Index: sbin/ifconfig/ifconfig.8
===================================================================
RCS file: /cvs/src/sbin/ifconfig/ifconfig.8,v
retrieving revision 1.299
diff -u -p -r1.299 ifconfig.8
--- sbin/ifconfig/ifconfig.8	15 Feb 2018 04:21:46 -0000	1.299
+++ sbin/ifconfig/ifconfig.8	15 Feb 2018 04:22:52 -0000
@@ -1603,6 +1603,7 @@ for a complete list of the available pro
 .Op Oo Fl Oc Ns Cm keepalive Ar period count
 .Op Oo Fl Oc Ns Cm tunnel Ar src_address dest_address
 .Op Cm tunneldomain Ar tableid
+.Op Oo Fl Oc Ns Cm tunneldf
 .Op Cm tunnelttl Ar ttl
 .Op Oo Fl Oc Ns Cm vnetid Ar network-id
 .Ek
@@ -1654,6 +1655,10 @@ interface itself.
 .Ar tableid
 can be set to any valid routing table ID;
 the corresponding routing domain is derived from this table.
+.It Cm tunneldf
+Do not allow fragmentation of encapsulated packets.
+.It Cm -tunneldf
+Allow fragmentation of the encapsulated packets. 
 .It Cm tunnelttl Ar ttl
 Set the IP or multicast TTL of the tunnel packets.
 If supported by the tunnel protocol,
Index: sbin/ifconfig/ifconfig.c
===================================================================
RCS file: /cvs/src/sbin/ifconfig/ifconfig.c,v
retrieving revision 1.357
diff -u -p -r1.357 ifconfig.c
--- sbin/ifconfig/ifconfig.c	10 Feb 2018 05:55:26 -0000	1.357
+++ sbin/ifconfig/ifconfig.c	15 Feb 2018 04:22:52 -0000
@@ -252,6 +252,8 @@ void	setpfsync_syncpeer(const char *, in
 void	unsetpfsync_syncpeer(const char *, int);
 void	setpfsync_defer(const char *, int);
 void	pfsync_status(void);
+void	settunneldf(const char *, int);
+void	settunnelnodf(const char *, int);
 void	setpppoe_dev(const char *,int);
 void	setpppoe_svc(const char *,int);
 void	setpppoe_ac(const char *,int);
@@ -434,6 +436,8 @@ const struct	cmd {
 	{ "deletetunnel",  0,		0,		deletetunnel },
 	{ "tunneldomain", NEXTARG,	0,		settunnelinst },
 	{ "tunnelttl",	NEXTARG,	0,		settunnelttl },
+	{ "tunneldf",	0,		0,		settunneldf },
+	{ "-tunneldf",	0,		0,		settunnelnodf },
 	{ "pppoedev",	NEXTARG,	0,		setpppoe_dev },
 	{ "pppoesvc",	NEXTARG,	0,		setpppoe_svc },
 	{ "-pppoesvc",	1,		0,		setpppoe_svc },
@@ -2750,6 +2754,10 @@ phys_status(int force)
 		else if (ifr.ifr_ttl > 0)
 			printf(" ttl %d", ifr.ifr_ttl);
 	}
+
+	if (ioctl(s, SIOCGLIFPHYDF, (caddr_t)&ifr) == 0)
+		printf(" %s", ifr.ifr_df ? "df" : "nodf");
+
 #ifndef SMALL
 	if (ioctl(s, SIOCGLIFPHYRTABLE, (caddr_t)&ifr) == 0 &&
 	    (rdomainid != 0 || ifr.ifr_rdomainid != 0))
@@ -3283,6 +3291,24 @@ settunnelttl(const char *id, int param)
 	ifr.ifr_ttl = ttl;
 	if (ioctl(s, SIOCSLIFPHYTTL, (caddr_t)&ifr) < 0)
 		warn("SIOCSLIFPHYTTL");
+}
+
+void
+settunneldf(const char *ignored, int alsoignored)
+{
+	strlcpy(ifr.ifr_name, name, sizeof(ifr.ifr_name));
+	ifr.ifr_df = 1;
+	if (ioctl(s, SIOCSLIFPHYDF, (caddr_t)&ifr) < 0)
+		warn("SIOCSLIFPHYDF");
+}
+
+void
+settunnelnodf(const char *ignored, int alsoignored)
+{
+	strlcpy(ifr.ifr_name, name, sizeof(ifr.ifr_name));
+	ifr.ifr_df = 0;
+	if (ioctl(s, SIOCSLIFPHYDF, (caddr_t)&ifr) < 0)
+		warn("SIOCSLIFPHYDF");
 }
 
 void
Index: sys/net/if.c
===================================================================
RCS file: /cvs/src/sys/net/if.c,v
retrieving revision 1.544
diff -u -p -r1.544 if.c
--- sys/net/if.c	10 Feb 2018 09:32:54 -0000	1.544
+++ sys/net/if.c	15 Feb 2018 04:22:52 -0000
@@ -2114,6 +2114,7 @@ ifioctl(struct socket *so, u_long cmd, c
 	case SIOCSLIFPHYADDR:
 	case SIOCSLIFPHYRTABLE:
 	case SIOCSLIFPHYTTL:
+	case SIOCSLIFPHYDF:
 	case SIOCADDMULTI:
 	case SIOCDELMULTI:
 	case SIOCSIFMEDIA:
Index: sys/net/if.h
===================================================================
RCS file: /cvs/src/sys/net/if.h,v
retrieving revision 1.191
diff -u -p -r1.191 if.h
--- sys/net/if.h	10 Feb 2018 05:52:08 -0000	1.191
+++ sys/net/if.h	15 Feb 2018 04:22:53 -0000
@@ -387,6 +387,7 @@ struct	ifreq {
 #define	ifr_rdomainid	ifr_ifru.ifru_metric	/* VRF instance (overload) */
 #define ifr_vnetid	ifr_ifru.ifru_vnetid	/* Virtual Net Id */
 #define ifr_ttl		ifr_ifru.ifru_metric	/* tunnel TTL (overload) */
+#define ifr_df		ifr_ifru.ifru_metric	/* tunnel DF (overload) */
 #define	ifr_data	ifr_ifru.ifru_data	/* for use by interface */
 #define ifr_index	ifr_ifru.ifru_index	/* interface index */
 #define ifr_llprio	ifr_ifru.ifru_metric	/* link layer priority */
Index: sys/net/if_etherip.c
===================================================================
RCS file: /cvs/src/sys/net/if_etherip.c,v
retrieving revision 1.35
diff -u -p -r1.35 if_etherip.c
--- sys/net/if_etherip.c	12 Feb 2018 01:43:42 -0000	1.35
+++ sys/net/if_etherip.c	15 Feb 2018 04:22:53 -0000
@@ -85,6 +85,7 @@ struct etherip_softc {
 	struct etherip_tunnel	sc_tunnel; /* must be first */
 	struct arpcom		sc_ac;
 	struct ifmedia		sc_media;
+	uint16_t		sc_df;
 	uint8_t			sc_ttl;
 };
 
@@ -136,6 +137,7 @@ etherip_clone_create(struct if_clone *if
 	    ifc->ifc_name, unit);
 
 	sc->sc_ttl = ip_defttl;
+	sc->sc_ttl = htons(0);
 
 	ifp->if_softc = sc;
 	ifp->if_ioctl = etherip_ioctl;
@@ -293,6 +295,14 @@ etherip_ioctl(struct ifnet *ifp, u_long 
 		ifr->ifr_ttl = (int)sc->sc_ttl;
 		break;
 
+	case SIOCSLIFPHYDF:
+		/* commit */
+		sc->sc_df = ifr->ifr_df ? htons(IP_DF) : htons(0);
+		break;
+	case SIOCGLIFPHYDF:
+		ifr->ifr_df = sc->sc_df ? 1 : 0;
+		break;
+
 	case SIOCSIFMEDIA:
 	case SIOCGIFMEDIA:
 		error = ifmedia_ioctl(ifp, ifr, &sc->sc_media, cmd);
@@ -476,11 +486,12 @@ ip_etherip_output(struct ifnet *ifp, str
 
 	ip->ip_v = IPVERSION;
 	ip->ip_hl = sizeof(*ip) >> 2;
-	ip->ip_id = htons(ip_randomid());
 	ip->ip_tos = IPTOS_LOWDELAY;
-	ip->ip_p = IPPROTO_ETHERIP;
 	ip->ip_len = htons(m->m_pkthdr.len);
+	ip->ip_id = htons(ip_randomid());
+	ip->ip_off = sc->sc_df;
 	ip->ip_ttl = sc->sc_ttl;
+	ip->ip_p = IPPROTO_ETHERIP;
 	ip->ip_src = sc->sc_tunnel.t_src4;
 	ip->ip_dst = sc->sc_tunnel.t_dst4;
 
@@ -639,6 +650,9 @@ ip6_etherip_output(struct ifnet *ifp, st
 	eip->eip_ver = ETHERIP_VERSION;
 	eip->eip_res = 0;
 	eip->eip_pad = 0;
+
+	if (sc->sc_df)
+		SET(m->m_pkthdr.csum_flags, M_IPV6_DF_OUT);
 
 	m->m_flags &= ~(M_BCAST|M_MCAST);
 	m->m_pkthdr.ph_rtableid = sc->sc_tunnel.t_rtableid;
Index: sys/sys/sockio.h
===================================================================
RCS file: /cvs/src/sys/sys/sockio.h,v
retrieving revision 1.73
diff -u -p -r1.73 sockio.h
--- sys/sys/sockio.h	8 Feb 2018 13:15:32 -0000	1.73
+++ sys/sys/sockio.h	15 Feb 2018 04:22:53 -0000
@@ -191,6 +191,9 @@
 #define	SIOCSUMBPARAM	 _IOW('i', 191, struct ifreq)	/* set MBIM param */
 #define	SIOCGUMBPARAM	_IOWR('i', 192, struct ifreq)	/* get MBIM param */
 
+#define	SIOCSLIFPHYDF	_IOW('i', 193, struct ifreq)	/* set tunnel df/nodf */
+#define	SIOCGLIFPHYDF	_IOWR('i', 194, struct ifreq)	/* set tunnel df/nodf */
+
 #define	SIOCSVH		_IOWR('i', 245, struct ifreq)	/* set carp param */
 #define	SIOCGVH		_IOWR('i', 246, struct ifreq)	/* get carp param */