Index: if_vxlan.c
===================================================================
RCS file: /cvs/src/sys/net/if_vxlan.c,v
retrieving revision 1.76
diff -u -p -r1.76 if_vxlan.c
--- if_vxlan.c	8 Nov 2019 07:16:29 -0000	1.76
+++ if_vxlan.c	12 Apr 2020 01:36:26 -0000
@@ -82,6 +82,8 @@ struct vxlan_softc {
 
 void	 vxlanattach(int);
 int	 vxlanioctl(struct ifnet *, u_long, caddr_t);
+int	 vxlanoutput(struct ifnet *, struct mbuf *, struct sockaddr *,
+	    struct rtentry *);
 void	 vxlanstart(struct ifnet *);
 int	 vxlan_clone_create(struct if_clone *, int);
 int	 vxlan_clone_destroy(struct ifnet *);
@@ -150,6 +152,7 @@ vxlan_clone_create(struct if_clone *ifc,
 
 	ifp->if_softc = sc;
 	ifp->if_ioctl = vxlanioctl;
+	ifp->if_output = vxlanoutput;
 	ifp->if_start = vxlanstart;
 	IFQ_SET_MAXLEN(&ifp->if_snd, IFQ_MAXLEN);
 
@@ -294,6 +297,33 @@ vxlan_multicast_join(struct ifnet *ifp, 
 	if_detachhook_add(mifp, &sc->sc_dtask);
 
 	return (0);
+}
+
+int
+vxlanoutput(struct ifnet *ifp, struct mbuf *m, struct sockaddr *dst,
+    struct rtentry *rt)
+{
+	struct m_tag *mtag;
+
+	/* Try to limit infinite recursion through misconfiguration. */
+	for (mtag = m_tag_find(m, PACKET_TAG_GRE, NULL); mtag;
+	    mtag = m_tag_find(m, PACKET_TAG_GRE, mtag)) {
+		if (memcmp((caddr_t)(mtag + 1), &ifp->if_index,
+		    sizeof(ifp->if_index)) == 0) {
+			m_freem(m);
+			return (EIO);
+		}
+	}
+
+	mtag = m_tag_get(PACKET_TAG_GRE, sizeof(ifp->if_index), M_NOWAIT);
+	if (mtag == NULL) {
+		m_freem(m);
+		return (ENOMEM);
+	}
+	memcpy((caddr_t)(mtag + 1), &ifp->if_index, sizeof(ifp->if_index));
+	m_tag_prepend(m, mtag);
+
+	return (ether_output(ifp, m, dst, rt));
 }
 
 void