sc_irs;
+	tp->t_port = sc->sc_port;
 	tcp_rcvseqinit(tp);
 	tcp_sendseqinit(tp);
 	blk = sototcpcb(lso)->t_fb;
@@ -1071,7 +1089,7 @@ syncache_socket(struct syncache *sc, struct socket *lso, struct mbuf *m)
  */
 int
 syncache_expand(struct in_conninfo *inc, struct tcpopt *to, struct tcphdr *th,
-    struct socket **lsop, struct mbuf *m)
+    struct socket **lsop, struct mbuf *m, uint16_t port)
 {
 	struct syncache *sc;
 	struct syncache_head *sch;
@@ -1099,7 +1117,7 @@ syncache_expand(struct in_conninfo *inc, struct tcpopt *to, struct tcphdr *th,
 	 * values with the reconstructed values from the cookie.
 	 */
 	if (sc != NULL)
-		syncookie_cmp(inc, sch, sc, th, to, *lsop);
+		syncookie_cmp(inc, sch, sc, th, to, *lsop, port);
 #endif
 
 	if (sc == NULL) {
@@ -1133,7 +1151,7 @@ syncache_expand(struct in_conninfo *inc, struct tcpopt *to, struct tcphdr *th,
 			goto failed;
 		}
 		bzero(&scs, sizeof(scs));
-		sc = syncookie_lookup(inc, sch, &scs, th, to, *lsop);
+		sc = syncookie_lookup(inc, sch, &scs, th, to, *lsop, port);
 		if (locked)
 			SCH_UNLOCK(sch);
 		if (sc == NULL) {
@@ -1160,6 +1178,10 @@ syncache_expand(struct in_conninfo *inc, struct tcpopt *to, struct tcphdr *th,
 		}
 #endif /* TCP_SIGNATURE */
 	} else {
+		if (sc->sc_port != port) {
+			SCH_UNLOCK(sch);
+			return (0);
+		}
 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE)
 		/*
 		 * If listening socket requested TCP digests, check that
@@ -1380,7 +1402,7 @@ syncache_tfo_expand(struct syncache *sc, struct socket *lso, struct mbuf *m,
 struct socket *
 syncache_add(struct in_conninfo *inc, struct tcpopt *to, struct tcphdr *th,
     struct inpcb *inp, struct socket *so, struct mbuf *m, void *tod,
-    void *todctx, uint8_t iptos)
+    void *todctx, uint8_t iptos, uint16_t port)
 {
 	struct tcpcb *tp;
 	struct socket *rv = NULL;
@@ -1640,6 +1662,7 @@ syncache_add(struct in_conninfo *inc, struct tcpopt *to, struct tcphdr *th,
 	sc->sc_label = maclabel;
 #endif
 	sc->sc_cred = cred;
+	sc->sc_port = port;
 	cred = NULL;
 	sc->sc_ipopts = ipopts;
 	bcopy(inc, &sc->sc_inc, sizeof(struct in_conninfo));
@@ -1797,8 +1820,9 @@ syncache_respond(struct syncache *sc, const struct mbuf *m0, int flags)
 	struct ip *ip = NULL;
 	struct mbuf *m;
 	struct tcphdr *th = NULL;
+	struct udphdr *udp = NULL;
 	int optlen, error = 0;	/* Make compiler happy */
-	u_int16_t hlen, tlen, mssopt;
+	u_int16_t hlen, tlen, mssopt, ulen;
 	struct tcpopt to;
 #ifdef INET6
 	struct ip6_hdr *ip6 = NULL;
@@ -1812,9 +1836,14 @@ syncache_respond(struct syncache *sc, const struct mbuf *m0, int flags)
 #endif
 		sizeof(struct ip);
 	tlen = hlen + sizeof(struct tcphdr);
-
+	if (sc->sc_port) {
+		tlen += sizeof(struct udphdr);
+	}
 	/* Determine MSS we advertize to other end of connection. */
-	mssopt = max(tcp_mssopt(&sc->sc_inc), V_tcp_minmss);
+	mssopt = tcp_mssopt(&sc->sc_inc);
+	if (sc->sc_port)
+		mssopt -= V_tcp_udp_tunneling_overhead;
+	mssopt = max(mssopt, V_tcp_minmss);
 
 	/* XXX: Assume that the entire packet will fit in a header mbuf. */
 	KASSERT(max_linkhdr + tlen + TCP_MAXOLEN <= MHLEN,
@@ -1836,7 +1865,6 @@ syncache_respond(struct syncache *sc, const struct mbuf *m0, int flags)
 	if (sc->sc_inc.inc_flags & INC_ISIPV6) {
 		ip6 = mtod(m, struct ip6_hdr *);
 		ip6->ip6_vfc = IPV6_VERSION;
-		ip6->ip6_nxt = IPPROTO_TCP;
 		ip6->ip6_src = sc->sc_inc.inc6_laddr;
 		ip6->ip6_dst = sc->sc_inc.inc6_faddr;
 		ip6->ip6_plen = htons(tlen - hlen);
@@ -1844,9 +1872,18 @@ syncache_respond(struct syncache *sc, const struct mbuf *m0, int flags)
 		/* Zero out traffic class and flow label. */
 		ip6->ip6_flow &= ~IPV6_FLOWINFO_MASK;
 		ip6->ip6_flow |= sc->sc_flowlabel;
+		if (sc->sc_port != 0) {
+			ip6->ip6_nxt = IPPROTO_UDP;
+			udp = (struct udphdr *)(ip6 + 1);
+			udp->uh_sport = htons(V_tcp_udp_tunneling_port);
+			udp->uh_dport = sc->sc_port;
+			ulen = (tlen - sizeof(struct ip6_hdr));
+			th = (struct tcphdr *)(udp + 1);
+		} else {
+			ip6->ip6_nxt = IPPROTO_TCP;
+			th = (struct tcphdr *)(ip6 + 1);
+		}
 		ip6->ip6_flow |= htonl(sc->sc_ip_tos << 20);
-
-		th = (struct tcphdr *)(ip6 + 1);
 	}
 #endif
 #if defined(INET6) && defined(INET)
@@ -1861,7 +1898,6 @@ syncache_respond(struct syncache *sc, const struct mbuf *m0, int flags)
 		ip->ip_id = 0;
 		ip->ip_off = 0;
 		ip->ip_sum = 0;
-		ip->ip_p = IPPROTO_TCP;
 		ip->ip_src = sc->sc_inc.inc_laddr;
 		ip->ip_dst = sc->sc_inc.inc_faddr;
 		ip->ip_ttl = sc->sc_ip_ttl;
@@ -1876,8 +1912,17 @@ syncache_respond(struct syncache *sc, const struct mbuf *m0, int flags)
 		 */
 		if (V_path_mtu_discovery && ((sc->sc_flags & SCF_UNREACH) == 0))
 		       ip->ip_off |= htons(IP_DF);
-
-		th = (struct tcphdr *)(ip + 1);
+		if (sc->sc_port == 0) {
+			ip->ip_p = IPPROTO_TCP;
+			th = (struct tcphdr *)(ip + 1);
+		} else {
+			ip->ip_p = IPPROTO_UDP;
+			udp = (struct udphdr *)(ip + 1);
+			udp->uh_sport = htons(V_tcp_udp_tunneling_port);
+			udp->uh_dport = sc->sc_port;
+			ulen = (tlen - sizeof(struct ip));
+			th = (struct tcphdr *)(udp + 1);
+		}
 	}
 #endif /* INET */
 	th->th_sport = sc->sc_inc.inc_lport;
@@ -1957,8 +2002,11 @@ syncache_respond(struct syncache *sc, const struct mbuf *m0, int flags)
 	} else
 		optlen = 0;
 
+	if (udp) {
+		ulen += optlen;
+		udp->uh_ulen = htons(ulen);
+	}
 	M_SETFIB(m, sc->sc_inc.inc_fibnum);
-	m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum);
 	/*
 	 * If we have peer's SYN and it has a flowid, then let's assign it to
 	 * our SYN|ACK.  ip6_output() and ip_output() will not assign flowid
@@ -1970,9 +2018,18 @@ syncache_respond(struct syncache *sc, const struct mbuf *m0, int flags)
 	}
 #ifdef INET6
 	if (sc->sc_inc.inc_flags & INC_ISIPV6) {
-		m->m_pkthdr.csum_flags = CSUM_TCP_IPV6;
-		th->th_sum = in6_cksum_pseudo(ip6, tlen + optlen - hlen,
-		    IPPROTO_TCP, 0);
+		if (sc->sc_port) {
+			m->m_pkthdr.csum_flags = CSUM_UDP_IPV6;
+			m->m_pkthdr.csum_data = offsetof(struct udphdr, uh_sum);
+			udp->uh_sum = in6_cksum_pseudo(ip6, ulen,
+			      IPPROTO_UDP, 0);
+			th->th_sum = htons(0);
+		} else {
+			m->m_pkthdr.csum_flags = CSUM_TCP_IPV6;
+			m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum);
+			th->th_sum = in6_cksum_pseudo(ip6, tlen + optlen - hlen,
+			    IPPROTO_TCP, 0);
+		}
 		ip6->ip6_hlim = sc->sc_ip_ttl;
 #ifdef TCP_OFFLOAD
 		if (ADDED_BY_TOE(sc)) {
@@ -1992,9 +2049,18 @@ syncache_respond(struct syncache *sc, const struct mbuf *m0, int flags)
 #endif
 #ifdef INET
 	{
-		m->m_pkthdr.csum_flags = CSUM_TCP;
-		th->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr,
-		    htons(tlen + optlen - hlen + IPPROTO_TCP));
+		if (sc->sc_port) {
+			m->m_pkthdr.csum_flags = CSUM_UDP;
+			m->m_pkthdr.csum_data = offsetof(struct udphdr, uh_sum);
+			udp->uh_sum = in_pseudo(ip->ip_src.s_addr,
+			      ip->ip_dst.s_addr, htons(ulen + IPPROTO_UDP));
+			th->th_sum = htons(0);
+		} else {
+			m->m_pkthdr.csum_flags = CSUM_TCP;
+			m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum);
+			th->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr,
+			    htons(tlen + optlen - hlen + IPPROTO_TCP));
+		}
 #ifdef TCP_OFFLOAD
 		if (ADDED_BY_TOE(sc)) {
 			struct toedev *tod = sc->sc_tod;
@@ -2224,7 +2290,7 @@ syncookie_generate(struct syncache_head *sch, struct syncache *sc)
 static struct syncache *
 syncookie_lookup(struct in_conninfo *inc, struct syncache_head *sch,
     struct syncache *sc, struct tcphdr *th, struct tcpopt *to,
-    struct socket *lso)
+    struct socket *lso, uint16_t port)
 {
 	uint32_t hash;
 	uint8_t *secbits;
@@ -2310,6 +2376,8 @@ syncookie_lookup(struct in_conninfo *inc, struct syncache_head *sch,
 
 	sc->sc_rxmits = 0;
 
+	sc->sc_port = port;
+
 	TCPSTAT_INC(tcps_sc_recvcookie);
 	return (sc);
 }
@@ -2318,13 +2386,13 @@ syncookie_lookup(struct in_conninfo *inc, struct syncache_head *sch,
 static int
 syncookie_cmp(struct in_conninfo *inc, struct syncache_head *sch,
     struct syncache *sc, struct tcphdr *th, struct tcpopt *to,
-    struct socket *lso)
+    struct socket *lso, uint16_t port)
 {
 	struct syncache scs, *scx;
 	char *s;
 
 	bzero(&scs, sizeof(scs));
-	scx = syncookie_lookup(inc, sch, &scs, th, to, lso);
+	scx = syncookie_lookup(inc, sch, &scs, th, to, lso, port);
 
 	if ((s = tcp_log_addrs(inc, th, NULL, NULL)) == NULL)
 		return (0);
@@ -2510,6 +2578,7 @@ syncache_pcblist(struct sysctl_req *req)
 				xt.xt_inp.inp_vflag = INP_IPV6;
 			else
 				xt.xt_inp.inp_vflag = INP_IPV4;
+			xt.xt_encaps_port = sc->sc_port;
 			bcopy(&sc->sc_inc, &xt.xt_inp.inp_inc,
 			    sizeof (struct in_conninfo));
 			error = SYSCTL_OUT(req, &xt, sizeof xt);
diff --git a/sys/netinet/tcp_syncache.h b/sys/netinet/tcp_syncache.h
index 03e34a89c112..a16a80c483d5 100644
--- a/sys/netinet/tcp_syncache.h
+++ b/sys/netinet/tcp_syncache.h
@@ -40,14 +40,15 @@ void	 syncache_init(void);
 #ifdef VIMAGE
 void	syncache_destroy(void);
 #endif
-void	 syncache_unreach(struct in_conninfo *, tcp_seq);
+void	 syncache_unreach(struct in_conninfo *, tcp_seq, uint16_t);
 int	 syncache_expand(struct in_conninfo *, struct tcpopt *,
-	     struct tcphdr *, struct socket **, struct mbuf *);
+	     struct tcphdr *, struct socket **, struct mbuf *, uint16_t);
 struct socket *	 syncache_add(struct in_conninfo *, struct tcpopt *,
 	     struct tcphdr *, struct inpcb *, struct socket *, struct mbuf *,
-	     void *, void *, uint8_t);
-void	 syncache_chkrst(struct in_conninfo *, struct tcphdr *, struct mbuf *);
-void	 syncache_badack(struct in_conninfo *);
+	     void *, void *, uint8_t, uint16_t);
+void	 syncache_chkrst(struct in_conninfo *, struct tcphdr *, struct mbuf *,
+	     uint16_t);
+void	 syncache_badack(struct in_conninfo *, uint16_t);
 int	 syncache_pcblist(struct sysctl_req *);
 
 struct syncache {
@@ -55,6 +56,7 @@ struct syncache {
 	struct		in_conninfo sc_inc;	/* addresses */
 	int		sc_rxttime;		/* retransmit time */
 	u_int16_t	sc_rxmits;		/* retransmit counter */
+	u_int16_t	sc_port;		/* remote UDP encaps port */
 	u_int32_t	sc_tsreflect;		/* timestamp to reflect */
 	u_int32_t	sc_tsoff;		/* ts offset w/ syncookies */
 	u_int32_t	sc_flowlabel;		/* IPv6 flowlabel */
diff --git a/sys/netinet/tcp_timewait.c b/sys/netinet/tcp_timewait.c
index f98927b196fc..b62386ddca05 100644
--- a/sys/netinet/tcp_timewait.c
+++ b/sys/netinet/tcp_timewait.c
@@ -93,6 +93,8 @@ __FBSDID("$FreeBSD$");
 #include <netinet6/ip6protosw.h>
 #endif
 
+#include <netinet/udp.h>
+#include <netinet/udp_var.h>
 #include <machine/in_cksum.h>
 
 #include <security/mac/mac_framework.h>
@@ -318,6 +320,7 @@ tcp_twstart(struct tcpcb *tp)
 	}
 
 	tw->snd_nxt = tp->snd_nxt;
+	tw->t_port = tp->t_port;
 	tw->rcv_nxt = tp->rcv_nxt;
 	tw->iss     = tp->iss;
 	tw->irs     = tp->irs;
@@ -436,12 +439,32 @@ tcp_twcheck(struct inpcb *inp, struct tcpopt *to, struct tcphdr *th,
 	 * while in TIME_WAIT, drop the old connection
 	 * and start over if the sequence numbers
 	 * are above the previous ones.
+	 * Allow UDP port number changes in this case.
 	 */
 	if ((thflags & TH_SYN) && SEQ_GT(th->th_seq, tw->rcv_nxt)) {
 		tcp_twclose(tw, 0);
 		return (1);
 	}
 
+	/*
+	 * Send RST if UDP port numbers don't match
+	 */
+	if (tw->t_port != m->m_pkthdr.tcp_tun_port) {
+		if (th->th_flags & TH_ACK) {
+			tcp_respond(NULL, mtod(m, void *), th, m,
+			    (tcp_seq)0, th->th_ack, TH_RST);
+		} else {
+			if (th->th_flags & TH_SYN)
+				tlen++;
+			if (th->th_flags & TH_FIN)
+				tlen++;
+			tcp_respond(NULL, mtod(m, void *), th, m,
+			    th->th_seq+tlen, (tcp_seq)0, TH_RST|TH_ACK);
+		}
+		INP_WUNLOCK(inp);
+		return (0);
+	}
+
 	/*
 	 * Drop the segment if it does not contain an ACK.
 	 */
@@ -555,13 +578,14 @@ tcp_twrespond(struct tcptw *tw, int flags)
 #ifdef INET
 	struct ip *ip = NULL;
 #endif
-	u_int hdrlen, optlen;
+	u_int hdrlen, optlen, ulen;
 	int error = 0;			/* Keep compiler happy */
 	struct tcpopt to;
 #ifdef INET6
 	struct ip6_hdr *ip6 = NULL;
 	int isipv6 = inp->inp_inc.inc_flags & INC_ISIPV6;
 #endif
+	struct udphdr *udp = NULL;
 	hdrlen = 0;                     /* Keep compiler happy */
 
 	INP_WLOCK_ASSERT(inp);
@@ -579,8 +603,16 @@ tcp_twrespond(struct tcptw *tw, int flags)
 	if (isipv6) {
 		hdrlen = sizeof(struct ip6_hdr) + sizeof(struct tcphdr);
 		ip6 = mtod(m, struct ip6_hdr *);
-		th = (struct tcphdr *)(ip6 + 1);
-		tcpip_fillheaders(inp, ip6, th);
+		if (tw->t_port) {
+			udp = (struct udphdr *)(ip6 + 1);
+			hdrlen += sizeof(struct udphdr);
+			udp->uh_sport = htons(V_tcp_udp_tunneling_port);
+			udp->uh_dport = tw->t_port;
+			ulen = (hdrlen - sizeof(struct ip6_hdr));
+			th = (struct tcphdr *)(udp + 1);
+		} else
+			th = (struct tcphdr *)(ip6 + 1);
+		tcpip_fillheaders(inp, tw->t_port, ip6, th);
 	}
 #endif
 #if defined(INET6) && defined(INET)
@@ -590,8 +622,16 @@ tcp_twrespond(struct tcptw *tw, int flags)
 	{
 		hdrlen = sizeof(struct tcpiphdr);
 		ip = mtod(m, struct ip *);
-		th = (struct tcphdr *)(ip + 1);
-		tcpip_fillheaders(inp, ip, th);
+		if (tw->t_port) {
+			udp = (struct udphdr *)(ip + 1);
+			hdrlen += sizeof(struct udphdr);
+			udp->uh_sport = htons(V_tcp_udp_tunneling_port);
+			udp->uh_dport = tw->t_port;
+			ulen = (hdrlen - sizeof(struct ip));
+			th = (struct tcphdr *)(udp + 1);
+		} else
+			th = (struct tcphdr *)(ip + 1);
+		tcpip_fillheaders(inp, tw->t_port, ip, th);
 	}
 #endif
 	to.to_flags = 0;
@@ -607,6 +647,10 @@ tcp_twrespond(struct tcptw *tw, int flags)
 	}
 	optlen = tcp_addoptions(&to, (u_char *)(th + 1));
 
+	if (udp) {
+		ulen += optlen;
+		udp->uh_ulen = htons(ulen);
+	}
 	m->m_len = hdrlen + optlen;
 	m->m_pkthdr.len = m->m_len;
 
@@ -618,12 +662,19 @@ tcp_twrespond(struct tcptw *tw, int flags)
 	th->th_flags = flags;
 	th->th_win = htons(tw->last_win);
 
-	m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum);
 #ifdef INET6
 	if (isipv6) {
-		m->m_pkthdr.csum_flags = CSUM_TCP_IPV6;
-		th->th_sum = in6_cksum_pseudo(ip6,
-		    sizeof(struct tcphdr) + optlen, IPPROTO_TCP, 0);
+		if (tw->t_port) {
+			m->m_pkthdr.csum_flags = CSUM_UDP_IPV6;
+			m->m_pkthdr.csum_data = offsetof(struct udphdr, uh_sum);
+			udp->uh_sum = in6_cksum_pseudo(ip6, ulen, IPPROTO_UDP, 0);
+			th->th_sum = htons(0);
+		} else {
+			m->m_pkthdr.csum_flags = CSUM_TCP_IPV6;
+			m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum);
+			th->th_sum = in6_cksum_pseudo(ip6,
+			    sizeof(struct tcphdr) + optlen, IPPROTO_TCP, 0);
+		}
 		ip6->ip6_hlim = in6_selecthlim(inp, NULL);
 		TCP_PROBE5(send, NULL, NULL, ip6, NULL, th);
 		error = ip6_output(m, inp->in6p_outputopts, NULL,
@@ -635,9 +686,18 @@ tcp_twrespond(struct tcptw *tw, int flags)
 #endif
 #ifdef INET
 	{
-		m->m_pkthdr.csum_flags = CSUM_TCP;
-		th->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr,
-		    htons(sizeof(struct tcphdr) + optlen + IPPROTO_TCP));
+		if (tw->t_port) {
+			m->m_pkthdr.csum_flags = CSUM_UDP;
+			m->m_pkthdr.csum_data = offsetof(struct udphdr, uh_sum);
+			udp->uh_sum = in_pseudo(ip->ip_src.s_addr,
+			    ip->ip_dst.s_addr, htons(ulen + IPPROTO_UDP));
+			th->th_sum = htons(0);
+		} else {
+			m->m_pkthdr.csum_flags = CSUM_TCP;
+			m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum);
+			th->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr,
+			    htons(sizeof(struct tcphdr) + optlen + IPPROTO_TCP));
+		}
 		ip->ip_len = htons(m->m_pkthdr.len);
 		if (V_path_mtu_discovery)
 			ip->ip_off |= htons(IP_DF);
diff --git a/sys/netinet/tcp_usrreq.c b/sys/netinet/tcp_usrreq.c
index 31b580bfafcc..c4cfb5ea199f 100644
--- a/sys/netinet/tcp_usrreq.c
+++ b/sys/netinet/tcp_usrreq.c
@@ -2049,6 +2049,31 @@ tcp_default_ctloutput(struct socket *so, struct sockopt *sopt, struct inpcb *inp
 			}
 			goto unlock_and_done;
 
+		case TCP_REMOTE_UDP_ENCAPS_PORT:
+			INP_WUNLOCK(inp);
+			error = sooptcopyin(sopt, &optval, sizeof optval,
+			    sizeof optval);
+			if (error)
+				return (error);
+			if ((optval < TCP_TUNNELING_PORT_MIN) ||
+			    (optval > TCP_TUNNELING_PORT_MAX)) {
+				/* Its got to be in range */
+				return (EINVAL);
+			}
+			if ((V_tcp_udp_tunneling_port == 0) && (optval != 0)) {
+				/* You have to have enabled a UDP tunneling port first */
+				return (EINVAL);
+			}
+			INP_WLOCK_RECHECK(inp);
+			if (tp->t_state != TCPS_CLOSED) {
+				/* You can't change after you are connected */
+				error = EINVAL;
+			} else {
+				/* Ok we are all good set the port */
+				tp->t_port = htons(optval);
+			}
+			goto unlock_and_done;
+
 		case TCP_MAXSEG:
 			INP_WUNLOCK(inp);
 			error = sooptcopyin(sopt, &optval, sizeof optval,
@@ -2388,6 +2413,11 @@ tcp_default_ctloutput(struct socket *so, struct sockopt *sopt, struct inpcb *inp
 			INP_WUNLOCK(inp);
 			error = sooptcopyout(sopt, &optval, sizeof optval);
 			break;
+		case TCP_REMOTE_UDP_ENCAPS_PORT:
+			optval = ntohs(tp->t_port);
+			INP_WUNLOCK(inp);
+			error = sooptcopyout(sopt, &optval, sizeof optval);
+			break;
 		case TCP_NOOPT:
 			optval = tp->t_flags & TF_NOOPT;
 			INP_WUNLOCK(inp);
diff --git a/sys/netinet/tcp_var.h b/sys/netinet/tcp_var.h
index 4d28cab80d89..dfd2f239d007 100644
--- a/sys/netinet/tcp_var.h
+++ b/sys/netinet/tcp_var.h
@@ -282,6 +282,16 @@ struct tcptemp {
 	struct	tcphdr tt_t;
 };
 
+/* Enable TCP/UDP tunneling port */
+#define TCP_TUNNELING_PORT_MIN		0
+#define TCP_TUNNELING_PORT_MAX		65535
+#define TCP_TUNNELING_PORT_DEFAULT	0
+
+/* Enable TCP/UDP tunneling port */
+#define TCP_TUNNELING_OVERHEAD_MIN	sizeof(struct udphdr)
+#define TCP_TUNNELING_OVERHEAD_MAX	1024
+#define TCP_TUNNELING_OVERHEAD_DEFAULT	TCP_TUNNELING_OVERHEAD_MIN
+
 /* Minimum map entries limit value, if set */
 #define TCP_MIN_MAP_ENTRIES_LIMIT	128
 
@@ -502,6 +512,8 @@ struct in_conninfo;
 
 struct tcptw {
 	struct inpcb	*tw_inpcb;	/* XXX back pointer to internet pcb */
+	uint32_t  t_port:16,		/* UDP port number if TCPoUDP */
+		t_unused:16;
 	tcp_seq		snd_nxt;
 	tcp_seq		rcv_nxt;
 	tcp_seq		iss;
@@ -678,7 +690,10 @@ struct	tcpstat {
 	uint64_t tcps_pmtud_blackhole_activated_min_mss; /* BH at min MSS Count */
 	uint64_t tcps_pmtud_blackhole_failed;		 /* Black Hole Failure Count */
 
-	uint64_t _pad[12];		/* 6 UTO, 6 TBD */
+	uint64_t tcps_tunneled_pkts;	/* Packets encap's in UDP received */
+	uint64_t tcps_tunneled_errs;	/* Packets that had errors that were UDP encaped */
+
+	uint64_t _pad[10];		/* 6 UTO, 6 TBD */
 };
 
 #define	tcps_rcvmemdrop	tcps_rcvreassfull	/* compat */
@@ -776,7 +791,9 @@ struct xtcpcb {
 	uint32_t	t_rcv_wnd;		/* (s) */
 	uint32_t	t_snd_wnd;		/* (s) */
 	uint32_t	xt_ecn;			/* (s) */
-	int32_t		spare32[26];
+	uint16_t	xt_encaps_port;		/* (s) */
+	int16_t		spare16;
+	int32_t		spare32[25];
 } __aligned(8);
 
 #ifdef _KERNEL
@@ -867,6 +884,8 @@ VNET_DECLARE(int, tcp_sack_globalmaxholes);
 VNET_DECLARE(int, tcp_sack_maxholes);
 VNET_DECLARE(int, tcp_sc_rst_sock_fail);
 VNET_DECLARE(int, tcp_sendspace);
+VNET_DECLARE(int, tcp_udp_tunneling_overhead);
+VNET_DECLARE(int, tcp_udp_tunneling_port);
 VNET_DECLARE(struct inpcbhead, tcb);
 VNET_DECLARE(struct inpcbinfo, tcbinfo);
 
@@ -929,6 +948,7 @@ void	 tcp_twstart(struct tcpcb *);
 void	 tcp_twclose(struct tcptw *, int);
 void	 tcp_ctlinput(int, struct sockaddr *, void *);
 int	 tcp_ctloutput(struct socket *, struct sockopt *);
+void 	 tcp_ctlinput_viaudp(int, struct sockaddr *, void *, void *);
 struct tcpcb *
 	 tcp_drop(struct tcpcb *, int);
 void	 tcp_drain(void);
@@ -963,6 +983,7 @@ void	hhook_run_tcp_est_in(struct tcpcb *tp,
 int	 tcp_input(struct mbuf **, int *, int);
 int	 tcp_autorcvbuf(struct mbuf *, struct tcphdr *, struct socket *,
 	    struct tcpcb *, int);
+int	 tcp_input_with_port(struct mbuf **, int *, int, uint16_t);
 void	 tcp_handle_wakeup(struct tcpcb *, struct socket *);
 void	 tcp_do_segment(struct mbuf *, struct tcphdr *,
 			struct socket *, struct tcpcb *, int, int, uint8_t);
@@ -1033,7 +1054,7 @@ void	 tcp_setpersist(struct tcpcb *);
 void	 tcp_slowtimo(void);
 struct tcptemp *
 	 tcpip_maketemplate(struct inpcb *);
-void	 tcpip_fillheaders(struct inpcb *, void *, void *);
+void	 tcpip_fillheaders(struct inpcb *, uint16_t, void *, void *);
 void	 tcp_timer_activate(struct tcpcb *, uint32_t, u_int);
 int	 tcp_timer_suspend(struct tcpcb *, uint32_t);
 void	 tcp_timers_unsuspend(struct tcpcb *, uint32_t);
diff --git a/sys/netinet/toecore.c b/sys/netinet/toecore.c
index 480aa64c1bf7..d8d499a6fde3 100644
--- a/sys/netinet/toecore.c
+++ b/sys/netinet/toecore.c
@@ -352,7 +352,7 @@ toe_syncache_add(struct in_conninfo *inc, struct tcpopt *to, struct tcphdr *th,
 	INP_RLOCK_ASSERT(inp);
 
 	(void )syncache_add(inc, to, th, inp, inp->inp_socket, NULL, tod,
-	    todctx, iptos);
+	    todctx, iptos, htons(0));
 }
 
 int
@@ -362,7 +362,7 @@ toe_syncache_expand(struct in_conninfo *inc, struct tcpopt *to,
 
 	NET_EPOCH_ASSERT();
 
-	return (syncache_expand(inc, to, th, lsop, NULL));
+	return (syncache_expand(inc, to, th, lsop, NULL, htons(0)));
 }
 
 /*
diff --git a/sys/netinet6/tcp6_var.h b/sys/netinet6/tcp6_var.h
index 7c758fbd3479..2e411963676e 100644
--- a/sys/netinet6/tcp6_var.h
+++ b/sys/netinet6/tcp6_var.h
@@ -74,8 +74,10 @@ VNET_DECLARE(int, tcp_v6mssdflt);	/* XXX */
 
 struct	ip6_hdr;
 void	tcp6_ctlinput(int, struct sockaddr *, void *);
+void 	tcp6_ctlinput_viaudp(int, struct sockaddr *, void *, void *);
 void	tcp6_init(void);
 int	tcp6_input(struct mbuf **, int *, int);
+int	tcp6_input_with_port(struct mbuf **, int *, int, uint16_t);
 
 extern struct	pr_usrreqs tcp6_usrreqs;
 
diff --git a/sys/sys/mbuf.h b/sys/sys/mbuf.h
index 371ae8feae46..dd92103cb1fd 100644
--- a/sys/sys/mbuf.h
+++ b/sys/sys/mbuf.h
@@ -198,6 +198,7 @@ struct pkthdr {
 	} PH_loc;
 };
 #define	ether_vtag	PH_per.sixteen[0]
+#define tcp_tun_port	PH_per.sixteen[0] /* outbound */
 #define	PH_vt		PH_per
 #define	vt_nrecs	sixteen[0]	  /* mld and v6-ND */
 #define	tso_segsz	PH_per.sixteen[1] /* inbound after LRO */
diff --git a/usr.bin/netstat/inet.c b/usr.bin/netstat/inet.c
index 95b0d8931b26..49478c4a9247 100644
--- a/usr.bin/netstat/inet.c
+++ b/usr.bin/netstat/inet.c
@@ -664,6 +664,10 @@ tcp_stats(u_long off, const char *name, int af1 __unused, int proto __unused)
 	    "{N:(for} {:received-ack-bytes/%ju} {N:/byte%s})\n");
 	p(tcps_rcvdupack, "\t\t{:received-duplicate-acks/%ju} "
 	    "{N:/duplicate ack%s}\n");
+	p(tcps_tunneled_pkts, "\t\t{:received-udp-tunneled-pkts/%ju} "
+	    "{N:/UDP tunneled pkt%s}\n");
+	p(tcps_tunneled_errs, "\t\t{:received-bad-udp-tunneled-pkts/%ju} "
+	    "{N:/UDP tunneled pkt cnt with error%s}\n");
 	p(tcps_rcvacktoomuch, "\t\t{:received-acks-for-unsent-data/%ju} "
 	    "{N:/ack%s for unsent data}\n");
 	p2(tcps_rcvpack, tcps_rcvbyte, "\t\t"
diff --git a/usr.bin/sockstat/sockstat.1 b/usr.bin/sockstat/sockstat.1
index 8521c50348c9..f602ad467f9f 100644
--- a/usr.bin/sockstat/sockstat.1
+++ b/usr.bin/sockstat/sockstat.1
@@ -27,7 +27,7 @@
 .\"
 .\" $FreeBSD$
 .\"
-.Dd December 30, 2020
+.Dd March 28, 2021
 .Dt SOCKSTAT 1
 .Os
 .Sh NAME
@@ -98,7 +98,7 @@ Display the protocol state, if applicable.
 This is currently only implemented for SCTP and TCP.
 .It Fl U
 Display the remote UDP encapsulation port number, if applicable.
-This is currently only implemented for SCTP.
+This is currently only implemented for SCTP and TCP.
 .It Fl u
 Show
 .Dv AF_LOCAL
@@ -163,7 +163,7 @@ The address the foreign end of the socket is bound to (see
 .It Li ENCAPS
 The remote UDP encapsulation port number if
 .Fl U
-is specified (only for SCTP).
+is specified (only for SCTP or TCP).
 .It Li PATH STATE
 The path state if
 .Fl s
diff --git a/usr.bin/sockstat/sockstat.c b/usr.bin/sockstat/sockstat.c
index 26f31d96b8e0..109b254b7438 100644
--- a/usr.bin/sockstat/sockstat.c
+++ b/usr.bin/sockstat/sockstat.c
@@ -710,6 +710,8 @@ gather_inet(int proto)
 			sockaddr(&faddr->address, sock->family,
 			    &xip->in6p_faddr, xip->inp_fport);
 		}
+		if (proto == IPPROTO_TCP)
+			faddr->encaps_port = xtp->xt_encaps_port;
 		laddr->next = NULL;
 		faddr->next = NULL;
 		sock->laddr = laddr;
@@ -1087,10 +1089,13 @@ displaysock(struct sock *s, int pos)
 		}
 		if (opt_U) {
 			if (faddr != NULL &&
-			    s->proto == IPPROTO_SCTP &&
-			    s->state != SCTP_CLOSED &&
-			    s->state != SCTP_BOUND &&
-			    s->state != SCTP_LISTEN) {
+			    ((s->proto == IPPROTO_SCTP &&
+			      s->state != SCTP_CLOSED &&
+			      s->state != SCTP_BOUND &&
+			      s->state != SCTP_LISTEN) ||
+			     (s->proto == IPPROTO_TCP &&
+			      s->state != TCPS_CLOSED &&
+			      s->state != TCPS_LISTEN))) {
 				while (pos < offset)
 					pos += xprintf(" ");
 				pos += xprintf("%u",