diff --git a/net/ipv4/ip_output.c b/net/ipv4/ip_output.c
index 34606ef..534650c 100644
--- a/net/ipv4/ip_output.c
+++ b/net/ipv4/ip_output.c
@@ -189,6 +189,14 @@
 	return -EINVAL;
 }
 
+static inline int ip_skb_dst_mtu(struct sk_buff *skb)
+{
+	struct inet_sock *inet = skb->sk ? inet_sk(skb->sk) : NULL;
+
+	return (inet && inet->pmtudisc == IP_PMTUDISC_PROBE) ?
+	       skb->dst->dev->mtu : dst_mtu(skb->dst);
+}
+
 static inline int ip_finish_output(struct sk_buff *skb)
 {
 #if defined(CONFIG_NETFILTER) && defined(CONFIG_XFRM)
@@ -198,7 +206,7 @@
 		return dst_output(skb);
 	}
 #endif
-	if (skb->len > dst_mtu(skb->dst) && !skb_is_gso(skb))
+	if (skb->len > ip_skb_dst_mtu(skb) && !skb_is_gso(skb))
 		return ip_fragment(skb, ip_finish_output2);
 	else
 		return ip_finish_output2(skb);
@@ -422,7 +430,7 @@
 	if (unlikely((iph->frag_off & htons(IP_DF)) && !skb->local_df)) {
 		IP_INC_STATS(IPSTATS_MIB_FRAGFAILS);
 		icmp_send(skb, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED,
-			  htonl(dst_mtu(&rt->u.dst)));
+			  htonl(ip_skb_dst_mtu(skb)));
 		kfree_skb(skb);
 		return -EMSGSIZE;
 	}
@@ -787,7 +795,9 @@
 			inet->cork.addr = ipc->addr;
 		}
 		dst_hold(&rt->u.dst);
-		inet->cork.fragsize = mtu = dst_mtu(rt->u.dst.path);
+		inet->cork.fragsize = mtu = inet->pmtudisc == IP_PMTUDISC_PROBE ?
+					    rt->u.dst.dev->mtu :
+					    dst_mtu(rt->u.dst.path);
 		inet->cork.rt = rt;
 		inet->cork.length = 0;
 		sk->sk_sndmsg_page = NULL;
@@ -1203,13 +1213,13 @@
 	 * to fragment the frame generated here. No matter, what transforms
 	 * how transforms change size of the packet, it will come out.
 	 */
-	if (inet->pmtudisc != IP_PMTUDISC_DO)
+	if (inet->pmtudisc < IP_PMTUDISC_DO)
 		skb->local_df = 1;
 
 	/* DF bit is set when we want to see DF on outgoing frames.
 	 * If local_df is set too, we still allow to fragment this frame
 	 * locally. */
-	if (inet->pmtudisc == IP_PMTUDISC_DO ||
+	if (inet->pmtudisc >= IP_PMTUDISC_DO ||
 	    (skb->len <= dst_mtu(&rt->u.dst) &&
 	     ip_dont_fragment(sk, &rt->u.dst)))
 		df = htons(IP_DF);