diff --git a/include/net/xfrm.h b/include/net/xfrm.h
index fdb41e8bb626..76aa6f11a540 100644
--- a/include/net/xfrm.h
+++ b/include/net/xfrm.h
@@ -1568,7 +1568,6 @@ void xfrm_sad_getinfo(struct net *net, struct xfrmk_sadinfo *si);
 void xfrm_spd_getinfo(struct net *net, struct xfrmk_spdinfo *si);
 u32 xfrm_replay_seqhi(struct xfrm_state *x, __be32 net_seq);
 int xfrm_init_replay(struct xfrm_state *x);
-u32 __xfrm_state_mtu(struct xfrm_state *x, int mtu);
 u32 xfrm_state_mtu(struct xfrm_state *x, int mtu);
 int __xfrm_init_state(struct xfrm_state *x, bool init_replay, bool offload);
 int xfrm_init_state(struct xfrm_state *x);
@@ -1681,14 +1680,15 @@ int km_migrate(const struct xfrm_selector *sel, u8 dir, u8 type,
 	       const struct xfrm_migrate *m, int num_bundles,
 	       const struct xfrm_kmaddress *k,
 	       const struct xfrm_encap_tmpl *encap);
-struct xfrm_state *xfrm_migrate_state_find(struct xfrm_migrate *m, struct net *net);
+struct xfrm_state *xfrm_migrate_state_find(struct xfrm_migrate *m, struct net *net,
+						u32 if_id);
 struct xfrm_state *xfrm_state_migrate(struct xfrm_state *x,
 				      struct xfrm_migrate *m,
 				      struct xfrm_encap_tmpl *encap);
 int xfrm_migrate(const struct xfrm_selector *sel, u8 dir, u8 type,
 		 struct xfrm_migrate *m, int num_bundles,
 		 struct xfrm_kmaddress *k, struct net *net,
-		 struct xfrm_encap_tmpl *encap);
+		 struct xfrm_encap_tmpl *encap, u32 if_id);
 #endif
 
 int km_new_mapping(struct xfrm_state *x, xfrm_address_t *ipaddr, __be16 sport);
diff --git a/include/uapi/linux/xfrm.h b/include/uapi/linux/xfrm.h
index 4e29d7851890..65e13a099b1a 100644
--- a/include/uapi/linux/xfrm.h
+++ b/include/uapi/linux/xfrm.h
@@ -511,6 +511,12 @@ struct xfrm_user_offload {
 	int				ifindex;
 	__u8				flags;
 };
+/* This flag was exposed without any kernel code that supporting it.
+ * Unfortunately, strongswan has the code that uses sets this flag,
+ * which makes impossible to reuse this bit.
+ *
+ * So leave it here to make sure that it won't be reused by mistake.
+ */
 #define XFRM_OFFLOAD_IPV6	1
 #define XFRM_OFFLOAD_INBOUND	2
 
diff --git a/net/ipv4/esp4.c b/net/ipv4/esp4.c
index 851f542928a3..e1b1d080e908 100644
--- a/net/ipv4/esp4.c
+++ b/net/ipv4/esp4.c
@@ -671,7 +671,7 @@ static int esp_output(struct xfrm_state *x, struct sk_buff *skb)
 		struct xfrm_dst *dst = (struct xfrm_dst *)skb_dst(skb);
 		u32 padto;
 
-		padto = min(x->tfcpad, __xfrm_state_mtu(x, dst->child_mtu_cached));
+		padto = min(x->tfcpad, xfrm_state_mtu(x, dst->child_mtu_cached));
 		if (skb->len < padto)
 			esp.tfclen = padto - skb->len;
 	}
diff --git a/net/ipv6/esp6.c b/net/ipv6/esp6.c
index 8bb2c407b46b..7591160edce1 100644
--- a/net/ipv6/esp6.c
+++ b/net/ipv6/esp6.c
@@ -707,7 +707,7 @@ static int esp6_output(struct xfrm_state *x, struct sk_buff *skb)
 		struct xfrm_dst *dst = (struct xfrm_dst *)skb_dst(skb);
 		u32 padto;
 
-		padto = min(x->tfcpad, __xfrm_state_mtu(x, dst->child_mtu_cached));
+		padto = min(x->tfcpad, xfrm_state_mtu(x, dst->child_mtu_cached));
 		if (skb->len < padto)
 			esp.tfclen = padto - skb->len;
 	}
diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c
index 304a295de84f..4788f6b37053 100644
--- a/net/ipv6/ip6_output.c
+++ b/net/ipv6/ip6_output.c
@@ -1408,8 +1408,6 @@ static int ip6_setup_cork(struct sock *sk, struct inet_cork_full *cork,
 		if (np->frag_size)
 			mtu = np->frag_size;
 	}
-	if (mtu < IPV6_MIN_MTU)
-		return -EINVAL;
 	cork->base.fragsize = mtu;
 	cork->base.gso_size = ipc6->gso_size;
 	cork->base.tx_flags = 0;
@@ -1471,8 +1469,6 @@ static int __ip6_append_data(struct sock *sk,
 
 	fragheaderlen = sizeof(struct ipv6hdr) + rt->rt6i_nfheader_len +
 			(opt ? opt->opt_nflen : 0);
-	maxfraglen = ((mtu - fragheaderlen) & ~7) + fragheaderlen -
-		     sizeof(struct frag_hdr);
 
 	headersize = sizeof(struct ipv6hdr) +
 		     (opt ? opt->opt_flen + opt->opt_nflen : 0) +
@@ -1480,6 +1476,13 @@ static int __ip6_append_data(struct sock *sk,
 		      sizeof(struct frag_hdr) : 0) +
 		     rt->rt6i_nfheader_len;
 
+	if (mtu < fragheaderlen ||
+	    ((mtu - fragheaderlen) & ~7) + fragheaderlen < sizeof(struct frag_hdr))
+		goto emsgsize;
+
+	maxfraglen = ((mtu - fragheaderlen) & ~7) + fragheaderlen -
+		     sizeof(struct frag_hdr);
+
 	/* as per RFC 7112 section 5, the entire IPv6 Header Chain must fit
 	 * the first fragment
 	 */
diff --git a/net/key/af_key.c b/net/key/af_key.c
index de24a7d474df..9bf52a09b5ff 100644
--- a/net/key/af_key.c
+++ b/net/key/af_key.c
@@ -2623,7 +2623,7 @@ static int pfkey_migrate(struct sock *sk, struct sk_buff *skb,
 	}
 
 	return xfrm_migrate(&sel, dir, XFRM_POLICY_TYPE_MAIN, m, i,
-			    kma ? &k : NULL, net, NULL);
+			    kma ? &k : NULL, net, NULL, 0);
 
  out:
 	return err;
diff --git a/net/xfrm/xfrm_device.c b/net/xfrm/xfrm_device.c
index 3fa066419d37..39bce5d764de 100644
--- a/net/xfrm/xfrm_device.c
+++ b/net/xfrm/xfrm_device.c
@@ -223,6 +223,9 @@ int xfrm_dev_state_add(struct net *net, struct xfrm_state *x,
 	if (x->encap || x->tfcpad)
 		return -EINVAL;
 
+	if (xuo->flags & ~(XFRM_OFFLOAD_IPV6 | XFRM_OFFLOAD_INBOUND))
+		return -EINVAL;
+
 	dev = dev_get_by_index(net, xuo->ifindex);
 	if (!dev) {
 		if (!(xuo->flags & XFRM_OFFLOAD_INBOUND)) {
@@ -262,7 +265,8 @@ int xfrm_dev_state_add(struct net *net, struct xfrm_state *x,
 	netdev_tracker_alloc(dev, &xso->dev_tracker, GFP_ATOMIC);
 	xso->real_dev = dev;
 	xso->num_exthdrs = 1;
-	xso->flags = xuo->flags;
+	/* Don't forward bit that is not implemented */
+	xso->flags = xuo->flags & ~XFRM_OFFLOAD_IPV6;
 
 	err = dev->xfrmdev_ops->xdo_dev_state_add(x);
 	if (err) {
diff --git a/net/xfrm/xfrm_interface.c b/net/xfrm/xfrm_interface.c
index 57448fc519fc..4e3c62d1ad9e 100644
--- a/net/xfrm/xfrm_interface.c
+++ b/net/xfrm/xfrm_interface.c
@@ -673,12 +673,12 @@ static int xfrmi_changelink(struct net_device *dev, struct nlattr *tb[],
 	struct net *net = xi->net;
 	struct xfrm_if_parms p = {};
 
+	xfrmi_netlink_parms(data, &p);
 	if (!p.if_id) {
 		NL_SET_ERR_MSG(extack, "if_id must be non zero");
 		return -EINVAL;
 	}
 
-	xfrmi_netlink_parms(data, &p);
 	xi = xfrmi_locate(net, &p);
 	if (!xi) {
 		xi = netdev_priv(dev);
diff --git a/net/xfrm/xfrm_policy.c b/net/xfrm/xfrm_policy.c
index 04d1ce9b510f..882526159d3a 100644
--- a/net/xfrm/xfrm_policy.c
+++ b/net/xfrm/xfrm_policy.c
@@ -4256,7 +4256,7 @@ static bool xfrm_migrate_selector_match(const struct xfrm_selector *sel_cmp,
 }
 
 static struct xfrm_policy *xfrm_migrate_policy_find(const struct xfrm_selector *sel,
-						    u8 dir, u8 type, struct net *net)
+						    u8 dir, u8 type, struct net *net, u32 if_id)
 {
 	struct xfrm_policy *pol, *ret = NULL;
 	struct hlist_head *chain;
@@ -4265,7 +4265,8 @@ static struct xfrm_policy *xfrm_migrate_policy_find(const struct xfrm_selector *
 	spin_lock_bh(&net->xfrm.xfrm_policy_lock);
 	chain = policy_hash_direct(net, &sel->daddr, &sel->saddr, sel->family, dir);
 	hlist_for_each_entry(pol, chain, bydst) {
-		if (xfrm_migrate_selector_match(sel, &pol->selector) &&
+		if ((if_id == 0 || pol->if_id == if_id) &&
+		    xfrm_migrate_selector_match(sel, &pol->selector) &&
 		    pol->type == type) {
 			ret = pol;
 			priority = ret->priority;
@@ -4277,7 +4278,8 @@ static struct xfrm_policy *xfrm_migrate_policy_find(const struct xfrm_selector *
 		if ((pol->priority >= priority) && ret)
 			break;
 
-		if (xfrm_migrate_selector_match(sel, &pol->selector) &&
+		if ((if_id == 0 || pol->if_id == if_id) &&
+		    xfrm_migrate_selector_match(sel, &pol->selector) &&
 		    pol->type == type) {
 			ret = pol;
 			break;
@@ -4393,7 +4395,7 @@ static int xfrm_migrate_check(const struct xfrm_migrate *m, int num_migrate)
 int xfrm_migrate(const struct xfrm_selector *sel, u8 dir, u8 type,
 		 struct xfrm_migrate *m, int num_migrate,
 		 struct xfrm_kmaddress *k, struct net *net,
-		 struct xfrm_encap_tmpl *encap)
+		 struct xfrm_encap_tmpl *encap, u32 if_id)
 {
 	int i, err, nx_cur = 0, nx_new = 0;
 	struct xfrm_policy *pol = NULL;
@@ -4412,14 +4414,14 @@ int xfrm_migrate(const struct xfrm_selector *sel, u8 dir, u8 type,
 	}
 
 	/* Stage 1 - find policy */
-	if ((pol = xfrm_migrate_policy_find(sel, dir, type, net)) == NULL) {
+	if ((pol = xfrm_migrate_policy_find(sel, dir, type, net, if_id)) == NULL) {
 		err = -ENOENT;
 		goto out;
 	}
 
 	/* Stage 2 - find and update state(s) */
 	for (i = 0, mp = m; i < num_migrate; i++, mp++) {
-		if ((x = xfrm_migrate_state_find(mp, net))) {
+		if ((x = xfrm_migrate_state_find(mp, net, if_id))) {
 			x_cur[nx_cur] = x;
 			nx_cur++;
 			xc = xfrm_state_migrate(x, mp, encap);
diff --git a/net/xfrm/xfrm_state.c b/net/xfrm/xfrm_state.c
index ca6bee18346d..b749935152ba 100644
--- a/net/xfrm/xfrm_state.c
+++ b/net/xfrm/xfrm_state.c
@@ -1579,9 +1579,6 @@ static struct xfrm_state *xfrm_state_clone(struct xfrm_state *orig,
 	memcpy(&x->mark, &orig->mark, sizeof(x->mark));
 	memcpy(&x->props.smark, &orig->props.smark, sizeof(x->props.smark));
 
-	if (xfrm_init_state(x) < 0)
-		goto error;
-
 	x->props.flags = orig->props.flags;
 	x->props.extra_flags = orig->props.extra_flags;
 
@@ -1606,7 +1603,8 @@ out:
 	return NULL;
 }
 
-struct xfrm_state *xfrm_migrate_state_find(struct xfrm_migrate *m, struct net *net)
+struct xfrm_state *xfrm_migrate_state_find(struct xfrm_migrate *m, struct net *net,
+						u32 if_id)
 {
 	unsigned int h;
 	struct xfrm_state *x = NULL;
@@ -1622,6 +1620,8 @@ struct xfrm_state *xfrm_migrate_state_find(struct xfrm_migrate *m, struct net *n
 				continue;
 			if (m->reqid && x->props.reqid != m->reqid)
 				continue;
+			if (if_id != 0 && x->if_id != if_id)
+				continue;
 			if (!xfrm_addr_equal(&x->id.daddr, &m->old_daddr,
 					     m->old_family) ||
 			    !xfrm_addr_equal(&x->props.saddr, &m->old_saddr,
@@ -1637,6 +1637,8 @@ struct xfrm_state *xfrm_migrate_state_find(struct xfrm_migrate *m, struct net *n
 			if (x->props.mode != m->mode ||
 			    x->id.proto != m->proto)
 				continue;
+			if (if_id != 0 && x->if_id != if_id)
+				continue;
 			if (!xfrm_addr_equal(&x->id.daddr, &m->old_daddr,
 					     m->old_family) ||
 			    !xfrm_addr_equal(&x->props.saddr, &m->old_saddr,
@@ -1663,6 +1665,11 @@ struct xfrm_state *xfrm_state_migrate(struct xfrm_state *x,
 	if (!xc)
 		return NULL;
 
+	xc->props.family = m->new_family;
+
+	if (xfrm_init_state(xc) < 0)
+		goto error;
+
 	memcpy(&xc->id.daddr, &m->new_daddr, sizeof(xc->id.daddr));
 	memcpy(&xc->props.saddr, &m->new_saddr, sizeof(xc->props.saddr));
 
@@ -2572,7 +2579,7 @@ void xfrm_state_delete_tunnel(struct xfrm_state *x)
 }
 EXPORT_SYMBOL(xfrm_state_delete_tunnel);
 
-u32 __xfrm_state_mtu(struct xfrm_state *x, int mtu)
+u32 xfrm_state_mtu(struct xfrm_state *x, int mtu)
 {
 	const struct xfrm_type *type = READ_ONCE(x->type);
 	struct crypto_aead *aead;
@@ -2603,17 +2610,7 @@ u32 __xfrm_state_mtu(struct xfrm_state *x, int mtu)
 	return ((mtu - x->props.header_len - crypto_aead_authsize(aead) -
 		 net_adj) & ~(blksize - 1)) + net_adj - 2;
 }
-EXPORT_SYMBOL_GPL(__xfrm_state_mtu);
-
-u32 xfrm_state_mtu(struct xfrm_state *x, int mtu)
-{
-	mtu = __xfrm_state_mtu(x, mtu);
-
-	if (x->props.family == AF_INET6 && mtu < IPV6_MIN_MTU)
-		return IPV6_MIN_MTU;
-
-	return mtu;
-}
+EXPORT_SYMBOL_GPL(xfrm_state_mtu);
 
 int __xfrm_init_state(struct xfrm_state *x, bool init_replay, bool offload)
 {
diff --git a/net/xfrm/xfrm_user.c b/net/xfrm/xfrm_user.c
index 8cd6c8129004..a4fb596e87af 100644
--- a/net/xfrm/xfrm_user.c
+++ b/net/xfrm/xfrm_user.c
@@ -2608,6 +2608,7 @@ static int xfrm_do_migrate(struct sk_buff *skb, struct nlmsghdr *nlh,
 	int n = 0;
 	struct net *net = sock_net(skb->sk);
 	struct xfrm_encap_tmpl  *encap = NULL;
+	u32 if_id = 0;
 
 	if (attrs[XFRMA_MIGRATE] == NULL)
 		return -EINVAL;
@@ -2632,7 +2633,10 @@ static int xfrm_do_migrate(struct sk_buff *skb, struct nlmsghdr *nlh,
 			return -ENOMEM;
 	}
 
-	err = xfrm_migrate(&pi->sel, pi->dir, type, m, n, kmp, net, encap);
+	if (attrs[XFRMA_IF_ID])
+		if_id = nla_get_u32(attrs[XFRMA_IF_ID]);
+
+	err = xfrm_migrate(&pi->sel, pi->dir, type, m, n, kmp, net, encap, if_id);
 
 	kfree(encap);